Dual simulated childbirth injuries result in slowed recovery of pudendal nerve and urethral function

Contribution of pudendal nerve injury to stress urinary incontinence in a male rat model

Urinary incontinence is a common complication following radical prostatectomy, as the surgery disturbs critical anatomical structures. This study explored how pudendal nerve (PN) injury affects urinary continence in male rats. In an acute study, leak point pressure (LPP) and external urethral sphincter electromyography (EMG) were performed on six male rats with an intact urethra, the urethra exposed (UE), the PN exposed (NE), and after PN transection (PNT). In a chronic study, LPP and EMG were tested in 67 rats 4 days, 3 weeks, or 6 weeks after sham PN injury, PN crush (PNC), or PNT. Urethras were assessed histologically. Acute PNT caused a significant decrease in LPP and EMG amplitude and firing rate compared to other groups. PNC resulted in a significant reduction in LPP and EMG firing rate 4 days, 3 weeks, and 6 weeks later. EMG amplitude was also significantly reduced 4 days and 6 weeks after PNC. Neuromuscular junctions were less organized and less innervated after PNC or PNT at all timepoints compared to sham injured animals. Collagen infiltration was significantly increased after PNC and PNT compared to sham at all timepoints. This rat model could facilitate preclinical testing of neuroregenerative therapies for post-prostatectomy incontinence.

Effects of mesenchymal stem cells and heparan sulfate mimetics on urethral function and vaginal wall biomechanics in a simulated rat childbirth injury model

INTRODUCTION AND HYPOTHESIS

New treatments are needed for pelvic floor disorders. ReGeneraTing Agent® (RGTA®) is a promising regenerative therapy. Therefore, the objective of this study was to compare regenerative abilities of mesenchymal stem cells (MSCs) and RGTA® on regeneration after simulated childbirth injury in rats.

METHODS

Rats underwent pudendal nerve crush and vaginal distension (PNC+VD) or sham injury. Rats that underwent PNC+VD were treated intravenously with vehicle, MSCs or RGTA® 1 h, 7 days, and 14 days after surgery. Sham rats received 1 ml vehicle at all time points. After 21 days, urethral function and pudendal nerve function were tested. Vaginal tissues were harvested for biomechanical testing and histology. Biaxial testing was performed to measure tissue stiffness.

RESULTS

PNC+VD decreased urethral and pudendal nerve function compared with sham. Vaginal wall stiffness was significantly decreased in longitudinal and transverse tissue axes after PNC+VD compared with sham. MSC or RGTA® did not restore urethral or pudendal nerve function. However, MSC treatment resolved loss in vaginal wall stiffness in both tissue axes and improved collagen content within the vaginal wall. RGTA® treatment increased vaginal wall anisotropy by increasing relative stiffness in the longitudinal direction. PNC+VD (with vehicle or MSCs) enhanced elastogenesis, which was not observed after RGTA® treatment.

CONCLUSIONS

Treatment with MSCs facilitated recovery of vaginal wall biomechanical properties and connective tissue composition after PNC+VD, whereas treatment with RGTA® resulted in anisotropic biomechanical changes. This indicates that MSCs and RGTA® promote different aspects of vaginal tissue regeneration after simulated childbirth injury.

VEGF overexpressed mesoangioblasts enhance urethral and vaginal recovery following simulated vaginal birth in rats

Vaginal birth causes pelvic floor injury which may lead to urinary incontinence. Cell therapy has been proposed to assist in functional recovery. We aim to assess if intra-arterial injection of rat mesoangioblasts (MABs) and stable Vascular Endothelial Growth Factor (VEGF)-expressing MABs, improve recovery of urethral and vaginal function following simulated vaginal delivery (SVD). Female rats (n = 86) were assigned to either injection of saline (control), allogeneic-MABs (MABs^allo), autologous-MABs (MABs^auto) or allogeneic-MABs transduced to stably expressed VEGF (MABs^allo-VEGF). One hour after SVD, 0.5 × 10⁶ MABs or saline were injected into the aorta. Primary outcome was urethral (7d and 14d) and vaginal (14d) function; others were bioluminescent imaging for cell tracking (1, 3 and 7d), morphometry (7, 14 and 60d) and mRNAseq (3 and 7d). All MABs injected rats had external urethral sphincter and vaginal function recovery within 14d, as compared to only half of saline controls. Functional recovery was paralleled by improved muscle regeneration and microvascularization. Recovery rate was not different between MABs^allo and MABs^auto. MABs^allo-VEGF accelerated functional recovery and increased GAP-43 expression at 7d. At 3d we detected major transcriptional changes in the urethra of both MABs^allo and MABs^allo-VEGF-injected animals, with upregulation of Rho/GTPase activity, epigenetic factors and dendrite development. MABS^allo also upregulated transcripts that encode proteins involved in myogenesis and downregulated pro-inflammatory processes. MABs^allo-VEGF also upregulated transcripts that encode proteins involved in neuron development and downregulated genes involved in hypoxia and oxidative stress. At 7d, urethras of MABs^allo-VEGF-injected rats showed downregulation of oxidative and inflammatory response compared to MABS^allo. Intra-arterial injection of MABs^allo-VEGF enhances neuromuscular regeneration induced by untransduced MABs and accelerates the functional urethral and vaginal recovery after SVD.

Analysis of urethral blood flow by high-resolution laser speckle contrast imaging in a rat model of vaginal distension

OBJECTIVE

To investigate the feasibility of laser speckle contrast imaging (LSCI) for monitoring urethral blood flow (UBF).

MATERIALS AND METHODS

In this study, 18 healthy, virgin female Sprague-Dawley rats aged 8-week-old were used. The animals were divided into the sham group (n = 9) and the vaginal distension (VD) group (n = 9). The sham group underwent one catheterization of the vagina without distension and the VD group underwent one VD. Following the VD or sham treatment for one week, LSCI assessment of urethral blood flow was performed during bladder filling and leak point pressure (LPP) process.

RESULTS

During the LPP process, in the VD group, the mean LPP was significantly lower than in the sham group (p < 0.05) and the mean UBF level was also significantly lower than in the sham group (p < 0.05) in the LPP condition. The mean relative change of UBF (Δ Flow) was significantly different between the sham group and VD group. The value was 0.646 ± 0.229 and 0.295 ± 0.19, respectively (p < 0.05). During the bladder filling process, the VD group had a significant lower mean UBF level than the sham group under full bladder conditions (p = 0.008). The mean ΔFlow was also significantly lower than in the sham group. The value was 0.115 ± 0.121 and 0.375 ± 0.127, respectively (p = 0.016).

CONCLUSIONS

The results confirmed that LSCI was able to determine UBF in female rats. The VD group had lower baseline UBF and lower increases in UBF during bladder filling and LPP process compared with the sham group.

Brain-Derived Neurotrophic Factor Is Indispensable to Continence Recovery after a Dual Nerve and Muscle Childbirth Injury Model

In women, stress urinary incontinence (SUI), leakage of urine from increased abdominal pressure, is correlated with pudendal nerve (PN) injury during childbirth. Expression of brain-derived neurotrophic factor (BDNF) is dysregulated in a dual nerve and muscle injury model of childbirth. We aimed to use tyrosine kinase B (TrkB), the receptor of BDNF, to bind free BDNF and inhibit spontaneous regeneration in a rat model of SUI. We hypothesized that BDNF is essential for functional recovery from the dual nerve and muscle injuries that can lead to SUI. Female Sprague-Dawley rats underwent PN crush (PNC) and vaginal distension (VD) and were implanted with osmotic pumps containing saline (Injury) or TrkB (Injury + TrkB). Sham Injury rats received sham PNC + VD. Six weeks after injury, animals underwent leak-point-pressure (LPP) testing with simultaneous external urethral sphincter (EUS) electromyography recording. The urethra was dissected for histology and immunofluorescence. LPP after injury and TrkB was significantly decreased compared to Injury rats. TrkB treatment inhibited reinnervation of neuromuscular junctions in the EUS and promoted atrophy of the EUS. These results demonstrate that BDNF is essential to neuroregeneration and reinnervation of the EUS. Treatments aimed at increasing BDNF periurethrally could promote neuroregeneration to treat SUI.

Brain-Derived Neurotrophic Factor Is an Important Therapeutic Factor in Mesenchymal Stem Cell Secretions for Treatment of Traumatic Peripheral Pelvic Injuries

Traumatic neuromuscular injury to the pudendal nerve and urethra during childbirth does not regenerate well and contributes to stress urinary incontinence in women. Mesenchymal stem cells (MSCs) can improve neuroregeneration via their secretions, or secretome, which includes brain-derived neurotrophic factor (BDNF). In this study, we investigated whether BDNF is a key factor in the secretome of MSCs for the facilitation of functional recovery following a dual simulated childbirth injury. BDNF knockdown (KD) MSCs were created using an anti-BDNF shRNA lentivirus vector. A scrambled sequence was used as a transduction control (scrambled). Cells were cultured for 24 h before media was concentrated 50x to create concentrated conditioned media (CCM) containing MSC secretome. CCM of unmanipulated MSCs was screened for high BDNF expression (high BDNF CCM). Concentrated control media (CM) was created by concentrating media not conditioned by cells. Female Sprague-Dawley rats underwent bilateral pudendal nerve crush and vaginal distension (Injury) or sham injury. One hour and 1 week after injury, sham injured rats received CM, and injured rats received CM, high BDNF CCM, KD CCM, or scrambled CCM (300 μl intraperitoneally). Three weeks after injury, rats underwent leak point pressure (LPP) and pudendal nerve sensory branch potential (PNSBP) recordings. The urethra and pudendal nerve were harvested for anatomical assessment. ANOVA followed by the Student-Newman-Keuls test determined significant differences between groups (p < 0.05). BDNF KD CCM had significantly decreased BDNF concentration compared to scrambled CCM, while the concentration in high BDNF CCM was significantly increased. LPP was significantly decreased in CM and KD CCM treated animals compared to sham injury, but not with scrambled or high BDNF CCM. PNSBP firing rate showed a significant decrease with CM treatment compared to sham injury. Neuromuscular junctions in the urethral sphincter in KD CCM, scrambled CCM, and high BDNF CCM were healthier than CM treated rats. While anatomical and nerve function tests demonstrate regeneration of the pudendal nerve with any CCM treatment, LPP results suggest it takes longer to recover continence with reduced BDNF in CCM. BDNF in MSC CCM is an important factor for the acceleration of recovery from a dual nerve and muscle injury.

Evaluation of Pelvic Floor Muscles in Pregnancy and Postpartum With Non-Invasive Magnetomyography

Objective: To record and characterize features of levator ani muscles (LAM) activity in pregnancy and postpartum using non-invasive and novel Magnetomyography (MMG) technique with amplitude and spectral parameters. Methods: Nulliparous women with uncomplicated pregnancies participated in the MMG data collection during rest and voluntary LAM contractions (Kegels) with modulated intensity in third trimester and approximately 2 months postpartum (PP). Simultaneous surface electromyography was recorded to document the recruitment of accessory muscles. Moderate strength Kegel (MK) MMG trials were analyzed. Amplitude and spectral parameters including root-mean square (RMS) amplitude, power spectrum density (PSD) and normalized PSD (rPSD) in three frequency bands (low, middle, high) were computed on MK epochs. Statistical comparisons between pregnancy and postpartum were calculated. Results: MMG recordings were measured from 10 pregnant women. Results showed decreased RMS and power between third trimester and postpartum, trending towards significance. rPSD values in the low frequency band decreased significantly (p = 0.028) from third trimester to postpartum, while significant increase was observed in the middle frequency band (p = 0.018). Conclusions: This study shows that MMG as non-invasive tool has the ability to detect and characterize changes of LAM activity with amplitude and spectral parameters during pregnancy and postpartum.

Transurethral versus suprapubic catheterization to test urethral function in rats

Transurethral and suprapubic catheterization have both been used to test urethral function in rats; however, it is unknown whether these methods affect urethral function or if the order of catheterization affects the results. The aim of this cross-over designed experiment was to compare the effects of catheterization methods and order on leak point pressure (LPP) testing. LPP and simultaneous external urethral sphincter electromyography (EUS EMG) were recorded in anesthetized female virgin Sprague-Dawley rats in a cross-over design to test the effects of transurethral and suprapubic catheterization. There was no significant difference in peak bladder pressure during LPP testing whether measured with a transurethral or suprapubic catheter. There was no significant difference in peak bladder pressure between the first and second catheter insertions. However, peak EMG firing rate, as well as peak EMG amplitude and EMG amplitude difference between peak and baseline were significantly higher after the first catheter insertion compared to the second insertion, regardless of the catheter method. Our results suggest that route of catheterization does not alter urethral function, e.g. create a functional partial outlet obstruction. Either catheterization method could be used for LPP and/or EUS EMG testing in rats.

Assessment of the strength and electrical activity of the pelvic floor muscles of male-to-female transgender patients submitted to gender-affirming surgery: A case series

AIMS

To assess the strength and electrical activity of the pelvic floor muscles (PFMs) of male-to-female transgender individuals submitted to gender-affirming surgery (GAS).

METHODS

A case series study was conducted from October 2016 to August 2018. Transgender women, who were scheduled for GAS, participated in the study. The volunteers were submitted to a clinical evaluation of the PFM followed by digital palpation (PERFECT method) and electromyography in the preoperative, 15, and 30 days after GAS. They responded to the International Consultation on Incontinence Questionnaire-Urinary Incontinence (UI)-Short Form to evaluate the effect of UI on quality of life and to questions related to the urinary, anorectal, and sexual symptoms. Fifteen days after the GAS, patients were instructed to perform perineal exercises at home, twice a day.

RESULTS

The study sample consisted of 15 transgender women with an average age of 30.6 (SD = 6.7) years. There was a decline in median strength and sustained muscle contraction duration (PERFECT), in the electrical muscle activity (RMSmean and RMSmax) between pre-GAS and 15 days after GAS (p < 0.05). However, there was an increase in these parameters between 15 and 30 days after GAS (p < 0.05). Moreover, six patients exhibited pre-GAS UI, which continued after surgery, with a worsening of urgency symptoms and improvement in nocturia and postmicturition leakage.

CONCLUSION

Strength, sustained muscle contraction duration, and PFM electrical activity may decline 15 days after GAS, returning to pre-GAS values in the first month after surgery.

Bone marrow stem cells secretome accelerates simulated birth trauma-induced stress urinary incontinence recovery in rats

Stress urinary incontinence (SUI) is defined as involuntary urine leakage during physical activities that increase the intra-abdominal pressure on the bladder. We studied bone marrow stem cell (BMSC) secretome-induced activation of anterior vaginal wall (AVW) fibroblasts and its ability to accelerate SUI recovery following vaginal distention (VD) in a rat model of birth trauma using BMSC-conditioned medium (BMSC-CM) and concentrated conditioned medium (CCM). BMSC-CM enhanced the proliferation, migration, and collagen synthesizing abilities of fibroblasts. Differentially expressed genes in BMSC-CM-induced fibroblasts were mainly enriched for cell adhesion, extracellular fibril organization and angiogenesis. Treatment with the JAK2 inhibitor AG490 reversed BMSC-CM-induced activation of the JAK2/STAT4 pathway. Periurethral injection with BMSC-CCM markedly enhanced the abdominal leak point pressure (LPP) in rats after VD. Histological analysis revealed increased numbers of fibroblasts, improved collagen fibers arrangement and elevated collagens content in the AVW of rats receiving BMSC-CCM. These findings suggest the BMSC secretome activates AVW fibroblasts and contributes to the functional and anatomic recovery of simulated birth trauma-induced SUI in rats.

Therapeutic potential of muscle growth promoters in a stress urinary incontinence model

Weakness of urinary sphincter and pelvic floor muscles can cause insufficient urethral closure and lead to stress urinary incontinence. Bimagrumab is a novel myostatin inhibitor that blocks activin type II receptors, inducing skeletal muscle hypertrophy and attenuating muscle weakness. β₂-Adrenergic agonists, such as 5-hydroxybenzothiazolone derivative (5-HOB) and clenbuterol, can enhance muscle growth. We hypothesized that promoting muscle growth would increase leak point pressure (LPP) by facilitating muscle recovery in a dual-injury (DI) stress urinary incontinence model. Rats underwent pudendal nerve crush (PNC) followed by vaginal distension (VD). One week after injury, each rat began subcutaneous (0.3 mL/rat) treatment daily in a blinded fashion with either bimagrumab (DI + Bim), clenbuterol (DI + Clen), 5-HOB (DI + 5-HOB), or PBS (DI + PBS). Sham-injured rats underwent sham PNC + VD and received PBS (sham + PBS). After 2 wk of treatment, rats were anesthetized for LPP and external urethral sphincter electromyography recordings. Hindlimb skeletal muscles and pelvic floor muscles were dissected and stained. At the end of 2 wk of treatment, all three treatment groups had a significant increase in body weight and individual muscle weight compared with both sham-treated and sham-injured rats. LPP in DI + Bim rats was significantly higher than LPP of DI + PBS and DI + Clen rats. There were more consistent urethral striated muscle fibers, elastin fibers in the urethra, and pelvic muscle recovery in DI + Bim rats compared with DI + PBS rats. In conclusion, bimagrumab was the most effective for increasing urethral pressure and continence by promoting injured external urethral sphincter and pelvic floor muscle recovery.

Combined Treatment With CCR1-Overexpressing Mesenchymal Stem Cells and CCL7 Enhances Engraftment and Promotes the Recovery of Simulated Birth Injury-Induced Stress Urinary Incontinence in Rats

Objective: To observe whether urethral injection of chemokine (c-c motif) ligand 7 (CCL7) and overexpressing CC receptor 1 (CCR1) in mesenchymal stem cells (MSCs) can promote their homing and engraftment to the injured tissue, and improve the recovery of simulated birth injury-induced stress urinary incontinence (SUI) in rats.

Methods: Female rats underwent a dual injury consisting of vaginal distension (VD) and pudendal nerve crush (PNC) to induce SUI. Bone marrow-derived MSCs were transduced with lentivirus carrying CCR1 (MSC-CCR1) and green fluorescent protein (GFP). Forty virgin Sprague–Dawley rats were evenly distributed into four groups: sham SUI + MSC-CCR1+CCL7, SUI + MSCs, SUI + MSC-CCR1, and SUI + MSC-CCR1+CCL7 group. The engrafted MSCs in urethra were quantified. Another three groups of rats, including sham SUI + sham MSC-CCR1+CCL7 treatment, SUI + sham MSC-CCR1+CCL7 treatment, and SUI + MSC-CCR1+CCL7 treatment group, were used to evaluate the functional recovery by testing external urethral sphincter electromyography (EUS EMG), pudendal nerve motor branch potentials (PNMBP), and leak point pressure (LPP) 1 week after injury and injection. Urethra and vagina were harvested for histological examination.

Results: The SUI + MSC-CCR1+CCL7 group received intravenous injection of CCR1-overexpressing MSCs and local injection of CCL7 after simulated birth injury had the most engraftment of MSCs to the injured tissues and best functional recovery from SUI compared to other groups. Histological examination showed a partial repair in the SUI + MSC-CCR1+CCL7 group.

Conclusions: Our study demonstrated combined treatment with CCR1-overexpressing MSCs and CCL7 can increase engraftment of MSCs and promote the functional recovery of simulated birth trauma-induced SUI in rats, which could be a new therapeutic strategy for SUI.

Are there relevant animal models to set research priorities in LUTD? ICI-RS 2019

AIM

To discuss animal models of lower urinary tract disorders (LUTD) and their translational impact.

METHODS

Report of discussions based on presented literature-search based reviews relevant for the purpose.

RESULTS

Animal models can be used to investigate fundamental biological mechanisms, but also as tools to elucidate aspects of the pathogenesis of disease and to provide early evidence of any safety risk. Several different models may be required to obtain information that can have a translational impact. The term "translational research" covers not only the process of directly transferring knowledge from basic sciences to human trials to produce new drugs, devices, and treatment options for patients (T1 type translation) but also the implementation of early clinical research findings (phases I-III) into practice to improve care for patients (T2 type). Direct transfer of animal data to T2 is rarely possible, and the process often does not continue after the first trials in humans (phase I). It should be emphasized that many preclinical observations do not have (and do not need to have) immediate translational impact.

CONCLUSIONS

No single animal model can mimic the complexity of the human disease. Still, animal models can be useful for gaining information on LUT function in humans, for elucidating pathophysiological mechanisms, and for the definition of targets for future drugs to treat LUT disorders.

Verification and Defined Dosage of Sodium Pentobarbital for a Urodynamic Study in the Possibility of Survival Experiments in Female Rat

Objectives

To evaluate the effects of pentobarbital dosages on lower urinary tract function and to define an appropriate dosage of sodium pentobarbital that would be suitable for urodynamic studies in which recovery from anesthesia and long term survive were needed for subsequent experiment.

Methods

Twenty-four 8-week-old, female, virgin, Sprague-Dawley rats (200-250 g) were used in this study. Rats in study groups received gradient doses of pentobarbital intraperitoneally, and those in the control group received urethane intraperitoneally. External urethral sphincter electromyography (EUS-EMG) was recorded simultaneously during cystometry and leak point pressure tests. The toe-pinch reflex was used to determine the level of anesthesia.

Results

Micturition was normally induced in both the urethane group and 32 mg/kg pentobarbital group. However, in groups of 40 mg/kg or 36 mg/kg pentobarbital, micturition failed to be induced; instead, nonvoiding contractions accompanied by EUS-EMG tonic activity were observed. There were no significant differences in leak point pressure or EUS-EMG amplitude or frequency between the urethane and 32 mg/kg pentobarbital groups.

Conclusions

This study confirmed significant dose-dependent effects of pentobarbital on lower urinary tract function and 32 mg/kg pentobarbital as an appropriate dosage for recovery urodynamic testing, which enable the achievement of expected essential micturition under satisfactory anesthesia in female rats.

Simulated vaginal delivery causes transients vaginal smooth muscle hypersensitivity and urethral sphincter dysfunction

BACKGROUND

Although pelvic floor dysfunction (PFD) has a multifactorial etiology, pregnancy and childbirth are considered crucial events predisposing to urinary incontinence as well as pelvic organ prolapse, which are highly prevalent. Rats are the most frequently used animal model and pudendal nerve crush (PNC) and vaginal distension (VD) are often used to mimic vaginal delivery.

OBJECTIVE

To document the time course of events after simulated vaginal delivery (SVD) on the urethral sphincter and the vaginal smooth muscle layer.

MATERIALS AND METHODS

Virgin female Sprague-Dawley rats were subjected to SVD (PNC + VD) or sham surgery and evaluated at 7, 14, 21, and 42 days after the injury. Urethral function was determined in vivo by microultrasound during cystometry and vaginal smooth muscle layer was harvested for in vitro pharmacologic investigation by isometric tension recording. Furthermore, vaginal and urethral samples were investigated by immunohistochemistry and real-time quantitative polymerase chain reaction.

RESULTS

Microultrasound showed no bursting of the urethral sphincter in the SVD group at 7 days with a functional recovery starting at 14 days, and normal bursting at 21 and 42 days. Vaginal smooth muscle showed higher sensitivity to carbachol at 14 and 21 days after injury; however, at 42 days, its sensitivity decreased when compared with sham.

CONCLUSION

SVD induces urethral dysfunction and a shift in vaginal smooth muscle contractile responses to carbachol.

Multiple doses of stem cells maintain urethral function in a model of neuromuscular injury resulting in stress urinary incontinence

Stress urinary incontinence (SUI) is more prevalent among women who deliver vaginally than women who have had a cesarean section, suggesting that tissue repair after vaginal delivery is insufficient. A single dose of mesenchymal stem cells (MSCs) has been shown to partially restore urethral function in a model of SUI. The aim of the present study was to determine if increasing the number of doses of MSCs improves urethral and pudendal nerve function and anatomy. We hypothesized that increasing the number of MSC doses would accelerate recovery from SUI compared with vehicle treatment. Rats underwent pudendal nerve crush and vaginal distension or a sham injury and were treated intravenously with vehicle or one, two, or three doses of 2 × 10⁶ MSCs at 1 h, 7 days, and 14 days after injury. Urethral leak point pressure testing with simultaneous external urethral sphincter electromyography and pudendal nerve electroneurography were performed 21 days after injury, and the urethrovaginal complex and pudendal nerve were harvested for semiquantitative morphometry of the external urethral sphincter, urethral elastin, and pudendal nerve. Two and three doses of MSCs significantly improved peak pressure; however, a single dose of MSCs did not. Single, as well as repeated, MSC doses improved urethral integrity by restoring urethral connective tissue composition and neuromuscular structures. MSC treatment improved elastogenesis, prevented disruption of the external urethral sphincter, and enhanced pudendal nerve morphology. These results suggest that MSC therapy for postpartum incontinence and SUI can be enhanced with multiple doses.

Daily bilateral pudendal nerve electrical stimulation improves recovery from stress urinary incontinence

Stress urinary incontinence (SUI) in women is strongly associated with childbirth which injures the pudendal nerve (PN) and the external urethral sphincter (EUS) during delivery. Electrical stimulation (ES) can increase brain-derived neurotrophic factor (BDNF) expression in injured neurons, activate Schwann cells and promote neuroregeneration after nerve injury. The aim of this study was to determine if more frequent ES would increase recovery from SUI in a rat model. Forty female Sprague-Dawley rats underwent either sham injury or pudendal nerve crush (PNC) and vaginal distention (VD) to establish SUI. Immediately after injury, electrodes were implanted at the pudendal nerve bilaterally. Each injured animal underwent sham ES, twice per week ES (2/week), or daily ES of 1 h duration for two weeks. Urethral and nerve function were assessed with leak point pressure (LPP), EUS electromyography and pudendal nerve sensory branch potential (PNSBP) recordings two weeks after injury. LPP was significantly increased after daily ES compared to 2/week ES. EUS neuromuscular junction innervation was decreased after injury with sham ES, but improved after 2/week or daily ES. This study demonstrates that daily bilateral ES to the pudendal nerve can accelerate recovery from SUI. Daily ES improved urethral function more than 2/week ES.

Effect of ASP2205 fumarate, a novel 5-HT2C receptor agonist, on urethral closure function in rats

The pharmacological profile of ASP2205 fumarate (ASP2205), a novel 5-HT_2C receptor agonist, was evaluated in vitro and in vivo. ASP2205 showed potent and selective agonistic activity for the human 5-HT_2C receptor, with an EC₅₀ of 0.85 nM in the intracellular Ca²⁺ mobilization assay. Rat 5-HT_2C receptor was also activated by ASP2205 with an EC₅₀ of 2.5 nM. Intraduodenal administration (i.d.) of ASP2205 (0.1-1 mg/kg) significantly elevated the leak point pressure (LPP) in anesthetized rats in a dose-dependent manner. This ASP2205 (0.3 mg/kg i.d.)-induced LPP elevation was inhibited by SB242084 (0.3 mg/kg i.v.), a selective 5-HT_2C receptor antagonist. Urethral closure responses induced by intravesical pressure loading in rats were enhanced by ASP2205 (0.3 mg/kg i.v.), which was abolished by pretreatment with SB242084 (0.3 mg/kg i.v.) and bilateral transection of the pudendal nerve. In contrast, ASP2205 (0.3 mg/kg i.v.) did not change the resting urethral pressure in rats. These results indicate that ASP2205 can enhance the pudendal nerve-mediated urethral closure reflex via the 5-HT_2C receptor, resulting in the prevention of involuntary urine loss.

Mechanical impact of parturition-related strains on rat pelvic striated sphincters

AIMS

To define the operational resting sarcomere length (Ls ) of the female rat external urethral sphincter (EUS) and external anal sphincter (EAS) and to determine the mechanism of parturition-related injury of EUS and EAS using a simulated birth injury (SBI) vaginal distention model.

METHODS

EUS and EAS of 3-month-old Sprague-Dawley control and injured rats were fixed in situ, harvested, and microdissected for Ls measurements and assessment of ultrastructure. EUS and EAS function was determined at baseline, and immediately and 4 weeks after SBI, using leak point pressure (LPP) and anorectal manometry (ARM), respectively. Operational L s was compared to species-specific optimal L s using one sample Student's t test. Data (mean ± SD) were compared between groups and time points using repeated measures one-way analysis of variance, followed by Tukey's post hoc pairwise comparisons, with significance set to 0.05.

RESULTS

The operational resting Ls of both sphincters (EUS: 2.09 ± 0.07 µm, EAS: 2.02 ± 0.03 µm) was significantly shorter than optimal rat Ls of 2.4 µm. Strains imposed on EUS and EAS during SBI resulted in significant sarcomere elongation and disruption, compared with the controls (EUS: 3.09 ± 0.11 µm, EAS: 3.37 ± 0.09 µm). Paralleling structural changes, LPP and ARM measures were significantly lower immediately (LPP: 21.5 ± 1.0 cmH2 O, ARM: 5.1 ± 2.31 cmH2 O) and 4 weeks (LPP: 27.7 ± 1.3cmH2 O, ARM: 2.5 ± 1.0 cmH2 O) after SBI relative to the baseline (LPP: 43.4 ± 8.5 cmH2 O, ARM: 8.2 ± 2.0 cmH2 O); P < 0.05.

CONCLUSIONS

Analogous to humans, the short resting Ls of rat EUS and EAS favors their sphincteric function. The insult experienced by these muscles during parturition leads to sarcomere hyperelongation, myofibrillar disruption, and dysfunction of the sphincters long-term.

Electrical stimulation of the pudendal nerve promotes neuroregeneration and functional recovery from stress urinary incontinence in a rat model

The pudendal nerve can be injured during vaginal delivery of children, and slowed pudendal nerve regeneration has been correlated with development of stress urinary incontinence (SUI). Simultaneous injury to the pudendal nerve and its target muscle, the external urethral sphincter (EUS), during delivery likely leads to slowed neuroregeneration. The goal of this study was to determine if repeat electrical stimulation of the pudendal nerve improves SUI recovery and promotes neuroregeneration in a dual muscle and nerve injury rat model of SUI. Rats received electrical stimulation or sham stimulation of the pudendal nerve twice weekly for up to 2 wk after injury. A separate cohort of rats received sham injury and sham stimulation. Expression of brain-derived neurotrophic factor (BDNF) and β_II-tubulin expression in Onuf's nucleus were measured 2, 7, and 14 days after injury. Urodynamics, leak point pressure (LPP), and EUS electromyography (EMG) were recorded 14 days after injury. Electrical stimulation significantly increased expression of BDNF at all time points and β_II-tubulin 1 and 2 wk after injury. Two weeks after injury, LPP and EUS EMG during voiding and LPP testing were significantly decreased compared with sham-injured animals. Electrical stimulation significantly increased EUS activity during voiding, although LPP did not fully recover. Repeat pudendal nerve stimulation promotes neuromuscular continence mechanism recovery possibly via a neuroregenerative response through BDNF upregulation in the pudendal motoneurons in this model of SUI. Electrical stimulation of the pudendal nerve may therefore improve recovery after childbirth and ameliorate symptoms of SUI by promoting neuroregeneration after injury.

Fate of mesoangioblasts in a vaginal birth injury model: influence of the route of administration

Currently cell therapy is considered as an experimental strategy to assist the healing process following simulated vaginal birth injury in rats, boosting the functional and morphologic recovery of pelvic floor muscles and nerves. However, the optimal administration route and dose still need to be determined. Mesangioblasts theoretically have the advantage that they can differentiate in skeletal and smooth muscle. We investigated the fate of mesoangioblasts transduced with luciferase and green fluorescent protein reporter genes (rMABseGFP/fLUC) using bioluminescence, immunofluorescence and RT-PCR in rats undergoing simulated birth injury. rMABseGFP/fLUC were injected locally, intravenously and intra-arterially (common iliacs and aorta). Intra-arterial delivery resulted in the highest amount of rMABseGFP/fLUC in the pelvic organs region and in a more homogeneous distribution over all relevant pelvic organs. Sham controls showed that the presence of the injury is important for recruitment of intra-arterially injected rMABseGFP/fLUC. Injection through the aorta or bilaterally in the common iliac arteries resulted in comparable numbers of rMABseGFP/fLUC in the pelvic organs, yet aortic injection was faster and gave less complications.

Controlled release of insulin-like growth factor 1 enhances urethral sphincter function and histological structure in the treatment of female stress urinary incontinence in a rat model

OBJECTIVES

To determine the effects of controlled release of insulin-like growth factor 1 (IGF-1) from alginate-poly-L-ornithine-gelatine (A-PLO-G) microbeads on external urethral sphincter (EUS) tissue regeneration in a rat model of stress urinary incontinence (SUI), as SUI diminishes the quality of life of millions, particularly women who have delivered vaginally, which can injure the urethral sphincter. Despite several well-established treatments for SUI, growth factor therapy might provide an alternative to promote urethral sphincter repair.

MATERIALS AND METHODS

In all, 44 female Sprague-Dawley rats were randomised into four groups: vaginal distension (VD) followed by periurethral injection of IGF-1-A-PLO-G microbeads (VD + IGF-1 microbeads; 1 × 10⁴ microbeads/1 mL normal saline); VD + empty microbeads; VD + saline; or sham-VD + saline (sham).

RESULTS

Urethral function (leak-point pressure, LPP) was significantly lesser 1 week after VD + saline [mean (sem) 23.9 (1.3) cmH₂ O] or VD + empty microbeads [mean (sem) 21.7 (0.8) cmH₂ O) compared to the sham group [mean (sem) 44.4 (3.4) cmH₂ O; P < 0.05), indicating that the microbeads themselves do not create a bulking or obstructive effect in the urethra. The LPP was significantly higher 1 week after VD + IGF-1 microbeads [mean (sem) 28.4 (1.2) cmH₂ O] compared to VD + empty microbeads (P < 0.05), and was not significantly different from the LPP in sham rats, demonstrating an initiation of a reparative effect even at 1 week after VD. Histological analysis showed well-organised skeletal muscle fibres and vascular development in the EUS at 1 week after VD + IGF-1 microbeads, compared to substantial muscle fibre attenuation and disorganisation, and less vascular formation at 1 week after VD + saline or VD + empty microbeads.

CONCLUSION

Periurethral administration of IGF-1-A-PLO-G microbeads facilitates recovery from SUI by promoting skeletal myogenesis and revascularisation. This therapy is promising, but detailed and longer term studies in animal models and humans are needed.

Cell-based secondary prevention of childbirth-induced pelvic floor trauma

With advancing population age, pelvic-floor dysfunction (PFD) will affect an increasing number of women. Many of these women wish to maintain active lifestyles, indicating an urgent need for effective strategies to treat or, preferably, prevent the occurrence of PFD. Childbirth and pregnancy have both long been recognized as crucial contributing factors in the pathophysiology of PFD. Vaginal delivery of a child is a serious traumatic event, causing anatomical and functional changes in the pelvic floor. Similar changes to those experienced during childbirth can be found in symptomatic women, often many years after delivery. Thus, women with such PFD symptoms might have incompletely recovered from the trauma caused by vaginal delivery. This hypothesis creates the possibility that preventive measures can be initiated around the time of delivery. Secondary prevention has been shown to be beneficial in patients with many other chronic conditions. The current general consensus is that clinicians should aim to minimize the extent of damage during delivery, and aim to optimize healing processes after delivery, therefore preventing later dysfunction. A substantial amount of research investigating the potential of stem-cell injections as a therapeutic strategy for achieving this purpose is currently ongoing. Data from small animal models have demonstrated positive effects of mesenchymal stem-cell injections on the healing process following simulated vaginal birth injury.

Smooth Muscle Precursor Cells Derived from Human Pluripotent Stem Cells for Treatment of Stress Urinary Incontinence

There is great interest in using stem cells (SC) to regenerate a deficient urethral sphincter in patients with urinary incontinence. The smooth muscle component of the sphincter is a significant contributor to sphincter function. However, current translational efforts for sphincter muscle restoration focus only on skeletal muscle regeneration because they rely on adult mesenchymal SC as cell source. These adult SC do not yield sufficient smooth muscle cells (SMCs) for transplantation. We may be able to overcome this limitation by using pluripotent stem cell (PSC) to derive SMCs. Hence, we sought to investigate whether smooth muscle precursor cells (pSMCs) derived from human PSCs can restore urethral function in an animal model generated by surgical urethrolysis and ovariectomy. Rats were divided into four groups: control (no intervention), sham saline (surgery + saline injection), bladder SMC (surgery + human bladder SMC injection), and treatment (surgery + pSMC injection, which includes human embryonic stem cell (hESC) H9-derived pSMC, episomal reprogrammed induced pluripotent stem cells (iPSCs)-derived pSMC, or viral reprogrammed iPSC-derived pSMC). pSMCs (2 × 10(6) cells/rat) were injected periurethrally 3 weeks postsurgery. Leak point pressure (LPP) and baseline external urethral sphincter electromyography were measured 5 weeks postinjection. Both iPSC-derived pSMC treatment groups showed significantly higher LPP compared to the sham saline group, consistent with restoration of urethral sphincter function. While the difference between the H9-derived pSMC treatment and sham saline group was not significant, it did show a trend toward restoration of the LPP to the level of intact controls. Our data indicate that pSMCs derived from human PSCs (hESC and iPSC) can restore sphincter function.

Neuroanatomic and behavioral correlates of urinary dysfunction induced by vaginal distension in rats

The aim of the present study was to use a model of simulated human childbirth in rats to determine the damage to genitourinary structures and behavioral signs of urinary dysfunction induced by vaginal distension (VD) in female rats. In experiment 1, the length of the genitourinary tract and the nerves associated with it were measured immediately after simulated human delivery induced by VD or sham (SH) procedures. Electroneurograms of the dorsal nerve of the clitoris (DNC) were also recorded. In experiment 2, histological characteristics of the bladder and major pelvic ganglion of VD and SH rats were evaluated. In experiment 3, urinary parameters were determined in conscious animals during 6 h of dark and 6 h of light before and 3 days after VD or SH procedures. VD significantly increased distal vagina width (P < 0.001) and the length of the motor branch of the sacral plexus (P < 0.05), DNC (P < 0.05), and vesical nerves (P < 0.01) and decreased DNC frequency and amplitude of firing. VD occluded the pelvic urethra, inducing urinary retention, hematomas in the bladder, and thinness of the epithelial (P < 0.05) and detrusor (P < 0.01) layers of the bladder. Major pelvic ganglion parameters were not modified after VD. Rats dripped urine in unusual places to void, without the stereotyped behavior of micturition after VD. The neuroanatomic injuries after VD occur alongside behavioral signs of urinary incontinence as determined by a new behavioral tool for assessing micturition in conscious animals.

A Method for Recording Urethral Pressure Profiles in Female Rats

Aims

Urethral pressure profile (UPP) and leak-point pressure (LPP) measurements as well as external urethral sphincter (EUS) electromyography (EMG) and videourodynamic analyses are the primary methods for evaluating urethral function in humans. However, UPP recording in female rats, a widely used animal model, is challenging due to their small body sizes. This study reports a novel method for recording UPP in female rats.

Materials and Methods

Seventeen anesthetized female rats were studied. LPP data for 14 rats were included. The other 3 rats were excluded because of death or abnormal urogenital organs. UPP curves were recorded using a modified water-perfusion catheter system, with the lateral hole facing the 3-, 6-, 9-, and 12-o’clock positions in a randomized sequence. LPP, functional urethral length (FUL) and maximum urethral closure pressure (MUCP) were analyzed.

Results

The mean LPP was 64.39 ± 20.29 cm H₂O. The mean FUL and MUCP values at the 3-, 6-, 9-, and 12-o’clock positions were 12.90 ± 1.20, 16.70 ± 1.95, 13.90 ± 2.42, and 11.60 ± 0.97 mm, respectively, and 38.70 ± 11.85, 33.90 ± 11.82, 37.40 ± 11.95, and 71.90 ± 23.01 cm H₂O, respectively. The FUL at the 6-o’clock position and MUCP at the 12-o’clock position were significantly greater than those at the other 3 positions. The FUL and MUCP of repeated UPP recordings were not significantly different than those of the first recordings.

Conclusions

UPP recording using a modified method based on a water-perfusion catheter system is feasible and replicable in female rats. It produces UPP curves that sensitively and appreciably reflect detailed pressure changes at different points within the urethra and thus provides opportunity to evaluate urethral structures, especially the urethral sphincter, in detail. These results may enhance the utility of female rat models in research of urinary sphincter mechanisms.

Combination histamine and serotonin treatment after simulated childbirth injury improves stress urinary incontinence

AIMS

Histamine and serotonin-related pharmaceuticals have the potential to modulate micturition and continence. The aim of this study was to determine if treatment with histamine and/or serotonin improves stress urinary incontinence (SUI) in female rats.

METHODS

Twenty-six age-matched female rats underwent pudendal nerve crush and vaginal distension (PNC + VD), to produce SUI. One week after injury, rats were treated subcutaneously with saline, histamine (1.1 μg), serotonin (2μg), or the combination of both twice daily for another week. A sham injured group received sham PNC + VD and were treated with saline (n = 7). Leak point pressure (LPP) testing with simultaneous external urethral sphincter (EUS) electromyography (EMG) was conducted 2 weeks after injury. The urethra was harvested for qualitative and quantitative histology. Data were analyzed with a one-way ANOVA and Student-Newman-Keuls posthoc test with P < 0.05 indicating statistically significant differences between groups.

RESULTS

Combination treatment significantly increased LPP after PNC + VD compared to injured sham treatment and treatment with either histamine or serotonin alone. Compared to injured sham treated rats, all three treatments significantly increased EUS EMG amplitude at both baseline and peak pressure and EUS EMG firing rate at peak pressure during LPP testing. There were more consistent urethral striated muscle fibers and thicker smooth and striated muscle with combination and histamine treatment. There was a statistically significant shift to a greater proportion of thicker collagen fibers in the urethra in serotonin and combination treated rats compared with injured sham treated rats.

CONCLUSIONS

Combination treatment was the most effective and may provide an effective therapy for SUI. Neurourol. Urodynam. 35:703-710, 2016. © 2015 Wiley Periodicals, Inc.

Slings for urinary incontinence and the application of cell-based therapy

The most commonly used technique for the treatment of stress urinary incontinence (SUI) in women is the suburethral polypropylene sling, using either a retropubic or transobturator tape approach This treatment results in a cure rate of over 80%, based on both subjective and objective evaluations. Biological slings have been largely abandoned due to lack of efficacy. Despite the high success rates, 10-20% of women remain incontinent. Cell-based therapy might offer solutions for the future both for the primary setting as for the treatment of failures. Preclinical studies suggest that stem cells (SC) can enhance the recovery of damaged tissue either by direct integration and replacement of damaged tissue (differentiation) or by secreting factors that influence host response mechanisms (paracrine effect). The clinical data to date do not allow strong efficacy conclusions, except that SC therapy seems to be safe in the short term. Most published studies use autologous cells. Allogeneic cell sources need to be investigated as well to allow ready-to-use solutions in the future. Most importantly, we need better insight into the mechanisms of action. We need more basic stem cell research, better acute and chronic animal models, better investigational tools and more efforts using tissue engineering approach.

The future of research in female pelvic medicine

Female pelvic medicine and reconstructive surgery (FPMRS) was recently recognized as a subspecialty by the American Board of Medical Specialties (ABMS). FPMRS treats female pelvic disorders (FPD) including pelvic organ prolapse (POP), urinary incontinence (UI), fecal incontinence (FI), lower urinary tract symptoms (LUTS), lower urinary tract infections (UTI), pelvic pain, and female sexual dysfunction (FSD). These conditions affect large numbers of individuals, resulting in significant patient, societal, medical, and financial burdens. Given that treatments utilize both medical and surgical approaches, areas of research in FPD necessarily cover a gamut of topics, ranging from mechanistically driven basic science research to randomized controlled trials. While basic science research is slow to impact clinical care, transformational changes in a field occur through basic investigations. On the other hand, clinical research yields incremental changes to clinical care. Basic research intends to change understanding whereas clinical research intends to change practice. However, the best approach is to incorporate both basic and clinical research into a translational program which makes new discoveries and effects positive changes to clinical practice. This review examines current research in FPD, with focus on translational potential, and ponders the future of FPD research. With a goal of improving the care and outcomes in patients with FPD, a strategic collaboration of stakeholders (patients, advocacy groups, physicians, researchers, professional medical associations, legislators, governmental biomedical research agencies, pharmaceutical companies, and medical device companies) is an absolute requirement in order to generate funding needed for FPD translational research.

Mesenchymal stem cells and their secretome partially restore nerve and urethral function in a dual muscle and nerve injury stress urinary incontinence model

Childbirth injures muscles and nerves responsible for urinary continence. Mesenchymal stem cells (MSCs) or their secretome given systemically could provide therapeutic benefit for this complex multisite injury. We investigated whether MSCs or their secretome, as collected from cell culture, facilitate recovery from simulated childbirth injury. Age-matched female Sprague-Dawley rats received pudendal nerve crush and vaginal distension (PNC+VD) and a single intravenous (iv) injection of 2 million MSCs or saline. Controls received sham injury and iv saline. Additional rats received PNC+VD and a single intraperitoneal (ip) injection of concentrated media conditioned by MSCs (CCM) or concentrated control media (CM). Controls received a sham injury and ip CM. Urethral and nerve function were assessed with leak point pressure (LPP) and pudendal nerve sensory branch potential (PNSBP) recordings 3 wk after injury. Urethral and pudendal nerve anatomy were assessed qualitatively by blinded investigators. Quantitative data were analyzed using one-way ANOVA and Holm-Sidak post hoc tests with P < 0.05 indicating significant differences. Both LPP and PNSBP were significantly decreased 3 wk after PNC+VD with saline or CM compared with sham-injured rats, but not with MSC or CCM. Elastic fiber density in the urethra increased and changed in orientation after PNC+VD, with a greater increase in elastic fibers with MSC or CCM. Pudendal nerve fascicles were less dense and irregularly shaped after PNC+VD and had reduced pathology with MSC or CCM. MSC and CCM provide similar protective effects after PNC+VD, suggesting that MSCs act via their secretions in this dual muscle and nerve injury.

Somatomotor and sensory urethral control of micturition in female rats

In rats, axons of external urethral sphincter (EUS) motoneurons travel through the anastomotic branch of the pudendal nerve (ABPD) and anastomotic branch of the lumbosacral trunk (ABLT) and converge in the motor branch of the sacral plexus (MBSP). The aim of the present study was to determine in female rats the contribution of these somatomotor pathways and urethral sensory innervation from the dorsal nerve of the clitoris on urinary continence and voiding. EUS electromyographic (EMG) activity during cystometry, leak point pressure (LPP), and voiding efficiency (VE) were assessed in anesthetized virgin Sprague-Dawley female rats before and after transection of the above nerve branches. Transection of the MBSP eliminated EUS EMG, decreased LPP by 50%, and significantly reduced bladder contraction duration, peak pressure, intercontraction interval, and VE. Transection of the ABPD or ABLT decreased EUS EMG discharge and LPP by 25% but did not affect VE. Transection of the dorsal nerve of the clitoris did not affect LPP but reduced contraction duration, peak pressure, intercontraction interval, and VE. We conclude that somatomotor control of micturition is provided by the MBSP with axons travelling through the ABPD and ABLT. Partial somatomotor urethral denervation induces mild urinary incontinence, whereas partial afferent denervation induces voiding dysfunction. ABPD and ABLT pathways could represent a safeguard ensuring innervation to the EUS in case of upper nerve damage. Detailed knowledge of neuroanatomy and functional innervation of the urethra will enable more accurate animal models of neural development, disease, and dysfunction in the future.

Brain-derived neurotrophic factor in urinary continence and incontinence

Urinary incontinence adversely affects quality of life and results in an increased financial burden for the elderly. Accumulating evidence suggests a connection between neurotrophins, such as brain-derived neurotrophic factor (BDNF), and lower urinary tract function, particularly with regard to normal physiological function and the pathophysiological mechanisms of stress urinary incontinence (SUI) and bladder pain syndrome/interstitial cystitis (BPS/IC). The interaction between BDNF and glutamate receptors affects both bladder and external urethral sphincter function during micturition. Clinical findings indicate reduced BDNF levels in antepartum and postpartum women, potentially correlating with postpartum SUI. Experiments with animal models demonstrate that BDNF is decreased after simulated childbirth injury, thereby impeding the recovery of injured nerves and the restoration of continence. Treatment with exogenous BDNF facilitates neural recovery and the restoration of continence. Serotonin and noradrenaline reuptake inhibitors, used to treat both depression and SUI, result in enhanced BDNF levels. Understanding the neurophysiological roles of BDNF in maintaining normal urinary function and in the pathogenesis of SUI and BPS/IC could lead to future therapies based on these mechanisms.

Long-term effects of simulated childbirth injury on function and innervation of the urethra

AIMS

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.

High-frequency micro-ultrasound: a novel method to assess external urethral sphincter function in rats following simulated birth injury

AIMS

We evaluated external urethral sphincter (EUS) function using high-frequency micro-ultrasound (US) in rats that were either uninjured (Control, C) or underwent vaginal distension (VD) as a substitute for vaginal birth injury induced stress urinary incontinence (SUI).

METHODS

Thirteen female nulliparous Sprague-Dawley rats of 12 weeks were divided into two groups, either C (n = 6) or VD (n = 7). Vaginal balloon distension was performed under pentobarbital anesthesia for 4 hours. Five days after the injury, all animals underwent US assessment of the urethra during high-rate bladder filling and urine leakage/voiding. Urinary leakage, the presence, absence, and pattern of EUS bursting during the voiding phase were registered, and pre-determined parameters of intercontraction interval (ICI), length of contraction (LOC), and rate of contraction (ROC) were registered.

RESULTS

Our ultrasound findings consistently showed the presence of rhythmic EUS bursting in all of the C rats (6/6), which were absent in all VD rats (0/7). The mean of ROC, ICI, and LOC in C group were 3.02 ± 0.12 contractions/sec, 471.43 ± 17.9 msec, and 103.41 ± 3.28 msec, respectively.

CONCLUSIONS

Pre-determined parameters of LOC, ICI, and ROC during US provide objective and measurable data on EUS function. US showed the total disappearance of EUS bursting in the VD group as compared to the C group. These results indicate that ultrasound testing may become a valuable non-invasive tool in future translational studies to investigate SUI/urethral function in rat models.

Rat mesenchymal stem cell secretome promotes elastogenesis and facilitates recovery from simulated childbirth injury

Vaginal delivery is a risk factor for stress urinary incontinence (SUI). Mesenchymal stem cells (MSCs) home to injured organs and can facilitate repair. The goal of this study was to determine if MSCs home to pelvic organs after simulated childbirth injury and facilitate recovery from SUI via paracrine factors. Three experiments were performed. Eighteen female rats received vaginal distension (VD) or sham VD and labeled intravenous (IV) MSCs to investigate if MSCs home to the pelvic organs. Whole-organ imaging and immunofluorescence were performed 1 week later. Thirty-four female rats received VD and IV MSCs, VD and IV saline, or sham VD and IV saline to investigate if MSCs accelerate recovery of continence. Twenty-nine female rats received VD and periurethral concentrated conditioned media (CCM), VD and periurethral control media, or sham VD and periurethral control media to investigate if factors secreted by MSCs accelerate recovery from VD. Urethral histology and function were assessed 1 week later. Significantly more MSCs were observed in the urethra, vagina, and spleen after VD compared to sham VD. Continence as measured by leak point pressure (LPP) was significantly reduced after VD in rats treated with saline or control media compared to sham VD but not in those given MSCs or CCM. External urethral sphincter (EUS) function as measured by electromyography (EMG) was not improved with MSCs or CCM. Rats treated with MSCs or CCM demonstrated an increase in elastin fibers near the EUS and urethral smooth muscle more similar to that of sham-injured animals than rats treated with saline or control media. MSCs homed to the urethra and vagina and facilitated recovery of continence most likely via secretion of paracrine factors. Both MSCs and CCM have promise as novel noninvasive therapies for SUI.

Comparison of three types of stress urinary incontinence rat models: electrocauterization, pudendal denervation, and vaginal distension

OBJECTIVE

To investigate the differences in the histopathologic and functional characteristics of 3 rat models of stress urinary incontinence.

MATERIALS AND METHODS

A total of 24 female, 10-week-old, Sprague-Dawley rats were randomly divided into 4 groups: normal, electrocauterization, pudendal denervation, and vaginal distension. At 2 weeks after surgery, the leak point pressure was measured to detect urinary leakage. Urethral tissue samples were collected for histological examination.

RESULTS

The smooth muscle content in the electrocauterization group was significantly decreased compared with that in all other groups, indicating that electrocauterization caused the most severe injury. A blood vessel marker, von Willebrand factor, was co-stained with α-smooth muscle actin to detect the blood vessel distribution. No significant differences were seen in von Willebrand factor expression among the 4 groups, other than in the electrocauterization group, in which we could hardly observe blood vessel expression. Protein gene product 9.5 staining was used to detect nerve fibers and cells. Protein gene product 9.5 expression was significantly lower in all the treatment groups compared with that in the normal group (P <.05), in particular, in the electrocauterization and pudendal denervation groups (P <.01). The leak point pressure was significantly lower in the electrocauterization (P <.01), pudendal denervation (P <.01), and vaginal distension (P <.05) groups than in the normal group.

CONCLUSION

The vaginal distension model should mainly be used as the myogenic damage stress urinary incontinence animal model; the pudendal denervation model mainly as the neurogenic damage stress urinary incontinence animal model; and the electrocauterization model as the vasculogenic, neurogenic, and myogenic damage animal model.

Effects of acute selective pudendal nerve electrical stimulation after simulated childbirth injury

During childbirth, a combinatorial injury occurs and can result in stress urinary incontinence (SUI). Simulated childbirth injury, consisting of vaginal distension (VD) and pudendal nerve crush (PNC), results in slowed recovery of continence, as well as decreased expression of brain-derived neurotrophic factor (BDNF), a regenerative cytokine. Electrical stimulation has been shown to upregulate BDNF in motor neurons and facilitate axon regrowth through the increase of β(II)-tubulin expression after injury. In this study, female rats underwent selective pudendal nerve motor branch (PNMB) stimulation after simulated childbirth injury or sham injury to determine whether such stimulation affects bladder and anal function after injury and whether the stimulation increases BDNF expression in Onuf's nucleus after injury. Rats received 4 h of VD followed by bilateral PNC and 1 h of subthreshold electrical stimulation of the left PNMB and sham stimulation of the right PNMB. Rats underwent filling cystometry and anal pressure recording before, during, and after the stimulation. Bladder and anal contractile function were partially disrupted after injury. PNMB stimulation temporarily inhibited bladder contraction after injury. Two days and 1 wk after injury, BDNF expression in Onuf's nucleus of the stimulated side was significantly increased compared with the sham-stimulated side, whereas β(II)-tubulin expression in Onuf's nucleus of the stimulated side was significantly increased only 1 wk after injury. Acute electrical stimulation of the pudendal nerve proximal to the crush site upregulates BDNF and β(II)-tubulin in Onuf's nucleus after simulated childbirth injury, which could be a potential preventive option for SUI after childbirth injury.

Stress incontinence in the era of regenerative medicine: reviewing the importance of the pudendal nerve

PURPOSE

Regenerative medicine will likely facilitate improved stress urinary incontinence treatment via the restoration of its neurogenic, myogenic and structural etiologies. Understanding these pathophysiologies and how each can optimally benefit from cellular, molecular and minimally invasive therapies will become necessary. While stem cells in sphincteric deficiency dominate the regenerative urology literature, little has been published on pudendal nerve regeneration or other regenerative targets. We discuss regenerative therapies for pudendal nerve injury in stress urinary incontinence.

MATERIALS AND METHODS

A PubMed® search for pudendal nerve combined individually with regeneration, injury, electrophysiology, measurement and activity produced a combined but nonindependent 621 results. English language articles were reviewed by title for relevance, which identified a combined but nonindependent 68 articles. A subsequent Google Scholar™ search and a review of the references of the articles obtained aided in broadening the discussion.

RESULTS

Electrophysiological studies have associated pudendal nerve dysfunction with stress urinary incontinence clinically and assessed pudendal nerve regeneration functionally, while animal models have provided physiological insight. Stem cell treatment has improved continence clinically, and ex vivo sphincteric bulk and muscle function gains have been noted in the laboratory. Stem cells, neurotrophic factors and electrical stimulation have benefited pudendal nerve regeneration in animal models.

CONCLUSIONS

Most regenerative studies to date have focused on stem cells restoring sphincteric function and bulk but whether a sphincter denervated by pudendal nerve injury will benefit is unclear. Pudendal nerve regeneration appears possible through minimally invasive therapies that show significant clinical potential. Treating poor central control and coordination of the neuromuscular continence mechanism remains another challenge.

Neurotrophin therapy improves recovery of the neuromuscular continence mechanism following simulated birth injury in rats

AIMS

Stress urinary incontinence (SUI) affects women both acutely and chronically after vaginal delivery. Current SUI treatments assume the neuromuscular continence mechanism, comprised of the pudendal nerve (PN) and external urethral sphincter (EUS), is either intact or irreparable. This study investigated the ability of neurotrophin therapy to facilitate recovery of the neuromuscular continence mechanism.

METHODS

Virgin, Sprague Dawley rats received simulated childbirth injury or sham injury and treatment with continuous infusion of brain-derived neurotrophic factor (BDNF) or saline placebo to the site of PN injury. Continence was assessed by leak point pressure (LPP) and EUS electromyography (EMG) 14 and 21 days after injury. Structural recovery was assessed histologically. Molecular assessment of the muscular and neuroregenerative response was determined via measurement of EUS BDNF and PN β(II) -tubulin expression respectively, 4, 8, and 12 days after injury.

RESULTS

Following injury, LPP was significantly reduced with saline compared to either BDNF treatment or sham injury. Similarly, compared to sham injury, resting EUS EMG amplitude and firing rate, as well as amplitude during LPP were significantly reduced with saline but not BDNF treatment. Histology confirmed improved EUS recovery with BDNF treatment. EUS BDNF and PN β(II)-tubulin expression demonstrated that BDNF treatment improved the neurogenerative response and may facilitate sphincteric recovery.

CONCLUSIONS

Continuous targeted neurotrophin therapy accelerates continence recovery after simulated childbirth injury likely through stimulating neuroregeneration and facilitating EUS recovery and re-innervation. Neurotrophins or other therapies targeting neuromuscular regeneration may be useful for treating SUI related to failure of the neuromuscular continence mechanism.

Pudendal nerve stretch reduces external urethral sphincter activity in rats

PURPOSE

Most animal models of stress urinary incontinence simulate maternal injuries of childbirth since delivery is a major risk factor but they do not reproduce the nerve stretch known to occur during human childbirth. We hypothesized that pudendal nerve stretch produces reversible dysfunction of the external urethral sphincter.

MATERIALS AND METHODS

Female virgin Sprague-Dawley® rats were anesthetized with urethane. Bilateral pudendal nerve stretch or sham injury was performed for 5 minutes. External urethral sphincter electromyography and leak point pressure were recorded immediately before and after, and 10, 30, 60 and 120 minutes after pudendal nerve stretch. Post-pudendal nerve stretch results were compared to prestretch values and to values in sham injured animals. The pudendal nerves underwent qualitative histological assessment. The nucleus of Onuf was evaluated by immunohistochemistry and polymerase chain reaction for β-APP and c-Fos expression as markers of neuronal activity and injury.

RESULTS

A total of 14 rats underwent bilateral pudendal nerve stretch (9) or sham injury (5). Each nerve was stretched a mean ± SEM of 74% ± 18% on the left side and 63% ± 13% on the right side. Electromyography amplitude decreased significantly immediately after stretch compared to before stretch and after sham injury (p = 0.003) but it recovered by 30 minutes after stretch. There was no significant change in leak point pressure at any time. Two hours after injury histology showed occasional neuronal degeneration. β-APP and c-Fos expression was similar in the 2 groups.

CONCLUSIONS

Acute pudendal nerve stretch produces reversible electrophysiological dysfunction but without leak point pressure impairment. Pudendal nerve stretch shows promise in modeling injury. It should be tested as part of a multi-injury, chronic, physiological model of human childbirth injury.

Chemokine upregulation in response to anal sphincter and pudendal nerve injury: potential signals for stem cell homing

PURPOSE

Stromal derived factor-1 (SDF-1) and monocyte chemotactic protein-3 (MCP-3) are signals forcing the migration of bone marrow-derived stem cells to ischemic tissue. This study investigates SDF-1 and MCP-3 expression following direct injury to the anal sphincter and pudendal nerve and to determine if these same mechanisms have any role.

METHODS

Chemokine expression was studied after anal sphincter injury in female rats after either a sphincterotomy (n = 15), pudendal nerve crush (PNC; n = 15), sham pudendal nerve crush (n = 15), or acted as unmanipulated controls (n = 5). Analysis was done at 1 h and 10 and 21 days after injury.

RESULTS

After injury, SDF-1 expression increased 40.2 ± 6.42 (P = 0.01) at 1 h and 28.2 ± 2.37 (P = 0.01) at 10 days, respectively, compared to controls. Likewise, MCP-3 expression increased 40.8 ± 8.17 (P = 0.02) at the same intervals compared to controls. After PNC, SDF-1 expression increased 46.4 ± 6.01 (P = 0.02) and 50.6 ± 10.11 (P = 0.01), and MCP-3 expression increased 46.3 ± 7.76 (P = 0.03) and 190.8 ± 22.15 (P = 0.01), respectively, at the same time intervals compared to controls. However, when PNC was compared to sham injured, a significant increase was seen in SDF-1 and MCP-3 at 10 days. At 21 days, PNC compared to sham injured was significantly low in expression for both SDF-1 and MCP-3 (P < 0.05).

CONCLUSIONS

Direct anal sphincter injury results in higher levels of SDF-1 and MCP-3 expression soon after injury, whereas denervation via pudendal nerve crush results in greater SDF-1 and MCP-3 expression 10 days after injury. Chemokine overexpression suggests the potential for cell-based therapeutic strategies.

Quantification of neurological and other contributors to continence in female rats

Smooth muscle, striated muscle, their central and peripheral innervations and control, and mucosal coaptation contribute to maintenance of continence. We used manual leak point pressure (mLPP) testing and electrical stimulation LPP (eLPP) testing in female rats to quantify the contribution of these factors to urethral resistance, a measure of continence. Abdominal muscles were electrically stimulated to induce leakage for eLPP. A Crede maneuver was applied for mLPP. These were repeated after complete T8 spinal cord injury (SCI) and/or bilateral pudendal nerve transection (PNT). After euthanasia, mLPP was repeated. MLPP was not significantly affected by opening the abdomen, suggesting that intra-abdominal pressure transmission contributes little to continence during slow pressure changes. ELPP was significantly higher than mLPP in intact rats, after PNT, and after SCI+PNT, suggesting that abdominal pressure transmission contributes to continence during rapid increases in intra-abdominal pressure. MLPP decreased significantly after PNT, indicating that urethral striated muscles contribute significantly to continence. ELPP decreased significantly after PNT with and without SCI, suggesting that supraspinal control significantly affects continence during rapid pressure changes, but not during slow pressure changes. MLPP after euthanasia was significantly decreased compared to mLPP after SCI+PNT, suggesting that urethral mucosal seal coaptation and tissue elasticity also contribute to continence. The urethra is a complex organ that maintains continence via a highly organized and hierarchical system involving both the central and peripheral nervous systems.

Neurogenic aspects of stress urinary incontinence

PURPOSE OF REVIEW

Vaginal childbirth is a significant risk factor for stress urinary incontinence (SUI). Women with SUI demonstrate dysfunction of the pelvic floor and pudendal nerve. Animal models of SUI have been developed to investigate its pathophysiology and for preclinical testing of potential treatments.

RECENT FINDINGS

Vaginal distension, a method of simulating childbirth injury in animals, produces a reliable decrease in leak point pressure (LPP), a measure of urethral resistance to leakage and quantification of SUI severity in animals. In addition to ischemia and direct tissue damage, vaginal distension causes denervation of the external urethral sphincter (EUS). Pudendal nerve crush produces a similar decrease in LPP, whereas combined PNC and vaginal distension injury delays recovery of LPP compared with either single injury alone. Neurophysiologic studies have elucidated the results of each injury and their combination on pudendal nerve and EUS function. Urethrolysis, electrocautery, and pudendal nerve transection produce more durable functional impairment via both structural damage and denervation. Pubourethral ligament injury eliminates the structural support of the urethra, but its neurologic effects are unknown.

SUMMARY

Animal models demonstrate a complex interplay between tissue damage and pudendal nerve dysfunction, and provide insight into the importance of neuroregeneration in the recovery of continence.

Animal models of stress urinary incontinence

Stress urinary incontinence (SUI) is a common health problem significantly affecting the quality of life of women worldwide. Animal models that simulate SUI enable the assessment of the mechanism of risk factors for SUI in a controlled fashion, including childbirth injuries, and enable preclinical testing of new treatments and therapies for SUI. Animal models that simulate childbirth are presently being utilized to determine the mechanisms of the maternal injuries of childbirth that lead to SUI with the goal of developing prophylactic treatments. Methods of assessing SUI in animals that mimic diagnostic methods used clinically have been developed to evaluate the animal models. Use of these animal models to test innovative treatment strategies has the potential to improve clinical management of SUI. This chapter provides a review of the available animal models of SUI, as well as a review of the methods of assessing SUI in animal models, and potential treatments that have been tested on these models.

Postpartum stress urinary incontinence: lessons from animal models

Postpartum stress urinary incontinence (SUI) is associated with chronic SUI in later life, which is 240% more likely to occur in women who deliver vaginally than those who did not. The etiology of SUI is multifactoral and has been associated with defects in both neuromuscular and structural components of continence. Specifically, clinical studies have demonstrated that pudendal nerve damage occurs during vaginal delivery, supporting the concept that neuromuscular damage to the continence mechanism can result in postpartum SUI. Urethral hypermobility and the loss of pelvic floor support, such as that involved in pelvic organ prolapse, have also been associated with SUI. Animal models provide an opportunity to investigate these injuries, individually and in combination, enabling researchers to gain further insight into their relative contributions to the development of SUI and the effectiveness of potential therapies for it. This article discusses the use of animal models of postpartum SUI in addition to the broad insights into treatment efficacy they provide.

Pelvic floor muscles and the external urethral sphincter have different responses to applied bladder pressure during continence

OBJECTIVES

To determine the functional innervation of the pelvic floor muscles (PFM) and whether there is PFM activity during an external pressure increase to the bladder in female rats.

METHODS

Thirty-one female adult virgin Sprague-Dawley rats received an external increase in bladder pressure until urinary leakage was noted while bladder pressure was recorded (leak point pressure [LPP]) under urethane anesthesia. Six of the rats underwent repeat LPP testing after bilateral transection of the levator ani nerve. Another 6 rats underwent repeat LPP testing after bilateral transection of the pudendal nerve. Simultaneous recordings of PFM (pubo- and iliococcygeus muscles), electromyogram (EMG), and external urethral sphincter (EUS) EMG were recorded during cystometry and LPP testing.

RESULTS

Thirteen rats (42%) showed tonic PFM EMG activity during filling cystometry. Eighteen rats (58%) showed no tonic PFM EMG activity at baseline, but PFM EMG could be activated by pinching the perineal skin. This activity could be maintained unless voiding occurred. The external increase in bladder pressure caused significantly increased EUS EMG activity as demonstrated by increased amplitude and frequency. However, there was no such response in PFM EMG. LPP was not significantly different after levator ani nerve transection, but was significantly decreased after pudendal nerve transection.

CONCLUSIONS

PFM activity was not increased during external pressure increases to the bladder in female rats. Experimental designs using rats should consider this result. The PFM, unlike the EUS, does not contribute to the bladder-to-urethra continence reflex. PFM strengthening may nonetheless facilitate urinary continence clinically by stabilizing the bladder neck.