Proliferative diabetic retinopathy (PDR) is a serious microangiopathic complication of diabetes mellitus and a major cause of blindness in working-age adults. Diabetes-induced alterations in the vitreous protein composition in diabetic patients with PDR may be responsible for the presence of PDR. Therefore, we performed a comprehensive proteomic analysis and compared the protein profiles of vitreous humor from type 2 diabetic patients with PDR (n = 8) and that from normal human eyes donated for corneal transplant (n = 8). Using reversed phase high-performance liquid chromatography (RP-HPLC) coupled to electrospray Ionization tandem mass spectrometry (ESI-MS/MS), we identified 96 significant differentially expressed proteins (abundance ratio > 1.5, p < 0.05), including 37 and 59 proteins up- and downregulated in PDR vitreous compared with the control, respectively. Biological pathway analysis revealed 44 proteins involved in 56 biological pathways; among them, the most remarkable pathways differentially represented between PDR and normal vitreous were the glycolysis/gluconeogenesis, complement and coagulation cascades, gap junction, and phagosome pathways. The differential expressions of angiopoietin-related protein 6, apolipoprotein A-I, estrogen receptor alpha, and tubulin were confirmed by western blot analysis. These data provide insight into the molecular events possibly involved in the pathogenesis of PDR and widen the scope of potential avenues for new therapies for PDR.
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