CYSTOMETRIC EVALUATION OF BLADDER FUNCTION IN NON-ANESTHETIZED MICE WITH AND WITHOUT BLADDER OUTLET OBSTRUCTION

Can Urinary Bladder Innervation Be Restored After Outlet Obstruction and Denervation?

Transurethral resection of the prostate, or other methods to decrease outlet resistance usually leads to relief of symptoms in patients with bladder outlet obstruction (BOO). If symptoms of underactivity persist after normalization of outflow conditions, treatment options are limited. In this review, we hypothesize, based on results from basic research, what might become treatment options for such patients in the future. The primary local treatment will still aim at reducing outlet obstruction. We speculate that local secondary treatment in the future might include transplantation of stem cells or mature bladder ganglion cells into the bladder wall. There has been some success in transplanting ganglion cells into the rat bladder. The ganglion cells will sprout into the surrounding tissue but functional connections between the axons of the transplanted neurons, and the detrusor smooth muscle have so far not been demonstrated. Neurotrophins or neurotrimin might be injected into the bladder wall to increase the sprouting of existing or transplanted neurons. Stem cell transplantation has been performed and improves detrusor function, but it has so far, been difficult to demonstrate transplanted stem cells. BOO, persisting detrusor underactivity, and decreased nerve density are often combined with inflammatory activity of the lower urinary tract. NLR family pyrin domain containing 3 (NLRP3) and its messenger RNA (mRNA) as well as cyclooxygenase-2 (Cox-2) mRNA are increased in obstructed bladders. Systemic treatment with the NLRP3 inhibitor glyburide normalized nerve density in rat bladder, and, to some extent, bladder function. It is unclear whether Cox-2 is involved in the decreased nerve density following obstruction, but Cox-2 mRNA increases 5-fold in obstructed bladder. Future therapy against bladder underactivity remaining following relief of obstruction includes either systemic treatment, perhaps by anti-inflammatory drugs, or local treatment by injection of stem cells, mature ganglion cells, and/or neurotrophins or neurotrimin into the bladder wall.

Assessing Neurogenic Lower Urinary Tract Dysfunction after Spinal Cord Injury: Animal Models in Preclinical Neuro-Urology Research

Neurogenic bladder dysfunction is a condition that affects both bladder storage and voiding function and remains one of the leading causes of morbidity after spinal cord injury (SCI). The vast majority of individuals with severe SCI develop neurogenic lower urinary tract dysfunction (NLUTD), with symptoms ranging from neurogenic detrusor overactivity, detrusor sphincter dyssynergia, or sphincter underactivity depending on the location and extent of the spinal lesion. Animal models are critical to our fundamental understanding of lower urinary tract function and its dysfunction after SCI, in addition to providing a platform for the assessment of potential therapies. Given the need to develop and evaluate novel assessment tools, as well as therapeutic approaches in animal models of SCI prior to human translation, urodynamics assessment techniques have been implemented to measure NLUTD function in a variety of animals, including rats, mice, cats, dogs and pigs. In this narrative review, we summarize the literature on the use of animal models for cystometry testing in the assessment of SCI-related NLUTD. We also discuss the advantages and disadvantages of various animal models, and opportunities for future research.

Molecular Characterization of Non-Neurogenic and Neurogenic Lower Urinary Tract Dysfunction (LUTD) in SCI-Induced and Partial Bladder Outlet Obstruction Mouse Models

We examined bladder function following spinal cord injury (SCI) by repeated urodynamic investigation (UDI), including external urethral sphincter (EUS) electromyography (EMG) in awake restrained mice and correlated micturition parameters to gene expression and morphological changes in the bladder. A partial bladder outlet obstruction (pBOO) model was used for comparison to elucidate both the common and specific features of obstructive and neurogenic lower urinary tract dysfunction (LUTD). Thirty female C57Bl/6J mice in each group received an implanted bladder catheter with additional electrodes placed next to the EUS in the SCI group. UDI assessments were performed weekly for 7 weeks (pBOO group) or 8 weeks (SCI group), after which bladders were harvested for histological and transcriptome analysis. SCI mice developed detrusor sphincter dyssynergia (DSD) one week after injury with high-pressure oscillations and a significantly increased maximal bladder pressure P_max and were unable to void spontaneously during the whole observation period. They showed an increased bladder-to-bodyweight ratio, bladder fibrosis, and transcriptome changes indicative of extracellular matrix remodeling and alterations of neuronal signaling and muscle contraction. In contrast, pBOO led to a significantly increased P_max after one week, which normalized at later time points. Increased bladder-to-bodyweight ratio and pronounced gene expression changes involving immune and inflammatory pathways were observed 7 weeks after pBOO. Comparative transcriptome analysis of SCI and pBOO bladders revealed the activation of Wnt and TGF-beta signaling in both the neurogenic and obstructive LUTD and highlighted FGF2 as a major upregulated transcription factor during organ remodeling. We conclude that SCI-induced DSD in mice leads to profound changes in neuronal signaling and muscle contractility, leading to bladder fibrosis. In a similar time frame, significant bladder remodeling following pBOO allowed for functional compensation, preserving normal micturition parameters.

Adaptation to partial urethral obstruction in healthy aging LOU rats and the role of nerve growth factor signaling pathway in the bladder

AIM

Aging is associated with poor ability to adapt to stress and abnormal nerve growth factor (NGF) profile. Lower urinary tract symptoms frequently disturb the quality of life of the aging population with no optimal treatment for both genders. The aim of the study was to compare the bladder response to bladder outflow obstruction in young and old LOU rats, a model of healthy aging that does not develop insulin resistance, and its relation to proNGF/NGF imbalance.

METHODS

6- and 36-month-old female LOU rats were subjected to partial bladder urethral obstruction (PUO) for 2 weeks. Morphometric parameters (body and bladder weight) and glycemia were evaluated. Cystometry was carried out to measure functional parameters followed by ex vivo assessment of muscle strip contractile characteristics. Tissue proteins were examined by immunoblotting and morphology was examined by microscopy.

RESULTS

Body weight and glycaemia were not affected by surgery. PUO increases significantly bladder weight with increased thickness and fibrosis of the bladder wall as revealed by histological examination in both age groups. Cystometry showed that old PUO rats had a significant reduction in the intercontraction interval and the bladder capacity, a pattern opposite to young rats with PUO. Contractile properties of bladder strip were not affected by age or PUO. On the molecular level, the old rats had lower abundance of the mature NGF relative to proNGF, with signs of p75^NTR activation suggested by the higher expression of TNF-α and JNK phosphorylation in the bladder tissue.

CONCLUSION

Bladder adaptation to PUO occurs only in young LOU rats to maintain efficient bladder contractility. Old LOU rats display proNGF/NGF imbalance and the associated p75^NTR activation. This can further induce tissue damage and degeneration through activation of JNK pathway and release of TNF-α which in turn interferes with the necessary bladder adaptation.

X-ray videocystometry for high-speed monitoring of urinary tract function in mice

Lower urinary tract dysfunction (LUTd) represents a major health care problem with a high, unmet medical need. Design of additional therapies for LUTd requires precise tools to study bladder storage and voiding (dys)function in animal models. We developed videocystometry in mice, combining intravesical pressure measurements with high-speed fluoroscopy of the urinary tract. Videocystometry substantially outperforms current state-of-the-art methods to monitor the urine storage and voiding process, by enabling quantitative analysis of voiding efficiency, urethral flow, vesicoureteral reflux, and the relation between intravesical pressure and flow, in both anesthetized and awake, nonrestrained mice. Using videocystometry, we identified localized bladder wall micromotions correlated with different states of the filling/voiding cycle, revealed an acute effect of TRPV1 channel activation on voiding efficiency, and pinpointed the effects of urethane anesthesia on urine storage and urethral flow. Videocystometry has broad applications, ranging from the elucidation of molecular mechanisms of bladder control to drug development for LUTd.

Acyloxyacyl hydrolase regulates voiding activity

Corticotropin-releasing factor (CRF) regulates diverse physiological functions, including bladder control. We recently reported that Crf expression is under genetic control of Aoah, the locus encoding acyloxyacyl hydrolase (AOAH), suggesting that AOAH may also modulate voiding. Here, we examined the role of AOAH in bladder function. AOAH-deficient mice exhibited enlarged bladders relative to wild-type mice and had decreased voiding frequency and increased void volumes. AOAH-deficient mice had increased nonvoiding contractions and increased peak voiding pressure in awake cystometry. AOAH-deficient mice also exhibited increased bladder permeability and higher neuronal firing rates of bladder afferents in response to stretch. In wild-type mice, AOAH was expressed in bladder projecting neurons and colocalized in CRF-expressing neurons in Barrington's nucleus, an important brain area for voiding behavior, and Crf was elevated in Barrington's nucleus of AOAH-deficient mice. We had previously identified aryl hydrocarbon receptor (AhR) and peroxisome proliferator-activated receptor-γ as transcriptional regulators of Crf, and conditional knockout of AhR or peroxisome proliferator-activated receptor-γ in Crf-expressing cells restored normal voiding in AOAH-deficient mice. Finally, an AhR antagonist improved voiding in AOAH-deficient mice. Together, these data demonstrate that AOAH regulates bladder function and that the AOAH-Crf axis is a therapeutic target for treating voiding dysfunction.

Micturition video thermography in awake, behaving mice

BACKGROUND

Our understanding of the neural circuits controlling micturition and continence is constrained by a paucity of techniques for measuring voiding in awake, behaving mice.

NEW METHOD

To facilitate progress in this area, we developed a new, non-invasive assay, micturition video thermography (MVT), using a down-facing thermal camera above mice on a filter paper floor.

RESULTS

Most C57B6/J mice void infrequently, with a stereotyped behavioral sequence, and usually in a corner. The timing of each void is indicated by the warm thermal contrast of freshly voided urine. Over the following 10-15 min, urine cools to ∼3 °C below the ambient temperature and spreads radially in the filter paper. By measuring the area of cool contrast comprising this "thermal void spot," we can derive the initially voided volume. Thermal videos also reveal mouse behaviors including a home-corner preference apart from void spots, and a stereotyped, seconds-long pause while voiding.

COMPARISON WITH EXISTING METHODS AND CONCLUSIONS

MVT is a robust, non-invasive method for measuring the timing, volume, and location of voiding. It improves on an existing technique, the void spot assay, by adding timing information, and unlike the cystometrogram preparation, MVT does not require surgical catheterization. Combining MVT with current neuroscience techniques will improve our understanding of the neural circuits that control continence, which is important for addressing the growing number of patients with urinary incontinence as the population ages.

Functional changes in low- and high-threshold afferents in obstruction-induced bladder overactivity

Neural mechanisms of lower urinary tract symptoms in obstruction-induced bladder overactivity remain unclear. We made the first single unit recordings from different types of spinal afferents to determine the effects of bladder outlet obstruction in guinea pigs. A model of gradual bladder outlet obstruction in male guinea pigs was used to produce overactive bladder. Conscious voiding was assessed in metabolic cages, and micturition was recorded in anesthetized guinea pigs in vivo. Single unit extracellular recordings were made ex vivo from spinal afferent nerves in flat sheet preparations of the bladder. Guinea pigs with partially obstructed bladders showed a significant increase in conscious voiding frequency compared with sham-operated guinea pigs. Also, nonvoiding contractions increased significantly in both frequency and amplitude. Although spontaneous firing of low-threshold bladder afferents was increased, their stretch-induced firing was reduced. The proportion of capsaicin-sensitive low-threshold afferents increased in obstructed bladders. Interestingly, spontaneous and stretch-induced firing were both significantly increased in high-threshold afferents after obstruction. In summary, sensory signaling increased in the obstructed bladder during the filling phase. This is largely mediated by low-threshold stretch-sensitive afferents that are activated by increased local nonvoiding contractions. Increased spontaneous firing by high-threshold afferents also contributes. Our findings revealed a complex effect of bladder outlet obstruction on different types of bladder afferents that needs consideration for potential therapeutic targeting of lower urinary tract symptoms in obstruction-induced bladder overactivity.

Elevated hydrostatic pressure stimulates ATP release which mediates activation of the NLRP3 inflammasome via P2X4 in rat urothelial cells

Partial bladder outlet obstruction (pBOO) is a prevalent urological condition commonly accompanied by increased intravesical pressure, inflammation, and fibrosis. Studies have demonstrated that pBOO results in increased NLRP3 inflammasome and caspase-1 activation and that ATP is released from urothelial cells in response to elevated pressure. In the present study, we investigated the role of elevated pressure in triggering caspase-1 activation via purinergic receptors activation in urothelial cells. Rat urothelial cell line, MYP3 cells, was subjected to hydrostatic pressures of 15 cmH₂O for 60 min, or 40 cmH₂O for 1 min to simulate elevated storage and voiding pressure conditions, respectively. ATP concentration in the supernatant media and intracellular caspase-1 activity in cell lysates were measured. Pressure experiments were repeated in the presence of antagonists for purinergic receptors to determine the mechanism for pressure-induced caspase-1 activation. Exposure of MYP3 cells to both pressure conditions resulted in an increase in extracellular ATP levels and intracellular caspase-1 activity. Treatment with P2X₇ antagonist led to a decrease in pressure-induced ATP release by MYP3 cells, while P2X₄ antagonist had no effect but both antagonists inhibited pressure-induced caspase-1 activation. Moreover, when MYP3 cells were treated with extracellular ATP (500 µM), P2X₄ antagonist inhibited ATP-induced caspase-1 activation, but not P2X₇ antagonist. We concluded that pressure-induced extracellular ATP in urothelial cells is amplified by P2X₇ receptor activation and ATP-induced-ATP release. The amplified ATP signal then activates P2X₄ receptors, which mediate activation of the caspase-1 inflammatory response.

Therapeutic effect of TAC-302, a cyclohexenoic fatty alcohol derivative, on bladder denervation-related storage and voiding dysfunctions in rats

AIMS

To evaluate the therapeutic effect of TAC-302, a cyclohexenoic fatty alcohol derivative, on bladder denervation-related storage and voiding dysfunctions in rats with bladder outlet obstruction (BOO).

METHODS

BOO was achieved by partial ligature of the proximal urethra in female rats. Two weeks later, BOO rats were divided into two groups and treated orally with vehicle or 10 mg/kg TAC-302 twice a day for 4 weeks. Urodynamic and immunohistochemical evaluation of the bladder muscle layer was performed. In another study, the BOO rats were treated with intravenous tamsulosin at cystometry. The detrusor contractility in each group was evaluated using the modified Shafer's nomogram.

RESULTS

Two weeks after BOO, the rats showed significant increases in non-voiding contraction (NVCs) and residual urine volume (RUV) compared to the sham group. Moreover, 6 weeks after BOO, BOO vehicle rats showed significant increases in NVCs and RUV and decreases in detrusor contractility and in the nerve fiber density in the urinary bladder compared to the sham group. BOO-induced denervation of the urinary bladder was partially improved by oral treatment with TAC-302. Oral treatment with TAC-302 significantly reduced the amplitude and frequency of NVCs (P < 0.05) and increased detrusor contractility and tended to reduce RUV compared with the BOO vehicle group. In contrast, the intravenous administration of tamsulosin significantly reduced the frequency of NVCs, but not RUV.

CONCLUSIONS

TAC-302 improved storage and voiding dysfunctions by improving bladder denervation and detrusor underactivity even when the treatment was started after storage and voiding dysfunctions had already occurred.

Activation of bitter taste receptors (tas2rs) relaxes detrusor smooth muscle and suppresses overactive bladder symptoms

Bitter taste receptors (TAS2Rs) are traditionally thought to be expressed exclusively on the taste buds of the tongue. However, accumulating evidence has indicated that this receptor family performs non-gustatory functions outside the mouth in addition to taste. Here, we examined the role of TAS2Rs in human and mouse detrusor smooth muscle (DSM). We showed that mRNA for various TAS2R subtypes was expressed in both human and mouse detrusor smooth muscle (DSM) at distinct levels. Chloroquine (CLQ), an agonist for TAS2Rs, concentration-dependently relaxed carbachol- and KCl-induced contractions of human DSM strips. Moreover, 100 μM of CLQ significantly inhibited spontaneous and electrical field stimulation (EFS)-induced contractions of human DSM strips. After a slight contraction, CLQ (1 mM) entirely relaxed carbachol-induced contraction of mouse DSM strips. Furthermore, denatonium and quinine concentration-dependently decreased carbachol-induced contractions of mouse DSM strips. Finally, we demonstrated that CLQ treatment significantly suppressed the overactive bladder (OAB) symptoms of mice with partial bladder outlet obstruction (PBOO). In conclusion, we for the first time provide evidence of the existence of TAS2Rs in the urinary DSM and demonstrate that TAS2Rs may represent a potential target for OAB. These findings open a new approach to develop drugs for OAB in the future.

Benefits and limitations of animal models in partial bladder outlet obstruction for translational research

The functions of the lower urinary tract have been investigated for more than a century. Lower urinary tract symptoms, such as incomplete bladder emptying, weak urine stream, daytime urinary frequency, urgency, urge incontinence and nocturia after partial bladder outlet obstruction, is a frequent cause of benign prostatic hyperplasia in aging men. However, the pathophysiological mechanisms have not been fully elucidated. The use of animal models is absolutely imperative for understanding the pathophysiological processes involved in bladder dysfunction. Surgical induction has been used to study lower urinary tract functions of numerous animal species, such as pig, dog, rabbit, guinea pig, rat and mouse, of both sexes. Several morphological and functional modifications under partial bladder outlet obstruction have not only been observed in the bladder, but also in the central nervous system. Understanding the changes of the lower urinary tract functions induced by partial bladder outlet obstruction would also contribute to appropriate drug development for treating these pathophysiological conditions. In the present review, we discuss techniques for creating partial bladder outlet obstruction, the characteristics of several species, as well as issues of each model, and their translational value.

Effects of nitric oxide inhibitors in mice with bladder outlet obstruction

PURPOSE

To investigate the lower urinary tract changes in mice treated with L-NAME, a non-selective competitive inhibitor of nitric oxide synthase (NOS), or aminoguanidine, a competitive inhibitor of inducible nitric oxide synthase (iNOS), after 5 weeks of partial bladder outlet obstruction (BOO), in order to evaluate the role of constitutive and non-constitutive NOS in the pathogenesis of this experimental condition.

MATERIALS AND METHODS

C57BL6 male mice were partially obstructed and randomly allocated into 6 groups: Sham, Sham + L-NAME, Sham + aminoguanidine, BOO, BOO + L-NAME and BOO + aminoguanidine. After 5 weeks, bladder weight was obtained and cystometry and tissue bath contractile studies were performed.

RESULTS

BOO animals showed increase of non-voiding contractions (NVC) and bladder capacity, and also less contractile response to Carbachol and Electric Field Stimulation. Inhibition of NOS isoforms improved bladder capacity and compliance in BOO animals. L-NAME caused more NVC, prevented bladder weight gain and leaded to augmented contractile responses at muscarinic and electric stimulation. Aminoguanidine diminished NVC, but did not avoid bladder weight gain in BOO animals and did not improve contractile responses.

CONCLUSION

It can be hypothesized that chronic inhibition of three NOS isoforms in BOO animals leaded to worsening of bladder function, while selective inhibition of iNOS did not improve responses, what suggests that, in BOO animals, alterations are related to constitutive NOS.

Preventative effects of a HIF inhibitor, 17-DMAG, on partial bladder outlet obstruction-induced bladder dysfunction

Posterior urethral valves are the most common cause of partial bladder outlet obstruction (PBOO) in the pediatric population. Pathological changes in the bladder developed during PBOO are responsible for long-lasting voiding dysfunction in this population despite early surgical interventions. Increasing evidence showed PBOO induces an upregulation of hypoxia-inducible factors (HIFs) and their transcriptional target genes, and they play a role in pathophysiological changes in the obstructed bladders. We hypothesized that blocking HIF pathways can prevent PBOO-induced bladder dysfunction. PBOO was surgically created by ligation of the bladder neck in male C57BL/6J mice for 2 wk. PBOO mice received intraperitoneal injection of either saline or 17-DMAG (alvespimycin, 3 mg/kg) every 48 h starting from day 1 postsurgery. Sham-operated animals received injection of saline on the same schedule as PBOO mice and served as controls. The bladders were harvested after 2 wk, and basal activity and evoked contractility of the detrusor smooth muscle (DSM) were evaluated in vitro. Bladder function was assessed in vivo by void spot assay and cystometry in conscious, unrestrained mice. Results indicated the 17-DMAG treatment preserved DSM contractility and partially prevented the development of detrusor over activity in obstructed bladders. In addition, PBOO caused a significant increase in the frequency of micturition, which was significantly reduced by 17-DMAG treatment. The 17-DMAG treatment improved urodynamic parameters, including increases in the bladder pressure at micturition and nonvoid contractions observed in PBOO mice. These results demonstrate that treatment with 17-DMAG, a HIF inhibitor, significantly alleviated PBOO-induced bladder pathology in vivo.

TAC-302 promotes neurite outgrowth of isolated peripheral neurons and prevents bladder denervation related bladder dysfunctions following bladder outlet obstruction in rats

AIMS

To evaluate the ability of TAC-302, a cyclohexenoic fatty alcohol derivative, to enhance neurite outgrowth in cultured rat dorsal root ganglion (DRG) neurons, and the preventive effects of TAC-302 on bladder denervation-related storage and voiding dysfunctions in rats with bladder outlet obstruction (BOO).

METHODS

Rat DRG neurons were cultured in the presence of TAC-302. Cell numbers and neurite lengths were quantified after a 24 h culture. BOO was achieved by partial ligature of the proximal urethra in female rats. BOO rats were divided into three groups and orally treated with vehicle of 3 or 30 mg/kg TAC-302 twice a day for 4 weeks. Cystometry was performed under conscious conditions. Immunohistochemical staining using anti-PGP9.5 of the bladder muscle layer was performed, and the innervation area was scored.

RESULTS

TAC-302 significantly and dose-dependently increased neurite outgrowth in cultured DRG neurons. BOO rats showed a decreased innervation area in the urinary bladder compared to sham-operated rats. BOO-induced denervation of the urinary bladder was partially prevented by oral treatment with TAC-302. TAC-302 significantly reduced the frequency of non-voiding contraction (NVC) and residual urine volume (RUV) compared with the BOO vehicle group (P < 0.05). The innervation area score exhibited significant negative correlations with NVC and RUV, indicating that they increased according to the progression of denervation.

CONCLUSIONS

Our data indicate that TAC-302 promotes neurite outgrowth in vitro. In addition, TAC-302 prevents BOO-induced bladder dysfunction in rats, and has a protective effect on bladder denervation.

Addressing challenges in underactive bladder: recommendations and insights from the Congress on Underactive Bladder (CURE-UAB)

Underactive bladder (UAB) is an expanding troublesome health issue, exerting a major influence on the health and independence of older people with a disproportionally low level of attention received. The 2nd International Congress on Underactive Bladder (CURE-UAB 2) convened in Denver, CO on December 3 and 4, 2015, and comprised of top clinicians, scientists, and other stakeholders to address the challenges in UAB. A series of workshops aimed to define UAB and its phenotype, define detrusor underactivity (DU) and create a subtyping of DU, evaluate existing animal models for DU, and lastly to establish research priorities for UAB.

Muro-Neuro-Urodynamics; a Review of the Functional Assessment of Mouse Lower Urinary Tract Function

Background: Mouse urodynamic tests are fundamental to understanding normal lower urinary tract (LUT) function. These experiments also contribute to our understanding of neurological dysfunction, pathophysiological processes, and potential mechanisms of therapy.

Objectives: Systematic assessment of published evidence on urodynamics, advantages and limitations of different urodynamic measurements in mice, and consideration of potential implications for the clinical field.

Methods: A search using specific search-terms for urodynamic studies and mice was conducted on PubMed (from inception to 1 July 2016).

Results: We identified 55 studies examining or describing mouse neuro-urodynamics. We summarize reported features of mouse urodynamic function deriving from frequency-volume chart (FVC) measurements, voiding spot assays, filling cystometry, and pressure-flow studies. Similarly, an influence of the diurnal cycle on voiding is observed in mice and should be considered when interpreting rodent urodynamic studies, especially FVC measurements and voiding spot assays. Anaesthesia, restraint conditions, or filling rate influence mouse neuro-urodynamics. Mouse cystometric studies have observed intravesical pressure oscillations that accompany urine flow, attributed to high frequency opening and closing of the urethra. This characterization is not seen in other species, except rats. In contrast to human clinical urodynamics, the terminology of these examinations has not been standardized although many rodent urodynamic studies have been described.

Conclusion: Mice have many anatomical and physiological similarities to humans and they are generally cost effective, and allow investigation of the effects of aging because of their short lifespan. There are some differences between mouse and human urodynamics. These must be considered when interpreting LUT function in mice, and translational value of murine disease models.

Intravital imaging of mouse urothelium reveals activation of extracellular signal-regulated kinase by stretch-induced intravesical release of ATP

To better understand the roles played by signaling molecules in the bladder, we established a protocol of intravital imaging of the bladder of mice expressing a Förster/fluorescence resonance energy transfer (FRET) biosensor for extracellular signal‐regulated kinase (ERK), which plays critical roles not only in cell growth but also stress responses. With an upright two‐photon excitation microscope and a vacuum‐stabilized imaging window, cellular ERK activity was visualized in the whole bladder wall, from adventitia to urothelium. We found that bladder distention caused by elevated intravesical pressure (IVP) activated ERK in the urothelium, but not in the detrusor smooth muscle. When bladder distension was prevented, high IVP failed to activate ERK, suggesting that mechanical stretch, but not the high IVP, caused ERK activation. To delineate its molecular mechanism, the stretch‐induced ERK activation was reproduced in an hTERT‐immortalized human urothelial cell line (TRT‐HU1) in vitro. We found that uniaxial stretch raised the ATP concentration in the culture medium and that inhibition of ATP signaling by apyrase or suramin suppressed the stretch‐induced ERK activation in TRT‐HU1 cells. In agreement with this in vitro observation, pretreatment with apyrase or suramin suppressed the high IVP‐induced urothelial ERK activation in vivo. Thus, we propose that mechanical stretch induces intravesical secretion of ATP and thereby activates ERK in the urothelium. Our method of intravital imaging of the bladder of FRET biosensor‐expressing mice should open a pathway for the future association of physiological stimuli with the activities of intracellular signaling networks.

Pannexin 1 channels play essential roles in urothelial mechanotransduction and intercellular signaling

Urothelial cells respond to bladder distension with ATP release, and ATP signaling within the bladder and from the bladder to the CNS is essential for proper bladder function. In other cell types, pannexin 1 (Panx1) channels provide a pathway for mechanically-induced ATP efflux and for ATP-induced ATP release through interaction with P2X₇ receptors (P2X₇Rs). We report that Panx1 and P2X₇R are functionally expressed in the bladder mucosa and in immortalized human urothelial cells (TRT-HU1), and participate in urothelial ATP release and signaling. ATP release from isolated rat bladders induced by distention was reduced by the Panx1 channel blocker mefloquine (MFQ) and was blunted in mice lacking Panx1 or P2X₇R expression. Hypoosmotic shock induced YoPro dye uptake was inhibited by MFQ and the P2X₇R blocker A438079 in TRT-HU1 cells, and was also blunted in primary urothelial cells derived from mice lacking Panx1 or P2X₇R expression. Rinsing-induced mechanical stimulation of TRT-HU1 cells triggered ATP release, which was reduced by MFQ and potentiated in low divalent cation solution (LDPBS), a condition known to enhance P2X₇R activation. ATP signaling evaluated as intercellular Ca²⁺ wave radius was significantly larger in LDPBS, reduced by MFQ and by apyrase (ATP scavenger). These findings indicate that Panx1 participates in urothelial mechanotransduction and signaling by providing a direct pathway for mechanically-induced ATP release and by functionally interacting with P2X₇Rs.

Duration of urination does not change with body size

Many urological studies rely on models of animals, such as rats and pigs, but their relation to the human urinary system is poorly understood. Here, we elucidate the hydrodynamics of urination across five orders of magnitude in body mass. Using high-speed videography and flow-rate measurement obtained at Zoo Atlanta, we discover that all mammals above 3 kg in weight empty their bladders over nearly constant duration of 21 ± 13 s. This feat is possible, because larger animals have longer urethras and thus, higher gravitational force and higher flow speed. Smaller mammals are challenged during urination by high viscous and capillary forces that limit their urine to single drops. Our findings reveal that the urethra is a flow-enhancing device, enabling the urinary system to be scaled up by a factor of 3,600 in volume without compromising its function. This study may help to diagnose urinary problems in animals as well as inspire the design of scalable hydrodynamic systems based on those in nature.

Visceral pain

Modeling visceral pain requires an appreciation of the underlying neurobiology of visceral sensation, including characteristics of visceral pain that distinguish it from pain arising from other tissues, the unique sensory innervation of visceral organs, the functional basis of visceral pain, and the concept of viscero-somatic and viscero-visceral convergence. Further, stimuli that are noxious when applied to the viscera are different than stimuli noxious to skin, muscle, and joints, thus informing model development and assessment. Visceral pain remains an important and understudied area of pain research and basic science knowledge and mechanisms acquired using animal models can translate into approaches that can be applied to the study and development of future therapeutics.

Autonomic nervous control of the urinary bladder

The autonomic nervous system plays an important role in the regulation of the urinary bladder function. Under physiological circumstances, noradrenaline, acting mainly on β(3) -adrenoceptors in the detrusor and on α(1) (A) -adrenoceptors in the bladder outflow tract, promotes urine storage, whereas neuronally released acetylcholine acting mainly on M(3) receptors promotes bladder emptying. Under pathophysiological conditions, however, this system may change in several ways. Firstly, there may be plasticity at the levels of innervation and receptor expression and function. Secondly, non-neuronal acetylcholine synthesis and release from the urothelium may occur during the storage phase, leading to a concomitant exposure of detrusor smooth muscle, urothelium and afferent nerves to acetylcholine and noradrenaline. This can cause interactions between the adrenergic and cholinergic system, which have been studied mostly at the post-junctional smooth muscle level until now. The implications of such plasticity are being discussed.

Latest treatment for lower urinary tract dysfunction: therapeutic agents and mechanism of action

Recent studies suggest that antimuscarinics might suppress bladder afferent activity by blocking muscarinic receptors in the urothelium, myofibroblasts and detrusor, thereby improving overactive bladder symptoms. β(3)-Adrenoceptors are predominantly expressed in the human bladder and mediate relaxation of detrusor muscle. β(3)-Adrenoceptor agonists increase bladder capacity and prolong micturition interval. It is assumed that β(3)-adrenoceptor agonists could exert an inhibitory effect on bladder afferent through β(3)-adrenoceptors in the urothelium and detrusor, which eventually improve the symptom of urgency. Mirabegron is a potent and selective β(3)-adrenoceptor agonist. A Japanese phase 3 study showed that mirabegron has excellent efficacy and safety for treating overactive bladder. α(1)-Adrenoceptor antagonists (α(1)-blockers) have become a mainstay of male lower urinary tract symptoms treatment. The α(1)(A) subtype is known to mediate functional obstruction as a result of benign prostatic enlargement. Recent studies have suggested that α(1)(A)-adrenoceptors are additionally involved in the generation of storage symptoms. The α(1)(D) subtype is thought to play a role in the facilitation of voiding reflex; that is; storage symptoms. α(1)-Blockers often fail to alleviate overactive bladder symptoms. In this context, combination therapy with α(1)-blockers and antimuscarinics has been recommended. Treatment with 5α-reductase inhibitor for 1 year improves urinary symptoms and flow rate by reducing prostatic volume in men with benign prostatic enlargement. A pooled analysis showed that the long-term (2 or 4 years) treatment with 5α-reductase inhibitor reduced the rate of progression to acute urinary retention and surgery. Combination therapy with 5α-reductase inhibitor and α(1)-blocker was shown to provide a rapid improvement in lower urinary tract symptoms, and reduce the relative risk of acute urinary retention and benign prostatic hyperplasia-related surgery. Phosphodiesterase inhibitors might target a nitric oxide-cyclic guanosine monophosphate pathway in the prostate, urethra and bladder. Phosphodiesterase-5 inhibitors (sildenafil or tadalafil) were shown to provide clinically relevant improvements in both male lower urinary tract symptoms and erectile dysfunction.

Function of the Cold Receptor (TRPM8) Associated with Voiding Dysfunction in Bladder Outlet Obstruction in Rats

Purpose

Bladder outlet obstruction (BOO) causes storage and voiding dysfunction in the lower urinary tract. We investigated the expression of transient receptor potential cation channel subfamily M member 8 (TRPM8) to evaluate the relationship between TRPM8 expression and overactive bladder (OAB) in a rat model of BOO.

Methods

Fifty female Sprague-Dawley rats were divided into 4 groups; normal (n=10), normal-menthol (n=10), BOO (n=15), BOO-menthol (n=15). After 3 weeks, cystometry was performed by infusing physiological saline and menthol (3 mM) into the bladder at a slow infusion rate. The histological changes and expression of TRPM8 in the bladder were investigated by Masson's trichrome staining, immunofluorescence and reverse transcription-polymerase chain reaction.

Results

Cystometry showed that the intercontraction interval (ICI; 428.2±23.4 vs. 880.4±51.2, P<0.001), micturition pressure (MP; 25.7±1.01 vs. 71.80±3.01, P<0.001), and threshold pressure (2.9±0.25 vs. 9.2±1.58, P<0.01) were significantly increased in BOO rats. The bladder wall was significantly dilated compared with the control. Detrusor muscle hypertrophy and a thick mucosa layer were observed in BOO bladder. After menthol treatment, ICIs were decreased and MPs were increased in the menthol treatment groups. TRPM8-positive cells and mRNA were predominantly increased in the bladder and dorsal root ganglia of all groups compared with the normal group.

Conclusions

Increased bladder wall thickness and proportion of collagen probably affect voiding dysfunction. Furthermore, an increase of TRPM8 expression in BOO may induce entry of Ca²⁺ from the extracellular space or stores. The increase of Ca²⁺ probably causes contraction of smooth muscle in BOO. However, OAB symptoms were not observed after menthol treatment although the expression of TRPM8 was abundant in the bladder epithelium after menthol treatment. Although OAB in BOO models may be caused by complex pathways, regulation of TRPM8 presents possibilities for OAB treatment.

Impact of partial urethral obstruction on bladder function: time-dependent changes and functional correlates of altered expression of Ca²⁺ signaling regulators

In animal models of partial urethral obstruction (PUO), altered smooth muscle function/contractility may be linked to changes in molecules that regulate calcium signaling/sensitization. PUO was created in male rats, and urodynamic studies were conducted 2 and 6 wk post-PUO. Cystometric recordings were analyzed for the presence or absence of nonvoiding contractions [i.e., detrusor overactivity (DO)]. RT-PCR and Western blots were performed on a subpopulation of rats to study the relationship between the expression of RhoA, L-type Ca(2+) channels, Rho kinase-1, Rho kinase-2, inositol 1,4,5-trisphosphate, ryanodine receptor, sarco(endo)plasmic reticulum Ca(2+)-ATPase 2 and protein kinase C (PKC)-potentiated phosphatase inhibitor of 17 kDa, and urodynamic findings in the same animal. Animals displayed DO at 2 (38%) and 6 wk (43%) post-PUO, increases were seen in in vivo pressures at 2 wk, and residual volume at 6 wk. Statistical analysis of RT-PCR and Western blot data at 2 wk, during the compensatory phase of detrusor hypertrophy, documented that expression of molecules that regulate calcium signaling and sensitization was consistently lower in obstructed rats without DO than those with DO or control rats. Among rats with DO at 2 wk, linear regression analysis revealed positive correlations between in vivo pressures and protein and mRNA expression of several regulatory molecules. At 6 wk, in the presence of overt signs of bladder decompensation, no clear or consistent alterations in expression of these same targets were observed at the protein level. These data extend prior work to suggest that molecular profiling of key regulatory molecules during the progression of PUO-mediated bladder dysfunction may shed new light on potential biomarkers and/or therapeutic targets.

Altered bladder function in elastin-deficient mice at baseline and in response to partial bladder outlet obstruction

OBJECTIVE

• To examine functional and molecular changes of the bladders from elastin-haploinsufficient mice (Eln(+/-) ) at baseline as well as in response to partial bladder outlet obstruction (pBOO).

MATERIALS AND METHODS

• Female Eln(+/-) and wild type (Wt) mice (3-4 months old) were studied. • The bladder elastin content was quantified by measuring desmosine. • Mice were divided into two groups to undergo surgery to create pBOO or to undergo sham surgery. Three days after surgery, bladder function was evaluated by in vivo cystometry, and the contractile response of bladder strips exposed to electrical field stimulation (EFS) and carbachol was examined by ex vivo myography.

RESULTS

• The Eln(+/-) -sham mice had a 33.6% decrease in bladder elastin compared with Wt-sham mice. • Cystometry showed significantly decreased bladder compliance and capacity in Eln(+/-) -sham vs Wt-sham mice; pBOO increased bladder compliance and capacity to a greater extent in Eln(+/-) mice compared with Wt mice. • Bladder strips from Eln(+/-) -sham mice showed a significantly heightened contractile response to both EFS and carbachol compared with Wt-sham mice. • A significantly increased contractile response to carbachol was detected in Wt-pBOO vs Wt-sham but not between Eln(+/-) -pBOO and Eln(+/-) -sham mice.

CONCLUSION

• The results that elastin-deficient mice had decreased bladder compliance and capacity and increased bladder contractility; and that Wt-pBOO mice showed an enhanced contractile response to carbachol, but Eln(+/-) -pBOO mice did not, suggest that elastin is critical for normal bladder function and is involved in bladder response to pBOO.

Rodent models for urodynamic investigation

Rodents, most commonly rats, mice, and guinea pigs are widely used to investigate urinary storage and voiding functions, both in normal animals and in models of disease. An often used methodology is cystometry. Micturitions in rodents and humans differ significantly and this must be considered when cystometry is used to interpret voiding in rodent models. Cystometry in humans requires active participation of the investigated patient (subject), and this can for obvious reasons not be achieved in the animals. Cystometric parameters in rodents are often poorly defined and do not correspond to those used in humans. This means that it is important that the terminology used for description of what is measured should be defined, and that the specific terminology used in human cystometry should be avoided. Available disease models in rodents have limited translational value, but despite many limitations, rodent cystometry may give important information on bladder physiology and pharmacology. The present review discusses the principles of urodynamics in rodents, techniques, and terminology, as well as some commonly used disease models, and their translational value.

Mesenchymal stem cell recruitment and improved bladder function after bladder outlet obstruction: preliminary data

PURPOSE

Mesenchymal stem cells have various therapeutic benefits in various organ injury models. Bladder outlet obstruction causes smooth muscle hypertrophy and fibrosis, leading to lowered compliance, increased storage pressures and renal injury. Decreased blood flow and hypoxia may contribute to obstruction related bladder decompensation. We used a mouse model to determine whether mesenchymal stem cell recruitment occurred after bladder outlet obstruction and whether this was associated with changes in bladder hypoxia, histology and function. We also identified potential chemokines involved in mesenchymal stem cell recruitment.

MATERIALS AND METHODS

A total of 20 female mice underwent bladder outlet obstruction. Three days later 2 million green fluorescent protein labeled mesenchymal stem cells were intravenously administered. After 4 weeks urodynamic and histological evaluation was performed. Quantitative reverse transcriptase-polymerase chain reaction was done to determine relative expression of the chemokines CCL2, CCL20, CCL25, CXCL9 and CXCL16. We simultaneously studied mice with bladder outlet obstruction only without mesenchymal stem cell injection and a control group.

RESULTS

In 10 of 15 surviving mesenchymal stem cell injected mice mesenchymal stem cells were identified in the detrusor, and decreased hypoxia, hypertrophy and fibrosis was seen. Nine of 10 mice with mesenchymal stem cell engraftment had improved compliance compared to those without engraftment (mean±SD 9.6±5.1 vs 3.9±2.6 μl/cm H2O, p=0.012). Polymerase chain reaction revealed a 2-fold increase in CCL2 expression but there were no significant changes in other chemokine levels.

CONCLUSIONS

Mesenchymal stem cell recruitment to the bladder after bladder outlet obstruction appears to be associated with increased blood flow and decreased tissue hypoxia, which may contribute to improvement in histopathological and functional parameters. Mesenchymal stem cell recruitment may be related to CCL2 over expression. Additional studies in larger samples are needed but these initial results suggest a potential role for mesenchymal stem cell based therapy for bladder outlet obstruction related bladder injury.

Muscarinic acetylcholine receptors in the urinary tract

Muscarinic receptors comprise five cloned subtypes, encoded by five distinct genes, which correspond to pharmacologically defined receptors (M(1)-M(5)). They belong to the family of G-protein-coupled receptors and couple differentially to the G-proteins. Preferentially, the inhibitory muscarinic M(2) and M(4) receptors couple to G(i/o), whereas the excitatory muscarinic M(1), M(3), and M(5) receptors preferentially couple to G(q/11). In general, muscarinic M(1), M(3), and M(5) receptors increase intracellular calcium by mobilizing phosphoinositides that generate inositol 1,4,5-trisphosphate (InsP3) and 1,2-diacylglycerol (DAG), whereas M(2) and M(4) receptors are negatively coupled to adenylyl cyclase. Muscarinic receptors are distributed to all parts of the lower urinary tract. The clinical use of antimuscarinic drugs in the treatment of detrusor overactivity and the overactive bladder syndrome has focused interest on the muscarinic receptors not only of the detrusor, but also of other components of the bladder wall, and these have been widely studied. However, the muscarinic receptors in the urethra, prostate, and ureter, and the effects they mediate in the normal state and in different urinary tract pathologies, have so far not been well characterized. In this review, the expression of and the functional effects mediated by muscarinic receptors in the bladder, urethra, prostate, and ureters, under normal conditions and in different pathologies, are discussed.

Cannabinor, a selective cannabinoid-2 receptor agonist, improves bladder emptying in rats with partial urethral obstruction

PURPOSE

We studied the effects of chronic treatment with the novel selective cannabinoid 2 receptor agonist cannabinor (Procter & Gamble Pharmaceuticals, Cincinnati, Ohio) on bladder function in conscious rats with partial urethral obstruction and on the functional properties of isolated detrusor muscle.

MATERIALS AND METHODS

A total of 24 female Sprague-Dawley® rats with surgically created partial urethral obstruction received daily intraperitoneal injections of 3 mg/kg cannabinor (12) or saline as controls (12) for 2 weeks. Cystometry was done, the rats were sacrificed and the bladders were prepared for in vitro studies.

RESULTS

Mean ± SEM bladder weight was 0.97 ± 0.15 gm in controls and 0.53 ± 0.08 gm in cannabinor treated rats (p <0.05). There was no difference between the groups in the mean micturition interval, or mean baseline, threshold, flow or maximum pressure. In controls and cannabinor treated rats mean post-void residual volume was 0.28 ± 0.07 and 0.06 ± 0.02 ml, mean micturition compliance was 0.032 ± 0.006 and 0.069 ± 0.016 ml/cm H(2)O, and mean bladder wall force at the start of flow was 950 ± 280 and 1,647 ± 325 mN/gm, respectively (each p <0.05). Nonvoiding contractions were significantly less frequent in cannabinor treated rats than in controls. We noted no difference in carbachol (Sigma®) half maximum concentration between the groups but the carbachol maximum response in detrusor strips from cannabinor treated rats was significantly higher than that in control strips.

CONCLUSIONS

In rats with partial urethral obstruction treated daily for 14 days with cannabinor bladder weight was lower, the ability to empty the bladder was preserved and nonvoiding contraction frequency was low compared to those in controls. Detrusor preparations from cannabinor treated rats showed a higher response to nerve stimulation than those from controls. Selective cannabinoid 2 receptor activation may be a novel principle to enable improved bladder function after partial urethral obstruction.

Alterations in bladder function associated with urothelial defects in uroplakin II and IIIa knockout mice

AIMS

The effects of deleting genes encoding uroplakins II (UPII) and III (UPIIIa) on mouse bladder physiology/dysfunction were studied in male and female wild type and knockout (KO) mice.

METHODS

UPII, UPIIIa, and WT mice were catheterized using previously described techniques. Continuous cystometry was conducted in conscious, freely moving animals. Bladder strips were harvested after animal sacrifice and pharmacological studies and EFS were conducted in an organ chamber. Histological studies were also carried on with H&E staining to identify differences among the three mouse types.

RESULTS

These studies have revealed numerous alterations, some of which were apparently gender-specific. Nonvoiding contractions were common in both UPII and UPIIIa KO mice, although more severe in the former. In particular, the increased bladder capacity, micturition pressure and demonstrable nonvoiding contractions observed in the male UPII KO's, were reminiscent of an obstruction-like syndrome accompanied by evidence of emerging bladder decompensation, as reflected by an increased residual volume. Pharmacological studies revealed a modest, gender-specific reduction in sensitivity of isolated detrusor strips from UPII KO female mice to carbachol-induced contractions. A similar reduction was observed in UPIIIa KO female mice. Histological investigation showed urothelial hyperplasia in both UPII KO and UPIIIa KO mice, although again, apparently more severe in the former.

CONCLUSIONS

These results confirm and extend previous work to indicate that urothelial defects due to uroplakin deficiency are associated with significant alterations in bladder function and further highlight the importance of the urothelium to bladder physiology/dysfunction.

The medical management of urinary incontinence

Urinary incontinence is the involuntary leakage of urine; it affects millions of people worldwide, causing significant detrimental effects on their quality of life. Direct expenses, such as containment products, long-term drug prescriptions and surgery, complemented by indirect costs, such as reduced employment productivity, result in overall expenditure running to billions of dollars. Stress urinary incontinence (SUI) occurs on physical exertion, and results from weakness of the bladder outlet. Urgency urinary incontinence (UUI) results from inability to resist a sudden compelling desire to pass urine, arising as a consequence of bladder dysfunction. Clinical evaluation clarifies the underlying mechanisms and excludes diseases causing similar symptoms. Urodynamic studies to measure bladder and abdominal pressures and deduce the bladder and outlet function are undertaken when invasive treatments are being considered or when the nature of the incontinence is not entirely clear. Initial management of SUI involves pelvic floor muscle exercise training; if insufficient symptom improvement results, surgical measures are needed. UUI treatment commences with advice on suitable fluid intake and measures to improve ability to defer voiding, followed by antimuscarinic drugs. Refractory UUI is a difficult problem, currently managed with a range of surgical interventions, including bladder injections of botulinum-A neurotoxin, augmentation cystoplasty and nerve stimulation methods. New treatment options are needed, because of the risk of impeding voiding function, resulting in urinary retention. Persistent leakage is controlled with containment products, such as pads, or collection devices, such as catheters.

Effect of partial bladder outlet obstruction on detrusor compliance, excitability and contractility in rats

OBJECTIVE

Partial bladder outlet obstruction (PBOO) is believed to change the functions of the detrusor, and can lead to an overactive detrusor (OD). The aim of this study was to investigate changes in bladder compliance, excitability and contractility after PBOO in rats.

MATERIAL AND METHODS

PBOO was performed for 6 weeks in 20 Wistar rats, 13 of which (OD group) had an OD and seven of which (non-OD group) did not. Simultaneously, 10 rats that underwent sham operations (control group) were also studied. Bladder compliance and cystometric capacity were identified in vivo, but bladder compliance was detected without elimination of bladder capacity. Isolated bladder smooth muscle strip (BSMS) was dissected to determine excitability and contractility.

RESULTS

After 6 weeks of PBOO, cystometric capacity and compliance were significantly higher than those in the control group. Compliance was 0.170+/-0.029 and 0.149+/-0.042 ml/cmH2O in the OD and non-OD groups, respectively, compared to 0.037+/-0.017 ml/cmH2O in the control group. The corresponding cystometric capacities were 3.66+/-0.490, 3.08+/-0.590 and 1.14+/-0.225 ml. The excitability in the OD group increased significantly compared to that in the non-OD and control groups. The tension threshold for BSMS contraction was lower in the OD group, and BSMS contracted more frequently at the same tension. The contractility of the BSMS in the OD group decreased significantly compared to that in the non-OD and control groups.

CONCLUSIONS

PBOO can cause a higher cystometric capacity and compliance. After PBOO, there is a chance that an OD may develop. When this occurs, the detrusor excitability increases and contractility decreases.

Signaling processes for initiating smooth muscle contraction upon neural stimulation

Relationships among biochemical signaling processes involved in Ca2+/calmodulin (CaM)-dependent phosphorylation of smooth muscle myosin regulatory light chain (RLC) by myosin light chain kinase (MLCK) were determined. A genetically-encoded biosensor MLCK for measuring Ca(2+)-dependent CaM binding and activation was expressed in smooth muscles of transgenic mice. We performed real-time evaluations of the relationships among [Ca2+](i), MLCK activation, and contraction in urinary bladder smooth muscle strips neurally stimulated for 3 s. Latencies for the onset of [Ca2+](i) and kinase activation were 55 +/- 8 and 65 +/- 6 ms, respectively. Both increased with RLC phosphorylation at 100 ms, whereas force latency was 109 +/- 3 ms. [Ca2+](i), kinase activation, and RLC phosphorylation responses were maximal by 1.2 s, whereas force increased more slowly to a maximal value at 3 s. A delayed temporal response between RLC phosphorylation and force is probably due to mechanical effects associated with elastic elements in the tissue. MLCK activation partially declined at 3 s of stimulation with no change in [Ca2+](i) and also declined more rapidly than [Ca2+](i) during relaxation. The apparent desensitization of MLCK to Ca2+ activation appears to be due to phosphorylation in its calmodulin binding segment. Phosphorylation of two myosin light chain phosphatase regulatory proteins (MYPT1 and CPI-17) or a protein implicated in strengthening membrane adhesion complexes for force transmission (paxillin) did not change during force development. Thus, neural stimulation leads to rapid increases in [Ca2+](i), MLCK activation, and RLC phosphorylation in phasic smooth muscle, showing a tightly coupled Ca2+ signaling complex as an elementary mechanism initiating contraction.

Biochemical alterations in partial bladder outlet obstruction in mice: up-regulation of the mitogen activated protein kinase pathway

PURPOSE

We evaluated the effect of partial bladder outlet obstruction on bladder weight, protein synthesis, mitotic markers and the mitogen activated protein kinase pathway in a mouse model.

MATERIALS AND METHODS

Mice were divided into 3 groups, including control, sham treated and partially obstructed. Bladders were harvested from the mice in the partially obstructed group 12, 24, 48, 72 and 168 hours after surgical partial outlet obstruction, respectively. Partially obstructed bladders were compared to bladders in the control and sham treated groups by weight, protein content, and expression of proliferating cellular nuclear antigen, cyclin D3, HsP 70, c-jun and phosphorylated c-jun. Bladders were examined histologically for changes occurring with partial obstruction.

RESULTS

We tested 3 groups of mice, including control, sham treated and partially obstructed mice, to understand the pathophysiology of the bladder response to partial obstruction. We found no statistical difference in body weight among the groups. Furthermore, there was a significant increase in bladder weight and protein content in partially obstructed mice compared to those in controls and sham operated mice. There was up-regulation of proliferating cellular nuclear antigen, cyclin D3, HsP70, c-jun and phosphorylated c-jun with partial obstruction. Fibrosis was prominent at 168 hours compared to that in controls.

CONCLUSIONS

Bladder weight and protein content increase with partial bladder outlet obstruction in mice. Cell cycle proteins and elements of the mitogen activated protein kinase pathway are up-regulated during this process.