Vitamin D Enhances Adipose Stem Cell Proliferation And Alters Metabolic Energy Utilization Under Hypoxic Conditions
Anya Singh-Varma, BS, Shawn Loder, MD, Phoebe Lee, BS, Wayne Nerone, BS, David Guerrero, BS, Lauren J. Kokai, BS.
University of Pittsburgh, Pittsburgh, PA, USA.
BACKGROUND: Post-operative reabsorption of engrafted adipose results in up to 50% tissue loss in the first post-operative year and is limits reliable volumetric results. We previously demonstrated that Vitamin D (VD3) enhances adipose retention in xenograft fat transfer and enhances adipose stem cell (ASC) viability ex vivo. To approach a mechanism, we evaluated how VD3 affected the metabolism and proliferative indices of ASCs and adipocytes.
METHODS: Lipoaspirate was either a) enzymatically dissociation to free the stromal vascular fraction (SVF) or maintained ex vivo for 7-days. A fraction of these SVF was assessed for general metabolic and proliferative indices utilizing MTT assay under hypoxic or normoxic conditions. Calcein/PI cytometry was utilized to assess cell size and survival. ASCs and differentiated adipocytes were treated and analyzed without and without CoCl2 using a seahorse bioanalyzer (Agilent) for real time kinetics of metabolic flux in live cells.
RESULTS: When maintained ex vivo VD3-treated SVF demonstrated enhanced viability, in vitro SVF demonstrated enhanced proliferation (p<0.05). This effect was present; under persistent hypoxic stress for up to 6-days post-harvest (p<0.05). Furthermore, when we compared the change in oxygen consumption under stressed vs. conditions VD3 significantly reduced oxygen consumption rates is SVF and increased cellular energetic reserve capacity.
CONCLUSIONS: We previously demonstrated that Vitamin D offers a safe and effective option for the prevention of graft loss. Here we demonstrate cell dependent changes in metabolism and proliferation with VD3 supporting a more proliferative and energetic profile in those adipose stem cells necessary for fat graft renewal.
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