SMAD7 and idiopathic pulmonary fibrosis: A systematic review on overlapping miRNA signatures in SSc and idiopathic pulmonary fibrosis (IPF), including miR-21, was conducted by Bagnato et al. Since miR-21 exerts putative functions impacting the extracellular matrix, collagen expression, and Smad7 expression, the authors summarized the data on miR-21 and SSc fibrosis [57,58].