Platelet-derived growth factor (PDGF) was discovered as a major mitogenic factor present in serum but absent from plasma. In vitro, PDGF-BB stimulated MAP kinase activity and cell motility of isolated lymphatic endothelial cells. In vivo, PDGF-BB potently induced growth of lymphatic vessels. Expression of PDGF-BB in murine fibrosarcoma cells induced tumor lymphangiogenesis, leading to enhanced metastasis in lymph nodes. The PDGF signaling system contributes to and vascular remodeling. Growth factors such as PDGF exert potent effects on wound healing including the regeneration of tooth-supporting structures. Some research reports findings in this chronic myocardial infarction model were that bFGF, PDGF-BB and their combination all had a more pronounced angiogenic effect on the arteriolar than the capillary level. bFGF stimulated both capillary and arteriolar growth while PDGF-BB preferentially stimulated arterioles.