C3a and C5a plasma concentrations in patients with diabetic retinopathy: a cross-sectional study

Diabetic retinopathy (DR) is the leading cause of irreversible blindness in adults, with inflammation playing a critical role in its pathogenesis, particularly involving the complement system (CS). Components of the complement cascade, such as C3a and C5a, have been identified in both vitreous and plasma samples from individuals with DR. This study aimed to evaluate plasma concentrations of C3a and C5a in relation to DR onset and severity. A total of 150 patients with diabetes mellitus (DM) underwent ophthalmic examination and were categorized into groups: without DR (control group), mild/moderate/severe non-proliferative DR (NPDR) and proliferative DR (PDR). Plasma C3a and C5a levels were measured using sandwich enzyme-linked immunosorbent assays (ELISA). Significant elevations in C3a levels were found in severe NPDR (p = 0.02) and PDR (p < 0.05) groups compared to controls. Furthermore, severe/proliferative DR exhibited higher C3a levels than mild/moderate NPDR (p = 0.015). No significant differences in C5a concentrations were observed among the groups. These findings suggest the involvement of complement in the pathogenesis of DR, and the association of C3a with DR severity highlights its potential as a prognostic biomarker and therapeutic target.