Circular Ribonucleic Acid circFTO Promotes Angiogenesis and Impairs Blood–Retinal Barrier Via Targeting the miR-128-3p/Thioredoxin Interacting Protein Axis in Diabetic Retinopathy

Background: Increasing attention has been attracted by the role of circular RNAs (circRNAs) in ocular diseases. Previous study has revealed that circ_0005941 (also known as circFTO, an alpha-ketoglutarate–dependent dioxygenase) was upregulated in the vitreous humor of diabetic retinopathy (DR), while its underlying mechanism in DR remains unknown. Methods: Retinal vascular endothelial cells (RVECs) treated with high glucose (HG) were used to establish the DR cell model. The in vivo assays were conducted using streptozotocin-induced diabetic mice. The circular structure and stability of circFTO were identified by Sanger sequencing and RNase R treatment. RT-qPCR analysis was used to detect the RNA expression. The levels of the mRNA-encoded protein thioredoxin-interacting protein (TXNIP) or angiogenesis-associated proteins (VEGFA, PDGF, and ANG2) and blood–retinal barrier (BRB)-related proteins (ZO-1, Occludin, and Claudin-5) were measured by Western blot. The viability of RVECs was measured using CCK-8 assays. The angiogenesis of RVECs was assessed using tube formation assays in vitro. Endothelial permeability assays were conducted to examine the function of the BRB. The binding between genes was explored using RNA pulldown and luciferase reporter assays. Results: CircFTO was upregulated in HG-treated RVECs. CircFTO deficiency reversed the HG-induced increase in the viability and angiogenesis of RVECs and alleviated HG-mediated impairment of the BRB. MiR-128-3p bound with circFTO and was downregulated in HG-treated RVECs. TXNIP was a downstream target gene of miR-128-3p. TXNIP was highly expressed in the DR cell model. Rescue assays revealed that circFTO promoted angiogenesis and impaired the blood–retinal barrier by upregulating TXNIP. In the DR mouse model, circFTO silencing inhibited angiogenesis and promoted BRB recovery in vivo. Conclusion: CircFTO promotes angiogenesis and impairs the blood–retinal barrier in vitro and in vivo by binding with miR-128-3p to upregulate TXNIP in DR.