Lab Affiliations


All Publications


  • Continuous hemoadsorption with a cytokine adsorber during sepsis - a review of the literature. International journal of artificial organs Houschyar, K. S., Pyles, M. N., Rein, S., Nietzschmann, I., Duscher, D., Maan, Z. N., Weissenberg, K., Philipps, H. M., Strauss, C., Reichelt, B., Siemers, F. 2017; 40 (5): 205-211

    Abstract

    Sepsis is a well-recognized healthcare issue worldwide, ultimately resulting in significant mortality, morbidity and resource utilization during and after critical illness. In its most severe form, sepsis causes multi-organ dysfunction that produces a state of critical illness characterized by severe immune dysfunction and catabolism. Sepsis induces the activation of complement factor via 3 pathways and the release of inflammatory cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin-1beta (IL-1β), resulting in a systemic inflammatory response. The inflammatory cytokines and nitric oxide release induced by sepsis decrease systemic vascular resistance, resulting in profound hypotension. The combination of hypotension and microvascular occlusion results in tissue ischemia and ultimately leads to multiple organ failure. Several clinical and experimental studies have reported that treatment using adsorption of cytokines is beneficial during endotoxemia and sepsis. This review article analyzes the efficacy of CytoSorb® adsorber in reducing the inflammatory response during sepsis. The CytoSorb® adsorber is known to have excellent adsorption rates for inflammatory cytokines such as IL-1β, IL-6, IL-8, IL-10, and TNF-α. Studies have demonstrated that treatment with cytokine adsorbing columns has beneficial effects on the survival rate and inflammatory responses in animal septic models. Additionally, several cases have been reported in which treatment with cytokine adsorbing columns is very effective in hemodynamic stabilization and in preventing organ failure in critically ill patients. Although further investigations and clinical trials are needed, treatment with cytokine adsorbing columns may play an important role in the treatment of sepsis in the near future.

    View details for DOI 10.5301/ijao.5000591

    View details for PubMedID 28525674

  • Reverse Radial Forearm Flap. Plastic and reconstructive surgery. Global open Maan, Z. N., Legrand, A., Long, C., Chang, J. C. 2017; 5 (4)

    Abstract

    Supplemental Digital Content is available in the text.

    View details for DOI 10.1097/GOX.0000000000001287

    View details for PubMedID 28507856

    View details for PubMedCentralID PMC5426875

  • 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

  • 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

  • Multiple Subsets of Brain Tumor Initiating Cells Coexist in Glioblastoma STEM CELLS Rennert, R. C., Achrol, A. S., Januszyk, M., Kahn, S. A., Liu, T. T., Liu, Y., Sahoo, D., Rodrigues, M., Maan, Z. N., Wong, V. W., Cheshier, S. H., Chang, S. D., Steinberg, G. K., Harsh, G. R., Gurtner, G. C. 2016; 34 (6): 1702-1707

    Abstract

    Brain tumor-initiating cells (BTICs) are self-renewing multipotent cells critical for tumor maintenance and growth. Using single-cell microfluidic profiling, we identified multiple subpopulations of BTICs co-existing in human glioblastoma, characterized by distinct surface marker expression and single-cell molecular profiles relating to distinct bulk tissue molecular subtypes. These data suggest BTIC subpopulation heterogeneity as an underlying source of intra-tumoral bulk tissue molecular heterogeneity, and will support future studies into BTIC subpopulation-specific therapies. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1002/stem.2359

    View details for Web of Science ID 000378089500025

    View details for PubMedID 26991945

  • Microfluidic single-cell transcriptional analysis rationally identifies novel surface marker profiles to enhance cell-based therapies NATURE COMMUNICATIONS Rennert, R. C., Januszyk, M., Sorkin, M., Rodrigues, M., Maan, Z. N., Duscher, D., Whittam, A. J., Kosaraju, R., Chung, M. T., Paik, K., Li, A. Y., Findlay, M., Glotzbach, J. P., Butte, A. J., Gurtner, G. C. 2016; 7

    Abstract

    Current progenitor cell therapies have only modest efficacy, which has limited their clinical adoption. This may be the result of a cellular heterogeneity that decreases the number of functional progenitors delivered to diseased tissue, and prevents correction of underlying pathologic cell population disruptions. Here, we develop a high-resolution method of identifying phenotypically distinct progenitor cell subpopulations via single-cell transcriptional analysis and advanced bioinformatics. When combined with high-throughput cell surface marker screening, this approach facilitates the rational selection of surface markers for prospective isolation of cell subpopulations with desired transcriptional profiles. We establish the usefulness of this platform in costly and highly morbid diabetic wounds by identifying a subpopulation of progenitor cells that is dysfunctional in the diabetic state, and normalizes diabetic wound healing rates following allogeneic application. We believe this work presents a logical framework for the development of targeted cell therapies that can be customized to any clinical application.

    View details for DOI 10.1038/ncomms11945

    View details for Web of Science ID 000379085200001

    View details for PubMedID 27324848

  • 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

  • High-Resolution Microfluidic Single-Cell Transcriptional Profiling Reveals Clinically Relevant Subtypes among Human Stem Cell Populations Commonly Utilized in Cell-Based Therapies FRONTIERS IN NEUROLOGY Rennert, R. C., Schaefer, R., Bliss, T., Januszyk, M., Sorkin, M., Achrol, A. S., Rodrigues, M., Maan, Z. N., Kluba, T., Steinberg, G. K., Gurtner, G. C. 2016; 7
  • Extracellular superoxide dismutase deficiency impairs wound healing in advanced age by reducing neovascularization and fibroblast function EXPERIMENTAL DERMATOLOGY Fujiwara, T., Duscher, D., Rustad, K. C., Kosaraju, R., Rodrigues, M., Whittam, A. J., Januszyk, M., Maan, Z. N., Gurtner, G. C. 2016; 25 (3): 206-211

    View details for DOI 10.1111/exd.12909

    View details for Web of Science ID 000373072800285

  • Sutureless Microsurgical Anastomosis Using an Optimized Thermoreversible Intravascular Poloxamer Stent. Plastic and reconstructive surgery Davis, C. R., Rappleye, C. T., Than, P. A., Rodrigues, M., Findlay, M. W., Bishop, S. N., Whitmore, A. J., Maan, Z. N., McGoldrick, R. B., Grobbelaar, A. O., Gurtner, G. C. 2016; 137 (2): 546-556

    Abstract

    Sutureless microvascular anastomosis has great translational potential to simplify microvascular surgery, shorten operative times, and improve clinical outcomes. The authors developed a transient thermoreversible microvascular stent using a poloxamer to maintain vessel lumen patency before application of commercially available adhesives to seal the anastomosis instead of sutures. Despite technical success, human application necessitates bovine serum albumin removal from existing formulations; rapid poloxamer transition between states; and increased stiffness for reliable, reproducible, and precise microvascular approximation.Two commercially available poloxamers were used in this study (P407 and P188). After removing bovine serum albumin, each poloxamer was tested at varying concentrations either alone or in combination to determine the optimal preparation for sutureless microvascular anastomosis. Transition temperature and formulation stiffness were tested in vitro by rheometry, with the most promising combinations tested in an established in vivo model.Increasing poloxamer concentration resulted in an increase in stiffness and decrease in transition temperature. Pure P188 without bovine serum albumin, dissolved in phosphate-buffered saline to a 45% concentration, demonstrated desirable rheologic behavior, with precise gel transition and increased gel stiffness compared with our previous formulation of 17% P407 (96 kPa versus 10 kPa). These characteristics were optimal for microsurgical intravascular use, offering surgical precision and control between liquid and solid states, depending on the surgically controlled local temperature.Use of 45% P188 without bovine serum albumin demonstrated optimal rheologic and translational properties as a microvascular stent for sutureless anastomosis. Rapid transition, increased stiffness, and safety profile demonstrate safe translational application for human clinical trials.

    View details for DOI 10.1097/01.prs.0000475774.37267.3f

    View details for PubMedID 26818289

  • Challenges and Opportunities in Drug Delivery for Wound Healing. Advances in wound care Whittam, A. J., Maan, Z. N., Duscher, D., Wong, V. W., Barrera, J. A., Januszyk, M., Gurtner, G. C. 2016; 5 (2): 79-88

    Abstract

    Significance: Chronic wounds remain a significant public health problem. Alterations in normal physiological processes caused by aging or diabetes lead to impaired tissue repair and the development of chronic and nonhealing wounds. Understanding the unique features of the wound environment will be required to develop new therapeutics that impact these disabling conditions. New drug-delivery systems (DDSs) may enhance current and future therapies for this challenging clinical problem. Recent Advances: Historically, physical barriers and biological degradation limited the efficacy of DDSs in wound healing. In aiming at improving and optimizing drug delivery, recent data suggest that combinations of delivery mechanisms, such as hydrogels, small molecules, RNA interference (RNAi), as well as growth factor and stem cell-based therapies (biologics), could offer exciting new opportunities for improving tissue repair. Critical Issues: The lack of effective therapeutic approaches to combat the significant disability associated with chronic wounds has become an area of increasing clinical concern. However, the unique challenges of the wound environment have limited the development of effective therapeutic options for clinical use. Future Directions: New platforms presented in this review may provide clinicians and scientists with an improved understanding of the alternatives for drug delivery in wound care, which may facilitate the development of new therapeutic approaches for patients.

    View details for PubMedID 26862465

  • Adipose-Derived Stem Cell-Seeded Hydrogels Increase Endogenous Progenitor Cell Recruitment and Neovascularization in Wounds TISSUE ENGINEERING PART A Kosaraju, R., Rennert, R. C., Maan, Z. N., Duscher, D., Barrera, J., Whittam, A. J., Januszyk, M., Rajadas, J., Rodrigues, M., Gurtner, G. C. 2016; 22 (3-4): 295-305

    Abstract

    Adipose-derived mesenchymal stem cells (ASCs) are appealing for cell-based wound therapies because of their accessibility and ease of harvest, but their utility is limited by poor cell survival within the harsh wound microenvironment. In prior work, our laboratory has demonstrated that seeding ASCs within a soft pullulan-collagen hydrogel enhances ASC survival and improves wound healing. To more fully understand the mechanism of this therapy, we examined whether ASC-seeded hydrogels were able to modulate the recruitment and/or functionality of endogenous progenitor cells. Employing a parabiosis model and fluorescence-activated cell sorting analysis, we demonstrate that application of ASC-seeded hydrogels to wounds, when compared with injected ASCs or a noncell control, increased the recruitment of provascular circulating bone marrow-derived mesenchymal progenitor cells (BM-MPCs). BM-MPCs comprised 23.0% of recruited circulating progenitor cells in wounds treated with ASC-seeded hydrogels versus 8.4% and 2.1% in those treated with controls, p < 0.05. Exploring the potential for functional modulation of BM-MPCs, we demonstrate a statistically significant increase in BM-MPC migration, proliferation, and tubulization when exposed to hydrogel-seeded ASC-conditioned medium versus control ASC-conditioned medium (73.8% vs. 51.4% scratch assay closure; 9.1% vs. 1.4% proliferation rate; 10.2 vs. 5.5 tubules/HPF; p < 0.05 for all assays). BM-MPC expression of genes related to cell stemness and angiogenesis was also significantly increased following exposure to hydrogel-seeded ASC-conditioned medium (p < 0.05). These data suggest that ASC-seeded hydrogels improve both progenitor cell recruitment and functionality to effect greater neovascularization.

    View details for DOI 10.1089/ten.tea.2015.0277

    View details for Web of Science ID 000369987900012

    View details for PubMedID 26871860

    View details for PubMedCentralID PMC4779321

  • 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

  • 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
  • Stem Cells in Wound Healing: The Future of Regenerative Medicine? A Mini-Review. Gerontology Duscher, D., Barrera, J., Wong, V. W., Maan, Z. N., Whittam, A. J., Januszyk, M., Gurtner, G. C. 2016; 62 (2): 216-225

    Abstract

    The increased risk of disease and decreased capacity to respond to tissue insult in the setting of aging results from complex changes in homeostatic mechanisms, including the regulation of oxidative stress and cellular heterogeneity. In aged skin, the healing capacity is markedly diminished resulting in a high risk for chronic wounds. Stem cell-based therapies have the potential to enhance cutaneous regeneration, largely through trophic and paracrine activity. Candidate cell populations for therapeutic application include adult mesenchymal stem cells, embryonic stem cells and induced pluripotent stem cells. Autologous cell-based approaches are ideal to minimize immune rejection but may be limited by the declining cellular function associated with aging. One strategy to overcome age-related impairments in various stem cell populations is to identify and enrich with functionally superior stem cell subsets via single cell transcriptomics. Another approach is to optimize cell delivery to the harsh environment of aged wounds via scaffold-based cell applications to enhance engraftment and paracrine activity of therapeutic stem cells. In this review, we shed light on challenges and recent advances surrounding stem cell therapies for wound healing and discuss limitations for their clinical adoption.

    View details for DOI 10.1159/000381877

    View details for PubMedID 26045256

  • 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

  • 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

    View details for DOI 10.3791/53430

    View details for Web of Science ID 000368577400023

  • The Role of Current Techniques and Concepts in Peripheral Nerve Repair. Plastic surgery international Houschyar, K. S., Momeni, A., Pyles, M. N., Cha, J. Y., Maan, Z. N., Duscher, D., Jew, O. S., Siemers, F., van Schoonhoven, J. 2016; 2016: 4175293-?

    Abstract

    Patients with peripheral nerve injuries, especially severe injury, often face poor nerve regeneration and incomplete functional recovery, even after surgical nerve repair. This review summarizes treatment options of peripheral nerve injuries with current techniques and concepts and reviews developments in research and clinical application of these therapies.

    View details for DOI 10.1155/2016/4175293

    View details for PubMedID 26904282

    View details for PubMedCentralID PMC4745297

  • Fibroblast-Specific Deletion of Hypoxia Inducible Factor-1 Critically Impairs Murine Cutaneous Neovascularization and Wound Healing PLASTIC AND RECONSTRUCTIVE SURGERY Duscher, D., Maan, Z. N., Whittam, A. J., Sorkin, M., Hu, M. S., Walmsley, G. G., Baker, H., Fischer, L. H., Januszyk, M., Wong, V. W., Gurtner, G. C. 2015; 136 (5): 1004-1013

    View details for Web of Science ID 000364092800001

    View details for PubMedID 26505703

  • Medical leech therapy in plastic reconstructive surgery. Wiener medizinische Wochenschrift Houschyar, K. S., Momeni, A., Maan, Z. N., Pyles, M. N., Jew, O. S., Strathe, M., Michalsen, A. 2015; 165 (19-20): 419-425

    Abstract

    The use of Hirudo medicinalis in clinical practice has increased in recent years. The primary indication in plastic surgery has traditionally been venous congestion. However, other reported clinical applications were in varicose veins, thrombophlebitis, and osteoarthritis. In this review, we summarize recent data elucidating the role that medicinal leeches play in the field of plastic surgery.

    View details for DOI 10.1007/s10354-015-0382-5

    View details for PubMedID 26297126

  • Gigantic LCFA-SCIP Mosaic Flap for Upper Extremity Reconstruction. Plastic and reconstructive surgery. Global open Pollhammer, M. S., Duscher, D., Maan, Z. N., Schmidt, M., Huemer, G. M. 2015; 3 (9)

    View details for DOI 10.1097/GOX.0000000000000463

    View details for PubMedID 26495219

  • 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

  • Wnt signaling induces epithelial differentiation during cutaneous wound healing. Organogenesis Houschyar, K. S., Momeni, A., Pyles, M. N., Maan, Z. N., Whittam, A. J., Siemers, F. 2015; 11 (3): 95-104

    View details for DOI 10.1080/15476278.2015.1086052

    View details for PubMedID 26309090

  • 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

  • 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

  • Injuries to Appendage Extremities and Digit Tips: A Clinical and Cellular Update DEVELOPMENTAL DYNAMICS Rinkevich, Y., Maan, Z. N., Walmsley, G. G., Sen, S. K. 2015; 244 (5): 641-650

    Abstract

    The regrowth of amputated appendage extremities and the distal tips of digits represent models of tissue regeneration in multiple vertebrate taxa. In humans, digit tip injuries, including traumatic amputation and crush injuries, are among the most common type of injury to the human hand. Despite clinical reports demonstrating natural regeneration of appendages in lower vertebrates and human digits, current treatment options are suboptimal, and are complicated by the anatomical complexities and functions of the different tissues within the digits.In light of these challenges, we focus on recent advancements in understanding appendage regeneration from model organisms. We pay special attention to the cellular programs underlying appendage regeneration, where cumulative data from salamanders, fish, frogs, and mice indicate that regeneration occurs by the actions of lineage-restricted precursors. We focus on pathologic states and the interdependency that exists, in both humans and animal models, between the nail organ and the peripheral nerves for successful regeneration.The increased understanding of regeneration in animal models may open new opportunities for basic and translational research aimed at understanding the mechanisms that support limb regeneration, as well as amelioration of limb abnormalities and pathologies.

    View details for DOI 10.1002/dvdy.24265

    View details for Web of Science ID 000353953600002

    View details for PubMedID 25715837

  • 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-?
  • 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

  • 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

  • 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

  • Cell recruitment by amnion chorion grafts promotes neovascularization JOURNAL OF SURGICAL RESEARCH Maan, Z. N., Rennert, R. C., Koob, T. J., Januszyk, M., Li, W. W., Gurtner, G. C. 2015; 193 (2): 953-962

    Abstract

    Nonhealing wounds are a significant health burden. Stem and progenitor cells can accelerate wound repair and regeneration. Human amniotic membrane has demonstrated efficacy in promoting wound healing, though the underlying mechanisms remain unknown. A dehydrated human amnion chorion membrane (dHACM) was tested for its ability to recruit hematopoietic progenitor cells to a surgically implanted graft in a murine model of cutaneous ischemia.dHACM was subcutaneously implanted under elevated skin (ischemic stimulus) in either wild-type mice or mice surgically parabiosed to green fluorescent protein (GFP) + reporter mice. A control acellular dermal matrix, elevated skin without an implant, and normal unwounded skin were used as controls. Wound tissue was harvested and processed for histology and flow cytometric analysis.Implanted dHACMs recruited significantly more progenitor cells compared with controls (*P < 0.05) and displayed in vivo SDF-1 expression with incorporation of CD34 + progenitor cells within the matrix. Parabiosis modeling confirmed the circulatory origin of recruited cells, which coexpressed progenitor cell markers and were localized to foci of neovascularization within implanted matrices.In summary, dHACM effectively recruits circulating progenitor cells, likely because of stromal derived factor 1 (SDF-1) expression. The recruited cells express markers of "stemness" and localize to sites of neovascularization, providing a partial mechanism for the clinical efficacy of human amniotic membrane in the treatment of chronic wounds.

    View details for DOI 10.1016/j.jss.2014.08.045

    View details for Web of Science ID 000346244300056

    View details for PubMedID 25266600

  • 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

  • Transdermal deferoxamine prevents pressure-induced diabetic ulcers. Proceedings of the National Academy of Sciences of the United States of America Duscher, D., Neofytou, E., Wong, V. W., Maan, Z. N., Rennert, R. C., Inayathullah, M., Januszyk, M., Rodrigues, M., Malkovskiy, A. V., Whitmore, A. J., Walmsley, G. G., Galvez, M. G., Whittam, A. J., Brownlee, M., Rajadas, J., Gurtner, G. C. 2015; 112 (1): 94-99

    Abstract

    There is a high mortality in patients with diabetes and severe pressure ulcers. For example, chronic pressure sores of the heels often lead to limb loss in diabetic patients. A major factor underlying this is reduced neovascularization caused by impaired activity of the transcription factor hypoxia inducible factor-1 alpha (HIF-1α). In diabetes, HIF-1α function is compromised by a high glucose-induced and reactive oxygen species-mediated modification of its coactivator p300, leading to impaired HIF-1α transactivation. We examined whether local enhancement of HIF-1α activity would improve diabetic wound healing and minimize the severity of diabetic ulcers. To improve HIF-1α activity we designed a transdermal drug delivery system (TDDS) containing the FDA-approved small molecule deferoxamine (DFO), an iron chelator that increases HIF-1α transactivation in diabetes by preventing iron-catalyzed reactive oxygen stress. Applying this TDDS to a pressure-induced ulcer model in diabetic mice, we found that transdermal delivery of DFO significantly improved wound healing. Unexpectedly, prophylactic application of this transdermal delivery system also prevented diabetic ulcer formation. DFO-treated wounds demonstrated increased collagen density, improved neovascularization, and reduction of free radical formation, leading to decreased cell death. These findings suggest that transdermal delivery of DFO provides a targeted means to both prevent ulcer formation and accelerate diabetic wound healing with the potential for rapid clinical translation.

    View details for DOI 10.1073/pnas.1413445112

    View details for PubMedID 25535360

  • Evaluating the Effect of Cell Culture on Gene Expression in Primary Tissue Samples Using Microfluidic-Based Single Cell Transcriptional Analysis. Microarrays (Basel, Switzerland) Januszyk, M., Rennert, R. C., Sorkin, M., Maan, Z. N., Wong, L. K., Whittam, A. J., Whitmore, A., Duscher, D., Gurtner, G. C. 2015; 4 (4): 540-550

    Abstract

    Significant transcriptional heterogeneity is an inherent property of complex tissues such as tumors and healing wounds. Traditional methods of high-throughput analysis rely on pooling gene expression data from hundreds of thousands of cells and reporting a population-wide average that is unable to capture differences within distinct cell subsets. Recent advances in microfluidic technology have permitted the development of large-scale single cell analytic methods that overcome this limitation. The increased granularity afforded by such approaches allows us to answer the critical question of whether expansion in cell culture significantly alters the transcriptional characteristics of cells isolated from primary tissue. Here we examine an established population of human adipose-derived stem cells (ASCs) using a novel, microfluidic-based method for high-throughput transcriptional interrogation, coupled with advanced bioinformatic analysis, to evaluate the dynamics of single cell gene expression among primary, passage 0, and passage 1 stem cells. We find significant differences in the transcriptional profiles of cells from each group, as well as a considerable shift in subpopulation dynamics as those subgroups better able to adhere and proliferate under these culture conditions gradually emerge as dominant. Taken together, these findings reinforce the importance of using primary or very early passage cells in future studies.

    View details for DOI 10.3390/microarrays4040540

    View details for PubMedID 27600239

  • 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

  • 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

  • Burns ITU admissions: Length of stay in specific levels of care for adult and paediatric patients BURNS Maan, Z. N., Frew, Q., Din, A. H., Unluer, Z., Smailes, S., Philp, B., El-Muttardi, N., Dziewulski, P. 2014; 40 (8): 1458-1462
  • Aging disrupts cell subpopulation dynamics and diminishes the function of mesenchymal stem cells SCIENTIFIC REPORTS Duscher, D., Rennert, R. C., Januszyk, M., Anghel, E., Maan, Z. N., Whittam, A. J., Perez, M. G., Kosaraju, R., Hu, M. S., Walmsley, G. G., Atashroo, D., Khong, S., Butte, A. J., Gurtner, G. C. 2014; 4

    View details for DOI 10.1038/srep07144

    View details for Web of Science ID 000346178900001

    View details for PubMedID 25413454

  • 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

  • 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

  • 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

  • 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

  • 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

  • Diabetes impairs the angiogenic potential of adipose-derived stem cells by selectively depleting cellular subpopulations STEM CELL RESEARCH & THERAPY Rennert, R. C., Sorkin, M., Januszyk, M., Duscher, D., Kosaraju, R., Chung, M. T., Lennon, J., Radiya-Dixit, A., Raghvendra, S., Maan, Z. N., Hu, M. S., Rajadas, J., Rodrigues, M., Gurtner, G. C. 2014; 5

    View details for DOI 10.1186/scrt468

    View details for Web of Science ID 000338465500001

  • 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 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 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 15: Characterization of the Endothelial Progenitor Cell from Adult Tissue using Vav/Cre RFP-GFP Murine Model and Single Cell Microfluidics. Plastic and reconstructive surgery Rodrigues, M., Rennert, R. C., Bishop, S., Januszyk, M., Maan, Z., Sorkin, M., Duscher, D., Gurtner, G. C. 2014; 133 (3): 25-?

    View details for DOI 10.1097/01.prs.0000445018.79483.78

    View details for PubMedID 25942126

  • 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

    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

  • 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