Restoring the dampened expression of the core clock molecule BMAL1 protects against compression-induced intervertebral disc degeneration

Dong Wang,Pengzhen Cheng,Junnian Zheng ,Judith A Hoyland,Xu He ,Huanbo Wang,Qiliang Shang,Michal Dudek,Xiaolong Xu,Pandi Peng,Bo Gao,Xueyu Hu,Zhuojing Luo,Cuifang Zheng ,Han Wang,Jianxin Mao,Huixian Jia ,Chu Gao,Qing‐Jun Meng ,Liu Yang

doi:10.1038/s41413-022-00187-z

Abstract

The circadian clock participates in maintaining homeostasis in peripheral tissues, including intervertebral discs (IVDs). Abnormal mechanical loading is a known risk factor for intervertebral disc degeneration (IDD). Based on the rhythmic daily loading pattern of rest and activity, we hypothesized that abnormal mechanical loading could dampen the IVD clock, contributing to IDD. Here, we investigated the effects of abnormal loading on the IVD clock and aimed to inhibit compression-induced IDD by targeting the core clock molecule brain and muscle Arnt-like protein-1 (BMAL1). In this study, we showed that BMAL1 KO mice exhibit radiographic features similar to those of human IDD and that BMAL1 expression was negatively correlated with IDD severity by systematic analysis based on 149 human IVD samples. The intrinsic circadian clock in the IVD was dampened by excessive loading, and BMAL1 overexpression by lentivirus attenuated compression-induced IDD. Inhibition of the RhoA/ROCK pathway by Y-27632 or melatonin attenuated the compression-induced decrease in BMAL1 expression. Finally, the two drugs partially restored BMAL1 expression and alleviated IDD in a diurnal compression model. Our results first show that excessive loading dampens the circadian clock of nucleus pulposus tissues via the RhoA/ROCK pathway, the inhibition of which potentially protects against compression-induced IDD by preserving BMAL1 expression. These findings underline the importance of the circadian clock for IVD homeostasis and provide a potentially effective therapeutic strategy for IDD.

Highlights

The circadian clock is an evolutionarily conserved internal timekeeping system that maintains body physiology and behavior in a constant 24 h diurnal cycle.[1]
We showed that human nucleus pulposus (NP) cells express and extracellular matrix (ECM) homeostasis, we placed NP cells in a compression culture brain and muscle Arnt-like protein-1 (BMAL1) and CLOCK proteins.[30]
We hypothesized that RhoA/ROCK signaling may participate in mediating the effect of compression stress on the intervertebral discs (IVDs) circadian clock

Summary

RESULTS

Grade IV and V samples were combined into a severe group) All These results indicate that excessive compression impairs BMAL1 eight patients had a moderate IDD segment and a severe expression and leads to dysfunction of NP cells. Western blot assays confirmed that BMAL1 overexpression restored NP cell metabolic homeostasis under age and sex on BMAL1 expression, we performed Multivariate compression stress (Fig. 3g, h). These results suggest that loss of linear regression analysis. Immunofluorescence staining further revealed IDD we transduced human primary NP cells with lentiviral Per-Luc and molecular mechanisms induced by Bmal[1] deletion Reduced monitored their bioluminescence for 4 days (Fig. 2a).

20 Grade IV

Control

Findings

MATERIALS AND METHODS