Fig. 1

Induction of ROS level in IVD degeneration. a Mid-sagittal T2-weighted MRI findings of IVDs 2 months after the puncture confirm lower signal intensity than that of the sham group. b Compared with the sham group, the ratio of the high-intensity area to IVD areas was significantly decreased by needle puncture. c Hematoxylin and eosin (H/E) staining shows smaller NP and less-organized lamellae of AF in the punctured group. Scale bars, 300 μm. d Real-time RT-PCR analysis. mRNA expression of TNFα, MMP-3, and COX-2 was significantly induced in the AF of the punctured model, whereas that of aggrecan tended to be reduced. Data presented as mean ± SD of three independent experiments performed in triplicate (n = 3). e Numbers of nitrotyrosine-positive cells were increased in AF of the punctured model, correlated with elevated expression of TNFα and IL-1β. Scale bars, 100 μm. f Western blotting and densitometry analysis. The protein expression level of nitrotyrosine was significantly higher as well as TNFα and IL-1β in the rat degenerative model. g Immunohistochemistry of human degenerative disc samples with each grade including healthy disc. Scale bars, 100 μm. h More than grade 3 degenerative discs had significantly higher frequency of nitrotyrosine-positive cells compared with healthy disc. *p <0.05. COX cyclooxygenase, IL interleukin, MMP matrix metalloprotease, ns not significant, TNF tumor necrosis factor