Established senescence biomarkers, including p16, p21 and senescence-associated β-galactosidase activity (SA-β-gal), have been observed in both fibroblasts and epithelial cells in human IPF lung tissue12, 13, and human IPF cells show increased senescence propensity ex vivo14. This evidence concerns the gene CDKN2A and idiopathic pulmonary fibrosis.