Purpose MicroRNAs (miRNAs) are endogenous, small noncoding RNAs that play important roles in various cellular functions. Recent studies have indicated that miR-126 is one of the important miRNAs associated with vascular growth during embryo development, but the role and molecular mechanism of miR-126 inregulating angiogenesis under pathological condition remain to be unknown. We investigated miR-126 alterations in diabetic retinopathy and endothelial cells by hypoxia, and its possible function in retinal angiogenesis.

Methods  Real time-PCR was used to examine miR-126 expression in the retinas of streptozotocin-induced diabetic rats and choroidoretinal vascular endothelial cells (RF/6Acells) induced by hypoxia. Localization of miR-126 and its functional analysis in the rat retina was also performed. Cell proliferation and apoptosis were examined by flow cytometry in RF/6Acells transfected with miR-126 mimics or inhibitors. VEGF and MMP-9 were detected by Western blot in RF/6Acells transfected with miR-126 mimics or inhibitors.

Results  Down-regulation of miR-126 was observed in retina in diabetes and in cells under hypoxia. Transfection of RF/6Acells of miR-126 mimics inhibited hypoxia-induced increased VEGF and MMP-9 mRNA and protein expression. It also prevented hypoxia-induced increased angiogenesis.

Conclusions These studies show that miR-126 can regulate VEGF and MMP-9 expression and may inhibit retinal angiogenesis induced by hypoxia.