Fig. 2
Dickkopf-related protein 1 (DKK1) levels in human umbilical vein endothelial cell (HUVEC) synovial fibroblast co-cultures. a DKK1 release from tumour necrosis factor (TNF)-α + interferon (IFN)-γ-treated endothelial cells cultured alone (none; n = 7) or with synovial fibroblasts from non-inflamed joints (n = 4), patients with resolving rheumatoid arthritis (RA; n = 5) or patients with very early rheumatoid arthritis (VeRA; n = 5). Significantly higher DKK1 levels were observed in the supernatant of VeRA-HUVEC co-cultures than HUVEC alone (p < 0.01). No statistical differences were found between the different co-culture constructs. Data are shown as mean and standard error of the mean. Kruskal-Wallis test with Dunn’s post-test analysis were performed. **p < 0.01. b Photomicrographs showing lymphocyte adhesion to (i) endothelial cells cultured alone, with fibroblasts from (ii) patients with resolving RA or (iii) patients with VeRA in response to TNF-α + IFN-γ treatment. The number of adherent lymphocytes was averaged per field and is expressed per square millimetre per 106 cells perfused. Arrows indicate adherent lymphocytes. c DKK1 release positively correlated with lymphocyte adhesion to cytokine-treated co-cultures (p = 0.0054). Correlation assessed by Spearman’s test with a non-parametric correlation coefficient of r = 0.7129. Each independent experiment incorporated a different donor for all cell types