Platelet-derived growth factor and angiogenesis

Angiogenesis, the formation of new vessels from existing microvessels, is important in embryogenesis, wound healing, inflammation, ischemic heart- and peripheral vascular disease, myocardial infarction, diabetic retinopathy, and cancer. Platelet-derived growth factor (PDGF) has been implicated in most of these processes and can induce the generation of a vascularized connective tissue stroma. PDGF homo- and heterodimers, composed of a PDGF A- and/or B-chain, and PDGF receptor subunits (alpha- and beta) are widely expressed upon tissue injury and repair. Hypoxia and other angiogenesis-related stimuli can induce expression of the PDGF B-chain. PDGF may modulate angiogenesis by attracting inflammatory or connective tissue cells which in turn control angiogenesis. Additionally, PDGF may act directly on specific phenotypes of endothelial cells that are engaged in angiogenesis or that are of microvascular origin and that express PDGF receptor beta-subunits. PDGF induces the formation of a vascularized connective tissue stroma upon exogenous administration or local overexpression. The presence of PDGF and its receptors in angiogenesis-related processes or diseases such as placenta formation, embryogenesis, wound healing, atherosclerosis, and cancer is consistent with a role for PDGF in angiogenesis. Thus, PDGF-BB can elicit the formation of a vascularized connective tissue stroma. New vessel formation in response to PDGF-BB may be partially due to its direct effects on endothelial cells that express PDGF receptor beta-subunits.