Exosomes derived from miR-375-overexpressing human adipose mesenchymal stem cells promote bone regeneration

The present study aimed to investigate whether exosomes derived from miR-375-overexpressing human adipose mesenchymal stem cells (hASCs) could enhance bone regeneration.

Exosomes enriched with miR-375 (Exo [miR-375]) were generated from hASCs stably overexpressing miR-375 after lentiviral transfection and identified with transmission electron microscopy, nanosight and western blotting. The construction efficiency of Exo (miR-375) was evaluated with qRT-PCR and incubated with human bone marrow mesenchymal stem cells (hBMSCs) to optimize the effective dosage. Then, the osteogenic capability of Exo (miR-375) was investigated with ALP and ARS assays. Furthermore, dual-luciferase reporter assay and western blotting were conducted to reveal the underlying mechanism of miR-375 in osteogenic regulation. Finally, Exo (miR-375) were embedded with hydrogel and applied to a rat model of calvarial defect, and μ-CT analysis and histological examination were conducted to evaluate the therapeutic effects of Exo (miR-375) in bone regeneration.

miR-375 could be enriched in exosomes by overexpressing in the parent cells. Administration of Exo (miR-375) at 50 μg/mL improved the osteogenic differentiation of hBMSCs. With miR-375 absorbed by hBMSCs, insulin-like growth factor binding protein 3 (IGFBP3) was inhibited by binding to its 3'UTR, and recombinant IGFBP3 protein reduced the osteogenic effects triggered by Exo (miR-375). After incorporated with hydrogel, Exo (miR-375) displayed a slow and controlled release, and further in vivo analysis demonstrated that Exo (miR-375) enhanced the bone regenerative capacity in a rat model of calvarial defect.

Taken together, our study demonstrated that exosomes derived from miR-375-overexpressing hASCs promoted bone regeneration.