Identification of new pathogenic candidates for diabetic macular edema using fluorescence-based difference gel electrophoresis analysis.

BACKGROUND: Diabetic macular edema is the main cause of visual impairment in diabetic patients. The aim of the present study was to explore the differential proteomic pattern of the vitreous fluid from diabetic macular edema patients by means of fluorescence-based difference gel electrophoresis (DIGE). METHODS: Samples of vitreous from eight type 2 diabetic patients [four with diabetic macular edema without proliferative diabetic retinopathy and four with proliferative diabetic retinopathy without diabetic macular edema), and eight from non-diabetic subjects with idiopathic macular hole (control group) were selected from our vitreous bank for proteomic analysis. To further confirm the potential candidates identified by DIGE, 18 additional samples (six proliferative diabetic retinopathy, six diabetic macular edema and six macular hole, matched by age) were analysed by enzyme-linked immuno sorbent assay (ELISA). RESULTS: Selecting an abundance ratio of 1.5-fold, p < 0.05, as the threshold for the study, four proteins were specifically associated with diabetic macular edema. Hemopexin was significantly higher in the vitreous fluid of patients with diabetic macular edema in comparison with both control subjects and proliferative diabetic retinopathy patients. By contrast, clusterin, transthyretin and crystallin S were significantly decreased in the vitreous of patients with diabetic macular edema. The differential production of hemopexin, clusterin and transthyretin was further confirmed by ELISA. CONCLUSIONS: Proteomic analysis by DIGE was useful in identifying new potential candidates involved in the pathogenesis of diabetic macular edema. These results could open up new strategies in the treatment of diabetic macular edema.

Lipopolysaccharide-binding protein and soluble CD14 in the vitreous fluid of patients with proliferative diabetic retinopathy.

PURPOSE: The purpose of this study was to compare intravitreous levels of lipopolysaccharide-binding protein and soluble CD14 (sCD14) between patients with proliferative diabetic retinopathy (PDR) and nondiabetic subjects. METHODS: This study included 19 consecutive Type 2 diabetic patients with PDR in whom a vitrectomy was performed. Sixteen vitreous humors from nondiabetic patients matched by age, with idiopathic macular holes, were selected from our vitreous bank and used as a control group. Lipopolysaccharide-binding protein was assessed by enzyme-linked immunosorbent assay and sCD14 by a solid-phase enzyme-amplified sensitive immunoassay. RESULTS: Lipopolysaccharide-binding protein and sCD14 levels were significantly higher in patients with PDR than in the control group (lipopolysaccharide-binding protein, P < 0.001; sCD14, P < 0.01). After correcting for vitreal proteins, the results remained significantly higher in patients with PDR. No differences in serum levels were observed, and we did not find any correlation between serum and vitreous levels. A direct correlation between lipopolysaccharide-binding protein and sCD14 was detected in the vitreous fluid (r = 0.57; P < 0.001) but not in the plasma. Finally, a significant correlation between intravitreal levels of both lipopolysaccharide-binding protein and sCD14 and interleukin-8 and monocyte chemotactic protein-1 was also detected. CONCLUSION: Lipopolysaccharide-binding protein and sCD14 are elevated in the vitreous fluid of patients with PDR and thus may play a role in the innate immune response triggered by the inflammatory injury characteristic of PDR.