Transforming growth factor- beta 1 adsorbed to tricalcium phosphate coated implants increases peri-implant bone remodeling

Increasing experimental interest has emerged for the use of growth factors to stimulate bone healing and bone formation in various clinical situations. We and others have demonstrated that recombinant human transforming growth factor- beta 1 (rhTGF- beta 1) adsorbed onto tricalcium phosphate (TCP)-coated implants can improve mechanical fixation and bone ongrowth. The present study evaluated bone remodeling in newly formed bone and adjacent trabecular bone around TCP-coated implants with and without rhTGF- beta 1 adsorption. Unloaded cylindrical grit-blasted titanium alloy implants coated with TCP were inserted bilaterally into the femoral condyles of 10 skeletally mature mongrel dogs. The implants were initially surrounded by a 2 mm gap. Implants with 0.3 mu g rhTGF- beta 1 were compared with implants without growth factor. The dogs were sacrificed after six weeks. Bone remodeling was evaluated by histomorphometry on Goldner-stained undecalcified sections. The bone volume in the gap was increased significantly from 17.6% in the control group to 25.6% in the rhTGF- beta 1 group (p = 0.03). Also bone surface was increased in the rhTGF- beta 1 group. The osteoclast covered surfaces were increased from 3.6% in the control group to 5.9% in the rhTGF- beta 1 group (p = 0.02). In the surrounding trabecular bone no significant changes in bone remodeling parameters was demonstrated. This study suggests that rhTGF- beta 1 adsorbed onto TCP-ceramic coated implants accelerates repair activity in the newly formed bone close to the implant, but it does not seem to influence bone remodeling in preexisting bone at a greater distance from the implant.