title: Expression and Distribution of Receptor Activator of Nuclear Factor Kappa B, Receptor Activator of Nuclear Factor Kappa B Ligand, and Osteoprotegerin in Periradicular Cysts.
abstract: BACKGROUND
  The receptor activator of nuclear factor kappa B (RANK)-RANK ligand (RANKL)-osteoprotegerin (OPG) system is important in osteoclastogenesis and may play a role in the development of apical periodontitis. This immunohistochemical study evaluated the distribution of the expression of these regulators of bone resorption in periradicular cysts.
  
  
  METHODS
  Biopsy specimens from 40 consecutive periradicular cysts registered in the files of the Oral Pathology Laboratory were selected for the study on the basis of an initial analysis of archived histopathologic slides. Sections were stained with hematoxylin-eosin for preliminary analysis, and then silanized slides were used for immunohistochemical reactions with anti-RANK, anti-RANKL, and anti-OPG antibodies by the immunoperoxidase technique. The expression of these molecules in different tissue compartments and in the inflammatory infiltrate of cysts was compared.
  
  
  RESULTS
  Analysis of the distribution of each marker in different areas of the cyst revealed no significant difference in the expression of RANK, RANKL, or OPG in areas of normal epithelium when compared with areas of hyperplastic epithelium. As for the connective tissue, higher expression of both RANK (P < .05) and RANKL (P < .05), but not OPG, was observed in the chronic inflammatory infiltrate, in comparison with the acute infiltrate. When the expression of the 3 molecules was compared per area of the cystic lesion, higher expression of RANK in comparison with OPG was verified in the areas of both normal and hyperplastic epithelium. RANKL was also significantly more expressed in the normal epithelium than OPG (P < .05). In the connective tissue, RANK expression was higher than OPG in both chronic and mixed infiltrates (P < .05) and also higher than RANKL expression in mixed infiltrate (P < .05). RANKL expression in chronic infiltrate was higher in comparison with OPG expression (P < .05).
  
  
  CONCLUSIONS
  The results demonstrated that the type of inflammatory infiltrate present in periradicular cysts appears to influence the expression of RANK, RANKL, and OPG. The chronic infiltrate is likely to have increased osteolytic activity because of a higher RANKL/OPG ratio.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, Rio de Janeiro, Brazil. Electronic address: luadias@hotmail.com.
authors.forename: Luciana
authors.initials: L
authors.lastname: Armada
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Patrícia dos Santos
authors.initials: Pdos S
authors.lastname: Marotta
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Fábio Ramôa
authors.initials: FR
authors.lastname: Pires
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: José F
authors.initials: JF
authors.lastname: Siqueira
mesh_terms: D001862:Bone Resorption / Q000378:metabolism / Q000473:pathology; D004848:Epithelium / Q000276:immunology* / Q000473:pathology / Q000601:surgery; D006801:Humans; D007124:Immunoenzyme Techniques; D053244:Osteoprotegerin / Q000378:metabolism*; D053245:RANK Ligand / Q000378:metabolism*; D011842:Radicular Cyst / Q000378:metabolism* / Q000473:pathology / Q000601:surgery; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000378:metabolism*
chemical_list: D053244:Osteoprotegerin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human
keywords: Osteoprotegerin; RANK ligand; periradicular cyst; receptor activator of nuclear factor-κB