CDKN1A and pulmonary fibrosis: To this aim, we induced lung fibrosis in mice by administration of bleomycin (BLM) (1.5 u/kg), or PBS vehicle as a control, to wild-type (WT) or p21 knockout (p21−/−) (Deng et al, 1995) 8-week-old female mice by a single intra-tracheal installation (Aoshiba et al, 2003).