SMAD7 and liver dysplastic nodule: Lin and co-workers have recently reported functional interactions of miR-21 and TGF-β signalling by confirming that SMAD7, an inhibitor of TGF-β signalling, is a direct target of miR-21 and targets TGF-β by repressing SMAD7 expression, thus preventing rat renal tubular epithelial cell proliferation in an in vitro DN model [44].