Vitreous proteome analysis: An approach to the etiology of Diabetic Macular edema

Abstract

Abstract: : Purpose: Even in patients without vitreomacular traction, vitreous surgery can improve diabetic macular edema (DME). The effective mechanism(s) may be attributable to the removal of chemical mediators that prevail in the posterior vitreous cortex. To date, investigations have primarily focused on single DME–related proteins such as interleukin–6 (IL–6) and vascular endothelial growth factor (VEGE). We attempted to identify and analyze en mass the vitreous proteins of DME–related proteins using 2–dimensional electrophoresis and mass–spectrometry (MS). Methods: In the course of vitrectomy, samples (100 ul) were collected from the pre–macular posterior vitreous body of 4 eyes from 4 patients with non–DME pre–proliferative diabetic retinopathy (PPDR) (group 1) and 16 eyes from 14 DME patients (group 2). The total protein content in all samples was adjusted before two–dimensional electrophoresis. Spots visualized by silver staining were extracted for protein identification using the LC–MS/MS method and analysis software (PDQuestTM) was used to assess differences between the 2 groups. Results: A total of 212spots was detected in both groups. Of these, 64 spots from group 1 and 72 spots from group 2 were subjected to MS analysis. We found that 21 spots from group 1 and 22 spots from group 2 contained 13 and 14 proteins, respectively. Of these, 6 proteins in 10 spots from group 1 manifested intensity that was greater than 2–fold that of proteins found in group 2 and 2 protein in 2 spots from group 2 manifested intensity that was greater than 2–fold that of proteins found in group 1. Among the high–intensity proteins of group 1, we identified pigment epithelium–derived factor (PEDF) and apolipoprotein A–4 (ApoA–4) prostaglandin D2 synthetase. Conclusions: Our findings show that specific proteins not present in serum exist in the vitreous body of DME and PPDR patients. Moreover, the 2 groups differed with respect to protein types and their intensity, we posit that these chemical mediators presence in the posteriol vitreous fluid may play a role in the induction and/or pathogenesis of DME.

Keywords: proteomics • diabetic retinopathy • vitreous