Effect of intravitreal bevacizumab on serum, aqueous, and vitreous humor levels of erythropoietin in patients with proliferative diabetic retinopathy

Aim. The aim of this study was to evaluate concentrations of erythropoietin (EPO) and vascular endothelial growth factor (VEGF) in serum, aqueous and vitreous humour of diabetic patients with proliferative retinopathy (PDR) and to verify their possible modifications induced by intravitreal injection of bevacizumab (IVB). Methods. This prospective observational study was performed on patients who underwent vitrectomy for proliferative diabetic retinopathy and macular hole or pucker. The study sample consisted of 33 patients with proliferative diabetic retinopathy and 20 non-diabetic patients with macular hole or pucker. EPO and VEGF levels in serum, aqueous and vitreous humour were measured in both groups. In diabetic patients measures were performed before and after IVB. Results. EPO and VEGF levels in aqueous and vitreous humour were markedly increased in diabetic patients with PDR as compared with those recorded in the control group (P<0.001); contrarily, EPO serum levels were similar in both groups (p=not significant). IVB did not affect EPO levels (aqueous 39.1±29.2 vs. 38.6±26.1; vitreous 179.3±88.3 vs. 131.6±67.8; serum 9.2±5.8 vs. 6.9±3.7mUI/mL); conversely, VEGF concentration significantly decreased 15 days after IVB in serum and ocular fluids (aqueous 141.6±12.3 vs. 81.4±5.4; vitreous 180.4±45.8 vs. 95.8±23.6; serum 113.9±52.8 vs. 73.2±65.6mUI/mL). Conclusion. These findings demonstrate that the production of VEGF and EPO is regulated by different mechanisms. Intraocular levels of EPO in diabetic patients were significantly higher than those recorded in serum, suggesting a local production. In addition, bevacizumab does not influence intraocular levels of EPO.