MicroRNA-199a-3p, microRNA-193b, and microRNA-320c are correlated to aging and regulate human cartilage metabolism.

MicroRNAs (miRNAs) are small RNAs of ∼22 base pairs that regulate gene expression. We harvested cartilage tissue from patients with polydactylism, anterior cruciate ligament injury, and osteoarthritis undergoing total knee arthroplasty and used microarrays to identify miRNAs whose expression is upregulated or downregulated with age. The results were assessed by real-time PCR and MTT assay in a mimic group, in which synthetic double-stranded RNA from the isolated miRNA was transfected to upregulate expression, and in an inhibitor group, in which the miRNA was bound specifically to downregulate expression. The expression of two miRNAs (miR-199a-3p and miR-193b) was upregulated with age and that of one miRNA (miR-320c) was downregulated with age. A real-time PCR assay showed that type 2 collagen, aggrecan, and SOX9 expression were downregulated in the miR-199a-3p mimic group but was upregulated in the inhibitor group. Similar results were observed for miR-193b. By contrast, ADAMTS5 expression was downregulated in the miR-320c mimic group and upregulated in the inhibitor group. Cell proliferative activity was upregulated significantly in the miR-193b inhibitor group compared with the control group. We believe that miR-199a-3p and miR-193b are involved in the senescence of chondrocytes, and miR-320c is involved in the juvenile properties of chondrocytes.