Abstract 700: Identification of a Human Coronary Vasculature Progenitor Cell
C-kit positive cardiac progenitor cells correspond to a category of myocardial progenitors which acquire predominantly the cardiomyogenic fate. Vessel growth is modest and strikingly inferior to myocyte formation. In analogy to myogenesis, we tested whether endothelial cell (EC) and smooth muscle cell (SMC) turnover and vasculogenesis in the human heart are regulated by resident c-kit positive vascular progenitor cells (VPCs). For this purpose, the expression of VEGFR2/KDR, which represents the earliest marker of angioblast precursors, was employed to recognize and sort VPCs from the pool of human c-kit positive progenitor cells. KDR positive VPCs were negative for markers of hematopoietic cell lineages including CD34, CD41, CD45, CD133 and a cocktail of antibodies against bone marrow derived cells: CD2 (T cells and natural killer cells), CD3 (T cells), CD8 (T cells), CD14 (monocytes), CD16 (neutrophils/monocytes), CD19 (B cells), CD20 (B cells), CD24 (B cells), CD56 (natural killer cells), CD66b (granulocytes) and glycophorin A (red blood cells). Also, only a small fraction of human VPCs was positive for the EC adhesion protein CD31 and the SMC TGF-beta-1 receptor protein. The question was then whether VPCs are self-renewing, clonogenic and multipotent which are the fundamental properties of stem cells. VPCs were sorted and deposited in single wells. After ~3 weeks multicellular clones were obtained. Differentiating VPCs acquired almost exclusively the EC and SMC phenotype and minimally the myocyte lineage. To determine the functional import of VPCs, a critical stenosis was created in chronically instrumented immunosuppressed dogs and EGFP-tagged human VPCs were injected above, laterally and below the constriction in an attempt to promote the formation of a biological bypass. Serial measurements of coronary blood flow (CBF) during and after transient coronary occlusion showed a time dependent increase in CBF to the distal myocardium. Importantly, newly formed EGFP-positive coronary vessels were detected in proximity of the stenotic coronary artery. In conclusion, the human heart contains a pool of VPCs that can be implemented clinically to form functionally competent coronary vessels and improve CBF in patients with ischemic cardiomyopathy.