Wnt11 expression in rat dental pulp and promotional effects of Wnt signaling on odontoblast differentiation

Congenital anomalies of wingless-type mouse mammary tumor virus (MMTV) integration site family (Wnt) are frequently accompanied with tooth and dentin abnormality. The aim of this study was to investigate the effects of Wnt signaling on odontoblast differentiation of mouse dental papilla cells (MDPs). Mouse dental papilla cells were cultured in alpha-modified minimum essential medium containing 10% fetal bovine serum and antibiotics. Odontoblast differentiation was induced by bone morphogenic protein 2 (BMP2), and the expression of odontoblast-specific markers and Wnt-related signaling molecules was analyzed by real-time reverse transcription-polymerase chain reaction and immunohistochemistry. Odontoblast differentiation was evaluated by dentin sialophosphoprotein (Dspp) and dentin matrix protein (DMP) 1 expression. Localization of beta-catenin in MDPs was detected by immunocytochemistry using an anti-beta-catenin antibody. Dspp expression in MDPs was upregulated in the presence of BMP2. Wnt5a, Wnt11, Lef1 and Tcf4 expression was upregulated in BMP2-treated MDPs. Wnt11 expression was detected in rat dental pulp in vivo, and particularly strong expression of Wnt11 was detected in odontoblasts. Enhanced Dspp and DMP1 expression and alkaline phosphatase activity induced by BMP2 were completely negated by the Wnt antagonist: IWR-1-endo treatment. Nuclear translocation of beta-catenin observed in BMP2-treated MDPs was also negated by IWR-1-endo treatment. These results indicate that Wnt signaling upregulates odontoblast marker expression in MDPs, suggesting a promoting effect of Wnt signaling on odontoblast differentiation.