Effect of recombinant human transforming growth factor-beta2 dose on bone formation in rat femur titanium implant...

Previously, we reported that application of 10 microg recombinant human TGF-beta2 (rhTGF-beta2) enhanced peri-implant bone formation and bone-implant contact in a rat model. To further investigate the dose effect, the present experiment evaluated doses of rhTGF-beta2 bracketed around 10 microg (5, 10, 20 microg) using the same model. Four groups (including buffer-only control) received femoral implantation of hydroxyapatite/tricalcium phosphate-coated titanium implants. Four weeks post-surgery, all femurs were collected and analyzed by micro computed tomography followed by a mechanical test or histology. Compared with control, all rhTGF-beta2-treated groups had significantly higher bone volume. Bone-implant contact was not different between the control, 5, and 10 microg groups; however, the 20 microg group had less contact than the control. There were significant decreases in the strength of fixation in all rhTGF-beta2 treated groups compared with the control. In particular, while rhTGF-beta2 was able to enhance bone formation in the vicinity of the implant, the relative lack of bone-implant contact in the 20 microg group depressed the strength of fixation, suggesting that the location as well as the amount of new bone formed is important for implant fixation.