Abstract
Senescent mandibular bone repair poses a formidable challenge without a completely satisfactory strategy. Endogenous cell recruitment and osteogenic differentiation are two sequential stages in bone regeneration, and disruptions in these two processes present significant obstacles to senescent bone repair. To address these issues, engineered extracellular vesicles (EV) with sequential stem cell recruitment and osteogenic functions were developed. This study demonstrated that Apt19s-engineered extracellular vesicles (Apt19s-EV) recognize and recruit bone marrow mesenchymal stem cells derived from old rats (O-BMSCs) specifically and effectively. MiR-376b-5p, identified by RNA sequencing and transfection, was significantly decreased in O-BMSCs, and it was selected to construct miR-376b-5p-engineered extracellular vesicles (376b-EV). 376b-EV could promote osteogenesis and alleviate senescence of O-BMSCs by targeting Camsap1. To combine the advantages of Apt19s and miR-376b-5p, dual engineered extracellular vesicles (Apt-376b-EV) comprising both Apt19s and miR-376b-5p modifications were constructed. To further validate its function, Gelatin methacryloyl (GelMA) hydrogel was used as a carrier to construct the Apt-376b-EV@GelMA delivery system. The in vitro results have demonstrated that Apt-376b-EV@GelMA could recruit O-BMSCs, alleviate senescence and promote osteogenic differentiation sequentially. Notably, the in vivo study also showed that Apt-376b-EV@GelMA could sequentially recruit endogenous stem cells and enhance new bone formation in senescent bone fracture and critical-sized defect models. In summary, the dual engineered extracellular vesicles, Apt-376b-EV, offer an appealing solution for recruiting endogenous stem cells and promoting bone repair sequentially in the senescent microenvironment, which may broaden the clinical applications of engineered EV and provide valuable strategies for treating senescent bone-related diseases in the future clinical work.