Concurrently bioprinted scaffolds with autologous bone and allogeneic BMSCs promote bone regeneration through native BMSC recruitment

Autologous bone marrow-derived mesenchymal stem cells (BMSCs) have been shown to promote osteogenesis; however, the effects of allogeneic BMSCs (allo-BMSCs) on bone regeneration remain unclear. Therefore, we explored the bone regeneration promotion effect of allo-BMSCs in 3D-printed autologous bone particle (ABP) scaffolds. First, we concurrently printed scaffolds with polycaprolactone, ABPs, and allo-BMSCs for appropriate support, providing bioactive factors and seed cells to promote osteogenesis. In vitro studies showed that ABP scaffolds promoted allo-BMSC osteogenic differentiation. In vivo studies revealed that the implantation of scaffolds loaded with ABPs and allo-BMSCs into canine skull defects for nine months promoted osteogenesis. Further experiments suggested that only a small portion of implanted allo-BMSCs survived and differentiated into vascular endothelial cells, chondrocytes, and osteocytes. The implanted allo-BMSCs released stromal cell-derived factor 1 through paracrine signaling to recruit native BMSCs into the defect, promoting bone regeneration. This study contributes to our understanding of allo-BMSCs, providing information relevant to their future application.