Fig. 2

HMGB1 promoted NOD2 expression and macrophage activation. A, B Intensity score of HMGB1 in osteoarthritic and non-osteoarthritic synovial tissue (scale bar = 100 μm) (n = 3 in Ctrl group, n = 6 in mild OA group, and n = 4 in severe OA group). C NOD2 expression at mRNA level in response to HMGB1. D TNF-α expression at mRNA level in response to HMGB1. E Enhanced secretion of TNF-α from macrophages in response to HMGB1. F Increased TNF-α expression at protein level in macrophages stimulated by HMGB1. G HMGB1-induced translocation of p65 from cytoplasm to nucleus. H Activation of NF-κB and MAPK pathway in macrophages upon HMGB1 stimulation. I M1 polarization of macrophages induced by HMGB1. *p < 0.05, **p < 0.01, and ***p < 0.001. Data were presented as boxplots (center line, median; box limits, 25 to 75th percentiles; whiskers, min to max), or mean ± s.e.m. values. n = 3 biologically independent replicates for in vitro experiments. Kruskal–Wallis test followed by Dunn’s multiple comparisons test for ODS scores of IHC images and two-way ANOVA with Bonferroni’s test for PCR