Epithelial Rests Colocalize with Cementoblasts Forming Acellular Cementum but Not with Cementoblasts Forming Cellular Cementum

Abstract

Epithelial rests of Malassez and cementoblasts were examined in the rat molars during the early stages of root formation using an antilaminin antibody and/or peanut agglutinin (PNA), and an antiosteocalcin (OC) antibody, respectively. The roots of the first molars were used for study. The antilaminin antibody stained the basement membrane surrounding the epithelial root sheath and epithelial rests. The basement membrane of the epithelial root sheath was continuous, but that of the epithelial rests was discontinuous. The cells of epithelial rests and epithelial root sheath were positive for PNA. The structural characteristics of the epithelial rests were seen in the sections stained doubly with PNA and the antilaminin antibody. The cells of epithelial rests were fibroblast-like and formed a fine mesh in 2-week-old rats. In 3-week-old rats, the epithelial rests were also present at the coronal half of root surface, showing typical cell cords, but were not present at the apical part of the root surface where the cellular cementum covered the root dentin. At the root apex of 3-week-old rats, the cells of epithelial rests forming fine meshes were seen near the epithelial root sheath. The anti-OC antibody stained cementoblasts lining acellular and cellular cementum. The sections doubly stained with the anti-OC and the antilaminin antibodies or PNA further revealed the close relation between epithelial rests and cementoblasts. The OC-positive cells lining acellular cementum or dentin were localized very close to the epithelial rests. In contrast, the OC-positive cells lining cellular cementum did not show close association with the epithelial cells, except the cells located most apically where the basement membrane of the epithelial root sheath is disrupted and the initial cellular cementum begins to be formed. The present results suggest that the epithelial rests and/or the discontinuous basement membrane of them may have a role for the acellular cementum formation at least in the early stage of root formation.

Smad4-Shh-Nfic signaling cascade–mediated epithelial-mesenchymal interaction is crucial in regulating tooth root development

“…During root development, the transition from dental cervical loop to HERS is generally regarded as the beginning of root formation 38, 39. However, the functional mechanism of HERS in guiding root development is still unclear 38–41. In this study we investigated the functional significance of TGF‐β/BMP signaling in regulating the fate of HERS cells and epithelial‐mesenchymal interaction during root development.…”

Role of Hertwig's epithelial root sheath cells in tooth root development

“…Studies suggest that the basement membrane remains intact on the root dentine surface (MacNeil and Thomas, 1993), and it is disrupted when the cells start secreting osteocalcin (Kagayama et al, 1998). These investigators assumed that the cells producing the osteocalcin were mesenchymal-derived cementoblasts, based on the assumption that only mesenchymal cells express osteocalcin.…”

Observations on continuously growing roots of the sloth and the K14‐Eda transgenic mice indicate that epithelial stem cells can give rise to both the ameloblast and root epithelium cell lineage creating distinct tooth patterns

“…Through this network the follicular mesenchyme cells can migrate to the dentin surface and differentiate into cementoblasts depositing the cementum. The ERM functions in the induction of cementoblast differentiation and regulation of their function (Thomas 1995;Bosshardt and Schroeder 1996;Kagayama et al 1998). Fibers of the periodontal ligament are embedded in the cementum and connect the root to the jaw bone.…”