FIG. 5.

Two types of endothelial progenitor cells (EPCs) promote therapeutic angiogenesis with different mechanisms. From human peripheral blood mononuclear cells cultured in endothelial cell growth medium, spindle-shaped Early EPCs appear as soon as 4 days of culture, while cobblestone-shaped Late EPCs appear around 3 weeks. Early EPCs express hematopoietic markers abd possess strong proangiogenic paracrine, but not vasculogenic properties, while Late EPCs are devoid of hematopoietic markers, have a weak paracrine potential, but strong proliferative and vasculogenic ability. When transplanted in models of tissue ischemia, both cell types can promote therapeutic angiogenesis in vivo. Images adapted from Hur et al., (50). (To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/ars.)