Upregulation of FSTL1 expression induced by inflammatory mediators in fibroblast-like synoviocytes (FLSs) from patients with RA. (A) RA FLSs (n = 6) were treated with the indicated stimuli for 24 hours or were left untreated (medium). FSTL1 mRNA was determined using RT-PCR. The results are presented in relative units, and the P values derived from paired t-tests are indicated for each comparison. (B) FLSs from two RA patients (RA1 and RA2) were stimulated by combined IL-1β and TNFα or by TGFβ, or they were left untreated for 36 hours or 72 hours. Cell lysates were collected and analyzed by Western blot analysis using the anti-FSTL1 polyclonal antibody. β-Actin was used as a loading control. FSTL1, follistatin-like protein 1; RA, rheumatoid arthritis; PCR, polymerase chain reaction; IL-1β, interleukin-1β; TNFα, tumor necrosis factor α; TGFβ, transforming growth factor β; LPS, lipopolysaccharide; bLP, bacterial lipoprotein; PIC, polyinosinic:polycytidylic acid.