A Study Of Effect Of Cbfa1 On Tooth Development

Core binding factor a1 is a specific kind of transcription factor, that can control the differentiation and formation of osteoblasts. It is a critical gene during the formation of bone, and is, therefore, very important for bone development. With the progress in the study of cbfal on the bone, the relationship of cbfal and tooth has already become a focus of interest for scientist because tooth is in fact the same mineralized tissue as bone. Some foreign researchers found recently that cbfa1 is not only expressed during the tooth development, and also in the whole bone development of the cbfal knock-out mice. That suggested that cbfal might play an important role during the development of teeth. However, many problems about this protein remain unsolved yet. We attempted to discuss the effect of cbfal on tooth development and mineraliztion by organ culture in vitro, antisense technology,- immunohistochemistry, etc.First of all, in order to understand the role of cbfal during tooth development, two experiments were carried out. Firstly, we set up a model of cultivation of mouse maxillary first molar germs in vitro. The germs from embryonic 17th days mice were cultured in DMEM culture solution with 10% serum. We founded the tooth germs able to develop into a more progressive stage, some mesenchymal cellsdifferentiated into odontoblasts and deposited predentine. Secondly, we designed and prefabricated AS-ODN. Some explants were cultured in the presence of 22bp antisense oligodeoxynucleotide targeted to cbfal mRNA.. On the termination date, the cultured explants were all examined by Western blot, HE and transmission electron microscope. Our results showed that after 9-days' culture, the cultivation treated with AS-ODN reduced the synthesis of cbfal and had a deformed dental cusp with thinner matrix.. Ultrastructure analyses showed that on average the matrix of AS-ODN treated group was thinner compared with that in the control group. Furthermore, the collagen fibers in extracellular matrix were found disorganized. The development of odontoblasts and ameloblasts was less mature than that in the control group. These findings seemed to provide an evidence which tended to indicate that the arrested cbfal translation in the cultured tooth germs might result in the delay of the tooth development.Thirdly, with the culture model, we observed the effect of cbfal on the development and mineralization of tooth germ. After treated with antisense cbfal, the cells downreguleted the amount of expression significantly, cbfal could regulate the expression of ALP and OC during the tooth development, as well as the bone development. These data might indicate that ALP and OC could also be the target genes of cbfal.At last, immunohistochemical techniques were applied to examine the cbfal specificities during the stage of the replacement of dogs' primary and permanent teeth. Expressions of cbfal were examined in the tissues around the deciduous tooth root of immature dog at the resorption stage. It was found that cbfal positive signals were in the periodontium of the deciduous teeth and alveolar bone.Their positive signals were also observed in the osteoclasts above the tooth germ, where there were some odontoclasts in the medial wall of the pulp cavity. It indicated that cbfal might get involved in the eruption of dog's permanent teeth during the stage of the replacement of the primary and permanent teeth.Above of all, it could be concluded that cbfal might participated in the progress of tooth development and mineralization. It could also induce the differentiation of odontoblasts and ameloblasts, and might get involved in tooth mineralization by regulating the amoune of the expression of ALP and OC. cbfal might also participate in remodeling of the alveolar bone in the eruption of teeth.