Expression of ephrinB2 and its receptors on fibroproliferative membranes in ocular angiogenic diseases

PURPOSE: To determine whether ephrinB2 plays a role in ocular angiogenesis, we investigated the expression of ephrinB2 and EphB receptors on retinal fibroproliferative membranes. DESIGN: Experimental study of the expression of ephrinB2 and EphB receptors within fibroproliferative membranes in patients with ocular angiogenic diseases collected during vitrectomy. METHODS: Fibroproliferative membranes were obtained at the time of vitrectomy from 20 patients with proliferative diabetic retinopathy (PDR) and from 40 patients who had stage 5 retinopathy of prematurity. Specimens were investigated with immunohistochemistry using polyclonal antibodies directed against ephrinB2 and the EphB2, EphB3, and EphB4 receptors. Immunoreactivity for von Willebrand factor (factor VIII) and alpha-smooth muscle actin (alpha-SMA) was also determined to confirm the identity of the target vascular endothelial cells. RESULTS: Positive staining for ephrinB2 was observed on fibroproliferative membranes that were obtained from patients with PDR (65.0%) and retinopathy of prematurity (25.0%). Specifically, ephrinB2 was found to be present on endothelial cells, as confirmed by its colocalization with factor VIII and alpha-SMA staining. EphB2 and EphB3 expression was observed on fibroproliferative membranes that were harvested from patients with PDR (EphB2, 90.0%; EphB3, 70.0%) and retinopathy of prematurity (EphB2, 35.0%; EphB3, 45.0%). However, EphB4 expression was not observed in any of the membranes derived from patients with PDR or retinopathy of prematurity. The rate of ephrinB2 expression in patients with PDR was significantly higher than that seen in patients with retinopathy of prematurity, which probably reflected differences in the vascular density of their fibroproliferative membranes. CONCLUSION: These data suggest that the ephrinB2-EphB2/B3 system may play an important role in ocular angiogenesis.