ADAR1-p110 and ADAR1-p150 regulate the processing of the pri-miR-Let-7d and mature Let-7d in such a way that the sub-expression of the latter deregulated, in turn, the expression of COL3A1 and SMAD2, proteins involved in the development of idiopathic pulmonary fibrosis. This evidence concerns the gene SMAD2 and idiopathic pulmonary fibrosis.