Journal
SPINE
Volume 28, Issue 10, Pages 973-981Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1097/00007632-200305150-00004
Keywords
aggrecan; anabolic and catabolic gene expression; collagen; intervertebral disc degeneration; matrix metalloproteinase; mechanobiology; spine biomechanics
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Funding
- NIAMS NIH HHS [1-K01AR02078] Funding Source: Medline
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Study Design. 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. Summary of Background Data. 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 llizarov-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 down-regulation 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.
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