Bone Regeneration for Murine Femur Fracture by Gelatin Hydrogels Incorporating Basic Fibroblast Growth Factor with Different Release Profiles

Biodegradable hydrogels with three different water contents were prepared through the glutaraldehyde crosslinking of gelatin with an isoelectric point of 5.0 under varied reaction conditions. The objective of this study is to investigate the effect of time period of basic fibroblast growth factor (bFGF) release that is modified by the hydrogel water content, on the bone regeneration. A bone fracture was prepared at the femur bone of mice, while gelatin hydrogels incorporating bFGF or bFGF solution was applied at the fracture site. The gelatin hydrogels incorporating bFGF exhibited significantly stronger bone regeneration than the bFGF solution, although the extent depended on the water content of hydrogels. Bone regeneration induced by gelatin hydrogels incorporating bFGF increased with a decrease in their water content. Histological and biochemical examinations indicated that the area of bone tissue newly formed and the level of osteogenic genes were enhanced for the hydrogels incorporating bFGF of lower water content compared with those of higher one. It is possible that the hydrogels that slowly degraded released bFGF for a longer time period, resulting in an enhanced bone regeneration. It is concluded that the time profile of bFGF release is one of the factors contributing to the bFGF-induced bone regeneration.