title: Cementocytes Express Receptor Activator of the Nuclear Factor Kappa-B Ligand in Response to Endodontic Infection in Mice.
abstract: BACKGROUND
  Although studies have recently shown that osteocytes embedded in mineralized bone matrix play an important role in bone diseases, the participation of cementocytes in apical periodontitis has not been evaluated. The aim of the present study was to evaluate the possible involvement of cementocytes in the development of apical periodontitis.
  
  
  METHODS
  Apical periodontitis was experimentally induced in the lower first molars of wild-type mice by pulp exposure to the oral environment. At 0, 7, 21, and 42 days after pulp infection, the animals were euthanized, and the jaws were prepared for analysis under conventional and fluorescence microscopy (morphologic and morphometric analysis), immunohistochemistry and immunofluorescence (receptor activator of nuclear factor kappa-B [RANK], receptor activator of the nuclear factor kappa-B ligand [RANKL], and osteoprotegerin [OPG]), enzyme histochemistry (osteoclasts and cementoclasts), and real-time polymerase chain reaction (RANK, RANKL, OPG, and cathepsin K).
  
  
  RESULTS
  At 7, 21, and 42 days after pulp exposure, there was a progressive increase in periodontal ligament, cementum and bone resorption areas, osteoclasts, and cementoclast counts as well as higher messenger RNA levels of RANK, RANKL, OPG, and cathepsin K. In intact teeth, cementocytes and osteocytes did not express RANKL. After infection, RANKL was strongly expressed in cementocytes, but not in osteocytes, and its expression increased with lesion progression.
  
  
  CONCLUSIONS
  Our findings show that cementocytes express RANKL in response to endodontic infection and may be involved in the pathogenesis of apical periodontitis.
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, São Paulo, Brazil. Electronic address: andiara@usp.br.
authors.forename: Andiara
authors.initials: A
authors.lastname: De Rossi
authors.affiliation: Department of Physics and Chemistry, School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Sandra Yasuyo
authors.initials: SY
authors.lastname: Fukada
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Moara
authors.initials: M
authors.lastname: De Rossi
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Raquel Assed Bezerra
authors.initials: RA
authors.lastname: da Silva
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Alexandra Mussolino
authors.initials: AM
authors.lastname: Queiroz
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Paulo
authors.initials: P
authors.lastname: Nelson-Filho
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry of Ribeirão Preto, University of São Paulo, São Paulo, Brazil.
authors.forename: Léa Assed Bezerra
authors.initials: LA
authors.lastname: da Silva
mesh_terms: D000818:Animals; D056657:Cathepsin K / Q000378:metabolism; D003739:Dental Cementum / Q000166:cytology*; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008856:Microscopy, Fluorescence; D008963:Molar; D053244:Osteoprotegerin / Q000378:metabolism; D010485:Periapical Periodontitis / Q000378:metabolism*; D053245:RANK Ligand / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D053244:Osteoprotegerin; D053245:RANK Ligand; D056657:Cathepsin K
keywords: Apical periodontitis; dental cementum; osteocytes; receptor activator of the nuclear factor kappa-B ligand