Exosome-Derived miR21/SMAD7 Derived from Donor Osteoporosis Mesenchymal Stem Cells Inhibits Osteogenic Differentiation of Reconstituted Hosts

Abstract

Exogenous bone marrow mesenchymal stem cells (MSCs) can regulate osteogenic differentiation. MicroRNA-21 has been shown to target SMAD7. This study explored the mechanism by which miR-21/SMAD7 inhibits osteogenic differentiation from exosomes secreted by osteoporosis patients-derived MSCs. Exosomes were obtained from MSCs and miR-21 expression was detected. Normal MSCs were treated with exosomes secreted by MSCs from different sources for osteogenic differentiation followed by detection of ALP, Bglap and Runx2 level and ALP activity. Normal MSCs were divided into three groups, which were treated with exosomes from normal adult MSCs, osteoporosis patients-derived MSCs and osteoporosis patients-derived MSCs + SMAD7 overexpression followed by analysis of the mRNA expression of ALP, Bglap and Runx2 by qRT-PCR and ALP activity. miR-21 expression in exosomes from osteoporosis patients-derived MSCs was significantly higher than that from normal adults MSCs. After treatment with exosomes from osteoporosis patients-derived MSCs, Runx2 expression and ALP activity was significantly decreased. SMAD7 expression in osteoporosis patients was significantly lower than that in normal adults. The expression of ALP, Bglap and Runx2 is significantly decreased after overexpression of SMAD7. SMAD7 is a target gene of miR-21 and plays a role in inhibiting osteogenic differentiation induced by exosomes from osteoporosis-derived MSCs.