Local application of rhTGF-β2 enhances peri-implant bone volume and bone-implant contact in a rat model

Orthopedic and dental implant fixation depends upon bone regeneration. Growth factors such as transforming growth factor-beta (TGF-β) have been shown to enhance bone repair and strengthen the mechanical connection between implant and host skeleton in canine models. To provide a platform for studying molecular mechanisms of growth factor stimulated bone regeneration and implant fixation, the present study examined peri-implant bone volume as a response to TGF-β treatment in a rodent model. The rat femoral ablation model in which an implant is placed in the medullary cavity of the femur was used to examine the dose response to TGF-β2 applied to the implant (0, 0.1, 1.0, or 10 μg). The study included a total of 40 rats (10 per dose) examined at 28 days. Peri-implant bone volume and bone-implant contact were assessed through microcomputed tomography and implant fixation strength was determined by a mechanical pullout test. Treatment of the implant with 10 μg TGF-β2 led to a 2-fold increase in bone volume (P < 0.001) and a 1.5-fold increase in bone-implant contact (P < 0.01) with a trend of increasing fixation strength (non-significant increase of 1.4-fold). TGF-β2 treatment with 10 μg led to uniform peri-implant bone volume and bone-implant contact along the length of the implant, whereas the other groups had less bone at the mid-point compared to the proximal and distal aspects of the implant. About 50% of the variance in implant fixation strength was explained by a regression model involving both bone-implant contact and peri-implant bone volume.