All Publications

  • Blockchain, Information Security, Control, and Integrity - Who Is in Charge? Plastic and reconstructive surgery Barrera, J. A., Trotsyuk, A. A., Henn, D., Sivaraj, D., Chen, K., Mittal, S., Mermin-Bunnell, A. M., Larson, M. R., Padmanabhan, J., Kinney, B., Nachbar, J., Sacks, J., Terkonda, S. P., Jeffers, L., Gurtner, G. C. 2023

    Abstract

    Blockchain technology has attracted significant interest in recent years, most notably for its effect on global economics through the advent of cryptocurrency. Within the healthcare domain, blockchain technology has actively been explored as a tool for improving personal health data management, medical device security, and clinical trial management. Despite a strong demand for innovation and cutting-edge technology in Plastic Surgery, integration of Blockchain technologies within our specialty is still in its infancy. Recent advances and mainstream adoption of blockchain are gaining​ momentum​ and have shown significant promise for improving patient care and information management. In this article, we explain what defines a blockchain, and we discuss its history and potential applications in the field of Plastic Surgery. Existing evidence suggests that Blockchain can enable patient-centered data management, improve privacy, and provide additional safeguards against human error. Integration of Blockchain technology into clinical practice requires further research and development to demonstrate its safety and efficacy for patients and providers.

    View details for DOI 10.1097/PRS.0000000000010409

    View details for PubMedID 36917745

  • Postoperative Antibiotics Confer No Protective Association After Fat Grafting for Breast Reconstruction. Annals of plastic surgery Thawanyarat, K., Johnstone, T., Rowley, M., Kim, T., Francis, S., Barrera, J., Cheeseborough, J., Sheckter, C., Nazerali, R. 2023

    Abstract

    INTRODUCTION: Autologous fat grafting after breast reconstruction is a commonly used technique to address asymmetry and irregularities in breast contour. While many studies have attempted to optimize patient outcomes after fat grafting, a key postoperative protocol that lacks consensus is the optimal use of perioperative and postoperative antibiotics. Reports suggest that complication rates for fat grafting are low relative to rates after reconstruction and have been shown to not be correlated to antibiotic protocol. Studies have additionally demonstrated that the use of prolonged prophylactic antibiotics do not lower the complication rates, stressing the need for a more conservative, standardized antibiotic protocol. This study aims to identify the optimal use of perioperative and postoperative antibiotics that optimizes patient outcomes.METHODS: Patients in the Optum Clinformatics Data Mart who underwent all billable forms of breast reconstruction followed by fat grafting were identified via Current Procedural Terminology codes. Patients meeting inclusion criteria had an index reconstructive procedure at least 90 days before fat grafting. Data concerning these patient's demographics, comorbidities, breast reconstructions, perioperative and postoperative antibiotics, and outcomes were collected via querying relevant reports of Current Procedural Terminology; International Classification of Diseases, Ninth Revision; International Classification of Diseases, Tenth Revision; National Drug Code Directory, and Healthcare Common Procedure Coding System codes. Antibiotics were classified by type and temporal delivery: perioperatively or postoperatively. If a patient received postoperative antibiotics, the duration of antibiotic exposure was recorded. Outcomes analysis was limited to the 90-day postoperative period. Multivariable logistic regression was performed to ascertain the effects of age, coexisting conditions, reconstruction type (autologous or implant-based), perioperative antibiotic class, postoperative antibiotic class, and postoperative antibiotic duration on the likelihood of any common postoperative complication occurring. All statistical assumptions made by logistic regression were met successfully. Odds ratios and corresponding 95% confidence intervals were calculated.RESULTS: From more than 86 million longitudinal patient records between March 2004 and June 2019, our study population included 7456 unique records of reconstruction-fat grafting pairs, with 4661 of those pairs receiving some form of prophylactic antibiotics. Age, prior radiation, and perioperative antibiotic administration were consistent independent predictors of increased all-cause complication likelihood. However, administration of perioperative antibiotics approached a statistically significant protective association against infection likelihood. No postoperative antibiotics of any duration or class conferred a protective association against infections or all-cause complications.CONCLUSIONS: This study provides national, claims-level support for antibiotic stewardship during and after fat grafting procedures. Postoperative antibiotics did not confer a protective benefit association against infection or all-cause complication likelihood, while administering perioperative antibiotics conferred a statistically significant increase in the likelihood that a patient experienced postoperative complication. However, perioperative antibiotics approach a significant protective association against postoperative infection likelihood, in line with current guidelines for infection prevention. These findings may encourage the adoption of more conservative postoperative prescription practices for clinicians who perform breast reconstruction, followed by fat grafting, reducing the nonindicated use of antibiotics.

    View details for DOI 10.1097/SAP.0000000000003420

    View details for PubMedID 36880783

  • A bioactive compliant vascular graft modulates macrophage polarization and maintains patency with robust vascular remodeling. Bioactive materials Stahl, A., Hao, D., Barrera, J., Henn, D., Lin, S., Moeinzadeh, S., Kim, S., Maloney, W., Gurtner, G., Wang, A., Yang, Y. P. 2023; 19: 167-178

    Abstract

    Conventional synthetic vascular grafts are associated with significant failure rates due to their mismatched mechanical properties with the native vessel and poor regenerative potential. Though different tissue engineering approaches have been used to improve the biocompatibility of synthetic vascular grafts, it is still crucial to develop a new generation of synthetic grafts that can match the dynamics of native vessel and direct the host response to achieve robust vascular regeneration. The size of pores within implanted biomaterials has shown significant effects on macrophage polarization, which has been further confirmed as necessary for efficient vascular formation and remodeling. Here, we developed biodegradable, autoclavable synthetic vascular grafts from a new polyurethane elastomer and tailored the grafts' interconnected pore sizes to promote macrophage populations with a pro-regenerative phenotype and improve vascular regeneration and patency rate. The synthetic vascular grafts showed similar mechanical properties to native blood vessels, encouraged macrophage populations with varying M2 to M1 phenotypic expression, and maintained patency and vascular regeneration in a one-month rat carotid interposition model and in a four-month rat aortic interposition model. This innovative bioactive synthetic vascular graft holds promise to treat clinical vascular diseases.

    View details for DOI 10.1016/j.bioactmat.2022.04.004

    View details for PubMedID 35510174

  • Two Independent Capsules Surrounding a Single Textured Implant in Ehlers-Danlos Syndrome PLASTIC AND RECONSTRUCTIVE SURGERY-GLOBAL OPEN Padmanabhan, J., Liu, F. C., Sivaraj, D., Henn, D., Chen, K., Simon, D. R., Barrera, J. A., Gunner, G. C. 2022; 10 (8): e4470

    Abstract

    Textured breast implants are associated with prolonged inflammation leading to increased risk for complications such as the development of anaplastic large cell lymphoma. The underlying molecular mechanisms that drive increased inflammation toward textured implants (compared with smooth implants) remain poorly understood. Here, we present the first known case of a patient with Ehlers-Danlos syndrome (EDS) who developed two independent fibrotic capsules around a single textured silicone implant. The patient was found to have one internal capsule tightly adherent to the implant and a second external capsule that was attached to the surrounding tissue. We observed that the internal implant-adherent capsule was composed of a highly aligned and dense collagen network, completely atypical for EDS and indicative of a high mechanical stress environment. In contrast, the external nonadherent capsule, which primarily interacted with the smooth surface of the internal capsule, displayed disorganized collagen fibers with no discernible alignment, classic for EDS. Remarkably, we found that the internal capsule displayed high activation of monocyte chemoattractant protein-1, a mechanoresponsive inflammatory mediator that was not elevated in the disorganized external capsule. Taken together, these findings demonstrate that the tight adhesion between the textured implant surface and the internal capsule creates a high mechanical stress environment, which is responsible for the increased local inflammation observed in the internal capsule. This unique case demonstrates that mechanical stress is able to override genetic defects locally in collagen organization and directly connects the textured surface of implants to prolonged inflammation.

    View details for DOI 10.1097/GOX.0000000000004470

    View details for Web of Science ID 000843700600002

    View details for PubMedID 36032379

    View details for PubMedCentralID PMC9410635

  • 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

  • Arthroscopic Management of Thumb Carpometacarpal Joint Arthritis and Pathology. Hand clinics Barrera, J., Yao, J. 2022; 38 (2): 183-197

    Abstract

    Basilar thumb arthritis is a debilitating condition characterized by pain, reduced joint stability, and reduced capacity for daily activities. Various arthroscopic approaches have been described based on patient factors, as well as radiographic and arthroscopic staging criteria. Here we provide an overview of arthroscopic management of basilar thumb arthritis, including patient evaluation, surgical techniques, outcomes, and new developments. We describe our preferred approach for Eaton stage I-III disease, consisting of arthroscopic hemitrapeziectomy with suture button suspensionplasty. This technique is safe, reliable, and allows for early range of motion and quicker recovery while minimizing scarring and reducing the risk of nerve injury.

    View details for DOI 10.1016/j.hcl.2021.11.002

    View details for PubMedID 35465936

  • Allometric Tissue-Scale Forces Activate Mechanoresponsive Immune Cells To Drive Pathological Foreign Body Response To Biomedical Implants Padmanabhan, J., Chen, K., Sivaraj, D., Kuehlmann, B., Bonham, C., Dohi, T., Henn, D., Stern-Buchbinder, Z., Than, P., Hosseini, H., Barrera, J., Kussie, H., Magbual, N., Borrelli, M., Trotsyuk, A. A., Kwon, S., Dunn, J., Maan, Z., Januszyk, M., Prantl, L., Gurtner, G. C. WILEY. 2022: A19-A20

    View details for Web of Science ID 000763583000048

  • Reinforced Biologic Mesh Reduces Postoperative Complications Compared to Biologic Mesh after Ventral Hernia Repair. Plastic and reconstructive surgery. Global open Sivaraj, D., Henn, D., Fischer, K. S., Kim, T. S., Black, C. K., Lin, J. Q., Barrera, J. A., Leeolou, M. C., Makarewicz, N. S., Chen, K., Perrault, D. P., Gurtner, G. C., Lee, G. K., Nazerali, R. 2022; 10 (2): e4083

    Abstract

    The use of biologic mesh to reinforce the abdominal wall in ventral hernia repair has been proposed as a viable alternative to synthetic mesh, particularly for high-risk patients and in contaminated settings. However, a comparison of clinical outcomes between the currently available biologic mesh types has yet to be performed.We performed a retrospective analysis of 141 patients who had undergone ventral hernia repair with biologic mesh, including noncross-linked porcine ADM (NC-PADM) (n = 51), cross-linked porcine ADM (C-PADM) (n = 17), reinforced biologic ovine rumen (RBOR) (n = 36), and bovine ADM (BADM) (n = 37) at the Stanford University Medical Center between 2002 and 2020. Postoperative donor site complications and rates of hernia recurrence were compared between patients with different biologic mesh types.Abdominal complications occurred in 47.1% of patients with NC-PADM, 52.9% of patients with C-PADM, 16.7% of patients with RBOR, and 43.2% of patients with BADM (P = 0.015). Relative risk for overall complications was higher in patients who had received NC-PADM (RR = 2.64, P = 0.0182), C-PADM (RR = 3.19, P = 0.0127), and BADM (RR = 2.11, P = 0.0773) compared with those who had received RBOR. Furthermore, relative risk for hernia recurrence was also higher in all other mesh types compared with RBOR.Our data indicate that RBOR decreases abdominal complications and recurrence rates after ventral hernia repair compared with NC-PADM, C-PADM, and BADM.

    View details for DOI 10.1097/GOX.0000000000004083

    View details for PubMedID 35141102

    View details for PubMedCentralID PMC8820910

  • Combining Breast and Ovarian Operations Increases Complications. Plastic and reconstructive surgery Henn, D., Barrera, J. A., Sivaraj, D., Lin, J. Q., Rizk, N. M., Ma, I., Gurtner, G. C., Lee, G. K., Nazerali, R. S. 2022

    Abstract

    Breast cancer resulting from a genetic mutation, such as BRCA1 or BRCA2, is seen in 5 to 10 percent of patients. More widespread genetic testing has increased the number of affected women undergoing prophylactic mastectomy and oophorectomy. Recent studies have yielded mixed results regarding complication rates after combined breast and ovarian operations. The authors compared surgical outcomes of breast operations performed in combination with salpingo-oophorectomies or as separate procedures.The authors retrospectively analyzed surgical complications and length of hospital stay in 145 female patients, from which 87 had undergone combined breast surgery and salpingo-oophorectomy, and 58 had undergone these procedures separately. Multivariate logistic regression models were used to calculate odds ratios and 95 percent confidence intervals.Patients undergoing combined breast and ovarian operations experienced higher rates of overall complications (46.5 percent versus 19 percent; p < 0.001), infections (22.2 percent versus 8.6 percent; p < 0.05), and delayed wound healing (13.2 percent versus 0 percent; p < 0.05) related to the breast surgery, when compared with patients undergoing separate procedures. Multivariate logistic regression analysis confirmed a significant association between combined surgery and overall postoperative complications (OR, 5.87; 95 percent CI, 2.03 to 16.91; p = 0.02). Patients undergoing tissue expander-based breast reconstruction combined with ovarian surgery had significantly longer hospital stays compared to patients undergoing separate procedures (3.5 days versus 1.8 days; p < 0.001).The authors' data indicate that combining breast and ovarian operations is associated with a higher risk of postoperative complications related to the breast procedure and increases the duration of hospital stay in patients with tissue expander-based reconstructions. The authors' study provides valuable information for preoperative counseling of patients considering both breast and ovarian surgery.Therapeutic, III.

    View details for DOI 10.1097/PRS.0000000000008984

    View details for PubMedID 35245249

  • IQGAP1-mediated mechanical signaling promotes the foreign body response to biomedical implants. FASEB journal : official publication of the Federation of American Societies for Experimental Biology Sivaraj, D., Padmanabhan, J., Chen, K., Henn, D., Noishiki, C., Trotsyuk, A. A., Kussie, H. C., Leeolou, M. C., Magbual, N. J., Andrikopoulos, S., Perrault, D. P., Barrera, J. A., Januszyk, M., Gurtner, G. C. 2022; 36 (2): e22007

    Abstract

    The aim of this study was to further elucidate the molecular mechanisms that mediate pathologic foreign body response (FBR) to biomedical implants. The longevity of biomedical implants is limited by the FBR, which leads to implant failure and patient morbidity. Since the specific molecular mechanisms underlying fibrotic responses to biomedical implants have yet to be fully described, there are currently no targeted approaches to reduce pathologic FBR. We utilized proteomics analysis of human FBR samples to identify potential molecular targets for therapeutic inhibition of FBR. We then employed a murine model of FBR to further evaluate the role of this potential target. We performed histological and immunohistochemical analysis on the murine FBR capsule tissue, as well as single-cell RNA sequencing (scRNA-seq) on cells isolated from the capsules. We identified IQ motif containing GTPase activating protein 1 (IQGAP1) as the most promising of several targets, serving as a central molecular mediator in human and murine FBR compared to control subcutaneous tissue. IQGAP1-deficient mice displayed a significantly reduced FBR compared to wild-type mice as evidenced by lower levels of collagen deposition and maturity. Our scRNA-seq analysis revealed that decreasing IQGAP1 resulted in diminished transcription of mechanotransduction, inflammation, and fibrosis-related genes, which was confirmed on the protein level with immunofluorescent staining. The deficiency of IQGAP1 significantly attenuates FBR by deactivating downstream mechanotransduction signaling, inflammation, and fibrotic pathways. IQGAP1 may be a promising target for rational therapeutic design to mitigate pathologic FBR around biomedical implants.

    View details for DOI 10.1096/fj.202101354

    View details for PubMedID 35051300

  • The Plane of Mesh Placement Does Not Impact Abdominal Donor Site Complications in Microsurgical Breast Reconstruction. Annals of plastic surgery Henn, D., Sivaraj, D., Barrera, J. A., Lin, J. Q., Chattopadhyay, A., Maan, Z. N., Chen, K., Nguyen, A., Cheesborough, J., Gurtner, G. C., Lee, G. K., Nazerali, R. 2021; 87 (5): 542-546

    Abstract

    BACKGROUND: Reinforcement of the abdominal wall with synthetic mesh in autologous breast reconstruction using abdominal free tissue transfer decreases the risk of bulging and herniation. However, the impact of the plane of mesh placement on donor site complications has not yet been investigated.METHODS: We performed a retrospective analysis of 312 patients who had undergone autologous breast reconstruction with muscle-sparing transverse rectus abdominis myocutaneous (MS-TRAM) flaps or deep inferior epigastric perforator (DIEP) flaps as well as polypropylene mesh implantation at the donor site. Donor site complications were compared among patients with different flap types and different mesh positions including overlay (n = 90), inlay and overlay (I-O; n = 134), and sublay (n = 88).RESULTS: Abdominal hernias occurred in 2.86% of patients who had undergone MS-TRAM reconstructions and in 2.63% of patients who had undergone DIEP reconstructions. When comparing patients with different mesh positions, donor site complications occurred in 14.4% of patients with overlay mesh, 13.4% of patients with I-O mesh, and 10.2% of patients with sublay mesh (P = 0.68). Abdominal hernias occurred in 4.44% of patients with overlay mesh, 2.24% of patients with I-O mesh, and 2.27% of patients with sublay mesh (P = 0.69). Multivariable logistic regression analysis did not identify a significant association between mesh position and hernia rates as well as wound complications.CONCLUSIONS: Our data indicate that the plane of synthetic mesh placement in relation to the rectus abdominis muscle does not impact the rate of postoperative donor site complications in patients undergoing breast reconstruction with MS-TRAM or DIEP flaps.

    View details for DOI 10.1097/SAP.0000000000002897

    View details for PubMedID 34699433

  • 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

  • CRISPR/Cas9 Editing Of Autologous Dendritic Cells To Enhance Angiogenesis And Wound Healing Henn, D., Zhao, D., Bonham, C. A., Chen, K., Greco, A. H., Padmanabhan, J., Sivaraj, D., Trotsyuk, A., Barrera, J. A., Januszyk, M., Qi, L., Gurtner, G. C. WILEY. 2021: A31-A32

    View details for Web of Science ID 000650720500079

  • Adipose-derived stromal cells seeded in pullulan-collagen hydrogels improve healing in murine burns. Tissue engineering. Part A Barrera, J., Trotsyuk, A., Maan, Z. N., Bonham, C. A., Larson, M. R., Mittermiller, P. A., Henn, D., Chen, K., Mays, C. J., Mittal, S., Mermin-Bunnell, A. M., Sivaraj, D., Jing, S., Rodrigues, M., Kwon, S. H., Noishiki, C., Padmanabhan, J., Jiang, Y., Niu, S., Inayathullah, M., Rajadas, J., Januszyk, M., Gurtner, G. C. 2021

    Abstract

    Burn scars and scar contractures cause significant morbidity for patients. Recently, cell-based therapies have been proposed as an option for improving healing and reducing scarring after burn injury, through their known pro-angiogenic and immunomodulatory paracrine effects. Our lab has developed a pullulan-collagen hydrogel that, when seeded with mesenchymal stem cells (MSCs), improves cell viability and augments their pro-angiogenic capacity in vivo. Concurrently, recent research suggests that prospective isolation of cell subpopulations with desirable transcriptional profiles can be used to further improve cell-based therapies. In this study, we examined whether adipose-derived stem cell-seeded hydrogels could improve wound healing following thermal injury using a murine contact burn model. Partial thickness contact burns were created on the dorsum of mice. On days 5 and 10 following injury, burns were debrided and received either ASC-hydrogel, ASC injection alone, hydrogel alone, or no treatment. On days 10 and 25, burns were harvested for histologic and molecular analysis. This experiment was repeated using CD26+/CD55+ FACS-enriched ASCs to further evaluate the regenerative potential of ASCs in wound healing. ASC-hydrogel-treated burns demonstrated accelerated time to re-epithelialization, greater vascularity, and increased expression of the pro-angiogenic genes MCP-1, VEGF, and SDF-1 at both the mRNA and protein level. Expression of the pro-fibrotic gene Timp1 and pro-inflammatory gene Tnfa were down-regulated in ASC-hydrogel treated burns. ASC-hydrogel treated burns exhibited reduced scar area compared to hydrogel-treated and control wounds, with equivalent scar density. CD26+/CD55+ ASC-hydrogel treatment resulted in accelerated healing, increased dermal appendage count, and improved scar quality with a more reticular collagen pattern. Here we find that ASC-hydrogel therapy is effective for treating burns, with demonstrated pro-angiogenic, fibro-modulatory and immunomodulatory effects. Enrichment for CD26+/CD55+ ASCs has additive benefits for tissue architecture and collagen remodeling post-burn injury. Research is ongoing to further facilitate clinical translation of this promising therapeutic approach.

    View details for DOI 10.1089/ten.TEA.2020.0320

    View details for PubMedID 33789446

  • 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

  • Hydrogel Scaffolds to Deliver Cell Therapies for Wound Healing. Frontiers in bioengineering and biotechnology Sivaraj, D., Chen, K., Chattopadhyay, A., Henn, D., Wu, W., Noishiki, C., Magbual, N. J., Mittal, S., Mermin-Bunnell, A. M., Bonham, C. A., Trotsyuk, A. A., Barrera, J. A., Padmanabhan, J., Januszyk, M., Gurtner, G. C. 2021; 9: 660145

    Abstract

    Cutaneous wounds are a growing global health burden as a result of an aging population coupled with increasing incidence of diabetes, obesity, and cancer. Cell-based approaches have been used to treat wounds due to their secretory, immunomodulatory, and regenerative effects, and recent studies have highlighted that delivery of stem cells may provide the most benefits. Delivering these cells to wounds with direct injection has been associated with low viability, transient retention, and overall poor efficacy. The use of bioactive scaffolds provides a promising method to improve cell therapy delivery. Specifically, hydrogels provide a physiologic microenvironment for transplanted cells, including mechanical support and protection from native immune cells, and cell-hydrogel interactions may be tailored based on specific tissue properties. In this review, we describe the current and future directions of various cell therapies and usage of hydrogels to deliver these cells for wound healing applications.

    View details for DOI 10.3389/fbioe.2021.660145

    View details for PubMedID 34012956

  • 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

  • A multivariable miRNA signature delineates the systemic hemodynamic impact of arteriovenous shunt placement in a pilot study. Scientific reports Henn, D., Abu-Halima, M., Kahraman, M., Falkner, F., Fischer, K. S., Barrera, J. A., Chen, K., Gurtner, G. C., Keller, A., Kneser, U., Meese, E., Schmidt, V. J. 2020; 10 (1): 21809

    Abstract

    Arteriovenous (AV) fistulas for hemodialysis can lead to cardiac volume loading and increased serum brain natriuretic peptide (BNP) levels. Whether short-term AV loop placement in patients undergoing microsurgery has an impact on cardiac biomarkers and circulating microRNAs (miRNAs), potentially indicating an increased hemodynamic risk, remains elusive. Fifteen patients underwent AV loop placement with delayed free flap anastomosis for microsurgical reconstructions of lower extremity soft-tissue defects. N-terminal pro-BNP (NT-proBNP), copeptin (CT-proAVP), and miRNA expression profiles were determined in the peripheral blood before and after AV loop placement. MiRNA expression in the blood was correlated with miRNA expression from AV loop vascular tissue. Serum NT-proBNP and copeptin levels exceeded the upper reference limit after AV loop placement, with an especially strong NT-proBNP increase in patients with preexistent cardiac diseases. A miRNA signature of 4 up-regulated (miR-3198, miR-3127-5p, miR-1305, miR-1288-3p) and 2 down-regulated miRNAs (miR30a-5p, miR-145-5p) which are related to cardiovascular physiology, showed a significant systemic deregulation in blood and venous tissue after AV loop placement. AV loop placement causes serum elevations of NT-proBNP, copeptin as well as specific circulating miRNAs, indicating a potentially increased hemodynamic risk for patients with cardiovascular comorbidities, if free flap anastomosis is delayed.

    View details for DOI 10.1038/s41598-020-78905-y

    View details for PubMedID 33311598

  • 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

  • Single-Cell RNA Sequencing Uncovers Antifibrotic Subpopulations of Macrophages in the Cellular Response to Skin Xenografts Henn, D., Chen, K., Maan, Z., Illouz, S., Bonham, C. A., Barrera, J. A., Momeni, A., Wan, D. C., Januszyk, M., Gurtner, G. C. ELSEVIER SCIENCE INC. 2020: S232

    View details for Web of Science ID 000582792300425

  • Tissue Engineering of Axially Vascularized Soft-Tissue Flaps with a Poly-(ɛ-Caprolactone) Nanofiber-Hydrogel Composite. Advances in wound care Henn, D., Chen, K., Fischer, K., Rauh, A., Barrera, J. A., Kim, Y. J., Martin, R. A., Hannig, M., Niedoba, P., Reddy, S. K., Mao, H. Q., Kneser, U., Gurtner, G. C., Sacks, J. M., Schmidt, V. J. 2020; 9 (7): 365-377

    Abstract

    Objective: To develop a novel approach for tissue engineering of soft-tissue flaps suitable for free microsurgical transfer, using an injectable nanofiber hydrogel composite (NHC) vascularized by an arteriovenous (AV) loop. Approach: A rat AV loop model was used for tissue engineering of vascularized soft-tissue flaps. NHC or collagen-elastin (CE) scaffolds were implanted into isolation chambers together with an AV loop and explanted after 15 days. Saphenous veins were implanted into the scaffolds as controls. Neoangiogenesis, ultrastructure, and protein expression of SYNJ2BP, EPHA2, and FOXC1 were analyzed by immunohistochemistry and compared between the groups. Rheological properties were compared between the two scaffolds and native human adipose tissue. Results: A functional neovascularization was evident in NHC flaps with its amount being comparable with CE flaps. Scanning electron microscopy revealed a strong mononuclear cell infiltration along the nanofibers in NHC flaps and a trend toward higher fiber alignment compared with CE flaps. SYNJ2BP and EPHA2 expression in endothelial cells (ECs) was lower in NHC flaps compared with CE flaps, whereas FOXC1 expression was increased in NHC flaps. Compared with the stiffer CE flaps, the NHC flaps showed similar rheological properties to native human adipose tissue. Innovation: This is the first study to demonstrate the feasibility of tissue engineering of soft-tissue flaps with similar rheological properties as human fat, suitable for microsurgical transfer using an injectable nanofiber hydrogel composite. Conclusions: The injectable NHC scaffold is suitable for tissue engineering of axially vascularized soft-tissue flaps with a solid neovascularization, strong cellular infiltration, and biomechanical properties similar to human fat. Our data indicate that SYNJ2BP, EPHA2, and FOXC1 are involved in AV loop-associated angiogenesis and that the scaffold material has an impact on protein expression in ECs.

    View details for DOI 10.1089/wound.2019.0975

    View details for PubMedID 32587789

    View details for PubMedCentralID PMC7307685

  • Flexible smart bandage for wireless wound healing Trotsyuk, A. A., Jiang, Y., Niu, S., Larson, M., Beard, E., Saberi, A., Henn, D., Kwon, S., Bonham, C., Chen, K., Januszyk, M., Maan, Z., Barrera, J., Padmanabhan, J., Fischer, K. S., Bao, Z., Gurtner, G. C. WILEY. 2020: S24

    View details for Web of Science ID 000548418300050

  • Digit tip regeneration relies on germ layer restricted Wnt and Hedgehog signaling Barrera, J., Maan, Z., Rinkevich, Y., Henn, D., Chen, K., Bonham, C. A., Padmanabhan, J., Januszyk, M., Weissman, I. L., Gurtner, G. C. WILEY. 2020: S5

    View details for Web of Science ID 000548418300006

  • Human cryopreserved skingrafts recruit M2-macrophages and induce angiogenesis in a murine xenograft model Henn, D., Chen, K., Maan, Z. N., Illouz, S., Bonham, C. A., Fischer, K. S., Padmanabhan, J., Barrera, J. A., Wan, D. C., Januszyk, M., Gurtner, G. C. WILEY. 2020: S62–S63

    View details for Web of Science ID 000548418300144

  • 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

  • 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

  • Conformable hyaluronic acid hydrogel delivers adipose-derived stem cells and promotes regeneration of burn injury. Acta biomaterialia Dong, Y., Cui, M., Qu, J., Wang, X., Kwon, S. H., Barrera, J., Elvassore, N., Gurtner, G. C. 2020

    Abstract

    Injury to the skin from severe burns can cause debilitating physical and psychosocial distress to the patients. Upon healing, deep dermal burns often result in devastating hypertrophic scar formation. For many decades, stem cell-based therapies have shown significant potential in improving wound healing. However, current cell delivery methods are often insufficient to maintain cell viability in a harmful burn wound environment to promote skin regeneration. In this study, we developed an enhanced approach to deliver adipose-derived stem cells (ASCs) for the treatment of burn wounds, using an in-situ-formed hydrogel system comprised of a multifunctional hyperbranched poly(ethylene glycol) diacrylate (HB-PEGDA) polymer, a commercially available thiol-functionalized hyaluronic acid (HA-SH) and a short RGD peptide. Stable hydrogels with tunable swelling and mechanical properties form within five minutes under physiological conditions via the Michael-type addition reaction. Combining with RGD peptide, as a cell adhesion motif, significantly alters the cellular morphology, enhances cell proliferation, and increases the paracrine activity of angiogenesis and tissue remodeling cytokines. Bioluminescence imaging of luciferase+ ASCs indicated that the hydrogel protected the implanted cells from the harmful wound environment in burns. Hydrogel-ASC treatment significantly enhanced neovascularization, accelerated wound closure and reduced the scar formation. Our findings suggest that PEG-HA-RGD-based hydrogel provides an effective niche capable of augmenting the regenerative potential of ASCs and promoting burn wound healing. Statement of Significance Burn injury is one of the most devastating injures, and patients suffer from many complications and post-burn scar formation despite modern therapies. Here, we designed a conformable hydrogel-based stem cell delivery platform that allows rapid in-situ gelation upon contact with wounds. Adipose-derived stem cells were encapsulated into a PEG-HA-RGD hydrogels. Introducing of RGD motif significantly improved the cellular morphology, proliferation, and secretion of angiogenesis and remodeling cytokines. A deep second-degree burn murine model was utilized to evaluate in-vivo cell retention and therapeutic effect of the hydrogel-ASC-based therapy on burn wound healing. Our hydrogel remarkably improved ASCs viability in burn wounds and the hydrogel-ASC treatment enhanced the neovascularization, promoted wound closure, and reduced scar formation.

    View details for DOI 10.1016/j.actbio.2020.03.040

    View details for PubMedID 32251786

  • Tissue Engineering of Axially Vascularized Soft-Tissue Flaps with a Poly-(e-Caprolactone) Nanofiber-Hydrogel Composite ADVANCES IN WOUND CARE Henn, D., Chen, K., Fischer, K., Rauh, A., Barrera, J. A., Kim, Y., Martin, R., Hannig, M., Niedoba, P., Reddy, S., Mao, H., Kneser, U., Gurtner, G., Sacks, J. M., Schmidt, V. J. 2020

    View details for DOI 10.1089/wound.2019.0975

    View details for Web of Science ID 000507502700001

  • Cryopreserved human skin allografts promote angiogenesis and dermal regeneration in a murine model. International wound journal Henn, D. n., Chen, K. n., Maan, Z. N., Greco, A. H., Moortgat Illouz, S. E., Bonham, C. A., Barrera, J. A., Trotsyuk, A. A., Padmanabhan, J. n., Momeni, A. n., Wan, D. C., Nguyen, D. n., Januszyk, M. n., Gurtner, G. C. 2020

    Abstract

    Cryopreserved human skin allografts (CHSAs) are used for the coverage of major burns when donor sites for autografts are insufficiently available and have clinically shown beneficial effects on chronic non-healing wounds. However, the biologic mechanisms behind the regenerative properties of CHSA remain elusive. Furthermore, the impact of cryopreservation on the immunogenicity of CHSA has not been thoroughly investigated and raised concerns with regard to their clinical application. To investigate the importance and fate of living cells, we compared cryopreserved CHSA with human acellular dermal matrix (ADM) grafts in which living cells had been removed by chemical processing. Both grafts were subcutaneously implanted into C57BL/6 mice and explanted after 1, 3, 7, and 28 days (n = 5 per group). A sham surgery where no graft was implanted served as a control. Transmission electron microscopy (TEM) and flow cytometry were used to characterise the ultrastructure and cells within CHSA before implantation. Immunofluorescent staining of tissue sections was used to determine the immune reaction against the implanted grafts, the rate of apoptotic cells, and vascularisation as well as collagen content of the overlaying murine dermis. Digital quantification of collagen fibre alignment on tissue sections was used to quantify the degree of fibrosis within the murine dermis. A substantial population of live human cells with intact organelles was identified in CHSA prior to implantation. Subcutaneous pockets with implanted xenografts or ADMs healed without clinically apparent rejection and with a similar cellular immune response. CHSA implantation largely preserved the cellularity of the overlying murine dermis, whereas ADM was associated with a significantly higher rate of cellular apoptosis, identified by cleaved caspase-3 staining, and a stronger dendritic cell infiltration of the murine dermis. CHSA was found to induce a local angiogenic response, leading to significantly more vascularisation of the murine dermis compared with ADM and sham surgery on day 7. By day 28, aggregate collagen-1 content within the murine dermis was greater following CHSA implantation compared with ADM. Collagen fibre alignment of the murine dermis, correlating with the degree of fibrosis, was significantly greater in the ADM group, whereas CHSA maintained the characteristic basket weave pattern of the native murine dermis. Our data indicate that CHSAs promote angiogenesis and collagen-1 production without eliciting a significant fibrotic response in a xenograft model. These findings may provide insight into the beneficial effects clinically observed after treatment of chronic wounds and burns with CHSA.

    View details for DOI 10.1111/iwj.13349

    View details for PubMedID 32227459

  • Current and Emerging Topical Scar Mitigation Therapies for Craniofacial Burn Wound Healing. Frontiers in physiology Kwon, S. H., Barrera, J. A., Noishiki, C. n., Chen, K. n., Henn, D. n., Sheckter, C. C., Gurtner, G. C. 2020; 11: 916

    Abstract

    Burn injury in the craniofacial region causes significant health and psychosocial consequences and presents unique reconstructive challenges. Healing of severely burned skin and underlying soft tissue is a dynamic process involving many pathophysiological factors, often leading to devastating outcomes such as the formation of hypertrophic scars and debilitating contractures. There are limited treatment options currently used for post-burn scar mitigation but recent advances in our knowledge of the cellular and molecular wound and scar pathophysiology have allowed for development of new treatment concepts. Clinical effectiveness of these experimental therapies is currently being evaluated. In this review, we discuss current topical therapies for craniofacial burn injuries and emerging new therapeutic concepts that are highly translational.

    View details for DOI 10.3389/fphys.2020.00916

    View details for PubMedID 32848859

    View details for PubMedCentralID PMC7403506

  • 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

  • Optimization of transdermal deferoxamine leads to enhanced efficacy in healing skin wounds. Journal of controlled release : official journal of the Controlled Release Society Duscher, D. n., Trotsyuk, A. A., Maan, Z. N., Kwon, S. H., Rodrigues, M. n., Engel, K. n., Stern-Buchbinder, Z. A., Bonham, C. A., Whittam, A. J., Barrera, J. n., Hu, M. S., Inayathullah, M. n., Rajadas, J. n., Gurtner, G. C. 2019

    Abstract

    Chronic wounds remain a significant burden to both the healthcare system and individual patients, indicating an urgent need for new interventions. Deferoxamine (DFO), an iron-chelating agent clinically used to treat iron toxicity, has been shown to reduce oxidative stress and increase hypoxia-inducible factor-1 alpha (HIF-1α) activation, thereby promoting neovascularization and enhancing regeneration in chronic wounds. However due to its short half-life and adverse side effects associated with systemic absorption, there is a pressing need for targeted DFO delivery. We recently published a preclinical proof of concept drug delivery system (TDDS) which showed that transdermally applied DFO is effective in improving chronic wound healing. Here we present an enhanced TDDS (eTDDS) comprised exclusively of FDA-compliant constituents to optimize drug release and expedite clinical translation. We evaluate the eTDDS to the original TDDS and compare this with other commonly used delivery methods including DFO drip-on and polymer spray applications. The eTDDS displayed excellent physicochemical characteristics and markedly improved DFO delivery into human skin when compared to other topical application techniques. We demonstrate an accelerated wound healing response with the eTDDS treatment resulting in significantly increased wound vascularity, dermal thickness, collagen deposition and tensile strength. Together, these findings highlight the immediate clinical potential of DFO eTDDS to treating diabetic wounds. Further, the topical drug delivery platform has important implications for targeted pharmacologic therapy of a wide range of cutaneous diseases.

    View details for DOI 10.1016/j.jconrel.2019.07.009

    View details for PubMedID 31299261

  • Bony Incarceration of the Extensor Pollicis Longus Tendon Mimicking Rupture. Journal of wrist surgery Barrera, J. n., Ryu, J. n., Yao, J. n. 2019; 8 (3): 245–49

    Abstract

    Background  Distal radius fractures are a relatively common injury, and rupture of the extensor pollicis longus (EPL) has been known to occur in a small number of nondisplaced distal radius fractures. In contrast, bony incarceration of the EPL tendon is an exceedingly rare occurrence and warrants special attention. Case Description  Here we present a case of bony incarceration of the EPL tendon following distal radius fracture that mimicked tendon rupture. Following EPL release, the patient had improved function and pain in the wrist. Literature Review  We identified three case reports of EPL tendon entrapment following distal radius fracture, and compared and contrasted the clinical features of tendon rupture versus bony entrapment. Clinical Relevance  Our results suggest that both the type of fracture (displaced vs. nondisplaced) and the chronicity of symptoms may provide important diagnostic clues for the hand surgeon managing distal radius fracture patients presenting with EPL dysfunction.

    View details for DOI 10.1055/s-0038-1675562

    View details for PubMedID 31192048

    View details for PubMedCentralID PMC6546488

  • 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

  • Acceleration of Diabetic Wound Healing with PHD2- and miR-210-targeting Oligonucleotides. Tissue engineering. Part A Dallas, A. n., Trotsyuk, A. n., Ilves, H. n., Bonham, C. A., Rodrigues, M. n., Engel, K. n., Barrera, J. A., Kosaric, N. n., Stern-Buchbinder, Z. A., White, A. n., Mandell, K. J., Hammond, P. n., Mansbridge, J. N., Jayasena, S. n., Gurtner, G. C., Johnston, B. H. 2018

    Abstract

    [PLACEHOLDER].

    View details for PubMedID 29644938

  • 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

  • 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

  • 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