To investigate the role of micro ribonucleic acid (miR)-181 in the inflammatory responses of osteoarthritis (OA) and related mechanism.
The rat model of OA was established by anterior cruciate ligament (ACL) transection, and an automatic immuno-analyzer was applied to detect the bone metabolism indexes in the serum. The levels of relevant inflammatory factors in the joint fluid and serum were measured using enzyme-linked immunosorbent assay (ELISA). The cartilage specimens were collected to determine the expression of miR-181 in OA and normal cartilage tissues. Meanwhile, isolated cartilage cells were cultured and transfected with miR-181 mimics and inhibitor separately, and a blank control group was also included. Quantitative Real-time polymerase chain reaction (qRT-PCR) was adopted to detect the messenger RNA (mRNA) expressions of inflammatory factors [tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6)] in the cartilage cells. The expression levels of NF-κB and matrix metalloproteinase-13 (MMP-13) proteins related to the NF-κB signaling pathway were determined via Western blotting.
In OA model group, the content of serum osteocalcin (OSTEOC) and vitamin D (VD) declined markedly (p<0.05), the content of parathyroid hormone (PTH) increased notably (p<0.05), whereas the change of β-Cross Laps was not significant. ELISA results showed that the levels of TNF-α, IL-6 and MMP-9 were elevated remarkably in OA model group (p<0.05). Compared with that in normal cartilage tissues, miR-181 expression was increased evidently in OA cartilage tissues (p<0.05). Moreover, miR-181 expression was also significantly elevated in miR-181 mimics group after transfection (p<0.05). The expressions of inflammatory factors TNF-α and IL-6 in the cartilage cells were increased remarkably in miR-181 mimics group compared with those in control group (p<0.05). The miR-181 inhibitor could significantly lower the expressions of inflammatory factors TNF-α and IL-6 (p<0.05). According to the results of Western blotting, the protein expressions of MMP-13 and NF-κB were decreased notably in miR-181 inhibitor group (p<0.05), but were evidently up-regulated in miR-181 mimics group (p<0.05).
The decrease of miR-181 can reduce the expressions of inflammatory factors TNF-α and IL-6 through downregulating the NF-κB signaling pathway, thus repressing the occurrence of OA.