| Caries, dental pulp illness and tooth heteroplasia often taken place in human. They can cause injuries of tooth and dental pulp, and even result in tooth becoming flexible or breaking off. The study of elucidating the mechanism of the restoration of dental pulp lesion and tooth development has become the highlight of oral medicine. Odontoblasts differentiation is the key point during restoration of odonto-pulpal lesion and the important stage in tooth development.Bone morphogenetic proteins(BMPs), members of TGF-βsuperfamily, are the factors which play important regulatory roles in cell growth, differentiation, apoptosis and morphologic development of tissue and organs in body. BMPs have been paid great attention to for regulatory roles in tooth development, odontoblasts differentiation and dental pulp repair by scholars all of the world in the field of endodontics. Results of recent studies have indicated that BMP2, as an induced signals mediating epithelial-mesenchymal interaction, could regulate tooth development and odontoblasts differentiation. The odontoblast plays an important regulatory role during tooth calcification and dental pulp repair, the studies on its mechanism of differentiation have been a highlight of endodontics.The dental papilla cells are an specific mesenchymal condensation from which odontoblasts differentiate during tooth development and contain information on the size and shape of the tooth. Thus, the cultured dental papillacells in vitro provide a useful model to study many aspects of odontoblast function. Investigating BMP2 signals pathway will help to provide evidences for the differentiating mechanism of odontoblast differentiation and dentinogensis and tooth calcification. But until now these mechanisms have not been fully elucidated.In 1996, Smadl was first identified and cloned by Hoodless, and thenSmad5,6 were also cloned. These achievements make great progress in the studyof BMP signals transudation pathway. Results of function study demonstratedSmadS could specifically transducer BMP signals into nucleus to regulate genestranscription as a downstream signal factor of BMP receptor. Whereas Smad6, aninhibiting factor in BMP signals transudation pathway, could interact withactivated type I receptors and compete with R-Smad(Smad5) for activation bythe receptors. Whether the expression of SmadS, 6 was present during humantooth development or in cultured human and what their roles in BMP2 signalstransudation pathway regulating tooth development and dental papilla cellsdifferentiations have not been reported.The present study was undertaken to demonstrate whether the expression of SmadS ,6 was present during human and mouse tooth development, also to observe whether Smad5,6 was expressed in cultured human dental papilla cells. In order to gain insights into the regulation of the BMP2 signaling pathway in cultured human dental papilla cells, we also investigated whether SmadS, 6 participated in BMP2 signal transudation pathway and whether the expression level of SmadS, 6 was regulate by BMP2 in these cells. Our study explored the molecular mechanism of the differentiation and calcification of dental papilla cells. The study can be divided into four parts as following:1. The expression of SmadS,6 protein during mouse and human tooth development?immunohistochemical study: the successive tissue sections ofmouse and human tooth germ were subjected to immunohistochemical staining with conventional method.Different location of SmadS expressed in each stage of mouse tooth germ Cap stage: strong positive expression of SmadS located in inner enamel epithelial cells, negtive expression in stellate reticulum cells, positive expression in dental sac cells and dental papilla cells.Early bell Stage: strong positive expression of SmadS located in inner enamel epithelial cells, positve expression in stratum intermedium cells, weak positive of Smadl in dental papilla cells.Late bell Stage: strong p...
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