Tnfa , Il6 , Cxcl1 , and Adam8 Genes Are the Early Markers After Mouse Tail Intervertebral Disc Injury.

OBJECTIVES: The early molecular events after intervertebral disc injury remain unclear. In this study, we aimed to compare inflammatory markers from 1 day to 4 wks after injury to have a comprehensive understanding of the intervertebral disc response to injury. DESIGN: Mouse tail intervertebral disc injury was induced by a needle puncture. Inflammatory marker gene expression and morphological changes were recorded at 1 day, 1 wk, and 4 wks after injury. RESULTS: Tnfa , Il6 , and Cxcl1 gene expression peaked at day 1 post-needle puncture of the mouse intervertebral disc, Adam8 gene expression peaked at 1-wk time point, while Tipe2 gene expression was upregulated at week 4 postinjury. F4/80 positive cells, likely to be macrophages, are present as early as day 1 in the injured intervertebral discs and consistently present at week 4 postinjury. Loss of Safranin O staining and increased histological scores of the injured intervertebral discs are consistent with progressive degeneration after injury. CONCLUSIONS: Inflammatory cytokines including Tnfa precede Tipe2 , suggesting that Tipe2 is likely induced by Tnfa . Upregulation of Adam8 and Cxcl1 gene expression persisted at week 4, suggesting that they play a role in the transition to chronic phase of intervertebral disc degeneration.

Expression of Human Interleukin 8 in Mice Alters Their Natural Behaviors.

Objective: To examine the effects of human interleukin (IL) 8 expression on mouse behavior. Methods: A mouse line expressing human IL8 in the intervertebral discs (IVD) and cartilaginous tissues (hIL8+ ) was generated. Mouse spontaneous behaviors, including locomotion, climbing, rearing, grooming, eating, drinking, and immobility were recorded with a fully automatic, non-invasive platform. Results: Distance traveled by the hIL8+ mice declined with age compared with control littermates, and male hIL8+ mice traveled a shorter distance than male controls and females of either genotype (p <0.05). The hIL8+ mice also spent less time in locomotion than control mice (p <0.01), and male hIL8+ mice spent the least amount of time and had lowest count in locomotion compared with the other 3 groups at 12 weeks of age or greater (p <0.05). The hIL8+ mice spent less time climbing than controls, and male mice spent less time climbing than female mice of the same genotype (p <0.01). The hIL8+ mice spent more time eating and less time drinking than controls, and all mice spent less time eating and more time drinking with increasing age. Finally, hIL8+ mice spent more time immobile than controls, and male hIL8+ mice spent more time immobile than any other group (p <0.05). Conclusion: The hIL8+ mice, especially hIL8+ males, showed reduced ambulation and climbing. Mice showed age-related decrease in eating and increase in drinking and grooming time that was also influenced by expression of hIL8. These changes in natural behaviors in control mice are consistent with functional decline with age. Effects of hIL8 superimposed on the natural aging process could involve systemic (e.g., on the brain) and local (e.g., in the spine and joint tissues) mechanisms. Future exploration of these mechanisms might be productive.