Urinary incontinence: anatomy, physiology and pathophysiology

Endoscopic implantation of autologous myoblasts for stress urinary incontinence and evaluation of its efficacy in sphincterotomized rabbits

INTRODUCTION

Stress urinary incontinence (SUI) is one of the health problems with more impact on patients' lives. The aim of the present work was to develop a therapy for SUI using tissue engineering by isolation and culture of autologous myoblasts (CAM) followed by endoscopic implantation. We also evaluated the efficacy of this therapy in a rabbit model of incontinence after sphincterotomy.

MATERIALS AND METHODS

We used healthy male New Zealand rabbits. The animals were first bled to obtain platelet-poor plasma (PPP) and biopsied for myoblast isolation. Post-sphincterotomy, they were divided into two groups: the treatment group (including animals that received CAM resuspended in PPP) and the control group (including animals receiving only PPP). The leak-point pressure (LPP) was used to measure continence in both groups at different time points. The results were evaluated with hierarchical linear regression models. Histological evaluation of the rabbits' sphincters was also performed at the end of follow-up.

RESULTS

No statistically significant differences were observed between the baseline LPP values of each group. The post-sphincterotomy values of both groups were below 50% of the baseline value, which was a mandatory condition for incontinence. The post-implantation values of the treatment group were higher than 50% of the baseline value, which led us to assume continence recovery. A statistically significant difference was observed in the LPP values between the two treatment groups (p=0.003). Histological study revealed interconnected islands formed by muscle fibers in the treatment group, and connective tissue surrounding the urethral lumen and inflammatory infiltrate in the control group.

DISCUSSION AND CONCLUSIONS

The implantation of CAM significantly improved LPP values in the treatment group, and the improvement remained throughout the evaluation period. It may be associated with the consistency of the implant and its stability at the injection site. Longer follow-up studies and human clinical investigations are required to consider CAM implantation as an alternative treatment for stress urinary incontinence.

Role of Ano1 Ca2+-activated Cl- channels in generating urethral tone

Urinary continence is maintained in the lower urinary tract by the contracture of urethral sphincters, including smooth muscle of the internal urethral sphincter. These contractions occlude the urethral lumen, preventing urine leakage from the bladder to the exterior. Over the past 20 years, research on the ionic conductances that contribute to urethral smooth muscle contractility has greatly accelerated. A debate has emerged over the role of interstitial cell of Cajal (ICC)-like cells in the urethra and their expression of Ca²⁺-activated Cl^- channels encoded by anoctamin-1 [Ano1; transmembrane member 16 A (Tmem16a) gene]. It has been proposed that Ano1 channels expressed in urethral ICC serve as a source of depolarization for smooth muscle cells, increasing their excitability and contributing to tone. Although a clear role for Ano1 channels expressed in ICC is evident in other smooth muscle organs, such as the gastrointestinal tract, the role of these channels in the urethra is unclear, owing to differences in the species (rabbit, rat, guinea pig, sheep, and mouse) examined and experimental approaches by different groups. The importance of clarifying this situation is evident as effective targeting of Ano1 channels may lead to new treatments for urinary incontinence. In this review, we summarize the key findings from different species on the role of ICC and Ano1 channels in urethral contractility. Finally, we outline proposals for clarifying this controversial and important topic by addressing how cell-specific optogenetic and inducible cell-specific genetic deletion strategies coupled with advances in Ano1 channel pharmacology may clarify this area in future studies.NEW & NOTEWORTHY Studies from the rabbit have shown that anoctamin-1 (Ano1) channels expressed in urethral interstitial cells of Cajal (ICC) serve as a source of depolarization for smooth muscle cells, increasing excitability and tone. However, the role of urethral Ano1 channels is unclear, owing to differences in the species examined and experimental approaches. We summarize findings from different species on the role of urethral ICC and Ano1 channels in urethral contractility and outline proposals for clarifying this topic using cell-specific optogenetic approaches.

The intracellular Ca2+ release channel TRPML1 regulates lower urinary tract smooth muscle contractility

TRPML1 (transient receptor potential mucolipin 1) is a Ca²⁺-permeable, nonselective cation channel that is localized to late endosomes and lysosomes. Here, we investigated the function of TRPML1 channels in regulating lower urinary tract (LUT) smooth muscle cell (SMC) contractility. We found that TRPML1 forms a stable signaling complex with ryanodine receptors (RyRs) in the sarcoplasmic reticulum (SR). We further showed that TRPML1 channels are important for initiating an essential Ca²⁺-signaling negative feedback mechanism between RyRs on SR membranes and K⁺ channels on the plasma membrane. Knockout of TRPML1 channels in mice impaired this pathway, resulting in LUT smooth muscle hypercontractility and symptoms of overactive bladder. Our findings demonstrate a critical role for TRPML1 in LUT function.

TRPML1 (transient receptor potential mucolipin 1) is a Ca²⁺-permeable, nonselective cation channel that is predominantly localized to the membranes of late endosomes and lysosomes (LELs). Intracellular release of Ca²⁺ through TRPML1 is thought to be pivotal for maintenance of intravesicular acidic pH as well as the maturation, fusion, and trafficking of LELs. Interestingly, genetic ablation of TRPML1 in mice (Mcoln1^−/−) induces a hyperdistended/hypertrophic bladder phenotype. Here, we investigated this phenomenon further by exploring an unconventional role for TRPML1 channels in the regulation of Ca²⁺-signaling activity and contractility in bladder and urethral smooth muscle cells (SMCs). Four-dimensional (4D) lattice light-sheet live-cell imaging showed that the majority of LELs in freshly isolated bladder SMCs were essentially immobile. Superresolution microscopy revealed distinct nanoscale colocalization of LEL-expressing TRPML1 channels with ryanodine type 2 receptors (RyR2) in bladder SMCs. Spontaneous intracellular release of Ca²⁺ from the sarcoplasmic reticulum (SR) through RyR2 generates localized elevations of Ca²⁺ (“Ca²⁺ sparks”) that activate plasmalemmal large-conductance Ca²⁺-activated K⁺ (BK) channels, a critical negative feedback mechanism that regulates smooth muscle contractility. This mechanism was impaired in Mcoln1^−/− mice, which showed diminished spontaneous Ca²⁺ sparks and BK channel activity in bladder and urethra SMCs. Additionally, ex vivo contractility experiments showed that loss of Ca²⁺ spark–BK channel signaling in Mcoln1^−/− mice rendered both bladder and urethra smooth muscle hypercontractile. Voiding activity analyses revealed bladder overactivity in Mcoln1^−/− mice. We conclude that TRPML1 is critically important for Ca²⁺ spark signaling, and thus regulation of contractility and function, in lower urinary tract SMCs.

Contribution of Cav1.2 Ca2+ channels and store-operated Ca2+ entry to pig urethral smooth muscle contraction

Urethral smooth muscle (USM) generates tone to prevent urine leakage from the bladder during filling. USM tone has been thought to be a voltage-dependent process, relying on Ca²⁺ influx via voltage-dependent Ca²⁺ channels in USM cells, modulated by the activation of Ca²⁺-activated Cl^- channels encoded by Ano1. However, recent findings in the mouse have suggested that USM tone is voltage independent, relying on Ca²⁺ influx through Orai channels via store-operated Ca²⁺ entry (SOCE). We explored if this pathway also occurred in the pig using isometric tension recordings of USM tone. Pig USM strips generated myogenic tone, which was nearly abolished by the Ca_v1.2 channel antagonist nifedipine and the ATP-dependent K⁺ channel agonist pinacidil. Pig USM tone was reduced by the Orai channel blocker GSK-7975A. Electrical field stimulation (EFS) led to phentolamine-sensitive contractions of USM strips. Contractions of pig USM were also induced by phenylephrine. Phenylephrine-evoked and EFS-evoked contractions of pig USM were reduced by ~50-75% by nifedipine and ~30% by GSK-7975A. Inhibition of Ano1 channels had no effect on tone or EFS-evoked contractions of pig USM. In conclusion, unlike the mouse, pig USM exhibited voltage-dependent tone and agonist/EFS-evoked contractions. Whereas SOCE plays a role in generating tone and agonist/neural-evoked contractions in both species, this dominates in the mouse. Tone and agonist/EFS-evoked contractions of pig USM are the result of Ca²⁺ influx primarily through Ca_v1.2 channels, and no evidence was found supporting a role of Ano1 channels in modulating these mechanisms.

Laboratory practical to study the differential innervation pathways of urinary tract smooth muscle

In the mammalian lower urinary tract, there is a reciprocal relationship between the contractile state of the bladder and urethra. As the bladder fills with urine, it remains relaxed to accommodate increases in volume, while the urethra remains contracted to prevent leakage of urine from the bladder to the exterior. Disruptions to the normal contractile state of the bladder and urethra can lead to abnormal micturition patterns and urinary incontinence. While both the bladder and urethra are smooth-muscle organs, they are differentially contracted by input from cholinergic and sympathetic nerves, respectively. The laboratory practical described here provides an experiential approach to understanding the anatomy of the lower urinary tract. Several key factors in urinary tract physiology are outlined, e.g., the bladder is contracted by activation of the parasympathetic pathway via cholinergic stimulation on muscarinic receptors, whereas the urethra is contracted by activation of the sympathetic pathway via adrenergic stimulation on α₁-adrenoceptors. This is achieved by measuring the force generated by bladder and urethra smooth muscle to demonstrate that acetylcholine contracts the smooth muscle of the bladder, whereas adrenergic agonists contract the urethral smooth muscle. An inhibition of these effects is also demonstrated by application of the muscarinic receptor antagonist atropine and the α₁-adrenergic receptor blocker phentolamine. A list of suggested techniques and exam questions to evaluate student understanding on this topic is also provided.

Ion channels of the mammalian urethra

The mammalian urethra is a muscular tube responsible for ensuring that urine remains in the urinary bladder until urination. In order to prevent involuntary urine leakage, the urethral musculature must be capable of constricting the urethral lumen to an extent that exceeds bladder intravesicular pressure during the urine-filling phase. The main challenge in anti-incontinence treatments involves selectively-controlling the excitability of the smooth muscles in the lower urinary tract. Almost all strategies to battle urinary incontinence involve targeting the bladder and as a result, this tissue has been the focus for the majority of research and development efforts. There is now increasing recognition of the value of targeting the urethral musculature in the treatment and management of urinary incontinence. Newly-identified and characterized ion channels and pathways in the smooth muscle of the urethra provides a range of potential therapeutic targets for the treatment of urinary incontinence. This review provides a summary of the current state of knowledge of the ion channels discovered in urethral smooth muscle cells that regulate their excitability.

Pharmacological approach to overactive bladder and urge urinary incontinence in women: an overview

Besides life-style changes, electrical stimulation or surgery, pharmacological treatment is becoming the first-choice approach in women suffering from lower urinary tract symptoms (LUTS), including urge urinary incontinence (UUI) and overactive bladder (OAB). Several drugs for the treatment of bladder storage and voiding disorders are currently available and, in the near future, novel compounds with higher specificity for the lower urinary tract receptors will be accessible. This will bring optimization of therapy, reducing side effects and increasing compliance, especially in patients with comorbidities and in women. The purpose of this paper is to give an overview on the pharmacotherapy of two common inter-correlated urological conditions, UUI and OAB. The study was conducted by analyzing and comparing the data of the recent international literature on this topic. Advances in the discovery of pharmacological options have dramatically improved the quality of life of patients affected by incontinence, but further studies are needed to increase the effectiveness and safety of the therapies used in this field.

Urethral striated muscle and extracellular matrix morphological characteristics among mildly diabetic pregnant rats: translational approach

INTRODUCTION AND HYPOTHESIS

Diabetes mellitus (DM) during pregnancy is associated with high levels of urinary incontinence (UI) and pelvic floor muscle dysfunction. Mild DM can lead to changes in urethral striated muscle and extracellular matrix (ECM) in pregnant rats considering both structures as an entire system responsible for urinary continence.

METHODS

Ninety-two female Wistar rats were distributed in four experimental groups: virgin, pregnant, diabetic, and diabetic pregnant. In adult life, parental nondiabetic female rats were mated with nondiabetic male rats to obtain newborns. At the first day of birth, newborns received citrate buffer (nondiabetic group) or streptozotocin 100 mg/kg body weight, subcutaneous route (mild DM group). At day 21 of the pregnancy, the rats were lethally anesthetized and the urethra and vagina were extracted as a unit. Urethral and vaginal sections were cut and analyzed by: (a) cytochemical staining for ECM and muscle structural components, (b) immunohistochemistry to identify fast- and slow-muscle fibers, and (c) transmission electron microscopy for ultrastructural analysis of urethral striated muscle.

RESULTS

In comparison with the three control groups, variations in the urethral striated muscle and ECM from diabetic pregnant rats were observed including thinning, atrophy, fibrosis, increased area of blood vessels, mitochondria accumulation, increased lipid droplets, glycogen granules associated with colocalization of fast and slow fibers, and a steady decrease in the proportion of fast to slow fibers.

CONCLUSIONS

Mild DM and pregnancy can lead to a time-dependent disorder and tissue remodeling in which the urethral striated muscle and ECM has a fundamental function.

Does childbirth alter the reflex pelvic floor response to coughing?

OBJECTIVE

To determine the prevalence of and to quantify the effect of reflex pelvic floor activation on coughing in nulliparous pregnant women, and to assess peripartal changes and any association with stress urinary incontinence.

METHODS

Between April 2008 and March 2010, 131 nulliparous pregnant women were recruited from an antenatal clinic. All participants were interviewed and underwent four-dimensional translabial ultrasound examination at antepartum (35.8 (mean) weeks' gestation) and postpartum (4.6 (mean) months) visits. Four-dimensional ultrasound volume datasets of the pelvic floor during coughs were obtained at a minimum frame rate of 16 Hz, using a 10° volume acquisition angle. To quantify a reflex levator contraction we measured the midsagittal hiatal diameter at multiple time points. Levator integrity was determined using tomographic ultrasound imaging.

RESULTS

From 131 women recruited, 47 datasets were technically suboptimal, leaving 84. There was a visible pelvic floor reflex in 82 (98%) cases. At the postpartum visit this was reduced to 63/84, i.e. 75% (P < 0.001). The magnitude of a reflex contraction was markedly reduced postpartum, from 4.8 mm to 2.0 mm (P < 0.001), and this effect was associated with delivery mode (P = 0.042). There was a trend towards an association between lower reflex contraction magnitude and stress incontinence (0.87 ± 3.18 mm vs. 2.36 ± 3.5 mm; P = 0.08) at the postpartum follow-up visit.

CONCLUSIONS

Pelvic floor reflexes are altered by childbirth. This alteration may be associated with vaginal delivery. Reflex magnitude may be associated with postpartum stress urinary incontinence. The clinical significance of this finding is uncertain.

Surgical management of stress urinary incontinence in women: safety, effectiveness and cost-utility of trans-obturator tape (TOT) versus tension-free vaginal tape (TVT) five years after a randomized surgical trial

BACKGROUND

We recently completed a randomized clinical trial of two minimally invasive surgical procedures for stress urinary incontinence, the retropubic tension-free vaginal tape (TVT) versus the trans-obturator tape (TOT) procedure. At one year postoperatively, we were concerned to find that a significant number of women had tape that was palpable when a vaginal examination was undertaken. Because the risk factors for adverse outcomes of tape surgery are not clearly understood, we are unable to say whether palpable tapes will lead to vaginal erosions or whether they merge into vaginal tissue. We do not know whether patients go on to have further adverse consequences of surgery, leading to additional cost to patients and healthcare system. Our current study is a 5 year follow-up of the women who took part in our original trial.

METHODS/DESIGN

All 199 women who participated in our original trial will be contacted and invited to take part in the follow-up study. Consenting women will attend a clinic visit where they will have a physical examination to identify vaginal erosion or other serious adverse outcomes of surgery, undertake a standardized pad test for urinary incontinence, and complete several health-related quality of life questionnaires (15D, UDI-6, IIQ-7). Analyses will compare the outcomes for women in the TOT versus TVT groups. The cost-effectiveness of TOT versus TVT over the 5 years after surgery, will be assessed with the use of disease-specific health service administrative data and an objective health outcome measure. A cost-utility analysis may also be undertaken, based on economic modeling, data from the clinical trial and inputs obtained from published literature.

DISCUSSION

This study is needed now, because TOT and TVT are among the most frequently conducted surgical procedures for stress urinary incontinence in Canada. Because stress urinary incontinence is so common, the impact of selecting an approach that causes more adverse events, or is less effective, will have a significant impact on individual quality of life, and societal and health care costs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00234754. Registered October 2005.

Role of botulinum toxin-A in management of refractory idiopathic detrusor overactive bladder: Single center experience

BACKGROUND

Overactive bladder (OAB) is a bothersome condition affecting the quality of life, financial constraint on the individual, and community. Anticholinergic drugs cannot be used for long term due to adverse side effects. Botulinum toxin has recently shown promising and encouraging result in management of OAB.

AIM

Aim was to study the safety, efficacy, tolerability, and duration of effect of 200 units of botulinum toxin in refractory idiopathic detrusor overactivity.

MATERIALS AND METHODS

Thirty-nine female patients (average age of 52 years) clinically and urodynamically diagnosed as idiopathic OAB were injected 200 units of botulinum toxin-A mixed with 20 ml of normal saline, intradetrusally at the rate of 1 mL at each site for 20 such sites sparing the trigone and ureteric orifices. Follow up at 3rd, 6th, 9th, and 12th month with clinical and urodynamical questionnaire was done.

RESULTS

There were 4 dropouts and 35 patients were evaluated, of which 30 patients (85.7%) showed improvement in clinical features like frequency, urgency, nocturia, and incontinence within 1 week of injection, which lasted for mean period of 7 months (varying from 6 to 9 months). Volume at first desire to void improved from median baseline of 104-204 ml and maximum cystometric capacity of bladder increased from mean baseline value of 205-330 ml. The detrusor pressure decreased by 49% from the baseline and postresidual urine volume increased by 30% of maximum cystometric capacity of bladder. There was no adverse effect on our patient.

CONCLUSION

Intradetrusor injection of Botox-A in management of refractory overactive idiopathic bladder is not only safe and well tolerated, but also very effective with practically no side effects.

Goal achievement as a patient-generated outcome measure for stress urinary incontinence

OBJECTIVES

To explore women's goals and goal attainment for the conservative and surgical treatment of stress urinary incontinence (SUI), and to examine the feasibility of Goal Attainment Scaling (GAS) as an outcome measure in this population.

BACKGROUND

Despite the range of treatments for SUI, little is known about the outcomes patients consider important. Current instruments measure the impact of SUI on the ability to live a 'normal' life without addressing what normal looks like for the patient. Patient-generated measures that address what a patient aims to achieve may fill this gap.

DESIGN

A mixed-methods exploratory design combined semi-structured interviews with validated questionnaires and individualized rating of goal achievement. SETTING AND PARTICIPANTS PARTICIPANTS: with SUI (n = 18) were interviewed in their homes prior to initiation of treatment and 3-6 months afterwards.

MAIN VARIABLES

Participants reported individualized goals pre-treatment and rated goal attainment after surgical and conservative therapy. Quality of life impact and change were measured using short forms of the Incontinence Impact Questionnaire and Urinary Distress Inventory.

RESULTS

Women expressed a median of four highly individualized treatment-related goals but goal achievement following conservative treatment was poor. GAS was not feasible as an outcome measure; women readily identified personal goals but could not independently identify graded levels of attainment for each goal.

CONCLUSIONS

Although further work is needed to examine the most feasible, valid, and reliable method of measuring goal achievement in research, asking patients with UI to identify pre-treatment goals may provide useful information to guide treatment-related decision making.

Efficacy of interferential low frequency therapy for elderly wet overactive bladder patients

OBJECTIVES

Examining the clinical efficacy on the interferential low frequency therapy (IF) for elderly nonneurogenic (idiopathic) overactive bladder patients with urgent urinary incontinence (wet OAB) prospectively, for whom anticholinergics were not effective.

MATERIALS AND METHODS

Subjects are elderly 80 patients (69-78, median age 72.0) with urinary incontinence, who are clinically diagnosed with wet OAB without urodynamics (pressure/flow study). For 3 months, they were administered anticholinergics (propiverine hydrochloride 20 mg/once per day in the morning), but all their quality of life (QOL) score were 4 or over due to poor control of storage symptoms and urinary incontinence. We selected patients for whom anticholinergics were not effective (above-mentioned 80 patients) and they were provided with IF alone for 3 months with informed consent. Before and after IF, the followings were examined. (1) frequency of IF treatment required to show optimal effects, (2) average weekly frequency of incontinence, (3) 60-min pad test, (4) frequency and voided volume in the daytime and nighttime, (5) fluid intake volume, (6) International Prostate Symptom Score, quality of life score, (7) Uroflowmetry, (8) postvoid residual urine volume, (9) specific gravity of urine, (10) average hours spent outdoors, (11) average radius of action and activities of daily life score, (12) standing blood pressure (BP) and heart rate, (13) clinical laboratory findings, (14) adverse events, (15) plasma osmotic pressure (OP), and (16) Brain natriuretic peptide (BNP).

RESULTS

(1) The patients showed improvements for eight treatments (median). Improvement was observed in the followings: (2), (3), (4) voiding frequency, (6), (7) voided volume, maximum and average flow rate, (10), (11), (12) BP, (15) OP, and (16).

CONCLUSIONS

The IF has safe and better effects than anticholinergics on the elderly wet OAB patients.

The effect of maturation and age on oestrogen-induced functional hypertrophy of the female rabbit bladder

OBJECTIVE

To evaluate the effect of maturation and ageing on oestrogen-induced functional hypertrophy of the female rabbit bladder.

MATERIALS AND METHODS

Twenty female rabbits were separated into two groups of 10 each by age, young (immature) and old rabbits and each age group was subdivided into three subgroups. The rabbits in subgroup 1 were controls, subgroup 2 were ovariectomized (Ovx) and subgroup 3 were Ovx and received 17-beta oestradiol (1 mg/kg/day) by a subcutaneous slow-release tablet implant. After 15 days of treatment, the rabbits were killed, the bladder was excised, and the body and base separated; two full-thickness longitudinal strips from the ventral surface of the bladder body, and one full-thickness strip from the base, were prepared for contractile studies. The contractile responses to electrical-field stimulation, carbachol, ATP and KCl were determined for both the bladder body and base strips. In addition, full-thickness strips of bladder body and base were fixed in formalin for histological and immunohistological studies.

RESULTS

Ovx plus oestradiol resulted in significant increases in bladder weight and responses to all forms of stimulation in young and old rabbits (except for the response to KCl). Vascular density and the smooth muscle (SM)/collagen ratio significantly increased after oestradiol replacement. Interestingly, the increase in vascular density was greater in the young than in the old rabbits.

CONCLUSIONS

The present study shows that oestrogen supplementation mediates a functional hypertrophy characterized by increased contractile responses to all forms of stimulation in both young and old rabbits. The increased contractile responses might be explained by the increases in vascular density and SM/collagen ratio.

Differences in mRNA and protein expression of small proteoglycans in vaginal wall tissue from women with and without stress urinary incontinence

BACKGROUND

To investigate changes in mRNA and protein levels of biglycan (BGN), decorin (DCN) and fibromodulin (FMOD) in vaginal wall tissue from women with stress urinary incontinence (SUI) compared to menstrual-cycle matched continent women.

METHODS

We determined mRNA expressions of BGN, DCN and FMOD by quantitative real-time PCR. They were localized in vaginal wall tissue by immunohistochemistry. We performed western blot analysis to examine protein expression.

RESULTS

BGN, DCN and FMOD co-localized with collagen and elastin in the extracellular matrix (ECM) of vaginal wall tissue from both groups. The mRNA expression of FMOD was significantly lower in cases versus controls in the proliferative phase (P = 0.03). DCN mRNA expression in cases was higher in the proliferative (P = 0.05) and secretory phases (P = 0.02) versus controls. BGN mRNA expression showed no significant differences in either phase. Protein expression of FMOD in cases was lower in the proliferative phase versus controls (six out of nine pairs), whereas DCN and BGN protein expression in the secretory phase in cases was higher (seven out of nine pairs).

CONCLUSION

BGN, DCN and FMOD expressions in vaginal wall tissue differ in women with SUI and are hormonally modulated. Differences in small proteoglycans may contribute to the altered pelvic floor connective tissues found in these women.

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.

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.

Estrogen induced functional hypertrophy and increased force generation of the female rabbit bladder

AIMS

Estrogen is essential for physiological maintenance of the female urogenital tract. It is believed that alterations in female sex hormones play a major role in the etiology and response to urinary tract dysfunctions. In animal studies, ovariectomy (Ovx) results in smooth muscle (SM) weakness and atrophy whereas estrogen supplementation reverses these effects. Our study seeks to establish the mechanisms by which estrogen augmentation results in increased contractility.

METHODS

Twenty New Zealand White female rabbits were separated into five groups of four each. Group 1 served as control, rabbits of groups 2-5 were ovariectomized, group 2 ovariectomized received no estradiol, groups 3-5 were given 17-beta estradiol (1 mg/kg/day) by subcutaneous slow release tablet implant for 1, 3, and 7 days, respectively, beginning 2 weeks after Ovx. At the end of the experimental period, each rabbit was anesthetized and the urinary bladder was removed for contractile, histological, and biochemical studies.

RESULTS

Ovx resulted in significantly decreased bladder contractile function, whereas bladders tested after estradiol administration showed increased contractility. Ovx resulted in a decrease in SM/collagen ratio, whereas estrogen resulted in an increase. The estrogen receptor (ER) density significantly increased following Ovx. After 1 day of estrogen treatment, the ER density decreased significantly below control levels, but rose progressively during the estrogen treatment.

CONCLUSION

The present study demonstrates that estrogen supplementation mediates a "functional hypertrophy," that is a hypertrophy characterized by increased contractile responses to all forms of stimulation, and an increased ratio of SM/collagen.

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.

The overactive bladder: review of current pharmacotherapy in adults. Part 1: pathophysiology and anticholinergic therapy

Overactive bladder is a syndrome characterised by urinary urgency, with or without urge incontinence, and usually with frequency and nocturia. It affects millions of people of all ages worldwide and causes significant morbidity, especially in terms of health-related quality of life. It poses a huge economic burden on health resources. Managing such patients involves a thorough history, physical examination and the use of pertinent investigations before the initiation of treatment. Therapy consists of lifestyle changes, bladder training, anticholinergics, second-line agents such as resiniferatoxin instillation or botulinum toxin injections into the bladder in refractory cases and, finally, in intractable cases, surgery. In the first part of this review of pharmacotherapy for the treatment of this condition, the focus is on the pathophysiological factors potentially involved in overactive bladder and covers the wide range of currently available first-line anticholinergic agents. Treatment algorithms are suggested on the basis of current literature.

Failure of elastic fiber homeostasis leads to pelvic floor disorders

Pelvic floor disorders, a group of conditions affecting adult women, include pelvic organ prolapse and urinary incontinence. Vaginal childbirth and aging are risk factors, and weakening of the pelvic support structures is a major aspect of the pathology. However, the underlying molecular mechanism remains unknown. Female reproductive organs are rich in elastic fibers that turn over slowly in most adult tissues but undergo massive remodeling in the reproductive organs through pregnancy and birth. Here we show that a failure to maintain elastic fiber homeostasis in mice causes pelvic floor disorders. Lysyl oxidase-like-1 (LOXL1), a protein essential for the postnatal deposition of elastic fibers, was highly expressed and regulated in the reproductive tract of the mouse, and its expression was diminished during aging. LOXL1 deficiency caused an inability of reproductive tissues to replenish elastic fibers after parturition, leading to pelvic organ prolapse, weakening of the vaginal wall, paraurethral pathology, and lower urinary tract dysfunction. These data demonstrate the importance of elastic fibers for maintaining structural and functional integrity of the female pelvic floor. Our findings raise the possibility that a failure of elastic fiber homeostasis, either due to genetic predisposition or advancing age, could underlie the etiology of pelvic floor dysfunction in women.

Injection therapy for stress urinary incontinence in adult women

Stress urinary incontinence (SUI) is prevalent in adult women and has a considerable impact on quality of life. However, it often remains undiagnosed and therefore untreated. Noninvasive treatment is likely to be offered in mild cases and may entail pelvic floor muscle re-education, minimally invasive devices or pharmacotherapy. Surgical intervention is widely considered as the only effective option for more severe SUI, although it is not suitable for all patients. Injection therapy with urethral bulking agents represents an alternative minimally invasive procedure and can be used for all types of SUI. Many bulking agents have been developed, although the ideal remains to be discovered. The safety and durability of agents remain a concern. No differences in agents from an efficacy point of view have been found. For many years urethral injection could only be administered endoscopically. The recent development of devices for blind injection has increased the speed and convenience of urethral injection, removing the need for surgical facilities. The subjective cure rate after injection therapy is higher than the objective one. A focus on the patient's wishes and expectations with respect to success and risks of a treatment for SUI is required. In addition, randomized clinical trials are mandatory to establish the place and efficacy of urethral bulking agents compared with conservative therapy (pelvic floor muscle re-education) in treating SUI in adult women.

Innervation of the Female Human Urethral Sphincter: 3D Reconstruction of Immunohistochemical Studies in the Fetus

OBJECTIVES

The precise location, origin and nature of nerve fibers innervating the urethral sphincter have not been clearly established. Classical anatomical studies based on cadaver dissections have provided conflicting results concerning the location of pudendal and autonomic nerve fibers. This study was designed to identify nerve fibers innervating the urethral sphincter and to provide a three-dimensional representation of their tissue relations in the female human fetus.

MATERIALS AND METHODS

Histology and immunohistochemistry (Masson's Trichromic, Luxol Fast Blue, Protein S 100 immunostaining and smooth fiber actin immunostaining) were performed on the external urethral sphincter of ten female fetuses with a crown-rump length of 112 to 340mm. Three-dimensional reconstructions of the urethral structure and innervation were obtained from serial sections using Surf Driver 3.5.3 software (David Moody and Scott Lozanoff).

RESULTS

Three-dimensional reconstructions of the same sections with different stains demonstrated the precise structure of the muscle layers (smooth and striated muscle fibers) and nerve fibers (myelinated and unmyelinated) and their relations with the urethra and vaginal wall. The proximal third consisted of a circular smooth muscle sphincter, the middle third consisted of two circular layers of smooth and striated muscle fibers and the distal third consisted of a circular layer of smooth muscle fibers surrounded by an omega-shaped layer of striated muscle fibers. In the proximal third of the urethral sphincter, myelinated fibers were identified running with unmyelinated fibers from the pelvic plexus. These fibers were closely related to the lateral and anterior aspects of the vagina. Unmyelinated fibers entered the smooth muscle part of the sphincter at 4 o'clock and at 8 o'clock. Most myelinated fibers entered the sphincter at 3 o'clock and at 9 o'clock.

CONCLUSION

Histological and immunohistochemical three-dimensional reconstruction of the anatomical structures of the urethral sphincter provides a better understanding of the origin and nature of the Innervation participating in urinary continence. It provides a very informative view of the three-dimensional arrangement of sphincter muscle layers.

Botulinum toxin for the treatment of lower urinary tract symptoms: A review

AIMS

To review the available literature on the application of botulinum toxin in the urinary tract, with particular reference to its use in treating detrusor overactivity (DO).

METHODS

Botulinum toxin, overactive bladder (OAB), detrusor instability, DO, detrusor sphincter dyssynergia (DSD), and lower urinary tract dysfunction were used on Medline Services as a source of articles for the review process.

RESULTS

DO poses a significant burden on patients and their quality of life. Traditionally patients have been treated with anti-cholinergic drugs if symptomatic, however, a significant number find this treatment either ineffective or intolerable due to side effects. Recent developments in this field have instigated new treatment options, including botulinum toxin, for patients' refractory to first line medication. Botulinum toxin, one of the most poisonous substances known to man, is a neurotoxin produced by the bacterium Clostridium botulinum. Botulinum toxin injections into the external urethral sphincter to treat detrusor sphincter dyssynergia has been successfully used for some years but recently its use has expanded to include voiding dysfunction. Intradetrusal injections of botulinum toxin into patients with detrusor overactivity and symptoms of the overactive bladder have resulted in significant increases in mean maximum cystometric capacity and detrusor compliance with a reduction in mean maximum detrusor pressures. Subjective and objective assessments in these patients has shown significant improvements that last for 9-12 months. Repeated injections have had the same sustained benefits.

CONCLUSIONS

Application of botulinum toxin in the lower urinary tract has produced promising results in treating lower urinary tract dysfunction, which needs further evaluation with randomised, placebo-controlled trials.

Pelvic floor morbidity up to one year after difficult instrumental delivery and cesarean section in the second stage of labor: a cohort study

OBJECTIVE

This study was undertaken to assess symptoms of pelvic floor morbidity at 6 weeks and at 1 year after difficult instrumental vaginal delivery or cesarean section during the second stage of labor.

STUDY DESIGN

Prospective cohort study of 393 women with term, singleton, cephalic pregnancies who required operative delivery in surgery at full dilatation between February 1999 and February 2000. Postal questionnaires were used for follow-up at 6 weeks and at 1 year.

RESULTS

Instrumental delivery was associated with a greater risk of urinary incontinence at 6 weeks and at 1-year postdelivery, adjusted odds ratio [OR] 7.8 (95% CI, 2.6-23.6) and OR 3.1 (95% CI, 1.3-7.6), respectively. Although instrumental delivery was associated with an increased risk of moderate-to-severe dyspareunia at 6 weeks, adjusted OR 3.35 (95% CI, 1.36-8.25), this difference was not significant at 1 year. Cesarean section after attempted instrumental delivery was associated with an increased risk of moderate-to-severe pain during intercourse at 1 year compared with immediate cesarean section, (18% vs 9%) P=.01.

CONCLUSION

Although cesarean section at full dilatation does not completely protect women from pelvic floor morbidity, those that followed instrumental delivery had a significantly greater prevalence of urinary symptoms and dyspareunia. Urinary symptoms persist up to 1 year after delivery.

Membrane properties of single muscle cells of the rhabdosphincter of the male urethra

BACKGROUND

The electrophysiological properties of myoblast cultures established from the human and porcine rhabdosphincter (RS) and porcine lower limb muscle (LLSKM) were studied to elucidate their potential for tissue engineering applications in the lower urinary tract.

METHODS

Muscle biopsies were collected from the prostatic part of the RS, the RS of male pigs, and the porcine LLSKM. Ion channels were studied by means of the patch-clamp technique.

RESULTS

Only one subtype each of voltage gated Na+ and Ca2+ channels was observed in porcine RS and LLSKM. Two types of voltage gated Ca2+ channels were identified in human RS cells. The porcine RS and LLSKM myoblasts displayed similar fusion competence.

CONCLUSIONS

Porcine RS and LLSKM myoblasts and human RS and human skeletal muscle cells show a high degree of similarity. Injection of autologous skeletal muscle myoboblasts in the lower urinary tract might, therefore, represent a promising approach to treat stress incontinence after radical prostatectomy.

Treatment of stress urinary incontinence: recent developments in the role of urethral injection

Stress urinary incontinence is prevalent in adult women and has a considerable impact on quality of life. However, it often remains undiagnosed and therefore untreated. Non-invasive treatment is likely to be offered in mild cases and may entail physiotherapy, minimally invasive devices or pharmacotherapy. Surgical intervention is widely considered as the only effective option for more severe cases. These strategies are not suitable for all patients, and urethral injection represents an alternative, minimally invasive procedure. The choice of the bulking agent is the key to the success of this treatment: the most extensively studied are silicone, polytetrafluoroethylene and bovine collagen. However, doubts regarding the safety and efficacy of these materials has led to the development of carbon-coated zirconium beads, calcium hydroxylapatite and dextranomer/hyaluronic acid (Dx/HA) copolymer. Of these, the most clinical experience has been gained with Dx/HA copolymer. Until 2 years ago, urethral injection could only be administered endoscopically. The recent development of devices for 'blind' injection has increased the speed and convenience of urethral injection, removing the need for surgical facilities. Although few data are yet available, it is conceivable that urethral injection administered 'blind' may in future be considered as an option for all patients failing non-invasive treatment.