Mechanism of microRNA-124-3p targeting calpain-1 to affect the function of intervertebral disc nucleus pulposus cells.

Intervertebral disc degeneration (IVDD) represents a major cause of lower back pain, whose prevalence rises with age. This study probed into the mechanism of microRNA (miR)-124-3p regulating function of nucleus pulposus cells (NPCs) by targeting calpain-1 (CAPN1). Rat IVD NPCs were cultured in vitro and transfected with miR-124-3p mimics, miR-124-3p inhibitor, oe-CAPN1 and their negative controls. The mRNA levels of miR-124-3p and CAPN1 were assessed by RT-qPCR. Cell proliferation, apoptosis and migration were evaluated by CCK-8, flow cytometry and Transwell assays. Levels of CAPN1 protein, apoptosis-related proteins (BAX, Cleaved-Caspase3, BCL-2) and extracellular matrix (ECM) proteins (Collagen II, Aggrecan, Fibronectin, Collagen I, matrix metalloproteinase [MMP]-13) were determined by Western blot. The target binding relationship between miR-124-3p and CAPN1 was verified by dual-luciferase assay. miR-124-3p overexpression facilitated NPC function and the maintenance of ECM homeostasis, as evidenced by increased NPC proliferation and migration, decreased apoptosis, elevated apoptosis-related protein BCL-2 level, diminished BAX and Cleaved-Caspase3 levels, reduced levels of ECM homeostasis-associated factors Collagen I and MMP-13 proteins, as well as raised levels of Collagen II, Aggrecan and Fibronectin proteins. Conversely, miR-124-3p knockdown brought about the opposite results. miR-124-3p targeted CAPN1. Furthermore, overexpression of CAPN1 partially reversed the regulatory effects of miR-124-3p on the ECM homeostasis, proliferation and migration in NPCs, and promoted apoptosis. miR-124-3p contributed to proliferation and migration of IVD NPCs, and reduced their apoptosis by inhibiting CAPN1 expression, thereby modulating ECM homeostasis and maintaining the function of IVD NPCs.