Fig. 1.

Reduced TGFβ bioactivity of SSc serum on primary human fibroblasts. Primary human fibroblasts expressing a SMAD3-dependent luciferase construct (CAGA₁₂-luc) were stimulated with serum (a) or acidified serum (b) of SSc (n = 10) or age- and sex-matched controls (n = 10) for 16 h, and luciferase activity was measured. Using these results, TGFβ latency was calculated (c). A TGFβ1/2/3 neutralizing antibody was added to both normal and acidified serum to demonstrate the contribution of TGFβ to bioassay readout (c). Primary human fibroblasts expressing a SMAD1/5-dependent luciferase construct (BRE-luc) were stimulated with serum (e) or acidified serum (f) of SSc (n = 10) or age- and sex-matched controls (n = 10) for 16 h, and luciferase activity was measured. Using these results, BMP latency was calculated (g). Statistics of a, b, e, and f were calculated using t tests and of d using ANOVA