To investigate the potential role of TGFβ signalling in this model, we employed a highly selective, ATP-competitive activin receptor-like kinase 5 (ALK5; also known as TGF-βRI) inhibitor, SB525334, which has a proven therapeutic effect in single-hit models of experimental pulmonary fibrosis (Bonniaud et al., 2005; Scotton et al., 2013). This evidence concerns the gene TGFB1 and pulmonary fibrosis.