Effects of Semaphorin 3A on Retinal Pigment Epithelial Cell Activity

PURPOSE: Semaphorin 3A (Sema3A), a chemorepellant guidance protein, has been shown to be crucial for neural and vascular remodeling. This study is designed to examine the effects of Sema3A on RPE cell activity both in vitro and in vivo. METHODS: Retinal pigment epithelial were incubated with Sema3A, or VEGF- and Sema3A-containing medium. Cell proliferation, migration, cell cycle, apoptosis, cocultured human umbilical vein endothelial cells tube formation, VEGF receptor 2 (VEGFR2) and neuropilin 1 (Nrp1) receptor expression, VEGF- and pigment epithelium-derived factor (PEDF) concentration, and c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases (p38MAPK) signaling pathway studies were measured. A rabbit proliferative vitreoretinopathy (PVR) model was used for in vivo study. Subconfluent ARPE19 cells were injected intravitreously with or without Sema3A. Data were analyzed with Graphpad Prism 5.0 software. RESULTS: In vitro, Sema3A not only induced RPE cell cycle arrest and inhibited RPE migration under normal culture conditions, but also inhibited exogenous and endogenous VEGF165-induced cell activities. These activities included proliferation, migration, cell cycle arrest, JNK and p38MAPK signaling pathway phosphorylation, and cocultured endothelial cell tube formation. It is shown that both VEGF165 and Sema3A induced the upregulation of VEGFR2 and Nrp1 receptors. Activity inhibition was mediated by impeding VEGF165 utilization and possibly mediated by competitive inhibition of VEGF165 binding to its receptor VEGFR2, but not by the suppression of VEGF165 secretion. In vivo, Sema3A inhibited PVR, which is induced by RPE proliferation. CONCLUSIONS: These results suggested that Sema3A could be a useful therapeutic strategy for preventing RPE malfunction.