title: Long-term effects of simulated childbirth injury on function and innervation of the urethra.
abstract: OBJECTIVE
  Pudendal nerve and external urethral sphincter (EUS) injury during vaginal delivery are risk factors for stress urinary incontinence (SUI). Although most patients with short-term postpartum SUI regain continence within 1 year, they have a higher predisposition to develop recurrent SUI years later, suggesting a possible mechanistic relationship. In contrast, animal models generally recover spontaneously and have not been studied much in the long term. The aim of this study was to investigate the long-term effects of simulated childbirth injury in rats.
  
  
  METHODS
  Thirty-four Sprague-Dawley female rats underwent sham injury or pudendal nerve crush and vaginal distension (PNC + VD), a simulated childbirth injury. Nine weeks later, leak point pressure (LPP) and EUS electromyography (EMG) were recorded simultaneously. The pudendal nerve was harvested for histological analysis. EUS neuromuscular junctions (NMJs) and their innervation were qualitatively assessed using immunofluorescence. A t-test was used to compare quantitative outcomes between groups, with P < 0.05 indicating a significant difference.
  
  
  RESULTS
  There was no significant difference in LPP or EUS EMG amplitude or firing rate between the two groups. Nonetheless after PNC + VD, NMJs in the EUS were diffuse and were innervated by tortuous and multiple axons, demonstrating that reinnervation of the EUS was still in progress.
  
  
  CONCLUSIONS
  Although continence function recovered 9 weeks after simulated childbirth injury, innervation of EUS was not complete at this time point, suggestive of persistent neurogenic deficiency which when compounded by the effects of aging may lead to a delayed recurrence of SUI in this animal model with increased age.
authors: Department of Biomedical Engineering, The Cleveland Clinic, Cleveland, Ohio; Department of Urology, Changhai Hospital, The Second Military Medical University, Shanghai, People's Republic of China; Advanced Platform Technology Rehabilitation R&D Center of Excellence, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio.
authors: Qi-Xiang
authors: QX
authors: Song
authors: Brian M
authors: BM
authors: Balog
authors: James
authors: J
authors: Kerns
authors: Dan Li
authors: DL
authors: Lin
authors: Yinghao
authors: Y
authors: Sun
authors: Margot S
authors: MS
authors: Damaser
authors: Hai-Hong
authors: HH
authors: Jiang
mesh_terms: D000200:Action Potentials; D000818:Animals; D004106:Dilatation; D004195:Disease Models, Animal; D004576:Electromyography; D005260:Female; D009409:Nerve Crush; D009416:Nerve Regeneration; D009469:Neuromuscular Junction / Q000503:physiopathology*; D036801:Parturition; D059348:Peripheral Nerve Injuries / Q000209:etiology / Q000503:physiopathology*; D011247:Pregnancy; D011312:Pressure; D060525:Pudendal Nerve / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D017207:Rats, Sprague-Dawley; D020127:Recovery of Function; D013997:Time Factors; D014521:Urethra / Q000294:innervation*; D014550:Urinary Incontinence, Stress / Q000209:etiology / Q000503:physiopathology*; D014621:Vagina / Q000294:innervation / Q000503:physiopathology / Q000601:surgery*
keywords: electromyography; morphology; neuromuscular junction; pudendal nerve; rat; urethra; urinary incontinence