Mechanisms of Disease: specialized interstitial cells of the urinary tract--an assessment of current knowledge

Insights on Platelet-Derived Growth Factor Receptor α-Positive Interstitial Cells in the Male Reproductive Tract

Male infertility is a significant factor in approximately half of all infertility cases and is marked by a decreased sperm count and motility. A decreased sperm count is caused by not only a decreased production of sperm but also decreased numbers successfully passing through the male reproductive tract. Smooth muscle movement may play an important role in sperm transport in the male reproductive tract; thus, understanding the mechanism of this movement is necessary to elucidate the cause of sperm transport disorder. Recent studies have highlighted the presence of platelet-derived growth factor receptor α (PDGFRα)-positive interstitial cells (PICs) in various smooth muscle organs. Although research is ongoing, PICs in the male reproductive tract may be involved in the regulation of smooth muscle movement, as they are in other smooth muscle organs. This review summarizes the findings to date on PICs in male reproductive organs. Further exploration of the structural, functional, and molecular characteristics of PICs could provide valuable insights into the pathogenesis of male infertility and potentially lead to new therapeutic approaches.

Insight into SLC9A3 deficiency-mediated micturition dysfunction caused by electrolyte imbalance

BACKGROUND

Solute carrier family nine isoform 3 (SLC9A3) is an Na⁺/H⁺ exchanger that regulates Ca₂⁺ homeostasis. SLC9A3 is largely involved in the transepithelial absorption of Na⁺/H⁺ and frequently functions in pair with a Cl^-/HCO3^- exchanger.

OBJECTIVE

To investigate the impact and pathophysiological mechanisms of long-term SLC9A3 deficiency on lower urinary tract symptoms (LUTS) in a mouse model MATERIALS AND METHODS: Slc9a3 knockout and wild-type mice (average >6 months) were used. The effects of SLC9A3 depletion on bladder and urethral functions and effectiveness of voiding were assessed using a cystometrogram (CMG). Histology, blood electrolytes, and gene expression were also analyzed.

RESULTS

The SLC9A3-deficient mice had smaller gross bladders than the wild-type mice. The CMG analysis revealed normal peak micturition pressure, higher threshold pressure, short intercontraction interval, less voided volume, and poor compliance in the SLC9A3-deficient mice, similar to clinical LUTS. Histological analysis revealed loose detrusor muscle and loss of transformability of the urothelium in the SLC9A3-deficient mice. Masson's trichrome analysis revealed severe collagen deposition in the detrusor muscle. Immunofluorescence staining also demonstrated a significant decrease in cytokeratins 5 and 20. Gene and protein expression analyses confirmed that SLC9A3 does not act directly on bladder tissue. Homeostasis was correlated with bladder dysfunction in the SLC9A3-deficient mice.

DISCUSSION

Fibrosis and collagen deposition in the bladder of the SLC9A3-deficient mice is due to bladder inflammation because of decreased blood flow and deregulated systemic homeostasis. Long-term SLC9A3 depletion causes progressive bladder dysfunction, similar to human LUTS.

CONCLUSION

Electrolyte imbalance causes SLC9A3 deficiency-mediated progressive micturition dysfunction.

The influence of interstitial cells of Cajal density in the outcomes of pyeloplasty in adults: A prospective analysis

Purpose:

To evaluate if the density of interstitial cells of Cajal (ICC) in the ureteropelvic junction (UPJ) influences the outcomes of pyeloplasty in adults.

Methods:

Twenty-three patients with the diagnosis of ureteropelvic junction obstruction (UPJO) that underwent laparoscopic dismembered pyeloplasty were included. ICC density was measured using immunohistochemistry reaction for c-KIT expression in the resected UPJ segment. Pyeloplasty outcome was evaluated by patient self-report pain, urinary outflow using DTPA renogram and hydronephrosis assessment using ultrasound (US) at 12 months of follow-up. A logistic regression analysis was performed to assess the association of pyeloplasty outcomes and ICC density.

Results:

Low, moderate, and high ICC density were present in 17.4%, 30.4%, and 52.2% of the patients, respectively. Complete pain resolution was observed in 100%, 85.7%, and 75% of patients with low, moderate and high ICC density, respectively ( p = 0.791). DTPA renogram improved in 75%, 85.7%, and 91.7% of patients with low, moderate and high ICC density, respectively ( p = 0.739). Hydronephrosis improved in 25%, 85.7%, and 91.7% of patients with low, moderate and high ICC density, respectively ( p = 0.032).

Conclusions:

Patients with high ICC density have a significant amelioration of hydronephrosis after pyeloplasty. However, ICC density is not associated with functional outcomes.

The potential of Quercetin to protect against loperamide-induced constipation in rats

Constipation is the most common gastrointestinal complaint all over the world, and it is a risk factor of colorectal cancer. In this study, the protective of Quercetin against loperamide-induced constipation and its potential mechanism in a rat model were investigated. Results showed that Quercetin at 25 mg/kg and 50 mg/kg could significantly (p < .05) increase the intestinal transit rate, motilin, gastrin, substance P levels, and concentration of short-chain fatty acids (SCFAs), reduce the somatostatin levels, and improve the gastrointestinal peristalsis of rats. In addition, the expression levels of enteric nerve-related factors, glial cell line-derived neurotrophic factor (GDNF), transient receptor potential vanilloid 1 (TRPV1), nitric oxide synthase (NOS), c-Kit, stem cell factor (SCF), and aquaporin 3 (AQP3) were examined by RT-qPCR and/or Western blot analysis. The results suggest that Quercetin relieves loperamide-induced constipation by increasing the levels of interstitial cells of Cajal markers (c-Kit and SCF), as well as AQP3. In conclusion, the present study suggested that Quercetin exerted a protective effect against loperamide-induced constipation, which may be associated with its role in regulation of multiple signal pathways.

Long-Term Administration of Anthraquinone Rhein on Induction of Constipation in Sprague-Dawley Rats via SCF/c-Kit Signaling Pathways

Background and Study Aims. It has been shown that abuse of laxatives is becoming a serious problem; therefore, a comprehensive understanding of its effect and possible mechanism on colon motility is essential to select effective treatments and avoid their abuse. Herein, we aimed to investigate the long-term stimulation of rhein on induction of constipation in rats and its underlying mechanisms. Materials and Methods. After establishing rat models of constipation, the rats were randomly divided into two equal subgroups and administered daily with normal saline (model control group) or 10 ml/kg PEG4,000 (PEG-treated group). Simultaneously, normal Sprague-Dawley (SD) rats were administered with normal saline (normal group). Physiological and fecal parameters were calculated, and intestinal transmission function was evaluated. After scarification, colonic tissues were freshly prepared for histological localization detected by immunohistochemical analysis and for the expression of stem cell factor (SCF) and c-kit proteins determined by western blot assay. Results. Following the initiation of rhein-induced rat constipation, body weight was lost slightly, the first time of black stool discharge was obviously longer, and the fecal moisture and number of fecal pellets decreased distinctly as compared with normal group. A decreased expression of SCF and c-kit was detected in model control group in comparison with normal group. Notably, compared with model control group, neither the alterations of fecal parameters and intestinal transmission function were effectively restored, nor the expression of SCF and c-kit was markedly elevated after administration of PEG4,000 for 30 d. Conclusion. Long-term stimulation of rhein can develop the constipation via SCF/c-kit signaling pathway, yet the symptoms of constipation and colon power cannot be alleviated or restored by PEG4,000. Collectively, these findings strongly suggest that long-term use of anthraquinone laxatives should be avoided for clinical treatment of constipation.

Effects of Lactobacillus plantarum CQPC01-fermented soybean milk on activated carbon-induced constipation through its antioxidant activity in mice

A newly found strain, Lactobacillus plantarum CQPC01 (LP-CQPC01), was used for soybean milk fermentation, and its effects against constipation were determined. LP-CQPC01-FSM (LP-CQPC01-fermented soybean milk) was found to have six kinds of soybean isoflavones; the isoflavones of LP-CQPC01-FSM were more than those of Lactobacillus bulgaricus-fermented soybean milk (LB-FSM) and unfermented soybean milk (U-FSM). Animal experiment showed that the MTL, Gas, ET, AchE, SP, VIP, and GSH levels in the constipated mice were increased; however, the SS, MPO, NO, and MDA levels in the constipated mice were reduced by soybean milk treatment. Further, LP-CQPC01-FSM increased the mRNA and protein expression of Cu/Zn-SOD, Mn-SOD, CAT, c-Kit, SCF, and GDNF and reduced the expression of TRPV1 and NOS relative to those of the mice with untreated constipation. LP-CQPC01 could be used as a new starter to produce high-quality soybean milk, which might be used as a functional drink.

Lactobacillus plantarum YS-3 Prevents Activated Carbon-Induced Constipation in Mice

The aim of this study was to determine the effects of Lactobacillus plantarum YS-3 (LP-YS3) on activated carbon-induced constipation in Kunming mice. The results of the experiment show that the antigastric acid activity and bile salt tolerance of LP-YS3 were stronger than those of Lactobacillus bulgaricus (LB). LP-YS3 inhibited loss of body weight caused by constipation and further reductions in fecal weight, particle number, and water content in mice. Moreover, LP-YS3 elevated the gastrointestinal transit rate and reduced the time required for initial black stool defecation. LP-YS3 also elevated motilin (MTL), endothelin (ET), acetylcholinesterase (AChE), substance P (SP), and VIP serum levels and reduced somatostatin (SS) levels in constipated mice. Hematoxylin-eosin (H&E) staining revealed that high concentration of LP-YS3 reduced the incidence of injuries to small intestine villi and the intestinal wall compared to carbon-induced constipation groups. Reverse transcription-polymerase chain reaction and western blot experiments demonstrated that LP-YS3 upregulated c-Kit, stem cell factor, and glial cell line-derived neurotrophic factor mRNA and protein expression and downregulated transient receptor potential vanilloid 1 and nitric oxide synthase expression in small intestine tissue from constipated mice. In conclusion, high concentrations of LP-YS3 had stronger and more beneficial effects than LB. Based on these results, we conclude that LP-YS3 can effectively inhibit constipation.

Preventative effects of fermented Chimonobambusa quadrangularis shoot on activated carbon-induced constipation

The present study aimed to determine the preventative effects of fermented Chimonobambusa quadrangularis shoot (FCQS) on activated carbon constipation in Kun Ming mice. FCQS has a more loose fiber tissue structure than unfermented fresh C. quadrangularis shoot (CQS), which is preferable for relieving constipation. In mice fed with FCQS for 9 days the time from consumption to their first black stool defecation (117 min) was shorter than the control group (192 min) and the CQS group (148 min); however, it was longer than the normal (85 min) and bisacodyl treatment (99 min) groups. The gastrointestinal transit of the FCQS group (73.8%) was increased, as compared with the control (37.9%) and CQS (61.7%) groups; however, it was decreased as compared with the normal (100%) and bisacodyl (88.3%) groups. By observing the hemotoxylin and eosin-stained section of mice intestine, it was demonstrated that FCQS reduced injury to the intestinal tract resulting from constipation and alleviated the damage caused to the intestinal villi over the effects observed in the CQS group. Furthermore, FCQS was also able to increase the serum levels of motilin, endothelin-1, vasoactive intestinal peptide and acetylcholinesterase compared with the control group. c-Kit, stem cell factor (SCF), glial cell-derived neurotrophic factor (GDNF) mRNA and protein expression levels in the small intestinal cells of FCQS-fed mice were increased, as compared with CQS-fed mice. Transient receptor potential cation channel subfamily V member 1 (TRPV1) and nitric oxide synthase (NOS) expression levels of small intestinal cells of FCQS-fed mice were reduced, as compared with CQS-fed mice. These findings demonstrated that FCQS may induce improved preventative effects on constipation, compared with CQS.

Spontaneous Contractile Activity of the Detrusor Muscle and Its Role in the Pathogenesis of Overactive Bladder Syndrome

There is accumulated evidence that spontaneous contractions (SCs) in the bladder wall are associated with afferent nerve firing in the bladder. The role of the urothelium in bladder sensation might be restricted to pathological conditions, such as interstitial cystitis or chemical cystitis in which the release of urothelium-derived mediators such as adenosine triphosphate is increased. Recent publications imply that SCs in bladders with detrusor overactivity due to spinal cord injury or bladder outlet obstruction are modulated by intracellular signal transduction mechanisms such as the RhoA/Rho-kinase pathway, denervation-supersensitivity to acetylcholine, changes in ion channel activity, enhanced gap-junctional intercellular communication, alterations in interstitial cells of Cajal, the actions of local mediators in the detrusor and the influence of the urothelium. Spontaneous contractions and possible consequent afferent nerve firing might participate in the generation of overactive bladder syndrome.

Ion channels of the mammalian urethra

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

Therapeutic effects of Lactobacillus casei Qian treatment in activated carbon-induced constipated mice

In the present study, the therapeutic effects of Lactobacillus casei Qian (LC-Qian), the key microorganism in Tibetan yak yoghurt, on activated carbon-induced constipation were determined in vivo. ICR mice were treated with LC-Qian for nine days by oral administration. The body weight, defecation status, gastrointestinal transit and defecation time of mice were assessed, and the serum levels of motilin (MTL), gastrin (Gas), endothelin (ET), somatostatin (SS), acetylcholinesterase (AChE), substance P (SP) and vasoactive intestinal peptide (VIP) were further evaluated. Bisacodyl was used as the positive control. The time until the first black stool defecation following carbon intake of the normal, control, 100 mg/kg bisacodyl-treated, Lactobacillus bulgaricus (LB)-treated, LC-Qian (L)-and LC-Qian (H)-treated mice was 93, 231, 121, 194, 172 and 157 min, respectively. Following treatment with LC-Qian, the gastrointestinal transit was increased to 52.4% [LC-Qian (L)] and 65.8% [LC-Qian (H)], while that in the group treated with the common lactic acid bacteria of LB was 40.3%. The MTL, Gas, ET, AChE, SP and VIP serum levels were significantly increased and levels of SS were reduced in mice following LC-Qian treatment compared with those in the control mice (P<0.05). Reverse transcription quantitative polymerase chain reaction indicated that LC-Qian raised the c-Kit, GDNF as well as SCF mRNA expression levels and reduced the TRPV1 and NOS expression levels in tissue of the small intestine in mice. These results suggested that lactic acid bacteria prevent constipation in mice, among which LC-Qian was the most effective.

The urothelium: anatomy, review of the literature, perspectives for veterinary medicine

Over time, much knowledge has been accumulated about the active role of the urothelium, principally in rodents and human. Far from being a mere passive barrier, this specialized epithelium can alter the ion and protein composition of the urine, is able to sense and respond to mechanical stimuli such as pressure, and react to mechanical stimuli by epithelial cell communication with the nervous system. Most of the specialized functions of the urothelium are linked to a number of morpho-physiologic properties exhibited by the superficial umbrella cells, including specialized membrane lipids, asymmetric unit membrane particles and a plasmalemma with stiff plaques which function as a barrier to most substances found in urine, thus protecting the underlying tissues. Moreover, the entire mucosa lining the low urinary tract, composed of urothelium and sub-urothelium, forms a functional transduction unit, able to respond to eso- and endogenous physical and chemical stimuli in a manner assuring an adequate functional response. This review will summarize the available information on each area of inquiry from a morpho-functional point of view. Possible considerations pertaining to species of veterinary interest are reviewed as well. The review was prepared consulting the electronic databases PubMed and Cab Abstracts and retrieving all pertinent reports and the relative reference lists, in order to identify any potential additional studies that could be included. Full-length research articles and thematic reviews were considered. Information on the urothelium of some domestic animal species was also included.

Therapeutic effect of activated carbon-induced constipation mice with Lactobacillus fermentum Suo on treatment

The aim of this study was to investigate the effects of Lactobacillus fermentum Suo (LF-Suo) on activated carbon-induced constipation in ICR (Institute of Cancer Research) mice. ICR mice were orally administered with lactic acid bacteria for 9 days. Body weight, diet intake, drinking amount, defecation status, gastrointestinal transit and defecation time, and the serum levels of MTL (motilin), Gas (gastrin), ET (endothelin), SS (somatostatin), AChE (acetylcholinesterase), SP (substance P), VIP (vasoactive intestinal peptide) were used to evaluate the preventive effects of LF-Suo on constipation. Bisacodyl, a laxative drug, was used as a positive control. The normal, control, 100 mg/kg bisacodyl treatment, LB (Lactobacillus bulgaricus)-, LF-Suo (L)- and LF-Suo (H)-treated mice showed the time to the first black stool defecation at 90, 218, 117, 180, 155 and 137 min, respectively. By the oral administration of LB-, LF-Suo (L), LF-Suo (H) or bisacodyl (100 mg/kg), the gastrointestinal transit was reduced to 55.2%, 72.3%, 85.5% and 94.6%, respectively, of the transit in normal mice, respectively. In contrast to the control mice, the serum levels of MTL, Gas, ET, AChE, SP and VIP were significantly increased and the serum levels of SS were reduced in the mice treated with LF-Suo (p < 0.05). By the RT-PCR (reverse transcription–polymerase chain reaction) and western blot assays, LF-Suo increased the c-Kit, SCF (stem cell factor), GDNF (glial cell line-derived neurotrophic factor) and decreased TRPV1 (transient receptor potential vanilloid 1), NOS (nitric oxide synthase) expressions of small intestine tissue in mice. These results demonstrate that lactic acid bacteria has preventive effects on mouse constipation and LF-Suo demonstrated the best functional activity.

Effect of anticholinergics on the overactive bladder and bowel domain of the electronic personal assessment questionnaire (ePAQ)

INTRODUCTION AND HYPOTHESIS

Evidence suggests that OAB (overactive bladder) can occur alongside disorders of the colon, such as irritable bowel syndrome (IBS). Moreover, patients with constipation are more likely to develop OAB symptoms than those without. Anticholinergic medications (AcH) are commonly used for treating OAB, and can result in the unwanted side effects of constipation. We aimed to study the relationship of AcH, and their effects on quality of life using the electronic Personal Assessment Questionnaire (ePAQ) by assessing changes in the bowel and bladder domains, pre- and post-AcH treatment.

METHODS

Ninety patients completed the ePAQ pre- and post-AcH treatment from January 2011 to April 2014. Data were collected retrospectively and prospectively, and analysed using a paired t test. Effect size (ES) was calculated for OAB and bowel domains to quantify the effect on QoL.

RESULTS

There was a significant improvement in the OAB (p = 0.0005) and bowel domains (p = 0.0005). In the bowel domains, the largest effect size was seen for IBS (0.5) followed by continence (0.4), evacuation (0.375) and a small ES was seen for constipation (0.2). There was a reduction in the "degree of bother" in OAB and bowel domains.

CONCLUSIONS

Patients may benefit from the possible effects of AcH on their bowels, and assessment of all aspects of pelvic floor function is important before commencing AcH. This may help to counsel patients, with possibly improved compliance with therapy.

Macroscopic electrical propagation in the guinea pig urinary bladder

There is little knowledge about macroscopic electrical propagation in the wall of the urinary bladder. Recording simultaneously from a large number of extracellular electrodes is one technology that could be used to study the patterns of macroscopic electrical propagations. The urinary bladders from 14 guinea pigs were isolated and placed in an organ bath. A 16 × 4-electrode array was positioned at various sites on the serosal bladder surface, and recordings were performed at different intravesical volumes. In four experiments, carbachol (CCH; 10(-6) M), nifedipine (10 mM), or tetrodotoxin (TTX; 10(-6) M) was added to the superfusing fluid. After the experiments, the extracellular signals were analyzed and propagation maps were constructed. Electrical waves were detected at all sites on the bladder surface and propagated for a limited distance before terminating spontaneously. The majority of waves (>90%) propagated in the axial direction (i.e., from dome to base or vice versa). An increase in vesicle volume significantly decreased the conduction velocity (from 4.9 ± 1.5 to 2.7 ± 0.7 cm/s; P < 0.05). CCH increased, nifedipine decreased, while TTX had little effect on electrical activities. In addition, a new electrical phenomenon, termed a "patch," was discovered whereby a simultaneous electrical deflection was detected across an area of the bladder surface. Two types of electrical activities were detected on the bladder surface: 1) electrical waves propagating preferentially in the axial direction and 2) electrical patches. The propagating electrical waves could form the basis for local spontaneous contractions in the bladder during the filling phase.

Alterations of the myovesical plexus of the human overactive detrusor

Objectives. The human bladder shows spontaneous autonomous activity. Detrusor overactivity could be seen as a consequence of exaggerated autonomous activity. Interstitial cells (ICs) play a potential role in coordination of autonomous activity. As it is suggested that changes in ICs coexist with detrusor overactivity (DO), we investigated possible alterations to human bladder ICs. Methods. Biopsies were obtained from 23 patients and were categorized into four groups: genuine stress incontinence (without DO) (n = 5), neurogenic disease with DO (n = 6), bladder outlet obstruction with DO (n = 6), or idiopathic DO (n = 6). Specimens were processed to investigate expression of N-cadherin and PGP9.5. N-cadherin expression was semiquantitatively analyzed and correlated to PG9.5 expression and bladder wall morphology. Results. The population of cells expressing N-cadherin is altered in the overactive detrusor, making no difference between the sources of DO. Punctate distribution of morphological changes was found and downregulation of PGP9.5 expression seemed to coexist with upregulation of N-cadherin expression in the detrusor layer. Conclusions. The population of N-cadherin+ cells of the interstitial compartment of the human bladder has the ability to proliferate. As this proliferation seems to coexist with denervation, it could be possible that a highly developed network of interstitial cells replaces the loss of innervation in overactive detrusor.

Interstitial cells of Cajal modulate the tone of the human internal anal sphincter in vitro

BACKGROUND

Interstitial cells of Cajal, expressing the proto-oncogene c-kit, have been shown to regulate the spontaneous activity of the gastrointestinal tract. They have been described in the human internal anal sphincter; however, their function is still unclear.

OBJECTIVE

We examined the effects of the c-kit tyrosine kinase inhibitor imatinib mesylate on sphincter strips to investigate the function of the interstitial cells.

DESIGN

This was a case series study.

SETTIGS

This was a single-center study conducted at the University of Oxford.

PATIENTS

Internal anal sphincter strips were collected from 10 patients undergoing abdominoperineal resection or proctectomy and mounted in organ bath. Responses to electrical field stimulation and chemical agents were monitored in the absence of drugs and after the administration of increasing doses of imatinib mesylate. Immunohistochemistry was performed to identify interstitial cells.

MAIN OUTCOME MEASURES

The role of the interstitial cells in the internal anal sphincter was assessed.

RESULTS

Imatinib mesylate significantly reduced the tone and the spontaneous activity of the strips. In the absence of drugs, the tone generated was 147.7 ± 33.0 mg/mg of tissue. Administration of ≥5 μM of imatinib mesylate caused a dose-dependent reduction in the tone. Strips exhibited spontaneous activity characterized by intermittent low-amplitude contractions superimposed on basal tone (135.6 ± 4.6 contractions in 10 minutes). Imatinib mesylate significantly reduced the number of contractions at concentration >5 μM. No differences were observed in the responses to electrical field stimulation, carbachol, or phenylephrine. Immunohistochemistry showed c-kit-positive cells.

LIMITATIONS

This study was limited by the relatively small number of patients enrolled and thus the difficulty of finding human tissue for laboratory studies.

CONCLUSIONS

Our results suggest that the interstitial cells modulate the tone and the spontaneous activity of the internal anal sphincter. This provides a foundation for new approaches to preclinical and clinical research. Moreover, these cells may represent a target for drugs inhibiting the c-kit receptor and provide a new approach for treating anorectal diseases.

An update of the interstitial cell compartment in the normal human bladder

Aims. Interstitial cells, also called myofibroblasts, most probably play a major role in the pathogenesis of the overactive bladder. However, no specific phenotypic marker has been identified. We investigated whether N-cadherin could play a role as a discriminatory marker for interstitial cells in the human bladder. Methods. Bladder biopsies (n = 16) were collected from macroscopically nonpathological locations during cystectomy which was performed because of bladder cancer. Tissue was analyzed for expression of N-cadherin. N-cadherin+ cells were phenotyped using antibodies against PGP9.5, smoothelin, vimentin, and C-kit. Findings were related to bladder tissue histology and ultrastructure of myofibroblastic cells. Results. N-cadherin+/vimentin+ cells with branched cell bodies were found in the lamina propria and detrusor layer. They were closely associated with neurons and showed no colocalization of PGP9.5 or smoothelin. A second type of N-cadherin+ cells was found at the boundary of detrusor bundles and in the lamina propria. These cells colocalization C-kit. We assumed that N-cadherin+/vimentin+ cells are similar to the ultrastructurally defined myofibroblasts. Conclusions. N-cadherin can play a role as a discriminatory marker for interstitial cells in the human bladder, as the interstitial compartment of the human bladder houses a population of cells from mesenchymal origin, immunopositive for N-cadherin, vimentin, and C-kit.

Cajal-like interstitial cells as a novel target in detrusor overactivity treatment: true or myth?

Introduction

The Cajal–like intestitial cells (ICCs) act as a pacemaker and are responsible for generating smooth muscle activity in the gastrointestinal tract (GI). Interstitial cells that resemble ICCs in the GI have been identified in the urinary bladder.

Materials and methods

This review is based on a systemic literature research. The medline/pubmed, scopus, embase, and Web of Science databases were browsed in order to identify original and review articles, as well as editorials relating to cajal–like cells, urinary bladder, detrusor overactivity, overactive bladder, glivec, etc. The controlled vocabulary of the Medical Subject Headings (MeSH) database was used to ensure the sensitivity of the searches. 40 papers met the criteria and were used for this review.

Results

Cajal cells lie in close proximity to the muscle cells, autonomic nerve endings, and urothelial cells. There is increasing evidence that ICCs play role in urinary tract dysfunction development (e.g. detrusor overactivity, primary obstructive megaureter, congenital ureteropelvic junction obstruction, etc.). ICCs may be responsible for generating electrical potentials and induction of detrusor muscle contractions. Novel pathomechanisms of detrusor overactivity development have been postulated, as follows: 1) the disturbance of spontaneous contractility caused by altered signal transduction of ICCs between nerves and detrusor muscle cells, and 2). the alteration in signal transduction between urothelium and afferent nerve endings via suburothelial ICCs. The c–kit receptor is not only a detection marker of these cells, but may also play a crucial role in the control of bladder function.

Conclusions

Cajal cells in urinary bladder suggest that the c–kit receptor may provide a novel target for treating detrusor overactivity. The review presents the current knowledge of ICCs, its role in urinary bladder function, and potential novel therapeutic strategy.

Spatial analysis of slowly oscillating electric activity in the gut of mice using low impedance arrayed microelectrodes

Smooth and elaborate gut motility is based on cellular cooperation, including smooth muscle, enteric neurons and special interstitial cells acting as pacemaker cells. Therefore, spatial characterization of electric activity in tissues containing these electric excitable cells is required for a precise understanding of gut motility. Furthermore, tools to evaluate spatial electric activity in a small area would be useful for the investigation of model animals. We thus employed a microelectrode array (MEA) system to simultaneously measure a set of 8×8 field potentials in a square area of ∼1 mm². The size of each recording electrode was 50×50 µm², however the surface area was increased by fixing platinum black particles. The impedance of microelectrode was sufficiently low to apply a high-pass filter of 0.1 Hz. Mapping of spectral power, and auto-correlation and cross-correlation parameters characterized the spatial properties of spontaneous electric activity in the ileum of wild-type (WT) and W/W^v mice, the latter serving as a model of impaired network of pacemaking interstitial cells. Namely, electric activities measured varied in both size and cooperativity in W/W^v mice, despite the small area. In the ileum of WT mice, procedures suppressing the excitability of smooth muscle and neurons altered the propagation of spontaneous electric activity, but had little change in the period of oscillations. In conclusion, MEA with low impedance electrodes enables to measure slowly oscillating electric activity, and is useful to evaluate both histological and functional changes in the spatio-temporal property of gut electric activity.

Overactive bladder syndrome and the potential role of prostaglandins and phosphodiesterases: an introduction

In this paper, a general introduction is given, presenting the overactive bladder syndrome (OAB) and its impact on the quality of life and economical burden in patients affected. Moreover, the anatomy, physiology and histology of the lower urinary tract are discussed, followed by a brief overview on the possible role of prostaglandin (PG) and phosphodiesterase type 5 (PDE5) in the urinary bladder. The current literature on the role and distribution of PGE2 and its receptors in the urinary bladder is discussed. In both animal models and in human studies, high levels of signaling molecules such as PG and cGMP have been implicated, in decreased functional bladder capacity and micturition volume, as well as in increased voiding contraction amplitude. As a consequence, inhibition of prostanoid production, the use of prostanoid receptor antagonists, or PDE inhibitors might be a rational way to treat patients with detrusor overactivity. Similarly, prostanoid receptor agonists, or agents that stimulate their production, might have a function in treating bladder underactivity.

Spatio-temporal distribution of Smads and role of Smads/TGF-β/BMP-4 in the regulation of mouse bladder organogenesis

Although Shh, TGF-β and BMP-4 regulate radial patterning of the bladder mesenchyme and smooth muscle differentiation, it is not known what transcription factors, local environmental cues or signaling cascades mediate bladder smooth muscle differentiation. We investigated the expression patterns of signaling mediated by Smad2 and Smad3 in the mouse embryonic bladder from E12.5 to E16.5 by using qRT-PCR, in situ hybridization and antibodies specifically recognizing individual Smad proteins. The role of Smad2 and Smad3 during smooth muscle formation was examined by disrupting the Smad2/3 signaling pathway using TβR1 inhibitor SB-431542 in organ culture system. qRT-PCR results showed that R-Smads, Co-Smad and I-Smads were all expressed during bladder development. RNA ISH for BMP-4 and immunostaining of TGF-β1 showed that BMP-4 and TGF-β1 were expressed in the transitional epithelium, lamina propia and muscularis mucosa. Smad1, Smad5 and Smad8 were first expressed in the bladder epithelium and continued to be expressed in the transitional epithelium, muscularis mesenchyme and lamina propia as the bladder developed. Smad2, Smad3 and Smad4 were first detected in the bladder epithelium and subsequently were expressed in the muscularis mesenchyme and lamina propia. Smad6 and Smad7 showed overlapping expression with R-Smads, which are critical for bladder development. In bladder explants (E12.5 to E16.5) culture, Smad2 and Smad3 were found localized within the nuclei, suggesting critical transcriptional regulatory effects during bladder development. E12.5 to E16.5 bladders were cultured with and without TβR1 inhibitor SB-431542 and assessed by qRT-PCR and immunofluorescence. After three days in culture in SB-431542, α-SMA, Smad2 and Smad3 expressions were significantly decreased compared with controls, however, with no significant changes in the expression of smooth muscle myosin heavy chain (SM-Myh. Based on the Smad expression patterns, we suggest that individual or combinations of Smads may be necessary during mouse bladder organogenesis and may be critical mediators for bladder smooth muscle differentiation.

Role of SCF/c-Kit signaling pathway in the pathogenesis of cathartic colon

AIM: To investigate the role of SCF/c-Kit signaling pathway in the pathogenesis of cathartic colon.

METHODS: Thirty-six healthy adult SD rats were randomly divided into three groups (12 rats per group): control group, model group, and recovery group. The control group was given normal saline by gavage, and the model group and recovery group were given rhein suspension by gavage to induce cathartic colon. Specimens were taken immediately after modeling in the model group and 30 days after modeling in the recovery group. The intestinal transit function was assessed in each rats of each group by detecting the first melena discharge time. RT-PCR and Western blot were used to detect SCF/c-Kit mRNA and protein expression levels in colon tissue.

RESULTS: Compared to the control group, the first melena discharge time was significantly prolonged in the model group (491.5 ± 40.2 vs 373.4 ± 46.5, P < 0.01); however, there was no significant difference in the first melena discharge time between the model group and recovery group (477.9 ± 39.6 vs 491.5 ± 40.2, P > 0.05). Compared to the control group, c-Kit and SCF mRNA and protein expression levels were significantly decreased in both the model group and recovery group (all P < 0.01); however, there were no significant differences in c-Kit and SCF mRNA and protein expression levels between the model group and recovery group (both P > 0.05).

CONCLUSION: Reduced colonic motility in rats with cathartic colon may be associated with down-regulation of SCF/c-Kit signaling in colon tissue.

Systematic review of the relationship between bladder and bowel function: implications for patient management

BACKGROUND

The complex relationship between bladder and bowel function has implications for treating pelvic disorders. In this systematic review, we discuss the relationship between bladder and bowel function and its implications for managing coexisting constipation and overactive bladder (OAB) symptoms.

METHODS

Multiple PubMed searches of articles published in English from January 1990 through March 2011 were conducted using combinations of terms including bladder, bowel, crosstalk, lower urinary tract symptoms, OAB, incontinence, constipation, hypermotility, pathophysiology, prevalence, management and quality of life. Articles were selected for inclusion in the review based on their relevance to the topic.

RESULTS

Animal studies and clinical data support bladder-bowel cross-sensitization, or crosstalk. In the rat, convergent neurons in the bladder and bowel as well as some superficial and deeper lumbosacral spinal neurons receive afferent signals from both bladder and bowel. On a functional level, in animals and humans, bowel distention affects bladder activity and vice versa. Clinically, the bladder-bowel relationship is evident through the presence of urinary symptoms in patients with irritable bowel syndrome and bowel symptoms in patients with acute cystitis. Functional gastrointestinal disorders, such as constipation, can contribute to the development of lower urinary tract symptoms, including OAB symptoms, and treatment of OAB with antimuscarinics can worsen constipation, a common antimuscarinic adverse effect. The initial approach to treating coexisting constipation and OAB should be to relieve constipation, which may resolve urinary symptoms.

CONCLUSIONS

The relationship between bladder and bowel function should be considered when treating patients with urinary symptoms, bowel symptoms, or both.

Expression of β-Adrenoceptor Subtypes in Urothelium, Interstitial Cells and Detrusor of the Human Urinary Bladder

OBJECTIVE

We examined whether interstitial cells (ICs) of the human urinary bladder expressed β-adrenoceptor (AR) subtypes, and semiquantitatively compared the staining intensity among urothelium, ICs and detrusor muscles.

METHODS

Paraffin sections of the human urinary bladder were obtained from histologically normal areas of formalin-fixed specimens removed for bladder carcinoma. Double-labeling immunohistochemical methods using antibodies against each β-AR subtype and vimentin were performed to identify ICs of the human urinary bladder. The staining intensity of β-ARs was semiquantitatively compared among urothelium, ICs and detrusor muscles. Further, gender-related difference or age-related correlation in the staining intensity of β-ARs was compared in the same cell types.

RESULTS

The expression of β1 -, β2 -, and β3 -AR was observed in vimentin-positive ICs localized in suburothelium, between detrusor muscle bundles, and within these bundles of the human urinary bladder. The rank order of the staining intensity was urothelium > ICs = detrusor muscles in β1 -AR, urothelium > ICs > detrusor muscles in β2 -AR, whereas its order was ICs = detrusor muscles > urothelium in β3 -AR. Except for urothelial β1 -AR, there was no gender-related difference in the signal intensity of β-ARs in the urothelium, ICs or detrusor muscles. Age negatively correlated with the signal intensity of all β-AR subtypes.

CONCLUSION

β-ARs were expressed in vimentin-positive ICs of the human urinary bladder. As for β2 - and β3 -AR, there was no gender-related difference or age-related correlation in urothelium, ICs and detrusor muscles. In the human urinary bladder, β-ARs expressed in ICs may play a role in bladder physiology.

Bladder interstitial cells: an updated review of current knowledge

The field of bladder research has been energized by the study of novel interstitial cells (IC) over the last decade. Several subgroups of IC are located within the bladder wall and make structural interactions with nerves and smooth muscle, indicating integration with intercellular communication and key physiological functions. Significant progress has been made in the study of bladder ICs' cellular markers, ion channels and receptor expression, electrical and calcium signalling, yet their specific functions in normal bladder filling and emptying remain elusive. There is increasing evidence that the distribution of IC is altered in bladder pathophysiologies suggesting that changes in IC may be linked with the development of bladder dysfunction. This article summarizes the current state of the art of our knowledge of IC in normal bladder and reviews the literature on IC in dysfunctional bladder.

Identification of PDGFRα positive populations of interstitial cells in human and guinea pig bladders

PURPOSE

The bladder wall comprises a complex array of cells, including urothelium, smooth muscle, nerves and interstitial cells. Interstitial cells have several subtypes based on site, morphology and differential expression of markers such as anti-vimentin and anti-KIT. We examined whether a subpopulation of interstitial cells immunopositive for PDGFRα exists in human and guinea pig bladders.

MATERIALS AND METHODS

Human and guinea pig bladder tissues were processed for immunohistochemistry and examined by bright field or confocal microscopy. Whole mount tissues and paraffin sections were labeled with antibodies to PDGFRα, vimentin, KIT and PGP9.5. Protein expression was assessed by Western blot.

RESULTS

PDGFRα(+) cells were present in human and guinea pig bladders. In the guinea pig PDGFRα(+) cells had a branched stellate morphology and formed networks in the lamina propria. In human and guinea pig detrusors PDGFRα(+) cells were elongated on the boundary of smooth muscle bundles or were seen as groups of stellate cells in the interbundle spaces. PDGFRα(+) cells were located close to nerves labeled by PGP9.5. Double labeling revealed that PDGFRα(+) cells were a subgroup of the vimentin(+) population. A significant proportion of PDGFRα(+) cells were also KIT(+). Bands corresponding to PDGFRα, KIT and vimentin proteins were detected on Western blot.

CONCLUSIONS

To our knowledge this study is the first to identify PDGFRα(+)/KIT(+) cells in the bladder lamina propria and detrusor layers. These cells are a subgroup of the vimentin(+) population, showing the complexity of bladder interstitial cells. PDGFRα(+) cells are apparently structurally associated with intramural nerves, indicating integration with bladder control mechanisms.

Prostaglandin E2 induces spontaneous rhythmic activity in mouse urinary bladder independently of efferent nerves

BACKGROUND AND PURPOSE

The acute effects of PGE(2) on bladder smooth muscle and nerves were examined to determine the origin of PGE(2)-induced spontaneous rhythmic contractions.

EXPERIMENTAL APPROACH

Contraction studies, confocal Ca(2+) imaging and electrophysiological recordings in strips of mouse urinary bladder were used to differentiate the effects of PGE(2) on bladder smooth muscle and efferent nerves.

KEY RESULTS

PGE(2) (50 µM) increased the tone and caused phasic contractions of detrusor smooth muscle strips. Confocal Ca(2+) imaging showed that PGE(2) increased the frequency of whole-cell Ca(2+) transients (WCTs) (72 ± 5%) and intracellular recordings showed it increased the frequency of spontaneous depolarizations, from 0.31·s(-1) to 0.90·s(-1). Non-selective inhibition of EP receptors using SC-51322 and AH-6809 (10 µM), or the L-type Ca(2+) channel blocker nifedipine (1 µM), prevented these phasic contractions and WCTs, and reduced the tone (by 45 ± 7% and 59 ± 6%, respectively). Blocking P2X1 receptors with NF449 (10 µM) caused a small but significant reduction in the frequency of PGE(2)-induced phasic contractions (24 ± 9%) and WCTs (28 ± 17%) but had no significant effect on spontaneous depolarizations or tone. Inhibiting muscarinic receptors with cyclopentolate (1 µM) had no significant effect on these measures. Spontaneous WCTs became synchronous in PGE(2), implying enhanced functional coupling between neighbouring cells. However, the electrical input resistance was unchanged.

CONCLUSIONS AND IMPLICATIONS

It was concluded that depolarization alone is sufficient to explain a functional increase in intercellular coupling and the ability of PGE(2) to increase detrusor spontaneous rhythmic activity does not require parasympathetic nerves.

Spontaneous Ca2+ signaling of interstitial cells in the guinea pig prostate

PURPOSE

We investigated whether prostate interstitial cells generate spontaneous Ca(2+) oscillation, a proposed mechanism underlying pacemaker potentials to drive spontaneous activity in stromal smooth muscle cells.

MATERIALS AND METHODS

Intracellular free Ca(2+) in portions of guinea pig prostate and freshly isolated, single prostate interstitial cells were visualized using fluo-4 Ca(2+) fluorescence. Spontaneous electrical activity was recorded in situ with intracellular microelectrodes.

RESULTS

In whole tissue preparations spontaneous Ca(2+) flashes firing synchronously across all smooth muscle cells within the field of view resulted in muscle wall contractions. Nonpropagating Ca(2+) waves were also recorded in individual smooth muscle cells. Nifedipine (Sigma®) (1 μM) largely decreased or abolished these Ca(2+) flashes and suppressed slow wave discharge upon blockade of their superimposed action potentials. Isolated prostate interstitial cells were readily distinguished from smooth muscle cells by their spiky processes and lack of contraction during intracellular Ca(2+) increases. Prostate interstitial cells generated spontaneous Ca(2+) transients in the form of whole cell flashes, intracellular Ca(2+) waves or localized Ca(2+) sparks. All 3 Ca(2+) signals were abolished by nicardipine (1 μM), cyclopiazonic acid (10 μM), caffeine (Sigma) (10 mM) or extracellular Ca(2+) removal.

CONCLUSIONS

Prostate interstitial cells generate spontaneous Ca(2+) transients that occur at a frequency comparable to Ca(2+) flashes in situ or slow waves relying on functional internal Ca(2+) stores. However, unlike other interstitial cells in the urinary tract, Ca(2+) influx through L-type Ca(2+) channels is fundamental to Ca(2+) transient firings in prostate interstitial cells. Thus, it is not possible to conclude that prostate interstitial cells are responsible for pacemaker potential generation.

Serotonin augments gut pacemaker activity via 5-HT3 receptors

Serotonin (5-hydroxytryptamine: 5-HT) affects numerous functions in the gut, such as secretion, muscle contraction, and enteric nervous activity, and therefore to clarify details of 5-HT's actions leads to good therapeutic strategies for gut functional disorders. The role of interstitial cells of Cajal (ICC), as pacemaker cells, has been recognised relatively recently. We thus investigated 5-HT actions on ICC pacemaker activity. Muscle preparations with myenteric plexus were isolated from the murine ileum. Spatio-temporal measurements of intracellular Ca(2+) and electric activities in ICC were performed by employing fluorescent Ca(2+) imaging and microelectrode array (MEA) systems, respectively. Dihydropyridine (DHP) Ca(2+) antagonists and tetrodotoxin (TTX) were applied to suppress smooth muscle and nerve activities, respectively. 5-HT significantly enhanced spontaneous Ca(2+) oscillations that are considered to underlie electric pacemaker activity in ICC. LY-278584, a 5-HT(3) receptor antagonist suppressed spontaneous Ca(2+) activity in ICC, while 2-methylserotonin (2-Me-5-HT), a 5-HT(3) receptor agonist, restored it. GR113808, a selective antagonist for 5-HT(4), and O-methyl-5-HT (O-Me-5-HT), a non-selective 5-HT receptor agonist lacking affinity for 5-HT(3) receptors, had little effect on ICC Ca(2+) activity. In MEA measurements of ICC electric activity, 5-HT and 2-Me-5-HT caused excitatory effects. RT-PCR and immunostaining confirmed expression of 5-HT(3) receptors in ICC. The results indicate that 5-HT augments ICC pacemaker activity via 5-HT(3) receptors. ICC appear to be a promising target for treatment of functional motility disorders of the gut, for example, irritable bowel syndrome.

Imipramine inhibition of TRPM-like plasmalemmal Mg2+ transport in vascular smooth muscle cells

Depression is associated with vascular disease, such as myocardial infarction and stroke. Pharmacological treatments may contribute to this association. On the other hand, Mg²⁺ deficiency is also known to be a risk factor for the same category of diseases. In the present study, we examined the effect of imipramine on Mg²⁺ homeostasis in vascular smooth muscle, especially via melastatin-type transient receptor potential (TRPM)-like Mg²⁺-permeable channels. The intracellular free Mg²⁺ concentration ([Mg²⁺]_i) was measured using ³¹P-nuclear magnetic resonance (NMR) in porcine carotid arteries that express both TRPM6 and TRPM7, the latter being predominant. pH_i and intracellular phosphorus compounds were simultaneously monitored. To rule out Na⁺-dependent Mg²⁺ transport, and to facilitate the activity of Mg²⁺-permeable channels, experiments were carried out in the absence of Na⁺ and Ca²⁺. Changing the extracellular Mg²⁺ concentration to 0 and 6 mM significantly decreased and increased [Mg²⁺]_i, respectively, in a time-dependent manner. Imipramine statistically significantly attenuated both of the bi-directional [Mg²⁺]_i changes under the Na⁺- and Ca²⁺-free conditions. This inhibitory effect was comparable in influx, and much more potent in efflux to that of 2-aminoethoxydiphenyl borate, a well-known blocker of TRPM7, a channel that plays a major role in cellular Mg²⁺ homeostasis. Neither [ATP]_i nor pH_i correlated with changes in [Mg²⁺]_i. The results indicate that imipramine suppresses Mg²⁺-permeable channels presumably through a direct effect on the channel domain. This inhibitory effect appears to contribute, at least partially, to the link between antidepressants and the risk of vascular diseases.

M3 muscarinic receptor-like immunoreactivity in sham operated and obstructed guinea pig bladders

PURPOSE

Type 3 muscarinic receptors, which are present in the bladder wall, are important for bladder function. However, their role in the context of the urothelium is not well defined. Understanding the role of type 3 muscarinic receptors has been limited by the lack of specific type 3 muscarinic receptor antibodies. Thus, we identified a specific type 3 muscarinic receptor antibody and investigated the site of type 3 muscarinic receptors in sham operated and obstructed guinea pig bladders.

MATERIALS AND METHODS

The specificity of 4 commercially available type 3 muscarinic receptor antibodies was determined. Immunohistochemistry was then done in bladder tissue from sham operated and obstructed guinea pig bladders.

RESULTS

One of the 4 antibodies examined had the needed specificity in terms of blocking peptide and Western blot characterization. Using this antibody type 3 muscarinic receptor immunoreactivity was associated with muscle cells, nerves and interstitial cells. Four types of interstitial cells were identified, including suburothelial, lamina propria, surface muscle and intramuscular interstitial cells. In the obstructed model the bladder wall was hypertrophied and there was nerve fiber loss. The number of lamina propria, surface muscle and intramuscular interstitial cells was increased but not the number of suburothelial interstitial cells. Also, surface muscle interstitial cells appeared to form clusters or nodes with type 3 muscarinic receptor immunoreactivity.

CONCLUSIONS

Nerve loss and the up-regulation of interstitial cells with type 3 muscarinic receptor immunoreactivity may underlie major functional changes in the pathological bladder. This indicates that type 3 muscarinic receptor specific anticholinergic drugs may affect not only the detrusor muscle, as previously thought, but also interstitial cells and nerve fibers.

Ultrastructural properties of interstitial cells of Cajal in the Guinea pig bladder

PURPOSE

We investigated the ultrastructural characteristics of interstitial cells of Cajal in the guinea pig bladder.

MATERIALS AND METHODS

Bladders were removed from guinea pigs and processed for transmission electron microscopy. Some sections were labeled with c-Kit antibodies and colloidal gold particles for positive identification of interstitial cells of Cajal.

RESULTS

Kit positive cells, identified with 10 nm gold particles, were located on the periphery of detrusor smooth muscle bundles and in the interbundle spaces. Interstitial cells of Cajal in these regions contained mitochondria, rough and smooth endoplasmic reticulum, thin and intermediate filaments, caveolae, Golgi apparatus, free ribosomes, cytoplasmic vesicles and had a discontinuous basal lamina. They were distinct from smooth muscle cells by an absence of dense bodies, membrane attachment bands and thick filaments. The ultrastructure of interstitial cells of Cajal in all regions of the bladder wall examined were similar and the myofibroblast characteristic, fibronexus, was not evident in any of the cells examined. Interstitial cells of Cajal had lateral branches which extended toward other interstitial cells of Cajal, neighboring smooth muscle cells or nerves. Cells with the ultrastructural profile of interstitial cells of Cajal were associated with bladder microvessels and their branched processes were in close proximity to vascular smooth muscle cells.

CONCLUSIONS

Bladder interstitial cells of Cajal have typical ultrastructural characteristics of interstitial cells of Cajal from other tissues and were immunopositive for the interstitial cell of Cajal marker Kit. They were closely associated with detrusor smooth muscle and often networked with other interstitial cells of Cajal. The observation of perivascular cells with interstitial cells of Cajal characteristics indicates that there may be more subtypes of these cells in the bladder than previously considered.

Ion channel modulators and urinary tract function

The membrane potential fulfils an important role in initiating smooth muscle contraction, through its depolarization and the subsequent influx of Ca(2+) through voltage-gated Ca(2+) channels. Changes in membrane potential can also coordinate contraction across great distances, utilizing the speed of electrical current flow through gap junctions. Hence, regulating membrane potential can greatly influence smooth muscle function. In this chapter, we will consider the influence of ion channels, as dynamic gatekeepers of membrane permeability, on urogenital function. Through their ability to act as key regulators of both the resting membrane potential and its dynamic changes, they provide important pharmacological targets for influencing urogenital function.Urogenital smooth muscle and urothelia contain a diverse range of molecularly and functionally distinct K(+) channels, which are key to regulating the resting membrane and for re-establishing the normal membrane potential following both active and passive changes. The voltage-gated Ca(2+) channels are key to initiating contraction and causing rapid depolarization, supplemented in some smooth muscles by rapid Na(+) conductances. The Cl(-) channels, often assumed to be passive, can actively change the membrane potential, and hence, cellular function, because Cl(-) is not usually at its equilibrium potential. The useful ways in which these ion channels can be targeted therapeutically in the ureter, bladder and urethra are discussed, focussing particularly on treatments for ureteric obstruction and detrusor overactivity. Current treatments for many urinary tract disorders, particularly the overactive bladder, are complicated by side effects. While ion channels have traditionally been considered as poor therapeutic targets by the pharmaceutical industry, our increasing knowledge of the molecular diversity of K(+) and Cl(-) channels gives new hope for more narrowly focused drug targeting, while the exciting discoveries of active currents in interstitial cells give us a new set of cellular targets for drugs.

Interstitial cells of Cajal in the urinary tract

The study of novel interstitial cells in the tissues of the urinary tract has defined advances in the field in the last decade. These intriguing cells belong to the same family as the better known interstitial cells of Cajal (ICC) of the gastrointestinal tract, and their discovery has been interpreted to suggest that pacemaker cells may be present in the urinary tract, driving the spontaneous or myogenic activity of the neighboring smooth muscle. This scenario may be true for the urethra where ICC have been described as "loose pacemakers" providing multiple, random inputs to modulate urethral smooth muscle activity. However, there is a paucity of direct evidence available to support this hypothesis in the bladder (where the smooth muscle cells are spontaneously active) or the renal pelvis (where atypical smooth muscle cells are the pacemakers), and it now seems more likely that urinary tract ICC act as modulators of smooth muscle activity.Interestingly, the literature suggests that the role of urinary tract ICC may be more apparent in pathophysiological conditions such as the overactive bladder. Several reports have indicated that the numbers of ICC present in overactive bladder tissues are greater than those from normal tissues; moreover, the contractility of tissues from overactive bladders in vitro appears to be more sensitive to the Kit antagonist, glivec, than those from normal bladder. Future research on urinary tract ICC in the short to medium term is likely to be dynamic and exciting and will lead to increasing our understanding of the roles of these cells in both normal and dysfunctional bladder.

Urothelial signaling

The urinary bladder "mucosa" or innermost portion of the bladder is composed of transitional epithelium, basement membrane, and the lamina propria. This chapter reviews the specialized anatomy of the bladder epithelium (urothelium) and speculates on possible communication mechanisms from urothelial cells to various cell types within the bladder wall. For example, beyond serving as a simple barrier, there is growing evidence that the urinary bladder urothelium exhibits specialized sensory properties and plays a key role in the detection and transmission of both physiological and nociceptive stimuli. Findings from a number of studies suggest that the urothelium exhibits both "sensor" (expressing receptors/ion channels capable of responding to thermal, mechanical, and chemical stimuli) and "transducer" (ability to release chemicals) properties. Thus, urothelial cells exhibit the ability to sense changes in their extracellular environment including the ability to respond to chemical, mechanical, and thermal stimuli that may communicate the state of the urothelial environment to the underlying nervous and muscular systems.

Pseudosarcomatous proliferation of cx43- and kit-expressing interstitial cell in the urinary bladder

The authors report a case showing proliferation of KIT- and connexin 43-expressing mesenchymal cells of the urinary bladder. A 75-year-old woman had an ulcerated endophytic mass (size, approximately 2 × 2 cm) in the left posterolateral wall. She underwent transurethral resection and subsequent partial cystectomy. The suburothelial mass extended to the muscularis propria. The histopathological analysis revealed spindle-shaped mesenchymal cells that were loosely arranged with myxoid stroma and showed a focal compact fascicular arrangement. In the immunohistochemical analysis, these spindle cells were stained with specific antibodies to KIT and connexin 43. The patient is currently free of disease at 5 years after operation. The proliferating spindle cells in the present case might represent a phenotype of interstitial cells of the lamina propria.

Attenuation of bladder overactivity in KIT mutant rats

OBJECTIVES

To investigate morphological and physiological findings in the bladder of KIT mutant (WsRCWs/Ws) rats to clarify whether the disturbance of KIT pathways affects bladder activity. To discuss the potential role of KIT-positive interstitial cells of Cajal (ICC)-like cells in the urinary bladder.

MATERIALS AND METHODS

Reverse transcriptase-polymerase chain reaction and western blotting was used to confirm the absence of c-kit mRNA and protein in the bladders of 12-week-old WsRCWs/Ws rats. Light and transmission electron microscopy was used to identify the differences in morphological and ultrastructural characteristics of the bladder between WsRCWs/Ws and wild-type (WsRC+/+) rats. The voiding pattern of WsRCWs/Ws rats and the effects of cyclophosphamide (CYP) and protamine sulphate on bladder function were examined using cystometry.

RESULTS

In WsRC+/+ rats, c-kit mRNA and KIT protein expression were observed in the urinary bladder, while they were not detectable in WsRCWs/Ws rats. Deformation of ICC-like cells with the collapse of the organelle was not observed in the bladders of WsRCWs/Ws rats. Each cystometry variable in WsRCWs/Ws rats was similar to that in WsRC+/+ rats. The reduction in the intercontraction intervals in WsRCWs/Ws rats with chemically (CYP and protamine sulphate) induced cystitis was significantly lower than in WsRC+/+ rats (P < 0.05).

CONCLUSION

Certain voiding disturbances might be associated with impaired KIT signalling in ICC-like cells, therefore, KIT could be a candidate target for medical therapy in the future.

Morphological expression of KIT positive interstitial cells of Cajal in human bladder

PURPOSE

We investigated the 3-dimensional morphological arrangement of KIT positive interstitial cells of Cajal in the human bladder and explored their structural interactions with neighboring cells.

MATERIALS AND METHODS

Human bladder biopsy samples were prepared for immunohistochemistry/confocal or transmission electron microscopy.

RESULTS

Whole mount, flat sheet preparations labeled with anti-KIT (Merck, Darmstadt, Germany) contained several immunopositive interstitial cell of Cajal populations. A network of stellate interstitial cells of Cajal in the lamina propria made structural connections with a cholinergic nerve plexus. Vimentin positive cells of several morphologies were present in the lamina propria, presumably including fibroblasts, interstitial cells of Cajal and other cells of mesenchymal origin. Microvessels were abundant in this region and branched, elongated KIT positive interstitial cells of Cajal were found discretely along the vessel axis with each perivascular interstitial cell of Cajal associated with at least 6 vascular smooth muscle cells. Detrusor interstitial cells of Cajal were spindle-shaped, branched cells tracking the smooth muscle bundles, closely associated with smooth muscle cells and vesicular acetylcholine transferase nerves. Rounded, nonbranched KIT positive cells were more numerous in the lamina propria than in the detrusor and were immunopositive for anti-mast cell tryptase. Transmission electron microscopy revealed cells with the ultrastructural characteristics of interstitial cells of Cajal throughout the human bladder wall.

CONCLUSIONS

The human bladder contains a network of KIT positive interstitial cells of Cajal in the lamina propria, which make frequent connections with a cholinergic nerve plexus. Novel perivascular interstitial cells of Cajal were discovered close to vascular smooth muscle cells, suggesting interstitial cells of Cajal-vascular coupling in the bladder. KIT positive detrusor interstitial cells of Cajal tracked smooth muscle bundles and were associated with nerves, perhaps showing a functional tri-unit controlling bladder contractility.

Beyond neurons: Involvement of urothelial and glial cells in bladder function

AIM

The urothelium, or epithelial lining of the lower urinary tract (LUT), is likely to play an important role in bladder function by actively communicating with bladder nerves, smooth muscle, and cells of the immune and inflammatory systems. Recent evidence supports the importance of non-neuronal cells that may extend to both the peripheral and central processes of the neurons that transmit normal and nociceptive signals from the urinary bladder. Using cats diagnosed with a naturally occurring syndrome termed feline interstitial cystitis (FIC), we investigated whether changes in physiologic parameters occur within 3 cell types associated with sensory transduction in the urinary bladder: 1) the urothelium, 2) identified bladder dorsal root ganglion (DRG) neurons and 3) grey matter astrocytes in the lumbosacral (S1) spinal cord. As estrogen fluctuations may modulate the severity of many chronic pelvic pain syndromes, we also examined whether 17beta-estradiol (E2) alters cell signaling in rat urothelial cells.

RESULTS

We have identified an increase in nerve growth factor (NGF) and substance P (SP) in urothelium from FIC cats over that seen in urothelium from unaffected (control) bladders. The elevated NGF expression by FIC urothelium is a possible cause for the increased cell body size of DRG neurons from cats with FIC, reported in this study. At the level of the spinal cord, astrocytic GFAP immuno-intensity was significantly elevated and there was evidence for co-expression of the primitive intermediate filament, nestin (both indicative of a reactive state) in regions of the FIC S1 cord (superficial and deep dorsal horn, central canal and laminae V-VIl) that receive input from pelvic afferents. Finally, we find that E2 triggers an estrus-modifiable activation of p38 MAPK in rat urothelial cells. There were cyclic variations with E2-mediated elevation of p38 MAPK at both diestrus and estrus, and inhibition of p38 MAPK in proestrous urothelial cells.

CONCLUSION

Though urothelial cells are often viewed as bystanders in the processing of visceral sensation, these and other findings support the view that these cells function as primary transducers of some physical and chemical stimuli. In addition, the pronounced activation of spinal cord astrocytes in an animal model for bladder pain syndrome (BPS) may play an important role in the pain syndrome and open up new potential approaches for drug intervention.

Interstitial cells in the urinary bladder--localization and function

AIMS

This review summarizes the currently available literature on the localization and proposed functions of a novel group of cells in the urinary bladder known as interstitial cells or interstitial cells of Cajal (ICC).

METHODS

On-line searches of "Pubmed" for bladder, c-Kit, ICC, interstitial cell and myofibroblast were performed to identify relevant studies for the review.

RESULTS

The literature contains substantial data that several sub-populations of ICC are present in the wall of the mammalian urinary bladder. These are located in the lamina propria and within the detrusor with distinctive cell shapes and morphological arrangements. Bladder ICC are identified with transmission electron microscopy or by immunohistochemical labeling using antibodies to the Kit receptor which is an established ICC marker. Lamina propria-ICC form a loose network connected via Cx43 gap junctions and are associated with mucosal nerves. Detrusor ICC track the smooth muscle bundles and make frequent contacts with intramural nerves. Both groups of ICC exhibit spontaneous electrical and Ca2+-signalling and also respond to application of neurotransmitter substances including ATP and carbachol. There is emerging evidence that the expression of ICC is upregulated in pathophysiological conditions including the overactive bladder.

CONCLUSIONS

There is now a convincing body of evidence that specialized ICC are present in the urinary bladder making important associations with other cells that make up the bladder wall and possessing physiological properties consistent with a role of bladder activity modulation.