Comparison of leak point pressure methods in an animal model of stress urinary incontinence

Validation of a new rat model of urethral sphincter injury and leak point pressure measurements

AIMS

In vivo experiments were performed to establish and validate a rat model of urethral sphincter injury and to develop a method for leak point pressure (LPP) measurements performed repeatedly in the same animal.

METHODS

Twenty-four Sprague-Dawley female rats underwent bladder and epidural catheter implantation. Five days later, cystometry was performed using continuous infusion. Anesthesia with isoflurane, ketamine-xylazine (KX) or fentanyl-fluanisone-midazolam (FFM) was used. After three micturition cycles, intrathecal bupivacaine was administered leading to the suppression of reflex bladder contractions. LPP measurements were performed using vertical tilt. After the initial LPP measurement, animals underwent partial resection of the striated urethral sphincter. The effect was evaluated 6 weeks after surgery, by repeating the LPP measurement in the same animal.

RESULTS

Ten out of 19 animals showed full micturition cycles under isoflurane, and all 9 animals under KX anesthesia. No significant difference in micturition pressures (Mean ± SEM; 30.1 ± 2.3 vs. 26.8 ± 1.6 mmHg) and LPP (31.0 ± 2.4 vs. 28.0 ± 0.9 mmHg) was observed between isoflurane and KX groups, respectively. Reflex micturition was suppressed with FFM. Bupivacaine led to overflow incontinence in all cases. Sphincter injury caused fibrotic changes and a significant increase in LPP (26.4 ± 2.3 before vs. 46.9 ± 4.6 mmHg after injury, p < 0.05).

CONCLUSIONS

KX anesthesia preserves bladder contractions. Intrathecal bupivacaine eliminates reflex micturition, allowing for repeated LPP measurements in the same animal. Resection of striated sphincter resulted in increased LPP 6 weeks post injury. The site of urethral sphincter resection healed with fibrosis.

Secretomes of human pluripotent stem cell-derived smooth muscle cell progenitors upregulate extracellular matrix metabolism in the lower urinary tract and vagina

BACKGROUND

Adult mesenchymal stem cells (MSCs) have been studied extensively for regenerative medicine; however, they have limited proliferation in vitro, and the long culture time induces cell senescence. MSCs also contribute to tissue repair through their paracrine function. In this study, we sought to examine the paracrine effects of human smooth muscle cell progenitors (pSMC) on the urethra and adjacent vagina of stress urinary incontinence rodents. We use human pluripotent stem cell (PSC) lines to derive pSMCs to overcome the issue of decreased proliferation in tissue culture and to obtain a homogenous cell population.

METHOD

Three human PSC lines were differentiated into pSMCs. The conditioned medium (CM) from pSMC culture, which contain pSMC secretomes, was harvested. To examine the effect of the CM on the extracellular matrix of the lower urinary tract, human bladder smooth muscle cells (bSMCs) and vaginal fibroblasts were treated with pSMC-CM in vitro. Stress urinary incontinence (SUI) was induced in rats by surgical injury of the urethra and adjacent vagina. SUI rats were treated with pSMC-CM and monitored for 5 weeks. Urethral pressure testing was performed prior to euthanasia, and tissues were harvested for PCR, Western blot, and histological staining. Kruskal-Wallis one-way ANOVA test and Student t test were used for statistical comparisons.

RESULTS

pSMC-CM upregulated MMP-2, TIMP-2, collagen, and elastin gene expression, and MMP-9 activity in the human bladder and vaginal cells consistent with elastin metabolism modulation. pSMC-CM treatment in the SUI rat improved urethral pressure (increase in leak point pressure compared to intact controls, p < 0.05) and increased collagen and elastin expression in the urethra and the adjacent vagina.

CONCLUSION

Conditioned media from smooth muscle cell progenitors derived from human pluripotent stem cells improved urethral leak point pressure and collagen and elastin content in the SUI rat. These findings suggest a novel therapeutic potential for PSC-based treatments for SUI and pelvic floor disorders where tissues are affected by collagen, elastin, and smooth muscle loss.

BMMSC-sEV-derived miR-328a-3p promotes ECM remodeling of damaged urethral sphincters via the Sirt7/TGFβ signaling pathway

Background

Stress urinary incontinence (SUI) is a common and bothersome condition. Invasive surgery will always be considered after conservative treatment fails, but the rates of postoperative complications and long-term recurrence are high. Thus, a new treatment strategy is still needed. In recent years, bone marrow mesenchymal stem cells (BMMSC) have shown great promise for SUI treatment. The therapeutic effects of BMMSC on SUI are achieved mainly by paracrine pathway signaling molecules, such as small extracellular vesicles (sEV). sEV are recognized as essential mediators of cell-to-cell communication. However, the therapeutic effects and detailed mechanisms of BMMSC-derived sEV in SUI remain mostly unexplored.

Methods

The effects of BMMSC-sEV on extracellular matrix (ECM) metabolism were assessed in vitro and in vivo. In a SUI rat model, TGF-β1 signaling was examined with or without BMMSC-sEV stimulation. sEV miRNAs were deeply sequenced, and the most likely miRNAs were evaluated as mediators of the TGF-β1 signaling pathway.

Results

BMMSC-sEV enhanced the synthesis of ECM components, including elastin, collagen I, and collagen III, and improved urethral function. Furthermore, BMMSC-sEV activated TGF-β1 signaling in primary fibroblast cells and in rat urethras. Several differentially expressed miRNAs were identified in the BMMSC-sEV. Bioinformatics analysis and in vitro studies showed that BMMSC-sEV miR-328a-3p can be transferred from BMMSC to fibroblasts and can regulate the Sirt7/TGF-β1 signaling pathway.

Conclusion

BMMSC-sEV promote ECM remodeling of damaged urethral sphincters by transferring miR-328a-3p to regulate the Sirt7/TGF-β1 signaling pathway.

[Therapeutic new targets for stress urinary incontinence in the central nervous system]

Stress urinary incontinence (SUI) is a common and bothersome problem among middle-aged women. However, there are few useful drugs for SUI. Urethral hypermobility and intrinsic sphincter deficiency are two main causes of SUI. Various animal models of SUI, such as vaginal distention, pudendal nerve injury, or ovariectomy, have been developed to study the pathophysiology of SUI. In addition, we have previously reported that cerebral infarction rats also induce SUI. Leak point pressure measurements are the most commonly used methods to evaluate the urethral dysfunction in SUI animal models. Originally, we have developed microtransducer-tipped catheter measurements of urethral activity during sneezing. Previous or our basic research has clarified potential strategies for pharmacotherapy of SUI in the central nervous system. Therapeutic targets include adrenergic and serotonergic (5-HT) receptors in the spinal cord, which stimulate pudendal nerve innervating the external urethral sphincter and/or sympathetic nerve innervating urethral smooth muscle. Activation of α₁-adrenoceptors, 5-HT_2C, or 5-HT₇ receptors enhances the reflex at the spinal cord level whereas pre- or postsynaptic α₂-adrenoceptors and/or 5-HT_1A receptors inhibit the reflex. We have recently reported that stimulation of the spinal μ-opioid receptors by tramadol also enhances the reflex. Thus, we review the recent advances in basic SUI research and potential targets for pharmacotherapy of SUI in the central nervous system.

Analysis of continence reflexes by dynamic urethral pressure recordings in a rat stress urinary incontinence model induced by multiple simulated birth traumas

The present study evaluated real-time changes in urethral pressure during the storage phase using a rat model with stress urinary incontinence (SUI) induced by simulated multiple birth traumas and investigated the relationship between urethral continence function and dynamic parameters associated with the changes in urethral pressure. Sprague-Dawley rats were divided into the following two groups: the sham group, which underwent three catheterizations of the vagina without distension at 2-wk intervals, and the vaginal distension (VD) group, which underwent three VDs at 2-wk intervals. After transection of the T8-T9 spinal cord, simultaneous bladder and urethral pressure recordings were performed during intravesical pressure elevation. Urodynamic parameters such as leak point pressure (LPP), urethral baseline pressure (UBP), maximum urethral pressure (MUP), the MUP-UBP differential (dUP) during intravesical pressure elevation, the bladder pressure when urethral contraction begins (Puc), and the bladder pressure at bladder neck opening (Pno) were then measured and compared. Compared with the sham group, LPP, UBP, dUP, MUP, Puc, and Pno were significantly decreased in the VD group. Pressure differences between LPP and Pno and between LPP and UBP (LPP-UBP) were also significantly different in the two groups. However, difference values of LPP and MUP or Pno and UBP were not altered after VD. Our new methods of simultaneous recordings of dynamic changes in bladder and urethral pressures are useful to fully evaluate the functional alterations in urethral continence function in the SUI model induced by multiple VDs. Moreover, LPP-UBP values, which correspond to the difference between Valsalva LPP and maximum urethral closure pressure in clinical urodynamics, would be useful to evaluate the impaired urethral continence function after simulated birth traumas in animal models.

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.

Autologous and heterotopic transplantation of adipose stromal vascular fraction ameliorates stress urinary incontinence in rats with simulated childbirth trauma

Introduction

Autologous transplantation of adipose stromal vascular fraction (SVF) is a cost-effective and technically accessible option for cell therapy. Clinical study of SVF transplantation for male stress urinary incontinence (SUI) is underway, but the effectiveness remains unknown for female SUI, majority of which is caused by childbirth trauma.

Methods

Vaginal Distension (VD) rats were generated as in vivo model for female SUI. To quantitate the severity of SUI, leak point pressure (LPP) was measured by placing a bladder catheter. There was a characteristic waveform of LPP with two-peaks, and we counted the second peak as an LPP value. Adipose SVF was separated from inguinal fat and delivered into external urethral sphincter (EUS) through transperineal injection. LPP was measured 7 or 14 days after SVF transplantation. Tissue damage and collagen synthesis around the EUS were visualized by Masson's trichrome and eosin staining. Antibody against α-smooth muscle actin (α-SMA) was used to stain smooth muscle or activated stromal cells. Donor SVF cells were distinguished from recipient EUS tissue by tracking with GFP transgene.

Results

VD procedure decreased the frequency at which the normal LPP waveform appeared and lowered the LPP value. SVF injection normalized the waveform as well as the level of LPP. VD disrupted histological structure of EUS and SVF failed to differentiate into striatal muscles. Instead, SVF increased α-SMA positive cells and collagen synthesis but the phenomena depended on VD stimulus. GFP tracking indicated that the transplanted SVF cells persisted for four weeks and synthesized α-SMA protein simultaneously.

Conclusions

Autologous transplantation of adipose SVF displayed bulking effects through collagen synthesis. However, such heterotopic activation was dependent on tissue damage.

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VD rat is a reproducible in vivo model for female SUI.

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LPP waveform is a good indicator of normal EUS function.

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Transplantation of adipose SVF normalizes LPP decline caused by VD.

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Heterotopic SVF synthesizes collagen, depending on tissue damage.

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Heterotopic SVF does not display voiding obstruction.

Urethral function and histopathology in aged female rats as a stress urinary incontinence model

OBJECTIVE

Stress urinary incontinence (SUI) is a common disease condition in elderly women, suggesting that its etiology may be linked to aging. To investigate the hypothesis that urethral dysfunction and histopathological changes are possible contributors to SUI in elderly women, several parameters of urethral function, as well as histological parameters, were compared between young and aged rats.

METHODS

Virgin female rats were examined at 3 different ages, namely 3, 12, and 24 months, corresponding to young, middle-aged, and aged rats, respectively. Urethral function was assessed by measuring the leak point pressure (LPP), pudendal nerve stimulation (PNS)-induced elevation in urethral pressure, and phenylephrine-induced increase in urethral perfusion pressure (UPP). Histopathological assessments were performed following hematoxylin and eosin (HE), Masson's trichrome, and immunofluorescence staining of urethral tissue.

RESULTS

LPP of aged rats was significantly reduced compared to that of both young and middle-aged rats. PNS-induced elevation in urethral pressure in aged rats was also significantly lower than that in young rats. In contrast, there were no significant differences in the phenylephrine-induced increase in UPP between young and aged rats. Connective tissue area in the external urethral sphincter (EUS) layer was increased in aged rats, whereas the smooth muscle layer was histologically similar to that in young rats. The number of EUS fibers was significantly reduced in aged rats, whereas the cross-sectional area of EUS fibers increased from differed compared with young rats.

CONCLUSION

We have demonstrated age-related changes in EUS function and morphology in the rat urethra, which are considered to be etiological risk factors for SUI in humans.

Effects of multiple simulated birth traumas on urethral continence function in rats

Multiple vaginal parities have been reported to be an important risk factor for stress urinary incontinence (SUI). Simulated birth trauma with single vaginal distention (VD) has been used to induce the SUI condition in animals; however, the effect of multiple simulated birth traumas on the urethral continence function has not been well characterized. Therefore, we examined the effects of multiple VDs on urethral functions in vivo and the changes in gene expressions of several molecules in the urethra using female SD rats, which were divided into three groups; sham, VD-1 (single VD), and VD-3 groups (3 times of VDs every 2 wk). Two weeks after the final VD, leak point pressure (LPP) and urethral responses during sneezing were evaluated. Also, changes in mRNA levels of urethral molecules were quantified with RT-PCR.　The VD-1 group did not show any change in LPP with only a tendency of decrease in amplitudes of the urethral responses during sneezing (A-URS); however, the VD-3 group showed a significant decrease in LPP and urethral responses such as baseline urethral pressure and A-URS accompanied with SUI episodes during sneezing. Nicotinic receptor subtypes and transforming growth factor (TGF)-β1 were significantly increased in both VD-1 and VD-3 groups while TNF receptor (TNFR)-1, IL-6, collagens, and matrix metalloproteinases-9 were significantly increased only in the VD-3 group.　These data indicate that rats with multiple simulated birth traumas exhibit profound impairment of the urethral continence function and that these functional changes are associated with those in cytokines, extracellular matrix molecules, and nicotinic receptor subtypes in the urethra.

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.

Efficacy and Safety of Immuno-Magnetically Sorted Smooth Muscle Progenitor Cells Derived from Human-Induced Pluripotent Stem Cells for Restoring Urethral Sphincter Function

Human-induced pluripotent stem cells (hiPSCs)-based cell therapy holds promise for treating stress urinary incontinence (SUI). However, safety concerns, especially tumorgenic potential of residual undifferentiated cells in hiPSC derivatives, are major barriers for its clinical translation. An efficient, fast and clinical-scale strategy for purifying committed cells is also required. Our previous studies demonstrated the regenerative effects of hiPSC-derived smooth muscle progenitor cells (pSMCs) on the injured urethral sphincter in SUI, but the differentiation protocol required fluorescence-activated cell sorting (FACS) which is not practical for autologous clinical applications. In this study, we examined the efficacy and safety of hiPSC-derived pSMC populations sorted by FDA-approved magnetic-activated cell sorting (MACS) using cell-surface marker CD34 for restoring urethral sphincter function. Although the heterogeneity of MACS-sorted pSMCs was higher than that of FACS-sorted pSMCs, the percentage of undifferentiated cells dramatically decreased after directed differentiation in vitro. In vivo studies demonstrated long-term cell integration and no tumor formation of MACS-sorted pSMCs after transplantation. Furthermore, transplantation of MACS-sorted pSMCs into immunodeficient SUI rats was comparable to transplantation with FACS-sorted pSMCs for restoration of the extracellular matrix metabolism and function of the urethral sphincter. In summary, purification of hiPSC derivatives using MACS sorting for CD34 expression represent an efficient approach for production of clinical-scale pSMCs for autologous stem cell therapy for regeneration of smooth muscle tissues. Stem Cells Translational Medicine 2017;6:1158-1167.

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.

IGF-1 as an Important Endogenous Growth Factor for Recovery from Impaired Urethral Continence Function in Rats with Simulated Childbirth Injury

PURPOSE

We examined the functional role of endogenous IGF-1 (insulin-like growth factor-1) in the recovery phase of stress urinary incontinence induced by simulated childbirth trauma using an IGF-1 receptor inhibitor.

MATERIALS AND METHODS

Simulated birth trauma was induced by vaginal distension in female Sprague Dawley® rats. The IGF-1 receptor antagonist JB-1 (10 and 100 μg/kg per day) or vehicle was continuously delivered from 1 day before vaginal distension for 7 days using subcutaneous osmotic pumps. Seven, 14 and 21 days after vaginal distension the effect of JB-1 treatment was examined by functional analyses, including leak point and urethral baseline pressure, and urethral responses during passive increments in intravesical pressure, as well as molecular analyses in urethral tissues, including phosphorylation of Akt, apoptotic changes and peripheral nerve density using Western blot and immunohistochemistry.

RESULTS

On functional analyses vehicle treated rats with vaginal distension had significantly decreased leak point and urethral baseline pressure, and urethral responses at 7 days, which recovered to the normal level 14 and 21 days after vaginal distension. In the JB-1 treated vaginal distension group leak point and urethral baseline pressure, and urethral responses were still significantly reduced 21 days after vaginal distension. On molecular analyses JB-1 treatment increased apoptotic cells, induced a significant decrease in phosphorylated Akt and prolonged the decrease of peripheral nerve density in urethral tissues.

CONCLUSIONS

Suppression of endogenous IGF-1 activity delayed recovery from stress urinary incontinence induced by simulated childbirth trauma in rats. Thus, IGF-1 is likely to be an important endogenous mediator for functional recovery from childbirth related stress urinary incontinence. This suggests that IGF-1 could be an effective target for treating stress urinary incontinence in women.

Effects of Duloxetine on Urethral Continence Reflex and Bladder Activity in Rats with Cerebral Infarction

PURPOSE

We investigated the effect of duloxetine, a norepinephrine and serotonin reuptake inhibitor, on the sneeze induced continence reflex and on bladder function in rats with cerebral infarction.

MATERIALS AND METHODS

Using urethane anesthesia the effect of duloxetine (1 mg/kg intravenously) on the amplitude of urethral responses during sneezing as well as urethral baseline pressure at the mid urethra was evaluated in normal female adult rats and cerebral infarction rats. Tilt leak point pressure was also measured. In normal and cerebral infarction rats continuous cystometry was evaluated before and after duloxetine injection.

RESULTS

In cerebral infarction rats urethral baseline pressure was 43% lower than in normal rats but the amplitude of urethral responses during sneezing did not differ in the 2 groups. Duloxetine increased the amplitude of urethral responses during sneezing and urethral baseline pressure by 31% and 21%, respectively, in normal rats but did not affect either in cerebral infarction rats. Also, in cerebral infarction rats leak point pressure was 29% lower compared with normal rats. Duloxetine increased leak point pressure in normal rats but not in cerebral infarction rats. Cerebral infarction reduced intercontraction intervals without affecting the amplitude of bladder contractions compared with normal rats. Duloxetine prolonged intercontraction intervals in cerebral infarction rats but not in normal rats.

CONCLUSIONS

These results suggest that cerebral infarction induces not only bladder overactivity but also stress urinary incontinence, which may account for mixed incontinence in patients with cerebral infarction. After cerebral infarction duloxetine reduced bladder overactivity but failed to enhance active urethral closure mechanisms during sneezing, suggesting that disorganization of the brain network after cerebral infarction might influence the effect of duloxetine on lower urinary tract function.

Mesenchymal stromal cells for sphincter regeneration

Stress urinary incontinence (SUI), defined as the involuntary loss of considerable amounts of urine during increased abdominal pressure (exertion, effort, sneezing, coughing, etc.), is a severe problem to the individuals affected and a significant medical, social and economic challenge. SUI is associated with pelvic floor debility, absence of detrusor contraction, or a loss of control over the sphincter muscle apparatus. The pathology includes an increasing loss of muscle cells, replacement of muscular tissue with fibrous tissue, and general aging associated processes of the sphincter complex. When current therapies fail to cure or improve SUI, application of regeneration-competent cells may be an alternative therapeutic option. Here we discuss different aspects of the biology of mesenchymal stromal cells, which are relevant to their clinical applications and for regenerating the sphincter complex. However, there are reports in favor of and against cell-based therapies. We therefore summarize the potential and the risks of cell-based therapies for the treatment of SUI.

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.

Morphological and functional response to injury to the external urethral sphincter - similarities and differences between male and female rats

AIMS

The objective of this study was to evaluate the similarities and differences of the urethral morphological and functional changes following external urethral sphincter EUS injury in male and female rats.

METHODS

30 female and 30 male age-matched Wistar rats were used in the experiments. Half of them underwent electrocauterization of the surrounding tissues lateral to the urethra at the level of the (EUS) and the others, a sham operation. At 2, 6, and 16 weeks after surgeries they underwent anesthetized cystometry, measurement of leak point pressure (LPP) and their urethras were harvested for morphological analyses.

RESULTS

There were no differences in cystometric parameters between sex-time-matched animals, ensuring normal bladder function in the manipulated animals. The mean LPP in male and female rats was lower compared with sham animals. Age-time-matched sham operated male rats exhibited a higher LPP compared with female rats. The reduction in LPP comparing electrocauterized and sham time-matched animals was more pronounced in male rats than in female rats. Electrocauterization produced urethral collagen deposition and nerve damage in both male and female animals. Muscle atrophy and disruption also occurred, being more evident in female rats.

CONCLUSIONS

The urethras of male and female rats exhibited a similar morphological and functional response to electrocauterization. The time-course evaluation revealed that the male animal model is as reliable, reproducible and long-lasting as the female model. Intact males had a higher LPP than female rats and the nerve injury led to a more drastic impairment of this mechanism.

Towards a Treatment of Stress Urinary Incontinence: Application of Mesenchymal Stromal Cells for Regeneration of the Sphincter Muscle

Stress urinary incontinence is a significant social, medical, and economic problem. It is caused, at least in part, by degeneration of the sphincter muscle controlling the tightness of the urinary bladder. This muscular degeneration is characterized by a loss of muscle cells and a surplus of a fibrous connective tissue. In Western countries approximately 15% of all females and 10% of males are affected. The incidence is significantly higher among senior citizens, and more than 25% of the elderly suffer from incontinence. When other therapies, such as physical exercise, pharmacological intervention, or electrophysiological stimulation of the sphincter fail to improve the patient’s conditions, a cell-based therapy may improve the function of the sphincter muscle. Here, we briefly summarize current knowledge on stem cells suitable for therapy of urinary incontinence: mesenchymal stromal cells, urine-derived stem cells, and muscle-derived satellite cells. In addition, we report on ways to improve techniques for surgical navigation, injection of cells in the sphincter muscle, sensors for evaluation of post-treatment therapeutic outcome, and perspectives derived from recent pre-clinical studies.

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.

Sexually dimorphic urethral activity in response to pharmacological activation of 5-HT1A receptors in the rat

In this study, we examined the possibility that 5-HT1A receptors may underlie sexually dimorphic mechanisms affecting the regulation of urethral functions in anesthetized rats. Simultaneous recordings of intravesical pressure under isovolumetric conditions, external urethral sphincter-electromyography, and urethral perfusion pressure were used to examine the effects of a 5-HT1A receptor agonist [8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT)] and antagonist (WAY-100635) on bladder and urethral functions. This research also evaluated the effects of 8-OH-DPAT and α-bungarotoxin (a neuromuscular blockade agent) on urethral continence using leak point pressure testing, and the distribution of 5-HT1A receptors in the lower urinary tract was assessed by immunohistochemistry. The serotonergic mechanism that controls the urinary bladder and external urethral sphincter-electromyography activity showed no significant sexual differences, but urethral activity in urethral perfusion pressure and leak point pressure values exhibited some sexual differences. 8-OH-DPAT enhanced urethral pressure during continence in rats of both sexes, but the drug elevated the pressure during voiding in male rats and reduced it in female rats. The distribution of 5-HT1A receptors in the spinal cord also showed some sexual differences. The present study contributes to our understanding of the role of 5-HT1A receptors in physiological and immunohistochemical properties of urethral smooth muscle in rats of different sexes. These findings may be a basis for the future development of pharmacotherapies for stress urinary incontinence in men.

Neurophysiology and therapeutic receptor targets for stress urinary incontinence

Stress urinary incontinence is the most common type of urinary incontinence in women. Stress urinary incontinence involves involuntary leakage of urine in response to abdominal pressure caused by activities, such as sneezing and coughing. The condition affects millions of women worldwide, causing physical discomfort as well as social distress and even social isolation. This type of incontinence is often seen in women after middle age and it can be caused by impaired closure mechanisms of the urethra as a result of a weak pelvic floor or poorly supported urethral sphincter (urethral hypermobility) and/or a damaged urethral sphincter system (intrinsic sphincter deficiency). Until recently, stress urinary incontinence has been approached by clinicians as a purely anatomic problem as a result of urethral hypermobility requiring behavioral or surgical therapy. However, intrinsic sphincter deficiency has been reported to be more significantly associated with stress urinary incontinence than urethral hypermobility. Extensive basic and clinical research has enhanced our understanding of the complex neural circuitry regulating normal function of the lower urinary tract, as well as the pathophysiological mechanisms that might underlie the development of stress urinary incontinence and lead to the development of potential novel strategies for pharmacotherapy of stress urinary incontinence. Therapeutic targets include adrenergic and serotonergic receptors in the spinal cord, and adrenergic receptors at the urethral sphincter, which can enhance urethral reflex activity during stress conditions and increase baseline urethral pressure, respectively. This article therefore reviews the recent advances in stress urinary incontinence research and discusses the neurophysiology of urethral continence reflexes, the etiology of stress urinary incontinence and potential targets for pharmacotherapy of stress urinary incontinence.

Strain-dependent urethral response

AIMS

The Sprague-Dawley (SD) rat, an out-bred, all-purpose strain, has served well for lower urinary tract research. However, to test new cellular therapies for conditions such as stress urinary incontinence, an in-bred rat strain with immune tolerance, such as the Lewis rat, may be more useful. The objective of this study was to reveal any differences in lower urinary tract continence mechanisms between the Lewis and SD rat.

METHODS

The contribution of (1) the striated and smooth muscle to the mechanical and functional properties of the urethra in vitro, and (2) the striated sphincter to leak point pressure (LPP) and reflex continence mechanisms in vivo were assessed in normal (control) Lewis and SD rats and in a model of stress urinary incontinence produced by bilateral pudendal nerve transection.

RESULTS

Control, Lewis rats had significantly lower LPP, significantly less fast-twitch skeletal muscle and relied less on the striated sphincter for continence than control, SD rats, as indicated by the failure of neuromuscular blockade with alpha-bungarotoxin to reduce LPP. Nerve transection significantly decreased LPP in the SD rat, but not in the Lewis rat. Although the Lewis urethra contained more smooth muscle than the SD rat, it was less active in vitro as indicated by a low urethral baseline pressure and lack of response to phenylephrine.

CONCLUSIONS

We have observed distinct differences in functional and mechanical properties of the SD and Lewis urethra and have shown that the Lewis rat may not be suitable as a chronic model of SUI via nerve transection.

Swimming: effects on stress urinary incontinence and the expression of nerve growth factor in rats following transabdominal urethrolysis

PURPOSE

Stress urinary incontinence (SUI) commonly occurs in women, and it has an enormous impact on quality of life. Surgery, drugs, and exercise have been recommended for the treatment of this disease. Among these, exercise is known to be effective for the relief of symptoms of SUI; however, the efficacy and underlying mechanisms of the effect of exercise on SUI are poorly understood. We investigated the effect of swimming the symptom of SUI in relation to the expression of nerve growth factor (NGF) in rats.

METHODS

Transabdominal urethrolysis was used to induce SUI, in Sprague-Dawley rats. The experimental groups were divided into the following three groups: sham-operation group, transabdominal urethrolysis-induced group, and transabdominal urethrolysis-induced and swimming group. The rats in the swimming group were forced to swim for 30 minutes once daily starting 2 weeks after SUI induction and continuing for 4 weeks. For this study, determination of abdominal leak point pressure and immunohistochemistry for NGF in the urethra and in the neuronal voiding centers (medial preoptic nucleus [MPA], ventrolateral periaqueductal gray [vlPAG], pontine micturition center [PMC], and spinal cord [L4-L5]) were performed.

RESULTS

Transabdominal urethrolysis significantly reduced the abdominal leak point pressure, thereby contributing to the induction of SUI. Abdominal leak point pressure, however, was significantly improved by swimming. The expression of NGF in the urethra and in the neuronal voiding centers (MPA, vlPAG, PMC, and L4-L5) relating to micturition was enhanced by the induction of SUI. Swimming, however, significantly suppressed SUI-induced NGF expression.

CONCLUSIONS

Swimming alleviated symptoms of transabdominal urethrolysis-induced SUI, as assessed by an increase in abdominal leak point pressure. The underlying mechanisms of these effects of swimming might be ascribed to the inhibitory effect of swimming on NGF expression.

Effect of a 5-HT1A receptor agonist (8-OH-DPAT) on external urethral sphincter activity in a rat model of pudendal nerve injury

Although serotonergic agents have been used to treat patients with stress urinary incontinence, the characteristics of the external urethral sphincter (EUS) activity activated by 5-HT receptors have not been extensively studied. This study examined the effects of the 5-HT(1A) receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), on the EUS-electromyography and resistance of the urethra in a rat model with bilateral pudendal nerve injury (BPNI). Two measurements were utilized to assess the effects of the drug on bladder and urethral functions: the simultaneous recordings of transvesical pressure under isovolumetric conditions [isovolumetric intravesical pressure (IVP)] and urethral perfusion pressure, and the simultaneous recordings of IVP during continuously isotonic transvesical infusion with an open urethra (isotonic IVP) and EUS-electromyography. This study also evaluated the urethral continence using leak point pressure testing. The urethral perfusion pressure and leak point pressure measurements of BPNI rats reveal that 8-OH-DPAT significantly increased urethral resistance during the bladder storage phase, yet decreased resistance during the voiding phase. The entire EUS burst period was significantly prolonged, within which the average silent period increased and the frequency of burst discharges decreased. 8-OH-DPAT also improved the voiding efficiency, as evidenced by the detection of decreases in the contraction amplitude and residual volume, with increases in contraction duration and voided volume. These findings suggest that 8-OH-DPAT not only improved continence function, but also elevated the voiding function in a BPNI rat model.

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.

Effect of Treadmill Exercise on Leak-point pressure and Neuronal Activation in Brain of Rats with Stress Urinary Incontinence

PURPOSE

Stress urinary incontinence (SUI) commonly occurs in women, and it causes enormous impact on quality of life. Surgery, drugs, and exercise have been recommended for the treatment of this disease. Among these exercise is also known to be effective for relieving thesymptoms of SUI, however, the efficacy and underlying mechanisms of exercise on SUI are poorly understood. In the present study, we investigated the effect of treadmill exercise on abdominal leak-point pressure and neuronal activity in the medial preoptic nucleus (MPA), ventrolateral periaqueductal gray (vlPAG), and pontine micturition center (PMC) following urethrolysis in rats.

MATERIALS AND METHODS

Adult female Sprague-Dawley rats, weighing 250±10 g (9 weeks old), were used in this study. After having undergone transabdominal urethrolysis to induce SUI, the rats were divided into three groups (n=6 in each group): a sham operation group, an SUI-induced group, and an SUI-induced and treadmill exercise group. The rats in the exercise group performed treadmill running for 30 min once a day starting 2 weeks after the induction of SUI and continuing for 4 weeks after surgery. For this study, determination of abdominal leak point pressure and immunohistochemistry for c-Fos in the brain were performed.

RESULTS

Induction of transabdominal urethrolysis significantly reduced the abdominal leak point pressure, thereby contributing to the induction of SUI. In contrast, abdominal leak point pressure was significantly improved by treadmill exercise. The expression of c-Fosin the MPA, vlPAG, and PMC, the brain areas relating to micturition, was enhanced by the induction of SUI, whereas treadmill exercise significantly suppressed SUI-induced c-Fos expression, suggesting that neuronal activation in the micturition centers was suppressed by treadmill exercise.

CONCLUSION

The present results suggest that treadmill exercise may be an effective therapeutic modality for ameliorating the symptoms of SUI.

Transplantation of muscle-derived stem cells plus biodegradable fibrin glue restores the urethral sphincter in a pudendal nerve-transected rat model

We investigated whether fibrin glue (FG) could promote urethral sphincter restoration in muscle-derived stem cell (MDSC)-based injection therapies in a pudendal nerve-transected (PNT) rat, which was used as a stress urinary incontinence (SUI) model. MDSCs were purified from the gastrocnemius muscles of 4-week-old inbred female SPF Wistar rats and labeled with green fluorescent protein. Animals were divided into five groups (N = 15): sham (S), PNT (D), PNT+FG injection (F), PNT+MDSC injection (M), and PNT+MDSC+FG injection (FM). Each group was subdivided into 1- and 4-week groups. One and 4 weeks after injection into the proximal urethra, leak point pressure (LPP) was measured to assess urethral resistance function. Histology and immunohistochemistry were performed 4 weeks after injection. LPP was increased significantly in FM and M animals after implantation compared to group D (P < 0.01), but was not different from group S. LPP was slightly higher in the FM group than in the M group but there was no significant difference between them at different times. Histological and immunohistochemical examination demonstrated increased numbers of surviving MDSCs (109 ± 19 vs 82 ± 11/hpf, P = 0.026), increased muscle/collagen ratio (0.40 ± 0.02 vs 0.34 ± 0.02, P = 0.044), as well as increased microvessel density (16.9 ± 0.6 vs 14.1 ± 0.4/hpf, P = 0.001) at the injection sites in FM compared to M animals. Fibrin glue may potentially improve the action of transplanted MDSCs to restore the histology and function of the urethral sphincter in a SUI rat model. Injection of MDSCs with fibrin glue may provide a novel cellular therapy method for SUI.

Pudendal nerve injury reduces urethral outlet resistance in diabetic rats

Diabetics have voiding and continence dysfunction to which elevated levels of advanced glycation end products (AGE) may contribute. In addition, pudendal nerve injury is correlated with voiding dysfunction and stress incontinence in rats. The aim of this study was to investigate whether pudendal nerve crush (PNC) in diabetic rats alters urinary function. Female virgin Sprague-Dawley rats (144) were divided equally into diabetic, diuretic, and control groups. Half of the animals in each group were subjected to PNC, and the other half to sham PNC. Diabetes was induced 8 wk before PNC or sham PNC by streptozotocin injection (35 mg/kg). Animals underwent conscious cystometry and leak point pressure (LPP) testing 4 or 13 days after PNC or sham PNC. Tissues of half the animals were tested for levels of AGEs. Qualitative histological assessment was performed in the remaining animals. Diabetic rats 4 days after PNC voided significantly greater volume in a shorter time and with significantly less pressure than after sham PNC, suggesting that diabetic rats have a functional outlet obstruction that is relieved by PNC. LPP was significantly reduced 4 days after PNC in diabetic and diuretic animals and returned to normal 13 days after PNC. Diabetic rats with PNC demonstrated increased muscle fiber disruption and atrophy of the external urethral sphincter. AGEs were significantly elevated in diabetic rats. PNC relieves a functional outlet obstruction in diabetic rats. AGEs are elevated in diabetic rats and could play a role in urinary dysfunction and recovery from PNC.

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.

Human umbilical cord blood mononuclear cell transplantation in rats with intrinsic sphincter deficiency

To evaluate the effectiveness of the human umbilical cord blood (HUCB) transplantation for the treatment of intrinsic sphincter deficiency (ISD), we analyzed the short term effects of HUCB mononuclear cell transplantation in rats with induced-ISD. ISD was induced in rats by electro-cauterization of periurethral soft tissue with HUCB mononuclear cell injection after 1 week. The sphincter function measured by mean leak point pressure was significantly improved in the experimental group compared to the control group at 4 weeks. (91.75+/-18.99 mmHg vs. 65.02+/-22.09 mmHg, P=0.001). Histologically, the sphincter muscle was restored without damage while in the control group it appeared markedly disrupted with atrophic muscle layers and collagen deposit. We identified injected HUCB cells in the tissue sections by Di-I signal and Prussian blue staining. HUCB mononuclear cell injection significantly improved urethral sphincter function, suggesting its potential efficacy in the treatment of ISD.

Voiding function in obese and type 2 diabetic female rats

The effects of obesity and type 2 diabetes (DMII) on the lower urinary tract (LUT) were characterized by evaluating voiding function and anatomy in female Zucker diabetic fatty (ZDF) rats. Age-matched female virgin rats were separated into three experimental groups: Zucker lean rats (control; normal diet, n = 22), ZDF rats (obese+nondiabetic; low-fat diet, n = 22), and ZDF rats (obese+diabetic; high-fat diet, n = 20). Rats were placed on their specified diet for 10 wk before urodynamic LUT evaluation. A suprapubic catheter was implanted 2 days before urodynamic studies. Voiding function was evaluated by cystometric and leak point pressure (LPP) testing. The bladder, urethra, and vagina were immediately excised for qualitative histological evaluation. Compared with control rats, obese+nondiabetic and obese+diabetic rats had significantly decreased contraction pressure ( P = 0.003) and increased cystometric filling volume ( P < 0.001). Both obese groups exhibited significantly higher voided volumes ( P = 0.003), less frequent urinary events ( P < 0.001), and increased residual volumes ( P = 0.039). LPP studies showed a nonsignificant decrease in LPP ( P = 0.075) and baseline pressure ( P = 0.168) in both obese groups compared with control. Histology of the external urethral sphincter in obese rats showed increased fibrosis, leading to disruption of the skeletal muscle structure compared with control. Additionally, the bladder wall of the obese+nondiabetic and obese+diabetic rats demonstrated edema and vasculopathy. Voiding dysfunction was evident in both obese groups but with no significant differences due to DMII, suggesting that voiding dysfunction in DMII may be attributable at least in part to chronic obesity.

Two kinds of urinary continence reflexes during abrupt elevation of intravesical pressure in rats

Urethral closure mechanisms during abrupt elevation of intravesical pressure (P(ves)) were investigated. During sneezing, the middle urethral closing response was observed and it still remained after opening the abdomen. The middle urethral response was almost completely abolished after bilateral transection of somatic nerves innervating the external urethral sphincter and the pelvic floor muscles, while bilateral transection of both pelvic nerves and hypogastric nerves had no effects. Somatic nerve transection resulted in fluid leakage from the urethral orifice during sneezing. Passive increments of P(ves) for 120 seconds by elevating a saline reservoir connected to the bladder also induced the middle urethral closing response in rats with spinal cord transection at T8-T9. The response was totally abolished by cutting pelvic nerves bilaterally, and partially reduced after bilateral transection of pudendal nerves, nerves to pelvic floor muscles or hypogastric nerves. Electrical stimulation of abdominal muscles (ESAM) for 1 second elevated P(ves) in a stimulus-dependent manner in the spinal cord-transected rats, and the P(ves) rise was almost lost when the abdomen was opened. The P(ves) inducing fluid leakage from the urethral orifice was lowered in rats when pelvic nerves or somatic nerves were cut bilaterally, while transection of bilateral hypogastric nerves showed smaller effects. These results indicate that at least two kinds of urinary continence reflexes close the middle urethra during abrupt elevation of P(ves); one reflex observed during sneeze is preprogrammed so as to close the urethra automatically irrespective of bladder afferent activity, and the other reflex is triggered by bladder afferent excitation. During momentary stress events such as sneezing (<0.15 seconds) and ESAM (1 second), the striated muscles mainly contribute to the urethral closure, while during events for a relatively long period like passive P(ves) elevation for 120 seconds, both striated and smooth muscles are involved in the prevention of stress urinary incontinence.

Dual simulated childbirth injury delays anatomic recovery

A dual childbirth injury model, including vaginal distension (VD) and pudendal nerve crush (PNC), may best represent the injuries seen clinically. The objective of this study was to investigate urethral function, anatomy, and neurotrophin expression after several simulated childbirth injuries. Groups of 140 rats underwent PNC, VD, PNC+VD, or neither (C). Four days after injury, all injury groups had significantly decreased leak-point pressure (LPP) compared with C rats. Ten days after injury, LPP in PNC and PNC+VD rats remained significantly lower than C rats. Three weeks after injury, LPP in all injury groups had recovered to C values. Histological evidence of injury was still evident in the external urethral sphincter (EUS) after VD and PNC+VD 10 days after injury. Three weeks after injury, the EUS of PNC+VD rats remained disrupted. One day after VD, brain-derived neurotrophic factor (BDNF) expression in the EUS was reduced, while neurotrophin-4 (NT-4) and nerve growth factor (NGF) expression was unchanged. BDNF, NT-4, and NGF expression was dramatically upregulated in the EUS after PNC. After PNC+VD, NGF expression was upregulated, and BDNF and NT-4 expression was upregulated somewhat but not to the same extent as after PNC. Ten days after injury, PNC+VD had the least number of normal nerve fascicles near the EUS, followed by PNC and VD. Twenty-one days after injury, all injury groups had fewer normal nerve fascicles, but without significant differences compared with C rats. PNC+VD therefore provides a more severe injury than PNC or VD alone.

Pubo-urethral ligament injury causes long-term stress urinary incontinence in female rats: an animal model of the integral theory

PURPOSE

We examined the long-term effects of pubo-urethral ligament deficiency as a potential model of stress urinary incontinence compared to an established model of stress urinary incontinence.

MATERIALS AND METHODS

A total of 21 female Sprague-Dawley rats were randomly assigned to 1 of 3 groups, including pubo-urethral ligament transection, sham pubo-urethral ligament transection and bilateral pudendal nerve transection. Leak point pressure was measured 28 days later via an implanted suprapubic catheter. After leak point pressure measurement all animals were sacrificed. The pubic arch and pelvic organs were harvested for histological examination. The Wilcoxon rank sum test was used to evaluate differences in leak point pressure among the experimental groups.

RESULTS

At 28 days after pubo-urethral ligament transection mean +/- SD leak point pressure was significantly decreased when comparing pubo-urethral ligament transection and pudendal nerve transection to sham treatment (15.75 +/- 6.46 and 15.10 +/- 4.98 cm H(2)O, respectively, vs 42.56 +/- 11.58, p <0.001). No difference was noted when comparing pubo-urethral ligament transection to pudendal nerve transection (p = 0.76), indicating the long-term durability of pubo-urethral ligament transection on inducing stress urinary incontinence in the female rat. Histological examination of en bloc suprapubic areas demonstrated an absent pubo-urethral ligament in the pubo-urethral ligament transection group, and an intact pubo-urethral ligament in the sham treated and pudendal nerve transection groups.

CONCLUSIONS

Our results show that pubo-urethral ligament deficiency in the female rat induces long-term stress urinary incontinence that is comparable to that in the established stress urinary incontinence model via pudendal nerve transection. Our novel rat model could be used to investigate mechanisms of stress urinary incontinence in females, including the role of urethral hypermobility and potential therapeutic interventions for stress urinary incontinence.

Evaluation of different techniques to create chronic urinary incontinence in the rat

OBJECTIVE

To evaluate models for chronic urinary incontinence (UI) in the rat.

MATERIALS AND METHODS

Two models were fully evaluated: one of repeated dilatation of the vagina, simulating birth trauma, the vaginal dilatation (VD) group; the other, with surgical transposition of the urethra to a vertical position, the urethral transposition (UT) group. The VD rats were evaluated by the sneeze test. When negative, vaginal dilatation was repeated in a similar way. The UT group was evaluated by observation of continuous urine leakage. The leak-point pressure (LPP) was measured at study end in all the rats.

RESULTS

All the VD rats had occasional negative sneeze tests and all had to be dilated again. This resulted in persistent UI on sneeze testing for the entire period. In the UT group, 12 rats leaked continuously during the whole study period; in the other four UI became less at 4, 5, 6, and 7 weeks, respectively. The LPP in the rats with UI was significantly lower than in the respective control groups.

CONCLUSIONS

These models permit study of chronic stress UI and continuous UI in the rat. Spontaneous recovery of continence was seen mostly in the VD group.

Development of a device to standardize leak point pressure experiments in rats

AIMS

The objective of this study was to test a custom device aimed at increasing repeatability of abdominal leak point pressure (LPP) measurements in rodents.

METHODS

The device consisted of a soft-tipped force applicator with a force sensor which was moved in the vertical direction by a linear actuator, laser crosshairs for accurate positioning, and a hand-held wired remote control system. One expert and two novice experimenters acquired LPP measurements using manual and device methods by applying a gradually increasing force with the finger or the device, respectively, until a leak was visually observed at the urethral meatus. The device was tested at fast, medium, and slow speeds. A leak sensor was also tested to determine presence of a leak and reaction time of the user. The change in bladder pressure due to the externally applied force (LPP) was the primary outcome.

RESULTS

There were no significant differences in mean LPP value when compared across experiments (expert, novice), method (manual, device), or speeds. The pooled variance of LPP was significantly decreased (P < 0.05) compared to the manual method when using the device at medium speed; however the slower speed showed no further improvement over the medium speed. The wet sensor detected leaks 385 +/- 187 msec earlier than users' reaction.

CONCLUSIONS

Use of the device can decrease variability of the experiment but does not alter mean values. Reaction time, inherent in both the manual and device methods, has the potential for a significant impact on LPP outcomes.

The Fate of Implanted Syngenic Muscle Precursor Cells in Injured Striated Urethral Sphincter of Female Rats

We studied the outcome of syngenic skeletal muscle precursor cells (MPCs) implanted in the striated urethral sphincter of the female rat. These cells were injected at the site of a longitudinal sphincterotomy performed 21 days before implantation. MPCs were isolated from the striated hindlimb muscles of syngenic adult rats and were infected with a retrovirus carrying the gene for either the green fluorescent protein (GFP) or the β-galactosidase enzyme (β-gal). MPCs (2 × 105) were injected longitudinally at the site of the lesion in 48 animals using a 10-μl Hamilton syringe. Then the whole urethras were excised from 2 h up to 90 days for cross section immunocytochemistry analysis. All the urethras exhibited connective tissue in place of the injury of the striated fibers. Two hours after injection a cluster of small round basophilic cells was observable at the site of injection and some of them expressed GFP or β-gal. A few GFP- and β-gal-positive cells were already detectable 7 days after injection. A large amount of injected cells probably died after injection. Many striated fibers of the urethra became GFP positive from day 7 until day 21, suggesting that few MPCs were allowed to incorporate the divided extremities of the striated fibers from day 7. Unfortunately, we did not observe centronucleated regenerated fibers in this experiment.

Peripheral neural lesion-induced stress urinary incontinence in anaesthetized female cats

OBJECTIVES

To characterize the effect of acute unilateral and bilateral lesion of the pelvic and pudendal nerves, and nerves innervating the iliococcygeous and pubococcygeous muscles during sneezing in anaesthetized female cats, on intravesical pressure (IVP), urethral pressure (UPs) and external urethral sphincter (EUS) activity.

MATERIALS AND METHODS

In seven anaesthetized female cats UPs along the urethra (UPs1-4) and IVPs were recorded in the emptied bladder during sneezing before and after unilateral and then bilateral peripheral neural lesions. UPs were measured using microtip transducer catheters with UP4 positioned in the distal urethra where the EUS is located. Urine leakage was also noted, after urethral catheter removal and bladder filling.

RESULTS

During sneezing, in intact cats, the magnitude of UP4 was larger than those of IVP and UPs1-3. The area under the curve of both anal sphincter and EUS electromyography was increased. There was no urine leakage. After unilateral neural lesions, the mean magnitude of response was similar all along the urethra and in the bladder. The distal UP response was significantly lower than that recorded in intact cats. In addition, there was urine leakage in six of the seven cats. Bilateral neural lesions caused permanent urine leakage and significant decreases in all the UP responses.

CONCLUSION

In female cats, during sneezing, neurally driven reflex contractions of EUS leading to an increase in distal UP contribute to active urethral closure mechanisms and ensure urinary continence.