Plastic Surgery Research Council
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PSRC 60th Annual Meeting
Program and Abstracts

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Alternatively Activated M2 Macrophages Improve Autologous Fat Graft Survival via Induction of Angiogenesis in a Preclinical Model.
Simon Gebremeskel, BScH, Kyle Phipps, PhD, Joshua Gillis, MD, Paul Hong, MD, FRCSC, Brent Johnston, PhD, Michael Bezuhly, MD, FRCSC.
Dalhousie university, Halifax, NS, Canada.

PURPOSE:
Variability in graft retention remains a significant limitation of autologous fat grafting, with under-correction necessitating repeated procedures. The authors’ evaluated whether graft retention in a mouse model could be improved via graft supplementation with alternatively activated M2 macrophages, a cell type known to play a critical role in tissue repair.
METHODS:
Fat grafts from C57BL/6 mouse inguinal fat pads were supplemented with M2 macrophages generated via intraperitoneal Brewer’s thioglycollate injection and in vitro culture. Grafts with saline or M2 macrophages were injected under recipient mouse scalps and assessed by serial volumetric microCT analysis. Explanted grafts underwent immunohistochemical and flow cytometric analyses for vascular density and retained M2 numbers, respectively. M2 culture supernatants were added to stromal vascular fractions (SVF) containing adipose-derived stem cells (ASC) to assess their ability to induce adipogenic gene expression.
RESULTS:
One month following graft injection, no significant difference was noted between M2-supplemented (105±7.0 mm3) and control graft volumes (72±22 mm3). By three months post-injection, M2-supplemented grafts remained stable while controls experienced further volume loss (103±8 mm3 vs. 39.4±15 mm3, p=0.015). Presence of M2 macrophages in the supplemented grafts was confirmed by flow cytometry. M2-supplemented grafts demonstrated a 157% increase in vascular density compared to controls (p<0.05). Induction of adipogenic C/EBPα gene expression was observed when M2 supernatants were added to SVF containing ASC.
CONCLUSION:
M2 macrophages improve autologous fat graft volume retention by stimulating angiogenesis. These findings provide proof-of-principle for the development of fat grafting techniques that harness reparative properties of M2 macrophages.


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