title: Retinoic acid is a potential negative regulator for differentiation of human periodontal ligament cells.
abstract: OBJECTIVE
  Retinoic acid (RA) exerts a wide variety of effects on development, cellular differentiation and homeostasis in various tissues. However, little is known about the effects of RA on the differentiation of periodontal ligament cells. In this study, we investigated whether RA can affect the dexamethasone-induced differentiation of periodontal ligament cells.
  
  
  RESULTS
  Human periodontal ligament cells were differentiated via culturing in the presence of dexamethasone, ascorbic acid, and beta-glycerophosphate for mineralized nodule formation, as characterized by von Kossa staining. Continuous treatment with all-trans-RA inhibited the mineralization in a dose-dependent manner, with complete inhibition over 1 microm RA. Other RA analogs, 9-cis-RA and 13-cis-RA, were also effective. Furthermore, addition of RA for just the first 4 days completely inhibited the mineralization; however, as RA was added at later stages of culture, the inhibitory effect was diminished, suggesting that RA had a phase-dependent inhibition of mineralization. RA receptor (RAR)-alpha agonist (AM-580), but not retinoid X receptor agonist (methoprene acid), inhibited the mineralization, and reverse transcription-polymerase chain reaction analysis revealed that RAR-alpha was expressed on the cells, suggesting that RAR-alpha was involved in the inhibitory mechanism. This inhibition was accompanied by inhibition of alkaline phosphatase activity; however, neither expression of platelet-derived growth factor (PDGF) receptor-alpha, PDGF receptor-beta, or epidermal growth factor (EGF) receptor, nor phosphorylation of extracellular signal-regulated kinases triggered by PDGF-ascorbic acid or PDGF-BB was changed, as assessed by flow cytometry or western blot analyses.
  
  
  CONCLUSIONS
  These findings suggest that RA is a potential negative regulator for differentiation of human periodontal ligament cells.
authors.affiliation: Division of Periodontology and Endodontology, Tohoku University Graduate School of Dentistry, Sendai, Japan.
authors.forename: Natsuko
authors.initials: N
authors.lastname: Shibuya
authors.forename: Eiji
authors.initials: E
authors.lastname: Nemoto
authors.forename: Sousuke
authors.initials: S
authors.lastname: Kanaya
authors.forename: Ryotaro
authors.initials: R
authors.lastname: Kunii
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Shimauchi
mesh_terms: D000077556:Alitretinoin; D000469:Alkaline Phosphatase / Q000032:analysis / Q000037:antagonists & inhibitors; D001205:Ascorbic Acid / Q000494:pharmacology; D001565:Benzoates / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D025021:Cementogenesis / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000032:analysis; D048049:Extracellular Signal-Regulated MAP Kinases / Q000032:analysis; D005994:Glycerophosphates / Q000494:pharmacology; D006801:Humans; D015474:Isotretinoin / Q000494:pharmacology; D010513:Periodontal Ligament / Q000166:cytology / Q000187:drug effects*; D020796:Receptor, Platelet-Derived Growth Factor alpha / Q000032:analysis; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000032:analysis; D018168:Receptors, Retinoic Acid / Q000819:agonists; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors / Q000819:agonists; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000494:pharmacology*; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D001565:Benzoates; D004791:Enzyme Inhibitors; D005994:Glycerophosphates; C000607071:RARA protein, human; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D047488:Retinoid X Receptors; D013764:Tetrahydronaphthalenes; D014157:Transcription Factors; C068073:Am 580; D000077556:Alitretinoin; D014212:Tretinoin; D003907:Dexamethasone; D066246:ErbB Receptors; D020796:Receptor, Platelet-Derived Growth Factor alpha; D020797:Receptor, Platelet-Derived Growth Factor beta; D048049:Extracellular Signal-Regulated MAP Kinases; D000469:Alkaline Phosphatase; D015474:Isotretinoin; D001205:Ascorbic Acid; C031463:beta-glycerophosphoric acid