title: Activation and dynamic expression of Notch signalling in dental pulp cells after injury in vitro and in vivo.
abstract: OBJECTIVE
  To investigate the expression pattern of Notch signalling in odontoblast-like cells stimulated by lipopolysaccharide (LPS) in vitro, and in injured rat dental pulp in vivo.
  
  
  METHODS
  Mouse odontoblast-like cells (MDPC-23) were exposed to LPS. Expression of Notch-related genes was detected by real-time PCR. A rat pulpitis model was established by mechanical injury and LPS plus mechanical injury was followed by the analysis of expression of Notch2 by immunohistochemical staining. One-way analysis of variance (anova) was performed to examine the effect of differing concentrations of LPS on cell proliferation, and least significant difference test was used for paired comparisons. For independent sample, t-test was performed to compare the expression of Notch signalling genes between LPS group and control group in vitro.
  
  
  RESULTS
  The in vitro study revealed the proliferation of MDPC-23 cells on exposure to 10 ng mL-1to 1 μg mL-1LPS. Expression of Notch1 and Notch2 was significantly higher in the LPS group than that in the control group on day 1 and day 3 (P ˂ 0.05). The levels of both Delta1 and Jagged1 were higher in the study group than in the control group on day 3 (P = 0.019 and P = 0.034) and day 5 (P ˂ 0.001 and P = 0.046), respectively. In addition, Hes1 levels were significantly higher in the study group than in the control group on day 5 (P = 0.005). The in vivo study demonstrated positive staining for Notch2, both in the mechanical injury (MI) group and in the LPS plus mechanical injury (LMI) group from day 3 to day 7, which showed very weak or absent staining on day 14, thereby demonstrating the dynamic nature of the change.
  
  
  CONCLUSIONS
  Both in vitro and in vivo activation and dynamic expression of Notch signalling in dental pulp cells after injury were found. Notch signalling activation by LPS stimulation or mechanical injury showed a similar pattern in vivo.
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Operative Dentistry & Endodontics, The Fourth Military Medical University, Xi'an, China.
authors.forename: L
authors.initials: L
authors.lastname: Ma
authors.affiliation: Department of Preventive Dentistry, School of Stomatology, The Fourth Military Medical University, Xi'an, China.
authors.forename: S C
authors.initials: SC
authors.lastname: Wang
authors.affiliation: Department of Preventive Dentistry, School of Stomatology, The Fourth Military Medical University, Xi'an, China.
authors.forename: J
authors.initials: J
authors.lastname: Tong
authors.affiliation: Department of Preventive Dentistry, School of Stomatology, The Fourth Military Medical University, Xi'an, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Operative Dentistry & Endodontics, The Fourth Military Medical University, Xi'an, China.
authors.forename: Y Q
authors.initials: YQ
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Military Stomatology, Department of Operative Dentistry & Endodontics, The Fourth Military Medical University, Xi'an, China.
authors.forename: Q
authors.initials: Q
authors.lastname: Yu
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003782:Dental Pulp / Q000166:cytology* / Q000293:injuries / Q000378:metabolism; D005260:Female; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D009804:Odontoblasts / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D051883:Receptor, Notch2 / Q000502:physiology; D051880:Receptors, Notch / Q000502:physiology*
chemical_list: D008070:Lipopolysaccharides; C497766:Notch2 protein, rat; D051883:Receptor, Notch2; D051880:Receptors, Notch
keywords: Notch signalling; dental pulp injury; dynamic expression; lipopolysaccharide; odontoblast