Sequential construction of vascularized and mineralized bone organoids using engineered ECM-DNA-CPO-based bionic matrix for efficient bone regeneration

Given the limitations of allogeneic and artificial bone grafts, bone organoids have attracted extensive attention for their physiological properties that closely resemble natural bone, offering great potential to bone reconstruction for critical-sized bone defects. Although early-stage bone organoids such as osteo-callus organoids and woven bone organoids have been reported, functional bone organoids with vascularization and mineralization are currently unavailable due to the lack of bone-mimicking matrix and dynamic culture systems suitable for the long-term cultivation of mature bone organoids. Herein, a novel engineered bionic matrix hydrogels with multifunctional components and double network structure are developed by incorporating calcium phosphate oligomers (CPO) into a combination of bone-derived decellularized extracellular matrix (ECM) and salmon-derived deoxyribonucleic acid (DNA) via photo-crosslinking and dynamic self-assembly strategies. This kind of bionic matrix hydrogels facilitate recruitment, proliferation, osteogenesis and angiogenesis of bone marrow mesenchymal stromal cells (BMSCs). More importantly, vascularized and mineralized bone organoids are sequentially constructed using BMSCs-loaded engineered bionic matrix hydrogels via <i>in vitro</i> dynamic culture and <i>in vivo</i> heterotopic ossification. Meanwhile, this kind of engineered bionic matrix are capable of achieving efficient bone repair for cranial defect. These findings suggest that engineered bionic matrix hydrogels combined with such dynamic culture system, providing a promising strategy for functional bone organoids construction.