Histologic analysis of needle biopsy of urethral sphincter from women with normal and stress incontinence with comparison of electromyographic findings

Nitrergic inhibition of sympathetic arteriolar constrictions in the female rodent urethra

During the urine storage phase, tonically contracting urethral musculature would have a higher energy consumption than bladder muscle that develops phasic contractions. However, ischaemic dysfunction is less prevalent in the urethra than in the bladder, suggesting that urethral vasculature has intrinsic properties ensuring an adequate blood supply. Diameter changes in rat or mouse urethral arterioles were measured using a video-tracking system. Intercellular Ca2+ dynamics in arteriolar smooth muscle (SMCs) and endothelial cells were visualised using NG2- and parvalbumin-GCaMP6 mice, respectively. Fluorescence immunohistochemistry was used to visualise the perivascular innervation. In rat urethral arterioles, sympathetic vasoconstrictions were predominantly suppressed by α,β-methylene ATP (10 μM) but not prazosin (1 μM). Tadalafil (100 nM), a PDE5 inhibitor, diminished the vasoconstrictions in a manner reversed by N-ω-propyl-l-arginine hydrochloride (l-NPA, 1 μM), a neuronal NO synthesis (nNOS) inhibitor. Vesicular acetylcholine transporter immunoreactive perivascular nerve fibres co-expressing nNOS were intertwined with tyrosine hydroxylase immunoreactive sympathetic nerve fibres. In phenylephrine (1 μM) pre-constricted rat or mouse urethral arterioles, nerve-evoked vasodilatations or transient SMC Ca2+ reductions were largely diminished by l-nitroarginine (l-NA, 10 μM), a broad-spectrum NOS inhibitor, but not by l-NPA. The CGRP receptor antagonist BIBN-4096 (1 μM) shortened the vasodilatory responses, while atropine (1 μM) abolished the l-NA-resistant transient vasodilatory responses. Nerve-evoked endothelial Ca2+ transients were abolished by atropine plus guanethidine (10 μM), indicating its neurotransmitter origin and absence of non-adrenergic non-cholinergic endothelial NO release. In urethral arterioles, NO released from parasympathetic nerves counteracts sympathetic vasoconstrictions pre- and post-synaptically to restrict arteriolar contractility. KEY POINTS: Despite a higher energy consumption of the urethral musculature than the bladder detrusor muscle, ischaemic dysfunction of the urethra is less prevalent than that of the bladder. In the urethral arterioles, sympathetic vasoconstrictions are predominately mediated by ATP, not noradrenaline. NO released from parasympathetic nerves counteracts sympathetic vasoconstrictions by its pre-synaptic inhibition of sympathetic transmission as well as post-synaptic arteriolar smooth muscle relaxation. Acetylcholine released from parasympathetic nerves contributes to endothelium-dependent, transient vasodilatations, while CGRP released from sensory nerves prolongs NO-mediated vasodilatations. PDE5 inhibitors could be beneficial to maintain and/or improve urethral blood supply and in turn the volume and contractility of urethral musculature.

The pathophysiology of stress urinary incontinence: a systematic review and meta-analysis

Introduction and hypothesis

To evaluate the evidence for pathologies underlying stress urinary incontinence (SUI) in women.

Methods

For the data sources, a structured search of the peer-reviewed literature (English language; 1960–April 2020) was conducted using predefined key terms in PubMed and Embase. Google Scholar was also searched. Peer-reviewed manuscripts that reported on anatomical, physiological or functional differences between females with signs and/or symptoms consistent with SUI and a concurrently recruited control group of continent females without any substantive urogynecological symptoms. Of 4629 publications screened, 84 met the inclusion criteria and were retained, among which 24 were included in meta-analyses.

Results

Selection bias was moderate to high; < 25% of studies controlled for major confounding variables for SUI (e.g., age, BMI and parity). There was a lack of standardization of methods among studies, and several measurement issues were identified. Results were synthesized qualitatively, and, where possible, random-effects meta-analyses were conducted. Deficits in urethral and bladder neck structure and support, neuromuscular and mechanical function of the striated urethral sphincter (SUS) and levator ani muscles all appear to be associated with SUI. Meta-analyses showed that observed bladder neck dilation and lower functional urethral length, bladder neck support and maximum urethral closure pressures are strong characteristic signs of SUI.

Conclusion

The pathology of SUI is multifactorial, with strong evidence pointing to bladder neck and urethral incompetence. While there is also evidence of impaired urethral support and levator ani function, standardized approaches to measurement are needed to generate higher levels of evidence.

Cell sex affects extracellular matrix protein expression and proliferation of smooth muscle progenitor cells derived from human pluripotent stem cells

Background

Smooth muscle progenitor cells (pSMCs) differentiated from human pluripotent stem cells (hPSCs) hold great promise for treating diseases or degenerative conditions involving smooth muscle pathologies. However, the therapeutic potential of pSMCs derived from men and women may be very different. Cell sex can exert a profound impact on the differentiation process of stem cells into somatic cells. In spite of advances in translation of stem cell technologies, the role of cell sex and the effect of sex hormones on the differentiation towards mesenchymal lineage pSMCs remain largely unexplored.

Methods

Using a standard differentiation protocol, two human embryonic stem cell lines (one male line and one female line) and three induced pluripotent stem cell lines (one male line and two female lines) were differentiated into pSMCs. We examined differences in the differentiation of male and female hPSCs into pSMCs, and investigated the effect of 17β-estradiol (E2) on the extracellular matrix (ECM) metabolisms and cell proliferation rates of the pSMCs. Statistical analyses were performed by using Student’s t test or two-way ANOVA, p < 0.05.

Results

Male and female hPSCs had similar differentiation efficiencies and generated morphologically comparable pSMCs under a standard differentiation protocol, but the derived pSMCs showed sex differences in expression of ECM proteins, such as MMP-2 and TIMP-1, and cell proliferation rates. E2 treatment induced the expression of myogenic gene markers and suppressed ECM degradation activities through reduction of MMP activity and increased expression of TIMP-1 in female pSMCs, but not in male pSMCs.

Conclusions

hPSC-derived pSMCs from different sexes show differential expression of ECM proteins and proliferation rates. Estrogen appears to promote maturation and ECM protein expression in female pSMCs, but not in male pSMCs. These data suggest that intrinsic cell-sex differences may influence progenitor cell biology.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0606-2) contains supplementary material, which is available to authorized users.

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

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

Periurethral skeletal myofibre implantation in patients with urinary incontinence and intrinsic sphincter deficiency: a phase I clinical trial

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: Cell therapy using muscle precursor cell (MPC) injections has shown promise for urinary incontinence due to intrinsic sphincter deficiency (ISD), but the cell-preparation process is complex and costly. Implantation of freshly isolated myofibres carrying MPCs, mainly satellite cells, was very efficient in repairing muscle damage in recent animal experiments. In a phase I clinical trial, we investigated whether periurethral myofibre implantation generated local myogenesis and improved continence in 10 patients (five men and five women) with ISD. We found that myofibre implantation increased intraurethral pressure and periurethral electromyographic activity in patients with ISD. There were no serious side-effects.

OBJECTIVES

To assess the safety of periurethral myofibre implantation in patients with urinary incontinence due to intrinsic sphincter deficiency (ISD) To assess the resulting myogenic process and effects on urinary continence.

PATIENTS AND METHODS

An open-label non-randomised phase I clinical trial was conducted in five men and five women with ISD (mean age, 62.5 years). A free muscle strip from the patient's gracilis muscle was implanted around the urethra as a means to deliver locally myofibres and muscle precursor cells (MPCs). Patients were assessed for collection formation and incomplete bladder emptying. The maximum urethral closure pressure (MUCP) and concomitant periurethral electromyographic (EMG) activity were recorded before surgery and 1 and 3 months after surgery. Continence was assessed using the 24-h pad test and self-completed questionnaires, for 12 months.

RESULTS

There were no serious side-effects. Continence improved significantly during the 12-month follow-up in four of the five women, including two who recovered normal continence. In the women, MUCP increased two-fold and de novo EMG periurethral activity was recorded. In the men, MUCP and EMG recordings showed similar improvements but the effect on continence was moderate. The few patients enrolled could affect these results.

CONCLUSIONS

This is the first report of a one-step procedure for transferring autologous MPCs via myofibre implantation in patients with ISD. EMG and urodynamic assessments showed improvement of periurethral muscle activity. Further work is needed to confirm and improve the therapeutic efficiency of this procedure.

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

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

Myostatin inhibits proliferation of human urethral rhabdosphincter satellite cells

OBJECTIVES

Myostatin, a member of the transforming growth factor-β superfamily, is a negative regulator of myogenesis in skeletal muscle. We examined the effect of myostatin and myostatin inhibition by an antagonistic agent, follistatin, on growth of human urethral rhabdosphincter satellite cells (muscle stem cells) to develop a new strategy for treatment of stress urinary incontinence.

METHODS

Rhabdosphincter satellite cells were cultured and selected by magnetic affinity cell sorting using an anti-neural cell adhesion molecule antibody. The cells were transfected with simian virus-40 antigen to extend their lifespan. A cell proliferation assay, a cell cycle analysis and an investigation of signal transduction were carried out. The autocrine action of endogenous myostatin by western blotting, real-time reverse transcription polymerase chain reaction and immunoneutralization using an anti-myostatin antibody was also evaluated.

RESULTS

Selectively cultured cells expressed markers of striated muscles and successfully differentiated into myotubes. Myostatin inhibited proliferation of these cells through Smad2 phosphorylation and cell cycle arrest. Inhibitory effects of myostatin were reversed by addition of follistatin. However, rhabdosphincter satellite cells did not appear to use autocrine secretion of myostatin to regulate their proliferation.

CONCLUSIONS

Inhibition of myostatin function might be a useful pathway in the development of novel strategies for stimulating rhabdosphincter cells regeneration to treat stress urinary incontinence.

Continent women have better urethral neuromuscular function than those with stress incontinence

INTRODUCTION AND HYPOTHESIS

The objective of this study is to describe urethral neuromuscular function using concentric needle electromyography (EMG) in stress incontinent (SUI) and asymptomatic women.

METHODS

Following Institutional Review Board approval, we recruited SUI and asymptomatic women without urinary incontinence. Participants underwent quantitative urethral EMG and urodynamic testing.

RESULTS

Sixty-seven women (37 SUI, 30 continent) with mean ± SD age of 44 ± 12 years participated. Nearly all EMG parameters showed significant differences between continent and SUI women consistent with better motor unit recruitment in continent women. Continent women had larger-amplitude, longer-duration motor unit action potentials (MUP) with increased turns and better MUP recruitment during bladder filling (P < .05). Increasing age was inversely correlated with nearly all MUP parameters (P < .05), suggesting MUP to be consistent with neuropathy.

CONCLUSIONS

We found significant differences in multiple MUP parameters in urethral sphincter between continent and stress incontinent women, suggesting continent women have better urethral innervation. We also found significant neuropathic MUP changes with advancing age, regardless of continence status.

Vulnerability of continence structures to injury by simulated childbirth

The goal of this study was to examine acute morphological changes, edema, muscle damage, inflammation, and hypoxia in urethral and vaginal tissues with increasing duration of vaginal distension (VD) in a rat model. Twenty-nine virgin Sprague-Dawley rats underwent VD under anesthesia with the use of a modified Foley catheter inserted into the vagina and filled with saline for 0, 1, 4, or 6 h. Control animals were anesthetized for 4 h without catheter placement. Urogenital organs were harvested after intracardiac perfusion of fixative. Tissues were embedded, sectioned, and stained with Masson's trichrome or hematoxylin and eosin stains. Regions of hypoxia were measured by hypoxyprobe-1 immunohistochemistry. Within 1 h of VD, the urethra became vertically elongated and displaced anteriorly. Edema was most prominent in the external urethral sphincter (EUS) and urethral/vaginal septum within 4 h of VD, while muscle disruption and fragmentation of the EUS occurred after 6 h. Inflammatory damage was characterized by the presence of polymorphonuclear leukocytes in vessels and tissues after 4 h of VD, with the greatest degree of infiltration occurring in the EUS. Hypoxia localized mostly to the vaginal lamina propria, urethral smooth muscle, and EUS within 4 h of VD. Increasing duration of VD caused progressively greater tissue edema, muscle damage, and morphological changes in the urethra and vagina. The EUS underwent the greatest insult, demonstrating its vulnerability to childbirth injury.

Stem cells for stress urinary incontinence: the adipose promise

Stress urinary incontinence (SUI), the most common type of incontinence in women, is a frequent and costly ailment responsible for an alteration in the quality of life. Although medical treatment gives some rather deceiving results, surgical techniques that include colposuspension or tension-free vaginal tape, employed in cases of urethral support defect, give a 5-year cure rate of more than 80%. However, these techniques could lead to complications or recurrence of symptoms. Recently, the initiation of urethral cell therapy has been undertaken by doctors and researchers. One principal source of autologous adult stem cells is generally used: muscle precursor cells (MPCs) which are the progenitors of skeletal muscle cells. Recently, a few research groups have shown interest in the MPCs and their potential for the treatment of urinary incontinence. However, using MPCs or fibroblasts isolated from a striated muscle biopsy could be questionable on several points. One of them is the in vitro cultivation of cells, which raises issues over the potential cost of the technique. Besides, numerous studies have shown the multipotent or even the pluripotent nature of stromal vascular fraction (SVF) or adipose-derived stem cells (ASCs) from adipose tissue. These cells are capable of acquiring in vitro many different phenotypes. Furthermore, recent animal studies have highlighted the potential interest of SVF cells or ASCs in cell therapy, in particular for mesodermal tissue repair and revascularization. Moreover, the potential interest of SVF cells or ASCs for the treatment of urinary incontinence in women is supported by many other characteristics of these cells that are discussed here. Because access to these cells via lipoaspiration is simple, and because they are found in very large numbers in adipose tissue, their future potential as a stem cell reservoir for use in urethral or other types of cell therapy is enormous.

The role of calpain-calpastatin system in the development of stress urinary incontinence

INTRODUCTION AND HYPOTHESIS

The objective of this study is to investigate the expression of calpain-1, calpain-2, and calpastatin in the human periurethral vaginal tissues and to show the potential link between calpain system and stress urinary incontinence (SUI).

METHODS

The periurethral vaginal tissues of 39 women with SUI and 31 women without SUI were collected to detect the expressions of calpains and calpastatin by using semi-quantitative competitive reverse transcription-polymerase chain reaction and Western blotting.

RESULTS

There were no significant differences on the expressions of calpain-1 at the levels of messenger RNA (mRNA) and protein in both groups (P > 0.05), but the patients with SUI had significantly higher levels of calpain-2 mRNA and protein than the control (P < 0.05); and the mRNA expressions of calpastatin in women with SUI were significantly higher than the control (P < 0.05), while the protein expressions were significantly lower when compared to the control (P < 0.01).

CONCLUSIONS

Overexpression of calpain-2 and low expression of calpastatin may involve in the pathological development of SUI.

Recovery of continence function following simulated birth trauma involves repair of muscle and nerves in the urethra in the female mouse

BACKGROUND

The natural history and the mechanisms behind the alteration of vaginal distension (VD) in a mouse model are not clear.

OBJECTIVE

We examined the temporal sequelae of VD and pudendal nerve transection (PNT) on leak-point pressure (LPP) and the muscular and nerve components of the urethra in mice.

DESIGN, SETTING, AND PARTICIPANTS

Seventy-two virgin female C57BL/6 mice were equally distributed into three groups. The VD group underwent VD for 1h. The PNT group received bilateral PNT. A control group underwent sham VD.

INTERVENTION

Each group was divided into four subgroups of six mice for measurement of LPP at 0, 4, 10, and 20 d after VD or PNT.

MEASUREMENTS

LPP was measured. Morphology and neurofilament-immunoreactive nerve of the urethra were assessed.

RESULTS AND LIMITATIONS

LPP was decreased at 0, 4, and 10 d but not at 20 d after VD. Decreased LPP persisted to 20 d in the PNT group. The external urethral striated muscle appeared disrupted and/or wavy in two mice at 0 d, in three mice at 4 d, in one mouse at 10 d, and in one mouse in 20 d after VD. The density of neurofilament-immunoreactive nerve in the urethra was reduced at 4 and 10 d after VD, but not at 20 d, and at 4, 10, and 20 d after PNT compared with the corresponding values of the sham VD group. The limitation of this animal model is that the pelvic floor structure of the mouse is different from that of female humans. Therefore, results of this study should be carefully applied to human subjects.

CONCLUSIONS

VD causes reversible stress urinary incontinence in female mice. Recovery of continence function following VD is associated with repair of the external urethral sphincter and reinnervation of the urethra. This mouse model will be useful for mechanistic investigation and targeting of therapeutic intervention by taking advantage of genetic manipulation.

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.

Is balance different in women with and without stress urinary incontinence?

AIMS

This study investigated whether there are differences in center of pressure (COP) displacement, trunk motion, and trunk muscle activity in women with and without stress urinary incontinence (SUI) during static balance tasks when the bladder is empty and moderately full.

METHODS

Subjects stood on a force plate during six static balance conditions: eyes open, eyes closed, standing on foam with eyes open, standing on foam with eyes closed, tandem stance, and standing on a short base. Electromyographic activity (EMG) of the pelvic floor (PF), abdominal, and erector spinae muscles were recorded using surface electrodes. Motion of the lumbar spine, pelvis, and hips was measured with four inclinometers. Trials were performed with the bladder empty, and when the subject reported a sensation of moderate bladder fullness after drinking 250-1,000 ml of water.

RESULTS

Women with SUI had greater COP displacement (range and root mean square), and increased trunk muscle EMG during static balance tests compared to continent women. When tasks were performed with the bladder moderately full, COP displacement and abdominal muscle EMG were increased in both groups.

CONCLUSIONS

This study demonstrates that women with SUI have decreased balance ability compared to continent women. Increased activity of the PF and trunk muscles in women with SUI may impair balance as a result of a reduced contribution of trunk movement to postural correction or compromised proprioceptive acuity. As compromised balance has been linked to falls risk, further research into balance deficits and falls prevalence in this population is warranted.

Time course of neuroanatomical and functional recovery after bilateral pudendal nerve injury in female rats

The pudendal nerve innervates the external urethral sphincter (EUS) and is among the tissues injured during childbirth, which may lead to symptoms of stress urinary incontinence (SUI). To understand the mechanisms of injury and repair, urethral leak-point pressure (LPP) was measured 4 days, 2 wk, or 6 wk after bilateral pudendal nerve crush. Morphometric changes in the distal nerve and EUS were examined by light and electron microscopy. To determine whether recovery resulted from pudendal neuroregeneration, LPP was measured before and after pudendal nerve transection 2 wk after nerve crush. LPP was significantly decreased 4 days after pudendal nerve crush compared with sham-injured animals as well as 2 or 6 wk after nerve crush. LPP was not significantly different 2 or 6 wk after nerve crush compared with sham-injured animals, suggesting that urethral function had returned to normal. Four days after pudendal nerve crush, the EUS branch of the pudendal nerve distal to the injury site showed evidence of nerve degeneration and the EUS appeared disrupted. Two weeks after nerve crush, the distal nerve and EUS both showed evidence of both nerve degeneration and recovery. Two weeks after nerve crush, LPP was significantly decreased after nerve transection. Six weeks after nerve injury, evidence of neuroregeneration was observed in the pudendal nerve and the EUS. This study has demonstrated that functional recovery and neuroregeneration are significant 2 wk after nerve crush, although by anatomical assessment, recovery appears incomplete, suggesting that 2 wk represents an early time point of initial neuroregeneration.

Urethral sensory threshold and urethro-anal reflex latency in continent women

AIMS OF STUDY

The sensory evaluation of the lower urinary tract is summarized in the bladder proprioceptive sensitivity during cystometry. Experimental studies suggest that abnormalities of the urethral innervation and micturition reflex can be related to the presence of continence disturbances. This study aimed to measure the urethral sensory threshold and the urethro-anal reflex latency in healthy volunteers, establishing reading criteria, comparing the results and technique used with the literature and verifying the effect of physiological factors.

MATERIALS AND METHODS

Thirty healthy female volunteers were studied. They had an absence of genital or urinary complaints and had undergone no previous pelvic or vaginal procedures. The measurement of the urethral sensory threshold and urethro-anal reflex latency were performed as described.

RESULTS

The determination of the urethral sensory threshold and urethro-anal reflex latency were obtained in 96.6% of the volunteers. The electrophysiological parameters did not correlate with age, parity or number of vaginal deliveries. There was a positive association of the urethral sensory threshold with height. Technical aspects were considered and compared with those in the literature as well as the advantages and limitations of the method.

CONCLUSIONS

The measurement of the urethral sensory threshold and urethro-anal reflex latency presented consistent recordings. The urethral sensory threshold should be analyzed carefully in individuals with height above the population average. Subsequent observations are necessary to clarify their function in patients with continence disturbances and to measure the urethral function, but these values can be used as normal parameters for comparison.

Immunohistochemical analysis of collagen types I, III, IV and α-actin in the urethra of sexually intact and ovariectomized beagles

Urinary incontinence is a widespread problem in both postmenopausal women and ovariectomized dogs. The objective of this study was to investigate the influence of ovariectomy on the immunoreactivity and the distribution pattern of collagens I, III, IV and alpha-actin in the canine urethra. The immunohistochemical results were evaluated in five sexually intact and five ovariectomized beagles. The immunostaining of both collagens I and III delineated urethral connective tissue fibres and co-localized within in the fibres of both groups. The basement membranes of smooth muscle cells and sinusoids showed marked type IV collagen expression, whereas only faint immunoreactivity was present at the urothelial-stromal interface. No differences could be detected in the expression or distribution of the assessed collagen types and actin between ovariectomized and control animals. In conclusion, ovariectomy does not appear to have an effect on urethral collagens I, III, IV and smooth muscle actin in the dog, as ascertained by immunohistochemistry.

Postural response of the pelvic floor and abdominal muscles in women with and without incontinence

AIMS

To determine whether activity of the pelvic floor (PF) and abdominal muscles differs between continent and incontinent women in response to a postural perturbation with a moderately full or empty bladder.

METHODS

Electromyographic (EMG) activity of the PF and abdominal muscles was recorded with surface electrodes prior to and after a postural perturbation in which a 1 kg weight was dropped 30 cm into a bucket held by the subject. Perturbations were applied to the trunk in trials in which the timing of the weight drop was unknown (unexpected) or predictable (expected). Trials were performed with the bladder empty, and when the subject reported a sensation of moderate bladder fullness after drinking between 200 and 1,000 ml of water.

RESULTS

Women with incontinence demonstrated increased PF EMG compared to continent women both prior to and during the postural response associated with unexpected loading. In addition, obliquus externus abdominis EMG was increased in incontinent women during these trials. When the bladder was moderately full, PF EMG decreased, whereas abdominal muscle EMG tended to increase.

CONCLUSIONS

These data suggest that women with incontinence have increased PF and abdominal muscle activity associated with postural perturbations. This finding challenges the clinical assumption that incontinence is associated with reduced PF muscle activity, and suggests that training control and coordination of abdominal muscle activity may be important in treatment of this condition. The contrasting effects of increased bladder volume on PF and abdominal muscle EMG are likely to present further challenges to the maintenance of continence.

The striated urethral sphincter of the pig shows morphological and functional characteristics essential for the evaluation of treatments for sphincter insufficiency

PURPOSE

New treatments are currently under investigation for intrinsic sphincter insufficiency. However, animal models in which to study the resting urethral tone generated by the striated urethral sphincter are still lacking. We describe the striated urethral sphincter in the pig. We investigated its participation in resting urethral tone with the aim of developing new tools for evaluating therapies for sphincter insufficiency.

MATERIALS AND METHODS

A total of 15 female pigs were used in this study. Anatomy of the striated urethral sphincter was described via transpubic and endoscopic approaches. Participation of the striated urethral sphincter in resting urethral tone was assessed by analysis of urethral pressure profilometry (maximum urethral closure pressure, functional urethral length and area under the curve) before and after curare injection or by destruction of the striated urethral sphincter by endoscopic electrocautery. Serial urethral cross sections were immunostained for slow/fast myosin and digitalized for 3-dimensional reconstructions to determine striated urethral sphincter volume.

RESULTS

The striated urethral sphincter was Omega-shaped and it encircled the distal third of the urethra. A mean peak intraurethral pressure +/- SEM of 58.9 +/- 13.4 cm H(2)O was noted in front of the striated urethral sphincter. Curare injection and endoscopic injury decreased maximum urethral closure pressure by 48.4% and 51.1%, functional urethral length by 10.3% and 15.3%, and area under the curve by 47% and 64%, respectively. The striated urethral sphincter consisted of 52% slow and 48% fast myofibers. Its mean volume was 0.87 cm.

CONCLUSIONS

The striated urethral sphincter of the female pig shows the morphological and functional features of a tonic muscle. Methods of measuring resting urethral tone generated by the striated urethral sphincter represent original tools for evaluating therapies for intrinsic sphincter insufficiency.

Postural activity of the pelvic floor muscles is delayed during rapid arm movements in women with stress urinary incontinence

The aim of this study was to determine whether postural activity of the pelvic floor (PF) and abdominal muscles differs between continent and incontinent women during rapid arm movements that present a postural challenge to the trunk. A further aim was to study the effect of bladder filling. Electromyographic activity (EMG) of the PF, abdominal, erector spinae (ES), and deltoid muscles was recorded with surface electrodes. During rapid shoulder flexion and extension, PF EMG increased before that of the deltoid in continent women, but after the deltoid in incontinent women (p = 0.002). In many incontinent women, PF EMG decreased before the postural activation. Although delayed, postural PF EMG amplitude was greater in women with incontinence (p = 0.010). In both groups, PF EMG decreased and abdominal and ES EMG increased when the bladder was moderately full. These findings would be expected to have negative consequences for continence and lumbopelvic stability in women with incontinence.

The impact of pregnancy and childbirth in the urethra of female rats

The aim of this study was to evaluate the modifications in the amount of collagen, muscular, and elastic fibers in the mid-urethra of adult female rats during the pregnancy and after the natural childbirth, cesarean, and after simulated trauma of childbirth. The authors evaluated the histomorphometric aspects (collagen, muscular, and elastic fibers) in the mid-urethra of 70 animals distributed in seven groups: group 1 (n = 10)--control, group 2 (n = 10)--pregnant female rats, group 3 (n = 10)--female rats submitted to cesarean, group 4 (n = 10)--female rats with natural childbirth, group 5 (n = 10)--virgin female rats with simulated trauma of childbirth, group 6 (n = 10)--female rats submitted to cesarean followed by simulation of childbirth trauma, and group 7 (n = 10)--female rats with natural childbirth followed by simulation of childbirth trauma. The average concentration of collagen and elastic fibers and the collagen/muscular fiber correlation in groups 1, 2, and 3 were similar and significantly inferior to groups 4, 5, 6, and 7. The average of muscular fibers was similar in groups 1, 2, and 3 and significantly superior to groups 4, 5, 6, and 7. Pregnancy and cesarean did not induce alterations in collagen, muscular, and elastic fibers. However, the vaginal delivery and simulation of childbirth trauma determined the decrease in muscular fibers and the increase in collagen and elastic fibers and the correlation collagen/muscular fiber.

Risk of Stress Urinary Incontinence Twelve Years After the First Pregnancy and Delivery

OBJECTIVE

To estimate the impact of onset of stress urinary incontinence in first pregnancy or postpartum period, for the risk of symptoms 12 years after the first delivery.

METHODS

In a longitudinal cohort study, 241 women answered validated questions about stress urinary incontinence after first delivery and 12 years later.

RESULTS

Twelve years after first delivery the prevalence of stress urinary incontinence was 42% (102 of 241). The 12-year incidence was 30% (44 of 146). The prevalence of stress urinary incontinence 12 years after first pregnancy and delivery was significantly higher (P<.01) in women with onset during first pregnancy (56%, 37 of 66) and in women with onset shortly after delivery (78%, 14 of 18) compared with those without initial symptoms (30%, 44 of 146). In 70 women who had onset of symptoms during first pregnancy or shortly after the delivery but remission 3 months postpartum, a total of 40 (57%) had stress urinary incontinence 12 years later. In 11 women with onset of symptoms during the first pregnancy or shortly after delivery but no remission 3 months postpartum, a total of 10 (91%) had stress urinary incontinence 12 years later. Cesarean during first delivery was significantly associated with a lower risk of incontinence. Other obstetric factors were not significantly associated with the risk of incontinence 12 years later. Patients who were overweight before their first pregnancy were at increased risk.

CONCLUSION

Onset of stress urinary incontinence during first pregnancy or puerperal period carries an increased risk of long-lasting symptoms.

Biomechanical characterization of the urethral musculature

Rigorous study of the associations between urethral structural anatomy and biomechanical function is necessary to advance the understanding of the development, progression, and treatment of urethral pathologies. An ex vivo model was utilized to define the relative biomechanical contributions of the active (muscle) elements of the female urethra relative to its passive (noncontractile) elements. Whole urethras from female, adult rats were tested under a range of applied intraluminal pressures (0 to 20 mmHg) as a laser micrometer simultaneously measured midurethral outer diameter. Active tissue characterization was performed during induced contraction of either smooth muscle alone ( Nω-nitro-l-arginine, phenylephrine), striated muscle alone (sodium nitroprusside, atropine, hexamethonium, acetylcholine), or during collective activation of both muscles ( Nω-nitro-l-arginine, phenylephrine, acetylcholine). The subsequent collection of paired passive biomechanical responses permitted the determination of parameters related to intrinsic muscle contractile function. Activation of each muscle layer significantly influenced the biomechanical responses of the tissue. Measures of muscle responsiveness over a wide range of sustained opposing pressures indicated that an activated striated muscle component was approximately one-third as effective as activated smooth muscle in resisting tissue deformation. The maximum circumferential stress generated by the striated muscle component under these conditions was also determined to be approximately one-third of that generated by the smooth muscle (748 ± 379 vs. 2,229 ± 409 N/m2). The experiments quantitatively reveal the relative influence of the intrinsic urethral smooth and striated muscle layers with regard to their effect on the mechanical properties and maximum functional responses of the urethra to applied intralumenal stresses in the complete absence of extrinsic influences.

Recurrent stress incontinence is associated with decreased neuromuscular function in the striated urethral sphincter

OBJECTIVE

The study aim was to compare urethral neuromuscular function in stress incontinent women with and without previous incontinence surgery.

STUDY DESIGN

Urethral electromyographic (EMG) data for women with recurrent urodynamic stress incontinence following 1 previous continence procedure were compared to age- and parity-matched women with urodynamic stress incontinence (USI) without previous incontinence surgery. The cases with recurrent USI included 13 women with 1 previous sling and 13 women with 1 previous Burch. EMG signals were obtained at rest, with cough, and during pelvic floor contraction using an automated software program. EMG data from recurrent cases were compared with controls.

RESULTS

Women with recurrent stress incontinence after 1 previous continence procedure had lower quantitative EMG values than women without previous surgery. Specifically, we observed that women with previous sling had significantly lower quantitative EMG values with cough (P = .007), while baseline and squeeze values were not significantly different. Women with previous Burch had cough EMG values intermediate between the control and previous sling group, which trended toward statistical significance (P = .057).

CONCLUSION

Women with recurrent urodynamic stress incontinence after previous slings have poorer urethral neuromuscular function than stress incontinent women without previous incontinence surgery.

New postnatal urinary incontinence: obstetric and other risk factors in primiparae

OBJECTIVE

To identify obstetric and other risk factors for urinary incontinence that occurs during pregnancy or after childbirth.

DESIGN

Questionnaire survey of women.

SETTING

Maternity units in Aberdeen (Scotland), Birmingham (England) and Dunedin (New Zealand).

POPULATION

A total of 3405 primiparous women with singleton births delivered during 1 year.

METHODS

Questionnaire responses and obstetric case note data were analysed using multivariate analysis to identify associations with urinary incontinence.

MAIN OUTCOME MEASURES

Urinary incontinence at 3 months after delivery first starting in pregnancy or after birth.

RESULTS

The prevalence of urinary incontinence was 29%. New incontinence first beginning after delivery was associated with older maternal age (oldest versus youngest group, OR 2.02, 95% CI 1.35-3.02) and method of delivery (caesarean section versus spontaneous vaginal delivery, OR 0.28, 95% CI 0.19-0.41). There were no significant associations with forceps delivery (OR 1.18, 95% CI 0.92-1.51) or vacuum delivery (OR 1.16, 95% CI 0.83-1.63). Incontinence first occurring during pregnancy and still present at 3 months was associated with higher maternal body mass index (BMI>25, OR 1.68, 95% CI 1.16-2.43) and heavier babies (birthweight in top quartile, OR 1.56, 95% CI 1.12-2.19). In these women, caesarean section was associated with less incontinence (OR 0.39, 95% CI 0.27-0.58) but incontinence was not associated with age.

CONCLUSIONS

Women have less urinary incontinence after a first delivery by caesarean section whether or not that first starts during pregnancy. Older maternal age was associated with new postnatal incontinence, and higher BMI and heavier babies with incontinence first starting during pregnancy. The effect of further deliveries may modify these findings.

Morphology of the suburethral pubocervical fascia in women with stress urinary incontinence: a comparison of histologic and MRI findings

To correlate MRI with histologic findings of the suburethral pubocervical fascia in women with urodynamic stress incontinence. Thirty-one women with urodynamically proven stress urinary incontinence without relevant prolapse underwent preoperative MRI. Tissue specimens obtained from the pubocervical fascia were examined immunohistochemically (types I and III collagen, smooth muscle actin) and the results compared with the MRI findings. MRI demonstrated an intact pubocervical fascia in 61.3% of the cases and a fascial defect in 38.7%. A fascial defect demonstrated by MRI was associated with a decrease in actin (P<0.09) and an increase in collagen III (P<0.01) compared to an intact fascia. In women with stress urinary incontinence, smooth muscle actin in the pubocervical fascia is decreased, changed in structure, and replaced by type III collagen. MRI allows evaluation of the pubocervical fascia and its morphologic changes.

STRUCTURAL ASSESSMENT OF THE URETHRAL SPHINCTER IN WOMEN WITH URINARY RETENTION

PURPOSE

The pathophysiology of urinary retention in women is generally unknown but a subgroup of women with urinary retention have been diagnosed as having so-called primary disorder of sphincter relaxation on the basis of an abnormal urethral sphincter electromyogram. It was suggested this sphincter overactivity could lead to work hypertrophy of the urethral rhabdosphincter and in this study we looked for any evidence of such muscle fiber hypertrophy.

MATERIALS AND METHODS

In 9 women 18 to 45 years old (mean age 31.6) with urinary retention and overactive urethral sphincter electromyogram, light and electron microscopy were used to examine core needle biopsies of the urethral rhabdosphincter taken under transvaginal ultrasound control. Of the 9 patients only 5 biopsies processed for light microscopy and 4 processed for electron microscopy contained striated urethral muscle fibers. The results of these biopsies were compared to the morphology of a control specimen from a postmenopausal woman without a history of urinary retention.

RESULTS

On light microscopy the urethral rhabdosphincter fiber diameter did not differ among patients (mean average 7.6 mum), was less than that reported in the literature (15 to 20), but did not differ from that of the control (mean 9.9). In all patients electron microscopy showed excessive peripheral sarcoplasm with lipid and glycogen deposition, and sarcoplasmic accumulation of normal mitochondria. These ultrastructural abnormalities were not seen in the control.

CONCLUSIONS

To our knowledge this is the first morphological description of the urethral rhabdosphincter in a subgroup of women with urinary retention. Mean rhabdosphincter fiber diameter was approximately the same in patients and controls. This study does not support the previous theory that urethral sphincter overactivity in a subgroup of women with urinary retention leads to work hyperplasia of urethral rhabdosphincter fibers. An alternative hypothesis is suggested.

Effect of intravaginal electrical stimulation on pelvic floor muscle strength

The aim of this study was to evaluate the effect of intravaginal electrical stimulation (IES) on pelvic floor muscle (PFM) strength in patients with mixed urinary incontinence (MUI). Between January 2001 and February 2002, 40 MUI women (mean age: 48 years) were studied. Urge incontinence was the predominant symptom; 92.5% also presented mild stress urinary incontinence (SUI). Selection criteria were clinical history and urodynamics. Pre-treatment urodynamic study showed no statistical differences between the groups. Ten percent of the women in each group had involuntary detrusor contractions. Patients were randomly distributed, in a double-blind study, into two groups. Group G1 (n=20), effective IES, and group G2 (n=20), sham IES, with follow-up at 1 month. The following parameters were studied: (1) clinical questionnaire, (2) examiner's evaluation of perineal muscle strength, (3) objective evaluation of perineal muscle by perineometry, (4) vaginal weight test, and (5) urodynamic study. The IES protocol consisted of three 20-min sessions per week over a 7-week period using a Dualpex Uro 996 at 4 Hz. There was no statistically significant difference in the demographic data of both groups. The number of micturitions per 24 h after treatment was reduced significantly in both groups. Urge incontinence, present in all patients before treatment, was reduced to 15% in G1 and 31.5% in G2 post-treatment. The subjective evaluation of PFM strength demonstrated a significant improvement in G1. Objective evaluation of PFM force by perineometer showed a significant improvement in maximum peak contraction post-treatment in both groups. In the vaginal weight test, there was a significant increase in average number of cone retentions post-treatment in both groups. With regard to satisfaction level, after treatment, 80% of the patients in G1 and 65% of the patients in G2 were satisfied. There was no statistically significant difference between the groups. There was a significant improvement in PFM strength from both effective and sham electrostimulation, questioning the effectiveness of electrostimulation as a monotherapy in treating MUI.

Striated urethral sphincter activity does not alter urethral pressure during filling cystometry

OBJECTIVE

The purpose of this study was to determine the relationship between urethral pressure and the neuromuscular activity of the urethral sphincter with the use of quantitative electromyography during bladder filling.

STUDY DESIGN

Women who underwent multichannel urodynamic testing with concentric needle electromyography of the striated urethral sphincter between December 2000 and February 2002 were studied. Raw electromyography signals were processed by a electromyography instrument that was equipped with automated motor unit analysis software programs. Quantitative electromyography software was used to analyze the electrical activity of the urethral sphincter during filling cystometry.

RESULTS

One hundred women (mean age, 60 years [range, 22-82 years]; median parity, 3 children [range, 0-8 children]) were studied. Most women (79%) were postmenopausal, and 68% of those women were receiving hormone replacement therapy. Quantitative electromyography values increased significantly at 300 mL and maximum cystometric capacity; however, there was no significant increase in urethral pressure. The median change in urethral pressure at 300 mL and maximum cystometric capacity were 4 cm water (interquartile range, 0-8 cm) and 0 cm water (interquartile range, -4-8 cm), respectively (P = .229). The median change in quantitative electromyography at 300 mL and maximum cystometric capacity were 9 microV (range, 5-14 microV) and 10 microV (range, 7-19 microV), respectively (P < .0005). There was no correlation between change in urethral pressure and motor unit activation on quantitative electromyography at 300 mL or maximum cystometric capacity. Fifty-six women had no change or a decreased urethral pressure at maximum cystometric capacity, yet all but 1 of these women had increased motor unit activation on quantitative electromyography.

CONCLUSION

Urethral pressure does not increase during filling cystometry, despite increased activity of the striated urethral sphincter, which suggests that urethral pressure change does not reflect the integrity of the striated urethral sphincter.

Motor evoked potentials from the pelvic floor

AIMS

Proper function of the lower urinary tract depends on the integrity of the central and peripheral nervous pathways on multiple levels, and the complexity of this system leaves it susceptible to even minor lesions. While dysfunction of the lower urinary tract is prevalent amongst patients with nervous system disease, e.g., multiple sclerosis (MS), most women with lower urinary tract dysfunction (LUTD) have no overt neurological cause. Refined neuro-diagnostic approaches are needed to reveal neurogenicity in these patients. A potential method is transcranial magnetic stimulation (TMS), which is used routinely to test the motor innervation of limb muscles, but also can be applied to test pelvic floor efferents. To resolve the lack of methodological clarity and the need for normative values for the use of pelvic floor motor evoked potentials (MEPs), 30 healthy women and 16 women with MS were studied.

METHODS

The healthy women underwent MEP studies with various stimulus and recording modalities, and, to test reproducibility, 18 of them were retested at a separate session. The women with MS underwent MEP testing as well as urodynamic studies.

RESULTS

From the methodological studies of healthy women, the use of invasive concentric needle electrodes was found to be superior to surface electrodes. When applying magnetic stimuli over the sacral region, various methodological problems were encountered. In the healthy women, a large variability of responses was noted, the long-term reproducibility of pelvic floor MEP latencies was poor, and in some cases responses could not be obtained. In the study of women with MS, prolonged central conduction times were found, along with many cases of unevokable responses, and a poor correlation of MEPs to urodynamic findings. The problems of obtaining selective recordings from the inaccessible pelvic floor musculature are discussed, and possible sources of variability in MEPs from the pelvic floor are considered. By relating the findings in the present studies to those of others using different modalities, some reflections are presented on the nature of the neural pathways to the pelvic floor activated by magnetic stimulation. As unevokable responses from the pelvic floor were an occasional finding among the healthy women, it is argued that a pelvic floor non-response in a patient with suspected corticospinal lesion should be interpreted with care, and should not carry the same clinical significance as an absent limb response.

CONCLUSIONS

The inherent limitations of pelvic floor MEPs are discussed, and it is concluded that while there seems to be only limited clinical value of pelvic floor MEP testing, there might be some interesting scientific perspectives in studies that aim to control and explain the variability of responses.

Restoration of functional motor units in a rat model of sphincter injury by muscle precursor cell autografts1

BACKGROUND

Urinary incontinence is a debilitating condition that affects primarily elderly individuals. One major mechanism results from chronic denervation of the striated urethral sphincter with associated fibrosis. The authors investigated the fate of muscle precursor cells (MPC) injected into a model of striated urethral sphincter injury that reproduces the histopathologic changes of sphincter insufficiency.

METHODS

The striated urethral sphincter of older male rats was damaged by electrocoagulation. MPC were isolated from limb myofiber explants, infected with an adenovirus carrying the transgene encoding beta-galactosidase, and injected into the sphincter of the same animal 37 days after injury. Animals were killed 5 and 30 days after injection for assessment of sphincter function and the formation of motor units.

RESULTS

Electrocoagulation resulted in an irreversible destruction of both sphincteric myofibers and nerve endings, with a functional incapacity of the damaged sphincter to sustain an increase in bladder pressure; atrophy and fibrosis developed after 1 month. Injection of MPC resulted in the formation of beta-galactosidase-expressing myotubes in the sphincter that persisted beyond 30 days. The regenerated myotubes carried acetylcholine receptors associated with a nerve ending and were thus considered to form anatomic motor units. Urodynamic studies confirmed the restoration of 41% of sphincter function 1 month after MPC injection.

CONCLUSIONS

The authors showed that MPC isolated from limb muscles of an older animal can recapitulate a myogenic program when injected into an irreversibly injured sphincter. The maturation of MPC activates nerve regeneration and restores functional motor units.

The regeneration process of the striated urethral sphincter involves activation of intrinsic satellite cells

The regeneration of adult skeletal muscle is mediated by satellite cells. Classically, these are considered to be somitically derived cells that colonize the limbs during early embryogenesis. The striated urethral sphincter presents specific developmental characteristics that distinguish it from skeletal muscles, such as the non-somitic origin of its precursor cells and the late formation of its myofibers. This prompted us to determine whether the striated urethral sphincter can regenerate after injury by the same mechanism as skeletal muscles. By means of the single myofiber explant culture technique we investigated the presence of satellite cells in the striated urethral sphincter of male mice and evaluated their ability to recapitulate a myogenic program. In addition, a myotoxic substance (notexin) was injected into the sphincter in order to provoke rapid destruction of the myofibers; the regeneration process was studied by means of electrophysiological and histological techniques. Satellite cells expressing pax7 were found attached to the sphincteric myofibers. They proliferated and expressed MyoD, Myf5 and desmin after 2 days in culture. After 10 days, they formed multinucleated myotubes expressing alpha-actinin-2. In vivo, complete recovery of the striated urethral sphincter, as assessed by normalization of muscle strength and of myofiber number and diameter, was observed after 3 weeks, and resulted from the fusion of myogenic cells. These results demonstrate that the striated urethral sphincter can regenerate by means of a myogenic program involving intrinsic satellite cells. The therapeutic implications of this knowledge and the possible origin of the sphincteric satellite cells are discussed.

Neural control of the urethra and development of pharmacotherapy for stress urinary incontinence

This review discusses the control of the urethra by the central nervous system, emphasizing the importance of nervous system control and the role of serotonin and noradrenaline in storage, micturition and sphincter reflexes. The concept of pharmacological neuromodulation and the use of pharmacological therapy as first-line therapy for stress urinary incontinence (SUI) is presented. Coordination between the urinary bladder and urethra is mediated by many reflex pathways organized in the brain and spinal cord. During bladder filling, activation of mechanoreceptor afferent nerves in the bladder wall triggers firing in the cholinergic efferent pathways to the external urethral sphincter and in sympathetic adrenergic pathways to the urethral smooth muscle. These storage reflexes depend on interneuronal circuitry in the spinal cord and are modulated by descending pathways. It would therefore seem that neurotransmission in the central nervous system and periphery may be important in SUI, and moreover that pharmacological agents affecting these neurotransmitter pathways may be used to treat SUI. The central and peripheral mechanisms of action of duloxetine affect serotonin and noradrenaline neurotransmission in ways that may ameliorate the symptoms of SUI.

Long-term effect of ovariectomy and simulated birth trauma on the lower urinary tract of female rats

PURPOSE

Using an animal model we studied the long-term effects of ovariectomy and simulated birth trauma in the development of apoptosis as well as the urodynamic, histological and ultrastructural findings 9 months after such procedures.

MATERIALS AND METHODS

A total of 24 pregnant Sprague-Dawley female rats were used. Immediately after delivery 14 animals underwent vaginal ballooning and ovariectomy, while the remaining 10 served as controls. At 9 months the animals underwent urodynamic evaluation, which included the urethral pressure profile. The rats were then sacrificed and urogenital tissue was obtained for immunostaining using terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end-labeling, histomorphometry evaluation and electron microscopy.

RESULTS

Immunostaining demonstrated a significant increase in the apoptotic index in the urethra of castrated/ballooning rats with a predominance in the submucosa layer. Maximum urethral closure pressure was significantly lower in that group, although there was no correlation of apoptosis with maximum urethral closure pressure measurement. Urodynamic evaluation revealed only discrete alterations in cystometric parameters. Morphometric evaluation showed increased connective tissue in the vagina. Electron microscopy of urethral smooth muscle demonstrated altered cellular shape, increased intercellular space with collagen deposition and some degeneration of the mitochondria.

CONCLUSIONS

Apoptosis in the urethra occurs 9 months after castration and simulated birth trauma. However, this finding was not seen in the muscle layers or in other urogenital tissues. Some ultrastructural changes also occurred that may explain some symptoms that women have after vaginal childbirth and menopause.

Muscle precursor cell autografting in a murine model of urethral sphincter injury

OBJECTIVE

To determine whether muscle precursor cells (MPCs) harvested from limb skeletal muscle can enhance the regeneration process of the striated urethral sphincter after injury.

MATERIAL AND METHODS

Striated urethral sphincters of male mice were injured by an injection of a myotoxic substance (notexin). In the experimental group, 2 days after injury, MPCs were enzymatically harvested from striated muscles of the lower limbs and labelled with PKH 26, then immediately re-injected into the injured urethral sphincter of the same animal. In the control group, saline buffer was injected instead of MPCs. Animals were killed 7 days or 1 month after injury and the sphincters removed for histological study (the presence of PKH 26-labelled myofibres, measurement of myofibre diameter and total number of myofibres).

RESULTS

MPC autografting accelerated sphincter muscle repair, as shown by a higher myofibre diameter (P = 0.03) and number (P = 0.01) in the experimental group than in the controls at 7 days. One month after their injection MPCs were still detectable in the regenerating sphincters and participated in the formation of new myofibres.

CONCLUSION

This study provides the experimental basis for a new therapeutic approach to urethral sphincter insufficiency after surgical or obstetrical injury, based on MPC autografting.

Protocol for clinical neurophysiologic examination of the pelvic floor

Clinical neurophysiologic examination of the pelvic floor is performed worldwide, but there is no consensus on the choice of tests, nor on technical details of individual methods. Standardized methods are, however, necessary to obtain their valid application in different laboratories for the purpose of collection of normative data, comparison of patient data and organization of multi-center studies. It is proposed that in patients with suspected "lower motor neuron" type lesions concentric needle electromyography (CNEMG) is the most informative test to detect pelvic floor denervation/reinnervation, and the external anal sphincter (EAS) muscle is the most appropriate muscle to be examined (either in isolation-when a selective lesion is suspected-or in addition to examination of other muscles). An algorithm consisting of standardized tests including a standardized approach to CNEMG examination of the EAS is presented. The proposed electrophysiologic assessment consists of a computer-assisted analysis of denervation and reinnervation features of the CNEMG signal, a qualitative assessment of reflex and voluntary activation of EAS motor units, and of electrical (or mechanical) elicitation of the bulbocavernosus reflex in those patients in whom manual anogenital stimulation failed to elicit a robust response in the EAS. The proposed protocol could serve as a basis for further studies on validity, sensitivity and specificity of electrophysiologic assessment in patients with different types of "lower motor neuron" involvement of pelvic floor muscles and sacral dysfunction.

The pathophysiology of pelvic floor disorders: evidence from a histomorphologic study of the perineum and a mouse model of rectal prolapse

The muscle changes related to pelvic floor disorders are poorly understood. We conducted an anatomical and histological study of the perineum of the normal mouse and of a transgenic mouse strain deficient in urokinase-type plasminogen activator (uPA-/-) that was previously reported to develop a high incidence of rectal prolapse. We could clearly identify the iliococcygeus (ILC) and pubococcygeus (PC) muscles and anal (SPA) and urethral (SPU) sphincters in male and female mice. The bulbocavernosus (BC), ischiocavernosus (ISC) and levator ani (LA) muscles could be found only in male mice. Histochemical analysis of the pelvic floor muscles revealed a majority of type IIA fibres. Rectal prolapses were observed only in male uPA-/- mice. The most obvious finding was an irreducible evagination of the rectal mucosa and a swelling of the entire perineal region corresponding to an irreducible hernia of the seminal vesicles through the pelvic outlet. The hernia caused stretching and thinning of the ISC, BC and LA. Myopathic damage, with degenerated and centronucleated myofibres, were observed in these muscles. The PC, ILC, SPA and SPU were not affected. This study provides an original description of a model of pelvic floor disorder and illustrates the differences existing between the perineum of humans and that of a quadruped species. In spite of these differences, the histopathologic changes observed in the pelvic floor muscles of uPA-/- mice with rectal prolapse suggest that prolonged muscular stretching causes a primary myopathic injury. This should be taken into account in the evaluation of pelvic floor disorders.

Endocoil magnetic resonance imaging quantification of external anal sphincter atrophy

BACKGROUND

Anal function depends on the integrity and quality of the sphincter muscles. The diagnosis of external anal sphincter atrophy on endocoil magnetic resonography has been associated with poor outcome from sphincter repair, although the imaging criteria for atrophy remain unclear.

METHODS

Women with intact sphincters on endosonography and either normal (more than 60 cm H(2)O) (n = 9) or low (n = 16) squeeze pressures had endocoil magnetic resonography and electromyography. The area and fat content of the external anal sphincter and puborectalis were measured on mid-coronal magnetic resonography and images were graded as showing normal, intermediate or advanced atrophy. The definition of the external anal sphincter on endosonography and the thickness of the internal anal sphincter were also assessed.

RESULTS

Women with a normal anal squeeze pressure had a larger external anal sphincter cross-sectional area (mean(s.d.) 240(56) versus 193(62) mm(2); P = 0.01) with a lower mean fat content (mean(s.d.) 23(4) versus 30(6) per cent; P < 0.001) than those with low squeeze pressures. There was an overall correlation between squeeze pressure, cross-sectional area (r = 0.32, P = 0.02) and fat content (r = - 0.51, P < 0.001). Patients with a thin (less than 2 mm) internal anal sphincter and/or a poorly defined external sphincter on endosonography were more likely to have atrophy (positive predictive value 74 per cent).

CONCLUSION

: Potential endosonographic markers for external anal sphincter atrophy are suggested, and a visual scale for endocoil magnetic resonographic assessment has been validated.

Transvaginal ultrasound of urethral sphincter at the mid urethra in continent and incontinent women

PURPOSE

Few studies are available on imaging the urethral sphincter. We performed transvaginal ultrasonography to examine the muscle in continent and incontinent women.

MATERIALS AND METHODS

Transvaginal ultrasonography was performed using a 7.5 MHz. transrectal probe in 19 continent and 69 incontinent supine women. Incontinent cases were classified as urge (14) and stress (55), and included urethral hypermobility (22) and intrinsic sphincter deficiency (33). Cadaver specimens were also examined to confirm the anatomy of ultrasound images.

RESULTS

Transvaginal ultrasonography showed the urethra as a round structure consisting of a relatively high echogenic central zone and a relatively low echogenic peripheral zone. Matching ultrasound images with the anatomy of cadaver specimens indicated that the peripheral zone represents rhabdosphincter most reliably at the lateral aspects. Thus, its thickness was measured at the 9 o'clock position of the mid urethra. Mean thickness plus or minus standard error of mean was significantly decreased in stress incontinence compared with continence and urge incontinence (2.14 +/- 0.04, 2.78 +/- 0.08 and 2.87 +/- 0.11 mm., respectively, p <0. 001), while in intrinsic sphincter deficiency it was thinner than in hypermobility (2.00 +/- 0.05 versus 2.35 +/- 0.06 mm., p <0.01). There was no difference in central zone thickness according to continence status.

CONCLUSIONS

Urethral structures may be visualized by transvaginal ultrasonography. The rhabdosphincter image was thinner in stress incontinence, especially in intrinsic sphincter deficiency. Transvaginal ultrasonography may be a useful clinical test for examining the morphology of the urethral sphincter muscle in women.