Vascular endothelial growth factors and angiogenesis

VEGF was discovered in 1989. Research conducted over the past 10 years has demonstrated that VEGF is a major regulator of angiogenesis and vasculogenesis. This paper reviews the molecular data on the multiple forms of VEGF, their signalling and accessory receptors. Five genes encoding VEGF-like proteins have been identified; the different isoforms of each VEGF molecule are generated by alternative splicing mechanisms. The different VEGF's recognize signalling tyrosine kinase receptors (Fit-1, Flk-1 and Flt-4) and accessory receptors. VEGF expression is stimulated by hypoxia-dependent and -independent mechanisms. Hypoxic responses are mediated by specific transcription factors that are expressed in a tissue dependent fashion and that are developmentally regulated. VEGF is thought to play a role in tumor angiogenesis and may contribute to cardioprotection in ischemic heart diseases, its role in pulmonary hypertension induced by chronic hypoxia is discussed. This review also stresses the difficulty of applying results from in vitro studies to in vivo situations.