Cytochemical and molecular biological study of enamel proteins with special reference to dental hard tissue formation

用生化、免疫化学、免疫细胞化学和分子生物学方法对猪和大鼠的成釉过程进行了研究。主要研究结果如下：(1)釉原蛋白、釉质蛋白和鞘蛋白在猪牙胚中的表达始于牙胚的分化阶段，而在大鼠的切牙和磨牙牙胚中的表达一直持续到牙胚的早期成熟。这些结果提示，釉质蛋白在牙釉质成熟中的作用在猪和大鼠牙釉质发生中可能不同。(2)在牙根的形态发生和形成过程中，部分牙周细胞和牙骨质细胞表达了大鼠鞘蛋白(成釉蛋白和釉蛋白)，两者都具有张力丝束和桥粒等上皮起源的特征，表明起源于Hertwig上皮根鞘的细胞实际上合成和分泌了鞘蛋白。另一方面，在猪组织中，AMEL…既不表达除了成釉细胞外，牙胚的细胞成分中没有发现更多的生长素和鞘蛋白。这些结果表明，猪和大鼠的Hertwig上皮根鞘相关细胞中鞘蛋白的表达存在种属差异，并参与了成牙本质细胞的诱导。(3)成釉蛋白是一种釉质特异性基质金属蛋白酶，在猪和大鼠未成熟的釉质中以46 kDa和44 kDa蛋白的活化形式免疫定位。猪牙胚除分泌期未成熟釉质表层免疫反应较弱外，过渡期至早期成熟期釉质基质表层免疫反应较强。EMSP1(釉质丝氨酸基质蛋白酶1)在釉质基质的浅层也有较强的免疫反应。这些结果表明，在成釉细胞成熟吸收之前，过渡性成釉细胞在基质降解过程中起着重要作用。较少

Amelogenesis of the porcine and the rat was investigated by means of biochemical, immunochemical, immunocytochemical and molecular biological methods. The results are summarized as follows.(1) Amelogenins, enamelins and sheath proteins were expressed in porcine tooth germs from the differentiation to the transition stage, while they were expressed in rat incisor and molar tooth germs until early maturation stage. These results suggest that the role of enamel proteins in enamel maturation might be different between the pig and the rat amelogenesis.(2) During root morphogenesis and formation, rat sheath proteins (ameloblastin and amelin) were expressed in a part of periodontal cells and cementocytes, both of which have characteristic features of epithelial origin such as tonofilament bundles and desmosomes, suggesting that cells originated from Hertwig's epithelial root sheath actually synthesize and secret sheath proteins. On the other hand in porcine tissues, expression of neither amel … More ogenins nor sheath proteins was found any cellular elements of tooth germs except for ameloblast. These results suggest that presence of species difference of sheath proteins concerning the expression in cells related to Hertwig's epithelial root sheath and the role of induction of cementoblasts between the pig and that rat.(3) Enamelysin, one of enamel specific matrix metalloproteinases, was immunolocalized in the immature enamel of the pig and the rat as an activated form of 46 kDa and 44 kDa protein. In porcine tooth germs, immunoreaction was weak except for the surface layer of immature enamel at the secretory stage, while it was intense over the superficial layer of enamel matrix from the transition to the early maturation stage. Immunoreaction of EMSP1 (enamel serine matrix proteinase 1) was also intense over the superficial layer of enamel matrix from the transition to the early maturation stage. These results suggest that transitional ameloblasts play a important role on matrix degradation prior to resorption by maturation ameloblasts. Less