title: Mandibular functional positioning only in vertical dimension contributes to condylar adaptation evidenced by concomitant expressions of L-Sox5 and type II collagen.
abstract: OBJECTIVE
  Concerted expressions of L-Sox5 and type II collagen play an important part in osteogenic transition in epiphyseal cartilage. This study was designed to elucidate the role of mandibular vertical functional positioning in condylar adaptive remodelling by examining L-Sox5 and type II collagen expressions in condylar cartilage.
  
  
  METHODS
  40 female Sprague-Dawley rats at age of 5 weeks were randomly divided into the experimental (n=20) and control groups (n=20). Bite plates were fitted on the upper posterior teeth of the experimental animals to induce functional repositioning of mandible in vertical dimension. The animals in both experimental and matched control groups were sacrificed on days 3, 6, 9 and 12, respectively. Tissue sections were cut in the sagittal plane through the mandibular condyles and processed with histomorphological examination for cellular response and immunohistochemical test for expressions of L-Sox5 and type II collagen. Quantitative assessment was conducted with computer-assisted imaging system to reveal the correlation between these two factors.
  
  
  RESULTS
  (1) Both L-Sox5 and type II collagen were expressed in prechondroblastic cells and chondroblastic cells. (2) When mandible was downward positioned, the amount of L-Sox5 expression was significantly higher by 16.1% (day 9) and 24.2% (day 12) than that of the control (P<0.05); Similarly, type II collagen expression in the experimental group was also significantly stronger by 9.3% (day 9) and 12.3% (day 12) than control group (P<0.05), indicating an enhanced osteogenic transition occurring in condylar cartilage. (3) There was a similarity in temporospatial patterns between the expressions of these two factors, indicating their integral functions in facilitating condylar adaptation.
  
  
  CONCLUSIONS
  It is suggested that L-Sox5 plays a key role in adaptive remodelling of condylar cartilage resulting from downward positioning of the mandible. Integration with type II collagen enables L-Sox5 to induce osteogenic transition and consequently to encourage endochondral ossification.
authors.affiliation: Department of Orthodontics, School of Stomatology, Ninth People's Hospital, Shanghai Jiao Tong University, Shanghai, China.
authors.forename: Feng Ting
authors.initials: FT
authors.lastname: Chu
authors.forename: Guo Hua
authors.initials: GH
authors.lastname: Tang
authors.forename: Zheng
authors.initials: Z
authors.lastname: Hu
authors.forename: Yu Fen
authors.initials: YF
authors.lastname: Qian
authors.forename: Gang
authors.initials: G
authors.lastname: Shen
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D016022:Case-Control Studies; D024043:Collagen Type II / Q000378:metabolism*; D005260:Female; D006132:Growth Plate / Q000378:metabolism*; D008335:Mandibular Condyle / Q000378:metabolism / Q000502:physiology*; D010012:Osteogenesis / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D055755:SOXD Transcription Factors / Q000378:metabolism*; D014716:Vertical Dimension
chemical_list: D024043:Collagen Type II; C490301:SOX5 protein, human; D055755:SOXD Transcription Factors