Bone marrow stem cells-derived exosomes extracted from osteoporosis patients inhibit osteogenesis via microRNA-21/SMAD7

L.-B. Jiang, L. Tian, C.-G. Zhang

Department of Orthopedics, Guangzhou University of Chinese Medicine, Guangzhou, China. Shuangyugang@163.com

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• Orthopedics

OBJECTIVE: To explore whether bone marrow stem cells (MSCs)-derived exosomes extracted from osteoporosis patients could inhibit osteogenesis via microRNA-21/SMAD7.

PATIENTS AND METHODS: MSCs from osteoporosis patients were isolated and cultured. MSCs morphology was observed, and the specific surface antigens were identified by flow cytometry. The osteogenic ability of MSCs was detected by alizarin red staining and oil red staining. Exosomes were collected from MSCs suspension by ultracentrifugation, and microRNA-21 expression in MSCs derived-exosomes was detected. Moreover, protein and mRNA levels of ALP, Bglap, and Runx2 in MSCs treated with different sources of MSCs-derived exosomes were detected by qRT-PCR (quantitative real-time polymerase chain reaction) and Western blot, respectively. ALP activity in MSCs was accessed by a relative commercial kit. Furthermore, binding sites of microRNA-21 and SMAD7 were predicted by Targetscan, miRWalk, and miRDB, and were further verified by luciferase reporter gene assay. SMAD7 expression in MSCs derived-exosomes was also detected.

RESULTS: MSCs extracted from healthy adults, and osteoporosis patients were in adherent growth and exhibited elongated morphology, which could differentiate into osteoblasts and lipoblasts after different inductions. MicroRNA-21 expression in MSCs-derived exosomes extracted from osteoporosis patients was remarkably higher than those extracted from healthy adults. Decreased Runx2 expression and ALP activity were found after treatment of MSCs-derived exosomes extracted from osteoporosis patients. SMAD7 was confirmed to bind to microRNA-21 and was downregulated in osteoporosis patients in comparison with healthy adults. Overexpression of SMAD7 resulted in downregulated ALP, Bglap, and Runx2.

CONCLUSIONS: MicroRNA-21 inhibits osteogenesis through regulating MSCs-derived exosomes extracted from osteoporosis patients via targeting SMAD7.

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