Fig. 1. Characteristics of rabbit circulating endothelial progenitor cells. Mononuclear cells were isolated from peripheral blood of rabbits using the Ficoll centrifugation and cultured in supplementation with endothelial growth medium 2. These endothelial progenitors exhibited phenotyping of endothelial cells with incorporation of acetyl LDL ( A , red fluorescence ) and isolectin ( B , green fluorescence ). C and D show overlaying of acetyl LDL and isolectin in the cultured endothelial progenitor cells. Expression of Flk-1 was also detected on endothelial progenitor cells ( E , green fluorescence ). A – E were photographed under fluorescence confocal microscopy, and nuclei were counterstained in blue fluorescence . Colonies of outgrowth endothelial progenitor cells in the typical monolayer “cobblestone” appearance were obtained 2–3 weeks after plating ( F ).