Fig. 1. The expression of Nrf2 in human nucleus pulposus (NP) tissues.

a Real-time RT-PCR analysis showed expression level of Nrf2 mRNA decreased with the severity of IVD degeneration. b Gene expression of Nrf2 was negatively correlated with the Pfrrmann grades of 48 human NP tissues (n = 60, r = −0.623). c Representative western blot of Nrf2 in human NP tissue (n = 12, 3 for each grade of IVD). d Densitometry analysis of at least three western blot experiments shown in (c). e Immunohistochemistry of the human NP sections showed that the numbers of Nrf2-positive cells were decreased with IVD degeneration. Grade 2 represents non-degenerated IVD, whereas grades 3, 4, and 5 signify mild, moderate, and severe degeneration, respectively. Values are shown as the mean and standard deviation (SD). *P < 0.05, bars = 100 μm