title: Modulation of phosphate/pyrophosphate metabolism to regenerate the periodontium: a novel in vivo approach.
abstract: BACKGROUND
  The developing periodontium is sensitive to local levels of inorganic phosphate (P(i)) and inorganic pyrophosphate (PP(i)) as demonstrated by cementum phenotypes resulting from the loss of function of protein regulators of P(i)/PP(i) homeostasis. The progressive ankylosis protein (ANK) regulates the transport of PP(i), and progressive ankylosis gene (Ank) and knock-out (KO) mice feature a rapidly forming and thick cementum. We hypothesized that, besides affecting cementum formation, decreased extracellular PP(i) levels in Ank KO mice would also impact cementum regeneration.
  
  
  METHODS
  Periodontal fenestration defects (approximately 2 mm in length, 1 mm in width, and 0.5 mm in depth) were created on buccal aspects of mandibular molars in Ank KO and wild-type (WT) mice. Mandibles were harvested at 15 and 30 days post-surgery for histology, histomorphometry, evaluation of in vivo fluorochrome labeling, and immunohistochemistry (IHC) for proteins including bone sialoprotein (BSP), osteopontin (OPN), dentin matrix protein 1 (DMP1), and ectonucleotide pyrophosphatase/phosphodiesterase 1 (NPP1).
  
  
  RESULTS
  A greater amount of new cementum was observed in Ank KO mice at 15 and 30 days post-surgery (P <0.05), which was confirmed by fluorochrome labeling showing a higher new cementum appositional activity in defect areas in Ank KO mice versus controls. At days 15 and 30 during healing, regenerating cementum and associated cells in Ank KO samples recapitulated expression patterns mapped during development, including limited BSP and positive OPN and DMP1 in the cementum matrix as well as elevated NPP1 in cementoblasts.
  
  
  CONCLUSIONS
  Within the limits of the study, these findings suggest that reduced local levels of PP(i) could promote increased cementum regeneration. Therefore, the local modulation of P(i)/PP(i) may be a potential therapeutic approach for achieving improved cementum regeneration.
authors.affiliation: Department of Prosthodontics and Periodontics, Division of Periodontics, School of Dentistry, Campinas State University, Piracicaba, SP, Brazil.
authors.forename: Thaisângela L
authors.initials: TL
authors.lastname: Rodrigues
authors.forename: Kanako J
authors.initials: KJ
authors.lastname: Nagatomo
authors.forename: Brian L
authors.initials: BL
authors.lastname: Foster
authors.forename: Francisco H
authors.initials: FH
authors.lastname: Nociti
authors.forename: Martha J
authors.initials: MJ
authors.lastname: Somerman
mesh_terms: D000818:Animals; D003739:Dental Cementum / Q000502:physiology*; D011756:Diphosphates / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000096:biosynthesis; D058574:Integrin-Binding Sialoprotein / Q000096:biosynthesis; D051379:Mice; D018345:Mice, Knockout; D053495:Osteopontin / Q000096:biosynthesis; D028061:Phosphate Transport Proteins / Q000502:physiology*; D010710:Phosphates / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000096:biosynthesis; D011755:Pyrophosphatases / Q000096:biosynthesis; D012038:Regeneration / Q000235:genetics*
chemical_list: D011756:Diphosphates; C513308:Dmp1 protein, mouse; D016326:Extracellular Matrix Proteins; D058574:Integrin-Binding Sialoprotein; D028061:Phosphate Transport Proteins; D010710:Phosphates; C410982:ank protein, mouse; D053495:Osteopontin; C107241:diphosphoric acid; D010727:Phosphoric Diester Hydrolases; C065962:ectonucleotide pyrophosphatase phosphodiesterase 1; D011755:Pyrophosphatases