Abstract 1217: Jagged-1, but not Delta-like-1, Signal Promotes EPC Expansion and Commitment in Human Cord Blood CD133 Positive Cells for Postnatal Vasculogenesis in Ischemic Tissues
Little is known about Notch ligand signal function in human on endothelial progenitor cells (EPCs) to exploit the mechanism for clinical application, though we presented the significant effect of murine Notch ligands, Notch signals, Jagged-1 and Delta-like-4 on murine EPC biology. To investigate the therapeutic potential and functional importance of Notch signals on human EPC mediated neovascularization, we established in vitro expansion and differentiation co-culture system using HESS-5 stromal cells transfected by retrovirus empty vector or vectors encoding or Notch ligand genes, human Jagged-1 and Delta-like-1, (Empty cell, Jag-1 cell and Dll-1 cell respectively). CD133 positive cord blood cells as were directly co-cultured with one of Empty, Jag-1 and Dll-1 cells with the cytokine cocktail for EPC expansion culture for 7days. CD133+ cells co-cultured with Jag-1 cells significantly proliferated and differentiated into KDR(+) /CD31(+) cells by 1.5 folds than with Empty cells. But Dll-1 stimulated cells significantly decreased in number by half. Non-contact co-culture as well as contact co-culture with Notch signal inhibitor disclosed no effect on EPC proliferation and differentiation. In EPC colony assay, Dll-1 experienced cells promoted significantly less number of EPC-colonies in vitro compared with Empty and Jag-1 experienced cells. Expression analysis demonstrates high secretion of VEGF-A in Jag-1 stimulated cells. Furthermore, we investigated the regenerative property of Empty, Jag-1 and Dll-1 stimulated EPCs by intra muscular transplantation into hindlimb ischemic models of nude mice. The transplantation of Jag-1 experienced EPCs demonstrated high recovery of blood flow and capillary density in ischemic hindlimb muscles. In contrast, no effect was observed by Dll-1 or Empty stimulated cells. These findings indicate that human Notch signals subsequently contribute to EPC proliferation and differentiation and postnatal neovascularization. In conclusion, we here showed Notch signals are required for postnatal human neovascularization, providing us more critical clue of elucidating the mechanism of cell fate determination of human EPCs and its functional therapeutic cascade.