SERPINE1 and pulmonary fibrosis: Reconstitution of PAI-1–/–:VTN–/– mice with PAI-1RR, as in the AEC2 injury model, worsened lung fibrosis as assessed by hydroxyproline (Figure 2C) and lung histologic analysis that revealed more extensive fibrotic lesions in H&E- and Picrosirius red–stained sections (Figure 2D).