A. AT-MSCs were pretreated with a TGFβRI inhibitor SB431542 at 10 µM, or control DMSO for 1 h, and subsequently exposed to r.h. TGF-β1 at indicated concentrations. The cells were cultured for another 24 h and harvested for miR-21 assay. The expression of miR-21 was normalized on RNU6B. Data is given as mean ± SEM of three independent experiments. 