Recently, it was reported that miRNAs may play pivotal regulatory role also in the fibrotic processes ongoing in the lung: the downregulation of let-7 d in idiopathic pulmonary fibrosis (IPF) resulted in the pro-fibrotic effects [109] . Also, upregulation of miR-21 was reported in the lungs of IPF patients and in the murine lungs with bleomycin-induced fibrosis, whereas miR-21 expression was enhanced by pro-fibrotic TGF-β1 [110] . Another disease associated with miRNA change was cystic fibrosis. Downregulation of miR-126 was detected in cystic fibrosis bronchial epithelial cells and its expression correlated with upregulation of TOM1 mRNA both in vitro and in vivo [111] . TOM1, a miR-126 target, was reported to be involved in the regulation of innate immune responses through its involvement in the TLR2/4 and IL-1β and TNF-α-induced signalling pathways [111] .