Hertwig's Epithelial Cells Research Articles

Functional Roles and Fate of Hertwig's Epithelial Cells in Root Formation of the Molars of Mice

Functional Roles and Fate of Hertwig's Epithelial Cells in Root Formation of the Molars of Mice

Immunolocalization of the small proteoglycan decorin in human teeth

The immunolocalization of decorin was studied by confocal laser scanning microscopy and transmission electron microscopy. In the apical area of developing teeth, labelling for decorin was found in the dental papilla cells, preodontoblasts and also in the Hertwig's epithelial cells. Mantle dentine and the initial predentine were negative. In circumpulpal dentine, intense reactivity extended along the calcification front and dentinal tubules. Fluorescence was also evident in odontoblast cell bodies and their processes in predentine. None was perceived, however, in the predentinal matrix. Faint staining was observed on the calcified dentinal matrix. Immunoelectron microscopy revealed staining for decorin in collagen fibrils lining the predentine-dentine junction, and where arrays of labelled filaments were noted orthogonal to the collagen fibrils. Staining extending from the calcification front was observed in the matrix adjacent to the dentinal tubule. The decorin observed at the calcification front might regulate the mineralization of dentinal matrix.

Early mouse molar root development: Cellular changes and distribution of fibronectin, laminin and type-IV collagen

We analysed epithelial-mesenchymal interactions that occur during the early stages of the formation of mouse molar roots using light and electron microscopy. Morphological changes observed in the cells of Hertwig's epithelial sheath, the pulp and the follicular mesenchyme are described. The Hertwig's epithelial cells lose their cuboidal form and become flattened, apparently intermixing with the cells of the follicular mesenchyme. At the light- and electron-microscope levels, immunoperoxidase techniques were used to localize fibronectin, laminin and type-IV collagen. These appear to be closely associated with cell differentiation and matrix deposition in developing tooth roots. In addition, at the ultrastructural level, intracellular immunoreactivity was detected. The rough endoplasmic reticulum and nuclear envelope of some cells of the periodontal ligament facing the acellular cementum exhibited specific reactivity with laminin and type-IV collagen. Moreover, these periodontal ligament cells express keratin, but not vimentin, filaments. Our results demonstrate that Hertwig's epithelial cells maintain their capacity to synthesize laminin and type-IV collagen, as well as to express keratin filaments, despite basement membrane fragmentation and the disorganization of Hertwig's epithelial sheath. Thus, some Hertwig's epithelial cells remain in the periodontal ligament intermixed with follicular mesenchyme cells.