In autologous breast reconstruction, postoperative monitoring of free tissue flaps is a routine and critical aspect of plastic surgical care. [1][2][3] Flap monitoring seeks to detect signs of vascular compromise or flap failure to allow for early intervention, which can mitigate undesirable surgical outcomes and patient morbidity. 3,4 Frequent, skilled clinical examinations have long been considered the gold standard for free flap monitoring, with a reported flap salvage rate of 52.3 to 77 percent after detecting signs of flap failure. [5][6][7][8] Vioptix is a near-infrared spectroscopy tissue oximetry technology that allows for noninvasive monitoring of flap perfusion based on tissue oxygen levels. 9,10 The Vioptix device includes a sensor probe that is placed on a tissue flap postoperatively, and is connected to a computerized monitor to continuously track real-time tissue oxygen saturation. In contrast to clinical examination alone, the probability of free flap rescue after detecting signs of compromise while using Vioptix in addition to clinical examination ranges from 70

Background Autologous fat grafting, while broadly indicated, is limited by unsatisfactory retention and often requires multiple procedures to achieve durable outcomes. Graft survival is strongly influenced by magnitude and duration of post-engraftment ischemia. Calcitriol is a pleiotropic, safe, nutrient with cell-specific influence on viability and metabolic flux. Objectives Evaluate the efficacy of activated vitamin D3 (calcitriol) to improve grafting outcomes and examine its mechanisms. Methods Lipoaspirate was collected for ex vivo culture (7 unique donors), in vitro bioenergetic analysis (6 unique donors), and in vivo transplantation (5 unique donors). Ex vivo samples were incubated for up to 2-weeks prior to extraction of the stromal vascular fraction (SVF) for viability or flow cytometry. SVF was collected for Seahorse analysis of metabolic activity. Human endothelial cell-lines were utilized for analyses of endothelial function. In vivo, samples were implanted into athymic mice with calcitriol-treatment either a) once locally or b) thrice weekly via intraperitoneal injection. Grafts were assessed photographically, volumetrically, and histologically at 1, 4, and 12-weeks. H&E, Sirius Red, perilipin, Hif1α, and CD31 were performed. Results Calcitriol-treated lipoaspirate demonstrated dose-dependent increases in SVF viability and metabolic reserve during hypoxic-stress. Calcitriol-treatment enhanced endothelial mobility ex vivo and endothelial function in vitro. In vivo, calcitriol enhanced adipocyte viability, reduced fibrosis, and improved vascularity. Continuous calcitriol was sufficient to improve graft retention at 12-weeks (p < 0.05). Conclusions Calcitriol increased fat graft retention in a xenograft model through. Calcitriol has potential to be a simple, economical means of increasing fat graft retention and long-term outcomes.

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.