Down-Regulation of circCOL1A2 Suppresses the Dysfunction of Diabetes-Related Retinal Microvascular Endothelial Cells via miR-646/FGF7 Axis.

Purpose: Diabetic retinopathy (DR), the major complication of diabetes, is the leading cause of vision loss and blindness globally. Altered circular RNAs (circRNAs) expression has been found to be involved in DR process. Hence, this work aimed to explore the role and mechanism of circCOL1A2 in DR.
Methods: Human retinal microvascular endothelial cells (RMECs) treated with high glucose (HG) were used for functional analysis. Levels of genes and proteins were detected using quantitative real-time polymerase chain reaction and western blotting. In vitro experiments were conducted by transwell, tube formation, CCK-8 assays and ELISA, respectively. The binding interaction between miR-646 and circCOL1A2 or FGF7 (Fibroblast Growth Factor 7) was confirmed using dual-luciferase reporter and RNA immunoprecipitation assays.
Results: CircCOL1A2 was highly expressed in retinal tissues of DR patients and HG-induced RMECs. Then RMECs were exposed to HG treatment to mimic the diabetic conditions in vitro. Functionally, circCOL1A2 knockdown attenuated HG-evoked RMEC migration, proliferation, angiogenesis, blood-retina barrier (BRB) injury and inflammation. Mechanistically, circCOL1A2 functioned as a sponge for miR-646, and miR-646 directly targeted FGF7. Further rescue experiments showed that miR-646 inhibition abated the protective effects of circCOL1A2 knockdown on RMEC function under HG treatment. Besides that, miR-646 was decreased in HG-induced RMECs, re-expression of miR-646 reversed HG-evoked RMEC dysfunction, which was rescued by FGF7 overexpression.
Conclusion: CircCOL1A2 silencing can suppress HG-induced migration, proliferation, angiogenesis, BRB injury and inflammation in RMECs through miR-646/FGF7 axis, suggesting the potential involvement of circCOL1A2 in DR process.