Reconstruction Of Tooth Germ In Vitro And Relative Studies About Immuno-regulation Mechanism

Epithelial–mesenchymal interactions are necessary for cell differentiation, tissue regeneration and morphogenesis in various organs. Similar, sequential and reciprocal epithelial–mesenchymal interactions govern the tooth initiation, morphogenesis, primary dentinogenesis, and cell differentiation through several signaling pathways. At the beginning of odontogenesis, the epithelial and mesenchymal seems to supply the initial inductive signals, which are followed by the formation of tooth germ through cell proliferation, migration, polarization, and differentiation of the epithelium and mesenchyme contribute to the tooth morphogenesis. Studies on the development of tooth have provided evidences that tooth germ cells (epithelial–mesenchymal) have maintain the signal of tooth development and can recombinant and result in tooth-like morphogenesis. However, most studies on the reconstruction of tooth have focused on the processes helping the formation of soft and hard tissue, without detailed observations of the biological characteristics of tooth itself. Moreover, characterization of the molecular and cellular events during development of tooth is critical to our understanding of the reconstruction of tissue engineered tooth. However, the molecular basis of tooth germ differentiation and mature is difficult to be elucidated with traditional methods. Together, the understanding the molecular basis and regulation of tissue engineered tooth germ differentiation into mature tooth is important. In this study, we provide a different model for approaching the study of the molecular requirements to construction of tissue engineered tooth.We compare growth and development of tissue engineered tooth germ with implanting into renal subcapsule, the mesenteries and subcutaneous tissues to explore a suitable growing environment for the tissue engineered teeth in vivo. the enamel and pulp-dentin complex were observed within the graft implanted in the subrenal capsule, further growth were not observed in the other tooth germ.Moreover, partial grafts were fall off and lose after implanted in the subcutaneous tissues and there were obvious lymphocyte infiltrations in the mesenteries. On the basis, we design the injectable tissue engineering tooth constructed with tooth germ cells and dermal matrix. The feasibility of the odontogenic potential was evaluated during implanted into renal capsule. The development of distinctive pulp-dentin complex and enamel like structures were observed 14 days after injection. For further clinical application, we investigate the immune response of porcine transplanted with allogeneic tissue-engineered tooth germ and the influence of IL-2 and CD4/8 with inductive immunosuppressive drugs FK506. There were obvious lymphocyte infiltrations in the graft after implantation of mesenteries. The levels of CD4+T cells and IL-2 were significantly decreased and the further growth of allogeneic tissue engineered tooth germ in vivo was obvious after administration of FK506. These studies proved a promising environment for the further growth of allogeneic tooth reconstruction and can be used as a new alternative for reconstruction method in vitro. Moreover, these studies provided a promising experimental foundation for the clinical application of tooth reconstruction with tooth germ cells in future.Above all, there are a serial of studies at first time focused on the reconstruction of tooth germ and regulation mechanism. Moreover, the immune response transplanted with allogeneic tooth germ and the influences of inductive immunosuppressive drugs also were investigated in these studies. These researches have provided a new pathway for application of reconstruction of tooth with tooth germ cell in vivo.