RGD and rhBMP-7 immobilized on zirconia scaffold with interweaved human dental pulp stem cells for promoting bone regeneration

Biomimetic surface modification of scaffolds with osteoinductive molecules is a promising strategy for improving the bioactivity of scaffold and stimulating stem cell signals in bone tissue engineering. Zirconia (ZrO2) offers excellent mechanical properties and biocompatibility, but its bio-inert nature hinders its use in bone regeneration applications. Recombinant human bone morphogenetic protein 7 (rhBMP-7) and arginine-glycine-aspartate (RGD) peptide were investigated for their potential use as surface-modifying biomolecules on the ZrO2 scaffold. Our results showed that human dental pulp stem cells (hDPSCs) were induced to osteogenic differentiation by rhBMP-7 and RGD in a dose-dependent manner. Significantly enhanced alkaline phosphatase activity and up-regulated expression of osteogenic genes in hDPSCs were associated with rhBMP-7 and RGD grafting onto the ZrO2 scaffold. Western blot analysis revealed that rhBMP-7 and RGD grafting led to activation of the SMAD1/5, p38 MARK, and ERK signaling pathways during hDPSCs differentiation. After 4 and 8 weeks of transplantation, the hDPSCs-seeded ZrO2-RGD-BMP-7 scaffold facilitated osteogenic differentiation and enhanced in vivo bone formation in critical-sized calvarial bone defects. The results support the simultaneous use of rhBMP-7 and RGD as surface-modifying biomolecules and hDPSCs as a source of osteogenic stem cells in conjugation with ZrO2-based porous scaffold for bone tissue engineering.