Ectopic Osteogenesis And Scaffold Biodegradation Of Hydroxyapatite-Collagen I Scaffold In A Rabbit Mode

Tissue engineering provides promising modalities for bone regeneration. Numerous investigations have confirmed the feasibility of reconstructing bone tissue via hydroxyapatite-collagen I scaffold and mesenchymal stromal cells. This study aimed to determine the osteogenic ability of hydroxyapatite-collagen I scaffold combined with osteo-induced mesenchymal stromal cells and to explore the relationships between bone formation and scaffold degradation. We extracted mesenchymal stromal cells from rabbit bone marrow (BMSCs). BMSCs at passage 4 were subjected to osteogenic differentiation for 2 weeks and were then implanted into hydroxyapatite-collagen I scaffolds. Osteo-induced BMSC composites (HA-Col I+ cells group) and the HA-Col I scaffolds (HA-Col I group) were then implanted into the dorsal subcutaneous tissue of New Zealand rabbits. At 2, 4, 8 and 12 weeks post-implantation, the implants were harvested and subjected to hematoxylin and eosin (HE) and TRAP staining. Osteogenic and osteoclastic gene expression levels were examined by qRT-PCR. Histological analysis revealed that de novo bone gradually increased from 2 weeks post-implantation in both groups and that the scaffold gradually degraded as bone formation proceeded. However, more de novo bone and less scaffold degradation occurred in the HA-Col I+ cells group than in the HA-Col I group at the same time points (P < 0.05). In conclusion, HA-Col I scaffolds combined with osteo-induced BMSCs are promising bone tissue engineering substitutes. Osteo-induced BMSCs significantly enhanced the osteogenic ability and inhibited overly rapid scaffold degradation in de novo bone formation.