The Role of Hypoxia, Hypoxia-Inducible Factor (HIF), and VEGF in Retinal Angiomatous Proliferation

In industrialized countries, age-related macular degeneration (AMD) is the leading cause of blindness in elderly people. Hallmarks of the non-neovascular (dry) form of AMD are the formation of drusen and geographic atrophy, whereas the exudative (wet) form of the disease is characterized by invading blood vessels. In retinal angiomatous proliferation (RAP), a special form of wet AMD, intraretinal vessels grow from the deep plexus into the subretinal space. Little is known about the mechanisms leading to intraretinal neovascularization, but age-related changes such as reduction of choroidal blood flow, accumulation of drusen, and thickening of the Bruch's membrane may lead to reduced oxygen availability in photoreceptors. Such a chronic hypoxic situation may induce several cellular response pathways including the stabilization of hypoxia-inducible factors (HIFs) and the production of angiogenic factors, such as vascular endothelial growth factor (VEGF). Here, we discuss the potential contribution of hypoxia and HIFs in RAP disease pathology and in some mouse models for subretinal neovascularization.