Fig. 7. A scheme of synergistic effects of VEGF-A and FGF-2 in neovasculature formation through enhancement of endogenous PDGF-B–PDGFRß signaling. VEGF-A induces secretion of PDGF-BB from endothelial cells in addition to its mitogenic effects on endothelium. FGF-2 enhances PDGFRß expression in mural cells, in addition to its mitogenic effects on both endothelial and mural cells. Combined stimulation with these two angiogenic molecules thus synergistically enhances intercellular communication through PDGF-B–PDGFRß signaling and causes mural cell recruitment and formation of mature vessels. These effects are blocked by either addition of exogenous PDGF-BB, which could overwhelm the local distribution of endogenous PDGF-BB, or inhibition of PDGFRß by specific antibodies, leading to formation of leaky and hemorrhaging vessels.