Evaluation of two techniques of partial urethral obstruction in the male rat model of bladder outlet obstruction

Urethral monopolar cauterization: alternative infravesical obstruction model in male rats

OBJECTIVE:

We aimed to determine which method gives the most consistent results between urethral monopolar cauterization and standard urethral partial ligation methods for the urethral obstruction model.

METHODS:

Thirty male rats were randomly divided into control, partial ligation, and monopolar cauterization groups. Six weeks after experimental procedures, the experimental groups were evaluated cystometrically, biochemically, and histologically.

RESULTS:

According to the cystometric results, bladder capacity, baseline bladder pressure, and compliance data of the monopolar cauterization group were higher than those of the partial ligation and monopolar cauterization groups (p<0.05 and p<0.01, respectively). As a biochemical evaluation, malondialdehyde levels in bladder tissues of group control were higher than partial ligation and monopolar cauterization groups (p<0.05 and p<0.01, respectively). The collagen type I level of the control group was higher than the partial ligation and monopolar cauterization groups (p<0.01 and p<0.05, respectively). Collagen type III levels of the monopolar cauterization group were higher than those of the control group (p<0.01), but the Collagen type I/Collagen type III and transforming growth factor-β levels of the monopolar cauterization group were significantly lower than those of the control group (p<0.001). As a histological evaluation (hematoxylin and eosin), fibrosis in the lamina propria was more prominent in the monopolar cauterization group than in the control group (p<0.05). In addition, the muscular thickness was higher in the monopolar cauterization group compared with control and partial ligation groups (p<0.001 and p<0.01, respectively).

CONCLUSION:

The needle-tipped monopolar cauterization of the posterior urethra may be the method of choice for creating a chronic infravesical obstruction model of infravesical obstruction in male rats.

Role of human adipose-derived stem cells (hADSC) on TGF-β1, type I collagen, and fibrosis degree in bladder obstruction model of Wistar rats

Introduction

Bladder outlet obstruction (BOO) was caused by a series of histological and biochemical changes in the bladder wall, through the inflammation process in the bladder wall, hypertrophy and fibrosis. ADSC has an important role in bladder regeneration.

Methods and materials

This study was an experimental randomized study using male Wistar rats which were monitored at 2 and 4 weeks to determine the effect of ADSC therapy on TGF-β1 type I collagen, and degree of fibrosis.

Result

Rats were divided into 5 groups. In the week 2 BOO group, 1 sample included in the category of moderate fibrosis, 1 sample that was given ADSC with mild fibrosis category, 3 samples included in severe fibrosis category, 3 samples that were given ADSC included in the category of moderate fibrosis. The concentration of TGF-β1 in the hADSC therapy group was significantly lower than the control group at the 2nd and 4th week of monitoring (p2 = 0.048, p4 = 0.048), and also with more type I collagen on 2nd and the 4th week (p2 = 0.048, p4 = 0.048).

Conclusion

ADSC therapy can reduce the concentration of TGF-β1, type I collagen, and degree of fibrosis in the male Wistar BOO model.

Review: Correlation between bladder obstruction with bladder function and erectile dysfunction in mice

Bladder obstruction, including due to benign prostate enlargement (BPH), will trigger its anatomy and physiological function changes. Men with BPH have a 6 times higher risk of erectile dysfunction than those without BPH. Morphological and functional changes in subjects with partial bladder outlet obstruction (pBOO) occur differently depending on the duration of pBOO that has been experienced. The underlying pathophysiology of BPH is closely related to erectile dysfunction. Anatomically, functionally, and psychologically changes due to BPH will also have an impact on sexual function. Chronic pBOO causes lower urinary tract symptoms (LUTS) through a complex pathophysiological pathway. LUTS and bladder obstruction can lead to erectile dysfunction. The severity of LUTS and sexual dysfunction is inversely related to the quality of life. The treatment of LUTS symptoms will also enhance sexual function.

•

Bladder morphology and functional changes are depending on the partial bladder outlet obstruction (pBOO) duration that is experienced and also have an impact on sexual function.

•

Ischemia leads to increased production of reactive oxygen species (ROS), malondialdehyde (MDA). Free radicals from ischemia-reperfusion injury are one of the major causes of bladder obstruction.

•

Obstruction of the bladder neck nerve may be associated with impaired sensory axons.

•

PBOO play a modulating role alongside key mechanisms such as vascular changes, altered CCSM tone/contractility, phosphodiesterase-dependent pathway.

•

Chronic pBOO are increased risk of infection through complex pathophysiological pathway involving nitric oxide guanosine monophosphate and RhoA/Rho-kinase, metabolic syndrome, autonomic hyperactivity, pelvic ischemia, psychological factors, imbalance of sex hormones, and inflammatory pathways.

Inhibition of LIM kinase reduces contraction and proliferation in bladder smooth muscle

Overactive bladder (OAB) is the most bothersome symptom in lower urinary tract symptoms (LUTS). Current pharmacologic treatment aims to inhibit detrusor contraction; however, shows unsatisfied efficacy and high discontinuation rate. LIM kinases (LIMKs) promote smooth muscle contraction in the prostate; however, their function in the bladder smooth muscle remains unclear. Here, we studied effects of the LIMK inhibitors on bladder smooth muscle contraction and proliferation both in vitro and in vivo experiments. Bladder expressions of LIMKs are elevated in OAB rat detrusor tissues. Two LIMK inhibitors, SR7826 and LIMKi3, inhibit contraction of human detrusor strip, and cause actin filament breakdown, as well as cell proliferation reduction in cultured human bladder smooth muscle cells (HBSMCs), paralleled by reduced cofilin phosphorylation. Silencing of LIMK1 and LIMK2 in HBSMCs resulted in breakdown of actin filaments and decreased cell proliferation. Treatment with SR7826 or LIMKi3 decreased micturition frequency and bladder detrusor hypertrophy in rats with bladder outlet obstruction. Our study suggests that LIMKs may promote contraction and proliferation in the bladder smooth muscle, which could be inhibited by small molecule LIMK inhibitors. LIMK inhibitors could be a potential therapeutic strategy for OAB- related LUTS.

Influence of Experimental Autoimmune Prostatitis on Sexual Function and the Anti-inflammatory Efficacy of Celecoxib in a Rat Model

Experimental autoimmune prostatitis (EAP) is a well-established model induced by an autoimmune response to prostate antigen. The symptomatic, pathological, and immunological characteristics of EAP animals are highly consistent with human chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS), which makes EAP an ideal model for this disease. Here, we investigate the influence of EAP on male rat sexual function and the efficacy of anti-inflammatory therapy with celecoxib. EAP rat models were established using male Wistar rats. Rats were randomly assigned to a normal control group, an EAP model group, or an EAP model with celecoxib treatment group (celecoxib group). Behavioral changes, sexual behavioral changes, and erectile function were estimated using an open-field test, a sucrose consumption test, mating experiments, and by intracavernous pressure/mean arterial pressure ratio (ICP/MAP). Histological changes in the prostate were observed by HE staining, and the serum inflammatory factors IL-1β and TNF-α levels were measured by enzyme-linked immunosorbent assay. In addition, serotonin (5-hydroxytryptamine, 5-HT), 5-HT_1A receptor, 5-HT_2C receptor, and serotonin transporter (SERT) expression levels in the hippocampus and spinal cord (T13–L1, L5–S2) were examined by immunohistochemistry and western blot analysis. Results showed that EAP rats exhibited characteristics of depression, decreased sexual drive, premature ejaculation, and increased threshold of penile erection. Moreover, all these changes were effectively alleviated by celecoxib. Significant increases in prostatic interstitial infiltration by inflammatory cells and in serum IL-1β and TNF-α levels were observed in EAP rats, and these were partially reduced by celecoxib. Additionally, the expression pattern of serotonin system regulators in the hippocampus and spinal cord were altered in EAP model rats, including a decrease in 5-HT levels and an increase in 5-HT_1A receptor levels. In conclusion, autoimmune prostatitis impaired rat sexual function, and this was effectively prevented by anti-inflammatory therapy with celecoxib. Moreover, a serotonin system disorder in the central nervous system was likely mediated via inflammation in EAP rats.

Increased expression of neuregulin 1 in the urothelium of rat bladder with partial bladder outlet obstruction

Background

This study determined whether changes in the expression of neuregulin (NRG) 1, erbB2 tyrosine kinase (ErbB2) and the M2 muscarinic receptor in the urothelium and detrusor muscle of the rat bladder were associated with partial bladder outlet obstruction (PBOO).

Methods

Male Sprague-Dawley rats (body weight 250–300 g) were used and subdivided into control (n = 10) and PBOO groups (n = 20). PBOO was induced for 21 days, and the expression of NRG1, ErbB2 and M2 muscarinic receptor mRNA and protein was evaluated using reverse transcriptase-polymerase chain reaction (RT-PCR) and western blotting, respectively.

Results

In the urothelium of rat bladder samples, protein expression and mRNA expression of NRG1, ErbB2 and M2 muscarinic receptor were significantly increased in the PBOO group compared to the control group (p < 0.05). Only mRNA expression levels of NRG1/ ErbB2 were higher in the detrusor muscle of the PBOO group compared to the control group (p < 0.05).

Conclusions

Our study demonstrated remarkable changes in the expression of NRG1/ErbB2 receptor mRNA and protein in the urothelium and muscle layer. These results suggest that NRG1 overexpression plays some kind of role against the PBOO-induced upregulated muscarinic receptors in detrusor overactivity.

Pathophysiology of the underactive bladder

Underactive bladder (UAB), which has been described as a symptom complex suggestive of detrusor underactivity, is usually characterized by prolonged urination time with or without a sensation of incomplete bladder emptying, usually with hesitancy, reduced sensation on filling, and slow stream often with storage symptoms. Several causes such as aging, bladder outlet obstruction, diabetes mellitus, neurologic disorders, and nervous injury to the spinal cord, cauda equine, and peripheral pelvic nerve have been assumed to be responsible for the development of UAB. Several contributing factors have been suggested in the pathophysiology of UAB, including myogenic failure, efferent and/or afferent dysfunctions, and central nervous system dysfunction. In this review article, we have described relationships between individual contributing factors and the pathophysiology of UAB based on previous reports. However, many pathophysiological uncertainties still remain, which require more investigations using appropriate animal models.

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

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

Evaluation of the effects of omega-3 & interferon alpha-2b administration on partial bladder outlet obstruction in a rat model

BACKGROUND & OBJECTIVES

In bladder outlet obstruction-induced rat models, the transforming growth factor-beta (TGF-β) and collagen ratios have been shown to be increased. Increased TGF-β leads to fibrosis. In this study, the effect of omega-3 and interferon alpha-2b (IFN α-2b) was investigated on oxidative stress, inflammation and fibrosis in bladder structure in a partial bladder outlet obstruction (PBOO) rat model.

METHODS

A total of 35 male Wistar albino rats, weighing 300-350 g, were used in the study. The rats were randomly divided into five groups. At the end of the experimental period, bladders were harvested from all the rats, and pathological analysis of the rat bladder tissues was performed. In addition, investigations were carried out with enzymatic and non-enzymatic antioxidant systems to study the antioxidant properties of omega-3 fatty acid and IFN alpha-2b.

RESULTS

Increased bladder weight in the PBOO group, in comparison to the control group, was decreased by the administration of omega-3 and IFN α-2b (P=0.002). Significantly higher superoxide dismutase (SOD) levels were detected in group 2 in comparison to the control group. It was also detected that serum SOD, glutathione peroxidase and nitric oxide (NO) levels were significantly higher in group 2 when compared to the control group (P<0.05). In the pathologic evaluation, group 2 showed significantly increased inflammation and fibrosis compared to the control group. Omega-3 treatment significantly decreased inflammation. It was shown that IFN α-2b application partially decreased inflammation.

INTERPRETATION & CONCLUSIONS

The results of the present study showed that in addition to the standard primary approaches to prevent the damage to the upper urinary tract secondary to PBOO, omega-3 fatty acid and IFN α-2b could be beneficial as adjunct treatment in clinical practice. However, this needs to be further investigated with prospective, randomized clinical trials with larger sample sizes.

Intraprostatic Reflux of Urine Induces Inflammation in a Rat

BACKGROUND

We examined whether urine reflux into the prostate can induce prostatic inflammation in a rat and evaluated the effect of α1-adrenoreceptor antagonist.

METHODS

Experiment 1: Male Sprague-Dawley rats were injected with 500 µl of Evans Blue through the urethral orifice. Intravesical pressure was measured, and the prostate was excised to evaluate urine reflux. Experiment 2: Rats were injected with 500 µl urine or saline (control) from the urethral orifice. Silodosin (200 µg/kg/day) was administered to the silodosin group. We evaluated histopathology, the expression of proinflammatory cytokines and oxidative stress markers of the prostate on day 7, after assessing the prostatic microcirculation and cystometrogram.

RESULTS

Experiment 1: The histopathology showed that Evans Blue instilled through the urethral orifice entered the prostatic ducts. Intravesical pressure during Evans Blue instillation was 47.7 ± 1.6 cmH₂ O (mean ± standard error). Experiment 2: On day 7 after urine instillation through the urethral orifice, histopathology showed infiltrated inflammatory cells in the peri-glandular stroma. Inflammation-associated proteins (IL-1α, IL-1β, IL-6, and TNFα) were upregulated in the urine-instilled rats but not in the silodosin group. Erythrocyte speed on the prostatic surface, immunostaining for hypoxyprobe, and quantification of oxidative stress markers (MDA and HIF-1α) demonstrated prostatic hypoxia in the urine-instilled rats, which was ameliorated in the silodosin group. Cystometrogram revealed a shorter intercontraction interval in the urine-instilled rats, which was prolonged in the silodosin group.

CONCLUSIONS

Urine reflux into the prostatic duct induces abacterial prostatitis. Silodosin relieved prostatic inflammation and bladder overactivity by increasing microcirculation in the prostate. Prostate 77:164-172, 2017. © 2016 Wiley Periodicals, Inc.

Expression of brain derived-neurotrophic factor and granulocyte-colony stimulating factor in the urothelium: relation with voiding function

BACKGROUND

We designed this experiment to elucidate the relationship between the expression of brain derived-neurotrophic factor (BDNF), the expression of granulocyte-colony stimulating factor (G-CSF), and the development of overactive bladder (OAB). In our previous study, the urothelium was observed to be more than a simple mechanosensory receptor and was found to be a potential therapeutic target for OAB. Moreover, neuregulin-1 and BDNF were found to be potential new biomarkers of OAB. Here, we investigated the relationship between changes in the voiding pattern and the expression of BDNF and G-CSF in the urothelium and evaluated the effects of 5-hydroxymethyl tolterodine (5-HMT) on rats with bladder outlet obstruction (BOO).

METHODS

A total of 100 Sprague-Dawley rats were divided into the following groups: 20 control rats; 40 BOO rats; and 40 BOO rats administered 5-HMT (0.1 mg/kg). After BOO was induced for 4 weeks, the rats were assessed by cystometrography. The changes in BDNF and G-CSF expression were examined in both separated urothelial tissues and in cultured urothelial cells by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

BOO rats showed increased non-voiding activity [NVA; (number/10 voidings)] and bladder weight and decreased micturition volume (MV), micturition interval (MI), and micturition time (MT) relative to the controls. Moreover, the 5-HMT administration rats showed decreased NVA and bladder weight and increased MV and MI in comparison to the BOO rats. BDNF and G-CSF expression was increased in BOO rats and decreased following 5-HMT administration. In this model, voiding dysfunction developed as a result of BOO. As a therapeutic agent for OAB, the administration of 5-HMT improved the voiding dysfunction.

CONCLUSIONS

BDNF and G-CSF might modulate voiding patterns through micturition pathways and might be involved only in the urothelium. Moreover, the expression of both genes in the urothelium might be related to voiding dysfunction in OAB patients. Thus, the urothelium has an important role in the manifestation of voiding symptoms.

Bladder outlet obstruction causes up-regulation of nicotinic acetylcholine receptors in bladder-projecting pelvic ganglion neurons

Pelvic ganglion (PG) neurons relay sympathetic and parasympathetic signals to the lower urinary tract, comprising the urinary bladder and bladder outlet, and are thus essential for both storage and voiding reflexes. Autonomic transmission is mediated by activation of the nicotinic acetylcholine receptor (nAChR) in PG neurons. Previously, bladder outlet obstruction (BOO), secondary to benign prostatic hyperplasia, was found to increase soma sizes of bladder-projecting PG neurons. To date, however, it remains unknown whether these morphological changes are accompanied by functional plasticity in PG neurons. In the present study, we investigated whether BOO alters acetylcholine receptor (nAChR) transcript expression and current density in bladder PG neurons. Partial ligation of the rat urethra for six weeks induced detrusor overactivity (DO), as observed during cystometrical measurement. In rats exhibiting DO, membrane capacitance of parasympathetic bladder PG neurons was selectively increased. Real-time PCR analysis revealed that BOO enhanced the expression of the transcripts encoding the nAChR α3 and β4 subunits in PG neurons. Notably, BOO significantly increased ACh-evoked current density in parasympathetic bladder PG neurons, whereas no changes were observed in sympathetic bladder and parasympathetic penile PG neurons. In addition, other ligand-gated ionic currents were immune to BOO in bladder PG neurons. Taken together, these data suggest that BOO causes upregulation of nAChR in parasympathetic bladder PG neurons, which in turn may potentiate ganglionic transmission and contribute to the development of DO.

Spinal neuronal cannabinoid receptors mediate urodynamic effects of systemic fatty acid amide hydrolase (FAAH) inhibition in rats

AIMS

To test if urodynamic effects from systemic Fatty Acid Amide Hydrolase (FAAH) inhibition involve sacral spinal cannabinoid type 1 (CB1) or type 2 (CB2) receptors.

METHODS

Male rats with or without partial urethral obstruction were used for cystometry or immunohistochemistry. Urodynamic effects of intravenous (IV) 0.3 mg/kg Oleoyl Ethyl Amide (OEtA; FAAH inhibitor), and intrathecal (IT) 5 μg rimonabant (CB1 antagonist) or 5 μg SR144528 (CB2 antagonist) were studied in awake rats.

RESULTS

After administration of rimonabant or SR144528, non-obstructed rats with normal bladder function developed bladder overactivity (BO), which was counteracted by OEtA. OEtA also counteracted BO in obstructed rats. SR144528 did not affect bladder function in obstructed rats but counteracted the urodynamic effects of OEtA. Surprisingly, rimonabant (and AM251, another CB1 antagonist) reduced BO in obstructed rats, whereafter OEtA produced no additional urodynamic effects. CB1 expression increased in the sacral spinal cord of obstructed rats whereas no changes were observed for CB2 or FAAH.

CONCLUSIONS

Urodynamic effects of systemic FAAH inhibition involve activities at spinal neuronal CB1 and CB2 receptors in normal and obstructed rats. Endogenous spinal CB receptor ligands seem to regulate normal micturition and BO. Altered spinal CB receptor functions may be involved in the pathogenesis of obstruction-induced BO. Neurourol. Urodynam. 35:464-470, 2016. © 2015 Wiley Periodicals, Inc.

Adipose-derived stem cells (ADSCs) and muscle precursor cells (MPCs) for the treatment of bladder voiding dysfunction

PURPOSE

Bladder outflow obstruction (BOO) is common in the elderly and can result in bladder voiding dysfunction (BVD) due to severe bladder muscle damage. The goal of this research was to evaluate the use of adult stem cells for the treatment of BVD due to decreased muscle contractility in a rat model.

MATERIALS AND METHODS

Adipose-derived stem cells (ADSCs) and muscle precursor cells (MPCs) were harvested from male Lewis rats and expanded in culture. BOO was induced by tying a suture around the urethra. Six weeks after obstruction, the development of BVD was confirmed by cystometric analysis in conscious rats, histology and molecular investigations. Injection of ADSCs or MPCs into the bladder wall and synchronous deligation was performed 6 weeks after the obstruction. After stem-cell treatment, morphological and functional changes were assessed. Age-matched rats and animals without cellular therapy but deligation-only served as controls.

RESULTS

Voiding pressures decreased progressively 6 weeks after obstruction with increased bladder capacities. Structural changes of the detrusor muscle occurred during the time of obstruction with an increased connective tissue-to-smooth muscle ratio and decreased SMA/smoothelin expression. After stem-cell injection, improved voiding pressures and voiding volumes were observed together with recovered tissue architecture. RT-PCR and Western blotting showed an up-regulation of important contractile proteins.

CONCLUSIONS

We established a reliable model for BVD and demonstrated that ADSCs and MPCs can prevent pathophysiological remodelling and provide regenerated bladder tissue and function.

Changes of neuregulin-1 (NRG-1) expression in a rat model of overactive bladder induced by partial urethral obstruction: is NRG-1 a new biomarker of overactive bladder?

Background

To determine whether neuregulin-1(NRG-1) is a potential new biomarker of overactive bladder (OAB) induced by partial urethral obstruction in a rat model of OAB and to evaluate the urothelium as a therapeutic target of OAB.

Methods

Female Sprague–Dawley rats were separated into three 20-animal groups: normal, OAB, and 5-hydroxymethyl tolterodine (5-HMT)-treated OAB. In the OAB and OAB + 5-HMT groups, the urethra of each animal was partially obstructed; the OAB + 5-HMT group received intravenous 5-HMT for 3 weeks. At the conclusion of the 5-HMT dosing, the rats in each group underwent cystometrography, and the bladders were histologically evaluated. The expression of brain derived-neurotrophic factor (BDNF) and NRG-1 were evaluated in the urothelium.

Results

Compared with the control group, the OAB group showed a markedly increased bladder weight and a significant decrease in the micturition interval and volume; rats in the OAB + 5-HMT group showed decreased bladder weights and an improved micturition interval and volume. BDNF and NRG-1 were expressed at significantly higher levels in the OAB group, and were significantly reduced in the OAB + 5-HMT group compared with the control group.

Conclusions

The study suggests that NRG-1 is a potential new biomarker of OAB; the urothelium might be a therapeutic target for OAB treatment.

Bladder outlet obstruction triggers neural plasticity in sensory pathways and contributes to impaired sensitivity in erectile dysfunction

Lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) are common problems in aging males worldwide. The objective of this work was to evaluate the effects of bladder neck nerve damage induced by partial bladder outlet obstruction (PBOO) on sensory innervation of the corpus cavernosum (CC) and CC smooth muscle (CCSM) using a rat model of PBOO induced by a partial ligation of the bladder neck. Retrograde labeling technique was used to label dorsal root ganglion (DRG) neurons that innervate the urinary bladder and CC. Contractility and relaxation of the CCSM was studied in vitro, and expression of nitric oxide synthase (NOS) was evaluated by Western blotting. Concentration of the sensory neuropeptides substance P (SP) and calcitonin gene-related peptide was measured by ELISA. Partial obstruction of the bladder neck caused a significant hypertrophy of the urinary bladders (2.5-fold increase at 2 wk). Analysis of L6-S2 DRG sections determined that sensory ganglia received input from both the urinary bladder and CC with 5-7% of all neurons double labeled from both organs. The contractile responses of CC muscle strips to KCl and phenylephrine were decreased after PBOO, followed by a reduced relaxation response to nitroprusside. A significant decrease in neuronal NOS expression, but not in endothelial NOS or protein kinase G (PKG-1), was detected in the CCSM of the obstructed animals. Additionally, PBOO caused some impairment to sensory nerves as evidenced by a fivefold downregulation of SP in the CC (P ≤ 0.001). Our results provide evidence that PBOO leads to the impairment of bladder neck afferent innervation followed by a decrease in CCSM relaxation, downregulation of nNOS expression, and reduced content of sensory neuropeptides in the CC smooth muscle. These results suggest that nerve damage in PBOO may contribute to LUTS-ED comorbidity and trigger secondary changes in the contraction/relaxation mechanisms of CCSM.

Spinal cord FAAH in normal micturition control and bladder overactivity in awake rats

PURPOSE

We assessed whether spinal inhibition of the cannabinoid degrading enzyme FAAH would have urodynamic effects in normal rats and rats with bladder overactivity induced by partial urethral obstruction or prostaglandin E2. We also determined the expression of FAAH, and the cannabinoid receptors CB1 and CB2 in the sacral spinal cord.

MATERIALS AND METHODS

We used 44 rats for functional (cystometry) and Western blot experiments. The FAAH inhibitor oleoyl ethyl amide (3 to 300 nmol) was administered intrathecally (subarachnoidally) or intravenously. The expression of FAAH and CB1/CB2 receptors was determined by Western blot.

RESULTS

Oleoyl ethyl amide given intrathecally affected micturition in normal rats and rats with bladder overactivity but effects were more pronounced in the latter. In normal rats oleoyl ethyl amide only decreased micturition frequency, while it decreased frequency and bladder pressures in rats with bladder overactivity. Intravenous oleoyl ethyl amide (3 to 300 nmol) had no urodynamic effect. FAAH and CB1/CB2 receptors were expressed in the rat sacral spinal cord. The expression of CB1/CB2 receptors but not FAAH was higher in obstructed than in normal rats.

CONCLUSIONS

FAAH inhibition in the sacral spinal cord by oleoyl ethyl amide resulted in urodynamic effects in normal rats and rats with bladder overactivity. The spinal endocannabinoid system may be involved in normal micturition control and it appears altered when there is bladder overactivity.

Large-conductance calcium-activated potassium channel activity, as determined by whole-cell patch clamp recording, is decreased in urinary bladder smooth muscle cells from male rats with partial urethral obstruction

OBJECTIVES

To examine the effect of partial urethral obstruction (PUO) on bladder smooth muscle outward potassium current and the contribution of the large-conductance calcium-activated potassium (Maxi-K, BKCa) channel to this activity in smooth muscle cells isolated from bladders of sham-operated and PUO male rats using whole-cell patch clamp recording techniques. To determine the effect of PUO on the expression of the Maxi-K channel α and β1 subunits and in vitro detrusor contractility.

MATERIALS AND METHODS

Twenty adult male Sprague-Dawley rats were divided equally into two groups and subjected to surgical ligation of the urethra (PUO) or sham surgery (SHAM). After 2 weeks, the detrusors from PUO and SHAM rats were used for molecular analyses (mRNA and protein quantification of Maxi-K subunits) or organ bath contractility studies, or myocytes were isolated for conventional whole-cell patch clamp analyses.

RESULTS

PUO increased bladder mass 2.5-fold and detrusor strips exhibited a more tonic-type contraction and increased contractility compared with controls (SHAM). Iberiotoxin (300 nM) sensitive Maxi-K channel current comprised about 40% of the outward whole-cell current in SHAM bladders but only about 8% in PUO bladders. Expression of the α subunit of the Maxi-K channel was significantly decreased ~40% while the expression of the β1 subunit was increased ~2-fold at the mRNA level. The increase in β1 expression was confirmed by Western blotting.

CONCLUSIONS

Our findings show that obstruction of the rat bladder is associated with decreased Maxi-K channel activity of bladder smooth muscle cells, determined via direct current measurement. Increased expression of the β1 subunit points to a compensatory reaction to decreased Maxi-K channel activity. Maxi-K channel openers or gene therapy may therefore provide therapeutic benefit for the overactive bladder.

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

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

Intradetrusor botulinum neurotoxin A (BoNT-A) injections decrease bladder fibrosis secondary to partial urethral obstruction in the male rat model

AIMS

We evaluated effects of BoNT-A injections on bladder function and histomorphology in a male-rat-overactive-bladder model, created by partial urethral obstruction.

METHODS

A total of 45 male Sprague-Dawley rats were separated into 5 groups. Partial urethral obstruction (PUO) was created in all rats except the control group. At the 6th week after PUO, intradetrusor injections of 50 µl of saline (2 sham groups) or 50 µl BoNT-A (2 treatment groups) was performed. Treatment and sham groups were studied 5 and 30 days after injection and neuropharmacological and histomorphological findings on bladder tissues were compared to the control group.

RESULTS

Bladder muscle hypertrophy and connective tissue increase were detected at 5th and more prominent at 30th day after saline injection. Intradetrusor BoNT-A injection significantly reduced PUO-induced histological changes in the bladder tissue both at 5th and 30th day after injection. At 5th day after saline injection, a significantly increased contractile response to electrical field stimulation (EFS) and carbachol were recorded in the saline group and this effect disappeared at 30th day. There was no statistically significant difference between BoNT-A and control groups in terms of contractile responses to EFS and carbachol, both at 5th and 30th days.

CONCLUSION

Partial urethral obstruction induces increased bladder tissue contractile responses to neurogenic and pharmacological stimulation and intradetrusor BoNT-A injections decrease these responses at 5th days after injection. As the unique finding of this study, intradetrusor BoNT-A injections appear to decrease bladder fibrosis secondary to PUO in the male rat model.

Rodent models for urodynamic investigation

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

Blebbistain, a myosin II inhibitor, as a novel strategy to regulate detrusor contractility in a rat model of partial bladder outlet obstruction

Partial bladder outlet obstruction (PBOO), a common urologic pathology mostly caused by benign prostatic hyperplasia, can coexist in 40–45% of patients with overactive bladder (OAB) and is associated with detrusor overactivity (DO). PBOO that induces DO results in alteration in bladder myosin II type and isoform composition. Blebbistatin (BLEB) is a myosin II inhibitor we recently demonstrated potently relaxed normal detrusor smooth muscle (SM) and reports suggest varied BLEB efficacy for different SM myosin (SMM) isoforms and/or SMM vs nonmuscle myosin (NMM). We hypothesize BLEB inhibition of myosin II as a novel contraction protein targeted strategy to regulate DO. Using a surgically-induced male rat PBOO model, organ bath contractility, competitive and Real-Time-RT-PCR were performed. It was found that obstructed-bladder weight significantly increased 2.74-fold while in vitro contractility of detrusor to various stimuli was impaired ∼50% along with decreased shortening velocity. Obstruction also altered detrusor spontaneous activities with significantly increased amplitude but depressed frequency. PBOO switched bladder from a phasic-type to a more tonic-type SM. Expression of 5’ myosin heavy chain (MHC) alternatively spliced isoform SM-A (associated with tonic-type SM) increased 3-fold while 3’ MHC SM1 and essential light chain isoform MLC_17b also exhibited increased relative expression. Total SMMHC expression was decreased by 25% while the expression of NMM IIB (SMemb) was greatly increased by 4.5-fold. BLEB was found to completely relax detrusor strips from both sham-operated and PBOO rats pre-contracted with KCl, carbachol or electrical field stimulation although sensitivity was slightly decreased (20%) only at lower doses for PBOO. Thus we provide the first thorough characterization of the response of rat bladder myosin to PBOO and demonstrate complete BLEB-induced PBOO bladder SM relaxation. Furthermore, the present study provides valuable evidence that BLEB may be a novel type of potential therapeutic agent for regulation of myogenic and nerve-evoked DO in OAB.

Beta3-adrenoceptors in the rat sacral spinal cord and their functional relevance in micturition under normal conditions and in a model of partial urethral obstruction

AIMS

Beta3-adrenoceptor selective agonists are evaluated as a new treatment for patients with lower urinary tract symptoms . It is believed that β3-AR selective agonists exert their effects via a peripheral site of action. However, β3-ARs have been found in brain tissue. This study examined whether β3-ARs are present in rat sacral spinal cord, and whether there are differences in β3-AR expression between normal and partial urethral obstruction (PUO) animals, and furthermore assessed the functional relevance of spinal β3-ARs for micturition.

METHODS

Thirty-eight male Sprague-Dawley rats underwent either PUO or sham-operation. Two weeks after operation, half of the animals were used for histomorphological analysis. Remaining animals were used for functional experiments, where a β3-AR selective agonist, BRL 37344, was given intrathecally. Bladder function was assessed by continuous cystometry in non-anesthetized animals before and after drug administration.

RESULTS

Beta3-ARs were found in sacral spinal cord segments with an accumulation in the ventral horn. There was a significant increase of β3-AR expression in obstructed rats. In functional experiments obstructed rats showed increased bladder weight, micturition frequency, spontaneous activity, and bladder pressures (all P < 0.05) compared to controls. Intrathecally administered BRL 37344 showed no effect in non-obstructed rats. In obstructed rats intrathecal BRL 37344 significantly reduced bladder pressures, spontaneous activity, and micturition frequency (all P < 0.05).

CONCLUSIONS

Beta3-ARs are present in rat sacral spinal cord, and are significantly up-regulated after PUO. Besides their well-established peripheral site of action in the treatment of voiding dysfunction, β3-AR selective agonists might exert relevant effects at a central nervous site of action.

Effects of pentoxifylline on renal structure after urethral obstruction in rat: A stereological study

Objective

Chronic renal failure due to tubulointerstitial fibrosis is one of complications of lower urinary tract obstruction. Since pentoxifylline is a xanthine derivative that inhibits some inflammatory mediators, we conducted this study to investigate whether pentoxifylline inhibits renal fibrosis in a rat model of partial urethral obstruction (PUO).

Methods

All the rats underwent experimental PUO. Then, the animals were divided randomly into two groups: positive control group and experimental group. The experimental group received pentoxifylline 100 mg/kg per day via oral gavages for 4-weeks. The control group received the same dose of normal saline. After 4-weeks, all the rats underwent left nephrectomy. Kidney volume and weight and fractional and absolute volumes of the glomeruli, tubules, interstitium and vessels were determined with stereological methods. To reduce the workload of reference (kidney) volume estimation, the total kidney volume was determined after estimation of tissue shrinkage on isotropic uniform random histological sections. The total volume (amount) of each renal structure including fibrosis was estimated to avoid the bias conclusion due to relying on volume density alone.

Results

The absolute volume of interstitial fibrosis was lower in the experimental group (PUO with pentoxifylline treatment) (~84%; p ≤0.006) in comparison with the control group (PUO with no treatment).

Conclusion

Pentoxifylline reduces interstitial renal fibrosis after partial urethral obstruction in rats.