Immunolocalization of the Factors Related to Wnt Signaling Pathway in Developing Rat Molar

Abstract

In the Wnt/β-catenin signaling pathway, Wnt signal is transmitted to glycogen synthase kinase-3β (GSK-3β) through Dishevelled (Dvl), GSK-3β activity is inhibited, β-catenin phosphorylation is inhibited by the inactive-type GSK-3β, and β-catenin is transferred to the nucleus where it interacts with lymphoid enhancing factor (LEF)/T-cell factor (TCF), a transcription factor, which is considered to induce and regulate gene expression. In tooth development, it has been reported that Wnt and LEF are expressed at the earliest stage and are related to tooth development, but there are few reports on the situation at a later stage, and there have been no reports on Dvl and GSK-3β. In this study, we immunohistochemically examined the distribution of factors related to the Wnt/β-catenin signaling pathway, Wnt10, Dvl, GSK-3β, p-GSK-3β (inactive GSK-3β), and β-catenin, using serial sections of rat first molar germ to investigate the role of the Wnt signaling pathway in tooth germ development and tooth morphogenesis. Immunostaining for anti-Wnt10, anti-Dvl, anti-GSK-3β, anti-p-GSK-3β, and anti-β-catenin showed positive reactions at the inner enamel epithelium of tooth germ and weakly positive reactions at the dental papilla cells in contact with the inner enamel epithelium at embryonic day 19. At 8 days after birth, immunostaining for every antibody showed positive reactions for preameloblasts and preodontoblasts and more clearly positive reactions for secretory ameloblasts and odontoblasts. These results suggest that Wnt10, Dvl, GSK-3β, p-GSK-3β, and β-catenin are distributed in inner enamel epithelium, secretory ameloblasts, and odontoblasts, and that the Wnt/β-catenin signaling pathway via Dvl and p-GSK-3β is involved in these cells. In addition, for each of the factors, differentiated secretory cells showed more clearly positive reactions than undifferentiated cells; therefore, we conclude that the Wnt10 signaling pathway may be involved in differentiation to ameloblasts and odontoblasts, as well as secretory functions of ameloblasts and odontoblasts.