SERPINE1 and pulmonary fibrosis: To determine whether deletion of PAI‐1 specifically in ATII cells protects mice from bleomycin‐induced lung fibrosis, 8‐ to 10‐week‐old CKO and wild‐type (PAI‐1fl/fl) mice were injected with tamoxifen, challenged with 2 U/kg bleomycin, and euthanized 14 days after bleomycin instillation.