Abstract 1146: Semaphorin 3E/Plexin D1 as a Novel Target for Therapeutic Angiogenesis
Class 3 semaphorins and their receptor plexins are known to play important roles in axon and dendritic guidance during neural development. It has been also reported that semaphorin 3E (sema 3E) and its specific receptor plexin D1 regulate the patterning of vessels during embryogenesis. However, it remains unclear whether these molecules are involved in postnatal angiogenesis. To elucidate the role of sema 3E/plexin D1, we first performed angiogenesis assay in which human umbilical vein endothelial cells were co-cultured with fibroblasts in the presence or absence of sema 3E. Treatment with vascular endothelial growth factor (VEGF) markedly increased tube formation and this increase was significantly inhibited by sema 3E.Moreover, treatment with the plexinD1-Fc fusion protein antagonized the effect of sema 3E on VEGF-induced tube formation, suggesting an anti-angiogenic activity of sema 3E. To further elucidate the role of sema 3E/plexin D1 in postnatal angiogenesis, we generated a murine model of hind limb ischemia. Expression of sema 3E and plexin D1 was markedly upregulated in ischemic limbs 3 days after surgery. To examine the effect of inhibition of sema 3E, we injected the expression vector encoding the plexin D1-Fc gene into ischemic limbs and analyzed blood flow recovery after ischemia. Laser Doppler perfusion imaging revealed that blood flow was significantly improved 10 days after surgery in the plexinD1-Fc-treated group compared with the control group. Immunohistochemical analyses showed that the number of CD31-positive cells was significantly greater in the plexinD1-Fc group than in the control group. Conversely, introduction of the sema 3E gene into ischemic limbs led to impaired blood flow recovery. It has been reported that other members of the sema 3 family are transcriptionally regulated by p53, a tumor suppressor protein that inhibits neovascularization in tumors. Consistent with these reports, expression of p53 was markedly increased in ischemic limbs and forced expression of p53 upregulated sema 3E expression. These results indicate that sema 3E/plexin D1 negatively regulates postnatal angiogenesis and suggest that inhibition of sema 3E would be a novel strategy for therapeutic angiogenesis.