Figure 1: The angiogenic balance between angiogenic activators and angiogenic inhibitors regulate vascular homeostasis. Angiogenesis under physiological and pathological conditions is associated with up-regulation of angiogenic factors and/or down-regulation of angiogenic inhibitors. Up-regulation of angiogenic inhibitors and/or down-regulation of angiogenic activators may be associated with impaired neovascularization capacity. VEGF, vascular endothelial growth factor; bFGF, basic fibroblast growth factor; IGF-I, insulin-like growth factor-I; IL-8, interleukin-8; PDGF, plateletderived growth factor; PlGF, placenta growth factor; TGF-α and β, transforming growth factor-α and β.