title: Effects of immobilization and dynamic compression on intervertebral disc cell gene expression in vivo.
abstract: METHODS
  An in vivo analysis of the intervertebral disc's cellular response to dynamic compression and immobilization was performed using a rat-tail model.
  
  
  OBJECTIVE
  To assess the effects of immobilization and short-term dynamic compression on intervertebral disc cell expression of anabolic and catabolic genes.
  
  
  BACKGROUND
  Static compressive loads applied in vivo alter the composition of the disc matrix and cell viability in a dose-dependent manner. The effects of in vivo dynamic compression, which is a more physiologic load, and reported risk factor for low back pain have not been investigated.
  
  
  METHODS
  An Ilizarov-type device was implanted on the rat tail and used to determine the effects from 72 hours of immobilization (n = 6), 2 hours of dynamic compression (1 MPa/0.2 Hz) (n = 8), and the coupled effect of immobilization followed by compression (n = 8). Real-time reverse transcription-polymerase chain reaction was used to measure changes in anabolic and catabolic gene levels relative to both internal control subjects and a sham-operated group (n = 7).
  
  
  RESULTS
  Immobilization and dynamic compression affect anabolic and catabolic genes, with an overall downregulation of types 1 and 2 collagen and upregulation of aggrecanase, collagenase, and stromelysin in the anulus. The effects of immobilization and compression appear to be additive for collagen types 1 and 2 in the anulus, but not in the nucleus, and not for catabolic genes.
  
  
  CONCLUSIONS
  Short-duration dynamic compression and immobilization alter gene expression in the rat disc. In studying the response of the disc to loading, it is necessary to look at both anabolic and catabolic pathways, and to consider strain history.
authors.affiliation: Department of Mechanical Engineering, University of Vermont, Burlington 05405-0156, USA.
authors.forename: Jeffery J
authors.initials: JJ
authors.lastname: MacLean
authors.forename: Cynthia R
authors.initials: CR
authors.lastname: Lee
authors.forename: Sibylle
authors.initials: S
authors.lastname: Grad
authors.forename: Keita
authors.initials: K
authors.lastname: Ito
authors.forename: Mauro
authors.initials: M
authors.lastname: Alini
authors.forename: James C
authors.initials: JC
authors.lastname: Iatridis
mesh_terms: D053674:Aggrecans; D000818:Animals; D001696:Biomechanical Phenomena / Q000295:instrumentation; D024042:Collagen Type I / Q000235:genetics; D024043:Collagen Type II / Q000235:genetics; D017364:Collagenases / Q000235:genetics; D010450:Endopeptidases / Q000235:genetics; D016326:Extracellular Matrix Proteins; D020869:Gene Expression Profiling; D007103:Immobilization; D007403:Intervertebral Disc / Q000166:cytology / Q000378:metabolism*; D037181:Lectins, C-Type; D019278:Matrix Metalloproteinase 3 / Q000235:genetics; D011509:Proteoglycans / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: C508321:Acan protein, rat; D053674:Aggrecans; D024042:Collagen Type I; D024043:Collagen Type II; D016326:Extracellular Matrix Proteins; D037181:Lectins, C-Type; D011509:Proteoglycans; D012333:RNA, Messenger; D010450:Endopeptidases; D017364:Collagenases; D019278:Matrix Metalloproteinase 3; C083641:aggrecanase