P9. Mechanism of Botulinum Toxin Type A in Enhancing Fat Graft Survival

PURPOSE: Enhancing fat graft survival is a key objective in adipose regenerative medicine. While it is established that botulinum toxin type A (BoNT-A) improves graft survival by inhibiting muscle activity, it remains debated whether other mechanisms contribute to this effect. Given the lack of muscle in the subcutaneous skull area of nude mice, this study aimed to investigate the specific mechanism by which BoNT-A enhances fat graft survival, independent of muscle activity, through sequential BoNT-A and fat injections. METHODS: Nude mice were divided into three groups: a control group receiving only fat graft and saline, and two experimental groups receiving BoNT-A either simultaneously with or one week before the fat graft. Observations at 1, 4, 8, and 12 weeks post-transplantation included graft volume, collagen deposition, fat integrity, and markers for fibrosis, inflammation, and adipogenesis. Vascular formation in the graft and surrounding tissue was evaluated by immunofluorescence for endothelial cell markers. RESULTS: Fat graft survival rates were significantly higher in both experimental groups compared to the control. Histology and immunohistochemistry showed less fibrosis, lower inflammation, and greater adipogenic activity in the experimental groups than in controls. Immunofluorescence confirmed higher vascular density around the grafts in both experimental groups compared to the control. CONCLUSION: The findings suggest that BoNT-A may enhance fat graft survival by directly promoting vascular proliferation around the graft and reducing inflammatory responses.