Bone marrow as a source of endothelial cells for natural and iatrogenic vascular repair.

Postnatal neovascularization has previously been considered synonymous with angiogenesis, but the finding that circulating endothelial progenitor cells (EPCs) may home to sites of neovascularization and there differentiate into endothelial cells (ECs) is consistent with "vasculogenesis," through which the primordial vascular network is established in the embryo. Our findings suggest that growth and development of new blood vessels in the adult are not restricted to angiogenesis but encompass vasculogenesis as well, although the proportional contributions remain to be clarified. Likewise, augmented or retarded neovascularization probably involves enhancement or impariment of the vasculogenesis process.