Exosomes from isobavachin-modified bone marrow mesenchymal stem cells promote osteoblast proliferation and alleviate osteoporosis by targeting the miR-127-3p/KIF3B/Wnt/β-catenin pathway

Background: Mesenchymal stem cell-derived exosomes (MSC-exosome), a promising cell-free strategy, show attractive applications in the treatment of osteoporosis. Pretreatment of MSCs before application can effectively improve the therapeutic efficacy of MSC-exosomes. Our study investigated the effects of exosomes from isobavachin (IBA)-pretreated human bone marrow-derived MSCs (hBMSC^IBA-exosomes) on osteoporosis progression and further unveil the underlying molecular mechanism.

Methods: hBMSCs were treated with IBA alone, transfected with miR-NC/miR-127-3p alone, or pre-treated with IBA and then transfected with NC inhibitor/miR-inhibitor, followed by the collection of exosomes. Human hFOB1.19 osteoblasts were co-cultured with hBMSC-exosomes, and osteoblast proliferation and differentiation were detected. The target gene of miR-127-3p was predicted using bioinformatic analysis and validated by dual-luciferase reporter assay. The KIF3B silencing vector (sh-KIF3B) and the Wnt/β-catenin pathway agonist LiCl were used to respectively validate the involvement of KIF3B and the Wnt/β-catenin pathway in the effects of exosomal miR-127-3p from IBA-treated hBMSCs on osteoblast proliferation and differentiation. Ovariectomy (OVX)-induced rat models of osteoporosis were injected with hBMSC^IBA-exosomes. Their anti-osteoporotic and pro-osteogenic effects in vivo were confirmed through micro-CT analysis, histological examination, and detection of osteogenesis markers.

Results: IBA enhanced the promotive effects of hBMSC-exosomes on osteoblast proliferation and differentiation. IBA pretreatment upregulated miR-127-3p expression in hBMSCs and derived exosomes. Overexpressing exosomal miR-127-3p facilitated while downregulating exosomal miR-127-3p suppressed osteoblast proliferation and differentiation Mechanistically, miR-127-3p targeted KIF3B to facilitate the Wnt/β-catenin pathway. KIF3B silencing or LiCl pretreatment reversed the effects of exosomal miR-127-3p knockdown on osteoblast proliferation and differentiation. Additionally, IBA enhanced the anti-osteoporotic and pro-osteogenic effects of hBMSC-exosomes in osteoporosis rat models. However, inhibition of exosomal miR-127-3p abrogated the beneficial effects of hBMSC^IBA-exosomes in osteoporotic rats.

Conclusion: Exosomes derived from IBA-pretreated hBMSCs markedly stimulate osteogenesis and ameliorate osteoporosis by delivering miR-127-3p, which inhibits KIF3B and activates the Wnt/β-catenin pathway. Our results reveal the potential of IBA in improving the efficacy of hBMSC-exosomes in the treatment of osteoporosis.

Bone marrow mesenchymal stem cells; Exosomes; Isobavachin; Osteogenesis; Osteoporosis; miR-127-3p.