title: Combined degenerative and regenerative remodeling responses of the mandibular condyle to experimentally induced disordered occlusion.
abstract: BACKGROUND
  The purposes of this research were to investigate the long-term responses of mandibular condylar cartilage to experimentally induced disordered occlusion and to evaluate changes in the expression of the SDF-1/CXCR4 axis.
  
  
  METHODS
  Experimentally induced disordered occlusions were created in 8-week-old female Sprague-Dawley rats by orthodontic methods. After 24 weeks, remodeling of the mandibular condylar cartilage was assessed by hematoxylin and eosin staining. Protein and mRNA expression of SDF-1, CXCR4, MMP9, IL6, OPG, and RANKL were investigated by means of immunohistochemical staining and real-time polymerase chain reaction.
  
  
  RESULTS
  Obvious cartilage degenerative remodeling responses were observed; they appeared as uneven distributions of cellular disposition, loss of cartilage surface integrity, and cell-free areas. Regenerative responses presenting as thickening of the whole and the calcified cartilage layers in the experimental group were also observed. Compared with the age-matched controls, the protein and mRNA levels of SDF-1, CXCR4, MMP9, IL6, and OPG, but not RANKL, were increased in the experimental group (all, P <0.05). In addition, the mRNA level of RANKL/OPG showed a decreasing trend in the experimental group compared with the age-matched controls (P = 0.052).
  
  
  CONCLUSIONS
  This study demonstrated that long-term experimentally induced disordered occlusion leads to a combined response in degeneration and regeneration of mandibular cartilage, accompanied by active interaction of the SDF-1/CXCR4 axis and local upregulation of MMP9, IL6, and OPG.
authors.affiliation: Postgraduate student, Department of Orthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Kuang
authors.forename: Juan
authors.initials: J
authors.lastname: Dai
authors.forename: Qing-Yu
authors.initials: QY
authors.lastname: Wang
authors.forename: Rong
authors.initials: R
authors.lastname: Song
authors.forename: Kai
authors.initials: K
authors.lastname: Jiao
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Xiao-Guang
authors.initials: XG
authors.lastname: Tian
authors.forename: Yin-Zhong
authors.initials: YZ
authors.lastname: Duan
authors.forename: Mei-Qing
authors.initials: MQ
authors.lastname: Wang
mesh_terms: D000818:Animals; D016723:Bone Remodeling; D002358:Cartilage, Articular / Q000378:metabolism* / Q000473:pathology*; D054377:Chemokine CXCL12 / Q000378:metabolism; D005260:Female; D015850:Interleukin-6 / Q000378:metabolism; D008310:Malocclusion / Q000150:complications*; D008335:Mandibular Condyle / Q000503:physiopathology*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D010003:Osteoarthritis / Q000209:etiology / Q000473:pathology*; D053244:Osteoprotegerin / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D019718:Receptors, CXCR4 / Q000378:metabolism; D012038:Regeneration; D013705:Temporomandibular Joint Disorders / Q000209:etiology / Q000473:pathology*
chemical_list: C575935:CXCL12 protein, rat; D054377:Chemokine CXCL12; C486264:Cxcr4 protein, rat; D015850:Interleukin-6; D053244:Osteoprotegerin; D053245:RANK Ligand; D019718:Receptors, CXCR4; D020780:Matrix Metalloproteinase 9