Role of microRNA-15a-5p/Sox9/NF-κB axis in inflammatory factors and apoptosis of murine nucleus pulposus cells in intervertebral disc degeneration.

ABSTRACT

OBJECTIVE: MicroRNAs are well-established players in post-transcriptional gene modulation. We aim to explore the role of microRNA-15a-5p (miR-15a-5p)/sex determining region Y-box 9 (Sox9)/nuclear factor-κB (NF-κB) axis in inflammation and apoptosis of murine nucleus pulposus cells (NPCs) in intervertebral disc degeneration (IVDD). METHODS: Expression levels of miR-15a-5p and Sox9 in disc tissues from IVDD patients were determined. The IVDD mouse models were established by disc puncture, and the modeled mice were accordingly injected with miR-15a-5p antagomir and/or overexpressed Sox9 plasmid, or their negative controls. Then, the expression of miR-15a-5p, Sox9 and p-p65, pathological changes and the apoptosis of NPCs in IVDD mouse intervertebral disc tissues were measured. The NPCs were isolated and cultured, which were then transfected with miR-15a-5p inhibitor, overexpressed or silenced Sox9 plasmids, or the NCs. Next, the expression of miR-15a-5p and Sox9, apoptosis, proliferation and cell cycle distribution of NPCs, and the contents of inflammatory factors in the NPCs were evaluated. RESULTS: MiR-15a-5p expression was increased while Sox9 expression was reduced in intervertebral disc tissues from IVDD patients and mice. Mouse NPCs were successfully isolated. The down-regulated miR-15a-5p could elevate Sox9 to activate p-p65 expression, suppress NPC apoptosis and inflammatory factor contents, promote proliferation of NPCs, and arrest the NPCs at S and G2/M phases. However, these effects could be reversed by silencing Sox9. CONCLUSION: Reduction of miR-15a-5p elevated Sox9 to inhibit the inflammatory response and apoptosis of NPCs in IVDD mice through the NF-κB pathway. This study may be helpful for IVDD treatment.