Impaired MSC differentiation by MRTF-A knockdown. (a) Expression of MRTF-A and myofibroblastic marker genes upon TGF-β1 treatment (24 h) following transient knockdown by MRTF-A siRNA (siMRTF-A) or control siRNA (siCtrl.). The relative mRNA amounts were determined by quantitative RT-PCR, normalized to the starved siCtrl. Error bars correspond to SEM (n = 4). Asterisks indicate significant differences (*p ≤ 0.05) according to an unpaired Student’s t test. (b) Western blot of MRTF-A, α-SMA and calponin 1 in lentivirally transduced MRTF-A knockdown MSC of three individual donors. Control infected cells (shCtrl.) as well as MRTF-A knockdown cells obtained by three independent shRNA constructs (#41, #77, #78) were treated with TCM or TGF-β1 (TGF) for 48 h. The relative protein amounts were normalized to α-tubulin signals. For quantification, data were normalized to the value for the starved shCtrl., which was set to 1. Shown are averages of 3 individual donor MSC. Error bars correspond to SD (n = 3). Asterisks indicate significant differences (*p ≤ 0.05) according to a one-way ANOVA with Dunnett’s multi comparison test (post-hoc).