Focus on biological identity of endothelial progenitors cells.

Circulating Endothelial Progenitor Cells (EPCs) were discovered by Asahara et al in 1997 and defined as bone marrow CD34+/KDR+ cells endowed with angiogenic potentialities in vitro and in vivo. The most likely assumption is that EPCs consist of several cell subpopulations with functions targeted at accomplishing the post-natal neovascularization process in a synergic and complementary fashion. Indeed, the subsequent identification of numerous and differentiated hematic populations, characterized by the capacity to develop an endothelial phenotype, has posed a number of questions as to the real identity of EPCs. This concept does not represent a sterile speculation but rather it suggests important implications for the future practice of stem cell therapy. The aim of this report was to explore through a critical analysis the two main experimental methodologies, in vitro culture and flow cytometry, applied to EPCs, followed by a brief revaluation of the endothelial progenitors employing a globally functional approach.