Molecullar Biology on the Calcification of Cartilages and Tooth Germs in Vito.

1)Meckel's软骨细胞在体外合成骨型标志蛋白如骨钙素、骨桥蛋白和I型胶原的过程中可表达成骨细胞表型。Meckel软骨的中部可分为前、后两个区域，我们的结果提示Meckel软骨中部的细胞有两种不同的命运。前部被TRAP阳性细胞溶解，2）磨牙无釉区发育的研究采用原位杂交和荧光原位杂交技术，检测了大鼠磨牙无釉区釉原蛋白mRNA的表达和分泌情况，结果表明：无釉区的发育过程中，釉原蛋白mRNA的表达和分泌与牙釉质的发育过程有关，而牙釉质的发育过程中，釉原蛋白mRNA的表达和分泌与牙釉质的发育过程有关。游离区细胞分化为釉原蛋白分泌细胞，即成釉细胞，但在牙齿发育的早期阶段，这种分泌仅持续很短的时间。釉原蛋白在牙齿发育早期的内釉上皮中的作用有待于进一步研究。3）牙骨质形成的体外研究建立了一种新的用于体外研究小鼠磨牙牙骨质形成的器官培养体系。这种培养方法保持了牙胚的三维结构。培养第43天，在脱细胞牙骨质上形成脱细胞牙骨质样层，明显不同于牙周膜本身。

1) The study on the fate of Meckel's cartilage.The Meckel's cartilage chondrocytes can express the osteocytic phenotype in vitro during synthesis of bone-type marker proteins such as osteocalcin, osteopontin and type I collagen. The midportion of Meckel's cartilage was subdivided into two regions, the anterior and posterior regions.The our results suggest that cells in the midportion of Meckels cartilage have two different possible fates. The anterior is dissolved by TRAP-positive cells, while chondrocytes in the posterior midportion are transformed directly into fibroblastic cells by phenotypic conversion.2) The study on the development of enanamel-free area of rodent molarsBoth the expression of amelogenin mRNA and secretion of amelogenin were investigated in rat molars by in situ hybridization and immunohistohemistry.Our results suggest that enamel-free area cells differentiated into amelogenin secreting cells, I.e. ameloblasts, but that the seretion lasts for only a short period at the early stage of tooth development. A role for amelogenin in inner enamel epithelium at the early stage of tooth development may emerge in the future.3)The study on the formation of cementum in vitro.A new organ culture system for in vitro study of cementogenesis in mouse molars teeth was developed. This culture method maintained the three-dimensional architecture of tooth germ. By the 43rd culture day, acellular cementum-like layer, clearly different from the periodontal ligament proper, was formed on the acellular cementum.