The Odontogenic Potential Of Human Embryonic Tooth Germ

The occurrence and development of tooth is regulated by reciprocal epithelial-mesenchymal interactions. There are a large number of studies about dental development on mouse. However, little is known about the induction of each part of dental organizations in human. In this study, we will identify the potential of odontogenesis induction in each part of dental organizations in human. It is also a expectation that using the dental organization which has the potential of odontogenesis to achieve tooth regeneration.We began with the experiments by analyze the potential of odontogenesis in the tissue of human tooth germ at the cap stage and the bell stage. Human dental mesenchyme of the cap stage was divided and recombined with the epithelium from second branchial arch in mouse or human keratinocyte stem cells. There was no dental like tissue found in the recombination. It showed that the human cap stage dental mesenchyme loss the potential of odontogenetic differentiation recombined with the second branchial arch mesenchyme in mouse or human keratinocyte stem cells. Human dental epithelium of the cap stage was divided and recombined with the non-odontogenic mesenchyme.we found dental like tissue in the recombination after transplanted in the nude mouse kidney capsule for4weeks. At the same time, we detected the tooth differentiation marker genes in the recombination. The result showed that the recombination could express PITX2, PAX9in a specific location. It showed that non-odontogenic mesenchyme was induced to tooth by human cap stage dental epithelium. Human dental mesenchyme of the bell stage was divided and recombined with the epithelium from second branchial arch in mouse or human keratinocyte stem cells. We found dental like tissue in the recombination. At the same time, we detected the tooth differentiation marker genes in the recombination. The result showed that the recombination could express AMELOBLASTIN, AMELOGENIN, and MMP20in a specific location. It showed that the epithelium from second branchial arch in mouse or human keratinocyte stem cells were induced to form the ameloblasts by human bell stage dental mesenchyme.Human dental epithelium of the bell stage was divided and recombined with the non-odontogenic mesenchyme.There was no dental like tissue found in the recombination. It showed that the human bell stage dental epithelium loss the potential of odontogenetic differentiation recombined with non-odontogenic mesenchyme.Meanwhile,we also detected the potential of odontogenic in dental mesenchymal cells at the human bell stage tooth germ. The result showed that, The second branchial arch epithelium were induced to form the ameloblasts by human bell stage dental mesenchyme cells which were cultured in dish for5days long while the human bell stage dental mesenchyme cells could not induce human keratinocytes to form the ameloblasts which could secret enamel.In sum, in this study, we demonstrated that the potential of odontogenic in the early human tooth germ is transferred from tooth epithelium at the cap stage to the tooth mesenchymal at the bell stage.The bell-tage tooth germ which was dissolved into single cells was still remain the potential of odontogenic.The result has a very important significance in using the tissue of tooth germ to achieve tooth regeneration researches in the future.