Inhibition of microRNA-30d attenuates the apoptosis and extracellular matrix degradation of degenerative human nucleus pulposus cells by up-regulating SOX9.

Accumulating evidence has suggested that microRNAs are critical regulators of intervertebral disc degeneration (IDD). The excessive apoptosis and extracellular matrix degradation of nucleus pulposus (NP) cells contribute to the initiation of IDD. However, the precise regulatory role of miRNAs in NP cell apoptosis and extracellular matrix degradation remains largely unknown. MicroRNA-30d (miR-30d) has been reported to be involved in regulating apoptosis and bone homeostasis. In this study, we aimed to investigate the role of miR-30d in regulating apoptosis and the extracellular matrix degradation of NP cells, along with the potential underlying molecular mechanism. Herein, our results showed that miR-30d was significantly increased in degenerative NP tissues compared with normal controls. Functional experiments showed that the inhibition of miR-30d promoted the viability and reduced the apoptosis of NP cells in vitro. Moreover, miR-30d inhibition increased the expression of type II collagen and aggrecan and inhibited the expression of matrix metalloproteinase. In contrast, the overexpression of miR-30d showed the opposite effects. Bioinformatics analysis, the dual-luciferase reporter assay, real-time quantitative PCR and western blot analysis showed that miR-30d directly targeted the 3'-untranslated region of SRY-related high mobility group box 9 (SOX9) and negatively regulated SOX9 expression. Correlation analysis showed that miR-30d expression was inversely correlated with SOX9 expression in degenerative NP tissues. Moreover, siRNA-mediated silencing of SOX9 expression significantly blocked the protective effects of miR-30d inhibition against NP cell apoptosis and extracellular matrix degradation. Overall, these results demonstrate that the inhibition of miR-30d attenuates the apoptosis and extracellular matrix degradation of degenerative human NP cells by up-regulating SOX9, suggesting a potential therapeutic target for IDD.