Isolation and characterization of cells derived from human epithelial rests of Malassez

Abstract

The epithelial rests of Malassez (ERMs) might represent a valuable source of oral epithelial cells with stem cell properties. The purpose of this study was to isolate and characterize cells derived from human ERM, and compare them with cells derived from matched normal oral mucosa (NOM). Matched tissue specimens of the periodontal ligament of extracted tooth and NOM were collected. Cells were isolated in culture, then characterized by immunohistochemistry and flow cytometry for expression of pancytokeratin, ESA, PDGFRB, CD31 and CD44. 3D organotypic cultures were constructed by growing epithelial cells on top of fibroblast-populated collagen gels. Both ERM and NOM-isolated cells expressed the markers of epithelial lineage (ESA and pancytokeratin), and to some extent PDGFR, an indicator of a more mesenchymal phenotype, but not the endothelial cell marker CD31. Cells with epithelial morphology were isolated from periodontium of cervical, middle and apical parts of the root, but contained a significantly lower percentage of ESA and pancytokeratin-positive cells than when isolating cells from NOM ( p < 0.001). ERM cells expressed a significantly higher percentage of the stem cell-related molecule CD44 (cervical 92.93 ± 0.25%, middle 93.8 ± 0.26%, apical 94.36 ± 0.41%) than cells isolated from NOM (27.8 ± 1.47%, p < 0.001). When grown in 3D organotypic cultures and in collagen gels, ERM cells formed a less differentiated epithelium than NOM cells, but expressing pancytokeratin and vimentin. In conclusion, epithelial cells could be isolated from human periodontium and grown in culture; their in vitro characterization indicates that they have a less differentiated phenotype compared with cells derived from normal oral epithelium.

Epithelial Cell Rests of Malassez Provide a Favorable Microenvironment for Ameliorating the Impaired Osteogenic Potential of Human Periodontal Ligament Stem Cells

“…Since there are only a small amount of the ERM cells in PDL, it is difficult to obtain and culture human ERM cells. While several studies have cultured the human ERM cells in vitro and evaluated their characteristics (Nam et al, 2011;Lee et al, 2012;Kitajima et al, 2019). As the ERM coexist with PDL cells and close to gingival cells, the improvement of purification of the ERM is a matter of considerable interest in order to clarify the function of this subpopulation (Athanassiou-Papaefthymiou et al, 2015).…”

“…Summarizing the methods of others, we mechanically scraping the periodontal tissue of upper 1/3 of root to avoid the effects of gingival epithelial cells. Additionally, enzymatic digestion of the explants culture, which contains PDL cells and ERM, allows the less-adherent periodontal ligament fibroblasts to be released and separated from the more-adherent ERM (Nam et al, 2014;Kitajima et al, 2019). However, eliminating any residual other cells from the remaining adherent ERM remains difficult which needs advanced technology such as flow cytometry sorting.…”

Periapical Cyst and Odontogenic Remnants on Osseous Mandibulectomy Margins: Two Diagnostic Pitfalls

“…One of the posterior osseous margins showed a small single intraosseous epithelial nest, with squamous differentiation and bland cytonuclear features (Figure 2C). Morphologically, this second focus was strikingly different from the squamous cell carcinoma, and it was consistent with an odontogenic rest (so-called epithelial rests of Malassez 1 ).…”

“…5 They may show elliptical, funicular, or tufted shapes, and molecularly they can demonstrate stem cell properties. 1,5…”