SMAD3 and atrial fibrillation: PCR profiling array of fibroblasts incubated with AF, SR or control medium and later treated with either mocetinostat or anti-miR-21 showed that inhibition of miR-21 reversed the activation of the pro-fibrotic transcripts with the exception of Smad3 and restored the expression of the TGF-β pathway inhibitors smad7 and decorin (Figure 4B).