The effect of tumor necrosis factor-alpha (TNF-α) on collagen gel contraction. (a) Images of the three-dimensional collagen gel contraction assay shown are representative of all (Table 1) independently performed experiments. Three collagen gels of each group are shown before (day 6) and after (day 8) releasing the gels from the culture plates, revealing distinct differences in gel contraction in the groups upon TNF-α and infliximab (IFX) or diclofenac (Diclo) coincubation. White circles in the first rows of the plates illustrate the margins of the gels comprising the gel surface areas. (b) Gel surfaces of the floating gels in the presence or absence of TNF-α (1 and 10 ng/mL), the TNF-α inhibitor IFX (10 μg/mL), or diclofenac (10 μg/mL) were scanned and calculated as described in Materials and methods. Data are representative of 10 (Table 1) independently performed TNF-α ± IFX experiments and three independently performed TNF-α ± diclofenac experiments with four replicate measurements from each individual patient sample (n = 52 for the 'control' and 'TNF-α 10 ng/mL' groups, n = 12 for the 'TNF-α 10 ng/mL+diclofenac' group, and n = 40 for all other groups). Results are plotted as fold changes of the respective samples in the control group according to the paired non-parametric Wilcoxon test used for the statistical analysis. **P < 0.01, ***P < 0.001.