Neurotrophins: novel mediators of angiogenesis

Angiogenesis is a highly coordinated physiological process in which new blood vessels are formed to meet the oxygenation demands of local tissues. Several classes of growth factors, including members of the vascular endothelial growth factor family, angiopoietins, platelet derived growth factor, fibroblast growth factors and ephrins have been implicated in regulating specific aspects of angiogenesis, both during embryonic development and in response to injury. This review focuses on a distinct family of growth factors, the neurotrophins, and their receptors as newly identified angiogenic molecules. The expression of neurotrophins and their receptors are regulated both temporally and spatially by the vasculature of the embryo and adult, and dynamic changes occur following vascular injury. Recent studies that identify the vascular cells responsive to neurotrophins, that genetically dissect neurotrophin actions in vessel development and remodeling, and that uncover neurotrophin effects in models of tissue ischemia are discussed.