CircKMT2E Participates in Osteoarthritis through Promotes Apoptosis of Chondrocytes Via Sponging miR-140-5p to Activate TLR4

OBJECTIVE: To explore the latent pathogenesis of circRNAs in osteoarthritis (OA), as well as their function mechanism. METHODS: The murine chondrocytes with and without OA were involved and used for in-depth sequencing. Herein, we carried out subsequent bioinformatics analysis to disclose the expression pattern, characteristics of circRNAs based on gene ontology, and the KEGG pathway analyses. Then sequencing data were used to deduce the interaction between circRNA and miRNA. The potential miRNA response elements for the annotated circRNAs and relevant target genes were forecasted on the basis of TargetScan and miRanda. For chondrocytes, the effect of the overexpression of the screened circRNA for apoptosis was spotted by flow cytometry as well as Western Blot. RESULTS: 466 diverse circRNAs in the 23,787 spotted circRNAs were both significantly and differentially transcribed. CircKMT2E was upregulated more than two folds in chondrocytes with OA compared with normal tissues, exhibiting an expression trend opposite to miR-140-5p. We disclosed that circKMT2E could possess mutual effect with miR-140-5p by way of AGO proteins. Thus, circKMT2E was verified to have functioned as a molecular sponge targeting miR-140-5p. Therefore, circKMT2E may be at work in the pathogenesis of OA. Further, the sponge connection between circKMT2E and miR-140-5p was proved on the basis of a dual-luciferase reporter assay. Besides, miR-140-5p was speculated can bind TLR4 by bioinformatics analysis. Further PCR analysis found the relative expression level of TLR4, caspase-3, and Bax in the OA groups presented significant upregulation. Overexpression of circKMT2E can promote apoptosis of chondrocytes. CONCLUSION: The upregulation of circKMT2E is involved in the chondrocyte apoptosis of the pathogenesis of OA through activation of TLR4 by the sponge function of miR-140-5p.