MiR ‐20b‐Overexpressed BMSC ‐Derived Exosomes Target SIRT1 / BMP2 to Regulate Mitochondrial Autophagy and Osteogenesis in Osteoporosis

Bone marrow mesenchymal stem cells (BMSCs) can differentiate into osteoblasts and promote osteogenesis (OP), and the miRNAs carried by BMSCs-derived exosomes (BMSC-Exo) regulate osteoblast differentiation in bone-related diseases. Additionally, abnormal mitochondrial autophagy in osteoblasts mediated by the SIRT1/PINK1/Parkin signaling axis affects differentiation and contributes to OP progression. Our preliminary study has demonstrated that miR-20b can target SIRT1 and osteogenic protein BMP2. The aim of the present study was to investigate the effect of BMSC-Exo harboring miR-20b to mediate the SIRT1/BMP2 in OP. Initially, through the successful isolation and characterization of BMSC-Exo in vitro, we co-cultured these exosomes with osteoblasts and observed a significant enhancement in osteoblast differentiation, alkaline phosphatase activity, and mineral accumulation. Subsequent cell transfection experiments revealed that miR-20b-overexpressed BMSC-Exo further augmented osteogenic differentiation of osteoblasts, whereas interference with BMP2 expression attenuated this pro-osteogenic effect. In a bilateral ovariectomised rat model of OP, we demonstrated that miR-20b-overexpressed BMSC-Exo treatment promoted bone formation and mitigated bone damage. Additionally, these exosomes restored mitochondrial membrane potential and autophagy, which were reversed by SIRT1 interference. Finally, osteoblasts isolated from OP model rats were used to further validate that miR-20b-overexpressed BMSC-Exo enhanced osteoblast differentiation and facilitated osteogenesis by activating SIRT1. These findings have collectively underscored the therapeutic potential of miR-20b-enriched BMSC-Exo in regard to OP treatment, providing a foundation for developing novel, targeted therapies for OP.