Dr. Michael T. Longaker

All Publications

• Charles "Chuck" K.F. Chan (1975-2024). Cell stem cell Ambrosi, T. H., Longaker, M. T. 2024; 31 (10): 1391-1392

  View details for DOI 10.1016/j.stem.2024.09.005

  View details for PubMedID 39366359

• Clinical, mechanistic, and therapeutic landscape of cutaneous fibrosis. Science translational medicine Li, D. J., Berry, C. E., Wan, D. C., Longaker, M. T. 2024; 16 (766): eadn7871

  Abstract

  When dysregulated, skin fibrosis can lead to a multitude of pathologies. We provide a framework for understanding the wide clinical spectrum, mechanisms, and management of cutaneous fibrosis encompassing a variety of matrix disorders, fibrohistiocytic neoplasms, injury-induced scarring, and autoimmune scleroses. Underlying such entities are common mechanistic pathways that leverage morphogenic signaling, immune activation, and mechanotransduction to modulate fibroblast function. In light of the limited array of available treatments for cutaneous fibrosis, scientific insights have opened new therapeutic and investigative avenues for conditions that still lack effective interventions.

  View details for DOI 10.1126/scitranslmed.adn7871

  View details for PubMedID 39321265

• Author Correction: Sexually dimorphic estrogen sensing in skeletal stem cells controls skeletal regeneration. Nature communications Andrew, T. W., Koepke, L. S., Wang, Y., Lopez, M., Steininger, H., Struck, D., Boyko, T., Ambrosi, T. H., Tong, X., Sun, Y., Gulati, G. S., Murphy, M. P., Marecic, O., Tevlin, R., Schallmoser, K., Strunk, D., Seita, J., Goodman, S. B., Yang, F., Longaker, M. T., Yang, G. P., Chan, C. K. 2024; 15 (1): 8030

  View details for DOI 10.1038/s41467-024-51829-1

  View details for PubMedID 39271692

• Editorial for Special Issue on Artificial Intelligence in Tissue Engineering and Biology. Tissue engineering. Part A Guo, J. L., Januszyk, M., Longaker, M. T. 2024

  Abstract

  N/A.

  View details for DOI 10.1089/ten.TEA.2024.0240

  View details for PubMedID 39162812

• Marvels of spiny mouse regeneration: cellular players and their interactions in restoring tissue architecture in mammals. Current opinion in genetics & development Tomasso, A., Disela, V., Longaker, M. T., Bartscherer, K. 2024; 87: 102228

  Abstract

  Understanding the cellular and molecular determinants of mammalian tissue regeneration and repair is crucial for developing effective therapies that restore tissue architecture and function. In this review, we focus on the cell types involved in scarless wound response and regeneration of spiny mice (Acomys). Comparative -omics approaches with scar-prone mammals have revealed species-specific peculiarities in cellular behavior during the divergent healing trajectories. We discuss the developing views on which cell types engage in restoring the architecture of spiny mouse tissues through a co-ordinated spatiotemporal response to injury. While yet at the beginning of understanding how cells interact in these fascinating animals to regenerate tissues, spiny mice hold great promise for scar prevention and anti-fibrotic treatments.

  View details for DOI 10.1016/j.gde.2024.102228

  View details for PubMedID 39047585

• Understanding the Foreign Body Response via Single-Cell Meta-Analysis. Biology Liang, N. E., Parker, J. B., Lu, J. M., Januszyk, M., Wan, D. C., Griffin, M., Longaker, M. T. 2024; 13 (7)

  Abstract

  Foreign body response (FBR) is a universal reaction to implanted biomaterial that can affect the function and longevity of the implant. A few studies have attempted to identify targets for treating FBR through the use of single-cell RNA sequencing (scRNA-seq), though the generalizability of these findings from an individual study may be limited. In our study, we perform a meta-analysis of scRNA-seq data from all available FBR mouse studies and integrate these data to identify gene signatures specific to FBR across different models and anatomic locations. We identify subclusters of fibroblasts and macrophages that emerge in response to foreign bodies and characterize their signaling pathways, gene ontology terms, and downstream mediators. The fibroblast subpopulations enriched in the setting of FBR demonstrated significant signaling interactions in the transforming growth factor-beta (TGF-beta) signaling pathway, with known pro-fibrotic mediators identified as top expressed genes in these FBR-derived fibroblasts. In contrast, FBR-enriched macrophage subclusters highly expressed pro-fibrotic and pro-inflammatory mediators downstream of tumor necrosis factor (TNF) signaling. Cell-cell interactions were additionally interrogated using CellChat, with identification of key signaling interactions enriched between fibroblasts and macrophages in FBR. By combining multiple FBR datasets, our meta-analysis study identifies common cell-specific gene signatures enriched in foreign body reactions, providing potential therapeutic targets for patients requiring medical implants across a myriad of devices and indications.

  View details for DOI 10.3390/biology13070540

  View details for PubMedID 39056733

• Role of ferroptosis in radiation-induced soft tissue injury. Cell death discovery Berry, C. E., Kendig, C. B., An, N., Fazilat, A. Z., Churukian, A. A., Griffin, M., Pan, P. M., Longaker, M. T., Dixon, S. J., Wan, D. C. 2024; 10 (1): 313

  Abstract

  Ionizing radiation has been pivotal in cancer therapy since its discovery. Despite its therapeutic benefits, IR causes significant acute and chronic complications due to DNA damage and the generation of reactive oxygen species, which harm nucleic acids, lipids, and proteins. While cancer cells are more vulnerable to ionizing radiation due to their inefficiency in repairing damage, healthy cells in the irradiated area also suffer. Various types of cell death occur, including apoptosis, necrosis, pyroptosis, autophagy-dependent cell death, immunogenic cell death, and ferroptosis. Ferroptosis, driven by iron-dependent lipid peroxide accumulation, has been recognized as crucial in radiation therapy's therapeutic effects and complications, with extensive research across various tissues. This review aims to summarize the pathways involved in radiation-related ferroptosis, findings in different organs, and drugs targeting ferroptosis to mitigate its harmful effects.

  View details for DOI 10.1038/s41420-024-02003-5

  View details for PubMedID 38969638

  View details for PubMedCentralID PMC11226648

• Single-cell transcriptional analysis of irradiated skin reveals changes in fibroblast subpopulations and variability in caveolin expression. Radiation oncology (London, England) Kameni, L. E., Griffin, M., Berry, C. E., Shariatzadeh, S., Downer, M. A., Valencia, C., Fazilat, A. Z., Nazerali, R., Momeni, A., Januszyk, M., Longaker, M. T., Wan, D. C. 2024; 19 (1): 82

  Abstract

  Radiation-induced fibrosis (RIF) is an important late complication of radiation therapy, and the resulting damaging effects of RIF can significantly impact reconstructive outcomes. There is currently a paucity of effective treatment options available, likely due to the continuing knowledge gap surrounding the cellular mechanisms involved. In this study, detailed analyses of irradiated and non-irradiated human skin samples were performed incorporating histological and single-cell transcriptional analysis to identify novel features guiding development of skin fibrosis following radiation injury.Paired irradiated and contralateral non-irradiated skin samples were obtained from six female patients undergoing post-oncologic breast reconstruction. Skin samples underwent histological evaluation, immunohistochemistry, and biomechanical testing. Single-cell RNA sequencing was performed using the 10X single cell platform. Cells were separated into clusters using Seurat in R. The SingleR classifier was applied to ascribe cell type identities to each cluster. Differentially expressed genes characteristic to each cluster were then determined using non-parametric testing.Comparing irradiated and non-irradiated skin, epidermal atrophy, dermal thickening, and evidence of thick, disorganized collagen deposition within the extracellular matrix of irradiated skin were readily appreciated on histology. These histologic features were associated with stiffness that was higher in irradiated skin. Single-cell RNA sequencing revealed six predominant cell types. Focusing on fibroblasts/stromal lineage cells, five distinct transcriptional clusters (Clusters 0-4) were identified. Interestingly, while all clusters were noted to express Cav1, Cluster 2 was the only one to also express Cav2. Immunohistochemistry demonstrated increased expression of Cav2 in irradiated skin, whereas Cav1 was more readily identified in non-irradiated skin, suggesting Cav1 and Cav2 may act antagonistically to modulate fibrotic cellular responses.In response to radiation therapy, specific changes to fibroblast subpopulations and enhanced Cav2 expression may contribute to fibrosis. Altogether, this study introduces a novel pathway of caveolin involvement which may contribute to fibrotic development following radiation injury.

  View details for DOI 10.1186/s13014-024-02472-z

  View details for PubMedID 38926892

  View details for PubMedCentralID 6329848

• Hematoxylin and Eosin Architecture Uncovers Clinically Divergent Niches in Pancreatic Cancer. Tissue engineering. Part A Guo, J. L., Lopez, D. M., Mascharak, S., Foster, D. S., Khan, A., Davitt, M. F., Nguyen, A. T., Burcham, A. R., Chinta, M. S., Guardino, N. J., Griffin, M., Miller, E., Januszyk, M., Raghavan, S. S., Longacre, T. A., Delitto, D. J., Norton, J. A., Longaker, M. T. 2024

  Abstract

  Pancreatic ductal adenocarcinoma (PDAC) represents one of the only cancers with an increasing incidence rate and is often associated with intra- and peri-tumoral scarring, referred to as desmoplasia. This scarring is highly heterogeneous in extracellular matrix (ECM) architecture and plays complex roles in both tumor biology and clinical outcomes that are not yet fully understood. Using hematoxylin and eosin (H&E), a routine histological stain utilized in existing clinical workflows, we quantified ECM architecture in 85 patient samples to assess relationships between desmoplastic architecture and clinical outcomes such as survival time and disease recurrence. By utilizing unsupervised machine learning (ML) to summarize a latent space across 147 local (e.g. fiber length, solidity) and global (e.g. fiber branching, porosity) H&E-based features, we identified a continuum of histological architectures that were associated with differences in both survival and recurrence. Further, we mapped H&E architectures to a CO-Detection by indEXing (CODEX) reference atlas, revealing localized cell- and protein-based niches associated with outcome-positive vs. outcome-negative scarring in the tumor microenvironment. Overall, our study utilizes standard H&E staining to uncover clinically relevant associations between desmoplastic organization and PDAC outcomes, offering a translatable pipeline to support prognostic decision-making and a blueprint of spatial-biological factors for modeling by tissue engineering methods.

  View details for DOI 10.1089/ten.TEA.2024.0039

  View details for PubMedID 38874979

• Ferroptosis Inhibition with Deferoxamine Alleviates Radiation-Induced Fibrosis. Research square Berry, C. E., Kendig, C., Bs, T. L., Brenac, C., Griffin, M., Guo, J., Kameni, L., Dixon, S. J., Longaker, M. T., Wan, D. 2024

  Abstract

  Radiation-induced fibrosis (RIF) is a debilitating sequelae of radiation therapy that has been shown to improve with topical treatment with the iron chelator deferoxamine (DFO). We investigated whether DFO exerts this effect through attenuation of ferroptosis, a recently described iron-dependent pathway of cell death.Adult C57BL/6J mice were treated with topical DFO or ferrostastin-1 (Fer-1) and irradiated with 30 Grays of ionizing radiation to the dorsal skin to promote development of chronic RIF. Immunofluorescent staining with 4-hydroxynonenal (4-HNE) antibody was carried out directly following irradiation to assess ferroptosis activity. Perfusion testing with laser Doppler was performed throughout the healing interval. Eight weeks following radiation, dorsal skin was harvested and analyzed histologically and biomechanically.Immunohistochemical staining demonstrated lower presence of 4-HNE in non-irradiated skin, DFO-treated skin, and Fer-1-treated skin compared to irradiated, untreated skin. DFO resulted in histological measurements (dermal thickness and collagen content) that resembled normal skin, while Fer-1 treatment yielded less significant improvements. These results were mirrored by analysis of extracellular matrix ultrastructure and biomechanical testing, which recapitulated the ability of topical DFO treatment to alleviate RIF across these parameters while Fer-1 resulted in less notable improvement. Finally, perfusion levels in DFO treated irradiated skin were similar to measurements in normal skin, while Fer-1 treatment did not impact this feature.Ferroptosis contributes to the development of RIF and attenuation of this process leads to reduced skin injury. DFO further improves RIF through additional enhancement of perfusion not seen with Fer-1.

  View details for DOI 10.21203/rs.3.rs-4314380/v1

  View details for PubMedID 38853919

  View details for PubMedCentralID PMC11160928

• Understanding Tendon Fibroblast Biology and Heterogeneity. Biomedicines DiIorio, S. E., Young, B., Parker, J. B., Griffin, M. F., Longaker, M. T. 2024; 12 (4)

  Abstract

  Tendon regeneration has emerged as an area of interest due to the challenging healing process of avascular tendon tissue. During tendon healing after injury, the formation of a fibrous scar can limit tendon strength and lead to subsequent complications. The specific biological mechanisms that cause fibrosis across different cellular subtypes within the tendon and across different tendons in the body continue to remain unknown. Herein, we review the current understanding of tendon healing, fibrosis mechanisms, and future directions for treatments. We summarize recent research on the role of fibroblasts throughout tendon healing and describe the functional and cellular heterogeneity of fibroblasts and tendons. The review notes gaps in tendon fibrosis research, with a focus on characterizing distinct fibroblast subpopulations in the tendon. We highlight new techniques in the field that can be used to enhance our understanding of complex tendon pathologies such as fibrosis. Finally, we explore bioengineering tools for tendon regeneration and discuss future areas for innovation. Exploring the heterogeneity of tendon fibroblasts on the cellular level can inform therapeutic strategies for addressing tendon fibrosis and ultimately reduce its clinical burden.

  View details for DOI 10.3390/biomedicines12040859

  View details for PubMedID 38672213

  View details for PubMedCentralID PMC11048404

• Deferoxamine topical cream superior to patch in rescuing radiation-induced fibrosis of unwounded and wounded skin. Journal of cellular and molecular medicine Berry, C. E., Abbas, D. B., Griffin, M., Lintel, H., Guo, J., Kameni, L., Churukian, A. A., Fazilat, A. Z., Chen, K., Gurtner, G. C., Longaker, M. T., Momeni, A., Wan, D. C. 2024; 28 (8): e18306

  Abstract

  Topical patch delivery of deferoxamine (DFO) has been studied as a treatment for this fibrotic transformation in irradiated tissue. Efficacy of a novel cream formulation of DFO was studied as a RIF therapeutic in unwounded and excisionally wounded irradiated skin. C57BL/6J mice underwent 30 Gy of radiation to the dorsum followed by 4 weeks of recovery. In a first experiment, mice were separated into six conditions: DFO 50 mg cream (D50), DFO 100 mg cream (D100), soluble DFO injections (DI), DFO 1 mg patch (DP), control cream (Vehicle), and irradiated untreated skin (IR). In a second experiment, excisional wounds were created on the irradiated dorsum of mice and then divided into four treatment groups: DFO 100 mg Cream (W-D100), DFO 1 mg patch (W-DP), control cream (W-Vehicle), and irradiated untreated wounds (W-IR). Laser Doppler perfusion scans, biomechanical testing, and histological analysis were performed. In irradiated skin, D100 improved perfusion compared to D50 or DP. Both D100 and DP enhanced dermal characteristics, including thickness, collagen density and 8-isoprostane staining compared to untreated irradiated skin. D100 outperformed DP in CD31 staining, indicating higher vascular density. Extracellular matrix features of D100 and DP resembled normal skin more closely than DI or control. In radiated excisional wounds, D100 facilitated faster wound healing and increased perfusion compared to DP. The 100 mg DFO cream formulation rescued RIF of unwounded irradiated skin and improved excisional wound healing in murine skin relative to patch delivery of DFO.

  View details for DOI 10.1111/jcmm.18306

  View details for PubMedID 38613357

• Understanding wound healing in obesity. World journal of experimental medicine Cotterell, A., Griffin, M., Downer, M. A., Parker, J. B., Wan, D., Longaker, M. T. 2024; 14 (1): 86898

  Abstract

  Obesity has become more prevalent in the global population. It is associated with the development of several diseases including diabetes mellitus, coronary heart disease, and metabolic syndrome. There are a multitude of factors impacted by obesity that may contribute to poor wound healing outcomes. With millions worldwide classified as obese, it is imperative to understand wound healing in these patients. Despite advances in the understanding of wound healing in both healthy and diabetic populations, much is unknown about wound healing in obese patients. This review examines the impact of obesity on wound healing and several animal models that may be used to broaden our understanding in this area. As a growing portion of the population identifies as obese, understanding the underlying mechanisms and how to overcome poor wound healing is of the utmost importance.

  View details for DOI 10.5493/wjem.v14.i1.86898

  View details for PubMedID 38590299

  View details for PubMedCentralID PMC10999071

• Successful topical treatment of human biofilms using multiple antibiotic elution from a collagen-rich hydrogel. Scientific reports Sharma, A. D., Jarman, E. H., Kuppalli, K., Murphy, M. J., Longaker, M. T., Gurtner, G., Fox, P. M. 2024; 14 (1): 5621

  Abstract

  Chronic non-healing wounds significantly strain modern healthcare systems, affecting 1-2% of the population in developed countries with costs ranging between $28.1 and $96.8 billion annually. Additionally, it has been established that chronic wounds resulting from comorbidities, such as peripheral vascular disease and diabetes mellitus, tend to be polymicrobial in nature. Treatment of polymicrobial chronic wounds with oral and IV antibiotics can result in antimicrobial resistance, leading to more difficult-to-treat wounds. Ideally, chronic ulcers would be topically treated with antibiotic combinations tailored to the microbiome of a patient's wound. We have previously shown that a topical collagen-rich hydrogel (cHG) can elute single antibiotics to inhibit bacterial growth in a manner that is nontoxic to mammalian cells. Here, we analyzed the microbiology of cultures taken from human patients diagnosed with diabetes mellitus suffering from chronic wounds present for more than 6 weeks. Additionally, we examined the safety of the elution of multiple antibiotics from collagen-rich hydrogel in mammalian cells in vivo. Finally, we aimed to create tailored combinations of antibiotics impregnated into cHG to successfully target and treat infections and eradicate biofilms cultured from human chronic diabetic wound tissue. We found that the majority of human chronic wounds in our study were polymicrobial in nature. The elution of multiple antibiotics from cHG was well-tolerated in mammalian cells, making it a potential topical treatment of the polymicrobial chronic wound. Finally, combinations of antibiotics tailored to each patient's microbiome eluted from a collagen-rich hydrogel successfully treated bacterial cultures isolated from patient samples via an in vitro assay.

  View details for DOI 10.1038/s41598-024-54477-z

  View details for PubMedID 38454046

• A tension offloading patch mitigates dermal fibrosis induced by pro-fibrotic skin injections. Research square Talbott, H. E., Griffin, M. F., Mascharak, S., Parker, J. B., Kuhnert, M. M., Guo, J. L., Diaz Deleon, N. M., Lavin, C., Abbas, D., Guardino, N., Morgan, A., Valencia, C., Cotterell, A., Longaker, M. T., Wan, D. C. 2024

  Abstract

  Skin fibrosis is a clinical problem with devastating impacts but limited treatment options. In the setting of diabetes, insulin administration often causes local dermal fibrosis, leading to a range of clinical sequelae including impeded insulin absorption. Mechanical forces are important drivers of fibrosis and, clinically, physical tension offloading at the skin level using an elastomeric patch significantly reduces wound scarring. However, it is not known whether tension offloading could similarly prevent skin fibrosis in the setting of pro-fibrotic injections. Here, we develop a porcine model using repeated local injections of bleomycin to recapitulate key features of insulin-induced skin fibrosis. Using histologic, tissue ultrastructural, and biomechanical analyses, we show that application of a tension-offloading patch both prevents and rescues existing skin fibrosis from bleomycin injections. By applying single-cell transcriptomic analysis, we find that the fibrotic response to bleomycin involves shifts in myeloid cell dynamics from favoring putatively pro-regenerative to pro-fibrotic myeloid subtypes; in a mechanomodulatory in vitro platform, we show that these shifts are mechanically driven and reversed by exogenous IL4. Finally, using a human foreskin xenograft model, we show that IL4 treatment mitigates bleomycin-induced dermal fibrosis. Overall, this study highlights that skin tension offloading, using an FDA cleared, commercially available patch, could have significant potential clinical benefit for the millions of patients dependent on insulin.

  View details for DOI 10.21203/rs.3.rs-3915097/v1

  View details for PubMedID 38464040

• Single cell pharmacogenic pipeline identifies novel opportunities in uterine leiomyosarcoma Daniel, S. K., Foster, D., Nosrati, F., Korah, M., Fallah, M., Sun, B. J., Loftus, T., Hu, D., Dua, M., Visser, B., Poultsides, G., Kirane, A., Longaker, M., Ganjoo, K., Lee, B., Delitto, D. SPRINGER. 2024: S42

  View details for Web of Science ID 001185577500085

• IL-1RA and IL-12 Decrease Pancreatic Ductal Adenocarcinoma Tumor Mass and Prolong Survival by Inhibiting Mechanoresponsive Cafs Morgan, A., Griffin, M., Downer, M., Lindsay, H., Parker, J. B., Guo, J. L., Longaker, M. T., Norton, J. A. LIPPINCOTT WILLIAMS & WILKINS. 2023: S455-S456

  View details for Web of Science ID 001094086301392

• Single-Cell RNA-Seq Analysis Reveals Similar Fibroblasts in Irradiated Skin of Humans, Mice, and Pigs Kameni, L., Berry, C., Griffin, M., Januszyk, M., Downer, M., Huber, J. L., Parker, J., Momeni, A., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2023: S389

  View details for Web of Science ID 001094086301247

• Single-Cell RNA-Sequencing Identifies Modulator of Foreign Body Response with Use of Acellular Dermal Matrix in Breast Reconstruction Liang, N., Tevlin, R., Griffin, M., Parker, J. B., Henn, D., Navarro, R. S., Dung Nguyen, Momeni, A., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2023: S389-S390

  View details for Web of Science ID 001094086301248

• Tissue Microenvironment a Key Driver in Fibrotic Capsules Formed During Foreign Body Response Parker, J. B., Griffin, M., Downer, M., Morgan, A., Guo, J. L., Liang, N., Berry, C., Diiorio, S., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2023: S393

  View details for Web of Science ID 001094086301255

• Fat Grafting Treatment for Radiation-Induced Fibrosis Results in Downregulation of Inflammatory and Fibrotic Signaling Pathways Berry, C., Abbas, D., Kameni, L., Griffin, M., Downer, M., Parker, J. B., Guo, J. L., Januszyk, M., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2023: S381-S382

  View details for Web of Science ID 001094086301232

• Investigating Dysmotility and the Expansion of Glial Cells and Interstitial Cells of Cajal in Crohn's Disease Strictures Using a Novel Surgical Mouse Model Kim, A., Bauer-rowe, K. E., Griffin, M., Foster, D., Longaker, M. T., Hyun, J. S. LIPPINCOTT WILLIAMS & WILKINS. 2023: S355

  View details for Web of Science ID 001094086301169

• Analysis of Collagen Extracellular Matrix Ultrastructure in Mouse Long Bone Distraction Osteogenesis Diiorio, S., Guo, J. L., Griffin, M., Huber, J. L., Downer, M., Berry, C., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2023: S378-S379

  View details for Web of Science ID 001094086301225

• Grafting of Human Foreskin onto Murine Dorsum Provides a Novel Model of Chronic Radiation-Induced Fibrosis Berry, C., Abbas, D., Griffin, M., Kameni, L., Downer, M., Parker, J. B., Liang, N., Dilorio, S., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2023: S398

  View details for Web of Science ID 001094086301270

• Meta-Analysis of Single-Cell Transcriptomics Data of Cardiac Fibroblasts Reveals Temporal Heterogeneity of Cardiac Fibroblast Response after MI Lu, J., Januszyk, M., Griffin, M., Guo, J. L., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2023: S68

  View details for Web of Science ID 001094086300124

• Novel Deferoxamine Cream Formulation Improves Perfusion, Elasticity, and Tissue Architecture in Chronically Irradiated Murine Skin Compared to Transdermal Patch Berry, C., Abbas, D., Kameni, L., Griffin, M., Downer, M., Parker, J. B., Liang, N., Guo, J. L., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2023: S386

  View details for Web of Science ID 001094086301241

• Pioglitazone Decreases Adipogenisis Leading to Melanoma Skin Tumor Suppression Downer, M., Griffin, M., Morgan, A., Parker, J. B., Berry, C., Li, D. J., Liang, N., Kameni, L., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2023: S387-S388

  View details for Web of Science ID 001094086301244

• Ferropotosis Levels Decrease in Response to Deferoxamine Treatment in Irradiated Murine Skin Berry, C., Kameni, L., Griffin, M., Downer, M., Parker, J. B., Guo, J. L., Liang, N., Januszyk, M., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2023: S382

  View details for Web of Science ID 001094086301233

• Healing of Chronically Irradiated Excisional Wounds Improved by Topical Deferoxamine Treatment Berry, C., Griffin, M., Kameni, L., Abbas, D., Downer, M., Parker, J. B., Liang, N., Januszyk, M., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2023: S382-S383

  View details for Web of Science ID 001094086301234

• Where There Is Fat, There Is Fibrosis: Elucidating the Mechanisms of Creeping Fat-Driven Stricture Formation Bauer-Rowe, K. E., Kim, A., Griffin, M., Liang, N., Foster, D., Guo, J. L., Norton, J. A., Longaker, M. T., Hyun, J. S. LIPPINCOTT WILLIAMS & WILKINS. 2023: S365-S366

  View details for Web of Science ID 001094086301190

• A Review of Radiation-Induced Vascular Injury and Clinical Impact. Annals of plastic surgery Kameni, L. E., Januszyk, M., Berry, C. E., Downer, M. A., Parker, J. B., Morgan, A. G., Valencia, C., Griffin, M., Li, D. J., Liang, N. E., Momeni, A., Longaker, M. T., Wan, D. C. 2023

  Abstract

  ABSTRACT: The number of cancer survivors continues to increase because of advances in therapeutic modalities. Along with surgery and chemotherapy, radiotherapy is a commonly used treatment modality in roughly half of all cancer patients. It is particularly helpful in the oncologic treatment of patients with breast, head and neck, and prostate malignancies. Unfortunately, among patients receiving radiation therapy, long-term sequalae are often unavoidable, and there is accumulating clinical evidence suggesting significant radiation-related damage to the vascular endothelium. Ionizing radiation has been known to cause obliterative fibrosis and increased wall thickness in irradiated blood vessels. Clinically, these vascular changes induced by ionizing radiation can pose unique surgical challenges when operating in radiated fields. Here, we review the relevant literature on radiation-induced vascular damage focusing on mechanisms and signaling pathways involved and highlight microsurgical anastomotic outcomes after radiotherapy. In addition, we briefly comment on potential therapeutic strategies, which may have the ability to mitigate radiation injury to the vascular endothelium.

  View details for DOI 10.1097/SAP.0000000000003723

  View details for PubMedID 37962260

• Optimized Nuclei Isolation from Fresh and Frozen Solid Tumor Specimens for Multiome Sequencing. Journal of visualized experiments : JoVE Foster, D. S., Griffin, M., Januszyk, M., Delitto, D., Norton, J. A., Longaker, M. T. 2023

  Abstract

  Multiome sequencing, which provides same-cell/paired single-cell RNA- and the assay for transposase-accessible chromatin with sequencing (ATAC-sequencing) data, represents a breakthrough in our ability to discern tumor cell heterogeneity-a primary focus of translational cancer research at this time. However, the quality of sequencing data acquired using this advanced modality is highly dependent on the quality of the input material. Digestion conditions need to be optimized to maximize cell yield without sacrificing quality. This is particularly challenging in the context of solid tumors with dense desmoplastic matrices that must be gently broken down for cell release. Freshly isolated cells from solid tumor tissue are more fragile than those isolated from cell lines. Additionally, as the cell types isolated are heterogeneous, conditions should be selected to support the total cell population. Finally, nuclear isolation conditions must be optimized based on these qualities in terms of lysis times and reagent types/ratios. In this article, we describe our experience with nuclear isolation for the 10x Genomics multiome sequencing platform from solid tumor specimens. We provide recommendations for tissue digestion, storage of single-cell suspensions (if desired), and nuclear isolation and assessment.

  View details for DOI 10.3791/65831

  View details for PubMedID 37902368

• Desmoplastic stromal signatures predict patient outcomes in pancreatic ductal adenocarcinoma. Cell reports. Medicine Mascharak, S., Guo, J. L., Foster, D. S., Khan, A., Davitt, M. F., Nguyen, A. T., Burcham, A. R., Chinta, M. S., Guardino, N. J., Griffin, M., Lopez, D. M., Miller, E., Januszyk, M., Raghavan, S. S., Longacre, T. A., Delitto, D. J., Norton, J. A., Longaker, M. T. 2023: 101248

  Abstract

  Pancreatic ductal adenocarcinoma (PDAC) is projected to become the second leading cause of cancer-related death. Hallmarks include desmoplasia with variable extracellular matrix (ECM) architecture and a complex microenvironment with spatially defined tumor, stromal, and immune populations. Nevertheless, the role of desmoplastic spatial organization in patient/tumor variability remains underexplored, which we elucidate using two technologies. First, we quantify ECM patterning in 437 patients, revealing architectures associated with disease-free and overall survival. Second, we spatially profile the cellular milieu of 78 specimens using codetection by indexing, identifying an axis of pro-inflammatory cell interactions predictive of poorer outcomes. We discover that clinical characteristics, including neoadjuvant chemotherapy status, tumor stage, and ECM architecture, correlate with differential stromal-immune organization, including fibroblast subtypes with distinct niches. Lastly, we define unified signatures that predict survival with areas under the receiver operating characteristic curve (AUCs) of 0.872-0.903, differentiating survivorship by 655 days. Overall, our findings establish matrix ultrastructural and cellular organizations of fibrosis linked to poorer outcomes.

  View details for DOI 10.1016/j.xcrm.2023.101248

  View details for PubMedID 37865092

• Allele-specific expression reveals genetic drivers of tissue regeneration in mice. Cell stem cell Mack, K. L., Talbott, H. E., Griffin, M. F., Parker, J. B., Guardino, N. J., Spielman, A. F., Davitt, M. F., Mascharak, S., Downer, M., Morgan, A., Valencia, C., Akras, D., Berger, M. J., Wan, D. C., Fraser, H. B., Longaker, M. T. 2023

  Abstract

  In adult mammals, skin wounds typically heal by scarring rather than through regeneration. In contrast, "super-healer" Murphy Roths Large (MRL) mice have the unusual ability to regenerate ear punch wounds; however, the molecular basis for this regeneration remains elusive. Here, in hybrid crosses between MRL and non-regenerating mice, we used allele-specific gene expression to identify cis-regulatory variation associated with ear regeneration. Analyzing three major cell populations (immune, fibroblast, and endothelial), we found that genes with cis-regulatory differences specifically in fibroblasts were associated with wound-healing pathways and also co-localized with quantitative trait loci for ear wound-healing. Ectopic treatment with one of these proteins, complement factor H (CFH), accelerated wound repair and induced regeneration in typically fibrotic wounds. Through single-cell RNA sequencing (RNA-seq), we observed that CFH treatment dramatically reduced immune cell recruitment to wounds, suggesting a potential mechanism for CFH's effect. Overall, our results provide insights into the molecular drivers of regeneration with potential clinical implications.

  View details for DOI 10.1016/j.stem.2023.08.010

  View details for PubMedID 37714154

• Commentary on: Postoperative Mechanomodulation Decreases T-Junction Dehiscence After Reduction Mammaplasty: Early Scar Analysis From a Randomized Controlled Trial. Aesthetic surgery journal Berry, C. E., Longaker, M. T., Wan, D. C. 2023

  View details for DOI 10.1093/asj/sjad281

  View details for PubMedID 37625787

• Understanding Fibroblast Heterogeneity in Form and Function. Biomedicines Parker, J. B., Valencia, C., Akras, D., DiIorio, S. E., Griffin, M. F., Longaker, M. T., Wan, D. C. 2023; 11 (8)

  Abstract

  Historically believed to be a homogeneous cell type that is often overlooked, fibroblasts are more and more understood to be heterogeneous in nature. Though the mechanisms behind how fibroblasts participate in homeostasis and pathology are just beginning to be understood, these cells are believed to be highly dynamic and play key roles in fibrosis and remodeling. Focusing primarily on fibroblasts within the skin and during wound healing, we describe the field's current understanding of fibroblast heterogeneity in form and function. From differences due to embryonic origins to anatomical variations, we explore the diverse contributions that fibroblasts have in fibrosis and plasticity. Following this, we describe molecular techniques used in the field to provide deeper insights into subpopulations of fibroblasts and their varied roles in complex processes such as wound healing. Limitations to current work are also discussed, with a focus on future directions that investigators are recommended to take in order to gain a deeper understanding of fibroblast biology and to develop potential targets for translational applications in a clinical setting.

  View details for DOI 10.3390/biomedicines11082264

  View details for PubMedID 37626760

• Understanding the Role of Adipocytes and Fibroblasts in Cancer. Annals of plastic surgery Downer, M. A., Griffin, M. F., Morgan, A. G., Parker, J. B., Li, D. J., Berry, C. E., Liang, N. E., Kameni, L., Cotterell, A. C., Akras, D., Valencia, C., Longaker, M. T., Wan, D. C. 2023

  Abstract

  Cancer is currently the second leading cause of death in the United States. There is increasing evidence that the tumor microenvironment (TME) is pivotal for tumorigenesis and metastasis. Recently, adipocytes and cancer-associated fibroblasts (CAFs) in the TME have been shown to play a major role in tumorigenesis of different cancers, specifically melanoma. Animal studies have shown that CAFs and adipocytes within the TME help tumors evade the immune system, for example, by releasing chemokines to blunt the effectiveness of the host defense. Although studies have identified that adipocytes and CAFs play a role in tumorigenesis, adipocyte transition to fibroblast within the TME is fairly unknown. This review intends to elucidate the potential that adipocytes may have to transition to fibroblasts and, as part of the TME, a critical role that CAFs may play in affecting the growth and invasion of tumor cells. Future studies that illuminate the function of adipocytes and CAFs in the TME may pave way for new antitumor therapies.

  View details for DOI 10.1097/SAP.0000000000003658

  View details for PubMedID 37553786

• Cas9-mediated knockout of Ndrg2 enhances the regenerative potential of dendritic cells for wound healing. Nature communications Henn, D., Zhao, D., Sivaraj, D., Trotsyuk, A., Bonham, C. A., Fischer, K. S., Kehl, T., Fehlmann, T., Greco, A. H., Kussie, H. C., Moortgat Illouz, S. E., Padmanabhan, J., Barrera, J. A., Kneser, U., Lenhof, H., Januszyk, M., Levi, B., Keller, A., Longaker, M. T., Chen, K., Qi, L. S., Gurtner, G. C. 2023; 14 (1): 4729

  Abstract

  Chronic wounds impose a significant healthcare burden to a broad patient population. Cell-based therapies, while having shown benefits for the treatment of chronic wounds, have not yet achieved widespread adoption into clinical practice. We developed a CRISPR/Cas9 approach to precisely edit murine dendritic cells to enhance their therapeutic potential for healing chronic wounds. Using single-cell RNA sequencing of tolerogenic dendritic cells, we identified N-myc downregulated gene 2 (Ndrg2), which marks a specific population of dendritic cell progenitors, as a promising target for CRISPR knockout. Ndrg2-knockout alters the transcriptomic profile of dendritic cells and preserves an immature cell state with a strong pro-angiogenic and regenerative capacity. We then incorporated our CRISPR-based cell engineering within a therapeutic hydrogel for in vivo cell delivery and developed an effective translational approach for dendritic cell-based immunotherapy that accelerated healing of full-thickness wounds in both non-diabetic and diabetic mouse models. These findings could open the door to future clinical trials using safe gene editing in dendritic cells for treating various types of chronic wounds.

  View details for DOI 10.1038/s41467-023-40519-z

  View details for PubMedID 37550295

• Del1 Is a Growth Factor for Skeletal Progenitor Cells in the Fracture Callus. Biomolecules Sun, Y., Boyko, T., Marecic, O., Struck, D., Mann, R. K., Andrew, T. W., Lopez, M., Tong, X., Goodman, S. B., Yang, F., Longaker, M. T., Chan, C. K., Yang, G. P. 2023; 13 (8)

  Abstract

  Failure to properly form bone or integrate surgical implants can lead to morbidity and additional surgical interventions in a significant proportion of orthopedic surgeries. While the role of skeletal stem cells (SSCs) in bone formation and repair is well-established, very little is known about the factors that regulate the downstream Bone, Cartilage, Stromal, Progenitors (BCSPs). BCSPs, as transit amplifying progenitor cells, undergo multiple mitotic divisions to expand the pool of lineage committed progenitors allowing stem cells to preserve their self-renewal and stemness. Del1 is a protein widely expressed in the skeletal system, but its deletion led to minimal phenotype changes in the uninjured mouse. In this paper, we demonstrate that Del1 is a key regulator of BCSP expansion following injury. In Del1 knockout mice, there is a significant reduction in the number of BCSPs which leads to a smaller callus and decreased bone formation compared with wildtype (WT) littermates. Del1 serves to promote BCSP proliferation and prevent apoptosis in vivo and in vitro. Moreover, exogenous Del1 promotes proliferation of aged human BCSPs. Our results highlight the potential of Del1 as a therapeutic target for improving bone formation and implant success. Del1 injections may improve the success of orthopedic surgeries and fracture healing by enhancing the proliferation and survival of BCSPs, which are crucial for generating new bone tissue during the process of bone formation and repair.

  View details for DOI 10.3390/biom13081214

  View details for PubMedID 37627279

• Medical Biology of Cancer-Associated Fibroblasts in Pancreatic Cancer. Biology Morgan, A., Griffin, M., Kameni, L., Wan, D. C., Longaker, M. T., Norton, J. A. 2023; 12 (8)

  Abstract

  Pancreatic cancer is one of the deadliest forms of cancer with one of the lowest 5-year survival rates of all cancer types. A defining characteristic of pancreatic cancer is the existence of dense desmoplastic stroma that, when exposed to stimuli such as cytokines, growth factors, and chemokines, generate a tumor-promoting environment. Cancer-associated fibroblasts (CAFs) are activated during the progression of pancreatic cancer and are a crucial component of the tumor microenvironment (TME). CAFs are primarily pro-tumorigenic in their activated state and function as promoters of cancer invasion, proliferation, metastasis, and immune modulation. Aided by many signaling pathways, cytokines, and chemokines in the tumor microenvironment, CAFs can originate from many cell types including resident fibroblasts, mesenchymal stem cells, pancreatic stellate cells, adipocytes, epithelial cells, endothelial cells, and other cell types. CAFs are a highly heterogeneous cell type expressing a variety of surface markers and performing a wide range of tumor promoting and inhibiting functions. Single-cell transcriptomic analyses have revealed a high degree of specialization among CAFs. Some examples of CAF subpopulations include myofibrotic CAFs (myCAFs), which exhibit a matrix-producing contractile phenotype; inflammatory CAFs (iCAF) that are classified by their immunomodulating, secretory phenotype; and antigen-presenting CAFs (apCAFs), which have antigen-presenting capabilities and express Major Histocompatibility Complex II (MHC II). Over the last several years, various attempts have been undertaken to describe the mechanisms of CAF-tumor cell interaction, as well as CAF-immune cell interaction, that contribute to tumor proliferation, invasion, and metastasis. Although our understanding of CAF biology in cancer has steadily increased, the extent of CAFs heterogeneity and their role in the pathobiology of pancreatic cancer remains elusive. In this regard, it becomes increasingly evident that further research on CAFs in pancreatic cancer is necessary.

  View details for DOI 10.3390/biology12081044

  View details for PubMedID 37626931

• Call for Special Issue Papers: Artificial Intelligence in Tissue Engineering and Biology. Tissue engineering. Part A Guo, J. L., Januszyk, M., Longaker, M. T. 2023

  View details for DOI 10.1089/ten.tea.2023.29049.cfp

  View details for PubMedID 37466469

• Call for Special Issue Papers: Artificial Intelligence in Tissue Engineering and Biology. Tissue engineering. Part B, Reviews Guo, J. L., Januszyk, M., Longaker, M. T. 2023

  View details for DOI 10.1089/ten.teb.2023.29019.cfp

  View details for PubMedID 37466464

• Call for Special Issue Papers: Artificial Intelligence in Tissue Engineering and Biology. Tissue engineering. Part C, Methods Guo, J. L., Januszyk, M., Longaker, M. T. 2023

  View details for DOI 10.1089/ten.tec.2023.29040.cfp

  View details for PubMedID 37466465

• Thumb Osteoarthritis: Stem Cell Activation, Niche Augmentation and Tissue Regeneration Murphy, M., Takematsu, E., Koepke, L., Tong, X., Butler, G., Ambrosi, T., Hoover, M., Wang, Y., Zhao, L., Wong, J., Reid, A., Longaker, M., Chan, C. MARY ANN LIEBERT, INC. 2023

  View details for Web of Science ID 001126807000330

• Thumb Osteoarthritis: Stem Cell Activation, Niche Augmentation and Tissue Regeneration Murphy, M., Takematsu, E., Koepke, L., Tong, X., Butler, G., Ambrosi, T., Hoover, M., Wang, Y., Zhao, L., Wong, J., Reid, A., Longaker, M., Chant, C. MARY ANN LIEBERT, INC. 2023

  View details for Web of Science ID 001057609600337

• Reduction of Tendon Fibrosis Using Galectin-3 Inhibitors. Plastic and reconstructive surgery Spielman, A. F., Griffin, M. F., Titan, A. L., Guardino, N., Cotterell, A. C., Akras, D., Wan, D. C., Longaker, M. T. 2023

  Abstract

  BACKGROUND: Fibrosis is a complication of both tendon injuries and repairs. We aim to develop a mouse model to assess tendon fibrosis and to identify an antifibrotic agent capable of overcoming tendon fibrosis.METHODS: Adult C57Bl/6 mice underwent a skin incision to expose the Achilles tendon, followed by 50% tendon injury and abrasion with sandpaper. Sham surgeries were conducted on contralateral hindlimbs. Histology and immunofluorescent staining for fibrotic markers (Col1, alpha-SMA) were used to confirm that the model induced tendon fibrosis. A second experiment was conducted to further examine the role of alpha-SMA in adhesion formation using alpha-SMA.mTmG mice (6-8 weeks old) (n=3) with the same injury model. The control group (tendon injury) was compared to the sham group, using the contralateral limb with skin incision only. A second experiment was conducted to further examine the role of alpha-SMA in adhesion formation using alpha-SMA.mTmG mice (6-8 weeks old) (n=3) with the same injury model. The control group (tendon injury) was compared to the sham group, using the contralateral limb with skin incision only. Lastly, alpha-SMA.mTmG mice were randomized to either condition 1. Tendon injury (control group) or 2. Tendon injury with Galectin-3 inhibitor (Gal3i) treatment at time of injury (treatment group).RESULTS: Histological analyses confirmed tendon thickening and collagen deposition after tendon injury and abrasion compared to control. Immunofluorescence showed higher levels of Col1 and alpha-SMA protein expression after injury compared to sham (*p<0.05). RT-qPCR also demonstrated increased gene expression of Col1 and alpha-SMA after injury compared to sham (*p<0.05). Gal3 protein expression also increased after injury and co-localized with alpha-SMA positive fibroblasts surrounding the fibrotic tendon. Gal3i treatment decreased collagen deposition and scarring observed in the treatment group (*p<0.05). Flow cytometry analysis further showed reduced numbers of profibrotic fibroblasts (CD26+) in the treatment compared to the control group (*p<0.05).CONCLUSIONS: Our study provides a reproducible and reliable model to investigate tendon fibrosis. Findings suggest the potential of Gal3i to overcome fibrosis resulting from tendon injuries.

  View details for DOI 10.1097/PRS.0000000000010880

  View details for PubMedID 37344932

• Purification and functional characterization of novel human skeletal stem cell lineages. Nature protocols Hoover, M. Y., Ambrosi, T. H., Steininger, H. M., Koepke, L. S., Wang, Y., Zhao, L., Murphy, M. P., Alam, A. A., Arouge, E. J., Butler, M. G., Takematsu, E., Stavitsky, S. P., Hu, S., Sahoo, D., Sinha, R., Morri, M., Neff, N., Bishop, J., Gardner, M., Goodman, S., Longaker, M., Chan, C. K. 2023

  Abstract

  Human skeletal stem cells (hSSCs) hold tremendous therapeutic potential for developing new clinical strategies to effectively combat congenital and age-related musculoskeletal disorders. Unfortunately, refined methodologies for the proper isolation of bona fide hSSCs and the development of functional assays that accurately recapitulate their physiology within the skeleton have been lacking. Bone marrow-derived mesenchymal stromal cells (BMSCs), commonly used to describe the source of precursors for osteoblasts, chondrocytes, adipocytes and stroma, have held great promise as the basis of various approaches for cell therapy. However, the reproducibility and clinical efficacy of these attempts have been obscured by the heterogeneous nature of BMSCs due to their isolation by plastic adherence techniques. To address these limitations, our group has refined the purity of individual progenitor populations that are encompassed by BMSCs by identifying defined populations of bona fide hSSCs and their downstream progenitors that strictly give rise to skeletally restricted cell lineages. Here, we describe an advanced flow cytometric approach that utilizes an extensive panel of eight cell surface markers to define hSSCs; bone, cartilage and stromal progenitors; and more differentiated unipotent subtypes, including an osteogenic subset and three chondroprogenitors. We provide detailed instructions for the FACS-based isolation of hSSCs from various tissue sources, in vitro and in vivo skeletogenic functional assays, human xenograft mouse models and single-cell RNA sequencing analysis. This application of hSSC isolation can be performed by any researcher with basic skills in biology and flow cytometry within 1-2 days. The downstream functional assays can be performed within a range of 1-2 months.

  View details for DOI 10.1038/s41596-023-00836-5

  View details for PubMedID 37316563

  View details for PubMedCentralID 6568007

• Emerging frontiers in regenerative medicine. Science (New York, N.Y.) McKinley, K. L., Longaker, M. T., Naik, S. 2023; 380 (6647): 796-798

  Abstract

  Bridging knowledge gaps could enable regenerative therapy.

  View details for DOI 10.1126/science.add6492

  View details for PubMedID 37228215

• Circulating and extracellular vesicle-derived microRNAs as biomarkers in bone-related diseases. Frontiers in endocrinology Huber, J., Longaker, M. T., Quarto, N. 2023; 14: 1168898

  Abstract

  MicroRNAs (miRNA) are small non-coding RNA molecules that regulate posttranscriptional gene expression by repressing messengerRNA-targets. MiRNAs are abundant in many cell types and are secreted into extracellular fluids, protected from degradation by packaging in extracellular vesicles. These circulating miRNAs are easily accessible, disease-specific and sensitive to small changes, which makes them ideal biomarkers for diagnostic, prognostic, predictive or monitoring purposes. Specific miRNA signatures can be reflective of disease status and development or indicators of poor treatment response. This is especially important in malignant diseases, as the ease of accessibility of circulating miRNAs circumvents the need for invasive tissue biopsy. In osteogenesis, miRNAs can act either osteo-enhancing or osteo-repressing by targeting key transcription factors and signaling pathways. This review highlights the role of circulating and extracellular vesicle-derived miRNAs as biomarkers in bone-related diseases, with a specific focus on osteoporosis and osteosarcoma. To this end, a comprehensive literature search has been performed. The first part of the review discusses the history and biology of miRNAs, followed by a description of different types of biomarkers and an update of the current knowledge of miRNAs as biomarkers in bone related diseases. Finally, limitations of miRNAs biomarker research and future perspectives will be presented.

  View details for DOI 10.3389/fendo.2023.1168898

  View details for PubMedID 37293498

  View details for PubMedCentralID PMC10244776

• Attenuating Chronic Fibrosis: Decreasing Foreign Body Response with Acellular Dermal Matrix. Tissue engineering. Part B, Reviews Liang, N. E., Griffin, M., Berry, C. E., Parker, J. B., Downer, M. A., Wan, D. C., Longaker, M. T. 2023

  Abstract

  Surgical implants are increasingly used across multiple medical disciplines, with applications ranging from tissue reconstruction to improving compromised organ and limb function. Despite their significant potential for improving health and quality of life, biomaterial implant function is severely limited by the body's immune response to its presence: this is known as the foreign body response and is characterized by chronic inflammation and fibrotic capsule formation. This response can result in life-threatening sequelae such as implant malfunction, superimposed infection and associated vessel thrombosis, in addition to soft tissue disfigurement. Patients may require frequent medical visits, as well as repeated invasive procedures, increasing the burden on an already strained healthcare system. Currently, the foreign body response and the cells and molecular mechanisms that mediate it are poorly understood. With applications across a wide array of surgical specialties, acellular dermal matrix has emerged as a potential solution to the fibrotic reaction seen with FBR. Though the mechanisms by which acellular dermal matrix decreases chronic fibrosis remain to be clearly characterized, animal studies across diverse surgical models point to its biomimetic properties that facilitate decreased periprosthetic inflammation and improved host cell incorporation.

  View details for DOI 10.1089/ten.TEB.2023.0060

  View details for PubMedID 37212342

• Craniofacial Dysmorphology and Impaired Suture Patterning in a Mouse Model of Frank-Ter-Haar Syndrome Huber, J., Menon, S., Lopez-Torres, M., Guo, J. L., Longaker, M. T., Quarto, N. LIPPINCOTT WILLIAMS & WILKINS. 2023: S89

  View details for Web of Science ID 000989943300229

• Topical Vanadate Improves Excisional Wound Healing in Murine Model Lintel, H., Abbas, D., Mackay, D. D., Griffin, M., Spielman, A., Guardino, N., Churukian, A., Guo, J. L., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2023: S91

  View details for Web of Science ID 000989943300234

• Lineage Tracing Reveals Adipocytes Are Responsible for Muscle Fibrosis Following Nerve Injury Spielman, A., Griffin, M., Cotterell, A. C., Erich, K., Guo, B. L., Abbas, D., Parker, J. L., Lintel, H., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2023: S92

  View details for Web of Science ID 000989943300237

• Developing a Mouse Model to Evaluate Tibial Distraction Osteogenesis DiIorio, S., Tevlin, R., Shah, H. N., Salhotra, A., Griffin, M., Januszyk, M., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2023: S90

  View details for Web of Science ID 000989943300230

• Radiation Injury Genetically Alters Fibroblast Subpopulations to Induce Fibrosis Abbas, D., Griffin, M., Guo, J. L., Lavin, C. V., Fahy, E. J., Guardino, N. J., Lintel, H., Januszyk, M., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2023: S94

  View details for Web of Science ID 000989943300243

• Radiation Injury Therapy with Transdermal Deferoxamine Patch is Dose Dependent Abbas, D., Griffin, M., Lavin, C. V., Fahy, E. J., Lintel, H., Guardino, N. J., Guo, J. L., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2023: S91

  View details for Web of Science ID 000989943300233

• Quantitative Analysis of the Collagen Matrix Ultrastructure in Mouse Hearts after Myocardial Infarction Lu, J., Griffin, M., Guo, J. L., Mascharak, S., Guardino, N. J., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2023: S13-S14

  View details for Web of Science ID 000989943300035

• Overcoming Radiation Induced Oral Fibrosis through the Down Regulation of Wnt Signaling Using Bmp-7 Inhibitors Cotterell, A. C., Griffin, M., Spielman, A., Guardino, N., Lintel, H., Abbas, D., Guo, J. L., Parker, J., Wan, D., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2023: S90

  View details for Web of Science ID 000989943300232

• The effects of mechanical force on fibroblast behavior in cutaneous injury. Frontiers in surgery Berry, C. E., Downer, M., Morgan, A. G., Griffin, M., Liang, N. E., Kameni, L., Laufey Parker, J. B., Guo, J., Longaker, M. T., Wan, D. C. 2023; 10: 1167067

  Abstract

  Wound healing results in the formation of scar tissue which can be associated with functional impairment, psychological stress, and significant socioeconomic cost which exceeds 20 billion dollars annually in the United States alone. Pathologic scarring is often associated with exaggerated action of fibroblasts and subsequent excessive accumulation of extracellular matrix proteins which results in fibrotic thickening of the dermis. In skin wounds, fibroblasts transition to myofibroblasts which contract the wound and contribute to remodeling of the extracellular matrix. Mechanical stress on wounds has long been clinically observed to result in increased pathologic scar formation, and studies over the past decade have begun to uncover the cellular mechanisms that underly this phenomenon. In this article, we will review the investigations which have identified proteins involved in mechano-sensing, such as focal adhesion kinase, as well as other important pathway components that relay the transcriptional effects of mechanical forces, such as RhoA/ROCK, the hippo pathway, YAP/TAZ, and Piezo1. Additionally, we will discuss findings in animal models which show the inhibition of these pathways to promote wound healing, reduce contracture, mitigate scar formation, and restore normal extracellular matrix architecture. Recent advances in single cell RNA sequencing and spatial transcriptomics and the resulting ability to further characterize mechanoresponsive fibroblast subpopulations and the genes that define them will be summarized. Given the importance of mechanical signaling in scar formation, several clinical treatments focused on reducing tension on the wound have been developed and are described here. Finally, we will look toward future research which may reveal novel cellular pathways and deepen our understanding of the pathogenesis of pathologic scarring. The past decade of scientific inquiry has drawn many lines connecting these cellular mechanisms that may lead to a map for the development of transitional treatments for patients on the path to scarless healing.

  View details for DOI 10.3389/fsurg.2023.1167067

  View details for PubMedID 37143767

  View details for PubMedCentralID PMC10151708

• Combination of Distinct Vascular Stem/Progenitor Cells for Neovascularization and Ischemic Rescue. Arteriosclerosis, thrombosis, and vascular biology Zhao, L., Lee, A. S., Sasagawa, K., Sokol, J., Wang, Y., Ransom, R. C., Zhao, X., Ma, C., Steininger, H. M., Koepke, L. S., Borrelli, M. R., Brewer, R. E., Lee, L. L., Huang, X., Ambrosi, T. H., Sinha, R., Hoover, M. Y., Seita, J., Weissman, I. L., Wu, J. C., Wan, D. C., Xiao, J., Longaker, M. T., Nguyen, P. K., Chan, C. K. 2023

  Abstract

  Peripheral vascular disease remains a leading cause of vascular morbidity and mortality worldwide despite advances in medical and surgical therapy. Besides traditional approaches, which can only restore blood flow to native arteries, an alternative approach is to enhance the growth of new vessels, thereby facilitating the physiological response to ischemia.The ActinCreER/R26VT2/GK3 Rainbow reporter mouse was used for unbiased in vivo survey of injury-responsive vasculogenic clonal formation. Prospective isolation and transplantation were used to determine vessel-forming capacity of different populations. Single-cell RNA-sequencing was used to characterize distinct vessel-forming populations and their interactions.Two populations of distinct vascular stem/progenitor cells (VSPCs) were identified from adipose-derived mesenchymal stromal cells: VSPC1 is CD45-Ter119-Tie2+PDGFRa-CD31+CD105highSca1low, which gives rise to stunted vessels (incomplete tubular structures) in a transplant setting, and VSPC2 which is CD45-Ter119-Tie2+PDGFRa+CD31-CD105lowSca1high and forms stunted vessels and fat. Interestingly, cotransplantation of VSPC1 and VSPC2 is required to form functional vessels that improve perfusion in the mouse hindlimb ischemia model. Similarly, VSPC1 and VSPC2 populations isolated from human adipose tissue could rescue the ischemic condition in mice.These findings suggest that autologous cotransplantation of synergistic VSPCs from nonessential adipose tissue can promote neovascularization and represents a promising treatment for ischemic disease.

  View details for DOI 10.1161/ATVBAHA.122.317943

  View details for PubMedID 37051932

• Establishing a xenograft model with CD-1 nude mice to study human skin wound repair. Plastic and reconstructive surgery Abbas, D. B., Griffin, M., Fahy, E. J., Spielman, A. F., Guardino, N. J., Pu, A., Lintel, H., Lorenz, H. P., Longaker, M. T., Wan, D. C. 2023

  Abstract

  A significant gap exists in the translatability of small animal models to human subjects. One important factor is poor laboratory models involving human tissue. Thus, we have created a viable postnatal human skin xenograft model using athymic mice.Discarded human foreskins were collected following circumcision. All subcutaneous tissue was removed from these samples sterilely. Host CD-1 nude mice were then anesthetized, and dorsal skin was sterilized. A 1.2cm diameter, full-thickness section of dorsal skin was excised. The foreskin sample was then placed into the full-thickness defect in the host mice and sutured into place. Xenografts underwent dermal wounding using a 4 mm punch biopsy after engraftment. Xenografts were monitored for 14 days after wounding and then harvested.At 14 days postoperatively, all mice survived the procedure. Grossly, the xenograft wounds showed formation of a human scar at POD-14. H&E and Masson Trichome staining confirmed scar formation in the wounded human skin. Using a novel Artificial Intelligence (AI) algorithm using Picrosirius-Red staining, scar formation was confirmed in human wounded skin compared to the unwounded skin. Histologically, CD31 + immunostaining confirmed vascularization of the xenograft. The xenograft exclusively showed human collagen I, CD26 +, and human nuclear antigen in the human scar without any staining of these human markers in the murine skin.The proposed model demonstrates wound healing to be a local response from tissue resident human fibroblasts and allows for reproducible evaluation of human skin wound repair in a preclinical model.

  View details for DOI 10.1097/PRS.0000000000010465

  View details for PubMedID 36988644

• Mechanoresponsive Pancreatic Ductal Adenocarcinoma Cancer Associated Fibroblasts Shows an FAK-Dependent Subtype Divergent from Canonical Fibrotic TGFB-Pathway Dependence Foster, D., Delitto, D., Januszyk, M., Yost, K., Griffin, M., Guo, J., Guardino, N., Delitto, A., Chinta, M., Burcham, A., Nguyen, A., Bauer-, K., Berry, C., Kim, A., Nosrati, F., Wapnir, I., Chang, H., Norton, J. A., Longaker, M. SPRINGER. 2023: S30-S31

  View details for Web of Science ID 001046841200059

• Denervation during mandibular distraction osteogenesis results in impaired bone formation. Scientific reports Tevlin, R., Griffin, M., Chen, K., Januszyk, M., Guardino, N., Spielman, A., Walters, S., Gold, G. E., Chan, C. K., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2023; 13 (1): 2097

  Abstract

  Mandibular distraction osteogenesis (DO) is mediated by skeletal stem cells (SSCs) in mice, which enact bone regeneration via neural crest re-activation. As peripheral nerves are essential to progenitor function during development and in response to injury, we questioned if denervation impairs mandibular DO. C57Bl6 mice were divided into two groups: DO with a segmental defect in the inferior alveolar nerve (IAN) at the time of mandibular osteotomy ("DO Den") and DO with IAN intact ("DO Inn"). DO Den demonstrated significantly reduced histological and radiological osteogenesis relative to DO Inn. Denervation preceding DO results in reduced SSC amplification and osteogenic potential in mice. Single cell RNA sequencing analysis revealed that there was a predominance of innervated SSCs in clusters dominated by pathways related to bone formation. A rare human patient specimen was also analyzed and suggested that histological, radiological, and transcriptional alterations seen in mouse DO may be conserved in the setting of denervated human mandible distraction. Fibromodulin (FMOD) transcriptional and protein expression were reduced in denervated relative to innervated mouse and human mandible regenerate. Finally, when exogenous FMOD was added to DO-Den and DO-Inn SSCs undergoing in vitro osteogenic differentiation, the osteogenic potential of DO-Den SSCs was increased in comparison to control untreated DO-Den SSCs, modeling the superior osteogenic potential of DO-Inn SSCs.

  View details for DOI 10.1038/s41598-023-27921-9

  View details for PubMedID 36747028

• An Inexpensive 3D Printed Mouse Model of Successful, Complication-free Long Bone Distraction Osteogenesis. Plastic and reconstructive surgery. Global open Tevlin, R., Shah, H. N., Salhotra, A., Di Iorio, S. E., Griffin, M., Januszyk, M., Wan, D. C., Longaker, M. T. 2023; 11 (2): e4674

  Abstract

  Distraction osteogenesis (DO) is used for skeletal defects; however, up to 50% of cases exhibit complications. Previous mouse models of long bone DO have been anecdotally hampered by postoperative complications, expense, and availability. To improve clinical techniques, cost-effective, reliable animal models are needed. Our focus was to develop a new mouse tibial distractor, hypothesized to result in successful, complication-free DO.A lightweight tibial distractor was developed using CAD and 3D printing. The device was fixed to the tibia of C57Bl/6J mice prior to osteotomy. Postoperatively, mice underwent 5 days latency, 10 days distraction (0.15 mm every 12 hours), and 28 days consolidation. Bone regeneration was examined on postoperative day 43 using micro-computed tomography (μCT) and Movat's modified pentachrome staining on histology (mineralized volume fraction and pixels, respectively). Costs were recorded. We compared cohorts of 11 mice undergoing sham, DO, or acute lengthening (distractor acutely lengthened 3.0 mm).The histological bone regenerate was significantly increased in DO (1,879,257 ± 155,415 pixels) compared to acute lengthening (32847 ± 1589 pixels) (P < 0.0001). The mineralized volume fraction (bone/total tissue volume) of the regenerate was significantly increased in DO (0.9 ± 0.1) compared to acute lengthening (0.7 ± 0.1) (P < 0.001). There was no significant difference in bone regenerate between DO and sham. The distractor was relatively low cost ($11), with no complications.Histology and µCT analysis confirmed that the proposed tibial DO model resulted in successful bone formation. Our model is cost-effective and reproducible, enabling implementation in genetically dissectible transgenic mice.

  View details for DOI 10.1097/GOX.0000000000004674

  View details for PubMedID 36798717

  View details for PubMedCentralID PMC9925097

• Chelating the valley of death: Deferoxamine's path from bench to wound clinic. Frontiers in medicine Parker, J. B., Griffin, M. F., Downer, M. A., Akras, D., Berry, C. E., Cotterell, A. C., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2023; 10: 1015711

  Abstract

  There is undisputable benefit in translating basic science research concretely into clinical practice, and yet, the vast majority of therapies and treatments fail to achieve approval. The rift between basic research and approved treatment continues to grow, and in cases where a drug is granted approval, the average time from initiation of human trials to regulatory marketing authorization spans almost a decade. Albeit with these hurdles, recent research with deferoxamine (DFO) bodes significant promise as a potential treatment for chronic, radiation-induced soft tissue injury. DFO was originally approved by the Food and Drug Administration (FDA) in 1968 for the treatment of iron overload. However, investigators more recently have posited that its angiogenic and antioxidant properties could be beneficial in treating the hypovascular and reactive-oxygen species-rich tissues seen in chronic wounds and radiation-induced fibrosis (RIF). Small animal experiments of various chronic wound and RIF models confirmed that treatment with DFO improved blood flow and collagen ultrastructure. With a well-established safety profile, and now a strong foundation of basic scientific research that supports its potential use in chronic wounds and RIF, we believe that the next steps required for DFO to achieve FDA marketing approval will include large animal studies and, if those prove successful, human clinical trials. Though these milestones remain, the extensive research thus far leaves hope for DFO to bridge the gap between bench and wound clinic in the near future.

  View details for DOI 10.3389/fmed.2023.1015711

  View details for PubMedID 36873870

• Bioprinted Hydrogels for Fibrosis and Wound Healing: Treatment and Modeling. Gels (Basel, Switzerland) Guo, J. L., Longaker, M. T. 2022; 9 (1)

  Abstract

  Three-dimensional (3D) printing has been used to fabricate biomaterial scaffolds with finely controlled physical architecture and user-defined patterning of biological ligands. Excitingly, recent advances in bioprinting have enabled the development of highly biomimetic hydrogels for the treatment of fibrosis and the promotion of wound healing. Bioprinted hydrogels offer more accurate spatial recapitulation of the biochemical and biophysical cues that inhibit fibrosis and promote tissue regeneration, augmenting the therapeutic potential of hydrogel-based therapies. Accordingly, bioprinted hydrogels have been used for the treatment of fibrosis in a diverse array of tissues and organs, including the skin, heart, and endometrium. Furthermore, bioprinted hydrogels have been utilized for the healing of both acute and chronic wounds, which present unique biological microenvironments. In addition to these therapeutic applications, hydrogel bioprinting has been used to generate in vitro models of fibrosis in a variety of soft tissues such as the skin, heart, and liver, enabling high-throughput drug screening and tissue analysis at relatively low cost. As biological research begins to uncover the spatial biological features that underlie fibrosis and wound healing, bioprinting offers a powerful toolkit to recapitulate spatially defined pro-regenerative and anti-fibrotic cues for an array of translational applications.

  View details for DOI 10.3390/gels9010019

  View details for PubMedID 36661787

• Multiplexed evaluation of mouse wound tissue using oligonucleotide barcoding with single-cell RNA sequencing. STAR protocols Januszyk, M., Griffin, M., Mascharak, S., Talbott, H. E., Chen, K., Henn, D., Spielman, A. F., Parker, J. B., Liang, N. E., Cotterell, A., Guardino, N., Foster, D. S., Wagh, D., Coller, J., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2022; 4 (1): 101946

  Abstract

  Despite its rapidly increased availability for the study of complex tissue, single-cell RNA sequencing remains prohibitively expensive for large studies. Here, we present a protocol using oligonucleotide barcoding for the tagging and pooling of multiple samples from healing wounds, which are among the most challenging tissue types for this application. We describe steps to generate skin wounds in mice, followed by tissue harvest and oligonucleotide barcoding. This protocol is also applicable to other species including rats, pigs, and humans. For complete details on the use and execution of this protocol, please refer to Stoeckius etal. (2018),1 Galiano etal. (2004),2 and Mascharak etal. (2022).3.

  View details for DOI 10.1016/j.xpro.2022.101946

  View details for PubMedID 36525348

• Topical vanadate improves tensile strength and alters collagen organization of excisional wounds in a mouse model. Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society Lintel, H., Abbas, D. B., Mackay, D. J., Griffin, M., Lavin, C. V., Berry, C. E., Guardino, N. J., Guo, J. L., Momeni, A., Mackay, D. R., Longaker, M. T., Wan, D. C. 2022

  Abstract

  Wound dehiscence, oftentimes a result of the poor tensile strength of early healing wounds, is a significant threat to the postoperative patient, potentially causing life-threatening complications. Vanadate, a protein tyrosine phosphatase inhibitor, has been shown to alter the organization of deposited collagen in healing wounds and significantly improve the tensile strength of incisional wounds in rats. In this study, we sought to explore the effects of locally administered vanadate on tensile strength and collagen organization in both the early and remodeling phases of excisional wound healing in a murine model. Wild-type mice underwent stented excisional wounding on their dorsal skin and were divided equally into three treatment conditions: vanadate injection, saline injection control, and an untreated control. Tensile strength testing, in vivo suction Cutometer analysis, gross wound measurements, and histologic analysis were performed during healing, immediately upon wound closure, and after four weeks of remodeling. We found that vanadate treatment significantly increased the tensile strength of wounds and their stiffness relative to control wounds, both immediately upon healing and into the remodeling phase. Histologic analysis revealed that these biomechanical changes were likely the result of increased collagen deposition and an altered collagen organization composed of thicker and distinctly organized collagen bundles. Given the risk that dehiscence poses to all operative patients, vanadate presents an interesting therapeutic avenue to improve the strength of post-operative wounds and unstable chronic wounds in order to reduce the risk of dehiscence.

  View details for DOI 10.1111/wrr.13062

  View details for PubMedID 36484112

• Macrophage inflammatory and regenerative response periodicity is programmed by cell cycle and chromatin state. Molecular cell Daniel, B., Belk, J. A., Meier, S. L., Chen, A. Y., Sandor, K., Czimmerer, Z., Varga, Z., Bene, K., Buquicchio, F. A., Qi, Y., Kitano, H., Wheeler, J. R., Foster, D. S., Januszyk, M., Longaker, M. T., Chang, H. Y., Satpathy, A. T. 2022

  Abstract

  Cell cycle (CC) facilitates cell division via robust, cyclical gene expression. Protective immunity requires the expansion of pathogen-responsive cell types, but whether CC confers unique gene expression programs that direct the subsequent immunological response remains unclear. Here, we demonstrate that single macrophages (MFs) adopt different plasticity states in CC, which leads to heterogeneous cytokine-induced polarization, priming, and repolarization programs. Specifically, MF plasticity to interferon gamma (IFNG) is substantially reduced during S-G2/M, whereas interleukin 4 (IL-4) induces S-G2/M-biased gene expression, mediated by CC-biased enhancers. Additionally, IL-4 polarization shifts the CC-phase distribution of MFs toward the G2/M phase, providing a subpopulation-specific mechanism for IL-4-induced, dampened IFNG responsiveness. Finally, we demonstrate CC-dependent MF responses in murine and human disease settings invivo, including Th2-driven airway inflammation and pulmonary fibrosis, where MFs express an S-G2/M-biased tissue remodeling gene program. Therefore, MF inflammatory and regenerative responses are gated by CC in a cyclical, phase-dependent manner.

  View details for DOI 10.1016/j.molcel.2022.11.017

  View details for PubMedID 36521490

• Standardized Quantitative Sensory Testing to assess insufficient recovery of touch discrimination in free flap surgery in extremity reconstruction. Plastic and reconstructive surgery Huber, J., Scharberth, A., Maier, C., Wallner, C., Wagner, J. M., Dadras, M., Longaker, M. T., Lehnhardt, M., Behr, B. 2022

  Abstract

  BACKGROUND: With major advances in microsurgical techniques, free tissue transfer has become a widely adopted approach to treat complex soft tissue defects. However, sensory recovery is poor leaving the anaesthetic skin prone to injuries.METHODS: 28 patients with 22 anterior lateral thigh flaps and 6 latissimus dorsi flaps on their extremities participated in the study. Quantitative sensory testing and 2 points discrimination was performed in three test areas and one control on the contralateral unaffected extremity. Physical disability, mental health, quality of life and characteristics of pain were assessed by the painDetect, DASH, LEFS and sf12 questionnaires, respectively.RESULTS: Somatosensory profiles of all flaps were characterized by an overall loss of nerve function. Small-fibre function was mostly recovered while large-fibre function and thus touch discrimination was severely impaired. Mechanical detection thresholds improved over time and from periphery to the centre. Reported pain was mild to moderate and correlated with decreased physical function.CONCLUSION: Standardized Quantitative sensory testing provides a useful tool kit to assess the sensory regeneration after surgical treatment of soft tissue defects. After free tissue transfer small-fibre function recovers with nerve ingrowth in a centripetal direction from the flap margins to the centre, likely via collateral axonal sprouting from the undamaged nerves surrounding the flap. Myelinated fibres recover slowly and inefficiently.

  View details for DOI 10.1097/PRS.0000000000009860

  View details for PubMedID 36374559

• Adipose-Derived Stromal Cell-based Therapies for Radiation-Induced Fibrosis. Advances in wound care Berry, C., Abbas, D. B., Lintel, H., Churukian, A., Griffin, M., Guo, J., Cotterell, A. C., Parker, J., Downer, M. A., Longaker, M. T., Wan, D. C. 2022

  Abstract

  SIGNIFICANCE: Half of all cancer patients receive radiation therapy as a component of their treatment regimen, and the most common resulting complication is radiation-induced fibrosis of the skin and soft tissue. This thickening of the dermis paired with decreased vascularity results in functional limitations, aesthetic concerns, and poses unique challenges when considering surgical exploration or reconstruction. Existing therapeutic options for radiation-induced fibrosis of the skin are limited both in scope and efficacy. Cell-based therapies have emerged as a promising means of utilizing regenerative cell populations to improve both functional and aesthetic outcomes, and even as prophylaxis for radiation-induced fibrosis.RECENT ADVANCES: As one of the leading areas of cell-based therapy research, adipose-derived stromal cells (ADSCs) demonstrate significant therapeutic potential in the treatment of radiation-induced fibrosis (RIF). The introduction of the ADSC-augmented fat graft has shown clinical utility. Recent research dedicated to characterizing specific ADSC subpopulations points toward further granularity in understanding of the mechanisms driving the well-established clinical outcomes seen with fat grafting therapy.CRITICAL ISSUES: Various animal models of radiation-induced fibrosis demonstrated improved clinical outcomes following treatment with cell-based therapies, but the cellular and molecular basis underlying these effects remains poorly understood.FUTURE DIRECTIONS: Recent literature has focused on improving the efficacy of cell-based therapies, most notably through 1) augmentation of fat grafts with platelet-rich plasma and 2) the modification of expressed RNA through epitranscriptomics. For the latter, new and promising gene targets continue to be identified which have the potential to reverse the effects of fibrosis by increasing angiogenesis, decreasing inflammation, and promoting adipogenesis.

  View details for DOI 10.1089/wound.2022.0103

  View details for PubMedID 36345216

• Machine Learning-Based Desmoplastic Signatures Predict Patient Outcomes in Pancreatic Ductal Adenocarcinoma Guo, J. L., Mascharak, S., Foster, D. S., Guardino, N. J., Griffin, M., Miller, E., Raghavan, S., Longacre, T. A., Norton, J. A., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2022: S53-S54

  View details for Web of Science ID 000867877000135

• Inhibition of Yes-Associated Protein Promotes Skin Wound Regeneration in Large Animals Januszyk, M., Talbott, H. E., Griffin, M., Guardino, N., Spielman, A., Guo, J. L., Mascharak, S., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2022: S196

  View details for DOI 10.1097/01.XCS.0000894508.92389.a2

  View details for Web of Science ID 000867889300379

• Denervation During Mouse and Human Mandibular Distraction Osteogenesis Results in Impaired Osteogenesis Tevlin, R., Griffin, M., Chen, K., Januszyk, M., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2022: S202

  View details for DOI 10.1097/01.XCS.0000894560.64479.80

  View details for Web of Science ID 000867889300393

• Adipocytes the Forgotten Culprit in Skin Fibrosis: Exploring the Mechanism of Fat Driven Skin Fibrosis Griffin, M., Guardino, N., Spielman, A. F., Mascharak, S., Parker, J. L., Guo, J. L., Abbas, D., Wan, D. C., Bauer-Rowe, K. E., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2022: S199

  View details for DOI 10.1097/01.XCS.0000894536.38023.90

  View details for Web of Science ID 000867889300387

• Adipocyte Progenitor Cells Embedded in Collagen Gels Accelerate Bone Formation in a Murine Calvarial Critical Defect Model Cotterell, A. C., Griffin, M., Guardino, N., Spielman, A. F., Lintel, H., Abbas, D., Guo, J. L., Parker, J. L., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2022: S198-S199

  View details for DOI 10.1097/01.XCS.0000894532.90979.c9

  View details for Web of Science ID 000867889300386

• Transdermal Deferoxamine Improves Acute Wound Healing in Chronic Irradiated Skin in a Mouse Model Lintel, H., Abbas, D., Lavin, C., Griffin, M., Guo, J. L., Guardino, N., Churukian, A., Chen, K., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2022: S211-S212

  View details for DOI 10.1097/01.XCS.0000894656.51739.b7

  View details for Web of Science ID 000867889300416

• Fibroblast Subpopulations Are Modified with Fat Grafting to Treat Radiation-Induced Fibrosis Abbas, D. B., Guo, J. L., Griffin, M., Lintel, H., Guardino, N. J., Berry, C. E., Pu, A., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2022: S202-S203

  View details for DOI 10.1097/01.XCS.0000894568.35895.12

  View details for Web of Science ID 000867889300395

• Semantics Matter: Cheiloschisis Web-Based Information Differs from Cleft Lip Abbas, D. B., Lintel, H., Guardino, N. J., Griffin, M., Guo, J. L., Cotterell, A. C., Spielman, A. F., Parker, J. L., Longaker, M. T., Wan, D. C. LIPPINCOTT WILLIAMS & WILKINS. 2022: S209

  View details for DOI 10.1097/01.XCS.0000894628.90579.08

  View details for Web of Science ID 000867889300410

• Where There Is Fat There Is Fibrosis: Elucidating the Mechanisms of Creeping Fat-Driven Stricture Formation Bauer-Rowe, K. E., Kim, A., Griffin, M., Foster, D., Guardino, N., Guo, J. L., Talbott, H. E., Norton, J. A., Hyun, J. S., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2022: S59-S60

  View details for DOI 10.1097/01.XCS.0000893384.03562.27

  View details for Web of Science ID 000867889300098

• Multi-Modal Analysis of Cell Populations and Architectural States Mediating the Progression and Resolution of Pulmonary Fibrosis Guo, J. L., Griffin, M., Guardino, N. J., Abbas, D., Lu, J., Spielman, A., Lintel, H., Cotterell, A. C., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2022: S82

  View details for Web of Science ID 000867877000204

• Engrailed-Positive Fibroblasts: The Primary Cell Type Present in Fibrotic Capsules During Foreign Body Response Parker, J. B., Griffin, M., Mascharak, S., Spielman, A., Cotterell, A. C., Abbas, D., Lintel, H., Januszyk, M., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2022: S68

  View details for Web of Science ID 000867877000171

• Reversal of Senescence in Skin-derived Fibroblasts Using Exogenous Mechanical Stimulation Guo, J. L., Griffin, M., Guardino, N. J., Chen, K., Cotterell, A. C., Abbas, D., Spielman, A., Lintel, H., Wan, D. C., Longaker, M. T. LIPPINCOTT WILLIAMS & WILKINS. 2022: S70

  View details for Web of Science ID 000867877000176

• Sexually dimorphic estrogen sensing in skeletal stem cells controls skeletal regeneration. Nature communications Andrew, T. W., Koepke, L. S., Wang, Y., Lopez, M., Steininger, H., Struck, D., Boyko, T., Ambrosi, T. H., Tong, X., Sun, Y., Gulati, G. S., Murphy, M. P., Marecic, O., Telvin, R., Schallmoser, K., Strunk, D., Seita, J., Goodman, S. B., Yang, F., Longaker, M. T., Yang, G. P., Chan, C. K. 2022; 13 (1): 6491

  Abstract

  Sexually dimorphic tissues are formed by cells that are regulated by sex hormones. While a number of systemic hormones and transcription factors are known to regulate proliferation and differentiation of osteoblasts and osteoclasts, the mechanisms that determine sexually dimorphic differences in bone regeneration are unclear. To explore how sex hormones regulate bone regeneration, we compared bone fracture repair between adult male and female mice. We found that skeletal stem cell (SSC) mediated regeneration in female mice is dependent on estrogen signaling but SSCs from male mice do not exhibit similar estrogen responsiveness. Mechanistically, we found that estrogen acts directly on the SSC lineage in mice and humans by up-regulating multiple skeletogenic pathways and is necessary for the stem cell's ability to self- renew and differentiate. Our results also suggest a clinically applicable strategy to accelerate bone healing using localized estrogen hormone therapy.

  View details for DOI 10.1038/s41467-022-34063-5

  View details for PubMedID 36310174

• Multiomic analysis reveals conservation of cancer-associated fibroblast phenotypes across species and tissue of origin. Cancer cell Foster, D. S., Januszyk, M., Delitto, D., Yost, K. E., Griffin, M., Guo, J., Guardino, N., Delitto, A. E., Chinta, M., Burcham, A. R., Nguyen, A. T., Bauer-Rowe, K. E., Titan, A. L., Salhotra, A., Jones, R. E., da Silva, O., Lindsay, H. G., Berry, C. E., Chen, K., Henn, D., Mascharak, S., Talbott, H. E., Kim, A., Nosrati, F., Sivaraj, D., Ransom, R. C., Matthews, M., Khan, A., Wagh, D., Coller, J., Gurtner, G. C., Wan, D. C., Wapnir, I. L., Chang, H. Y., Norton, J. A., Longaker, M. T. 2022

  Abstract

  Cancer-associated fibroblasts (CAFs) are integral to the solid tumor microenvironment. CAFs were once thought to be a relatively uniform population of matrix-producing cells, but single-cell RNA sequencing has revealed diverse CAF phenotypes. Here, we further probed CAF heterogeneity with a comprehensive multiomics approach. Using paired, same-cell chromatin accessibility and transcriptome analysis, we provided an integrated analysis of CAF subpopulations over a complex spatial transcriptomic and proteomic landscape to identify three superclusters: steady state-like (SSL), mechanoresponsive (MR), and immunomodulatory (IM) CAFs. These superclusters are recapitulated across multiple tissue types and species. Selective disruption of underlying mechanical force or immune checkpoint inhibition therapy results in shifts in CAF subpopulation distributions and affected tumor growth. As such, the balance among CAF superclusters may have considerable translational implications. Collectively, this research expands our understanding of CAF biology, identifying regulatory pathways in CAF differentiation and elucidating therapeutic targets in a species- and tumor-agnostic manner.

  View details for DOI 10.1016/j.ccell.2022.09.015

  View details for PubMedID 36270275

• Characterization of Mechanoresponsive Inflammatory Cells during Wound Healing Chen, K., Griffin, M., Henn, D., Bonham, C. A., Fischer, K., Padmanabhan, J., Trotsyuk, A. A., Sivaraj, D., Leeolou, M., Kussie, H. C., Huskins, S., Steele, S., Perrault, D., Longaker, M. T., Gurtner, G. C. WILEY. 2022: A22

  View details for Web of Science ID 000847524300054

• Machine Learning in Tissue Engineering. Tissue engineering. Part A Guo, J. L., Januszyk, M., Longaker, M. T. 2022

  Abstract

  Machine learning (ML) and artificial intelligence have accelerated scientific discovery, augmented clinical practice, and deepened fundamental understanding of many biological phenomena. ML technologies have now been applied to diverse areas of tissue engineering research, including biomaterial design, scaffold fabrication, and cell/tissue modeling. Emerging ML-empowered strategies include machine-optimized polymer synthesis, predictive modeling of scaffold fabrication processes, complex analyses of structure-function relationships, and deep learning of spatialized cell phenotypes and tissue composition. The emergence of ML in tissue engineering, while relatively recent, has already enabled increasingly complex and multivariate analyses of the relationships between biological, chemical, and physical factors in driving tissue regenerative outcomes. This review highlights the novel methodologies, emerging strategies, and areas of potential growth within this rapidly evolving area of research.

  View details for DOI 10.1089/ten.TEA.2022.0128

  View details for PubMedID 35943870

• Wound healing, fibroblast heterogeneity, and fibrosis. Cell stem cell Talbott, H. E., Mascharak, S., Griffin, M., Wan, D. C., Longaker, M. T. 2022; 29 (8): 1161-1180

  Abstract

  Fibroblasts are highly dynamic cells that play a central role in tissue repair and fibrosis. However, the mechanisms by which they contribute to both physiologic and pathologic states of extracellular matrix deposition and remodeling are just starting to be understood. In this review article, we discuss the current state of knowledge in fibroblast biology and heterogeneity, with a primary focus on the role of fibroblasts in skin wound repair. We also consider emerging techniques in the field, which enable an increasingly nuanced and contextualized understanding of these complex systems, and evaluate limitations of existing methodologies and knowledge. Collectively, this review spotlights a diverse body of research examining an often-overlooked cell type-the fibroblast-and its critical functions in wound repair and beyond.

  View details for DOI 10.1016/j.stem.2022.07.006

  View details for PubMedID 35931028

• Exploring the Overlooked Roles and Mechanisms of Fibroblasts in the Foreign Body Response. Advances in wound care Parker, J., Griffin, M., Spielman, A. F., Wan, D. C., Longaker, M. T. 2022

  Abstract

  Significance Foreign body response (FBR), wherein a fibrotic capsule forms around an implanted structure, is a common surgical complication that often leads to pain, discomfort, and eventual revision surgeries. Though believed to have some mechanistic overlap with normal wound healing, much remains to be discovered about the specific mechanism by which this occurs. Recent Advances Current understanding of FBR has focused on the roles of the immune system and the biomaterial, both major contributors to FBR. However, another key player, the fibroblast, is often overlooked. This review summarizes key contributors of FBR, focusing on the roles of fibroblasts. As much remains to be discovered about fibroblasts' specific roles in FBR, we draw on current knowledge of fibroblast subpopulations and functions during wound healing. We also provide an overview on candidate biomaterials and signalling pathways involved in FBR. Critical Issues and Future Directions While the global implantable medical devices market is considerable and continues to appreciate in value, FBR remains one of the most common surgical implant complications. In parallel with the continued development of candidate biomaterials, further exploration of potential fibroblast subpopulations at a transcriptional level would provide key insights into further understanding the underlying mechanisms by which fibrous encapsulation occurs, and unveil novel directions for anti-fibrotic and regenerative therapies in the future.

  View details for DOI 10.1089/wound.2022.0066

  View details for PubMedID 35819293

• Transdermal deferoxamine administration improves excisional wound healing in chronically irradiated murine skin. Journal of translational medicine Lintel, H., Abbas, D. B., Lavin, C. V., Griffin, M., Guo, J. L., Guardino, N., Churukian, A., Gurtner, G. C., Momeni, A., Longaker, M. T., Wan, D. C. 2022; 20 (1): 274

  Abstract

  BACKGROUND: Radiation-induced skin injury is a well-known risk factor for impaired wound healing. Over time, the deleterious effects of radiation on skin produce a fibrotic, hypovascular dermis poorly suited to wound healing. Despite increasing understanding of the underlying pathophysiology, therapeutic options remain elusive. Deferoxamine (DFO), an iron-chelating drug, has been shown in prior murine studies to ameliorate radiation-induced skin injury as well as improve wound healing outcomes in various pathologic conditions when administered transdermally. In this preclinical study, we evaluated the effects of deferoxamine on wound healing outcomes in chronically irradiated murine skin.METHODS: Wild-type mice received 30Gy of irradiation to their dorsal skin and were left to develop chronic fibrosis. Stented excisional wounds were created on their dorsal skin. Wound healing outcomes were compared across 4 experimental conditions: DFO patch treatment, vehicle-only patch treatment, untreated irradiated wound, and untreated nonirradiated wounds. Gross closure rate, wound perfusion, scar elasticity, histology, and nitric oxide assays were compared across the conditions.RESULTS: Relative to vehicle and untreated irradiated wounds, DFO accelerated wound closure and reduced the frequency of healing failure in irradiated wounds. DFO augmented wound perfusion throughout healing and upregulated angiogenesis to levels observed in nonirradiated wounds. Histology revealed DFO increased wound thickness, collagen density, and improved collagen fiber organization to more closely resemble nonirradiated wounds, likely contributing to the observed improved scar elasticity. Lastly, DFO upregulated inducible nitric oxide synthase and increased nitric oxide production in early healing wounds.CONCLUSION: Deferoxamine treatment presents a potential therapeutic avenue through which to target impaired wound healing in patients following radiotherapy.

  View details for DOI 10.1186/s12967-022-03479-4

  View details for PubMedID 35715816

• Profibrotic Signaling Pathways and Surface Markers Are Upregulated in Fibroblasts of Human Striae Distensae and in a Mouse Model System. Plastic and reconstructive surgery Borrelli, M. R., Griffin, M., Chen, K., Diaz, N. M., Adem, S., Mascharak, S., Shen, A. H., Ngaage, L. M., Lewis, N., Longaker, M. T., Gurtner, G., Wan, D. C., Lorenz, H. P. 2022

  Abstract

  INTRODUCTION: Striae distensae (SD) are common disfiguring cutaneous lesions but lack effective treatments due to an incomplete understanding of their pathophysiology. Dermal fibroblasts likely play an important role. We investigate the cellular-molecular features distinguishing fibroblasts from human SD and normal skin (NS). We also develop a mouse model of SD.METHODS: Human SD and NS samples were compared for tensile strength and histological structure. Fibroblasts from SD and NS were isolated by fluorescence-activated cell sorting (FACS) for gene expression analysis. Immunofluorescence staining and FACS were used to confirm gene expression data at the protein level. A mouse model of SD formation was created by administering corticosteroids and mechanically loading the dorsal skin.RESULTS: Human SD exhibited reduced tensile strength, more disordered collagen fibers, and epidermal atrophy compared to human NS. There were 296 upregulated genes in SD fibroblasts, including the profibrotic lineage and surface marker CD26. Upregulated genes were involved in profibrotic and mechanoresponsive signaling pathways (TGFbeta and FAK-PI3-AKT-signaling). In contrast, 571 genes were downregulated, including CD74 and genes of the AMPK pathway. Increased CD26 and decreased CD74 expression was confirmed by FACS and immunofluorescence. Similar cutaneous histological and gene expression changes were induced in hypercortisolemic mice by mechanically loading the dorsal skin.CONCLUSIONS: Fibroblasts from human SD exhibit increased profibrotic and decreased antifibrotic signaling. CD26 and CD74 are promising surface markers that may be targeted therapeutically. Our mouse model of SD can be used as a platform to test the efficacy of potential therapeutic agents.

  View details for DOI 10.1097/PRS.0000000000009363

  View details for PubMedID 35666152

• Beyond the Scar: A Basic Science Review of Wound Remodeling. Advances in wound care Spielman, A. F., Griffin, M., Parker, J., Cotterell, A. C., Wan, D. C., Longaker, M. T. 2022

  Abstract

  SIGNIFICANCE: Increasing development of experimental animal models has allowed for the study of scar formation. However, many pathophysiological unknowns remain in the longest stage of healing, the remodeling stage, which may continue for a year or more. The wound healing process results in different types of scarring classified as normal or pathological depending on failures at each stage. Failures can also occur during wound remodeling, but the molecular mechanisms driving the wound remodeling process have yet to be investigated.RECENT ADVANCES: While current understanding of wound repair is based on investigations of acute healing, these experimental models have informed knowledge of key components of remodeling. This review examines the components that contribute to collagen organization and the final scar, including cell types, their regulation, and signaling pathways. Dysregulation in any one of these components causes pathologic healing.CRITICAL ISSUES AND FUTURE DIRECTIONS: As wounds continue to remodel months to years after re-epithelization, new models to better understand long-term remodeling will be critical for improving healing outcomes. Further investigation of the contributions of fibroblasts and cell signaling pathways involved during remodeling as well as their potential failures may inform new approaches in promoting regenerative healing beyond re-epithelization.

  View details for DOI 10.1089/wound.2022.0049

  View details for PubMedID 35658581

• Partial Tendon Injury at the Tendon-to-Bone Enthesis Activates Skeletal Stem Cells. Stem cells translational medicine Titan, A. L., Davitt, M., Foster, D., Salhotra, A., Menon, S., Chen, K., Fahy, E., Lopez, M., Jones, R. E., Baiu, I., Burcham, A., Januszyk, M., Gurtner, G., Fox, P., Chan, C., Quarto, N., Longaker, M. 2022

  Abstract

  The tendon enthesis plays a critical role in facilitating movement and reducing stress within joints. Partial enthesis injuries heal in a mechanically inferior manner and never achieve healthy tissue function. The cells responsible for tendon-to-bone healing remain incompletely characterized and their origin is unknown. Here, we evaluated the putative role of mouse skeletal stem cells (mSSCs) in the enthesis after partial-injury. We found that mSSCs were present at elevated levels within the enthesis following injury and that these cells downregulated TGFβ signaling pathway elements at both the RNA and protein levels. Exogenous application of TGFβ post-injury led to a reduced mSSC response and impaired healing, whereas treatment with a TGFβ inhibitor (SB43154) resulted in a more robust mSSC response. Collectively, these data suggest that mSSCs may augment tendon-to-bone healing by dampening the effects of TGFβ signaling within the mSSC niche.

  View details for DOI 10.1093/stcltm/szac027

  View details for PubMedID 35640155

• Disrupting mechanotransduction decreases fibrosis and contracture in split-thickness skin grafting. Science translational medicine Chen, K., Henn, D., Januszyk, M., Barrera, J. A., Noishiki, C., Bonham, C. A., Griffin, M., Tevlin, R., Carlomagno, T., Shannon, T., Fehlmann, T., Trotsyuk, A. A., Padmanabhan, J., Sivaraj, D., Perrault, D. P., Zamaleeva, A. I., Mays, C. J., Greco, A. H., Kwon, S. H., Leeolou, M. C., Huskins, S. L., Steele, S. R., Fischer, K. S., Kussie, H. C., Mittal, S., Mermin-Bunnell, A. M., Diaz Deleon, N. M., Lavin, C., Keller, A., Longaker, M. T., Gurtner, G. C. 2022; 14 (645): eabj9152

  Abstract

  Burns and other traumatic injuries represent a substantial biomedical burden. The current standard of care for deep injuries is autologous split-thickness skin grafting (STSG), which frequently results in contractures, abnormal pigmentation, and loss of biomechanical function. Currently, there are no effective therapies that can prevent fibrosis and contracture after STSG. Here, we have developed a clinically relevant porcine model of STSG and comprehensively characterized porcine cell populations involved in healing with single-cell resolution. We identified an up-regulation of proinflammatory and mechanotransduction signaling pathways in standard STSGs. Blocking mechanotransduction with a small-molecule focal adhesion kinase (FAK) inhibitor promoted healing, reduced contracture, mitigated scar formation, restored collagen architecture, and ultimately improved graft biomechanical properties. Acute mechanotransduction blockade up-regulated myeloid CXCL10-mediated anti-inflammation with decreased CXCL14-mediated myeloid and fibroblast recruitment. At later time points, mechanical signaling shifted fibroblasts toward profibrotic differentiation fates, and disruption of mechanotransduction modulated mesenchymal fibroblast differentiation states to block those responses, instead driving fibroblasts toward proregenerative, adipogenic states similar to unwounded skin. We then confirmed these two diverging fibroblast transcriptional trajectories in human skin, human scar, and a three-dimensional organotypic model of human skin. Together, pharmacological blockade of mechanotransduction markedly improved large animal healing after STSG by promoting both early, anti-inflammatory and late, regenerative transcriptional programs, resulting in healed tissue similar to unwounded skin. FAK inhibition could therefore supplement the current standard of care for traumatic and burn injuries.

  View details for DOI 10.1126/scitranslmed.abj9152

  View details for PubMedID 35584231

• Pullulan-Collagen Hydrogel Wound Dressing Promotes Dermal Remodeling and Wound Healing Compared to Commercially Available Collagen Dressings. Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society Chen, K., Sivaraj, D., Davitt, M., Leeolou, M. C., Henn, D., Steele, S. R., Huskins, S. L., Trotsyuk, A. A., Kussie, H. C., Greco, A., Padmanabhan, J., Perrault, D. P., Zamaleeva, A. I., Longaker, M. T., Gurtner, G. C. 2022

  Abstract

  Biological scaffolds such as hydrogels provide an ideal, physio-mimetic of native ECM that can improve wound healing outcomes after cutaneous injury. While most studies have focused on the benefits of hydrogels in accelerating wound healing, there is minimal data directly comparing different hydrogel material compositions. In this study, we utilized a splinted excisional wound model that recapitulates human-like wound healing in mice and treated wounds with three different collagen hydrogel dressings. We assessed the feasibility of applying each dressing and performed histologic and histopathologic analysis on the explanted scar tissues to assess variations in collagen architecture and alignment, as well as tissue response. Our data indicate that the material properties of hydrogel dressings can significantly influence healing time, cellular response, and resulting architecture of healed scars. Specifically, our pullulan-collagen hydrogel dressing accelerated wound closure and promoted healed tissue with less dense, more randomly aligned, and shorter collagen fibers. Further understanding of how hydrogel properties affect the healing and resulting scar architecture of wounds may lead to novel insights and further optimization of the material properties of wound dressings. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1111/wrr.13012

  View details for PubMedID 35384131

• REGENERATION OF CARTILAGE THOUGH ACTIVATION OF TISSUE RESIDENT SKELETAL STEM CELLS AND AUGMENTATION OF THE NICHE Murphy, M. P., Koepke, L. S., Lopez, M. T., Tong, X., Ambrosi, T. H., Gulati, G., Marecic, O., Wang, Y., Ransom, R. C., Hoover, M., Longaker, M. T., Chan, C. F. MARY ANN LIEBERT, INC. 2022: S375

  View details for Web of Science ID 000821187301490

• Fat Grafts Augmented With Vitamin E Improve Volume Retention and Radiation-Induced Fibrosis. Aesthetic surgery journal Abbas, D. B., Lavin, C. V., Fahy, E. J., Griffin, M., Guardino, N. J., Nazerali, R. S., Nguyen, D. H., Momeni, A., Longaker, M. T., Wan, D. C. 2022

  Abstract

  Treatments for radiation-induced fibrosis range from vitamin E and pentoxifylline systemically to deferoxamine and fat grafting locally. Regarding fat grafting, volume retention hinders its long-term functionality and is affected by two factors: inflammation and necrosis secondary to hypovascularity.We aimed to simultaneously improve fat graft retention and radiation-induced fibrosis by integrating vitamin E and pentoxifylline into fat grafts locally.Forty adult CD-1 nude male mice at 6 weeks of age underwent scalp irradiation and recovered for four weeks to allow for the development of fibrosis. Mice received 200μL of donor human fat graft to the scalp. Mice were separated into 4 conditions: no grafting, fat graft without treatment, graft treated with pentoxifylline, and graft treated with vitamin E. Fat graft volume retention was monitored in-vivo using microCT scans at weeks 0, 1, 2, 4, 6, and 8 after grafting. Histological and cytokine analysis of the scalp skin and fat grafts were also performed.Vitamin E (VE) treated grafts had significant improvement in dermal thickness and collagen density of overlying skin compared to all other groups. VE decreased 8-isoprostane and increased CD31 + staining compared to the other grafted groups. Cytokine analysis revealed decreased inflammatory and increased angiogenic markers in both the fat graft and overlying skin of the vitamin E group. Fat graft volume retention was significantly improved in the vitamin E group starting at 1 week post grafting.Radiation-induced fibrosis and fat graft volume retention are both simultaneously improved with local administration of vitamin E.

  View details for DOI 10.1093/asj/sjac066

  View details for PubMedID 35350074

• Characterization of Mechanoresponsive Inflammatory Cells during Wound Healing Chen, K., Griffin, M., Henn, D., Bonham, C. A., Fischer, K., Padmanabhan, J., Trotsyuk, A. A., Sivaraj, D., Leeolou, M. C., Kussie, H. C., Huskins, S. L., Steele, S., Perrault, D., Longaker, M. T., Gurtner, G. C. WILEY. 2022: A5

  View details for Web of Science ID 000763583000021

• Overcoming Radiation Induced Oral Fibrosis Through The Down Regulation Of WNT Signaling Using BMP-7 Inhibitors Guardino, N., Griffin, M., Spielman, A. F., Abbas, D. B., King, M., Parker, J., Wan, D., Longaker, M. T. WILEY. 2022: A5

  View details for Web of Science ID 000763583000022

• Adipocytes Transition To Pro-Fibrotic Fibroblasts And Contribute To Muscle Fibrosis Following Nerve Injury Spielman, A. F., Griffin, M., Guardino, N., desJardins-Park, H. E., Bauer-Rowe, K. E., Guo, J. L., Parker, J., Abbas, D. B., Wan, D., Longaker, M. T. WILEY. 2022: A3-A4

  View details for Web of Science ID 000763583000018

• Vitamin E Treated Fat Grafts Demonstrate Improved Volume Retention And Decreased Radiation-Induced Fibrosis Abbas, D. B., Lavin, C. V., Fahy, E. J., Lintel, H., Griffin, M., Nazerali, R., Dung Nguyen, Momeni, A., Longaker, M. T., Wan, D. WILEY. 2022: A16

  View details for Web of Science ID 000763583000040

• Mechanical Stimulation Reverses Pro-Fibrotic Transcriptional States in Senescent Fibroblasts Guo, J. L., Griffin, M., Guardino, N., Chen, K., Gurtner, G. C., Longaker, M. T. WILEY. 2022: A14-A16

  View details for Web of Science ID 000763583000039

• Interactions Of Fibroblasts Versus Macrophages In An In Vitro Model Of Scar Formation And Wound Healing Huskins, S. L., Griffin, M., Steele, S., Thomas, B., Kussie, H. C., Sivaraj, D., Leeolou, M. C., Trotsyuk, A. A., Padmanabhan, J., Longaker, M. T., Gurtner, G. C., Chen, K. WILEY. 2022: A53-A54

  View details for Web of Science ID 000763583000115

• Pullulan-Collagen Hydrogel Wound Dressing Promotes Dermal Remodeling and Healing in an Excisional Wound Model Leeolou, M. C., Sivaraj, D., Davitt, M., Henn, D., Steele, S., Huskins, S. L., Trotsyuk, A. A., Kussie, H. C., Greco, A., Perrault, D., Padmanabhan, J., Longaker, M. T., Chen, K., Gurtner, G. C. WILEY. 2022: A24

  View details for Web of Science ID 000763583000056

• The Oral Mucosa Hosts Distinct Fibroblast Subpopulations to Facilitate Regenerative Wound Repair Griffin, M., Cook, J., Bofelli, D., Guardino, N., Spielman, A. F., Januszyk, M., Chen, K., Abbas, D. B., Zwick, R., Klein, O., Longaker, M. T. WILEY. 2022: A12-A13

  View details for Web of Science ID 000763583000035

• Transdermal Deferoxamine Enhances Wound Healing In Chronically Irradiated Skin In Mice Lintel, H., Abbas, D. B., Lavin, C. V., Griffin, M., Guardino, N., Guo, J. L., Spielman, A. F., Gurtner, G. C., Longaker, M. T., Wan, D. WILEY. 2022: A29-A30

  View details for Web of Science ID 000763583000068

• Characterization of Mechanoresponsive Inflammatory Cells during Wound Healing Chen, K., Griffin, M., Henn, D., Bonham, C. A., Fischer, K., Padmanabhan, J., Trotsyuk, A. A., Sivaraj, D., Leeolou, M. C., Kussie, H. C., Huskins, S. L., Steele, S., Perrault, D., Longaker, M. T., Gurtner, G. C. WILEY. 2022: A31-A32

  View details for Web of Science ID 000763583000072

• Mechanical Stimulation Reverses Pro-Fibrotic Transcriptional States in Senescent Fibroblasts Guo, J. L., Griffin, M., Guardino, N., Chen, K., Gurtner, G. C., Longaker, M. T. WILEY. 2022: A33-A34

  View details for Web of Science ID 000763583000075

• Discussion: Beyond the Scalpel: Attracting and Nurturing Surgeon-Scientists in Plastic Surgery. Plastic and reconstructive surgery Liao, E. C., Longaker, M. T. 1800; 149 (2): 517-518

  View details for DOI 10.1097/PRS.0000000000008787

  View details for PubMedID 35077431

• Tractable Human Skeletal Stem Cell Diversity Shapes Bone Development and Regeneration Ambrosi, T., Taheri, S., Sinha, R., Goodnough, L., Steininger, H., Weissman, I., Longaker, M., Sahoo, D., Chan, C. WILEY. 2022: 266-267

  View details for Web of Science ID 000778074501234

• Multi-omic analysis reveals divergent molecular events in scarring and regenerative wound healing. Cell stem cell Mascharak, S., Talbott, H. E., Januszyk, M., Griffin, M., Chen, K., Davitt, M. F., Demeter, J., Henn, D., Bonham, C. A., Foster, D. S., Mooney, N., Cheng, R., Jackson, P. K., Wan, D. C., Gurtner, G. C., Longaker, M. T. 1800

  Abstract

  Regeneration is the holy grail of tissue repair, but skin injury typically yields fibrotic, non-functional scars. Developing pro-regenerative therapies requires rigorous understanding of the molecular progression from injury to fibrosis or regeneration. Here, we report the divergent molecular events driving skin wound cells toward scarring or regenerative fates. We profile scarring versus YAP-inhibition-induced wound regeneration at the transcriptional (single-cell RNA sequencing), protein (timsTOF proteomics), and tissue (extracellular matrix ultrastructural analysis) levels. Using cell-surface barcoding, we integrate these data to reveal fibrotic and regenerative "molecular trajectories" of healing. We show that disrupting YAP mechanotransduction yields regenerative repair by fibroblasts with activated Trps1 and Wnt signaling. Finally, via invivo gene knockdown and overexpression in wounds, we identify Trps1 as a key regulatory gene that is necessary and partially sufficient for wound regeneration. Our findings serve as a multi-omic map of wound regeneration and could have therapeutic implications for pathologic fibroses.

  View details for DOI 10.1016/j.stem.2021.12.011

  View details for PubMedID 35077667

• Harnessing a Feasible and Versatile ex vivo Calvarial Suture 2-D Culture System to Study Suture Biology. Frontiers in physiology Quarto, N., Menon, S., Griffin, M., Huber, J., Longaker, M. T. 2022; 13: 823661

  Abstract

  As a basic science, craniofacial research embraces multiple facets spanning from molecular regulation of craniofacial development, cell biology/signaling and ultimately translational craniofacial biology. Calvarial sutures coordinate development of the skull, and the premature fusion of one or more, leads to craniosynostosis. Animal models provide significant contributions toward craniofacial biology and clinical/surgical treatments of patients with craniofacial disorders. Studies employing mouse models are costly and time consuming for housing/breeding. Herein, we present the establishment of a calvarial suture explant 2-D culture method that has been proven to be a reliable system showing fidelity with the in vivo harvesting procedure to isolate high yields of skeletal stem/progenitor cells from small number of mice. Moreover, this method allows the opportunity to phenocopying models of craniosynostosis and in vitro tamoxifen-induction of ActincreERT2;R26Rainbow suture explants to trace clonal expansion. This versatile method tackles needs of large number of mice to perform calvarial suture research.

  View details for DOI 10.3389/fphys.2022.823661

  View details for PubMedID 35222087

• So You Want to Be an Innovator? Plastic and reconstructive surgery Rohrich, R. J., Rosen, J., Longaker, M. T. 2021; 148 (5S): 55S-57S

  View details for DOI 10.1097/01.prs.0000794856.25019.d0

  View details for PubMedID 34699492

• Osteoskeletal Regenerative Ability of Exosomes Derived From Adipose-derived Stem Cells Upon Inhibition of Transforming Growth Factor-beta-signaling Huber, J. L., Menon, S., Longaker, M. T., Quarto, N. ELSEVIER SCIENCE INC. 2021: E194

  View details for Web of Science ID 000718306700472

• Transdermal Deferoxamine in a Porcine Model Is a Safe Treatment to Improve Elasticity Secondary to Radiation-induced Fibrosis Abbas, D. B., Fahy, E. J., Lavin, C. V., Griffin, M., Deleon, N., King, M. E., Gurtner, G. C., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: E164

  View details for Web of Science ID 000718306700398

• CD34+CD146+Adipose-derived Stromal Cells (ASCs) Enrichment of Fat Grafts Enhance Regeneration of Irradiated Skin and Graft Retention Deleon, N., Abbas, D. B., Borrelli, M. R., Adem, S., Lavin, C. V., Griffin, M., King, M. E., Lee, D., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: E198

  View details for Web of Science ID 000718306700482

• Dermal Iron Chelation Reduces Indirect Radiation Injury Lavin, C. V., Fahy, E. J., Abbas, D. B., Griffin, M., Lee, D. K., Deleon, N., Guardino, N., Gurtner, G. C., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: E155

  View details for Web of Science ID 000718306700375

• Dorsal Skin Fibrosis Secondary to Radiation Is Mitigated by Fat Grafting in Engrailed-1 Mice Abbas, D. B., Fahy, E. J., Griffin, M., Lavin, C. V., Deleon, N., King, M. E., Lee, D., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: E159-E160

  View details for Web of Science ID 000718306700387

• Suprazygomatic Maxillary Nerve Blocking Reduces Postoperative Pain and Opioid Use Following Bimaxillary Osteotomy Lavin, C. V., Lee, D. K., Fahy, E. J., Abbas, D. B., Griffin, M., King, M. E., Momeni, A., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: E157

  View details for Web of Science ID 000718306700380

• Optimizing Cutometer Mpa 580 Calculated Parameters to Determine In-vivo Elasticity of Human Skin Abbas, D. B., Lavin, C. V., Fahy, E., Griffin, M., Guardino, N., Lee, D., Gurtner, G. C., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: E162

  View details for Web of Science ID 000718306700394

• Temperature Influence on Scanning Laser Doppler Flowmetry in Anesthetized Mice Fahy, E. J., Lavin, C. V., Abbas, D., Griffin, M., King, M. E., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: E157

  View details for Web of Science ID 000718306700381

• Acellular Dermal Matrix Grafts Decrease Radiation-Induced Contracture and Dermal Thickening Deleon, N., Lavin, C. D., Abbas, D., Griffin, M., King, M. E., Fahy, E. J., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: E197

  View details for Web of Science ID 000718306700480

• Adipose-Derived Stromal Cell (ASC) Subpopulation with Adipogenic Capabilities Increase Fat Graft Quality in Irradiated Tissue Deleon, N., Adem, S., Borrelli, M. R., Abbas, D. B., Lavin, C. V., Griffin, M., King, M. E., Lee, D., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: E197-E198

  View details for Web of Science ID 000718306700481

• Cancer-Associated Fibroblasts Share Highly Conserved Phenotypes and Functions Across Tumor Types and Species Foster, D. S., Januszyk, M., Yost, K. E., Chinta, M., Titan, A. L., Wapnir, I. L., Gurtner, G. C., Chang, H. Y., Norton, J. A., Longaker, M. T. ELSEVIER SCIENCE INC. 2021: S243-S244

  View details for Web of Science ID 000718303100463

• Acellular Dermal Matrix Modulation of the Peri-Prosthetic Breast Microenvironment During Breast Reconstruction Tevlin, R., Januszyk, M., Griffin, M., Shefren, K., Chan, C. F., Momeni, A., Wan, D. C., Longaker, M. T. ELSEVIER SCIENCE INC. 2021: S195-S196

  View details for Web of Science ID 000718303100367

• Fibroblast Sub-Populations Dynamically Change Composition to Heal Dorsal Skin Radiation Wounds in Wild-Type Mice Abbas, D. B., Griffin, M., Fahy, E. J., Lavin, C., Lee, D., Mascharak, S., King, M., Januszyk, M., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: S207-S208

  View details for Web of Science ID 000718303100389

• Adipose Precursor Cell-Embedded Collagen Gels Attenuate Inflammation and Improve Tissue Perfusion in Cutaneous Wounds Fahy, E. J., Griffin, M., Abbas, D., Lavin, C. V., King, M. E., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: S196

  View details for Web of Science ID 000718303100368

• Denervation During Mandibular Distraction Osteogenesis Results in Impaired Osteogenesis Tevlin, R., Januszyk, M., Griffin, M., Salhotra, A., Wan, D. C., Chan, C. F., Longaker, M. T. ELSEVIER SCIENCE INC. 2021: S196-S197

  View details for Web of Science ID 000718303100369

• Topical Deferoxamine Patch Is Superior to Direct Injection for the Treatment of Radiation-Induced Skin Fibrosis Lavin, C. V., Abbas, D. B., Fahy, E. J., Lee, D. K., Griffin, M., Deleon, N., Mascharak, S., Gurtner, G. C., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: S202-S203

  View details for Web of Science ID 000718303100381

• Effects of beta(3) Adrenergic Receptor Agonist Treatment in Murine Full Thickness Dorsal Cutaneous Wounds Fahy, E. J., Griffin, M., Abbas, D., Lavin, C. V., King, M. E., Lee, D., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: S197-S198

  View details for Web of Science ID 000718303100371

• Where There Is Fat There Is Fibrosis: Elucidating the Mechanisms of Creeping Fat-Driven Stricture Formation Bauer-Rowe, K. E., Griffin, M., Foster, D., desJardins-Park, H. E., Mascharak, S., Norton, J. A., Hyun, J. S., Longaker, M. T. ELSEVIER SCIENCE INC. 2021: S65

  View details for Web of Science ID 000718303100105

• Single-Cell RNA Sequencing Reveals Fibroblast Heterogeneity Across Mouse and Human Embryonic Origins Griffin, M., King, M. W., Guardino, N., Tevlin, R., Fahy, E. J., Mascharak, S., Abbas, D., Lavin, C. V., Wan, D., Longaker, M. ELSEVIER SCIENCE INC. 2021: S201-S202

  View details for Web of Science ID 000718303100378

• Local Vitamin E Administration Improves Fat Graft Retention and Radiation-Induced Fibrosis in a Mouse Model Abbas, D. B., Lavin, C. V., Fahy, E. J., Griffin, M., King, M. E., Lee, D., Dung Nguyen, Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2021: S199

  View details for Web of Science ID 000718303100374

• Integrated spatial multiomics reveals fibroblast fate during tissue repair. Proceedings of the National Academy of Sciences of the United States of America Foster, D. S., Januszyk, M., Yost, K. E., Chinta, M. S., Gulati, G. S., Nguyen, A. T., Burcham, A. R., Salhotra, A., Ransom, R. C., Henn, D., Chen, K., Mascharak, S., Tolentino, K., Titan, A. L., Jones, R. E., da Silva, O., Leavitt, W. T., Marshall, C. D., des Jardins-Park, H. E., Hu, M. S., Wan, D. C., Wernig, G., Wagh, D., Coller, J., Norton, J. A., Gurtner, G. C., Newman, A. M., Chang, H. Y., Longaker, M. T. 2021; 118 (41)

  Abstract

  In the skin, tissue injury results in fibrosis in the form of scars composed of dense extracellular matrix deposited by fibroblasts. The therapeutic goal of regenerative wound healing has remained elusive, in part because principles of fibroblast programming and adaptive response to injury remain incompletely understood. Here, we present a multimodal -omics platform for the comprehensive study of cell populations in complex tissue, which has allowed us to characterize the cells involved in wound healing across both time and space. We employ a stented wound model that recapitulates human tissue repair kinetics and multiple Rainbow transgenic lines to precisely track fibroblast fate during the physiologic response to skin injury. Through integrated analysis of single cell chromatin landscapes and gene expression states, coupled with spatial transcriptomic profiling, we are able to impute fibroblast epigenomes with temporospatial resolution. This has allowed us to reveal potential mechanisms controlling fibroblast fate during migration, proliferation, and differentiation following skin injury, and thereby reexamine the canonical phases of wound healing. These findings have broad implications for the study of tissue repair in complex organ systems.

  View details for DOI 10.1073/pnas.2110025118

  View details for PubMedID 34620713

• A comparative analysis of deferoxamine treatment modalities for dermal radiation-induced fibrosis. Journal of cellular and molecular medicine Lavin, C. V., Abbas, D. B., Fahy, E. J., Lee, D. K., Griffin, M., Diaz Deleon, N. M., Mascharak, S., Chen, K., Momeni, A., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2021

  Abstract

  The iron chelator, deferoxamine (DFO), has been shown to potentially improve dermal radiation-induced fibrosis (RIF) in mice through increased angiogenesis and reduced oxidative damage. This preclinical study evaluated the efficacy of two DFO administration modalities, transdermal delivery and direct injection, as well as temporal treatment strategies in relation to radiation therapy to address collateral soft tissue fibrosis. The dorsum of CD-1 nude mice received 30Gy radiation, and DFO (3mg) was administered daily via patch or injection. Treatment regimens were prophylactic, during acute recovery, post-recovery, or continuously throughout the experiment (n=5 per condition). Measures included ROS-detection, histology, biomechanics and vascularity changes. Compared with irradiated control skin, DFO treatment decreased oxidative damage, dermal thickness and collagen content, and increased skin elasticity and vascularity. Metrics of improvement in irradiated skin were most pronounced with continuous transdermal delivery of DFO. In summary, DFO administration reduces dermal fibrosis induced by radiation. Although both treatment modalities were efficacious, the transdermal delivery showed greater effect than injection for each temporal treatment strategy. Interestingly, the continuous patch group was more similar to normal skin than to irradiated control skin by most measures, highlighting a promising approach to address detrimental collateral soft tissue injury following radiation therapy.

  View details for DOI 10.1111/jcmm.16913

  View details for PubMedID 34612609

• Inhibiting Fibroblast Mechanotransduction Modulates Severity of Idiopathic Pulmonary Fibrosis. Advances in wound care Trotsyuk, A. A., Chen, K., Kwon, S. H., Ma, K. C., Henn, D., Mermin-Bunnell, A. M., Mittal, S., Padmanabhan, J., Larson, M. R., Steele, S. R., Sivaraj, D., Bonham, C. A., Noishiki, C., Rodrigues, M., Jiang, Y., Jing, S., Niu, S., Chattopadhyay, A., Perrault, D. P., Leeolou, M. C., Fischer, K., Gurusankar, G., Choi Kussie, H., Wan, D. C., Januszyk, M., Longaker, M. T., Gurtner, G. C. 2021

  Abstract

  OBJECTIVE: Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease that affects 63 in every 100,000 Americans. Its etiology remains unknown, although inflammatory pathways appear to be important. Given the dynamic environment of the lung, we examined the significance of mechanotransduction on both inflammatory and fibrotic signaling during IPF.INNOVATION: Mechanotransduction pathways have not been thoroughly examined in the context of lung disease and pharmacologic approaches for IPF do not currently target these pathways. The interplay between mechanical strain and inflammation in pulmonary fibrosis remain incompletely understood.APPROACH: In this study, we used conditional KO mice to block mechanotransduction by knocking out FAK (Focal Adhesion Kinase) expression in fibroblasts, followed by induction of pulmonary fibrosis using bleomycin. We examined both normal human and human IPF fibroblasts and used immunohistochemistry, qRT-PCR, and Western Blot to evaluate the effects of FAK inhibition (FAKI) on modulating fibrotic and inflammatory genes.RESULTS: Our data indicate that deletion of FAK in mice reduces expression of fibrotic and inflammatory genes in lungs. Similarly, mechanical straining in normal human lung fibroblasts activates inflammatory and fibrotic pathways. FAK inhibition decreases these signals but has less effect on IPF fibroblasts as compared to normal human fibroblasts.CONCLUSION: Administering FAKI at early stages of fibrosis may attenuate the FAK-mediated fibrotic response pathway in IPF, potentially mediating disease progression.

  View details for DOI 10.1089/wound.2021.0077

  View details for PubMedID 34544267

• From Chronic Wounds to Scarring: The Growing Healthcare Burden of Under- and Over-healing Wounds. Advances in wound care desJardins-Park, H. E., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2021

  Abstract

  SIGNIFICANCE: Wound healing is the largest medical market without an existing small molecule/drug treatment. Both "under-healing" (chronic wounds) and "over-healing" (scarring) cause a substantial biomedical burden and lifelong consequences for patients. These problems cost tens of billions of dollars per year in the United States alone, a number expected to grow as the population ages and the prevalence of common comorbidities (e.g., diabetes) rises. However, no therapies currently exist to produce the "ideal" healing outcome: efficient wound repair via regeneration of normal tissue. Recent Advances: Ongoing research continues to illuminate possible therapeutic avenues for wound healing. By identifying underlying mechanisms of wound repair - for instance, tissue mechanics' role in fibrosis, or cell populations that modulate wound healing and scarring - novel molecular targets may be defined. This Advances in Wound Care Forum issue includes reviews of scientific literature and original research from the Hagey Laboratory for Pediatric Regenerative Medicine at Stanford and its alumni, including developing approaches for encouraging wound healing, minimizing fibrosis, and coaxing regeneration.CRITICAL ISSUES: Wound healing problems reflect an enormous and rapidly expanding clinical burden. The issues of both under- and over-healing wound outcomes will continue to expand as their underlying causes (e.g., diabetes) grow. Targeted treatments are needed to enable wound repair with functional tissue restoration and decreased scarring.FUTURE DIRECTIONS: Basic scientists will continue to refine understanding of factors driving undesirable wound outcomes. These discoveries are beginning to be translated and, in the coming years, will hopefully form the foundation for anti-scarring drugs and other wound therapeutics.

  View details for DOI 10.1089/wound.2021.0039

  View details for PubMedID 34521257

• A Novel Xenograft Model Demonstrates Human Fibroblast Behavior During Skin Wound Repair and Fibrosis. Advances in wound care Borrelli, M., Shen, A. H., Griffin, M., Mascharak, S., Adem, S., Diaz Deleon, N. M., Ngaage, L. M., Longaker, M. T., Wan, D. C., Lorenz, H. P. 2021

  Abstract

  OBJECTIVE: Xenografts of human skin on immunodeficient mice provide a means of assessing human skin physiology and its response to wounding.APPROACH: We describe a novel xenograft model using full-thickness human neonatal foreskin to examine human skin wound repair and fibroblast heterogeneity. Full-thickness 8-mm human neonatal foreskin biopsies were sutured into the dorsum of NSG (NOD.Cg-Prkdc scidIl2rgtm1Wjl/SzJ) pups as subcutaneous grafts and exposed to cutaneous grafts at the time of weaning (postnatal day 21). To model fibrosis, xenografts were wounded with 5-mm linear incisions and monitored until post-wound day (PWD) 14. To explore whether our model can be used to test the efficacy of topical therapies, wounded xenografts were injected with fibroblast growth factor-2 (FGF2) for the first four consecutive PWDs. Xenografts were harvested for analysis by histology and fluorescence-activated cell sorting (FACS).RESULTS: Xenografts successfully engrafted with evidence of mouse-human anastomoses and resembled native neonatal foreskin at the gross and microscopic level. Wounded xenografted skin scarred with human collagen and an expansion of CD26-positive human fibroblasts. Collagen scar was quantitated by neural network analysis, which revealed distinct clustering of collagen fiber networks from unwounded skin and wounded skin at PWD7 and PWD14. Collagen fiber networks within FGF2-treated wounds at PWD14 resembled those in untreated wounded xenografts at PWD7, suggesting that FGF2 treatment at time of wounding can reduce fibrosis. Innovation and Conclusion: This novel xenograft model can be used to investigate acute fibrosis, fibroblast heterogeneity, and the efficacy of antifibrotic agents during wound repair in human skin.

  View details for DOI 10.1089/wound.2020.1392

  View details for PubMedID 34521222

• Understanding Scarring in the Oral Mucosa. Advances in wound care Griffin, M., Fahy, E., King, M., Guardino, N., Chen, K., Abbas, D. B., Lavin, C., Diaz Deleon, N. M., Lorenz, H. P., Longaker, M. T., Wan, D. C. 2021

  Abstract

  SIGNIFICANCE: Skin inevitably heals with the formation of a fibrotic scar. Patients affected by skin fibrosis suffer from long-term psychological and physical burdens. Recent Advances: Since the discovery of fetal scarless skin-wound healing, research has hoped to identify and mimic scarless healing for adult skin. Oral mucosa healing in adults provides the closest example to fetal scarless healing. Injuries to the oral mucosa heal with very minimal scarring. Understanding the mechanisms through which this process occurs may bring us closer to achieving scarless healing in adults.CRITICAL ISSUES: In this review, we summarize the current evidence that illustrates distinct mechanisms involved in oral mucosal healing. We discuss the role of the oral niche in contributing to wound repair. The intrinsic properties of immune cells, fibroblasts, and keratinocytes within the oral mucosa that support regenerative repair are provided. We highlight the contribution of cytokines, growth factors, and chemokine secretion in permitting a scarless mucosal environment. Furthermore, we discuss the role of stem cell-like progenitor populations in the mucosa that may contribute to wound healing. We also provide suggestions for future studies that are needed to achieve scarless healing in adults.FUTURE DIRECTIONS: Many characteristics of the oral mucosa have been shown to contribute to decreased scarring, but the specific mechanism(s) is unclear. Advancing our understanding of oral healing may yield therapeutic therapies that can be used to overcome dermal fibrosis and scarring.

  View details for DOI 10.1089/wound.2021.0038

  View details for PubMedID 34470520

• Standardizing dimensionless cutometer parameters to determine in-vivo elasticity of human skin. Advances in wound care Abbas, D. B., Lavin, C., Fahy, E., Griffin, M., Guardino, N., King, M., Chen, K., Lorenz, H. P., Gurtner, G. C., Longaker, M. T., Momeni, A., Wan, D. C. 2021

  Abstract

  OBJECTIVE: Skin fibrosis places an enormous burden on patients and society, but disagreement exists over methods to quantify severity of skin scarring. A suction cutometer measures skin elasticity in-vivo, but it has not been widely adopted due to inconsistency in data produced. We investigated variability of several dimensionless parameters generated by the cutometer to improve their precision and accuracy.APPROACH: Twenty adult human subjects underwent suction cutometer measurement of normal skin and fibrotic scars. Using Mode 1, each subject underwent 5 trials with each trial containing 4 curves. R0/2/5/6/7 and Q1/2/3 data were collected. Analyses were performed on these calculated parameters.RESULTS: R0/2/5/6/7 and Q1/2 parameters from curves 1-4 demonstrated significant differences, while these same parameters were not significantly different when only using curves 2-4. Individual analysis of all parameters between curve 1 and every subsequent curve was statistically significant for R0, R2, R5, R6, R7, Q1, and Q2. No differences were appreciated for parameter Q3. Comparison between normal skin and fibrotic scars were significantly different for parameters R5, Q1, and Q3.INNOVATION: Our study is the first demonstration of accurate comparison between normal skin and fibrotic scars using the dimensionless parameters of a suction cutometer.CONCLUSION: Measured parameters from the first curve of each trial were significantly different from subsequent curves for both normal skin and fibrotic scars. Precision and reproducibility of data from dimensionless parameters can therefore be improved by removing the first curve. R5, Q1, and Q3 parameters differentiated normal skin as more elastic than fibrotic scars.

  View details for DOI 10.1089/wound.2021.0082

  View details for PubMedID 34470542

• JUN promotes hypertrophic skin scarring via CD36 in preclinical in vitro and in vivo models. Science translational medicine Griffin, M. F., Borrelli, M. R., Garcia, J. T., Januszyk, M., King, M., Lerbs, T., Cui, L., Moore, A. L., Shen, A. H., Mascharak, S., Diaz Deleon, N. M., Adem, S., Taylor, W. L., desJardins-Park, H. E., Gastou, M., Patel, R. A., Duoto, B. A., Sokol, J., Wei, Y., Foster, D., Chen, K., Wan, D. C., Gurtner, G. C., Lorenz, H. P., Chang, H. Y., Wernig, G., Longaker, M. T. 2021; 13 (609): eabb3312

  Abstract

  [Figure: see text].

  View details for DOI 10.1126/scitranslmed.abb3312

  View details for PubMedID 34516825

• Modulating cellular responses to mechanical forces to promote wound regeneration. Advances in wound care Mascharak, S., desJardins-Park, H. E., Davitt, M. F., Guardino, N. J., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2021

  Abstract

  SIGNIFICANCE: Skin scarring poses a major biomedical burden for hundreds of millions of patients annually. However, this burden could be mitigated by therapies that promote wound regeneration, with full recovery of skin's normal adnexa, matrix ultrastructure, and mechanical strength. Recent Advances: The observation of wound regeneration in several mouse models suggests a retained capacity for postnatal mammalian skin to regenerate under the right conditions. Mechanical forces are a major contributor to skin fibrosis and a prime target for devices and therapeutics that could promote skin regeneration.CRITICAL ISSUES: Wound induced hair neogenesis, Acomys "spiny" mice, Murphy Roths Large (MRL) mice, and mice treated with mechanotransduction inhibitors all show various degrees of wound regeneration. Comparison of regenerating wounds in these models against scarring wounds reveals differences in ECM interactions and in mechanosensitive activation of key signaling pathways, including Wnt, Sonic hedgehog, Focal Adhesion Kinase, and Yes-associated protein. The advent of single cell "omics" technologies has deepened this understanding and revealed that regeneration may recapitulate development in certain contexts, though it is unknown whether these mechanisms are relevant to healing in tight-skinned animals such as humans.FUTURE DIRECTIONS: While early findings in mice are promising, comparison across model systems is needed to resolve conflicting mechanisms and to identify conserved master regulators of skin regeneration. There also remains a dire need for studies on mechanomodulation of wounds in large, tight-skinned animals such as red Duroc pigs, which better approximate human wound healing.

  View details for DOI 10.1089/wound.2021.0040

  View details for PubMedID 34465219

• The role of Wnt signaling in skin fibrosis. Medicinal research reviews Griffin, M. F., Huber, J., Evan, F. J., Quarto, N., Longaker, M. T. 2021

  Abstract

  Skin fibrosis is the excessive deposition of extracellular matrix in the dermis. Cutaneous fibrosis can occur following tissue injury, including burns, trauma, and surgery, resulting in scars that are disfiguring, limit movement and cause significant psychological distress for patients. Many molecular pathways have been implicated in the development of skin fibrosis, yet effective treatments to prevent or reverse scarring are unknown. The Wnt signaling pathways are known to play an important role in skin homeostasis, skin injury, and in the development of fibrotic skin diseases. This review provides a detailed overview of the role of the canonical Wnt signaling pathways in regulating skin scarring. We also discuss how Wnt signaling interacts with other known fibrotic molecular pathways to cause skin fibrosis. We further provide a summary of the different Wnt inhibitor types available for treating skin scarring. Understanding the role of the Wnt pathway in cutaneous fibrosis will accelerate the development of effective Wnt modulators for the treatment of skin fibrosis.

  View details for DOI 10.1002/med.21853

  View details for PubMedID 34431110

• Decellularized Adipose Matrices can Alleviate Radiation-induced Skin Fibrosis. Advances in wound care Adem, S., Abbas, D. B., Lavin, C., Fahy, E., Griffin, M., Diaz Deleon, N. M., Borrelli, M. R., Mascharak, S., Shen, A. H., Patel, R. A., Longaker, M. T., Nazerali, R. S., Wan, D. C. 2021

  Abstract

  OBJECTIVE: Radiation therapy is commonplace for cancer treatment but often results in fibrosis and atrophy of surrounding soft tissue. Decellularized adipose matrices (DAMs) have been reported to improve these soft tissue defects through the promotion of adipogenesis. These matrices are decellularized by a combination of physical, chemical, and enzymatic methods to minimize their immunologic effects while promoting their regenerative effects. In this study, we aimed to explore the regenerative ability of a DAM (Renuva, MTF Biologics, New Jersey, USA) in radiation-induced soft tissue injury.APPROACH: Fresh human lipoaspirate or DAM was injected into the irradiated scalp of CD-1 nude mice, and volume retention was monitored radiographically over 8 weeks. Explanted grafts were histologically assessed, and overlying skin was examined histologically and biomechanically. Irradiated human skin was also evaluated from patients following fat grafting or DAM injection. However, integrating data between murine and human skin in all cohorts is limited given the genetic variability between the two species.RESULTS: Volume retention was found to be greater with fat grafts, though DAM retention was nonetheless appreciated at irradiated sites. Improvement in both mouse and human irradiated skin overlying fat and DAM grafts was observed in terms of biomechanical stiffness, dermal thickness, collagen density, collagen fiber networks, and skin vascularity.INNOVATION: This is the first demonstration of the use of DAMs for augmenting the regenerative potential of irradiated mouse and human skin.CONCLUSIONS: These findings support use of DAMs to address soft tissue atrophy following radiation therapy. Morphological characteristics of the irradiated skin can also be improved with DAM grafting.

  View details for DOI 10.1089/wound.2021.0008

  View details for PubMedID 34346243

• Skeletal stem and progenitor cells maintain cranial suture patency and prevent craniosynostosis. Nature communications Menon, S., Salhotra, A., Shailendra, S., Tevlin, R., Ransom, R. C., Januszyk, M., Chan, C. K., Behr, B., Wan, D. C., Longaker, M. T., Quarto, N. 2021; 12 (1): 4640

  Abstract

  Cranial sutures are major growth centers for the calvarial vault, and their premature fusion leads to a pathologic condition called craniosynostosis. This study investigates whether skeletal stem/progenitor cells are resident in the cranial sutures. Prospective isolation by FACS identifies this population with a significant difference in spatio-temporal representation between fusing versus patent sutures. Transcriptomic analysis highlights a distinct signature in cellsderived from the physiological closing PF suture, and scRNA sequencing identifies transcriptional heterogeneity among sutures. Wnt-signaling activation increases skeletal stem/progenitor cells in sutures, whereas its inhibition decreases. Crossing Axin2LacZ/+ mouse, endowing enhanced Wnt activation, to a Twist1+/- mouse model of coronal craniosynostosis enriches skeletal stem/progenitor cells in sutures restoring patency. Co-transplantation of these cells with Wnt3a prevents resynostosis following suturectomy in Twist1+/- mice. Our study reveals that decrease and/or imbalance of skeletal stem/progenitor cells representation within sutures may underlie craniosynostosis. These findings have translational implications toward therapeutic approaches for craniosynostosis.

  View details for DOI 10.1038/s41467-021-24801-6

  View details for PubMedID 34330896

• Distinct skeletal stem cell types orchestrate long bone skeletogenesis. eLife Ambrosi, T. H., Sinha, R., Steininger, H. M., Hoover, M. Y., Murphy, M. P., Koepke, L. S., Wang, Y., Lu, W., Morri, M., Neff, N. F., Weissman, I. L., Longaker, M. T., Chan, C. K. 2021; 10

  Abstract

  Skeletal stem and progenitor cell populations are crucial for bone physiology. Characterization of these cell types remains restricted to heterogenous bulk populations with limited information on whether they are unique or overlap with previously characterized cell types. Here we show, through comprehensive functional and single-cell transcriptomic analyses, that postnatal long bones of mice contain at least two types of bone progenitors with bona fide skeletal stem cell (SSC) characteristics. An early osteochondral SSC (ocSSC) facilitates long bone growth and repair, while a second type, a perivascular SSC (pvSSC), co-emerges with long bone marrow and contributes to shape the hematopoietic stem cell niche and regenerative demand. We establish that pvSSCs, but not ocSSCs, are the origin of bone marrow adipose tissue. Lastly, we also provide insight into residual SSC heterogeneity as well as potential crosstalk between the two spatially distinct cell populations. These findings comprehensively address previously unappreciated shortcomings of SSC research.

  View details for DOI 10.7554/eLife.66063

  View details for PubMedID 34280086

• Mechanical Strain Drives Myeloid Cell Differentiation Toward Pro-Inflammatory Subpopulations. Advances in wound care Chen, K., Henn, D., Sivaraj, D., Bonham, C. A., Griffin, M., Choi Kussie, H., Padmanabhan, J., Trotsyuk, A. A., Wan, D. C., Januszyk, M., Longaker, M. T., Gurtner, G. C. 2021

  Abstract

  OBJECTIVE: After injury, humans and other mammals heal by forming fibrotic scar tissue with diminished function, and this healing process involves the dynamic interplay between resident cells within the skin and cells recruited from the circulation. Recent studies have provided mounting evidence that external mechanical forces stimulate intracellular signaling pathways to drive fibrotic processes.INNOVATION: While most studies have focused on studying mechanotransduction in fibroblasts, recent data suggest that mechanical stimulation may also shape the behavior of immune cells, referred to as "mechano-immunomodulation". However, the effect of mechanical strain on myeloid cell recruitment and differentiation remains poorly understood and has never been investigated at the single cell level.APPROACH: In this study, we utilized a three-dimensional (3D) in vitro culture system that permits the precise manipulation of mechanical strain applied to cells. We cultured myeloid cells and used single cell RNA-sequencing to interrogate the effects of strain on myeloid differentiation and transcriptional programming.RESULTS: Our data indicate that myeloid cells are indeed mechanoresponsive, with mechanical stress influencing myeloid differentiation. Mechanical strain also upregulated a cascade of inflammatory chemokines, most notably from the Ccl family.CONCLUSION: Further understanding of how mechanical stress affects myeloid cells in conjunction with other cell types in the complicated, multicellular milieu of wound healing may lead to novel insights and therapies for the treatment of fibrosis.

  View details for DOI 10.1089/wound.2021.0036

  View details for PubMedID 34278820

• Deferoxamine to minimize fibrosis during radiation therapy. Advances in wound care Tevlin, R., Longaker, M. T., Wan, D. 2021

  Abstract

  Significance By 2030, there will be over 4 million radiation-treated cancer survivors living in the US. Irradiation triggers inflammation, fibroblast activation, and extracellular matrix deposition in addition to reactive oxygen species (ROS) generation, leading to a chronic inflammatory response. Radiation-induced fibrosis (RIF) is a progressive pathology resulting in skin pigmentation, reduced elasticity, ulceration and dermal thickening, cosmetic deformity, pain, and the need for reconstructive surgery. Recent Advances Deferoxamine (DFO) is an FDA-approved iron chelator for blood dyscrasia management, which has been found to be pro-angiogenic, to decrease free radical formation, and reduce cell death. DFO has shown great promise in the treatment and prophylaxis of RIF in preclinical studies. Critical Issues Systemic DFO has a short half-life and is cumbersome to deliver to patients intravenously. Transdermal DFO delivery is complicated by its high atomic mass and hydrophilicity, preventing stratum corneum penetration. A transdermal drug delivery system was developed to address these challenges, in addition to a strategy for topical administration. Future Directions DFO has great potential to translate from bench to bedside. An important step in translation of DFO for RIF prophylaxis is to ensure that DFO treatment does not affect the efficacy of radiation therapy. Furthermore, following an initial plethora of studies reporting DFO treatment by intravenous and subcutaneous routes, a significant advantage of recent studies is the success of transdermal and topical delivery. Given the strong foundation of basic scientific research supporting the use of DFO treatment on RIF, clinicians will be closely following the results of the ongoing human studies.

  View details for DOI 10.1089/wound.2021.0021

  View details for PubMedID 34074152

• Disrupting Mechanotransduction Reduces Scar Formation And Restores Cellular Subpopulations In A Large Animal Model Of Skin Grafting Chen, K., Henn, D., Bonham, C. A., Noishiki, C., Barrera, J. A., Carlomagno, T. C., Shannon, T., Mays, C. J., Trotsyuk, A. A., Padmanabhan, J., Longaker, M. T., Januszyk, M., Gurtner, G. C. WILEY. 2021: A12-A13

  View details for Web of Science ID 000650720500039

• Single Cell RNA Sequencing Reveals Fibroblast Heterogeneity Across Embryonic Origins Of Skin Griffin, M., King, M., Chen, K., desJardins-Park, H., Mascharak, S., Fahy, E., Guardino, N., Lavin, C., Abbas, D., Januszyk, M., Wan, D., Longaker, M. WILEY. 2021: A11-A12

  View details for Web of Science ID 000650720500037

• Novel Genetic Analysis Of MRL Mice Reveals That Complement Inhibition By Factor H Reduces Scarring desJardins-Park, H. E., Mack, K. L., Guardino, N., Griffin, M., Davitt, M. F., Mascharak, S., Wan, D. C., Fraser, H. B., Longaker, M. T. WILEY. 2021: A13

  View details for Web of Science ID 000650720500040

• Adipocytes In Dermal Wounds Undergo Conversion To Pro-fibrotic Fibroblasts That Contribute To Scar Formation Guardino, N., desJardins-Park, H. E., Griffin, M., Bauer-Rowe, K. E., King, M. E., King, M. E., Mascharak, S., Longaker, M. T. WILEY. 2021: A31

  View details for Web of Science ID 000650720500078

• Transgenic Inhibition Of Engrailed-1 Results In Endogenous Postnatal Skin Regeneration Mascharak, S., desJardins-Park, H. E., Davitt, M. F., Chen, K., Griffin, M., Guardino, N., Lorenz, H., Wan, D. C., Gurtner, G. C., Longaker, M. T. WILEY. 2021: A14-A15

  View details for Web of Science ID 000650720500043

• Wnt-active Engrailed-1 Lineage-negative Fibroblasts Mediate Postnatal Skin Regeneration Mascharak, S., desJardins-Park, H. E., Januszyk, M., Chen, K., Davitt, M. F., Demeter, J., Henn, D., Griffin, M., Bonham, C. A., Mooney, N., Cheng, R., Jackson, P. K., Wan, D. C., Gurtner, G. C., Longaker, M. T. WILEY. 2021: A30

  View details for Web of Science ID 000650720500076

• Preventing Engrailed-1 activation in fibroblasts yields wound regeneration without scarring. Science (New York, N.Y.) Mascharak, S., desJardins-Park, H. E., Davitt, M. F., Griffin, M., Borrelli, M. R., Moore, A. L., Chen, K., Duoto, B., Chinta, M., Foster, D. S., Shen, A. H., Januszyk, M., Kwon, S. H., Wernig, G., Wan, D. C., Lorenz, H. P., Gurtner, G. C., Longaker, M. T. 2021; 372 (6540)

  Abstract

  Skin scarring, the end result of adult wound healing, is detrimental to tissue form and function. Engrailed-1 lineage-positive fibroblasts (EPFs) are known to function in scarring, but Engrailed-1 lineage-negative fibroblasts (ENFs) remain poorly characterized. Using cell transplantation and transgenic mouse models, we identified a dermal ENF subpopulation that gives rise to postnatally derived EPFs by activating Engrailed-1 expression during adult wound healing. By studying ENF responses to substrate mechanics, we found that mechanical tension drives Engrailed-1 activation via canonical mechanotransduction signaling. Finally, we showed that blocking mechanotransduction signaling with either verteporfin, an inhibitor of Yes-associated protein (YAP), or fibroblast-specific transgenic YAP knockout prevents Engrailed-1 activation and promotes wound regeneration by ENFs, with recovery of skin appendages, ultrastructure, and mechanical strength. This finding suggests that there are two possible outcomes to postnatal wound healing: a fibrotic response (EPF-mediated) and a regenerative response (ENF-mediated).

  View details for DOI 10.1126/science.aba2374

  View details for PubMedID 33888614

• Wounds Inhibit Tumor Growth In Vivo ANNALS OF SURGERY Hu, M. S., Maan, Z. N., Leavitt, T., Hong, W., Rennert, R. C., Marshall, C. D., Borrelli, M. R., Zhu, T. N., Esquivel, M., Zimmermann, A., McArdle, A., Chung, M. T., Foster, D. S., Jones, R., Gurtner, G. C., Giaccia, A. J., Lorenz, H., Weissman, I. L., Longaker, M. T. 2021; 273 (1): 173–80

  View details for DOI 10.1097/SLA.0000000000003255

  View details for Web of Science ID 000613348700039

• An Evolutionary Conserved Signaling Network Between Mouse and Human Underlies the Differential Osteoskeletal Potential of Frontal and Parietal Calvarial Bones. Frontiers in physiology Menon, S., Huber, J., Duldulao, C., Longaker, M. T., Quarto, N. 2021; 12: 747091

  Abstract

  The mammalian calvarial vault is an ancient and highly conserved structure among species, however, the mechanisms governing osteogenesis of the calvarial vault and how they might be conserved across mammalian species remain unclear. The aim of this study was to determine if regional differences in osteogenic potential of the calvarial vault, first described in mice, extend to humans. We derived human frontal and parietal osteoblasts from fetal calvarial tissue, demonstrating enhanced osteogenic potential both in vitro and in vivo of human frontal derived osteoblasts compared to parietal derived osteoblasts. Furthermore, we found shared differential signaling patterns in the canonical WNT, TGF-beta, BMP, and FGF pathways previously described in the mouse to govern these regional differences in osteogenic potential. Taken together, our findings unveil evolutionary conserved similarities both at functional and molecular level between the mouse and human calvarial bones, providing further support that studies employing mouse models, are suitable for translational studies to human.

  View details for DOI 10.3389/fphys.2021.747091

  View details for PubMedID 34744787

• Striae Distensae: Scars without Wounds. Plastic and reconstructive surgery Borrelli, M. R., Griffin, M., Ngaage, L. M., Longaker, M. T., Lorenz, H. P. 2021; 148 (1): 77-87

  Abstract

  Striae distensae, or stretch marks, are common linear lesions of atrophic skin characterized histologically by epidermal atrophy, absent rete ridges, and alterations in connective tissue architecture. Hormonal excess, mechanical stress, and genetic predisposition are all associated with striae distensae, but their exact pathogenesis remains unknown. Despite a multitude of options, no single treatment has yet proven effective. In this article, the authors describe an up-to-date overview of striae distensae in terms of their etiology, pathophysiology, and therapeutic options. Further research is required to better elucidate their pathophysiology and to develop targeted effective treatments.

  View details for DOI 10.1097/PRS.0000000000008065

  View details for PubMedID 34181606

• Aged skeletal stem cells generate an inflammatory degenerative niche. Nature Ambrosi, T. H., Marecic, O., McArdle, A., Sinha, R., Gulati, G. S., Tong, X., Wang, Y., Steininger, H. M., Hoover, M. Y., Koepke, L. S., Murphy, M. P., Sokol, J., Seo, E. Y., Tevlin, R., Lopez, M., Brewer, R. E., Mascharak, S., Lu, L., Ajanaku, O., Conley, S. D., Seita, J., Morri, M., Neff, N. F., Sahoo, D., Yang, F., Weissman, I. L., Longaker, M. T., Chan, C. K. 2021

  Abstract

  Loss of skeletal integrity during ageing and disease is associated with an imbalance in the opposing actions of osteoblasts and osteoclasts1. Here we show that intrinsic ageing of skeletal stem cells (SSCs)2 in mice alters signalling in the bone marrow niche and skews the differentiation of bone and blood lineages, leading to fragile bones that regenerate poorly. Functionally, aged SSCs have a decreased bone- and cartilage-forming potential but produce more stromal lineages that express high levels of pro-inflammatory and pro-resorptive cytokines. Single-cell RNA-sequencing studies link the functional loss to a diminished transcriptomic diversity of SSCs in aged mice, which thereby contributes to the transformation of the bone marrow niche. Exposure to a youthful circulation through heterochronic parabiosis or systemic reconstitution with young haematopoietic stem cells did not reverse the diminished osteochondrogenic activity of aged SSCs, or improve bone mass or skeletal healing parameters in aged mice. Conversely, the aged SSC lineage promoted osteoclastic activity and myeloid skewing by haematopoietic stem and progenitor cells, suggesting that the ageing of SSCs is a driver of haematopoietic ageing. Deficient bone regeneration in aged mice could only be returned to youthful levels by applying a combinatorial treatment of BMP2 and a CSF1 antagonist locally to fractures, which reactivated aged SSCs and simultaneously ablated the inflammatory, pro-osteoclastic milieu. Our findings provide mechanistic insights into the complex, multifactorial mechanisms that underlie skeletal ageing and offer prospects for rejuvenating the aged skeletal system.

  View details for DOI 10.1038/s41586-021-03795-7

  View details for PubMedID 34381212

• Disrupting biological sensors of force promotes tissue regeneration in large organisms. Nature communications Chen, K., Kwon, S. H., Henn, D., Kuehlmann, B. A., Tevlin, R., Bonham, C. A., Griffin, M., Trotsyuk, A. A., Borrelli, M. R., Noishiki, C., Padmanabhan, J., Barrera, J. A., Maan, Z. N., Dohi, T., Mays, C. J., Greco, A. H., Sivaraj, D., Lin, J. Q., Fehlmann, T., Mermin-Bunnell, A. M., Mittal, S., Hu, M. S., Zamaleeva, A. I., Keller, A., Rajadas, J., Longaker, M. T., Januszyk, M., Gurtner, G. C. 2021; 12 (1): 5256

  Abstract

  Tissue repair and healing remain among the most complicated processes that occur during postnatal life. Humans and other large organisms heal by forming fibrotic scar tissue with diminished function, while smaller organisms respond with scarless tissue regeneration and functional restoration. Well-established scaling principles reveal that organism size exponentially correlates with peak tissue forces during movement, and evolutionary responses have compensated by strengthening organ-level mechanical properties. How these adaptations may affect tissue injury has not been previously examined in large animals and humans. Here, we show that blocking mechanotransduction signaling through the focal adhesion kinase pathway in large animals significantly accelerates wound healing and enhances regeneration of skin with secondary structures such as hair follicles. In human cells, we demonstrate that mechanical forces shift fibroblasts toward pro-fibrotic phenotypes driven by ERK-YAP activation, leading to myofibroblast differentiation and excessive collagen production. Disruption of mechanical signaling specifically abrogates these responses and instead promotes regenerative fibroblast clusters characterized by AKT-EGR1.

  View details for DOI 10.1038/s41467-021-25410-z

  View details for PubMedID 34489407

• Xenogeneic skin transplantation promotes angiogenesis and tissue regeneration through activated Trem2+ macrophages. Science advances Henn, D., Chen, K., Fehlmann, T., Trotsyuk, A. A., Sivaraj, D., Maan, Z. N., Bonham, C. A., Barrera, J. A., Mays, C. J., Greco, A. H., Moortgat Illouz, S. E., Lin, J. Q., Steele, S. R., Foster, D. S., Padmanabhan, J., Momeni, A., Nguyen, D., Wan, D. C., Kneser, U., Januszyk, M., Keller, A., Longaker, M. T., Gurtner, G. C. 2021; 7 (49): eabi4528

  Abstract

  [Figure: see text].

  View details for DOI 10.1126/sciadv.abi4528

  View details for PubMedID 34851663

• Endogenous Mechanisms of Craniomaxillofacial Repair: Toward Novel Regenerative Therapies. Frontiers in oral health desJardins-Park, H. E., Mascharak, S., Longaker, M. T., Wan, D. C. 1800; 2: 676258

  Abstract

  In the fields of oral and craniomaxillofacial surgery, regeneration of multiple tissue types-including bone, skin, teeth, and mucosal soft tissue-is often a desired outcome. However, limited endogenous capacity for regeneration, as well as predisposition of many tissues to fibrotic healing, may prevent recovery of normal form and function for patients. Recent basic science research has advanced our understanding of molecular and cellular pathways of repair in the oral/craniofacial region and how these are influenced by local microenvironment and embryonic origin. Here, we review the current state of knowledge in oral and craniomaxillofacial tissue repair/regeneration in four key areas: bone (in the context of calvarial defects and mandibular regeneration during distraction osteogenesis); skin (in the context of cleft lip/palate surgery); oral mucosa (in the context of minimally scarring repair of mucosal injuries); and teeth (in the context of dental disease/decay). These represent four distinct healing processes and outcomes. We will discuss both divergent and conserved pathways of repair in these contexts, with an eye toward fundamental mechanisms of regeneration vs. fibrosis as well as translational research directions. Ultimately, this knowledge can be leveraged to develop new cell-based and molecular treatment strategies to encourage bone and soft tissue regeneration in oral and craniomaxillofacial surgery.

  View details for DOI 10.3389/froh.2021.676258

  View details for PubMedID 35048022

• Angiogenic CD34+CD146+ adipose-derived stromal cells augment recovery of soft tissue after radiotherapy. Journal of tissue engineering and regenerative medicine Diaz Deleon, N. M., Adem, S., Lavin, C. V., Abbas, D. B., Griffin, M., King, M. E., Borrelli, M. R., Patel, R. A., Fahy, E. J., Lee, D., Shen, A. H., Momeni, A., Longaker, M. T., Wan, D. C. 2021

  Abstract

  Radiation therapy is effective for cancer treatment but may also result in collateral soft tissue contracture, contour deformities, and non-healing wounds. Autologous fat transfer has been described to improve tissue architecture and function of radiation-induced fibrosis and these effects may be augmented by enrichment with specific adipose-derived stromal cells (ASCs) with enhanced angiogenic potential. CD34+CD146+, CD34+CD146-, or CD34+ unfractionated (UF) human ASCs were isolated by flow cytometry and used to supplement human lipoaspirate placed beneath the scalp of irradiated mice. Volume retention was followed radiographically and fat grafts as well as overlying soft tissue were harvested after eight weeks for histologic and biomechanical analyses. Radiographic evaluation revealed the highest volume retention in fat grafts supplemented with CD34+CD146+ ASCs, and these grafts were also found to have greater histologic integrity than other groups. Irradiated skin overlying CD34+CD146+ ASC-enriched grafts was significantly more vascularized than other treatment groups, had significantly less dermal thickness and collagen deposition, and the greatest improvement in fibrillin staining and return of elasticity. Radiation therapy obliterates vascularity and contributes to scarring and loss of tissue function. ASC-enrichment of fat grafts with CD34+CD146+ ASCs not only enhances fat graft vascularization and retention, but also significantly promotes improvement in overlying radiation-injured soft tissue. This regenerative effect on skin is highly promising for patients with impaired wound healing and deformities following radiotherapy. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1002/term.3253

  View details for PubMedID 34582109

• Epidermal-Derived Hedgehog Signaling Drives Mesenchymal Proliferation during Digit Tip Regeneration. Journal of clinical medicine Maan, Z. N., Rinkevich, Y., Barrera, J., Chen, K., Henn, D., Foster, D., Bonham, C. A., Padmanabhan, J., Sivaraj, D., Duscher, D., Hu, M., Yan, K., Januszyk, M., Longaker, M. T., Weissman, I. L., Gurtner, G. C. 2021; 10 (18)

  Abstract

  Hand injuries often result in significant functional impairments and are rarely completely restored. The spontaneous regeneration of injured appendages, which occurs in salamanders and newts, for example, has been reported in human fingertips after distal amputation, but this type of regeneration is rare in mammals and is incompletely understood. Here, we study fingertip regeneration by amputating murine digit tips, either distally to initiate regeneration, or proximally, causing fibrosis. Using an unbiased microarray analysis, we found that digit tip regeneration is significantly associated with hair follicle differentiation, Wnt, and sonic hedgehog (SHH) signaling pathways. Viral over-expression and genetic knockouts showed the functional significance of these pathways during regeneration. Using transgenic reporter mice, we demonstrated that, while both canonical Wnt and HH signaling were limited to epidermal tissues, downstream hedgehog signaling (through Gli) occurred in mesenchymal tissues. These findings reveal a mechanism for epidermal/mesenchyme interactions, governed by canonical hedgehog signaling, during digit regeneration. Further research into these pathways could lead to improved therapeutic outcomes after hand injuries in humans.

  View details for DOI 10.3390/jcm10184261

  View details for PubMedID 34575372

• Discussion: Overcoming the Patent Gap: A Guide to Patenting for Plastic Surgeons. Plastic and reconstructive surgery Januszyk, M., desJardins-Park, H. E., Gurtner, G. C., Longaker, M. T. 2021; 148 (4): 918-919

  View details for DOI 10.1097/PRS.0000000000008394

  View details for PubMedID 34550949

• The Adrenergic System in Plastic and Reconstructive Surgery: Physiology and Clinical Considerations. Annals of plastic surgery Fahy, E. J., Griffin, M. n., Lavin, C. n., Abbas, D. n., Longaker, M. T., Wan, D. n. 2021

  Abstract

  The primary organ systems and tissues concerning plastic and reconstructive surgery include the integument, vasculature, subcutis, and peripheral nerves, because these may individually or collectively be injured requiring reconstruction, or indeed be used in reconstruction themselves through grafts, flaps, or anastomoses. Adrenergic receptors are present throughout these anatomic components on the vasculature, adipose, platelets, immune cells, keratinocytes, melanocytes, fibroblasts, peripheral nerves, and tendons. Herein, the influence of adrenergic signaling on the physiology of anatomic components related to plastic surgery is discussed, along with clinical considerations of this systems involvement in procedures, such as free flap reconstruction, skin grafting, fat grafting, and other areas relevant to plastic and reconstructive surgery. Current evidence as well as potential for further investigation is discussed.

  View details for DOI 10.1097/SAP.0000000000002706

  View details for PubMedID 33833152

• Proceed with Caution: Mouse Deep Digit Flexor Tendon Injury Model. Plastic and reconstructive surgery. Global open Titan, A. L., Fahy, E. n., Chen, K. n., Foster, D. S., Bennett-Kennett, R. n., Dauskardt, R. H., Gurtner, G. C., Chang, J. n., Fox, P. M., Longaker, M. T. 2021; 9 (1): e3359

  Abstract

  The purpose of this study was to determine the feasibility of using mouse models for translational study of flexor tendon repair and reconstruction.Quantitative data detailing the gross anatomy, biomechanical characteristics, and microscopic structure of the deep digit flexor tendon (DDF) of the mouse hindpaw were obtained. Histological characterization of the DDF and the anatomy of the digit in the mouse hindpaw are detailed. Biomechanical testing determined the load-to-failure, stress, elastic modulus, and the site of tendon failure.In gross anatomy, the origins and insertions of the mouse deep digit flexor tendon are similar to those of the human digit, surrounded by a synovial sheath that is only 1- to 2-cells thick. A neurovascular network runs on each side of the digit outside the synovial sheath, but does not clearly penetrate it. The thickness of the DDF is 0.14 ± 0.03 mm and the width is 0.3 ± 0.03 mm. The thickness of the DDF is less than that of 9-0 nylon needle. The mean failure force of the deep flexor tendon was 2.79 ± 0.53N.The gross anatomy of the mouse hindpaw digit is similar to that of the human digit except for key differences seen in the synovial sheath and vascular supply. The dimensions of the mouse DDF make it challenging to create a clinically translatable repair model using currently available surgical techniques. Despite the similarities between the human and mouse anatomy, and the powerful basic science tools available in murine models, mice are an unreliable model for assessing flexor tendon injury and repair.

  View details for DOI 10.1097/GOX.0000000000003359

  View details for PubMedID 33552814

  View details for PubMedCentralID PMC7859083

• Craniofacial and Long Bone Development in the Context of Distraction Osteogenesis. Plastic and reconstructive surgery Shah, H. N., Jones, R. E., Borrelli, M. R., Robertson, K. n., Salhotra, A. n., Wan, D. C., Longaker, M. T. 2021; 147 (1): 54e–65e

  Abstract

  Bone retains regenerative potential into adulthood, and surgeons harness this plasticity during distraction osteogenesis. The underlying biology governing bone development, repair, and regeneration is divergent between the craniofacial and appendicular skeleton. Each type of bone formation is characterized by unique molecular signaling and cellular behavior. Recent discoveries have elucidated the cellular and genetic processes underlying skeletal development and regeneration, providing an opportunity to couple biological and clinical knowledge to improve patient care.A comprehensive literature review of basic and clinical literature regarding craniofacial and long bone development, regeneration, and distraction osteogenesis was performed.The current understanding in craniofacial and long bone development and regeneration is discussed, and clinical considerations for the respective distraction osteogenesis procedures are presented.Distraction osteogenesis is a powerful tool to regenerate bone and thus address a number of craniofacial and appendicular skeletal deficiencies. The molecular mechanisms underlying bone regeneration, however, remain elusive. Recent work has determined that embryologic morphogen gradients constitute important signals during regeneration. In addition, striking discoveries have illuminated the cellular processes underlying mandibular regeneration during distraction osteogenesis, showing that skeletal stem cells reactivate embryologic neural crest transcriptomic processes to carry out bone formation during regeneration. Furthermore, innovative adjuvant therapies to complement distraction osteogenesis use biological processes active in embryogenesis and regeneration. Additional research is needed to further characterize the underlying cellular mechanisms responsible for improved bone formation through adjuvant therapies and the role skeletal stem cells play during regeneration.

  View details for DOI 10.1097/PRS.0000000000007451

  View details for PubMedID 33370054

• Exosomes - a tool for bone tissue engineering. Tissue engineering. Part B, Reviews Huber, J. L., Griffin, M., Longaker, M. T., Quarto, N. 2020

  Abstract

  Mesenchymal stem cells (MSC) have been repeatedly shown to be a valuable source for cell-based therapy in regenerative medicine, including bony tissue repair. However, engraftment at the injury site is poor. Recently, it has been suggested that MSCs and other cells act via a paracrine signaling mechanism. Exosomes are nanostructures that have been implicated in this process. They carry DNA, RNA, proteins and lipids and play an important role in cell-to-cell communication directly modulating their target cell at a transcriptional level. In a bone microenvironment, they have been shown to increase osteogenesis and osteogenic differentiation in vivo and in vitro. In the following review, we will discuss the most advanced and significant knowledge of biological functions of exosomes in bone regeneration and their clinical applications in osseous diseases.

  View details for DOI 10.1089/ten.TEB.2020.0246

  View details for PubMedID 33297857

• Prrx1 Fibroblasts Represent a Pro-fibrotic Lineage in the Mouse Ventral Dermis. Cell reports Leavitt, T., Hu, M. S., Borrelli, M. R., Januszyk, M., Garcia, J. T., Ransom, R. C., Mascharak, S., desJardins-Park, H. E., Litzenburger, U. M., Walmsley, G. G., Marshall, C. D., Moore, A. L., Duoto, B., Adem, S., Foster, D. S., Salhotra, A., Shen, A. H., Griffin, M., Shen, E. Z., Barnes, L. A., Zielins, E. R., Maan, Z. N., Wei, Y., Chan, C. K., Wan, D. C., Lorenz, H. P., Chang, H. Y., Gurtner, G. C., Longaker, M. T. 2020; 33 (6): 108356

  Abstract

  Fibroblast heterogeneity has been shown within the unwounded mouse dorsal dermis, with fibroblast subpopulations being identified according to anatomical location and embryonic lineage. Using lineage tracing, we demonstrate that paired related homeobox 1 (Prrx1)-expressing fibroblasts are responsible for acute and chronic fibroses in the ventral dermis. Single-cell transcriptomics further corroborated the inherent fibrotic characteristics of Prrx1 fibroblasts during wound repair. In summary, we identify and characterize a fibroblast subpopulation in the mouse ventral dermis with intrinsic scar-forming potential.

  View details for DOI 10.1016/j.celrep.2020.108356

  View details for PubMedID 33176144

• Skeletal Stem Cells-A Paradigm Shift in the Field of Craniofacial Bone Tissue Engineering. Frontiers in dental medicine Tevlin, R., Longaker, M. T., Wan, D. C. 2020; 1

  Abstract

  Defects of the craniofacial skeleton arise as a direct result of trauma, diseases, oncological resection, or congenital anomalies. Current treatment options are limited, highlighting the importance for developing new strategies to restore form, function, and aesthetics of missing or damaged bone in the face and the cranium. For optimal reconstruction, the goal is to replace "like with like." With the inherent challenges of existing options, there is a clear need to develop alternative strategies to reconstruct the craniofacial skeleton. The success of mesenchymal stem cell-based approaches has been hampered by high heterogeneity of transplanted cell populations with inconsistent preclinical and clinical trial outcomes. Here, we discuss the novel characterization and isolation of mouse skeletal stem cell (SSC) populations and their response to injury, systemic disease, and how their re-activation in vivo can contribute to tissue regeneration. These studies led to the characterization of human SSCs which are able to self-renew, give rise to increasingly fate restricted progenitors, and differentiate into bone, cartilage, and bone marrow stroma, all on the clonal level in vivo without prior in vitro culture. SSCs hold great potential for implementation in craniofacial bone tissue engineering and regenerative medicine. As we begin to better understand the diversity and the nature of skeletal stem and progenitor cells, there is a tangible future whereby a subset of human adult SSCs can be readily purified from bone or activated in situ with broad potential applications in craniofacial tissue engineering.

  View details for DOI 10.3389/fdmed.2020.596706

  View details for PubMedID 35664558

  View details for PubMedCentralID PMC9161996

• Ectoderm-Derived Wnt and Hedgehog Signaling Drive Digit Tip Regeneration Barrera, J., Maan, Z. N., Foster, D., Henn, D., Chen, K., Bonham, C., Januszyk, M., Longaker, M. T., Weissman, I., Gurtner, G. C. ELSEVIER SCIENCE INC. 2020: S186

  View details for Web of Science ID 000582792300339

• Understanding Long Bone Regeneration through the Development of a Novel Murine Distraction Device Shah, H. N., Salhotra, A., Wan, D. C., Longaker, M. T. ELSEVIER SCIENCE INC. 2020: E173

  View details for Web of Science ID 000582798100387

• Detection, Scoring, and Classification of Solid Organ Fibroses with Machine Learning Analysis Mascharak, S., desJardins-Park, H. E., Davitt, M., Foster, D. S., Chinta, M., Wan, D. C., Wernig, G., Longaker, M. T. ELSEVIER SCIENCE INC. 2020: S222

  View details for Web of Science ID 000582792300403

• Adipose-Derived Stromal Cells within Transplanted Fat Hone to Blood Vessels and Assume a Pericyte Structure Borrelli, M. R., Adem, S., Deleon, N., Abbas, D., Momeni, A., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2020: E183

  View details for Web of Science ID 000582798100412

• A Surgical Model for Investigating the Role of Creeping Fat in Intestinal Fibrosis Bauer-Rowe, K. E., Foster, D., Titan, A., Chinta, M., desJardins-Park, H., Griffin, M., Longaker, M. T. ELSEVIER SCIENCE INC. 2020: S50–S51

  View details for Web of Science ID 000582792300070

• Grafted Fat Depletes the Profibrotic Engrailed-1-Positive Fibroblast Subpopulation and Ameliorates Radiation-Induced Scalp Fibrosis Borrelli, M. R., Deleon, N., Adem, S., Abbas, D., Momeni, A., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2020: E186

  View details for Web of Science ID 000582798100420

• Elucidating Molecular Drivers of Wound Regeneration in MRL Mice Via Novel Transcriptomic Analyses desJardins-Park, H. E., Mack, K. L., Davitt, M. F., Griffin, M., Mascharak, S., Fraser, H. B., Longaker, M. T. ELSEVIER SCIENCE INC. 2020: S225

  View details for Web of Science ID 000582792300410

• Radiation-Induced Soft Tissue Atrophy Impaired by Enhancement of Fat Grafts with CD146+Subpopulation of Adipose-Derived Stromal Cells Deleon, N., Borrelli, M. R., Adem, S., Shen, A., Abbas, D., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2020: E186

  View details for Web of Science ID 000582798100421

• Fat Grafting Depletes Profibrotic Prrx1-Positive Fibroblasts in Irradiated Skin and Mitigates Radiation-Induced Groin Contracture Borrelli, M. R., Adem, S., Deleon, N., Abbas, D., Chen, K., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2020: S225–S226

  View details for Web of Science ID 000582792300411

• Transdermal Deferoxamine Reduces Radiation-Induced Damage in Porcine Skin Adem, S., Deleon, N., Chen, K., Borrelli, M. R., Shen, A. H., Noishiki, C., Patel, R. A., Gurtner, G. C., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2020: E46–E47

  View details for Web of Science ID 000582798100088

• Transdermal Deferoxamine Treatment Mitigates Fibrosis in Irradiated Skin Shen, A. H., Borrelli, M. R., Deleon, N., Adem, S., Mascharak, S., Salhotra, A., Shah, H., Longaker, M. T., Gurtner, G. C., Wan, D. C. ELSEVIER SCIENCE INC. 2020: S235

  View details for Web of Science ID 000582792300431

• Wounds Heal by Tissue-Resident Fibroblast Progenitors that Proliferate Polyclonally and Mechanoresponsively Foster, D. S., Chinta, M., Salhotra, A., Nguyen, A. T., Burcham, A., Mascharak, S., Januszyk, M., Gurtner, G. C., Wernig, G., Longaker, M. T. ELSEVIER SCIENCE INC. 2020: S236–S237

  View details for Web of Science ID 000582792300433

• Peripheral Motor Neuron Activity Influences over Local Sarcoma Progression Davitt, M., Foster, D., Mascharak, S., desJardins-Park, H., Norton, J., Longaker, M. T. ELSEVIER SCIENCE INC. 2020: S230–S231

  View details for Web of Science ID 000582792300421

• Mechanisms of bone development and repair. Nature reviews. Molecular cell biology Salhotra, A., Shah, H. N., Levi, B., Longaker, M. T. 2020

  Abstract

  Bone development occurs through a series of synchronous events that result in the formation of the body scaffold. The repair potential of bone and its surrounding microenvironment - including inflammatory, endothelial and Schwann cells - persists throughout adulthood, enabling restoration of tissue to its homeostatic functional state. The isolation of a single skeletal stem cell population through cell surface markers and the development of single-cell technologies are enabling precise elucidation of cellular activity and fate during bone repair by providing key insights into the mechanisms that maintain and regenerate bone during homeostasis and repair. Increased understanding of bone development, as well as normal and aberrant bone repair, has important therapeutic implications for the treatment of bone disease and ageing-related degeneration.

  View details for DOI 10.1038/s41580-020-00279-w

  View details for PubMedID 32901139

• Characterization of Diabetic and Non-Diabetic Foot Ulcers Using Single-Cell RNA-Sequencing. Micromachines Januszyk, M., Chen, K., Henn, D., Foster, D. S., Borrelli, M. R., Bonham, C. A., Sivaraj, D., Wagh, D., Longaker, M. T., Wan, D. C., Gurtner, G. C. 2020; 11 (9)

  Abstract

  Background: Recent advances in high-throughput single-cell sequencing technologies have led to their increasingly widespread adoption for clinical applications. However, challenges associated with tissue viability, cell yield, and delayed time-to-capture have created unique obstacles for data processing. Chronic wounds, in particular, represent some of the most difficult target specimens, due to the significant amount of fibrinous debris, extracellular matrix components, and non-viable cells inherent in tissue routinely obtained from debridement. Methods: Here, we examined the feasibility of single cell RNA sequencing (scRNA-seq) analysis to evaluate human chronic wound samples acquired in the clinic, subjected to prolonged cold ischemia time, and processed without FACS sorting. Wound tissue from human diabetic and non-diabetic plantar foot ulcers were evaluated using an optimized 10X Genomics scRNA-seq platform and analyzed using a modified data pipeline designed for low-yield specimens. Cell subtypes were identified informatically and their distributions and transcriptional programs were compared between diabetic and non-diabetic tissue. Results: 139,000 diabetic and non-diabetic wound cells were delivered for 10X capture after either 90 or 180 min of cold ischemia time. cDNA library concentrations were 858.7 and 364.7 pg/L, respectively, prior to sequencing. Among all barcoded fragments, we found that 83.5% successfully aligned to the human transcriptome and 68% met the minimum cell viability threshold. The average mitochondrial mRNA fraction was 8.5% for diabetic cells and 6.6% for non-diabetic cells, correlating with differences in cold ischemia time. A total of 384 individual cells were of sufficient quality for subsequent analyses; from this cell pool, we identified transcriptionally-distinct cell clusters whose gene expression profiles corresponded to fibroblasts, keratinocytes, neutrophils, monocytes, and endothelial cells. Fibroblast subpopulations with differing fibrotic potentials were identified, and their distributions were found to be altered in diabetic vs. non-diabetic cells. Conclusions: scRNA-seq of clinical wound samples can be achieved using minor modifications to standard processing protocols and data analysis methods. This simple approach can capture widespread transcriptional differences between diabetic and non-diabetic tissue obtained from matched wound locations.

  View details for DOI 10.3390/mi11090815

  View details for PubMedID 32872278

• Articular cartilage regeneration by activated skeletal stem cells. Nature medicine Murphy, M. P., Koepke, L. S., Lopez, M. T., Tong, X., Ambrosi, T. H., Gulati, G. S., Marecic, O., Wang, Y., Ransom, R. C., Hoover, M. Y., Steininger, H., Zhao, L., Walkiewicz, M. P., Quarto, N., Levi, B., Wan, D. C., Weissman, I. L., Goodman, S. B., Yang, F., Longaker, M. T., Chan, C. K. 2020

  Abstract

  Osteoarthritis (OA) is a degenerative disease resulting in irreversible, progressive destruction of articular cartilage1. The etiology of OA is complex and involves a variety of factors, including genetic predisposition, acute injury and chronic inflammation2-4. Here we investigate the ability of resident skeletal stem-cell (SSC) populations to regenerate cartilage in relation to age, a possible contributor to the development of osteoarthritis5-7. We demonstrate that aging is associated with progressive loss of SSCs and diminished chondrogenesis in the joints of both mice and humans. However, a local expansion of SSCs could still be triggered in the chondral surface of adult limb joints in mice by stimulating a regenerative response using microfracture (MF) surgery. Although MF-activated SSCs tended to form fibrous tissues, localized co-delivery of BMP2 and soluble VEGFR1 (sVEGFR1), a VEGF receptor antagonist, in a hydrogel skewed differentiation of MF-activated SSCs toward articular cartilage. These data indicate that following MF, a resident stem-cell population can be induced to generate cartilage for treatment of localized chondral disease in OA.

  View details for DOI 10.1038/s41591-020-1013-2

  View details for PubMedID 32807933

• Fibroblast Heterogeneity in Wound Healing: Hurdles to Clinical Translation. Trends in molecular medicine Mascharak, S., desJardins-Park, H. E., Longaker, M. T. 2020

  Abstract

  Recent work has revealed that fibroblasts are remarkably heterogeneous cells, but the appropriate lens through which to study this variation (lineage, phenotype, and plasticity) and its relevance to human biology remain unclear. In this opinion article, we comment on recent breakthroughs in our understanding of fibroblast heterogeneity during skin wound healing, and on open questions that must be addressed to clinically translate these findings in order to minimize scarring in patients. We emphasize the need for experimental models of wound healing that better approximate human biology, as well as comparison of scarring and regenerative phenotypes to uncover master regulators of fibrosis.

  View details for DOI 10.1016/j.molmed.2020.07.008

  View details for PubMedID 32800679

• Rewriting the Future: Promises and Limits of Germline Gene Editing in Craniofacial Surgery. The Journal of craniofacial surgery Davitt, M., Mascharak, S., desJardins-Park, H., Chinta, M., Wan, D. C., Longaker, M. T. 2020

  View details for DOI 10.1097/SCS.0000000000006602

  View details for PubMedID 32796298

• Prophylactic treatment with transdermal deferoxamine mitigates radiation-induced skin fibrosis. Scientific reports Shen, A. H., Borrelli, M. R., Adem, S., Deleon, N. M., Patel, R. A., Mascharak, S., Yen, S. J., Sun, B. Y., Taylor, W. L., Januszyk, M., Nguyen, D. H., Momeni, A., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2020; 10 (1): 12346

  Abstract

  Radiation therapy can result in pathological fibrosis of healthy soft tissue. The iron chelator deferoxamine (DFO) has been shown to improve skin vascularization when injected into radiated tissue prior to fat grafting. Here, we evaluated whether topical DFO administration using a transdermal drug delivery system prior to and immediately following irradiation (IR) can mitigate the chronic effects of radiation damage to the skin. CD-1 nude immunodeficient mice were split into four experimental groups: (1) IR alone (IR only), (2) DFO treatment for two weeks after recovery from IR (DFO post-IR), (3) DFO prophylaxis with treatment through and post-IR (DFO ppx), or (4) no irradiation or DFO (No IR). Immediately following IR, reactive oxygen species and apoptotic markers were significantly decreased and laser doppler analysis revealed significantly improved skin perfusion in mice receiving prophylactic DFO. Six weeks following IR, mice in the DFO post-IR and DFO ppx groups had improved skin perfusion and increased vascularization. DFO-treated groups also had evidence of reduced dermal thickness and collagen fiber network organization akin to non-irradiated skin. Thus, transdermal delivery of DFO improves tissue perfusion and mitigates chronic radiation-induced skin fibrosis, highlighting a potential role for DFO in the treatment of oncological patients.

  View details for DOI 10.1038/s41598-020-69293-4

  View details for PubMedID 32704071

• Inhibiting mechanotransduction signaling changes fibroblast heterogeneity and promotes tissue regeneration in healing wounds Chen, K., Kwon, S., Henn, D., Kuehlmann, B. A., Bonham, C. A., Padmanabhan, J., Noishiki, C., Barrera, J., Longaker, M. T., Januszyk, M., Gurtner, G. C. WILEY. 2020: S12–S13

  View details for Web of Science ID 000548418300023

• Radiation-induced skin fibrosis is reversed by transdermal delivery of deferoxamine Borrelli, M. R., Adem, S., Diaz, N., Mascharak, S., Sen, A., Januszyk, M., Nguyen, D., Momeni, A., Gurtner, G. C., Longaker, M. T., Wan, D. C. WILEY. 2020: S51–S52

  View details for Web of Science ID 000548418300116

• Reactive oxygen species and apoptotic proteins in irradiated murine skin decrease with deferoxamine treatment Shen, A. H., Deleon, N., Adem, S., Borrelli, M. R., Salhotra, A., Shah, H., Gurtner, G. C., Longaker, M. T., Wan, D. C. WILEY. 2020: S32–S33

  View details for Web of Science ID 000548418300070

• Activation of skeletal stems cells in response to long bone distraction osteogenesis Salhotra, A., Shah, H. N., Lopez, M. T., Wan, D. C., Longaker, M. T. WILEY. 2020: S25–S26

  View details for Web of Science ID 000548418300053

• Stretch marks are abundant in CD26-positive human dermal fibroblasts and exhibit increased profibrotic mechanosensitive signaling Borrelli, M. R., Griffin, M., Ngaage, L. M., Mascharak, S., Lewis, N., Januszyk, M., Wan, D. C., Longaker, M. T., Lorenz, H. P. WILEY. 2020: S32

  View details for Web of Science ID 000548418300069

• A novel murine distraction device investigating long bone regeneration Shah, H. N., Salhotra, A., Lopez, M. T., Wan, D. C., Longaker, M. T. WILEY. 2020: S16

  View details for Web of Science ID 000548418300032

• Radiation-induced fibrosis in porcine skin improves with transdermal deferoxamine treatment Adem, S., Borrelli, M. R., Deleon, N., Shen, A. H., Chen, K., Noishiki, C., Gurtner, G. C., Longaker, M. T., Wan, D. C. WILEY. 2020: S31–S32

  View details for Web of Science ID 000548418300068

• Harnessing novel gene expression analyses to identify drivers of regenerative ear wound healing in MRL mice desJardins-Park, H. E., Mack, K. L., Davitt, M. F., Griffin, M., Fraser, H. B., Longaker, M. T. WILEY. 2020: S25

  View details for Web of Science ID 000548418300052

• Doxycycline Reduces Scar Thickness and Improves Collagen Architecture ANNALS OF SURGERY Moore, A. L., desJardins-Park, H. E., Duoto, B. A., Mascharak, S., Murphy, M. P., Irizarry, D. M., Foster, D. S., Jones, R. E., Barnes, L. A., Marshall, C. D., Ransom, R. C., Wernig, G., Longaker, M. T. 2020; 272 (1): 183–93

  View details for DOI 10.1097/SLA.0000000000003172

  View details for Web of Science ID 000568895500044

• Inhibiting mechanotransduction signaling changes fibroblast heterogeneity and promotes tissue regeneration in healing wounds Chen, K., Kwon, S., Henn, D., Kuehlmann, B. A., Bonham, C. A., Padmanabhan, J., Noishiki, C., Barrera, J., Longaker, M. T., Januszyk, M., Gurtner, G. C. WILEY. 2020: S13–S14

  View details for Web of Science ID 000548418300026

• Fibroblast Heterogeneity in and Its Implications for Plastic and Reconstructive Surgery: A Basic Science Review PLASTIC AND RECONSTRUCTIVE SURGERY-GLOBAL OPEN desJardins-Park, H. E., Chinta, M. S., Foster, D. S., Borrelli, M. R., Shen, A. H., Wan, D. C., Longaker, M. T. 2020; 8 (6)

  View details for DOI 10.1097/GOX.0000000000002927

  View details for Web of Science ID 000552760800046

• Fibroblast Heterogeneity in and Its Implications for Plastic and Reconstructive Surgery: A Basic Science Review. Plastic and reconstructive surgery. Global open desJardins-Park, H. E., Chinta, M. S., Foster, D. S., Borrelli, M. R., Shen, A. H., Wan, D. C., Longaker, M. T. 2020; 8 (6): e2927

  Abstract

  Fibroblasts' integral role in tissue development, maintenance, and disease represents a fast-growing field of basic science research. Although fibroblasts were long thought to be a homogeneous cell population, recent research has illuminated the unforeseen complexity of these cells, giving rise to the rapidly expanding research field of "fibroblast heterogeneity." Fibroblasts play a critical role in states of tissue fibrosis such as skin scarring, which affects hundreds of millions of patients annually and causes severe aesthetic, developmental, and functional morbidity. Beyond scarring, major organ fibrosis is an enormous public health concern responsible for nearly half of all deaths in the United States. Because fibrosis is a conserved response to tissue damage in all organs, the study of fibroblasts throughout the body may help us to understand their role in the conditions most relevant to plastic and reconstructive surgery-for instance, skin scarring (eg, from burns, traumatic lacerations, or surgical incisions), "pathological" scarring (hypertrophic scars, keloids), and capsular contracture. Here, we present a basic science review of fibroblast heterogeneity in wound healing, cancer, organ fibrosis, and human dermal architecture. The field of fibroblast heterogeneity is young, and many of the insights discussed have yet to be translated clinically. However, plastic surgeons stand in a unique position to bridge these discoveries into clinical realities. We hope this information can spur readers to consider both what questions in plastic surgery can be studied from the lens of fibroblast heterogeneity, and how these preclinical insights can be translated to improving care of our patients.

  View details for DOI 10.1097/GOX.0000000000002927

  View details for PubMedID 32766071

  View details for PubMedCentralID PMC7339369

• Spen links RNA-mediated endogenous retrovirus silencing and X chromosome inactivation. eLife Carter, A. C., Xu, J., Nakamoto, M. Y., Wei, Y., Zarnegar, B. J., Shi, Q., Broughton, J. P., Ransom, R. C., Salhotra, A., Nagaraja, S. D., Li, R., Dou, D. R., Yost, K. E., Cho, S., Mistry, A., Longaker, M. T., Khavari, P. A., Batey, R. T., Wuttke, D. S., Chang, H. Y. 2020; 9

  Abstract

  The Xist lncRNA mediates X chromosome inactivation (XCI)1,2. Here we show that Spen, an Xist-binding repressor protein essential for XCI3-9, binds to ancient retroviral RNA, performing a surveillance role to recruit chromatin silencing machinery to these parasitic loci. Spen inactivation activates a subset of endogenous retroviral (ERV) elements in mouse embryonic stem cells, with gain of chromatin accessibility, active histone modifications, and ERV RNA transcription. Spen binds directly to ERV RNAs that show structural similarity to the A-repeat of Xist, a region critical for Xist-mediated gene silencing10-11. ERV RNA and Xist A-repeat bind the RRM domains of Spen in a competitive manner. Insertion of an ERV into an A-repeat deficient Xist rescues binding of Xist RNA to Spen and results in strictly local gene silencing in cis. These results suggest that Xist may coopt transposable element RNA-protein interactions to repurpose powerful antiviral chromatin silencing machinery for sex chromosome dosage compensation.

  View details for DOI 10.7554/eLife.54508

  View details for PubMedID 32379046

• Pro-Fibrotic CD26-Positive Fibroblasts Are Present in Greater Abundance in Breast Capsule Tissue of Irradiated Breasts AESTHETIC SURGERY JOURNAL Borrelli, M. R., Irizzary, D., Patel, R. A., Dung Nguyen, Momeni, A., Longaker, M. T., Wan, D. C. 2020; 40 (4): 369–79

  View details for DOI 10.1093/asj/sjz109

  View details for Web of Science ID 000558971600024

• Pancreatic Cancer Associated Fibroblasts (CAF): Under-Explored Target for Pancreatic Cancer Treatment. Cancers Norton, J. n., Foster, D. n., Chinta, M. n., Titan, A. n., Longaker, M. n. 2020; 12 (5)

  Abstract

  Pancreatic cancer is the 4th leading cause of cancer deaths in the United States. The pancreatic cancer phenotype is primarily a consequence of oncogenes disturbing the resident pancreas parenchymal cell repair program. Many solid tumor types including pancreatic cancer have severe tumor fibrosis called desmoplasia. Desmoplastic stroma is coopted by the tumor as a support structure and CAFs aid in tumor growth, invasion, and metastases. This stroma is caused by cancer associated fibroblasts (CAFs), which lay down extensive connective tissue in and around the tumor cells. CAFs represent a heterogeneous population of cells that produce various paracrine molecules such as transforming growth factor-beta (TGF-beta) and platelet derived growth factors (PDGFs) that aid tumor growth, local invasion, and development of metastases. The hard, fibrotic shell of desmoplasia serves as a barrier to the infiltration of both chemo- and immunotherapy drugs and host immune cells to the tumor. Although there have been recent improvements in chemotherapy and surgical techniques for management of pancreatic cancer, the majority of patients will die from this disease. Therefore, new treatment strategies are clearly needed. CAFs represent an under-explored potential therapeutic target. This paper discusses what we know about the role of CAFs in pancreatic cancer cell growth, invasion, and metastases. Additionally, we present different strategies that are being and could be explored as anti-CAF treatments for pancreatic cancer.

  View details for DOI 10.3390/cancers12051347

  View details for PubMedID 32466266

• Understanding the impact of fibroblast heterogeneity on skin fibrosis. Disease models & mechanisms Griffin, M. F., desJardins-Park, H. E., Mascharak, S. n., Borrelli, M. R., Longaker, M. T. 2020; 13 (6)

  Abstract

  Tissue fibrosis is the deposition of excessive extracellular matrix and can occur as part of the body's natural wound healing process upon injury, or as a consequence of diseases such as systemic sclerosis. Skin fibrosis contributes to significant morbidity due to the prevalence of injuries resulting from trauma and burn. Fibroblasts, the principal cells of the dermis, synthesize extracellular matrix to maintain the skin during homeostasis and also play a pivotal role in all stages of wound healing. Although it was previously believed that fibroblasts are homogeneous and mostly quiescent cells, it has become increasingly recognized that numerous fibroblast subtypes with unique functions and morphologies exist. This Review provides an overview of fibroblast heterogeneity in the mammalian dermis. We explain how fibroblast identity relates to their developmental origin, anatomical site and precise location within the skin tissue architecture in both human and mouse dermis. We discuss current evidence for the varied functionality of fibroblasts within the dermis and the relationships between fibroblast subtypes, and explain the current understanding of how fibroblast subpopulations may be controlled through transcriptional regulatory networks and paracrine communications. We consider how fibroblast heterogeneity can influence wound healing and fibrosis, and how insight into fibroblast heterogeneity could lead to novel therapeutic developments and targets for skin fibrosis. Finally, we contemplate how future studies should be shaped to implement knowledge of fibroblast heterogeneity into clinical practice in order to lessen the burden of skin fibrosis.

  View details for DOI 10.1242/dmm.044164

  View details for PubMedID 32541065

• CD34+CD146+ adipose-derived stromal cells enhance engraftment of transplanted fat. Stem cells translational medicine Borrelli, M. R., Patel, R. A., Blackshear, C. n., Vistnes, S. n., Diaz Deleon, N. M., Adem, S. n., Shen, A. H., Sokol, J. n., Momeni, A. n., Nguyen, D. n., Longaker, M. T., Wan, D. C. 2020

  Abstract

  Fat grafting is a surgical technique able to reconstruct and regenerate soft tissue. The adipose-derived stromal cells (ASCs) within the stromal vascular fraction are believed to drive these beneficial effects. ASCs are increasingly recognized to be a heterogeneous group, comprised of multiple stem and progenitor subpopulations with distinct functions. We hypothesized the existence of an ASC subpopulation with enhanced angiogenic potential. Human ASCs that were CD34+CD146+, CD34+CD146-, or CD34+ unfractionated (UF) were isolated by flow cytometry for comparison of expression of proangiogenic factors and endothelial tube-forming potential. Next, lipoaspirate was enriched with either CD34+CD146+, CD34+CD146-, CD34+ UF ASCs, or was not enriched, and grafted beneath the scalp skin of immunodeficient CD-1 Nude mice (10 000 cells/200 μL/graft). Fat retention was monitored radiographically more than 8 weeks and fat grafts were harvested for histological assessment of quality and vascularization. The CD34+CD146+ subpopulation comprised ~30% of ASCs, and exhibited increased expression of vascular endothelial growth factor and angiopoietin-1 compared to CD34+CD146- and CD34+ UF ASCs, and increased expression of fibroblast growth factor-2 compared to CD34+CD146- ASCs. The CD34+CD146+ subpopulation exhibited enhanced induction of tube-formation compared to CD34+CD146- ASCs. Upon transplantation, fat enriched CD34+CD146+ ASCs underwent less resorption and had improved histologic quality and vascularization. We have identified a subpopulation of CD34+ ASCs with enhanced angiogenic effects in vitro and in vivo, likely mediated by increased expression of potent proangiogenic factors. These findings suggest that enriching lipoaspirate with CD34+CD146+ ASCs may enhance fat graft vascularization and retention in the clinical setting.

  View details for DOI 10.1002/sctm.19-0195

  View details for PubMedID 32543083

• "Tissues in a Dish": A Review of Organoids in Plastic Surgery. Plastic and reconstructive surgery. Global open Chinta, M. S., desJardins-Park, H. E., Wan, D. C., Longaker, M. T. 2020; 8 (4): e2787

  Abstract

  Organoids are in vitro miniaturized organ models-or, colloquially, "organs in a dish." These 3-dimensional, multicellular structures are classically derived from pluripotent or multipotent stem cells. When guided by tissue-specific molecular factors, these cells exhibit self-organizing abilities that allow them to accurately recapitulate the architecture and function of the organ of interest. Organoid technology is a rapidly expanding field that endows researchers with an unprecedented ability to recreate, study, and manipulate complex biologic processes in vitro. When compared with standard 2- and 3-dimensional culture systems, which rely on co-culturing pre-established cell types, organoids provide a more biomimetic model with which to study the intercellular interactions necessary for in vivo organ function and architecture. Organoids have the potential to impact all avenues of medicine, including those fields most relevant to plastic and reconstructive surgery such as wound healing, oncology, craniofacial reconstruction, and burn care. In addition to their ability to serve as a novel tool for studying human-specific disease, organoids may be used for tissue engineering with the goal of developing biomimetic soft-tissue substitutes, which would be especially valuable to the plastic surgeon. Although organoids hold great promise for the field of plastic surgery, technical challenges in creating vascularized, multilineage organoids must be overcome to allow for the integration of this technology in clinical practice. This review provides a brief history of the organoid, highlights its potential clinical applications, discusses certain limitations, and examines the impact that this technology may have on the field of plastic and reconstructive surgery.

  View details for DOI 10.1097/GOX.0000000000002787

  View details for PubMedID 32440447

  View details for PubMedCentralID PMC7209840

• Tuning Macrophage Phenotype to Mitigate Skeletal Muscle Fibrosis. Journal of immunology (Baltimore, Md. : 1950) Stepien, D. M., Hwang, C. n., Marini, S. n., Pagani, C. A., Sorkin, M. n., Visser, N. D., Huber, A. K., Edwards, N. J., Loder, S. J., Vasquez, K. n., Aguilar, C. A., Kumar, R. n., Mascharak, S. n., Longaker, M. T., Li, J. n., Levi, B. n. 2020

  Abstract

  Myeloid cells are critical to the development of fibrosis following muscle injury; however, the mechanism of their role in fibrosis formation remains unclear. In this study, we demonstrate that myeloid cell-derived TGF-β1 signaling is increased in a profibrotic ischemia reperfusion and cardiotoxin muscle injury model. We found that myeloid-specific deletion of Tgfb1 abrogates the fibrotic response in this injury model and reduces fibro/adipogenic progenitor cell proliferation while simultaneously enhancing muscle regeneration, which is abrogated by adaptive transfer of normal macrophages. Similarly, a murine TGFBRII-Fc ligand trap administered after injury significantly reduced muscle fibrosis and improved muscle regeneration. This study ultimately demonstrates that infiltrating myeloid cell TGF-β1 is responsible for the development of traumatic muscle fibrosis, and its blockade offers a promising therapeutic target for preventing muscle fibrosis after ischemic injury.

  View details for DOI 10.4049/jimmunol.1900814

  View details for PubMedID 32161098

• Macrophage Subpopulation Dynamics Shift following Intravenous Infusion of Mesenchymal Stromal Cells. Molecular therapy : the journal of the American Society of Gene Therapy Kosaric, N. n., Srifa, W. n., Bonham, C. A., Kiwanuka, H. n., Chen, K. n., Kuehlmann, B. A., Maan, Z. N., Noishiki, C. n., Porteus, M. H., Longaker, M. T., Gurtner, G. C. 2020

  Abstract

  Intravenous infusion of mesenchymal stromal cells (MSCs) is thought to be a viable treatment for numerous disorders. Although the intrinsic immunosuppressive ability of MSCs has been credited for this therapeutic effect, their exact impact on endogenous tissue-resident cells following delivery has not been clearly characterized. Moreover, multiple studies have reported pulmonary sequestration of MSCs upon intravenous delivery. Despite substantial efforts to improve MSC homing, it remains unclear whether MSC migration to the site of injury is necessary to achieve a therapeutic effect. Using a murine excisional wound healing model, we offer an explanation of how sequestered MSCs improve healing through their systemic impact on macrophage subpopulations. We demonstrate that infusion of MSCs leads to pulmonary entrapment followed by rapid clearance, but also significantly accelerates wound closure. Using single-cell RNA sequencing of the wound, we show that following MSC delivery, innate immune cells, particularly macrophages, exhibit distinctive transcriptional changes. We identify the appearance of a pro-angiogenic CD9+ macrophage subpopulation, whose induction is mediated by several proteins secreted by MSCs, including COL6A1, PRG4, and TGFB3. Our findings suggest that MSCs do not need to act locally to induce broad changes in the immune system and ultimately treat disease.

  View details for DOI 10.1016/j.ymthe.2020.05.022

  View details for PubMedID 32531238

• Elucidating the fundamental fibrotic processes driving abdominal adhesion formation. Nature communications Foster, D. S., Marshall, C. D., Gulati, G. S., Chinta, M. S., Nguyen, A. n., Salhotra, A. n., Jones, R. E., Burcham, A. n., Lerbs, T. n., Cui, L. n., King, M. E., Titan, A. L., Ransom, R. C., Manjunath, A. n., Hu, M. S., Blackshear, C. P., Mascharak, S. n., Moore, A. L., Norton, J. A., Kin, C. J., Shelton, A. A., Januszyk, M. n., Gurtner, G. C., Wernig, G. n., Longaker, M. T. 2020; 11 (1): 4061

  Abstract

  Adhesions are fibrotic scars that form between abdominal organs following surgery or infection, and may cause bowel obstruction, chronic pain, or infertility. Our understanding of adhesion biology is limited, which explains the paucity of anti-adhesion treatments. Here we present a systematic analysis of mouse and human adhesion tissues. First, we show that adhesions derive primarily from the visceral peritoneum, consistent with our clinical experience that adhesions form primarily following laparotomy rather than laparoscopy. Second, adhesions are formed by poly-clonal proliferating tissue-resident fibroblasts. Third, using single cell RNA-sequencing, we identify heterogeneity among adhesion fibroblasts, which is more pronounced at early timepoints. Fourth, JUN promotes adhesion formation and results in upregulation of PDGFRA expression. With JUN suppression, adhesion formation is diminished. Our findings support JUN as a therapeutic target to prevent adhesions. An anti-JUN therapy that could be applied intra-operatively to prevent adhesion formation could dramatically improve the lives of surgical patients.

  View details for DOI 10.1038/s41467-020-17883-1

  View details for PubMedID 32792541

• Evaluation of Outcomes Following Surgery for Locally Advanced Pancreatic Neuroendocrine Tumors. JAMA network open Titan, A. L., Norton, J. A., Fisher, A. T., Foster, D. S., Harris, E. J., Worhunsky, D. J., Worth, P. J., Dua, M. M., Visser, B. C., Poultsides, G. A., Longaker, M. T., Jensen, R. T. 2020; 3 (11): e2024318

  Abstract

  Although outcome of surgical resection of liver metastases from pancreatic neuroendocrine tumors (PNETs) has been extensively studied, little is known about surgery for locally advanced PNETs; it was listed recently by the European neuroendocrine tumor society as a major unmet need.To evaluate the outcome of patients who underwent surgery for locally aggressive PNETs.This retrospective single-center case series reviewed consecutive patients who underwent resection of T3/T4 PNETs at a single academic institution. Data collection occurred from 2003 to 2018. Data analysis was performed in August 2019.Disease-free survival (primary outcome) and overall mortality (secondary outcome) were assessed with Kaplan-Meier analysis. Recurrence risk (secondary outcome, defined as identification of tumor recurrence on imaging) was assessed with Cox proportional hazard models adjusting for covariates.In this case series, 99 patients with locally advanced nondistant metastatic PNET (56 men [57%]) with a mean (SEM) age of 57.0 (1.4) years and a mean (SEM) follow-up of 5.3 (0.1) years underwent surgically aggressive resections. Of those, 4 patients (4%) underwent preoperative neoadjuvant treatment (including peptide receptor radionuclide therapy and chemotherapy); 18 patients (18%) underwent pancreaticoduodenectomy, 68 patients (69%) had distal or subtotal pancreatic resection, 10 patients (10%) had total resection, and 3 patients (3%) had other pancreatic procedures. Additional organ resection was required in 86 patients (87%): spleen (71 patients [71%]), major blood vessel (17 patients [17%]), bowel (2 patients [2%]), stomach (4 patients [4%]), and kidney (2 patients [2%]). Five-year disease-free survival was 61% (61 patients) and 5-year overall survival was 91% (91 patients). Of those living, 75 patients (76%) had an Eastern Cooperative Oncology Group score of less than or equal to 1 at last followup. Lymph node involvement (HR, 7.66; 95% CI, 2.78-21.12; P < .001), additional organ resected (HR, 6.15; 95% CI, 1.61-23.55; P = .008), and male sex (HR, 3.77; 95% CI, 1.68-8.97; P = .003) were associated with increased risk of recurrence. Functional tumors had a lower risk of recurrence (HR, 0.23; CI, 0.06-0.89; P = .03). Required resection of blood vessels was not associated with a significant increase recurrence risk.In this case series, positive lymph node involvement and resection of organs with tumor involvement were associated with an increased recurrence risk. These subgroups may require adjuvant systemic treatment. These findings suggest that patients with locally advanced PNETs who undergo surgical resection have excellent disease-free and overall survival.

  View details for DOI 10.1001/jamanetworkopen.2020.24318

  View details for PubMedID 33146734

• The antifibrotic adipose-derived stromal cell: Grafted fat enriched with CD74+ adipose-derived stromal cells reduces chronic radiation-induced skin fibrosis. Stem cells translational medicine Borrelli, M. R., Patel, R. A., Adem, S. n., Diaz Deleon, N. M., Shen, A. H., Sokol, J. n., Yen, S. n., Chang, E. Y., Nazerali, R. n., Nguyen, D. n., Momeni, A. n., Wang, K. C., Longaker, M. T., Wan, D. C. 2020

  Abstract

  Fat grafting can reduce radiation-induced fibrosis. Improved outcomes are found when fat grafts are enriched with adipose-derived stromal cells (ASCs), implicating ASCs as key drivers of soft tissue regeneration. We have identified a subpopulation of ASCs positive for CD74 with enhanced antifibrotic effects. Compared to CD74- and unsorted (US) ASCs, CD74+ ASCs have increased expression of hepatocyte growth factor, fibroblast growth factor 2, and transforming growth factor β3 (TGF-β3) and decreased levels of TGF-β1. Dermal fibroblasts incubated with conditioned media from CD74+ ASCs produced less collagen upon stimulation, compared to fibroblasts incubated with media from CD74- or US ASCs. Upon transplantation, fat grafts enriched with CD74+ ASCs reduced the stiffness, dermal thickness, and collagen content of overlying skin, and decreased the relative proportions of more fibrotic dermal fibroblasts. Improvements in several extracellular matrix components were also appreciated on immunofluorescent staining. Together these findings indicate CD74+ ASCs have antifibrotic qualities and may play an important role in future strategies to address fibrotic remodeling following radiation-induced fibrosis.

  View details for DOI 10.1002/sctm.19-0317

  View details for PubMedID 32563212

• Immobilization after injury alters extracellular matrix and stem cell fate. The Journal of clinical investigation Huber, A. K., Patel, N. n., Pagani, C. A., Marini, S. n., Padmanabhan, K. n., Matera, D. L., Said, M. n., Hwang, C. n., Hsu, G. C., Poli, A. A., Strong, A. L., Visser, N. D., Greenstein, J. A., Nelson, R. n., Li, S. n., Longaker, M. T., Tang, Y. n., Weiss, S. J., Baker, B. M., James, A. W., Levi, B. n. 2020

  Abstract

  Cells sense extracellular environment and mechanical stimuli and translate these signals into intracellular responses through mechanotransduction and alters cell maintenance, proliferation, and differentiation. Here we use a mouse model of trauma induced heterotopic ossification (HO) to examine how cell-extrinsic forces impact MPC fate. After injury, single cell (sc) RNA sequencing of the injury site reveals an early increase in MPC genes associated with pathways of cell adhesion and ECM-receptor interactions, and MPC trajectories to cartilage and bone. Immunostaining uncovers active mechanotransduction after injury with increased focal adhesion kinase signaling and nuclear translocation of transcriptional co-activator TAZ, inhibition of which mitigates HO. Similarly, joint immobilization decreases mechanotransductive signaling, and completely inhibits HO. Joint immobilization decreases collagen alignment and increases adipogenesis. Further, scRNA sequencing of the HO site after injury with or without immobilization identifies gene signatures in mobile MPCs correlating with osteogenesis, while signatures from immobile MPCs with adipogenesis. scATAC-seq in these same MPCs confirm that in mobile MPCs, chromatin regions around osteogenic genes are open, while in immobile MPCs, regions around adipogenic genes are open. Together these data suggest that joint immobilization after injury results in decreased ECM alignment, altered MPC mechanotransduction, and changes in genomic architecture favoring adipogenesis over osteogenesis, resulting in decreased formation of HO.

  View details for DOI 10.1172/JCI136142

  View details for PubMedID 32673290

• Mechanisms of bone development and repair Nature reviews. Molecular cell biology Shah, H. N., Salhotra, A., Levi, B., Longaker, M. T. 2020

  Abstract

  Bone development occurs through a series of synchronous events that result in the formation of the body scaffold. The repair potential of bone and its surrounding microenvironment - including inflammatory, endothelial and Schwann cells - persists throughout adulthood, enabling restoration of tissue to its homeostatic functional state. The isolation of a single skeletal stem cell population through cell surface markers and the development of single-cell technologies are enabling precise elucidation of cellular activity and fate during bone repair by providing key insights into the mechanisms that maintain and regenerate bone during homeostasis and repair. Increased understanding of bone development, as well as normal and aberrant bone repair, has important therapeutic implications for the treatment of bone disease and ageing-related degeneration.

  View details for DOI 10.1038/s41580-020-00279-w

• Fat Grafting Rescues Radiation-Induced Joint Contracture. Stem cells (Dayton, Ohio) Borrelli, M. R., Diaz Deleon, N. M., Adem, S., Patel, R. A., Mascharak, S., Shen, A. H., Irizarry, D., Nguyen, D., Momeni, A., Longaker, M. T., Wan, D. C. 2019

  Abstract

  The aim of this study was to explore the therapeutic effects of fat grafting on radiation-induced hind limb contracture. Radiation therapy (RT) is used to palliate and/or cure a range of malignancies but causes inevitable and progressive fibrosis of surrounding soft tissue. Pathological fibrosis may lead to painful contractures which limit movement and negatively impact quality of life. Fat grafting is able to reduce and/or reverse radiation-induced soft tissue fibrosis. We explored whether fat grafting could improve extensibility in irradiated and contracted hind limbs of mice. Right hind limbs of female 60-day-old CD-1 nude mice were irradiated. Chronic skin fibrosis and limb contracture developed. After 4weeks, irradiated hind limbs were then injected with (a) fat enriched with stromal vascular cells (SVCs); (b) fat only; (c) saline; or (d) nothing (n = 10/group). Limb extension was measured at baseline and every 2weeks for 12weeks. Hind limb skin then underwent histological analysis and biomechanical strength testing. Irradiation significantly reduced limb extension but was progressively rescued by fat grafting. Fat grafting also reduced skin stiffness and reversed the radiation-induced histological changes in the skin. The greatest benefits were found in mice injected with fat enriched with SVCs. Hind limb radiation induces contracture in our mouse model which can be improved with fat grafting. Enriching fat with SVCs enhances these beneficial effects. These results underscore an attractive approach to address challenging soft tissue fibrosis in patients following RT.

  View details for DOI 10.1002/stem.3115

  View details for PubMedID 31793745

• A fine balance in tendon healing. Nature cell biology Titan, A. L., Longaker, M. T. 2019

  View details for DOI 10.1038/s41556-019-0432-0

  View details for PubMedID 31768049

• Macrophage Transplantation Fails to Improve Repair of Critical-Sized Calvarial Defects. The Journal of craniofacial surgery Borrelli, M. R., Hu, M. S., Hong, W. X., Oliver, J. D., Duscher, D., Longaker, M. T., Lorenz, H. P. 2019

  Abstract

  INTRODUCTION: Over 500,000 bone grafting procedures are performed every year in the United States for neoplastic and traumatic lesions of the craniofacial skeleton, costing $585 million in medical care. Current bone grafting procedures are limited, and full-thickness critical-sized defects (CSDs) of the adult human skull thus pose a substantial reconstructive challenge for the craniofacial surgeon. Cell-based strategies have been shown to safely and efficaciously accelerate the rate of bone formation in CSDs in animals. The authors recently demonstrated that supraphysiological transplantation of macrophages seeded in pullalan-collagen composite hydrogels significantly accelerated wound healing in wild type and diabetic mice, an effect mediated in part by enhancing angiogenesis. In this study, the authors investigated the bone healing effects of macrophage transplantation into CSDs of mice.METHODS: CD1 athymic nude mice (60 days of age) were anesthetized, and unilateral full-thickness critical-sized (4 mm in diameter) cranial defects were created in the right parietal bone, avoiding cranial sutures. Macrophages were isolated from FVB-L2G mice and seeded onto hydroxyapatite-poly (lactic-co-glycolic acid) (HA-PLGA) scaffolds (1.0 * 10 cells per CSD). Scaffolds were incubated for 24 hours before they were placed into the CSDs. Macrophage survival was assessed using three-dimensional in vivo imaging system (3D IVIS)/micro-CT. Micro-CT at 0, 2, 4, 6, and 8 weeks was performed to evaluate gross bone formation, which was quantified using Adobe Photoshop. Microscopic evidence of bone regeneration was assessed at 8 weeks by histology. Bone formation and macrophage survival were compared at each time point using independent samples t tests.RESULTS: Transplantation of macrophages at supraphysiological concentration had no effect on the formation of bones in CSDs as assessed by either micro-CT data at any time point analyzed (all P > 0.05). These results were corroborated by histology. 3D IVIS/micro-CT demonstrated survival of macrophages through 8 weeks.CONCLUSION: Supraphysiologic delivery of macrophages to CSDs of mice had no effect on bone formation despite survival of transplanted macrophages through to 8 weeks posttransplantation. Further research into the physiological effects of macrophages on bone regeneration is needed to assess whether recapitulation of these conditions in macrophage-based therapy can promote the healing of large cranial defects.

  View details for DOI 10.1097/SCS.0000000000005797

  View details for PubMedID 31609958

• Much-Needed Clarification and Guidance on Cell-Based Therapies for Musculoskeletal Disorders - Secondary Publication. Journal of orthopaedic research : official publication of the Orthopaedic Research Society Murphy, M. P., Wan, D. C., Longaker, M. T. 2019

  View details for DOI 10.1002/jor.24486

  View details for PubMedID 31573106

• Role of the Skeletal Stem Cell in Achilles Tendon to Bone Interface Healing Titan, A. L., Jones, R., Salhotra, A., Robertson, K. S., Foster, D., Menon, S., Murphy, M., Lucero, G. V., Chan, C. K., Longaker, M. T. ELSEVIER SCIENCE INC. 2019: S228–S229

  View details for Web of Science ID 000492740900438

• Effect of Mechanical Loading on Clonality of Injured Flexor Tendons after Repair Titan, A. L., Foster, D., Jones, R., Salhotra, A., Nguyen, A. T., Longaker, M. T. ELSEVIER SCIENCE INC. 2019: S221

  View details for Web of Science ID 000492740900423

• JUN Drives Pathologic Scarring by Activating Key Fibroproliferative Pathways in Fibroblast Subpopulations Borrelli, M. R., Garcia, J. T., Moore, A. L., Patel, R. A., Mascharak, S., Duoto, B., Cui, L., Wan, D. C., Wernig, G., Longaker, M. T. ELSEVIER SCIENCE INC. 2019: E215–E216

  View details for Web of Science ID 000492749600516

• Fibroblast Proliferation in Wound Healing Is Clonal and Focal Adhesion Kinase-Dependent Chinta, M., Foster, D., Nguyen, A. T., Salhotra, A., Ransom, R. C., Jones, R., Titan, A. L., Marshall, C., Mascharak, S., Longaker, M. T. ELSEVIER SCIENCE INC. 2019: S223

  View details for Web of Science ID 000492740900427

• CD74+Adipose-Derived Stromal Cells Have Anti-Fibrotic Effects in Grafted Fat in the Irradiated and Non-Irradiated Setting Borrelli, M. R., Patel, R. A., Sokol, J., Dung Nguyen, Momeni, A., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2019: E214

  View details for Web of Science ID 000492749600512

• Regenerative Skin Healing Through Targeted Modulation of Engrailed1-Negative Fibroblasts Mascharak, S., desJardins-Park, H. E., Moore, A. L., Borrelli, M. R., Chinta, M., Foster, D., Lorenz, H., Longaker, M. T. ELSEVIER SCIENCE INC. 2019: S228

  View details for Web of Science ID 000492740900437

• CD26(+) Fibroblasts Increase in Abundance in Breast Capsule Tissue Surrounding Irradiated Breasts Borrelli, M. R., Patel, R. A., Dung Nguyen, Momeni, A., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2019: S220

  View details for Web of Science ID 000492740900421

• Intrinsic Chromatin State and Extrinsic Wound-Related Cues Can Coordinate to Activate Fibroblasts for Scarring desJardins-Park, H. E., Moore, A. L., Litzenburger, U., Mascharak, S., Chinta, M., Ransom, R. C., Hu, M. S., Lorenz, H. P., Chang, H. Y., Longaker, M. T. ELSEVIER SCIENCE INC. 2019: S223–S224

  View details for Web of Science ID 000492740900428

• Outcomes of Fat Grafting in Irradiated Tissue Are Improved by Pre-Treatment with Transdermal Deferoxamine Borrelli, M. R., Patel, R. A., Sokol, J., Momeni, A., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2019: E216

  View details for Web of Science ID 000492749600518

• CD146(+) Adipose-Derived Stromal Cells Have Proangiogenic Qualities and Enhance the Regenerative Potential of Grafted Fat Borrelli, M. R., Patel, R. A., Blackshear, C., Vistnes, S., Deleon, N., Nazerali, R., Momeni, A., Dung Nguyen, Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2019: S284

  View details for Web of Science ID 000492740900554

• Cancer-Associated Fibroblasts Persist but Show Decreased Fibroblast Activation Protein Expression after Neoadjuvant Chemotherapy in Human Pancreatic Ductal Adenocarcinoma Foster, D. S., Nguyen, A. T., Chinta, M., Titan, A. L., Salhotra, A., Jones, R., Mascharak, S., Norton, J., Longaker, M. T. ELSEVIER SCIENCE INC. 2019: S257–S258

  View details for Web of Science ID 000492740900501

• Tumors Co-Opt Fibroblast Wound Healing Capacity Foster, D. S., Mascharak, S., Nguyen, A. T., Chinta, M., Salhotra, A., Titan, A. L., Jones, R., da Silva, O., Norton, J. A., Longaker, M. T. ELSEVIER SCIENCE INC. 2019: S231–S232

  View details for Web of Science ID 000492740900444

• Endogenous Breast Cancer Shows Clonal Proliferation of Cancer Associated Fibroblasts at Primary Tumor and Metastatic Sites Foster, D. S., Chinta, M., Nguyen, A. T., Salhotra, A., Ransom, R., Jones, R., Titan, A. L., Mascharak, S., Norton, J. A., Longaker, M. T. ELSEVIER SCIENCE INC. 2019: S262

  View details for Web of Science ID 000492740900510

• A Revised Perspective of Skeletal Stem Cell Biology. Frontiers in cell and developmental biology Ambrosi, T. H., Longaker, M. T., Chan, C. K. 2019; 7: 189

  Abstract

  Bone-related maladies are a major health burden on modern society. Loss of skeletal integrity and regeneration capacity through aging, obesity, and disease follows from a detrimental shift in bone formation and resorption dynamics. Targeting tissue-resident adult stem cells offers a potentially innovative paradigm in the development of therapeutic strategies against organ dysfunction. While the essential role of skeletal stem cells (SSCs) for development, growth, and maintenance of the skeleton has been generally established, a common consensus on the exact identity and definition of a pure bona fide SSC population remains elusive. The controversies stem from conflicting results between different approaches and criteria for isolation, detection, and functional evaluation; along with the interchangeable usage of the terms SSC and "mesenchymal stromal/stem cell (MSC)". A great number of prospective bone-forming stem cell populations have been reported with various characteristic markers, often describing overlapping cell populations with widely unexplored heterogeneity, species specificity, and distribution at distinct skeletal sites, bone regions, and microenvironments, thereby creating confusion that may complicate future advances in the field. In this review, we examine the state-of-the-art knowledge of SSC biology and try to establish a common ground for the definition and terminology of specific bone-resident stem cells. We also discuss recent advances in the identification of highly purified SSCs, which will allow detailed interrogation of SSC diversity and regulation at the single-cell level.

  View details for DOI 10.3389/fcell.2019.00189

  View details for PubMedID 31572721

  View details for PubMedCentralID PMC6753172

• A Revised Perspective of Skeletal Stem Cell Biology FRONTIERS IN CELL AND DEVELOPMENTAL BIOLOGY Ambrosi, T. H., Longaker, M. T., Chan, C. F. 2019; 7

  View details for DOI 10.3389/fcell.2019.00189

  View details for Web of Science ID 000485330300001

• Coordinating Tissue Regeneration Through Transforming Growth Factor-beta Activated Kinase 1 Inactivation and Reactivation STEM CELLS Hsieh, H., Agarwal, S., Cholok, D. J., Loder, S. J., Kaneko, K., Huber, A., Chung, M. T., Ranganathan, K., Habbouche, J., Li, J., Butts, J., Reimer, J., Kaura, A., Drake, J., Breuler, C., Priest, C. R., Nguyen, J., Brownley, C., Peterson, J., Ozgurel, S., Niknafs, Y. S., Li, S., Inagaki, M., Scott, G., Krebsbach, P. H., Longaker, M. T., Westover, K., Gray, N., Ninomiya-Tsuji, J., Mishina, Y., Levi, B. 2019; 37 (6): 766–78

  View details for DOI 10.1002/stem.2991

  View details for Web of Science ID 000474038500008

• TOPICAL FOCAL ADHESION KINASE INHIBITOR PROMOTES SKIN REGENERATION AND SCAR PREVENTION IN A PRECLINICAL PORCINE MODEL Kwon, S., Kuehlmann, B., Dohi, T., Trotsyuk, A. A., Hu, M. S., Inayathullah, M., Rajadas, J., Longaker, M. T., Gurtner, G. C. WILEY. 2019: A11–A12

  View details for Web of Science ID 000463117000043

• Pro-Fibrotic CD26-Positive Fibroblasts are Present in Greater Abundance in Breast Capsule Tissue of Irradiated Breasts. Aesthetic surgery journal Borrelli, M. R., Irizzary, D., Patel, R. A., Nguyen, D., Momeni, A., Longaker, M. T., Wan, D. C. 2019

  Abstract

  BACKGROUND: Breast capsular contracture is a major problem following implant-based breast reconstruction, particularly in the setting of radiation therapy. Recent work has identified a fibrogenic fibroblast subpopulation characterized by CD26 surface marker expression.OBJECTIVE: This work aimed to investigate the role of CD26-positive fibroblasts in the formation of breast implant capsules following radiation therapy.METHODS: Breast capsule specimens were obtained from irradiated and non-irradiated breasts of 10 patients following bilateral mastectomy and unilateral irradiation at the time of expander-implant exchange, under institutional review board approval. Specimens were processed for Hematoxylin and Eosin staining, as well as for immunohistochemistry and fluorescence activated cell sorting (FACS) for CD26-positive fibroblasts. Expression of fibrotic genes and production of collagen was compared between CD26-positive, CD26-negative, and unsorted fibroblasts.RESULTS: Capsule specimens from irradiated breast tissue were thicker and had greater CD26-postive cells on immunofluorescence imaging and on FACS analysis, than did capsule specimens from the non-irradiated breast. Compared to CD26-negative fibroblasts, CD26-positive fibroblasts produced more collagen and had increased expression of the profibrotic genes IL8, TGF-beta1, COL1A1, and TIMP4.CONCLUSIONS: CD26-positive fibroblasts were found in a significantly greater abundance in capsules of irradiated compared to non-irradiated breasts and demonstrated greater fibrotic potential. This fibrogenic fibroblast subpopulation may play an important role in the development of capsular contracture following irradiation, and its targeted depletion or moderation may represent a potential therapeutic option.

  View details for PubMedID 30972420

• Fat Grafting into Younger Recipients Improves Volume Retention in an Animal Model PLASTIC AND RECONSTRUCTIVE SURGERY Chung, N. N., Ransom, R. C., Blackshear, C. P., Irizarry, D. M., Yen, D., Momeni, A., Lee, G. K., Nguyen, D. H., Longaker, M. T., Wan, D. C. 2019; 143 (4): 1067–75

  View details for DOI 10.1097/PRS.0000000000005483

  View details for Web of Science ID 000474582600052

• The Spectrum of Scarring in Craniofacial Wound Repair. Frontiers in physiology desJardins-Park, H. E., Mascharak, S., Chinta, M. S., Wan, D. C., Longaker, M. T. 2019; 10: 322

  Abstract

  Fibrosis is intimately linked to wound healing and is one of the largest causes of wound-related morbidity. While scar formation is the normal and inevitable outcome of adult mammalian cutaneous wound healing, scarring varies widely between different anatomical sites. The spectrum of craniofacial wound healing spans a particularly diverse range of outcomes. While most craniofacial wounds heal by scarring, which can be functionally and aesthetically devastating, healing of the oral mucosa represents a rare example of nearly scarless postnatal healing in humans. In this review, we describe the typical wound healing process in both skin and the oral cavity. We present clinical correlates and current therapies and discuss the current state of research into mechanisms of scarless healing, toward the ultimate goal of achieving scarless adult skin healing.

  View details for DOI 10.3389/fphys.2019.00322

  View details for PubMedID 30984020

  View details for PubMedCentralID PMC6450464

• The Spectrum of Scarring in Craniofacial Wound Repair FRONTIERS IN PHYSIOLOGY desJardins-Park, H. E., Mascharak, S., Chinta, M. S., Wan, D. C., Longaker, M. T. 2019; 10

  View details for DOI 10.3389/fphys.2019.00322

  View details for Web of Science ID 000462815300002

• Small molecule inhibition of dipeptidyl peptidase-4 enhances bone marrow progenitor cell function and angiogenesis in diabetic wounds TRANSLATIONAL RESEARCH Whittam, A. J., Maan, Z. N., Duscher, D., Barrera, J. A., Hu, M. S., Fischer, L. H., Khong, S., Kwon, S., Wong, V. W., Walmsley, G. G., Giacco, F., Januszyk, M., Brownlee, M., Longaker, M. T., Gurtner, G. C. 2019; 205: 51–63

  View details for DOI 10.1016/j.trsl.2018.10.006

  View details for Web of Science ID 000459843700005

• Wounds Inhibit Tumor Growth In Vivo. Annals of surgery Hu, M. S., Maan, Z. N., Leavitt, T., Hong, W. X., Rennert, R. C., Marshall, C. D., Borrelli, M. R., Zhu, T. N., Esquivel, M., Zimmermann, A., McArdle, A., Chung, M. T., Foster, D. S., Jones, R. E., Gurtner, G. C., Giaccia, A. J., Lorenz, H. P., Weissman, I. L., Longaker, M. T. 2019

  Abstract

  OBJECTIVE: The aim of this study was to determine the interaction of full thickness excisional wounds and tumors in vivo.SUMMARY OF BACKGROUND DATA: Tumors have been described as wounds that do not heal due to similarities in stromal composition. On the basis of observations of slowed tumor growth after ulceration, we hypothesized that full thickness excisional wounds would inhibit tumor progression in vivo.METHODS: To determine the interaction of tumors and wounds, we developed a tumor xenograft/allograft (human head and neck squamous cell carcinoma SAS/mouse breast carcinoma 4T1) wound mouse model. We examined tumor growth with varying temporospatial placement of tumors and wounds or ischemic flap. In addition, we developed a tumor/wound parabiosis model to understand the ability of tumors and wounds to recruit circulating progenitor cells.RESULTS: Tumor growth inhibition by full thickness excisional wounds was dose-dependent, maintained by sequential wounding, and relative to distance. This effect was recapitulated by placement of an ischemic flap directly adjacent to a xenograft tumor. Using a parabiosis model, we demonstrated that a healing wound was able to recruit significantly more circulating progenitor cells than a growing tumor. Tumor inhibition by wound was unaffected by presence of an immune response in an immunocompetent model using a mammary carcinoma. Utilizing functional proteomics, we identified 100 proteins differentially expressed in tumors and wounds.CONCLUSION: Full thickness excisional wounds have the ability to inhibit tumor growth in vivo. Further research may provide an exact mechanism for this remarkable finding and new advances in wound healing and tumor biology.

  View details for PubMedID 30829705

• Coordinating Tissue Regeneration through TGF-beta Activated Kinase 1 (TAK1) In-activation and Re-activation. Stem cells (Dayton, Ohio) Sung Hsieh, H. H., Agarwal, S., Cholok, D. J., Loder, S. J., Kaneko, K., Huber, A., Chung, M. T., Ranganathan, K., Habbouche, J., Li, J., Butts, J., Reimer, J., Kaura, A., Drake, J., Breuler, C., Priest, C. R., Nguyen, J., Brownley, C., Peterson, J., Ozgurel, S. U., Niknafs, Y. S., Li, S., Inagaki, M., Scott, G., Krebsbach, P., Longaker, M. T., Westover, K., Gray, N., Ninomiya-Tsuji, J., Mishina, Y., Levi, B. 2019

  Abstract

  Aberrant wound healing presents as inappropriate or insufficient tissue formation. Using a model of musculoskeletal injury, we demonstrate that loss of TGF-beta activated kinase 1 (TAK1) signaling reduces inappropriate tissue formation (heterotopic ossification) through reduced cellular differentiation. Upon identifying increased proliferation with loss of TAK1 signaling, we considered a regenerative approach to address insufficient tissue production through coordinated inactivation of TAK1 to promote cellular proliferation, followed by re-activation to elicit differentiation and extracellular matrix (ECM) production. While the current regenerative medicine paradigm is centered on the effects of drug treatment ("drug on"), the impact of drug withdrawal ("drug off") implicit in these regimens are unknown. Because current TAK1 inhibitors are unable to phenocopy genetic Tak1 loss, we introduce the dual-inducible COmbinational Sequential Inversion ENgineering (COSIEN) mouse model. The COSIEN mouse model, which allows us to study the response to targeted drug treatment ("drug on") and subsequent withdrawal ("drug off") through genetic modification, was used here to inactivate and re-activate Tak1 with the purpose of augmenting tissue regeneration in a calvarial defect model. Our study reveals the importance of both the "drug on" (Cre-mediated inactivation) and "drug off" (Flp-mediated re-activation) states during regenerative therapy using a mouse model with broad utility to study targeted therapies for disease. SIGNIFICANCE STATEMENT: We target the TAK1 pathway to reduce heterotopic ossification, a pathologic condition in which bone develops within muscle or soft tissues. We show that Tak1 knockout leads to cellular proliferation; this can be harnessed to increase the number of cells present at the injury site. Using a mouse model, we inactivate and reactivate the Tak1 gene. We show that inactivation and reactivation of Tak1 can improve bony healing through the coordination of increased proliferation (inactivation) followed by differentiation (reactivation). This approach elucidates a new paradigm in regenerative medicine in which coordination between treatment and withdrawal of treatment can augment healing. © AlphaMed Press 2019.

  View details for PubMedID 30786091

• Fat Chance: The Rejuvenation of Irradiated Skin PLASTIC AND RECONSTRUCTIVE SURGERY-GLOBAL OPEN Borrelli, M. R., Patel, R. A., Sokol, J., Dung Nguyen, Momeni, A., Longaker, M. T., Wan, D. C. 2019; 7 (2): e2092

  Abstract

  Radiotherapy (RT) helps cure and palliate thousands of patients with a range of malignant diseases. A major drawback, however, is the collateral damage done to tissues surrounding the tumor in the radiation field. The skin and subcutaneous tissue are among the most severely affected regions. Immediately following RT, the skin may be inflamed, hyperemic, and can form ulcers. With time, the dermis becomes progressively indurated. These acute and chronic changes cause substantial patient morbidity, yet there are few effective treatment modalities able to reduce radiodermatitis. Fat grafting is increasingly recognized as a tool able to reverse the fibrotic skin changes and rejuvenate the irradiated skin. This review outlines the current progress toward describing and understanding the cellular and molecular effects of fat grafting in irradiated skin. Identification of the key factors involved in the pathophysiology of fibrosis following RT will inform therapeutic interventions to enhance its beneficial effects.

  View details for PubMedID 30881833

• Wound healing and fibrosis: current stem cell therapies. Transfusion Jones, R. E., Foster, D. S., Hu, M. S., Longaker, M. T. 2019; 59 (S1): 884-892

  Abstract

  Scarring is a result of the wound healing response and causes tissue dysfunction after injury. This process is readily evident in the skin, but also occurs internally across organ systems in the form of fibrosis. Stem cells are crucial to the innate tissue healing response and, as such, present a possible modality to therapeutically promote regenerative healing while minimizing scaring. In this review, the cellular basis of scaring and fibrosis is examined. Current stem cell therapies under exploration for skin wound healing and internal organ fibrosis are discussed. While most therapeutic approaches rely on the direct application of progenitor-type cells to injured tissue to promote healing, novel strategies to manipulate the scarring response are also presented. As our understanding of developmental and stem cell biology continues to increase, therapies to encourage regeneration of healthy functional tissue after damage secondary to injury or disease will continue to expand.

  View details for DOI 10.1111/trf.14836

  View details for PubMedID 30737822

• Fat Grafting into Younger Recipients Improves Volume Retention in an Animal Model. Plastic and reconstructive surgery Chung, N. N., Ransom, R. C., Blackshear, C. P., Irizarry, D. M., Yen, D., Momeni, A., Lee, G. K., Nguyen, D. H., Longaker, M. T., Wan, D. C. 2019

  Abstract

  BACKGROUND: Soft tissue deficits associated with various craniofacial anomalies can be addressed by fat grafting, although outcomes remain unpredictable. Furthermore, consensus does not exist for timing of these procedures. While some advocate approaching soft tissue reconstruction after the underlying skeletal foundation has been corrected, other studies have suggested earlier grafting may exploit a younger recipient niche that is more conducive for fat graft survival. As there is a dearth of research investigating effects of recipient age on fat graft volume retention, this study compared the effectiveness of fat grafting in younger versus older animals through a longitudinal, in vivo analysis.METHODS: Human lipoaspirate from three healthy female donors was grafted subcutaneously over the calvarium of immunocompromised mice. Volume retention over 8 weeks was evaluated using micro-computed tomography in three experimental ages - 3-weeks old, 6-months old, and 1-year old. Histology was performed on explanted grafts to evaluate graft health and vascularity. Recipient site vascularity was also evaluated by confocal microscopy.RESULTS: Greatest retention of fat graft volume was noted in the youngest group compared to both older groups (*p < 0.05) at 6 and 8 weeks following grafting. Histological and immunohistochemical analyses revealed that improved retention in younger groups was associated with greater fat graft integrity and more robust vascularization.CONCLUSION: Our study provides evidence that grafting fat into a younger recipient site correlates with improved volume retention over time, suggesting that beginning soft tissue reconstruction with fat grafting in patients at an earlier age may be preferable to late correction.

  View details for PubMedID 30730498

• Tissue Engineering and Regenerative Medicine in Craniofacial Reconstruction and Facial Aesthetics. The Journal of craniofacial surgery Borrelli, M. R., Hu, M. S., Longaker, M. T., Lorenz, H. P. 2019

  Abstract

  The craniofacial region is anatomically complex and is of critical functional and cosmetic importance, making reconstruction challenging. The limitations of current surgical options highlight the importance of developing new strategies to restore the form, function, and esthetics of missing or damaged soft tissue and skeletal tissue in the face and cranium. Regenerative medicine (RM) is an expanding field which combines the principles of tissue engineering (TE) and self-healing in the regeneration of cells, tissues, and organs, to restore their impaired function. RM offers many advantages over current treatments as tissue can be engineered for specific defects, using an unlimited supply of bioengineered resources, and does not require immunosuppression. In the craniofacial region, TE and RM are being increasingly used in preclinical and clinical studies to reconstruct bone, cartilage, soft tissue, nerves, and blood vessels. This review outlines the current progress that has been made toward the engineering of these tissues for craniofacial reconstruction and facial esthetics.

  View details for DOI 10.1097/SCS.0000000000005840

  View details for PubMedID 31369496

• Induction of the Fetal Scarless Phenotype in Adult Wounds: Impossible? REGENERATIVE MEDICINE AND PLASTIC SURGERY: SKIN AND SOFT TISSUE, BONE, CARTILAGE, MUSCLE, TENDON AND NERVES Hu, M. S., Borrelli, M. R., Longaker, M. T., Lorenz, H., Duscher, D., Shiffman, M. A. 2019: 3-17

  View details for DOI 10.1007/978-3-030-19962-3_1

  View details for Web of Science ID 000652015400003

• In Vitro and In Vivo Osteogenic Differentiation of Human Adipose-Derived Stromal Cells BONE MORPHOGENETIC PROTEINS Marshall, C. D., Brett, E. A., Moore, A. L., Wan, D. C., Longaker, M. T., Rogers, M. B. 2019; 1891: 9-18

  View details for DOI 10.1007/978-1-4939-8904-1_2

  View details for Web of Science ID 000693352500003

• Skeletal Stem Cell-Schwann Cell Circuitry in Mandibular Repair. Cell reports Jones, R. E., Salhotra, A. n., Robertson, K. S., Ransom, R. C., Foster, D. S., Shah, H. N., Quarto, N. n., Wan, D. C., Longaker, M. T. 2019; 28 (11): 2757–66.e5

  Abstract

  Regenerative paradigms exhibit nerve dependency, including regeneration of the mouse digit tip and salamander limb. Denervation impairs regeneration and produces morphological aberrancy in these contexts, but the direct effect of innervation on the stem and progenitor cells enacting these processes is unknown. We devised a model to examine nerve dependency of the mouse skeletal stem cell (mSSC), the progenitor responsible for skeletal development and repair. We show that after inferior alveolar denervation, mandibular bone repair is compromised because of functional defects in mSSCs. We present mSSC reliance on paracrine factors secreted by Schwann cells as the underlying mechanism, with partial rescue of the denervated phenotype by Schwann cell transplantation and by Schwann-derived growth factors. This work sheds light on the nerve dependency of mSSCs and has implications for clinical treatment of mandibular defects.

  View details for DOI 10.1016/j.celrep.2019.08.021

  View details for PubMedID 31509739

• Radiation-Induced Skin Fibrosis: Pathogenesis, Current Treatment Options, and Emerging Therapeutics. Annals of plastic surgery Borrelli, M. R., Shen, A. H., Lee, G. K., Momeni, A. n., Longaker, M. T., Wan, D. C. 2019; 83 (4S Suppl 1): S59–S64

  Abstract

  Radiotherapy (RT) has become an indispensable part of oncologic treatment protocols for a range of malignancies. However, a serious adverse effect of RT is radiodermatitis; almost 95% of patients develop moderate to severe skin reactions following radiation treatment. In the acute setting, these can be erythema, desquamation, ulceration, and pain. Chronically, soft tissue atrophy, alopecia, and stiffness can be noted. Radiodermatitis can delay oncologic treatment protocols and significantly impair quality of life. There is currently a paucity of effective treatment options and prevention strategies for radiodermatitis. Importantly, recent preclinical and clinical studies have suggested that fat grafting may be of therapeutic benefit, reversing detrimental changes to soft tissue following RT. This review outlines the damaging effects of RT on the skin and soft tissue as well as discusses available treatment options for radiodermatitis. Emerging strategies to mitigate detrimental, chronic radiation-induced changes are also presented.

  View details for DOI 10.1097/SAP.0000000000002098

  View details for PubMedID 31513068

• Pressure Injury. Annals of surgery Hajhosseini, B. n., Longaker, M. T., Gurtner, G. C. 2019

  Abstract

  Pressure injury is seen across all healthcare settings and affects people of any age and health condition. It imposes a significant burden, with annual costs of up to $17.8 billion in the United States alone. Despite considerable resources it exhausts, the disease remains very prevalent, and the incidence is on the rise. This is in part due to aging population, growing number of nursing home residents, poorly understood biology, and dismal track record of clinical research in this field.In our Review Article, we discuss the disease pathophysiology, clinical manifestation, evidence based recommendations for risk assessment, prevention and timely management, existing challenges, and directions to improve research on the field. This article encompasses dedicated sections on the full spectrum of the pressure related pathologies including "conventional pressure ulcers", "medical device related pressure injuries", "pressure injuries in mucosal membranes", "pressure injuries in pediatric population", "pressure injury at end of life", and the "role of pressure in pathogenesis of diabetic foot ulcers".

  View details for DOI 10.1097/SLA.0000000000003567

  View details for PubMedID 31460882

• Discussion: Adipose-Derived Stem Cells and Ceiling Culture-Derived Preadipocytes Cultured from Subcutaneous Fat Tissue Differ in Their Epigenetic Characteristics and Osteogenic Potential. Plastic and reconstructive surgery Borrelli, M. R., Longaker, M. T., Wan, D. C. 2019; 144 (3): 656–57

  View details for DOI 10.1097/PRS.0000000000005914

  View details for PubMedID 31461021

• Flexor Tendon: Development, Healing, Adhesion Formation, and Contributing Growth Factors. Plastic and reconstructive surgery Titan, A. L., Foster, D. S., Chang, J. n., Longaker, M. T. 2019; 144 (4): 639e–647e

  Abstract

  Management of flexor tendon injuries of the hand remains a major clinical problem. Even with intricate repair, adhesion formation remains a common complication. Significant progress has been made to better understand the mechanisms of healing and adhesion formation. However, there has been slow progress in the clinical prevention and reversal of flexor tendon adhesions. The goal of this article is to discuss recent literature relating to tendon development, tendon healing, and adhesion formation to identify areas in need of further research. Additional research is needed to understand and compare the molecular, cellular, and genetic mechanisms involved in flexor tendon morphogenesis, postoperative healing, and mechanical loading. Such knowledge is critical to determine how to improve repair outcomes and identify new therapeutic strategies to promote tissue regeneration and prevent adhesion formation.

  View details for DOI 10.1097/PRS.0000000000006048

  View details for PubMedID 31568303

• A Clearing Technique to Enhance Endogenous Fluorophores in Skin and Soft Tissue. Scientific reports Foster, D. S., Nguyen, A. T., Chinta, M. n., Salhotra, A. n., Jones, R. E., Mascharak, S. n., Titan, A. L., Ransom, R. C., da Silva, O. L., Foley, E. n., Briger, E. n., Longaker, M. T. 2019; 9 (1): 15791

  Abstract

  Fluorescent proteins are used extensively in transgenic animal models to label and study specific cell and tissue types. Expression of these proteins can be imaged and analyzed using fluorescent and confocal microscopy. Conventional confocal microscopes cannot penetrate through tissue more than 4-6 μm thick. Tissue clearing procedures overcome this challenge by rendering thick specimens into translucent tissue. However, most tissue clearing techniques do not satisfactorily preserve expression of endogenous fluorophores. Using simple adjustments to the BABB (Benzoic Acid Benzyl Benzoate) clearing methodology, preservation of fluorophore expression can be maintained. Modified BABB tissue clearing is a reliable technique to clear skin and soft tissue specimens for the study of dermal biology, wound healing and fibrotic pathologies.

  View details for DOI 10.1038/s41598-019-50359-x

  View details for PubMedID 31673001

• Much-Needed Clarification and Guidance on Cell-Based Therapies for Musculoskeletal Disorders. Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research Murphy, M. P., Wan, D. C., Longaker, M. T. 2019

  View details for DOI 10.1002/jbmr.3841

  View details for PubMedID 31545871

• In Vitro and In Vivo Osteogenic Differentiation of Human Adipose-Derived Stromal Cells. Methods in molecular biology (Clifton, N.J.) Marshall, C. D., Brett, E. A., Moore, A. L., Wan, D. C., Longaker, M. T. 2019; 1891: 9–18

  Abstract

  Adipose-derived stromal cells (ASCs) are a promising population of cells that may be useful for the regeneration of human tissue defects. ASCs are capable of forming bone tissue in vitro and in vivo. Further work is required to determine the optimal conditions that will allow human ASCs to regenerate tissue in clinically significant tissue defects. Here we present three experimental protocols that are indispensable for the study of ASC osteogenic activity.

  View details for PubMedID 30414122

• Heterogeneity in old fibroblasts is linked to variability in reprogramming and wound healing. Nature Mahmoudi, S. n., Mancini, E. n., Xu, L. n., Moore, A. n., Jahanbani, F. n., Hebestreit, K. n., Srinivasan, R. n., Li, X. n., Devarajan, K. n., Prélot, L. n., Ang, C. E., Shibuya, Y. n., Benayoun, B. A., Chang, A. L., Wernig, M. n., Wysocka, J. n., Longaker, M. T., Snyder, M. P., Brunet, A. n. 2019; 574 (7779): 553–58

  Abstract

  Age-associated chronic inflammation (inflammageing) is a central hallmark of ageing1, but its influence on specific cells remains largely unknown. Fibroblasts are present in most tissues and contribute to wound healing2,3. They are also the most widely used cell type for reprogramming to induced pluripotent stem (iPS) cells, a process that has implications for regenerative medicine and rejuvenation strategies4. Here we show that fibroblast cultures from old mice secrete inflammatory cytokines and exhibit increased variability in the efficiency of iPS cell reprogramming between mice. Variability between individuals is emerging as a feature of old age5-8, but the underlying mechanisms remain unknown. To identify drivers of this variability, we performed multi-omics profiling of fibroblast cultures from young and old mice that have different reprogramming efficiencies. This approach revealed that fibroblast cultures from old mice contain 'activated fibroblasts' that secrete inflammatory cytokines, and that the proportion of activated fibroblasts in a culture correlates with the reprogramming efficiency of that culture. Experiments in which conditioned medium was swapped between cultures showed that extrinsic factors secreted by activated fibroblasts underlie part of the variability between mice in reprogramming efficiency, and we have identified inflammatory cytokines, including TNF, as key contributors. Notably, old mice also exhibited variability in wound healing rate in vivo. Single-cell RNA-sequencing analysis identified distinct subpopulations of fibroblasts with different cytokine expression and signalling in the wounds of old mice with slow versus fast healing rates. Hence, a shift in fibroblast composition, and the ratio of inflammatory cytokines that they secrete, may drive the variability between mice in reprogramming in vitro and influence wound healing rate in vivo. This variability may reflect distinct stochastic ageing trajectories between individuals, and could help in developing personalized strategies to improve iPS cell generation and wound healing in elderly individuals.

  View details for DOI 10.1038/s41586-019-1658-5

  View details for PubMedID 31645721

• Doxycycline Reduces Scar Thickness and Improves Collagen Architecture. Annals of surgery Moore, A. L., desJardins-Park, H. E., Duoto, B. A., Mascharak, S., Murphy, M. P., Irizarry, D. M., Foster, D. S., Jones, R. E., Barnes, L. A., Marshall, C. D., Ransom, R. C., Wernig, G., Longaker, M. T. 2018

  Abstract

  OBJECTIVE: To investigate the effects of local doxycycline administration on skin scarring.BACKGROUND: Skin scarring represents a major source of morbidity for surgical patients. Doxycycline, a tetracycline antibiotic with off-target effects on the extracellular matrix, has demonstrated antifibrotic effects in multiple organs. However, doxycycline's potential effects on skin scarring have not been explored in vivo.METHODS: Female C57BL/6J mice underwent dorsal wounding following an established splinted excisional skin wounding model. Doxycycline was administered by local injection into the wound base following injury. Wounds were harvested upon complete wound closure (postoperative day 15) for histological examination and biomechanical testing of scar tissue.RESULTS: A one-time dose of 3.90 mM doxycycline (2 mg/mL) within 12 hours of injury was found to significantly reduce scar thickness by 24.8% (P < 0.0001) without compromising tensile strength. The same effect could not be achieved by oral dosing. In doxycycline-treated scar matrices, collagen I content was significantly reduced (P = 0.0317) and fibers were favorably arranged with significantly increased fiber randomness (P = 0.0115). Common culprits of altered wound healing mechanics, including angiogenesis and inflammation, were not impacted by doxycycline treatment. However, engrailed1 profibrotic fibroblasts, responsible for scar extracellular matrix deposition, were significantly reduced with doxycycline treatment (P = 0.0005).CONCLUSIONS: Due to the substantial improvement in skin scarring and well-established clinical safety profile, locally administered doxycycline represents a promising vulnerary agent. As such, we favor rapid translation to human patients as an antiscarring therapy.

  View details for PubMedID 30585822

• Mechanoresponsive stem cells acquire neural crest fate in jaw regeneration NATURE Ransom, R. C., Carter, A. C., Salhotra, A., Leavitt, T., Marecic, O., Murphy, M. P., Lopez, M. L., Wei, Y., Marshall, C. D., Shen, E. Z., Jones, R., Sharir, A., Klein, O. D., Chan, C. F., Wan, D. C., Chang, H. Y., Longaker, M. T. 2018; 563 (7732): 514-+

  View details for DOI 10.1038/s41586-018-0650-9

  View details for Web of Science ID 000450960000045

• Small molecule inhibition of dipeptidyl peptidase-4 enhances bone marrow progenitor cell function and angiogenesis in diabetic wounds. Translational research : the journal of laboratory and clinical medicine Whittam, A. J., Maan, Z. N., Duscher, D., Barrera, J. A., Hu, M. S., Fischer, L. H., Khong, S., Kwon, S. H., Wong, V. W., Walmsley, G. G., Giacco, F., Januszyk, M., Brownlee, M., Longaker, M. T., Gurtner, G. C. 2018

  Abstract

  In diabetes, stromal cell-derived factor-1 (SDF-1) expression and progenitor cell recruitment are reduced. Dipeptidyl peptidase-4 (DPP-4) inhibits SDF-1 expression and progenitor cell recruitment. Here we examined the impact of the DPP-4 inhibitor, MK0626, on progenitor cell kinetics in the context of wound healing. Wildtype (WT) murine fibroblasts cultured under high-glucose to reproduce a diabetic microenvironment were exposed to MK0626, glipizide, or no treatment, and SDF-1 expression was measured with ELISA. Diabetic mice received MK0626, glipizide, or no treatment for 6 weeks and then were wounded. Immunohistochemistry was used to quantify neovascularization and SDF-1 expression. Gene expression was measured at the RNA and protein level using quantitative polymerase chain reaction and ELISA, respectively. Flow cytometry was used to characterize bone marrow-derived mesenchymal progenitor cell (BM-MPC) population recruitment to wounds. BM-MPC gene expression was assayed using microfluidic single cell analysis. WT murine fibroblasts exposed to MK0626 demonstrated increased SDF-1 expression. MK0626 treatment significantly accelerated wound healing and increased wound vascularity, SDF-1 expression, and dermal thickness in diabetic wounds. MK0626 treatment increased the number of BM-MPCs present in bone marrow and in diabetic wounds. MK0626 had no effect on BM-MPC population dynamics. BM-MPCs harvested from MK0626-treated mice exhibited increased chemotaxis in response to SDF-1 when compared to diabetic controls. Treatment with a DPP-4 inhibitor significantly improved wound healing, angiogenesis, and endogenous progenitor cell recruitment in the setting of diabetes.

  View details for PubMedID 30452888

• DEL1 protects against chondrocyte apoptosis through integrin binding. The Journal of surgical research Wang, Z., Boyko, T., Tran, M. C., LaRussa, M., Bhatia, N., Rashidi, V., Longaker, M. T., Yang, G. P. 2018; 231: 1–9

  Abstract

  BACKGROUND: Osteoarthritis (OA) is a debilitating disease process, affecting mobility and overall health of millions. Current treatment is for symptomatic relief and discovery of approaches to halt or reverse damage is imperative. Deletion of developmental endothelial locus-1 (Del1) has been shown to increase severity of OA in knockout mice. We examined the intracellular pathways involved in the ability of DEL1 to protect chondrocytes from apoptosis and anoikis and hypothesized that it functioned via integrin signaling.MATERIALS AND METHODS: Primary human chondrocytes were treated with various inducers of apoptosis, including anoikis, in the presence of added DEL1 or bovine serum albumin as control. Various inhibitors of integrin binding were examined for their effect on DEL1 activity. Downstream signaling pathway components were detected by immunoblotting.RESULTS: The addition of DEL1 protected chondrocytes from multiple inducers of apoptosis as measured by cell survival, terminal deoxynucleotidyl transferase dUTP nick end labeling and caspase 3/7 assays (P<0.05). The effect of DEL1 was blocked by RGD peptides and by antibodies directed to integrin alphaVbeta3, but not by controls or antibody to integrin alpha1 (P<0.05). Treatment with DEL1 promoted ERK and AKT activation when cells were attached, but only AKT activation under conditions of anoikis.CONCLUSIONS: DEL1 protected chondrocytes from apoptosis in response to activators of either the intrinsic or extrinsic pathways, and to anoikis. This effect was mediated primarily through integrin alphaVbeta3. This represents a therapeutic target for therapies to prevent cartilage degeneration in OA.

  View details for PubMedID 30278915

• DEL1 protects against chondrocyte apoptosis through integrin binding JOURNAL OF SURGICAL RESEARCH Wang, Z., Boyko, T., Tran, M. C., LaRussa, M., Bhatia, N., Rashidi, V., Longaker, M. T., Yang, G. P. 2018; 231: 1–9

  View details for DOI 10.1016/j.jss.2018.04.066

  View details for Web of Science ID 000445911700001

• Discussion: CRISPR Craft: DNA Editing the Reconstructive Ladder PLASTIC AND RECONSTRUCTIVE SURGERY Hu, M. S., Longaker, M. T., Wan, D. C. 2018; 142 (5): 1365–66

  View details for DOI 10.1097/PRS.0000000000004949

  View details for Web of Science ID 000448330200083

• Discussion: CRISPR Craft: DNA Editing the Reconstructive Ladder. Plastic and reconstructive surgery Hu, M. S., Longaker, M. T., Wan, D. C. 2018; 142 (5): 1365-1366

  View details for DOI 10.1097/PRS.0000000000004949

  View details for PubMedID 30511993

• Mechanoresponsive stem cells acquire neural crest fate in jaw regeneration. Nature Ransom, R. C., Carter, A. C., Salhotra, A., Leavitt, T., Marecic, O., Murphy, M. P., Lopez, M. L., Wei, Y., Marshall, C. D., Shen, E. Z., Jones, R. E., Sharir, A., Klein, O. D., Chan, C. K., Wan, D. C., Chang, H. Y., Longaker, M. T. 2018

  Abstract

  During both embryonic development and adult tissue regeneration, changes in chromatin structure driven by master transcription factors lead to stimulus-responsive transcriptional programs. A thorough understanding of how stem cells in the skeleton interpret mechanical stimuli and enact regeneration would shed light on how forces are transduced to the nucleus in regenerative processes. Here we develop a genetically dissectible mouse model of mandibular distraction osteogenesis-which isa process that is used in humans to correct an undersized lower jawthat involves surgically separating the jaw bone, whichelicits new bone growth in the gap. We use this model to show that regions of newly formed bone are clonally derived from stem cells that reside in the skeleton. Using chromatin and transcriptional profiling, we show that these stem-cell populations gain activity within the focal adhesion kinase (FAK) signalling pathway, and that inhibiting FAK abolishes new bone formation. Mechanotransduction via FAK in skeletal stem cells during distraction activates a gene-regulatory program and retrotransposons that are normally active in primitive neural crest cells, from which skeletal stem cells arise during development. This reversion to a developmental state underlies the robust tissue growth that facilitates stem-cell-based regeneration of adult skeletal tissue.

  View details for PubMedID 30356216

• Author Correction: Genetic dissection of clonal lineage relationships with hydroxytamoxifen liposomes. Nature communications Ransom, R. C., Foster, D. S., Salhotra, A., Jones, R. E., Marshall, C. D., Leavitt, T., Murphy, M. P., Moore, A. L., Blackshear, C. P., Brett, E. A., Wan, D. C., Longaker, M. T. 2018; 9 (1): 4411

  Abstract

  In the original version of this Article, the authors inadvertently omitted Elizabeth A. Brett, who contributed to the generation of the histology figures, from the author list.This has now been corrected in both the PDF and HTML versions of the Article.

  View details for PubMedID 30341306

• Genetic dissection of clonal lineage relationships with hydroxytamoxifen liposomes (vol 9, 2971, 2018) NATURE COMMUNICATIONS Ransom, R. C., Foster, D. S., Salhotra, A., Jones, R., Marshall, C. D., Leavitt, T., Murphy, M. P., Moore, A. L., Blackshear, C. P., Brett, E. A., Wan, D. C., Longaker, M. T. 2018; 9

  View details for DOI 10.1038/s41467-018-06927-2

  View details for Web of Science ID 000447698700001

• Twist1-Haploinsufficiency Selectively Enhances the Osteoskeletal Capacity of Mesoderm-Derived Parietal Bone Through Downregulation of Fgf23. Frontiers in physiology Quarto, N., Shailendra, S., Meyer, N. P., Menon, S., Renda, A., Longaker, M. T. 2018; 9: 1426

  Abstract

  Craniofacial development is a program exquisitely orchestrated by tissue contributions and regulation of genes expression. The basic helix-loop-helix (bHLH) transcription factor Twist1 expressed in the skeletal mesenchyme is a key regulator of craniofacial development playing an important role during osteoskeletogenesis. This study investigates the postnatal impact of Twist1 haploinsufficiency on the osteoskeletal ability and regeneration on two calvarial bones arising from tissues of different embryonic origin: the neural crest-derived frontal and the mesoderm-derived parietal bones. We show that Twist1 haplonsufficiency as well Twist1-sh-mediated silencing selectively enhanced osteogenic and tissue regeneration ability of mesoderm-derived bones. Transcriptomic profiling, gain-and loss-of-function experiments revealed that Twist1 haplonsufficiency triggers its selective activity on mesoderm-derived bone through a sharp downregulation of the bone-derived hormone Fgf23 that is upregulated exclusively in wild-type parietal bone.

  View details for DOI 10.3389/fphys.2018.01426

  View details for PubMedID 30374308

  View details for PubMedCentralID PMC6196243

• Twist1-Haploinsufficiency Selectively Enhances the Osteoskeletal Capacity of Mesoderm-Derived Parietal Bone Through Downregulation of Fgf23 FRONTIERS IN PHYSIOLOGY Quarto, N., Shailendra, S., Meyer, N. P., Menon, S., Renda, A., Longaker, M. T. 2018; 9

  View details for DOI 10.3389/fphys.2018.01426

  View details for Web of Science ID 000447266900001

• Management of Chronic Wounds-2018. JAMA Jones, R. E., Foster, D. S., Longaker, M. T. 2018; 320 (14): 1481-1482

  View details for DOI 10.1001/jama.2018.12426

  View details for PubMedID 30326512

• Iron Chelation with Transdermal Deferoxamine Accelerates Healing of Murine Sickle Cell Ulcers. Advances in wound care Rodrigues, M., Bonham, C. A., Minniti, C. P., Gupta, K., Longaker, M. T., Gurtner, G. C. 2018; 7 (10): 323-332

  Abstract

  Objective: Sickle cell ulcers (SCUs) are a devastating comorbidity affecting patients with sickle cell disease (SCD). SCUs form over the medial or lateral malleoli of the lower extremity, are slow to heal, and prone to recidivism. Some SCUs may never heal, leading to chronic pain and foot deformities. There is no specific and effective therapy for SCUs. Systemic deferoxamine (DFO) has been demonstrated to prevent some of the sequelae of SCD by chelating iron. In this study, we tested the ability of DFO delivered via a transdermal delivery system (DFO-TDDS) to accelerate healing in a murine model of SCU. Approach: Excisional wounds were created in a transgenic murine model of SCD expressing >99% human sickle hemoglobin, and healing rates were compared with wounds in wild-type mice. Next, excisional wounds in SCD mice were treated with DFO-TDDS, DFO injection, or left untreated. Wound closure rates, histology, and iron in the healed wounds were analyzed. Results: Wounds in SCD mice healed significantly slower than wild-type mice (***p < 0.001). DFO-TDDS-treated wounds demonstrated significantly accelerated time to closure, reduced size, and improved wound remodeling compared with untreated wounds (***p < 0.001) and DFO injection treatment (*p < 0.05). DFO released from the TDDS into wounds resulted in chelation of excessive dermal-free iron. Innovation: DFO-TDDS is a novel therapeutic that is effective in healing wounds in sickle cell mice. Conclusion: DFO-TDDS significantly accelerates healing of murine SCUs by chelation of excessive free iron and is currently manufactured in an FDA-compliant facility to be translated for treating human SCUs.

  View details for DOI 10.1089/wound.2018.0789

  View details for PubMedID 30374417

  View details for PubMedCentralID PMC6203233

• Utilizing Confocal Microscopy to Characterize Human and Mouse Adipose Tissue TISSUE ENGINEERING PART C-METHODS Blackshear, C. P., Borrelli, M. R., Shen, E. Z., Ransom, R., Chung, N. N., Vistnes, S. M., Irizarry, D., Nazerali, R., Momeni, A., Longaker, M. T., Wan, D. C. 2018; 24 (10): 566–77

  View details for DOI 10.1089/ten.tec.2018.0154

  View details for Web of Science ID 000447725200002

• Engrailed1-Positive Fibroblasts May Modulate Transcription of the TGF-beta Pathway in the Transition from Scarless Healing to Scarring Phenotype Moore, A. L., Marshall, C. D., Des Jardins-Park, H. E., Duoto, B. A., Mascharak, S., Barnes, A., Ransom, R. C., Hu, M. S., Lorenz, H., Longaker, M. T. ELSEVIER SCIENCE INC. 2018: E221–E222

  View details for DOI 10.1016/j.jamcollsurg.2018.08.599

  View details for Web of Science ID 000447772500535

• Nerve-Dependent Mandibular Regeneration by Skeletal Stem Cells in Fracture Repair Jones, R., Ransom, R. C., Salhotra, A., Foster, D. S., Wan, D. C., Longaker, M. T. ELSEVIER SCIENCE INC. 2018: S197

  View details for DOI 10.1016/j.jamcollsurg.2018.07.434

  View details for Web of Science ID 000447760600388

• Mouse Model with cJUN Over-Expression Eludes to Deep Dermal Fibroblast Expansion and Immune Cell Recruitment as the Biologic Mechanism of Hypertrophic Scarring Moore, A. L., Duoto, B. A., Des Jardins-Park, H. E., Mascharak, S., Wernig, G., Longaker, M. T. ELSEVIER SCIENCE INC. 2018: S208

  View details for DOI 10.1016/j.jamcollsurg.2018.07.456

  View details for Web of Science ID 000447760600409

• Translational Approach Using Trimodal Manipulation of Resident Skeletal Stem Cells for Articular Cartilage Repair Murphy, M. P., Koepke, L. S., Lopez, M., Ransom, R. C., Brewer, R. E., Borrelli, M. R., Marecic, O., Chan, C. F., Longaker, M. T. ELSEVIER SCIENCE INC. 2018: S213–S214

  View details for DOI 10.1016/j.jamcollsurg.2018.07.457

  View details for Web of Science ID 000447760600420

• Automated Quantification of Vessel Structure: A Novel Method for Analysis of Angiogenesis in Wound Healing Jardins-Park, H., Mascharak, S., Moore, A. L., Duoto, B. A., Longaker, M. T. ELSEVIER SCIENCE INC. 2018: E196

  View details for Web of Science ID 000447772500469

• Acta2, Tnc, and Col24a1 Expression Are Associated with Abdominal Adhesion Formation Marshall, C. D., Foster, D. S., Ransom, R. C., Manjunath, A., Gulati, G., Hu, M. S., Moore, A. L., Barnes, L. A., Longaker, M. T. ELSEVIER SCIENCE INC. 2018: E128

  View details for DOI 10.1016/j.jamcollsurg.2018.08.347

  View details for Web of Science ID 000447772500304

• Reduced Scar Thickness Achieved by Topical Doxycycline Is Mediated by Specific Skin Fibroblast Populations and Not Immune Cell Infiltrate Moore, A. L., Murphy, M. P., Irizarry, D. M., Des Jardins-Park, H. E., Duoto, B. A., Mascharak, S., Foster, D. S., Jones, R., Wernig, G., Longaker, M. T. ELSEVIER SCIENCE INC. 2018: S210–S211

  View details for DOI 10.1016/j.jamcollsurg.2018.07.462

  View details for Web of Science ID 000447760600413

• Method of Isolating and Transplanting the Hematopoietic Stem Cell with Its Microenvironment Which Improves Functional Hematopoietic Engraftment Borrelli, M. R., Lopez, M., Gulati, G., Murphy, M. P., Sinha, R., Longaker, M. T., Weissman, I. L., Newman, A. M., Chan, C. K., Sokol, J. ELSEVIER SCIENCE INC. 2018: E224

  View details for DOI 10.1016/j.jamcollsurg.2018.08.605

  View details for Web of Science ID 000447772500541

• Clonal Analysis of Local Fibroblasts in Wound Healing and Tumor Stroma Foster, D. S., Ransom, R. C., Nguyen, A. T., Salhotra, A., Jones, R. E., Hu, M. S., Norton, J. A., Longaker, M. T. ELSEVIER SCIENCE INC. 2018: S236

  View details for DOI 10.1016/j.jamcollsurg.2018.07.623

  View details for Web of Science ID 000447760600466

• Identification of the Human Skeletal Stem Cell. Cell Chan, C. K., Gulati, G. S., Sinha, R., Tompkins, J. V., Lopez, M., Carter, A. C., Ransom, R. C., Reinisch, A., Wearda, T., Murphy, M., Brewer, R. E., Koepke, L. S., Marecic, O., Manjunath, A., Seo, E. Y., Leavitt, T., Lu, W., Nguyen, A., Conley, S. D., Salhotra, A., Ambrosi, T. H., Borrelli, M. R., Siebel, T., Chan, K., Schallmoser, K., Seita, J., Sahoo, D., Goodnough, H., Bishop, J., Gardner, M., Majeti, R., Wan, D. C., Goodman, S., Weissman, I. L., Chang, H. Y., Longaker, M. T. 2018; 175 (1): 43

  Abstract

  Stem cell regulation and hierarchical organization ofhuman skeletal progenitors remain largely unexplored. Here, we report the isolation of a self-renewing and multipotent human skeletal stem cell (hSSC) that generates progenitors of bone, cartilage, and stroma, but not fat. Self-renewing and multipotent hSSCs are present in fetal and adult bones and can also be derived from BMP2-treated human adipose stroma (B-HAS) and induced pluripotent stem cells (iPSCs). Gene expression analysis of individual hSSCs reveals overall similarity between hSSCs obtained from different sources and partially explains skewed differentiation toward cartilage in fetal and iPSC-derived hSSCs. hSSCs undergo local expansion in response to acute skeletal injury. In addition, hSSC-derived stroma can maintain human hematopoietic stem cells (hHSCs) in serum-free culture conditions. Finally, we combine gene expression and epigenetic data of mouse skeletal stem cells (mSSCs) and hSSCs to identify evolutionarily conserved and divergent pathways driving SSC-mediated skeletogenesis. VIDEO ABSTRACT.

  View details for PubMedID 30241615

• Identification of the Human Skeletal Stem Cell CELL Chan, C. F., Gulati, G. S., Sinha, R., Tompkins, J., Lopez, M., Carter, A. C., Ransom, R. C., Reinisch, A., Wearda, T., Murphy, M., Brewer, R. E., Koepke, L. S., Marecic, O., Manjunath, A., Seo, E., Leavitt, T., Lu, W., Allison Nguyen, Conley, S. D., Salhotra, A., Ambrosi, T. H., Borrelli, M. R., Siebel, T., Chan, K., Schallmoser, K., Seita, J., Sahoo, D., Goodnough, H., Bishop, J., Gardner, M., Majeti, R., Wan, D. C., Goodman, S., Weissman, I. L., Chang, H. Y., Longaker, M. T. 2018; 175 (1): 43-+

  View details for DOI 10.1016/j.cell.2018.07.029

  View details for Web of Science ID 000445120000013

• The evolving relationship of wound healing and tumor stroma. JCI insight Foster, D. S., Jones, R. E., Ransom, R. C., Longaker, M. T., Norton, J. A. 2018; 3 (18)

  Abstract

  The stroma in solid tumors contains a variety of cellular phenotypes and signaling pathways associated with wound healing, leading to the concept that a tumor behaves as a wound that does not heal. Similarities between tumors and healing wounds include fibroblast recruitment and activation, extracellular matrix (ECM) component deposition, infiltration of immune cells, neovascularization, and cellular lineage plasticity. However, unlike a wound that heals, the edges of a tumor are constantly expanding. Cell migration occurs both inward and outward as the tumor proliferates and invades adjacent tissues, often disregarding organ boundaries. The focus of our review is cancer associated fibroblast (CAF) cellular heterogeneity and plasticity and the acellular matrix components that accompany these cells. We explore how similarities and differences between healing wounds and tumor stroma continue to evolve as research progresses, shedding light on possible therapeutic targets that can result in innovative stromal-based treatments for cancer.

  View details for DOI 10.1172/jci.insight.99911

  View details for PubMedID 30232274

• Utilizing Confocal Microscopy to Characterize Human and Mouse Adipose Tissue. Tissue engineering. Part C, Methods Blackshear, C., Borrelli, M. R., Shen, E. Z., Ransom, R. C., Chung, N. N., Vistnes, S., Irizarry, D., Nazerali, R., Momeni, A., Longaker, M. T., Wan, D. C. 2018

  Abstract

  Significant advances in our understanding of human obesity, endocrinology, and metabolism have been made possible by murine comparative models, in which anatomically analogous fat depots are utilized; however, current research has questioned how truly analogous these depots are. In this study, we assess the validity of the analogy from the perspective of cellular architecture. Whole tissue mounting, confocal microscopy, and image reconstruction software were employed to characterize the three-dimensional structure of the inguinal fat pad in mice, gluteofemoral fat in humans, and subcutaneous adipose tissue of the human abdominal wall. Abdominal and gluteofemoral adipose tissue specimens from 12 human patients and bilateral inguinal fat pads from 12 mice were stained for adipocytes, blood vessels, and a putative marker for adipose-derived multipotent progenitor cells, CD34. Samples were whole-mounted and imaged with laser scanning confocal microscopy. Expectedly, human adipocytes were larger and demonstrated greater size heterogeneity. Mouse fat displayed significantly higher vascular density compared to human fat when normalized to adipocyte count. There was no significant difference in the concentration of CD34+ stromal cells from either species. However, the mean distance between CD34+ stromal cells and blood vessels was significantly greater in human fat. Finally, mouse inguinal fat contained larger numbers of brown adipocytes than did human gluteofemoral or human abdominal fat. Overall, the basic architecture of human adipose tissue differs significantly from that of mice. Insofar as human gluteofemoral fat differs from human abdominal adipose tissue, it was closer to mouse inguinal fat, being its comparative developmental analogue. These differences likely confer variance in functional properties between the two sources, and thus must be considered when designing murine models of human disease.

  View details for PubMedID 30215305

• Pathway Analysis of Gene Expression in Murine Fetal and Adult Wounds. Advances in wound care Hu, M. S., Hong, W. X., Januszyk, M., Walmsley, G. G., Luan, A., Maan, Z. N., Moshrefi, S., Tevlin, R., Wan, D. C., Gurtner, G. C., Longaker, M. T., Lorenz, H. P. 2018; 7 (8): 262-275

  Abstract

  Objective: In early gestation, fetal wounds heal without fibrosis in a process resembling regeneration. Elucidating this remarkable mechanism can result in tremendous benefits to prevent scarring. Fetal mouse cutaneous wounds before embryonic day (E)18 heal without scar. Herein, we analyze expression profiles of fetal and postnatal wounds utilizing updated gene annotations and pathway analysis to further delineate between repair and regeneration. Approach: Dorsal wounds from time-dated pregnant BALB/c mouse fetuses and adult mice at various time points were collected. Total RNA was isolated and microarray analysis was performed using chips with 42,000 genes. Significance analysis of microarrays was utilized to select genes with >2-fold expression differences with a false discovery rate of <2. Enrichment analysis was performed on significant genes to identify differentially expressed pathways. Results: Our analysis identified 471 differentially expressed genes in fetal versus adult wounds following injury. Utilizing enrichment analysis of significant genes, we identified the top 20 signaling pathways that were upregulated and downregulated at 1 and 12 h after injury. At 24 h after injury, we discovered 18 signaling pathways upregulated in adult wounds and 11 pathways upregulated in fetal wounds. Innovation: These novel target genes and pathways may reveal repair mechanisms of the early fetus that promote regeneration over fibrosis. Conclusion: Our microarray analysis recognizes hundreds of possible genes as candidates for regulators of scarless versus scarring wound repair. Enrichment analysis reveals 109 signaling pathways related to fetal scarless wound healing.

  View details for DOI 10.1089/wound.2017.0779

  View details for PubMedID 30087802

  View details for PubMedCentralID PMC6080120

• Wound Healing Research at the Hagey Laboratory for Pediatric Regenerative Medicine at Stanford University School of Medicine. Advances in wound care Hu, M. S., Longaker, M. T. 2018; 7 (8): 257-261

  View details for DOI 10.1089/wound.2018.0787

  View details for PubMedID 30087801

  View details for PubMedCentralID PMC6080091

• Fibroblasts and wound healing: an update. Regenerative medicine des Jardins-Park, H. E., Foster, D. S., Longaker, M. T. 2018

  View details for PubMedID 30062921

• Genetic dissection of clonal lineage relationships with hydroxytamoxifen liposomes. Nature communications Ransom, R. C., Foster, D. S., Salhotra, A., Jones, R. E., Marshall, C. D., Leavitt, T., Murphy, M. P., Moore, A. L., Blackshear, C. P., Wan, D. C., Longaker, M. T. 2018; 9 (1): 2971

  Abstract

  Targeted genetic dissection of tissues to identify precise cell populations has vast biological and therapeutic applications. Here we develop an approach, through thepackaging and delivery of 4-hydroxytamoxifen liposomes (LiTMX), that enables localized induction of CreERT2 recombinase in mice. Our method permits precise, in vivo, tissue-specific clonal analysis with both spatial and temporal control. This technology is effective using mice with both specific and ubiquitous Cre drivers in a variety of tissue types, under conditions of homeostasis and post-injury repair, and is highly efficient for lineage tracing and genetic analysis. This methodology is directly and immediately applicable to the developmental biology, stem cell biology and regenerative medicine, and cancer biology fields.

  View details for PubMedID 30061668

• Genetic dissection of clonal lineage relationships with hydroxytamoxifen liposomes NATURE COMMUNICATIONS Ransom, R. C., Foster, D. S., Salhotra, A., Jones, R., Marshall, C. D., Leavitt, T., Murphy, M. P., Moore, A. L., Blackshear, C. P., Wan, D. C., Longaker, M. T. 2018; 9

  View details for DOI 10.1038/s41467-018-05436-6

  View details for Web of Science ID 000440149300004

• Fibroblasts and wound healing: an update REGENERATIVE MEDICINE desJardins-Park, H. E., Foster, D. S., Longaker, M. T. 2018; 13 (5): 491–95

  View details for DOI 10.2217/rme-2018-0073

  View details for Web of Science ID 000449034700001

• Iron Chelation with Transdermal Deferoxamine Accelerates Healing of Murine Sickle Cell Ulcers ADVANCES IN WOUND CARE Rodrigues, M., Bonham, C. A., Minniti, C. P., Gupta, K., Longaker, M. T., Gurtner, G. C. 2018

  View details for DOI 10.1089/wound.2018.0789

  View details for Web of Science ID 000435552200001

• Isolation and functional assessment of mouse skeletal stem cell lineage NATURE PROTOCOLS Gulati, G. S., Murphy, M. P., Marecic, O., Lopez, M., Brewer, R. E., Koepke, L. S., Manjunath, A., Ransom, R. C., Salhotra, A., Weissman, I. L., Longaker, M. T., Chan, C. F. 2018; 13 (6): 1294–1309

  Abstract

  There are limited methods available to study skeletal stem, progenitor, and progeny cell activity in normal and diseased contexts. Most protocols for skeletal stem cell isolation are based on the extent to which cells adhere to plastic or whether they express a limited repertoire of surface markers. Here, we describe a flow cytometry-based approach that does not require in vitro selection and that uses eight surface markers to distinguish and isolate mouse skeletal stem cells (mSSCs); bone, cartilage, and stromal progenitors (mBCSPs); and five downstream differentiated subtypes, including chondroprogenitors, two types of osteoprogenitors, and two types of hematopoiesis-supportive stroma. We provide instructions for the optimal mechanical and chemical digestion of bone and bone marrow, as well as the subsequent flow-cytometry-activated cell sorting (FACS) gating schemes required to maximally yield viable skeletal-lineage cells. We also describe a methodology for renal subcapsular transplantation and in vitro colony-formation assays on the isolated mSSCs. The isolation of mSSCs can be completed in 9 h, with at least 1 h more required for transplantation. Experience with flow cytometry and mouse surgical procedures is recommended before attempting the protocol. Our system has wide applications and has already been used to study skeletal response to fracture, diabetes, and osteoarthritis, as well as hematopoietic stem cell-niche interactions in the bone marrow.

  View details for PubMedID 29748647

• Wound Healing Research at the Hagey Laboratory for Pediatric Regenerative Medicine at Stanford University School of Medicine ADVANCES IN WOUND CARE Hu, M. S., Longaker, M. T. 2018: 1–5

  View details for DOI 10.1089/wound.2018.0787

  View details for Web of Science ID 000429094900001

• A Fibroblast Is Not a Fibroblast Is Not a Fibroblast JOURNAL OF INVESTIGATIVE DERMATOLOGY Hu, M. S., Moore, A. L., Longaker, M. T. 2018; 138 (4): 729–30

  Abstract

  Fibrosis after injury is a huge public health concern, leading to morbidity, mortality, and expenditure of billions of health care dollars. Recent mouse studies have shown that dermal fibroblasts are heterogeneous. New research using single-cell RNA sequencing to identify major fibroblast populations in humans is paving the way to a better understanding of fibroblast heterogeneity and fibrosis.

  View details for PubMedID 29579454

• Pathway Analysis of Gene Expression in Murine Fetal and Adult Wounds ADVANCES IN WOUND CARE Hu, M. S., Hong, W., Januszyk, M., Walmsley, G. G., Luan, A., Maan, Z. N., Moshrefi, S., Tevlin, R., Wan, D. C., Gurtner, G. C., Longaker, M. T., Lorenz, H. 2018

  View details for DOI 10.1089/wound.2017.0779

  View details for Web of Science ID 000429548900001

• Three-Dimensional Ultrasound Versus Computerized Tomography in Fat Graft Volumetric Analysis ANNALS OF PLASTIC SURGERY Blackshear, C., Rector, M., Chung, N., Irizarry, D., Flacco, J., Brett, E., Momeni, A., Lee, G., Longaker, M. T., Wan, D. C. 2018; 80 (3): 293–96

  Abstract

  Studies evaluating fat grafting in mice have frequently used micro-computed tomography (micro-CT) as an accurate radiographic tool to measure longitudinal volume retention without killing the animal. Over the past decade, however, microultrasonography has emerged as an equally powerful preclinical imaging tool. Given their respective strengths in 3-dimensional reconstruction, there is no study to our knowledge that directly compares micro-CT with microultrasound in volumetric analysis. In this study, we compared the performance of micro-CT with microultrasound in the evaluation of adipose tissue graft volume in a murine model. Fifteen immunodeficient mice were given 200 μL of adipose tissue grafts. In vivo volumetric analysis of the grafts by micro-CT and microultrasound was conducted at discrete time points up to postoperative day 105. Three mice were killed at multiple time points, and explanted grafts were reimaged by CT and ultrasound, as mentioned previously. Analysis revealed that in vivo graft volumes measured by micro-CT do not differ significantly from those of microultrasound. Furthermore, both micro-CT and microultrasound were capable of accurately measuring fat grafts as in vivo volumes closely correlated with explanted volumes. Finally, ultrasound was found to yield improved soft tissue contrast compared with micro-CT. Therefore, either modality may be used, depending on experimental needs.

  View details for DOI 10.1097/SAP.0000000000001183

  View details for Web of Science ID 000425352000021

  View details for PubMedID 28678028

  View details for PubMedCentralID PMC5752634

• beta-Catenin-Dependent Wnt Signaling: A Pathway in Acute Cutaneous Wounding PLASTIC AND RECONSTRUCTIVE SURGERY Carre, A. L., Hu, M. S., James, A. W., Kawai, K., Galvez, M. G., Longaker, M. T., Lorenz, H. 2018; 141 (3): 669–78

  Abstract

  Acute wound healing is a dynamic process that results in the formation of scar tissue. The mechanisms of this process are not well understood; numerous signaling pathways are thought to play a major role. Here, the authors have identified β-catenin-dependent Wnt signaling as an early acute-phase reactant in acute wound healing and scar formation.The authors created 6-mm full-thickness excisional cutaneous wounds on adult β-catenin-dependent Wnt signal (BAT-gal) reporter mice. The expression of canonical Wnt after wounding was analyzed using X-gal staining and quantitative real-time polymerase chain reaction. Next, recombinant mouse Wnt3a (rmWnt3a) was injected subcutaneously to the wound edge, daily. The mice were killed at stratified time points, up to 15 days after injury. Histologic analysis, quantitative real-time polymerase chain reaction, and Western blot were performed.Numerous individual Wnt ligands increased in expression after wounding, including Wnt3a, Wnt4, Wnt10a, and Wnt11. A specific pattern of Wnt activity was observed, localized to the hair follicle and epidermis. Mice injected with rmWnt3a exhibited faster wound closure, increased scar size, and greater expression of fibroblast growth factor receptor-2 and type I collagen.The authors' data suggest that β-catenin-dependent Wnt signaling expression increases shortly after cutaneous wounding, and exogenous rmWnt3a accelerates reepithelialization, wound matrix maturation, and scar formation. Future experiments will focus on the intersection of Wnt signaling and other known profibrotic cytokines.

  View details for PubMedID 29481398

• Deferoxamine Preconditioning of Irradiated Tissue Improves Perfusion and Fat Graft Retention PLASTIC AND RECONSTRUCTIVE SURGERY Flacco, J., Chung, N., Blackshear, C. P., Irizarry, D., Momeni, A., Lee, G. K., Dung Nguyen, Gurtner, G. C., Longaker, M. T., Wan, D. C. 2018; 141 (3): 655–65

  Abstract

  Radiation therapy is a mainstay in the treatment of many malignancies, but collateral damage to surrounding tissue, with resultant hypovascularity, fibrosis, and atrophy, can be difficult to reconstruct. Fat grafting has been shown to improve the quality of irradiated skin, but volume retention of the graft is significantly decreased. Deferoxamine is a U.S. Food and Drug Administration-approved iron-chelating medication for acute iron intoxication and chronic iron overload that has also been shown to increase angiogenesis. The present study evaluates the effects of deferoxamine treatment on irradiated skin and subsequent fat graft volume retention.Mice underwent irradiation to the scalp followed by treatment with deferoxamine or saline and perfusion and were analyzed using laser Doppler analysis. Human fat grafts were then placed beneath the scalp and retention was also followed up to 8 weeks radiographically. Finally, histologic evaluation of overlying skin was performed to evaluate the effects of deferoxamine preconditioning.Treatment with deferoxamine resulted in significantly increased perfusion, as demonstrated by laser Doppler analysis and CD31 immunofluorescent staining (p < 0.05). Increased dermal thickness and collagen content secondary to irradiation, however, were not affected by deferoxamine (p > 0.05). Importantly, fat graft volume retention was significantly increased when the irradiated recipient site was preconditioned with deferoxamine (p < 0.05).The authors' results demonstrated increased perfusion with deferoxamine treatment, which was also associated with improved fat graft volume retention. Preconditioning with deferoxamine may thus enhance fat graft outcomes for soft-tissue reconstruction following radiation therapy.

  View details for PubMedID 29135894

  View details for PubMedCentralID PMC5826842

• Embryonic skin development and repair. Organogenesis Hu, M. S., Borrelli, M. R., Hong, W. X., Malhotra, S., Cheung, A. T., Ransom, R. C., Rennert, R. C., Morrison, S. D., Lorenz, H. P., Longaker, M. T. 2018: 1–18

  Abstract

  Fetal cutaneous wounds have the unique ability to completely regenerate wounded skin and heal without scarring. However, adult cutaneous wounds heal via a fibroproliferative response which results in the formation of a scar. Understanding the mechanism(s) of scarless wound healing leads to enormous clinical potential in facilitating an environment conducive to scarless healing in adult cutaneous wounds. This article reviews the embryonic development of the skin and outlines the structural and functional differences in adult and fetal wound healing phenotypes. A review of current developments made towards applying this clinical knowledge to promote scarless healing in adult wounds is addressed.

  View details for PubMedID 29420124

• Review of the Current Management of Pressure Ulcers ADVANCES IN WOUND CARE Boyko, T. V., Longaker, M. T., Yang, G. P. 2018; 7 (2): 57–67

  Abstract

  Significance: The incidence of pressure ulcers is increasing due to our aging population and the increase in the elderly living with disability. Learning how to manage pressure ulcers appropriately is increasingly important for all professionals in wound care. Recent Advances: Many new dressings and treatment modalities have been developed over the recent years and the goal of this review is to highlight their benefits and drawbacks to help providers choose their tools appropriately. Critical Issues: Despite an increased number of therapies available on the market, none has demonstrated any clear benefit over the others and pressure ulcer treatment remains frustrating and time-consuming. Future Directions: Additional research is needed to develop products more effective in prevention and treatment of pressure ulcers.

  View details for PubMedID 29392094

  View details for PubMedCentralID PMC5792240

• Cutaneous Scarring: Basic Science, Current Treatments, and Future Directions ADVANCES IN WOUND CARE Marshall, C. D., Hu, M. S., Leavitt, T., Barnes, L. A., Lorenz, H., Longaker, M. T. 2018; 7 (2): 29–45

  Abstract

  Significance: Scarring of the skin from burns, surgery, and injury constitutes a major burden on the healthcare system. Patients affected by major scars, particularly children, suffer from long-term functional and psychological problems. Recent Advances: Scarring in humans is the end result of the wound healing process, which has evolved to rapidly repair injuries. Wound healing and scar formation are well described on the cellular and molecular levels, but truly effective molecular or cell-based antiscarring treatments still do not exist. Recent discoveries have clarified the role of skin stem cells and fibroblasts in the regeneration of injuries and formation of scar. Critical Issues: It will be important to show that new advances in the stem cell and fibroblast biology of scarring can be translated into therapies that prevent and reduce scarring in humans without major side effects. Future Directions: Novel therapies involving the use of purified human cells as well as agents that target specific cells and modulate the immune response to injury are currently undergoing testing. In the basic science realm, researchers continue to refine our understanding of the role that particular cell types play in the development of scar.

  View details for PubMedID 29392092

  View details for PubMedCentralID PMC5792238

• Mechanical Forces in Cutaneous Wound Healing: Emerging Therapies to Minimize Scar Formation ADVANCES IN WOUND CARE Barnes, L. A., Marshall, C. D., Leavitt, T., Hu, M. S., Moore, A. L., Gonzalez, J. G., Longaker, M. T., Gurtner, G. C. 2018; 7 (2): 47–56

  Abstract

  Significance: Excessive scarring is major clinical and financial burden in the United States. Improved therapies are necessary to reduce scarring, especially in patients affected by hypertrophic and keloid scars. Recent Advances: Advances in our understanding of mechanical forces in the wound environment enable us to target mechanical forces to minimize scar formation. Fetal wounds experience much lower resting stress when compared with adult wounds, and they heal without scars. Therapies that modulate mechanical forces in the wound environment are able to reduce scar size. Critical Issues: Increased mechanical stresses in the wound environment induce hypertrophic scarring via activation of mechanotransduction pathways. Mechanical stimulation modulates integrin, Wingless-type, protein kinase B, and focal adhesion kinase, resulting in cell proliferation and, ultimately, fibrosis. Therefore, the development of therapies that reduce mechanical forces in the wound environment would decrease the risk of developing excessive scars. Future Directions: The development of novel mechanotherapies is necessary to minimize scar formation and advance adult wound healing toward the scarless ideal. Mechanotransduction pathways are potential targets to reduce excessive scar formation, and thus, continued studies on therapies that utilize mechanical offloading and mechanomodulation are needed.

  View details for PubMedID 29392093

  View details for PubMedCentralID PMC5792236

• Mesenchymal Stromal Cells and Cutaneous Wound Healing: A Comprehensive Review of the Background, Role, and Therapeutic Potential STEM CELLS INTERNATIONAL Hu, M. S., Borrelli, M. R., Lorenz, H., Longaker, M. T., Wan, D. C. 2018: 6901983

  Abstract

  Cutaneous wound repair is a highly coordinated cascade of cellular responses to injury which restores the epidermal integrity and its barrier functions. Even under optimal healing conditions, normal wound repair of adult human skin is imperfect and delayed healing and scarring are frequent occurrences. Dysregulated wound healing is a major concern for global healthcare, and, given the rise in diabetic and aging populations, this medicoeconomic disease burden will continue to rise. Therapies to reliably improve nonhealing wounds and reduce scarring are currently unavailable. Mesenchymal stromal cells (MSCs) have emerged as a powerful technique to improve skin wound healing. Their differentiation potential, ease of harvest, low immunogenicity, and integral role in native wound healing physiology make MSCs an attractive therapeutic remedy. MSCs promote cell migration, angiogenesis, epithelialization, and granulation tissue formation, which result in accelerated wound closure. MSCs encourage a regenerative, rather than fibrotic, wound healing microenvironment. Recent translational research efforts using modern bioengineering approaches have made progress in creating novel techniques for stromal cell delivery into healing wounds. This paper discusses experimental applications of various stromal cells to promote wound healing and discusses the novel methods used to increase MSC delivery and efficacy.

  View details for PubMedID 29887893

  View details for PubMedCentralID PMC5985130

• Embryonic skin development and repair ORGANOGENESIS Hu, M. S., Borrelli, M. R., Hong, W., Malhotra, S., Cheung, A. M., Ransom, R. C., Rennert, R. C., Morrison, S. D., Lorenz, H., Longaker, M. T. 2018; 14 (1): 46–63

  View details for DOI 10.1080/15476278.2017.1421882

  View details for Web of Science ID 000435701100005

• Skin development and regeneration, and the control of fibrosis REGENERATIVE ENGINEERING AND DEVELOPMENTAL BIOLOGY: PRINCIPLES AND APPLICATIONS Hu, M. S., Lorenz, H., Longaker, M. T., Gardiner, D. M. 2018: 543–53

  View details for Web of Science ID 000461747900026

• Management of Chronic Wounds—2018 JAMA Jones, R., Foster, D. S., Longaker, M. T. 2018

  View details for DOI 10.1001/jama.2018.12426

• Wound Healing and Fibrosis: Current Stem Cell Therapies Transfusion Jones, R., Foster, D. S., Hu, M., Longaker, M. T. 2018

  View details for DOI 10.1111/trf.14836

• The evolving relationship of wound healing and tumor stroma JCI Insight Foster, D. S., Jones, R., Ransom, R., Longaker, M. T., Norton, J. A. 2018

  Abstract

  The stroma in solid tumors contains a variety of cellular phenotypes and signaling pathways associated with wound healing, leading to the concept that a tumor behaves as a wound that does not heal. Similarities between tumors and healing wounds include fibroblast recruitment and activation, extracellular matrix (ECM) component deposition, infiltration of immune cells, neovascularization, and cellular lineage plasticity. However, unlike a wound that heals, the edges of a tumor are constantly expanding. Cell migration occurs both inward and outward as the tumor proliferates and invades adjacent tissues, often disregarding organ boundaries. The focus of our review is cancer associated fibroblast (CAF) cellular heterogeneity and plasticity and the acellular matrix components that accompany these cells. We explore how similarities and differences between healing wounds and tumor stroma continue to evolve as research progresses, shedding light on possible therapeutic targets that can result in innovative stromal-based treatments for cancer.

  View details for DOI 10.1172/jci.insight.99911

• Scarless wound healing: Transitioning from fetal research to regenerative healing. Wiley interdisciplinary reviews. Developmental biology Moore, A. L., Marshall, C. D., Barnes, L. A., Murphy, M. P., Ransom, R. C., Longaker, M. T. 2018; 7 (2)

  Abstract

  Since the discovery of scarless fetal skin wound healing, research in the field has expanded significantly with the hopes of advancing the finding to adult human patients. There are several differences between fetal and adult skin that have been exploited to facilitate scarless healing in adults including growth factors, cytokines, and extracellular matrix substitutes. However, no one therapy, pathway, or cell subtype is sufficient to support scarless wound healing in adult skin. More recently, products that contain or mimic fetal and adult uninjured dermis were introduced to the wound healing market with promising clinical outcomes. Through our review of the major experimental targets of fetal wound healing, we hope to encourage research in areas that may have a significant clinical impact. Additionally, we will investigate therapies currently in clinical use and evaluate whether they represent a legitimate advance in regenerative medicine or a vulnerary agent. WIREs Dev Biol 2018, 7:e309. doi: 10.1002/wdev.309 This article is categorized under: Adult Stem Cells, Tissue Renewal, and Regeneration > Regeneration Plant Development > Cell Growth and Differentiation Adult Stem Cells, Tissue Renewal, and Regeneration > Environmental Control of Stem Cells.

  View details for PubMedID 29316315

• Pathway Analysis of Gene Expression of E14 Versus E18 Fetal Fibroblasts ADVANCES IN WOUND CARE Hu, M. S., Borrelli, M. R., Januszyk, M., Luan, A., Malhotra, S., Walmsley, G. G., Hong, W., Tevlin, R., Gurtner, G. C., Longaker, M. T., Lorenz, H. P. 2018; 7 (1): 1–10

  Abstract

  Objective: Fetuses early in gestation heal skin wounds without forming scars. The biological mechanisms behind this process are largely unknown. Fibroblasts, however, are cells known to be intimately involved in wound healing and scar formation. We examined fibroblasts in different stages of development to characterize differences in gene expression that may result in the switch from regenerative wound repair to repair with scarring. Approach: Fibroblasts were isolated and cultured from the back skin of BALB/c wild-type mouse fetuses at embryonic day (E)14 and E18 (n = 10). The fibroblast total RNA was extracted, and microarray analysis was conducted using chips containing 42,000 genes. Significance analysis of microarrays was performed to identify genes with greater than twofold expression difference and a false discovery rate of less than two. Identified genes subsequently underwent enrichment analysis to detect differentially expressed pathways. Results: Two hundred seventy-five genes were differentially expressed between E14 and E18 in fetal fibroblasts. Thirty genes were significantly downregulated and 245 genes were significantly upregulated at E18 compared with E14. Ingenuity pathway analysis identified the top 20 signaling pathways differentially activated in fetal fibroblasts between the E18 and E14 time points. Innovation: To our knowledge, this work represents the first instance where differentially expressed genes and signaling pathways between fetal fibroblasts at E14 and E18 have been studied. Conclusion: The genes and pathways identified here potentially underlie the mechanism behind the transition from fetal wound healing via regeneration to wound healing by repair, and may prove to be key targets for future therapeutics.

  View details for PubMedID 29344429

• An Improved Humanized Mouse Model for Excisional Wound Healing Using Double Transgenic Mice ADVANCES IN WOUND CARE Hu, M. S., Cheng, J., Borrelli, M. R., Leavitt, T., Walmsley, G. G., Zielins, E. R., Hong, W., Cheung, A. M., Duscher, D., Maan, Z. N., Irizarry, D. M., Stephan, B., Parsa, F., Wan, D. C., Gurtner, G. C., Lorenz, H., Longaker, M. T. 2018; 7 (1): 11–17

  Abstract

  Objective: Splinting full-thickness cutaneous wounds in mice has allowed for a humanized model of wound healing. Delineating the epithelial edge and assessing time to closure of these healing wounds via macroscopic visualization have remained a challenge. Approach: Double transgenic mice were created by crossbreeding K14-Cre and ROSAmT/mG reporter mice. Full-thickness excisional wounds were created in K14-Cre/ROSAmT/mG mice (n = 5) and imaged using both normal and fluorescent light on the day of surgery, and every other postoperative day (POD) until wound healing was complete. Ten blinded observers analyzed a series of images from a single representative healing wound, taken using normal or fluorescent light, to decide the POD when healing was complete. K14-Cre/ROSAmT/mG mice (n = 4) were subsequently sacrificed at the four potential days of rated wound closure to accurately determine the histological point of wound closure using microscopic fluorescence imaging. Results: Average time to wound closure was rated significantly longer in the wound series images taken using normal light, compared with fluorescent light (mean POD 13.6 vs. 11.6, *p = 0.008). Fluorescence imaging of histological samples indicated that reepithelialization was complete at 12 days postwounding. Innovation: We describe a novel technique, using double transgenic mice K14-Cre/ROSAmT/mG and fluorescence imaging, to more accurately determine the healing time of wounds in mice upon macroscopic evaluation. Conclusion: The accuracy by which wound healing can be macroscopically determined in vivo in mouse models of wound healing is significantly enhanced using K14-Cre/ROSAmT/mG double transgenic mice and fluorescence imaging.

  View details for PubMedID 29344430

• Transdermal Deferoxamine Significantly Enhances Healing of Sickle Cell Ulcers Rodrigues, M., Bonham, C. A., Inayathullah, M., Rajadas, J., Yang, G. P., Caterina, M. P., Gupta, K., Longaker, M. T., Gurtner, G. C. WILEY. 2018: A11

  View details for Web of Science ID 000430308600039

• Inhibition of IRE1 results in decreased scar formation. Wound repair and regeneration : official publication of the Wound Healing Society [and] the European Tissue Repair Society Boyko, T. V., Bam, R. n., Jiang, D. n., Wang, Z. n., Bhatia, N. n., Tran, M. C., Longaker, M. T., Koong, A. C., Yang, G. P. 2018

  Abstract

  Wound healing is characterized by the production of large amounts of protein necessary to replace lost cellular mass and extracellular matrix. The unfolded protein response (UPR) is an important adaptive cellular response to increased protein synthesis. One of the main components of the UPR is IRE1, an endoplasmic reticulum transmembrane protein with endonuclease activity that produces the activated form of the transcription factor XBP1. Using luciferase reporter mice for Xbp1 splicing, we showed that IRE1 was up-regulated during excisional wound healing at the time in wound healing consistent with that of the proliferative phase, when the majority of protein synthesis for cellular proliferation and matrix deposition occurs. Furthermore, using a small molecule inhibitor of IRE1 we demonstrated that inhibition of IRE1 led to decreased scar formation in treated mice. Results were recapitulated in a hypertrophic scar mouse model. These data help provide a cellular pathway to target in the treatment of hypertrophic scarring and keloid disorders.

  View details for PubMedID 29316036

• PHD-2 Suppression in Mesenchymal Stromal Cells Enhances Wound Healing PLASTIC AND RECONSTRUCTIVE SURGERY Ko, S., Nauta, A. C., Morrison, S. D., Hu, M. S., Zimmermann, A. S., Chung, M. T., Glotzbach, J. P., Wong, V. W., Walmsley, G. G., Lorenz, H., Chan, D. A., Gurtner, G. C., Giaccia, A. J., Longaker, M. T. 2018; 141 (1): 55E–67E

  Abstract

  Cell therapy with mesenchymal stromal cells is a promising strategy for tissue repair. Restoration of blood flow to ischemic tissues is a key step in wound repair, and mesenchymal stromal cells have been shown to be proangiogenic. Angiogenesis is critically regulated by the hypoxia-inducible factor (HIF) superfamily, consisting of transcription factors targeted for degradation by prolyl hydroxylase domain (PHD)-2. The aim of this study was to enhance the proangiogenic capability of mesenchymal stromal cells and to use these modified cells to promote wound healing.Mesenchymal stromal cells harvested from mouse bone marrow were transduced with short hairpin RNA (shRNA) against PHD-2; control cells were transduced with scrambled shRNA (shScramble) construct. Gene expression quantification, human umbilical vein endothelial cell tube formation assays, and wound healing assays were used to assess the effect of PHD knockdown mesenchymal stromal cells on wound healing dynamics.PHD-2 knockdown mesenchymal stromal cells overexpressed HIF-1α and multiple angiogenic factors compared to control (p < 0.05). Human umbilical vein endothelial cells treated with conditioned medium from PHD-2 knockdown mesenchymal stromal cells exhibited increased formation of capillary-like structures and enhanced migration compared with human umbilical vein endothelial cells treated with conditioned medium from shScramble-transduced mesenchymal stromal cells (p < 0.05). Wounds treated with PHD-2 knockdown mesenchymal stromal cells healed at a significantly accelerated rate compared with wounds treated with shScramble mesenchymal stromal cells (p < 0.05). Histologic studies revealed increased blood vessel density and increased cellularity in the wounds treated with PHD-2 knockdown mesenchymal stromal cells (p < 0.05).Silencing PHD-2 in mesenchymal stromal cells augments their proangiogenic potential in wound healing therapy. This effect appears to be mediated by overexpression of HIF family transcription factors and up-regulation of multiple downstream angiogenic factors.

  View details for PubMedID 29280872

  View details for PubMedCentralID PMC5747314

• Prrx1 Labels the Fibrogenic Fibroblast in the Ventral Dermis Hu, M., Leavitt, T., Garcia, J., Ransom, R., Litzenburger, U., Walmsley, G., Marshall, C., Moore, A., Mascharak, S., Chan, C., Wan, D., Lorenz, P., Chang, H., Longaker, M. WILEY. 2018: A4

  View details for Web of Science ID 000430308600009

• Noncoding RNAs in Wound Healing: A New and Vast Frontier ADVANCES IN WOUND CARE Luan, A., Hu, M. S., Leavitt, T., Brett, E. A., Wang, K. C., Longaker, M. T., Wan, D. C. 2018; 7 (1): 19–27

  Abstract

  Significance: Wound healing requires a highly orchestrated coordination of processes that are not yet fully understood. Therefore, available clinical therapies are thus far limited in their efficacy in preventing and treating both chronic wounds and scars. Current gene-based therapeutics is largely based on our understanding of the protein-coding genome and proteins involved in known wound healing pathways. Recent Advances: Noncoding RNAs such as microRNAs and long noncoding RNAs have recently been found to be significant modulators of gene expression in diverse cellular pathways. Research has now implicated noncoding RNAs in nearly every stage of the wound healing process, suggesting that they may serve as clinical therapeutic targets. Noncoding RNAs are critical regulators in processes such as angiogenesis and cutaneous cell migration and proliferation, including classically described biological pathways previously attributed to mostly protein constituents. Critical Issues: The complexity and diversity of the interactions of noncoding RNAs with their targets and other binding partners require thorough characterization and understanding of their functions before they may be altered to modulate human wound healing pathways. Future Directions: Research in the area of noncoding RNAs continues to rapidly expand our understanding of their potential roles in physiological and pathological wound healing. Coupled with improving technologies to enhance or suppress target noncoding RNA in vivo, these advances hold great promise in the development of new therapies for wound healing.

  View details for PubMedID 29344431

  View details for PubMedCentralID PMC5770091

• Ultrasound-assisted liposuction provides a source for functional adipose-derived stromal cells CYTOTHERAPY Duscher, D., Maan, Z. N., Luan, A., Aitzetmueller, M. M., Brett, E. A., Atashroo, D., Whittam, A. J., Hu, M. S., Walmsley, G. G., Houschyar, K. S., Schilling, A. F., Machens, H., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2017; 19 (12): 1491–1500

  Abstract

  Regenerative medicine employs human mesenchymal stromal cells (MSCs) for their multi-lineage plasticity and their pro-regenerative cytokine secretome. Adipose-derived mesenchymal stromal cells (ASCs) are concentrated in fat tissue, and the ease of harvest via liposuction makes them a particularly interesting cell source. However, there are various liposuction methods, and few have been assessed regarding their impact on ASC functionality. Here we study the impact of the two most popular ultrasound-assisted liposuction (UAL) devices currently in clinical use, VASER (Solta Medical) and Lysonix 3000 (Mentor) on ASCs.After lipoaspirate harvest and processing, we sorted for ASCs using fluorescent-assisted cell sorting based on an established surface marker profile (CD34+CD31-CD45-). ASC yield, viability, osteogenic and adipogenic differentiation capacity and in vivo regenerative performance were assessed.Both UAL samples demonstrated equivalent ASC yield and viability. VASER UAL ASCs showed higher osteogenic and adipogenic marker expression, but a comparable differentiation capacity was observed. Soft tissue healing and neovascularization were significantly enhanced via both UAL-derived ASCs in vivo, and there was no significant difference between the cell therapy groups.Taken together, our data suggest that UAL allows safe and efficient harvesting of the mesenchymal stromal cellular fraction of adipose tissue and that cells harvested via this approach are suitable for cell therapy and tissue engineering applications.

  View details for PubMedID 28917626

  View details for PubMedCentralID PMC5723208

• Cell-Based Soft Tissue Reconstruction in a Hydrogel Scaffold ANNALS OF PLASTIC SURGERY Blackshear, C. P., Flacco, J. S., Vistnes, S. M., Chung, N. N., Irizarry, D., Brett, E. A., Yen, D. J., Momeni, A., Longaker, M. T., Wan, D. C. 2017; 79 (6): 618–22

  Abstract

  Renevia is a hyaluronin-gelatin crosslinked matrix scaffold that has been studied as an alternative to adipose transfer in soft tissue reconstruction. It is designed to emulate the native extracellular matrix environment by supporting stromal vascular fraction (SVF) cell attachment, survival, and proliferation, thus promoting cell-based volume restoration. However, the concentration of incorporated cells for a clinically relevant result has yet to be determined.Five experimental groups of seven CD-1 nude immunodeficient mice were given 250 μL grafts of the following composition: 1 million human SVF cells per mL of Renevia scaffold, 6 million human SVF cells per mL scaffold, 12 million human SVF cells per mL scaffold, Renevia scaffold-alone or human adipose tissue-alone. Volumetric analysis was conducted at discrete time points over 16 weeks using 3-dimensional ultrasound, after which time the grafts were explanted for histologic analysis.At the conclusion of the study at week 16, the Renevia scaffold group incorporating the highest concentration of human SVF cells (12 million cells per mL scaffold) had significantly greater volume retention compared with the 2 lower concentrations, scaffold-alone and fat-alone groups. Histology of the 12 million scaffold group revealed abundant adipocyte formation within the scaffold, exceeding that observed in the 6 million, 1 million, and scaffold-alone groups. The 12 million group also demonstrated significantly increased vascularity per CD31 staining.Stromal vascular fraction cells coupled with Renevia hydrogel scaffold can enhance soft tissue volume reconstruction. In this study, we observed the greatest effect with 12 million cells per mL. From the perspective of volume retention, incorporation of higher concentrations of SVF cells with Renevia may be an alternative to conventional adipose tissue grafting.

  View details for PubMedID 28671889

  View details for PubMedCentralID PMC5677558

• A MUSE for Skin Regeneration JOURNAL OF INVESTIGATIVE DERMATOLOGY Hu, M. S., Longaker, M. T. 2017; 137 (12): 2471–72

  Abstract

  With a rise in the prevalence of chronic wounds and other soft tissue defects, there is an urgent need to regenerate skin. Multilineage-differentiating stress-enduring cells were identified as distinct pluripotent stem cells in mesenchymal cell populations in humans. New research demonstrates the ability to effectively differentiate multilineage-differentiating stress-enduring cells into fibroblasts and keratinocytes for skin reconstitution.

  View details for PubMedID 29169463

• Calvarial Defects: Cell-Based Reconstructive Strategies in the Murine Model TISSUE ENGINEERING PART C-METHODS Murphy, M. P., Quarto, N., Longaker, M. T., Wan, D. C. 2017; 23 (12): 971–81

  Abstract

  Calvarial defects pose a continued clinical dilemma for reconstruction. Advancements within the fields of stem cell biology and tissue engineering have enabled researchers to develop reconstructive strategies using animal models. We review the utility of various animal models and focus on the mouse, which has aided investigators in understanding cranial development and calvarial bone healing. The murine model has also been used to study regenerative approaches to critical-sized calvarial defects, and we discuss the application of stem cells such as bone marrow-derived mesenchymal stromal cells, adipose-derived stromal cells, muscle-derived stem cells, and pluripotent stem cells to address deficient bone in this animal. Finally, we highlight strategies to manipulate stem cells using various growth factors and inhibitors and ultimately how these factors may prove crucial in future advancements within calvarial reconstruction using native skeletal stem cells.

  View details for PubMedID 28825366

  View details for PubMedCentralID PMC5734144

• Epigenetic Analysis of Scar Forming Fibroblasts Reveals Key Differences in Genes Associated with Fibrosis Moore, A. L., Marshall, C. D., Litzenburger, U., Barnes, L., Ransom, R., Hu, M., Leavitt, T., Chang, H. Y., Longaker, M. T. ELSEVIER SCIENCE INC. 2017: S200–S201

  View details for DOI 10.1016/j.jamcollsurg.2017.07.460

  View details for Web of Science ID 000413315300436

• Fat Graft Retention Decreases with Recipient Age Montenegro, C. F., Flacco, J., Chung, N. N., Irizarry, D. M., Brett, E. A., Blackshear, C. P., Nguyen, D., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2017: E144–E145

  View details for DOI 10.1016/j.jamcollsurg.2017.07.917

  View details for Web of Science ID 000413319300353

• Shifting Skeletal Stem Cell Dynamics Underlie Skeletal Aging in Mice Marecic, O., McArdle, A., Seo, E., Tevlin, R., Gulati, G. S., Murphy, M. P., Lopez, M., Weissman, I. L., Chan, C. K., Longaker, M. T. ELSEVIER SCIENCE INC. 2017: S166

  View details for DOI 10.1016/j.jamcollsurg.2017.07.374

  View details for Web of Science ID 000413315300353

• Cellular Mechanisms Underlying Regeneration in Mandibular Distraction Osteogenesis Ransom, R. C., Leavitt, T., Murphy, M. P., Marecic, O., Lopez, M., Marshall, C. D., Barnes, L. A., Wan, D. C., Chan, C. K., Longaker, M. T. ELSEVIER SCIENCE INC. 2017: E143–E144

  View details for DOI 10.1016/j.jamcollsurg.2017.07.914

  View details for Web of Science ID 000413319300350

• Activation of the Mouse Resident Skeletal Stem Cell for Articular Cartilage Repair Murphy, M. P., Lopez, M., Ransom, R. C., Marecic, O., Gulati, G. S., Chan, C. K., Longaker, M. T. ELSEVIER SCIENCE INC. 2017: S160

  View details for DOI 10.1016/j.jamcollsurg.2017.07.360

  View details for Web of Science ID 000413315300339

• Rescue of Del1 Knock Out Phenotype in Bone Fracture Healing in Mice Boyko, T. V., Marecic, O., Lopez, M., Seo, E., Tong, X., Chan, C., Longaker, M. T., Yang, G. P. ELSEVIER SCIENCE INC. 2017: S89–S90

  View details for DOI 10.1016/j.jamcollsurg.2017.07.192

  View details for Web of Science ID 000413315300183

• Doxycyline Improves Wound Healing via Nonantibiotic Associated Mechanisms Moore, A. L., Murphy, M. P., Irizarry, D. M., Brett, E. A., Wernig, G., Longaker, M. T. ELSEVIER SCIENCE INC. 2017: S162–S163

  View details for DOI 10.1016/j.jamcollsurg.2017.07.366

  View details for Web of Science ID 000413315300345

• Invited Commentary on: Role of Notch Signaling in the Physiological Patterning of Posterofrontal and Sagittal Cranial Sutures JOURNAL OF CRANIOFACIAL SURGERY Quarto, N., Longaker, M. T. 2017; 28 (6): 1626–27

  View details for PubMedID 28796102

• Strategic Targeting of Multiple BMP Receptors Prevents Trauma-Induced Heterotopic Ossification MOLECULAR THERAPY Agarwal, S., Loder, S. J., Breuler, C., Li, J., Cholok, D., Brownley, C., Peterson, J., Hsieh, H. H., Drake, J., Ranganathan, K., Niknafs, Y. S., Xiao, W., Li, S., Kumar, R., Tompkins, R., Longaker, M. T., Davis, T. A., Yu, P. B., Mishina, Y., Levi, B. 2017; 25 (8): 1974–87

  Abstract

  Trauma-induced heterotopic ossification (tHO) is a condition of pathologic wound healing, defined by the progressive formation of ectopic bone in soft tissue following severe burns or trauma. Because previous studies have shown that genetic variants of HO, such as fibrodysplasia ossificans progressiva (FOP), are caused by hyperactivating mutations of the type I bone morphogenetic protein receptor (T1-BMPR) ACVR1/ALK2, studies evaluating therapies for HO have been directed primarily toward drugs for this specific receptor. However, patients with tHO do not carry known T1-BMPR mutations. Here we show that, although BMP signaling is required for tHO, no single T1-BMPR (ACVR1/ALK2, BMPR1a/ALK3, or BMPR1b/ALK6) alone is necessary for this disease, suggesting that these receptors have functional redundancy in the setting of tHO. By utilizing two different classes of BMP signaling inhibitors, we developed a translational approach to treatment, integrating treatment choice with existing diagnostic options. Our treatment paradigm balances either immediate therapy with reduced risk for adverse effects (Alk3-Fc) or delayed therapy with improved patient selection but greater risk for adverse effects (LDN-212854).

  View details for PubMedID 28716575

  View details for PubMedCentralID PMC5542633

• Isotretinoin and Timing of Procedural Interventions A Systematic Review With Consensus Recommendations JAMA DERMATOLOGY Spring, L. K., Krakowski, A. C., Alam, M., Bhatia, A., Brauer, J., Cohen, J., Del Rosso, J. Q., Diaz, L., Dover, J., Eichenfield, L. F., Gurtner, G. C., Hanke, C., Jahnke, M. N., Kelly, K. M., Khetarpal, S., Kinney, M. A., Levy, M. L., Leyden, J., Longaker, M. T., Munavalli, G. S., Ozog, D. M., Prather, H., Shumaker, P. R., Tanzi, E., Torres, A., Velez, M., Waldman, A. B., Yan, A. C., Zaenglein, A. L. 2017; 153 (8): 802–9

  Abstract

  The notion that systemic isotretinoin taken within 6 to 12 months of cutaneous surgery contributes to abnormal scarring or delayed wound healing is widely taught and practiced; however, it is based on 3 small case series from the mid-1980s.To evaluate the body of literature to provide evidence-based recommendations regarding the safety of procedural interventions performed either concurrently with, or immediately following the cessation of systemic isotretinoin therapy.A panel of national experts in pediatric dermatology, procedural/cosmetic dermatology, plastic surgery, scars, wound healing, acne, and isotretinoin was convened. A systematic PubMed review of English-language articles published from 1982 to 2017 was performed using the following search terms: isotretinoin, 13-cis-retinoic acid, Accutane, retinoids, acitretin, surgery, surgical, laser, ablative laser, nonablative laser, laser hair removal, chemical peel, dermabrasion, wound healing, safety, scarring, hypertrophic scar, and keloid. Evidence was graded, and expert consensus was obtained.Thirty-two relevant publications reported 1485 procedures. There was insufficient evidence to support delaying manual dermabrasion, superficial chemical peels, cutaneous surgery, laser hair removal, and fractional ablative and nonablative laser procedures for patients currently receiving or having recently completed isotretinoin therapy. Based on the available literature, mechanical dermabrasion and fully ablative laser are not recommended in the setting of systemic isotretinoin treatment.Physicians and patients may have an evidence-based discussion regarding the known risk of cutaneous surgical procedures in the setting of systemic isotretinoin therapy. For some patients and some conditions, an informed decision may lead to earlier and potentially more effective interventions.

  View details for PubMedID 28658462

• Discussion: Combining Smoothened Agonist and NEL-Like Protein-1 Enhances Bone Healing. Plastic and reconstructive surgery Ransom, R. C., Longaker, M. T. 2017; 139 (6): 1397-1398

  View details for DOI 10.1097/PRS.0000000000003368

  View details for PubMedID 28538564

• Dynamic Rheology for the Prediction of Surgical Outcomes in Autologous Fat Grafting. Plastic and reconstructive surgery Luan, A., Zielins, E. R., Wearda, T., Atashroo, D. A., Blackshear, C. P., Raphel, J., Brett, E. A., Flacco, J., Alyono, M. C., Momeni, A., Heilshorn, S., Longaker, M. T., Wan, D. C. 2017

  Abstract

  Due to the abundance and biocompatibility of fat, lipotransfer has become an attractive method for treating soft tissue deficits. However, it is limited by unpredictable graft survival and retention. Currently, little is known about the viscoelastic properties of fat after various injection methods. Here, we assess the effects of cannula diameter, length, and shape on the viscoelastic properties, structure, and retention of fat.Human lipoaspirate was harvested using suction-assisted liposuction and prepared for grafting. A syringe pump was used to inject fat at a controlled flow rate through cannulas of varying gauge, length, and shape. Processed samples were tested in triplicate on an oscillatory rheometer to measure their viscoelastic properties. Fat grafts from each group were placed into the scalps of immunocompromised mice. After 8 weeks, graft retention was measured using micro-CT and grafts were explanted for histological analysis.Lipoaspirate injected through narrower, longer, and bent cannulas exhibited more shear thinning with diminished quality. The storage modulus (G') of fat processed with 18-gauge cannulas was significantly lower than when processed with 14-gauge or larger cannulas, which also corresponded with inferior in vivo histological structure. Similarly, the longer cannula group had a significantly lower G' than the shorter cannula, and was associated with decreased graft retention.Discrete modifications in the methods used for fat placement can have a significant impact on immediate graft integrity, and ultimately on graft survival and quality. Respecting these biomechanical influences during the placement phase of lipotransfer may allow surgeons to optimize outcomes.

  View details for DOI 10.1097/PRS.0000000000003578

  View details for PubMedID 28574947

• Protein-Nanoparticle Hydrogels That Self-assemble in Response to Peptide-Based Molecular Recognition. ACS biomaterials science & engineering Parisi-Amon, A., Lo, D. D., Montoro, D. T., Dewi, R. E., Longaker, M. T., Heilshorn, S. C. 2017; 3 (5): 750-756

  Abstract

  Recently, supramolecular hydrogels assembled through nonspecific interactions between polymers and nanoparticles (termed PNP systems) were reported to have rapid shear-thinning and self-healing properties amenable for cell-delivery applications in regenerative medicine. Here, we introduce protein engineering concepts into the design of a new family of PNP hydrogels to enable direct control over the polymer-nanoparticle interactions using peptide-based molecular recognition motifs. Specifically, we have designed a bifunctional peptide that induces supramolecular hydrogel assembly between hydroxy apatite nanoparticles and an engineered, recombinant protein. We demonstrate that this supramolecular assembly critically requires molecular recognition, as no assembly is observed in the presence of control peptides with a scrambled amino acid sequence. Titration of the bifunctional peptide enables direct control over the number of physical cross-links within the system and hence the resulting hydrogel mechanical properties. As with previous PNP systems, these materials are rapidly shear-thinning and self-healing. As proof-of-concept, we demonstrate that these materials are suitable for therapeutic cell delivery applications in a preclinical murine calvarial defect model.

  View details for DOI 10.1021/acsbiomaterials.6b00286

  View details for PubMedID 33440497

• Isolation of CD248-expressing stromal vascular fraction for targeted improvement of wound healing. Wound repair and regeneration Brett, E., Zielins, E. R., Chin, M., Januszyk, M., Blackshear, C. P., Findlay, M., Momeni, A., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2017

  Abstract

  Wound healing remains a global issue of disability, cost, and health. Addition of cells from the stromal vascular fraction (SVF) of adipose tissue has been shown to increase the rate of full thickness wound closure. This study aimed to investigate the angiogenic mechanisms of CD248+ SVF cells in the context of full thickness excisional wounds. Single cell transcriptional analysis was used to identify and cluster angiogenic gene-expressing cells, which was then correlated with surface marker expression. SVF cells isolated from human lipoaspirate were FACS sorted based on the presence of CD248. Cells were analyzed for angiogenic gene expression and ability to promote microvascular tubule formation in vitro. Following this, 6mm full thickness dermal wounds were created on the dorsa of immunocompromised mice and then treated with CD248+, CD248-, or unsorted SVF cells delivered in a pullalan-collagen hydrogel or the hydrogel alone. Wounds were measured every other day photometrically until closure. Wounds were also evaluated histologically at 7 and 14 days post-wounding and when fully healed to assess for reepithelialization and development of neovasculature. Wounds treated with CD248+ cells healed significantly faster than other treatment groups, and at 7 days, had quantitatively more reepithelialization. Concurrently, immunohistochemistry of CD31 revealed a much higher presence of vascularity in the CD248+ SVF cells treated group at the time of healing and at 14 days post-op, consistent with a pro-angiogenic effect of CD248+ cells in vivo. Therefore, using CD248+ pro-angiogenic cells obtained from SVF presents a viable strategy in wound healing by promoting increased vessel growth in the wound.

  View details for DOI 10.1111/wrr.12542

  View details for PubMedID 28464475

• Protein-Nanoparticle Hydrogels That Self-assemble in Response to Peptide-Based Molecular Recognition ACS BIOMATERIALS SCIENCE & ENGINEERING Parisi-Amon, A., Lo, D. D., Montoro, D. T., Dew, R. E., Longaker, M. T., Heilshorn, S. C. 2017; 3 (5): 750-756

  View details for DOI 10.1021/acsbiomaterials.6b00286

  View details for Web of Science ID 000401053800009

• A Review of Cell-Based Strategies for Soft Tissue Reconstruction. Tissue engineering. Part B, Reviews Brett, E., Chung, N., Leavitt, W. T., Momeni, A., Longaker, M. T., Wan, D. C. 2017

  Abstract

  Soft tissue reconstruction to restore volume to damaged or deficient tissue beneath the skin remains a challenging endeavor. Current techniques are centered around autologous fat transfer, or the use of synthetic substitutes, however, a great deal of scientific inquiry has been made into both the molecular mechanisms involved in, and limitations of, de novo adipogenesis, that is, the formation of new adipose tissue from precursor cells. To best comprehend these mechanisms, an understanding of defined markers for adipogenic differentiation, and knowledge of both commercially available and primary cell lines that enable in vitro and in vivo studies is necessary. We review the growth factors, proteins, cytokines, drugs, and molecular pathways that have shown promise in enhancing adipogenesis and vasculogenesis, in addition to the multitude of scaffolds that act as delivery vehicles to support these processes. While progress continues on these fronts, equally important is how researchers are optimizing clinically employed strategies such as autologous fat transfer through cell-based intervention, and the potential to augment this approach through isolation of preferentially adipogenic or angiogenic precursor subpopulations, which exists on the horizon. This review will highlight the novel molecular and synthetic modifications currently being studied for inducing adipose tissue regeneration on a cellular level, which will expand our arsenal of techniques for approaching soft tissue reconstruction.

  View details for DOI 10.1089/ten.TEB.2016.0455

  View details for PubMedID 28372485

• Purified Adipose-Derived Stromal Cells Provide Superior Fat Graft Retention Compared with Unenriched Stromal Vascular Fraction PLASTIC AND RECONSTRUCTIVE SURGERY Zielins, E. R., Brett, E. A., Blackshear, C. P., Flacco, J., Ransom, R. C., Longaker, M. T., Wan, D. C. 2017; 139 (4): 911–14

  Abstract

  Cell-assisted lipotransfer has shown much promise as a technique to improve fat graft retention in both mouse and human studies. However, the literature varies as to whether fresh stromal vascular fraction or culture-expanded adipose-derived stromal cells are used to augment volume retention. The authors' study sought to determine whether there was a significant advantage to using adipose-derived stromal cells over unpurified stromal vascular fraction cells in a mouse model of cell-assisted lipotransfer.

  View details for PubMedID 28350672

  View details for PubMedCentralID PMC5398091

• Discussion: Regeneration of Vascularized Corticocancellous Bone and Diploic Space Using Muscle- Derived Stem Cells: A Translational Biologic Alternative for Healing Critical Bone Defects PLASTIC AND RECONSTRUCTIVE SURGERY Murphy, M. P., Chan, C. K., Longaker, M. T. 2017; 139 (4): 906-907

  View details for DOI 10.1097/PRS.0000000000003210

  View details for PubMedID 28350669

• Discussion: Towards Microsurgical Correction of Cleft Lip Ex Utero via Restoration of Craniofacial Developmental Programs. Plastic and reconstructive surgery Ransom, R. C., Lorenz, H. P., Longaker, M. T. 2017

  View details for DOI 10.1097/PRS.0000000000003424

  View details for PubMedID 28338583

• Comparison of the Hydroxylase Inhibitor Dimethyloxalylglycine and the Iron Chelator Deferoxamine in Diabetic and Aged Wound Healing. Plastic and reconstructive surgery Duscher, D., Januszyk, M., Maan, Z. N., Whittam, A. J., Hu, M. S., Walmsley, G. G., Dong, Y., Khong, S. M., Longaker, M. T., Gurtner, G. C. 2017; 139 (3): 695e-706e

  Abstract

  A hallmark of diabetes mellitus is the breakdown of almost every reparative process in the human body, leading to critical impairments of wound healing. Stabilization and activity of the transcription factor hypoxia-inducible factor (HIF)-1α is impaired in diabetes, leading to deficits in new blood vessel formation in response to injury. In this article, the authors compare the effectiveness of two promising small-molecule therapeutics, the hydroxylase inhibitor dimethyloxalylglycine and the iron chelator deferoxamine, for attenuating diabetes-associated deficits in cutaneous wound healing by enhancing HIF-1α activation.HIF-1α stabilization, phosphorylation, and transactivation were measured in murine fibroblasts cultured under normoxic or hypoxic and low-glucose or high-glucose conditions following treatment with deferoxamine or dimethyloxalylglycine. In addition, diabetic wound healing and neovascularization were evaluated in db/db mice treated with topical solutions of either deferoxamine or dimethyloxalylglycine, and the efficacy of these molecules was also compared in aged mice.The authors show that deferoxamine stabilizes HIF-1α expression and improves HIF-1α transactivity in hypoxic and hyperglycemic states in vitro, whereas the effects of dimethyloxalylglycine are significantly blunted under hyperglycemic hypoxic conditions. In vivo, both dimethyloxalylglycine and deferoxamine enhance wound healing and vascularity in aged mice, but only deferoxamine universally augmented wound healing and neovascularization in the setting of both advanced age and diabetes.This first direct comparison of deferoxamine and dimethyloxalylglycine in the treatment of impaired wound healing suggests significant therapeutic potential for topical deferoxamine treatment in ischemic and diabetic disease.

  View details for DOI 10.1097/PRS.0000000000003072

  View details for PubMedID 28234841

  View details for PubMedCentralID PMC5327844

• Minimizing Skin Scarring through Biomaterial Design JOURNAL OF FUNCTIONAL BIOMATERIALS Moore, A. L., Marshall, C. D., Longaker, M. T. 2017; 8 (1)

  View details for DOI 10.3390/jfb8010003

  View details for Web of Science ID 000446638700002

• Laboratory Models for the Study of Normal and Pathologic Wound Healing. Plastic and reconstructive surgery Boyko, T. V., Longaker, M. T., Yang, G. P. 2017; 139 (3): 654-662

  Abstract

  Current knowledge of wound healing is based on studies using various in vitro and in vivo wound models. In vitro models allow for biological examination of specific cell types involved in wound healing. In vivo models generally provide the full spectrum of biological responses required for wound healing, including inflammation and angiogenesis, and provide cell-cell interactions not seen in vitro. In this review, the authors aim to delineate the most relevant wound healing models currently available and to discuss their strengths and limitations in their approximation of the human wound healing processes to aid scientists in choosing the most appropriate wound healing models for designing, testing, and validating their experiments.

  View details for DOI 10.1097/PRS.0000000000003077

  View details for PubMedID 28234843

• Fibroblasts become fat to reduce scarring. Science Chan, C. K., Longaker, M. T. 2017; 355 (6326): 693-694

  View details for DOI 10.1126/science.aam6748

  View details for PubMedID 28209860

• Excess Dermal Tissue Remodeling In Vivo: Does It Settle? Plastic and reconstructive surgery Leavitt, T., Hu, M. S., Zielins, E. R., Barnes, L. A., Marshall, C. D., Wan, D. C., Lorenz, H. P., Gurtner, G. C., Longaker, M. T. 2017; 139 (2): 415e-424e

  Abstract

  Surgical manipulation of skin may result in undesired puckering of excess tissue, which is generally assumed to settle over time. In this article, the authors address the novel question of how this excess tissue remodels.Purse-string sutures (6-0 nylon) were placed at the midline dorsum of 22 wild-type BALB/c mice in a circular pattern marked with tattoo ink. Sutures were cinched and tied under tension in the treatment group, creating an excess tissue deformity, whereas control group sutures were tied without tension. After 2 or 4 weeks, sutures were removed. The area of tattooed skin was measured up to 56 days after suture removal. Histologic analysis was performed on samples harvested 14 days after suture removal.The majority of excess tissue deformities flattened within 2 days after suture removal. However, the sutured skin in the treatment group decreased in area by an average of 18 percent from baseline (n = 9), compared to a 1 percent increase in the control group (n = 10) at 14 days after suture removal (p < 0.05). This was similarly observed at 28 days (treatment, -11.7 percent; control, 4.5 percent; n = 5; p = 0.0243). Despite flattening, deformation with purse-string suture correlated with increased collagen content of skin, in addition to increased numbers of myofibroblasts. Change in area did not correlate with duration of suture placement.Excess dermal tissue deformities demonstrate the ability to remodel with gross flattening of the skin, increased collagen deposition, and incomplete reexpansion to baseline area. Further studies will reveal whether our findings in this mouse model translate to humans.

  View details for DOI 10.1097/PRS.0000000000003026

  View details for PubMedID 28121870

• Rapid Isolation of BMPR-IB plus Adipose-Derived Stromal Cells for Use in a Calvarial Defect Healing Model JOVE-JOURNAL OF VISUALIZED EXPERIMENTS Marshall, C. D., Zielins, E. R., Brett, E. A., Blackshear, C. P., Hu, M. S., Leavitt, T., Barnes, L. A., Lorenz, H. P., Longaker, M. T., Wan, D. C. 2017

  Abstract

  Invasive cancers, major injuries, and infection can cause bone defects that are too large to be reconstructed with preexisting bone from the patient's own body. The ability to grow bone de novo using a patient's own cells would allow bony defects to be filled with adequate tissue without the morbidity of harvesting native bone. There is interest in the use of adipose-derived stromal cells (ASCs) as a source for tissue engineering because these are obtained from an abundant source: the patient's own adipose tissue. However, ASCs are a heterogeneous population and some subpopulations may be more effective in this application than others. Isolation of the most osteogenic population of ASCs could improve the efficiency and effectiveness of a bone engineering process. In this protocol, ASCs are obtained from subcutaneous fat tissue from a human donor. The subpopulation of ASCs expressing the marker BMPR-IB is isolated using FACS. These cells are then applied to an in vivo calvarial defect healing assay and are found to have improved osteogenic regenerative potential compared with unsorted cells.

  View details for DOI 10.3791/55120

  View details for Web of Science ID 000397847700048

  View details for PubMedID 28287559

• Rapid Isolation of BMPR-IB plus Adipose-Derived Stromal Cells for Use in a Calvarial Defect Healing Model JOVE-JOURNAL OF VISUALIZED EXPERIMENTS Marshall, C. D., Zielins, E. R., Brett, E. A., Blackshear, C. P., Hu, M. S., Leavitt, T., Barnes, L. A., Lorenz, H. P., Longaker, M. T., Wan, D. C. 2017

  Abstract

  Invasive cancers, major injuries, and infection can cause bone defects that are too large to be reconstructed with preexisting bone from the patient's own body. The ability to grow bone de novo using a patient's own cells would allow bony defects to be filled with adequate tissue without the morbidity of harvesting native bone. There is interest in the use of adipose-derived stromal cells (ASCs) as a source for tissue engineering because these are obtained from an abundant source: the patient's own adipose tissue. However, ASCs are a heterogeneous population and some subpopulations may be more effective in this application than others. Isolation of the most osteogenic population of ASCs could improve the efficiency and effectiveness of a bone engineering process. In this protocol, ASCs are obtained from subcutaneous fat tissue from a human donor. The subpopulation of ASCs expressing the marker BMPR-IB is isolated using FACS. These cells are then applied to an in vivo calvarial defect healing assay and are found to have improved osteogenic regenerative potential compared with unsorted cells.

  View details for DOI 10.3791/55120

  View details for Web of Science ID 000397847700048

  View details for PubMedID 28287559

• Sanativo Wound Healing Product Does Not Accelerate Reepithelialization in a Mouse Cutaneous Wound Healing Model. Plastic and reconstructive surgery Marshall, C. D., Hu, M. S., Leavitt, T., Barnes, L. A., Cheung, A. T., Malhotra, S., Lorenz, H. P., Delp, S. L., Quake, S. R., Longaker, M. T. 2017; 139 (2): 343-352

  Abstract

  Sanativo is an over-the-counter Brazilian product derived from Amazon rainforest plant extract that is purported to improve the healing of skin wounds. Two experimental studies have shown accelerated closure of nonsplinted excisional wounds in rat models. However, these models allow for significant contraction of the wound and do not approximate healing in the tight skin of humans.Full-thickness excisional wounds were created on the dorsal skin of mice and were splinted with silicone rings, a model that forces the wound to heal by granulation and reepithelialization. Sanativo or a control solution was applied either daily or every other day to the wounds. Photographs were taken every other day, and the degree of reepithelialization of the wounds was determined.With both daily and every-other-day applications, Sanativo delayed reepithelialization of the wounds. Average time to complete healing was faster with control solution versus Sanativo in the daily application group (9.4 versus 15.2 days; p < 0.0001) and the every-other-day application group (11 versus 13 days; p = 0.017). The size of visible scar at the last time point of the study was not significantly different between the groups, and no differences were found on histologic examination.Sanativo wound healing compound delayed wound reepithelialization in a mouse splinted excisional wound model that approximates human wound healing. The size of visible scar after complete healing was not improved with the application of Sanativo. These results should cast doubt on claims that this product can improve wound healing in humans.

  View details for DOI 10.1097/PRS.0000000000003013

  View details for PubMedID 28121865

• Detection of Stem Cell Transplant Rejection with Ferumoxytol MR Imaging: Correlation of MR Imaging Findings with Those at Intravital Microscopy. Radiology Daldrup-Link, H. E., Chan, C., Lenkov, O., Taghavigarmestani, S., Nazekati, T., Nejadnik, H., Chapelin, F., Khurana, A., Tong, X., Yang, F., Pisani, L., Longaker, M., Gambhir, S. S. 2017: 161139-?

  Abstract

  Purpose To determine whether endogenous labeling of macrophages with clinically applicable nanoparticles enables noninvasive detection of innate immune responses to stem cell transplants with magnetic resonance (MR) imaging. Materials and Methods Work with human stem cells was approved by the institutional review board and the stem cell research oversight committee, and animal experiments were approved by the administrative panel on laboratory animal care. Nine immunocompetent Sprague-Dawley rats received intravenous injection of ferumoxytol, and 18 Jax C57BL/6-Tg (Csf1r-EGFP-NGFR/FKBP1A/TNFRSF6) 2Bck/J mice received rhodamine-conjugated ferumoxytol. Then, 48 hours later, immune-matched or mismatched stem cells were implanted into osteochondral defects of the knee joints of experimental rats and calvarial defects of Jax mice. All animals underwent serial MR imaging and intravital microscopy (IVM) up to 4 weeks after surgery. Macrophages of Jax C57BL/6-Tg (Csf1r-EGFP-NGFR/FKBP1A/TNFRSF6) 2Bck/J mice express enhanced green fluorescent protein (GFP), which enables in vivo correlation of ferumoxytol enhancement at MR imaging with macrophage quantities at IVM. All quantitative data were compared between experimental groups by using a mixed linear model and t tests. Results Immune-mismatched stem cell implants demonstrated stronger ferumoxytol enhancement than did matched stem cell implants. At 4 weeks, T2 values of mismatched implants were significantly lower than those of matched implants in osteochondral defects of female rats (mean, 10.72 msec for human stem cells and 11.55 msec for male rat stem cells vs 15.45 msec for sex-matched rat stem cells; P = .02 and P = .04, respectively) and calvarial defects of recipient mice (mean, 21.7 msec vs 27.1 msec, respectively; P = .0444). This corresponded to increased recruitment of enhanced GFP- and rhodamine-ferumoxytol-positive macrophages into stem cell transplants, as visualized with IVM and histopathologic examination. Conclusion Endogenous labeling of macrophages with ferumoxytol enables noninvasive detection of innate immune responses to stem cell transplants with MR imaging. (©) RSNA, 2017 Online supplemental material is available for this article.

  View details for DOI 10.1148/radiol.2017161139

  View details for PubMedID 28128708

• Minimizing Skin Scarring through Biomaterial Design. Journal of functional biomaterials Moore, A. L., Marshall, C. D., Longaker, M. T. 2017; 8 (1)

  Abstract

  Wound healing continues to be a major burden to patients, though research in the field has expanded significantly. Due to an aging population and increasing comorbid conditions, the cost of chronic wounds is expected to increase for patients and the U.S. healthcare system alike. With this knowledge, the number of engineered products to facilitate wound healing has also increased dramatically, with some already in clinical use. In this review, the major biomaterials used to facilitate skin wound healing will be examined, with particular attention allocated to the science behind their development. Experimental therapies will also be evaluated.

  View details for DOI 10.3390/jfb8010003

  View details for PubMedID 28117733

• Pharmacological rescue of diabetic skeletal stem cell niches. Science translational medicine Tevlin, R., Seo, E. Y., Marecic, O., McArdle, A., Tong, X., Zimdahl, B., Malkovskiy, A., Sinha, R., Gulati, G., Li, X., Wearda, T., Morganti, R., Lopez, M., Ransom, R. C., Duldulao, C. R., Rodrigues, M., Nguyen, A., Januszyk, M., Maan, Z., Paik, K., Yapa, K., Rajadas, J., Wan, D. C., Gurtner, G. C., Snyder, M., Beachy, P. A., Yang, F., Goodman, S. B., Weissman, I. L., Chan, C. K., Longaker, M. T. 2017; 9 (372)

  Abstract

  Diabetes mellitus (DM) is a metabolic disease frequently associated with impaired bone healing. Despite its increasing prevalence worldwide, the molecular etiology of DM-linked skeletal complications remains poorly defined. Using advanced stem cell characterization techniques, we analyzed intrinsic and extrinsic determinants of mouse skeletal stem cell (mSSC) function to identify specific mSSC niche-related abnormalities that could impair skeletal repair in diabetic (Db) mice. We discovered that high serum concentrations of tumor necrosis factor-α directly repressed the expression of Indian hedgehog (Ihh) in mSSCs and in their downstream skeletogenic progenitors in Db mice. When hedgehog signaling was inhibited during fracture repair, injury-induced mSSC expansion was suppressed, resulting in impaired healing. We reversed this deficiency by precise delivery of purified Ihh to the fracture site via a specially formulated, slow-release hydrogel. In the presence of exogenous Ihh, the injury-induced expansion and osteogenic potential of mSSCs were restored, culminating in the rescue of Db bone healing. Our results present a feasible strategy for precise treatment of molecular aberrations in stem and progenitor cell populations to correct skeletal manifestations of systemic disease.

  View details for DOI 10.1126/scitranslmed.aag2809

  View details for PubMedID 28077677

• Pharmacological rescue of diabetic skeletal stem cell niches SCIENCE TRANSLATIONAL MEDICINE Tevlin, R., Seo, E., Marecic, O., McArdle, A., Tong, X., Zimdahl, B., Malkovskiy, A., Sinha, R., Gulati, G., Li, X., Wearda, T., Morganti, R., Lopez, M., Ransom, R. C., Duldulao, C. R., Rodrigues, M., Nguyen, A., Januszyk, M., Maan, Z., Paik, K., Yapa, K., Rajadas, J., Wan, D. C., Gurtner, G. C., Snyder, M., Beachy, P. A., Yang, F., Goodman, S. B., Weissman, I. L., Chan, C. F., Longaker, M. T. 2017; 9 (372)

  View details for DOI 10.1126/scitranslmed.aag2809

  View details for Web of Science ID 000394445700005

• Hyaluronic acid synthesis is required for zebrafish tail fin regeneration. PloS one Ouyang, X., Panetta, N. J., Talbott, M. D., Payumo, A. Y., Halluin, C., Longaker, M. T., Chen, J. K. 2017; 12 (2)

  Abstract

  Using genome-wide transcriptional profiling and whole-mount expression analyses of zebrafish larvae, we have identified hyaluronan synthase 3 (has3) as an upregulated gene during caudal fin regeneration. has3 expression is induced in the wound epithelium within hours after tail amputation, and its onset and maintenance requires fibroblast growth factor, phosphoinositide 3-kinase, and transforming growth factor-ß signaling. Inhibition of hyaluronic acid (HA) synthesis by the small molecule 4-methylumbelliferone (4-MU) impairs tail regeneration in zebrafish larvae by preventing injury-induced cell proliferation. In addition, 4-MU reduces the expression of genes associated with wound epithelium and blastema function. Treatment with glycogen synthase kinase 3 inhibitors rescues 4-MU-induced defects in cell proliferation and tail regeneration, while restoring a subset of wound epithelium and blastema markers. Our findings demonstrate a role for HA biosynthesis in zebrafish tail regeneration and delineate its epistatic relationships with other regenerative processes.

  View details for DOI 10.1371/journal.pone.0171898

  View details for PubMedID 28207787

  View details for PubMedCentralID PMC5313160

• The Role of Skeletal Stem Cells in the Reconstruction of Bone Defects. The Journal of craniofacial surgery Murphy, M. P., Irizarry, D. n., Lopez, M. n., Moore, A. L., Ransom, R. C., Longaker, M. T., Wan, D. C., Chan, C. K. 2017; 28 (5): 1136–41

  Abstract

  Craniofacial surgery, since its inauguration, has been the culmination of collaborative efforts to solve complex congenital, dysplastic, oncological, and traumatic cranial bone defects. Now, 50 years on from the first craniofacial meeting, the collaborative efforts between surgeons, scientists, and bioengineers are further advancing craniofacial surgery with new discoveries in tissue regeneration. Recent advances in regenerative medicine and stem cell biology have transformed the authors' understanding of bone healing, the role of stem cells governing bone healing, and the effects of the niche environment and extracellular matrix on stem cell fate. This review aims at summarizing the advances within each of these fields.

  View details for PubMedID 28665863

• Human Adipose-Derived Stromal Cell Isolation Methods and Use in Osteogenic and Adipogenic In Vivo Applications. Current protocols in stem cell biology Brett, E., Tevlin, R., McArdle, A., Seo, E. Y., Chan, C. K., Wan, D. C., Longaker, M. T. 2017; 43

  Abstract

  Adipose tissue represents an abundant and easily accessible source of multipotent cells, which may serve as excellent building blocks for tissue engineering. This article presents a newly described protocol for isolating adipose-derived stromal cells (ASCs) from human lipoaspirate, compared to the standard protocol for harvesting ASCs established in 2001. Human ASC isolation is performed using two methods, and resultant cells are compared through cell yield, cell viability, cell proliferation and regenerative potential. The osteogenic and adipogenic potential of ASCs isolated using both protocols are assessed invitro and gene expression analysis is performed. The focus of this series of protocols is the regenerative potential of both cell populations in vivo. As such, the two in vivo animal models described are fat graft retention (soft tissue reconstruction) and calvarial defect healing (bone regeneration). The techniques described comprise fat grafting with cell assisted lipotransfer, and calvarial defect creation healed with cell-seeded scaffolds. © 2017 by John Wiley & Sons, Inc.

  View details for PubMedID 29140567

• Isolation of Live Fibroblasts by Fluorescence-Activated Cell Sorting FIBROSIS: METHODS AND PROTOCOLS Leavitt, T., Hu, M. S., Longaker, M. T., Rittie, L. 2017; 1627: 205–12

  Abstract

  Flow cytometry is a powerful tool in cell biology in that it allows real-time characterization of cellular phenotypes. Additionally, through the process of fluorescence-activated cell sorting (FACS), living cells can be isolated for future in vitro experiments, including single cell analysis. Here we describe the isolation of live fibroblasts from the dermis of the skin in mice using FACS. This method circumvents the need for ex vivo expansion in cell culture, which can alter phenotypic and functional characteristics of cells.

  View details for PubMedID 28836203

• Delivery of monocyte lineage cells in a biomimetic scaffold enhances tissue repair. JCI insight Hu, M. S., Walmsley, G. G., Barnes, L. A., Weiskopf, K. n., Rennert, R. C., Duscher, D. n., Januszyk, M. n., Maan, Z. N., Hong, W. X., Cheung, A. T., Leavitt, T. n., Marshall, C. D., Ransom, R. C., Malhotra, S. n., Moore, A. L., Rajadas, J. n., Lorenz, H. P., Weissman, I. L., Gurtner, G. C., Longaker, M. T. 2017; 2 (19)

  Abstract

  The monocyte lineage is essential to normal wound healing. Macrophage inhibition or knockout in mice results in impaired wound healing through reduced neovascularization, granulation tissue formation, and reepithelialization. Numerous studies have either depleted macrophages or reduced their activity in the context of wound healing. Here, we demonstrate that by increasing the number of macrophages or monocytes in the wound site above physiologic levels via pullulan-collagen composite dermal hydrogel scaffold delivery, the rate of wound healing can be significantly accelerated in both wild-type and diabetic mice, with no adverse effect on the quality of repair. Macrophages transplanted onto wounds differentiate into M1 and M2 phenotypes of different proportions at various time points, ultimately increasing angiogenesis. Given that monocytes can be readily isolated from peripheral blood without in vitro manipulation, these findings hold promise for translational medicine aimed at accelerating wound healing across a broad spectrum of diseases.

  View details for PubMedID 28978794

• Magnetic Nanoparticle-Based Upregulation of B-Cell Lymphoma 2 Enhances Bone Regeneration. Stem cells translational medicine Brett, E., Zielins, E. R., Luan, A., Ooi, C. C., Shailendra, S., Atashroo, D., Menon, S., Blackshear, C., Flacco, J., Quarto, N., Wang, S. X., Longaker, M. T., Wan, D. C. 2017; 6 (1): 151-160

  Abstract

  Clinical translation of cell-based strategies for tissue regeneration remains challenging because survival of implanted cells within hostile, hypoxic wound environments is uncertain. Overexpression of B-cell lymphoma 2 (Bcl-2) has been shown to inhibit apoptosis in implanted cells. The present study describes an "off the shelf" prefabricated scaffold integrated with magnetic nanoparticles (MNPs) used to upregulate Bcl-2 expression in implanted adipose-derived stromal cells for bone regeneration. Iron oxide cores were sequentially coated with branched polyethyleneimine, minicircle plasmid encoding green fluorescent protein and Bcl-2, and poly-β-amino ester. Through in vitro assays, increased osteogenic potential and biological resilience were demonstrated in the magnetofected group over control and nucleofected groups. Similarly, our in vivo calvarial defect study showed that magnetofection had an efficiency rate of 30%, which in turn resulted in significantly more healing compared with control group and nucleofected group. Our novel, prefabricated MNP-integrated scaffold allows for in situ postimplant temporospatial control of cell transfection to augment bone regeneration. Stem Cells Translational Medicine 2017;6:151-160.

  View details for DOI 10.5966/sctm.2016-0051

  View details for PubMedID 28170185

• Biomimetics of Bone Implants: The Regenerative Road. BioResearch open access Brett, E., Flacco, J., Blackshear, C., Longaker, M. T., Wan, D. C. 2017; 6 (1): 1-6

  Abstract

  The current strategies for healing bone defects are numerous and varied. At the core of each bone healing therapy is a biomimetic mechanism, which works to enhance bone growth. These range from porous scaffolds, bone mineral usage, collagen, and glycosaminoglycan substitutes to transplanted cell populations. Bone defects face a range of difficulty in their healing, given the composite of dense outer compact bone and blood-rich inner trabecular bone. As such, the tissue possesses a number of inherent characteristics, which may be clinically harnessed as promoters of bone healing. These include mechanical characteristics, mineral composition, native collagen content, and cellular fraction of bone. This review charts multiple biomimetic strategies to help heal bony defects in large and small osseous injury sites, with a special focus on cell transplantation.

  View details for DOI 10.1089/biores.2016.0044

  View details for PubMedID 28163982

• Commentary on: Adipose Stem Cell Function Maintained with Age: An Intra-Subject Study of Long-Term Cryopreserved Cells. Aesthetic surgery journal Irizarry, D., Longaker, M. T., Wan, D. C. 2016

  View details for DOI 10.1093/asj/sjw224

  View details for PubMedID 28039122

• Lectins bring benefits to bones ELIFE Chan, C. F., Ransom, R. C., Longaker, M. T. 2016; 5

  Abstract

  The discovery that proteins called c-type lectins promote bone growth could lead to new treatments for age-related bone disorders.

  View details for PubMedID 27960074

• A Novel Method of Human Adipose-Derived Stem Cell Isolation with Resultant Increased Cell Yield PLASTIC AND RECONSTRUCTIVE SURGERY Tevlin, R., McArdle, A., Brett, E., Chung, M. T., Paik, K., Seo, E. Y., Walmsley, G. G., Duldulao, C. R., Atashroo, D., Zielins, E., Vistnes, S., Chan, C. K., Wan, D. C., Longaker, M. T. 2016; 138 (6): 983E-996E

  Abstract

  The authors have developed a novel protocol for isolating adipose-derived stem cells from human lipoaspirate. In this study, they compare their new method to a previously published standard protocol.Human adipose-derived stem cell isolation was performed using two methods to compare cell yield, cell viability, cell proliferation, and regenerative potential. The new and conventional isolation methods differ in two key areas: the collagenase digestion buffer constituents and the use of an orbital shaker. The osteogenic and adipogenic potential of adipose-derived stem cells isolated using both protocols was assessed in vitro, and gene expression analysis was performed. To assess the ability of the isolated cells to generate bone in vivo, the authors created critical-size calvarial defects in mice, which were treated with adipose-derived stem cells loaded onto hydroxyapatite-coated poly(lactic-co-glycolic acid) scaffolds. To test the ability of the isolated cells to enhance adipogenesis, the cells were added to lipoaspirate and placed beneath the scalp of immunocompromised mice. Fat graft volume retention was subsequently assessed by serial computed tomographic volumetric scanning.The new method resulted in a 10-fold increased yield of adipose-derived stem cells compared with the conventional method. Cells harvested using the new method demonstrated significantly increased cell viability and proliferation in vitro (p < 0.05). New method cells also demonstrated significantly enhanced osteogenic and adipogenic differentiation capacity in vitro (p < 0.05) in comparison with the conventional method cells. Both cell groups demonstrated equivalent osteogenic and adipogenic regenerative potential in mice.The authors have developed a protocol that maximizes the yield of adipose-derived stem cells derived from lipoaspirate. The new method cells have increased osteogenic and adipogenic potential in vitro and are not inferior to conventional method cells in terms of their ability to generate bone and fat in vivo.Therapeutic, V.

  View details for DOI 10.1097/PRS.0000000000002790

  View details for PubMedID 27537222

• Commentary on: The Effects of Fat Harvesting and Preparation, Air Exposure, Obesity, and Stem Cell Enrichment on Adipocyte Viability Prior to Graft Transplantation. Aesthetic surgery journal Blackshear, C. P., Longaker, M. T., Wan, D. C. 2016; 36 (10): 1174-1175

  View details for PubMedID 27474768

• Dipeptidyl Peptidase-4, Wound Healing, Scarring, and Fibrosis. Plastic and reconstructive surgery Hu, M. S., Longaker, M. T. 2016; 138 (5): 1026-1031

  Abstract

  Scarring and fibrosis are an enormous public health concern, resulting in excessive morbidity and mortality in addition to countless lost health care dollars. Recent advances in cell and developmental biology promise a better understanding of scarring and fibrosis and may translate to new clinical therapies.

  View details for PubMedID 27782998

• Stem Cells in Bone Regeneration STEM CELL REVIEWS AND REPORTS Walmsley, G. G., Ransom, R. C., Zielins, E. R., Leavitt, T., Flacco, J. S., Hu, M. S., Lee, A. S., Longaker, M. T., Wan, D. C. 2016; 12 (5): 524-529

  Abstract

  Bone has the capacity to regenerate and repair itself. However, this capacity may be impaired or lost depending on the size of the defect or the presence of certain disease states. In this review, we discuss the key principles underlying bone healing, efforts to characterize bone stem and progenitor cell populations, and the current status of translational and clinical studies in cell-based bone tissue engineering. Though barriers to clinical implementation still exist, the application of stem and progenitor cell populations to bone engineering strategies has the potential to profoundly impact regenerative medicine.

  View details for DOI 10.1007/s12015-016-9665-5

  View details for Web of Science ID 000385138500003

  View details for PubMedID 27250635

  View details for PubMedCentralID PMC5053855

• Intestinal Smooth Muscle Cell Migration May Contribute to Abdominal Adhesion Formation Marshall, C. D., Hu, M. S., Leavitt, T., Ransom, R. C., Barnes, L. A., Lorenz, H., Longaker, M. T. ELSEVIER SCIENCE INC. 2016: E106–E107

  View details for DOI 10.1016/j.jamcollsurg.2016.08.269

  View details for Web of Science ID 000395825100229

• Inhibition of Unfolded Protein Response Decreases Scar Formation Boyko, T. V., Jiang, D., Cao, H., Koong, A. C., Longaker, M. T., Yang, G. P. ELSEVIER SCIENCE INC. 2016: S98

  View details for DOI 10.1016/j.jamcollsurg.2016.06.198

  View details for Web of Science ID 000393077500168

• Scarless wound healing: finding the right cells and signals. Cell and tissue research Leavitt, T., Hu, M. S., Marshall, C. D., Barnes, L. A., Lorenz, H. P., Longaker, M. T. 2016; 365 (3): 483-493

  Abstract

  From the moment we are born, every injury to the skin has the potential to form a scar, many of which can impair form and/or function. As such, scar management constitutes a billion-dollar industry. However, effectively promoting scarless wound healing remains an elusive goal. The complex interactions of wound healing contribute to our inability to recapitulate scarless wound repair as it occurs in nature, such as in fetal skin and the oral mucosa. However, many new advances have occurred in recent years, some of which have translated scientific findings from bench to bedside. In vivo lineage tracing has helped establish a variety of novel cellular culprits that may act as key drivers of the fibrotic response. These newly characterized cell populations present further targets for therapeutic intervention, some of which have previously demonstrated promising results in animal models. Here, we discuss several recent studies that identify exciting approaches for diminishing scar formation. Particular attention will also be paid to the canonical Wnt/β-catenin signaling pathway, which plays an important role in both embryogenesis and tissue repair. New insights into the differential effects of Wnt signaling on heterogeneous fibroblast and keratinocyte populations within the skin further demonstrate methods by which wound healing can be re-directed to a more fetal scarless phenotype. Graphical abstract Recent approaches to reducing scar formation. Representation showing novel scientific approaches for decreasing scar formation, including the targeting of pro-fibrotic cell populations based on surface molecule expression (e.g. DPP4(+) fibroblasts, ADAM12(+) pericytes). Modulation of cellular mechanotransduction pathways are another means to reduce scar formation, both at the molecular level or, macroscopically with dressings designed to offload tension, at cutaneous wound sites (ADAM12 a disintegrin and metalloprotease 12, DPP4 dipeptidyl peptidase-4, FAK focal adhesion kinase).

  View details for DOI 10.1007/s00441-016-2424-8

  View details for PubMedID 27256396

  View details for PubMedCentralID PMC5010960

• Mechanical Stimulation Increases Knee Meniscus Gene RNA-level Expression in Adipose-derived Stromal Cells PLASTIC AND RECONSTRUCTIVE SURGERY-GLOBAL OPEN Meier, E. M., Wu, B., Siddiqui, A., Tepper, D. G., Longaker, M. T., Lam, M. T. 2016; 4 (9): e864

  Abstract

  Efforts have been made to engineer knee meniscus tissue for injury repair, yet most attempts have been unsuccessful. Creating a cell source that resembles the complex, heterogeneous phenotype of the meniscus cell remains difficult. Stem cell differentiation has been investigated, mainly using bone marrow mesenchymal cells and biochemical means for differentiation, resulting in no solution. Mechanical stimulation has been investigated to an extent with no conclusion. Here, we explore the potential for and effectiveness of mechanical stimulation to induce the meniscal phenotype in adipose-derived stromal cells.Human adipose-derived stromal cells were chosen for their fibrogenic nature and conduciveness for chondrogenesis. Biochemical and mechanical stimulation were investigated. Biochemical stimulation included fibrogenic and chondrogenic media. For mechanical stimulation, a custom-built device was used to apply constant, cyclical, uniaxial strain for up to 6 hours. Strain and frequency varied.Under biochemical stimulation, both fibrogenic (collagen I, versican) and chondrogenic (collagen II, Sox9, aggrecan) genes were expressed by cells exposed to either fibrogenic or chondrogenic biochemical factors. Mechanical strain was found to preferentially promote fibrogenesis over chondrogenesis, confirming that tensile strain is an effective fibrogenic cue. Three hours at 10% strain and 1 Hz in chondrogenic media resulted in the highest expression of fibrochondrogenic genes. Although mechanical stimulation did not seem to affect protein level expression, biochemical means did affect protein level presence of collagen fibers.Mechanical stimulation can be a useful differentiation tool for mechanoresponsive cell types as long as biochemical factors are also integrated.

  View details for PubMedID 27757329

• Magnetic Nanoparticle-Based Upregulation of B-Cell Lymphoma 2 Enhances Bone Regeneration. Stem cells translational medicine Brett, E., Zielins, E. R., Luan, A., Ooi, C. C., Shailendra, S., Atashroo, D., Menon, S., Blackshear, C., Flacco, J., Quarto, N., Wang, S. X., Longaker, M. T., Wan, D. C. 2016

  Abstract

  : Clinical translation of cell-based strategies for tissue regeneration remains challenging because survival of implanted cells within hostile, hypoxic wound environments is uncertain. Overexpression of B-cell lymphoma 2 (Bcl-2) has been shown to inhibit apoptosis in implanted cells. The present study describes an "off the shelf" prefabricated scaffold integrated with magnetic nanoparticles (MNPs) used to upregulate Bcl-2 expression in implanted adipose-derived stromal cells for bone regeneration. Iron oxide cores were sequentially coated with branched polyethyleneimine, minicircle plasmid encoding green fluorescent protein and Bcl-2, and poly-β-amino ester. Through in vitro assays, increased osteogenic potential and biological resilience were demonstrated in the magnetofected group over control and nucleofected groups. Similarly, our in vivo calvarial defect study showed that magnetofection had an efficiency rate of 30%, which in turn resulted in significantly more healing compared with control group and nucleofected group. Our novel, prefabricated MNP-integrated scaffold allows for in situ postimplant temporospatial control of cell transfection to augment bone regeneration.The use of adipose-derived stem cells as transplanted cells in wounded areas is desirable for their regenerative potential, but they are difficult to use owing to their fragility. Enhancing their survival in the context of a calvarial defect can be achieved by stimulating antiapoptotic protein expression in the cells themselves, through a plasmid expression vector. The present study used a nonintegrating minicircle plasmid encoding B-cell lymphoma 2 attached to a magnetic nanoparticle to facilitate in vivo transfection with temporospatial control (external magnetic field). This in situ system stimulates cell survival through gene expression and knock-on bone regeneration through cell survival.

  View details for PubMedID 27484867

• Scaffold-mediated BMP-2 minicircle DNA delivery accelerated bone repair in a mouse critical-size calvarial defect model JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A Keeney, M., Chung, M. T., Zielins, E. R., Paik, K. J., McArdle, A., Morrison, S. D., Ransom, R. C., Barbhaiya, N., Atashroo, D., Jacobson, G., Zare, R. N., Longaker, M. T., Wan, D. C., Yang, F. 2016; 104 (8): 2099-2107

  Abstract

  Scaffold-mediated gene delivery holds great promise for tissue regeneration. However, previous attempts to induce bone regeneration using scaffold-mediated non-viral gene delivery rarely resulted in satisfactory healing. We report a novel platform with sustained release of minicircle DNA (MC) from PLGA scaffolds to accelerate bone repair. MC was encapsulated inside PLGA scaffolds using supercritical CO2 , which showed prolonged release of MC. Skull-derived osteoblasts transfected with BMP-2 MC in vitro result in higher osteocalcin gene expression and mineralized bone formation. When implanted in a critical-size mouse calvarial defect, scaffolds containing luciferase MC lead to robust in situ protein production up to at least 60 days. Scaffold-mediated BMP-2 MC delivery leads to substantially accelerated bone repair as early as two weeks, which continues to progress over 12 weeks. This platform represents an efficient, long-term nonviral gene delivery system, and may be applicable for enhancing repair of a broad range of tissues types. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2099-2107, 2016.

  View details for DOI 10.1002/jbm.a.35735

  View details for Web of Science ID 000379736500025

  View details for PubMedID 27059085

• Creation of Abdominal Adhesions in Mice JOVE-JOURNAL OF VISUALIZED EXPERIMENTS Marshall, C. D., Hu, M. S., Leavitt, T., Barnes, L. A., Cheung, A. T., Malhotra, S., Lorenz, H. P., Longaker, M. T. 2016

  Abstract

  Abdominal adhesions consist of fibrotic tissue that forms in the peritoneal space in response to an inflammatory insult, typically surgery or intraabdominal infection. The precise mechanisms underlying adhesion formation are poorly understood. Many compounds and physical barriers have been tested for their ability to prevent adhesions after surgery with varying levels of success. The mouse and rat are important models for the study of abdominal adhesions. Several different techniques for the creation of adhesions in the mouse and rat exist in the literature. Here we describe a protocol utilizing abrasion of the cecum with sandpaper and sutures placed in the right abdominal sidewall. The mouse is anesthetized and the abdomen is prepped. A midline laparotomy is created and the cecum is identified. Sandpaper is used to gently abrade the surface of the cecum. Next, several figure-of-eight sutures are placed into the peritoneum of the right abdominal sidewall. The abdominal cavity is irrigated, a small amount of starch is applied, and the incision is closed. We have found that this technique produces the most consistent adhesions with the lowest mortality rate.

  View details for DOI 10.3791/54450

  View details for Web of Science ID 000391742700091

  View details for PubMedID 27685681

• Winner of the Young Investigator Award of the Society for Biomaterials at the 10th World Biomaterials Congress, May 17-22, 2016, Montreal QC, Canada: Microribbon-based hydrogels accelerate stem cell-based bone regeneration in a mouse critical-size cranial defect model JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A Han, L., Conrad, B., Chung, M. T., Deveza, L., Jiang, X., Wang, A., Butte, M. J., Longaker, M. T., Wan, D., Yang, F. 2016; 104 (6): 1321-1331

  Abstract

  Stem cell-based therapies hold great promise for enhancing tissue regeneration. However, the majority of cells die shortly after transplantation, which greatly diminishes the efficacy of stem cell-based therapies. Poor cell engraftment and survival remain a major bottleneck to fully exploiting the power of stem cells for regenerative medicine. Biomaterials such as hydrogels can serve as artificial matrices to protect cells during delivery and guide desirable cell fates. However, conventional hydrogels often lack macroporosity, which restricts cell proliferation and delays matrix deposition. Here we report the use of injectable, macroporous microribbon (μRB) hydrogels as stem cell carriers for bone repair, which supports direct cell encapsulation into a macroporous scaffold with rapid spreading. When transplanted in a critical-sized, mouse cranial defect model, μRB-based hydrogels significantly enhanced the survival of transplanted adipose-derived stromal cells (ADSCs) (81%) and enabled up to three-fold cell proliferation after 7 days. In contrast, conventional hydrogels only led to 27% cell survival, which continued to decrease over time. MicroCT imaging showed μRBs enhanced and accelerated mineralized bone repair compared to hydrogels (61% vs. 34% by week 6), and stem cells were required for bone repair to occur. These results suggest that paracrine signaling of transplanted stem cells are responsible for the observed bone repair, and enhancing cell survival and proliferation using μRBs further promoted the paracrine-signaling effects of ADSCs for stimulating endogenous bone repair. We envision μRB-based scaffolds can be broadly useful as a novel scaffold for enhancing stem cell survival and regeneration of other tissue types. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1321-1331, 2016.

  View details for DOI 10.1002/jbm.a.35715

  View details for Web of Science ID 000375117200001

  View details for PubMedID 26991141

  View details for PubMedCentralID PMC5142823

• Expansion and Hepatic Differentiation of Adult Blood-Derived CD34(+) Progenitor Cells and Promotion of Liver Regeneration After Acute Injury STEM CELLS TRANSLATIONAL MEDICINE Hu, M., Li, S., Menon, S., Liu, B., Hu, M. S., Longaker, M. T., Lorenz, H. P. 2016; 5 (6): 723-732

  Abstract

  The low availability of functional hepatocytes has been an unmet demand for basic scientific research, new drug development, and cell-based clinical applications for decades. Because of the inability to expand hepatocytes in vitro, alternative sources of hepatocytes are a focus of liver regenerative medicine. We report a new group of blood-derived CD34(+) progenitor cells (BDPCs) that have the ability to expand and differentiate into functional hepatocyte-like cells and promote liver regeneration. BDPCs were obtained from the peripheral blood of an adult mouse with expression of surface markers CD34, CD45, Sca-1, c-kit, and Thy1.1. BDPCs can proliferate in vitro and differentiate into hepatocyte-like cells expressing hepatocyte markers, including CK8, CK18, CK19, α-fetoprotein, integrin-β1, and A6. The differentiated BDPCs (dBDPCs) also display liver-specific functional activities, such as glycogen storage, urea production, and albumin secretion. dBDPCs have cytochrome P450 activity and express specific hepatic transcription factors, such as hepatic nuclear factor 1α. To demonstrate liver regenerative activity, dBDPCs were injected into mice with severe acute liver damage caused by a high-dose injection of carbon tetrachloride (CCl4). dBDPC treatment rescued the mice from severe acute liver injury, increased survival, and induced liver regeneration. Because of their ease of access and application through peripheral blood and their capability of rapid expansion and hepatic differentiation, BDPCs have great potential as a cell-based therapy for liver disease.Hematopoietic stem/progenitor cell expansion and tissue-specific differentiation in vitro are challenges in regenerative medicine, although stem cell therapy has raised hope for the treatment of liver diseases by overcoming the scarcity of hepatocytes. This study identified and characterized a group of blood-derived progenitor cells (BDPCs) from the peripheral blood of an adult mouse. The CD34(+) progenitor-dominant BDPCs were rapidly expanded and hepatically differentiated into functional hepatocyte-like cells with our established coculture system. BDPC treatment increased animal survival and produced full regeneration in a severe liver injury mouse model caused by CCl4. BDPCs could have potential for liver cell therapies.

  View details for DOI 10.5966/sctm.2015-0268

  View details for PubMedID 27075766

  View details for PubMedCentralID PMC4878335

• Suction assisted liposuction does not impair the regenerative potential of adipose derived stem cells JOURNAL OF TRANSLATIONAL MEDICINE Duscher, D., Luan, A., Rennert, R. C., Atashroo, D., Maan, Z. N., Brett, E. A., Whittam, A. J., Ho, N., Lin, M., Hu, M. S., Walmsley, G. G., Wenny, R., Schmidt, M., Schilling, A. F., Machens, H., Huemer, G. M., Wan, D. C., Longaker, M. T., Gurtner, G. C. 2016; 14

  Abstract

  Adipose-derived stem cells (ASCs) have been identified as a population of multipotent cells with promising applications in tissue engineering and regenerative medicine. ASCs are abundant in fat tissue, which can be safely harvested through the minimally invasive procedure of liposuction. However, there exist a variety of different harvesting methods, with unclear impact on ASC regenerative potential. The aim of this study was thus to compare the functionality of ASCs derived from the common technique of suction-assisted lipoaspiration (SAL) versus resection.Human adipose tissue was obtained from paired abdominoplasty and SAL samples from three female donors, and was processed to isolate the stromal vascular fraction. Fluorescence-activated cell sorting was used to determine ASC yield, and cell viability was assayed. Adipogenic and osteogenic differentiation capacity were assessed in vitro using phenotypic staining and quantification of gene expression. Finally, ASCs were applied in an in vivo model of tissue repair to evaluate their regenerative potential.SAL specimens provided significantly fewer ASCs when compared to excised fat tissue, however, with equivalent viability. SAL-derived ASCs demonstrated greater expression of the adipogenic markers FABP-4 and LPL, although this did not result in a difference in adipogenic differentiation. There were no differences detected in osteogenic differentiation capacity as measured by alkaline phosphatase, mineralization or osteogenic gene expression. Both SAL- and resection-derived ASCs enhanced significantly cutaneous healing and vascularization in vivo, with no significant difference between the two groups.SAL provides viable ASCs with full capacity for multi-lineage differentiation and tissue regeneration, and is an effective method of obtaining ASCs for cell-based therapies.

  View details for DOI 10.1186/s12967-016-0881-1

  View details for Web of Science ID 000375475200004

  View details for PubMedID 27153799

  View details for PubMedCentralID PMC4859988

• Small Molecule Inhibition of Transforming Growth Factor Beta Signaling Enables the Endogenous Regenerative Potential of the Mammalian Calvarium TISSUE ENGINEERING PART A Senarath-Yapa, K., Li, S., Walmsley, G. G., Zielins, E., Paik, K., Britto, J. A., Grigoriadis, A. E., Wan, D. C., Liu, K. J., Longaker, M. T., Quarto, N. 2016; 22 (9-10): 707-720

  Abstract

  Current approaches for the treatment of skeletal defects are suboptimal, principally because the ability of bone to repair and regenerate is poor. Although the promise of effective cellular therapies for skeletal repair is encouraging, these approaches are limited by the risks of infection, cellular contamination, and tumorigenicity. Development of a pharmacological approach would therefore help avoid some of these potential risks. This study identifies transforming growth factor beta (TGFβ) signaling as a potential pathway for pharmacological modulation in vivo. We demonstrate that inhibition of TGFβ signaling by the small molecule SB431542 potentiates calvarial skeletal repair through activation of bone morphogenetic protein (BMP) signaling on osteoblasts and dura mater cells participating in healing of calvarial defects. Cells respond to inhibition of TGFβ signaling by producing higher levels of BMP2 that upregulates inhibitory Smad6 expression, thus providing a negative feedback loop to contain excessive BMP signaling. Importantly, study on human osteoblasts indicates that molecular mechanism(s) triggered by SB431542 are conserved. Collectively, these data provide insights into the use of small molecules to modulate key signaling pathways for repairing skeletal defects.

  View details for DOI 10.1089/ten.tea.2015.0527

  View details for Web of Science ID 000377380600001

  View details for PubMedID 27036931

  View details for PubMedCentralID PMC4876548

• Stem and progenitor cells: advancing bone tissue engineering. Drug delivery and translational research Tevlin, R., Walmsley, G. G., Marecic, O., Hu, M. S., Wan, D. C., Longaker, M. T. 2016; 6 (2): 159-173

  Abstract

  Unlike many other postnatal tissues, bone can regenerate and repair itself; nevertheless, this capacity can be overcome. Traditionally, surgical reconstructive strategies have implemented autologous, allogeneic, and prosthetic materials. Autologous bone-the best option-is limited in supply and also mandates an additional surgical procedure. In regenerative tissue engineering, there are myriad issues to consider in the creation of a functional, implantable replacement tissue. Importantly, there must exist an easily accessible, abundant cell source with the capacity to express the phenotype of the desired tissue, and a biocompatible scaffold to deliver the cells to the damaged region. A literature review was performed using PubMed; peer-reviewed publications were screened for relevance in order to identify key advances in stem and progenitor cell contribution to the field of bone tissue engineering. In this review, we briefly introduce various adult stem cells implemented in bone tissue engineering such as mesenchymal stem cells (including bone marrow- and adipose-derived stem cells), endothelial progenitor cells, and induced pluripotent stem cells. We then discuss numerous advances associated with their application and subsequently focus on technological advances in the field, before addressing key regenerative strategies currently used in clinical practice. Stem and progenitor cell implementation in bone tissue engineering strategies have the ability to make a major impact on regenerative medicine and reduce patient morbidity. As the field of regenerative medicine endeavors to harness the body's own cells for treatment, scientific innovation has led to great advances in stem cell-based therapies in the past decade.

  View details for DOI 10.1007/s13346-015-0235-1

  View details for PubMedID 25990836

  View details for PubMedCentralID PMC4654714

• Discussion: In Vitro Validation of a Closed Device Enabling the Purification of the Fluid Portion of Liposuction Aspirates. Plastic and reconstructive surgery Zielins, E. R., Longaker, M. T., Wan, D. C. 2016; 137 (4): 1168-1170

  View details for DOI 10.1097/PRS.0000000000002035

  View details for PubMedID 27018671

• Autologous Fat Grafting: The Science Behind the Surgery. Aesthetic surgery journal Zielins, E. R., Brett, E. A., Longaker, M. T., Wan, D. C. 2016; 36 (4): 488-496

  Abstract

  An invaluable part of the plastic surgeon's technical arsenal for soft tissue contouring, fat grafting continues to be plagued by unpredictable outcomes, resulting in either reoperation and/or patient dissatisfaction. Thus, extensive research has been conducted into the effects of adipose tissue procurement, processing, and placement on fat graft quality at both the cellular level and in terms of overall volume retention. Herein, we present an overview of the vast body of literature in these areas, with additional discussion of cell-assisted lipotransfer as a therapy to improve volume retention, and on the controversial use of autologous fat in the setting of prior irradiation.

  View details for DOI 10.1093/asj/sjw004

  View details for PubMedID 26961989

• Cell-Assisted Lipotransfer Improves Volume Retention in Irradiated Recipient Sites and Rescues Radiation-Induced Skin Changes STEM CELLS Luan, A., Duscher, D., Whittam, A. J., Paik, K. J., Zielins, E. R., Brett, E. A., Atashroo, D. A., Hu, M. S., Lee, G. K., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2016; 34 (3): 668-673

  Abstract

  Radiation therapy is not only a mainstay in the treatment of many malignancies but also results in collateral obliteration of microvasculature and dermal/subcutaneous fibrosis. Soft tissue reconstruction of hypovascular, irradiated recipient sites through fat grafting remains challenging; however, a coincident improvement in surrounding skin quality has been noted. Cell-assisted lipotransfer (CAL), the enrichment of fat with additional adipose-derived stem cells (ASCs) from the stromal vascular fraction, has been shown to improve fat volume retention, and enhanced outcomes may also be achieved with CAL at irradiated sites. Supplementing fat grafts with additional ASCs may also augment the regenerative effect on radiation-damaged skin. In this study, we demonstrate the ability for CAL to enhance fat graft volume retention when placed beneath the irradiated scalps of immunocompromised mice. Histologic metrics of fat graft survival were also appreciated, with improved structural qualities and vascularity. Finally, rehabilitation of radiation-induced soft tissue changes were also noted, as enhanced amelioration of dermal thickness, collagen content, skin vascularity, and biomechanical measures were all observed with CAL compared to unsupplemented fat grafts. Supplementation of fat grafts with ASCs therefore shows promise for reconstruction of complex soft tissue defects following adjuvant radiotherapy. Stem Cells 2016;34:668-673.

  View details for DOI 10.1002/stem.2256

  View details for Web of Science ID 000372552600013

• Cell-Assisted Lipotransfer Improves Volume Retention in Irradiated Recipient Sites and Rescues Radiation-Induced Skin Changes. Stem cells Luan, A., Duscher, D., Whittam, A. J., Paik, K. J., Zielins, E. R., Brett, E. A., Atashroo, D. A., Hu, M. S., Lee, G. K., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2016; 34 (3): 668-673

  Abstract

  Radiation therapy is not only a mainstay in the treatment of many malignancies but also results in collateral obliteration of microvasculature and dermal/subcutaneous fibrosis. Soft tissue reconstruction of hypovascular, irradiated recipient sites through fat grafting remains challenging; however, a coincident improvement in surrounding skin quality has been noted. Cell-assisted lipotransfer (CAL), the enrichment of fat with additional adipose-derived stem cells (ASCs) from the stromal vascular fraction, has been shown to improve fat volume retention, and enhanced outcomes may also be achieved with CAL at irradiated sites. Supplementing fat grafts with additional ASCs may also augment the regenerative effect on radiation-damaged skin. In this study, we demonstrate the ability for CAL to enhance fat graft volume retention when placed beneath the irradiated scalps of immunocompromised mice. Histologic metrics of fat graft survival were also appreciated, with improved structural qualities and vascularity. Finally, rehabilitation of radiation-induced soft tissue changes were also noted, as enhanced amelioration of dermal thickness, collagen content, skin vascularity, and biomechanical measures were all observed with CAL compared to unsupplemented fat grafts. Supplementation of fat grafts with ASCs therefore shows promise for reconstruction of complex soft tissue defects following adjuvant radiotherapy. Stem Cells 2016;34:668-673.

  View details for DOI 10.1002/stem.2256

  View details for PubMedID 26661694

• Enrichment of Adipose-Derived Stromal Cells for BMPR1A Facilitates Enhanced Adipogenesis TISSUE ENGINEERING PART A Zielins, E. R., Paik, K., Ransom, R. C., Brett, E. A., Blackshear, C. P., Luan, A., Walmsley, G. G., Atashroo, D. A., Senarath-Yapa, K., Momeni, A., Rennert, R., Sorkin, M., Seo, E. Y., Chan, C. K., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2016; 22 (3-4): 214-221

  Abstract

  Reconstruction of soft tissue defects has traditionally relied on the use of grafts and flaps, which may be associated with variable resorption and/or significant donor site morbidity. Cell-based strategies employing adipose-derived stromal cells (ASCs), found within the stromal vascular fraction (SVF) of adipose tissue, may offer an alternative strategy for soft tissue reconstruction. In this study, we investigated the potential of a bone morphogenetic protein receptor type 1A (BMPR1A)(+) subpopulation of ASCs to enhance de novo adipogenesis.Human lipoaspirate was enzymatically digested to isolate SVF and magnetic-activated cell separation was utilized to obtain BMPR1A(+) and BMPR1A(-) cells. These cells, along with unenriched cells, were expanded in culture and evaluated for adipogenic gene expression and in vitro adipocyte formation. Cells from each group were also labeled with a green fluorescent protein (GFP) lentivirus and transplanted into the inguinal fat pads, an adipogenic niche, of immunocompromised mice to determine their potential for de novo adipogenesis. Confocal microscopy along with staining of lipid droplets and vasculature was performed to evaluate the formation of mature adipocytes by transplanted cells.In comparison to BMPR1A(-) and unenriched ASCs, BMPR1A(+) cells demonstrated significantly enhanced adipogenesis when cultured in an adipogenic differentiation medium, as evidenced by increased staining with Oil Red O and increased expression of peroxisome proliferator-activating receptor gamma (PPAR-γ) and fatty acid-binding protein 4 (FABP4). BMPR1A(+) cells also formed significantly more adipocytes in vivo, as demonstrated by quantification of GFP+ adipocytes. Minimal formation of mature adipocytes was appreciated by BMPR1A(-) cells.BMPR1A(+) ASCs show an enhanced ability for adipogenesis in vitro, as shown by gene expression and histological staining. Furthermore, within an adipogenic niche, BMPR1A(+) cells possessed an increased capacity to generate de novo fat compared to BMPR1A(-) and unenriched cells. This suggests utility for the BMPR1A(+) subpopulation in cell-based strategies for soft tissue reconstruction.

  View details for DOI 10.1089/ten.tea.2015.0278

  View details for PubMedID 26585335

• Discussion: Transplantation of an LGR6(+) Epithelial Stem Cell-Enriched Scaffold for Repair of Full-Thickness Soft-Tissue Defects: The In Vitro Development of Polarized Hair-Bearing Skin PLASTIC AND RECONSTRUCTIVE SURGERY Hu, M. S., Longaker, M. T., Lorenz, H. 2016; 137 (2): 508–9

  View details for PubMedID 26818285

• Ultrasound-Assisted Liposuction Does Not Compromise the Regenerative Potential of Adipose-Derived Stem Cells. Stem cells translational medicine Duscher, D., Atashroo, D., Maan, Z. N., Luan, A., Brett, E. A., Barrera, J., Khong, S. M., Zielins, E. R., Whittam, A. J., Hu, M. S., Walmsley, G. G., Pollhammer, M. S., Schmidt, M., Schilling, A. F., Machens, H., Huemer, G. M., Wan, D. C., Longaker, M. T., Gurtner, G. C. 2016; 5 (2): 248-257

  Abstract

  Human mesenchymal stem cells (MSCs) have recently become a focus of regenerative medicine, both for their multilineage differentiation capacity and their excretion of proregenerative cytokines. Adipose-derived mesenchymal stem cells (ASCs) are of particular interest because of their abundance in fat tissue and the ease of harvest via liposuction. However, little is known about the impact of different liposuction methods on the functionality of ASCs. Here we evaluate the regenerative abilities of ASCs harvested via a third-generation ultrasound-assisted liposuction (UAL) device versus ASCs obtained via standard suction-assisted lipoaspiration (SAL). Lipoaspirates were sorted using fluorescent assisted cell sorting based on an established surface-marker profile (CD34+/CD31-/CD45-), to obtain viable ASCs. Yield and viability were compared and the differentiation capacities of the ASCs were assessed. Finally, the regenerative potential of ASCs was examined using an in vivo model of tissue regeneration. UAL- and SAL-derived samples demonstrated equivalent ASC yield and viability, and UAL ASCs were not impaired in their osteogenic, adipogenic, or chondrogenic differentiation capacity. Equally, quantitative real-time polymerase chain reaction showed comparable expression of most osteogenic, adipogenic, and key regenerative genes between both ASC groups. Cutaneous regeneration and neovascularization were significantly enhanced in mice treated with ASCs obtained by either UAL or SAL compared with controls, but there were no significant differences in healing between cell-therapy groups. We conclude that UAL is a successful method of obtaining fully functional ASCs for regenerative medicine purposes. Cells harvested with this alternative approach to liposuction are suitable for cell therapy and tissue engineering applications. Significance: Adipose-derived mesenchymal stem cells (ASCs) are an appealing source of therapeutic progenitor cells because of their multipotency, diverse cytokine profile, and ease of harvest via liposuction. Alternative approaches to classical suction-assisted liposuction are gaining popularity; however, little evidence exists regarding the impact of different liposuction methods on the regenerative functionality of ASCs. Human ASC characteristics and regenerative capacity were assessed when harvested via ultrasound-assisted (UAL) versus standard suction-assisted liposuction. ASCs obtained via UAL were of equal quality when directly compared with the current gold standard harvest method. UAL is an adjunctive source of fully functional mesenchymal stem cells for applications in basic research and clinical therapy.

  View details for DOI 10.5966/sctm.2015-0064

  View details for PubMedID 26702129

  View details for PubMedCentralID PMC4729547

• Murine Dermal Fibroblast Isolation by FACS. Journal of visualized experiments : JoVE Walmsley, G. G., Maan, Z. N., Hu, M. S., Atashroo, D. A., Whittam, A. J., Duscher, D., Tevlin, R., Marecic, O., Lorenz, H. P., Gurtner, G. C., Longaker, M. T. 2016

  Abstract

  Fibroblasts are the principle cell type responsible for secreting extracellular matrix and are a critical component of many organs and tissues. Fibroblast physiology and pathology underlie a spectrum of clinical entities, including fibroses in multiple organs, hypertrophic scarring following burns, loss of cardiac function following ischemia, and the formation of cancer stroma. However, fibroblasts remain a poorly characterized type of cell, largely due to their inherent heterogeneity. Existing methods for the isolation of fibroblasts require time in cell culture that profoundly influences cell phenotype and behavior. Consequently, many studies investigating fibroblast biology rely upon in vitro manipulation and do not accurately capture fibroblast behavior in vivo. To overcome this problem, we developed a FACS-based protocol for the isolation of fibroblasts from the dorsal skin of adult mice that does not require cell culture, thereby preserving the physiologic transcriptional and proteomic profile of each cell. Our strategy allows for exclusion of non-mesenchymal lineages via a lineage negative gate (Lin(-)) rather than a positive selection strategy to avoid pre-selection or enrichment of a subpopulation of fibroblasts expressing specific surface markers and be as inclusive as possible across this heterogeneous cell type.

  View details for DOI 10.3791/53430

  View details for PubMedID 26780559

  View details for PubMedCentralID PMC4781205

• Murine Dermal Fibroblast Isolation by FACS JOVE-JOURNAL OF VISUALIZED EXPERIMENTS Walmsley, G. G., Maan, Z. N., Hu, M. S., Atashroo, D. A., Whittam, A. J., Duscher, D., Tevlin, R., Marecic, O., Lorenz, H. P., Gurtner, G. C., Longaker, M. T. 2016

  Abstract

  Fibroblasts are the principle cell type responsible for secreting extracellular matrix and are a critical component of many organs and tissues. Fibroblast physiology and pathology underlie a spectrum of clinical entities, including fibroses in multiple organs, hypertrophic scarring following burns, loss of cardiac function following ischemia, and the formation of cancer stroma. However, fibroblasts remain a poorly characterized type of cell, largely due to their inherent heterogeneity. Existing methods for the isolation of fibroblasts require time in cell culture that profoundly influences cell phenotype and behavior. Consequently, many studies investigating fibroblast biology rely upon in vitro manipulation and do not accurately capture fibroblast behavior in vivo. To overcome this problem, we developed a FACS-based protocol for the isolation of fibroblasts from the dorsal skin of adult mice that does not require cell culture, thereby preserving the physiologic transcriptional and proteomic profile of each cell. Our strategy allows for exclusion of non-mesenchymal lineages via a lineage negative gate (Lin(-)) rather than a positive selection strategy to avoid pre-selection or enrichment of a subpopulation of fibroblasts expressing specific surface markers and be as inclusive as possible across this heterogeneous cell type.

  View details for DOI 10.3791/53430

  View details for Web of Science ID 000368577400023

  View details for PubMedCentralID PMC4781205

• Stem cells and chronic wound healing: state of the art CHRONIC WOUND CARE MANAGEMENT AND RESEARCH Leavitt, T., Hu, M. S., Marshall, C. D., Barnes, L. A., Longaker, M. T., Lorenz, H. 2016; 3: 7–27

  View details for DOI 10.2147/CWCMR.S84369

  View details for Web of Science ID 000382881200001

• Surveillance of Stem Cell Fate and Function: A System for Assessing Cell Survival and Collagen Expression In Situ. Tissue engineering. Part A Walmsley, G. G., Senarath-Yapa, K., Wearda, T. L., Menon, S., Hu, M. S., Duscher, D., Maan, Z. N., Tsai, J. M., Zielins, E. R., Weissman, I. L., Gurtner, G. C., Lorenz, H. P., Longaker, M. T. 2016; 22 (1-2): 31-40

  Abstract

  Cell-based therapy is an emerging paradigm in skeletal regenerative medicine. However, the primary means by which transplanted cells contribute to bone repair and regeneration remain controversial. To gain an insight into the mechanisms of how both transplanted and endogenous cells mediate skeletal healing, we used a transgenic mouse strain expressing both the topaz variant of green fluorescent protein under the control of the collagen, type I, alpha 1 promoter/enhancer sequence (Col1a1(GFP)) and membrane-bound tomato red fluorescent protein constitutively in all cell types (R26(mTmG)). A comparison of healing in parietal versus frontal calvarial defects in these mice revealed that frontal osteoblasts express Col1a1 to a greater degree than parietal osteoblasts. Furthermore, the scaffold-based application of adipose-derived stromal cells (ASCs), bone marrow-derived mesenchymal stem cells (BM-MSCs), and osteoblasts derived from these mice to critical-sized calvarial defects allowed for investigation of cell survival and function following transplantation. We found that ASCs led to significantly faster rates of bone healing in comparison to BM-MSCs and osteoblasts. ASCs displayed both increased survival and increased Col1a1 expression compared to BM-MSCs and osteoblasts following calvarial defect transplantation, which may explain their superior regenerative capacity in the context of bone healing. Using this novel reporter system, we were able to elucidate how cell-based therapies impact bone healing and identify ASCs as an attractive candidate for cell-based skeletal regenerative therapy. These insights potentially influence stem cell selection in translational clinical trials evaluating cell-based therapeutics for osseous repair and regeneration.

  View details for DOI 10.1089/ten.TEA.2015.0221

  View details for PubMedID 26486617

  View details for PubMedCentralID PMC4741228

• Getting nervous about regeneration. Stem cell investigation Montoro, D. T., Muhonen, E. G., Longaker, M. T. 2016; 3: 71

  View details for PubMedID 27868053

• Local and Circulating Endothelial Cells Undergo Endothelial to Mesenchymal Transition (EndMT) in Response to Musculoskeletal Injury. Scientific reports Agarwal, S., Loder, S., Cholok, D., Peterson, J., Li, J., Fireman, D., Breuler, C., Hsieh, H. S., Ranganathan, K., Hwang, C., Drake, J., Li, S., Chan, C. K., Longaker, M. T., Levi, B. 2016; 6: 32514-?

  Abstract

  Endothelial-to-mesenchymal transition (EndMT) has been implicated in a variety of aberrant wound healing conditions. However, unambiguous evidence of EndMT has been elusive due to limitations of in vitro experimental designs and animal models. In vitro experiments cannot account for the myriad ligands and cells which regulate differentiation, and in vivo tissue injury models may induce lineage-independent endothelial marker expression in mesenchymal cells. By using an inducible Cre model to mark mesenchymal cells (Scx-creERT/tdTomato + ) prior to injury, we demonstrate that musculoskeletal injury induces expression of CD31, VeCadherin, or Tie2 in mesenchymal cells. VeCadherin and Tie2 were expressed in non-endothelial cells (CD31-) present in marrow from uninjured adult mice, thereby limiting the specificity of these markers in inducible models (e.g. VeCadherin- or Tie2-creERT). However, cell transplantation assays confirmed that endothelial cells (ΔVeCadherin/CD31+/CD45-) isolated from uninjured hindlimb muscle tissue undergo in vivo EndMT when transplanted directly into the wound without intervening cell culture using PDGFRα, Osterix (OSX), SOX9, and Aggrecan (ACAN) as mesenchymal markers. These in vivo findings support EndMT in the presence of myriad ligands and cell types, using cell transplantation assays which can be applied for other pathologies implicated in EndMT including tissue fibrosis and atherosclerosis. Additionally, endothelial cell recruitment and trafficking are potential therapeutic targets to prevent EndMT.

  View details for DOI 10.1038/srep32514

  View details for PubMedID 27616463

• The role of stem cells in limb regeneration ORGANOGENESIS Zielins, E. R., Ransom, R. C., Leavitt, T. E., Longaker, M. T., Wan, D. C. 2016; 12 (1): 16-27

  Abstract

  Limb regeneration is a complex yet fascinating process observed to some extent in many animal species, though seen in its entirety in urodele amphibians. Accomplished by formation of a morphologically uniform intermediate, the blastema, scientists have long attempted to define the cellular constituents that enable regrowth of a functional appendage. Today, we know that the blastema consists of a variety of multipotent progenitor cells originating from a variety of tissues, and which contribute to limb tissue regeneration in a lineage-restricted manner. By continuing to dissect the role of stem cells in limb regeneration, we can hope to one day modulate the human response to limb amputation and facilitate regrowth of a working replacement.

  View details for DOI 10.1080/15476278.2016.1163463

  View details for Web of Science ID 000377930900002

  View details for PubMedID 27008101

  View details for PubMedCentralID PMC4882123

• Del1 Knockout Mice Developed More Severe Osteoarthritis Associated with Increased Susceptibility of Chondrocytes to Apoptosis. PloS one Wang, Z., Tran, M. C., Bhatia, N. J., Hsing, A. W., Chen, C., LaRussa, M. F., Fattakhov, E., Rashidi, V., Jang, K. Y., Choo, K. J., Nie, X., Mathy, J. A., Longaker, M. T., Dauskardt, R. H., Helms, J. A., Yang, G. P. 2016; 11 (8)

  Abstract

  We identified significant expression of the matricellular protein, DEL1, in hypertrophic and mature cartilage during development. We hypothesized that this tissue-specific expression indicated a biological role for DEL1 in cartilage biology.Del1 KO and WT mice had cartilage thickness evaluated by histomorphometry. Additional mice underwent medial meniscectomy to induce osteoarthritis, and were assayed at 1 week for apoptosis by TUNEL staining and at 8 weeks for histology and OA scoring. In vitro proliferation and apoptosis assays were performed on primary chondrocytes.Deletion of the Del1 gene led to decreased amounts of cartilage in the ears and knee joints in mice with otherwise normal skeletal morphology. Destabilization of the knee led to more severe OA compared to controls. In vitro, DEL1 blocked apoptosis in chondrocytes.Osteoarthritis is among the most prevalent diseases worldwide and increasing in incidence as our population ages. Initiation begins with an injury resulting in the release of inflammatory mediators. Excessive production of inflammatory mediators results in apoptosis of chondrocytes. Because of the limited ability of chondrocytes to regenerate, articular cartilage deteriorates leading to the clinical symptoms including severe pain and decreased mobility. No treatments effectively block the progression of OA. We propose that direct modulation of chondrocyte apoptosis is a key variable in the etiology of OA, and therapies aimed at preventing this important step represent a new class of regenerative medicine targets.

  View details for DOI 10.1371/journal.pone.0160684

  View details for PubMedID 27505251

• Short Hairpin RNA Silencing of PHD-2 Improves Neovascularization and Functional Outcomes in Diabetic Wounds and Ischemic Limbs. PloS one Paik, K. J., Maan, Z. N., Zielins, E. R., Duscher, D., Whittam, A. J., Morrison, S. D., Brett, E. A., Ransom, R. C., Hu, M. S., Wu, J. C., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2016; 11 (3)

  Abstract

  The transcription factor hypoxia-inducible factor 1-alpha (HIF-1α) is responsible for the downstream expression of over 60 genes that regulate cell survival and metabolism in hypoxic conditions as well as those that enhance angiogenesis to alleviate hypoxia. However, under normoxic conditions, HIF-1α is hydroxylated by prolyl hydroxylase 2, and subsequently degraded, with a biological half-life of less than five minutes. Here we investigated the therapeutic potential of inhibiting HIF-1α degradation through short hairpin RNA silencing of PHD-2 in the setting of diabetic wounds and limb ischemia. Treatment of diabetic mouse fibroblasts with shPHD-2 in vitro resulted in decreased levels of PHD-2 transcript demonstrated by qRT-PCR, higher levels of HIF-1α as measured by western blot, and higher expression of the downstream angiogenic genes SDF-1 and VEGFα, as measured by qRT-PCR. In vivo, shPHD-2 accelerated healing of full thickness excisional wounds in diabetic mice compared to shScr control, (14.33 ± 0.45 days vs. 19 ± 0.33 days) and was associated with an increased vascular density. Delivery of shPHD-2 also resulted in improved perfusion of ischemic hind limbs compared to shScr, prevention of distal digit tip necrosis, and increased survival of muscle tissue. Knockdown of PHD-2 through shRNA treatment has the potential to stimulate angiogenesis through overexpression of HIF-1α and upregulation of pro-angiogenic genes downstream of HIF-1α, and may represent a viable, non-viral approach to gene therapy for ischemia related applications.

  View details for DOI 10.1371/journal.pone.0150927

  View details for PubMedID 26967994

  View details for PubMedCentralID PMC4788284

• An Overview of Direct Somatic Reprogramming: The Ins and Outs of iPSCs. International journal of molecular sciences Menon, S., Shailendra, S., Renda, A., Longaker, M., Quarto, N. 2016; 17 (1)

  Abstract

  Stem cells are classified into embryonic stem cells and adult stem cells. An evolving alternative to conventional stem cell therapies is induced pluripotent stem cells (iPSCs), which have a multi-lineage potential comparable to conventionally acquired embryonic stem cells with the additional benefits of being less immunoreactive and avoiding many of the ethical concerns raised with the use of embryonic material. The ability to generate iPSCs from somatic cells provides tremendous promise for regenerative medicine. The breakthrough of iPSCs has raised the possibility that patient-specific iPSCs can provide autologous cells for cell therapy without the concern for immune rejection. iPSCs are also relevant tools for modeling human diseases and drugs screening. However, there are still several hurdles to overcome before iPSCs can be used for translational purposes. Here, we review the recent advances in somatic reprogramming and the challenges that must be overcome to move this strategy closer to clinical application.

  View details for DOI 10.3390/ijms17010141

  View details for PubMedID 26805822

  View details for PubMedCentralID PMC4730380

• Mesenchymal Stromal Cells as Cell-Based Therapeutics for Wound Healing STEM CELLS INTERNATIONAL Malhotra, S., Hu, M. S., Marshall, C. D., Leavitt, T., Cheung, A. T., Gonzalez, J. G., Kaur, H., Lorenz, H. P., Longaker, M. T. 2016

  Abstract

  Chronic wounds are a source of substantial morbidity for patients and are a major financial burden for the healthcare system. There are no current therapies that reliably improve nonhealing wounds or reverse pathological scarring. Mesenchymal stromal cells (MSCs) are a promising source of novel cell-based therapies due to the ease of their harvest and their integral role in the native wound repair process. Recent work has addressed the problems of loss of plasticity and off-target delivery through use of modern bioengineering techniques. Here we describe the applications of MSCs harvested from different sources to the wound healing process and recent advances in delivery of MSCs to targeted sites of injury.

  View details for DOI 10.1155/2016/4157934

  View details for Web of Science ID 000373501200001

  View details for PubMedID 26966438

  View details for PubMedCentralID PMC4757746

• Surveillance of Stem Cell Fate and Function: A System for Assessing Cell Survival and Collagen Expression In Situ TISSUE ENGINEERING PART A Walmsley, G. G., Senarath-Yapa, K., Wearda, T. L., Menon, S., Hu, M. S., Duscher, D., Maan, Z. N., Tsai, J. M., Zielins, E. R., Weissman, I. L., Gurtner, G. C., Lorenz, H. P., Longaker, M. T. 2016; 22 (1-2): 31-40

  Abstract

  Cell-based therapy is an emerging paradigm in skeletal regenerative medicine. However, the primary means by which transplanted cells contribute to bone repair and regeneration remain controversial. To gain an insight into the mechanisms of how both transplanted and endogenous cells mediate skeletal healing, we used a transgenic mouse strain expressing both the topaz variant of green fluorescent protein under the control of the collagen, type I, alpha 1 promoter/enhancer sequence (Col1a1(GFP)) and membrane-bound tomato red fluorescent protein constitutively in all cell types (R26(mTmG)). A comparison of healing in parietal versus frontal calvarial defects in these mice revealed that frontal osteoblasts express Col1a1 to a greater degree than parietal osteoblasts. Furthermore, the scaffold-based application of adipose-derived stromal cells (ASCs), bone marrow-derived mesenchymal stem cells (BM-MSCs), and osteoblasts derived from these mice to critical-sized calvarial defects allowed for investigation of cell survival and function following transplantation. We found that ASCs led to significantly faster rates of bone healing in comparison to BM-MSCs and osteoblasts. ASCs displayed both increased survival and increased Col1a1 expression compared to BM-MSCs and osteoblasts following calvarial defect transplantation, which may explain their superior regenerative capacity in the context of bone healing. Using this novel reporter system, we were able to elucidate how cell-based therapies impact bone healing and identify ASCs as an attractive candidate for cell-based skeletal regenerative therapy. These insights potentially influence stem cell selection in translational clinical trials evaluating cell-based therapeutics for osseous repair and regeneration.

  View details for DOI 10.1089/ten.tea.2015.0221

  View details for Web of Science ID 000368520300005

  View details for PubMedCentralID PMC4741228

• Reply: Studies in Fat Grafting: Part V. Cell-Assisted Lipotransfer to Enhance Fat Graft Retention Is Dose Dependent PLASTIC AND RECONSTRUCTIVE SURGERY Zielins, E. R., Longaker, M. T., Wan, D. C. 2015; 136 (6): 850E–851E

  View details for PubMedID 26322809

• Enhanced Activation of Canonical Wnt Signaling Confers Mesoderm-Derived Parietal Bone with Similar Osteogenic and Skeletal Healing Capacity to Neural Crest-Derived Frontal Bone PLOS ONE Li, S., Quarto, N., Senarath-Yapa, K., Grey, N., Bai, X., Longaker, M. T. 2015; 10 (10)

  Abstract

  Bone formation and skeletal repair are dynamic processes involving a fine-tuned balance between osteoblast proliferation and differentiation orchestrated by multiple signaling pathways. Canonical Wnt (cWnt) signaling is known to playing a key role in these processes. In the current study, using a transgenic mouse model with targeted disruption of axin2, a negative regulator of cWnt signaling, we investigated the impact of enhanced activation of cWnt signaling on the osteogenic capacity and skeletal repair. Specifically, we looked at two calvarial bones of different embryonic tissue origin: the neural crest-derived frontal bone and the mesoderm-derived parietal bone, and we investigated the proliferation and apoptotic activity of frontal and parietal bones and derived osteoblasts. We found dramatic differences in cell proliferation and apoptotic activity between Axin2-/- and wild type calvarial bones, with Axin2-/- showing increased proliferative activity and reduced levels of apoptosis. Furthermore, we compared osteoblast differentiation and bone regeneration in Axin2-/- and wild type neural crest-derived frontal and mesoderm-derived parietal bones, respectively. Our results demonstrate a significant increase either in osteoblast differentiation or bone regeneration in Axin2-/- mice as compared to wild type, with Axin2-/- parietal bone and derived osteoblasts displaying a "neural crest-derived frontal bone-like" profile, which is typically characterized by higher osteogenic capacity and skeletal repair than parietal bone. Taken together, our results strongly suggest that enhanced activation of cWnt signaling increases the skeletal potential of a calvarial bone of mesoderm origin, such as the parietial bone to a degree similar to that of a neural crest origin bone, like the frontal bone. Thus, providing further evidence for the central role played by the cWnt signaling in osteogenesis and skeletal-bone regeneration.

  View details for DOI 10.1371/journal.pone.0138059

  View details for Web of Science ID 000362178700009

  View details for PubMedID 26431534

  View details for PubMedCentralID PMC4592195

• RNA Sequencing for Identification of Differentially Expressed Noncoding Transcripts during Adipogenic Differentiation of Adipose-Derived Stromal Cells. Plastic and reconstructive surgery Luan, A., Paik, K. J., Li, J., Zielins, E. R., Atashroo, D. A., Spencley, A., Momeni, A., Longaker, M. T., Wang, K. C., Wan, D. C. 2015; 136 (4): 752-763

  Abstract

  Adipose-derived stromal cells represent a relatively abundant source of multipotent cells, with many potential applications in regenerative medicine. The present study sought to demonstrate the use of RNA sequencing in identifying differentially expressed transcripts, particularly long noncoding RNAs, associated with adipogenic differentiation to gain a clearer picture of the mechanisms responsible for directing adipose-derived stromal cell fate toward the adipogenic lineage.Human adipose-derived stromal cells were cultured in adipogenic differentiation media, and RNA was harvested at days 0, 1, 3, 5, and 7. Directional RNA sequencing libraries were prepared and sequenced. Paired-end reads were mapped to the human genome reference sequence hg19. Transcriptome assembly was performed and significantly differentially expressed transcripts were identified. Gene ontology term analysis was then performed to identify coding and noncoding transcripts of interest. Differential expression was verified by quantitative real-time polymerase chain reaction.Of 2868 significantly differentially expressed transcripts identified, 207 were noncoding. Enriched gene ontology terms among up-regulated coding transcripts notably reflected differentiation toward the adipogenic lineage. Enriched gene ontology terms among down-regulated coding transcripts reflected growth arrest. Guilt-by-association analysis revealed noncoding RNA candidates with potential roles in the process of adipogenic differentiation.The precise mechanisms that guide lineage-specific differentiation in multipotent cells are not yet fully understood. Defining long noncoding RNAs associated with adipogenic differentiation allows for potential manipulation of regulatory pathways in novel ways. The authors present RNA sequencing as a powerful tool for expanding the understanding of adipose-derived stromal cells and developing novel applications within regenerative medicine.

  View details for DOI 10.1097/PRS.0000000000001582

  View details for PubMedID 26090763

• Delivery of Macrophages in a Biomimetic Scaffold Accelerates Diabetic Wound Healing Through Enhanced Angiogenesis Walmsley, G. G., Hu, M. S., Duscher, D., Januszyk, M., Maan, Z. N., Senarath-Yapa, K., Tevlin, R., Zielins, E. R., Gurtner, G. C., Longaker, M. T. ELSEVIER SCIENCE INC. 2015: S113–S114

  View details for DOI 10.1016/j.jamcollsurg.2015.07.264

  View details for Web of Science ID 000361119700227

• Impairment in Fracture Healing in a Mouse Model of Type 2 Diabetes Is Driven by Skeletal Stem Cell Niche Dysregulation Tevlin, R., Seo, E., Mc Ardle, A., Tong, X., Januszyk, M., Yang, F., Gurtner, G. C., Chan, C. F., Weissman, I. L., Longaker, M. T. ELSEVIER SCIENCE INC. 2015: S115

  View details for DOI 10.1016/j.jamcollsurg.2015.07.268

  View details for Web of Science ID 000361119700230

• Microfluidic single cell transcriptional analysis reveals subpopulations of adipose derived stromal cells with enhanced angiogenic potential Zielins, E. R., Januszyk, M., Luan, A., Brett, E. A., Paik, K., Walmsley, G. G., Gurtner, G. C., Longaker, M. T., Wan, D. C. ELSEVIER SCIENCE INC. 2015: E26

  View details for DOI 10.1016/j.jamcollsurg.2015.08.366

  View details for Web of Science ID 000386899000059

• Melanoma Progression Depends on CXCL12 Expression by Host Endothelium Maan, Z. N., Hu, M. S., Whittam, A., Fischer, L. H., Duscher, D., Walmsley, G. G., Januszyk, M., Whitmore, A. J., Longaker, M. T., Gurtner, G. C. ELSEVIER SCIENCE INC. 2015: S116

  View details for DOI 10.1016/j.jamcollsurg.2015.07.272

  View details for Web of Science ID 000361119700234

• Wounds outcompete tumors for neovascularization Hu, M. S., Maan, Z. N., Hong, W., Walmsley, G. G., Rennert, R. C., Atashroo, D., Gurtner, G. C., Giaccia, A. J., Lorenz, H., Longaker, M. T. ELSEVIER SCIENCE INC. 2015: E124

  View details for DOI 10.1016/j.jamcollsurg.2015.08.230

  View details for Web of Science ID 000386899000304

• Adipose-Derived Stem Cells Improve Engraftment of Full-Thickness Skin Grafts by Increasing Angiogenesis Hu, M. S., Hong, W., Maan, Z. N., Hu, M., Zimmermann, A. S., Walmsley, G. G., Chung, M., Lorenz, H., Longaker, M. T. ELSEVIER SCIENCE INC. 2015: S112

  View details for DOI 10.1016/j.jamcollsurg.2015.07.260

  View details for Web of Science ID 000361119700223

• Progenitor Cell Dysfunctions Underlie Some Diabetic Complications AMERICAN JOURNAL OF PATHOLOGY Rodrigues, M., Wong, V. W., Rennert, R. C., Davis, C. R., Longaker, M. T., Gurtner, G. C. 2015; 185 (10): 2607-2618

  Abstract

  Stem cells and progenitor cells are integral to tissue homeostasis and repair. They contribute to health through their ability to self-renew and commit to specialized effector cells. Recently, defects in a variety of progenitor cell populations have been described in both preclinical and human diabetes. These deficits affect multiple aspects of stem cell biology, including quiescence, renewal, and differentiation, as well as homing, cytokine production, and neovascularization, through mechanisms that are still unclear. More important, stem cell aberrations resulting from diabetes have direct implications on tissue function and seem to persist even after return to normoglycemia. Understanding how diabetes alters stem cell signaling and homeostasis is critical for understanding the complex pathophysiology of many diabetic complications. Moreover, the success of cell-based therapies will depend on a more comprehensive understanding of these deficiencies. This review has three goals: to analyze stem cell pathways dysregulated during diabetes, to highlight the effects of hyperglycemic memory on stem cells, and to define ways of using stem cell therapy to overcome diabetic complications.

  View details for DOI 10.1016/j.ajpath.2015.05.003

  View details for Web of Science ID 000362698300003

  View details for PubMedID 26079815

  View details for PubMedCentralID PMC4607762

• Skeletal Stem Cell Niche Aberrancies Underlie Impaired Fracture Healing in a Mouse Model of Type 2 Diabetes. Plastic and reconstructive surgery Tevlin, R., Young Seo, E., Marecic, O., Wearda, T., Mc Ardle, A., Januszyk, M., Gulati, G., Maan, Z., Hu, M. S., Walmsley, G. G., Gurtner, G. C., Chan, C. K., Weissman, I. L., Longaker, M. T. 2015; 136 (4): 73-?

  View details for DOI 10.1097/01.prs.0000472372.96995.3e

  View details for PubMedID 26397581

• My Journey as a Surgeon-Scientist Ten Years after Receiving the Inaugural Jacobson Promising Investigator Award JOURNAL OF THE AMERICAN COLLEGE OF SURGEONS Longaker, M. T. 2015; 221 (4): 880-882

  Abstract

  The First Joan L and Julius H Jacobson Promising Investigator Awardee, Michael T Longaker MD, FACS In 2005, the research committee of the American College of Surgeons was tasked with selecting the recipient of a newly established award, "The Joan L and Julius H Jacobson Promising Investigator Award." According to the Jacobsons, the $30,000 award funded by Dr Jacobson should be given at least once every 2 years to a surgeon investigator at "the tipping point," who can demonstrate that his/her research shows the promise of leading to a significant contribution to the practice of surgery and patient safety. Every year, the research committee receives many excellent nominations and has the difficult task of selecting 1 awardee. In 2005, the awardee was a young promising investigator, Michael T Longaker, MD, FACS. Ten years later, Dr Longaker, a prominent researcher in the field of "scar formation," presents his journey in research and the impact of the Jacobson award on his career. Dr Longaker is now a national and international figure in the field of wound healing, tissue regeneration, and stem cell research. Kamal MF Itani, MD, FACS and Gail Besner, MD, FACS, on behalf of the Research Committee of the American College of Surgeons.

  View details for DOI 10.1016/j.jamcollsurg.2015.06.018

  View details for Web of Science ID 000361067200015

  View details for PubMedID 26304185

• Identification and characterization of an injury-induced skeletal progenitor PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Marecic, O., Tevlin, R., McArdle, A., Seo, E. Y., Wearda, T., Duldulao, C., Walmsley, G. G., Nguyen, A., Weissman, I. L., Chan, C. K., Longaker, M. T. 2015; 112 (32): 9920-9925

  Abstract

  The postnatal skeleton undergoes growth, remodeling, and repair. We hypothesized that skeletal progenitor cells active during these disparate phases are genetically and phenotypically distinct. We identified a highly potent regenerative cell type that we term the fracture-induced bone, cartilage, stromal progenitor (f-BCSP) in the fracture callus of adult mice. The f-BCSP possesses significantly enhanced skeletogenic potential compared with BCSPs harvested from uninjured bone. It also recapitulates many gene expression patterns involved in perinatal skeletogenesis. Our results indicate that the skeletal progenitor population is functionally stratified, containing distinct subsets responsible for growth, regeneration, and repair. Furthermore, our findings suggest that injury-induced changes to the skeletal stem and progenitor microenvironments could activate these cells and enhance their regenerative potential.

  View details for DOI 10.1073/pnas.1513066112

  View details for PubMedID 26216955

• High-Throughput Screening of Surface Marker Expression on Undifferentiated and Differentiated Human Adipose-Derived Stromal Cells TISSUE ENGINEERING PART A Walmsley, G. G., Atashroo, D. A., Maan, Z. N., Hu, M. S., Zielins, E. R., Tsai, J. M., Duscher, D., Paik, K., Tevlin, R., Marecic, O., Wan, D. C., Gurtner, G. C., Longaker, M. T. 2015; 21 (15-16): 2281-2291

  Abstract

  Adipose tissue contains an abundant source of multipotent mesenchymal cells termed "adipose-derived stromal cells" (ASCs) that hold potential for regenerative medicine. However, the heterogeneity inherent to ASCs harvested using standard methodologies remains largely undefined, particularly in regards to differences across donors. Identifying the subpopulations of ASCs predisposed toward differentiation along distinct lineages holds value for improving graft survival, predictability, and efficiency. Human ASCs (hASCs) from three different donors were independently isolated by density-based centrifugation from adipose tissue and maintained in culture or differentiated along either adipogenic or osteogenic lineages using differentiation media. Undifferentiated and differentiated hASCs were then analyzed for the presence of 242 human surface markers by flow cytometry analysis. By comprehensively characterizing the surface marker profile of undifferentiated hASCs using flow cytometry, we gained novel insights into the heterogeneity underlying protein expression on the surface of cultured undifferentiated hASCs across different donors. Comparison of the surface marker profile of undifferentiated hASCs with hASCs that have undergone osteogenic or adipogenic differentiation allowed for the identification of surface markers that were upregulated and downregulated by osteogenic or adipogenic differentiation. Osteogenic differentiation induced upregulation of CD164 and downregulation of CD49a, CD49b, CD49c, CD49d, CD55, CD58, CD105, and CD166 while adipogenic differentiation induced upregulation of CD36, CD40, CD146, CD164, and CD271 and downregulation of CD49b, CD49c, CD49d, CD71, CD105, and CD166. These results lend support to the notion that hASCs isolated using standard methodologies represent a heterogeneous population and serve as a foundation for future studies seeking to maximize their regenerative potential through fluorescence-activated cell sorting-based selection before therapy.

  View details for DOI 10.1089/ten.tea.2015.0039

  View details for Web of Science ID 000359812700014

  View details for PubMedID 26020286

  View details for PubMedCentralID PMC4529076

• En1 fibroblasts and melanoma. Melanoma management Walmsley, G. G., Hu, M. S., Maan, Z. N., Rinkevich, Y., Weissman, I. L., Longaker, M. T. 2015; 2 (3): 191-192

  View details for DOI 10.2217/mmt.15.23

  View details for PubMedID 30190847

  View details for PubMedCentralID PMC6094637

• What Makes a Plastic Surgery Residency Program Attractive? An Applicant's Perspective PLASTIC AND RECONSTRUCTIVE SURGERY Atashroo, D. A., Luan, A., Vyas, K. S., Zielins, E. R., Maan, Z., Duscher, D., Walmsley, G. G., Lynch, M. P., Davenport, D. L., Wan, D. C., Longaker, M. T., Vasconez, H. C. 2015; 136 (1): 189-196

  Abstract

  Plastic surgery is among the most competitive specialties in medicine, but little is known about the attributes of programs that are most attractive to successful applicants. This study aimed to understand and provide insights regarding program characteristics that are most influential to students when ranking plastic surgery programs.An anonymous online survey was conducted with newly matched plastic surgery residents for the integrated and combined Match in 2012 and 2013. Subjects were queried regarding their demographics, qualifications, application experiences, and motivations for residency program selection.A total of 92 of 245 matched plastic surgery residents (38 percent) responded to the survey. The perception of resident happiness was the most positive factor influencing program ranking, followed by high operative volume, faculty mentorship, and strong research infrastructure. Perception of a program as "malignant" was the most negative attribute. Applicants with Step 1 scores greater than 245 received significantly more interviews (p =0.001) and considered resident benefits less important (p < 0.05), but geographic location more important (p =0.005). Applicants who published more than two articles also received more interviews (p =0.001) and ranked a strong research infrastructure and program reputation as significantly more important (p < 0.05). Forty-two percent of applicants completed an away rotation at the program with which they matched, and these applicants were more likely to match at their number one ranked program (p = 0.001).Plastic surgery applicants have differing preferences regarding the ideal training program, but some attributes resonate. These trends can guide programs for improvement in attracting the best applicants.

  View details for DOI 10.1097/PRS.0000000000001365

  View details for Web of Science ID 000357097900001

  View details for PubMedID 26111321

• Nanotechnology in bone tissue engineering NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE Walmsley, G. G., McArdle, A., Tevlin, R., Momeni, A., Atashroo, D., Hu, M. S., Feroze, A. H., Wong, V. W., Lorenz, P. H., Longaker, M. T., Wan, D. C. 2015; 11 (5): 1253-1263

  Abstract

  Nanotechnology represents a major frontier with potential to significantly advance the field of bone tissue engineering. Current limitations in regenerative strategies include impaired cellular proliferation and differentiation, insufficient mechanical strength of scaffolds, and inadequate production of extrinsic factors necessary for efficient osteogenesis. Here we review several major areas of research in nanotechnology with potential implications in bone regeneration: 1) nanoparticle-based methods for delivery of bioactive molecules, growth factors, and genetic material, 2) nanoparticle-mediated cell labeling and targeting, and 3) nano-based scaffold construction and modification to enhance physicochemical interactions, biocompatibility, mechanical stability, and cellular attachment/survival. As these technologies continue to evolve, ultimate translation to the clinical environment may allow for improved therapeutic outcomes in patients with large bone deficits and osteodegenerative diseases.Traditionally, the reconstruction of bony defects has relied on the use of bone grafts. With advances in nanotechnology, there has been significant development of synthetic biomaterials. In this article, the authors provided a comprehensive review on current research in nanoparticle-based therapies for bone tissue engineering, which should be useful reading for clinicians as well as researchers in this field.

  View details for DOI 10.1016/j.nano.2015.02.013

  View details for Web of Science ID 000363967100022

  View details for PubMedID 25791811

  View details for PubMedCentralID PMC4476906

• Studies in Fat Grafting: Part V. Cell-Assisted Lipotransfer to Enhance Fat Graft Retention Is Dose Dependent PLASTIC AND RECONSTRUCTIVE SURGERY Paik, K. J., Zielins, E. R., Atashroo, D. A., Maan, Z. N., Duscher, D., Luan, A., Walmsley, G. G., Momeni, A., Vistnes, S., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2015; 136 (1): 67-75

  Abstract

  Cell-assisted lipotransfer has shown much promise as a technique for improving fat graft take. However, the concentration of stromal vascular fraction cells required to optimally enhance fat graft retention remains unknown.Human lipoaspirate was processed for both fat transfer and harvest of stromal vascular fraction cells. Cells were then mixed back with fat at varying concentrations ranging from 10,000 to 10 million cells per 200 μl of fat. Fat graft volume retention was assessed by means of computed tomographic scanning over 8 weeks, and then fat grafts were explanted and compared histologically for overall architecture and vascularity.Maximum fat graft retention was seen at a concentration of 10,000 cells per 200 μl of fat. The addition of higher number of cells negatively impacted fat graft retention, with supplementation of 10 million cells producing the lowest final volumes, lower than fat alone. Interestingly, fat grafts supplemented with 10,000 cells showed significantly increased vascularity and decreased inflammation, whereas fat grafts supplemented with 10 million cells showed significant lipodegeneration compared with fat alone: The authors' study demonstrates dose dependence in the number of stromal vascular fraction cells that can be added to a fat graft to enhance retention. Although cell-assisted lipotransfer may help promote graft survival, this effect may need to be balanced with the increased metabolic load of added cells that may compete with adipocytes for nutrients during the postgraft period.

  View details for DOI 10.1097/PRS.0000000000001367

  View details for Web of Science ID 000357096300002

  View details for PubMedID 25829158

  View details for PubMedCentralID PMC4483157

• Emerging drugs for the treatment of wound healing EXPERT OPINION ON EMERGING DRUGS Zielins, E. R., Brett, E. A., Luan, A., Hu, M. S., Walmsley, G. G., Paik, K., Senarath-Yapa, K., Atashroo, D. A., Wearda, T., Lorenz, H. P., Wan, D. C., Longaker, M. T. 2015; 20 (2): 235-246

  Abstract

  Wound healing can be characterized as underhealing, as in the setting of chronic wounds, or overhealing, occurring with hypertrophic scar formation after burn injury. Topical therapies targeting specific biochemical and molecular pathways represent a promising avenue for improving and, in some cases normalizing, the healing process.A brief overview of both normal and pathological wound healing has been provided, along with a review of the current clinical guidelines and treatment modalities for chronic wounds, burn wounds and scar formation. Next, the major avenues for wound healing drugs, along with drugs currently in development, are discussed. Finally, potential challenges to further drug development, and future research directions are discussed.The large body of research concerning wound healing pathophysiology has provided multiple targets for topical therapies. Growth factor therapies with the ability to be targeted for localized release in the wound microenvironment are most promising, particularly when they modulate processes in the proliferative phase of wound healing.

  View details for DOI 10.1517/14728214.2015.1018176

  View details for Web of Science ID 000356118400007

  View details for PubMedID 25704608

• The Foreign Body Response: At the Interface of Surgery and Bioengineering PLASTIC AND RECONSTRUCTIVE SURGERY Major, M. R., Wong, V. W., Nelson, E. R., Longaker, M. T., Gurtner, G. C. 2015; 135 (5): 1489-1498

  Abstract

  The surgical implantation of materials and devices has dramatically increased over the past decade. This trend is expected to continue with the broadening application of biomaterials and rapid expansion of aging populations. One major factor that limits the potential of implantable materials and devices is the foreign body response, an immunologic reaction characterized by chronic inflammation, foreign body giant cell formation, and fibrotic capsule formation.The English literature on the foreign body response to implanted materials and devices is reviewed.Fibrotic encapsulation can cause device malfunction and dramatically limit the function of an implanted medical device or material. Basic science studies suggest a role for immune and inflammatory pathways at the implant-host interface that drive the foreign body response. Current strategies that aim to modulate the host response and improve construct biocompatibility appear promising.This review article summarizes recent basic science, preclinical, and clinicopathologic studies examining the mechanisms driving the foreign body response, with particular focus on breast implants and synthetic meshes. Understanding these molecular and cellular mechanisms will be critical for achieving the full potential of implanted biomaterials to restore human tissues and organs.

  View details for DOI 10.1097/PRS.0000000000001193

  View details for Web of Science ID 000353647100060

  View details for PubMedID 25919260

• Skin fibrosis. Identification and isolation of a dermal lineage with intrinsic fibrogenic potential. Science Rinkevich, Y., Walmsley, G. G., Hu, M. S., Maan, Z. N., Newman, A. M., Drukker, M., Januszyk, M., Krampitz, G. W., Gurtner, G. C., Lorenz, H. P., Weissman, I. L., Longaker, M. T. 2015; 348 (6232)

  Abstract

  Dermal fibroblasts represent a heterogeneous population of cells with diverse features that remain largely undefined. We reveal the presence of at least two fibroblast lineages in murine dorsal skin. Lineage tracing and transplantation assays demonstrate that a single fibroblast lineage is responsible for the bulk of connective tissue deposition during embryonic development, cutaneous wound healing, radiation fibrosis, and cancer stroma formation. Lineage-specific cell ablation leads to diminished connective tissue deposition in wounds and reduces melanoma growth. Using flow cytometry, we identify CD26/DPP4 as a surface marker that allows isolation of this lineage. Small molecule-based inhibition of CD26/DPP4 enzymatic activity during wound healing results in diminished cutaneous scarring. Identification and isolation of these lineages hold promise for translational medicine aimed at in vivo modulation of fibrogenic behavior.

  View details for DOI 10.1126/science.aaa2151

  View details for PubMedID 25883361

  View details for PubMedCentralID PMC5088503

• Identification and isolation of a dermal lineage with intrinsic fibrogenic potential SCIENCE Rinkevich, Y., Walmsley, G. G., Hu, M. S., Maan, Z. N., Newman, A. M., Drukker, M., Januszyk, M., Krampitz, G. W., Gurtner, G. C., Lorenz, H. P., Weissman, I. L., Longaker, M. T. 2015; 348 (6232): 302-?

  Abstract

  Dermal fibroblasts represent a heterogeneous population of cells with diverse features that remain largely undefined. We reveal the presence of at least two fibroblast lineages in murine dorsal skin. Lineage tracing and transplantation assays demonstrate that a single fibroblast lineage is responsible for the bulk of connective tissue deposition during embryonic development, cutaneous wound healing, radiation fibrosis, and cancer stroma formation. Lineage-specific cell ablation leads to diminished connective tissue deposition in wounds and reduces melanoma growth. Using flow cytometry, we identify CD26/DPP4 as a surface marker that allows isolation of this lineage. Small molecule-based inhibition of CD26/DPP4 enzymatic activity during wound healing results in diminished cutaneous scarring. Identification and isolation of these lineages hold promise for translational medicine aimed at in vivo modulation of fibrogenic behavior.

  View details for DOI 10.1126/science.aaa2151

  View details for Web of Science ID 000352999000034

  View details for PubMedCentralID PMC5088503

• Studies in Fat Grafting: Part IV. Adipose-Derived Stromal Cell Gene Expression in Cell-Assisted Lipotransfer PLASTIC AND RECONSTRUCTIVE SURGERY Garza, R. M., Rennert, R. C., Paik, K. J., Atashroo, D., Chung, M. T., Duscher, D., Januszyk, M., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2015; 135 (4): 1045-1055

  Abstract

  Fat graft volume retention remains highly unpredictable, but addition of adipose-derived stromal cells to fat grafts has been shown to improve retention. The present study aimed to investigate the mechanisms involved in adipose-derived stromal cell enhancement of fat grafting.Adipose-derived stromal cells isolated from human lipoaspirate were labeled with green fluorescent protein and luciferase. Fat grafts enhanced with adipose-derived stromal cells were injected into the scalp and bioluminescent imaging was performed to follow retention of adipose-derived stromal cells within the fat graft. Fat grafts were also explanted at days 1, 5, and 10 after grafting for adipose-derived stromal cell extraction and single-cell gene analysis. Finally, CD31 immunohistochemical staining was performed on fat grafts enriched with adipose-derived stromal cells.Bioluminescent imaging demonstrated significant reduction in luciferase-positive adipose-derived stromal cells within fat grafts at 5 days after grafting. A similar reduction in viable green fluorescent protein-positive adipose-derived stromal cells retrieved from explanted grafts was also noted. Single-cell analysis revealed expression of multiple genes/markers related to cell survival and angiogenesis, including BMPR2, CD90, CD105, FGF2, CD248, TGFß1, and VEGFA. Genes involved in adipogenesis were not expressed by adipose-derived stromal cells. Finally, CD31 staining revealed significantly higher vascular density in fat grafts explanted at day 10 after grafting.Although adipose-derived stromal cell survival in the hypoxic graft environment decreases significantly over time, these cells provide multiple angiogenic growth factors. Therefore, improved fat graft volume retention with adipose-derived stromal cell enrichment may be attributable to improved graft vascularization.

  View details for DOI 10.1097/PRS.0000000000001104

  View details for Web of Science ID 000351910200043

  View details for PubMedID 25502860

  View details for PubMedCentralID PMC4376612

• Therapeutic applications of human adipose-derived stromal cells for soft tissue reconstruction. Discovery medicine Zielins, E. R., Luan, A., Brett, E. A., Longaker, M. T., Wan, D. C. 2015; 19 (105): 245-253

  Abstract

  Adipose derived stromal cells (ASCs) are a multipotent cell population derived from the stromal vascular fraction of lipoaspirate. Given their relatively broad differentiation potential and paracrine capabilities, ASCs represent a readily accessible, endogenous resource for novel reconstructive strategies. In particular, augmentation of autologous fat grafts with ASCs has already been employed clinically for restoration of soft tissue defects. While fat grafting alone remains highly unpredictable, enrichment of fat with supplemental ASCs, also known as cell-assisted lipotransfer (CAL), has been shown to significantly enhance volume retention. How addition of these cells to fat grafts results in improved outcomes, however, remains poorly understood. Furthermore, the safety of CAL in the setting of prior malignancy and post-radiation wound beds has yet to be fully determined, an important consideration for its use in cancer reconstruction. Thus, further studies to determine the how and why behind the efficacy of CAL are necessary before it can be widely adopted as a safe and reliable surgical technique.

  View details for PubMedID 25977187

• Therapeutic Applications of Human Adipose-Derived Stromal Cells for Soft Tissue Reconstruction DISCOVERY MEDICINE Zielins, E. R., Luan, A., Brett, E. A., Longaker, M. T., Wan, D. C. 2015; 105: 245-253

  Abstract

  Adipose derived stromal cells (ASCs) are a multipotent cell population derived from the stromal vascular fraction of lipoaspirate. Given their relatively broad differentiation potential and paracrine capabilities, ASCs represent a readily accessible, endogenous resource for novel reconstructive strategies. In particular, augmentation of autologous fat grafts with ASCs has already been employed clinically for restoration of soft tissue defects. While fat grafting alone remains highly unpredictable, enrichment of fat with supplemental ASCs, also known as cell-assisted lipotransfer (CAL), has been shown to significantly enhance volume retention. How addition of these cells to fat grafts results in improved outcomes, however, remains poorly understood. Furthermore, the safety of CAL in the setting of prior malignancy and post-radiation wound beds has yet to be fully determined, an important consideration for its use in cancer reconstruction. Thus, further studies to determine the how and why behind the efficacy of CAL are necessary before it can be widely adopted as a safe and reliable surgical technique.

  View details for Web of Science ID 000356922200001

• Peripheral blood-derived mesenchymal stem cells: candidate cells responsible for healing critical-sized calvarial bone defects. Stem cells translational medicine Li, S., Huang, K., Wu, J., Hu, M. S., Sanyal, M., Hu, M., Longaker, M. T., Lorenz, H. P. 2015; 4 (4): 359-368

  Abstract

  Postnatal tissue-specific stem/progenitor cells hold great promise to enhance repair of damaged tissues. Many of these cells are retrieved from bone marrow or adipose tissue via invasive procedures. Peripheral blood is an ideal alternative source for the stem/progenitor cells because of its ease of retrieval. We present a coculture system that routinely produces a group of cells from adult peripheral blood. Treatment with these cells enhanced healing of critical-size bone defects in the mouse calvarium, a proof of principle that peripheral blood-derived cells can be used to heal bone defects. From these cells, we isolated a subset of CD45(-) cells with a fibroblastic morphology. The CD45(-) cells were responsible for most of the differentiation-induced calcification activity and were most likely responsible for the enhanced healing process. These CD45(-) fibroblastic cells are plastic-adherent and exhibit a surface marker profile negative for CD34, CD19, CD11b, lineage, and c-kit and positive for stem cell antigen 1, CD73, CD44, CD90.1, CD29, CD105, CD106, and CD140α. Furthermore, these cells exhibited osteogenesis, chondrogenesis, and adipogenesis capabilities. The CD45(-) fibroblastic cells are the first peripheral blood-derived cells that fulfill the criteria of mesenchymal stem cells as defined by the International Society for Cellular Therapy. We have named these cells "blood-derived mesenchymal stem cells."

  View details for DOI 10.5966/sctm.2014-0150

  View details for PubMedID 25742693

  View details for PubMedCentralID PMC4367504

• TWIST1 Silencing Enhances In Vitro and In Vivo Osteogenic Differentiation of Human Adipose-Derived Stem Cells by Triggering Activation of BMP-ERK/FGF Signaling and TAZ Upregulation. Stem cells Quarto, N., Senarath-Yapa, K., Renda, A., Longaker, M. T. 2015; 33 (3): 833-847

  Abstract

  Mesenchymal stem cells (MSCs) show promise for cellular therapy and regenerative medicine. Human adipose tissue-derived stem cells (hASCs) represent an attractive source of seed cells in bone regeneration. How to effectively improve osteogenic differentiation of hASCs in the bone tissue engineering has become a very important question with profound translational implications. Numerous regulatory pathways dominate osteogenic differentiation of hASCs involving transcriptional factors and signaling molecules. However, how these factors combine with each other to regulate hASCs osteogenic differentiation still remains to be illustrated. The highly conserved developmental proteins TWIST play key roles for transcriptional regulation in mesenchymal cell lineages. This study investigates TWIST1 function in hASCs osteogenesis. Our results show that TWIST1 shRNA silencing increased the osteogenic potential of hASCs in vitro and their skeletal regenerative ability when applied in vivo. We demonstrate that the increased osteogenic capacity observed with TWIST1 knockdown in hASCs is mediated through endogenous activation of BMP and ERK/FGF signaling leading, in turn, to upregulation of TAZ, a transcriptional modulator of MSCs differentiation along the osteoblast lineage. Inhibition either of BMP or ERK/FGF signaling suppressed TAZ upregulation and the enhanced osteogenesis in shTWIST1 hASCs. Cosilencing of both TWIST1 and TAZ abrogated the effect elicited by TWIST1 knockdown thus, identifying TAZ as a downstream mediator through which TWIST1 knockdown enhanced osteogenic differentiation in hASCs. Our functional study contributes to a better knowledge of molecular mechanisms governing the osteogenic ability of hASCs, and highlights TWIST1 as a potential target to facilitate in vivo bone healing. Stem Cells 2015;33:833-847.

  View details for DOI 10.1002/stem.1907

  View details for PubMedID 25446627

• Live Fibroblast Harvest Reveals Surface Marker Shift In Vitro TISSUE ENGINEERING PART C-METHODS Walmsley, G. G., Rinkevich, Y., Hu, M. S., Montoro, D. T., Lo, D. D., McArdle, A., Maan, Z. N., Morrison, S. D., Duscher, D., Whittam, A. J., Wong, V. W., Weissman, I. L., Gurtner, G. C., Longaker, M. T. 2015; 21 (3): 314-321

  Abstract

  Current methods for the isolation of fibroblasts require extended ex vivo manipulation in cell culture. As a consequence, prior studies investigating fibroblast biology may fail to adequately represent cellular phenotypes in vivo. To overcome this problem, we describe a detailed protocol for the isolation of fibroblasts from the dorsal dermis of adult mice that bypasses the need for cell culture, thereby preserving the physiological, transcriptional, and proteomic profiles of each cell. Using the described protocol we characterized the transcriptional programs and the surface expression of 176 CD markers in cultured versus uncultured fibroblasts. The differential expression patterns we observed highlight the importance of a live harvest for investigations of fibroblast biology.

  View details for DOI 10.1089/ten.tec.2014.0118

  View details for Web of Science ID 000350043400009

  View details for PubMedID 25275778

  View details for PubMedCentralID PMC4346232

• The role and regulation of osteoclasts in normal bone homeostasis and in response to injury. Plastic and reconstructive surgery McArdle, A., Marecic, O., Tevlin, R., Walmsley, G. G., Chan, C. K., Longaker, M. T., Wan, D. C. 2015; 135 (3): 808-816

  Abstract

  Bone is a dynamic tissue, with a range of diverse functions, including locomotion, protection of internal organs, and hematopoiesis. Optimum treatment of fractures and/or bone defects requires knowledge of the complex cellular interactions involved with bone healing and remodeling. Emerging data have underscored the importance of osteoclasts in this process, playing a key role both in normal bone turnover and in facilitating bone regeneration. In this review, the authors discuss the basic principles of osteoclast biology, including its cellular origins, its function, and key regulatory mechanisms, in addition to conditions that arise when osteoclast function is altered.

  View details for DOI 10.1097/PRS.0000000000000963

  View details for PubMedID 25719699

• Scarless wound healing: chasing the holy grail. Plastic and reconstructive surgery Walmsley, G. G., Maan, Z. N., Wong, V. W., Duscher, D., Hu, M. S., Zielins, E. R., Wearda, T., Muhonen, E., McArdle, A., Tevlin, R., Atashroo, D. A., Senarath-Yapa, K., Lorenz, H. P., Gurtner, G. C., Longaker, M. T. 2015; 135 (3): 907-917

  Abstract

  Over 100 million patients acquire scars in the industrialized world each year, primarily as a result of elective operations. Although undefined, the global incidence of scarring is even larger, extending to significant numbers of burn and other trauma-related wounds. Scars have the potential to exert a profound psychological and physical impact on the individual. Beyond aesthetic considerations and potential disfigurement, scarring can result in restriction of movement and reduced quality of life. The formation of a scar following skin injury is a consequence of wound healing occurring through reparative rather than regenerative mechanisms. In this article, the authors review the basic stages of wound healing; differences between adult and fetal wound healing; various mechanical, genetic, and pharmacologic strategies to reduce scarring; and the biology of skin stem/progenitor cells that may hold the key to scarless regeneration.

  View details for DOI 10.1097/PRS.0000000000000972

  View details for PubMedID 25719706

• Exercise induces stromal cell-derived factor-1a-mediated release of endothelial progenitor cells with increased vasculogenic function. Plastic and reconstructive surgery Chang, E., Paterno, J., Duscher, D., Maan, Z. N., Chen, J. S., Januszyk, M., Rodrigues, M., Rennert, R. C., Bishop, S., Whitmore, A. J., Whittam, A. J., Longaker, M. T., Gurtner, G. C. 2015; 135 (2): 340e-50e

  Abstract

  Endothelial progenitor cells have been shown to traffic to and incorporate into ischemic tissues, where they participate in new blood vessel formation, a process termed vasculogenesis. Previous investigation has demonstrated that endothelial progenitor cells appear to mobilize from bone marrow to the peripheral circulation after exercise. In this study, the authors investigate potential etiologic factors driving this mobilization and investigate whether the mobilized endothelial progenitor cells are the same as those present at baseline.Healthy volunteers (n = 5) performed a monitored 30-minute run to maintain a heart rate greater than 140 beats/min. Venous blood samples were collected before, 10 minutes after, and 24 hours after exercise. Endothelial progenitor cells were isolated and evaluated.Plasma levels of stromal cell-derived factor-1α significantly increased nearly two-fold immediately after exercise, with a nearly four-fold increase in circulating endothelial progenitor cells 24 hours later. The endothelial progenitor cells isolated following exercise demonstrated increased colony formation, proliferation, differentiation, and secretion of angiogenic cytokines. Postexercise endothelial progenitor cells also exhibited a more robust response to hypoxic stimulation.Exercise appears to mobilize endothelial progenitor cells and augment their function by means of stromal cell-derived factor 1α-dependent signaling. The population of endothelial progenitor cells mobilized following exercise is primed for vasculogenesis with increased capacity for proliferation, differentiation, secretion of cytokines, and responsiveness to hypoxia. Given the evidence demonstrating positive regenerative effects of exercise, this may be one possible mechanism for its benefits.

  View details for DOI 10.1097/PRS.0000000000000917

  View details for PubMedID 25626819

• Reply: Studies in fat grafting: part I. Effects of injection technique on in vitro fat viability and in vivo volume retention; and studies in fat grafting: part II. Effects of injection mechanics on material properties of fat. Plastic and reconstructive surgery Wan, D. C., Gurtner, G. C., Longaker, M. T. 2015; 135 (2): 448e-9e

  View details for DOI 10.1097/PRS.0000000000000978

  View details for PubMedID 25626833

• Identification and specification of the mouse skeletal stem cell. Cell Chan, C. K., Seo, E. Y., Chen, J. Y., Lo, D., McArdle, A., Sinha, R., Tevlin, R., Seita, J., Vincent-Tompkins, J., Wearda, T., Lu, W., Senarath-Yapa, K., Chung, M. T., Marecic, O., Tran, M., Yan, K. S., Upton, R., Walmsley, G. G., Lee, A. S., Sahoo, D., Kuo, C. J., Weissman, I. L., Longaker, M. T. 2015; 160 (1-2): 285-298

  Abstract

  How are skeletal tissues derived from skeletal stem cells? Here, we map bone, cartilage, and stromal development from a population of highly pure, postnatal skeletal stem cells (mouse skeletal stem cells, mSSCs) to their downstream progenitors of bone, cartilage, and stromal tissue. We then investigated the transcriptome of the stem/progenitor cells for unique gene-expression patterns that would indicate potential regulators of mSSC lineage commitment. We demonstrate that mSSC niche factors can be potent inducers of osteogenesis, and several specific combinations of recombinant mSSC niche factors can activate mSSC genetic programs in situ, even in nonskeletal tissues, resulting in de novo formation of cartilage or bone and bone marrow stroma. Inducing mSSC formation with soluble factors and subsequently regulating the mSSC niche to specify its differentiation toward bone, cartilage, or stromal cells could represent a paradigm shift in the therapeutic regeneration of skeletal tissues.

  View details for DOI 10.1016/j.cell.2014.12.002

  View details for PubMedID 25594184

• Epigenetic and in vivo comparison of diverse MSC sources reveals an endochondral signature for human hematopoietic niche formation. Blood Reinisch, A., Etchart, N., Thomas, D., Hofmann, N. A., Fruehwirth, M., Sinha, S., Chan, C. K., Senarath-Yapa, K., Seo, E., Wearda, T., Hartwig, U. F., Beham-Schmid, C., Trajanoski, S., Lin, Q., Wagner, W., Dullin, C., Alves, F., Andreeff, M., Weissman, I. L., Longaker, M. T., Schallmoser, K., Majeti, R., Strunk, D. 2015; 125 (2): 249-260

  Abstract

  In the last decade there has been a rapid expansion in clinical trials using mesenchymal stromal cells (MSCs) from a variety of tissues. However, despite similarities in morphology, immunophenotype and differentiation behavior in vitro, MSCs sourced from distinct tissues do not necessarily have equivalent biological properties. We performed a genome-wide methylation, transcription and in vivo evaluation of MSCs from human bone marrow (BM), white adipose tissue, umbilical cord and skin cultured in humanized media. Surprisingly, only BM-derived MSCs spontaneously formed a bone marrow cavity through a vascularized cartilage intermediate in vivo that was progressively replaced by hematopoietic tissue and bone. Only BM-derived MSCs exhibited a chondrogenic transcriptional program with hypomethylation and increased expression of RUNX3, RUNX2, BGLAP, MMP13 and ITGA10 consistent with a latent and primed skeletal developmental potential. The humanized MSC-derived microenvironment permitted homing and maintenance of long-term murine SLAM(+) hematopoietic stem cells (HSCs) as well as human CD34(+)/CD38(-)/CD90(+)/CD45RA(+) HSCs after cord blood transplantation. These studies underscore the profound differences in developmental potential between MSC sources independent of donor age with implications for their clinical use. We also demonstrate a tractable human niche model for studying homing and engraftment of human hematopoietic cells in normal and neoplastic states.

  View details for DOI 10.1182/blood-2014-04-572255

  View details for PubMedID 25406351

• Isolation and Enrichment of Human Adipose-derived Stromal Cells for Enhanced Osteogenesis. Journal of visualized experiments : JoVE Zielins, E. R., Tevlin, R., Hu, M. S., Chung, M. T., McArdle, A., Paik, K. J., Atashroo, D., Duldulao, C. R., Luan, A., Senarath-Yapa, K., Walmsley, G. G., Wearda, T., Longaker, M. T., Wan, D. C. 2015

  View details for DOI 10.3791/52181

  View details for PubMedID 25650785

• Differences in Foetal, Adult Skin and Mucosal Repair STEM CELL BIOLOGY AND TISSUE ENGINEERING IN DENTAL SCIENCES Lo, D. D., Hu, M. S., Zimmermann, A. S., Longaker, M. T., Lorenz, H., Vishwakarma, A., Sharpe, P., Shi, S., Ramalingam, M. 2015: 691–702

  View details for DOI 10.1016/B978-0-12-397157-9.00055-2

  View details for Web of Science ID 000444643800052

• Stem Cell-Based Therapeutics to Improve Wound Healing. Plastic surgery international Hu, M. S., Leavitt, T., Malhotra, S., Duscher, D., Pollhammer, M. S., Walmsley, G. G., Maan, Z. N., Cheung, A. T., Schmidt, M., Huemer, G. M., Longaker, M. T., Lorenz, H. P. 2015; 2015: 383581-?

  Abstract

  Issues surrounding wound healing have garnered deep scientific interest as well as booming financial markets invested in novel wound therapies. Much progress has been made in the field, but it is unsurprising to find that recent successes reveal new challenges to be addressed. With regard to wound healing, large tissue deficits, recalcitrant wounds, and pathological scar formation remain but a few of our most pressing challenges. Stem cell-based therapies have been heralded as a promising means by which to surpass current limitations in wound management. The wide differentiation potential of stem cells allows for the possibility of restoring lost or damaged tissue, while their ability to immunomodulate the wound bed from afar suggests that their clinical applications need not be restricted to direct tissue formation. The clinical utility of stem cells has been demonstrated across dozens of clinical trials in chronic wound therapy, but there is hope that other aspects of wound care will inherit similar benefit. Scientific inquiry into stem cell-based wound therapy abounds in research labs around the world. While their clinical applications remain in their infancy, the heavy investment in their potential makes it a worthwhile subject to review for plastic surgeons, in terms of both their current and future applications.

  View details for DOI 10.1155/2015/383581

  View details for PubMedID 26649195

  View details for PubMedCentralID PMC4663003

• Assessment of viability of human fat injection into nude mice with micro-computed tomography. Journal of visualized experiments : JoVE Atashroo, D. A., Paik, K. J., Chung, M. T., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C. R., Walmsley, G. G., Wearda, T., Marecic, O., Longaker, M. T., Wan, D. C. 2015

  View details for DOI 10.3791/52217

  View details for PubMedID 25590561

• A mouse fetal skin model of scarless wound repair. Journal of visualized experiments : JoVE Walmsley, G. G., Hu, M. S., Hong, W. X., Maan, Z. N., Lorenz, H. P., Longaker, M. T. 2015

  View details for DOI 10.3791/52297

  View details for PubMedID 25650841

• Impact of surgical innovation on tissue repair in the surgical patient. British journal of surgery Tevlin, R., Atashroo, D., Duscher, D., Mc Ardle, A., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2015; 102 (2): e41-55

  View details for DOI 10.1002/bjs.9672

  View details for PubMedID 25627135

• A mouse fetal skin model of scarless wound repair. Journal of visualized experiments : JoVE Walmsley, G. G., Hu, M. S., Hong, W. X., Maan, Z. N., Lorenz, H. P., Longaker, M. T. 2015: 52297-?

  Abstract

  Early in utero, but not in postnatal life, cutaneous wounds undergo regeneration and heal without formation of a scar. Scarless fetal wound healing occurs across species but is age dependent. The transition from a scarless to scarring phenotype occurs in the third trimester of pregnancy in humans and around embryonic day 18 (E18) in mice. However, this varies with the size of the wound with larger defects generating a scar at an earlier gestational age. The emergence of lineage tracing and other genetic tools in the mouse has opened promising new avenues for investigation of fetal scarless wound healing. However, given the inherently high rates of morbidity and premature uterine contraction associated with fetal surgery, investigations of fetal scarless wound healing in vivo require a precise and reproducible surgical model. Here we detail a reliable model of fetal scarless wound healing in the dorsum of E16.5 (scarless) and E18.5 (scarring) mouse embryos.

  View details for DOI 10.3791/52297

  View details for PubMedID 25650841

• Isolation and enrichment of human adipose-derived stromal cells for enhanced osteogenesis. Journal of visualized experiments : JoVE Zielins, E. R., Tevlin, R., Hu, M. S., Chung, M. T., McArdle, A., Paik, K. J., Atashroo, D., Duldulao, C. R., Luan, A., Senarath-Yapa, K., Walmsley, G. G., Wearda, T., Longaker, M. T., Wan, D. C. 2015: 52181-?

  Abstract

  Bone marrow-derived mesenchymal stromal cells (BM-MSCs) are considered the gold standard for stem cell-based tissue engineering applications. However, the process by which they must be harvested can be associated with significant donor site morbidity. In contrast, adipose-derived stromal cells (ASCs) are more readily abundant and more easily harvested, making them an appealing alternative to BM-MSCs. Like BM-MSCs, ASCs can differentiate into osteogenic lineage cells and can be used in tissue engineering applications, such as seeding onto scaffolds for use in craniofacial skeletal defects. ASCs are obtained from the stromal vascular fraction (SVF) of digested adipose tissue, which is a heterogeneous mixture of ASCs, vascular endothelial and mural cells, smooth muscle cells, pericytes, fibroblasts, and circulating cells. Flow cytometric analysis has shown that the surface marker profile for ASCs is similar to that for BM-MSCs. Despite several published reports establishing markers for the ASC phenotype, there is still a lack of consensus over profiles identifying osteoprogenitor cells in this heterogeneous population. This protocol describes how to isolate and use a subpopulation of ASCs with enhanced osteogenic capacity to repair critical-sized calvarial defects.

  View details for DOI 10.3791/52181

  View details for PubMedID 25650785

• Assessment of viability of human fat injection into nude mice with micro-computed tomography. Journal of visualized experiments : JoVE Atashroo, D. A., Paik, K. J., Chung, M. T., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C. R., Walmsley, G. G., Wearda, T., Marecic, O., Longaker, M. T., Wan, D. C. 2015

  Abstract

  Lipotransfer is a vital tool in the surgeon's armamentarium for the treatment of soft tissue deficits of throughout the body. Fat is the ideal soft tissue filler as it is readily available, easily obtained, inexpensive, and inherently biocompatible.(1) However, despite its burgeoning popularity, fat grafting is hampered by unpredictable results and variable graft survival, with published retention rates ranging anywhere from 10-80%. (1-3) To facilitate investigations on fat grafting, we have therefore developed an animal model that allows for real-time analysis of injected fat volume retention. Briefly, a small cut is made in the scalp of a CD-1 nude mouse and 200-400 µl of processed lipoaspirate is placed over the skull. The scalp is chosen as the recipient site because of its absence of native subcutaneous fat, and because of the excellent background contrast provided by the calvarium, which aids in the analysis process. Micro-computed tomography (micro-CT) is used to scan the graft at baseline and every two weeks thereafter. The CT images are reconstructed, and an imaging software is used to quantify graft volumes. Traditionally, techniques to assess fat graft volume have necessitated euthanizing the study animal to provide just a single assessment of graft weight and volume by physical measurement ex vivo. Biochemical and histological comparisons have likewise required the study animal to be euthanized. This described imaging technique offers the advantage of visualizing and objectively quantifying volume at multiple time points after initial grafting without having to sacrifice the study animal. The technique is limited by the size of the graft able to be injected as larger grafts risk skin and fat necrosis. This method has utility for all studies evaluating fat graft viability and volume retention. It is particularly well-suited to providing a visual representation of fat grafts and following changes in volume over time.

  View details for DOI 10.3791/52217

  View details for PubMedID 25590561

• Impact of surgical innovation on tissue repair in the surgical patient. British journal of surgery Tevlin, R., Atashroo, D., Duscher, D., Mc Ardle, A., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2015; 102 (2): e41-55

  Abstract

  Throughout history, surgeons have been prolific innovators, which is hardly surprising as most surgeons innovate daily, tailoring their intervention to the intrinsic uniqueness of each operation, each patient and each disease. Innovation can be defined as the application of better solutions that meet new requirements, unarticulated needs or existing market needs. In the past two decades, surgical innovation has significantly improved patient outcomes, complication rates and length of hospital stay. There is one key area that has great potential to change the face of surgical practice and which is still in its infancy: the realm of regenerative medicine and tissue engineering.A literature review was performed using PubMed; peer-reviewed publications were screened for relevance in order to identify key surgical innovations influencing regenerative medicine, with a focus on osseous, cutaneous and soft tissue reconstruction.This review describes recent advances in regenerative medicine, documenting key innovations in osseous, cutaneous and soft tissue regeneration that have brought regenerative medicine to the forefront of the surgical imagination.Surgical innovation in the emerging field of regenerative medicine has the ability to make a major impact on surgery on a daily basis.

  View details for DOI 10.1002/bjs.9672

  View details for PubMedID 25627135

• Wnts produced by Osterix-expressing osteolineage cells regulate their proliferation and differentiation. Proceedings of the National Academy of Sciences of the United States of America Tan, S. H., Senarath-Yapa, K., Chung, M. T., Longaker, M. T., Wu, J. Y., Nusse, R. 2014; 111 (49): E5262-71

  Abstract

  Wnt signaling is a critical regulator of bone development, but the identity and role of the Wnt-producing cells are still unclear. We addressed these questions through in situ hybridization, lineage tracing, and genetic experiments. First, we surveyed the expression of all 19 Wnt genes and Wnt target gene Axin2 in the neonatal mouse bone by in situ hybridization, and demonstrated-to our knowledge for the first time-that Osterix-expressing cells coexpress Wnt and Axin2. To track the behavior and cell fate of Axin2-expressing osteolineage cells, we performed lineage tracing and showed that they sustain bone formation over the long term. Finally, to examine the role of Wnts produced by Osterix-expressing cells, we inhibited Wnt secretion in vivo, and observed inappropriate differentiation, impaired proliferation, and diminished Wnt signaling response. Therefore, Osterix-expressing cells produce their own Wnts that in turn induce Wnt signaling response, thereby regulating their proliferation and differentiation.

  View details for DOI 10.1073/pnas.1420463111

  View details for PubMedID 25422448

• Wnts produced by Osterix-expressing osteolineage cells regulate their proliferation and differentiation PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Tan, S. H., Senarath-Yapa, K., Chung, M. T., Longaker, M. T., Wu, J. Y., Nusse, R. 2014; 111 (49): E5262-E5271

  Abstract

  Wnt signaling is a critical regulator of bone development, but the identity and role of the Wnt-producing cells are still unclear. We addressed these questions through in situ hybridization, lineage tracing, and genetic experiments. First, we surveyed the expression of all 19 Wnt genes and Wnt target gene Axin2 in the neonatal mouse bone by in situ hybridization, and demonstrated-to our knowledge for the first time-that Osterix-expressing cells coexpress Wnt and Axin2. To track the behavior and cell fate of Axin2-expressing osteolineage cells, we performed lineage tracing and showed that they sustain bone formation over the long term. Finally, to examine the role of Wnts produced by Osterix-expressing cells, we inhibited Wnt secretion in vivo, and observed inappropriate differentiation, impaired proliferation, and diminished Wnt signaling response. Therefore, Osterix-expressing cells produce their own Wnts that in turn induce Wnt signaling response, thereby regulating their proliferation and differentiation.

  View details for DOI 10.1073/pnas.1420463111

  View details for Web of Science ID 000345921500004

  View details for PubMedID 25422448

• Biomaterials for Craniofacial Bone Engineering JOURNAL OF DENTAL RESEARCH Tevlin, R., Mcardle, A., Atashroo, D., Walmsley, G. G., Senarath-Yapa, K., Zielins, E. R., Paik, K. J., Longaker, M. T., Wan, D. C. 2014; 93 (12): 1187-1195

  View details for DOI 10.1177/0022034514547271

  View details for Web of Science ID 000345340400002

• Loss of keratinocyte focal adhesion kinase stimulates dermal proteolysis through upregulation of MMP9 in wound healing. Annals of surgery Wong, V. W., Garg, R. K., Sorkin, M., Rustad, K. C., Akaishi, S., Levi, K., Nelson, E. R., Tran, M., Rennert, R., Liu, W., Longaker, M. T., Dauskardt, R. H., Gurtner, G. C. 2014; 260 (6): 1138-1146

  Abstract

  To investigate how epithelial mechanotransduction pathways impact wound repair.Mechanical forces are increasingly recognized to influence tissue repair, but their role in chronic wound pathophysiology remains unknown. Studies have shown that chronic wounds exhibit high levels of matrix metalloproteinase 9 (MMP9), a key proteolytic enzyme that regulates wound remodeling. We hypothesized that epithelial mechanosensory pathways regulated by keratinocyte-specific focal adhesion kinase (FAK) control dermal remodeling via MMP9.A standard wound model was applied to keratinocyte-specific FAK knockout (KO) and control mice. Rates of wound healing were measured and tissue was obtained for histologic and molecular analyses. Transcriptional and immunoblot assays were used to assess the activation of FAK, intracellular kinases, and MMP9 in vitro. A cell suspension model was designed to validate the importance of FAK mechanosensing, p38, and MMP9 secretion in human cells. Biomechanical testing was utilized to evaluate matrix tensile properties in FAK KO and control wounds.Wound healing in FAK KO mice was significantly delayed compared with controls (closure at 15 days compared with 20 days, P = 0.0003). FAK KO wounds demonstrated decreased dermal thickness and collagen density. FAK KO keratinocytes exhibited overactive p38 and MMP9 signaling in vitro, findings recapitulated in human keratinocytes via the deactivation of FAK in the cell suspension model. Functionally, FAK KO wounds were significantly weaker and more brittle than control wounds, results consistent with the histologic and molecular analyses.Keratinocyte FAK is highly responsive to mechanical cues and may play a critical role in matrix remodeling via regulation of p38 and MMP9. These findings suggest that aberrant epithelial mechanosensory pathways may contribute to pathologic dermal proteolysis and wound chronicity.

  View details for DOI 10.1097/SLA.0000000000000219

  View details for PubMedID 25389925

• Loss of Keratinocyte Focal Adhesion Kinase Stimulates Dermal Proteolysis Through Upregulation of MMP9 in Wound Healing ANNALS OF SURGERY Wong, V. W., Garg, R. K., Sorkin, M., Rustad, K. C., Akaishi, S., Levi, K., Nelson, E. R., Tran, M., Rennert, R., Liu, W., Longaker, M. T., Dauskardt, R. H., Gurtner, G. C. 2014; 260 (6): 1138-1146

  Abstract

  To investigate how epithelial mechanotransduction pathways impact wound repair.Mechanical forces are increasingly recognized to influence tissue repair, but their role in chronic wound pathophysiology remains unknown. Studies have shown that chronic wounds exhibit high levels of matrix metalloproteinase 9 (MMP9), a key proteolytic enzyme that regulates wound remodeling. We hypothesized that epithelial mechanosensory pathways regulated by keratinocyte-specific focal adhesion kinase (FAK) control dermal remodeling via MMP9.A standard wound model was applied to keratinocyte-specific FAK knockout (KO) and control mice. Rates of wound healing were measured and tissue was obtained for histologic and molecular analyses. Transcriptional and immunoblot assays were used to assess the activation of FAK, intracellular kinases, and MMP9 in vitro. A cell suspension model was designed to validate the importance of FAK mechanosensing, p38, and MMP9 secretion in human cells. Biomechanical testing was utilized to evaluate matrix tensile properties in FAK KO and control wounds.Wound healing in FAK KO mice was significantly delayed compared with controls (closure at 15 days compared with 20 days, P = 0.0003). FAK KO wounds demonstrated decreased dermal thickness and collagen density. FAK KO keratinocytes exhibited overactive p38 and MMP9 signaling in vitro, findings recapitulated in human keratinocytes via the deactivation of FAK in the cell suspension model. Functionally, FAK KO wounds were significantly weaker and more brittle than control wounds, results consistent with the histologic and molecular analyses.Keratinocyte FAK is highly responsive to mechanical cues and may play a critical role in matrix remodeling via regulation of p38 and MMP9. These findings suggest that aberrant epithelial mechanosensory pathways may contribute to pathologic dermal proteolysis and wound chronicity.

  View details for DOI 10.1097/SLA.0000000000000219

  View details for Web of Science ID 000345217200030

• Positive Selection for Bone Morphogenetic Protein Receptor Type-IB Promotes Differentiation and Specification of Human Adipose-Derived Stromal Cells Toward an Osteogenic Lineage TISSUE ENGINEERING PART A McArdle, A., Chung, M. T., Paik, K. J., Duldulao, C., Chan, C., Rennert, R., Walmsley, G. G., Senarath-Yapa, K., Hu, M., Seo, E., Lee, M., Wan, D. C., Longaker, M. T. 2014; 20 (21-22): 3031-3040

  Abstract

  Adipose tissue represents an abundant and easily accessible source of multipotent cells that may serve as an excellent building block for tissue engineering. However, adipose-derived stromal cells (ASCs) are a heterogeneous group and subpopulations may be identified with enhanced osteogenic potential.Human ASC subpopulations were prospectively isolated based on expression of bone morphogenetic protein receptor type-IB (BMPR-IB). Unsorted, BMPR-IB(+), and BMPR-IB(-) cells were analyzed for their osteogenic capacity through histological staining and gene expression. To evaluate their in vivo osteogenic potential, critical-sized calvarial defects were created in immunocompromised mice and treated with unsorted, BMPR-IB(+), or BMPR-IB(-) cells. Healing was assessed using microcomputed tomography and pentachrome staining of specimens at 8 weeks.Increased osteogenic differentiation was noted in the BMPR-IB(+) subpopulation, as demonstrated by alkaline phosphatase staining at day 7 and extracellular matrix mineralization with Alizarin red staining at day 14. This was also associated with increased expression for osteocalcin, a late marker of osteogenesis. Radiographic analysis demonstrated significantly enhanced healing of critical-sized calvarial defects treated with BMPR-IB(+) ASCs compared with unsorted or BMPR-IB(-) cells. This was confirmed through pentachrome staining, which revealed more robust bone regeneration in the BMPR-IB(+) group.BMPR-IB(+) human ASCs have an enhanced ability to form bone both in vitro and in vivo. These data suggest that positive selection for BMPR-IB(+) and manipulation of the BMP pathway in these cells may yield a highly osteogenic subpopulation of cells for bone tissue engineering.

  View details for DOI 10.1089/ten.tea.2014.0101

  View details for Web of Science ID 000344592600021

  View details for PubMedCentralID PMC4229710

• Positive selection for bone morphogenetic protein receptor type-IB promotes differentiation and specification of human adipose-derived stromal cells toward an osteogenic lineage. Tissue engineering. Part A McArdle, A., Chung, M. T., Paik, K. J., Duldulao, C., Chan, C., Rennert, R., Walmsley, G. G., Senarath-Yapa, K., Hu, M., Seo, E., Lee, M., Wan, D. C., Longaker, M. T. 2014; 20 (21-22): 3031-3040

  Abstract

  Adipose tissue represents an abundant and easily accessible source of multipotent cells that may serve as an excellent building block for tissue engineering. However, adipose-derived stromal cells (ASCs) are a heterogeneous group and subpopulations may be identified with enhanced osteogenic potential.Human ASC subpopulations were prospectively isolated based on expression of bone morphogenetic protein receptor type-IB (BMPR-IB). Unsorted, BMPR-IB(+), and BMPR-IB(-) cells were analyzed for their osteogenic capacity through histological staining and gene expression. To evaluate their in vivo osteogenic potential, critical-sized calvarial defects were created in immunocompromised mice and treated with unsorted, BMPR-IB(+), or BMPR-IB(-) cells. Healing was assessed using microcomputed tomography and pentachrome staining of specimens at 8 weeks.Increased osteogenic differentiation was noted in the BMPR-IB(+) subpopulation, as demonstrated by alkaline phosphatase staining at day 7 and extracellular matrix mineralization with Alizarin red staining at day 14. This was also associated with increased expression for osteocalcin, a late marker of osteogenesis. Radiographic analysis demonstrated significantly enhanced healing of critical-sized calvarial defects treated with BMPR-IB(+) ASCs compared with unsorted or BMPR-IB(-) cells. This was confirmed through pentachrome staining, which revealed more robust bone regeneration in the BMPR-IB(+) group.BMPR-IB(+) human ASCs have an enhanced ability to form bone both in vitro and in vivo. These data suggest that positive selection for BMPR-IB(+) and manipulation of the BMP pathway in these cells may yield a highly osteogenic subpopulation of cells for bone tissue engineering.

  View details for DOI 10.1089/ten.TEA.2014.0101

  View details for PubMedID 24854876

• Reply: tension shielding with the embrace device: does it really improve scars? Plastic and reconstructive surgery Gurtner, G. C., Longaker, M. T. 2014; 134 (4): 664e-6e

  View details for DOI 10.1097/PRS.0000000000000560

  View details for PubMedID 25357068

• Diabetes irreversibly depletes bone marrow-derived mesenchymal progenitor cell subpopulations. Diabetes Januszyk, M., Sorkin, M., Glotzbach, J. P., Vial, I. N., Maan, Z. N., Rennert, R. C., Duscher, D., Thangarajah, H., Longaker, M. T., Butte, A. J., Gurtner, G. C. 2014; 63 (9): 3047-3056

  Abstract

  Diabetic vascular pathology is largely attributable to impairments in tissue recovery from hypoxia. Circulating progenitor cells have been postulated to play a role in ischemic recovery and deficiencies in these cells have been well described in diabetic patients. Here, we examine bone marrow-derived mesenchymal progenitor cells (BM-MPCs) that have previously been shown to be important for new blood vessel formation, and demonstrate significant deficits in the context of diabetes. Further, we determine that this dysfunction is attributable to intrinsic defects in diabetic BM-MPCs that are not correctable by restoring glucose homeostasis. We identify two transcriptionally distinct subpopulations that are selectively depleted by both type 1 and type 2 diabetes, and these subpopulations have pro-vasculogenic expression profiles, suggesting that they are vascular progenitor cells. These results suggest that the clinically observed deficits in progenitor cells may be attributable to selective and irreversible depletion of progenitor cell subsets in patients with diabetes.

  View details for DOI 10.2337/db13-1366

  View details for PubMedID 24740572

• Reduced Regenerative Capacity of Aged Adipose Derived Stem Cells is Caused by Alterations of Cell Subpopulation Dynamics Duscher, D., Rennert, R. C., Januszyk, M., Maan, Z. N., Whittam, A. J., Hu, M. S., Walmsley, G. G., Atashroo, D., Longaker, M. T., Gurtner, G. C. ELSEVIER SCIENCE INC. 2014: S136

  View details for DOI 10.1016/j.jamcollsurg.2014.07.326

  View details for Web of Science ID 000342420900287

• Diminished Recruitment of Resident Skeletal Progenitor Cells in Diabetic Fracture Healing Tevlin, R., Seo, E., McArdle, A., Marecic, O., Wearda, T., Senarath-Yapa, K., Zielins, E. R., Chan, C. K., Weissman, I. L., Longaker, M. T. ELSEVIER SCIENCE INC. 2014: S82

  View details for DOI 10.1016/j.jamcollsurg.2014.07.193

  View details for Web of Science ID 000342420900165

• Heterochronic Parabiosis Rejuvenates Aged Bones McArdle, A., Tevlin, R., Marecic, O., Wearda, T., Senarath-Yapa, K., Walmsley, G. G., Snyder, M. P., Weissman, I. L., Chan, C. K., Longaker, M. T. ELSEVIER SCIENCE INC. 2014: S82–S83

  View details for DOI 10.1016/j.jamcollsurg.2014.07.195

  View details for Web of Science ID 000342420900167

• Response of Skeletal Progenitor Cells to Fracture Injury in a Mouse Model Marecic, O., McArdle, A., Seo, E., Tevlin, R., Duldulao, C., Wearda, T., Chan, C., Weissman, I. L., Longaker, M. T. ELSEVIER SCIENCE INC. 2014: S86

  View details for DOI 10.1016/j.jamcollsurg.2014.07.204

  View details for Web of Science ID 000342420900176

• The Optimal Fat Graft: Evaluating the Biomechanical Effects of Diameter, Length, and Flow Rate during Fat Placement Atashroo, D., Wearda, T., Raphel, J., Paik, K., Zielins, E. R., Walmsley, G. G., Tevlin, R., Wan, D. C., Heilshorn, S., Longaker, M. T. ELSEVIER SCIENCE INC. 2014: S90

  View details for DOI 10.1016/j.jamcollsurg.2014.07.215

  View details for Web of Science ID 000342420900186

• Capillary force seeding of hydrogels for adipose-derived stem cell delivery in wounds. Stem cells translational medicine Garg, R. K., Rennert, R. C., Duscher, D., Sorkin, M., Kosaraju, R., Auerbach, L. J., Lennon, J., Chung, M. T., Paik, K., Nimpf, J., Rajadas, J., Longaker, M. T., Gurtner, G. C. 2014; 3 (9): 1079-1089

  Abstract

  Effective skin regeneration therapies require a successful interface between progenitor cells and biocompatible delivery systems. We previously demonstrated the efficiency of a biomimetic pullulan-collagen hydrogel scaffold for improving bone marrow-derived mesenchymal stem cell survival within ischemic skin wounds by creating a "stem cell niche" that enhances regenerative cytokine secretion. Adipose-derived mesenchymal stem cells (ASCs) represent an even more appealing source of stem cells because of their abundance and accessibility, and in this study we explored the utility of ASCs for hydrogel-based therapies. To optimize hydrogel cell seeding, a rapid, capillary force-based approach was developed and compared with previously established cell seeding methods. ASC viability and functionality following capillary hydrogel seeding were then analyzed in vitro and in vivo. In these experiments, ASCs were seeded more efficiently by capillary force than by traditional methods and remained viable and functional in this niche for up to 14 days. Additionally, hydrogel seeding of ASCs resulted in the enhanced expression of multiple stemness and angiogenesis-related genes, including Oct4, Vegf, Mcp-1, and Sdf-1. Moving in vivo, hydrogel delivery improved ASC survival, and application of both murine and human ASC-seeded hydrogels to splinted murine wounds resulted in accelerated wound closure and increased vascularity when compared with control wounds treated with unseeded hydrogels. In conclusion, capillary seeding of ASCs within a pullulan-collagen hydrogel bioscaffold provides a convenient and simple way to deliver therapeutic cells to wound environments. Moreover, ASC-seeded constructs display a significant potential to accelerate wound healing that can be easily translated to a clinical setting.

  View details for DOI 10.5966/sctm.2014-0007

  View details for PubMedID 25038246

  View details for PubMedCentralID PMC4149299

• Noncontact, low-frequency ultrasound therapy enhances neovascularization and wound healing in diabetic mice. Plastic and reconstructive surgery Maan, Z. N., Januszyk, M., Rennert, R. C., Duscher, D., Rodrigues, M., Fujiwara, T., Ho, N., Whitmore, A., Hu, M. S., Longaker, M. T., Gurtner, G. C. 2014; 134 (3): 402e-11e

  Abstract

  Chronic wounds are a major source of morbidity for patients and represent a significant health burden. Implementing noninvasive techniques that accelerate healing of these wounds would provide great benefit. Ultrasound appears to be an effective modality for the treatment of chronic wounds in humans. MIST Therapy is a noncontact, low-frequency ultrasound treatment delivered through a saline mist. A variety of mechanisms have been proposed to explain the efficacy of ultrasound therapy, but the underlying molecular and cellular pathways impacted by this technique remain unclear. The in vivo effect of noncontact, low-frequency ultrasound was therefore examined in a humanized excisional wound model.The treatment group received noncontact, low-frequency ultrasound therapy three times per week, whereas the control group received a standard dressing change. Wounds were photographed at regular intervals to calculate healing kinetics. Wound tissue was harvested and processed for histology, quantitative polymerase chain reaction, and enzyme-linked immunosorbent assay.The MIST group demonstrated significantly accelerated wound healing, with 17.3 days to wound closure compared with 24 days in the controls (p < 0.05). This improvement became evident by day 9, with healing evidenced by significantly decreased mean wound area relative to original size (68 percent versus 80 percent; p < 0.01). Expression of markers of neovascularization (stromal cell-derived factor 1, vascular endothelial growth factor, and CD31) was also increased in the wound beds of noncontact, low-frequency ultrasound-treated mice compared with controls.Noncontact, low-frequency ultrasound treatment improves neovascularization and wound closure rates in excisional wounds for diabetic mice, likely because of the stimulated release of angiogenic factors.

  View details for DOI 10.1097/PRS.0000000000000467

  View details for PubMedID 25158717

• A Randomized Controlled Trial of the embrace Advanced Scar Therapy Device to Reduce Incisional Scar Formation. Plastic and reconstructive surgery Longaker, M. T., Rohrich, R. J., Greenberg, L., Furnas, H., Wald, R., Bansal, V., Seify, H., Tran, A., Weston, J., Korman, J. M., Chan, R., Kaufman, D., Dev, V. R., Mele, J. A., Januszyk, M., Cowley, C., McLaughlin, P., Beasley, B., Gurtner, G. C. 2014; 134 (3): 536-546

  Abstract

  Scarring represents a significant biomedical burden in clinical medicine. Mechanomodulation has been linked to scarring through inflammation, but until now a systematic approach to attenuate mechanical force and reduce scarring has not been possible.The authors conducted a 12-month, prospective, open-label, randomized, multicenter clinical trial to evaluate abdominoplasty scar appearance following postoperative treatment with the embrace Advanced Scar Therapy device to reduce mechanical forces on healing surgical incisions. Incisions from 65 healthy adult subjects were randomized to receive embrace treatment on one half of an abdominoplasty incision and control treatment (surgeon's optimal care methods) on the other half. The primary endpoint for this study was the difference between assessments of scar appearance for the treated and control sides using the visual analogue scale scar score.Final 12-month study photographs were obtained from 36 subjects who completed at least 5 weeks of dressing application. The mean visual analogue scale score for embrace-treated scars (2.90) was significantly improved compared with control-treated scars (3.29) at 12 months (difference, 0.39; 95 percent confidence interval, 0.14 to 0.66; p = 0.027). Both subjects and investigators found that embrace-treated scars demonstrated significant improvements in overall appearance at 12 months using the Patient and Observer Scar Assessment Scale evaluation (p = 0.02 and p < 0.001, respectively). No serious adverse events were reported.These results demonstrate that the embrace device significantly reduces scarring following abdominoplasty surgery. To the authors' knowledge, this represents the first level I evidence for postoperative scar reduction.Therapeutic, II.

  View details for DOI 10.1097/PRS.0000000000000417

  View details for PubMedID 24804638

• The role of stem cells in aesthetic surgery: fact or fiction? Plastic and reconstructive surgery McArdle, A., Senarath-Yapa, K., Walmsley, G. G., Hu, M., Atashroo, D. A., Tevlin, R., Zielins, E., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2014; 134 (2): 193-200

  Abstract

  Stem cells are attractive candidates for the development of novel therapies, targeting indications that involve functional restoration of defective tissue. Although most stem cell therapies are new and highly experimental, there are clinics around the world that exploit vulnerable patients with the hope of offering supposed stem cell therapies, many of which operate without credible scientific merit, oversight, or other patient protection.We review the potential, as well as drawbacks, for incorporation of stem cells in cosmetic procedures. A review of FDA-approved indications and ongoing clinical trials with adipose stem cells is provided. Furthermore, a "snapshot" analysis of websites using the search terms "stem cell therapy" or "stem cell treatment" or "stem cell facelift" was performed.Despite the protective net cast by regulatory agencies such as the FDA and professional societies such as the American Society of Plastic Surgeons, we are witnessing worrying advertisements for procedures such as stem cell facelifts, stem cell breast augmentations, and even stem cell vaginal rejuvenation. The marketing and promotion of stem cell procedures in aesthetic surgery is not adequately supported by clinical evidence in the majority of cases.Stem cells offer tremendous potential, but the marketplace is saturated with unsubstantiated and sometimes fraudulent claims that may place patients at risk. With plastic surgeons at the forefront of stem cell-based regenerative medicine, it is critically important that we provide an example of a rigorous approach to research, data collection, and advertising of stem cell therapies.

  View details for DOI 10.1097/PRS.0000000000000404

  View details for PubMedID 24732654

• Studies in Fat Grafting: Part III. Fat Grafting Irradiated Tissue-Improved Skin Quality and Decreased Fat Graft Retention. Plastic and reconstructive surgery Garza, R. M., Paik, K. J., Chung, M. T., Duscher, D., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2014; 134 (2): 249-257

  Abstract

  Following radiation therapy, skin becomes fibrotic and can present a difficult problem for reconstructive surgeons. There is an increasing belief that fat grafting under irradiated skin can reverse the damage caused by radiation. The present study evaluated the effect of fat grafting on irradiated skin, along with fat graft quality and retention rates in irradiated tissue.Nine adult Crl:NU-Foxn1 CD-1 mice underwent 30-Gy external beam irradiation of the scalp. Four weeks after irradiation, scalp skin from irradiated and nonirradiated mice was harvested and compared histologically for dermal thickness, collagen content, and vascular density. Human fat grafts were then injected in the subcutaneous plane of the scalp. Skin assessment was performed in the irradiated group at 2 and 8 weeks after grafting, and fat graft retention was measured at baseline and every 2 weeks up to 8 weeks after grafting using micro-computed tomography. Finally, fat graft samples were explanted at 8 weeks, and quality scoring was performed.Fat grafting resulted in decreased dermal thickness, decreased collagen content, and increased vascular density in irradiated skin. Computed tomographic analysis revealed significantly decreased fat graft survival in the irradiated group compared with the nonirradiated group. Histologic scoring of explanted fat grafts demonstrated no difference in quality between the irradiated and nonirradiated groups.Fat grafting attenuates dermal collagen deposition and vessel depletion characteristic of radiation fibrosis. Although fat graft retention rates are significantly lower in irradiated than in nonirradiated tissue, the quality of retained fat between the groups is similar.

  View details for DOI 10.1097/PRS.0000000000000326

  View details for PubMedID 25068325

  View details for PubMedCentralID PMC4116637

• Clonal analysis reveals nerve-dependent and independent roles on mammalian hind limb tissue maintenance and regeneration PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Rinkevich, Y., Montoro, D. T., Muhonen, E., Walmsley, G. G., Lo, D., Hasegawa, M., Januszyk, M., Connolly, A. J., Weissman, I. L., Longaker, M. T. 2014; 111 (27): 9846-9851

  Abstract

  The requirement and influence of the peripheral nervous system on tissue replacement in mammalian appendages remain largely undefined. To explore this question, we have performed genetic lineage tracing and clonal analysis of individual cells of mouse hind limb tissues devoid of nerve supply during regeneration of the digit tip, normal maintenance, and cutaneous wound healing. We show that cellular turnover, replacement, and cellular differentiation from presumed tissue stem/progenitor cells within hind limb tissues remain largely intact independent of nerve and nerve-derived factors. However, regenerated digit tips in the absence of nerves displayed patterning defects in bone and nail matrix. These nerve-dependent phenotypes mimic clinical observations of patients with nerve damage resulting from spinal cord injury and are of significant interest for translational medicine aimed at understanding the effects of nerves on etiologies of human injury.

  View details for DOI 10.1073/pnas.1410097111

  View details for Web of Science ID 000338514800040

  View details for PubMedCentralID PMC4103362

• Clonal analysis reveals nerve-dependent and independent roles on mammalian hind limb tissue maintenance and regeneration. Proceedings of the National Academy of Sciences of the United States of America Rinkevich, Y., Montoro, D. T., Muhonen, E., Walmsley, G. G., Lo, D., Hasegawa, M., Januszyk, M., Connolly, A. J., Weissman, I. L., Longaker, M. T. 2014; 111 (27): 9846-9851

  Abstract

  The requirement and influence of the peripheral nervous system on tissue replacement in mammalian appendages remain largely undefined. To explore this question, we have performed genetic lineage tracing and clonal analysis of individual cells of mouse hind limb tissues devoid of nerve supply during regeneration of the digit tip, normal maintenance, and cutaneous wound healing. We show that cellular turnover, replacement, and cellular differentiation from presumed tissue stem/progenitor cells within hind limb tissues remain largely intact independent of nerve and nerve-derived factors. However, regenerated digit tips in the absence of nerves displayed patterning defects in bone and nail matrix. These nerve-dependent phenotypes mimic clinical observations of patients with nerve damage resulting from spinal cord injury and are of significant interest for translational medicine aimed at understanding the effects of nerves on etiologies of human injury.

  View details for DOI 10.1073/pnas.1410097111

  View details for PubMedID 24958860

• Studies in Fat Grafting: Part II. Effects of Injection Mechanics on Material Properties of Fat PLASTIC AND RECONSTRUCTIVE SURGERY Atashroo, D., Raphel, J., Chung, M. T., Paik, K. J., Parisi-Amon, A., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C., Walmsley, G. G., Hu, M. S., Momeni, A., Domecus, B., Rimsa, J. R., Greenberg, L., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2014; 134 (1): 39-46

  Abstract

  Although fat grafting can address many soft-tissue deficits, results remain inconsistent. In this study, the authors compared physical properties of fat following injection using an automated, low-shear device or the modified Coleman technique.Lipoaspirate was obtained from nine patients and processed for injection using either a modified Coleman technique or an automated, low-shear device. Fat was passed through a 2-mm cannula and compared with minimally processed fat. A rheometer was used to measure the storage modulus and shear rate at which tissues began to lose their solid-like properties. Viscosity was also measured, and gross properties of treatment groups were evaluated qualitatively with a glass slide test.Fat injected through an automated, low-shear device closely matched physical properties of minimally processed fat. The storage modulus (G') of fat for the device group was greater than for the modified Coleman group, and the onset of breakdown was delayed. Similarly, viscosity measurement of fat from the automated device closely matched minimally processed fat and was greater than that of othe modified Coleman group.The physical properties of lipoaspirate processed using an automated, low-shear device with a 2-mm cannula preserved the intactness of fat more than the modified Coleman technique. The authors' rheologic data demonstrate less damage using an automated device compared with the modified Coleman technique and potentially support its use for improved fat graft integrity.

  View details for DOI 10.1097/PRS.0000000000000289

  View details for Web of Science ID 000338116400043

  View details for PubMedCentralID PMC4101917

• Studies in fat grafting: Part I. Effects of injection technique on in vitro fat viability and in vivo volume retention. Plastic and reconstructive surgery Chung, M. T., Paik, K. J., Atashroo, D. A., Hyun, J. S., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C., Hu, M. S., Walmsley, G. G., Parisi-Amon, A., Momeni, A., Rimsa, J. R., Commons, G. W., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2014; 134 (1): 29-38

  Abstract

  Fat grafting has become increasingly popular for the correction of soft tissue deficits at many sites throughout the body. Long-term outcomes, however, depend on delivery of fat in the least traumatic fashion to optimize viability of the transplanted tissue. In this study, we compare the biologic properties of fat following injection using two methods.Lipoaspiration samples were obtained from five female donors and cellular viability, proliferation, and lipolysis were evaluated following injection using either a modified Coleman technique or an automated, low shear device. Comparisons were made to minimally processed, uninjected fat. Volume retention was also measured over twelve weeks following injection of fat under the scalp of immunodeficient mice using either the modified Coleman technique or the Adipose Tissue Injector. Finally, fat grafts were analyzed histologically.Fat viability and cellular proliferation were both significantly greater with the Adipose Tissue Injector relative to injection with the modified Coleman technique. In contrast, significantly less lipolysis was noted using the automated device. In vivo fat volume retention was significantly greater than with the modified Coleman technique at 4, 6, 8, and 12 week time points. This corresponded with significantly greater histological scores for healthy fat and lower scores for injury following injection with the device.Biological properties of injected tissues reflect how disruptive and harmful techniques for placement of fat may be, and our in vitro and in vivo data both support the use of the automated, low shear devices compared to the modified Coleman technique.

  View details for DOI 10.1097/PRS.0000000000000290

  View details for PubMedID 24622574

• Studies in fat grafting: Part II. Effects of injection mechanics on material properties of fat. Plastic and reconstructive surgery Atashroo, D., Raphel, J., Chung, M. T., Paik, K. J., Parisi-Amon, A., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C., Walmsley, G. G., Hu, M. S., Momeni, A., Domecus, B., Rimsa, J. R., Greenberg, L., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2014; 134 (1): 39-46

  Abstract

  Although fat grafting can address many soft-tissue deficits, results remain inconsistent. In this study, the authors compared physical properties of fat following injection using an automated, low-shear device or the modified Coleman technique.Lipoaspirate was obtained from nine patients and processed for injection using either a modified Coleman technique or an automated, low-shear device. Fat was passed through a 2-mm cannula and compared with minimally processed fat. A rheometer was used to measure the storage modulus and shear rate at which tissues began to lose their solid-like properties. Viscosity was also measured, and gross properties of treatment groups were evaluated qualitatively with a glass slide test.Fat injected through an automated, low-shear device closely matched physical properties of minimally processed fat. The storage modulus (G') of fat for the device group was greater than for the modified Coleman group, and the onset of breakdown was delayed. Similarly, viscosity measurement of fat from the automated device closely matched minimally processed fat and was greater than that of othe modified Coleman group.The physical properties of lipoaspirate processed using an automated, low-shear device with a 2-mm cannula preserved the intactness of fat more than the modified Coleman technique. The authors' rheologic data demonstrate less damage using an automated device compared with the modified Coleman technique and potentially support its use for improved fat graft integrity.

  View details for DOI 10.1097/PRS.0000000000000289

  View details for PubMedID 25028817

• Tissue engineering and regenerative repair in wound healing. Annals of biomedical engineering Hu, M. S., Maan, Z. N., Wu, J., Rennert, R. C., Hong, W. X., Lai, T. S., Cheung, A. T., Walmsley, G. G., Chung, M. T., McArdle, A., Longaker, M. T., Lorenz, H. P. 2014; 42 (7): 1494-1507

  Abstract

  Wound healing is a highly evolved defense mechanism against infection and further injury. It is a complex process involving multiple cell types and biological pathways. Mammalian adult cutaneous wound healing is mediated by a fibroproliferative response leading to scar formation. In contrast, early to mid-gestational fetal cutaneous wound healing is more akin to regeneration and occurs without scar formation. This early observation has led to extensive research seeking to unlock the mechanism underlying fetal scarless regenerative repair. Building upon recent advances in biomaterials and stem cell applications, tissue engineering approaches are working towards a recapitulation of this phenomenon. In this review, we describe the elements that distinguish fetal scarless and adult scarring wound healing, and discuss current trends in tissue engineering aimed at achieving scarless tissue regeneration.

  View details for DOI 10.1007/s10439-014-1010-z

  View details for PubMedID 24788648

• Gene expression in fetal murine keratinocytes and fibroblasts JOURNAL OF SURGICAL RESEARCH Hu, M. S., Januszyk, M., Hong, W. X., Walmsley, G. G., Zielins, E. R., Atashroo, D. A., Maan, Z. N., McArdle, A., Takanishi, D. M., Gurtner, G. C., Longaker, M. T., Lorenz, H. P. 2014; 190 (1): 344-357

  Abstract

  Early fetuses heal wounds without the formation of a scar. Many studies have attempted to explain this remarkable phenomenon. However, the exact mechanism remains unknown. Herein, we examine the predominant cell types of the epidermis and dermis-the keratinocyte and fibroblast-during different stages of fetal development to better understand the changes that lead to scarring wound repair versus regeneration.Keratinocytes and fibroblasts were harvested and cultured from the dorsal skin of time-dated BALB/c fetuses. Total RNA was isolated and microarray analysis was performed using chips with 42,000 genes. Significance analysis of microarrays was used to select genes with >2-fold expression differences with a false discovery rate <2. Enrichment analysis was performed on significant genes to identify differentially expressed pathways.By comparing the gene expression profile of keratinocytes from E16 versus E18 fetuses, we identified 24 genes that were downregulated at E16. Analysis of E16 and E18 fibroblasts revealed 522 differentially expressed genes. Enrichment analysis showed the top 20 signaling pathways that were downregulated in E16 keratinocytes and upregulated or downregulated in E16 fibroblasts.Our data reveal 546 differentially expressed genes in keratinocytes and fibroblasts between the scarless and scarring transition. In addition, a total of 60 signaling pathways have been identified to be either upregulated or downregulated in these cell types. The genes and pathways recognized by our study may prove to be essential targets that may discriminate between fetal wound regeneration and adult wound repair.

  View details for DOI 10.1016/j.jss.2014.02.030

  View details for Web of Science ID 000338444700051

• Studies in Fat Grafting: Part I. Effects of Injection Technique on In Vitro Fat Viability and In Vivo Volume Retention PLASTIC AND RECONSTRUCTIVE SURGERY Chung, M. T., Paik, K. J., Atashroo, D. A., Hyun, J. S., McArdle, A., Senarath-Yapa, K., Zielins, E. R., Tevlin, R., Duldulao, C., Hu, M. S., Walmsley, G. G., Parisi-Amon, A., Momeni, A., Rimsa, J. R., Commons, G. W., Gurtner, G. C., Wan, D. C., Longaker, M. T. 2014; 134 (1): 29-38

  Abstract

  Fat grafting has become increasingly popular for the correction of soft tissue deficits at many sites throughout the body. Long-term outcomes, however, depend on delivery of fat in the least traumatic fashion to optimize viability of the transplanted tissue. In this study, we compare the biologic properties of fat following injection using two methods.Lipoaspiration samples were obtained from five female donors and cellular viability, proliferation, and lipolysis were evaluated following injection using either a modified Coleman technique or an automated, low shear device. Comparisons were made to minimally processed, uninjected fat. Volume retention was also measured over twelve weeks following injection of fat under the scalp of immunodeficient mice using either the modified Coleman technique or the Adipose Tissue Injector. Finally, fat grafts were analyzed histologically.Fat viability and cellular proliferation were both significantly greater with the Adipose Tissue Injector relative to injection with the modified Coleman technique. In contrast, significantly less lipolysis was noted using the automated device. In vivo fat volume retention was significantly greater than with the modified Coleman technique at 4, 6, 8, and 12 week time points. This corresponded with significantly greater histological scores for healthy fat and lower scores for injury following injection with the device.Biological properties of injected tissues reflect how disruptive and harmful techniques for placement of fat may be, and our in vitro and in vivo data both support the use of the automated, low shear devices compared to the modified Coleman technique.

  View details for DOI 10.1097/PRS.0000000000000290

  View details for Web of Science ID 000338116400042

• Mechanotransduction and fibrosis JOURNAL OF BIOMECHANICS Duscher, D., Maan, Z. N., Wong, V. W., Rennert, R. C., Januszyk, M., Rodrigues, M., Hu, M., Whitmore, A. J., Whittam, A. J., Longaker, M. T., Gurtner, G. C. 2014; 47 (9): 1997-2005

  Abstract

  Scarring and tissue fibrosis represent a significant source of morbidity in the United States. Despite considerable research focused on elucidating the mechanisms underlying cutaneous scar formation, effective clinical therapies are still in the early stages of development. A thorough understanding of the various signaling pathways involved is essential to formulate strategies to combat fibrosis and scarring. While initial efforts focused primarily on the biochemical mechanisms involved in scar formation, more recent research has revealed a central role for mechanical forces in modulating these pathways. Mechanotransduction, which refers to the mechanisms by which mechanical forces are converted to biochemical stimuli, has been closely linked to inflammation and fibrosis and is believed to play a critical role in scarring. This review provides an overview of our current understanding of the mechanisms underlying scar formation, with an emphasis on the relationship between mechanotransduction pathways and their therapeutic implications.

  View details for DOI 10.1016/j.jbiomech.2014.03.031

  View details for Web of Science ID 000338621900009

• Fat or fiction: origins matter. Cell metabolism Wan, D. C., Longaker, M. T. 2014; 19 (6): 900-901

  Abstract

  Cell-lineage tracing has revealed a complex heterogeneity present in postnatal tissue and adult progenitors. Chau et al. (2014) and Long et al. (2014) provide further evidence for this among adipocytes, and their findings underscore the importance of cellular ontogeny not just for development but also for potential treatment of disease.

  View details for DOI 10.1016/j.cmet.2014.05.007

  View details for PubMedID 24896537

• Adipose-Derived Stem Cells: A Review of Signaling Networks Governing Cell Fate and Regenerative Potential in the Context of Craniofacial and Long Bone Skeletal Repair INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Senarath-Yapa, K., McArdle, A., Renda, A., Longaker, M. T., Quarto, N. 2014; 15 (6): 9314-9330

  Abstract

  Improvements in medical care, nutrition and social care are resulting in a commendable change in world population demographics with an ever increasing skew towards an aging population. As the proportion of the world's population that is considered elderly increases, so does the incidence of osteodegenerative disease and the resultant burden on healthcare. The increasing demand coupled with the limitations of contemporary approaches, have provided the impetus to develop novel tissue regeneration therapies. The use of stem cells, with their potential for self-renewal and differentiation, is one potential solution. Adipose-derived stem cells (ASCs), which are relatively easy to harvest and readily available have emerged as an ideal candidate. In this review, we explore the potential for ASCs to provide tangible therapies for craniofacial and long bone skeletal defects, outline key signaling pathways that direct these cells and describe how the developmental signaling program may provide clues on how to guide these cells in vivo. This review also provides an overview of the importance of establishing an osteogenic microniche using appropriately customized scaffolds and delineates some of the key challenges that still need to be overcome for adult stem cell skeletal regenerative therapy to become a clinical reality.

  View details for DOI 10.3390/ijms15069314

  View details for Web of Science ID 000338639000009

• Moisturizing different racial skin types. The Journal of clinical and aesthetic dermatology Wan, D. C., Wong, V. W., Longaker, M. T., Yang, G. P., Wei, F. 2014; 7 (6): 25-32

  Abstract

  The skin is a complex organ involved in thermoregulation, gas exchange, protection against pathogens, and barrier function to maintain proper hydration. When dry, the ability for skin to execute these tasks becomes impaired. Dry skin affects almost everyone as we age, but it is also dependent on external factors, such as dry climate, colder temperatures, and repeated washing. In addition, increasing evidence has shown racial variability in the physiological properties of skin, which directly impacts water content of the stratum corneum and sensitivity to exogenously applied agents. A multitude of products have been developed to treat dry skin, and as a group, moisturizers have been designed to either impart or restore hydration in the stratum corneum. Given the large number of moisturizers presently available, depending on individual components, several different mechanisms may be employed to promote skin hydration. As there exists dramatic racial variability in skin properties, certain moisturizers may thus be more effective in some and less effective in others to treat the common condition of dry skin.

  View details for PubMedID 25013536

• Adipose-derived stem cells: a review of signaling networks governing cell fate and regenerative potential in the context of craniofacial and long bone skeletal repair. International journal of molecular sciences Senarath-Yapa, K., McArdle, A., Renda, A., Longaker, M. T., Quarto, N. 2014; 15 (6): 9314-30

  Abstract

  Improvements in medical care, nutrition and social care are resulting in a commendable change in world population demographics with an ever increasing skew towards an aging population. As the proportion of the world's population that is considered elderly increases, so does the incidence of osteodegenerative disease and the resultant burden on healthcare. The increasing demand coupled with the limitations of contemporary approaches, have provided the impetus to develop novel tissue regeneration therapies. The use of stem cells, with their potential for self-renewal and differentiation, is one potential solution. Adipose-derived stem cells (ASCs), which are relatively easy to harvest and readily available have emerged as an ideal candidate. In this review, we explore the potential for ASCs to provide tangible therapies for craniofacial and long bone skeletal defects, outline key signaling pathways that direct these cells and describe how the developmental signaling program may provide clues on how to guide these cells in vivo. This review also provides an overview of the importance of establishing an osteogenic microniche using appropriately customized scaffolds and delineates some of the key challenges that still need to be overcome for adult stem cell skeletal regenerative therapy to become a clinical reality.

  View details for DOI 10.3390/ijms15069314

  View details for PubMedID 24865492

• In Vivo clonal analysis reveals lineage-restricted progenitor characteristics in Mammalian kidney development, maintenance, and regeneration. Cell reports Rinkevich, Y., Montoro, D. T., Contreras-Trujillo, H., Harari-Steinberg, O., Newman, A. M., Tsai, J. M., Lim, X., Van-Amerongen, R., Bowman, A., Januszyk, M., Pleniceanu, O., Nusse, R., Longaker, M. T., Weissman, I. L., Dekel, B. 2014; 7 (4): 1270-1283

  Abstract

  The mechanism and magnitude by which the mammalian kidney generates and maintains its proximal tubules, distal tubules, and collecting ducts remain controversial. Here, we use long-term in vivo genetic lineage tracing and clonal analysis of individual cells from kidneys undergoing development, maintenance, and regeneration. We show that the adult mammalian kidney undergoes continuous tubulogenesis via expansions of fate-restricted clones. Kidneys recovering from damage undergo tubulogenesis through expansions of clones with segment-specific borders, and renal spheres developing in vitro from individual cells maintain distinct, segment-specific fates. Analysis of mice derived by transfer of color-marked embryonic stem cells (ESCs) into uncolored blastocysts demonstrates that nephrons are polyclonal, developing from expansions of singly fated clones. Finally, we show that adult renal clones are derived from Wnt-responsive precursors, and their tracing in vivo generates tubules that are segment specific. Collectively, these analyses demonstrate that fate-restricted precursors functioning as unipotent progenitors continuously maintain and self-preserve the mouse kidney throughout life.

  View details for DOI 10.1016/j.celrep.2014.04.018

  View details for PubMedID 24835991

  View details for PubMedCentralID PMC4425291

• Tracking the elusive fibrocyte: identification and characterization of collagen-producing hematopoietic lineage cells during murine wound healing. Stem cells Suga, H., Rennert, R. C., Rodrigues, M., Sorkin, M., Glotzbach, J. P., Januszyk, M., Fujiwara, T., Longaker, M. T., Gurtner, G. C. 2014; 32 (5): 1347-1360

  Abstract

  Fibrocytes are a unique population of circulating cells reported to exhibit characteristics of both hematopoietic and mesenchymal cells, and play an important role in wound healing. However, putative fibrocytes have been found to lose expression of hematopoietic surface markers such as CD45 during differentiation, making it difficult to track these cells in vivo with conventional methodologies. In this study, to distinguish hematopoietic and nonhematopoietic cells without surface markers, we took advantage of the gene vav 1, which is expressed solely on hematopoietic cells but not on other cell types, and established a novel transgenic mouse, in which hematopoietic cells are irreversibly labeled with green fluorescent protein and nonhematopoietic cells with red fluorescent protein. Use of single-cell transcriptional analysis in this mouse model revealed two discrete types of collagen I (Col I) expressing cells of hematopoietic lineage recruited into excisional skin wounds. We confirmed this finding on a protein level, with one subset of these Col I synthesizing cells being CD45+ and CD11b+, consistent with the traditional definition of a fibrocyte, while another was CD45- and Cd11b-, representing a previously unidentified population. Both cell types were found to initially peak, then reduce posthealing, consistent with a disappearance from the wound site and not a loss of identifying surface marker expression. Taken together, we have unambiguously identified two cells of hematopoietic origin that are recruited to the wound site and deposit collagen, definitively confirming the existence and natural time course of fibrocytes in cutaneous healing. Stem Cells 2014;32:1347-1360.

  View details for DOI 10.1002/stem.1648

  View details for PubMedID 24446236

• The Role of Hypoxia-Inducible Factor in Wound Healing ADVANCES IN WOUND CARE Hong, W., Hu, M. S., Esquivel, M., Liang, G. Y., Rennert, R. C., McArdle, A., Paik, K. J., Duscher, D., Gurtner, G. C., Lorenz, H., Longaker, M. T. 2014; 3 (5): 390–99

  View details for DOI 10.1089/wound.2013.0520

  View details for Web of Science ID 000214959300004

• The Role of Hypoxia-Inducible Factor in Wound Healing. Advances in wound care Hong, W. X., Hu, M. S., Esquivel, M., Liang, G. Y., Rennert, R. C., McArdle, A., Paik, K. J., Duscher, D., Gurtner, G. C., Lorenz, H. P., Longaker, M. T. 2014; 3 (5): 390-399

  Abstract

  Significance: Poor wound healing remains a significant health issue for a large number of patients in the United States. The physiologic response to local wound hypoxia plays a critical role in determining the success of the normal healing process. Hypoxia-inducible factor-1 (HIF-1), as the master regulator of oxygen homeostasis, is an important determinant of healing outcomes. HIF-1 contributes to all stages of wound healing through its role in cell migration, cell survival under hypoxic conditions, cell division, growth factor release, and matrix synthesis throughout the healing process. Recent Advances: Positive regulators of HIF-1, such as prolyl-4-hydroxylase inhibitors, have been shown to be beneficial in enhancing diabetic ischemic wound closure and are currently undergoing clinical trials for treatment of several human-ischemia-based conditions. Critical Issues: HIF-1 deficiency and subsequent failure to respond to hypoxic stimuli leads to chronic hypoxia, which has been shown to contribute to the formation of nonhealing ulcers. In contrast, overexpression of HIF-1 has been implicated in fibrotic disease through its role in increasing myofibroblast differentiation leading to excessive matrix production and deposition. Both positive and negative regulators of HIF-1 therefore provide important therapeutic targets that can be used to manipulate HIF-1 expression where an excess or deficiency in HIF-1 is known to correlate with pathogenesis. Future Directions: Targeting HIF-1 during wound healing has many important clinical implications for tissue repair. Counteracting the detrimental effects of excessive or deficient HIF-1 signaling by modulating HIF-1 expression may improve future management of poorly healing wounds.

  View details for PubMedID 24804159

• Fat Transfer in 2014: What We Do Not Know PLASTIC AND RECONSTRUCTIVE SURGERY Longaker, M. T., Aston, S. J., Baker, D. C., Rohrich, R. J. 2014; 133 (5): 1305–7

  View details for PubMedID 24776560

• Mechanical offloading of incisional wounds is associated with transcriptional downregulation of inflammatory pathways in a large animal model ORGANOGENESIS Januszyk, M., Wong, V. W., Bhatt, K. A., Vial, I. N., Paterno, J., Longaker, M. T., Gurtner, G. C. 2014; 10 (2): 186-193

  Abstract

  Cutaneous scarring is a major source of morbidity and current therapies to mitigate scar formation remain ineffective. Although wound fibrosis and inflammation are highly linked, only recently have mechanical forces been implicated in these pathways. Our group has developed a topical polymer device that significantly reduces post-injury scar formation via the manipulation of mechanical forces. Here we extend these studies to examine the genomewide transcriptional effects of mechanomodulation during scar formation using a validated large animal model, the red Duroc pig. We demonstrate that mechanical loading of incisional wounds upregulates expression of genes associated with inflammatory and fibrotic pathways, and that device-mediated offloading of these wounds reverses these effects. Validation studies are needed to clarify the clinical significance of these findings.

  View details for DOI 10.4161/org.28818

  View details for Web of Science ID 000341807300005

  View details for PubMedID 24739276

  View details for PubMedCentralID PMC4154952

• LOW DOSE RADIATION FROM CARDIAC COMPUTED TOMOGRAPHY IS ASSOCIATED WITH DNA DAMAGE AND CELLULAR DEATH Hong, W., Lee, W., Liang, G., Chan, C., Sanchez-Freire, V., Hu, S., Longaker, M. T., Wu, J., Nguyen, P. ELSEVIER SCIENCE INC. 2014: A1047

  View details for DOI 10.1016/S0735-1097(14)61047-0

  View details for Web of Science ID 000359579101705

• The Role of Stem Cells During Scarless Skin Wound Healing. Advances in wound care Hu, M. S., Rennert, R. C., McArdle, A., Chung, M. T., Walmsley, G. G., Longaker, M. T., Lorenz, H. P. 2014; 3 (4): 304-314

  Abstract

  Significance: In early gestation, fetal skin wounds undergo regeneration and healing without a scar. This phenomenon is intrinsic to early fetal skin but disappears during late gestation. Adult wounds undergo repair via a fibroproliferative response that leads to incomplete regeneration of the original tissue and a resultant scar. This outcome can have devastating effects for patients and is a significant financial burden to the healthcare system. Recent Advances: Studies have demonstrated the possible role of several stem cells in wound healing. In particular, epidermal stem cells and mesenchymal stem cells have been implicated in wound repair and regeneration. Recently, stem cells with adult epidermal stem cell markers have been found in fetal skin dermis. These cells are thought to play a role in scarless fetal wound healing. Critical Issues: Despite numerous studies on scarless fetal wound healing, the exact mechanism is still largely unknown. Although inflammation is greatly reduced, the stem cell profile of regenerating fetal skin wounds remains unknown. Without a detailed understanding of stem cell differences between fetal and adult wounds, the ability to prevent or treat both normal and pathologic excessive scarring, in the form of keloids and hypertrophic scars, is limited. Future Directions: Further studies on differences between fetal and adult skin-specific stem cells may elucidate the mechanism of scarless wound healing in the early fetus. With this knowledge, the potential to reduce scarring in adult wounds may be achieved.

  View details for PubMedID 24761362

• The Role of Stem Cells During Scarless Skin Wound Healing ADVANCES IN WOUND CARE Hu, M., Rennert, R. C., McArdle, A., Chung, M. T., Walmsley, G. G., Longaker, M. T., Lorenz, H. 2014; 3 (4): 304–14

  View details for DOI 10.1089/wound.2013.0471

  View details for Web of Science ID 000214959200002

• Mechanotransduction and fibrosis. Journal of biomechanics Duscher, D., Maan, Z. N., Wong, V. W., Rennert, R. C., Januszyk, M., Rodrigues, M., Hu, M., Whitmore, A. J., Whittam, A. J., Longaker, M. T., Gurtner, G. C. 2014

  Abstract

  Scarring and tissue fibrosis represent a significant source of morbidity in the United States. Despite considerable research focused on elucidating the mechanisms underlying cutaneous scar formation, effective clinical therapies are still in the early stages of development. A thorough understanding of the various signaling pathways involved is essential to formulate strategies to combat fibrosis and scarring. While initial efforts focused primarily on the biochemical mechanisms involved in scar formation, more recent research has revealed a central role for mechanical forces in modulating these pathways. Mechanotransduction, which refers to the mechanisms by which mechanical forces are converted to biochemical stimuli, has been closely linked to inflammation and fibrosis and is believed to play a critical role in scarring. This review provides an overview of our current understanding of the mechanisms underlying scar formation, with an emphasis on the relationship between mechanotransduction pathways and their therapeutic implications.

  View details for DOI 10.1016/j.jbiomech.2014.03.031

  View details for PubMedID 24709567

• Induced pluripotent stem cells in regenerative medicine and disease modeling. Current stem cell research & therapy Walmsley, G. G., Hyun, J., McArdle, A., Senarath-Yapa, K., Hu, M. S., Chung, M. T., Wong, V. W., Longaker, M. T., Wan, D. C. 2014; 9 (2): 73-81

  Abstract

  In 2006, Dr. Yamanaka created the induced pluripotent stem cell (iPSC) by reprogramming adult fibroblasts back to an immature, pluripotent state. Effectively bypassing the ethical constraints of human embryonic stem cells, iPSCs have expanded the horizons of regenerative medicine by offering a means to derive autologous patient-matched cells and tissues for clinical transplantation. However, persisting safety concerns must be addressed prior to their widespread clinical application. In this review, we discuss the history of iPSCs, derivation strategies, and current research involving gene therapy and disease modeling. We review the potential of iPSCs for improving a range of cell-based therapies and obstacles to their clinical implementation.

  View details for PubMedID 24359141

• Abstract 8: SDF-1 Regulates Adipose Niche Homeostasis and Adipose Derived Stromal Cell Function. Plastic and reconstructive surgery Maan, Z. N., Rennert, R. C., Duscher, D., Januszyk, M., Paik, K., Chung, M. T., Paik, K., Fujiwara, T., Rodrigues, M., Ho, N., Baker, H., Perez, M., Hu, M., Sorkin, M., Longaker, M. T., Gurtner, G. C. 2014; 133 (3): 15-16

  View details for DOI 10.1097/01.prs.0000444941.23852.ce

  View details for PubMedID 25942119

• Abstract 10: Global and Endothelial Cell Specific Deletion of SDF-1 Results in Delayed Wound Healing. Plastic and reconstructive surgery Maan, Z. N., Ho, N., Rennert, R. C., Duscher, D., Sorkin, M., Rodrigues, M., Chen, J., Vial, I. N., Januszyk, M., Findlay, M., Hu, M., Walmsley, G., Longaker, M. T., Gurtner, G. C. 2014; 133 (3): 20-?

  View details for DOI 10.1097/01.prs.0000444963.66915.ba

  View details for PubMedID 25942121

• Abstract 135: improved engraftment of autologous skin grafts in diabetic mice with adipose-derived stem cells. Plastic and reconstructive surgery Hu, M., Hong, W. X., Senarath-Yapa, K., Zimmermann, A., Chung, M., Esquivel, M., McArdle, A., Walmsley, G., Maan, Z., Garza, R., Lorenz, H. P., Longaker, M. 2014; 133 (3): 151-?

  View details for DOI 10.1097/01.prs.0000444962.89785.8e

  View details for PubMedID 25942246

• Abstract 33: Stress Offloading through Mechanomodulation is Associated with Down-Regulation of Inflammatory Pathways in a Large Animal Model. Plastic and reconstructive surgery Januszyk, M., Wong, V. W., Bhatt, K., Vial, I. N., Dauskardt, R., Longaker, M. T., Gurtner, G. C. 2014; 133 (3): 44-?

  View details for DOI 10.1097/01.prs.0000445066.09978.3b

  View details for PubMedID 25942144

• Abstract 161: identification of cell-intrinsic mechanisms and differentially regulated genetic pathways responsible for the age-related functional decline in aged skeletal stem cells. Plastic and reconstructive surgery McArdle, A., Chan, C., Seita, J., Senarath-Yapa, K., Hu, M., Walmsley, G. G., Zielins, E., Atashroo, D., Tevlin, R., Weissman, I., Longaker, M. T. 2014; 133 (3): 178-?

  View details for DOI 10.1097/01.prs.0000444990.75431.f1

  View details for PubMedID 25942271

• Abstract 140: identification, characterization, and prospective isolation of a fibroblast lineage contributing to dermal development, cutaneous scarring, radiation fibrosis, and cancer stroma. Plastic and reconstructive surgery Walmsley, G. G., Rinkevich, Y., Hu, M. S., McArdle, A., Maan, Z. N., Lorenz, H. P., Weissman, I. L., Longaker, M. T. 2014; 133 (3): 157-?

  View details for DOI 10.1097/01.prs.0000444968.20280.4d

  View details for PubMedID 25942251

• Abstract 165: Enhanced Adipose-Derived Stromal Cell Osteogenesis through Surface Marker Enrichment and BMP Modulation using Magnet-assisted Transfection. Plastic and reconstructive surgery Chung, M. T., Morrison, S. D., Paik, K. J., McArdle, A., Walmsley, G., Senarath-Yapa, K., Hu, M. S., Tevlin, R., Zielins, E., Atashroo, D., Hong, W. X., Duldulao, C., Wearda, T., Garza, R. M., Momeni, A., Longaker, M. T., Wan, D. C. 2014; 133 (3): 181-182

  View details for DOI 10.1097/01.prs.0000444994.28797.34

  View details for PubMedID 25942275

• Abstract 54: TGF Beta and BMP Signaling Pathways Influence Regenerative Capacity of Calvarial Bones via Cross-Talk and Modulation of Apoptosis: The Potential Therapeutic Role of Small Molecule Inhibitors of TGF Beta Signaling. Plastic and reconstructive surgery Senarath-Yapa, K., Meyer, N., Li, S., Longaker, M. T., Quarto, N. 2014; 133 (3): 65-66

  View details for DOI 10.1097/01.prs.0000445087.68975.92

  View details for PubMedID 25942165

• Abstract 151: short hairpin RNA interference therapy for diabetic murine wound closure and hindlimb ischemia. Plastic and reconstructive surgery Paik, K. J., Rennert, R., Chung, M. T., Sorkin, M., Duscher, D., Atashroo, D., Chen, H., Morrison, S. D., Zimmermann, A., Nauta, A., Ko, S., Tevlin, R., Zielins, E., Hu, M. S., McArdle, A., Walmsley, G., Senarath-Yapa, K., Hong, W. X., Garza, R. M., Duldulao, C., Wearda, T., Momeni, A., Wu, J. C., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2014; 133 (3): 167-168

  View details for DOI 10.1097/01.prs.0000444979.14443.08

  View details for PubMedID 25942261

• Abstract 158: Identification of BMP-Responsive Long Noncoding RNAs in Pluripotent Cells. Plastic and reconstructive surgery Paik, K. J., Qu, K., Hsueh, B., Torre, E. A., Flynn, R. A., Chung, M. T., Spencley, A., Wang, K. C., Wu, J. C., Longaker, M. T., Chang, H. Y., Wan, D. C. 2014; 133 (3): 174-?

  View details for DOI 10.1097/01.prs.0000444987.90678.b2

  View details for PubMedID 25942268

• Gene expression in fetal murine keratinocytes and fibroblasts. The Journal of surgical research Hu, M. S., Januszyk, M., Hong, W. X., Walmsley, G. G., Zielins, E. R., Atashroo, D. A., Maan, Z. N., McArdle, A., Takanishi, D. M., Gurtner, G. C., Longaker, M. T., Lorenz, H. P. 2014

  Abstract

  Early fetuses heal wounds without the formation of a scar. Many studies have attempted to explain this remarkable phenomenon. However, the exact mechanism remains unknown. Herein, we examine the predominant cell types of the epidermis and dermis-the keratinocyte and fibroblast-during different stages of fetal development to better understand the changes that lead to scarring wound repair versus regeneration.Keratinocytes and fibroblasts were harvested and cultured from the dorsal skin of time-dated BALB/c fetuses. Total RNA was isolated and microarray analysis was performed using chips with 42,000 genes. Significance analysis of microarrays was used to select genes with >2-fold expression differences with a false discovery rate <2. Enrichment analysis was performed on significant genes to identify differentially expressed pathways.By comparing the gene expression profile of keratinocytes from E16 versus E18 fetuses, we identified 24 genes that were downregulated at E16. Analysis of E16 and E18 fibroblasts revealed 522 differentially expressed genes. Enrichment analysis showed the top 20 signaling pathways that were downregulated in E16 keratinocytes and upregulated or downregulated in E16 fibroblasts.Our data reveal 546 differentially expressed genes in keratinocytes and fibroblasts between the scarless and scarring transition. In addition, a total of 60 signaling pathways have been identified to be either upregulated or downregulated in these cell types. The genes and pathways recognized by our study may prove to be essential targets that may discriminate between fetal wound regeneration and adult wound repair.

  View details for DOI 10.1016/j.jss.2014.02.030

  View details for PubMedID 24726057

• Paracrine Mechanism of Angiogenesis in Adipose-Derived Stem Cell Transplantation ANNALS OF PLASTIC SURGERY Suga, H., Glotzbach, J. P., Sorkin, M., Longaker, M. T., Gurtner, G. C. 2014; 72 (2): 234-241

  Abstract

  INTRODUCTION: Adipose-derived stem cells (ASCs) have shown potential for cell-based therapy in the field of plastic surgery. However, the fate of ASCs after transplantation and the mechanism(s) of their biologic capabilities remain unclear. METHODS: We isolated and cultured ASCs from transgenic mice that express both luciferase and green fluorescent protein and injected the cells into the inguinal fat pads of wild-type mice. We tested 4 experimental groups, namely, ischemic fat pads with/without ASCs and control fat pads with/without ASCs. RESULTS: Transplanted ASCs were tracked with bioluminescence imaging. The luminescence gradually decreased over 28 days, indicating cell death after transplantation. More ASCs were retained in ischemic fat pads on day 7 compared to control fat pads. On day 14, adipose tissue vascular density was higher in the ASC transplantation groups compared to those without ASCs. On day 28, there was decreased atrophy of adipose tissue in ASC-treated ischemic fat pads. Transplanted ASCs were detected as nonproliferating green fluorescent protein-positive cells, whereas native endothelial cells adjacent to the transplanted ASCs were proliferative. Protein analysis demonstrated higher expression of hepatocyte growth factor and vascular endothelial growth factor in the ASC transplantation groups, suggesting a paracrine mechanism, which was confirmed by in vitro experiments with conditioned media from ASCs. CONCLUSIONS: Transplanted ASCs are preferentially retained in ischemic adipose tissue, although most of the cells eventually undergo cell death. They exert an angiogenic effect on adipose tissue mainly through a paracrine mechanism. Increased understanding of these effects will help develop ASCs as a tool for cell-based therapy.

  View details for DOI 10.1097/SAP.0b013e318264fd6a

  View details for Web of Science ID 000338013700024

• The embrace Device Significantly Decreases Scarring following Scar Revision Surgery in a Randomized Controlled Trial. Plastic and reconstructive surgery Lim, A. F., Weintraub, J., Kaplan, E. N., Januszyk, M., Cowley, C., McLaughlin, P., Beasley, B., Gurtner, G. C., Longaker, M. T. 2014; 133 (2): 398-405

  Abstract

  Mechanically offloading or shielding an incision significantly reduces scarring in both animal and first-in-human studies. Whether or not this strategy would be effective following scar revision surgery was previously unknown. In this article, the authors report that the embrace device, which uses principles of mechanomodulation, significantly improves aesthetic outcomes following scar revision surgery.A prospective, open-label, randomized, single-center study was conducted to evaluate the appearance of scars following revision and embrace treatment. Revision surgery was performed on 12 patients, each acting as his or her own control, and outcomes were assessed at 6 months. A visual analogue scale was used to evaluate each scar, rated by four independent surgeons who were not involved in the study.Evaluation of 6-month scar images by four independent surgeons using the visual analogue scale demonstrated a highly significant improvement in scar appearance following embrace treatment (p < 0.005).The embrace device represents a powerful new technology for significantly improving scar appearance following revision surgery.Therapeutic, II.

  View details for DOI 10.1097/01.prs.0000436526.64046.d0

  View details for PubMedID 24105084

• Concurrent Generation of Functional Smooth Muscle and Endothelial Cells via a Vascular Progenitor. Stem cells translational medicine Marchand, M., Anderson, E. K., Phadnis, S. M., Longaker, M. T., Cooke, J. P., Chen, B., Reijo Pera, R. A. 2014; 3 (1): 91-97

  Abstract

  Smooth muscle cells (SMCs) and endothelial cells (ECs) are typically derived separately, with low efficiencies, from human pluripotent stem cells (hPSCs). The concurrent generation of these cell types might lead to potential applications in regenerative medicine to model, elucidate, and eventually treat vascular diseases. Here we report a robust two-step protocol that can be used to simultaneously generate large numbers of functional SMCs and ECs from a common proliferative vascular progenitor population via a two-dimensional culture system. We show here that coculturing hPSCs with OP9 cells in media supplemented with vascular endothelial growth factor, basic fibroblast growth factor, and bone morphogenetic protein 4 yields a higher percentage of CD31(+)CD34(+) cells on day 8 of differentiation. Upon exposure to endothelial differentiation media and SM differentiation media, these vascular progenitors were able to differentiate and mature into functional endothelial cells and smooth muscle cells, respectively. Furthermore, we were able to expand the intermediate population more than a billionfold to generate sufficient numbers of ECs and SMCs in parallel for potential therapeutic transplantations.

  View details for DOI 10.5966/sctm.2013-0124

  View details for PubMedID 24311701

  View details for PubMedCentralID PMC3902294

• Transplanted terminally differentiated induced pluripotent stem cells are accepted by immune mechanisms similar to self-tolerance. Nature communications de Almeida, P. E., Meyer, E. H., Kooreman, N. G., Diecke, S., Dey, D., Sanchez-Freire, V., Hu, S., Ebert, A., Odegaard, J., Mordwinkin, N. M., Brouwer, T. P., Lo, D., Montoro, D. T., Longaker, M. T., Negrin, R. S., Wu, J. C. 2014; 5: 3903-?

  Abstract

  The exact nature of the immune response elicited by autologous-induced pluripotent stem cell (iPSC) progeny is still not well understood. Here we show in murine models that autologous iPSC-derived endothelial cells (iECs) elicit an immune response that resembles the one against a comparable somatic cell, the aortic endothelial cell (AEC). These cells exhibit long-term survival in vivo and prompt a tolerogenic immune response characterized by elevated IL-10 expression. In contrast, undifferentiated iPSCs elicit a very different immune response with high lymphocytic infiltration and elevated IFN-γ, granzyme-B and perforin intragraft. Furthermore, the clonal structure of infiltrating T cells from iEC grafts is statistically indistinguishable from that of AECs, but is different from that of undifferentiated iPSC grafts. Taken together, our results indicate that the differentiation of iPSCs results in a loss of immunogenicity and leads to the induction of tolerance, despite expected antigen expression differences between iPSC-derived versus original somatic cells.

  View details for DOI 10.1038/ncomms4903

  View details for PubMedID 24875164

• Wound healing: an update. Regenerative medicine Zielins, E. R., Atashroo, D. A., Maan, Z. N., Duscher, D., Walmsley, G. G., Hu, M., Senarath-Yapa, K., McArdle, A., Tevlin, R., Wearda, T., Paik, K. J., Duldulao, C., Hong, W. X., Gurtner, G. C., Longaker, M. T. 2014; 9 (6): 817-830

  Abstract

  Wounds, both chronic and acute, continue to be a tremendous socioeconomic burden. As such, technologies drawn from many disciplines within science and engineering are constantly being incorporated into innovative wound healing therapies. While many of these therapies are experimental, they have resulted in new insights into the pathophysiology of wound healing, and in turn the development of more specialized treatments for both normal and abnormal wound healing states. Herein, we review some of the emerging technologies that are currently being developed to aid and improve wound healing after cutaneous injury.

  View details for DOI 10.2217/rme.14.54

  View details for PubMedID 25431917

• Skeletal Tissue Engineering PRINCIPLES OF TISSUE ENGINEERING, 4TH EDITION Montoro, D. T., Wan, D. C., Longaker, M. T., Lanza, R., Langer, R., Vacanti, J. 2014: 1289–1302

  View details for DOI 10.1016/B978-0-12-398358-9.00060-4

  View details for Web of Science ID 000427825200065

• Epidermal or dermal specific knockout of PHD-2 enhances wound healing and minimizes ischemic injury. PloS one Zimmermann, A. S., Morrison, S. D., Hu, M. S., Li, S., Nauta, A., Sorkin, M., Meyer, N. P., Walmsley, G. G., Maan, Z. N., Chan, D. A., Gurtner, G. C., Giaccia, A. J., Longaker, M. T. 2014; 9 (4)

  Abstract

  Hypoxia-inducible factor (HIF)-1α, part of the heterodimeric transcription factor that mediates the cellular response to hypoxia, is critical for the expression of multiple angiogenic growth factors, cell motility, and the recruitment of endothelial progenitor cells. Inhibition of the oxygen-dependent negative regulator of HIF-1α, prolyl hydroxylase domain-2 (PHD-2), leads to increased HIF-1α and mimics various cellular and physiological responses to hypoxia. The roles of PHD-2 in the epidermis and dermis have not been clearly defined in wound healing.Epidermal and dermal specific PHD-2 knockout (KO) mice were developed in a C57BL/6J (wild type) background by crossing homozygous floxed PHD-2 mice with heterozygous K14-Cre mice and heterozygous Col1A2-Cre-ER mice to get homozygous floxed PHD-2/heterozygous K14-Cre and homozygous floxed PHD-2/heterozygous floxed Col1A2-Cre-ER mice, respectively. Ten to twelve-week-old PHD-2 KO and wild type (WT) mice were subjected to wounding and ischemic pedicle flap model. The amount of healing was grossly quantified with ImageJ software. Western blot and qRT-PCR was run on protein and RNA from primary cells cultured in vitro.qRT-PCR demonstrated a significant decrease of PHD-2 in keratinocytes and fibroblasts derived from tissue specific KO mice relative to control mice (*p<0.05). Western blot analysis showed a significant increase in HIF-1α and VEGF protein levels in PHD-2 KO mice relative to control mice (*p<0.05). PHD-2 KO mice showed significantly accelerated wound closure relative to WT (*p<0.05). When ischemia was analyzed at day nine post-surgery in a flap model, the PHD-2 tissue specific knockout mice showed significantly more viable flaps than WT (*p<0.05).PHD-2 plays a significant role in the rates of wound healing and response to ischemic insult in mice. Further exploration shows PHD-2 KO increases cellular levels of HIF-1α and this increase leads to the transcription of downstream angiogenic factors such as VEGF.

  View details for DOI 10.1371/journal.pone.0093373

  View details for PubMedID 24695462

  View details for PubMedCentralID PMC3973687

• Osteoclast derivation from mouse bone marrow. Journal of visualized experiments : JoVE Tevlin, R., McArdle, A., Chan, C. K., Pluvinage, J., Walmsley, G. G., Wearda, T., Marecic, O., Hu, M. S., Paik, K. J., Senarath-Yapa, K., Atashroo, D. A., Zielins, E. R., Wan, D. C., Weissman, I. L., Longaker, M. T. 2014

  View details for DOI 10.3791/52056

  View details for PubMedID 25407120

• Osteoclast derivation from mouse bone marrow. Journal of visualized experiments : JoVE Tevlin, R., McArdle, A., Chan, C. K., Pluvinage, J., Walmsley, G. G., Wearda, T., Marecic, O., Hu, M. S., Paik, K. J., Senarath-Yapa, K., Atashroo, D. A., Zielins, E. R., Wan, D. C., Weissman, I. L., Longaker, M. T. 2014

  Abstract

  Osteoclasts are highly specialized cells that are derived from the monocyte/macrophage lineage of the bone marrow. Their unique ability to resorb both the organic and inorganic matrices of bone means that they play a key role in regulating skeletal remodeling. Together, osteoblasts and osteoclasts are responsible for the dynamic coupling process that involves both bone resorption and bone formation acting together to maintain the normal skeleton during health and disease. As the principal bone-resorbing cell in the body, changes in osteoclast differentiation or function can result in profound effects in the body. Diseases associated with altered osteoclast function can range in severity from lethal neonatal disease due to failure to form a marrow space for hematopoiesis, to more commonly observed pathologies such as osteoporosis, in which excessive osteoclastic bone resorption predisposes to fracture formation. An ability to isolate osteoclasts in high numbers in vitro has allowed for significant advances in the understanding of the bone remodeling cycle and has paved the way for the discovery of novel therapeutic strategies that combat these diseases. Here, we describe a protocol to isolate and cultivate osteoclasts from mouse bone marrow that will yield large numbers of osteoclasts.

  View details for DOI 10.3791/52056

  View details for PubMedID 25407120

• Wound healing: an update REGENERATIVE MEDICINE Zielins, E. R., Atashroo, D. A., Maan, Z. N., Duscher, D., Walmsley, G. G., Marecic, O., Hu, M., Senarath-Yapa, K., McArdle, A., Tevlin, R., Wearda, T., Paik, K. J., Duldulao, C., Hong, W. X., Gurtner, G. C., Longaker, M. T. 2014; 9 (6): 817-830

  Abstract

  Wounds, both chronic and acute, continue to be a tremendous socioeconomic burden. As such, technologies drawn from many disciplines within science and engineering are constantly being incorporated into innovative wound healing therapies. While many of these therapies are experimental, they have resulted in new insights into the pathophysiology of wound healing, and in turn the development of more specialized treatments for both normal and abnormal wound healing states. Herein, we review some of the emerging technologies that are currently being developed to aid and improve wound healing after cutaneous injury.

  View details for DOI 10.2217/RME.14.54

  View details for Web of Science ID 000345620600012

• Epidermal or Dermal Specific Knockout of PHD-2 Enhances Wound Healing and Minimizes Ischemic Injury. PloS one Zimmermann, A. S., Morrison, S. D., Hu, M. S., Li, S., Nauta, A., Sorkin, M., Meyer, N. P., Walmsley, G. G., Maan, Z. N., Chan, D. A., Gurtner, G. C., Giaccia, A. J., Longaker, M. T. 2014; 9 (4)

  View details for DOI 10.1371/journal.pone.0093373

  View details for PubMedID 24695462

• Transplanted terminally differentiated induced pluripotent stem cells are accepted by immune mechanisms similar to self-tolerance. Nature communications de Almeida, P. E., Meyer, E. H., Kooreman, N. G., Diecke, S., Dey, D., Sanchez-Freire, V., Hu, S., Ebert, A., Odegaard, J., Mordwinkin, N. M., Brouwer, T. P., Lo, D., Montoro, D. T., Longaker, M. T., Negrin, R. S., Wu, J. C. 2014; 5: 3903-?

  View details for DOI 10.1038/ncomms4903

  View details for PubMedID 24875164

• Biological therapies for the treatment of cutaneous wounds: Phase III and launched therapies EXPERT OPINION ON BIOLOGICAL THERAPY Rennert, R. C., Rodrigues, M., Wong, V. W., Duscher, D., Hu, M., Maan, Z., Sorkin, M., Gurtner, G. C., Longaker, M. T. 2013; 13 (11): 1523-1541

  Abstract

  Normal wound healing mechanisms can be overwhelmed in the setting of complex acute and chronic tissue injury. Biological therapies are designed to augment and/or restore the body's natural wound healing abilities. There are a variety of available and emerging technologies utilizing this approach that have demonstrated the ability to augment wound healing.In this review, the clinical data on launched and emerging biological therapies for wound healing applications are summarized. The methodologies discussed include biological skin equivalents, growth factors/small molecules and stem cell-based therapies.While many products possess convincing clinical data demonstrating their efficacy in comparison to standard treatment options, more robust, controlled studies are needed to determine the relative value among established and emerging biological therapies. Future bioengineering and stem cell-based approaches are of particular interest due to the simultaneous correction of multiple deficiencies present in the nonhealing wound.

  View details for DOI 10.1517/14712598.2013.842972

  View details for Web of Science ID 000325712100007

  View details for PubMedID 24093722

• Biological therapies for the treatment of cutaneous wounds: phase III and launched therapies. Expert opinion on biological therapy Rennert, R. C., Rodrigues, M., Wong, V. W., Duscher, D., Hu, M., Maan, Z., Sorkin, M., Gurtner, G. C., Longaker, M. T. 2013; 13 (11): 1523-1541

  Abstract

  Normal wound healing mechanisms can be overwhelmed in the setting of complex acute and chronic tissue injury. Biological therapies are designed to augment and/or restore the body's natural wound healing abilities. There are a variety of available and emerging technologies utilizing this approach that have demonstrated the ability to augment wound healing.In this review, the clinical data on launched and emerging biological therapies for wound healing applications are summarized. The methodologies discussed include biological skin equivalents, growth factors/small molecules and stem cell-based therapies.While many products possess convincing clinical data demonstrating their efficacy in comparison to standard treatment options, more robust, controlled studies are needed to determine the relative value among established and emerging biological therapies. Future bioengineering and stem cell-based approaches are of particular interest due to the simultaneous correction of multiple deficiencies present in the nonhealing wound.

  View details for DOI 10.1517/14712598.2013.842972

  View details for PubMedID 24093722

• From Germ Theory to Germ Therapy: Skin Microbiota, Chronic Wounds, and Probiotics PLASTIC AND RECONSTRUCTIVE SURGERY Wong, V. W., Martindale, R. G., Longaker, M. T., Gurtner, G. C. 2013; 132 (5): 854E-861E

  Abstract

  Microorganisms living throughout the body comprise the human "microbiota" and play an important role in health and disease. Recent research suggests that alterations in the skin microbiota may underlie chronic wound pathology. Probiotics are bacteria or yeast that confer a health benefit on the host and may have a role in preventing and treating nonhealing wounds by modulating host-microbe interactions.The English literature on skin microbiota, chronic wounds, biofilms, and probiotics is reviewed.Recent evidence indicates that disruption of microbial communities and bacteria-host interactions may contribute to impaired wound healing. Preclinical and human studies highlight the potential of probiotics to prevent or treat various infectious, immune-mediated, and inflammatory diseases.Advances in molecular sequencing and microbiology have shed light on the importance of the human microbiota in development, health, and disease. Probiotics represent a novel approach to altering the microbial environment with beneficial bacteria. Ongoing challenges include the need for better understanding of therapeutic mechanisms, improved regulation of manufacturing practices, and validation in controlled human trials. Current evidence suggests that probiotic-based therapies have considerable potential to exploit host-microbe relationships and improve clinical outcomes.

  View details for DOI 10.1097/PRS.0b013e3182a3c11e

  View details for PubMedID 24165637

• Isolation of human adipose-derived stromal cells using laser-assisted liposuction and their therapeutic potential in regenerative medicine. Stem cells translational medicine Chung, M. T., Zimmermann, A. S., Paik, K. J., Morrison, S. D., Hyun, J. S., Lo, D. D., McArdle, A., Montoro, D. T., Walmsley, G. G., Senarath-Yapa, K., Sorkin, M., Rennert, R., Chen, H., Chung, A. S., Vistnes, D., Gurtner, G. C., Longaker, M. T., Wan, D. C. 2013; 2 (10): 808-817

  Abstract

  Harvesting adipose-derived stromal cells (ASCs) for tissue engineering is frequently done through liposuction. However, several different techniques exist. Although third-generation ultrasound-assisted liposuction has been shown to not have a negative effect on ASCs, the impact of laser-assisted liposuction on the quality and differentiation potential of ASCs has not been studied. Therefore, ASCs were harvested from laser-assisted lipoaspirate and suction-assisted lipoaspirate. Next, in vitro parameters of cell yield, cell viability and proliferation, surface marker phenotype, osteogenic differentiation, and adipogenic differentiation were performed. Finally, in vivo bone formation was assessed using a critical-sized cranial defect in athymic nude mice. Although ASCs isolated from suction-assisted lipoaspirate and laser-assisted lipoaspirate both successfully underwent osteogenic and adipogenic differentiation, the cell yield, viability, proliferation, and frequency of ASCs (CD34(+)CD31(-)CD45(-)) in the stromal vascular fraction were all significantly less with laser-assisted liposuction in vitro (p < .05). In vivo, quantification of osseous healing by micro-computed tomography revealed significantly more healing with ASCs isolated from suction-assisted lipoaspirate relative to laser-assisted lipoaspirate at the 4-, 6-, and 8-week time points (p < .05). Therefore, as laser-assisted liposuction appears to negatively impact the biology of ASCs, cell harvest using suction-assisted liposuction is preferable for tissue-engineering purposes.

  View details for DOI 10.5966/sctm.2012-0183

  View details for PubMedID 24018794

  View details for PubMedCentralID PMC3785265

• Enhancing stem cell survival in vivo for tissue repair BIOTECHNOLOGY ADVANCES Hyun, J. S., Tran, M. C., Wong, V. W., Chung, M. T., Lo, D. D., Montoro, D. T., Wan, D. C., Longaker, M. T. 2013; 31 (5): 736-743

  Abstract

  The ability to use progenitor cells for regenerative medicine remains an evolving but elusive clinical goal. A serious obstacle towards widespread use of stem cells for tissue regeneration is the challenges that face these cells when they are placed in vivo into a wound for therapy. These environments are hypoxic, acidic, and have an upregulation of inflammatory mediators creating a region that is hostile towards cellular survival. Within this environment, the majority of progenitor cells undergo apoptosis prior to participating in lineage differentiation and cellular integration. In order to maximize the clinical utility of stem cells, strategies must be employed to increase the cell's ability to survive in vivo through manipulation of both the stem cell and the surrounding environment. This review focuses on current advances and techniques being used to increase in vivo stem cell survival for the purpose of tissue regeneration.

  View details for DOI 10.1016/j.biotechadv.2012.11.003

  View details for Web of Science ID 000322058900019

  View details for PubMedID 23153460

• Cell surface marker profiling of human adipose derived stem cells using single cell transcriptional analysis identifies heterogeneous subpopulations Sorkin, M., Rennert, R. C., Januszyk, M., Glotzbach, J. P., Chung, M. T., Longaker, M. T., Gurtner, G. C. ELSEVIER SCIENCE INC. 2013: S96–S97

  View details for DOI 10.1016/j.jamcollsurg.2013.07.219

  View details for Web of Science ID 000325577900190

• Molecular analysis and differentiation capacity of adipose-derived stem cells from lymphedema tissue. Plastic and reconstructive surgery Levi, B., Glotzbach, J. P., Sorkin, M., Hyun, J., Januszyk, M., Wan, D. C., Li, S., Nelson, E. R., Longaker, M. T., Gurtner, G. C. 2013; 132 (3): 580-589

  Abstract

  Many breast cancer patients are plagued by the disabling complication of upper limb lymphedema after axillary surgery. Conservative treatments using massage and compression therapy do not offer a lasting relief, as they fail to address the chronic transformation of edema into excess adipose tissue. Liposuction to address the adipose nature of the lymphedema has provided an opportunity for a detailed analysis of the stromal fraction of lymphedema-associated fat to clarify the molecular mechanisms for this adipogenic transformation.Adipose-derived stem cells were harvested from human lipoaspirate of the upper extremity from age-matched patients with lymphedema (n = 3) or subcutaneous adipose tissue from control patients undergoing cosmetic procedures (n = 3). Immediately after harvest, adipose-derived stem cells were analyzed using single-cell transcriptional profiling techniques. Osteogenic, adipogenic, and vasculogenic gene expression and differentiation were assessed by quantitative real-time polymerase chain reaction and standard in vitro differentiation assays.Differential transcriptional clusters of adipose-derived stem cells were found between lymphedema and subcutaneous fat. Interestingly, lymphedema-associated stem cells had a much higher adipogenic gene expression and enhanced ability to undergo adipogenic differentiation. Conversely, they had lower vasculogenic gene expression and diminished capability to form tubules in vitro, whereas the osteogenic differentiation capacity was not significantly altered.Adipose-derived stem cells from extremities affected by lymphedema appear to exhibit transcriptional profiles similar to those of abdominal adipose-derived stem cells; however, their adipogenic differentiation potential is strongly increased and their vasculogenic capacity is compromised. These results suggest that the underlying pathophysiology of lymphedema drives adipose-derived stem cells toward adipogenic differentiation.

  View details for DOI 10.1097/PRS.0b013e31829ace13

  View details for PubMedID 23985633

• Wound healing: a paradigm for regeneration. Mayo Clinic proceedings. Mayo Clinic Wong, V. W., Gurtner, G. C., Longaker, M. T. 2013; 88 (9): 1022-1031

  Abstract

  Human skin is a remarkably plastic organ that sustains insult and injury throughout life. Its ability to expeditiously repair wounds is paramount to survival and is thought to be regulated by wound components such as differentiated cells, stem cells, cytokine networks, extracellular matrix, and mechanical forces. These intrinsic regenerative pathways are integrated across different skin compartments and are being elucidated on the cellular and molecular levels. Recent advances in bioengineering and nanotechnology have allowed researchers to manipulate these microenvironments in increasingly precise spatial and temporal scales, recapitulating key homeostatic cues that may drive regeneration. The ultimate goal is to translate these bench achievements into viable bedside therapies that address the growing global burden of acute and chronic wounds. In this review, we highlight current concepts in cutaneous wound repair and propose that many of these evolving paradigms may underlie regenerative processes across diverse organ systems.

  View details for DOI 10.1016/j.mayocp.2013.04.012

  View details for PubMedID 24001495

• Enhancing in vivo survival of adipose-derived stromal cells through bcl-2 overexpression using a minicircle vector. Stem cells translational medicine Hyun, J., Grova, M., Nejadnik, H., Lo, D., Morrison, S., Montoro, D., Chung, M., Zimmermann, A., Walmsley, G. G., Lee, M., Daldrup-Link, H., Wan, D. C., Longaker, M. T. 2013; 2 (9): 690-702

  Abstract

  Tissue regeneration using progenitor cell-based therapy has the potential to aid in the healing of a diverse range of pathologies, ranging from short-gut syndrome to spinal cord lesions. However, there are numerous hurdles to be overcome prior to the widespread application of these cells in the clinical setting. One of the primary barriers to effective stem cell therapy is the hostile environment that progenitor cells encounter in the clinical injury wound setting. In order to promote cellular survival, stem cell differentiation, and participation in tissue regeneration, relevant cells and delivery scaffolds must be paired with strategies to prevent cell death to ensure that these cells can survive to form de novo tissue. The Bcl-2 protein is a prosurvival member of a family of proteins that regulate the mitochondrial pathway of apoptosis. Using several strategies to overexpress the Bcl-2 protein, we demonstrated a decrease in the mediators of apoptosis in vitro and in vivo. This was shown through the use of two different clinical tissue repair models. Cells overexpressing Bcl-2 not only survived within the wound environment at a statistically significantly higher rate than control cells, but also increased tissue regeneration. Finally, we used a nonintegrating minicircle technology to achieve this in a potentially clinically applicable strategy for stem cell therapy.

  View details for DOI 10.5966/sctm.2013-0035

  View details for PubMedID 23934910

• Molecular analysis and differentiation capacity of adipose-derived stem cells from lymphedema tissue. Plastic and reconstructive surgery Levi, B., Glotzbach, J. P., Sorkin, M., Hyun, J., Januszyk, M., Wan, D. C., Li, S., Nelson, E. R., Longaker, M. T., Gurtner, G. C. 2013; 132 (3): 580-589

  Abstract

  Many breast cancer patients are plagued by the disabling complication of upper limb lymphedema after axillary surgery. Conservative treatments using massage and compression therapy do not offer a lasting relief, as they fail to address the chronic transformation of edema into excess adipose tissue. Liposuction to address the adipose nature of the lymphedema has provided an opportunity for a detailed analysis of the stromal fraction of lymphedema-associated fat to clarify the molecular mechanisms for this adipogenic transformation.Adipose-derived stem cells were harvested from human lipoaspirate of the upper extremity from age-matched patients with lymphedema (n = 3) or subcutaneous adipose tissue from control patients undergoing cosmetic procedures (n = 3). Immediately after harvest, adipose-derived stem cells were analyzed using single-cell transcriptional profiling techniques. Osteogenic, adipogenic, and vasculogenic gene expression and differentiation were assessed by quantitative real-time polymerase chain reaction and standard in vitro differentiation assays.Differential transcriptional clusters of adipose-derived stem cells were found between lymphedema and subcutaneous fat. Interestingly, lymphedema-associated stem cells had a much higher adipogenic gene expression and enhanced ability to undergo adipogenic differentiation. Conversely, they had lower vasculogenic gene expression and diminished capability to form tubules in vitro, whereas the osteogenic differentiation capacity was not significantly altered.Adipose-derived stem cells from extremities affected by lymphedema appear to exhibit transcriptional profiles similar to those of abdominal adipose-derived stem cells; however, their adipogenic differentiation potential is strongly increased and their vasculogenic capacity is compromised. These results suggest that the underlying pathophysiology of lymphedema drives adipose-derived stem cells toward adipogenic differentiation.

  View details for DOI 10.1097/PRS.0b013e31829ace13

  View details for PubMedID 23985633

• Clonal precursor of bone, cartilage, and hematopoietic niche stromal cells PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Chan, C. K., Lindau, P., Jiang, W., Chen, J. Y., Zhang, L. F., Chen, C., Seita, J., Sahoo, D., Kim, J., Lee, A., Park, S., Nag, D., Gong, Y., Kulkarni, S., Luppen, C. A., Theologis, A. A., Wan, D. C., DeBoer, A., Seo, E. Y., Vincent-Tompkins, J. D., Loh, K., Walmsley, G. G., Kraft, D. L., Wu, J. C., Longaker, M. T., Weissman, I. L. 2013; 110 (31): 12643-12648

  Abstract

  Organs are composites of tissue types with diverse developmental origins, and they rely on distinct stem and progenitor cells to meet physiological demands for cellular production and homeostasis. How diverse stem cell activity is coordinated within organs is not well understood. Here we describe a lineage-restricted, self-renewing common skeletal progenitor (bone, cartilage, stromal progenitor; BCSP) isolated from limb bones and bone marrow tissue of fetal, neonatal, and adult mice. The BCSP clonally produces chondrocytes (cartilage-forming) and osteogenic (bone-forming) cells and at least three subsets of stromal cells that exhibit differential expression of cell surface markers, including CD105 (or endoglin), Thy1 [or CD90 (cluster of differentiation 90)], and 6C3 [ENPEP glutamyl aminopeptidase (aminopeptidase A)]. These three stromal subsets exhibit differential capacities to support hematopoietic (blood-forming) stem and progenitor cells. Although the 6C3-expressing subset demonstrates functional stem cell niche activity by maintaining primitive hematopoietic stem cell (HSC) renewal in vitro, the other stromal populations promote HSC differentiation to more committed lines of hematopoiesis, such as the B-cell lineage. Gene expression analysis and microscopic studies further reveal a microenvironment in which CD105-, Thy1-, and 6C3-expressing marrow stroma collaborate to provide cytokine signaling to HSCs and more committed hematopoietic progenitors. As a result, within the context of bone as a blood-forming organ, the BCSP plays a critical role in supporting hematopoiesis through its generation of diverse osteogenic and hematopoietic-promoting stroma, including HSC supportive 6C3(+) niche cells.

  View details for DOI 10.1073/pnas.1310212110

  View details for PubMedID 23858471

• Wnt3a reestablishes osteogenic capacity to bone grafts from aged animals. journal of bone and joint surgery. American volume Leucht, P., Jiang, J., Cheng, D., Liu, B., Dhamdhere, G., Fang, M. Y., Monica, S. D., Urena, J. J., Cole, W., Smith, L. R., Castillo, A. B., Longaker, M. T., Helms, J. A. 2013; 95 (14): 1278-1288

  Abstract

  Age-related fatty degeneration of the bone marrow contributes to delayed fracture-healing and osteoporosis-related fractures in the elderly. The mechanisms underlying this fatty change are unknown, but they may relate to the level of Wnt signaling within the aged marrow cavity.Transgenic mice were used in conjunction with a syngeneic bone-graft model to follow the fates of cells involved in the engraftment. Immunohistochemistry along with quantitative assays were used to evaluate Wnt signaling and adipogenic and osteogenic gene expression in bone grafts from young and aged mice. Liposomal Wnt3a protein (L-Wnt3a) was tested for its ability to restore osteogenic potential to aged bone grafts in critical-size defect models created in mice and in rabbits. Radiography, microquantitative computed tomography (micro-CT) reconstruction, histology, and histomorphometric measurements were used to quantify bone-healing resulting from L-Wnt3a or a control substance (liposomal phosphate-buffered saline solution [L-PBS]).Expression profiling of cells in a bone graft demonstrated a shift away from an osteogenic gene profile and toward an adipogenic one with age. This age-related adipogenic shift was accompanied by a significant reduction (p < 0.05) in Wnt signaling and a loss in osteogenic potential. In both large and small animal models, osteogenic competence was restored to aged bone grafts by a brief incubation with the stem-cell factor Wnt3a. In addition, liposomal Wnt3a significantly reduced cell death in the bone graft, resulting in significantly more osseous regenerate in comparison with controls.Liposomal Wnt3a enhances cell survival and reestablishes the osteogenic capacity of bone grafts from aged animals.We developed an effective, clinically applicable, regenerative medicine-based strategy for revitalizing bone grafts from aged patients.

  View details for DOI 10.2106/JBJS.L.01502

  View details for PubMedID 23864176

• Wnt3a Reestablishes Osteogenic Capacity to Bone Grafts from Aged Animals JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME Leucht, P., Jiang, J., Cheng, D., Liu, B., Dhamdhere, G., Fang, M. Y., Monica, S. D., Urena, J. J., Cole, W., Smith, L. R., Castillo, A. B., Longaker, M. T., Helms, J. A. 2013; 95A (14): 1278-1288

  Abstract

  Age-related fatty degeneration of the bone marrow contributes to delayed fracture-healing and osteoporosis-related fractures in the elderly. The mechanisms underlying this fatty change are unknown, but they may relate to the level of Wnt signaling within the aged marrow cavity.Transgenic mice were used in conjunction with a syngeneic bone-graft model to follow the fates of cells involved in the engraftment. Immunohistochemistry along with quantitative assays were used to evaluate Wnt signaling and adipogenic and osteogenic gene expression in bone grafts from young and aged mice. Liposomal Wnt3a protein (L-Wnt3a) was tested for its ability to restore osteogenic potential to aged bone grafts in critical-size defect models created in mice and in rabbits. Radiography, microquantitative computed tomography (micro-CT) reconstruction, histology, and histomorphometric measurements were used to quantify bone-healing resulting from L-Wnt3a or a control substance (liposomal phosphate-buffered saline solution [L-PBS]).Expression profiling of cells in a bone graft demonstrated a shift away from an osteogenic gene profile and toward an adipogenic one with age. This age-related adipogenic shift was accompanied by a significant reduction (p < 0.05) in Wnt signaling and a loss in osteogenic potential. In both large and small animal models, osteogenic competence was restored to aged bone grafts by a brief incubation with the stem-cell factor Wnt3a. In addition, liposomal Wnt3a significantly reduced cell death in the bone graft, resulting in significantly more osseous regenerate in comparison with controls.Liposomal Wnt3a enhances cell survival and reestablishes the osteogenic capacity of bone grafts from aged animals.We developed an effective, clinically applicable, regenerative medicine-based strategy for revitalizing bone grafts from aged patients.

  View details for DOI 10.2106/JBJS.L01502

  View details for Web of Science ID 000321885000005

• A Mechanomodulatory Device to Minimize Incisional Scar Formation. Advances in wound care Wong, V. W., Beasley, B., Zepeda, J., Dauskardt, R. H., Yock, P. G., Longaker, M. T., Gurtner, G. C. 2013; 2 (4): 185-194

  Abstract

  To mechanically control the wound environment and prevent cutaneous scar formation.We subjected various material substrates to biomechanical testing to investigate their ability to modulate skin behavior. Combinations of elastomeric materials, adhesives, and strain applicators were evaluated to develop topical stress-shielding devices. Noninvasive imaging modalities were utilized to characterize anatomic site-specific differences in skin biomechanical properties in humans. The devices were tested in a validated large animal model of hypertrophic scarring. Phase I within-patient controlled clinical trials were conducted to confirm their safety and efficacy in scar reduction in patients undergoing abdominoplasty surgery.Among the tested materials and device applicators, a polymer device was developed that effectively off-loaded high tension wounds and blocked pro-fibrotic pathways and excess scar formation in red Duroc swine. In humans, different anatomic sites exhibit unique biomechanical properties that may correlate with the propensity to form scars. In the clinical trial, utilization of this device significantly reduced incisional scar formation and improved scar appearance for up to 12 months compared with control incisions that underwent routine postoperative care.This is the first device that is able to precisely control the mechanical environment of incisional wounds and has been demonstrated in multiple clinical trials to significantly reduce scar formation after surgery.Mechanomodulatory strategies to control the incisional wound environment can significantly reduce pathologic scarring and fibrosis after surgery.

  View details for PubMedID 24527342

• A Mechanomodulatory Device to Minimize Incisional Scar Formation ADVANCES IN WOUND CARE Wong, V. W., Beasley, B., Zepeda, J., Dauskardt, R. H., Yock, P. G., Longaker, M. T., Gurtner, G. C. 2013; 2 (4): 185–94

  View details for DOI 10.1089/wound.2012.0396

  View details for Web of Science ID 000214927500008

• Paracrine Mechanism of Angiogenesis in Adipose-Derived Stem Cell Transplantation. Annals of plastic surgery Suga, H., Glotzbach, J. P., Sorkin, M., Longaker, M. T., Gurtner, G. C. 2013

  Abstract

  INTRODUCTION: Adipose-derived stem cells (ASCs) have shown potential for cell-based therapy in the field of plastic surgery. However, the fate of ASCs after transplantation and the mechanism(s) of their biologic capabilities remain unclear. METHODS: We isolated and cultured ASCs from transgenic mice that express both luciferase and green fluorescent protein and injected the cells into the inguinal fat pads of wild-type mice. We tested 4 experimental groups, namely, ischemic fat pads with/without ASCs and control fat pads with/without ASCs. RESULTS: Transplanted ASCs were tracked with bioluminescence imaging. The luminescence gradually decreased over 28 days, indicating cell death after transplantation. More ASCs were retained in ischemic fat pads on day 7 compared to control fat pads. On day 14, adipose tissue vascular density was higher in the ASC transplantation groups compared to those without ASCs. On day 28, there was decreased atrophy of adipose tissue in ASC-treated ischemic fat pads. Transplanted ASCs were detected as nonproliferating green fluorescent protein-positive cells, whereas native endothelial cells adjacent to the transplanted ASCs were proliferative. Protein analysis demonstrated higher expression of hepatocyte growth factor and vascular endothelial growth factor in the ASC transplantation groups, suggesting a paracrine mechanism, which was confirmed by in vitro experiments with conditioned media from ASCs. CONCLUSIONS: Transplanted ASCs are preferentially retained in ischemic adipose tissue, although most of the cells eventually undergo cell death. They exert an angiogenic effect on adipose tissue mainly through a paracrine mechanism. Increased understanding of these effects will help develop ASCs as a tool for cell-based therapy.

  View details for DOI 10.1097/SAP.0b013e318264fd6a

  View details for PubMedID 23636112

• Brg1 governs a positive feedback circuit in the hair follicle for tissue regeneration and repair. Developmental cell Xiong, Y., Li, W., Shang, C., Chen, R. M., Han, P., Yang, J., Stankunas, K., Wu, B., Pan, M., Zhou, B., Longaker, M. T., Chang, C. 2013; 25 (2): 169-181

  Abstract

  Hair follicle stem cells (bulge cells) are essential for hair regeneration and early epidermal repair after wounding. Here we show that Brg1, a key enzyme in the chromatin-remodeling machinery, is dynamically expressed in bulge cells to control tissue regeneration and repair. In mice, sonic hedgehog (Shh) signals Gli to activate Brg1 in bulge cells to begin hair regeneration, whereas Brg1 recruits NF-κB to activate Shh in matrix cells to sustain hair growth. Such reciprocal Brg1-Shh interaction is essential for hair regeneration. Moreover, Brg1 is indispensable for maintaining the bulge cell reservoir. Without Brg1, bulge cells are depleted over time, partly through the ectopic expression of the cell-cycle inhibitor p27(Kip1). Also, bulge Brg1 is activated by skin injury to facilitate early epidermal repair. Our studies demonstrate a molecular circuit that integrates chromatin remodeling (Brg1), transcriptional regulation (NF-κB, Gli), and intercellular signaling (Shh) to control bulge stem cells during tissue regeneration.

  View details for DOI 10.1016/j.devcel.2013.03.015

  View details for PubMedID 23602386

• CD90 (Thy-1)-Positive Selection Enhances Osteogenic Capacity of Human Adipose-Derived Stromal Cells TISSUE ENGINEERING PART A Chung, M. T., Liu, C., Hyun, J. S., Lo, D. D., Montoro, D. T., Hasegawa, M., Li, S., Sorkin, M., Rennert, R., Keeney, M., Yang, F., Quarto, N., Longaker, M. T., Wan, D. C. 2013; 19 (7-8): 989-997

  Abstract

  Stem cell-based bone tissue engineering with adipose-derived stromal cells (ASCs) has shown great promise for revolutionizing treatment of large bone deficits. However, there is still a lack of consensus on cell surface markers identifying osteoprogenitors. Fluorescence-activated cell sorting has identified a subpopulation of CD105(low) cells with enhanced osteogenic differentiation. The purpose of the present study was to compare the ability of CD90 (Thy-1) to identify osteoprogenitors relative to CD(105).Unsorted cells, CD90(+), CD90(-), CD105(high), and CD105(low) cells were treated with an osteogenic differentiation medium. For evaluation of in vitro osteogenesis, alkaline phosphatase (ALP) staining and alizarin red staining were performed at 7 days and 14 days, respectively. RNA was harvested after 7 and 14 days of differentiation, and osteogenic gene expression was examined by quantitative real-time polymerase chain reaction. For evaluation of in vivo osteogenesis, critical-sized (4-mm) calvarial defects in nude mice were treated with the hydroxyapatite-poly(lactic-co-glycolic acid) scaffold seeded with the above-mentioned subpopulations. Healing was followed using micro-CT scans for 8 weeks. Calvaria were harvested at 8 weeks postoperatively, and sections were stained with Movat's Pentachrome.Transcriptional analysis revealed that the CD90(+) subpopulation was enriched for a more osteogenic subtype relative to the CD105(low) subpopulation. Staining at day 7 for ALP was greatest in the CD90(+) cells, followed by the CD105(low) cells. Staining at day 14 for alizarin red demonstrated the greatest amount of mineralized extracellular matrix in the CD90(+) cells, again followed by the CD105(low) cells. Quantification of in vivo healing at 2, 4, 6, and 8weeks postoperatively demonstrated increased bone formation in defects treated with CD90(+) ASCs relative to all other groups. On Movat's Pentachrome-stained sections, defects treated with CD90(+) cells showed the most robust bony regeneration. Defects treated with CD90(-) cells, CD105(high) cells, and CD105(low) cells demonstrated some bone formation, but to a lesser degree when compared with the CD90(+) group.While CD105(low) cells have previously been shown to possess an enhanced osteogenic potential, we found that CD90(+) cells are more capable of forming bone both in vitro and in vivo. These data therefore suggest that CD90 may be a more effective marker than CD105 to isolate a highly osteogenic subpopulation for bone tissue engineering.

  View details for DOI 10.1089/ten.tea.2012.0370

  View details for PubMedID 23216074

• Integration of Multiple Signaling Regulates through Apoptosis the Differential Osteogenic Potential of Neural Crest-Derived and Mesoderm-Derived Osteoblasts PLOS ONE Li, S., Meyer, N. P., Quarto, N., Longaker, M. T. 2013; 8 (3)

  Abstract

  Neural crest-derived (FOb) and mesoderm-derived (POb) calvarial osteoblasts are characterized by distinct differences in their osteogenic potential. We have previously demonstrated that enhanced activation of endogenous FGF and Wnt signaling confers greater osteogenic potential to FOb. Apoptosis, a key player in bone formation, is the main focus of this study. In the current work, we have investigated the apoptotic activity of FOb and POb cells during differentiation. We found that lower apoptosis, as measured by caspase-3 activity is a major feature of neural crest-derived osteoblast which also have higher osteogenic capacity. Further investigation indicated TGF-β signaling as main positive regulator of apoptosis in these two populations of calvarial osteoblasts, while BMP and canonical Wnt signaling negatively regulate the process. By either inducing or inhibiting these signaling pathways we could modulate apoptotic events and improve the osteogenic potential of POb. Taken together, our findings demonstrate that integration of multiple signaling pathways contribute to imparting greater osteogenic potential to FOb by decreasing apoptosis.

  View details for DOI 10.1371/journal.pone.0058610

  View details for Web of Science ID 000317397200008

  View details for PubMedID 23536803

  View details for PubMedCentralID PMC3607600

• Micro-Computed Tomography Evaluation of Human Fat Grafts in Nude Mice TISSUE ENGINEERING PART C-METHODS Chung, M. T., Hyun, J. S., Lo, D. D., Montoro, D. T., Hasegawa, M., Levi, B., Januszyk, M., Longaker, M. T., Wan, D. C. 2013; 19 (3): 227-232

  Abstract

  Although autologous fat grafting has revolutionized the field of soft tissue reconstruction and augmentation, long-term maintenance of fat grafts is unpredictable. Recent studies have reported survival rates of fat grafts to vary anywhere between 10% and 80% over time. The present study evaluated the long-term viability of human fat grafts in a murine model using a novel imaging technique allowing for in vivo volumetric analysis.Human fat grafts were prepared from lipoaspirate samples using the Coleman technique. Fat was injected subcutaneously into the scalp of 10 adult Crl:NU-Foxn1(nu) CD-1 male mice. Micro-computed tomography (CT) was performed immediately following injection and then weekly thereafter. Fat volume was rendered by reconstructing a three-dimensional (3D) surface through cubic-spline interpolation. Specimens were also harvested at various time points and sections were prepared and stained with hematoxylin and eosin (H&E), for macrophages using CD68 and for the cannabinoid receptor 1 (CB1). Finally, samples were explanted at 8- and 12-week time points to validate calculated micro-CT volumes.Weekly CT scanning demonstrated progressive volume loss over the time course. However, volumetric analysis at the 8- and 12-week time points stabilized, showing an average of 62.2% and 60.9% survival, respectively. Gross analysis showed the fat graft to be healthy and vascularized. H&E analysis and staining for CD68 showed minimal inflammatory reaction with viable adipocytes. Immunohistochemical staining with anti-human CB1 antibodies confirmed human origin of the adipocytes.Studies assessing the fate of autologous fat grafts in animals have focused on nonimaging modalities, including histological and biochemical analyses, which require euthanasia of the animals. In this study, we have demonstrated the ability to employ micro-CT for 3D reconstruction and volumetric analysis of human fat grafts in a mouse model. Importantly, this model provides a platform for subsequent study of fat manipulation and soft tissue engineering.

  View details for DOI 10.1089/ten.tec.2012.0371

  View details for Web of Science ID 000314179900006

  View details for PubMedID 22916732

  View details for PubMedCentralID PMC3557441

• Primary cilia act as mechanosensors during bone healing around an implant MEDICAL ENGINEERING & PHYSICS Leucht, P., Monica, S. D., Temiyasathit, S., Lenton, K., Manu, A., Longaker, M. T., Jacobs, C. R., Spilkere, R. L., Guo, H., Brunski, J. B., Helms, J. A. 2013; 35 (3): 392-402

  Abstract

  The primary cilium is an organelle that senses cues in a cell's local environment. Some of these cues constitute molecular signals; here, we investigate the extent to which primary cilia can also sense mechanical stimuli. We used a conditional approach to delete Kif3a in pre-osteoblasts and then employed a motion device that generated a spatial distribution of strain around an intra-osseous implant positioned in the mouse tibia. We correlated interfacial strain fields with cell behaviors ranging from proliferation through all stages of osteogenic differentiation. We found that peri-implant cells in the Col1Cre;Kif3a(fl/fl) mice were unable to proliferate in response to a mechanical stimulus, failed to deposit and then orient collagen fibers to the strain fields caused by implant displacement, and failed to differentiate into bone-forming osteoblasts. Collectively, these data demonstrate that the lack of a functioning primary cilium blunts the normal response of a cell to a defined mechanical stimulus. The ability to manipulate the genetic background of peri-implant cells within the context of a whole, living tissue provides a rare opportunity to explore mechanotransduction from a multi-scale perspective.

  View details for DOI 10.1016/j.medengphy.2012.06.005

  View details for Web of Science ID 000315931400013

  View details for PubMedID 22784673

  View details for PubMedCentralID PMC3517784

• Integration of Multiple Signaling Pathways Determines Differences in the Osteogenic Potential and Tissue Regeneration of Neural Crest-Derived and Mesoderm-Derived Calvarial Bone INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Senarath-Yapa, K., Li, S., Meyer, N. P., Longaker, M. T., Quarto, N. 2013; 14 (3): 5978-5997

  Abstract

  The mammalian skull vault, a product of a unique and tightly regulated evolutionary process, in which components of disparate embryonic origin are integrated, is an elegant model with which to study osteoblast biology. Our laboratory has demonstrated that this distinct embryonic origin of frontal and parietal bones confer differences in embryonic and postnatal osteogenic potential and skeletal regenerative capacity, with frontal neural crest derived osteoblasts benefitting from greater osteogenic potential. We outline how this model has been used to elucidate some of the molecular mechanisms which underlie these differences and place these findings into the context of our current understanding of the key, highly conserved, pathways which govern the osteoblast lineage including FGF, BMP, Wnt and TGFβ signaling. Furthermore, we explore recent studies which have provided a tantalizing insight into way these pathways interact, with evidence accumulating for certain transcription factors, such as Runx2, acting as a nexus for cross-talk.

  View details for DOI 10.3390/ijms14035978

  View details for Web of Science ID 000316609800086

  View details for PubMedID 23502464

  View details for PubMedCentralID PMC3634461

• Commentary on the differential healing capacity of calvarial bone. journal of craniofacial surgery Lo, D. D., McArdle, A., Senarath-Yapa, K., Longaker, M. T. 2013; 24 (2): 344-345

  View details for DOI 10.1097/SCS.0b013e3182802256

  View details for PubMedID 23524689

• Effective Delivery of Stem Cells Using an Extracellular Matrix Patch Results in Increased Cell Survival and Proliferation and Reduced Scarring in Skin Wound Healing TISSUE ENGINEERING PART A Lam, M. T., Nauta, A., Meyer, N. P., Wu, J. C., Longaker, M. T. 2013; 19 (5-6): 738-747

  Abstract

  Wound healing is one of the most complex biological processes and occurs in all tissues and organs of the body. In humans, fibrotic tissue, or scar, hinders function and is aesthetically unappealing. Stem cell therapy offers a promising new technique for aiding in wound healing; however, current findings show that stem cells typically die and/or migrate from the wound site, greatly decreasing efficacy of the treatment. Here, we demonstrate effectiveness of a stem cell therapy for improving wound healing in the skin and reducing scarring by introducing stem cells using a natural patch material. Adipose-derived stromal cells were introduced to excisional wounds created in mice using a nonimmunogenic extracellular matrix (ECM) patch material derived from porcine small-intestine submucosa (SIS). The SIS served as an attractive delivery vehicle because of its natural ECM components, including its collagen fiber network, providing the stem cells with a familiar structure. Experimental groups consisted of wounds with stem cell-seeded patches removed at different time points after wounding to determine an optimal treatment protocol. Stem cells delivered alone to skin wounds did not survive post-transplantation as evidenced by bioluminescence in vivo imaging. In contrast, delivery with the patch enabled a significant increase in stem cell proliferation and survival. Wound healing rates were moderately improved by treatment with stem cells on the patch; however, areas of fibrosis, indicating scarring, were significantly reduced in wounds treated with the stem cells on the patch compared to untreated wounds.

  View details for DOI 10.1089/ten.tea.2012.0480

  View details for Web of Science ID 000314581100015

  View details for PubMedID 23072446

  View details for PubMedCentralID PMC3566655

• Adipose-derived Stromal Cells Overexpressing Vascular Endothelial Growth Factor Accelerate Mouse Excisional Wound Healing MOLECULAR THERAPY Nauta, A., Seidel, C., Deveza, L., Montoro, D., Grova, M., Ko, S. H., Hyun, J., Gurtner, G. C., Longaker, M. T., Yang, F. 2013; 21 (2): 445-455

  Abstract

  Angiogenesis is essential to wound repair, and vascular endothelial growth factor (VEGF) is a potent factor to stimulate angiogenesis. Here, we examine the potential of VEGF-overexpressing adipose-derived stromal cells (ASCs) for accelerating wound healing using nonviral, biodegradable polymeric vectors. Mouse ASCs were transfected with DNA plasmid encoding VEGF or green fluorescent protein (GFP) using biodegradable poly (β-amino) esters (PBAE). Cells transfected using Lipofectamine 2000, a commercially available transfection reagent, were included as controls. ASCs transfected using PBAEs showed enhanced transfection efficiency and 12-15-fold higher VEGF production compared with cells transfected using Lipofectamine 2000 (*P < 0.05). When transplanted into a mouse wild-type excisional wound model, VEGF-overexpressing ASCs led to significantly accelerated wound healing, with full wound closure observed at 8 days compared to 10-12 days in groups treated with ASCs alone or saline control (*P < 0.05). Histology and polarized microscopy showed increased collagen deposition and more mature collagen fibers in the dermis of wound beds treated using PBAE/VEGF-modified ASCs than ASCs alone. Our results demonstrate the efficacy of using nonviral-engineered ASCs to accelerate wound healing, which may provide an alternative therapy for treating many diseases in which wound healing is impaired.

  View details for DOI 10.1038/mt.2012.234

  View details for Web of Science ID 000314434600021

  View details for PubMedID 23164936

  View details for PubMedCentralID PMC3594010

• Discussion: A report of the ASPS Task Force on regenerative medicine: opportunities for plastic surgery. Plastic and reconstructive surgery McArdle, A., Lo, D. D., Hyun, J. S., Senarath-Yapa, K., Chung, M. T., Wan, D. C., Longaker, M. T. 2013; 131 (2): 400-403

  View details for DOI 10.1097/PRS.0b013e318278d88c

  View details for PubMedID 23358002

• The Seed and the Soil Optimizing Stem Cells and Their Environment for Tissue Regeneration ANNALS OF PLASTIC SURGERY Hyun, J. S., Montoro, D. T., Lo, D. D., Flynn, R. A., Wong, V., Chung, M. T., Longaker, M. T., Wan, D. C. 2013; 70 (2): 235-239

  Abstract

  The potential for stem cells to serve as cellular building blocks for reconstruction of complex defects has prompted significant enthusiasm in the field of regenerative medicine. Clinical application, however, is still limited, as implantation of cells into hostile wound environments may greatly hinder their tissue forming capacity. To circumvent this obstacle, novel approaches have been developed to manipulate both the stem cell itself and its surrounding environmental niche. By understanding this paradigm of seed and soil optimization, innovative strategies may thus be developed to harness the true promise of stem cells for tissue regeneration.

  View details for DOI 10.1097/SAP.0b013e31826a18fb

  View details for Web of Science ID 000313964300024

  View details for PubMedID 23295233

• Abnormal Calcium Handling Properties Underlie Familial Hypertrophic Cardiomyopathy Pathology in Patient-Specific Induced Pluripotent Stem Cells CELL STEM CELL Lan, F., Lee, A. S., Liang, P., Sanchez-Freire, V., Nguyen, P. K., Wang, L., Han, L., Yen, M., Wang, Y., Sun, N., Abilez, O. J., Hu, S., Ebert, A. D., Navarrete, E. G., Simmons, C. S., Wheeler, M., Pruitt, B., Lewis, R., Yamaguchi, Y., Ashley, E. A., Bers, D. M., Robbins, R. C., Longaker, M. T., Wu, J. C. 2013; 12 (1): 101-113

  Abstract

  Familial hypertrophic cardiomyopathy (HCM) is a prevalent hereditary cardiac disorder linked to arrhythmia and sudden cardiac death. While the causes of HCM have been identified as genetic mutations in the cardiac sarcomere, the pathways by which sarcomeric mutations engender myocyte hypertrophy and electrophysiological abnormalities are not understood. To elucidate the mechanisms underlying HCM development, we generated patient-specific induced pluripotent stem cell cardiomyocytes (iPSC-CMs) from a ten-member family cohort carrying a hereditary HCM missense mutation (Arg663His) in the MYH7 gene. Diseased iPSC-CMs recapitulated numerous aspects of the HCM phenotype including cellular enlargement and contractile arrhythmia at the single-cell level. Calcium (Ca(2+)) imaging indicated dysregulation of Ca(2+) cycling and elevation in intracellular Ca(2+) ([Ca(2+)](i)) are central mechanisms for disease pathogenesis. Pharmacological restoration of Ca(2+) homeostasis prevented development of hypertrophy and electrophysiological irregularities. We anticipate that these findings will help elucidate the mechanisms underlying HCM development and identify novel therapies for the disease.

  View details for DOI 10.1016/j.stem.2012.10.010

  View details for Web of Science ID 000313839500014

  View details for PubMedID 23290139

  View details for PubMedCentralID PMC3638033

• Evidence that mast cells are not required for healing of splinted cutaneous excisional wounds in mice. PloS one Nauta, A. C., Grova, M., Montoro, D. T., Zimmermann, A., Tsai, M., Gurtner, G. C., Galli, S. J., Longaker, M. T. 2013; 8 (3)

  Abstract

  Wound healing is a complex biological process involving the interaction of many cell types to replace lost or damaged tissue. Although the biology of wound healing has been extensively investigated, few studies have focused on the role of mast cells. In this study, we investigated the possible role of mast cells in wound healing by analyzing aspects of cutaneous excisional wound healing in three types of genetically mast cell-deficient mice. We found that C57BL/6-Kit(W-sh/W-sh), WBB6F1-Kit(W/W-v), and Cpa3-Cre; Mcl-1(fl/fl) mice re-epithelialized splinted excisional skin wounds at rates very similar to those in the corresponding wild type or control mice. Furthermore, at the time of closure, scars were similar in the genetically mast cell-deficient mice and the corresponding wild type or control mice in both quantity of collagen deposition and maturity of collagen fibers, as evaluated by Masson's Trichrome and Picro-Sirius red staining. These data indicate that mast cells do not play a significant non-redundant role in these features of the healing of splinted full thickness excisional cutaneous wounds in mice.

  View details for DOI 10.1371/journal.pone.0059167

  View details for PubMedID 23544053

  View details for PubMedCentralID PMC3609818

• STEM CELL-BASED BIOENGINEERING OF CRANIOFACIAL BONE STEM CELLS IN CRANIOFACIAL DEVELOPMENT AND REGENERATION Lo, D. D., Montoro, D. T., Grova, M., Hyun, J. S., Chung, M. T., Wan, D. C., Longaker, M. T., Huang, G. T., Thesleff 2013: 379–94

  View details for Web of Science ID 000327996200022

• Murine models of human wound healing. Methods in molecular biology (Clifton, N.J.) Chen, J. S., Longaker, M. T., Gurtner, G. C. 2013; 1037: 265-274

  Abstract

  In vivo wound healing experiments remain the most predictive models for studying human wound healing, allowing an accurate representation of the complete wound healing environment including various cell types, environmental cues, and paracrine interactions. Small animals are economical, easy to maintain, and allow researchers to take advantage of the numerous transgenic strains that have been developed to investigate the specific mechanisms involved in wound healing and regeneration. Here we describe three reproducible murine wound healing models that recapitulate the human wound healing process.

  View details for DOI 10.1007/978-1-62703-505-7_15

  View details for PubMedID 24029941

• Adult stem cells in small animal wound healing models. Methods in molecular biology (Clifton, N.J.) Nauta, A. C., Gurtner, G. C., Longaker, M. T. 2013; 1037: 81-98

  Abstract

  This chapter broadly reviews the use of stem cells as a means to accelerate wound healing, focusing first on the properties of stem cells that make them attractive agents to influence repair, both alone and as vehicles for growth factor delivery. Major stem cell reservoirs are described, including adult, embryonic, and induced pluripotent cell sources, outlining the advantages and limitations of each source as wound healing agents, as well as the possible mechanisms responsible for wound healing acceleration. Finally, the chapter includes a materials and methods section that provides an in-depth description of adult tissue harvest techniques.

  View details for DOI 10.1007/978-1-62703-505-7_5

  View details for PubMedID 24029931

• Absence of endochondral ossification and craniosynostosis in posterior frontal cranial sutures of axin2(-/-) mice. PloS one Behr, B., Longaker, M. T., Quarto, N. 2013; 8 (8)

  Abstract

  During the first month of life, the murine posterior-frontal suture (PF) of the cranial vault closes through endochondral ossification, while other sutures remain patent. These processes are tightly regulated by canonical Wnt signaling. Low levels of active canonical Wnt signaling enable endochondral ossification and therefore PF-suture closure, whereas constitutive activation of canonical Wnt causes PF-suture patency. We therefore sought to test this concept with a knockout mouse model. PF-sutures of Axin2(-/-) mice, which resemble a state of constantly activated canonical Wnt signaling, were investigated during the physiological time course of PF-suture closure and compared in detail with wild type littermates. Histological analysis revealed that the architecture in Axin2(-/-) PF-sutures was significantly altered in comparison to wild type. The distance between the endocranial layers was dramatically increased and suture closure was significantly delayed. Moreover, physiological endochondral ossification did not occur, rather an ectopic cartilage appeared between the endocranial and ectocranial bone layers at P7 which eventually involutes at P13. Quantitative PCR analysis showed the lack of Col10α1 upregulation in Axin2(-/-) PF-suture. Immunohistochemistry and gene expression analysis also revealed high levels of type II collagen as compared to type I collagen and absence of Mmp-9 in the cartilage of Axin2(-/-) PF-suture. Moreover, TUNEL staining showed a high percentage of apoptotic chondrocytes in Axin2(-/-) PF-sutures at P9 and P11 as compared to wild type. These data indicated that Axin2(-/-) PF-sutures lack physiological endochondral ossification, contain ectopic cartilage and display delayed suture closure.

  View details for DOI 10.1371/journal.pone.0070240

  View details for PubMedID 23936395

  View details for PubMedCentralID PMC3731366

• In vivo directed differentiation of pluripotent stem cells for skeletal regeneration PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Levi, B., Hyun, J. S., Montoro, D. T., Lo, D. D., Chan, C. K., Hu, S., Sun, N., Lee, M., Grova, M., Connolly, A. J., Wu, J. C., Gurtner, G. C., Weissman, I. L., Wan, D. C., Longaker, M. T. 2012; 109 (50): 20379-20384

  Abstract

  Pluripotent cells represent a powerful tool for tissue regeneration, but their clinical utility is limited by their propensity to form teratomas. Little is known about their interaction with the surrounding niche following implantation and how this may be applied to promote survival and functional engraftment. In this study, we evaluated the ability of an osteogenic microniche consisting of a hydroxyapatite-coated, bone morphogenetic protein-2-releasing poly-L-lactic acid scaffold placed within the context of a macroenvironmental skeletal defect to guide in vivo differentiation of both embryonic and induced pluripotent stem cells. In this setting, we found de novo bone formation and participation by implanted cells in skeletal regeneration without the formation of a teratoma. This finding suggests that local cues from both the implanted scaffold/cell micro- and surrounding macroniche may act in concert to promote cellular survival and the in vivo acquisition of a terminal cell fate, thereby allowing for functional engraftment of pluripotent cells into regenerating tissue.

  View details for DOI 10.1073/pnas.1218052109

  View details for PubMedID 23169671

• Femtosecond plasma mediated laser ablation has advantages over mechanical osteotomy of cranial bone LASERS IN SURGERY AND MEDICINE Lo, D. D., Mackanos, M. A., Chung, M. T., Hyun, J. S., Montoro, D. T., Grova, M., Liu, C., Wang, J., Palanker, D., Connolly, A. J., Longaker, M. T., Contag, C. H., Wan, D. C. 2012; 44 (10): 805-814

  Abstract

  Although mechanical osteotomies are frequently made on the craniofacial skeleton, collateral thermal, and mechanical trauma to adjacent bone tissue causes cell death and may delay healing. The present study evaluated the use of plasma-mediated laser ablation using a femtosecond laser to circumvent thermal damage and improve bone regeneration.Critical-size circular calvarial defects were created with a trephine drill bit or with a Ti:Sapphire femtosecond pulsed laser. Healing was followed using micro-CT scans for 8 weeks. Calvaria were also harvested at various time points for histological analysis. Finally, scanning electron microscopy was used to analyze the microstructure of bone tissue treated with the Ti:Sapphire laser, and compared to that treated with the trephine bur.Laser-created defects healed significantly faster than those created mechanically at 2, 4, and 6 weeks post-surgery. However, at 8 weeks post-surgery, there was no significant difference. In the drill osteotomy treatment group, empty osteocyte lacunae were seen to extend 699 ± 27 µm away from the edge of the defect. In marked contrast, empty osteocyte lacunae were seen to extend only 182 ± 22 µm away from the edge of the laser-created craters. Significantly less ossification and formation of irregular woven bone was noted on histological analysis for drill defects.We demonstrate accelerated bone healing after femtosecond laser ablation in a calvarial defect model compared to traditional mechanical drilling techniques. Improved rates of early regeneration make plasma-mediated ablation of the craniofacial skeleton advantageous for applications to osteotomy.

  View details for DOI 10.1002/lsm.22098

  View details for Web of Science ID 000312941600004

  View details for PubMedID 23184427

• Exogenous Activation of BMP-2 Signaling Overcomes TGF beta-Mediated Inhibition of Osteogenesis in Marfan Embryonic Stem Cells and Marfan Patient-Specific Induced Pluripotent Stem Cells STEM CELLS Quarto, N., Li, S., Renda, A., Longaker, M. T. 2012; 30 (12): 2709-2719

  Abstract

  Marfan syndrome (MFS) is a hereditary disease caused by mutations in the gene encoding Fibrillin-1 (FBN1) and characterized by a number of skeletal abnormalities, aortic root dilatation, and sometimes ectopia lentis. Although the molecular pathogenesis of MFS was attributed initially to a structural weakness of the fibrillin-rich microfibrils within the extracellular matrix, more recent results have documented that many of the pathogenic abnormalities in MFS are the result of alterations in TGFβ signaling. Mutations in FBN1 are therefore associated with increased activity and bioavailability of TGF-β1, which is suspected to be the basis for phenotypical similarities of FBN1 mutations in MFS and mutations in the receptors for TGFβ in Marfan syndrome-related diseases. We have previously demonstrated that unique skeletal phenotypes observed in human embryonic stem cells carrying the monogenic FBN1 mutation (MFS cells) are faithfully phenocopied by cells differentiated from induced pluripotent-stem cells (MFSiPS) derived independently from MFS patient fibroblasts. In this study, we aimed to determine further the biochemical features of transducing signaling(s) in MFS stem cells and MFSiPS cells highlighting a crosstalk between TGFβ and BMP signaling. Our results revealed that enhanced activation of TGFβ signaling observed in MFS cells decreased their endogenous BMP signaling. Moreover, exogenous BMP antagonized the enhanced TGFβ signaling in both MFS stem cells and MFSiPS cells therefore, rescuing their ability to undergo osteogenic differentiation. This study advances our understanding of molecular mechanisms underlying the pathogenesis of bone loss/abnormal skeletogenesis in human diseases caused by mutations in FBN1.

  View details for DOI 10.1002/stem.1250

  View details for PubMedID 23037987

• Introduction: Wound repair SEMINARS IN CELL & DEVELOPMENTAL BIOLOGY Longaker, M. T. 2012; 23 (9): 945-945

  View details for DOI 10.1016/j.semcdb.2012.10.002

  View details for Web of Science ID 000311962800001

  View details for PubMedID 23059792

• Soft tissue mechanotransduction in wound healing and fibrosis SEMINARS IN CELL & DEVELOPMENTAL BIOLOGY Wong, V. W., Longaker, M. T., Gurtner, G. C. 2012; 23 (9): 981-986

  Abstract

  Recent evidence suggests that mechanical forces can significantly impact the biologic response to injury. Integrated mechanical and chemical signaling networks have been discovered that enable physical cues to regulate disease processes such as pathologic scar formation. Distinct molecular mechanisms control how tensional forces influence wound healing and fibrosis. Conceptual frameworks to understand cutaneous repair have expanded beyond traditional cell-cytokine models to include dynamic interactions driven by mechanical force and the extracellular matrix. Strategies to manipulate these biomechanical signaling networks have tremendous therapeutic potential to reduce scar formation and promote skin regeneration.

  View details for DOI 10.1016/j.semcdb.2012.09.010

  View details for Web of Science ID 000311962800006

  View details for PubMedID 23036529

• Comparison of several attachment methods for human iPS, embryonic and adipose-derived stem cells for tissue engineering JOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE Lam, M. T., Longaker, M. T. 2012; 6: s80-s86

  Abstract

  As actual stem cell application quickly approaches tissue engineering and regenerative medicine, aspects such as cell attachment to scaffolds and biomaterials become important and are often overlooked. Here, we compare the effects of several attachment proteins on the adhesion, proliferation and stem cell identity of three promising human stem cell types: human adipose-derived stem cells (hASCs), human embryonic stem cells (hESCs) and human induced pluripotent stem cells (hiPSCs). Traditional tissue culture polystyrene plates (TCPS), Matrigel (Mat), laminin (Lam), fibronectin (FN) and poly-L-lysine (PLL) were investigated as attachment protein surfaces. For hASCs typically cultured on TCPS, laminin resulted in the greatest cell attachment and proliferation with largest cell areas, indicating favourability by cell spreading. However, mesenchymal stem cell markers indicative of hASCs were slightly more expressed on surfaces with lowest cell attachment, corresponding to increased cell roundness, a newly observed attribute in hASCs possibly indicating a more stem cell-like character. hESCs preferred Matrigel as a feeder-free culture surface. Interestingly, hiPSCs favoured laminin over Matrigel for colony expansion, shown by larger cell colony area and perimeter lengths, although cell numbers and stem cell marker expression level remained highest on Matrigel. These data provide a practical reference guide for selecting a suitable attachment method for using human induced pluripotent, embryonic or adipose stem cells in tissue engineering and regenerative medicine applications.

  View details for DOI 10.1002/term.1499

  View details for Web of Science ID 000313431100009

  View details for PubMedID 22610948

• Microfluidic Single Cell Analysis Shows Porcine Induced Pluripotent Stem Cell-Derived Endothelial Cells Improve Myocardial Function by Paracrine Activation Gu, M., Nguyen, P., Hu, S., Plews, J. R., Lee, A. S., Huber, B. C., Lee, W., Gong, Y., Almeida, P. E., Connolly, A., Robbins, R. C., Longaker, M. T., Wu, J. C. LIPPINCOTT WILLIAMS & WILKINS. 2012

  View details for Web of Science ID 000208885005075

• Models of cranial suture biology. journal of craniofacial surgery Grova, M., Lo, D. D., Montoro, D., Hyun, J. S., Chung, M. T., Wan, D. C., Longaker, M. T. 2012; 23 (7): 1954-1958

  Abstract

  Craniosynostosis is a common congenital defect caused by premature fusion of cranial sutures. The severe morphologic abnormalities and cognitive deficits resulting from craniosynostosis and the potential morbidity of surgical correction espouse the need for a deeper understanding of the complex etiology for this condition. Work in animal models for the past 20 years has been pivotal in advancing our understanding of normal suture biology and elucidating pathologic disease mechanisms. This article provides an overview of milestone studies in suture development, embryonic origins, and signaling mechanisms from an array of animal models including transgenic mice, rats, rabbits, fetal sheep, zebrafish, and frogs. This work contributes to an ongoing effort toward continued development of novel treatment strategies.

  View details for DOI 10.1097/SCS.0b013e318258ba53

  View details for PubMedID 23154351

• Models of Cranial Suture Biology JOURNAL OF CRANIOFACIAL SURGERY Grova, M., Lo, D. D., Montoro, D., Hyun, J. S., Chung, M. T., Wan, D. C., Longaker, M. T. 2012; 23: 1954-1958

  Abstract

  Craniosynostosis is a common congenital defect caused by premature fusion of cranial sutures. The severe morphologic abnormalities and cognitive deficits resulting from craniosynostosis and the potential morbidity of surgical correction espouse the need for a deeper understanding of the complex etiology for this condition. Work in animal models for the past 20 years has been pivotal in advancing our understanding of normal suture biology and elucidating pathologic disease mechanisms. This article provides an overview of milestone studies in suture development, embryonic origins, and signaling mechanisms from an array of animal models including transgenic mice, rats, rabbits, fetal sheep, zebrafish, and frogs. This work contributes to an ongoing effort toward continued development of novel treatment strategies.

  View details for DOI 10.1097/SCS.0b013e318258ba53

  View details for Web of Science ID 000209481500006

• Pierre Robin Sequence and Treacher Collins Hypoplastic Mandible Comparison Using Three-Dimensional Morphometric Analysis JOURNAL OF CRANIOFACIAL SURGERY Chung, M. T., Levi, B., Hyun, J. S., Lo, D. D., Montoro, D. T., Lisiecki, J., Bradley, J. P., Buchman, S. R., Longaker, M. T., Wan, D. C. 2012; 23: 1959-1963

  Abstract

  Pierre Robin sequence and Treacher Collins syndrome are both associated with mandibular hypoplasia. It has been hypothesized, however, that the mandible may be differentially affected. The purpose of this study was to therefore compare mandibular morphology in children with Pierre Robin sequence with children with Treacher Collins syndrome using three-dimensional analysis of computed tomographic scans. A retrospective analysis was performed identifying children with Pierre Robin sequence and Treacher Collins syndrome undergoing computed tomography. Three-dimensional reconstruction was performed, and ramus height, mandibular body length, and gonial angle were measured. These were then compared with those in control children with normal mandibles and with the clinical norms corrected for age and sex based on previously published measurements. Mandibular body length was found to be significantly shorter for children with Pierre Robin sequence, whereas ramus height was significantly shorter for children with Treacher Collins syndrome. This resulted in distinctly different ramus height-mandibular body length ratios. In addition, the gonial angle was more obtuse in both the Pierre Robin sequence and Treacher Collins syndrome groups compared with the controls. Three-dimensional mandibular morphometric analysis in patients with Pierre Robin sequence and Treacher Collins syndrome thus revealed distinctly different patterns of mandibular hypoplasia relative to normal controls. These findings underscore distinct considerations that must be made in surgical planning for reconstruction.

  View details for DOI 10.1097/SCS.0b013e318258bcf1

  View details for Web of Science ID 000209481500007

  View details for PubMedCentralID PMC3544559

• Pierre Robin sequence and Treacher Collins hypoplastic mandible comparison using three-dimensional morphometric analysis. journal of craniofacial surgery Chung, M. T., Levi, B., Hyun, J. S., Lo, D. D., Montoro, D. T., Lisiecki, J., Bradley, J. P., Buchman, S. R., Longaker, M. T., Wan, D. C. 2012; 23 (7): 1959-1963

  Abstract

  Pierre Robin sequence and Treacher Collins syndrome are both associated with mandibular hypoplasia. It has been hypothesized, however, that the mandible may be differentially affected. The purpose of this study was to therefore compare mandibular morphology in children with Pierre Robin sequence with children with Treacher Collins syndrome using three-dimensional analysis of computed tomographic scans. A retrospective analysis was performed identifying children with Pierre Robin sequence and Treacher Collins syndrome undergoing computed tomography. Three-dimensional reconstruction was performed, and ramus height, mandibular body length, and gonial angle were measured. These were then compared with those in control children with normal mandibles and with the clinical norms corrected for age and sex based on previously published measurements. Mandibular body length was found to be significantly shorter for children with Pierre Robin sequence, whereas ramus height was significantly shorter for children with Treacher Collins syndrome. This resulted in distinctly different ramus height-mandibular body length ratios. In addition, the gonial angle was more obtuse in both the Pierre Robin sequence and Treacher Collins syndrome groups compared with the controls. Three-dimensional mandibular morphometric analysis in patients with Pierre Robin sequence and Treacher Collins syndrome thus revealed distinctly different patterns of mandibular hypoplasia relative to normal controls. These findings underscore distinct considerations that must be made in surgical planning for reconstruction.

  View details for DOI 10.1097/SCS.0b013e318258bcf1

  View details for PubMedID 23154353

  View details for PubMedCentralID PMC3544559

• Craniosynostosis: Molecular pathways and future pharmacologic therapy. Organogenesis Senarath-Yapa, K., Chung, M. T., McArdle, A., Wong, V. W., Quarto, N., Longaker, M. T., Wan, D. C. 2012; 8 (4)

  Abstract

  Craniosynostosis describes the premature fusion of one or more cranial sutures and can lead to dramatic manifestations in terms of appearance and functional impairment. Contemporary approaches for this condition are primarily surgical and are associated with considerable morbidity and mortality. The additional post-operative problems of suture refusion and bony relapse may also necessitate repeated surgeries with their own attendant risks. Therefore, a need exists to not only optimize current strategies but also to develop novel biological therapies which could obviate the need for surgery and potentially treat or even prevent premature suture fusion. Clinical studies of patients with syndromic craniosynostosis have provided some useful insights into the important signaling pathways and molecular events guiding suture fate. Furthermore, the highly conserved nature of craniofacial development between humans and other species have permitted more focused and step-wise elucidation of the molecular underpinnings of craniosynostosis. This review will describe the clinical manifestations of craniosynostosis, reflect on our understanding of syndromic and non-syndromic craniosynostoses and outline the different approaches that have been adopted in our laboratory and elsewhere to better understand the pathogenesis of premature suture fusion. Finally, we will assess to what extent our improved understanding of the pathogenesis of craniosynostosis, achieved through laboratory-based and clinical studies, have made the possibility of a non-surgical pharmacological approach both realistic and tangible.

  View details for PubMedID 23249483

• Repair of a Critical-sized Calvarial Defect Model Using Adipose-derived Stromal Cells Harvested from Lipoaspirate JOVE-JOURNAL OF VISUALIZED EXPERIMENTS Lo, D. D., Hyun, J. S., Chung, M. T., Montoro, D. T., Zimmermann, A., Grova, M. M., Lee, M., Wan, D. C., Longaker, M. T. 2012

  View details for DOI 10.3791/4221

  View details for Web of Science ID 000209225700022

• Craniosynostosis Molecular pathways and future pharmacologic therapy ORGANOGENESIS Senarath-Yapa, K., Chung, M. T., McArdle, A., Wong, V. W., Quarto, N., Longaker, M. T., Wan, D. C. 2012; 8 (4): 103-113

  View details for DOI 10.4161/org.23307

  View details for Web of Science ID 000314500600002

• Regenerative Surgery: Tissue Engineering in General Surgical Practice WORLD JOURNAL OF SURGERY Wong, V. W., Wan, D. C., Gurtner, G. C., Longaker, M. T. 2012; 36 (10): 2288-2299

  Abstract

  Tissue engineering is a broad interdisciplinary field that aims to develop complex tissue and organ constructs through a combination of cell-, biomaterial-, and molecular-based approaches. This approach has the potential to transform the surgical treatment for diseases including trauma, cancer, and congenital malformations. A fundamental knowledge of key concepts in regenerative medicine is imperative for surgeons to maintain a leading role in developing and implementing these technologies. Researchers have started to elucidate the biologic mechanisms that maintain organ homeostasis throughout life, indicating that humans may have the latent capacity to regenerate complex tissues. By exploiting this intrinsic potential of the body, we can move even closer to developing functional, autologous replacement parts for a wide range of surgical diseases.

  View details for DOI 10.1007/s00268-012-1710-1

  View details for PubMedID 22777416

• Microfluidic Single-Cell Analysis Shows That Porcine Induced Pluripotent Stem Cell-Derived Endothelial Cells Improve Myocardial Function by Paracrine Activation CIRCULATION RESEARCH Gu, M., Nguyen, P. K., Lee, A. S., Xu, D., Hu, S., Plews, J. R., Han, L., Huber, B. C., Lee, W. H., Gong, Y., de Almeida, P. E., Lyons, J., Ikeno, F., Pacharinsak, C., Connolly, A. J., Gambhir, S. S., Robbins, R. C., Longaker, M. T., Wu, J. C. 2012; 111 (7): 882-893

  Abstract

  Induced pluripotent stem cells (iPSCs) hold great promise for the development of patient-specific therapies for cardiovascular disease. However, clinical translation will require preclinical optimization and validation of large-animal iPSC models.To successfully derive endothelial cells from porcine iPSCs and demonstrate their potential utility for the treatment of myocardial ischemia.Porcine adipose stromal cells were reprogrammed to generate porcine iPSCs (piPSCs). Immunohistochemistry, quantitative PCR, microarray hybridization, and angiogenic assays confirmed that piPSC-derived endothelial cells (piPSC-ECs) shared similar morphological and functional properties as endothelial cells isolated from the autologous pig aorta. To demonstrate their therapeutic potential, piPSC-ECs were transplanted into mice with myocardial infarction. Compared with control, animals transplanted with piPSC-ECs showed significant functional improvement measured by echocardiography (fractional shortening at week 4: 27.2±1.3% versus 22.3±1.1%; P<0.001) and MRI (ejection fraction at week 4: 45.8±1.3% versus 42.3±0.9%; P<0.05). Quantitative protein assays and microfluidic single-cell PCR profiling showed that piPSC-ECs released proangiogenic and antiapoptotic factors in the ischemic microenvironment, which promoted neovascularization and cardiomyocyte survival, respectively. Release of paracrine factors varied significantly among subpopulations of transplanted cells, suggesting that transplantation of specific cell populations may result in greater functional recovery.In summary, this is the first study to successfully differentiate piPSCs-ECs from piPSCs and demonstrate that transplantation of piPSC-ECs improved cardiac function after myocardial infarction via paracrine activation. Further development of these large animal iPSC models will yield significant insights into their therapeutic potential and accelerate the clinical translation of autologous iPSC-based therapy.

  View details for DOI 10.1161/CIRCRESAHA.112.269001

  View details for PubMedID 22821929

• Scarless fetal skin wound healing update BIRTH DEFECTS RESEARCH PART C-EMBRYO TODAY-REVIEWS Lo, D. D., Zimmermann, A. S., Nauta, A., Longaker, M. T., Lorenz, H. P. 2012; 96 (3): 237-247

  Abstract

  Scar formation, a physiologic process in adult wound healing, can have devastating effects for patients; a multitude of pathologic outcomes, affecting all organ systems, stems from an amplification of this process. In contrast to adult wound repair, the early-gestation fetal skin wound heals without scar formation, a phenomenon that appears to be intrinsic to fetal skin. An intensive research effort has focused on unraveling the mechanisms that underlie scarless fetal wound healing in an attempt to improve the quality of healing in both children and adults. Unique properties of fetal cells, extracellular matrix, cytokine profile, and gene expression contribute to this scarless repair. Despite the great increase in knowledge gained over the past decades, the precise mechanisms regulating scarless fetal healing remain unknown. Herein, we describe the current proposed mechanisms underlying fetal scarless wound healing in an effort to recapitulate the fetal phenotype in the postnatal environment.

  View details for DOI 10.1002/bdrc.21018

  View details for Web of Science ID 000310475000003

  View details for PubMedID 23109319

• Fetal Mouse Skin Heals Scarlessly in a Chick Chorioallantoic Membrane Model System ANNALS OF PLASTIC SURGERY Carre, A. L., Larson, B. J., Knowles, J. A., Kawai, K., Longaker, M. T., Lorenz, H. P. 2012; 69 (1): 85-90

  Abstract

  In mammals, the early-gestation fetus has the regenerative ability to heal skin wounds without scar formation. This observation was first reported more than 3 decades ago, and has been confirmed in a number of in vivo animal models. Although an intensive research effort has focused on unraveling the mechanisms underlying scarless fetal wound repair, no suitable model of in vitro fetal skin healing has been developed. In this article, we report a novel model for the study of fetal wound healing. Fetal skin from gestational day 16.5 Balb/c mice (total gestation, 20 days) was grafted onto the chorioallantoic membrane of 12-day-old chicken embryos and cultured for up to 7 days. At 48 hours postengraftment, circular wounds (diameter = 1 mm) were made in the fetal skin using a rotating titanium sapphire laser (N = 45). The tissue was examined daily by visual inspection to look for signs of infection and ischemia. The grafts and the surrounding host tissue were examined histologically. In all fetal skin grafts, the wounds completely reepithelialized by postinjury day 7, with regeneration of the dermis. Fetal mouse skin xenografts transplanted onto the chorioallantoic membrane of fertilized chicken eggs provides a useful model for the study of fetal wound healing. This model can be used as an adjunct to traditional in vivo mammalian models of fetal repair.

  View details for DOI 10.1097/SAP.0b013e31822128a9

  View details for Web of Science ID 000305485200020

  View details for PubMedID 21712703

• Large animal induced pluripotent stem cells as pre-clinical models for studying human disease JOURNAL OF CELLULAR AND MOLECULAR MEDICINE Plews, J. R., Gu, M., Longaker, M. T., Wu, J. C. 2012; 16 (6): 1196-1202

  Abstract

  The path to induced pluripotency Discovery of a pan-species pluripotency network Animal iPSCs and disease modelling Issues with large animal iPSCs Conclusions The derivation of human embryonic stem cells and subsequently human induced pluripotent stem cells (iPSCs) has energized regenerative medicine research and enabled seemingly limitless applications. Although small animal models, such as mouse models, have played an important role in the progression of the field, typically, they are poor representations of the human disease phenotype. As an alternative, large animal models should be explored as a potentially better approach for clinical translation of cellular therapies. However, only fragmented information regarding the derivation, characterization and clinical usefulness of pluripotent large animal cells is currently available. Here, we briefly review the latest advances regarding the derivation and use of large animal iPSCs.

  View details for DOI 10.1111/j.1582-4934.2012.01521.x

  View details for Web of Science ID 000304468600005

  View details for PubMedID 22212700

  View details for PubMedCentralID PMC3340484

• Craniofacial Reconstruction With Induced Pluripotent Stem Cells JOURNAL OF CRANIOFACIAL SURGERY Wan, D. C., Wong, V. W., Longaker, M. T. 2012; 23 (3): 623-626

  View details for DOI 10.1097/SCS.0b013e318252f41b

  View details for Web of Science ID 000304479600041

  View details for PubMedID 22627398

  View details for PubMedCentralID PMC3544558

• Rethinking the Blastema PLASTIC AND RECONSTRUCTIVE SURGERY Hyun, J. S., Chung, M. T., Wong, V. W., Montoro, D., Longaker, M. T., Wan, D. C. 2012; 129 (5): 1097-1103

  Abstract

  The phenomenon of tissue regeneration has been well documented across many species. Although some possess the capacity to completely restore an entire amputated limb, others are limited to just the distal digit tip. Initiation of limb regeneration has been described to start with the formation of a blastema, the composition of which has long been thought to consist of undifferentiated pluripotent cells derived through the process of dedifferentiation. Competing theories have been proposed, however, including cellular contributions through transdifferentiation and tissue-specific stem cells. Recent studies have now begun to shed light on this controversy, demonstrating tissue resident stem cells to be an evolutionarily conserved measure for limb regeneration.

  View details for DOI 10.1097/PRS.0b013e31824a2c49

  View details for Web of Science ID 000303497300059

  View details for PubMedID 22544093

• A Comparative Analysis of the Osteogenic Effects of BMP-2, FGF-2, and VEGFA in a Calvarial Defect Model TISSUE ENGINEERING PART A Behr, B., Sorkin, M., Lehnhardt, M., Renda, A., Longaker, M. T., Quarto, N. 2012; 18 (9-10): 1079-1086

  Abstract

  The utilization of growth factors for bone regeneration is a widely studied field. Since the approval of bone morphogenetic protein-2 (BMP-2) for therapeutic use in humans, the concept of utilizing growth factors for bone regeneration in translational medicine has become even more attractive. Despite many studies published on individual growth factors in various bone models, comparative analysis is largely lacking. The aim of our study was to compare three different proosteogenic factors under identical in vivo conditions. Thus, we tested the bone regeneration capacity of the three different growth factors BMP-2, fibroblast growth factor-2 (FGF-2), and vascular endothelial growth factor A (VEGFA) in a calvarial defect model. We demonstrated that BMP-2 and VEGFA had similar bone healing capacities, resulting in complete calvarial healing as early as week 3. FGF-2 also showed a significantly higher bone regeneration capacity; however, the healing rate was lower than with BMP-2 and VEGFA. Interestingly, these findings were paralleled by an increased angiogenic response upon healing in BMP-2- and VEGFA-treated calvarial defects as compared with FGF-2. Immunohistochemistry for proliferating and osteoprogenitor cells revealed activity at different points after surgery among the groups. In conclusion, we demonstrated an efficient bone regeneration capacity of both BMP-2 and VEGFA, which was superior to FGF-2. Moreover, this study highlights the efficient bone regeneration of VEGFA, which was comparable with BMP-2. These data provide a valuable comparative analysis, which can be used to further optimize growth factor-based strategies in skeletal tissue engineering.

  View details for DOI 10.1089/ten.tea.2011.0537

  View details for Web of Science ID 000303540400019

  View details for PubMedID 22195699

  View details for PubMedCentralID PMC3338108

• Patient-Specific Induced Pluripotent Stem Cells as a Model for Familial Dilated Cardiomyopathy SCIENCE TRANSLATIONAL MEDICINE Sun, N., Yazawa, M., Liu, J., Han, L., Sanchez-Freire, V., Abilez, O. J., Navarrete, E. G., Hu, S., Wang, L., Lee, A., Pavlovic, A., Lin, S., Chen, R., Hajjar, R. J., Snyder, M. P., Dolmetsch, R. E., Butte, M. J., Ashley, E. A., Longaker, M. T., Robbins, R. C., Wu, J. C. 2012; 4 (130)

  Abstract

  Characterized by ventricular dilatation, systolic dysfunction, and progressive heart failure, dilated cardiomyopathy (DCM) is the most common form of cardiomyopathy in patients. DCM is the most common diagnosis leading to heart transplantation and places a significant burden on healthcare worldwide. The advent of induced pluripotent stem cells (iPSCs) offers an exceptional opportunity for creating disease-specific cellular models, investigating underlying mechanisms, and optimizing therapy. Here, we generated cardiomyocytes from iPSCs derived from patients in a DCM family carrying a point mutation (R173W) in the gene encoding sarcomeric protein cardiac troponin T. Compared to control healthy individuals in the same family cohort, cardiomyocytes derived from iPSCs from DCM patients exhibited altered regulation of calcium ion (Ca(2+)), decreased contractility, and abnormal distribution of sarcomeric α-actinin. When stimulated with a β-adrenergic agonist, DCM iPSC-derived cardiomyocytes showed characteristics of cellular stress such as reduced beating rates, compromised contraction, and a greater number of cells with abnormal sarcomeric α-actinin distribution. Treatment with β-adrenergic blockers or overexpression of sarcoplasmic reticulum Ca(2+) adenosine triphosphatase (Serca2a) improved the function of iPSC-derived cardiomyocytes from DCM patients. Thus, iPSC-derived cardiomyocytes from DCM patients recapitulate to some extent the morphological and functional phenotypes of DCM and may serve as a useful platform for exploring disease mechanisms and for drug screening.

  View details for DOI 10.1126/scitranslmed.3003552

  View details for Web of Science ID 000303045900004

  View details for PubMedID 22517884

  View details for PubMedCentralID PMC3657516

• Training the Contemporary Surgeon-Scientist PLASTIC AND RECONSTRUCTIVE SURGERY Wan, D. C., Wang, K. C., Longaker, M. T. 2012; 129 (4): 1023-1025

  View details for DOI 10.1097/PRS.0b013e31824421e8

  View details for Web of Science ID 000302227100076

  View details for PubMedID 22456371

• Delivery Strategies for Stem Cell-Based Therapy JOURNAL OF HEALTHCARE ENGINEERING Glotzbach, J. P., Wong, V. W., Levi, B., Longaker, M. T., Gurtner, G. C. 2012; 3 (1): 1-20

  View details for DOI 10.1260/2040-2295.3.1.1

  View details for Web of Science ID 000311674000001

• The angiogenic factor Dell prevents apoptosis of endothelial cells through integrin binding SURGERY Wang, Z., Kundu, R. K., Longaker, M. T., Quertermous, T., Yang, G. P. 2012; 151 (2): 296-305

  Abstract

  Del1 is a secreted protein that is expressed in the endothelium during development and can stimulate angiogenesis through integrin binding and signaling. We were interested in the specific effects of del1 on endothelial cell biology to gain insight into its biologic role during angiogenesis.Primary endothelial cells were treated with a variety of inducers of apoptosis and anoikis followed by assays for numbers of apoptotic cells, and harvest of total protein for immunoblot analysis.Del1 prevented endothelial cell apoptosis in response to TNFα/IFNγ, etoposide, and anoikis, but had no effect on proliferation. The anti-apoptotic effect was mediated specifically through binding of integrin αvβ3 by the RGD motif. FAK/ERK and Akt signaling were both necessary to mediate the anti-apoptotic effect of Del1 with the exception of anoikis, which required only Akt activation.Del1 has been previously shown to promote vascular smooth muscle cell adhesion, migration, and proliferation. We demonstrate here that Del1 prevented apoptosis of endothelial cells in cell culture through integrin binding without any effect on proliferation.

  View details for DOI 10.1016/j.surg.2011.07.013

  View details for Web of Science ID 000299607800019

  View details for PubMedID 21893328

• Skeletogenic phenotype of human Marfan embryonic stem cells faithfully phenocopied by patient-specific induced-pluripotent stem cells PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Quarto, N., Leonard, B., Li, S., Marchand, M., Anderson, E., Behr, B., Francke, U., Reijo-Pera, R., Chiao, E., Longaker, M. T. 2012; 109 (1): 215-220

  Abstract

  Marfan syndrome (MFS) is a heritable connective tissue disorder caused by mutations in the gene coding for FIBRILLIN-1 (FBN1), an extracellular matrix protein. MFS is inherited as an autosomal dominant trait and displays major manifestations in the ocular, skeletal, and cardiovascular systems. Here we report molecular and phenotypic profiles of skeletogenesis in tissues differentiated from human embryonic stem cells and induced pluripotent stem cells that carry a heritable mutation in FBN1. We demonstrate that, as a biological consequence of the activation of TGF-β signaling, osteogenic differentiation of embryonic stem cells with a FBN1 mutation is inhibited; osteogenesis is rescued by inhibition of TGF-β signaling. In contrast, chondrogenesis is not perturbated and occurs in a TGF-β cell-autonomous fashion. Importantly, skeletal phenotypes observed in human embryonic stem cells carrying the monogenic FBN1 mutation (MFS cells) are faithfully phenocopied by cells differentiated from induced pluripotent-stem cells derived independently from MFS patient fibroblasts. Results indicate a unique phenotype uncovered by examination of mutant pluripotent stem cells and further demonstrate the faithful alignment of phenotypes in differentiated cells obtained from both human embryonic stem cells and induced pluripotent-stem cells, providing complementary and powerful tools to gain further insights into human molecular pathogenesis, especially of MFS.

  View details for DOI 10.1073/pnas.1113442109

  View details for Web of Science ID 000298876500045

  View details for PubMedID 22178754

  View details for PubMedCentralID PMC3252902

• Enhancement of Human Adipose-Derived Stromal Cell Angiogenesis through Knockdown of a BMP-2 Inhibitor PLASTIC AND RECONSTRUCTIVE SURGERY Levi, B., Nelson, E. R., Hyun, J. S., Glotzbach, J. P., Li, S., Nauta, A., Montoro, D. T., Lee, M., Commons, G. C., Hu, S., Wu, J. C., Gurtner, G. C., Longaker, M. T. 2012; 129 (1): 53-66

  Abstract

  Previous studies have demonstrated the role of noggin, a bone morphogenetic protein-2 inhibitor, in vascular development and angiogenesis. The authors hypothesized that noggin suppression in human adipose-derived stromal cells would enhance vascular endothelial growth factor secretion and angiogenesis in vitro and in vivo to a greater extent than bone morphogenetic protein-2 alone.Human adipose-derived stromal cells were isolated from human lipoaspirate (n = 6) noggin was knocked down using lentiviral techniques. Knockdown was confirmed and angiogenesis was assessed by tubule formation and quantitative real-time polymerase chain reaction. Cells were seeded onto scaffolds and implanted into a 4-mm critical size calvarial defect. In vivo angiogenic signaling was assessed by immunofluorescence and immunohistochemistry.Human adipose-derived stromal cells with noggin suppression secreted significantly higher amounts of angiogenic proteins, expressed higher levels of angiogenic genes, and formed more tubules in vitro. In vivo, calvarial defects seeded with noggin shRNA human adipose-derived stromal cells exhibited a significantly higher number of vessels in the defect site than controls by immunohistochemistry (p < 0.05). In addition, bone morphogenetic protein-2-releasing scaffolds significantly enhanced vascular signaling in the defect site.Human adipose-derived stromal cells demonstrate significant increases in angiogenesis in vitro and in vivo with both noggin suppression and BMP-2 supplementation. By creating a cell with noggin suppressed and by using a scaffold with increased bone morphogenetic protein-2 signaling, a more angiogenic niche can be created.

  View details for DOI 10.1097/PRS.0b013e3182361ff5

  View details for PubMedID 21915082

• Focal adhesion kinase links mechanical force to skin fibrosis via inflammatory signaling NATURE MEDICINE Wong, V. W., Rustad, K. C., Akaishi, S., Sorkin, M., Glotzbach, J. P., Januszyk, M., Nelson, E. R., Levi, K., Paterno, J., Vial, I. N., Kuang, A. A., Longaker, M. T., Gurtner, G. C. 2012; 18 (1): 148-152

  Abstract

  Exuberant fibroproliferation is a common complication after injury for reasons that are not well understood. One key component of wound repair that is often overlooked is mechanical force, which regulates cell-matrix interactions through intracellular focal adhesion components, including focal adhesion kinase (FAK). Here we report that FAK is activated after cutaneous injury and that this process is potentiated by mechanical loading. Fibroblast-specific FAK knockout mice have substantially less inflammation and fibrosis than control mice in a model of hypertrophic scar formation. We show that FAK acts through extracellular-related kinase (ERK) to mechanically trigger the secretion of monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), a potent chemokine that is linked to human fibrotic disorders. Similarly, MCP-1 knockout mice form minimal scars, indicating that inflammatory chemokine pathways are a major mechanism by which FAK mechanotransduction induces fibrosis. Small-molecule inhibition of FAK blocks these effects in human cells and reduces scar formation in vivo through attenuated MCP-1 signaling and inflammatory cell recruitment. These findings collectively indicate that physical force regulates fibrosis through inflammatory FAK-ERK-MCP-1 pathways and that molecular strategies targeting FAK can effectively uncouple mechanical force from pathologic scar formation.

  View details for DOI 10.1038/nm.2574

  View details for Web of Science ID 000299018600041

• Stem cell niches for skin regeneration. International journal of biomaterials Wong, V. W., Levi, B., Rajadas, J., Longaker, M. T., Gurtner, G. C. 2012; 2012: 926059-?

  Abstract

  Stem cell-based therapies offer tremendous potential for skin regeneration following injury and disease. Functional stem cell units have been described throughout all layers of human skin and the collective physical and chemical microenvironmental cues that enable this regenerative potential are known as the stem cell niche. Stem cells in the hair follicle bulge, interfollicular epidermis, dermal papillae, and perivascular space have been closely investigated as model systems for niche-driven regeneration. These studies suggest that stem cell strategies for skin engineering must consider the intricate molecular and biologic features of these niches. Innovative biomaterial systems that successfully recapitulate these microenvironments will facilitate progenitor cell-mediated skin repair and regeneration.

  View details for DOI 10.1155/2012/926059

  View details for PubMedID 22701121

• Enhancement of mesenchymal stem cell angiogenic capacity and stemness by a biomimetic hydrogel scaffold BIOMATERIALS Rustad, K. C., Wong, V. W., Sorkin, M., Glotzbach, J. P., Major, M. R., Rajadas, J., Longaker, M. T., Gurtner, G. C. 2012; 33 (1): 80-90

  Abstract

  In this study, we examined the capacity of a biomimetic pullulan-collagen hydrogel to create a functional biomaterial-based stem cell niche for the delivery of mesenchymal stem cells (MSCs) into wounds. Murine bone marrow-derived MSCs were seeded into hydrogels and compared to MSCs grown in standard culture conditions. Hydrogels induced MSC secretion of angiogenic cytokines and expression of transcription factors associated with maintenance of pluripotency and self-renewal (Oct4, Sox2, Klf4) when compared to MSCs grown in standard conditions. An excisonal wound healing model was used to compare the ability of MSC-hydrogel constructs versus MSC injection alone to accelerate wound healing. Injection of MSCs did not significantly improve time to wound closure. In contrast, wounds treated with MSC-seeded hydrogels showed significantly accelerated healing and a return of skin appendages. Bioluminescence imaging and FACS analysis of luciferase+/GFP+ MSCs indicated that stem cells delivered within the hydrogel remained viable longer and demonstrated enhanced engraftment efficiency than those delivered via injection. Engrafted MSCs were found to differentiate into fibroblasts, pericytes and endothelial cells but did not contribute to the epidermis. Wounds treated with MSC-seeded hydrogels demonstrated significantly enhanced angiogenesis, which was associated with increased levels of VEGF and other angiogenic cytokines within the wounds. Our data suggest that biomimetic hydrogels provide a functional niche capable of augmenting MSC regenerative potential and enhancing wound healing.

  View details for DOI 10.1016/j.biomaterials.2011.09.041

  View details for Web of Science ID 000297399700009

  View details for PubMedID 21963148

• Focal adhesion kinase links mechanical force to skin fibrosis via inflammatory signaling. Nature medicine Wong, V. W., Rustad, K. C., Akaishi, S., Sorkin, M., Glotzbach, J. P., Januszyk, M., Nelson, E. R., Levi, K., Paterno, J., Vial, I. N., Kuang, A. A., Longaker, M. T., Gurtner, G. C. 2012; 18 (1): 148-152

  Abstract

  Exuberant fibroproliferation is a common complication after injury for reasons that are not well understood. One key component of wound repair that is often overlooked is mechanical force, which regulates cell-matrix interactions through intracellular focal adhesion components, including focal adhesion kinase (FAK). Here we report that FAK is activated after cutaneous injury and that this process is potentiated by mechanical loading. Fibroblast-specific FAK knockout mice have substantially less inflammation and fibrosis than control mice in a model of hypertrophic scar formation. We show that FAK acts through extracellular-related kinase (ERK) to mechanically trigger the secretion of monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), a potent chemokine that is linked to human fibrotic disorders. Similarly, MCP-1 knockout mice form minimal scars, indicating that inflammatory chemokine pathways are a major mechanism by which FAK mechanotransduction induces fibrosis. Small-molecule inhibition of FAK blocks these effects in human cells and reduces scar formation in vivo through attenuated MCP-1 signaling and inflammatory cell recruitment. These findings collectively indicate that physical force regulates fibrosis through inflammatory FAK-ERK-MCP-1 pathways and that molecular strategies targeting FAK can effectively uncouple mechanical force from pathologic scar formation.

  View details for DOI 10.1038/nm.2574

  View details for PubMedID 22157678

• Craniofacial Surgery: Innovation, Design, and Strategy JOURNAL OF CRANIOFACIAL SURGERY Warren, S. M., Longaker, M. T. 2012; 23 (1): 7-7

  View details for DOI 10.1097/SCS.0b013e31824209e8

  View details for Web of Science ID 000300234900029

  View details for PubMedID 22337364

• Cranial Suture Biology: From Pathways to Patient Care JOURNAL OF CRANIOFACIAL SURGERY Levi, B., Wan, D. C., Wong, V. W., Nelson, E., Hyun, J., Longaker, M. T. 2012; 23 (1): 13-19

  Abstract

  Craniosynostosis describes the premature pathologic partial or complete fusion of 1 or more of the cranial sutures. Over the past few decades, research on craniosynostosis has progressed from gross description of deformities to an understanding of some of the molecular etiologies behind premature suture fusion. Studies on patients with syndromic craniosynostosis have resulted in the identification of several genes, molecular events, and deformational forces involved in abnormal growth and development of the cranial vault. Conservation of craniofacial development and sequence homology between humans and other species have also led to insightful discoveries in cranial suture development. In this review, we discuss the development of the cranial vault and explain the basic science behind craniosynostosis in humans as well as in animal models and how these studies may lead to future advances in craniosynostosis treatments.

  View details for DOI 10.1097/SCS.0b013e318240c6c0

  View details for Web of Science ID 000300234900033

  View details for PubMedID 22337368

• Repair of a critical-sized calvarial defect model using adipose-derived stromal cells harvested from lipoaspirate. Journal of visualized experiments : JoVE Lo, D. D., Hyun, J. S., Chung, M. T., Montoro, D. T., Zimmermann, A., Grova, M. M., Lee, M., Wan, D. C., Longaker, M. T. 2012

  Abstract

  Craniofacial skeletal repair and regeneration offers the promise of de novo tissue formation through a cell-based approach utilizing stem cells. Adipose-derived stromal cells (ASCs) have proven to be an abundant source of multipotent stem cells capable of undergoing osteogenic, chondrogenic, adipogenic, and myogenic differentiation. Many studies have explored the osteogenic potential of these cells in vivo with the use of various scaffolding biomaterials for cellular delivery. It has been demonstrated that by utilizing an osteoconductive, hydroxyapatite-coated poly(lactic-co-glycolic acid) (HA-PLGA) scaffold seeded with ASCs, a critical-sized calvarial defect, a defect that is defined by its inability to undergo spontaneous healing over the lifetime of the animal, can be effectively show robust osseous regeneration. This in vivo model demonstrates the basis of translational approaches aimed to regenerate the bone tissue - the cellular component and biological matrix. This method serves as a model for the ultimate clinical application of a progenitor cell towards the repair of a specific tissue defect.

  View details for DOI 10.3791/4221

  View details for PubMedID 23149856

  View details for PubMedCentralID PMC3499066

• Stem Cells: Update and Impact on Craniofacial Surgery JOURNAL OF CRANIOFACIAL SURGERY Levi, B., Glotzbach, J. P., Wong, V. W., Nelson, E. R., Hyun, J., Wan, D. C., Gurtner, G. C., Longaker, M. T. 2012; 23 (1): 319-322

  View details for DOI 10.1097/SCS.0b013e318241dbaf

  View details for Web of Science ID 000300234900099

  View details for PubMedID 22337434

  View details for PubMedCentralID PMC3282019

• Nonintegrating Knockdown and Customized Scaffold Design Enhances Human Adipose-Derived Stem Cells in Skeletal Repair STEM CELLS Levi, B., Hyun, J. S., Nelson, E. R., Li, S., Montoro, D. T., Wan, D. C., Jia, F. J., Glotzbach, J. C., James, A. W., Lee, M., Huang, M., Quarto, N., Gurtner, G. C., Wu, J. C., Longaker, M. T. 2011; 29 (12): 2018-2029

  Abstract

  An urgent need exists in clinical medicine for suitable alternatives to available techniques for bone tissue repair. Human adipose-derived stem cells (hASCs) represent a readily available, autogenous cell source with well-documented in vivo osteogenic potential. In this article, we manipulated Noggin expression levels in hASCs using lentiviral and nonintegrating minicircle short hairpin ribonucleic acid (shRNA) methodologies in vitro and in vivo to enhance hASC osteogenesis. Human ASCs with Noggin knockdown showed significantly increased bone morphogenetic protein (BMP) signaling and osteogenic differentiation both in vitro and in vivo, and when placed onto a BMP-releasing scaffold embedded with lentiviral Noggin shRNA particles, hASCs more rapidly healed mouse calvarial defects. This study therefore suggests that genetic targeting of hASCs combined with custom scaffold design can optimize hASCs for skeletal regenerative medicine.

  View details for DOI 10.1002/stem.757

  View details for PubMedID 21997852

• Mechanical force prolongs acute inflammation via T-cell-dependent pathways during scar formation FASEB JOURNAL Wong, V. W., Paterno, J., Sorkin, M., Glotzbach, J. P., Levi, K., Januszyk, M., Rustad, K. C., Longaker, M. T., Gurtner, G. C. 2011; 25 (12): 4498-4510

  Abstract

  Mechanical force significantly modulates both inflammation and fibrosis, yet the fundamental mechanisms that regulate these interactions remain poorly understood. Here we performed microarray analysis to compare gene expression in mechanically loaded wounds vs. unloaded control wounds in an established murine hypertrophic scar (HTS) model. We identified 853 mechanically regulated genes (false discovery rate <2) at d 14 postinjury, a subset of which were enriched for T-cell-regulated pathways. To substantiate the role of T cells in scar mechanotransduction, we applied the HTS model to T-cell-deficient mice and wild-type mice. We found that scar formation in T-cell-deficient mice was reduced by almost 9-fold (P < 0.001) with attenuated epidermal (by 2.6-fold, P < 0.01) and dermal (3.9-fold, P < 0.05) proliferation. Mechanical stimulation was highly associated with sustained T-cell-dependent Th2 cytokine (IL-4 and IL-13) and chemokine (MCP-1) signaling. Further, T-cell-deficient mice failed to recruit systemic inflammatory cells such as macrophages or monocytic fibroblast precursors in response to mechanical loading. These findings indicate that T-cell-regulated fibrogenic pathways are highly mechanoresponsive and suggest that mechanical forces induce a chronic-like inflammatory state through immune-dependent activation of both local and systemic cell populations.

  View details for DOI 10.1096/fj.10-178087

  View details for Web of Science ID 000298138100040

  View details for PubMedID 21911593

• Antimycotic Ciclopirox Olamine in the Diabetic Environment Promotes Angiogenesis and Enhances Wound Healing PLOS ONE Ko, S. H., Nauta, A., Morrison, S. D., Zhou, H., Zimmermann, A., Gurtner, G. C., Ding, S., Longaker, M. T. 2011; 6 (11)

  Abstract

  Diabetic wounds remain a major medical challenge with often disappointing outcomes despite the best available care. An impaired response to tissue hypoxia and insufficient angiogenesis are major factors responsible for poor healing in diabetic wounds. Here we show that the antimycotic drug ciclopirox olamine (CPX) can induce therapeutic angiogenesis in diabetic wounds. Treatment with CPX in vitro led to upregulation of multiple angiogenic genes and increased availability of HIF-1α. Using an excisional wound splinting model in diabetic mice, we showed that serial topical treatment with CPX enhanced wound healing compared to vehicle control treatment, with significantly accelerated wound closure, increased angiogenesis, and increased dermal cellularity. These findings offer a promising new topical pharmacologic therapy for the treatment of diabetic wounds.

  View details for DOI 10.1371/journal.pone.0027844

  View details for Web of Science ID 000297789200029

  View details for PubMedID 22125629

  View details for PubMedCentralID PMC3220686

• CD105 Protein Depletion Enhances Human Adipose-derived Stromal Cell Osteogenesis through Reduction of Transforming Growth Factor beta 1 (TGF-beta 1) Signaling JOURNAL OF BIOLOGICAL CHEMISTRY Levi, B., Wan, D. C., Glotzbach, J. P., Hyun, J., Januszyk, M., Montoro, D., Sorkin, M., James, A. W., Nelson, E. R., Li, S., Quarto, N., Lee, M., Gurtner, G. C., Longaker, M. T. 2011; 286 (45): 39497-39509

  Abstract

  Clinically available sources of bone for repair and reconstruction are limited by the accessibility of autologous grafts, infectious risks of cadaveric materials, and durability of synthetic substitutes. Cell-based approaches for skeletal regeneration can potentially fill this need, and adipose tissue represents a promising source for development of such therapies. Here, we enriched for an osteogenic subpopulation of cells derived from human subcutaneous adipose tissue utilizing microfluidic-based single cell transcriptional analysis and fluorescence-activated cell sorting (FACS). Statistical analysis of single cell transcriptional profiles demonstrated that low expression of endoglin (CD105) correlated with a subgroup of adipose-derived cells with increased osteogenic gene expression. FACS-sorted CD105(low) cells demonstrated significantly enhanced in vitro osteogenic differentiation and in vivo bone regeneration when compared with either CD105(high) or unsorted cells. Evaluation of the endoglin pathway suggested that enhanced osteogenesis among CD105(low) adipose-derived cells is likely due to identification of a subpopulation with lower TGF-β1/Smad2 signaling. These findings thus highlight a potential avenue to promote osteogenesis in adipose-derived mesenchymal cells for skeletal regeneration.

  View details for DOI 10.1074/jbc.M111.256529

  View details for PubMedID 21949130

• Pullulan Hydrogels Improve Mesenchymal Stem Cell Delivery into High-Oxidative-Stress Wounds MACROMOLECULAR BIOSCIENCE Wong, V. W., Rustad, K. C., Glotzbach, J. P., Sorkin, M., Inayathullah, M., Major, M. R., Longaker, M. T., Rajadas, J., Gurtner, G. C. 2011; 11 (11): 1458-1466

  Abstract

  Cell-based therapies for wound repair are limited by inefficient delivery systems that fail to protect cells from the acute inflammatory environment. Here, a biomimetic hydrogel system is described that is based on the polymer pullulan, a carbohydrate glucan known to exhibit potent antioxidant capabilities. It is shown that pullulan hydrogels are an effective cell delivery system and improve mesenchymal stem cell survival and engraftment in high-oxidative-stress environments. The results suggest that glucan hydrogel systems may prove beneficial for progenitor-cell-based approaches to skin regeneration.

  View details for DOI 10.1002/mabi.201100180

  View details for Web of Science ID 000297555500002

  View details for PubMedID 21994074

• Calcium-Based Nanoparticles Accelerate Skin Wound Healing PLOS ONE Kawai, K., Larson, B. J., Ishise, H., Carre, A. L., Nishimoto, S., Longaker, M., Lorenz, H. P. 2011; 6 (11)

  Abstract

  Nanoparticles (NPs) are small entities that consist of a hydroxyapatite core, which can bind ions, proteins, and other organic molecules from the surrounding environment. These small conglomerations can influence environmental calcium levels and have the potential to modulate calcium homeostasis in vivo. Nanoparticles have been associated with various calcium-mediated disease processes, such as atherosclerosis and kidney stone formation. We hypothesized that nanoparticles could have an effect on other calcium-regulated processes, such as wound healing. In the present study, we synthesized pH-sensitive calcium-based nanoparticles and investigated their ability to enhance cutaneous wound repair.Different populations of nanoparticles were synthesized on collagen-coated plates under various growth conditions. Bilateral dorsal cutaneous wounds were made on 8-week-old female Balb/c mice. Nanoparticles were then either administered intravenously or applied topically to the wound bed. The rate of wound closure was quantified. Intravenously injected nanoparticles were tracked using a FLAG detection system. The effect of nanoparticles on fibroblast contraction and proliferation was assessed.A population of pH-sensitive calcium-based nanoparticles was identified. When intravenously administered, these nanoparticles acutely increased the rate of wound healing. Intravenously administered nanoparticles were localized to the wound site, as evidenced by FLAG staining. Nanoparticles increased fibroblast calcium uptake in vitro and caused contracture of a fibroblast populated collagen lattice in a dose-dependent manner. Nanoparticles also increased the rate of fibroblast proliferation.Intravenously administered, calcium-based nanoparticles can acutely decrease open wound size via contracture. We hypothesize that their contraction effect is mediated by the release of ionized calcium into the wound bed, which occurs when the pH-sensitive nanoparticles disintegrate in the acidic wound microenvironment. This is the first study to demonstrate that calcium-based nanoparticles can have a therapeutic benefit, which has important implications for the treatment of wounds.

  View details for DOI 10.1371/journal.pone.0027106

  View details for Web of Science ID 000297154900079

  View details for PubMedID 22073267

  View details for PubMedCentralID PMC3206933

• Pushing Back: Wound Mechanotransduction in Repair and Regeneration JOURNAL OF INVESTIGATIVE DERMATOLOGY Wong, V. W., Akaishi, S., Longaker, M. T., Gurtner, G. C. 2011; 131 (11): 2186-2196

  Abstract

  Human skin is a highly specialized mechanoresponsive interface separating our bodies from the external environment. It must constantly adapt to dynamic physical cues ranging from rapid expansion during embryonic and early postnatal development to ubiquitous external forces throughout life. Despite the suspected role of the physical environment in cutaneous processes, the fundamental molecular mechanisms responsible for how skin responds to force remain unclear. Intracellular pathways convert mechanical cues into biochemical responses (in a process known as mechanotransduction) via complex mechanoresponsive elements that often blur the distinction between physical and chemical signaling. For example, cellular focal adhesion components exhibit dual biochemical and scaffolding functions that are critically modulated by force. Moreover, the extracellular matrix itself is increasingly recognized to mechanically regulate the spatiotemporal distribution of soluble and matrix-bound ligands, underscoring the importance of bidirectional crosstalk between cells and their physical environment. It seems likely that a structural hierarchy exists to maintain both cells and matrix in mechanical homeostasis and that dysregulation of this architectural integrity may underlie or contribute to various skin disorders. An improved understanding of these interactions will facilitate the development of novel biophysical materials and mechanomodulatory approaches to augment wound repair and regeneration.

  View details for DOI 10.1038/jid.2011.212

  View details for Web of Science ID 000296240100012

  View details for PubMedID 21776006

• Role of GSK-3 beta in the Osteogenic Differentiation of Palatal Mesenchyme PLOS ONE Nelson, E. R., Levi, B., Sorkin, M., James, A. W., Liu, K. J., Quarto, N., Longaker, M. T. 2011; 6 (10)

  Abstract

  The function of Glycogen Synthase Kinases 3β (GSK-3β) has previously been shown to be necessary for normal secondary palate development. Using GSK-3ß null mouse embryos, we examine the potential coordinate roles of Wnt and Hedgehog signaling on palatal ossification.Palates were harvested from GSK-3β, embryonic days 15.0-18.5 (e15.0-e18.5), and e15.5 Indian Hedgehog (Ihh) null embryos, and their wild-type littermates. The phenotype of GSK-3β null embryos was analyzed with skeletal whole mount and pentachrome stains. Spatiotemporal regulation of osteogenic gene expression, in addition to Wnt and Hedgehog signaling activity, were examined in vivo on GSK-3β and Ihh +/+ and -/- e15.5 embryos using in situ hybridization and immunohistochemistry. To corroborate these results, expression of the same molecular targets were assessed by qRT-PCR of e15.5 palates, or e13.5 palate cultures treated with both Wnt and Hedgehog agonists and anatagonists.GSK-3β null embryos displayed a 48 percent decrease (*p<0.05) in palatine bone formation compared to wild-type littermates. GSK-3β null embryos also exhibited decreased osteogenic gene expression that was associated with increased Wnt and decreased Hedgehog signaling. e13.5 palate culture studies demonstrated that Wnt signaling negatively regulates both osteogenic gene expression and Hedgehog signaling activity, while inhibition of Wnt signaling augments both osteogenic gene expression and Hedgehog signaling activity. In addition, no differences in Wnt signaling activity were noted in Ihh null embryos, suggesting that canonical Wnt may be upstream of Hedgehog in secondary palate development. Lastly, we found that GSK-3β -/- palate cultures were "rescued" with the Wnt inhibitor, Dkk-1.Here, we identify a critical role for GSK-3β in palatogenesis through its direct regulation of canonical Wnt signaling. These findings shed light on critical developmental pathways involved in palatogenesis and may lead to novel molecular targets to prevent cleft palate formation.

  View details for DOI 10.1371/journal.pone.0025847

  View details for Web of Science ID 000295981600015

  View details for PubMedID 22022457

  View details for PubMedCentralID PMC3194817

• Indian Hedgehog Positively Regulates Calvarial Ossification and Modulates Bone Morphogenetic Protein Signaling GENESIS Lenton, K., James, A. W., Manu, A., Brugmann, S. A., Birker, D., Nelson, E. R., Leucht, P., Helms, J. A., Longaker, M. T. 2011; 49 (10): 784-796

  Abstract

  Much is known regarding the role of Indian hedgehog (Ihh) in endochondral ossification, where Ihh regulates multiple steps of chondrocyte differentiation. The Ihh-/- phenotype is most notable for severely foreshortened limbs and a complete absence of mature osteoblasts. A far less explored phenotype in the Ihh-/- mutant is found in the calvaria, where bones form predominately through intramembranous ossification. We investigated the role of Ihh in calvarial bone ossification, finding that proliferation was largely unaffected. Instead, our results indicate that Ihh is a pro-osteogenic factor that positively regulates intramembranous ossification. We confirmed through histologic and quantitative gene analysis that loss of Ihh results in reduction of cranial bone size and all markers of osteodifferentiation. Moreover, in vitro studies suggest that Ihh loss reduces Bmp expression within the calvaria, an observation that may underlie the Ihh-/- calvarial phenotype. In conjunction with the newly recognized roles of Hedgehog deregulation in craniosynostosis, our study defines Ihh as an important positive regulator of cranial bone ossification.

  View details for DOI 10.1002/dvg.20768

  View details for Web of Science ID 000296420300003

  View details for PubMedID 21557453

• Palatogenesis Engineering, pathways and pathologies ORGANOGENESIS Levi, B., Brugman, S., Wong, V. W., Grova, M., Longaker, M. T., Wan, D. C. 2011; 7 (4): 242-254

  Abstract

  Cleft palate represents the second most common birth defect and carries substantial physiologic and social challenges for affected patients, as they often require multiple surgical interventions during their lifetime. A number of genes have been identified to be associated with the cleft palate phenotype, but etiology in the majority of cases remains elusive. In order to better understand cleft palate and both surgical and potential tissue engineering approaches for repair, we have performed an in-depth literature review into cleft palate development in humans and mice, as well as into molecular pathways underlying these pathologic developments. We summarize the multitude of pathways underlying cleft palate development, with the transforming growth factor beta superfamily being the most commonly studied. Furthermore, while the majority of cleft palate studies are performed using a mouse model, studies focusing on tissue engineering have also focused heavily on mouse models. A paucity of human randomized controlled studies exists for cleft palate repair, and so far, tissue engineering approaches are limited. In this review, we discuss the development of the palate, explain the basic science behind normal and pathologic palate development in humans as well as mouse models and elaborate on how these studies may lead to future advances in palatal tissue engineering and cleft palate treatments.

  View details for DOI 10.4161/org.7.4.17926

  View details for Web of Science ID 000299593000002

  View details for PubMedID 21964245

  View details for PubMedCentralID PMC3265826

• Preclinical Derivation and Imaging of Autologously Transplanted Canine Induced Pluripotent Stem Cells JOURNAL OF BIOLOGICAL CHEMISTRY Lee, A. S., Xu, D., Plews, J. R., Nguyen, P. K., Nag, D., Lyons, J. K., Han, L., Hu, S., Lan, F., Liu, J., Huang, M., Narsinh, K. H., Long, C. T., de Almeida, P. E., Levi, B., Kooreman, N., Bangs, C., Pacharinsak, C., Ikeno, F., Yeung, A. C., Gambhir, S. S., Robbins, R. C., Longaker, M. T., Wu, J. C. 2011; 286 (37): 32697-32704

  Abstract

  Derivation of patient-specific induced pluripotent stem cells (iPSCs) opens a new avenue for future applications of regenerative medicine. However, before iPSCs can be used in a clinical setting, it is critical to validate their in vivo fate following autologous transplantation. Thus far, preclinical studies have been limited to small animals and have yet to be conducted in large animals that are physiologically more similar to humans. In this study, we report the first autologous transplantation of iPSCs in a large animal model through the generation of canine iPSCs (ciPSCs) from the canine adipose stromal cells and canine fibroblasts of adult mongrel dogs. We confirmed pluripotency of ciPSCs using the following techniques: (i) immunostaining and quantitative PCR for the presence of pluripotent and germ layer-specific markers in differentiated ciPSCs; (ii) microarray analysis that demonstrates similar gene expression profiles between ciPSCs and canine embryonic stem cells; (iii) teratoma formation assays; and (iv) karyotyping for genomic stability. Fate of ciPSCs autologously transplanted to the canine heart was tracked in vivo using clinical positron emission tomography, computed tomography, and magnetic resonance imaging. To demonstrate clinical potential of ciPSCs to treat models of injury, we generated endothelial cells (ciPSC-ECs) and used these cells to treat immunodeficient murine models of myocardial infarction and hindlimb ischemia.

  View details for DOI 10.1074/jbc.M111.235739

  View details for Web of Science ID 000294726800078

  View details for PubMedID 21719696

  View details for PubMedCentralID PMC3173214

• Wound healing and regenerative strategies ORAL DISEASES Nauta, A., Gurtner, G. C., Longaker, M. T. 2011; 17 (6): 541-549

  Abstract

  Wound healing is a complex biological process that affects multiple tissue types. Wounds in the oral cavity are particularly challenging given the variety of tissue types that exist in close proximity to one another. The goal of regenerative medicine is to facilitate the rapid replacement of lost or damaged tissue with tissue that is functional, and physiologically similar to what previously existed. This review provides a general overview of wound healing and regenerative medicine, focusing specifically on how recent advances in the fields of stem cell biology, tissue engineering, and oral disease could translate into improved clinical outcomes.

  View details for DOI 10.1111/j.1601-0825.2011.01787.x

  View details for Web of Science ID 000292985000001

  View details for PubMedID 21332599

• Recommendations on clinical proof of efficacy for potential scar prevention and reduction therapies WOUND REPAIR AND REGENERATION Bush, J. A., McGrouther, D. A., Young, V. L., Herndon, D. N., Longaker, M. T., Mustoe, T. A., Ferguson, M. W. 2011; 19: S32-S37

  Abstract

  Cutaneous scarring is an enormous medical problem with approximately 100 million patients acquiring scars each year. Scar prevention/reduction represents a significant, and largely unmet, clinical need. Research into the prophylactic modulation of scar outcome differs from research into other disease processes as the scar is not present at the start of the study; measurements of changes from baseline are impossible. Final scar morphology is influenced by many variables. A fundamental principle that should be observed in the prospective evaluation of scar prevention/reduction therapies is that, if left untreated, wounds in treatment and control groups should have healed with identical scars. Observation of this principle will allow the detection of true treatment effects. The many variables that influence scar morphology mean that the evaluation of potential pharmaceutical products for this indication favors the use of self-controlled designs in clinical trials. In this article, we review variables that affect scar morphology and recommend the self-controlled design for clinical trials aiming to establish proof of efficacy of scar prevention and reduction pharmaceuticals. With no pharmaceutical products currently licensed for this indication, this represents a new therapeutic area. The principles discussed will also have direct relevance to the wider fields of wound healing and regenerative medicine.

  View details for DOI 10.1111/j.1524-475X.2010.00607.x

  View details for Web of Science ID 000293237400006

  View details for PubMedID 21793964

• Commentary on Role of Apoptosis in Retinoic Acid-Induced Cleft Palate JOURNAL OF CRANIOFACIAL SURGERY Nelson, E. R., Levi, B., Longaker, M. T. 2011; 22 (5): 1572-1573

  View details for DOI 10.1097/SCS.0b013e31822e5ea6

  View details for Web of Science ID 000295398700007

  View details for PubMedID 21959389

• Vascular anastomosis using controlled phase transitions in poloxamer gels NATURE MEDICINE Chang, E. I., Galvez, M. G., Glotzbach, J. P., Hamou, C. D., El-Ftesi, S., Rappleye, C. T., Sommer, K., Rajadas, J., Abilez, O. J., Fuller, G. G., Longaker, M. T., Gurtner, G. C. 2011; 17 (9): 1147-U160

  Abstract

  Vascular anastomosis is the cornerstone of vascular, cardiovascular and transplant surgery. Most anastomoses are performed with sutures, which are technically challenging and can lead to failure from intimal hyperplasia and foreign body reaction. Numerous alternatives to sutures have been proposed, but none has proven superior, particularly in small or atherosclerotic vessels. We have developed a new method of sutureless and atraumatic vascular anastomosis that uses US Food and Drug Administration (FDA)-approved thermoreversible tri-block polymers to temporarily maintain an open lumen for precise approximation with commercially available glues. We performed end-to-end anastomoses five times more rapidly than we performed hand-sewn controls, and vessels that were too small (<1.0 mm) to sew were successfully reconstructed with this sutureless approach. Imaging of reconstructed rat aorta confirmed equivalent patency, flow and burst strength, and histological analysis demonstrated decreased inflammation and fibrosis at up to 2 years after the procedure. This new technology has potential for improving efficiency and outcomes in the surgical treatment of cardiovascular disease.

  View details for DOI 10.1038/nm.2424

  View details for Web of Science ID 000294605100038

  View details for PubMedID 21873986

• Germ-layer and lineage-restricted stem/progenitors regenerate the mouse digit tip NATURE Rinkevich, Y., Lindau, P., Ueno, H., Longaker, M. T., Weissman, I. L. 2011; 476 (7361): 409-U53

  Abstract

  The regrowth of amputated limbs and the distal tips of digits represent models of tissue regeneration in amphibians, fish and mice. For decades it had been assumed that limb regeneration derived from the blastema, an undifferentiated pluripotent cell population thought to be derived from mature cells via dedifferentiation. Here we show that a wide range of tissue stem/progenitor cells contribute towards the restoration of the mouse distal digit. Genetic fate mapping and clonal analysis of individual cells revealed that these stem cells are lineage restricted, mimicking digit growth during development. Transplantation of cyan-fluorescent-protein-expressing haematopoietic stem cells, and parabiosis between genetically marked mice, confirmed that the stem/progenitor cells are tissue resident, including the cells involved in angiogenesis. These results, combined with those from appendage regeneration in other vertebrate subphyla, collectively demonstrate that tissue stem cells rather than pluripotent blastema cells are an evolutionarily conserved cellular mode for limb regeneration after amputation.

  View details for DOI 10.1038/nature10346

  View details for Web of Science ID 000294209400027

  View details for PubMedID 21866153

• Differences in Osteogenic Differentiation of Adipose-Derived Stromal Cells from Murine, Canine, and Human Sources In Vitro and In Vivo PLASTIC AND RECONSTRUCTIVE SURGERY Levi, B., Nelson, E. R., Brown, K., James, A. W., Xu, D., Dunlevie, R., Wu, J. C., Lee, M., Wu, B., Commons, G. W., Vistnes, D., Longaker, M. T. 2011; 128 (2): 373-386

  Abstract

  Given the diversity of species from which adipose-derived stromal cells are derived and studied, the authors set out to delineate the differences in the basic cell biology that may exist across species. Briefly, the authors found that significant differences exist with regard to proliferation and osteogenic potentials of adipose-derived stromal cells across species.Adipose-derived stromal cells were derived from human, mouse, and canine sources as previously described. Retinoic acid, insulin-like growth factor-1, and bone morphogenetic protein-2 were added to culture medium; proliferation and osteogenic differentiation were assessed by standardized assays. In vivo methods included seeding 150,000 adipose-derived stromal cells on a biomimetic scaffold and analyzing healing by micro-computed tomography and histology.Adipose-derived stromal cells from all species had the capability to undergo osteogenic differentiation. Canine adipose-derived stromal cells were the most proliferative, whereas human adipose-derived stromal cells were the most osteogenic (p < 0.05). Human cells, however, had the most significant osteogenic response to osteogenic media. Retinoic acid stimulated osteogenesis in mouse and canine cells but not in human adipose-derived stromal cells. Insulin-like growth factor-1 enhanced osteogenesis across all species, most notably in human- and canine-derived cells.Adipose-derived stromal cells derived from human, mouse, and canine all have the capacity to undergo osteogenic differentiation. Canine adipose-derived stromal cells appear to be the most proliferative, whereas human adipose-derived stromal cells appear to be the most osteogenic. Different cytokines and chemicals can be used to modulate this osteogenic response. These results are promising as attempts are made to optimize tissue-engineered bone using adipose-derived stromal cells.

  View details for DOI 10.1097/PRS.0b013e31821e6e49

  View details for PubMedID 21788829

• Improving Cutaneous Scar Formation by Controlling the Mechanical Environment Large Animal and Phase I Studies ANNALS OF SURGERY Gurtner, G. C., Dauskardt, R. H., Wong, V. W., Bhatt, K. A., Wu, K., Vial, I. N., Padois, K., Korman, J. M., Longaker, M. T. 2011; 254 (2): 217-225

  Abstract

  To test the hypothesis that the mechanical environment of cutaneous wounds can control scar formation.Mechanical forces have been recognized to modulate myriad biologic processes, but the role of physical force in scar formation remains unclear. Furthermore, the therapeutic benefits of offloading cutaneous wounds with a device have not been rigorously tested.A mechanomodulating polymer device was utilized to manipulate the mechanical environment of closed cutaneous wounds in red Duroc swine. After 8 weeks, wounds subjected to different mechanical stress states underwent immunohistochemical analysis for fibrotic markers. In a phase I clinical study, 9 human patients undergoing elective abdominal surgery were treated postoperatively with a stress-shielding polymer on one side whereas the other side was treated as standard of care. Professional photographs were taken between 8 and 12 months postsurgery and evaluated using a visual analog scale by lay and professional panels. This study is registered with ClinicalTrials.gov, number NCT00766727.Stress shielding of swine incisions reduced histologic scar area by 6- and 9-fold compared to control and elevated stress states, respectively (P < 0.01 for both) and dramatically decreased the histologic expression of profibrotic markers. Closure of high-tension wounds induced human-like scar formation in the red Duroc, a phenotype effectively mitigated with stress shielding of wounds. In the study on humans, stress shielding of abdominal incisions significantly improved scar appearance (P = 0.004) compared with within-patient controls.These results indicate that mechanical manipulation of the wound environment with a dynamic stress-shielding polymer device can significantly reduce scar formation.

  View details for DOI 10.1097/SLA.0b013e318220b159

  View details for Web of Science ID 000292908700007

  View details for PubMedID 21606834

• Dura Mater Stimulates Human Adipose-Derived Stromal Cells to Undergo Bone Formation in Mouse Calvarial Defects STEM CELLS Levi, B., Nelson, E. R., Li, S., James, A. W., Hyun, J. S., Montoro, D. T., Lee, M., Glotzbach, J. P., Commons, G. W., Longaker, M. T. 2011; 29 (8): 1241-1255

  Abstract

  Human adipose-derived stromal cells (hASCs) have a proven capacity to aid in osseous repair of calvarial defects. However, the bone defect microenvironment necessary for osseous healing is not fully understood. In this study, we postulated that the cell-cell interaction between engrafted ASCs and host dura mater (DM) cells is critical for the healing of calvarial defects. hASCs were engrafted into critical sized calvarial mouse defects. The DM-hASC interaction was manipulated surgically by DM removal or by insertion of a semipermeable or nonpermeable membrane between DM and hASCs. Radiographic, histologic, and gene expression analyses were performed. Next, the hASC-DM interaction is assessed by conditioned media (CM) and coculture assays. Finally, bone morphogenetic protein (BMP) signaling from DM was investigated in vivo using novel BMP-2 and anti-BMP-2/4 slow releasing scaffolds. With intact DM, osseous healing occurs both from host DM and engrafted hASCs. Interference with the DM-hASC interaction dramatically reduced calvarial healing with abrogated BMP-2-Smad-1/5 signaling. Using CM and coculture assays, mouse DM cells stimulated hASC osteogenesis via BMP signaling. Through in vivo manipulation of the BMP-2 pathway, we found that BMP-2 plays an important role in DM stimulation of hASC osteogenesis in the context of calvarial bone healing. BMP-2 supplementation to a defect with disrupted DM allowed for bone formation in a nonhealing defect. DM is an osteogenic cell type that both participates in and stimulates osseous healing in a hASC-engrafted calvarial defect. Furthermore, DM-derived BMP-2 paracrine stimulation appears to play a key role for hASC mediated repair.

  View details for DOI 10.1002/stem.670

  View details for Web of Science ID 000293133900009

  View details for PubMedID 21656608

  View details for PubMedCentralID PMC4353733

• Fgf-18 Is Required for Osteogenesis But Not Angiogenesis During Long Bone Repair TISSUE ENGINEERING PART A Behr, B., Sorkin, M., Manu, A., Lehnhardt, M., Longaker, M. T., Quarto, N. 2011; 17 (15-16): 2061-2069

  Abstract

  Bone regeneration is a complex event that requires the interaction of numerous growth factors. Fibroblast growth factor (Fgf)-ligands have been previously described for their importance in osteogenesis during development. In the current study, we investigated the role of Fgf-18 during bone regeneration. By utilizing a unicortical tibial defect model, we revealed that mice haploinsufficient for Fgf-18 have a markedly reduced healing capacity as compared with wild-type mice. Reduced levels of Runx2 and Osteocalcin but not Vegfa accompanied the impaired bone regeneration. Interestingly, our data indicated that upon injury angiogenesis was not impaired in Fgf-18(+/-) mice. Moreover, other Fgf-ligands and Bmp-2 could not compensate for the loss of Fgf-18. Finally, application of FGF-18 protein was able to rescue the impaired healing in Fgf-18(+/-) mice. Thus, we identified Fgf-18 as an important mediator of bone regeneration, which is required during later stages of bone regeneration. This study provides hints on how to engineering efficiently programmed bony tissue for long bone repair.

  View details for DOI 10.1089/ten.tea.2010.0719

  View details for Web of Science ID 000293217700015

  View details for PubMedID 21457097

  View details for PubMedCentralID PMC3142654

• An Information Theoretic, Microfluidic-Based Single Cell Analysis Permits Identification of Subpopulations among Putatively Homogeneous Stem Cells PLOS ONE Glotzbach, J. P., Januszyk, M., Vial, I. N., Wong, V. W., Gelbard, A., Kalisky, T., Thangarajah, H., Longaker, M. T., Quake, S. R., Chu, G., Gurtner, G. C. 2011; 6 (6)

  Abstract

  An incomplete understanding of the nature of heterogeneity within stem cell populations remains a major impediment to the development of clinically effective cell-based therapies. Transcriptional events within a single cell are inherently stochastic and can produce tremendous variability, even among genetically identical cells. It remains unclear how mammalian cellular systems overcome this intrinsic noisiness of gene expression to produce consequential variations in function, and what impact this has on the biologic and clinical relevance of highly 'purified' cell subgroups. To address these questions, we have developed a novel method combining microfluidic-based single cell analysis and information theory to characterize and predict transcriptional programs across hundreds of individual cells. Using