Figure 1

FSTL1 increases expression and excretion of inflammatory cytokines in cultured OA FLS. (A) Cultured FLSs were treated with FSTL1 (dissolved in PBS solution) in different concentration (1 μg/ml or 5 μg/ml) for 24 hrs. (B) Cultured FLSs were stimulated with 5 μg/ml FSTL1 for two different durations (24 or 48 hrs). In (A) and (B), total RNA was extracted and reverse transcribed, and the relative levels of TNF-α, IL-1β and IL-6 mRNA were analyzed by real-time PCR. The relative level of mRNA expression was normalized to the level of housekeeping gene GAPDH expression, and presented as fold changes relative to the control (the level of the control was set as 1). (C-E) Cell supernatant was collected from the cultures treated with 5 μg/ml FSTL1 for 48 hrs. TNF-α, IL-1β and IL-6 concentrations were measured by ELISA. The above results are presented as mean ± (standard deviation) SD of three independent experiments (each FLS line from an individual OA patient was used for each experiment). ^* P <0.05, ^** P <0.01, ^*** P <0.001, compared to the control (the vehicle-treated group), Student t test. ELISA, enzyme-linked immunosorbent assay; FLS, fibroblast-like synoviocyte; FSTL1, follistatin-like protein 1; IL-1β, interleukin-1β; IL-6, interleukin-6; OA, osteoarthritis; PBS, phosphate-buffered saline; TNF-α, tumor necrosis factor alpha.