Inability of transforming growth factor-β1, combined with a bioabsorbable polymer paste, to promote healing of bone defects in the rat distal femur

Abstract

The ability of transforming growth factor-β1 (TGF-β1) to promote bone formation suggests that it may have potential as a therapeutic agent in bone defects. However, there still exists a need for an effective method of delivering TGF-β1 to the site of an osseous defect. In the present study, TGF-β1 was embedded in a bioabsorbable polymer paste (a blend of an l-lactide oligomer and a copolymer of ɛ-caprolactone and dl-lactide). The release of TGF-β1 from the polymer paste was examined in vitro with an enzyme-linked immunosorbent assay, which showed sustained release of active TGF-β1 over a 7-day period. Further, the polymer paste was used to fill a bone defect in the rat distal femur. The amount of TGF-β1 per rat was 50 μg, while in a control group we used an identical polymer paste without the growth factor. After a follow-up of 1 week and 3 weeks, the femurs were examined radiographically, histologically, histomorphometrically, microradiographically, and were also used for tetracycline-labeling studies. TGF-β1 did not enhance healing of the bone defect. A combination of growth factors would probably be a more potent osteoinductor than TGF-β1 alone.