Epithelial rests colocalize with cementoblasts forming acellular cementum but not with cementoblasts forming cellular cementum

Epithelial rests of Malassez and cementoblasts were examined in the rat mol ars during the early stages of root formation using an antilaminin antibody and/or peanut agglutinin (PNA), and an antiosteocalcin (OC) antibody, resp ectively. The roots of the first molars were used for study. The antilamini n antibody stained the basement membrane surrounding the epithelial root sh eath and epithelial rests. The basement membrane of the epithelial root she ath 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 s ections 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 cor onal 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 epithel ial rests forming fine meshes were seen near the epithelial root sheath. Th e anti-OC antibody stained cementoblasts lining acellular and cellular ceme ntum, The sections doubly stained with the anti-OC and the antilaminin anti bodies or PNA further revealed the close relation between epithelial rests and cementoblasts, The OC-positive cells lining acellular cementum or denti n were localized very close to the epithelial rests. In contrast, the OC-po sitive cells lining cellular cementum did not show close association with t he epithelial cells, except the cells located most apically where the basem ent membrane of the epithelial root sheath is disrupted and the initial cel lular cementum begins to be formed. The present results suggest that the ep ithelial 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.