The Efficacy of Minimally Invasive Implantable Wireless Electrical Stimulation for the Treatment of Stress Urinary Incontinence in a Rat Model

Purpose: Current therapies using midurethral sling mesh to treat stress urinary incontinence (SUI) are often considered insufficient. This study aims to evaluate the therapeutic efficacies of a minimally invasive implantable wireless electrical stimulator as an alternative treatment of SUI.Methods: SUI was induced in 12 female, 12-week-old Sprague-Dawley rats with a deteriorated urethral sphincter complex by mechanical dilatation of the vagina. Six rats underwent sham operations. Four weeks after inducing SUI, 12 rats with SUI were divided into 2 groups. One group received a transplantation of an implantable wireless electrical stimulator, and the other midline incision and suturing. A total of 4 electrical stimulations were applied for 30 minutes twice weekly for 4 weeks in implantation model. Cystometric parameters including leak point pressure, urethral pressure and electromyography, histological examinations, immunostaining for Masson trichrome stain were measured at 4 weeks after intervention.Results: After SUI induction, mean leak point pressure (LPP) was significantly lower in SUI groups than in controls (25.0±6.9 cm H<sub>2</sub>O vs. 62.6±4.1 cm H<sub>2</sub>O, P=0.012). At 4-week postintervention, the +ES group (SUI rat model with stimulation) demonstrated significantly higher LPP than the −ES group (48.8±8.4 cm H<sub>2</sub>O vs. 26.0±6.6 cm H<sub>2</sub>O, P=0.002). Urethral pressure showed a nonsignificant upward trend in the +ES group (SUI rat model without stimulation) compared with −ES (20.5±1.4 cm H<sub>2</sub>O vs. 18.1±1.1 cm H<sub>2</sub>O, P=0.070). Histology showed improved tissue organization with reduced inflammatory infiltration, and Masson staining demonstrated a trend toward higher collagen density in +ES (bladder: 28.3%±5.2% vs. 32.5%±7.6%, P=0.292; urethra: 44.2%±8.6% vs. 51.7%±8.2%, P=0.153).Conclusions: These results indicate that an implantation of a wireless electrical stimulator can help to improve urethral sphincter function in SUI rat model. Moreover, the minimally invasive wireless electrical strategy may represent a promising therapeutic modality for pelvic floor muscle rehabilitation in the treatment of SUI with potential for clinical translation.