Synergistic promotion of bone regeneration through co-culture of endothelial cells with mesenchymal stem cells in endochondral ossification organoids.

BACKGROUND: Endochondral ossification (ECO) is essential for bone regeneration, involving cartilage formation, hypertrophy, angiogenesis, and ossification. Co-culturing mesenchymal stem cells (MSCs) with endothelial cells (ECs) shows potential to enhance bone regeneration but has not been effectively applied to ECO strategy. METHODS: We examined the synergistic effects of MSCs and ECs on chondrogenesis, osteogenesis, and angiogenesis, followed by transcriptomic analysis. ECO organoids were formed in the scaffolds, and a critical-sized calvarial bone defect model was used for in vivo evaluation. RESULTS: Co-culture of ECs and MSCs promoted osteogenic differentiation and hypertrophic chondrogenic differentiation of MSCs. The ECO organoids exhibited enhanced vascularization and improved mineralization. In vivo, the co-culture group showed superior vascularization and bone repair compared to the MSCs-only group. CONCLUSIONS: Co-culturing ECs with MSCs in ECO organoids enhances bone regeneration, offering a promising alternative to traditional tissue engineering strategies. This approach may improve therapeutic outcomes by promoting endochondral bone formation.