Histone Deacetylase Inhibitors Induce Odontoblast Differentiation Through the Activation of Wnt/β-catenin Signaling

Objectives: We have previously demonstrated that histone deacetylase inhibitors (HDACi) enhances odontoblast differentiation through the induction of Nfic transcriiption factor. It has been demonstrated that HDACi activate Wnt/β-catenin signaling in many differenent types of cells including bone marrow cells and breast cancer cells. However, it has not been clarified whether HDACi regulate Wnt/β-catenin signaling in dental pulp/odontblast cells. Therefore, in this study, we examined the role of Wnt/β-catenin signaling in HDACi-induced odontoblast differentiation.
Methods: Among the HDACi, SAHA and trichostatin A (TSA) were used in this study. Primary cultured human dental pulp cells and murine MDPC23 cells were used in this study. Odontoblast differentiation was examined by quantitative RT-PCR and western blot analysis of odontoblast marker genes (dentin sialophosphoprotein, dentin matrix protein 1, nestin, Nfic) and by alizarin red staining of mineralized matrix. Gene knockdown was performed by transfecting cells with small interfering RNA targeting specific gene. Transcriptional activity of β-catenin/Tcf/Lef complexes was determined by Top-flash reporter assays.
Results: SAHA and TSA significantly increased expression levels of Wnt3a and β-catenin but not those of Wnt5a, Wnt10a and Wnt11. In addition, both HDACi induced Top-flash reporter activity, suggesting that HDACi activate canonical Wnt/β-catenin signaling in dental pulp/odontoblast cells. Wnt3a treatment or overexpression of β-catenin enhanced odontogenic differentiation in both MDPC23 and human dental pulp cells. Knockdown of Wnt3a or β-catenin blocked HDACi-induced odontoblast differentiation. Activation of Wnt/β-catenin signaling increased expression levels of Nfic, while silencing of Wnt3a or β-catenin blocked HDACi-induced Nfic expression.
Conclusions: These results suggest that HDACi enhance odontoblast differentiation through the induction of Wnt3a expression and subsequent activation of Wnt/β-catenin signaling.