A microarray analysis of miRNAs revealed that 18 miRNAs were significantly downregulated in IPF lung tissue, including let-7d located in epithelial cells, whose decrease is associated with increased mesenchymal proteins such as N-cadherin, vimentin, and α-smooth muscle actin (α-SMA) (Pandit et al., 2010). The gene discussed is ACTA1; the disease is idiopathic pulmonary fibrosis.