Ultrastructure of epithelial rests of Malassez in human periodontal ligament

doi:10.1016/0003-9969(89)90005-8

Archives of Oral Biology

Volume 34, Issue 3, 1989, Pages 179-185

https://doi.org/10.1016/0003-9969(89)90005-8 Get rights and content

Abstract

The cell rests in healthy periodontal ligament were studied by transmission electron microscopy. They consisted of clusters of cells surrounded by a basal lamina. These cells were characterized by an irregular nucleus with condensed heterochromatin, tonofilaments, relatively abundant mitochondria and poorly developed rough endoplasmic reticulum. They were connected to each other by desmosomes and gap junctions. Coated pits and vesicles were also seen at the periphery. In addition, a primary cilium accompanied by a centriole was often observed in association with the Golgi complex and rootlet-like structures. The findings suggest that the epithelial rests are more than a vestigial structure.

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Cited by (24)

The significance of epithelial rests of malassez in the periodontal ligament
2013, Journal of Endodontics
The purpose of this review was to describe the function of epithelial rests of Malassez (ERMs) in a variety of physiologic and pathologic conditions.
The authors performed a PubMed search on the term “epithelial rests” alone or in combination with “Malassez.” Relevant articles were categorized into primary subtopics and related to current and historic literature.
The review was divided into 7 subtopics. Those sections discuss possible roles for ERM in a variety of physiologic and pathologic processes.
ERMs have a fundamental role in root development, protect against root resorption, and are involved in reparative and regenerative functions of the pulp and periodontal tissues including apexogenesis and periodontal healing. They also appear to be involved in pathologic processes such as the development of oral cysts and tumors.
Immunofluorescence detection of cadherins in mouse tooth germs during root development
1999, Archives of Oral Biology
The distribution of two cell-adhesion molecules, E- and P-cadherin, was studied in relation to morphological changes in Hertwig’s epithelial root sheath. Before root dentinogenesis had started, the root sheath expressed both cadherins. As dentinogenesis proceeded, the sheath fragmented and lost P-cadherin rapidly and E-cadherin slowly, whereas the intact sheath at the apical end continued to express both. These results suggest that the two cadherins play a part in root as well as in crown development, and indicate that the decrease in the amount of these molecules and the fragmentation of the epithelial root sheath are interrelated.
Morphological changes of epithelial rests of Malassez in rat molars induced by local administration of N-methylnitrosourea
1998, Archives of Oral Biology
The objective was to examine the possibility that epithelial rests of Malassez can give origin to odontogenic tumours. A mixture of N-methylnitrosourea (MNU) and alginate impression material for dental use was injected onto the periostium of the buccal side of the left mandible of 5-week-old, male Wistar rats (300 mg/kg body wt). The mixture was left at the site for several months. The rats were killed 1, 3, 5, and 8 months after the injection. After 5 and 8 months, the epithelial rests of Malassez in the cervical and bifurcational regions of the first, second, and third left mandibular molars were significantly enlarged and the alveolar bone around the lesion was resorbed by multinucleated cells in all rats. The epithelial masses were characterized by enamel organ-like structures, deposition of eosinophilic amorphous material, duct-like structures, and squamous metaplasia. In addition to these masses in the molar regions, odontogenic tumours were induced in the incisal region and carcinomas and sarcomas in the buccal region, knee, bladder, and skin. Local administration of a mixture of MNU and alginate impression material can induce odontogenic tumours from the epithelial rests of Malassez at high incidence.
Production of amelogenin by enamel epithelium of Hertwig's root sheath
1996, Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontics
Objective. To study the multiple potentials of differentiating odontogenic epithelial cells.
Study design. Bilateral first and second maxillary molars of 30 immature rats were perforated into the pulp chambers with a round bur. The pulps were observed histologically and immunohistochemically for amelogenin 3, 7, and 14 days after the perforation.
Results. On day 7, the enamel epithelium of Hertwig's root sheath migrated and formed oval-shaped epithelial islands that resembled epithelial rests of Malassez. On day 14, the islands consisted of epithelial cells with large nuclei and cytoplasm partially surrounded by a subsequently formed osteodentin and cementum. Immunoreactivity for amelogenin was observed in the large epithelial cells and in the area between the cells as well as the calcified tissues. Some of the enamel epithelium resembling columnar ameloblasts of the enamel organ were also positive for amelogenin.
Conclusions. The enamel epithelium of Hertwig's root sheath appeared to differentiate into ameloblasts and produce amelogenin.
Maintenance of cell-type-specific cytoskeletal character in epithelial cells out of epithelial context: Cytokeratins and other cytoskeletal proteins in the rests of Malassez of the periodontal ligament
1995, Differentiation
We have determined the patterns of synthesis of cytokeratins and other epithelial marker proteins in the “rests of Malassez” of the periodontium of rabbits and humans, by immunofluorescence microscopy of cryosections prepared from fixed and decalcified rabbit teeth with attached ligament or from manually isolated human periodontal ligaments. Proteins of the major cell structures characterizing epithelial differentiation are present in Malassez cells: a complex set of cytokeratins as well as desmosomal, hemidesmosomal and basal lamina proteins. In addition, we have shown these cytoskeletal and extracellular matrix structures by electron microscopy. The cytokeratin complement of Malassez cells was found to be highly complex, as 8 of the total of 20 known epithelial cytokeratins were detected (nos. 5, 7, 8, 14, 15, 17, 18, 19). This pattern, together with the presence of the desmosomal cadherins Dsg2 and Dsc2 and the cytoplasmic desmosome plaque-associated protein plakophilin 1, indicates that the cells of the rests of Malassez are derived from the basal cell layer of a stratified squamous epithelium rather than from simple epithelial or neuroendocrine epithelial cells. Our observations show that Malassez cells retain the major characteristics of epithelial cells throughout their differentiation from the root sheath epithelium into the rests of Malassez, even though the surface location and the polar tissue architecture that typify epithelia are lost during this process. From this study we further conclude that the specific cytoskeletal complement of the Malassez cells re- presents an intrinsic gene expression program that neither depends on nor causes the formation of a stratified epithelium. We also compare the specific cytoskeletal features of Malassez cells with those of other persisting epithelial residues and discuss the potential value of these findings in relation to the histogenesis and diagnostic classification of dental and periodontal cysts and tumors.
Establishment and characterization of novel epithelial-like cell lines derived from human periodontal ligament tissue in vitro
2017, Human Cell

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Abstract

References (19)

Isolated cilia in inner retinal neurons and in retinal pigment epithelium

J. Ultrastruct. Res.

Ciliated secretory cells in the pars distalis of the mouse hypophysis

J. Ultrastruct. Res.

In vitro cultural parameters and protein and prostaglandin secretion of epithelial cells derived from porcine rests of Malassez

Archs oral Biol.

Inhibitor of collagenolytic enzymes synthesized by fibroblasts and epithelial cells from porcine and macaque periodontal tissues

Archs oral Biol.

Cilia in cardiac differentiation

J. Ultrastruct. Res.

The epithelial cell rests of Malassez and the genesis of dental cyst

Oral Surg.

Epithelial rests of Malassez in vitro; phagocytosis of collagen and the possible role of their lysosomal enzymes in collagen degradation

Lab. Invest.

Secretion of a bone resorbing factor by epithelial cells cultured from porcine rests of Malassez

J. periodont. Res.

A study of the fine structure of ciliated epithelia

J. Morph.

Cited by (24)

The significance of epithelial rests of malassez in the periodontal ligament

Immunofluorescence detection of cadherins in mouse tooth germs during root development

Morphological changes of epithelial rests of Malassez in rat molars induced by local administration of N-methylnitrosourea

Production of amelogenin by enamel epithelium of Hertwig's root sheath

Maintenance of cell-type-specific cytoskeletal character in epithelial cells out of epithelial context: Cytokeratins and other cytoskeletal proteins in the rests of Malassez of the periodontal ligament

Establishment and characterization of novel epithelial-like cell lines derived from human periodontal ligament tissue in vitro