INTS7-ABCD3 Interaction Stimulates the Proliferation and Osteoblastic Differentiation of Mouse Bone Marrow Mesenchymal Stem Cells by Suppressing Oxidative Stress.

Yubo Liu,Yijun Wang,Hui He,Yaozeng Xu,Renjie Xu,Suoyuan Li,Xiao Yu,Guangxiang Chen,Wei Geng,Bo Zheng,Anquan Huang,Xiangxin Zhang

doi:10.3389/fphys.2021.758607

Abstract

Increased adipocyte and decreased osteoblast differentiation, combined with the ectopic proliferation of bone marrow mesenchymal stem cells (BM-MSCs), represent the primary causes of osteoporosis. The dysregulation of numerous intracellular bioactive factors is responsible for the aberrant differentiation and growth of BM-MSCs. In this study, we focused on a new stimulative factor, integrator complex subunit 7 (INTS7), and its cooperative protein ATP-binding cassette subfamily D member 3 (ABCD3)/high-density lipoprotein-binding protein (HDLBP) in mouse BM-MSCs. We aimed to uncover the effects of the INTS7–ABCD3/HDLBP interaction on BM-MSC biological behaviors and the potential mechanism underlying these effects. Functional in vitro experiments showed that the suppression of the INTS7–ABCD3 interaction rather than HDLBP could impair BM-MSC proliferation and induce cell apoptosis. Moreover, Alizarin Red S and Oil Red O staining, respectively, revealed that INTS7 and ABCD3 knockdown but not HDLBP knockdown could decrease osteoblastic differentiation and accelerate the adipogenic differentiation of BM-MSCs. Mechanistically, reactive oxygen species (ROS) and histone γ-H2AX quantities significantly increased, whereas the levels of antioxidants declined due to INTS7 and ABCD3 inhibition in BM-MSCs. These findings indicated that the suppression of oxidative stress could be involved in the INTS7/ABCD3 co-regulatory mechanisms for BM-MSC proliferation and differentiation, identifying new potential candidates for osteoporosis therapy.

Highlights

Osteoporosis is a systemic and progressive bone disease generally associated with aging that has become one of the most common and expensive diseases worldwide (Johnell and Kanis, 2006; Burge et al, 2007)
CCK-8 assays showed that BMMSC viability was prominently impaired in the Inst7-MO group compared with the control MO (Ctr) group (Figure 1D)
To further understand whether cell proliferation or apoptosis regulation was involved in observed effects on bone marrow mesenchymal stem cells (BM-mesenchymal stem cells (MSCs)) growth following Integrator complex subunit 7 (INST7) depletion, an EdU-based flow cytometry analysis was performed, which revealed that the proportion of EdU-positive BM-MSCs in the integrator complex subunit 7 (INTS7)-depleted group was significantly reduced compared with the Ctr group (Figures 1G,H)

Summary

Introduction

Osteoporosis is a systemic and progressive bone disease generally associated with aging that has become one of the most common and expensive diseases worldwide (Johnell and Kanis, 2006; Burge et al, 2007). Evidence suggests that mesenchymal stem cells (MSCs) play vital roles in initial bone formation, the maintenance of bone ossification, and fracture repair (Bielby et al, 2007). Bone marrow MSCs (BM-MSCs) are MSCs that reside in the bone marrow and are capable of differentiating into osteoblasts and adipocytes. BM-MSCs more frequently differentiate into adipocytes than osteoblasts, leading to a reduction in bone formation and an increase in the accumulation of marrow fat (Moerman et al, 2004; Li et al, 2015). Due to self-renewal capabilities and multiple differentiation potential, BM-MSCs have become effective candidates for cell-based osteoporosis therapy (Wang et al, 2012; Jiang et al, 2021)

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