Publications by authors named "Dominic Henn"

44 Publications

Holy grail of tissue regeneration: Size.

Bioessays 2022 Jul 14:e2200047. Epub 2022 Jul 14.

Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, California, 94305, USA.

Cells and tissue within injured organs undergo a complicated healing process that still remains poorly understood. Interestingly, smaller organisms respond to injury with tissue regeneration and restoration of function, while humans and other large organisms respond to injury by forming dysfunctional, fibrotic scar tissue. Over the past few decades, allometric scaling principles have been well established to show that larger organisms experience exponentially higher tissue forces during movement and locomotion and throughout the organism's lifespan. How these evolutionary adaptations may affect tissue injury has not been thoroughly investigated in humans. We discuss how these adapations may affect healing and demonstrate that blocking the most evolutionary conserved biologic force sensor enables large organisms to heal after injury with true tissue regeneration. Future strategies to disrupt tissue force sensors may unlock the key to regenerating after injury in a wide range of organ systems.
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http://dx.doi.org/10.1002/bies.202200047DOI Listing
July 2022

Disrupting mechanotransduction decreases fibrosis and contracture in split-thickness skin grafting.

Sci Transl Med 2022 05 18;14(645):eabj9152. Epub 2022 May 18.

Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.

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.
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http://dx.doi.org/10.1126/scitranslmed.abj9152DOI Listing
May 2022

A bioactive compliant vascular graft modulates macrophage polarization and maintains patency with robust vascular remodeling.

Bioact Mater 2023 Jan 13;19:167-178. Epub 2022 Apr 13.

Department of Orthopaedic Surgery, Stanford University, 240 Pasteur Drive, Stanford, CA, 94304, USA.

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.
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http://dx.doi.org/10.1016/j.bioactmat.2022.04.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9034314PMC
January 2023

Mechanical tension mobilizes Lgr6 epidermal stem cells to drive skin growth.

Sci Adv 2022 04 27;8(17):eabl8698. Epub 2022 Apr 27.

Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21231, USA.

Uniquely among mammalian organs, skin is capable of marked size change in adults, yet the mechanisms underlying this notable capacity are unclear. Here, we use a system of controlled tissue expansion in mice to uncover cellular and molecular determinants of skin growth. Through machine learning-guided three-dimensional tissue reconstruction, we capture morphometric changes in growing skin. We find that most growth is driven by the proliferation of the epidermis in response to mechanical tension, with more limited changes in dermal and subdermal compartments. Epidermal growth is achieved through preferential activation and differentiation of Lgr6 stem cells of the epidermis, driven in part by the Hippo pathway. By single-cell RNA sequencing, we uncover further changes in mechanosensitive and metabolic pathways underlying growth control in the skin. These studies point to therapeutic strategies to enhance skin growth and establish a platform for understanding organ size dynamics in adult mammals.
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http://dx.doi.org/10.1126/sciadv.abl8698DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9045722PMC
April 2022

Pullulan-Collagen hydrogel wound dressing promotes dermal remodelling and wound healing compared to commercially available collagen dressings.

Wound Repair Regen 2022 05 18;30(3):397-408. Epub 2022 Apr 18.

Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, California, USA.

Biological scaffolds such as hydrogels provide an ideal, physio-mimetic of native extracellular matrix (ECM) that can improve wound healing outcomes after cutaneous injury. While most studies have focused on the benefits of hydrogels in accelerating wound healing, there are minimal data directly comparing different hydrogel material compositions. In this study, we utilized a splinted excisional wound model that recapitulates human-like wound healing in mice and treated wounds with three different collagen hydrogel dressings. We assessed the feasibility of applying each dressing and performed histologic and histopathologic analysis on the explanted scar tissues to assess variations in collagen architecture and alignment, as well as the tissue response. Our data indicate that the material properties of hydrogel dressings can significantly influence healing time, cellular response, and resulting architecture of healed scars. Specifically, our pullulan-collagen hydrogel dressing accelerated wound closure and promoted healed tissue with less dense, more randomly aligned, and shorter collagen fibres. Further understanding of how hydrogel properties affect the healing and resulting scar architecture of wounds may lead to novel insights and further optimization of the material properties of wound dressings.
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http://dx.doi.org/10.1111/wrr.13012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC9321852PMC
May 2022

Combining Breast and Ovarian Operations Increases Complications.

Plast Reconstr Surg 2022 05 2;149(5):1050-1059. Epub 2022 Mar 2.

From the Division of Plastic and Reconstructive Surgery, Stanford University Medical Center.

Background: Breast cancer resulting from a genetic mutations, 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.

Methods: 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.

Results: 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).

Conclusions: 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.

Clinical Question/level Of Evidence: Therapeutic, III.
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http://dx.doi.org/10.1097/PRS.0000000000008984DOI Listing
May 2022

Enrichment of Nanofiber Hydrogel Composite with Fractionated Fat Promotes Regenerative Macrophage Polarization and Vascularization for Soft-Tissue Engineering.

Plast Reconstr Surg 2022 Mar;149(3):433e-444e

From the Hagey Laboratory for Pediatric Regenerative Medicine, Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University; Department of Hand, Plastic, and Reconstructive Surgery, BG Trauma Center Ludwigshafen, Ruprecht-Karls-University of Heidelberg; Department of Materials Science and Engineering, Whiting School of Engineering, and Institute for NanoBioTechnology, Johns Hopkins University; Translational Tissue Engineering Center and Department of Biomedical Engineering, and Department of Plastic and Reconstructive Surgery, Johns Hopkins School of Medicine; Department for Plastic and Breast Surgery, Zealand University Hospital Roskilde; and Division of Plastic and Reconstructive Surgery, Department of Surgery, Washington University in St. Louis School of Medicine.

Background: Fractionated fat has been shown to promote dermal regeneration; however, the use of fat grafting for reconstruction of soft-tissue defects is limited because of volume loss over time. The authors have developed a novel approach for engineering of vascularized soft tissue using an injectable nanofiber hydrogel composite enriched with fractionated fat.

Methods: Fractionated fat was generated by emulsification of groin fat pads from rats and mixed in a 3:1 ratio with nanofiber hydrogel composite (nanofiber hydrogel composite with fractionated fat). Nanofiber hydrogel composite with fractionated fat or nanofiber hydrogel composite alone was placed into isolation chambers together with arteriovenous loops, which were subcutaneously implanted into the groin of rats (n = 8 per group). After 21 days, animals were euthanized and systemically perfused with ink, and tissue was explanted for histologic analysis. Immunofluorescent staining and confocal laser scanning microscopy were used to quantify CD34+ progenitor cell and macrophage subpopulations.

Results: Nanofiber hydrogel composite with fractionated fat tissue maintained its shape without shrinking and showed a significantly stronger functional vascularization compared to composite alone after 21 days of implantation (mean vessel count, 833.5 ± 206.1 versus 296.5 ± 114.1; p = 0.04). Tissue heterogeneity and cell count were greater in composite with fractionated fat (mean cell count, 49,707 ± 18,491 versus 9263 ± 3790; p = 0.005), with a significantly higher number of progenitor cells and regenerative CD163+ macrophages compared to composite alone.

Conclusions: Fractionated fat-enriched nanofiber hydrogel composite transforms into highly vascularized soft tissue over 21 days without signs of shrinking and promotes macrophage polarization toward regenerative phenotypes. Enrichment of injectable nanofiber hydrogel composite with fractionated fat represents a promising approach for durable reconstruction of soft-tissue defects.

Clinical Relevance Statement: The authors' approach for tissue engineering may ultimately lay the groundwork for clinically relevant applications with the goal of generating large volumes of vascularized soft tissue for defect reconstruction without donor site morbidity.
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http://dx.doi.org/10.1097/PRS.0000000000008872DOI Listing
March 2022

Reinforced Biologic Mesh Reduces Postoperative Complications Compared to Biologic Mesh after Ventral Hernia Repair.

Plast Reconstr Surg Glob Open 2022 Feb 7;10(2):e4083. Epub 2022 Feb 7.

Division of Plastic and Reconstructive Surgery, Stanford University Medical Center, Stanford, Calif.

Background: 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.

Methods: 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.

Results: 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 ( = 0.015). Relative risk for overall complications was higher in patients who had received NC-PADM (RR = 2.64, = 0.0182), C-PADM (RR = 3.19, = 0.0127), and BADM (RR = 2.11, = 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.

Conclusion: Our data indicate that RBOR decreases abdominal complications and recurrence rates after ventral hernia repair compared with NC-PADM, C-PADM, and BADM.
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http://dx.doi.org/10.1097/GOX.0000000000004083DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8820910PMC
February 2022

Multi-omic analysis reveals divergent molecular events in scarring and regenerative wound healing.

Cell Stem Cell 2022 02 24;29(2):315-327.e6. Epub 2022 Jan 24.

Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA. Electronic address:

Regeneration is the holy grail of tissue repair, but skin injury typically yields fibrotic, non-functional scars. Developing pro-regenerative therapies requires rigorous understanding of the molecular progression from injury to fibrosis or regeneration. Here, we report the divergent molecular events driving skin wound cells toward scarring or regenerative fates. We profile scarring versus YAP-inhibition-induced wound regeneration at the transcriptional (single-cell RNA sequencing), protein (timsTOF proteomics), and tissue (extracellular matrix ultrastructural analysis) levels. Using cell-surface barcoding, we integrate these data to reveal fibrotic and regenerative "molecular trajectories" of healing. We show that disrupting YAP mechanotransduction yields regenerative repair by fibroblasts with activated Trps1 and Wnt signaling. Finally, via in vivo gene knockdown and overexpression in wounds, we identify Trps1 as a key regulatory gene that is necessary and partially sufficient for wound regeneration. Our findings serve as a multi-omic map of wound regeneration and could have therapeutic implications for pathologic fibroses.
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http://dx.doi.org/10.1016/j.stem.2021.12.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8988390PMC
February 2022

IQGAP1-mediated mechanical signaling promotes the foreign body response to biomedical implants.

FASEB J 2022 02;36(2):e22007

Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, California, USA.

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.
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http://dx.doi.org/10.1096/fj.202101354DOI Listing
February 2022

Xenogeneic skin transplantation promotes angiogenesis and tissue regeneration through activated Trem2 macrophages.

Sci Adv 2021 Dec 1;7(49):eabi4528. Epub 2021 Dec 1.

Hagey Laboratory for Pediatric Regenerative Medicine, Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University, Stanford, CA, USA.

Skin allo- and xenotransplantation are the standard treatment for major burns when donor sites for autografts are not available. The relationship between the immune response to foreign grafts and their impact on wound healing has not been fully elucidated. Here, we investigated changes in collagen architecture after xenogeneic implantation of human biologic scaffolds. We show that collagen deposition in response to the implantation of human split-thickness skin grafts (hSTSGs) containing live cells recapitulates normal skin architecture, whereas human acellular dermal matrix (ADM) grafts led to a fibrotic collagen deposition. We show that macrophage differentiation in response to hSTSG implantation is driven toward regenerative Trem2 subpopulations and found that hydrogel delivery of these cells significantly accelerated wound closure. Our study identifies the preclinical therapeutic potential of Trem2 macrophages to mitigate fibrosis and promote wound healing, providing a novel effective strategy to develop advanced cell therapies for complex wounds.
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http://dx.doi.org/10.1126/sciadv.abi4528DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8635426PMC
December 2021

The Plane of Mesh Placement Does Not Impact Abdominal Donor Site Complications in Microsurgical Breast Reconstruction.

Ann Plast Surg 2021 11;87(5):542-546

From the Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University Medical Center, Stanford, CA.

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.
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http://dx.doi.org/10.1097/SAP.0000000000002897DOI Listing
November 2021

Advances in Tissue Expander Technology Enable Early Targeted Intervention in Prepectoral Breast Reconstruction.

Plast Reconstr Surg Glob Open 2021 Aug 19;9(8):e3781. Epub 2021 Aug 19.

Division of Plastic and Reconstructive Surgery, Stanford University, Stanford, Calif.

Seroma and infection are among the most common complications after staged prepectoral implant-based reconstruction. Advances in tissue expander technology permit seroma aspiration via an integrated drain port, thus, holding promise for improving clinical outcomes.

Methods: A prospectively maintained database of patients who had undergone immediate prepectoral breast reconstruction using the Sientra AlloX2 tissue expander was used to determine the rate of postoperative seroma formation, its volume and microbiological spectrum, as well as postoperative complications.

Results: 49 patients (mean age: 49 years, mean body mass index: 24.5 kg/m) underwent 79 prepectoral breast reconstructions. Seroma was clinically suspected in 26 reconstructions (32.9%) and was easily aspirated in all cases via the integrated drain port. Importantly, periprosthetic fluid was successfully aspirated in 45 reconstructions (57%) without any clinical evidence for seroma, with aspirated cumulative fluid volumes exceeding 10 cm in 12 reconstructions. Bacterial cultures from aspirated fluid were positive in six patients (12.2%), of whom two developed clinical signs of infection, at which point targeted antibiotic treatment was initiated.

Conclusions: Our study demonstrates that routine office-based aspiration of periprosthetic fluid via the integrated drain port of the AlloX2 tissue expander not only permits successful aspiration of periprosthetic fluid but also allows aspirated fluid to be sent for culture, thus, providing a lead-time advantage for initiation of targeted antibiotic therapy in cases of postoperative surgical site infection. Furthermore, our observations indicate that positive bacterial cultures in the absence of clinical signs of infection do not mandate antibiotic therapy.
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http://dx.doi.org/10.1097/GOX.0000000000003781DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8517312PMC
August 2021

Integrated spatial multiomics reveals fibroblast fate during tissue repair.

Proc Natl Acad Sci U S A 2021 10;118(41)

Hagey Laboratory for Pediatric Regenerative Medicine, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, CA 94305;

In the skin, tissue injury results in fibrosis in the form of scars composed of dense extracellular matrix deposited by fibroblasts. The therapeutic goal of regenerative wound healing has remained elusive, in part because principles of fibroblast programming and adaptive response to injury remain incompletely understood. Here, we present a multimodal -omics platform for the comprehensive study of cell populations in complex tissue, which has allowed us to characterize the cells involved in wound healing across both time and space. We employ a stented wound model that recapitulates human tissue repair kinetics and multiple Rainbow transgenic lines to precisely track fibroblast fate during the physiologic response to skin injury. Through integrated analysis of single cell chromatin landscapes and gene expression states, coupled with spatial transcriptomic profiling, we are able to impute fibroblast epigenomes with temporospatial resolution. This has allowed us to reveal potential mechanisms controlling fibroblast fate during migration, proliferation, and differentiation following skin injury, and thereby reexamine the canonical phases of wound healing. These findings have broad implications for the study of tissue repair in complex organ systems.
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http://dx.doi.org/10.1073/pnas.2110025118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8521719PMC
October 2021

Epidermal-Derived Hedgehog Signaling Drives Mesenchymal Proliferation during Digit Tip Regeneration.

J Clin Med 2021 Sep 20;10(18). Epub 2021 Sep 20.

Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.

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.
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http://dx.doi.org/10.3390/jcm10184261DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8467649PMC
September 2021

Inhibiting Fibroblast Mechanotransduction Modulates Severity of Idiopathic Pulmonary Fibrosis.

Adv Wound Care (New Rochelle) 2022 Oct 30;11(10):511-523. Epub 2021 Nov 30.

Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, California, USA.

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease that affects 63 in every 100,000 Americans. Its etiology remains unknown, although inflammatory pathways appear to be important. Given the dynamic environment of the lung, we examined the significance of mechanotransduction on both inflammatory and fibrotic signaling during IPF. Mechanotransduction pathways have not been thoroughly examined in the context of lung disease, and pharmacologic approaches for IPF do not currently target these pathways. The interplay between mechanical strain and inflammation in pulmonary fibrosis remains incompletely understood. In this study, we used conditional KO mice to block mechanotransduction by knocking out Focal Adhesion Kinase (FAK) expression in fibroblasts, followed by induction of pulmonary fibrosis using bleomycin. We examined both normal human and human IPF fibroblasts and used immunohistochemistry, quantitative real-time polymerase chain reaction, and Western Blot to evaluate the effects of FAK inhibitor (FAK-I) on modulating fibrotic and inflammatory genes. Our data indicate that the deletion of FAK in mice reduces expression of fibrotic and inflammatory genes in lungs. Similarly, mechanical straining in normal human lung fibroblasts activates inflammatory and fibrotic pathways. The FAK inhibition decreases these signals but has a less effect on IPF fibroblasts as compared with normal human fibroblasts. Administering FAK-I at early stages of fibrosis may attenuate the FAK-mediated fibrotic response pathway in IPF, potentially mediating disease progression.
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http://dx.doi.org/10.1089/wound.2021.0077DOI Listing
October 2022

Disrupting biological sensors of force promotes tissue regeneration in large organisms.

Nat Commun 2021 09 6;12(1):5256. Epub 2021 Sep 6.

Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, CA, USA.

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.
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http://dx.doi.org/10.1038/s41467-021-25410-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8421385PMC
September 2021

Mechanical Strain Drives Myeloid Cell Differentiation Toward Proinflammatory Subpopulations.

Adv Wound Care (New Rochelle) 2022 Sep 27;11(9):466-478. Epub 2021 Aug 27.

Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, California, USA.

After injury, humans and other mammals heal by forming fibrotic scar tissue with diminished function, and this healing process involves the dynamic interplay between resident cells within the skin and cells recruited from the circulation. Recent studies have provided mounting evidence that external mechanical forces stimulate intracellular signaling pathways to drive fibrotic processes. While most studies have focused on studying mechanotransduction in fibroblasts, recent data suggest that mechanical stimulation may also shape the behavior of immune cells, referred to as "mechano-immunomodulation." However, the effect of mechanical strain on myeloid cell recruitment and differentiation remains poorly understood and has never been investigated at the single-cell level. In this study, we utilized a three-dimensional (3D) culture system that permits the precise manipulation of mechanical strain applied to cells. We cultured myeloid cells and used single-cell RNA-sequencing to interrogate the effects of strain on myeloid differentiation and transcriptional programming. Our data indicate that myeloid cells are indeed mechanoresponsive, with mechanical stress influencing myeloid differentiation. Mechanical strain also upregulated a cascade of inflammatory chemokines, most notably from the family. Further understanding of how mechanical stress affects myeloid cells in conjunction with other cell types in the complicated, multicellular milieu of wound healing may lead to novel insights and therapies for the treatment of fibrosis.
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http://dx.doi.org/10.1089/wound.2021.0036DOI Listing
September 2022

Hydrogel Scaffolds to Deliver Cell Therapies for Wound Healing.

Front Bioeng Biotechnol 2021 3;9:660145. Epub 2021 May 3.

Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, CA, United States.

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.
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http://dx.doi.org/10.3389/fbioe.2021.660145DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8126987PMC
May 2021

Adipose-Derived Stromal Cells Seeded in Pullulan-Collagen Hydrogels Improve Healing in Murine Burns.

Tissue Eng Part A 2021 06 27;27(11-12):844-856. Epub 2021 May 27.

Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University School of Medicine, Stanford, California, USA.

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 proangiogenic and immunomodulatory paracrine effects. Our laboratory has developed a pullulan-collagen hydrogel that, when seeded with mesenchymal stem cells (MSCs), improves cell viability and augments their proangiogenic capacity . 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 (ASC)-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 reepithelialization, greater vascularity, and increased expression of the proangiogenic genes MCP-1, VEGF, and SDF-1 at both the mRNA and protein level. Expression of the profibrotic gene and proinflammatory gene was downregulated 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 proangiogenic, fibromodulatory, and immunomodulatory effects. Enrichment for CD26/CD55 ASCs has additive benefits for tissue architecture and collagen remodeling postburn injury. Research is ongoing to further facilitate clinical translation of this promising therapeutic approach. Impact statement Burns remain a significant public health burden. Stem cell therapy has gained attention as a promising approach for treating burns. We have developed a pullulan-collagen biomimetic hydrogel scaffold that can be seeded with adipose-derived stem cells (ASCs). We assessed the delivery and activity of our scaffold in a murine contact burn model. Our results suggest that localized delivery of ASC hydrogel treatment is a promising approach for the treatment of burn wounds, with the potential for rapid clinical translation. We believe our work will have broad implications for both hydrogel therapeutics and regenerative medicine and will be of interest to the general scientific community.
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http://dx.doi.org/10.1089/ten.TEA.2020.0320DOI Listing
June 2021

A multivariable miRNA signature delineates the systemic hemodynamic impact of arteriovenous shunt placement in a pilot study.

Sci Rep 2020 12 11;10(1):21809. Epub 2020 Dec 11.

BG Trauma Center Ludwigshafen, Heidelberg University, Ludwigshafen, Germany.

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.
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http://dx.doi.org/10.1038/s41598-020-78905-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7733519PMC
December 2020

Dysregulation of Endothelial Nitric Oxide Synthase Does Not Depend on Hemodynamic Alterations in Bicuspid Aortic Valve Aortopathy.

J Am Heart Assoc 2020 09 2;9(18):e016471. Epub 2020 Sep 2.

Department of Thoracic and Cardiovascular Surgery Saarland University Medical Center Homburg/Saar Germany.

Background Bicuspid aortic valves (BAVs) predispose to ascending aortic aneurysm. Turbulent blood flow and genetic factors have been proposed as underlying mechanisms. Endothelial nitric oxide synthase (eNOS) has been implicated in BAV aortopathy, and its expression is regulated by wall shear stress. We hypothesized that if turbulent flow induces aneurysm formation in patients with a BAV, regional differences in eNOS expression would be observed in BAVs. Methods and Results Ascending aortic specimens were harvested intraoperatively from 48 patients with tricuspid aortic valve (19 dilated, 29 nondilated) and 38 with BAV (28 dilated, 10 nondilated) undergoing cardiac surgery. eNOS mRNA and protein concentration were analyzed at the convex and concave aortic wall. In nondilated aortas, eNOS mRNA and protein concentration were decreased in BAV compared with tricuspid aortic valve (all <0.05). eNOS expression was increased in association with dilation in BAV aortas (=0.03), but not in tricuspid aortic valve aortas (=0.63). There were no regional differences in eNOS mRNA or protein concentration in BAV aortas (all >0.05). However, eNOS expression was increased at the concave wall (versus convexity) in tricuspid aortic valve dilated aortas (all <0.05). Conclusions Dysregulated eNOS occurs independent of dilation in BAV aortas, suggesting a potential role for aberrantly regulated eNOS expression in the development of BAV-associated aneurysms. The absence of regional variations of eNOS expression suggests that eNOS dysregulation in BAV aortas is the result of underlying genetic factors associated with BAV disease, rather than changes stimulated by hemodynamic alterations. These findings provide insight into the underlying mechanisms of aortic dilation in patients with a BAV.
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http://dx.doi.org/10.1161/JAHA.120.016471DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7726972PMC
September 2020

Characterization of Diabetic and Non-Diabetic Foot Ulcers Using Single-Cell RNA-Sequencing.

Micromachines (Basel) 2020 Aug 28;11(9). Epub 2020 Aug 28.

Department of Surgery, Division of Plastic and Reconstructive Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.

Recent advances in high-throughput single-cell sequencing technologies have led to their increasingly widespread adoption for clinical applications. However, challenges associated with tissue viability, cell yield, and delayed time-to-capture have created unique obstacles for data processing. Chronic wounds, in particular, represent some of the most difficult target specimens, due to the significant amount of fibrinous debris, extracellular matrix components, and non-viable cells inherent in tissue routinely obtained from debridement. Here, we examined the feasibility of single cell RNA sequencing (scRNA-seq) analysis to evaluate human chronic wound samples acquired in the clinic, subjected to prolonged cold ischemia time, and processed without FACS sorting. Wound tissue from human diabetic and non-diabetic plantar foot ulcers were evaluated using an optimized 10X Genomics scRNA-seq platform and analyzed using a modified data pipeline designed for low-yield specimens. Cell subtypes were identified informatically and their distributions and transcriptional programs were compared between diabetic and non-diabetic tissue. 139,000 diabetic and non-diabetic wound cells were delivered for 10X capture after either 90 or 180 min of cold ischemia time. cDNA library concentrations were 858.7 and 364.7 pg/µL, respectively, prior to sequencing. Among all barcoded fragments, we found that 83.5% successfully aligned to the human transcriptome and 68% met the minimum cell viability threshold. The average mitochondrial mRNA fraction was 8.5% for diabetic cells and 6.6% for non-diabetic cells, correlating with differences in cold ischemia time. A total of 384 individual cells were of sufficient quality for subsequent analyses; from this cell pool, we identified transcriptionally-distinct cell clusters whose gene expression profiles corresponded to fibroblasts, keratinocytes, neutrophils, monocytes, and endothelial cells. Fibroblast subpopulations with differing fibrotic potentials were identified, and their distributions were found to be altered in diabetic vs. non-diabetic cells. scRNA-seq of clinical wound samples can be achieved using minor modifications to standard processing protocols and data analysis methods. This simple approach can capture widespread transcriptional differences between diabetic and non-diabetic tissue obtained from matched wound locations.
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http://dx.doi.org/10.3390/mi11090815DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7570277PMC
August 2020

Current and Emerging Topical Scar Mitigation Therapies for Craniofacial Burn Wound Healing.

Front Physiol 2020 29;11:916. Epub 2020 Jul 29.

Department of Surgery, Stanford University School of Medicine, Stanford, CA, United States.

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.
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http://dx.doi.org/10.3389/fphys.2020.00916DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7403506PMC
July 2020

Tissue Engineering of Axially Vascularized Soft-Tissue Flaps with a Poly-(ɛ-Caprolactone) Nanofiber-Hydrogel Composite.

Adv Wound Care (New Rochelle) 2020 07 10;9(7):365-377. Epub 2020 Jun 10.

Department of Hand, Plastic, and Reconstructive Surgery, BG Trauma Center Ludwigshafen, Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany.

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. 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. 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. 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. 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.
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http://dx.doi.org/10.1089/wound.2019.0975DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7307685PMC
July 2020

A standardized patient education class as a vehicle to improving shared decision-making and increasing access to breast reconstruction.

J Plast Reconstr Aesthet Surg 2020 Aug 18;73(8):1534-1539. Epub 2020 Feb 18.

Division of Plastic and Reconstructive Surgery, Stanford University, Palo Alto, CA, United States; Hagey Laboratory for Pediatric Regenerative Medicine, Stanford University School of Medicine, Stanford, CA, United States. Electronic address:

Background: Shared decision-making is a key component of patient-centered care and has been shown to improve patient satisfaction and quality of life. Herein, we study the impact of a standardized patient education class for prospective breast reconstruction patients on clinic efficiency, access to care, and perception on shared decision-making.

Methods: The number of new patient consultations per clinic, as well as average duration of the first individual clinic encounter, was compared before and after the introduction of a standardized education class given by the senior author to all new breast reconstruction patients. To evaluate patients' perception of shared decision-making, the 9-item Shared Decision-Making Questionnaire (SDM-Q9) and the Satisfaction with Information scale of the BREAST-Q Reconstruction Module were electronically distributed among the patients and compared between the two groups.

Results: Introduction of the patient education class was associated with a significant reduction in the duration of new patient encounters compared to historic controls (31.8 min vs. 53.5 min, p < 0.01) along with permitting a 43% increase in new patient visits. No differences in self-perceived patient education and autonomy were seen between class participants and historic controls in the SDM-Q9 scores (p = 0.58) and BREAST-Q scores (p = 0.14).

Conclusion: The introducing a standardized patient education class translated into a significant reduction in the duration of individual new patient encounters, thereby increasing patient access to care, while maintaining high-quality standards of self-perceived patient education and shared decision-making.
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http://dx.doi.org/10.1016/j.bjps.2020.02.032DOI Listing
August 2020

Cryopreserved human skin allografts promote angiogenesis and dermal regeneration in a murine model.

Int Wound J 2020 Aug 30;17(4):925-936. Epub 2020 Mar 30.

Hagey Laboratory for Pediatric and Regenerative Medicine, Division of Plastic and Reconstructive Surgery, Department of Surgery, Stanford University, Stanford, California, USA.

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.
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http://dx.doi.org/10.1111/iwj.13349DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7949424PMC
August 2020

Micro-RNA signatures in monozygotic twins discordant for congenital heart defects.

PLoS One 2019 5;14(12):e0226164. Epub 2019 Dec 5.

Department of Pediatric Cardiology, Saarland University Medical Center, Homburg/Saar, Germany.

Background: MicroRNAs (miRNAs) are small RNAs regulating gene expression post-transcriptionally. Recent studies demonstrated that miRNAs are involved in the development of congenital heart defects (CHD). In this study, we aimed at identifying the specific patterns of miRNAs in blood of monozygotic twin pairs discordant for CHD and to assess whether miRNAs might be involved in the development or reflect the consequences of CHD.

Methods: miRNA microarray analysis and Real-Time Quantitative PCR (RT-qPCR) were employed to determine the miRNA abundance level from 12 monozygotic twins discordant for CHD and their non-CHD co-twins (n = 12). Enrichment analyses of altered miRNAs were performed using bioinformatics tools.

Results: Compared with non-CHD co-twins, profiling analysis indicated 34 miRNAs with a significant difference in abundance level (p<0.05, fold change ≥ 1.3), of which 11 miRNAs were up-regulated and 23 miRNAs were down-regulated. Seven miRNAs were validated with RT-qPCR including miR-511-3p, miR-1306-5p, miR-421, miR-4707-3p, miR-4732-3p, miR-5189-3p, and miR-890, and the results were consistent with microarray analysis. Five miRNAs namely miR-511-3p, miR-1306-5p, miR-4732-3p, miR-5189-3p, and miR-890 were found to be significantly up-regulated in twins < 10 years old. Bioinformatics analysis showed that the 7 validated miRNAs were involved in phosphatidylinositol signaling, gap junction signaling, and adrenergic signaling in cardiomyocytes.

Conclusions: Our data show deregulated miRNA abundance levels in the peripheral blood of monozygotic twins discordant for CHD, and identify new candidates for further analysis, which may contribute to understanding the development of CHD in the future. Bioinformatics analysis indicated that the target genes of these miRNAs are likely involved in signaling and communication of cardiomyocytes.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0226164PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6894838PMC
March 2020

Geriatric Patients with Free Flap Reconstruction: A Comparative Clinical Analysis of 256 Cases.

J Reconstr Microsurg 2020 Feb 23;36(2):127-135. Epub 2019 Sep 23.

Department of Hand-, Plastic and Reconstructive Surgery, Burn Center, BG Trauma Center Ludwigshafen, University of Heidelberg, Ludwigshafen, Germany.

Background:  In elderly patients, complex soft tissue defects are increasingly observed due to the prolonged life expectancy and accompanying comorbidities. The aim of this study is to evaluate whether free tissue transfer is safe in very old patients without additional risk and complications.

Methods:  All patients older than 65 years undergoing free tissue transfer between November 2007 and September 2016 were reviewed in a retrospective study. Two cohorts were compared regarding perioperative morbidity and postoperative outcome (cohort 1 [old patients, ages 65-79]; cohort 2 [very old patients, ages ≥ 80]).

Results:  In total, 256 patients were included in the study (cohort 1 [ = 217]; cohort 2 [ = 39]). Overall, 262 free flaps were performed due to a second microsurgical reconstruction in six cases. No statistically significant differences between cohorts were observed regarding surgical complications, total flap losses, and mortality. Detailed evaluation of cohort 2 revealed a significant learning curve during the observation period regarding the perioperative management and procedure of soft tissue reconstruction: operation length as well as postoperative intensive care unit stay decreased significantly over time ( < 0.05) and also surgical complications showed a positive trend ( = 0.07). We ascertained a shift toward a "more reliable" flap selection from predominantly anterolateral thigh flap) to axial flaps such as rectus abdominis and latissimus dorsi flaps.

Conclusion:  Our study showed that age is not associated with an increased risk of postoperative complications. Reliable muscle free flaps, two-stage procedures, and safe vascular supply are important strategic aspects to achieve microvascular tissue transfer with high success rates in geriatric patients.
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http://dx.doi.org/10.1055/s-0039-1697646DOI Listing
February 2020

Continuous Video-Rate Laser Speckle Imaging for Intra- and Postoperative Cutaneous Perfusion Imaging of Free Flaps.

J Reconstr Microsurg 2019 Sep 5;35(7):489-498. Epub 2019 Mar 5.

BG Trauma Center Ludwigshafen, Department of Hand, Plastic and Reconstructive Surgery, Microsurgery, Burn Center, University of Heidelberg, Heidelberg, Germany.

Background:  Success of free tissue transfer depends on standardized intraoperative flap design, microsurgical technique, and postoperative monitoring. We sought to investigate whether laser speckle imaging (LSI) is suitable for optimization of intraoperative flap design and postoperative monitoring of free flaps with skin paddles.

Methods:  Skin perfusion was assessed with LSI in 27 free flaps after dissection at the donor site, after anastomosis at the recipient site, after inset and on postoperative days (POD) 1, 5, and 10. Skin perfusion of the whole flap (ROI [region of interest]-1) and the area over the pedicle (ROI-2) were compared between patients with and without postoperative complications (POC+ and POC - , respectively). A receiver operating characteristic (ROC) analysis was performed to determine the optimal cutoff for perfusion during LSI-guided microsurgery.

Results:  In flaps without or only minor POC, intraoperatively measured perfusion over ROI-2 was significantly higher compared with ROI-1, whereas no significant differences were found for flaps with major POC. Perfusion of ROI-1 and 2 intraoperatively and on POD 1 was significantly lower in the POC+ compared with the POC- group ( < 0.05). ROC analysis yielded a threshold of 107 perfusion units (PU) at ROI-2 with an area under the curve (AUC) of > 0.8 for identification of flaps with major POC.

Conclusion:  LSI is an easy to use, noninvasive technique for identification of malperfused areas in free flaps, thus allowing for intraoperative decision-making on flap dimensions and postoperative monitoring. LSI therefore is a valuable tool for perfusion assessment with a high potential to become an established part of microsurgical practice.
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http://dx.doi.org/10.1055/s-0039-1681076DOI Listing
September 2019
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