Osteogenic effect of bone marrow mesenchymal stem cell-derived exosomes on steroid-induced osteonecrosis of the femoral head

Abstract

Background

Animal studies have demonstrated the therapeutic effect of mesenchymal stem cells (MSCs) on osteogenesis, but little is known about the functions of exosomes (Exos) released by bone MSCs (BMSCs). Here, we investigated the effect of BMSC Exos on steroid-induced femoral head necrosis (SFHN) and explored the vital genes involved in this process.

Materials and methods

BMSCs were isolated from healthy and SFHN rats. BMSC Exos were isolated using the Exosome Precipitation Kit and characterized by transmission electron microscopy and Western blotting. SFHN BMSCs were incubated with Exos from healthy BMSCs. Osteogenic ability was assessed by oil red O staining and alizarine red staining. Differentially expressed genes (DEGs) induced by Exos were screened using the Osteogenesis RT2 Profiler PCR Array. The effect of upregulated Sox9 was examined using lentivirus-mediated siRNA.

Results

The results revealed that BMSC Exos were 100–150 nm in size and expressed CD63. Moreover, BMSC Exo-treated SFHN cells exhibited suppressed adipogenesis compared to model cells. PCR array showed that eleven and nine genes were upregulated and downregulated, respectively, in the BMSC Exo-treated SFHN cells compared to the model group. Among the DEGs, osteogenesis-related genes, including Bmp2, Bmp6, Bmpr1b, Mmp9, and Sox9, may play important roles in SFHN. Furthermore, the DEGs were mainly involved in immune response, osteoblast differentiation, and in the transforming growth factor-β/bone morphogenetic protein signaling pathway. The level of the SOX9 protein was upregulated by Exos, and Sox9 silencing significantly decreased the osteogenic effect of BMSC Exos.

Conclusion

Our data suggest that Exos derived from BMSCs mainly affect SFHN osteogenesis, and this finding can be further investigated to develop a novel therapeutic agent for SFHN.

Keywords:

• exosome
• bone marrow mesenchymal stem cells
• steroid-induced femoral head necrosis
• gene expression
• ostosis

Acknowledgments

Thanks for all participants involved in this study. This work was sponsored by grants from the Fund of Fujian Provincial Finance Department (BPB-LJH2015-2), sponsored by the Key Clinical Specialty Discipline Construction Program of Fujian, the Youth Backbone Talent Training Program of Fujian Provincial Health System (2017-ZQN-48), Popularize Appropriate Technical Projects for Rural and Urban Communities of Fujian Provincial Health and Family Planning System (2017017), 2018 “13th Five-Year plan” project of Fujian Provincial Department of Education (FJJ-KCG18-021), Startup Fund for Scientific Research, Fujian Medical University (2017XQ1075) and Fujian Provincial Department of Health Youth Fund Project (2016-2-17).

Author contributions

PC designed the experiments. All authors contributed to data analysis, drafting and revising the article, gave final approval of the version to be published, and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest in this work.

Supplementary materials

Table S1 Primers used for qRT-PCR in this study

Table S2 Expression of differently expressed genes in SFHN after treatment with BMSCs Exo