AIM:This study was performed to investigate the impact of neutrophil extracellular traps(NETs)on scar formation following urethral trauma.METHODS:(1)Clinical samples were derived from patients of Department of Urology,The First Affiliated Hospital of Fujian Medical University,from June 2021 to December 2022.Levels of NETs in the blood and urine were compared between patients with urethral trauma(n=20)and those without urethral trauma(controls,n=20).The relationship between NETs and scar formation was analyzed.(2)Urethral fibroblasts were isolated from urethral scar tissues,and neutrophils were induced to produce NETs in vitro.The urethral fibroblasts were treated with normal saline,0.5 mg/L NETs,or 1.5 mg/L NETs to investigate the effects of NETs on activation and collagen syn-thesis of urethral fibroblasts.Additionally,a rabbit model of urethral trauma was established and the animals were dioided into four groups to explore the therapeutic potential of deoxyribonuclease I(DNase I)in preventing urethral scar forma-tion:control,operation + transforming growth factor-β1(TGF-β1),operation + normal saline,and operation+DNase I.RESULTS:The level of NETs in urine increased after urethral trauma(P<0.05),but the level of NETs in blood did not change(P>0.05).In the animal models,the urethral scar became more severe as the level of NETs in the urine increased(P<0.05).At the cellular level,NETs promoted the viability,migration,and collagen synthesis of urethral fibroblasts(P<0.05)..Additionally,urethral injection of DNase I after trauma reduced the level of NETs and inhibited the formation of urethral scar tissue in the animal models(P<0.05).CONCLUSION:Infiltration of NETs promotes activation of urethral fibroblasts and scar formation after urethral trauma.