Angiogenic growth factors.

Angiogenesis, the formation of new blood vessels, plays a central role in a variety of physiological and pathological processes such as embryonic development, wound healing and tumor growth. It is a complex, multi-step process that involves the migration and proliferation of capillary endothelial cells. Several factors that stimulate the proliferation of endothelial cells in vitro have been shown to induce angiogenesis in vivo. Among these angiogenic growth factors are wide-spectrum multifunctional mitogens (e.g. the fibroblast growth factors) and the recently identified factors with distinct specificity for vascular endothelial cells (e.g. the platelet-derived endothelial cell growth factor). Another group of factors apparently induce angiogenesis indirectly (e.g. transforming growth factor-beta) by stimulating target cells to release angiogenic factors or by other mechanisms. The differential expression, release and activation of these factors might regulate angiogenesis under various physiological and pathological conditions.