Platelet-derived growth factor (PDGF) is a dimeric glycoprotein consisting of two disulfide bridge-stabilized polypeptide chains, A and B, which are assembled as heterodimers (PDGF-AB) or homodimers (PDGF-AA and PDGF-BB) (Fretto et al.; Westermark & Heldin). PDGF signals through the receptor tyrosine kinases PDGFRalpha and PDGFRbeta. PDGF-induced migration has been shown to involve MEK/ERK, EGFR, Src, and PI3K/Akt signaling pathways (Kim et al.). PDGF is a potent mitogen for cells of mesenchymal origin- like fibroblasts, glial cells, and vascular smooth muscle cells. PDGF has been implicated in pathogenesis of atherosclerosis, glomerulonephritis, cancer, and in the contraction of vascular smooth muscle cells of rat aortic tissues (Fretto et al.; Sachinidis et al.). PDGF-BB is secreted by osteoblasts to induce mesenchymal stem cell migration and angiogenesis. It has also been shown that PDGF-BB is secreted by preosteoclasts during bone modeling and remodeling to induce angiogenesis and thus proper osteogenesis (Xie et al.). This product is animal component-free.