|Programm||"Degeneration und Regeneration– Grundlagen, Diagnostik und Therapie"|
Control Mechanisms of Retinal Neovascularization
Retinal neovascularization is a common complication in patients with advanced diabetic retinopathy, retinal vein occlusion, and retinopathy of prematurity. Blood vessel growth is characterized by actively migrating and proliferating endothelial cells and is associated with a shift in the balance of (i) pro-angiogenic mediators and (ii) endogenous angiogenesis inhibitors. Production of vascular endothelial growth factor (VEGF), a potent enhancer of angiogenesis and vascular permeability, is controlled by local oxygen concentrations; i.e., hypoxia results in increasing VEGF levels. Pigment epithelium-derived factor (PEDF) seems to counter the angiogenic effects of VEGF; PEDF levels remain high when oxygen concentration is normal but become decreased in hypoxic conditions. The VEGF/PEDF ratio determines whether neovascularization is inhibited (in healthy retinal tissue) or an abnormal blood vessel growth is stimulated (in hypoxic / ischemic conditions).