Proteomic Analysis of Vitreous in the Presence of Diabetic Macular Edema

Abstract

Abstract: : Purpose: Even patients with posterior vitreous detachment show improvement in their diabetic macular edema (DME) after vitreous surgery. This may be attributable to the removal of chemical mediators present in the posterior vitreous cortex. Earlier studies of DEM-related proteins have focused on single proteins such as interleukin-6 (IL-6) and vascular endothelial growth factor (VEGE). We are pursuing a global approach to identifying DEM-related proteins using 2D electrophoresis and mass-spectrometry (MS). Methods: We divided 44 patients who had undergone vitreous surgery into 4 groups; those with a macular hole/epiretinal membrane (MH/ERM) (n=11, 11 eyes); patients with non-DME pre-proliferative diabetic retinopathy (PPDR) (n=4, 4 eyes); those with DME (n=14, 16 eyes); and patients with proliferative diabetic retinopathy (PDR) (n=15, 15 eyes). Vitreous (~300 ul) were collected from the pre-macular vitreous body, total protein determined by the blood-fold method, and ~15 ug samples subjected to 2D electrophoresis and stained with SYPRO-Ruby. Proteins unique to DME vitreous were determined by comparsion of gel patterns using image analysis software, excised from the gel, digested in situ with trypsin and identified by LC MS/MS sequence analysis. Results: Compared with the PPDR group, the DME group exhibited many 2D gel spots with significantly greater staining intensities. Furthermore, three of the prominently demarcated spots from the DME group were identified as pigment epithelium derived factor (PEDF), apoliprotein A-4 (ApoA-4), and thyroid hormone receptor-interacting protein-11 (Trip-11). Conclusions: These findings suggest that PEDF, Apo-4 and Trip-11 may play a role in the pathogenesis of DME. The cytokine PEDF is involved in several retinal diseases, and high levels of the ApoA-4 are found in sera from diabetics and patients with renal failure. Further study of the possible relationships between these endogenous factors and DME is warranted.

Keywords: diabetic retinopathy • vitreous • macula/fovea