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

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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