Glucose-mediated regulation of transforming growth factor-beta (TGF-ß) and TGF-ß receptors in human retinal endothelial cells

Abstract

PURPOSE. Diabetic retinopathy is a micro-angiopathy affecting predominantly small vessels of the retina. Clinical trials have demonstrated a strong association between tight glucose control and a reduction in the incidence and the severity of diabetic retinopathy. Transforming growth factor beta (TGF-ß) is involved in the control of endothelial cell proliferation, adhesion, and deposition of extracellular matrix, thus TGF-ß may play a role in the control of endothelial cell proliferation seen in the disease. We wished to investigate the regulation of transforming growth factor beta and its receptors (type I and II) in human retinal endothelial cells exposed to a range of glucose concentrations. METHODS. Human retinal endothelial cells were isolated from donor eyes, cultured in vitro and exposed to a range of glucose concentrations (0–25 mmol/l). TGF-ß protein and mRNA levels were determined by ELISA and Northern analysis, respectively. The binding affinities and TGF-ß receptor numbers were defined using a binding assay. RESULTS. Northern hybridisation and ELISA showed that after 8 hours, the level of TGF-ß mRNA and protein was significantly higher at 15mmol/l compared to 5, 20 or 25mmol/ l. Binding assays showed that for high glucose (25 mmol/l), human retinal endothelial cells express a population of TGF-ß receptors with higher affinity for its ligand than at 5 or 15 mmol/l. CONCLUSIONS. These results demonstrate that glucose regulates TGF-ß mRNA and protein production and also TGF-ß receptor expression in human retinal endothelial cells. Thus, the glucose-mediated changes that occur in diabetic patients may expose human retinal endothelial cells to potential angiogenic factors which may influence disease progression.