Epithelial Cell Rests of Malassez and OX6‐Immunopositive Cells in the Periodontal Ligament of Rat Molars: A Light and Transmission Electron Microscope Study

Abstract

It has been shown that human and cat epithelial cell rests of Malassez (ERM) consist of heterogeneous cell populations. Immunohistochemical and immunoelectron microscopic analyses have verified the presence of neuroendocrine and Merkel-like cells in both of these epithelia. During experimental orthodontic tooth movement, immunocompetent cells have also been found in the vicinity of ERM in rat periodontal ligament (PDL), but have not been characterized in normal rat PDL. The aim of this study was to investigate the presence and distribution of MHC class II antigen presenting cells by using OX6 antibody in ERM of rat molars by light and transmission electron microscopy. Immunohistochemical and immunoelectron microscopic observations of rat maxillary molars confirmed the presence of OX6-positive cells in contact with ERM. Some immunopositive cytoplasmic processes containing vesicles interdigitated with cells of the Malassez epithelial clusters. Based on these findings it can be concluded that immunocompetent cells are localized close to Malassez epithelial clusters in normal rat PDL. Furthermore, the ultrastructural evidences indicate a possible interaction between the epithelial and immunocompent cells and suggest morphological and functional properties for ERM.

Epithelial and PGP9.5-immunoreactive cells of Malassez epithelium in the periodontal ligament of cats: a transmission electron microscopic study

“…Similar findings of cytoplasmic processes extending towards the outer surface of the ME and periodontal immunocompetent cells have been reported [17,18]. This morphology resembles that of sensory epithelial cells in glandular tissue, or the intestinal lumen.…”

Distribution of Epithelial Cells and Their Relationship to Immunocompetent Cells in Rat Molars: A Confocal and Transmission Electron Microscope Study

“…An analysis of the distribution of ED1-immunopostive cells in the PDL of first mandibular rat molars reported that they were most abundant in the tooth root bifurcation (Kan et al 2001), in the same area where large ERM cell clusters can be seen. Moreover, the same area houses DCs that have the characteristics of activated antigen-presenting cells and show cell-to-cell contact with lymphocytes (Hamamoto et al 1998;Kaneko et al 2008;Tadokoro et al 2008). In a recent study, we found that ERM were in contact with OX61 immunocompetent cells, and that OX6-immunopositive cells surrounding epithelial cells showed ultrastructural diversity, suggesting the involvement of several types of immunocompetent cells with periodontal epithelial cells (Tadokoro et al 2008).…”

“…The observation of the relation of cells immunoreactive to CK and ED1 was difficult because the immunoreaction products of ED1 were recognized only on organelles belonging to the phagolysosomal apparatus of macrophages and DCs, and did not define their shape near the root surface. On the other hand, the observation of the relationship between CK-and OX6-immunopositive cells was relatively easy, because the immunoreaction products of OX6 are recognized on the cell membrane (Kan et al 2001;Tadokoro et al 2008). It appeared that most of the OX6-immunopositive cells, which were close to or in contact with CK-immunopositive cells near cervical and furcational cementum contained few ED1 immunoreaction products.…”

“…The existence of an intercellular relationship between epithelial cells and cells expressing class II molecules (OX61 cells) has been verified (Tadokoro et al 2008). The diversity of the ultrastructure of these immunopositive cells indicates possible involvement of several types of immunocompetent cells (Tadokoro et al 2008).…”

Area of Rests of Malassez in Young and Adult Rat Molars: Evidences in the Formation of Large Rests

“…Bar, 10 mm. In (C), a furcation region of a root of 45-day-old rat shows a rest of these large RM contained cells joined to each other by desmosome junctions and bundles of cytokeratin filaments in their cytoplasm, characterizing their epithelial nature (Hasegawa et al, 2003;Luan et al, 2006;Suzuki et al, 2006;Tadokoro et al, 2008). It is known that the RM are usually found in the periodontal ligament Fig.…”