Purpose: To evaluate vitreous and plasma concentrations of vascular endothelial growth factor (VEGF) and apelin and to detect the expressions of VEGF and apelin on epiretinal fibrovascular membranes obtained during vitrectomy in eyes with proliferative diabetic retinopathy after intravitreal bevacizumab injection.
Methods: Forty-four eyes of 44 patients affected by active proliferative diabetic retinopathy were investigated. The bevacizumab study group consisted of 20 eyes that received an intravitreal bevacizumab injection (1.25 mg) 7 days before pars plana vitrectomy. The control group included 24 eyes that underwent pars plana vitrectomy without previous intravitreal bevacizumab injection. Using enzyme-linked immunosorbent assay, the concentrations of VEGF and apelin were measured in vitreous and plasma samples. The expressions of VEGF and apelin in the excised epiretinal membranes were examined by fluorescence immunostaining.
Results: Vitreous and plasma concentrations of VEGF were significantly lower in the bevacizumab group than in the control group (P < 0.001 and P = 0.003, respectively), while the vitreous and plasma concentrations of apelin did not vary significantly between the 2 groups (P = 0.62 and P = 0.09, respectively). In the epiretinal fibrovascular membranes of both the groups, a colocalization of the endothelial marker CD31 with the markers for apelin was observed.
Conclusion: Intravitreal bevacizumab injection may lead to a decrease in the intraocular and systemic concentrations of VEGF, suggesting a local and potentially a systemic effect on VEGF but may have no effect on apelin. Apelin may be associated with the development of epiretinal membranes in proliferative diabetic retinopathy and may not directly correlate with VEGF.