Effects of immobilization and dynamic compression on intervertebral disc cell gene expression in vivo.
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.
MacLean
Jeffery J
JJ
Department of Mechanical Engineering, University of Vermont, Burlington 05405-0156, USA.
Lee
Cynthia R
CR
Grad
Sibylle
S
Ito
Keita
K
Alini
Mauro
M
Iatridis
James C
JC
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
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