The epithelial cell rests of Malassez – a role in periodontal regeneration?

Abstract

This article reviews general aspects about the epithelial cell rests of Malassez (ERM). The historical and general morphological features of the ERM are briefly described. The embryological derivation of the ERM is presented as an important consideration in understanding the events associated with their origin and possible functional roles within the periodontal ligament. The ultrastructural description of the ERM is also included to complement the morphological characteristics which distinguish these cells as the unique epithelial element of the periodontal ligament. The unique ability of these cells to synthesize and secrete a number of proteins usually associated with cells of mesenchymal origin, rather than ectodermal origin, is discussed in light of their role in cementum repair and regeneration. Such considerations lead to our hypothesis that one of the functional roles of the ERM may lie not only their role in maintaining and contributing to the normal periodontal cellular elements and function but also contributing, in a significant manner, to periodontal regeneration.

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

“…throughout life (Spouge, 1980;Bosshardt and Selvig, 1997;Rincon et al, 2006). However, it has been shown that the number of RM decreases with aging (Wentz et al, 1950;Reeve and Wentz, 1962;Simpson, 1965;Lambrichts et al, 1993;Wesselink and Beertsen, 1993;Gonçalves et al, 2008); this result was confirmed by this study, which revealed a reduction of 88.5% in the numerical density of RM profiles from 29-to 120-day-old.…”

“…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.…”

“…Furthermore, the proliferative activity of epithelial cells is modulated by growth factors, inflammatory mediators, and cytokines such as tumor necrosis factor (TNF), transforming growth factor-a (TGF-a), prostaglandins (PGE 2 ), and interleukin-1 and interleukin-6 (Lin et al, 1996). 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.…”

“…However, under experimental or pathological conditions, the epithelial cells, in some RM, can proliferate, resulting in the increased number and size of these structures (Brice et al, 1991;Hamamoto et al, 1998;Hasegawa et al, 2003;Talic et al, 2003). In some circumstances, this proliferation leads to the formation of odontogenic cysts and tumors (Ten Cate, 1972;Hamamoto et al, 1998;Rincon et al, 2006).…”

Odontogenic epithelial stem cells: hidden sources

“…45 Recent research has demonstrated the role of the ERM in contributing to periodontal regeneration and the turnover of ERM cells throughout life. 46 The ERM exhibit a unique ability called the EMT. These cells are epithelial cells but live in the connective tissue environment with the ability to differentiate into mesenchyme-related tissues by losing their basal lamina.…”