Expression Of Beta-catenin And APC And Correlation Between Them In The Development Of Mouse Tooth Germ

Background: Tooth morphogenesis is a process that is regulated by sequential and reciprocal interactions between the epithelial and mesenchymal tissues,during which the simple oral ectoderm thickens, buds, grows and folds to form the complex shape of the tooth crown. During tooth initiation the ectoderm thickens and forms a placode that buds to the underlying neural-crest-derived mesenchyme. The epithelium signals to the mesenchyme, which then condenses around the epithelial bud. During subsequent morphogenesis the epithelium folds and grows to surround the dental papilla mesenchyme (cap stage).It is known that there are a serious of signals including WNT which plays an essential roal during tooth development with the research level from cell to melocular. In recent years, more and more reaearchers have confirmed the function of WNT and much correlatation factor's expression within the tooth germ. Beta-catenin and APC(adenomatous polyposis coli),two key factors in the WNT signal pathway have been frequently found in the tumorigenesis. But there are few study of them about tooth germ in domestic.Objective: In this research, through examining the gene distributions of and APC in the tooth germ. The message of function of the WNT signal pathway in the tooth development is obtained, and the functional relationship between beta-catenin and APC is also discussed.Method: Embryos are obtained by mating km male and female mouse.The age is determined by the day of apperance of the vaginal plug. Moalr tooth germ are dissected from day 13.5 to17.5. The distributions of beta-catenin and APC are examined in the paraffin-embedded sections by immunohistochemistry methods. Yellow staining in the cell are masculine.Result:1. beta-catenin: During the bud stages, weakly positive is found in the oral epithelium and the dental lamina, masculine expression are found in the top of the tooth bud .The staining were whole cell; During the cap stages, except the strong masculine staining in the middle of the inner dental epithelium (primary enamel knot),there are all weakly positive in other location. In the dental papilla,only adjacent cell have weakly positon. The staining were whole cell. In the bell stage, the outer enamal epithelium expresses the beta-catenin gene in the normal level, the inner dental epithelium is strong expression, and the stratum intermedium is weakly expression. No stainging in the dental papilla except for the cell that differented into odontoblast. The staining in the enmel organ were not found in cell nucleus.2. APC: During the bud stages, strong positive is found in the oral epithelium and the dental lamina, and weakly expression is found in the cytomembrane of mesenchymal cell nearby; During the cap stages, there is strong masculine staining in the inner dental epithelium and masculine in the oral epithelium and the stratum intermedium. In the outer enamal epithelium and the cytomembrane of mesenchymal cell in the dental follicle, there is weakly staining. In the bell stage, the inner enamal epithelium expressed the APC gene in the normal level, the expression in the dental follicle were weakly. There is no stainging in the dental papilla in all the stages.3. There is statistics sig correlation between beta-catenin and APC.Conclusion:1. Beta-catenin expression in the whole stages of tooth germ is in an up-regulation tendency.(P<0.01). In both the inner enamel epithelium and the enamel knot, the expression of beta-catenin is stronger than the other place. The staining in the mesenchymal cell is masculine .The result suggests its contribution in the early development of enamel organ and the proliferation of cell.2. APC expresses in the whole stages of the tooth germ for the most part in the inner enamel epithelium, but the expression displays an down-regulation tendency(.P<0.01)The result suggests it participates in the formation of early enamel organ, and the masculine in the dental papilla. It is supposed that it gives nutrition and sustain to the formation.3. Coincidance of the two factors staining site is found, and according to the statistics, there is sig correlation between them(P<0.01), which confirmes a negative correlation between APC and beta-catenin, it suggest Wnt/ beta-catenin signal transduction pathway participate in the development of tooth germ espically in the early stage.