Histology of fibrovascular membranes of proliferative diabetic retinopathy after intravitreal injection of bevacizumab.

PURPOSE: The purpose was to study the histology of the fibrovascular membranes in proliferative diabetic retinopathy (PDR) with an intravitreal injection of bevacizumab. METHODS: Light and electron microscopic studies were performed on surgical specimens obtained during a pars plana vitrectomy from 6 PDR eyes after intravitreal injection of bevacizumab. The patients had preoperatively received no or scant retinal photocoagulations. The presence and distribution of CD34 was assessed as a marker of vascular endothelium using immunostaining. The presence of vascular endothelial growth factor was stained with a method of immunostaining. As controls, we examined 7 surgical specimens from 7 PDR eyes obtained during pars plana vitrectomy without bevacizumab therapy. All control patients had preoperatively received full or nearly full pan retinal photocoagulations. RESULTS: Light microscopy showed that the CD34-positive vascular endothelial cells formed capillarylike structures in the fibrovascular membranes of all 13 PDR eyes. Vascular endothelial growth factor was positively stained in the vascular endothelium of both groups; however, the number of vascular endothelial growth factor-positive vascular endothelial cells significantly decreased in the fibrovascular membranes with intravitreal injection of bevacizumab. Electron microscopy showed the newly formed vascular endothelial cells with junctional complex in both groups. CONCLUSION: The vascular endothelial cells with decreased expression of vascular endothelial growth factor are still present in the fibrovascular membranes of patients with PDR after intravitreal injection of bevacizumab.