title: Factors regulating endochondral ossification in the spheno-occipital synchondrosis.
abstract: OBJECTIVE
  To identify the temporal pattern of core-binding factor alpha1 (Cbfa1) and vascular endothelial growth factor (VEGF) expressions in the spheno-occipital synchondrosis in vitro with and without tensile stress.
  
  
  METHODS
  Sixty male BALB/c mice were randomly divided into an experimental group (with tensile stress) and a control group (without tensile stress) at each of five time points. Animals were sacrificed and the cranial base synchondroses were aseptically removed. In the experimental groups, mechanical stress was applied on the surgical explants with helical springs and incubated as organ culture for 6, 24, 48, 72, and 168 hours. In the control group, the springs were kept at zero stress. Tissue sections were subjected to immunohistochemical staining for quantitative analysis of Cbfa1 and VEGF expression.
  
  
  RESULTS
  Quantitative analysis revealed that Cbfa1 and VEGF expressions reached a peak increase at 24 and 48 hours, respectively. Compared with the control groups, both Cbfa1 and VEGF were expressed consistently higher in the experimental groups at all time points.
  
  
  CONCLUSIONS
  Mechanical stress applied to the spheno-occipital synchondrosis elicits Cbfa1 expression and subsequently up-regulates the expression of VEGF. Increased levels of expression of both factors could play a role in the growth of the spheno-occipital synchondrosis.
authors.affiliation: Department of Orthodontics, University of Hong Kong, Hong Kong, China.
authors.forename: Wai Yip
authors.initials: WY
authors.lastname: Lei
authors.forename: Ricky W K
authors.initials: RW
authors.lastname: Wong
authors.forename: A B M
authors.initials: AB
authors.lastname: Rabie
mesh_terms: D000818:Animals; D019902:Chondrocytes / Q000378:metabolism*; D020219:Chondrogenesis / Q000502:physiology; D050659:Core Binding Factor Alpha 1 Subunit / Q000096:biosynthesis*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009777:Occipital Bone / Q000254:growth & development; D009924:Organ Culture Techniques; D010006:Osteoblasts / Q000378:metabolism; D010012:Osteogenesis / Q000502:physiology*; D019291:Skull Base / Q000254:growth & development*; D013100:Sphenoid Bone / Q000254:growth & development; D013314:Stress, Mechanical; D013718:Tensile Strength; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis*
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D042461:Vascular Endothelial Growth Factor A