Engineering preparation and sustained delivery of bone functional exosomes-laden biodegradable hydrogel for in situ bone regeneration

As an emerging cell-free therapy, exosomes derived from stem cells have been widely explored for tissue regeneration. However, it is still a great challenge to achieve the engineering extraction of bone-functionalized exosomes and their sustained delivery in tissue defects. Herein, a novel bone morphogenetic protein 2 (BMP2)-overexpressed engineered exosomes-loaded GelMA hydrogel was rationally constructed for in-situ bone regeneration. BMP2-overexpressed exosomes were engineering prepared using mouse embryonic fibroblasts (NIH-3T3) as tool cells via gene manipulations and ultracentrifugation techniques. The sustained delivery of exosomes in cranial defects was achieved by loading GelMA biodegradable hydrogel. In addition, the pre-prepared BMP2-overexpressed exosome-loaded GelMA hydrogel showed excellent porous structure, rheological property and biocompatibility. In vitro biological results indicated that BMP2-overexpressed exosomes significantly promoted proliferation and osteogenic differentiation of bone mesenchymal stem cells (BMSCs). In vivo animal experiments analysis revealed BMP2-overexpressed exsomes-laden biodegradable hydrogel effectively improved in situ bone regeneration via mice cranial defect model. Overall, this study provided a promising cell-free therapy of engineered exosomes-loaded biodegradable hydrogel for treating bone defects.