Biological and clinical implications of recruitment of stem cells into angiogenesis.

Emerging evidence suggests that bone marrow may represent a reservoir of endothelial progenitor cells (EPCs), which could contribute to postnatal tissue vasculogenesis. These cells can be mobilized to the circulation through the action of specific angiogenic factors and contribute to neoangiogenic processes. The level of circulating EPCs has been proposed as a surrogate biologic marker for vascular function suggesting that EPCs may have a role in maintenance and reparative processes and in tumor development. The phenotypic characterization of EPCs remains controversial because of the lack of specific endothelial markers and functional assays. The most promising areas of current research focus on the investigation and understanding of the role EPCs in cardiovascular disorders and tumors in order to develop therapeutic strategies that can modulate EPC trafficking and function.