3D Bioprinting of Prevascularized Bone Organoids for Rapid In Situ Cranial Bone Reconstruction

Abstract Despite rapid advances in the field of bone tissue engineering, cranial bone defects of critical size remain difficult to repair due to the limited self‐regeneration capacity of the bone. Developmental engineering with mesenchymal stem cells (MSCs) aggregates has shown promise for enhanced bone regeneration; however, these MSCs aggregates require extended in vitro osteogenic induction time and lack sufficient vascularization to enable rapid in situ osteogenesis. To address these issues, a novel strategy is introduced for the large‐scale generation of prevascularized bone organoids with self‐organized vascularization and enhanced osteogenic properties by combining MSCs, human umbilical vein endothelial cells, and osteogenic microparticles. The osteogenic differentiation effects across different microparticles were systematically evaluated and identified graphene oxide as the most effective, which primarily promoted osteogenesis through the focal adhesion and PI3K/Akt pathway. Further, the prevascularized bone organoid‐laden hydrogels can be 3D printed into complex tissue constructs with high cell density and osteogenic capacity. In vivo experiments confirmed that this approach promoted rapid vascularized bone tissue formation, achieving effective in situ regeneration and repair of cranial bone defects. This innovative developmental engineering strategy provides a promising, scalable, and effective approach to bone regeneration, advancing developmental tissue engineering for therapeutic applications.