“Fate of free fat grafts with or without adipogenic adjuncts to enhance graft outcomes”

Background: Free fat grafting is popular but it is still unclear how it works. Although focusing on graft survival seems an obvious direction for improving clinical results, our research suggests that long term volume retention is in part due to new fat regeneration. Measures to facilitate adipogenesis may therefore be equally important. Methods: To investigate the relative roles of survival and regeneration of fat grafts, we measured the fate of human lipoaspirate implanted into the scalps of immunodeficient mice, with and without stromal vascular fraction (SVF) and a porcine extracellular matrix (Adipogel). Specifically, we were interested in volume retention, as well as composition of implanted or regenerated tissue at 6 and 12 weeks. Results: Free fat grafts exhibited poor volume retention and survival. Almost all the injected human adipocytes died but new mouse fat formed peripheral to the encapsulated fat graft. Adipogel and SVF improved proliferation of murine fat and human vasculature. Human CD34+ stromal cells were present but only in the periphery, and there was no evidence that these cells differentiated into adipocytes. Conclusions: In our model most of the implanted tissue died but un-resorbed dead fat accounted substantially for the long term, reduced volume. A layer of host-derived, regenerated adipose tissue was present at the periphery. This regeneration may be driven by the presence of dying fat, and it was enhanced by addition of our adipogenic adjuncts. Future research should perhaps focus not only on improving graft survival but also enhancing the adipogenic environment conducive to fat regeneration. Financial disclosure statement: Nothing to disclose Not presented at conferxences etc. Acknowledgments: This research was funded by a National Health and Medical Research Council of Australia Project Grant (# 1064786), the Australian Catholic University AORTEC agreement, the Wicking Foundation, and the Stafford Fox Foundation and the Victorian State Government. Valuable surgical and technical assistance was provided by of the staff of the Experimental Medical and Surgical Unit, St Vincent's Hospital, Melbourne (Sue McKay, Liliana Pepe, Anna Deftereos and Amanda Rixon). Corresponding author: Jason Palmer BSc (Hons), O'Brien Institute Department at St Vincent's Institute, 42 Fitzroy St, Fitzroy Victoria 3065, Australia. jpalmer@svi.edu.au, ©2018American Society of Plastic Surgeons

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