Abstract
BACKGROUND: Adipose tissue provides a readily available source of autologous stem cells. Adipose-derived stem cells (ASCs) have been proposed as a source for endothelial cell substitutes for lining the luminal surface of tissue engineered bypass grafts. Endothelial nitric oxide synthase (eNOS) is a key protein in endothelial cell function. Currently, endothelial differentiation from ASCs is limited by poor eNOS expression. The goal of this study was to investigate the role of three molecules, sphingosine-1-phosphate (S1P), bradykinin, and prostaglandin-E1 (PGE1) in ASC endothelial differentiation. Endothelial differentiation markers (CD31, vWF and eNOS) were used to evaluate the level of ASCs differentiation capability. RESULTS: ASCs demonstrated differentiation capability toward to adipose, osteocyte and endothelial like cell phenotypes. Bradykinin, S1P and PGE were used to promote differentiation of ASCs to an endothelial phenotype. Real-time PCR showed that all three molecules induced significantly greater expression of endothelial differentiation markers CD31, vWF and eNOS than untreated cells. Among the three molecules, S1P showed the highest up-regulation on endothelial differentiation markers. Immunostaining confirmed presence of more eNOS in cells treated with S1P than the other groups. Cell growth measurements by MTT assay, cell counting and EdU DNA incorporation suggest that S1P promotes cell growth during ASCs endothelial differentiation. The S1P1 receptor was expressed in ASC-differentiated endothelial cells and S1P induced up-regulation of PI3K. CONCLUSIONS: S1P up-regulates endothelial cell markers including eNOS in ASCs differentiated to endothelial like cells. This up-regulation appears to be mediated by the up-regulation of PI3K via S1P1 receptor. ASCs treated with S1P offer promising use as endothelial cell substitutes for tissue engineered vascular grafts and vascular networks.