The Ca2+-binding protein calretinin is selectively enriched in a subpopulation of the epithelial rests of Malassez

Abstract

During tooth development, the inner and outer enamel epithelia fuse by mitotic activity to produce a bilayered epithelial sheath termed Hertwig's epithelial root sheath (HERS). The epithelial rests of Malassez (ERM) are the developmental residues of HERS and remain in the adult periodontal ligament (PDL). Although the cellular regulation of the Ca(2+)-binding proteins parvalbumin, calbindin-D28k, and calretinin has been reported in the inner and outer enamel epithelia during tooth development, an involvement of Ca(2+)-binding proteins in the ERM has not so far been characterized. Among the three Ca(2+)-binding proteins tested (calbindin D28k, parvalbumin, calretinin), we have only been able to detect calretinin in a subpopulation of adult rat molar ERM, by using quantitative immunohistochemical and confocal immunofluorescence techniques. TrkA (a marker for ERM) is present in numerous epithelial cell clusters, whereas calretinin has been localized in the cytosol and perinuclear region of a subpopulation of TrkA-positive cells. We conclude that, in inner and outer enamel epithelial cells, Ca(2+) is regulated by calbindin, parvalbumin, and calretinin during tooth development, whereas in the ERM of adult PDL, Ca(2+) is regulated only by calretinin. The expression of Ca(2+)-binding proteins is restricted in a developmental manner in the ERM.

Regulation of Calbindin-D28k Expression by Msx2 in the Dental Epithelium

“…In parallel, calbindin-D 28k was upregulated in the rests of Malassez of Msx2 +/mice and even more in Msx2 -/-. This pattern is not physiological (Korkmaz et al 2010), as confirmed here in Msx 2 +/+ control mice. The same observation was also repeated for amelogenin in the same pathophysiological context.…”

“…This study focused on calcium-binding proteins, as some of them are highly expressed in ameloblasts but not significantly expressed in the non-ameloblastic cells (Hotton et al 1995;Hubbard 1995;Berdal et al 1996;Korkmaz et al 2010).…”

“…However, dental epithelium also comprises other cells such as the stratum intermedium, the stellate reticulum, the outer dental epithelium, or the root epithelium that are not directly involved in amelogenesis (Bosshardt and Nanci 2004; Tummers and Thesleff 2009). In adult physiology, dental epithelium forms rests of Malassez that also express a limited number of genes involved in enamel formation (e.g., calretinin but not calbindin-D 28k ; Korkmaz et al 2010).…”

“…This study focused on calcium-binding proteins, as some of them are highly expressed in ameloblasts but not significantly expressed in the non-ameloblastic cells (Hotton et al 1995; Hubbard 1995; Berdal et al 1996; Korkmaz et al 2010). Calbindin-D 28k is an intracellular EF-hand calcium-binding protein that is highly concentrated in vitamin D–dependent calcium-transporting epithelia, including those in the kidney, intestine, and enamel.…”

Oral and Craniofacial Manifestations and Two Novel Missense Mutations of the NTRK1 Gene Identified in the Patient with Congenital Insensitivity to Pain with Anhidrosis

“…The features of shed teeth in CIPA patient suggest that NTRK1 could play an important role in root formation. Some studies have shown that TRKA is a convenient marker for identifying and characterizing Hertwig's root sheath and epithelial rests of Malasseze of the forming root [27], [28]. Moreover, NGF/TRKA expressed in human periodontal tissue may contribute to the regeneration and the innervation of periodontal tissue [29], [30].…”