Mesenchymal Stem/Stromal Cells-Derived Exosomal Micro-RNA Delivery Enhances Bone Repair in Osteoporotic Conditions.

Osteoporosis-associated bone fractures are a leading cause of disability in the elderly population. Developing effective therapeutic strategies to enhance bone repair under osteoporotic conditions remains a major clinical challenge. Increasing evidence indicates that aberrant lineage commitment of mesenchymal stem/stromal cells (MSCs) resident in bone marrow contributes to osteoporosis-related bone loss. However, incomplete understanding of the regulatory mechanisms governing MSC differentiation has limited the development of efficient therapeutic approaches. In this study, we identified micro-RNA-423 (miR-423) as a negative regulator of osteogenic differentiation, and demonstrated that inhibition of miR-423 significantly enhanced osteoblast differentiation of MSCs. To enable in vivo delivery of the miR-423 inhibitor for bone repair, MSC-derived exosomes (MSC-Exo) were used as a delivery vehicle, generating the Exo-miR-423 inhibitor construct. These exosomes were subsequently incorporated into an apatite-coated poly(lactic-co-glycolic acid) scaffold to form an Exo-miR-423 inhibitor/scaffold complex. Implantation of this complex significantly promoted bone healing in a calvarial defect model in ovariectomized mice. Collectively, these findings demonstrate a promising miRNA-modulated, exosome-based tissue engineering strategy for enhancing bone defect and fracture repair under osteoporotic conditions, and highlight its potential for further optimization and translational application.