title: Smad2 overexpression induces alveolar bone loss and up regulates TNF-α, and RANKL.
abstract: OBJECTIVE
  The aim of the current study was to investigate whether Smad2 overexpression in JE cells induced alveolar bone loss, and to understand the mechanisms regulating the bone loss.
  
  
  METHODS
  A mouse line was created that used a cytokeratin 14 (K14) promoter to overexpress Smad2 in the epithelium of the transgenic mice (K14-Smad2). Micro CT radiographs (μCT) were used to assess bone loss, bone volume, and bone density. The expression of Tnfα, Il1-β, Ifγ, Rankl, and Opg were assessed by RT-PCR. Western blots were used to detect the protein levels of TNF-α and IL1-β. Tartrate-resistant acid phosphatase (TRAP) was used as a marker for osteoclasts. Wild type (WT) mice were used as controls in all steps of the current study.
  
  
  RESULTS
  K14-Smad2 mice had 52.5% (±4.2) root exposed compared to 32.4%(±3.2) in the WT mice. There was a significant difference in alveolar bone volume in the K14-Smad2 mice when compared to WT mice 2.65mm3(±0.3) and 4.3mm3(±0.35) respectively. K14-Smad2 mice also had reduced bone density 696.8mg/cc (±70) at 12 months when compared to WT mice 845.9mg/cc(±10). The mRNA levels of Tnfα and Rankl increased by 3.26- and 2.5-fold respectively in the K14-Smad2 mice when compared to controls. The protein level of TNF-α was also significantly increased to 2.8-fold in K14-Smad2 mice when compared to WT mice. Smad2 overexpression increased the total numbers of osteoclasts in K14-Smad2 mice (3.4±0.2)-fold when compared to WT mice.
  
  
  CONCLUSIONS
  Smad2 overexpression induces alveolar bone loss and increases the numbers of osteoclasts. Also, Smad2 overexpression up-regulates TNF-α and RANKL.
authors.affiliation: Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Canada; Advanced Education in General Dentistry, Prince Abdulrahman Advanced Dental Institute, Kingdom of Saudi Arabia, Saudi Arabia.
authors.forename: Mazen K
authors.initials: MK
authors.lastname: Alotaibi
authors.affiliation: Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Canada.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Kitase
authors.affiliation: Department of Oral Biological and Medical Sciences, Faculty of Dentistry, University of British Columbia, Canada. Electronic address: cshuler@dentistry.ubc.ca.
authors.forename: Charles F
authors.initials: CF
authors.lastname: Shuler
mesh_terms: D016301:Alveolar Bone Loss / Q000000981:diagnostic imaging / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D015519:Bone Density; D005838:Genotype; D053583:Interleukin-1beta / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D053244:Osteoprotegerin / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D051899:Smad2 Protein / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D015854:Up-Regulation; D055114:X-Ray Microtomography
chemical_list: D053583:Interleukin-1beta; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger; D051899:Smad2 Protein; D014409:Tumor Necrosis Factor-alpha
keywords: IL1-β; Junctional epithelium; OPG; Rankl; TNFα; Transforming factor beta