| Co-Investigator(Kenkyū-buntansha) |
IMAI Hjime Tokyo Medical and Dental Univercity, Developmental Biology, Research Asoosiate, 歯学研究科, 特別研究員(PD)
ISEKI Sachiko Tokyo Medical and Dental Univercity, Developmental Biology, Research Asoosiate, 歯学研究科, 助手 (80251544)
IIMURA Tadahiro Tokyo Medical and Dental Univercity, Developmental Biology, Research Asoosiate, 歯学研究科, 助手 (20282775)
IKEDA Masaaki Tokyo Medical and Dental Univercity, Developmental Biology, Asoosiate Professer, 歯学研究科, 助教授 (20193211)
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| Research Abstract |
1. Teeth are formed by reciprocal interactions between the epithelium and mesenchyme in the first pharyng. Although the contribution of midbrain and hindbrain crest cells to the first pharyngeal arch has been previouined in rodent embryos no direct evidence exists that these cells are actually involved in the dental mesenc order to elucidate the contribution of the cranial neural crest cells in the tooth formation, we first identified th tion sites and stages poviding the crest, cells that, migrate to the presumed tooth-forming region of the m.prominence. Focal labeling with DiI was performed at the midbrain and anterior hindbrain crests in rat embryo labeled embryos were cultured for 30 or 60 hr. The resultant migration pattern indicated that posterior midb cells emigrating by the end of the 4-somite stage predominantly migrated to the region where tooth buds develop. Second, we established a new type of long-term culture system in which the whole embryo culture is by a mandibular org
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an culture. Using this system, rat embryos were maintained from the early somite stag molars in the explants were able to reach the bud stage within 8 days. Finally, to ascertain if posterior midb cells emigrating by the end of the 4-somite stage were involved in the dental mesenchyme, these cells were lat DiI and processed the long-term culture. Labeled crest cells were found to be clearly detectable in t mesenchyme. These findings indicate that the early-emigrating posterior midbrain crest cells ontribute to m molar tooth development in rat embryos.
2. Classical transplantation experiments with various amphibian tissues have shown that tooth development re* only oral ectoderm and neural crest but also foregut endoderm. In addition, histological observation of oral n showed that the tooth germs are initiated in some ectodermal cells and neural, crest cells adjacent to foregut e These studies suggest that tooth initiation requires the presence and cooperation of these three components. mals, however, there is no direct evidence that tooth formation is involved in the region of oral ectoderm a* foregut endoderm. In order to elucidate the contribution of foregut endoderm to tooth formation, we establist type of endodermal cell tracing system with a recombinant adenovirus called Adex-lacZ, and performed en cell tracing in a long term culture system. Cells labelled with Adex-lacZ were seen next to non-labelled th epithelium, presumptive incisor epithelium. These findings show the first direct evidence in mammals that too taks place in the specified part of oral ectoderm adjacent to foregut endoderm, suggesting that foregut plays a role in tooth initiation. Less
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