The discovery of circulating endothelial progenitor cells (EPCs) opened up a new era of EPC-based therapies for cardiovascular diseases. While researchers are enthusiastic about applying EPCs to clinical therapy, progress has been substantially limited due to the lack of a thorough characterization and understanding of early and late outgrowth EPCs (also called endothelial colony-forming cell, ECFCs) biology. As a means of facilitating the understanding of how late EPCs can most effectively be applied to clinical therapeutics, this article reviews the recent progress covering 5 important issues: (1) The best passages of ex vivo-cultivated EPCs for cell therapy; (2) inflammatory activation of late EPCs: a real world consideration; (3) late EPC is not an endothelial cell: an issue of cell contamination; (4) ways to improve EPC function and differentiation; and (5) how to separate and delete smooth muscle progenitor cells (SPCs).
Key words: Cardiovascular disease; Cell therapy; Endothelial progenitor cell; Smooth muscle progenitor cell.