IL-17A induces fibrosis and inflammation in vitro. (A) Effect of recombinant IL-17A on control and frozen shoulder fibroblasts viability, BCL2 gene expression, and mitochondrial and cytosolic cytochrome C content, mean ± SD, n = 4 control fibroblasts and n = 5 frozen shoulder fibroblasts, * indicates significant difference from untreated cells, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001, # indicates significant difference from control fibroblasts, #P < 0.05, ##P < 0.01. (B) Effect of IL-17A on COL3A1, FN1, MMP1, MMP3 gene expression and MMP3 protein secretion. mRNA gene expression expressed as fold change following normalization to housekeeping gene (GAPDH) and then to relevant untreated cells, n = 4 control fibroblasts and n = 5 frozen shoulder fibroblasts, * indicates significant difference from untreated cells *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001, # indicates significant difference from control fibroblasts, #P < 0.05, ##P < 0.01 ###P < 0.001. (C) Effect of IL-17A on IL-6, IL-8, CCL20 production from control or frozen shoulder fibroblasts, n = 4 control fibroblasts and n = 5 frozen shoulder fibroblasts, * indicates significant difference from untreated cells *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001, # indicates significant difference from control fibroblasts, #P < 0.05, ##P < 0.01 ###P < 0.001. All statistical analyses use two-way ANOVA with Dunnet’s correction or Sidak’s test for multiple comparisons.