Transforming growth factor-β1 incorporated during setting in calcium phosphate cement stimulates bone cell differentiation in vitro

Growth stimulation of periimplant tissues by growth factors like transforming growth factor‐β1 (TGF‐β1) may increase the indication for and success of implant use. Calcium phosphate as a material for implants or for coating of implants is known for its good biologic interaction with bone. Therefore, calcium phosphate implants combined with TGF‐β1 might improve osseointegration. In this study we hypothesise that the addition of recombinant human TGF‐β1 (rhTGF‐β1) to calcium phosphate cement (CPC) affects the differentiation of bone cells growing on the cement layer. rhTGF‐β1 incorporated during setting in a CPC layer at 20 ng rhTGF‐β1/60 mg cement was found to be gradually released into tissue culturing medium leading to a 20% release after 24 h. Two cell populations were obtained from collagenase‐treated fragments of adult rat long bones: preosteoblastic cells, which were released by the collagenase treatment, and osteoblastic cells, which grew from the collagenase‐stripped bone fragments. Both cell populations were tested for their osteoblastic characteristic phenotype by measuring their alkaline phosphatase (ALP) activity after vitamin D treatment and cyclic AMP after parathyroid hormone stimulation. After preculture the cells were plated on a layer of CPC containing 0 (control), 10, or 20 ng rhTGF‐β1/60 mg CPC. Bone cell differentiation was analyzed after 10 days by measuring the ALP activity, as well as the protein content of the cell layer. Incorporation of rhTGF‐β1 in the CPC did not change the ALP activity in osteoblastic cells, but a significant (analyzed by multivariate analysis of variance) increase was observed in preosteoblastic cells. Incorporation of 10 ng of rhTGF‐β1 in 60 mg of CPC increased the ALP activity in preosteoblastic cells by threefold and 20 ng rhTGF‐β1/60 mg CPC increased it by fivefold. The total protein content was not affected by rhTGF‐β1 in either of the cell populations. We conclude that rhTGF‐β1 incorporated during setting in CPC stimulates the differentiation of preosteoblastic cells in vitro. These results provide a basis for further studies on the use of this combination as an implant material in vivo. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 50, 67–74, 2000.