title: Effect of PGE₂ induced by compressive and tensile stresses on cementoblast differentiation in vitro.
abstract: OBJECTIVE
  The aim of the study was to clarify the mechanisms underlying orthodontically induced root resorption by characterizing the role of PGE(2) induced by compressive stress (CS) and tensile stress (TS) on cementoblast metabolism in vitro.
  
  
  METHODS
  Mouse cementoblast cell line OCCM-30 was continuously stimulated with 0.2 KPa CS or 5.0 KPa TS. COX-2 mRNA expression and PGE(2) production were thus quantified. In addition, cells were treated with COX-2 inhibitor and the role of PGE(2) induced by CS or TS on the expression of genes related to cementoblast differentiation was examined. PGE(2) receptors mRNA expression induced by CS or TS was also evaluated. Moreover, cells were treated with exogenous PGE(2) and the role of PGE(2) concentration on matrix mineralization was verified.
  
  
  RESULTS
  CS and TS enhanced COX-2 mRNA expression and PGE(2) production. PGE(2) synthesis, however, was markedly induced by CS. Gene expression of bone morphogenetic protein 2 (BMP-2), osteocalcin (OCN) and receptor activator for nuclear factor kappaB ligand (RANKL) was enhanced by CS on an endogenous PGE(2)-mediated manner. Osteoprotegerin (OPG) expression was not affected by CS. Meanwhile, TS up-regulated the expression of BMP-2 and alkaline phosphatase (ALP) on an endogenous PGE(2)-mediated manner. TS down-regulated RANKL mRNA expression, whilst OPG expression was not affected. Moreover, EP4 mRNA expression was considerably enhanced by TS. Regarding PGE(2) concentration, only cells treated with low concentration presented anabolic response.
  
  
  CONCLUSIONS
  Gene expression was differentially regulated according to the type of mechanical stimulation applied to cementoblasts. In addition, it is shown that PGE(2) plays an important role on mediating cementoblast mechanosensitivity.
authors.affiliation: Department of Orthodontics and Craniofacial Developmental Biology, Hiroshima University Graduate School of Biomedical Sciences, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan. emanuelbraga@hotmail.com
authors.forename: Emanuel Braga
authors.initials: EB
authors.lastname: Rego
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Inubushi
authors.forename: Aki
authors.initials: A
authors.lastname: Kawazoe
authors.forename: Mutsumi
authors.initials: M
authors.lastname: Miyauchi
authors.forename: Eiji
authors.initials: E
authors.lastname: Tanaka
authors.forename: Takashi
authors.initials: T
authors.lastname: Takata
authors.forename: Kazuo
authors.initials: K
authors.lastname: Tanne
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000096:biosynthesis; D002454:Cell Differentiation / Q000235:genetics; D002461:Cell Line, Transformed; D025021:Cementogenesis / Q000235:genetics*; D051546:Cyclooxygenase 2 / Q000096:biosynthesis; D003739:Dental Cementum / Q000166:cytology* / Q000378:metabolism* / Q000502:physiology; D003799:Dental Stress Analysis; D015232:Dinoprostone / Q000096:biosynthesis / Q000502:physiology*; D005786:Gene Expression Regulation; D040542:Mechanotransduction, Cellular; D051379:Mice; D008822:Mice, Transgenic; D015675:Osteocalcin / Q000096:biosynthesis; D010812:Physical Stimulation; D053245:RANK Ligand / Q000096:biosynthesis; D043562:Receptors, G-Protein-Coupled / Q000096:biosynthesis / Q000502:physiology; D012391:Root Resorption / Q000209:etiology; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques / Q000009:adverse effects
chemical_list: D055396:Bone Morphogenetic Protein 2; D053245:RANK Ligand; D043562:Receptors, G-Protein-Coupled; D015675:Osteocalcin; D051546:Cyclooxygenase 2; D015232:Dinoprostone