Imai H, Osumi N, Eto K
Department of Developmental Biology, Tokyo Medical and Dental University, Japan.
Eur J Oral Sci. 1998 Jan;106 Suppl 1:19-23. doi: 10.1111/j.1600-0722.1998.tb02148.x.
Classical transplantation experiments with various amphibian tissues have shown that tooth development requires not only oral ectoderm and neural crest but also foregut endoderm. In addition, histological observation of oral membrane showed that the tooth germs are initiated in some ectodermal cells and neural crest cells adjacent to foregut endoderm. These studies suggest that tooth initiation requires the presence and cooperation of these three components. In mammals, however, there is no direct evidence that tooth formation is involved in the region of oral ectoderm adjacent to foregut endoderm. In order to elucidate the contribution of foregut endoderm to tooth formation, we established a new type of endodermal cell tracing system with a recombinant adenovirus called Adex-lacZ, and performed endodermal cell tracing in a long-term culture system. Cells labelled with Adex-lacZ were seen next to non-labelled thickening epithelium, presumptive incisor epithelium. These findings show the first direct evidence in mammals that tooth formation takes place in the specified part of oral ectoderm adjacent to foregut endoderm, suggesting that foregut endoderm plays a role in tooth initiation.
对各种两栖动物组织进行的经典移植实验表明，牙齿发育不仅需要口腔外胚层和神经嵴，还需要前肠内胚层。此外，对口腔膜的组织学观察表明，牙胚在一些与前肠内胚层相邻的外胚层细胞和神经嵴细胞中起始。这些研究表明，牙齿起始需要这三个成分的存在与协同作用。然而，在哺乳动物中，尚无直接证据表明牙齿形成涉及与前肠内胚层相邻的口腔外胚层区域。为了阐明前肠内胚层对牙齿形成的作用，我们利用一种名为Adex-lacZ的重组腺病毒建立了一种新型的内胚层细胞追踪系统，并在长期培养系统中进行内胚层细胞追踪。在未标记的增厚上皮（即假定的切牙上皮）旁边可以看到用Adex-lacZ标记的细胞。这些发现首次在哺乳动物中提供了直接证据，表明牙齿形成发生在与前肠内胚层相邻的口腔外胚层特定部位，这表明前肠内胚层在牙齿起始中发挥作用。
