A mouse model of simulated birth trauma induced stress urinary incontinence

Aims: To facilitate future applications of transgenic or knockout technologies in studies of simulated birth trauma induced stress urinary incontinence (SUI), we aimed to create a mouse model of SUI and explore the possible pathogenesis of this condition. Methods: Thirty female C57BL/6 mice were randomly distributed into five groups. Four groups underwent vaginal distention (VD) for 1 hr, using a modified 6-Fr. Foley catheter with a balloon dilated to 0.3, 0.2, or 0.1 ml or sham distention. Four days after VD, all mice underwent leak-point pressure (LPP) measurement via an implanted suprapubic tube (SPT). The normal control group only had SPT placement and LPP measurement. After sacrifice, the urethras of the mice were harvested for routine histological examination and nerve staining. Results: LPPs were significantly lower in groups after VD with 0.3- or 0.2-ml balloon than in control and sham distention groups (10.29 +/- 6.70, 14.65 +/- 6.51, 37.78 +/- 5.10, and 30.30 +/- 5.30 cm H2O, respectively). There were no significant differences in LPP between control and sham groups. Histology showed no significant differences in urethral striated muscle among the five groups. The density of immunoreactive neurofilaments in the urethra decreased after VD with 0.3- or 0.2-ml balloon. Conclusion: As a model of birth trauma, VD can induce SUI in female mice, the severity of which is related to intravaginal balloon size. Partial urethral denervation plays a plausible role in the pathogenesis of SUI. This novel mouse model could be used for further mechanistic studies of female SUI.