Angiogenesis and its regulation: roles of vascular endothelial cell growth factor.

Neovascularization is well known to occur in human atherosclerotic plaques, proliferative retinopathies, and malignant neoplasias. However, its pathophysiologic roles and mechanisms still remain unclear. In this study, histochemical examination of atherosclerotic plaques showed that vascular endothelial cell growth factor (VEGF) was expressed by the smooth muscle cells and foamy macrophages in the atherosclerotic intimas. The number of VEGF-positive cells was positively correlated with the number of intimal blood vessels. Moreover, VEGF gene transfer into rabbit carotid arteries using the hemagglutinating virus of Japan (HVJ)-liposomes showed that VEGF overexpression could induce the angiomatoid proliferation. In diabetic rats, VEGF was overexpressed in diabetic retinas, and thus the local overexpression of VEGF seemed to play an important role in the development of blood-retinal barrier breakdown in simple diabetic retinopathy. These results indicated that the VEGF can act as a local and endogenous regulator of endothelial cell functions and that VEGF induces the neovascularization under pathophysiologic conditions. On the other hand, the transfer of a decoy for the cis-element in the promoter region of the angiogenic factors would be an effective method for regulating angiogenesis, because other angiogenic factors' expression promoted by such cis-element could be simultaneously suppressed. Therefore, this method may supply a useful therapeutic tool for the regulation of pathologic angiogenesis.