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Spine (Phila Pa 1976). 2004 May 15;29(10):1089-92; discussion 1093.

Interleukin-6 production is upregulated by interaction between disc tissue and macrophages.

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  • 1Department of Orthopedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.

Abstract

STUDY DESIGN:

Interleukin (IL)-6 production was investigated using a coculture system of disc tissue and macrophages.

OBJECTIVES:

The purpose of this study was to investigate the interaction between intervertebral disc tissue and macrophages in terms of IL-6 production.

SUMMARY OF BACKGROUND DATA:

IL-6 production is observed in human herniated disc specimens, and there is a correlation between IL-6 production and neurologic symptoms. However, the mechanism of IL-6 production in the herniated disc is not clear.

MATERIALS AND METHODS:

Coccygeal intervertebral discs and exudated peritoneal macrophages were obtained from male Sprague-Dawley rats. Macrophages and intervertebral disc without endplates were cocultured in a serum-free medium. Fat tissue culture with or without macrophages, intervertebral disc alone, and macrophages alone were used for controls. The supernatant fluid of the culture was utilized for the enzyme-linked immunosorbent assay. The precipitations of macrophages and disc coculture were used for semiquantitative RT-PCR for IL-6. Immunohistochemical staining for IL-6 and the macrophages marker (ED2) were also carried out using disc tissue cultured with macrophages.

RESULTS:

IL-6 production level was significantly increased in the coculture of intervertebral disc and macrophages (P < 0.01). However, there was no significant production of IL-6 in the control groups. The precipitations from coculture of macrophages and disc expressed IL-6 mRNA in semiquantitative RT-PCR. Immunohistochemical staining revealed most IL-6 producing cells were also positive for ED2, which adheres to or infiltrates the peripheral area of the nucleus pulposus.

CONCLUSIONS:

Our results demonstrated that interaction between disc tissue and macrophage is necessary for upregulation of IL-6 production. Immunohistochemical staining also indicated that infiltrated macrophages played a major role in production of IL-6, suggesting that infiltration of macrophages into herniated disc material may be a trigger for IL-6 production and associated neurologic symptoms.

PMID:
15131434
[PubMed - indexed for MEDLINE]
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