Transforming growth factor-beta 1 incorporated during setting in calcium phosphate cement stimulates bone cell differentiation in vitro

Growth stimulation of periimplant tissues by growth factors like transformi ng growth factor-beta 1 (TGF-beta 1) may increase the indication for and su ccess of implant use. Calcium phosphate as a material for implants or for c oating of implants is known for its good biologic interaction with bone. Th erefore, calcium phosphate implants combined with TGF-beta 1 might improve osseointegration. In this study we hypothesise that the addition of recombi nant human TGF-beta 1 (rhTGF-beta 1) to calcium phosphate cement (CPC) affe cts the differentiation of bone cells growing on the cement laver. rhTGF-be ta 1 incorporated during settings in a CPC layer at 20 ng rhTGF-beta 1/60 m g cement was found to be gradually released into tissue culturing medium le ading to a 20% release after 24 h. Two cell populations were obtained from collagenase-treated fragments of adult rat long hones: preosteoblastic cell s, which were released by the collagenase treatment, and osteoblastic cells , which grew from the collagenase-stripped bone fragments. Both cell popula tions were tested for their osteoblastic characteristic phenotype by measur ing their alkaline phosphatase (ALP) activity after vitamin D treatment and cyclic AMP after parathyroid hormone stimulation. After preculture the cel ls were plated on a layer of CPC containing 0 (control), 10, or 20 ng rhTGF -beta 1/60 mg CPC. Bone cell differentiation was analyzed after 10 days by measuring the ALP activity, as well as the protein content of the cell laye r. Incorporation of rhTGF-beta 1 in the CPC did not change the ALP activity in osteoblastic cells, but a significant (analyzed by multivariate analysi s of variance) increase was observed in preosteoblastic cells. Incorporatio n of 10 ng of rhTGF-beta 1 in 60 mg of CPC increased the ALP activity in pr eosteoblastic cells by threefold and 20 ng rhTGF-beta 1/60 mg CPC increased it by fivefold. The total protein content was not affected by rhTGF-beta 1 in either of the cell populations. We conclude that rhTGF-beta 1 incorpora ted during setting in CPC stimulates the differentiation of pre-osteoblasti c cells in vitro. These results provide a basis for further studies on the use of this combination as an implant material in vitro. (C) 2000 John Wile y & Sons, Inc.