title: Cell death and quantitative reduction of rests of Malassez according to age.
abstract: OBJECTIVE
  Rests of Malassez are clusters of epithelial cells that remain in the periodontal ligament throughout life. However, it has been reported that the number of these structures decreases with age, and some epithelial cells undergo apoptosis in rests of Malassez of young and adult rats. Therefore, the purpose of the present study was to investigate the incidence of epithelial cell death and the quantitative changes in the rests of Malassez in rat molars of different ages.
  
  
  METHODS
  Fragments containing the upper molars of rats aged 29, 45 and 120 d were fixed, decalcified and embedded for analysis by light microscopy. In the sections stained by hematoxylin and eosin, the number of rests of Malassez and the number of nuclei of these epithelial structures were obtained. Moreover, the nuclei exhibiting typical features of cell death were also counted in each rest of Malassez. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) method for detection of cell death was also carried out.
  
  
  RESULTS
  In all groups examined, some rests of Malassez exhibited epithelial cell nuclei with typical features of apoptosis and some of them were also TUNEL positive. From 29 to 120 d of age in rats, the quantitative analysis showed a significant decrease in the total number of rests of Malassez in the cervical, middle and furcation regions of the periodontal ligament. Moreover, a significant decrease of epithelial cell nuclei was concomitant to an increase in the frequency of cell death in the oldest rats.
  
  
  CONCLUSIONS
  These results suggest that epithelial cell death by apoptosis may be, at least in part, responsible for the reduction in the number of rests of Malassez according to age.
authors.affiliation: Department of Morphology, Laboratory of Histology and Embryology, Dental School, São Paulo State University (UNESP), Araraquara, SP, Brazil.
authors.forename: J S
authors.initials: JS
authors.lastname: Gonçalves
authors.forename: E
authors.initials: E
authors.lastname: Sasso-Cerri
authors.forename: P S
authors.initials: PS
authors.lastname: Cerri
mesh_terms: D000375:Aging / Q000473:pathology*; D000818:Animals; D017209:Apoptosis; D002452:Cell Count; D016923:Cell Death; D002467:Cell Nucleus / Q000648:ultrastructure; D002843:Chromatin / Q000648:ultrastructure; D004847:Epithelial Cells / Q000473:pathology; D020287:In Situ Nick-End Labeling; D008297:Male; D046529:Microscopy, Electron, Transmission; D010513:Periodontal Ligament / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002843:Chromatin