Deficiency of MIF Accentuates Overloaded Compression-Induced Nucleus Pulposus Cell Oxidative Damage via Depressing Mitophagy

Established studies proved that mechanical compression loading had multiple effects on the biological behavior of the intervertebral disc (IVD). However, the regulating mechanism involved in this process remains unclear. The current study is aimed at exploring the potential bioregulators and signaling pathways involved in the compression-associated biological changes of nucleus pulposus (NP) cells. Tandem mass tag- (TMT-) based quantitative proteomics was exerted to analyze the differentially expressed proteins (DEPs) and signal pathways among the different groups of NP cells cultured under noncompression, low-compression (LC), and high-compression (HC) loading. Eight potential protective bioregulators for the NP cell survival under different compression loading were predicted by the proteomics, among which macrophage migration inhibitory factor (MIF) and oxidative stress-related pathways were selected for further evaluation, due to its similar function in regulating the fate of the cartilage endplate- (CEP-) derived cells. We found that deficiency of MIF accentuates the accumulation of ROS, mitochondrial dysfunction, and senescence of NP cells under overloaded mechanical compression. The potential molecular mechanism involved in this process is related to the mitophagy regulating role of MIF. Our findings provide a better understanding of the regulatory role of mechanical compression on the cellular fate commitment and matrix metabolism of NP, and the potential strategies for treating disc degenerative diseases via using MIF-regulating agents.