Characterization of the Spontaneous Capillary-Like Network Formation by hSVF Cells

Adipose tissue is a novel source of the stromal vascular fraction (SVF), a heterogeneous vascular cell population. In subcutaneous in vivo models, SVF spontaneously forms patent vasculatures in collagen matrices weeks after implantation. We have shown that cultured human SVF can also spontaneously form endothelial capillary-like networks (CLN) over several days in in vitro cultures. This CLN formation might be beneficial in pre-vascularizing a cellular construct for implant, enhancing angiogenesis and engraftment and increasing viability of the construct’s cells. To characterize spontaneous CLN formation as a function of (a) cell passage (P1 through P4) and (b) signaling pathway inhibition through angiogenic inhibitors, endothelial cells, perivascular cells, and their nuclei were characterized through immunocytochemistry. Vessel length was quantified using Image-J software. The results indicate that optimal CLN formation occurs during P1, suggesting a loss or phenotypic change of endothelial cells with successive passaging. Furthermore, CLN length is significantly reduced by inhibition of PDGF-Rβ, VEGF-R2, and Wnt pathways, though c-Met and TGF-β inhibition elicited no effect. These findings can help maximize CLN formation, which could offer a novel in vitro angiogenic model for in vivo SVF performance and potentially function as a novel vascular interface.