An early molecular response induced by acute overdistension of the rabbit urinary bladder

Dysfunctional Bladder Morphology and Functional Impairments Are Identified in the Alzheimer's Disease APPNL-G-F/NL-G-F Murine Model

BACKGROUND

While symptoms related to lower urinary tract dysfunction (LUTD) are common in individuals with Alzheimer's disease (AD), pathophysiological links between AD and LUTD remain unclear.

OBJECTIVE

This study aimed to investigate whether AD neuropathology would cause autonomic dysfunction along the spinal cord-bladder axis, which could result in alterations in bladder muscle kinetics.

METHODS

We utilized APPNL-G-F/NL-G-F knock-in (APP KI) and APPwt/wt (wild-type) mice at two different ages, 4- and 10-month-old, to investigate how AD impacts bladder tissue function by immunohistochemistry, western blotting, and pharmacomyography.

RESULTS

We showed that the mucosal layer partially separated from the detrusor in 10-month-old APP KI mouse bladders. Although there was no detectable amyloid deposition in the APP KI bladder, we found amyloid plaques in APP KI lumbar spinal cord. Further immunoblot analysis revealed that tyrosine hydroxylase protein levels were significantly reduced in both 4- and 10-month-old bladder tissues, suggesting reduction of norepinephrine synthesis in APP KI mouse bladders. In contrast, the level of β2 adrenergic receptor was increased in 4-month-old but not 10-month-old APP KI bladders. In bladder strips, the adrenergic agonist isoproterenol induced increased relaxation in 4- but not 10-month-old APP KI bladders. With 10 Hz electrical field stimulation, 10-month-old APP KI bladder strips were more responsive than wild-type controls, with no differences observed in 4-month-old APP KI bladders.

CONCLUSIONS

APP KI mice exhibit LUTD, which is likely arising from amyloid pathology in the spinal cord, and results in maturational declines in presynaptic activity combined with compensatory postsynaptic upregulation.

Pathophysiological Mechanisms Involved in Overactive Bladder/Detrusor Overactivity

Purpose of Review

To examine the latest published findings on the pathophysiological mechanisms involved in the development of overactive bladder (OAB) and detrusor overactivity (DO), and to identify common pathways linked to the risk factors associated with these conditions.

Recent Findings

Evidence is accumulating, both clinical and experimental, that many of the factors linked to the development of OAB/DO, including ageing, bladder outlet obstruction, psychological stress, and obesity are associated with reduced bladder blood flow. This induces local tissue inflammation with cytokine release and enhanced oxidative stress, ultimately resulting in altered detrusor sensitivity, detrusor hypertrophy and fibrosis, together with afferent hypersensitivity. These mechanisms would explain the symptoms of urgency and frequency observed in OAB patients. Although not a characteristic of OAB, undetected low level bacterial infections of the bladder have been proposed to explain the OAB symptoms in patients resistant to standard treatments. In this condition, inflammatory responses without reductions in perfusion activate the inflammatory pathways.

Summary

Evidence is mounting that poor bladder perfusion and local inflammatory responses are central mechanisms involved in the development of OAB/DO. As our understanding of these pathophysiological mechanisms advances, new avenues for drug development will be identified and ultimately treatment may become more individualized depending on the particular pathway involved and the drugs available.

Molecular mechanisms of voiding dysfunction in a novel mouse model of acute urinary retention

Acute urinary retention (AUR) is a common urological emergency and affects a significant patient population. The inability to eliminate urine may lead to permanent damage to the bladder's structure and functioning. However, we know little about the underlying molecular sequelae to the urine retention. To closely mirror the potential high pressures that patients with AUR could experience, we catheterized anesthetized female mice via the urethra and filled the bladder by pumping saline (25 µL/min) into the bladder lumen to 50 cm or 80 cm water pressure. A water column with designated height (50 or 80 cm) was then adjusted to maintain constant pressure in the bladder lumen for 30 minutes. Functional and morphological evaluations were performed from 0 to 24 hours after AUR treatment. Mice exhibited incontinence and overactivity with diminished voiding pressure. Significant injury was confirmed which revealed bladders with disrupted urothelial barrier, edematous lamina propria, and distorted muscle bundles. Bladder smooth muscle (BSM) from pressure-treated mice have significantly diminished contraction force, suggesting that bladder voiding dysfunction can be attributed to impaired BSM contractility. Indeed, dysregulation of acetylcholine and purinergic signaling pathways were demonstrated, indicating that reduced efficacy of these pathways contributes to impaired BSM contractility. Finally, altered expression of β1-integrin and extracellular matrix mediated mechanotransduction pathways were detected, suggesting a profound remodeling process. These data demonstrated an easy to perform, quantifiable, and reproducible AUR mouse model, which mimics well the characteristics of human AUR patients, and our data generate new insights into the molecular mechanisms that occur following AUR.

Effects of Qianlie Tongqiao Capsule on Bladder Weight and Growth Factors in Bladder Tissue of Rats with Testosterone-Induced Benign Prostatic Hyperplasia

Qianlie Tongqiao Capsule (QTC) is clinically confirmed to be efficacious and safe in treating lower urinary tract syndromes and bladder dysfunction that are induced by benign prostatic hyperplasia (BPH). However, the functional mechanisms of QTC remain unclear. We aim to investigate the effects of QTC on both bladder weight and several growth factors in the bladder tissue of rats with testosterone-induced BPH. BPH in the rats was established through bilateral orchiectomy and subcutaneous administration of testosterone propionate (5 mg/kg) dissolved in corn oil. At the end of the study, all bladder tissues were collected and weighed, and a histological examination was conducted using H&E staining. Immunohistochemistry and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) were applied to detect the expression of nerve growth factor (NGF), basic fibroblast growth factor (bFGF), and transformation growth factor-β1 (TGF-β1) in the bladder tissue. The expression of Bcl-2 and Bax in the bladder tissue was tested by Western Blot and qRT-PCR. We found that QTC, especially when administered in high-dosages, had a significant inhibitory effect on bladder weight gain and overexpression of NGF, bFGF, and TGF-β1 in rats with BPH. In addition, QTC downregulated and upregulated protein and mRNA expression of Bcl-2 and Bax in the bladder after prostatic obstruction, respectively. Furthermore, QTC balanced the Bcl-2/Bax ratio. Overall, these results reveal possible functional mechanisms of QTC in treating BPH-caused bladder dysfunction, and further studies are needed.

Amitriptyline aggravates the fibrosis process in a rat model of infravesical obstruction

Infravesical obstruction (IVO) secondary to benign prostatic hypertrophy can affect up to 50% of men over 50 years old and may cause serious and irreversible alterations throughout the urinary tract, especially in the bladder. Therapeutic approaches are currently limited. Amitriptyline has recently been described as an analgesic, anti-inflammatory and myorelaxant in some experimental models. The objective of this study was to investigate the effects of amitriptyline hydrochloride on the process of fibrosis in a bladder outlet obstruction model in rats. Male Wistar rats were subjected to IVO and studied at intervals of 1 and 14 days postprocedure. The rats were randomly divided into five groups: sham, IVO1-T, IVO1-NT, IVO14-T and IVO14-NT. Bladder tissue was processed for histopathology, immunohistochemistry and RT-PCR. The IVO14 groups presented bladder fibrosis, smooth muscle cell hypertrophy and bladder wall thickening. The IVO14-T group demonstrated a higher intensity of fibrosis, higher macrophage infiltration rate and higher gene expression of Transforming growth factor (TGF) Tgf-β1. Thus this data shows that in this experimental mode amitriptyline had an amplifying effect on the process of fibrosis as a whole.

Role of Transforming Growth Factor β in Rat Bladder Smooth Muscle Cell Proliferation

Conditions associated with hypertrophy of the urinary bladder have repeatedly been associated with an increased urinary excretion of transforming growth factor (TGF) beta in both rats and patients. Because TGFbeta can have both growth-promoting and -inhibiting effects, we have studied its effects on cell growth and death in primary cultures of rat bladder smooth muscle cells. TGFbeta1, TGFbeta2, or TGFbeta3 did not cause apoptosis, but all three isoforms inhibited DNA synthesis with similar potency (EC(50) of approximately 0.1 ng/ml) and efficacy. Such inhibition was antagonized by a specific TGFbeta receptor antagonist and independent of the presence of serum. Mitogen-activated protein kinases (MAPKs) are involved in the control of cell growth, and all three TGFbeta isoforms inhibited activation of the extracellular signal-regulated kinase, c-Jun NH(2)-terminal kinase, and p38 MAPK subfamilies. Nevertheless, the inhibitory effects of the TGFbeta isoforms on DNA synthesis were not affected by presence of inhibitors of the three MAPK pathways. TGFbeta did not alter cell size as measured by flow cytometry or mitochondrial activity, an integrated measure of cell size and number. We conclude that our data do not support the hypothesis that TGFbeta is a mediator of rat bladder hypertrophy.

Investigation of early protein changes in the urinary bladder following partial bladder outlet obstruction by proteomic approach

We investigated the pathophysiological mechanism by proteomic approach as a possible tool to detect the marker proteins to develop lower urinary tract symptoms following bladder outlet obstruction (BOO). Rats were randomized into 3 groups; control, sham operation and BOO groups. BOO group was divided into 1, 3, and 5 day-group. Conventional proteomics was performed with high resolution 2-D gel electrophoresis followed by computational image analysis and protein identification using mass spectrometry using rat urinary bladders. A comparison of bladder of BOO group with control bladder showed that three proteins of optineurin, thioredoxin and preprohaptoglobin were over-expressed in the bladder of BOO group. In addition, four proteins, such as peroxiredoxin 2, transgelin, hippocampal cholinergic neurostimulating peptide (HCNP) and beta-galactoside-binding lectin, were under-expressed in the bladder of BOO group. These data supported that downregulation of HCNP might make detrusor muscle be supersensitive to acetylcholine, up-regulation of optineurin means the protection of nerve injury, and down-regulation of transgelin means the decreased contractility of detrusor muscle. Beside these proteins, other proteins are related to oxidative stress or have a nonspecific function in this study. However more information is needed in human bladder tissue for clinical usage.

Urinary bladder contraction and relaxation: physiology and pathophysiology

The detrusor smooth muscle is the main muscle component of the urinary bladder wall. Its ability to contract over a large length interval and to relax determines the bladder function during filling and micturition. These processes are regulated by several external nervous and hormonal control systems, and the detrusor contains multiple receptors and signaling pathways. Functional changes of the detrusor can be found in several clinically important conditions, e.g., lower urinary tract symptoms (LUTS) and bladder outlet obstruction. The aim of this review is to summarize and synthesize basic information and recent advances in the understanding of the properties of the detrusor smooth muscle, its contractile system, cellular signaling, membrane properties, and cellular receptors. Alterations in these systems in pathological conditions of the bladder wall are described, and some areas for future research are suggested.

THE MOLECULAR GENETIC BASIS OF MITOCHONDRIAL MALFUNCTION IN BLADDER TISSUE FOLLOWING OUTLET OBSTRUCTION

PURPOSE

Bladder dysfunction following partial outlet obstruction is a frequent consequence of benign prostatic hyperplasia and an increasingly common problem given the aging of the general population. Recent studies from this and other groups have begun to elucidate the molecular bases for the well described physiological malfunctions that characterize this clinical entity. We summarized and synthesized that information.

MATERIALS AND METHODS

Using modern methods of molecular genetics, including real-time polymerase chain reaction, real-time reverse transcriptase-polymerase chain reaction and others, as well as traditional experimental techniques such as electron microscopy we and others examined the transcriptional profile, morphology, etc of bladder smooth muscle mitochondria in experimental models of outlet obstruction.

RESULTS

Data from many studies have demonstrated that aberrant gene expression in the mitochondrial and mitochondria related nuclear genetic systems underlies the loss of compliance and other attributes of bladder dysfunction following outlet obstruction. Such aberrant transcriptional characteristics engender loss of function in the electron transport and oxidative phosphorylation systems. Morphological studies of mitochondria in the animal model systems support this conclusion.

CONCLUSIONS

In large part the loss of function in bladder smooth muscle following outlet obstruction results from the attenuation of mitochondrial energy production. In this article we reviewed and synthesized all available experimental observations relevant to this problem and we suggest future lines of inquiry that should prove fruitful in developing new strategies to treat the condition.

Morphological analysis of the acute effects of overdistension on the extracellular matrix of the rat urinary bladder wall

PURPOSE

To investigate the morphological effects of acute overdistension in the structure of the extracellular matrix of the bladder wall in rats.

MATERIALS AND METHODS

The bladders of a group of 6 male Wistar rats were transurethrally overdistended for 3 hours. Another identical group (the control group) was only submitted to a sham operation. Specimens from the bladder dome were analyzed with light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

RESULTS

LM--The control group bladders had a 4 to 5 layer urothelium, a lamina propria, and a smooth muscle layer with longitudinal and transversal fibers. The overdistended bladders presented an intense interstitial infiltrate in the lamina propria, and a less intense infiltrate among the smooth muscle fibers. TEM--The cells of the overdistended bladders had a significant amount of vacuoles, unlike the control bladders, where such vacuoles were scarce or absent. SEM--A delicate three-dimensional mesh of collagen fibrils was observed in the lamina propria of the bladder walls from the control group. Whilst for the control group this mesh consisted of distinct geometric structures, with mostly circular cellular spaces surrounded by the fibrils, the overdistended group showed evidence of distortion of the mesh, with flattened and elongated cellular spaces.

CONCLUSIONS

Acute bladder overdistension induces structural modifications, altering the arrangement and interaction of collagen fibrils, as well as incipient tissue damage as edema in the lamina propria and smooth muscle layers.

Estudio experimental de la expresión de las proteínas de la pared vesical en la obstrucción del tracto urinario inferior en el conejo

OBJECTIVES

To determine the relationship of the bladder wall levels of the contractile proteins: whole actin, beta-actin, alpha-sarcomeric-actina caldesmon and of the Heat Stress Protein HSP-70, with the partial bladder outlet obstruction.

MATERIAL AND METHODS

It was carried out an experimental study on 43 New-Zealand rabbits. These animals were divided into a control group and six experimental groups with partial bladder outlet obstruction induced by an incomplete tie around the urethra. The experimental groups were defined according the day when the animals were sacrified: at 24 hours, 7 days, 15 days, 1 month, 3 months and 6 months of the obstruction. It was determined in all animals the muscular bladder wall concentration of whole actin, beta-actin, alpha-sarcomeric-actin, caldesmon and HSP-70 protein, according to Western Blotting technique. The results were analyzed by means of ANOVA, using the Scheffe post hoc method.

RESULTS

The bladder weight of the obstructed animals increased significantly in two stages: until the day 15 and between the day 15 and the end of the study, corresponding to theoretical phases of initial hypertrophy and compensation. The level of whole actin showed a significant decrease at the beginning of compensation phase, while the beta-actin level increased in the phase of initial hypertrophy and the alpha-sarcomeric-actin level increased at the end of the compensation phase, while the caldesmon and the HSP-70 made it at the end of the initial hypertrophy phase.

CONCLUSIONS

Analysing our data we conclued that the determination of the caldesmon levels is the marker that better adjusts to the changes associated with partial bladder outlet obstruction in the rabbit.

Mechanical stretch regulates cell survival in human bladder smooth muscle cells in vitro

Our understanding of the pathophysiology of the overactive bladder is poor. It has been proposed that localized contractions result in the abnormal stretching of bladder smooth muscle. We hypothesize that stretch regulates the cellular processes that determine tissue size. The purpose of this study was to investigate the effect of stretch on apoptosis, proliferation, cell hypertrophy, and growth factor production in human bladder smooth muscle cells in vitro. Normal human detrusor muscle was obtained from patients undergoing radical cystectomy for invasive bladder cancer, and primary cultures were established. Cells were mechanically stretched on flexible plates at a range of pressures and times. Apoptosis was assessed by propidium iodide incorporation and flow cytometry. Radiolabeled thymidine and amino acid incorporation were used to assess proliferation and cell hypertrophy. ELISA and RT-PCR were used to assess growth factor production. Mechanical stretch inhibits apoptosis in a time- and dose-dependent manner and was associated with increases in the antiapoptotic proteins heat shock protein-70 and cIAP-1. Stretch also increases smooth muscle cell proliferation and hypertrophy, but hypertrophy is the more dominant response. These changes were associated with increases in IGF-1 and basic FGF and a decrease in transforming growth factor-beta1. Mechanical stretch regulates apoptosis, proliferation, and cell hypertrophy in human bladder smooth muscle cells.

The decision to undergo DNA or protein synthesis is determined by the degree of mechanical deformation in human bladder muscle cells

OBJECTIVES

To investigate the effect of varying levels of mechanical deformation (cyclic stretch-relaxation) on protein and DNA synthesis rates in human bladder smooth muscle cells (SMCs). Cells in the bladder wall respond to outlet obstruction by increasing rates of protein synthesis ("hypertrophy") and/or DNA synthesis ("hyperplasia"); however, it is not established how these distinct processes are initiated.

METHODS

Primary cultures of human bladder SMCs were generated and maintained according to published methods. Cells were plated on type I collagen-coated elastomer-bottomed plates and subjected to cyclical stretch-relaxation (0.1 Hz) at 6%, 12%, and 20% elongation using a computer-controlled stretch-inducing device. DNA and protein synthesis rates were determined by uptake of radiolabeled thymidine and leucine, respectively. Nonstretched cells served as controls.

RESULTS

Mechanical stretch stimulated DNA synthesis in a dose and time-dependent manner with marked upregulation (4.5-fold) in response to 20% elongation. Mechanical deformation also elicited changes in protein synthesis in bladder SMCs. However, in contrast to the DNA synthesis pattern, leucine uptake over time was stimulated at 6% and 12% elongation, and no protein synthesis response was seen at 20% elongation.

CONCLUSIONS

Our findings suggest that stretch, in isolation from other potential mediators such as pressure or hypoxia, can induce either a hyperplastic or hypertrophic response in bladder SMCs and that the cells' response is dependent on the intensity of the stretch stimulus. These observations may be relevant to the process of in vivo tissue remodeling stimulated by bladder distension or contractile dysfunction.

Effect of doxazosin on rat urinary bladder function after partial outlet obstruction

Hypoxia induced by partial outlet obstruction is believed to play a major role in both the hypertrophic and degenerative effects of partial outlet obstruction. Doxazosin (dox) is a clinically effective alpha-adrenergic antagonist used in the treatment of symptomatic benign prostatic hyperplasia (BPH). Although the major therapeutic effect of the agent is believed to occur on the smooth muscle components of the prostate by reducing prostatic urethral resistance and thus improving emptying, dox may have part of its clinical action via effects mediated by other actions, including via spinal alpha-adrenergic receptors or direct effects on the bladder, possibly via inhibition of vascular alpha receptors. The specific aim of the current study was to determine whether dox pretreatment on rats affects blood flow to the bladder and reduces the level of bladder dysfunction induced by partial outlet obstruction. In part 1, eight rats were separated into two groups of four rats each. Group 1 received oral administration of dox (30 mg/kg) for 4 weeks; group 2 received vehicle (5% dimethyl sulfoxide). After 4 weeks of treatment, blood flow studies were performed using fluorescent microspheres and the bladders excised, frozen, and submitted to Interactive Medical Technologies (IMT) for blood flow analysis. In part 2, 32 adult male rats were separated into four groups of eight rats each. Groups 1 and 2 received oral administration of dox (30 mg/kg) for 4 weeks, groups 3 and 4 received vehicle (5% dimethyl sulfoxide). At 4 weeks, the rats in groups 1 and 3 received partial outlet obstructions and treatment continued for an additional 2 weeks. After 6 weeks of treatment (total), each rat was anesthetized, the bladder excised, weighed, and isolated strips mounted and contractility studies performed. 1) Four weeks pretreatment of rats with dox increased blood flow to the bladder in both the control and obstructed groups. 2) Partial outlet obstruction induced a mild decrease in blood flow. 3) The magnitude of the increased bladder weight in the vehicle-treated obstructed group was significantly greater than in the dox-treated obstructed group. 4) Partial outlet obstruction resulted in significant decreases in the contractile response to field stimulation in both treated and non-treated rats. The magnitude of the decreased response was significantly greater in the non-treated rats. 5) The response to potassium chloride was significantly reduced by partial outlet obstruction in the vehicle-treated group but not in the dox-treated group. 6) The time to maximal tension was significantly increased in response to carbachol, adenosine triphosphate, and potassium chloride. However, the magnitude of the increase was significantly greater for the vehicle-treated obstructed groups stimulated by potassium chloride than for the dox-treated groups. Dox treatment of rats increased blood flow to the bladder and reduced the severity of the response to partial outlet obstruction. These beneficial effects would be due to pharmacological effects on alpha-adrenergic systems outside those present in the prostate. These include effects on blood flow to the bladder, effects on the micturition centers of the central nervous system, spinal reflexes, and alpha-adrenergic receptors in the urethra and bladder.

Extracellular matrix gene responses in a novel ex vivo model of bladder stretch injury

PURPOSE

Congenital bladder outlet obstruction from either mechanical or functional causes often results in clinical bladder fibrosis. We tested the hypothesis that early molecular changes relevant to fibrosis occur in response to stretch injury of the bladder wall and that specific extracellular matrix receptors mediate some of these responses. Furthermore, we introduce a novel ex vivo model of bladder injury which has advantages over previously described in vivo bladder outlet obstruction models by uniquely interrogating molecular responses to bladder distention.

MATERIALS AND METHODS

The bladders of Sprague Dawley rats were hydrodistended transurethrally, the ureters and bladder neck were ligated, and the whole bladder was excised and incubated in culture medium in the distended state. At fixed time-points control and stretch bladders were snap frozen, RNA was extracted, and semiquantitative reverse transcription polymerase chain reaction for collagens I, III and XII, and RHAMM (receptor for hyaluronic acid) messenger (m) RNA was performed to establish trends in stretch related gene expression. Bladder specimens were also subjected to routine histological evaluation.

RESULTS

An average 3-fold reduction in collagen I mRNA expression was seen with 8 hours of static stretch (p <0.05). Bladder stretch increased collagen III mRNA levels approximately 2.5-fold (p <0.05). Whole bladder collagen XII and RHAMM mRNA were elevated as much as 5-fold (p <0.05) with stretch. Blocking RHAMM function significantly attenuated these matrix gene responses (p = 0.01 to 0.005).

CONCLUSIONS

The ex vivo model of whole bladder stretch is viable and easily reproducible for the study of molecular pathophysiological mechanisms contributing to maladaptive bladder disease. Furthermore, collagen gene transcription is revealed to be rapidly responsive to stretch injury of the bladder. Intact RHAMM receptor function is involved in these responses. Elucidation of the intermediate steps in this response to injury may allow for the development of novel therapeutic strategies which may prevent pathological matrix remodeling seen in clinical bladder disease.

Extracellular matrix gene responses in a novel ex vivo model of bladder stretch injury

PURPOSE

Congenital bladder outlet obstruction from either mechanical or functional causes often results in clinical bladder fibrosis. We tested the hypothesis that early molecular changes relevant to fibrosis occur in response to stretch injury of the bladder wall and that specific extracellular matrix receptors mediate some of these responses. Furthermore, we introduce a novel ex vivo model of bladder injury which has advantages over previously described in vivo bladder outlet obstruction models by uniquely interrogating molecular responses to bladder distention.

MATERIALS AND METHODS

The bladders of Sprague Dawley rats were hydrodistended transurethrally, the ureters and bladder neck were ligated, and the whole bladder was excised and incubated in culture medium in the distended state. At fixed time-points control and stretch bladders were snap frozen, RNA was extracted, and semiquantitative reverse transcription polymerase chain reaction for collagens I, III and XII, and RHAMM (receptor for hyaluronic acid) messenger (m) RNA was performed to establish trends in stretch related gene expression. Bladder specimens were also subjected to routine histological evaluation.

RESULTS

An average 3-fold reduction in collagen I mRNA expression was seen with 8 hours of static stretch (p <0.05). Bladder stretch increased collagen III mRNA levels approximately 2.5-fold (p <0.05). Whole bladder collagen XII and RHAMM mRNA were elevated as much as 5-fold (p <0.05) with stretch. Blocking RHAMM function significantly attenuated these matrix gene responses (p = 0.01 to 0.005).

CONCLUSIONS

The ex vivo model of whole bladder stretch is viable and easily reproducible for the study of molecular pathophysiological mechanisms contributing to maladaptive bladder disease. Furthermore, collagen gene transcription is revealed to be rapidly responsive to stretch injury of the bladder. Intact RHAMM receptor function is involved in these responses. Elucidation of the intermediate steps in this response to injury may allow for the development of novel therapeutic strategies which may prevent pathological matrix remodeling seen in clinical bladder disease.

Activation of the transcription factors nuclear factor-kappaB and activator protein-1 in bladder smooth muscle exposed to outlet obstruction and mechanical stretching

PURPOSE

Transcriptional control of bladder genes in response to outlet obstruction, growth factors and mechanical force is poorly understood. We analyzed the effects of bladder obstruction, mechanical stretching and platelet derived growth factor on the activation of the major growth controlling transcription factors nuclear factor-kappaB and activator protein-1.

MATERIALS AND METHODS

Complete outlet obstruction was created in female rats by proximal urethral ligation and bladders were harvested 3, 6 and 24 hours later, respectively. Bladder cells were grown in culture and stimulated with 10 ng./ml. platelet derived growth factor or 10 cycles per minute of mechanical stretching for 0.5 to 4 hours. Nuclear proteins were high salt extracted and incubated with 32phosphorus double strand oligonucleotides containing a consensus binding sequence for activator protein-1 or nuclear factor-kappaB. The resulting DNA protein complexes were analyzed by electrophoretic mobility shift assay.

RESULTS

Nuclear extract isolated from obstructed bladders showed intense activator protein-1 binding activity 3, 6 and 24 hours after obstruction as well as increased nuclear factor-kappaB binding activity after 6 and 24 hours. Binding activity was absent or minimal in sham operated rats. Cultured cells exposed to mechanical stretching for 2 and 4 hours showed increased activator protein-1 and nuclear factor-kappaB DNA binding compared with unstretched cells. Likewise stimulation with platelet derived growth factor caused a consistent increase in activator protein-1 and nuclear factor-kappaB binding activity. The binding of nuclear proteins was abolished by a 40-fold excess of an unlabeled specific oligonucleotide but not by excess irrelevant oligonucleotide. Thus, the assays were specific for the factors involved.

CONCLUSIONS

Bladder obstruction and mechanical stretching cause the formation of activator protein-1 and nuclear factor-kappaB DNA complexes, consistent with a role of these transcription factors in the control of hypertrophy associated gene activation.

Changes in detrusor and urinary growth factors according to detrusor function after partial bladder outlet obstruction in the rat

OBJECTIVES

To investigate the changes in detrusor and urinary growth factors according to detrusor function after partial bladder outlet obstruction in the rat. Growth factors have been reported to play a role in the remodeling of the bladder after obstruction.

METHODS

Female rats (n = 40) were used and divided into three groups: sham-operated control, 2-week mild obstruction, and 2-week severe obstruction. The voided urine was collected and the detrusor contractility to electrical stimulation recorded. mRNA expression and the urinary concentration of transforming growth factor beta-1 (TGF-beta1) and basic fibroblast growth factor (bFGF) were analyzed.

RESULTS

The contractile response to electrical stimulation was increased in the mild obstruction group (P <0.05) but decreased in the severe obstruction group (P <0.05). The detrusor mRNA expression of TGF-beta1 in the mild obstruction group was not different from that in the control group. However, in the severe obstruction group, the mRNA expression of TGF-beta1 increased. The detrusor mRNA expression of bFGF was gradually increased in the mild and severe obstruction groups. The urinary concentration of TGF-beta1 in the mild obstruction group was not significantly different from that in the control group. However, in the severe obstruction group, the concentration of TGF-beta1 was significantly increased (P <0.05). The concentration of urinary bFGF was too small to compare the results in each group.

CONCLUSIONS

Growth factors such as TGF-beta1 and bFGF change in mRNA expression according to bladder function, and urinary TGF-beta1 reflects the change of detrusor mRNA. Thus, changes in TGF-beta1 may be a marker to evaluate detrusor function.

Acute increase in blood flow to the rat bladder subsequent to partial bladder outlet obstruction

Partial obstruction of the rat bladder outlet initiates a multi-step process during which the bladder progressively loses its functional ability. The first step in this progression is bladder hypertrophy; the organ dramatically increases in size and weight to compensate for the effects of obstruction. Unoperated female rats, age-matched, sham-obstructed rats, and rats that received a partial bladder outlet obstruction were studied. During the first 24 hours after partial bladder outlet obstruction, relative bladder blood flow was measured using a fluorescent microsphere infusion technique and laser Doppler imaging. Nitric oxide synthase (NOS) activities of control and obstructed rat bladder tissues were determined using an enzymatic assay that measures the conversion of (3)H-L-arginine to (3)H-L-citrulline. Using the microsphere infusion technique, a significant increase in blood flow to the obstructed rat bladder was observed during the first 24 hours after partial bladder outlet obstruction. Relative bladder blood flow increased approximately sixfold at 4 and 6 hours post-obstruction and remained elevated through 24 hours of obstruction. Sham operations (evaluated after 6 hours after surgery) resulted in a minor increase in blood flow that did not reach statistical significance. Relative blood flow to the spleen, measured in the same rats, was not significantly changed. Laser Doppler measurements also identified a significant increase in rat bladder blood flow after outlet obstruction and showed that increased blood flow could be detected as early as 1 hour post-obstruction. Interestingly, despite the significant differences in bladder blood flow between control and early post-obstructed rat bladders, NOS activities of control and obstructed rat bladders were comparable. The increase in bladder blood flow precedes the urothelial, fibroblast and smooth muscle cell hyperplasia, and the smooth muscle hypertrophy that occurs after obstruction. We propose that, in response to surgical induction of partial outlet obstruction, acute up-regulation of bladder blood flow may be an initiating factor for subsequent bladder cell proliferation and smooth muscle hypertrophy. Neurourol. Urodynam. 19:195-208, 2000.

Urothelium-derived inhibitory factor(s) influences on detrusor muscle contractility in vitro

The function of the bladder urothelium in modulating contractile responses of the underlying detrusor smooth muscle to muscarinic stimulation has been examined in the pig bladder. Saturation curves for [3H]-QNB binding demonstrated a greater muscarinic receptor density in the urothelium than in the detrusor smooth muscle. The presence of an intact urothelium on isolated bladder strips inhibited contractions induced by carbachol but not KCl. Contractions of a urothelium-denuded muscle strip were inhibited in the presence of a second bladder strip with an intact urothelium, but not if the second strip was denuded. The urothelium-induced inhibition of contractions was not prevented in the presence of L-NOARG, methylene blue, indomethacin, propranolol, suramin, TEA or apamin. The data suggest the presence of a diffusable, urothelium-derived inhibitory factor, which could not be identified but appears to be neither nitric oxide, a cyclo-oxygenase product, a catecholamine, adenosine, GABA nor an EDHF sensitive to apamin.

Structural changes in the rat bladder after acute outlet obstruction

The urinary bladder of adult female rats was subjected to complete outlet obstruction for periods of up to 24 h. Within 2 h the obstruction led to a rise in intravesical pressure to about 80 mmH2O. Subsequently, the pressure remained high but declined slightly. After 24 h of complete obstruction the bladder was maximally distended, but its volume was similar to that of a control bladder fully distended, indicating that overstretch (or overdistension) occurs only to a very limited degree. After 6 h of obstruction there was congestion of all the intramural blood vessels and extravasation of red blood cells from some vessels of the mucosa. At 12 h and 24 h the extravasation was very substantial and there was also infiltration of erythrocytes in the muscle layer. Ultrastructurally, there were several damaged nerve endings (but no changes in the nerve trunks) and, occasionally, damaged muscle cells. Removal of the obstruction after 24 h was followed by resorption of the extravasate, partly by phagocytosis by muscle cells, a process which lasted 4-6 days, and by 7 days damaged varicosities and muscle cells became uncommon. We conclude that the changes observed in the bladder wall following complete obstruction are caused more by haemorrhage and ischaemia than by overstretch and that the changes are reversed when outlet conditions are normalized.

The hyaluronic acid receptor RHAMM is induced by stretch injury of rat bladder in vivo and influences smooth muscle cell contraction in vitro [corrected]

PURPOSE

Loss of bladder compliance from hypercontractility and fibrosis may represent an injury response to excessive intravesical pressure. Together, interactions between cell and extracellular matrix components regulate cell response to injury and extracellular matrix remodeling. The receptor for hyaluronic acid mediated motility (RHAMM) is a recently described hyaluronic acid binding protein known to influence multiple types of cell extracellular matrix interaction in development, injury and cancer. We evaluate the role of RHAMM in mediating early events in bladder stretch injury.

MATERIALS AND METHODS

An acute stretch injury model was used. The rat bladder was injured by hydrodistention inducing gross hematuria. Tissues were analyzed for temporal and spatial expression of RHAMM in the mucosa and detrusor regions by immunostaining, western and reverse transcriptase polymerase chain reaction analyses. The contractile activity of smooth muscle cell primary cultures was analyzed using a gel contraction assay in the presence of peptide fragments known to block RHAMM function.

RESULTS

Acute hydrodistention caused immediate and significant injury to the bladder, with fracturing of smooth muscle cell bundles, edema and hemorrhage. RHAMM immunolocalized to the mucosa and detrusor within 2 hours of injury, peaking by 5 to 10 hours. A shift from low molecular weight (55 kD.) to high (120 kD.) receptor isoforms was prominent during the peak expression period noted by immunolocalization. RHAMM messenger ribonucleic acid increased only slightly (40%) by 5 hours after injury. Smooth muscle cell primary cultures actively initiated and maintained the contraction of collagen gels by more than 75% of baseline in vitro. Blocking RHAMM function significantly inhibited the ability to less than 25% of smooth muscle cells to contract the gels in vitro.

CONCLUSIONS

Increased expression of RHAMM is an early event precipitated by stretch injury to the bladder. Since extracellular matrix hyaluronic acid is found early in tissue repair responses, its receptor RHAMM may be mediating initial bladder responses to stretch injury, some of which (contraction) may be experimentally blocked in vitro. Since the receptor directly regulates protein kinase signaling which in turn mediates smooth muscle cell contraction and collagen synthesis, further studies of RHAMM function in bladder pathology are warranted.

Submucosal mesenchymal tumors of the mouse urinary bladder

A unique morphologic change has been described in the submucosa of the urinary bladder of mice since the 1950s. These lesions, variously referred to as vegetative changes, reactive lesions, submucosal granulomas, leiomyosarcomas, atypical hemangiosarcomas, or submucosal mesenchymal tumors have been considered rare and of questionable etiology. Although the morphologic criteria are fairly well defined, the pathobiology of the lesion is not well characterized and the previously listed nomenclature reflects this uncertainty. The lesion may not be limited to the urinary bladder, the cell of origin is controversial, the biology is unknown, and whether the lesion is granulomatous, hypertrophy, hyperplasia, metaplasia, or a benign or malignant neoplasm is not well defined. Data compiled from multiple sources are discussed to review the strain of mouse most often affected, sex, age at diagnosis, anatomic location, incidence, descriptive morphology, immunohistochemical staining results, and other features of the submucosal mesenchymal tumor of the mouse urinary bladder. Presented are suggested terminology for the lesion, submucosal mesenchymal tumor of the mouse urinary bladder; the relevance of the tumor for human risk assessment; and discussion of the possible histogenesis of this lesion from primitive mesenchymal cells of the submucosa (lamina propria) of the urinary bladder of mice.

Smooth and striated muscle development in the intrinsic urethral sphincter

PURPOSE

The intrinsic urethral sphincter is composed of adjacent striated and smooth muscle. We studied the sequential expression of smooth and striated muscle proteins to gain insight into the ontogeny of intrinsic sphincter development.

MATERIALS AND METHODS

The intrinsic urethral sphincters of timed Fischer 344 rat embryos at 14, 16 and 18 days of gestation, neonates on postnatal day 1 and adult animals were examined. Serial sections of the urethra and adjacent levator ani muscles were studied histologically with hematoxylin and eosin, anti-alpha-smooth muscle actin, anti-alpha-sarcomeric actin and antistriated muscle myosin heavy chain antibodies.

RESULTS

The intrinsic urethral sphincter was identified within the periurethral mesenchyma as early as day 14 of gestation. Although striated myotubules were identified within the urethra by hematoxylin and eosin staining starting on postnatal day 1, striated muscle myosin heavy chain protein was absent in the embryonic and neonatal development of the sphincter, and it was expressed only in the mature myotubule of adults. alpha-Smooth muscle actin was expressed throughout the urethral sphincter of embryonic and neonatal animals. In adults alpha-smooth muscle actin was confined to the smooth muscle component of the urethra. Co-expression of alpha-smooth and alpha-sarcomeric muscle actin by the striated sphincter myotubule was noted only in neonates.

CONCLUSIONS

Development of the intrinsic urethral sphincter is characterized by sequential expression of well characterized muscle marker proteins. The co-expression of smooth and striated muscle markers by developing sphincter myotubule suggests the possibility that trans-differentiation of smooth to striated muscle occurs in the developing genitourinary tract.

The effect of angiotensin converting enzyme inhibition and angiotensin II receptor antagonism on obstructed rat bladder

PURPOSE

Others have demonstrated that inhibition of angiotensin II production partially ameliorates obstructive changes in the neonatal rabbit bladder. We examined the effect of angiotensin II converting enzyme inhibition and receptor antagonism on the obstructed rat bladder.

MATERIALS AND METHODS

Three groups of animals were investigated. Partial bladder neck obstruction was created in 23 rats by placing a 2-zero silk ligature around the vesicourethral junction. Eight rats were given untreated tap water, 9 were given water supplemented with 50 mg./kg. of the angiotensin-converting enzyme inhibitor captopril and 6 were given water with 30 mg./kg. of the angiotensin II subtype AT1 receptor antagonist losartan potassium. Eight unobstructed rats served as controls. After 2 weeks of partial outlet obstruction the animals were sacrificed and bladders were harvested. Routine histological evaluation and assays for total protein, deoxyribonucleic acid and collagen content were performed.

RESULTS

Histological evaluation revealed that administration of captopril or losartan potassium resulted in a mild decrease in the degree of obstructive bladder changes. Biochemically neither captopril nor losartan potassium caused a significant decrease in the amount of total deoxyribonucleic acid, protein or collagen content per bladder compared to untreated obstructed bladders.

CONCLUSIONS

In contrast to previous studies in neonatal rabbits, neither captopril nor losartan potassium significantly ameliorated the histological or biochemical features of partial bladder outlet obstruction in the rat. Further investigation is necessary into species specific differences to understand better the role that angiotensin II may have in mediating the bladder changes of experimentally induced obstruction.

Mesenchymal-epithelial interactions in the bladder

During bladder development, undifferentiated mesenchymal and epithelial cells undergo an orderly sequence of differentiation defined by the expression of smooth-muscle (alpha-actin, myosin, vinculin, desmin, vimentin, and laminin) and epithelial (cytokeratins 5, 7, 8, 14, 18 and 19) protein markers. This process requires mesenchymal-epithelial interactions with bladder epithelium (urothelium) necessary for the differentiation of bladder smooth muscle. Peptide growth factors such as keratinocyte growth factor (KGF) and transforming growth factors (TGF) alpha and beta are likely candidates as mediators of these mesenchymal-epithelial interactions. Transcripts for KGF, TGF alpha, and TGF beta are regulated during bladder development and during smooth-muscle hypertrophy secondary to bladder-outlet obstruction. Finally, two experimental bladder models--(1) partial outlet obstruction and (2) regeneration of bladder smooth muscle into an acellular tissue matrix--are described in the context of mesenchymal-epithelial interactions in the bladder.

Assessment of stress gene mRNAs (HSP-27, 60 and 70) in obstructed rabbit urinary bladder using a semi-quantitative RT-PCR method

Stress proteins (HSPs) participate in the cellular response to various stresses including hyperthermia, hypoxia and injury. A previous work using northern blot analysis demonstrated increased expression of stress protein 70 (HSP-70) in rabbit bladder tissue subjected to partial outlet obstruction. In order to determine if the increased expression was specific for HSP-70 or, alternatively, indicated a generalized stress protein response, a modified quantitative RT-PCR technique was used to quantitate HSP mRNAs (HSP-27, 60, and 70) in normal and obstructed rabbit urinary bladder tissues. The results show the following: 1) The modified semi-quantitative RT-PCR is a sensitive and reproducible technique for detecting mRNA in bladder tissue. 2) Constitutive levels of HSP-27, HSP-60, and HSP-70 mRNAs were detected in control bladder tissues; the relative signal intensity was highest for HSP-70 and lowest for HSP-27. 3) A transient increase in HSP mRNAs was observed after obstruction; the mRNAs of HSP-27, 60 and 70 increased 4.3-, 5.6-, and 2.4-fold, respectively, at 24 h following obstruction, then gradually returned to control levels by the end of one week post-obstruction and remained stable up to 14 days post-obstruction. These data indicate that the modified quantitative RT-PCR is a useful technique for detecting mRNA in bladder tissue; the stress response which occurs in rabbit urinary bladder tissue following partial outlet obstruction is a general phenomenon.

Effects of diuresis on micturition

Micturition can be characterized experimentally by monitoring both the frequency and volume of micturition. Previous studies demonstrated that the functional capacity of the rat and rabbit bladder, as determined by cystometry, is approximately equal to the maximal single micturition volume as recorded over a 24 hour period. Studies in many laboratories have demonstrated that chronic increases in diuresis induce increases in micturition frequency and capacity, and an increase in bladder mass. The current study compares the temporal relationship among these parameters in three models of diuresis: streptozotocin-induced diabetes in rats, sucrose-induced diuresis in rats, and furosemide-induced diuresis in rabbits. In both sucrose diuresis in rats and furosemide diuresis in rabbits there were immediate increases in both the frequency and volume of micturition. The magnitude of the increases in micturition frequency and micturition volume paralleled the increase in the total volume of urine excreted. Bladder mass increased progressively over the time course of the study. Streptozotocin-induced diabetes resulted in a more gradual (but parallel) increase in micturition frequency and volume, and again a more gradual increase in bladder mass. These studies demonstrate that functional bladder capacity is increased immediately upon the initiation of diuresis with sucrose or furosemide, as is the frequency of micturition. This indicates that functional bladder capacity is probably under neuronal regulation and the change in capacity is not a function of the increased bladder mass which occurs at a later time period.(ABSTRACT TRUNCATED AT 250 WORDS)

Update on bladder smooth-muscle physiology

The urinary bladder responds to distension induced by a number of different stresses with rapid and substantial increases in bladder mass and concomitant alterations in the contractile responses to neuronal stimulation, pharmacological simulation by autonomic agonists, and membrane depolarization. Furosemide, sucrose, or diabetes-induced diuresis, as well as outlet obstruction and overdistension all produce similar effects on the bladder. Accompanying the increases in bladder mass and contractile changes are increases in DNA synthesis and [3H]-thymidine uptake. Autoradiographic studies have localized the increased DNA synthesis following bladder distension initially to the urothelium, followed by slower increases in labelling of the lamina propria and extramural connective tissue. The net result of these compartmental differences in DNA synthesis is a reorganization of the structural relationships between smooth-muscle cells, the connective-tissue matrix, and the extrinsic connective-tissue lamina. This may contribute to the functional changes which occur after severe overdistension. Increases in the expression of heat-shock protein-70, basic fibroblast growth factor, N-ras, and c-myc, and decreases in transforming growth factor-beta occurred acutely after obstruction, suggesting that these changes may play a role in obstruction-induced bladder hypertrophy. Removal of the obstruction induces apoptosis of urothelial and connective tissue elements in the bladder, accompanied by increases in transforming growth factor-beta and decreases in basic fibroblast growth factor genes, and a reversal of the bladder dysfunction. Therefore the bladder hyperplasia after outlet obstruction and the regression following removal of the obstruction seem to be directly opposing processes governed by gene expression.