Three-dimensional-printed hydroxyapatite/ zirconium dioxide composite scaffold incorporating bone morphogenetic protein-2 for lumbar vertebral bone defect repair in rhesus macaques

Bone defects caused by various factors have become a persistent challenge in orthopedic clinics, and traditional treatment methods mainly comprise artificial bone or autologous bone transplantation. However, these methods have considerable limitations, such as bone depletion, immune rejection, and the risk of secondary infection at the donor site. Therefore, considering these limitations and the rapid development of the field of bone tissue engineering, this study adopted light-curing stereolithography three-dimensional (3D)-printing technology to design bone scaffold materials. The technology was used to prepare hydroxyapatite (HA)/zirconium dioxide (ZrO2) porous composites with satisfactory mechanical properties as tissue engineering bone scaffold materials. A BMP-2 loaded gelatin/chitosan hydrogel sustained-release system was prepared via an emulsification and cross-linking process. Subsequently, rhesus macaque bone marrow mesenchymal stem cells (BMSCs) were seeded into the system acting as osteogenic progenitors. Novel HA/ZrO2 scaffolds were fabricated using stereolithography (SLA) 3D printing technology to serve as bone graft substitutes. The resulting scaffold exhibited a 3D interconnected porous structure and showed good biocompatibility and osteoinductive ability in a rhesus macaque lumbar vertebral bone defect model. The results confirmed that the scaffold achieved osteogenic efficiency comparable to that of autologous bone grafting in rhesus macaques. Therefore, the developed scaffold material has promising potential in bone defect repair.