Circ-POLR3A accelerates TGF-β2-induced promotion in cell viability, migration, and invasion of lens epithelial cells via miR-31/TXNIP signaling cascade.

Posterior capsular opacification (PCO) is the major complication after cataract surgery and can result in secondary vision loss. Circular RNAs (circRNAs) are reported to play critical regulatory roles in multiple cell biological processes. The most common working mechanism of circRNAs is by acting as microRNA sponges. Here, we analyzed the role and mechanism of circRNA RNA polymerase III subunit A (POLR3A) in PCO. Cell viability was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell motility was assessed by transwell and wound healing assays. Dual-luciferase reporter and RNA-pull-down assays were performed to verify the interaction between microRNA-31 (miR-31) and circ-POLR3A or thioredoxin interacting protein (TXNIP). PCO cell model was established by treating SRA01/04 cells with transforming growth factor-β2 (TGF-β2). We found that TGF-β2 enhanced SRA01/04 cell viability, migration, and invasion abilities. Circ-POLR3A expression was upregulated in PCO tissues and TGF-β2-induced SRA01/04 cells. TGF-β2 promoted the viability and motility of SRA01/04 cells largely by upregulating circ-POLR3A. Circ-POLR3A negatively regulated the miR-31 level by directly interacting with it. Circ-POLR3A absence-induced influences in TGF-β2-induced SRA01/04 cells were partly reversed by silencing miR-31. miR-31 is directly bound to the 3'-untranslated region of TXNIP. TXNIP overexpression largely attenuated miR-31 overexpression-mediated effects in TGF-β2-induced SRA01/04 cells. Circ-POLR3A could elevate the protein expression of TXNIP by sponging miR-31. Exosomes were involved in mediating the delivery of circ-POLR3A in SRA01/04 cells. In conclusion, circ-POLR3A contributed to TGF-β2-induced promotion of cell viability, migration, and invasion of SRA01/04 cells by targeting miR-31/TXNIP axis.