The effect of TGF-beta 2 on dentin apposition and hardness in transgenic mice.

Transforming growth factor beta, TGF-beta, is expressed during tooth formation and can induce pre-odontoblast differentiation and formation of functional odontoblast-like cells in vitro. In addition, exogenous TGF-beta can increase reparative dentin formation, presumably by acting on odontoblasts. In this study, we examined the tooth phenotype of transgenic mice, in which TGF-beta 2 expression is directed by the osteocalcin promoter. Previous studies have shown that these mice have a bone phenotype that resembles that of human osteoporosis, including the existence of spontaneous fractures. Microhardness testing of the enamel and dentin showed no differences in the molars of these transgenic mice as compared with those of their wild-type littermates. Consistent with the increase in bone mineral apposition rate previously reported in these mice, the dentin apposition rate appeared to be increased in the TGF-beta 2-overexpressing mice. Thus, in teeth, as in bone, TGF-beta 2 appears to stimulate the synthesis and deposition of matrix. Further studies are needed to understand the effect of TGF-beta 2 on distinct mineralized tissues (bone, dentin, and cementum) and to determine whether exogenous TGF-beta 2 may be useful for tooth repair.