Bone marrow mesenchymal stem cell-derived exosomes loaded with miR-26a through the novel immunomodulatory peptide DP7-C can promote osteogenesis

As small bioactive molecules, exosomes can deliver osteogenesis-related miRNAs to target cells and promote osteogenesis. This study aimed to investigate miR-26a as a therapeutic cargo to be loaded into bone marrow stromal cell exosomes through a novel immunomodulatory peptide (DP7-C).After transfecting BMSCs with DP7-C as a transfection agent, exosomes were extracted by ultracentrifugation from the culture supernatant of miR-26a-modified BMSCs. We then characterized and identified the engineered exosomes. The effect of the engineered exosomes on osteogenesis was then evaluated in vitro and in vivo, including transwell, wound healing, modified alizarin red staining, western blot, real-time quantitative PCR, and experimental periodontitis assays. Bioinformatics and data analyses were conducted to investigate the role of miR-26a in bone regeneration.The DP7-C/miR-26a complex successfully transfected miR-26a into BMSCs and stimulated them to release more than 300 times the amount of exosomes overexpressing miR-26a compared with the ExoNC group. Furthermore, exosomes loaded with miR-26a could enhance proliferation, migration, and osteogenic differentiation of BMSCs in vitro compared with the ExoNC and blank groups. In vivo, the ExomiR-26a group inhibited the destruction of periodontitis compared with the ExoNC and blank groups, as revealed by HE staining. Micro-CT indicated that treatment of ExomiR-26a increased the percent bone volume and the bone mineral density compared with those of the ExoNC (P < 0.05) and blank groups (P < 0.001). Target gene analysis indicated that the osteogenic effect of miR-26a is related to the mTOR pathway.miR-26a can be encapsulated into exosomes through DP7-C. Exosomes loaded with miR-26a can promote osteogenesis and inhibit bone loss in experimental periodontitis and serve as the foundation for a novel treatment strategy.