Osteopontin up-regulates Col IV expression through repressing miR-29a in human retinal vascular endothelial cells

Abnormal synthesis of extracellular matrix (ECM), especially collagen type IV (Col IV), in retinal vascular endothelial cells (RVECs) and resultant basement membrane (BM) thickening are the most prominent and characteristic feature of early diabetic retinopathy (DR). However, the molecular mechanism of abnormal Col IV expression in RVECs is unknown. In this study, small RNA sequencing was performed to identify differentially expressed miRNAs in retina of STZ-induced diabetic mice with DR. We identified 51 differentially expressed miRNAs (42 miRNAs up-regulated and 9 miRNAs down-regulated) in retina of STZ-induced diabetic mice with DR. Among these miRNAs, we identified miR-29a as a prominent miRNA that targeted and directly down-regulated Col IV expression through database prediction and dual-luciferase reporter assay, which was further confirmed in human RVECs using miR-29a mimic, miR-29a inhibitor and pre-miR-29a transfection. Furthermore, OPN up-regulated Col IV expression via a miR-29a-repressed pathway in human RVECs. Taken together, our results provided a miR-29a-repressing mechanism through which OPN played roles in abnormal synthesis of Col IV in human RVECs and resultant BM thickening and contributed to the pathogenesis of DR.