title: Autophagic activity and aging in human odontoblasts.
abstract: Odontoblasts are long-lived post-mitotic cells in the dental pulp, whose function is to form and maintain dentin. The survival mechanisms that preserve the viability of terminally differentiated odontoblasts during the life of a healthy tooth have not been described. In the present study, we characterized the autophagic-lysosomal system of human odontoblasts with transmission electron microscopy and immunocytochemistry, to analyze the mechanisms that maintain the functional viability of these dentinogenic cells. Odontoblasts were found to develop an autophagic-lysosomal system organized mainly by large autophagic vacuoles that are acid-phosphatase-positive to various degrees. These vacuoles expressed the autophagosomal and lysosomal markers LC3 and LAMP2, respectively, in an age-related pattern indicating the organization of a dynamic autophagic machinery. Progressive accumulation of lipofuscin within lysosomes indicates reduced lysosomal activity as a function of odontoblast aging. Our results suggest that autophagic activity in odontoblasts is a fundamental mechanism to ensure turnover and degradation of subcellular components. A reduction in the efficacy of this system might compromise cell viability and dentinogenic secretory capacity. In adult teeth, this condition is described as an 'old odontoblast' stage.
authors.affiliation: Departamento de Biología, Laboratorio de Microscopía Electrónica, Universidad de Valparaíso, Avda Gran Bretaña 1111, Casilla 5030, Correo 4, 2360102 Valparaíso, Chile. eduardo.couve@uv.cl
authors.forename: E
authors.initials: E
authors.lastname: Couve
authors.forename: O
authors.initials: O
authors.lastname: Schmachtenberg
mesh_terms: D000135:Acid Phosphatase / Q000032:analysis; D000293:Adolescent; D000328:Adult; D000368:Aged; D001343:Autophagy / Q000502:physiology*; D048429:Cell Size; D002470:Cell Survival / Q000502:physiology; D016922:Cellular Senescence / Q000502:physiology*; D002648:Child; D003782:Dental Pulp / Q000166:cytology*; D005110:Extracellular Space; D006801:Humans; D007150:Immunohistochemistry; D007425:Intracellular Membranes / Q000648:ultrastructure; D008062:Lipofuscin / Q000032:analysis; D052119:Lysosomal-Associated Membrane Protein 2; D051907:Lysosomal Membrane Proteins / Q000032:analysis; D008247:Lysosomes / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D008869:Microtubule-Associated Proteins / Q000032:analysis; D008875:Middle Aged; D009804:Odontoblasts / Q000166:cytology / Q000502:physiology*; D014617:Vacuoles / Q000648:ultrastructure; D055815:Young Adult
chemical_list: C497811:LAMP2 protein, human; D008062:Lipofuscin; D052119:Lysosomal-Associated Membrane Protein 2; D051907:Lysosomal Membrane Proteins; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D000135:Acid Phosphatase