On the calcification of cartilage and tooth germ in vitro.

(1)无牙釉质区：在啮齿动物的磨牙尖尖处，有一个没有牙釉质盖的牙本质区域，称为无牙釉质区（AFE）。为了阐明无釉质区形成的原因，我们对大鼠内釉质上皮基底膜和远端超微结构进行了观察。老鼠。在被牙釉质覆盖的牙本质上，胶原原纤维垂直于基底层排列。在EFA上，胶原原纤维平行于基板。这些发现表明，EFA和DCE之间胶原排列的差异与基底层非周期性微原纤维的发育状态有关。(2)关于梅克尔软骨软骨细胞的成骨细胞转化：梅克尔软骨是胎儿器官，出生后不久就有再吸收的最终命运。然而，我们发现当Meckel软骨维持在异位位点或细胞培养时，它表达骨型细胞元件和基质钙化。从这些体内和体外实验结果可以看出，细胞外基质、细胞增殖和血液等细胞微环境促进了梅克尔软骨细胞向成骨细胞的表型转化。(3)利用新的器官培养方法培养细胞牙骨质：我们报道了一种新的器官培养方法，通过这种方法可以获得近乎正常的根形成发育。通过这种培养方法可以维持三维器官发生和上皮-间质相互作用。在这项研究中，我们首次在体外的磨牙器官系统中发现了细胞骨质的形成。

(1) On the enamel-free area : At the cusp tip of rodent molar, there is a region of dentin without an enamelcap which is colled enamel-free area (AFE). To clarify the cause of enamel-free area, we observed the ultrastructure of the basement membrane and the distal ends of the inner enamel epithelium in rats. On rats. On the dentin covered with enamel (DCE), collagen fibrils were arranged perpendicular to the basal lamina. On EFA,collagen fibrils ran parallel to the basal lamina. These finding suggested that the differences in the collagen arrangement between the EFA and DCE are associated with the developmental state of aperiodic microfibrils in the basal lamina. (2) On the osteogenic cell transformation of Meckel's cartilage chondrocytes : The Meckel's cartilage is a fetal organ with a resorptive ultimate fate soon after birth. However, we showed that when Meckel's cartilage was maintained in heterotopic site or cell culture, it expressed bone-type cellular element and matrix calcification. From these results in vivo and in vitro, it is clear that the cellular microenvironment such as extracellular matrix, cellular multiplication and blood promote the phenotypic conversion of Meckel's cartilage cells into osteogenic cells.(3) On the development of the cellular cementum by the new organ culture method : We report a new organ culture method by which nearly normal development of root formation can be obtained. By this culture method the three-dimensional organogenesis and epithelial-mesenchymal interactions could be maintained.In this study, we showed for the first time the formation of cellular cementum in a molar organ system in vitro.