Effect of tensile force on expression of PTHrP and thickness of hypertrophic zone in organ-cultured mouse spheno-occipital synchondroses

Arch Oral Biol. 2008 Jul;53(7):690-9. doi: 10.1016/j.archoralbio.2008.02.004. Epub 2008 Mar 17.

Abstract

Objective: Responses of spheno-occipital synchondroses to direct tensile stress have not been identified before. This study was, therefore designed to evaluate expression of PTHrP, and thickness of hypertrophic zone in spheno-occipital synchondroses in response to such stress, using mouse in vitro model.

Methods: Spheno-occipital synchondroses together with adjacent structures were excised from fifty-five 2-day-old mice that were randomly assigned to 6 control and 5 experimental groups for 5 experimental periods (n=5). In the experimental groups, tensile force of 0.2g was applied across the synchondroses, using helical springs. In 5 control groups, the springs were made inactive. Both groups were then cultured for 6, 24, 48, 72 h and 7 days. Another control group was cultured without any springs for 7 days to compare with natural growth of the synchondroses from a group of five 9-day-old mice. Alcian blue-PAS staining was used to study growth of the synchondroses; immunohistochemical staining to identify PTHrP and type X collagen expression. The area of PTHrP expression and thickness of hypertrophic zone, demarcated by type X collagen expression, were measured.

Results: Quantitative analysis showed that PTHrP expression increased significantly at hour 24 of the force application in the experimental group (p<0.05), then reduced from hour 24 to 72 with a significant drop from hour 24 to 48 (p<0.01); and the thickness of hypertrophic zone significantly increased at hour 48 (p<0.01).

Conclusions: Our findings suggested that the growth of spheno-occipital synchondroses could be modified by tensile stress; and a light continuous force could enhance its growth, as evidenced by an increase in PTHrP expression and thickness of hypertrophic zone.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Proliferation
  • Chondrocytes / cytology
  • Chondrocytes / metabolism*
  • Chondrogenesis / physiology*
  • Gene Expression
  • Hypertrophy / genetics
  • Hypertrophy / metabolism
  • Mice
  • Mice, Inbred BALB C
  • Occipital Bone / anatomy & histology
  • Occipital Bone / growth & development*
  • Organ Culture Techniques
  • Osteogenesis / physiology*
  • Parathyroid Hormone-Related Protein / genetics
  • Parathyroid Hormone-Related Protein / metabolism*
  • Skull Base / anatomy & histology
  • Skull Base / growth & development
  • Sphenoid Bone / anatomy & histology
  • Sphenoid Bone / growth & development*
  • Stress, Mechanical
  • Tensile Strength / physiology
  • Up-Regulation / physiology

Substances

  • Parathyroid Hormone-Related Protein