Rapid and efficient animal models are needed for evaluating the effectiveness of many new candidate bone regenerative materials. We developed an in vivo model screening for calvarial bone regeneration in lipopolysaccharide (LPS)-treated mice, in which materials were overlaid on the periosteum of the calvaria in a 20 min surgery and results were detectable in 1 week. Intraperitoneal LPS injection reduced spontaneous bone formation, and local application of basic fibroblast growth factor (bFGF) increased the bone-forming activities of osteoblasts. A novel synthetic collagen gel, alkali-treated collagen (AlCol) cross-linked with trisuccinimidyl citrate (TSC), acted as a reservoir for basic substances such as bFGF. The AlCol-TSC gel in conjunction with bFGF activated osteoblast activity without the delay in osteoid maturation caused by bFGF administration alone. The AlCol-TSC gel may slow the release of bFGF to improve the imbalance between osteoid formation and bone mineralization. These findings suggest that our model is suitable for screening bone regenerative materials and that the AlCOl-TSC gel functions as a candidate reservoir for the slow release of bFGF.
