RESUMO
Adipose stem cells are considered one of the primary drivers of autologous fat graft biologic activity and survival. We have previously demonstrated that hormonally active VD3 improved adipose stem cell viability in ex vivo and in vivo fat grafting models. In this study, we evaluated the inactive form of VD3 (cholecalciferol) on adipose stromal cell (ASC) phenotype during hypoxia and the subsequent effect on human fat graft retention in the xenograft model. Lipoaspirate collected from six human donors was used for ex-vivo particle culture studies and isolated ASC studies. Adipose particles were treated with increasing doses of VD3 to determine impact on ASC survival. Expanded stromal cells were treated with VD3 during hypoxic culture and assessed for viability, apoptosis, mitochondrial activity, and nitric oxide release via caspase, DAF-FM, or TMRM. Finally, forty Nu/J mice receiving bilateral dorsal human lipoaspirate were treated thrice weekly with 1) Vehicle control, 2) 50ng calcitriol, 3) 50ng VD3, 4) 500ng VD3, and 5) 5000ng VD3 for 12 weeks, n=8 per group. Graft weight, volume, and architecture were analyzed. Adipose particles treated with dose escalating VD3 had significantly increased ASC viability compared to control (p<0.01). Under hypoxia, ASCs treated with 1nM VD3 had significantly greater viability than untreated and pre-treated cells (p<0.01, p<0.01) and significantly lower apoptosis-to-viability ratio (p<0.01). ASCs pre-treated with 1nM VD3 had significantly lower nitric oxide release (p<0.05) and lower mitochondrial polarization (p<0.05) compared to controls. In vivo results showed mice receiving 5000ng VD3 had significantly greater graft weight (p<0.05) and volume (p<0.05) after 12 weeks of treatment compared to controls. Grafts had enhanced neovascularization, intact adipocyte architecture, and absence of oil cysts. VD3 is an over-the-counter nutritional supplement with a known safety profile in humans. Our xenograft model suggests administering VD3 at the time of surgery may significantly improve fat graft retention.
