Downregulation of circRNA DMNT3B contributes to diabetic retinal vascular dysfunction through targeting miR-20b-5p and BAMBI

Background: Diabetic retinopathy, a vascular complication of diabetes mellitus, is the leading cause of visual impairment and blindness. circRNAs act as competing endogenous RNA, sponging target miRNA and thus influencing mRNA expression in vascular diseases. We investigated whether and how circDNMT3B is involved in retinal vascular dysfunction under diabetic conditions. Methods: qRT-PCR was performed to detect expression of circDNMT3B, miR-20b-5p, and BAMBI in retinal microvascular endothelial cells under diabetic conditions. Western blot, Cell Counting Kit-8, Transwell, Matrigel tube formation, and retinal trypsin digestion assays were conducted to explore the roles of circDNMT3B/miR-20b-5p/BAMBI in retinal vascular dysfunction. Bioinformatics analysis and luciferase reporter, siRNA, and overexpression assays were used to reveal the mechanisms of the circDNMT3B/miR-20b-5p/BAMBI interaction. Electroretinograms were used to evaluate visual function. Findings: Upregulation of miR-20b-5p under diabetic conditions promoted proliferation, migration, and tube formation of human retinal microvascular endothelial cells (HRMECs), which was mediated by downregulated BAMBI. Under diabetic conditions, circDNMT3B, which acts as a sponge of miR-20b-5p, is downregulated. circDNMT3B overexpression reduced retinal acellular capillary number and alleviated visual damage in diabetic rats. Changes in expression of circDNMT3B and miR-20b-5p were confirmed in the proliferative fibrovascular membranes of patients with diabetic retinopathy. Interpretation: Downregulation of circDNMT3B contributes to vascular dysfunction in diabetic retinas through regulating miR-20b-5p and BAMBI, providing a potential treatment strategy for diabetic retinopathy.