ANGIOGENESIS - AN UPDATE

Angiogenesis is the neovascularization or formation of new blood vesse ls from the established microcirculation. It is particularly important and indispensable in a large number of normal and pathological proces ses during pre- and post-natal life, including neoplasia, inflammation , wound repair and collaterization in response to ischemic stimuli. Th e current interest in the role of neovascularization in the transition from hyperplasia to neoplasia, as well as in the tumour growth and me tastasis, has brought about a large number of studies on angiogenesis. The complex processes of neovascularization, quiescent in the adult o rganism, may occur rapidly in several circumstances, with the implicat ion of the following events: a) endothelial cell (EC) and pericyte act ivation; b) basal lamina degradation; c) migration and proliferation o f EC and pericytes; d) formation of a new capillary vessel lumen; e) a ppearance of pericytes around the new capillaries; f) development of a new basal lamina; g) capillary loop formation; h) persistence or invo lution, and differentiation of the new vessels; and i) capillary netwo rk formation and, eventually, organization into larger microvessels. T he use of numerous ''in vivo'' and ''in vitro'' systems has facilitate d the assessment of angiogenesis control, in which angiogenic (fibrobl ast growth factors, vascular endothelial growth factor, platelet endot helial growth factor, E series prostaglandin, angiogenin, monobutyrin) and antiangiogenic (cartilage-derived angiogenic inhibitor, thrombosp ondin, protamine, platelet factor-4, interferon, angiostatic antibioti cs, steroids) substances intervene. Heparin and heparin sulphate also play a key role in these mechanisms. A greater knowledge of angiogenes is control may lead to the development of a potential therapy in angio genesis-related processes.