CircCOL5A1 inhibits proliferation, migration, invasion, and extracellular matrix production of keloid fibroblasts by regulating the miR-877-5p/EGR1 axis

Background: Circular RNA (circRNA) has been proved to mediate the biological functions of fibroblasts to participate in the regulation of keloid formation. However, the role of circCOL5A1 in keloid formation remains to be further confirmed.Methods: Primary keloid fibroblasts were isolated form keloid tissues. The expression of circCOL5A1, microRNA (miR)- 877-5p, and early growth response 1 (EGR1) were determined by quantitative real-time PCR. Transfection experiments were carried out to explore the effects of circCOL5A1, miR-877-5p, and EGR1 on cell functions. Cell proliferation, migration, invasion and apoptosis were detected using cell counting kit 8 assay, colony formation assay, transwell assay and flow cytometry. The protein levels of apoptosis markers, extracellular matrix (ECM) markers and EGR1 were measured by western blot analysis. The mechanism of circCOL5A1 was confirmed by RNA pull-down assay, dual-luciferase reporter assay and RIP assay.Results: Our data showed that circCOL5A1 was upregulated in keloid tissues and fibroblasts. Silencing of circCOL5A1 had an inhibition effect on proliferation, migration, invasion and ECM production, while had a promotion effect on apoptosis in keloid fibroblasts. MiR877-5p could be sponged by circCOL5A1, and its overexpression could repress the biological functions of keloid fibroblasts. The rescue experiments showed that miR-877-5p inhibitor could reverse the suppressive effect of circCOL5A1 knockdown on the biological functions of keloid fibroblasts. In addition, EGR1 was a target of miR-877-5p, and its expression was positively regulated by circCOL5A1. The inhibition effect of miR-877-5p on the biological functions of keloid fibroblasts could be abolished by EGR1 overexpression.