Quality and Quantity-Cultured Murine Endothelial Progenitor Cells Increase Vascularization and Decrease Fibrosis in the Fat Graft

Background: Fat grafting has become a valuable technique for soft-tissue reconstruction; however, long-lasting success depends on several determinants. An early blood supply to the transplanted adipocytes is important to prevent ischemia. The recently developed quality and quantity (QQ) culture increases the vasculogenic potential of endothelial progenitor cells. The authors used a murine fat grafting model to address the hypothesis that QQ-cultured endothelial progenitor cells stimulate the establishment of a blood vessel network and increase graft success. Methods: c-Kit(+)Sca-1(+)Lin(-) (KSL) cells were isolated as endothelial progenitor cell precursors from C57BL/6 mice. Adipose tissue was grafted with QQ-cultured KSL cells (QQKSL group), uncultured KSL cells (KSL group), adipose-derived stem cells (ASC group), and a combination (QQKSL+ASC group), and compared to a control group. Five and 10 weeks later, grafts were weighed, histologic and immunohistochemical parameters were evaluated, and gene expression was quantified by quantitative polymerase chain reaction. Results: The highest vessel density was observed in the combined QQKSL+ASC group (68.0 +/- 4.3/mm(2); p < 0.001) and the QQKSL group (53.9 +/- 3.0/mm(2); p < 0.001). QQKSL cells were engrafted in proximity to the graft vasculature. QQKSL cells decreased the fibrosis percentage (13.8 +/- 1.8 percent; p < 0.05). The combined QQKSL+ASC group (22.4 +/- 1.8/mm(2); p < 0.001) showed the fewest local inflammation units. A significant up-regulation of platelet-derived growth factor and adiponectin expression was observed in the QQKSL group and QQKSL+ASC group. Graft weight persistence was not significantly different between groups. Conclusions: Supplementing fat grafts with quality and quantity-cultured endothelial progenitor cells improves graft quality by stimulating vascularization. The increased vessel density is associated with less fibrosis, less inflammation, and better adipose tissue integrity. Enriching fat grafts with QQ-cultured endothelial progenitor cells is a potential solution to their clinical shortcomings.