Background: Critical-sized bone defects represent a major clinical challenge due to their limited capacity for spontaneous healing. Autologous bone grafting, while effective, is associated with donor-site morbidity and limited tissue availability. Tissue engineering approaches using osteoblasts combined with biocompatible scaffolds offer promising alternatives. We evaluated the effectiveness of homologous osteoblast transplantation on commercially available hydroxyapatite/beta-tricalcium phosphate (HA/β-TCP) scaffolds in promoting the repair of critical-sized tibial defects in a rabbit model.
Methods: Critical-sized defects (3 mm²) were surgically created in the tibia of 12 male New Zealand white rabbits. Animals were randomly assigned to receive either osteoblast-loaded HA/β-TCP scaffolds or acellular scaffolds. Contra-lateral limbs served as untreated controls. Bone regeneration was assessed 6 weeks post-implantation via histology, alkaline phosphatase (ALP) staining, and quantitative analysis of bone thickness and cellularity.
Results: Osteoblast-seeded scaffolds significantly improved bone healing compared to controls and acellular scaffold groups, demonstrated by increased new bone formation, enhanced tissue thickness, and higher osteoblast counts (P<0.05). Histological analyses revealed abundant collagen matrix and mineralized bone within the scaffold pores in the osteoblast group. 
Conclusion: Homologous osteoblast transplantation utilizing HA/β-TCP scaffolds significantly promotes bone regeneration in critical-sized tibial defects in rabbits, demonstrating superior efficacy compared to acellular scaffold treatment. This strategy represents a promising approach for advancing clinical bone repair therapies.