Ultrastructural and histochemical study on the morphogenesis of epithelial rests of Malassez.

Hamamoto, Yoshioki; Nakajima, Tamio; Ozawa, Hiroki

doi:10.1679/aohc.52.61

Cited by 39 publications

(38 citation statements)

References 14 publications

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“…It is well known that OX6-immunopositive macrophages are known to be capable of phagocytosis (Kawahara and Takano, 1995;Nishikawa and Sasaki, 1996), but ERM has also been shown to demonstrate phagocytotic abilities. ERM studies showed epithelial cells in direct contact with mesenchymal cells during root formation, suggesting epithelial-mesenchymal interaction, and phagocytosis and digestion of collagen fibrils by Malassez epithelial cells (Birek et al, 1980;Hamamoto et al, 1989b). In addition, ERM in mature PDL have demonstrated apoptotic cells being engulfed by neighboring epithelial cells of Malassez (Cerri and Katchburian, 2005).…”

Section: Discussionmentioning

confidence: 99%

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

Tadokoro

Radunović

Inoue

2008

The Anatomical Record

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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.

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Section: Discussionmentioning

confidence: 99%

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

Tadokoro

Radunović

Inoue

2008

The Anatomical Record

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“…In contrast, large RM have been demonstrated in determined circumstances, such as orthodontic tooth movement (Brice et al, 1991;Talic et al, 2003), inflammatory and wound healing processes of the periodontium (Johansen, 1970;Hamamoto et al, 1998;Hasegawa et al, 2003). In these abnormal conditions, the cells of RM may proliferate (Götz et al, 2003;Talic et al, 2003), resulting in the formation of odontogenic cysts and tumors (Ten Cate 1972;Spouge, 1980;Hamamoto et al, 1989Hamamoto et al, , 1998Rincon et al, 2006). Our morphometric results revealed that the number of epithelial cell profiles/RM increased according to the RM profile area; this is confirmed by the fact that either the numerical density or the area of the epithelial cells was similar in the groups.…”

Section: Discussionmentioning

confidence: 99%

“…The cervical region is usually susceptible to inflammatory processes (Rincon et al, 2006) and, then, several cytokines can be released. Considering that the RM are mainly located in the cervical region of the periodontal ligament (Hamamoto et al, 1989;Yamashiro et al, 2000;Cerri and Katchburian, 2005;Suzuki et al, 2006;Gonçalves et al, 2008), it is possible that cellular proliferation is induced by inflammatory mediators, resulting in the enlargement of some epithelial structures.…”

Section: Discussionmentioning

confidence: 99%

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

Cerri

Gonçalves

Sasso-Cerri

2008

The Anatomical Record

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Recently, we have demonstrated that the reduction in the number of rests of Malassez (RM) according to age may be due to epithelial cell death by apoptosis. It is known that, under experimental or pathological conditions, the epithelial cells of RM can proliferate, resulting in the formation of odontogenic cysts and tumors. In this study, the area of RM profiles and the number of profiles of epithelial cell nuclei/RM were investigated in young and adult rats. Fragments containing upper molars of rats aged 29, 45, and 120 days were fixed, decalcified, and embedded for light microscopy. In the sections stained by hematoxylin and eosin, the numerical density of RM profiles/mm 2 of periodontal ligament, the area of each RM profile and the number of epithelial cell nuclei profile/RM were obtained. Moreover, detection of cytokeratin by immunohistochemistry and ultrastructural analysis of RM were carried out. Smaller RM were found in all groups, but the very large RM were only observed in the 120-day-old rats. The presence of cells in close juxtaposition exhibiting cytokeratin filaments in their cytoplasm, including in the large RM, characterized their epithelial nature. The number of epithelial cells/RM varied proportionally to the area. Moreover, epithelial cells in mitosis were found in small and large RM, indicating that cellular proliferation can be responsible for the enlargement of RM, under physiological conditions. The results suggest that a possible disequilibrium between the proliferative and apoptotic processes can be related to the enlargement of some RM in the 120-day-old rats.

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“…This localization is consistent with the proposed origin of keratocysts from the epithelial rests of Malassez, cells that are left behind as much of the epithelial root sheath regresses during late stages of tooth formation. 55,56 Cysts at various stages of development could sometimes be identified in the same tissue section, with early lesions clearly arising within the periodontal ligament ( Figure 3C). Because epithelial rests express K5 protein ( Figure 3D), 57 …”

Section: Mouse Keratocysts Are Derived From Reactivated Epithelial Rementioning

confidence: 99%

Odontogenic Keratocysts Arise from Quiescent Epithelial Rests and Are Associated with Deregulated Hedgehog Signaling in Mice and Humans

Grachtchouk

Liu

Wang

et al. 2006

The American Journal of Pathology

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Odontogenic keratocysts in humans are aggressive, noninflammatory jaw cysts that may harbor PTCH1 mutations, leading to constitutive activity of the embryonic Hedgehog (Hh) signaling pathway. We show here that epithelial expression of the Hh transcriptional effector Gli2 is sufficient for highly penetrant keratocyst development in transgenic mice. Mouse and human keratocysts expressed similar markers, leading to tooth misalignment, bone remodeling, and craniofacial abnormalities. We detected Hh target gene expression in epithelial cells lining keratocysts from both species, implicating deregulated Hh signaling in their development. Most mouse keratocysts arose from rests of Malassez-quiescent, residual embryonic epithelial cells that remain embedded in the periodontal ligament surrounding mature teeth. In Gli2-expressing mice, these rests were stimulated to proliferate, stratify, and form a differentiated squamous epithelium. The frequent development of keratocysts in Gli2-expressing mice supports the idea that GLI transcription factor activity mediates pathological responses to deregulated Hh signaling in humans. Moreover, Gli2-mediated reactivation of quiescent epithelial rests to form keratocysts indicates that these cells retain the capacity to function as progenitor cells on activation by an appropriate developmental signal.

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Ultrastructural and histochemical study on the morphogenesis of epithelial rests of Malassez.

Cited by 39 publications

References 14 publications

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

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

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

Odontogenic Keratocysts Arise from Quiescent Epithelial Rests and Are Associated with Deregulated Hedgehog Signaling in Mice and Humans

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