The bone regenerative effect of platelet-derived growth factor-BB delivered with a chitosan/tricalcium phosphate sponge carrier

Background: In order to achieve optimal effects, growth factors including p latelet-derived growth factor (PDGF) should be delivered with a biodegradab le carrier that will release therapeutic concentrations over a sufficient l ength of time. The purpose of this study was to evaluate the bone regenerat ive effect of PDGF-BB delivered with a chitosan/tricalcium phosphate (TCP) sponge carrier in a rat calvarial defect model. Methods: The PDGF-BB-loaded chitosan/TCP sponge carrier was fabricated by f reeze-drying a mixture of chitosan solution and TCP powder and soaking in a PDGF-BB solution. The release kinetics of PDGF-BB loaded onto the sponge w ere measured in vitro with I-125-labeled PDGF-BB. Chitosan/TCP sponges with and without PDGF-BB were implanted into 8 mm calvarial defects in rats. Ra ts were sacrificed at 2 and 4 weeks following implantation, and histologic and histomorphometrical examinations were performed. Results: In vitro evaluation demonstrated that an effective therapeutic con centration of PDGF-BB following a high initial burst release was maintained throughout the examination period. In the histologic examination, the chit osan/TCP sponge carrier promoted osseous healing of the rat calvarial defec ts as compared to controls. The addition of PDGF-BB to the carrier further enhanced bone regeneration. Evidence of the degraded sponge matrix was obse rved mingled within the newly formed bone without connective tissue encapsu lation. Conclusions: The results of this study support the use of chitosan/TCP spon ges as a delivery system for growth factors and demonstrate that PDGF-BB lo aded onto chitosan/TCP sponge carriers has an osteogenic effect on bone reg eneration in vivo.