miR-424-5p regulates apoptosis and cell proliferation via targeting Bcl2 in nucleus pulposus cells.

miRNAs play an important role in the pathogenesis of intervertebral disc degeneration (IDD). The role and the underlying mechanism of miR-424-5p in human nucleus pulposus (NP) are still unknown. We aimed to explore the role of miR-424-5p in IDD. Real-time PCR was used to detect the expression of miR-424-5p and Bcl2 in IDD tissues and idiopathic scoliosis tissues. Human NP cells were used in our study. MTT and Hoechst apoptosis assays were used to detect the proliferation and apoptosis of NP cells, respectively. Western blotting assays were used to detect the expression levels of Bcl-2, cleaved caspase-3, cleaved caspase-9, caspase-3 and caspase-9 in degenerative NP cells. A luciferase reporter assay was applied to confirm the relationship between miR-424-5p and Bcl2. Our results showed that the expression of miR-424-5p was increased and Bcl2 was decreased in degenerative NP cells. miR-425-5p expression was negatively correlated with Bcl2 expression in IDD tissues. Suppression of miR-424-5p using an inhibitor increased Bcl2 expression at both the mRNA and protein levels, and it promoted cell viability and inhibited apoptosis. Furthermore, the levels of cleaved caspase-3 and cleaved caspase-9 were downregulated in miR-424-5p-silenced NP cells. Interestingly, we found that silencing miR-424-5p increased p62 expression at both the mRNA and protein levels. Finally, a luciferase reporter assay verified the binding of the miR-424-5p and the 3'UTR of Bcl2. These results suggested that silencing miR-424-5p suppressed NP cell apoptosis by upregulating Bcl2. Therefore, miR-424-5p might be a novel target for IDD therapies.