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

Long-term effects of vaginal surgery and endogenous ovarian hormones on the vagina and bladder

Background

Surgery is a common treatment for pelvic organ prolapse (POP); however, risk of recurrence and reoperation is high, resulting in a negative impact on quality of life and sexual function.

Aim

To examine the long-term effects of POP surgery and endogenous circulating ovarian hormones on the vagina and bladder.

Methods

Our animal model simulated surgical injury of the vagina and bladder during POP surgery. Female Rowett nude rats were divided into 4 groups: intact control (IC), vaginal surgery only (V), ovariectomy only (O), and ovariectomy + vaginal surgery (OV). Rats were euthanized 10 weeks postsurgery. Proximal vagina and bladder dome/trigone underwent (1) organ bath myography to assess smooth muscle contractility; (2) real-time quantitative polymerase chain reaction to quantify mRNA expression of elastin, collagen I and III, and PGP9.5 (protein gene product 9.5); (3) enzyme-linked immunosorbent assay for protein quantification of elastin and collagen I and III; and (4) hematoxylin-eosin/immunohistochemistry staining.

Outcomes

The primary outcome was tissue contractility as measured by organ bath myography. Secondary outcomes included gene and protein expression of collagen I and III and elastin.

Results

O and OV showed reduced vaginal wall contractility vs IC and V (P < .002). Bladder dome and trigone displayed different contractile patterns, with significant differences between O and OV (P < .05), suggesting a negative effect from surgery rather than ovariectomy. OV demonstrated consistent reductions in contractility and elastin/collagen protein expression for the vagina and bladder vs IC. V had similar contractility and increased collagen I expression vs IC, suggesting a protective effect of ovarian hormones. Vaginal epithelium thinning was confirmed in the ovariectomized groups (P = .001), although there was no statistical significance in muscularis thinning with surgery or ovariectomy. O, V, and OV showed significant downregulation of PGP9.5 mRNA expression vs IC.

Clinical Translation

These data allow researchers to gain insights into the long-term effects of surgery and deprivation of ovarian hormones. Future studies can use this animal model to investigate other mechanisms that may affect long-term tissue changes due to surgical intervention.

Strengths and Limitations

Major strengths are long-term data on the effects of POP surgery and development of an animal model for future studies. However, the animal model limits our ability to extrapolate to humans, where tissue healing is modulated by many factors.

Conclusion

Our animal model provides evidence that ovarian hormone deprivation and POP surgery result in negative long-term effects on tissue function and extracellular matrix.

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

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

Decreased urothelial expression of caveolin 1 and 2 in aging rats showing detrusor overactivity: Potential association with aging bladder

PURPOSE

The purpose of this study was to investigate the effect of aging on bladder function and caveolin protein expression in rat urothelium.

MATERIALS AND METHODS

Female Sprague-Dawley rats were divided into the following two groups: young age control group (12 weeks) and old-aged group of rats (80 weeks). Urodynamic measurements were taken to compare the contraction interval and the contraction pressure between the two groups. The expression and cellular localization of caveolin 1 and 2 in the urothelium of the rat urinary bladder were determined by Western blot and immunofluorescence microscopy.

RESULTS

In cystometrograms, the contraction interval (min) was significantly shorter in the old-aged group (3.7±0.5 min) than in the young age control group (6.2±0.8 min). Also, the average contraction pressure (mmHg) was lower in the old-aged group (8.4±0.6 mmHg) than in the young age control group (13.2±1.3 mmHg). Caveolin 1 and 2 were expressed in the subepithelial area in the urothelium. The protein expression of both caveolin 1 and 2 was significantly lower in the old-aged group than in the young age control group.

CONCLUSIONS

Aging caused a significant change in the expression of caveolin 1 and 2 in the urothelium of the rat urinary bladder. These findings suggest that these molecules might have specific roles in the functional change of the urinary bladder that occurs in association with aging.

Estrogens influence differentially on the pelvic floor muscles activation at somatovisceral reflexes involved in micturition of rabbits

OBJECTIVE

To determine the estrogen-dependency of the bladder and urethral function and the coordinated activation of pelvic floor muscles (PFM) during micturition.

METHODS

We allocated age-matched female rabbits to control, 1-month ovariectomized (OVX), and OVX plus 2-week estradiol benzoate (EB) groups to record cystometry, urethral pressure, and electromyograms of bulbospongiosus (Bsm), and pubococcygeus muscles (Pcm) simultaneously. We also measured serum estradiol levels and myofiber cross-sectional area. We assessed urodynamic and urethral variables, categorized the Bsm-Pcm activation patterns at storage and voiding phases, and obtained the power spectrum density of muscle activation around the voiding phase. We investigated the influence of ovarian hormones, in general, and the contribution of estrogen, particularly on the functions of the bladder, urethra, and PFM. Statistical significance was set at P < 0.05.

RESULTS

Ovarian hormones influence the bladder, urethral, and PFM functions. The urodynamics analyses indicated estrogens contribute to voiding duration and, to a lesser extent, to the time between bladder contractions. Urethral pressure at closure (maximal pressure-to-maximal urethral pressure ratio) improved partially (8%, P < 0.05) in the OVX plus 2-week estradiol benzoate compared with OVX, but urethral resistance increased (∼1.9-fold, P < 0.05) compared with control rabbits. Our findings support that Pcm activity at voiding is estrogen-sensitive, albeit EB administration reduced it at storage resume, which relates to high urethral resistance.

CONCLUSIONS

Ovariectomy impairs bladder and urethral pressures and Bsm and Pcm activation at micturition in anesthetized rabbits. Estrogen administration partially reverts some of these effects and influences Pcm activation.

Low-Intensity Extracorporeal Shock Wave Therapy Promotes Bladder Regeneration and Improves Overactive Bladder Induced by Ovarian Hormone Deficiency from Rat Animal Model to Human Clinical Trial

Postmenopausal women with ovary hormone deficiency (OHD) are subject to overactive bladder (OAB) symptoms. The present study attempted to elucidate whether low-intensity extracorporeal shock wave therapy (LiESWT) alters bladder angiogenesis, decreases inflammatory response, and ameliorates bladder hyperactivity to influence bladder function in OHD-induced OAB in human clinical trial and rat model. The ovariectomized (OVX) for 12 months Sprague–Dawley rat model mimicking the physiological condition of menopause was utilized to induce OAB and assess the potential therapeutic mechanism of LiESWT (0.12 mJ/mm², 300 pulses, and 3 pulses/second). The randomized, single-blinded clinical trial was enrolled 58 participants to investigate the therapeutic efficacy of LiESWT (0.25 mJ/mm², 3000 pulses, 3 pulses/second) on postmenopausal women with OAB. The results revealed that 8 weeks’ LiESWT inhibited interstitial fibrosis, promoted cell proliferation, enhanced angiogenesis protein expression, and elevated the protein phosphorylation of ErK1/2, P38, and Akt, leading to decreased urinary frequency, nocturia, urgency, urgency incontinence, and post-voided residual urine volume, but increased voided urine volume and the maximal flow rate of postmenopausal participants. In conclusion, LiESWT attenuated inflammatory responses, increased angiogenesis, and promoted proliferation and differentiation, thereby improved OAB symptoms, thereafter promoting social activity and the quality of life of postmenopausal participants.

Nongenomic modulation of the large conductance voltage- and Ca2+-activated K+ channels by estrogen: A novel regulatory mechanism in human detrusor smooth muscle

Estrogens have an important role in regulating detrusor smooth muscle (DSM) function. However, the underlying molecular and cellular mechanisms by which estrogens control human DSM excitability and contractility are not well known. Here, we used human DSM specimens from open bladder surgeries on 27 patients to elucidate the mechanism by which 17β-estradiol regulates large conductance voltage- and Ca²⁺-activated K⁺ (BK) channels, the most prominent K⁺ channels in human DSM We employed single BK channel recordings on inside-out excised membrane patches, perforated whole-cell patch-clamp on freshly isolated DSM cells, and isometric tension recordings on DSM-isolated strips to investigate the mechanism by which 17β-estradiol activates BK channels. 17β-Estradiol (100 nmol/L) rapidly increased depolarization-induced whole-cell K⁺ currents in DSM cells. The 17β-estradiol stimulatory effects on whole-cell BK currents were completely abolished by the selective BK channel inhibitor paxilline (1 μmol/L), clearly indicating that 17β-estradiol specifically activates BK channels. 17β-Estradiol also increased the frequency of ryanodine receptor-mediated transient BK currents. Single BK channel recordings showed that 17β-estradiol (100 nmol/L) significantly increased the BK channel open probability of inside-out excised membrane patches, revealing that 17β-estradiol activates BK channels directly. 17β-Estradiol reduced spontaneous phasic contractions of human DSM-isolated strips in a concentration-dependent manner (100 nmol/L-1 μmol/L), and this effect was blocked by paxilline (1 μmol/L). 17β-Estradiol (100 nmol/L) also reduced nerve-evoked contractions of human DSM-isolated strips. Collectively, our results reveal that 17β-estradiol plays a critical role in regulating human DSM function through a direct nongenomic activation of BK channels.

Altered expression of caveolin 2 and 3 in smooth muscle of rat urinary bladder by 17β-estradiol

Background

The purpose of this study was to investigate the effect of estrogen alteration on the expression of caveolin 2 and 3 in rat smooth muscle of urinary bladder.

Methods

Female Sprague–Dawley rats were divided into three groups: control, bilateral ovariectomy (Ovx), and bilateral ovariectomy followed by subcutaneous injections of 17β-estradiol (Ovx?+?Est). After 4 weeks, urodynamic measurements were taken to ascertain the contraction interval and contraction pressure. The expression and cellular localization of caveolin 2 and 3 were determined by Western blot and immunohistochemistry in rat urinary bladder smooth muscle.

Results

In cystometrograms, the contraction interval (min) was significantly lower in the Ovx group (3.1?±?1.5) than in the control group (5.6?±?1.2), but was increased after estrogen treatment (9.3?±?1.0). Conversely, the average contraction pressure (mmHg) was higher in the Ovx group (26.2?±?2.3) than in the control group (21.9?±?3.1), and was decreased after estrogen treatment (23.8?±?3.5). Caveolin 2 and 3 expression was localized in the cell membrane of the smooth muscle. The protein expression of both caveolin 2 and 3 was significantly lower after ovariectomy and was restored to the control levels after 17β-estradiol treatment.

Conclusions

Hormonal alteration causes a significant change in the expression of caveolin 2 and 3 in smooth muscle of rat urinary bladder. These findings suggest that these molecules might have functional roles in the detrusor overactivity that occurs in association with hormonal alteration.

Protective effects of estrogen on ischemia/reperfusion-induced bladder dysfunction in female rabbits

OBJECTIVE

The present study investigated the effects of ovarian hormone depletion and estrogen administration on ischemia/reperfusion (I/R)-induced bladder damage in female rabbits.

METHODS

Female New Zealand white rabbits were divided into five groups. A sham surgical procedure was performed on rabbits in group 1. In group 2, both vesical arteries were clamped for 2 hours and then released (I/R surgical procedure). In group 3, 17β-estradiol (100 μg/kg/d) was injected intramuscularly before I/R surgical procedure. In group 4, ovariectomies were performed before I/R surgical procedure. Group 5 had ovariectomy, recovered for 2 weeks, and then received 17β-estradiol for 2 weeks. I/R surgical procedure was performed thereafter. Rabbits were killed 7 days after I/R surgical procedure. Masson's trichrome stain was used, and immunohistochemical experiments were performed to evaluate interstitial fibrosis and intramural nerve changes. Western immunoblots were examined to determine the expressions of markers for inflammation, fibrosis, and oxidative stress.

RESULTS

I/R surgical procedure decreased bladder contractile responses by 30% to 50%. Ovarian hormone depletion further reduced bladder contractile function by 45% to 55% compared with the I/R group members that retained their ovaries. Moreover, I/R surgical procedure significantly decreased intramural neurofilament staining by two thirds compared with the control group. Estrogen replacement after ovariectomy significantly increased the density of nerve terminals. In addition, the expression of transforming growth factor-β and fibronectin increased twofold and fivefold after I/R, respectively. Ovarian hormone depletion further increased the expression of these inflammatory and fibrosis markers. Ovariectomy significantly exacerbated oxidative damage, whereas estrogen replacement diminished oxidative stress to a level approaching that of the control group.

CONCLUSIONS

I/R surgical procedure increases oxidative damage, enhances interstitial fibrosis, and results in bladder denervation. Ovarian hormone deficiency exacerbates this I/R-induced bladder damage, whereas estrogen therapy after ovariectomy attenuates this injury. These results reveal estrogen's protective effects on bladders subjected to I/R injury and the potential benefits of estrogen therapy on I/R-induced bladder damage.

[Role of estrogens in lower urinary tract physiology and physiopathology]

GOAL

The aim was to review the literature on estrogens and lower urinary tract.

MATERIAL

A review of literature through the PubMed library until December 31, 2012 was carried out using the following keywords: lower urinary tract, bladder, urethra, nervous central system, innervation, female, women, estrogen, estradiol, urogenital atrophy, urinary incontinence, overactive bladder, urinary tract infection.

RESULTS

On the bladder, estrogens are involved in the trophicity, vascularisation, alpha-adrenergic, cholinergic and muscarinic receptor density, detrusor contractility and inflammation. On the urethra, they impact vascularisation, contractility, urethral pulse and tone, anatomical and functional length. On the neurological control, they act on capsaicin-sensitive afferent fibres, neurological regeneration, nerve growth factor expression and viscerovisceral sensitisation.

CONCLUSION

Estrogens play a major role on the lower urinary tract physiology and physiopathology both on the urethra and the bladder.

Effect of estrogen on molecular and functional characteristics of the rodent vaginal muscularis

INTRODUCTION

Vaginal atrophy is a consequence of menopause; however, little is known concerning the effect of a decrease in systemic estrogen on vaginal smooth muscle structure and function. As the incidence of pelvic floor disorders increases with age, it is important to determine if estrogen regulates the molecular composition and contractility of the vaginal muscularis.

AIM

The goal of this study was to determine the effect of estrogen on molecular and functional characteristics of the vaginal muscularis utilizing a rodent model of surgical menopause.

METHODS

Three- to 4-month old Sprague-Dawley rats underwent sham laparotomy (Sham, N = 18) or ovariectomy (Ovx, N = 39). Two weeks following surgery, animals received a subcutaneous osmotic pump containing vehicle (Sham, Ovx) or 17β-estradiol (Ovx). Animals were euthanized 1 week later, and the proximal vagina was collected for analysis of contractile protein expression and in vitro studies of contractility. Measurements were analyzed using a one-way analysis of variance followed by Tukey's post hoc analysis (α = 0.05).

MAIN OUTCOME MEASURES

Protein and mRNA transcript expression levels of contractile proteins, in vitro measurements of vaginal contractility.

RESULTS

Ovariectomy decreased the expression of carboxyl-terminal myosin heavy chain isoform (SM1) and h-caldesmon and reduced the amplitude of contraction of the vaginal muscularis in response to KCl. Estradiol replacement reversed these changes. No differences were detected in the % vaginal muscularis, mRNA transcript expression of amino-terminal MHC isoforms, l-caldesmon expression, and maximal velocity of shortening.

CONCLUSION

Systemic estrogen replacement restores functional and molecular characteristics of the vaginal muscularis of ovariectomized rats. Our results indicate that menopause is associated with changes in the vaginal muscularis, which may contribute to the increased incidence of pelvic floor disorders with age.

Green tea catechins decrease oxidative stress in surgical menopause-induced overactive bladder in a rat model

What's known on the subject? and What does the study add? Ovary hormone deficiency and the age-related changes in post-menopausal women are subjected to a number of urological dysfunctions, including overactive bladder syndrome. Green tea is a popular healthy drink worldwide and its extract catechin has strong anti-inflammatory and antioxidant properties. EGCG, the major type of catechin, is an antioxidant polyphenol flavonoid isolated from green tea. EGCG supplement could prevent ovariectomy-induced bladder dysfunction in a dose-related manner through its anti-oxidant, anti-fibrosis and anti-apoptosis effects.

OBJECTIVE

To evaluate whether green tea extract, epigallocatechin gallate (EGCG), could prevent ovariectomy-induced overactive bladder (OAB) and to investigate its antioxidant, anti-apoptotic and anti-fibrosis effects.

MATERIALS AND METHODS

In all, 48 female Sprague-Dawley rats were divided into four groups. After bilateral ovariectomy, the first group served as the ovariectomy control, the second group received EGCG 1 µM/kg daily i.p. injection after ovariectomy surgery, and the third group received EGCG 10 µM/kg daily i.p. injection. The fourth group was taken as the sham without ovariectomy surgery. The rats were killed after 6 months after ovariectomy surgery. Cystometrograms were performed for the measure of bladder overactivity. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling (TUNEL) assay was used to evaluate apoptotic cells. Western immunoblots were performed to determine the expressions of inflammatory markers, apoptosis-associated proteins and oxidative stress markers.

RESULTS

Long-term ovariectomy significantly increased non-voiding contractions and decreased bladder compliance. Treatment with EGCG significantly increased bladder compliance and diminished non-voiding contractions. Ovariectomy significantly increased apoptotic cells and enhanced interstitial fibrosis in bladders. The expression of caspase-3 significantly increased, while that of Bcl-2 notably decreased after ovariectomy. Inflammatory and fibrosis markers, TGF-β, fibronectin and type I collagen expressions were significantly increased after 6 months of ovariectomy surgery. Treatment with EGCG significantly decreased TGF-β and type I collagen expressions. Oxidative stress markers, nitrotyrosine and protein carbonylation levels were significantly increased in the ovariectomy group. EGCG could attenuate this oxidative damage in dose-dependent fashion.

CONCLUSIONS

Ovariectomy increased oxidative damage, enhanced voiding frequency and decreased bladder compliance. EGCG could restore ovariectomy-induced bladder dysfunction in a dose-dependent fashion through antioxidant, anti-fibrosis and anti-apoptosis effects.

Effects of endogenous ovarian estrogen versus exogenous estrogen replacement on blood flow and ERβα and ERβ levels in the bladder

OBJECTIVE

Determine the effect of endogenous estrogen versus estrogen replacement therapy (ERT) on bladder blood flow (BBF) and estrogen receptors (ERs).

METHODS

BBF was determined with radiolabeled microspheres in luteal, follicular, pregnant, oophorectomized (Ovx) sheep, and Ovx sheep with ERT. Estrogen receptors (ERalpha, ERbeta) were quantified using Western blot analysis.

RESULTS

Compared to luteal and follicular ewes, BBF was reduced in pregnancy and following oophorectomy. Estrogen replacement therapy in Ovx sheep restored BBF to luteal levels. Estrogen receptor alpha predominated, whereas ERbeta was not detectable. Estrogen receptor-alpha levels were unaffected by the ovarian cycle and increased in pregnancy, as well as in Ovx sheep with and without chronic ERT.

CONCLUSION

The combination of diminished BBF and elevated ERalpha levels in both pregnant and Ovx sheep suggests an inverse relationship between BBF and ERalpha in the bladder. Although chronic ERT in Ovx sheep restored BBF, it did not restore ERalpha back to luteal levels.

Effects of estrogens on the expression of caveolin-1 in the urinary bladders of female rats

PURPOSE

The purposes of this study were to investigate the effect of hormonal alterations on the expression of caveolin-1 in the urinary bladders of ovariectomized rats and to determine the role of caveolin-1 in the overactivity of the detrusor muscle that occurs with hormonal alterations in rats.

METHODS

Female Sprague-Dawley rats were divided into three groups: a control group, a group that underwent bilateral ovariectomy (Ovx), and a group that underwent bilateral ovariectomy followed by subcutaneous injections of 17β-estradiol (Ovx+Est). After 4 weeks, urodynamic studies were done to measure the contraction interval and contraction pressure. The expression and cellular localization of caveolin-1 were determined by Western blot and immunofluorescence in the urinary bladders of rats.

RESULTS

On cystometrograms, the contraction interval was significantly shorter in the Ovx group (3.0±0.3 minute) than in the control group (5.6±0.5 minute) but was longer in the Ovx+Est group (9.2±0.4 minute) (P<0.05). Conversely, the average contraction pressure was higher in the Ovx group (26.4±0.48 mmHg) than in the control group (21.8±0.37 mmHg) but was lower in the Ovx+Est group (23.9±0.76 mmHg) (P<0.05). Caveolin-1 was expressed in the capillaries, arterioles, and venules. Expression of the protein caveolin-1 was significantly lower after ovariectomy and was restored to control levels after treatment with 17β-estradiol (P<0.05).

CONCLUSIONS

Hormonal alterations cause a significant change in the expression of caveolin-1, which suggests that caveolin-1 might have a functional role in the overactivity of the detrusor muscle related to hormonal alterations in the urinary bladders of rats.

The Expression of AQP1 and eNOS in Menopausal Rat Urinary Bladder

PURPOSE

Aquaporins (AQPs) have been reported to be expressed in rat and human urothelium. Nitric oxide (NO) is thought to play an important role in the bladder overactivity related to menopause. The purpose of this study was to investigate the effect of hormonal alteration on the expression of AQP1 and eNOS in menopausal rat urinary bladder.

MATERIALS AND METHODS

Female Sprague-Dawley rats (230-240 g, N=30) were divided into three groups: control (N=10), bilateral ovariectomy (Ovx, N=10), and bilateral ovariectomy followed by subcutaneous injections of 17β-estradiol (50 mg/kg/day, Ovx+Est, N=10). After 4 weeks, urodynamic studies measuring the contraction interval and contraction pressure were done. The expression and cellular localization of AQP1 and eNOS were determined by performing Western blotting and immunohistochemistry on the rat urinary bladder.

RESULTS

The approximate contraction interval (min) was significantly decreased in the Ovx group (3.9±0.25) compared to the control group (6.7±0.15), and was increased after estrogen treatment (9.7±0.22) (p<0.05). The AQP1 and eNOS immunoreactivities were localized in the same areas: capillaries, arterioles, and venules of the lamina propria. The protein expression of AQP1 was not changed significantly, whereas eNOS expression was significantly decreased in the Ovx group and restored to the control value in the Ovx+Est group.

CONCLUSIONS

This study showed that ovariectomy causes a significant change in e-NOS expression without a change in AQP1 in menopausal rat urinary bladder. This may imply that e-NOS has a functional role in the bladder overactivity that occurs in association with menopause.

Differential expression of vascular endothelial growth factor, and angiopoietin 1 and 2 in functionally divergent experimental rabbit models of bladder hypertrophy

PURPOSE

Partial bladder outlet obstruction or ovariectomy with subsequent estrogen replenishment induces bladder hypertrophy in rabbits and yet the functional outcomes of these procedures differ. We investigated whether these models might be distinguished by differential expression of the genes controlling angiogenesis.

MATERIALS AND METHODS

Groups of male rabbits underwent sham surgery or partial bladder outlet obstruction for 1 or 2 weeks. Groups of females underwent sham surgery, ovariectomy or ovariectomy plus estrogen for 1 or 2 weeks. Bladders from each group were weighed and assayed for the contractile response, smooth muscle content and vascular density. Mucosa and muscle layers were separated and RNA from the fractions was assayed by quantitative real-time polymerase chain reaction to measure the relative expression of vascular endothelial growth factor, and angiopoietin 1 and 2 mRNA.

RESULTS

Male bladders with partial outlet obstruction had attributes that typified hypertrophy with a loss of contractile function. Vascular endothelial growth factor expression was up-regulated in the mucosa and muscle layers but the effect was most pronounced in mucosa. Angiopoietin 1 expression was significantly up-regulated in muscle. Female bladders with ovariectomy plus estrogen had attributes that typified bladder hypertrophy with increased contractile function. Vascular endothelial growth factor expression was up-regulated early in mucosa but more highly and consistently increased in muscle. Angiopoietin 1 and 2 expression was not significantly affected.

CONCLUSIONS

Although these models have similar outcomes with regard to bladder hypertrophy, they have opposite functional outcomes that coincide with compartmental differences in the expression of genes involved in the regulation of angiogenesis. The disparity in gene expression might explain the difference in the functional outcomes.

Postmenopausal hormone therapy and incident urinary incontinence in middle-aged women

OBJECTIVE

The objective of the study was to examine the association of hormone therapy with incident urinary incontinence (UI) in postmenopausal women aged 37-54 years in the Nurses' Health Study II.

STUDY DESIGN

Participants reported use of hormone therapy, including hormone type, on biennial questionnaires from 1989 to 2001. Among 7341 postmenopausal women reporting no UI in 2001, we identified 1026 women who developed UI at least monthly between 2001 and 2003. Multivariable logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Women currently using hormone therapy had 1.39-fold (95% CI, 1.16-1.67) increased odds of incident UI, compared with women who never used hormone therapy. ORs were similar in current users of oral estrogen alone (OR, 1.35, 95% CI, 1.03-1.78) and oral estrogen with progestin (OR, 1.37, 95% CI, 1.13-1.67).

CONCLUSION

These findings suggest an increased risk of UI associated with use of postmenopausal hormone therapy in younger postmenopausal women.

Estradiol increases urethral tone through the local inhibition of neuronal nitric oxide synthase expression

Estrogens are known to modulate lower urinary tract (LUT) trophicity and neuronal nitric oxide synthase (nNOS) expression in several organs. The aim of this study was to explore the effects of endogenous and supraestrus levels of 17β-estradiol (E2) on LUT and urethral nNOS expression and function. LUT function and histology and urethral nNOS expression were studied in adult female mice subjected either to sham surgery, surgical castration, or castration plus chronic E2 supplementation (80 μg·kg−1·day−1, i.e., pregnancy level). The micturition pattern was profoundly altered by long-term supraestrus levels of E2 with decreased frequency paralleled by increased residual volumes higher than those of ovariectomized mice. Urethral resistance was increased twofold in E2-treated mice, with no structural changes in urethra, supporting a pure tonic mechanism. Acute nNOS inhibition by 7-nitroindazole decreased frequency and increased residual volumes in ovariectomized mice but had no additive effect on the micturition pattern of long-term supraestrus mice, showing that long-term supraestrus E2 levels and acute inhibition of nNOS activity had similar functional effects. Finally, E2 decreased urethral nNOS expression in ovariectomized mice. Long-term supraestrus levels of E2 increased urethral tone through inhibition of nNOS expression, whereas physiological levels of E2 had no effect.

Effect of letrozole on urinary bladder function in the female rabbit

OBJECTIVE

To investigate the effect of letrozole (a potent aromatase inhibitor that effectively inhibit the synthesis of oestrogen) on bladder contraction with changes in morphology and biochemistry.

MATERIALS AND METHODS

Sixteen female New Zealand white rabbits were separated into four equal groups; groups 1-3 were given oral letrozole for 1, 2 and 3 weeks, and group 4 was given saline and served as the control group. At the end of the medication period each rabbit was anaesthetized and the bladder muscle strips were used for contractile, histological and biochemical studies.

RESULTS

The concentration of serum oestrogen was significantly lower and testosterone was significantly higher in letrozole-treated rabbits than in the control group. The rabbits treated for 1 week with letrozole showed significant decreases in the contractile responses to electrical field stimulation, ATP and carbachol, but not to KCl. Contractility returned to normal in the rabbits treated for 2 and 3 weeks. Letrozole resulted in an increased volume percentage of collagens and decreased bladder compliance. The volume percentage of the smooth muscle component also changed, with a significant decrease at 1 week and then a gradual increase at 2 and 3 weeks. Contractile dysfunction was absent at 2 and 3 weeks, which was consistent with no change in sarcoplasmic reticulum Ca(2+)-ATPase content or mitochondrial function.

CONCLUSIONS

The bladder contractility decline in the first week and was restored at 2 and 3 weeks. The present study unexpectedly showed the possibility that testosterone might be as important as oestrogen in the contractile function of the female bladder.

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.

Alteration of contractile and regulatory proteins in estrogen-induced hypertrophy of female rabbit bladder

OBJECTIVES

Estrogen is essential to mediate physiologic functions in female bladders. Deficiency of estrogen has been speculated to be an etiologic factor for bladder dysfunction in postmenopausal women. Our previous studies have demonstrated that estrogen supplementation in female rabbits induces a "functional hypertrophy" of the urinary bladder smooth muscle. The present study investigated the alterations in the contractile and regulatory proteins in this model.

METHODS

Twenty New Zealand white female rabbits were separated into five groups of 4 rabbits each. Group 1 served as the control, groups 2 to 6 underwent ovariectomy (Ovx), and group 2 served as the Ovx without estradiol treatment group. Two weeks after Ovx, groups 3 to 5 were given 17-beta estradiol (1 mg/kg/day) by subcutaneous implant for 1, 3, and 7 days, respectively. The expression of the contractile and regulatory proteins, such as myosin light chain kinase, rho-kinase, and caldesmon, was analyzed by Western blotting.

RESULTS

The expression of myosin light chain kinase was enhanced by estradiol supplementation. The expression of rho-kinase-alpha was increased significantly (20-fold) after Ovx, which was downregulated after estrogen supplementation. No significant change was seen in rho-kinase-beta after Ovx or estradiol supplementation. The expression of caldesmon isoforms was enhanced by 1-day estradiol supplementation but decreased to lower levels than those of the control group by 3 and 7 days of estrogen treatment.

CONCLUSIONS

The results of the present study have provided more understanding about the role of the contractile and regulatory proteins in detrusor muscle, in both dysfunctional atrophy induced by Ovx and functional hypertrophy induced by estrogen supplementation.