Efficacy of a Self-Assembling Peptide Hydrogel, SPG-178-Gel, for Bone Regeneration and Three-Dimensional Osteogenic Induction of Dental Pulp Stem Cells

The aim of this study was to assess the efficacy of a self-assembling peptide hydrogel as a scaffold for bone regeneration. We used a neutral and injectable self-assembling peptide hydrogel, SPG-178-Gel. Bone defects (5mm in diameter) in rat calvarial bones were filled with a mixture of alpha-modified Eagle's medium and peptide hydrogel. Three weeks after surgery, soft X-ray and microcomputed tomography (micro-CT) images of the gel-treated bones showed new bone formations in the periphery and in central areas of the defects. Next, we evaluated the three-dimensional osteogenic induction of dental pulp stem cells (DPSCs), a type of mesenchymal stem cell, in SPG-178-Gel. We first confirmed that the osteogenic differentiation of DPSCs was significantly promoted by osteogenic induction medium containing recombinant human bone morphogenetic protein-4 (rhBMP-4) in a two-dimensional cell culture. Then, we verified DPSC proliferation and osteogenic differentiation in a three-dimensional cell culture using SPG-178-Gel. The gene expression levels of osteopontin, osteocalcin, and collagen type I were significantly increased when DPSCs were cultured in SPG-178-Gel with the osteogenic induction medium. Micro-CT observations showed the formation of widespread calcium deposition. In conclusion, SPG-178-Gel was adequately effective as a scaffold and can be a suitable tool for bone formation in vivo and in vitro. These findings suggest that the self-assembling peptide hydrogel, SPG-178-Gel, could be a promising tool for bone tissue engineering.