The strong induction by TGF-β1 of AQP1 expression specially observed in AECs (A549) in transition to a myofibroblast-like phenotype cell, or in the fibroblasts derived from an IPF patient (LL29), might be among the initial actions triggered by this potent fibrotic agent. This evidence concerns the gene TGFB1 and idiopathic pulmonary fibrosis.