Development of an odontoblast in vitro model to study dentin mineralization

The aim of the present work was to characterize the odontoblastic proliferation, differentiation, and matrix mineralization in culture of the recently established M2H4 rat cell line. Proliferation was assessed by cell counts, differentiation by RT-PCR analysis, and mineralization by alizarin red staining, atomic absorption spectrometry, and FTIR microspectroscopy. The results showed that M2H4 cell behavior closely mimics in vivo odontoblast differentiation, with, in particular, temporally regulated expression of DMP-1 and DSPP. Moreover, the mineral phase formed by M2H4 cells was similar to that in dentin from rat incisors. Finally, because in mice, transforming growth factor (TGF)-beta1 over-expression in vivo leads to an hypomineralization similar to that observed in dentinogenesis imperfecta type II, effects of TGF-beta1 on mineralization in M2H4 cell culture were studied. Treatment with TGF-beta1 dramatically reduced mineralization, whereas positive control treatment with bone morphogenetic protein-4 enhanced it, suggesting that M2H4 cell line is a promising tool to explore the mineralization mechanisms in physiopathologic conditions.