Acellular fishbone scaffolds loaded with bone marrow mesenchymal stem cell-derived exosomes for bone defect repairing

Tissue engineering scaffolds remain pivotal in bone defect repair. Contemporary research in this field predominantly focuses on enhancing bone regeneration by optimizing scaffold composition and structure, and incorporating bioactive components. Herein, we developed a decellularized fish bone (DFB) scaffold integrated with hypoxia-osteogenic exosomes (HO-Exos), derived from rat bone marrow mesenchymal stem cells (BMSCs) cultured under 5% oxygen tension with 7-day osteogenic priming, to promote osseous repair via their synergistic effect. The hierarchical porosity of DFB scaffolds creates a biomimetic microenvironment conducive to BMSC adhesion and osteogenic mineralization. Functionally, HO-Exos stimulate osteogenic differentiation of BMSCs via modulation of the Wnt/β-catenin pathway, enhance cellular migration, and promote tubulogenesis in human umbilical vein endothelial cells (HUVECs). These vesicles synergistically potentiate vascularized bone regeneration in vivo through coordinated osteogenic-angiogenic regulation. To achieve sustained therapeutic delivery, HO-Exos were encapsulated within DFB scaffolds, leveraging their structural network for tailored release kinetics. In a rat model of critical-sized femoral metaphyseal defects, the designed scaffolds exhibited significant improvements in both neovascularization density and bone volume fraction compared to controls. These findings underscore the potential of exosome-functionalized biomimetic scaffolds for treating bone defects.