Figure 4.

Effect of tumour necrosis factor-alpha (TNF-α) stimulation on interleukin-1 (IL-1) and IL-1 receptor gene expression in normal or degenerate nucleus pulposus (NP) cells. Normal or degenerate NP cells were cultured in alginate pellets and stimulated by the addition of 10 ng/mL IL-1β. Quantitative real-time polymerase chain reaction was used to analyse the effect of cytokine stimulation on gene expressions of IL-1α, IL-1β, IL-1-receptor 1 (IL-1R1) and IL-1-receptor antagonist (IL-1Ra). All samples are relative to the housekeeping gene GAPDH (glyceraldehyde-3-phosphate dehydrogenase) and normalised back to untreated controls. Results are given as mean ± standard error of the mean (n = 3). *P ≤ 0.05 when compared with untreated controls.