Postnatal vasculogenesis

It is generally accepted that vasculogenesis is limited to early embryogene sis and is believed not to occur in adult, whereas angiogenesis occurs in b oth the developing embryo and postnatal life. However, the distinction betw een them is not absolute, because both require endothelial cell proliferati on and migration and three-dimensional reorganization of newly formed blood vessels, nor are they mutually exclusive, inasmuch as angioblasts can be i ncorporated into expanding pre-existing blood vessels. Recent observations indicate that vasculogenesis may not be restricted to early embryogenesis, but may also have a physiological role or contribute to the pathology of va scular diseases in adults. The major evidence in favor of this new view com es from: (i) demonstration of the presence of circulating endothelial cells and endothelial precursor cells; (ii) newly described mechanisms of blood vessel formation in tumor growth. The potential biomedical applications of endothelial precursor cells and the new opportunities for the development o f new forms of tumor-targeted treatments are discussed. (C) 2001 Elsevier S cience ireland Ltd. All rights reserved.