Effects of miR-129-5p on inflammation and nucleus pulposus cell apoptosis in rats with intervertebral disc degeneration through JNK signaling pathway.

This study aimed to explore the effects of miR-129-5p on inflammation and nucleus pulposus (NP) cell apoptosis in rats with intervertebral disc degeneration (IVDD) through the c-Jun N-terminal kinase (JNK) signaling pathway. A total of 20 rats were randomly divided into control group (n=10) or IVDD group (n=10). The mRNA expressions of miR-129-5p and apoptosis index Fas in IVDD tissues were determined using RT-PCR. NP cell apoptosis rate was detected via TUNEL assay. NP cells were extracted from IVDD tissues for primary culture. Subsequently, the cells were transfected with miR-129-5p inhibitor or mimic to inhibit or overexpress miR-129-5p, respectively. Furthermore, the changes in the JNK pathway indexes and apoptosis indexes were detected using Western blotting. In IVDD group, the expression of miR-129-5p was significantly down-regulated, while the transcriptional level of Fas was up-regulated compared with those in control group. Pearson correlation analysis revealed a negative correlation between the expressions of miR-129-5p and Fas mRNA (r=-0.75, P<0.05). IVDD group exhibited significantly higher levels of serum TNF-α, IL-6 and IL-1 than control group. Subsequent TUNEL assay indicated that the apoptosis rate was evidently higher in IVDD group (60.6%) than control group (2.5%). The results of Western blotting showed that the protein expressions of JNK1, JNK2 and Fas remarkably rose in IVDD group compared with those in control group. However, they declined remarkably in miR-129-5p mimic group compared with those in control group. Furthermore, such trends were significantly reversed in miR-129-5p inhibitor group. MiR-129-5p was significantly down-regulated in IVDD, whose overexpression has anti-inflammatory and anti-apoptotic effects.