Abstract
Purpose To determine and interrelate the levels of heparanase, syndecan-1 and vascular endothelial growth factor (VEGF) in proliferative diabetic retinopathy (PDR), and to study the production of heparanase by human retinal microvascular endothelial cells (HRMEC) and its effect on HRMEC barrier function. Methods Vitreous samples from 33 PDR and 27 nondiabetic patients, epiretinal membranes from 16 patients with PDR and HRMEC were studied by enzyme-linked immunosorbent assay, immunohistochemistry, and Western blot analysis. The effect of heparanase on HRMEC barrier function was evaluated by transendothelial electrical resistance. Results We showed a significant increase in the expression of heparanase, syndecan-1 and VEGF in vitreous samples from PDR patients compared to nondiabetic controls. (p < 0.0001 for all comparisons). Significant positive correlations were found between the levels of heparanase and the levels of syndecan-1 (r = 0.75, p < 0.0001) and VEGF (r = 0.91, p < 0.0001) and between the levels of syndecan-1 and the levels of VEGF (r = 0.78, p < 0.0001). In epiretinal membranes, heparanase was expressed in vascular endothelial cells and CD45-expressing leukocytes. High-glucose, TNF-[alpha] and the combination of TNF-a and IL-1b, but not cobalt chloride induced upregulation of heparanase in HRMEC. Heparanase reduced transendothelial electrical resistance of HRMEC. Conclusions Our findings suggest a link between heparanase, syndecan-1 and VEGF in the progression of PDR and that heparanase is a potential target for therapy of diabetic retinopathy.