Animal models of female stress urinary incontinence

Birth trauma simulated by vaginal distention induced possible irreversible changes in the composition of the fiber types in the external urethral sphincter of rats

The external urethral sphincter (EUS) is crucial in urinary continence development. Understanding the morphological features of the EUS in female rats after vaginal distention (VD), using a model of birth trauma, would aid in evaluating its functional and metabolic properties. Our recent study demonstrated that the EUS in female rats expresses one slow (type 1) and two fast (types 2A and 2B) myosin heavy chain (MHC) isoforms. Our preliminary experiment revealed that type 2B isoform expression was markedly reduced in the EUS 4 weeks after VD. Here, we aimed to examine the expression patterns of these three types of MHC isoforms, and an embryonic MHC, a marker of regeneration fibers, in the EUS of rats 3 days and 1, 2, and 8 weeks after VD using immunofluorescence staining. Hence, type 2B fibers were selectively damaged early in post-VD and did not recover fully later. Muscle regeneration in the sphincter peaked 1 week after trauma using a marker of immature fibers, embryonic myosin heavy chain. Electron microscopy revealed that the EUS of female rats was composed of mitochondria-rich muscle fibers. Myoblasts or immature muscle fibers were discovered in the sphincter layer 1 week after trauma. These results suggest that myogenesis after VD may not contribute to restoring normal fiber composition in a female rat's EUS.

Effects of Age and Multiple Vaginal Births on Lower Urinary Tract Structure and Function in Nonhuman Primates

Purpose: The relative roles of urinary sphincter damage, aging, and childbirth in stress urinary incontinence (SUI), have not been established. This study was performed to elucidate the roles of these factors.Methods: The study included: (1) 8 female cynomolgus monkeys (17–19 years of age and 7–8 vaginal births each); (2) six 5-yearold nulliparous monkeys with surgically created chronic urinary sphincter dysfunction; and (3) six 5-year-old, nulliparous, nosurgery controls. Sedated abdominal leak point pressure (ALPP) and maximum urethral sphincter pressures (MUP) were measured. Sphincters, bladders, and pelvic support muscles were quantified for collagen content. Additionally, bladders were analyzed for collagen fiber thickness, length, and angle using CT-FIRE analysis of Picrosirius red-stained tissues.Results: Resting MUP values were similar in the controls and older multiparous monkeys (P>0.05). However, aging and multiple births reduced pudendal nerve-stimulated increases in MUP (P<0.05 vs. controls). ALPP values were lower in the older multiparous versus younger groups of monkeys (P<0.05). Sphincter collagen content was greater, and muscle content less, in the injury model (P<0.05 vs. controls). However, these measures were not affected by age and childbirth (P>0.05 vs. young groups). Bladder collagen content was greater, and muscle content less, in the old multiparous monkeys (P<0.05 vs. younger groups). Additionally, collagen fibers were thicker and more angular in the bladders of the older multiparous monkeys than in the other nonhuman primate groups (P<0.05). Pelvic support muscles had higher collagen and lower muscle content in the older multiparous monkeys than in the younger groups of monkeys (P<0.05).Conclusions: SUI, associated with aging and multiple childbirths, appeared to be more strongly associated with bladder dysfunction, reduced pelvic muscle support, and the compensatory response to neural stimulation than with selective urinary sphincter dysfunction.

Stem cell therapy combined with controlled release of growth factors for the treatment of sphincter dysfunction

Sphincter dysfunction often occurs at the end of tubule organs such as the urethra, anus, or gastroesophageal sphincters. It is the primary consequence of neuromuscular impairment caused by trauma, inflammation, and aging. Despite intensive efforts to recover sphincter function, pharmacological treatments have not achieved significant improvement. Cell- or growth factor-based therapy is a promising approach for neuromuscular regeneration and the recovery of sphincter function. However, a decrease in cell retention and viability, or the short half-life and rapid degradation of growth factors after implantation, remain obstacles to the translation of these therapies to the clinic. Natural biomaterials provide unique tools for controlled growth factor delivery, which leads to better outcomes for sphincter function recovery in vivo when stem cells and growth factors are co-administrated, in comparison to the delivery of single therapies. In this review, we discuss the role of stem cells combined with the controlled release of growth factors, the methods used for delivery, their potential therapeutic role in neuromuscular repair, and the outcomes of preclinical studies using combination therapy, with the hope of providing new therapeutic strategies to treat incontinence or sphincter dysfunction of the urethra, anus, or gastroesophageal tissues, respectively.

A study on etiology of incontinence in double knockout mouse model

INTRODUCTION AND OBJECTIVE

Stress urinary incontinence is of concern in both pediatric and adult population. Double mutant GLI family zinc finger Gli2^+/-; Gli3^Δ699/+ murine model of stress incontinence has been recently developed as a reliable model which does not require surgical manipulation to create incontinence and is shown to survive to adulthood. The aim of this study was to establish the etiology of incontinence in the double mutant Gli2^+/-; Gli3^Δ699/+ mice.

STUDY DESIGN

We used 13 cluster of differentiation 1 (CD-1) mice (7-9 weeks) for demonstration of histology of the bladder and urethra. There were 3 Wild Gli2^+/- females, 2 Wild Gli2^+/- males, 4 Gli2^+/-;Gli3^Δ699/+ females and 4 Gli2^+/-;Gli3^Δ699/+ males. The Wild Gli2^+/- mice served as the control group and Gli2^+/-;Gli3^Δ699/+ mice served as the test group. Additionally, eight 16.5 days mice (2 each of Wild Gli2^+/- females, Wild Gli2^+/- males, double knockout (DKO) Gli2^+/-;Gli3^Δ699/+ females and Gli2^+/-;Gli3^Δ699/+ males) were used to assess the histology of the spinal cord. The gross appearance of bladder and urethra was studied using ink injection assays. Immunohistochemistry was done for smooth muscle actin and cytokeratin.

RESULTS

Gross and histologic appearance confirmed the previously reported widening of bladder outlet and hypoplasia of smooth muscles in female urethra and also established them in the male urethra of Gli2^+/-;Gli3^Δ699/+ mice compared to Gli2^+/- mice. The double knockout mice were smaller than the Gli2 mice (5.2 vs 6.1 cm, p = 0.002). Immunohistochemistry demonstrated epithelial hyperplasia and smooth muscle hypoplasia. Additionally, there was prostatic hypoplasia in the Gli2^+/-;Gli3^Δ699/+ male mice. The spinal cord length for body size appeared comparable between the Gli2^+/- and Gli2^+/-;Gli3^Δ699/+ mice but histological evaluation revealed abnormal development of the caudal end of the vertebral body with premature termination of the spinal cord (Figure).

DISCUSSION

The histological changes in the bladder neck and urethra were consistent to those previously reported. While previous report described the findings in female mice only, we confirmed that these findings are also present in males as well as prostatic hypoplasia, a possible additional factor leading to stress incontinence. The most important finding in the present study however, was the detection of premature termination of spinal cord in the DKO Gli2^+/-; Gli3^Δ699/+ mice which has not been reported previously and is likely a major contributor to incontinence in this model.

CONCLUSION

The incontinence in male as well as female Gli2^+/-; Gli3^Δ699/+ mice is due to both myogenic and neurogenic involvement. These double knockout mice are a valuable model of stress incontinence related to neurogenic bladder due to low outlet resistance.

Platelet-rich Plasma Promotes Restoration of the Anterior Vaginal Wall for the Treatment of Pelvic Floor Dysfunction in Rats

STUDY OBJECTIVE

To determine the efficacy of using platelet-rich plasma (PRP) for vaginal wall repair in rats with vaginal wall impairment induced by vaginal distension (VD).

DESIGN

A single-blind, randomized study.

SETTING

A certified animal research facility.

ANIMALS

Twenty-four female Sprague Dawley rats.

INTERVENTIONS

Female Sprague Dawley rats were divided into sham (n = 8), VD (n = 8), and VD + PRP (n = 8) groups. Vaginal tissues from the VD group were dissected at 28-day post injury. VD + PRP rats received vaginal PRP injections on the 1st, 7th, 14th, and 21st day after VD and sacrificed on the 28th day.

MEASUREMENTS AND MAIN RESULTS

Urodynamic tests were performed in all rats. Immunohistochemistry was used to evaluate matrix metalloprotease-2 (MMP-2) and matrix metalloprotease-9 (MMP-9). Masson's staining was used to evaluate collagen fibers and calculate collagen volume fraction. Collagen fiber damage was confirmed in the VD group, evidenced by thinner and sparse distribution of collagen fibers, with significantly higher MMP-2 and MMP-9 expression than the sham group (p <.05). The collagen fiber damage in the vaginal wall likely led to pelvic floor dysfunction (PFD), evidenced by significantly decreased bladder leak-point pressure (p <.01) and abdominal leak-point pressure (p <.01) in the VD group compared with the sham group. After completion of the PRP treatment, a significantly higher collagen volume fraction (p <.01) and significantly increased bladder leak-point pressure (p <.05) and abdominal leak-point pressure (p <.01) were achieved in the VD + PRP compared with the VD group, thus indicating repair of the vaginal wall and improvement of PFD.

CONCLUSION

PRP injections facilitate the regeneration of vaginal wall tissue, particularly collagen fiber, after VD, leading to functional improvement of PFD. Findings support the feasibility of using PRP as a novel treatment for PFD.

Dimethyl fumarate ameliorates stress urinary incontinence by reversing ECM remodeling via the Nrf2-TGF-β1/Smad3 pathway in mice

INTRODUCTION AND HYPOTHESIS

Mechanical trauma and oxidative injury are involved in the pathogenesis of stress urinary incontinence (SUI), and oxidative stress (OS) is considered a potential therapeutic target. The antioxidant properties of dimethyl fumarate (DMF), a potent activator of Nrf2, have been highlighted recently. We therefore predicted that DMF might have therapeutic effects on mechanical trauma-induced SUI.

METHODS

The SUI mice model was established by vaginal distension (VD). Leak point pressure (LPP), serum OS biomarkers, cell proliferation and apoptosis, collagen, elastin, matrix metalloproteinases (MMP), Nrf2, the TGF-β1/Smad3 signaling pathway, and the associated tissue growth factors in the anterior vaginal wall were measured in either wild-type or Nrf2-knockout (Nrf2^-/^-) female C57BL/6 mice.

RESULTS

The results showed that DMF improved the VD-induced LPP reduction, alleviated oxidative injury, stimulated cell proliferation and inhibited apoptosis in the anterior vaginal wall tissue of mice. Moreover, DMF treatment reduced the hydrolysis of ECM proteins by MMP2 and MMP9. The above effects may be mediated by a series of tissue growth factors, including α-SMA, PAI-1, and TIMP-2, with the TGF-β1/Smad3 signaling pathway as the core regulatory mechanism. In further study, Nrf2^-/^- mice were used to replicate the SUI model. And the difference is that DMF failed to reactivate the TGF-β1/Smad3 pathway, nor did it improve LPP.

CONCLUSIONS

Dimethyl fumarate can ameliorate urethra closure dysfunction in the VD-induced SUI mice model, and the therapeutic effect of DMF is mediated by the Nrf2-dominated antioxidant system and its downstream TGF-β1/Smad3 signaling pathway.

Preclinical applications of high-definition manometry system to investigate pelvic floor muscle contribution to continence mechanisms in a rabbit model

External anal sphincter (EAS), external urethral sphincters, and puborectalis muscle (PRM) have important roles in the genesis of anal and urethral closure pressures. In the present study, we defined the contribution of these muscles alone and in combination with the sphincter closure function using a rabbit model and a high-definition manometry (HDM) system. A total of 12 female rabbits were anesthetized and prepared to measure anal, urethral, and vaginal canal pressures using a HDM system. Pressure was recorded at rest and during electrical stimulation of the EAS and PRM. A few rabbits (n = 6) were subjected to EAS injury and the impact of EAS injury on the closure pressure profile was also evaluated. Anal, urethral, and vaginal canal pressures recorded at rest and during electrical stimulation of EAS and PRM demonstrated distinct pressure profiles. EAS stimulation induced anal canal pressure increase, whereas PRM stimulation increased the pressures in all the three orifices. Electrical stimulation of EAS after injury resulted in about 19% decrease in anal canal pressure. Simultaneous electrical stimulation of EAS and PRM resulted in an insignificant increase of individual anal canal pressures when compared with pressures recorded after EAS or PRM stimulations alone. Our data confirm that HDM is a viable system to measure dynamic pressure changes within the three orifices and to define the role of each muscle in the development of closure pressures within these orifices in preclinical studies.NEW & NOTEWORTHY We anticipate that with this new HDM technology, physiological changes within these orifices may be redefined using the extensive data that are generated from 96 sensors. When compared with conventional methods, HDM offers the advantages of an increased response rate, as well as the utilization of 96 circumferential sensors to simultaneously measure pressure along the three orifices. Our findings suggest a potential use of this technology to better define urinary leak point pressure.

Perinatal mesenchymal stromal cells of the human decidua restore continence in rats with stress urinary incontinence induced by simulated birth trauma and regulate senescence of fibroblasts from women with stress urinary incontinence

Stress urinary incontinence (SUI) is a condition that causes the involuntary loss of urine when making small efforts, which seriously affects daily life of people who suffer from it. Women are more affected by this form of incontinence than men, since parity is the main risk factor. Weakening of the pelvic floor tissues is the cause of SUI, although a complete understanding of the cellular and molecular mechanisms of the pathology is still lacking. Reconstructive surgery to strengthen tissue in SUI patients is often associated with complications and/or is ineffective. Mesenchymal stromal cells from the maternal side of the placenta, i.e. the decidua, are proposed here as a therapeutic alternative based on the regenerative potential of mesenchymal cells. The animal model of SUI due to vaginal distention simulating labor has been used, and decidual mesenchymal stromal cell (DMSC) transplantation was effective in preventing a drop in pressure at the leak point in treated animals. Histological analysis of the urethras from DMSC-treated animals after VD showed recovery of the muscle fiber integrity, low or no extracellular matrix (ECM) infiltration and larger elastic fibers near the external urethral sphincter, compared to control animals. Cells isolated from the suburethral connective tissue of SUI patients were characterized as myofibroblasts, based on the expression of several specific genes and proteins, and were shown to achieve premature replicative senescence. Co-culture of SUI myofibroblasts with DMSC via transwell revealed a paracrine interaction between the cells through signals that mediated DMSC migration, SUI myofibroblast proliferation, and modulation of the proinflammatory and ECM-degrading milieu that is characteristic of senescence. In conclusion, DMSC could be an alternative therapeutic option for SUI by counteracting the effects of senescence in damaged pelvic tissue.

Time course for urethral neuromuscular reestablishment and its facilitated recovery by transcutaneous neuromodulation after simulated birth trauma in rats

The aims of the study were to determine the time-course of urinary incontinence recovery after vaginal distension (VD), elucidate the mechanisms of injury from VD leading to external urethral sphincter (EUS) dysfunction, and assess if transcutaneous electrical stimulation (TENS) of the dorsal nerve of the clitoris facilitates recovery of urinary continence after VD. Rats underwent 4-h VD, 4-h sham VD (SH-VD), VD plus 1-h DNC TENS, and VD plus 1-h sham TENS (SH-TENS). TENS or SH-TENS were applied immediately and at days 2 and 4 post-VD. Micturition behavior, urethral histochemistry and histology, EUS and nerve electrophysiology, and cystometrograms were evaluated. VD induced urine leakage and significantly disrupted EUS fibers and nerve-conduction (VD vs SH-VD group;p < 0.01). Urine leakage disappeared 13 days post-VD (p < 0.001). Structural and functional recovery of EUS neuromuscular circuitry started by day 6 post-VD, but did not fully recover by day 11 post-VD (p > 0.05). TENS significantly decreased the frequency of urine leakage post-VD (days 5–7;p < 0.01). We conclude that rat urinary continence after VD requires 2 weeks to recover, although urethra structure is not fully recovered. TENS facilitated urinary continence recovery after VD. Additional studies are necessary to assess if TENS could be used in postpartum women.

Large Animal Models for Investigating Cell Therapies of Stress Urinary Incontinence

Stress urinary incontinence (SUI) is a significant health concern for patients affected, impacting their quality of life severely. To investigate mechanisms contributing to SUI different animal models were developed. Incontinence was induced under defined conditions to explore the pathomechanisms involved, spontaneous recovery, or efficacy of therapies over time. The animal models were coined to mimic known SUI risk factors such as childbirth or surgical injury. However, animal models neither reflect the human situation completely nor the multiple mechanisms that ultimately contribute to the pathogenesis of SUI. In the past, most SUI animal studies took advantage of rodents or rabbits. Recent models present for instance transgenic rats developing severe obesity, to investigate metabolic interrelations between the disorder and incontinence. Using recombinant gene technologies, such as transgenic, gene knock-out or CRISPR-Cas animals may narrow the gap between the model and the clinical situation of patients. However, to investigate surgical regimens or cell therapies to improve or even cure SUI, large animal models such as pig, goat, dog and others provide several advantages. Among them, standard surgical instruments can be employed for minimally invasive transurethral diagnoses and therapies. We, therefore, focus in this review on large animal models of SUI.

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.

The extracellular matrix molecules versican and hyaluronan in urethral and vaginal tissues in stress urinary incontinence

PURPOSE

Abnormal extracellular matrix (ECM) changes are correlated with stress urinary incontinence (SUI). The ECM components versican (Vcan) and hyaluronan (HA) play key roles in regulating tissue inflammation and maintaining connective tissue homeostasis. We analyzed the localization and expression of these ECM components in urethral and vaginal tissues from a rat model of urinary incontinence and from human clinical specimens.

METHODS

Nulliparous rats underwent vaginal distension (VD), a rodent model of SUI, or a sham procedure. Tissues were harvested from six rats per group at days 1, 4, and 21 for immunohistochemistry and RNA expression analysis of ECM components. Periurethral vaginal samples from female patients with SUI were also examined.

RESULTS

High-intensity staining for Vcan was observed 1 day after procedure in both control and VD animals. This level of abundance persisted at day 4 in VD compared to control, with concurrent reduced messenger RNA (mRNA) expression of the Vcan-degrading enzymes ADAMTS5 and ADAMTS9 and reduced staining for the Vcan cleavage epitope DPEAAE. Abundance of HA was not different between VD and control, however mRNA expression of the HA synthase Has2 was significantly reduced in VD tissues at day 4. Abundant Vcan staining was observed in 60% of SUI patient samples, which was strongest in regions of disrupted elastin.

CONCLUSION

Reduction of Vcan-degrading enzymes and HA synthases at day 4 postsurgery indicates a potential delay in ECM turnover associated with SUI. Abundant Vcan is associated with inflammation and elastin fiber network disruption, warranting further investigation to determine its role in SUI pathogenesis.

Mesenchymal stem cell-based bioengineered constructs: foreign body response, cross-talk with macrophages and impact of biomaterial design strategies for pelvic floor disorders

An excessive foreign body response (FBR) has contributed to the adverse events associated with polypropylene mesh usage for augmenting pelvic organ prolapse surgery. Consequently, current biomaterial research considers the critical role of the FBR and now focuses on developing better biocompatible biomaterials rather than using inert implants to improve the clinical outcomes of their use. Tissue engineering approaches using mesenchymal stem cells (MSCs) have improved outcomes over traditional implants in other biological systems through their interaction with macrophages, the main cellular player in the FBR. The unique angiogenic, immunomodulatory and regenerative properties of MSCs have a direct impact on the FBR following biomaterial implantation. In this review, we focus on key aspects of the FBR to tissue-engineered MSC-based implants for supporting pelvic organs and beyond. We also discuss the immunomodulatory effects of the recently discovered endometrial MSCs on the macrophage response to new biomaterials designed for use in pelvic floor reconstructive surgery. We conclude with a focus on considerations in biomaterial design that take into account the FBR and will likely influence the development of the next generation of biomaterials for gynaecological applications.

The vaginal distention model in mice is not a reliable model of simulated birth trauma-induced stress urinary incontinence

AIMS

Vaginal distention (VD) is a validated model of birth-related trauma in rats. Recently a mouse VD model was reported. Our study was originally conducted to evaluate the impact of age on VD in mice. This manuscript describes the study and reports on the lack of reproducibility of VD models in mice.

METHODS

We utilized female C57BL/6 mice. A total of 190, 12-weeks old mice, were randomized into VD and sham groups. We inflated a modified Foley's balloon with 0.3 mL for 1 h inside the mice vagina. Afterwards, we measured the leak point pressure (LPP) at defined timepoints (0, 4, 10, 20, or 40 days). We randomized another 190, 40-week old, C57BL/6 mice into either VD or sham groups. We used an extra 20 mice as age - matched controls.

RESULTS

In both 12 and 40 weeks-old mice, LPP was significantly decreased versus the negative controls at day 0. Additionally, in both 12 and 40 weeks-old mice, the decrease in LPP was significantly higher in the VD group compared to the sham group at day 0. However, the LPP results were comparable between VD and sham at any other time point thereafter. Furthermore, there was no significant change in LPP values between instrumented (VD and sham) mice and control mice at any time after day 0.

CONCLUSIONS

The VD models previously described is not a reproducible model for the study of VD with large number of mice. Our results, unfortunately, do not support its use to study VD injury in mice.

Morphological changes in rat rectus abdominis muscle induced by diabetes and pregnancy

The urethral muscle of diabetic pregnant rats is affected by long-term mild diabetes and short-term severe diabetes, which plays a crucial role in the pathogenesis of pelvic floor disorders. We hypothesized that muscles outside the pelvis are subject to similar changes. The current study aimed at analyzing the effects of long-term mild and short-term severe diabetes on the structure and ultrastructure of fiber muscles and collagen in rats' rectus abdominis (RA) muscle. Therefore, the RA muscle of virgin, pregnant, long-term mild diabetic, short-term severe diabetic, long-term mild diabetic pregnant and short-term severe diabetic pregnant 3-month-old Wistar rats were collected. The structure was analyzed by picrosirius red staining, immunohistochemistry for fast and slow muscle fibers and transmission electron microscopy. We investigated two levels of STZ- induced diabetes: long-term mild diabetes (blood glucose level: 120–200 mg/dL) and short-term severe diabetes (blood glucose level >300 mg/dL). Long-term mild diabetic pregnant and short-term severe diabetic pregnant rats had decreased fast fibers and increased slow fibers, disrupted areas of sarcomere, intermyofibrillar mitochondria and myelin figures in the RA muscle. Both groups enabled us to analyze the specific influence of pregnancy, separately from diabetes. The current study demonstrated that diabetes and pregnancy induced intramuscular transformation and reorganization of RA muscle with a switch of fiber type adjusting their architecture according to intensity and duration of hyperglycemic insult within pregnancy.

Stem Cells for Urinary Incontinence: Functional Differentiation or Cytokine Effects?

Minimally invasive stem cell therapy for stress urinary incontinence may provide an effective nonsurgical treatment for this common condition. Clinical trials of periurethral stem cell injection have been under way, and basic science research has demonstrated the efficacy of both local and systemic stem cell therapies. Results differ as to whether stem cells have a therapeutic effect by differentiating into permanent, functional tissues or exert benefits through a transient presence and the secretion of regenerative factors. This review explores the fate of therapeutic stem cells for stress urinary incontinence and how this may relate to their mechanism of action.

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.

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.

Potential therapeutic role of punicalagin against mechanical-trauma-induced stress urinary incontinence via upregulation of Nrf2 and TGF-β1 signaling : Effect of punicalagin on mechanical trauma induced SUI

INTRODUCTION AND HYPOTHESIS

We investigated the effect of punicalagin (PUN; 2,3-hexahydroxydiphenoyl-gallagyl-D-glucose), on mechanical-trauma-induced stress urinary incontinence (SUI) in mouse and the mechanisms underlying any effects.

METHODS

Ninety virgin female C57BL/6 mice were randomized into six groups: five groups underwent vaginal distention (VD) for 1 h and leak-point pressure (LPP) was measured on the 1st, 3rd, 7th, 14th, and 28th day following (VD groups 1 d, 3 d, 7 d, 14 d, and 28 d). The sixth group was a noninstrumented control (NC) group. Then, 75 virgin female C57BL/6 mice were randomized into five groups: a VD group (that just underwent VD) and an NC group were orally administered saline every day for 7 days; and three VD + PUN groups that underwent VD and were orally administered PUN respectively at 2.5, 5, and 10 mg/kg every day for 7 days. LPP was tested on the day 7, then all mice were sacrificed and their urethras and anterior vaginal walls harvested for Masson staining, immunohistochemistry study, Western blot analysis, and quantitative polymerase chain reaction (qPCR).

RESULTS

LPPs after VD were significantly lower than the NC group, and the LPPs of mice on days 14 and 28 day after VD were significantly higher than on the days 1, 3, and 7. PUN significantly improved VD-induced drops in LPP and alleviated VD-induced decrease of collagen I, collagen III, α-smooth muscle actin (SMA), transforming growth factor (TGF)-β1, and p-Smad3, nuclear factor-erythroid 2 p45-related factor 2 (Nrf2), and glutathione peroxidase (GPx1) protein levels, and increase of 8-hydroxydeoxyguanosine (OHdG) in urethra and anterior vaginal wall. PUN also up-regulated the expression of manganese superoxide dismutase (MnSOD), whereas protein levels of Smad 2, p-Smad2, and Smad3 were not changed.

CONCLUSIONS

PUN exerts certain therapeutic effect on mechanical-trauma-induced SUI in mice, which might be through the activation of TGF-β1/Smad3 and Nrf2/antioxidant response element (ARE) signaling activation.

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.

A genetic female mouse model with congenital genitourinary anomalies and adult stages of urinary incontinence

AIMS

To characterize the urinary incontinence observed in adult Gli2^+/- ; Gli3^Δ699/+ female mice and identify the defects underlying the condition.

METHODS

Gli2^+/- and Gli3^Δ699/+ mice were crossed to generate: wild-type, mutant Gli2 (Gli2^+/- ), mutant Gli3 (Gli3^Δ699/+ ), and double mutant (Gli2^+/- ; Gli3^Δ699/+ ) female mice, verified via Polymerase Chain Reactions. Bladder functional studies including cystometrogram (CMG), leak point pressure (LPP), and voiding testing were performed on adult female mice. Female bladders and urethras were also analyzed via ink injection and histological assays.

RESULTS

CMG tracing showed no signal corresponding to the filling of the Gli2^+/- ; Gli3^Δ699/+ bladders. LPP were significantly reduced in Gli2^+/- ; Gli3^Δ699/+ mice compared to wild-type mice. CMG studies revealed a decrease in peak micturition pressure values in Gli2^+/- ; Gli3^Δ699/+ mice compared with all other groups. No significant differences between mutant and wild-type mice were detected in urinary output. Histological analyses revealed Gli2^+/- ; Gli3^Δ699/+ mice exhibited a widened urethra and a decrease in smooth muscle layer thickness in the bladder outlet and urethra, with increased mucosal folding.

CONCLUSIONS

Gli2^+/- ; Gli3^Δ699/+ adult female mice display persistent urinary incontinence due to the malformation of the bladder outlet and urethra. This presents a consistent and reliable genetic mouse model for female urinary incontinence and alludes to the key role of genetic factors involved in the condition.

A Novel Method of Urinary Sphincter Deficiency: Serial Histopathology Evaluation in a Rat Model of Urinary Incontinence

In this study, a novel technique of irreversible sphincter deficiency by pudendal nerve transection (PNT) using 40 female rats for studying the pathophysiology of stress urinary incontinence associated with childbirth was developed. Of the 40 rats, 10 served as controls and the remaining underwent bilateral PNT at the anastomotic lumbosacral trunk level. Urethral morphological changes following bilateral PNT were assessed with serial hematoxylin and eosin (H&E) and immunohistochemistry (IHC) staining methods at 50, 90, and 130 days post-intervention. Leak point pressure (LPP) measurement was used to determine the effect of pudendal injury on urethral outlet resistance after the transection. H&E and IHC staining showed irreversible loss of striated muscle mass of the sphincter region and increase in collagen deposition compatible with muscle atrophy. LPP measurements also significantly decreased following bilateral PNT. In conclusion, a novel method of irreversible sphincter insufficiency was developed. This model effectively decreased urethral outlet resistance and caused irreversible striated muscle atrophy. It was suggested that this technique can be used to develop a permanent sphincter deficiency model for the preclinical testing of treatment modalities exclusively triggering the pudendal nerve.

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.

Stress urinary incontinence animal models as a tool to study cell-based regenerative therapies targeting the urethral sphincter

Urinary incontinence (UI) is a major health problem causing a significant social and economic impact affecting more than 200million people (women and men) worldwide. Over the past few years researchers have been investigating cell therapy as a promising approach for the treatment of stress urinary incontinence (SUI) since such an approach may improve the function of a weakened sphincter. Currently, a diverse collection of SUI animal models is available. We describe the features of the different models of SUI/urethral dysfunction and the pros and cons of these animal models in regard to cell therapy applications. We also discuss different cell therapy approaches and cell types tested in preclinical animal models. Finally, we propose new research approaches and perspectives to ensure the use of cellular therapy becomes a real treatment option for SUI.

Urethral musculature and innervation in the female rat

AIMS

The urethral sphincter and urethral muscle innervation are critically involved in maintaining continence, especially in the female. However, the urethral muscle type and distribution, as well as the urethral nerves are far from being well documented. Our aim was to clearly identify the distribution of urethral striated muscle, smooth muscle, and urethral nerves.

METHODS

In a cohort analysis of 3-month-old female Sprague-Dawley rats, cross and longitudinal sections of female rat urethra were extensively investigated using morphological techniques. Urethras were harvested to the sections, in order to provide both global and detailed visions of the urethra. H&E, Masson's Trichrome, phalloidin and immunoflourence stains were used. The cytoarchitecture, nitrergic, and cholinergic innervations were mainly investigated. Different layers of the segments of urethra were traced to draw curve graphs that represent the thickness of each muscle layer of urethral wall.

RESULTS

The results showed that the primary peak of striated muscle is in the middle urethra. The inner layer close to mucosa was found to contain longitudinal smooth muscle. Near the bladder orifice, the circular smooth muscle dominates, which becomes thinner distally throughout the rest of urethra. In the middle urethra the vast majority of the urethral muscle are circularly oriented striated muscle cells. Typical nerve endings were present in high power images to show the different characteristic features of nerve innervation.

CONCLUSIONS

This study has illustrated the detailed morphological structure and innervations of the normal female rat urethra and can serve as a basis for further study of stress urinary incontinence (SUI).

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.

Urethral dysfunction in female mice with estrogen receptor β deficiency

Estrogen has various regulatory functions in the growth, development, and differentiation of the female urogenital system. This study investigated the roles of ERβ in stress urinary incontinence (SUI). Wild-type (ERβ^+/+) and knockout (ERβ^−/−) female mice were generated (aged 6–8 weeks, n = 6) and urethral function and protein expression were measured. Leak point pressures (LPP) and maximum urethral closure pressure (MUCP) were assessed in mice under urethane anesthesia. After the measurements, the urethras were removed for proteomic analysis using label-free quantitative proteomics by nano-liquid chromatography–mass spectrometry (LC-MS/MS) analysis. The interaction between these proteins was further analysed using MetaCore. Lastly, Western blot was used to confirm the candidate proteins. Compared with the ERβ^+/+ group, the LPP and MUCP values of the ERβ^−/− group were significantly decreased. Additionally, we identified 85 differentially expressed proteins in the urethra of ERβ^−/− female mice; 57 proteins were up-regulated and 28 were down-regulated. The majority of the ERβ knockout-modified proteins were involved in cell-matrix adhesion, metabolism, immune response, signal transduction, nuclear receptor translational regelation, and muscle contraction and development. Western blot confirmed the up-regulation of myosin and collagen in urethra. By contrast, elastin was down-regulated in the ERβ^−/− mice. This study is the first study to estimate protein expression changes in urethras from ERβ^−/− female mice. These changes could be related to the molecular mechanism of ERβ in SUI.

Synergistic effect of vaginal trauma and ovariectomy in a murine model of stress urinary incontinence: upregulation of urethral nitric oxide synthases and estrogen receptors

The molecular mechanisms underlying stress urinary incontinence (SUI) are unclear. We aimed to evaluate the molecular alterations in mice urethras following vaginal trauma and ovariectomy (OVX). Twenty-four virgin female mice were equally distributed into four groups: noninstrumented control; vaginal distension (VD) group; OVX group; and VD + OVX group. Changes in leak point pressures (LPPs), genital tract morphology, body weight gain, plasma 17β-estradiol level and expressions of neuronal nitric oxide synthase (nNOS), induced nitric oxide synthase (iNOS), and estrogen receptors (ERs—ERα and ERβ) were analyzed. Three weeks after VD, the four groups differed significantly in genital size and body weight gain. Compared with the control group, the plasma estradiol levels were significantly decreased in the OVX and VD + OVX groups, and LPPs were significantly decreased in all three groups. nNOS, iNOS, and ERα expressions in the urethra were significantly increased in the VD and VD + OVX groups, whereas ERβ expression was significantly increased only in the VD + OVX group. These results show that SUI following vaginal trauma and OVX involves urethral upregulations of nNOS, iNOS, and ERs, suggesting that NO- and ER-mediated signaling might play a role in the synergistic effect of birth trauma and OVX-related SUI pathogenesis.

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.

Stem cell homing factor, CCL7, expression in mouse models of stress urinary incontinence

OBJECTIVES

Animal models of vaginal distention (VD) have demonstrated increased expression of chemokine (C-C motif) ligand 7 (CCL7) In this study, we investigated the expression of CCL7 in mice models of simulated birth trauma-induced urinary incontinence using VD and pudendal nerve transection (PNT).

METHODS

Forty-nine mice were divided into 6 groups: VD, sham VD, PNT, sham PNT, anesthesia, and age-matched controls. The urethra, vagina, and rectum were harvested for the expression of CCL7 immediately or 24 hours after assigned procedure. Venous sampling for quantification of serum CCL7 was also performed. An analysis of variance model was used to compare the relative expression of CCL7 in each group.

RESULTS

Urethral CCL7 expression in the VD group was significantly higher than control group after 24 hours (P < 0.01). There was no difference in the urethral CCL7 expression in PNT, sham PNT, sham VD, or anesthesia groups compared with the controls. No statistically significant difference was noted in the vaginal and rectal expression of CCL7 between any of the groups except for sham PNT. Statistically significant differences were noted in the serum CCL7 expression in the VD, PNT, and sham PNT (P < 0.01 in all) groups after 24 hours compared with the control group.

CONCLUSIONS

This study demonstrates overexpression of urethral CCL7 after VD but not PNT. This suggests that nerve injury does not contribute to the CCL7 overexpression. The overexpression of CCL7 in the serum of mice after VD suggests a translational potential where CCL7 measurement could be used as a surrogate for injury after delivery.

The distribution of muscles fibers and their types in the female rat urethra: cytoarchitecture and three-dimensional reconstruction

An attempt to explore urethral cytoarchitecture including the distribution of smooth muscles and fast and slow striated muscles of adult female Sprague Dawley rat--a popular model in studying lower urinary tract function. Histological and immunohistochemical stainings were carried out to investigate the distribution of urethral muscle fibers and motor end plates. The urethral sphincter was furthermore three-dimensionally reconstructed from serial histological sections. The mucosa at the distal urethra was significantly thicker than that of other segments. A prominent inner longitudinal and outer circular layer of smooth muscles covered the proximal end of urethra. Thick circular smooth muscles of the bladder neck region (urethral portion) decreased significantly distalward and longitudinal smooth muscles became 2- to 3-fold thicker in the rest of the urethra. An additional layer of striated muscles appeared externally after neck region (urethra) and in association with motor end plates ran throughout the remaining urethra as the striated sphincter layer. Most striated muscles were fast fibers while relatively fewer slow fibers often concentrated at the periphery. A pair of extraneous striated muscles, resembling the human urethrovaginal sphincter muscles, connected both sides of mainly the distal vagina to the dorsal striated muscles in the wall of the middle urethra. The tension provided by this pair of muscles, and in conjunction with the striated sphincter of the urethral wall, was likely to function to suspend the middle urethra and facilitates its closure. Comprehensive morphological data of urethral sphincter offers solid basis for researchers conducting studies on dysfunction of bladder outlet.

Salutary effect of gastric pentadecapeptide BPC 157 in two different stress urinary incontinence models in female rats

Background

Since an originally anti-ulcer stable gastric pentadecapeptide BPC 157 (PL 14736) was shown to promote healing of injured striated muscle and smooth muscle in the gastrointestinal tract, we explored its therapeutic potentials for leak point pressure (LPP) recovery in rat stress urinary incontinence (SUI) after transabdominal urethrolysis (TU) and prolonged vaginal dilatation (VD).

Material/Methods

During a 7-day period, TU-rats and VD-rats (or healthy rats) received BPC 157, either (i) intraperitoneally, 10 μg/kg or 10 ng/kg, once daily (first administration 30 min after surgery, last 24 h before LPP-testing and sacrifice), or (ii) per-orally, 10 μg/kg in drinking water (0.16 μg/mL, 12 mL/rat/day). Vesicourethral segments were harvested for immunohistochemical evaluation.

Results

All BPC 157 regimens counteracted decrease of LPP values in TU-rats and VD-rats. Additionally, BPC 157-TU rats (μg-intraperitoneally or per-orally) and BPC 157-VD rats (μg intraperitoneally) reached LPP values originally noted in healthy rats. Conversely, in healthy rats, BPC 157 did not alter LPP. Immunohistochemical studies revealed higher desmin (delineates striated organization of skeletal muscle), smooth muscle actin, and CD34 (angiogenic marker) positivity within the urethral wall in BPC 157-treated rats vs. controls, as well as overall preserved muscle/connective tissue ratio assessed with Mallory’s trichrome staining.

Conclusions

Pentadecapeptide BPC 157, applied parenterally or per-orally, appears to ameliorate the SUI in rat models, improving the otherwise detrimental course of healing after VD and TU, which may be analogous to human injury. These beneficial effects may possibly be selectively used in future strategies for treatment of SUI.

Use of three types of synthetic mesh material in sling surgery: a prospective randomized clinical trial evaluating effectiveness and complications

OBJECTIVE

The aim of this study was to determine the surgical success and complication rates of mixed type of mesh materials compared with Prolene mesh in sling surgery over a 4-year follow-up period.

MATERIAL AND METHODS

Between 2005 and 2007, broad-based double-forced sling operations were performed in 144 women with stress incontinence using three different types of mesh material. Group I consisted of 48 patients in whom Vypro® mesh (Ethicon, USA) was used; group II of 48 patients in whom Ultrapro® mesh (Ethicon) and group III of 48 patients in whom Prolene® light mesh (Ethicon) was used. The patients' data and the success of the operation were evaluated based on the 24 h pad test, International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF) scoring and Korman questionnaire analysis.

RESULTS

The ICIQ-SF score, the number of pads used and the results of 24 h pad test were statistically lower in group II at postoperative month 48 (p < 0.05). The rate of postoperative complications was lower in Group II than in the other groups (p < 0.05). The continence rates of groups I, II and III were 84.7%, 91.6% and 85.1%, respectively, in the 48th postoperative month.

CONCLUSIONS

Ultrapro mesh can be used in sling surgery owing to its higher success rates, and lower vaginal and urethral extrusion and de novo urgency rates, which have also been shown in clinical studies.

A nonhuman primate model of stable urinary sphincter deficiency

PURPOSE

The pathophysiology of urinary sphincter deficiency in women remains incompletely understood and current treatment options have limitations. Female nonhuman primates may represent a relevant animal model for studies of pathophysiology and treatment interventions because of their human-like reproductive and age associated stages of life (premenopause, perimenopause and postmenopause), lower urinary tract structure and bipedal posture. We developed and characterized a nonhuman primate model of defined injury to the urethral sphincter complex.

MATERIALS AND METHODS

We used 22 adult female cynomolgus monkeys in which injury to the sphincter complex was created by cauterizing and then transecting its pudendal innervation. Urodynamic studies were performed before and during pudendal and hypogastric nerve stimulation at baseline, and 3, 6 and 12 months after injury. We also analyzed sphincter structure in vivo by cystourethrography, and ex vivo by quantitative histology and immunohistochemistry at these time points.

RESULTS

Injury produced a 47% to 50% decrease in maximal urethral pressure (vs baseline p <0.05). It also abolished the increase in maximal urethral pressure in response to pudendal and hypogastric nerve stimulation (vs baseline p >0.05), which persisted more than 12 months after injury. Urodynamic changes were consistent with decreased skeletal and smooth muscle content, decreased nerve responses and an associated decrease in somatic and adrenergic innervation in the sphincter complex.

CONCLUSIONS

These structural and urodynamic changes are consistent with those in patients with stress urinary incontinence. They support the usefulness of nonhuman primates as translatable surrogates for pathophysiological studies of urinary sphincter deficiency and testing novel therapies for that condition.

[Effects of delivery and oophorectomy on urethral collagen: an experimental study]

OBJECTIVE

Stereological evaluation of the concentration of type I and III collagen fibers in the urethral tissue of rats subjected to simulated labor and oophorectomy. To compare the concentrations of collagen between oophorectomized and non-oophorectomized rats.

MATERIAL AND METHOD

Sixty adult Wistar rats were divided into six groups. A group made up of virgin rats was used as control group and another group was made up of oophorectomized rats. Two groups underwent vaginal distention for 30 and 120 minutes, respectively. The two other groups were subjected to the same distension periods, followed by oophorectomy. Sixty days later, euthanasia and removal of urethral tissue was carried out for stereological analysis of type I and III collagen after staining with hematoxylin and eosin and picrosirius red.

RESULTS

A decrease in estrogen levels was observed in the oophorectomized rats. There was a reduction of type III collagen in the oophorectomized control group compared to the control group when analyzed independently. No significant differences were observed among the other groups. Type I collagen decreased in all groups compared to the control group. However, in the prolonged vaginal distension and oophorectomy group, these fibers increased.

CONCLUSION

In normal rats, simulation of labor does not alter the collagen III levels. In hypoestrogenic rats, the concentration of collagen type I and III decreased, except in those undergoing prolonged labor simulation in which collagen I increased.

Stress urinary incontinence following vaginal trauma involves remodeling of urethral connective tissue in female mice

OBJECTIVE

The molecular mechanisms underlying stress urinary incontinence (SUI) are not clear. This study was conducted to evaluate molecular alterations in the urethras of mice with experimentally induced SUI.

STUDY DESIGN

Eighteen virgin female mice were equally distributed into three groups as follows: two groups undergoing vaginal distension (VD) for 1 h with 3 mm and 8 mm dilators each, and a non-instrumented control group. Changes in leak point pressure (LPP), morphology, lysyl oxidase (LOX) expression and the metabolism of urethral connective tissue were assessed.

RESULTS

The LPP was significantly decreased in the 3 mm and 8 mm VD groups compared with that in the control group. Collagen and elastin expression in the urethra was significantly decreased in the 8 mm VD group compared with that in the control group, while LOX expression was significantly enhanced.

CONCLUSIONS

SUI following vaginal trauma involves over-expression of LOX and decreased synthesis of extracellular matrix components or increased proteolysis in the urethra.

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.

Setting a new standard: updating the vaginal distention translational model for stress urinary incontinence

AIMS

The vaginal distention (VD) translational model for postpartum stress urinary incontinence (SUI) is potentially biased for use in evaluating animals with increasing phenotypic size (obesity) due to a fixed VD volume. Our study had three principle and two secondary aims. First, to examine both ex vivo and in vivo catheter pressure changes during volume distention. Secondly, to determine mean pressure at current volume standard for use as target pressure (TP) for VD under isobaric (IB) conditions. Thirdly, to demonstrate feasibility and equivalence of VD at TP versus isovolumetric (IV) standard. Secondary aims were to demonstrate decreased variability (IB vs. IV) and to review the effect of weight.

METHODS

Ten French modified Foley catheters were inflated sequentially to 3.0 ml while connected (both in vivo and ex vivo) to a pressure transducer. Mean result generated TP. Thirty Sprague-Dawley rats (280-300 g) were then randomized to one of three groups: IV, IB at TP, or sham VD. Student's t-test was used to compare groups' leak point pressures (LPP) and simple linear regression was used to evaluate the effect of weight as a continuous variable.

RESULTS

Catheter pressure/volume responses were demonstrated. Calculated TP was 531 mm Hg. LPP under conditions of IB and IV were statistically equivalent and were statistically lower than Sham. Variability was not statistically different between IB and IV groups. When treated as a continuous variable, weight had no effect on LPP.

CONCLUSIONS

VD injury based on TP is feasible and reproducible. Understanding catheter pressure dynamics is valuable for investigating alternative rat phenotypes.

Models for sensory neurons of dorsal root ganglia and stress urinary incontinence

AIMS

To discuss (1) animal models for investigating bladder afferent pathways from the spinal cord to the brain and (2) animal models of stress urinary incontinence (SUI) with a special emphasis on functional and histopathological characteristics of each model.

METHODS

Literature review of spinal mechanisms of bladder afferent pathways and animal models of SUI.

RESULTS

Electrophysiological studies in the rat using pelvic nerve stimulation and recording of evoked potentials in the periaqueductal gray (PAG) prove to be a valuable tool to examine spinal mechanisms of bladder afferent pathways. Animal models of SUI in the rat include vaginal distention as simulated birth trauma, pudendal nerve crush or transection, urethral sphincter injury by electrocauterization, transabdominal urethrolysis, periurethral botulinum-A toxin injection, and pubo-urethral ligament transection. Functional and histopathological changes in the continence mechanism after injury are different between models.

CONCLUSIONS

Using animal models for sensory neurons, intrathecal and intravenous administration of certain drugs can be tested whether they affect the bladder afferent pathways from the spinal cord to the PAG. Animal models of SUI can serve as a tool to develop new pharmacologic therapies or periurethral injection therapies using stem cell implants.

Transplantation of mature adipocyte-derived dedifferentiated fat (DFAT) cells improves urethral sphincter contractility in a rat model

OBJECTIVES

To examine the effects of mature adipocyte-derived dedifferentiated fat (DFAT) cell transplantation on urethral tissue regeneration and sphincter function.

METHODS

Sixteen female Sprague-Dawley rats underwent vaginal distension (VD) for 3 h. Subsequently, green fluorescence protein (GFP)-labeled DFAT cells (1×10(6) in 20 µL saline, DFAT group, n=8) or saline (20 µL, control group, n=8) were injected into paraurethral connective tissue. Two weeks following VD, leak point pressure (LPP) was measured and an immunohistochemical analysis of the urethra was performed to evaluate urethral sphincter regeneration.

RESULTS

The VD model was characterized by atrophy of the urethral sphincter and showed a decrease in LPP. DFAT cell transplantation resulted in a significant improvement of LPP (DFAT group: 37.3±6.4 vs control group: 21.7±5.7 mmHg, P<0.01). Immunohistochemistry revealed that the striated muscle thickness and smooth muscle α-actin-positive area were significantly (P<0.05) larger in the DFAT group than in the control group. DFAT cell transplantation enhanced macrophage accumulation followed by an increased number of cells in the proliferative state. Transplanted DFAT cells were observed in the damaged smooth muscle layer and showed positive staining for smooth muscle α-actin, suggesting conversion into the smooth muscle cell phenotype.

CONCLUSIONS

DFAT cell transplantation promotes sphincter muscle regeneration and improves LPP in the rat VD model.

Pelvic organ distribution of mesenchymal stem cells injected intravenously after simulated childbirth injury in female rats

The local route of stem cell administration utilized presently in clinical trials for stress incontinence may not take full advantage of the capabilities of these cells. The goal of this study was to evaluate if intravenously injected mesenchymal stem cells (MSCs) home to pelvic organs after simulated childbirth injury in a rat model. Female rats underwent either vaginal distension (VD) or sham VD. All rats received 2 million GFP-labeled MSCs intravenously 1 hour after injury. Four or 10 days later pelvic organs and muscles were imaged for visualization of GFP-positive cells. Significantly more MSCs home to the urethra, vagina, rectum, and levator ani muscle 4 days after VD than after sham VD. MSCs were present 10 days after injection but GFP intensity had decreased. This study provides basic science evidence that intravenous administration of MSCs could provide an effective route for cell-based therapy to facilitate repair after injury and treat stress 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.

Adipose-derived stromal cell transplantation for treatment of stress urinary incontinence

We aimed to investigate the application of adipose-derived stromal cells in the treatment of stress urinary incontinence (SUI). Animal models of stress urinary incontinence were established with Sprague-Dawley female rats by complete cutting of the pudendal nerve. Rat adipose-derived stromal cells were isolated, cultured and successfully transplanted into animal models. Effects of stem cell transplantation were evaluated through urodynamic testing and morphologic changes of the urethra and surrounding tissues before and after transplantation. Main urodynamic outcome measures were measured. Intra-bladder pressure and leak point pressure were measured during filling phase. Morphologic examinations were performed. Transplantation of adipose-derived stem cells significantly strengthened local urethral muscle layers and significantly improved the morphology and function of sphincters. Urodynamic testing showed significant improvements in maximum bladder capacity, abdominal leak point pressure, maximum urethral closure pressure, and functional urethral length. Morphologic changes and significant improvement in urination control were consistent over time. It was concluded that periurethral injection of adipose-derived stromal cells improves function of the striated urethral sphincter, resulting in therapeutic effects on SUI. Reconstruction of the pelvic floor through transplantation of adipose-derived cells is a minimally invasive and effective treatment for SUI.