Purpose:The purpose was to measure the concentrations of various cytokines and growth factors (including vascular endothelial growth factor [VEGF] and pigment epithelium-derived factor [PEDF]) in the vitreous of patients with proliferative diabetic retinopathy (PDR) and to investigate interaction between inflammatory and proliferative factors in the genesis of PDR.Materials and Methods:Vitreous samples from 32 eyes with PDR and 25 eyes without diabetes mellitus and signs of DR (control) were collected. Vitreous concentrations of VEGF, PEDF, monocyte chemotactic protein-1 (MCP-1), interleukin-4 (IL-4), IL-6, IL-8, IL-10, IL-17A, and secretory immunoglobulin A (sIgA) were simultaneously measured using enzyme-linked immunoassay.Results:Vitreous levels of VEGF, PEDF, IL-17A, IL-6, IL-8, IL-4, and sIgA were significantly (Π < 0.05) higher in eyes with PDR compared to control. The concentration of VEGF was more than 17-times higher than in control, and the concentration of PEDF was not changed oppositely and was also higher (1.45-times) compared to control, that may indicate disturbances of compensatory mechanisms in angiogenesis regulation in PDR. Significant (P < 0.05) positive correlations were observed between vitreous concentrations of VEGF and IL-17A (r = 0.45), VEGF and IL-8 (r = 0.48), VEGF and IL-4 (r = 0.51), PEDF and IL-17A (r = 0.48), PEDF and IL-8 (r = 0.59), MCP-1 and PEDF (r = 0.72), MCP-1 and IL-8 (r = 0.45), IL-4 and IL-17A (r = 0.65), IL-4 and IL-8 (r = 0.71), IL-8 and IL-17A (r = 0.59).Conclusions:Significantly raised levels of inflammatory and proliferative factors and numerous positive correlations between them may demonstrate a significant role of activation of vascular proliferation and local inflammation in the pathogenesis of PDR.