title: EphB-EphrinB interaction controls odontogenic/osteogenic differentiation with calcium hydroxide.
abstract: BACKGROUND
  Calcium hydroxide is used in direct pulp capping of uncontaminated exposed vital pulps caused by mechanical or traumatic injury. Calcium hydroxide creates a high alkaline pH environment and initiates a mineralized tissue formation in the pulp. The exact mechanism by which calcium hydroxide induces the reparative dentin formation is unknown. Because Eph receptors and ephrin ligands play a role in pulp stem cell migration and proliferation, our hypothesis is that calcium hydroxide-related odontogenic/osteogenic differentiation may be associated with Eph-ephrin interaction. The aim of this study was to investigate whether Eph-ephrin interaction regulates odontogenic/osteogenic differentiation with calcium hydroxide.
  
  
  METHODS
  Primary pulp cells were harvested from the molars of C57BL/6 mice. The cells were treated with calcium hydroxide. Immunofluorescence was used to detect protein expression. A knockout of the ephrinB1 or EphB2 gene was performed with short hairpin RNAs. Cell migration, proliferation, and gene expression were then analyzed.
  
  
  RESULTS
  Calcium hydroxide stimulated EphB2 gene expression but suppressed ephrinB1 gene expression at the proliferation stage. However, calcium hydroxide stimulated both ephrinB1 and EphB2 gene expression at the differentiation stage. In addition, EphB2 localized at ephrinB1-positive cells at the area of Dentin sialoprotein (DSP) staining, which increased with calcium hydroxide treatment. Knockdown of ephrinB1-EphB2 significantly suppressed cell proliferation. Additionally, knockdown of the ephrinB1 gene caused cell migration, whereas a lack of the EphB2 gene suppressed calcium hydroxide-induced mineralization from primary pulp cells.
  
  
  CONCLUSIONS
  EphrinB1-EphB2 interaction contributes to calcium hydroxide-induced odontogenic/osteogenic differentiation. This observation is the first finding of the mechanism of calcium hydroxide-induced odontogenic/osteogenic differentiation.
authors.affiliation: Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, New York; Department of Preventive Dentistry, Peking University School and Hospital of Stomatology, Beijing, China.
authors.forename: Xiaozhe
authors.initials: X
authors.lastname: Wang
authors.forename: George
authors.initials: G
authors.lastname: Jong
authors.forename: Louis M
authors.initials: LM
authors.lastname: Lin
authors.forename: Emi
authors.initials: E
authors.lastname: Shimizu
mesh_terms: D000468:Alkalies; D000818:Animals; D002113:Calcification, Physiologic / Q000187:drug effects; D002126:Calcium Hydroxide / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D003782:Dental Pulp / Q000166:cytology* / Q000187:drug effects; D003809:Dentin, Secondary / Q000187:drug effects; D036387:Ephrin-B1 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D016326:Extracellular Matrix Proteins / Q000187:drug effects; D055786:Gene Knockout Techniques; D006863:Hydrogen-Ion Concentration; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009805:Odontogenesis / Q000187:drug effects / Q000502:physiology*; D010012:Osteogenesis / Q000187:drug effects / Q000502:physiology*; D010750:Phosphoproteins / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D036183:Receptor, EphB2 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012795:Sialoglycoproteins / Q000187:drug effects; D013234:Stem Cells / Q000187:drug effects / Q000502:physiology*; D000099311:Dentin Sialophosphoprotein
chemical_list: D000468:Alkalies; D002126:Calcium Hydroxide; D036387:Ephrin-B1; D016326:Extracellular Matrix Proteins; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D036183:Receptor, EphB2; D012795:Sialoglycoproteins; D000099311:Dentin Sialophosphoprotein; C586311:Ephb2 protein, mouse
keywords: Calcium hydroxide; Eph; ephrin; primary pulp cells; pulp capping