MSC-Derived Exosomes Protect Vertebral Endplate Chondrocytes against Apoptosis and Calcification via the miR-31-5p/ATF6 Axis

Lin Xie,Zhenhao Chen,Ming Liu,Weibo Huang,Fei Zou,Xiaosheng Ma,Jie Tao,Jingkang Guo,Xinlei Xia,Feizhou Lyu,Hongli Wang,Chaojun Zheng,Jianyuan Jiang

doi:10.1016/j.omtn.2020.09.026

Abstract

Apoptosis and calcification of endplate chondrocytes (EPCs) can exacerbate intervertebral disc degeneration (IVDD). Mesenchymal stem cell-derived exosomes (MSC-exosomes) are reported to have the therapeutic potential in IVDD. However, the effects and related mechanisms of MSC-exosomes on EPCs are still unclear. We aimed to investigate the role of MSC-exosomes on EPCs with a tert-butyl hydroperoxide (TBHP)-induced oxidative stress cell model and IVDD rat model. First, our study revealed that TBHP could result in apoptosis and calcification of EPCs, and MSC-exosomes could inhibit the detrimental effects. We also found that these protective effects were inhibited after miroRNA (miR)-31-5p levels were downregulated in MSC-exosomes. The target relationship between miR-31-5p and ATF6 was tested. miR-31-5p negatively regulated ATF6-related endoplasmic reticulum (ER) stress and inhibited apoptosis and calcification in EPCs. Our in vivo experiments indicated that sub-endplate injection of MSC-exosomes can ameliorate IVDD; however, after miR-31-5p levels were downregulated in MSC-exosomes, these protective effects were inhibited. In conclusion, MSC-exosomes reduced apoptosis and calcification in EPCs, and the underlying mechanism may be related to miR-31-5p/ATF6/ER stress pathway regulation.

Highlights

Intervertebral disc (IVD) degeneration (IVDD) leads to a series of spinal degenerative disc diseases that resulted in a huge burden on the global healthcare system.[1,2] The IVD is composed of the out-surrounded annulus fibrosus (AF), inner nucleus pulposus (NP), and updown cartilaginous endplate (CEP)
We investigated the effects of mesenchymal stem cell (MSC)-exosomes on apoptosis and calcification in endplate chondrocytes (EPCs) under oxidative stress induced by tert-butyl hydroperoxide (TBHP) and assessed their effects via sub-endplate injection in a rat-tail intervertebral disc degeneration (IVDD) model
EPCs We used transmission electron microscopy (TEM), dynamic light scattering (DLS), and western blotting to evaluate the exosomes isolated from MSCs

Summary

Introduction

Intervertebral disc (IVD) degeneration (IVDD) leads to a series of spinal degenerative disc diseases that resulted in a huge burden on the global healthcare system.[1,2] The IVD is composed of the out-surrounded annulus fibrosus (AF), inner nucleus pulposus (NP), and updown cartilaginous endplate (CEP). Degeneration of the CEP can act as a significant barrier to nutrient transport in the endplate.[3] Excessive endplate chondrocyte (EPC) apoptosis and calcification are the two major processes of CEP degeneration.[4] In addition, previous studies showed that stem cells in the adjacent vertebral body could migrate to the NP physiologically through the nutrition channel to maintain the IVD environment balance.[5,6] In IVDD, CEP degeneration leads to blockage of the nutrition channel in the endplate, which results in degeneration of the NP and endogenous repair failure.[7,8] finding an effective method to alleviate CEP degeneration to prevent or reverse IVDD is necessary

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