Background: Adipose stem cells (ASCs) are a promising cell-based immunotherapy because of their minimally invasive harvest, high yield, and immunomodulatory capacity. In this study, the authors investigated the effects of local versus systemic ASC delivery on vascularized composite allotransplant survival and alloimmune regulation. Methods: Lewis rats received hind-limb transplants from Brown Norway rats and were administered donor-derived ASCs (passage 3 or 4, 1 × 106 cells/rat) locally in the allograft, or contralateral limb, or systemically at postoperative day 1. Recipients were treated intraperitoneally with rabbit anti-rat lymphocyte serum on postoperative days 1 and 4 and daily tacrolimus for 21 days. Limb allografts were monitored for clinical signs of rejection. Donor cell chimerism, immune cell differentiation, and cytokine expression in recipient lymphoid organs were measured by flow cytometric analysis. The immunomodulation function of ASCs was tested by mixed lymphocyte reaction assay and ASC stimulation studies. Results: Local-ASC–treated recipients achieved significant prolonged allograft survival (85.7% survived >130 days; n = 6) compared with systemic-ASC and contralateral-ASC groups. Secondary donor skin allografts transplanted to the local-ASC long-term surviving recipients accepted permanently without additional immunosuppression. The increases in donor cell chimerism and regulatory T-cells were evident in blood and draining lymph nodes of the local-ASC group. Moreover, mixed lymphocyte reaction showed that ASCs inhibited donor-specific T-cell proliferation independent of direct ASC–T-cell contact. ASCs up-regulated antiinflammatory molecules in response to cytokine stimulation in vitro. Conclusion: Local delivery of ASCs promoted long-term survival and modulated alloimmune responses in a full major histocompatibility complex–mismatched vascularized composite allotransplantation model and was more effective than systemic administration. Clinical Relevance Statement: ASCs are a readily available and abundant source of therapeutic cells that could decrease the amount of systemic immunosuppression required to maintain limb and face allografts.

Background: Necrosis of the nipple-areolar complex (NAC) or surrounding skin has been reported in 6%–30% of nipple-sparing mastectomy (NSM) patients, with higher rates associated with larger breasts, previous breast surgery, previous radiation, and active smoking. The nipple delay (ND) procedure is known to improve viability of the NAC in NSM patients with high-risk factors. Methods: A single-institution retrospective review was done of patients who underwent ND and NSM or NSM alone from 2012 to 2022. Patient demographics, risk factors, and outcomes were compared. Results: Forty-two breasts received ND-NSM and 302 breasts received NSM alone. The ND-NSM group had significantly more high-risk factors, including elevated BMI (26.3 versus 22.9; P < 0.001), elevated prior breast surgery (50% versus 25%; P < 0.001), and greater mastectomy specimen weight (646.6 versus 303.2 g; P < 0.001). ND-NSM was more likely to have undergone preparatory mammoplasty before NSM (27% versus 1%; P < 0.001). There was no delay in NSM treatment from decision to pursue NSM (P = 0.483) or difference in skin necrosis (P = 0.256), NAC necrosis (P = 0.510), hematoma (P = 0.094), seroma (P = 0.137), or infection (P = 0.437) between groups. ND-NSM and NSM patients differed in total NAC necrosis (0% versus 3%) and implant loss (0% vs 13%), but not significantly. Conclusions: We demonstrated no NAC necrosis and no significant delay of treatment in higher risk ND-NSM patients. ND may allow higher risk patients to undergo NSM with similar morbidity as lower risk patients.

Introduction Complex burns are highly morbid injuries that can cause severe disfigurement and can be devastating to one’s quality of life and psychosocial well-being. Currently, there are no simple, single-stage procedures available for extensive or multifocal burns to address full-thickness trilaminar defects. Our team has previously demonstrated the viability of an adipose-first reconstruction to address hypodermal defects. In this study, we demonstrate the efficacy of a combined adipose plus finely minced skin to achieve a single-stage trilaminar skin reconstruction. Methods Full-thickness burns were created on female Yorkshire swine. After 48-hours, escharectomies were performed to the level of fascia. The wounds were layered with adipose harvested from female Yorkshire swine. In one group, autologous split-thickness skin grafts were cut into pixel size (0.3x0.3 mm) grafts and layered on top of the adipose. Pigs were maintained for 4-weeks with weekly photography, ultrasound, followed by endpoint histology and tension measurements. Results At the end of the 4-week period, adipose combined with pixel graft demonstrated improved epithelialization and less contracture (p&lt; 0.01). Thickness and mobility measurements were consistent in both groups. This findings were similar to our previous approaches using adipose following surgical debridement. Tissue pliability in the pixel grafting group was maintained to a high degree. Cross sections were performed which showed the persistence of fat graft at the base of the wounds. Conclusions Immediate, single-stage trilaminar reconstruction of full-thickness complex burns reduces contracture, mitigates adhesion, and restores normal soft-tissue thickness, therefore, presenting a paradigm changing approach in the current practice of burn injuries to the mobile surfaces. Applicability of Research to Practice Our results support the therapeutic potential of adipose-based soft-tissue reconstruction of burns to both enhance hypodermal augmentation and mitigate fibrotic complications including contracture and adhesions. Our data suggest that this approach is compatible with the standard of care skin grafting, and in fact provides improved epidermal thickness and pliability.

and thawed to room temperature prior to testing and half of which were freshly excised and at room temperature, were loaded onto a 100N load cell force-displacement apparatus. Samples were stretched at a constant strain rate (1mm/ sec) until failure. Durometer, stress-strain curves, Young's Modulus (YM), and ultimate tensile burst strength were analyzed. Wilcoxon Mann-Whitney tests were performed and p-value<0.05 were considered statistically significant. RESULTS:The centers, but not peripheries, of wounds had higher durometer at day 42 than day 28 (p=0.03). The mean and standard deviation of YM of 42-day (0.01000, 0.00743) scars was slightly higher than 28-day (0.00738, 0.00548) wounds, but not statistically significantly so. Burst strength of frozen samples were higher for 42-day scars (p=0.01). Frozen samples (blue) displayed more brittle and less viscoelastic behavior and higher YM (p=8.93x10 -8 ) than fresh samples (red). There was a 3-fold increase in YM standard deviation in the frozen samples (0.00602 MPa) compared to the fresh samples (0.00203 MPa). CONCLUSION:Durometer measurement is a nondestructive method of wound evaluation that can be used longitudinally for time series measurement and appears to track with wound maturity. Contrary to prior reports, sample storage has significant effects on both the viscoelastic properties and burst strength of skin, causing loss of elasticity. We recommend the use of fresh samples whenever possible to avoid misinterpretation of physical property data. Future work will compare alternate methods of storing tissue for reliable downstream analysis.

METHODS:Mice with a lineage-specific deletion of DDR2 (Pdgfra-CreER +/-;Ddr2 fl/fl ) and CreER -/controls as well as a congenital deletion of DDR2 (Ddr2 slie/slie ) and littermate controls (LC) received a 30% total body surface area dorsal burn with concurrent unilateral Achilles' tenotomy (burn/tenotomy, BT). C57B6 mice received BT and were treated with DDR2 inhibitor imatinib for 16 days post-injury to assess the role of DDR2 inhibition on HO. HO volume and collagen alignment were assessed by micro-CT and second-harmonic generation of collagen fibers, respectively. Confocal microscopy was performed to visualize expression of pFAK in MLin cells in vivo. Ddr2 slie/ slie and LC MLin cells were plated onto 3D collagen matrices or 2D collagen-coated plates to determine the effect of DDR2 on focal adhesion (FA) orientation and TAZ activation in vitro, respectively. Tamoxifen (TMX)-induced Pdgfra-CreER +/-;Ddr2 fl/fl and CreER -/control MLin cells were subjected to traction force microscopy (TFM) to determine strain forces on collagen-coated gels in vitro. TMX-treated Pdgfra-CreER +/-;Ddr2 fl/fl and WT MLin cells were treated with TRULI, an inhibitor of LATS, which phosphorylates and inhibits YAP and TAZ nuclear translocation, to define the role of DDR2 deletion in YAP/TAZ signaling in vitro. RESULTS:Previous analyses from our group identified Ddr2 as highly expressed and activated specifically in MLin cells following injury (omitted). Inhibition of DDR2 with imatinib decreased HO (A). Pdgfra-CreER +/-;Ddr2 fl/fl mice also showed reduced HO (B). Ddr2 slie/slie showed greater disorganization in collagen compared to LC following BT (C). FA analysis of vinculin showed altered FA orientation in Ddr2 slie/slie MLin cells which may explain the altered collagen alignment seen in vivo (D). TFM demonstrated the ability of MLin cells to provide strain on the ECM, though strain energy was similar between both groups (E). We hypothesized that DDR2 alters HO formation through a FAK and YAP/TAZ dependent process. Ddr2 slie/slie mice showed reduced activated pFAK in vivo at the HO site (F) and reduced nuclear (transcriptionally active) TAZ in vitro (G). TRULI-treated MLin cells with a DDR2 deletion showed reduced nuclear TAZ localization compared to WT MLin cells (H).CONCLUSION: These findings suggest that MLin-cell DDR2 signaling following injury promotes HO due to altered FA orientation and signaling through a FAK/YAP/ TAZ pathway to activate osteogenic differentiation. Collagen alignment alternations may be due to changes in FA orientation. Having identified the role of MLin DDR2 on HO and ECM alignment following injury, these results suggest that DDR2 may be an effective target in preventing aberrant MLin cell osteogenesis following injury.