Bone regeneration of tibial defects in rats with enzymatic hydrogelation of gelatin derivative and recombinant human platelet-derived growth factor-BB complex

Purpose: To evaluate the capabilities of gelatin derivatives that incorporate phenolic hydroxyl groups (gelatin- Ph) as a delivery carrier with recombinant human platelet-derived growth factor-BB (rhPDGF-BB) for bone regeneration. Materials and Methods: The growth factor release profile from gelatin-Ph gel or atelocollagen was analyzed to evaluate the capability of gelatin-Ph as a carrier. The biocompatibility of gelatin-Ph (ie, the survival rates of the cells during gelation, and the morphology and proliferation of the cells) were investigated with rat bone marrow cells (RBMCs) in vitro. To evaluate the effect of the gelatin-Ph-rhPDGF-BB complex on bone formation, the complex was applied to bone defects in rat tibiae and undecalcified specimens were fabricated for histologic analysis. Results: Scarce amounts of rhPDGF-BB from gelatin-Ph gel were detected during 30 days, but the addition of protease induced the release of rhPDGF-BB on day 31. No differences were observed in the survival rates of RBMCs during gelation and in the morphology and proliferation of RBMCs on the gel sheet between groups. Histological analyses demonstrated that the complex enhanced bone formation and mineralization at 2 and 4 weeks. Conclusion: These results suggest that gelatin-Ph gel can be an ideal delivery carrier, and the localized delivery of rhPDGF-BB in gelatin-Ph can contribute to bone formation.