Effects of local infusion of TGF beta on bone ingrowth in rabbit chambers

The local delivery of exogenous growth factors may help achieve a stable, l onglasting prosthetic interface around primary and revision joint replaceme nts. This study examines the effects of local infusion of transforming grow th factor beta (TGF beta) in an in vivo model of tissue differentiation wit hin bone. The Drug Test Chamber was implanted in the proximal medial tibial metaphysis of 8 mature rabbits unilaterally. The chamber contained a 1 x 1 x 5 mm canal for tissue ingrowth, The chamber was connected to an osmotic diffusion pump via polyvinyl tubing. 3.5 mu g of recombinant TGF beta 1 was infused for 1 day or 1 week with subsequent harvesting of the ingrown tiss ue after 3 weeks. Each TGF beta treatment was followed by two, 3-week infus ions of carrier alone and harvesting of the ingrown tissue. TGF beta for 1 day increased, and TGF beta for 1 week decreased the percentage of bone in the chamber, compared to the initial control harvest after carrier alone, T hese changes, however, did not reach statistical significance. The number o f vitronectin receptor positive cells in total, adjacent to bone and away f rom bone was higher after treatment with TGF beta for 1 day, compared to 1 week. In an "unperturbed" bone ingrowth system (i.e., if bone ingrowth is n ot initially suppressed by other stimuli), this dose of TGF beta did not en hance hone ingrowth using the DTC model. (C) 2000 John Wiley & Sons, Inc. J Biomed Mater Res (Appl Biomater) 53: 475-479, 2000.