Fast bone regeneration using injectable fully biomimetic organoids with biomineralized and organic microenvironments

Bone defects and congenital bone deficiencies are common clinical conditions. However, conventional non-degradable artificial materials often lead to serious complications, such as severe infections and material displacement. The emergence of tissue engineering and the organoid concept presents a promising approach for the repair of bone defects, facilitating physiological reconstruction while minimizing complications. Nevertheless, previous studies have not developed injectable organoids that incorporate fully mineralized and organic microenvironments to achieve rapid osteogenesis and convenient application in bone regeneration. Therefore, it is imperative to devise an effective strategy to address these challenges. This study first prepared injectable GL scaffolds with varying concentrations and identified the optimal GL concentration (0.8%) for osteogenesis through systematic evaluation of the osteogenic efficiency. Subsequently, 30% mixture of inorganic salts of native bone (NBIS) and extracellular matrix from the periosteum (pECM) was integrated into the optimal GL scaffold at a ratio of NBIS : pECM = 7 : 3 to create an injectable scaffold featuring biomimetic mineralized and organic microenvironments. This scaffold was further utilized for <i>in vitro</i> analysis of osteogenic mechanisms and injected subcutaneously into rabbits for only four weeks to assess its osteogenic efficacy <i>in vivo</i>. The results indicated that the incorporation of NBIS and pECM significantly enhanced the osteogenic efficacy by actively regulating ossification and ECM-receptor interaction signaling pathways, as well as upregulating RUNX2, ALP, COL1, and LAMA. This study introduces a promising injectable strategy for rapid osteogenesis using fully mineralized and organic biomimetic organoids.