Proangiogenic Role of ephrinB1/EphB1 in Basic Fibroblast Growth Factor-Induced Corneal Angiogenesis

Corneal neovascularization is a vision-threatening condition caused by various ocular pathological conditions. The aim of this study was to evaluate the function of the ephrin ligands and Eph receptors in vitro and in vivo in corneal angiogenesis in a mouse model. The Eph tyrosine kinase receptors and their ligands, ephrins, are expressed on the cell surface. The functions of Eph and ephrins have been shown to regulate axonal guidance, segmentation, cell migration, and angiogenesis. Understanding the roles of Eph and ephrin in corneal angiogenesis may provide a therapeutic intervention for the treatment of angiogenesis-related disorders. Immunohistochemical studies demonstrated that ephrinB1 and EphB1 were expressed in basic fibroblast growth factor (bFGF)-induced vascularized corneas. EphB1 was specifically colocalized with vascular endothelial marker CD31 surrounded by type IV collagen. EphrinB1 was expressed in corneal-resident keratocytes and neutrophils. Recombinant ephrinB1-Fc, which induces EphB receptor activation, enhanced bFGF-induced tube formation in an in vitro aortic ring assay and promoted bFGF-induced corneal angiogenesis in vivo in a corneal pocket assay. Synergistically enhanced and sustained activation of extracellular signal-regulated kinase was noted in vascular endothelial cell lines after stimulation with ephrin B1 and bFGF combinations. These results suggest that ephrinB1 plays a synergistic role in corneal neovascularization.