NETs are the major upstream trigger of fibrosis of infected venous thrombi. (A) Workflow for thrombus induction, thrombus infection with S aureus, and DNase1 treatment. (B) Thrombus volume as measured by high-frequency ultrasound (HFUS) in control, infected, and DNase1-treated mice (n = 5 mice per group). (C) Blood neutrophil counts, (D) CitH3, (E) extracellular dsDNA, and (F) DNase activity in mouse plasma at different time points post ligation (n = 6-8 mice per group). (G) Representative Ly6G stainings (scale bars, 200 µm) and (H) CitH3 stainings in day 3 thrombus of different groups (n = 3-5 mice per group). Left: lower magnification (scale bars, 200 µm); right: higher magnification (scale bars, 20 µm) of boxed area. Bar graph quantifications are shown right below the respective histochemistry panels. (I) Representative trichrome staining and collagen area relative to total thrombus area (scale bars, 200 µm). (J) qPCR analysis for genes associated with fibrosis (n = 4-6 mice per group) in mouse thrombus at different time points after ligation. Data are represented as mean ± SEM. *P < .05; **P < .01; ***P < .001 (1-way analysis of variance [ANOVA] with Tukey’s post hoc correction). DAPI, 4′,6-diamidino-2-phenylindole; NE, neutrophil elastase.