Gene expression changes in an early stage of intervertebral disc degeneration induced by passive cigarette smoking.
METHODS
This study attempts to determine the molecular changes in intervertebral disc degeneration of rats induced by passive cigarette smoking.


OBJECTIVE
To quantitate and compare the gene expression levels in intervertebral discs from passively cigarette smoking rats and nonsmoking rats.


BACKGROUND
The molecular mechanism of intervertebral disc degeneration has been investigated mainly in vitro but little in vivo, and gene expression analysis has been performed in a few studies. The cigarette smoking is a risk factor of low back pain. We developed a smoking box to create a rat model of intervertebral disc degeneration induced by passive cigarette smoking.


METHODS
Total RNA was extracted from intervertebral discs of rats that were raised in a cigarette-smoking box for 2 to 7 weeks. After synthesis of cDNA, the quantitative analysis of gene expression was performed by the real-time PCR. The remaining spines were subjected to the histologic examination.


RESULTS
Histologic changes of the nucleus pulposus and the anulus fibrosus were detected after 2 weeks of smoking and were frequently found after 7 weeks. Collagen genes were downregulated remarkably after 7 weeks of smoking. No significant increase was observed in the expressions of matrix metalloproteinase-3, but the expression of tissue inhibitor of metalloproteinases-1 started to increase at 4 weeks of smoking. Aggrecan also started to be up-regulated at 4 weeks.


CONCLUSIONS
Changes in gene expression by passive cigarette smoking precede the histologic changes in the intervertebral discs. Reactions to suppress the destruction of tissue matrix and to regenerate the intervertebral discs are occurring at the same time as the degenerative histologic changes.
Uei
Hiroshi
H
Department of Orthopaedic Surgery, Nihon University School of Medicine, Tokyo, Japan.
Matsuzaki
Hiromi
H
Oda
Hiroshi
H
Nakajima
Shinya
S
Tokuhashi
Yasuaki
Y
Esumi
Mariko
M
D000818:Animals; D003094:Collagen / Q000235:genetics* / Q000378:metabolism; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects*; D020869:Gene Expression Profiling; D019570:Inhalation Exposure; D007403:Intervertebral Disc / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D007405:Intervertebral Disc Displacement / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D008297:Male; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000235:genetics* / Q000378:metabolism; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
D012333:RNA, Messenger; D019715:Tissue Inhibitor of Metalloproteinase-1; D014028:Tobacco Smoke Pollution; D003094:Collagen