Mechanisms of endothelial to mesenchymal transition in the retina in diabetes

Hyperglycemia-induced endothelial damage is a key pathogenetic factor in diabetic retinopathy. Endothelial damage may lead to phenotypic changes in the cells manifested by reduced expression of endothelial markers and increased expression of mesenchymal markers, termed endothelial to mesenchymal transition (EndMT). We investigated mechanisms of such changes in the retinal endothelial cells and in the retina of diabetic animals. Human retinal microvascular endothelial cells were grown in medium containing 5 mM glucose or 25 mM glucose with or without TGFβ1 peptide or TGFβ1 inhibitor or miR-200b mimic transfection. Messenger RNA levels of endothelial markers, mesenchymal markers, and specific signaling molecules of TGFβ pathway were quantified. Expression of miR-200b and histone acetylator p300 was quantified. Retinal tissues from mice with endothelial-specific overexpression of miR-200b, with or without streptozotocin-induced diabetes, were similarly examined. Glucose caused decreased expression of mRNA and protein levels of endothelial markers and increased expression of mesenchymal markers with reduced miR-200b. A glucose-like effect was seen using TGFβ1 peptide. Such changes were mediated by miR-200b and p300. In the retinas of wild-type diabetic mice, EndMT was observed, which was prevented in miR-200b transgenic mice with diabetes. These data indicate glucose-induced EndMT in vitro and in vivo is possibly mediated through TGFβ and regulated by miR-200b and p300.