Characteristics of Spontaneous Activity in the Bladder Trigone

Bladder trigone sparing radiotherapy in prostate cancer treatment

INTRODUCTION

Evidence suggests the bladder trigone to be a potential organ at risk (OAR) in predicting acute and late genitourinary (GU) side effects when treating prostate cancer with radiotherapy.

METHODS

A search of MEDLINE, Cinahl, EMBASE, PubMed, the Cochrane Database of Systematic Reviews and OpenGrey was conducted and no current or underway systematic reviews or scoping reviews on the topic were identified. A systematic literature review was carried out assessing the quality of this evidence. All evidence that prospectively or retrospectively reviewed radiotherapy or modelled radiotherapy dose to the bladder trigone were included. The search was conducted on the 8th July 2021 with 32 studies included in this review. This was repeated 10th June 2023 and two additional studies were identified. Any evidence published since this date have not been included and are a limitation of this review.

RESULTS

MRI imaging is recommended to assist in delineating the trigone which has been shown to have a high amount of inter-observer variability and the use of specific training may reduce this. Across all radiotherapy treatment modalities, trigone dose contributed to GU acute and late toxicity symptoms. Trigone motion is relative to prostate motion but further research is required to confirm if the prostate can be used as a reliable surrogate for trigone position. The dose tolerance given for specific trigone related toxicities is debated within the literature, and on analysis the authors of this review suggest bladder trigone dose limits: Dmean < 45.8 Gy, V61.0Gy < 40%, V59.8Gy < 25%, V42.5Gy-V41.0Gy < 91% and V47.4Gy-V43.2Gy < 91% with α/β of 3 Gy to reduce acute and late GU toxicities.

CONCLUSION

There is evidence to support further research into bladder trigone sparing radiotherapy to improve patient outcomes.

IMPLICATION FOR PRACTICE

Using the bladder trigone as an organ at risk is possible and the authors are currently seeking funding for a feasibility trial to further investigate this.

Impact of Interfractional Bladder and Trigone Displacement and Deformation on Radiation Exposure and Subsequent Acute Genitourinary Toxicity: A Post Hoc Analysis of Patients Treated with Magnetic Resonance Imaging-Guided Prostate Stereotactic Body Radiation Therapy in a Phase 3 Randomized Trial

PURPOSE

Emerging data suggest that trigone dosimetry may be more associated with poststereotactic body radiation therapy (SBRT) urinary toxicity than whole bladder dosimetry. We quantify the dosimetric effect of interfractional displacement and deformation of the whole bladder and trigone during prostate SBRT using on-board, pretreatment 0.35T magnetic resonance images (MRI).

METHODS AND MATERIALS

Seventy-seven patients treated with MRI-guided prostate SBRT (40 Gy/5 fractions) on the MRI arm of a phase 3 single-center randomized trial were included. Bladder and trigone structures were contoured on images obtained from a 0.35T simulation MRI and 5 on-board pretreatment MRIs. Dice similarity coefficient (DSC) scores and changes in volume between simulation and daily treatments were calculated. Dosimetric parameters including Dmax, D0.03 cc, Dmean, V40 Gy, V39 Gy, V38 Gy, and V20 Gy for the bladder and trigone for the simulation and daily treatments were collected. Both physician-scored (Common Terminology Criteria for Adverse Events, version 4.03 scale) as well as patient-reported (International Prostate Symptom Scores and the Expanded Prostate Cancer Index Composite-26 scores) acute genitourinary (GU) toxicity outcomes were collected and analyzed.

RESULTS

The average treatment bladder volume was about 30% smaller than the simulation bladder volume; however, the trigone volume remained fairly consistent despite being positively correlated with total bladder volume. Overall, the trigone accounted for <2% of the bladder volume. Median DSC for the bladder was 0.79, whereas the median DSC of the trigone was only 0.33. No statistically significant associations between our selected bladder and trigonal dosimetric parameters and grade ≥2 GU toxicity were identified, although numerically, patients with GU toxicity (grade ≥2) had higher intermediate doses to the bladder (V20 Gy and Dmean) and larger volumes exposed to higher doses in the trigone (V40 Gy, V39 Gy, and V38 Gy).

CONCLUSIONS

The trigone exhibits little volume change, but considerable interfractional displacement/deformation. As a result, the relative volume of the trigone receiving high doses during prostate SBRT varies substantially between fractions, which could influence GU toxicity and may not be predicted by radiation planning dosimetry.

Dose-volume relationships of planned versus estimated delivered radiation doses to pelvic organs at risk and side effects in patients treated with salvage radiotherapy for recurrent prostate cancer

Purpose

To investigate estimated delivered dose distributions using weekly cone-beam computed tomography (CBCT) scans for pelvic organs at risk (OARs) in salvage radiotherapy (SRT) after radical prostatectomy. Furthermore, to compare them with the originally planned dose distributions and analyse associations with gastrointestinal (GI) and genitourinary (GU) side effects.

Methods

This study is part of a phase II trial involving SRT for recurrent prostate cancer. Treatment was personalised based on PSA response during SRT, classifying patients as PSA responders or non-responders. Estimated radiation dose distributions were obtained using deformable image registration from weekly CBCT scans. GI and GU toxicities were assessed using the RTOG toxicity scale, while patient-reported symptoms were monitored through self-assessment questionnaires.

Results

The study included 100 patients, with similar treatment-related side effects observed in both responders and non-responders. Differences in dose-volume metrics between the planned and estimated delivered doses for the examined OARs were mostly modest, although generally statistically significant. We identified statistically significant associations between QUANTEC-recommended dose-volume constraints and acute bowel toxicity, as well as late urinary patient-reported symptoms, for both the estimated delivered and planned dose distributions.

Conclusion

We found small but statistically significant differences between estimated delivered and planned doses to OARs. These differences showed trends toward improved associations for estimated delivered dose distributions with side effects. Enhanced registration methods and imaging techniques could potentially further enhance the assessment of truly delivered doses and yield more reliable dose-volume constraints for future therapies.

Adreno-Muscarinic Synergy of Contractile Responses From Human Hyperplastic Prostate

PURPOSE

Adreno-muscarinic synergy, a supra-additional contractile response to simultaneous application of α-adrenoreceptor and muscarinic receptor agonists, is a feature of several lower urinary tract regions that have dual sympathetic and parasympathetic innervation. We tested the hypothesis that synergy is also a feature of prostate tissue obtained from men with benign prostatic enlargement.

METHODS

Isolated tissue strips were dissected from prostate 'chips', collected after transurethral prostate resection procedures for in vitro experiments, to measure isometric tension at 36°C.

RESULTS

Added separately to the superfusate, phenylephrine and carbachol generated contractions with mean pEC50 (-log10EC50) values of 5.36 and 5.58, respectively, although phenylephrine maximal responses were about six-fold greater. In the presence of carbachol, the mean phenylephrine pEC50 was significantly increased to 5.84 and maximal response increased by 28%; overall, a significant synergistic response was demonstrated. The synergistic response was reduced by muscarinic receptor antagonists, most potently by the M3-selective agent 4-DAMP (1,1-dimethyl-4-diphenylacetoxypiperidinium iodide), and less so by M2 and M1-selective inhibitors gallamine and pirenzepine, but with an overall profile indicating M3/M2 mediation of the synergistic response. The magnitude of the synergistic response was variable between prostate chips that provided isolated preparations suggesting regional heterogenicity, although their zonal origin could not be determined.

CONCLUSION

These experiments show that adreno-muscarinic contractile synergy is a feature of human hyperplastic prostate tissue. This has implications for the use of a combination therapy of α-blockers and anti-muscarinic agent to relieve secondary symptoms associated with benign prostatic hyperplasia, at least in men who can tolerate antimuscarinics without a risk of retention.

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

Background

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

Aim

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

Methods

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

Outcomes

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

Results

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

Clinical Translation

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

Strengths and Limitations

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

Conclusion

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

Gene Expression-Based Functional Differences between the Bladder Body and Trigonal Urothelium in Adolescent Female Patients with Micturition Dysfunction

The aim of this study is to determine the molecular differences between the urothelial transcriptomes of the bladder body and trigone. The transcriptomes of the bladder body and trigonal epithelia were analyzed by massive sequencing of total epithelial RNA. The profiles of urothelial and urinal microbiomes were assessed by amplicon sequencing of bacterial 16S rRNA genes in 17 adolescent females with pain and micturition dysfunction and control female subjects. The RNA sequencing identified 10,261 differentially expressed genes (DEGs) in the urothelia of the bladder body and trigone, with the top 1000 DEGs at these locations annotated to 36 and 77 of the Reactome-related pathways in the bladder body and trigone, respectively. These pathways represented 11 categories enriched in the bladder body urothelium, including extracellular matrix organization, the neuronal system, and 15 categories enriched in the trigonal epithelium, including RHO GTPase effectors, cornified envelope formation, and neutrophil degranulation. Five bacterial taxa in urine differed significantly in patients and healthy adolescent controls. The evaluation of their transcriptomes indicated that the bladder body and trigonal urothelia were functionally different tissues. The molecular differences between the body and trigonal urothelia responsible for clinical symptoms in adolescents with bladder pain syndrome/interstitial cystitis remain unclear.

Validating Modern NRG Oncology Pelvic Nodal and Groupe Francophone de Radiothérapie Urologique Prostate Bed Contouring Guidelines for Post-Prostatectomy Salvage Radiation: A Secondary Analysis of the LOCATE Trial

PURPOSE

We used the patterns of recurrence on ¹⁸F-fluciclovine positron emission tomography (PET)-computed tomography (CT) in patients enrolled in the LOCATE trial after prostatectomy to evaluate how well the most recent NRG Oncology and Groupe Francophone de Radiothérapie Urologique (GFRU) contouring recommendations encompassed all sites of recurrence in the prostate fossa and pelvic nodes in comparison to former Radiation Therapy Oncology Group (RTOG) recommendations.

METHODS AND MATERIALS

Patients with biochemically recurrent prostate cancer after radical prostatectomy with a positive finding within the prostate fossa or pelvic nodes on ¹⁸F-fluciclovine PET/CTs were identified from the LOCATE patient population. Areas of gross disease were delineated. Prostate fossa contours were delineated using both the 2010 RTOG consensus guidelines and the recently published 2020 GFRU consensus guidelines. Pelvic nodes were contoured with both the 2009 RTOG consensus guidelines and the 2020 NRG consensus guidelines. The performance of the contouring guidelines was assessed by determining what proportion of gross recurrent lesions were encompassed completely or marginally.

RESULTS

Of the 213 patients within the LOCATE trial, 45 patients were eligible for analysis with positive ¹⁸F-fluciclovine PET findings. Of the 30 total prostate fossa recurrences, the 2010 RTOG contour covered 20 (67%) and missed or marginally covered 10 (33%). The 2020 GFRU contour covered 27 recurrences (90%), and missed or marginally covered 3 (10%). Of the 43 total nodal recurrences, the 2009 RTOG pelvic nodal contour covered 29 nodes (67%), and missed or marginally covered 14 (32%). The 2020 NRG pelvic nodal contour covered 43 nodes (100%), with no misses or marginal coverage.

CONCLUSIONS

This secondary analysis of the LOCATE trial exemplifies the improved coverage of the latest prostate fossa contouring recommendations from the GFRU. Similarly, it also validates the updated 2020 NRG pelvic nodal contouring guidelines by demonstrating improved coverage of recurrent disease in this patient population.

Proteomics as a Complementary Technique to Characterize Bladder Cancer

Simple Summary

Although immunohistochemistry is a routine technique in clinics, and genomics has been rapidly incorporated, proteomics is a step behind. This general situation is also the norm in bladder cancer research. This review shows the contributions of proteomics to the molecular classification of bladder cancer, and to the study of histopathology due to tissue insults caused by tumors. Furthermore, the importance of proteomics for understanding the cellular and molecular changes as a consequence of the therapy of bladder cancer cannot be neglected.

Abstract

Bladder cancer (BC) is the most common tumor of the urinary tract and is conventionally classified as either non-muscle invasive or muscle invasive. In addition, histological variants exist, as organized by the WHO-2016 classification. However, innovations in next-generation sequencing have led to molecular classifications of BC. These innovations have also allowed for the tracing of major tumorigenic pathways and, therefore, are positioned as strong supporters of precision medicine. In parallel, immunohistochemistry is still the clinical reference to discriminate histological layers and to stage BC. Key contributions have been made to enlarge the panel of protein immunomarkers. Moreover, the analysis of proteins in liquid biopsy has also provided potential markers. Notwithstanding, their clinical adoption is still low, with very few approved tests. In this context, mass spectrometry-based proteomics has remained a step behind; hence, we aimed to develop them in the community. Herein, the authors introduce the epidemiology and the conventional classifications to review the molecular classification of BC, highlighting the contributions of proteomics. Then, the advances in mass spectrometry techniques focusing on maintaining the integrity of the biological structures are presented, a milestone for the emergence of histoproteomics. Within this field, the review then discusses selected proteins for the comprehension of the pathophysiological mechanisms of BC. Finally, because there is still insufficient knowledge, this review considers proteomics as an important source for the development of BC therapies.

A single-blind randomized control trial of trigonal versus nontrigonal Botulinum toxin-A injections for patients with urinary incontinence and poor bladder compliance secondary to spinal cord injury

Objective: To evaluate the effect of trigonal Botulinum toxin-A (BTX-A) injections on patients with urinary incontinence (UI) and poor bladder compliance (BC) secondary to spinal cord injury (SCI).Design: A single-blind randomized control trial.Setting: Department of urology in three hospitals.Participants: SCI patients with UI and poor BC were randomly assigned to either the experimental group or the control group.Interventions: The experimental group received an injection of 240 U BTX-A into the detrusor plus 60 U BTX-A into the trigone, while the control group received 300 U BTX-A into the detrusor sparing the trigone.Outcome Measures: Video urodynamic outcomes, including vesicoureteric reflux (VUR), detrusor leak point pressure (DLPP), and detrusor leak point volume (DLPV), were measured at baseline and week 12. UI episodes, voiding volume, and Incontinence Quality of Life (I-QoL) were assessed at baseline, week 2, 4, 8 and 12.Results: No patient reported new-onset VUR. Compared with baseline data, a significant improvement was achieved in both groups, whereas compared with DLPP and DLPV, a significant difference was noted between the two groups 12 weeks after injection. In the experimental group, the improvement of mean weekly UI episodes, voiding volume, and I-QoL were significantly better than those in the control group at 4, 8, and 12 weeks, respectively (all P < 0.05). Systemic complications of BTX-A injection were not reported.Conclusion: Trigonal BTX-A injection is more effective and safer than nontrigonal BTX-A injection for SCI patients with UI secondary to neurogenic-poor BC and does not result in VUR.

Induction of bacterial cystitis in female rabbits by uropathogenic Escherichia coli and the differences between the bladder dome and trigone

This study is designed to evaluate the histological effects of uropathogenic Escherichia coli (UPEC) infection in the urinary bladder of female rabbits and compare the differences between the dome and trigone. Bacterial cystitis was induced in 13 female rabbits by transurethral inoculation of UPEC into the urinary bladder. Eight animals served as controls. Urine samples were collected by catheterization and cultured for bacterial growth after 12 and 24 hours then every 48 hours. Infection was defined as ≥(1X10⁵) colony-forming unit/ml of UPEC in the first two urine samples. Bladder dome and trigonal specimens were examined by light and scanning electron microscopy eight days after infection. There was a sustained increase in bacterial count, with urethral bleeding and rabbit weakness suggesting bladder colonization in the 10/13 study group (77%). Infection was not demonstrated in two animals and was spontaneously cleared in the third after 48 hours. No control animals developed an infection. In infected rabbits (n = 10), the dome showed inflammatory changes including the epithelial loss or thinning, inflammatory cell infiltration, and congested blood vessels compared to controls. The trigone showed a more pronounced inflammatory response than the dome. The presence of urinary bacterial growth, infection manifestations, and inflammatory changes that were more severe in the trigone than in the dome indicate successful bacterial inoculation and induction of cystitis. This animal model can be used for clinical trials on female cystitis. Our histological findings support a possible role of trigone in the pathogenesis of urinary tract infection.

Simulation of an HDR "Boost" with Stereotactic Proton versus Photon Therapy in Prostate Cancer: A Dosimetric Feasibility Study

Purpose/Objectives

To compare the dose escalation potential of stereotactic body proton therapy (SBPT) versus stereotactic body photon therapy (SBXT) using high-dose rate prostate brachytherapy (HDR-B) dose-prescription metrics.

Patients and Methods

Twenty-five patients previously treated with radiation for prostate cancer were identified and stratified by prostate size (≤ 50cc; n = 13, > 50cc; n = 12). Initial CT simulation scans were re-planned using SBXT and SBPT modalities using a prescription dose of 19Gy in 2 fractions. Target coverage goals were designed to mimic the dose distributions of HDR-B and maximized to the upper limit constraint for the rectum and urethra. Dosimetric parameters between SBPT and SBXT were compared using the signed-rank test and again after stratification for prostate size (≤ 50cm³ and >50cm³) using the Wilcoxon rank test.

Results

Prostate volume receiving 100% of the dose (V100) was significantly greater for SBXT (99%) versus SBPT (96%) (P ≤ 0.01), whereas the median V125 (82% vs. 73%, P < 0.01) and V200 (12% vs. 2%, P < 0.01) was significantly greater for SBPT compared to SBXT. Median V150 was 49% for both cohorts (P = 0.92). V125 and V200 were significantly correlated with prostate size. For prostates > 50cm³, V200 was significantly greater with SBPT compared to SBXT (14.5% vs. 1%, P = 0.005), but not for prostates 50cm³ (9% vs 4%, P = 0.11). Median dose to 2cm³ of the bladder neck was significantly lower with SBPT versus SBXT (9.6 Gy vs. 14 Gy, P < 0.01).

Conclusion

SBPT and SBXT can be used to simulate an HDR-B boost for locally advanced prostate cancer. SBPT demonstrated greater dose escalation potential than SBXT. These results are relevant for future trial design, particularly in patients with high risk prostate cancer who are not amenable to brachytherapy.

Spontaneous Activity and the Urinary Bladder

The urinary bladder has two functions: to store urine, when it is relaxed and highly compliant; and void its contents, when intravesical pressure rises due to co-ordinated contraction of detrusor smooth muscle in the bladder wall. Superimposed on this description are two observations: (1) the normal, relaxed bladder develops small transient increases of intravesical pressure, mirrored by local bladder wall movements; (2) pathological, larger pressure variations (detrusor overactivity) can occur that may cause involuntary urine loss and/or detrusor overactivity. Characterisation of these spontaneous contractions is important to understand: how normal bladder compliance is maintained during filling; and the pathophysiology of detrusor overactivity. Consideration of how spontaneous contractions originate should include the structural complexity of the bladder wall. Detrusor smooth muscle layer is overlain by a mucosa, itself a complex structure of urothelium and a lamina propria containing sensory nerves, micro-vasculature, interstitial cells and diffuse muscular elements.Several theories, not mutually exclusive, have been advanced for the origin of spontaneous contractions. These include intrinsic rhythmicity of detrusor muscle; modulation by non-muscular pacemaking cells in the bladder wall; motor input to detrusor by autonomic nerves; regulation of detrusor muscle excitability and contractility by the adjacent mucosa and spontaneous contraction of elements of the lamina propria. This chapter will consider evidence for each theory in both normal and overactive bladder and how their significance may vary during ageing and development. Further understanding of these mechanisms may also identify novel drug targets to ameliorate the clinical consequences of large contractions associated with detrusor overactivity.

Properties of single-channel and whole cell Cl- currents in guinea pig detrusor smooth muscle cells

Multiple types of Cl^- channels regulate smooth muscle excitability and contractility in vascular, gastrointestinal, and airway smooth muscle cells. However, little is known about Cl^- channels in detrusor smooth muscle (DSM) cells. Here, we used inside-out single channel and whole cell patch-clamp recordings for detailed biophysical and pharmacological characterizations of Cl^- channels in freshly isolated guinea pig DSM cells. The recorded single Cl^- channels displayed unique gating with multiple subconductive states, a fully opened single-channel conductance of 164 pS, and a reversal potential of -41.5 mV, which is close to the E_Cl of -65 mV, confirming preferential permeability to Cl^-. The Cl^- channel demonstrated strong voltage dependence of activation (half-maximum of mean open probability, V_0.5, ~-20 mV) and robust prolonged openings at depolarizing voltages. The channel displayed similar gating when exposed intracellularly to solutions containing Ca²⁺-free or 1 mM Ca²⁺. In whole cell patch-clamp recordings, macroscopic current demonstrated outward rectification, inhibitions by 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid (DIDS) and niflumic acid, and insensitivity to chlorotoxin. The outward current was reversibly reduced by 94% replacement of extracellular Cl^- with I^-, Br^-, or methanesulfonate (MsO^-), resulting in anionic permeability sequence: Cl^->Br^->I^->MsO^-. While intracellular Ca²⁺ levels (0, 300 nM, and 1 mM) did not affect the amplitude of Cl^- current and outward rectification, high Ca²⁺ slowed voltage-step current activation at depolarizing voltages. In conclusion, our data reveal for the first time the presence of a Ca²⁺-independent DIDS and niflumic acid-sensitive, voltage-dependent Cl^- channel in the plasma membrane of DSM cells. This channel may be a key regulator of DSM excitability.

Pharmacological modulation of the spatiotemporal disposition of micromotions in the intact resting urinary bladder of the rabbit; their pattern is under both myogenic and autonomic control

OBJECTIVES

To explore and characterize the disposition and dynamics of micromotions in the wall of the intact resting teradotoxinized urinary bladder of the rabbit before and after the administration of adrenergic and cholinergic pharmaceutical agents.

METHODS

Spatiotemporal maps and related intravesical pressure were used to analyse propagating patches of contractions (PPCs) and their component individual myogenic contractions [propagating individual contractions (PICs)] in the wall of the tetradotoxinized urinary bladder.

RESULTS

The bladder wall exhibited two contractile states that were of similar frequencies to those of the two types of electrophysiological discharge described in previous studies; the first, in which cyclic PPCs predominated, the second in which small irregular PICs predominated. The addition of carbachol increased the size, frequency, speed and distance of propagation of PPCs, whereas the addition of isoprenaline temporarily halted the incorporation of PICs into PPCs, and reduced patch size and total area undergoing contraction. The RhoA kinase (ROCK) inhibitor Y-27632 reduced both largest patch index and mean patch size. Both carbenoxolone and ROCK inhibition decreased the duration of PPCs. Carbenoxolone also prolonged duration and accelerated PPC propagation velocity. The authors postulate that these differences arise from differing effects of these agents on myocytes and interstitial cells within the stress environment of the bladder, influencing the development, coordination and propagation of PPCs.

CONCLUSIONS

The timings and structure of spontaneous micromotions in the wall of the isolated bladder change when it is treated with sympathetic/parasympathetic agonists and with myogenically active agents. Correspondingly, disorders of bladder wall contraction may result from disorders of either neurogenic or myogenic signalling and may be amenable to treatment with combinations of agents that influence both.

An Investigation of Dosimetric Correlates of Acute Toxicity in Prostate Stereotactic Body Radiotherapy: Dose to Urinary Trigone is Associated with Acute Urinary Toxicity

AIMS

There are limited data on dosimetric correlates of toxicity in stereotactic body radiotherapy (SBRT) for prostate cancer. We aimed to identify potential relationships between dose and toxicity using conventional dose-volume histograms (DVHs) and dose-surface maps (DSMs).

MATERIALS AND METHODS

Urinary bladder trigone and rectum DSMs were produced for a single-institution service evaluation cohort of 50 patients receiving SBRT for localised prostate cancer, together with conventional DVHs for bladder and rectum. Patients had been prospectively recruited to this cohort and treated according to a pre-defined protocol to a dose of 36.25 Gy in five fractions. Radiation Therapy Oncology Group (RTOG) and International Prostate Symptom Score (IPSS) toxicity data were recorded prospectively. Logistic regression was used to identify dosimetric predictors of acute IPSS+10 (rise of 10 points or more above baseline) and grade 2+ RTOG toxicity.

RESULTS

On univariate analysis, trigone area receiving 40 Gy and trigone Dmax were associated with IPSS+10 (odds ratio 1.06 [1.02-1.11], P = 0.007 and odds ratio 1.54 [1.06-2.25], P = 0.024, respectively). These two variables were highly correlated. In a multivariate model, including all baseline variables, trigone Dmax remained associated with IPSS+10 (odds ratio 1.91 [1.13-3.22], P = 0.016). These findings were not significant with Holm-Bonferroni correction for multiple testing (corrected P value threshold 0.006). No associations were seen between rectal toxicity and DVH or DSM parameters.

CONCLUSIONS

Our study suggests a potential relationship between high doses to the urinary bladder trigone and patient-reported urinary toxicity in prostate SBRT, and is consistent with previous studies in conventionally fractionated radiotherapy, justifying further evaluation in larger cohorts.

Location-dependent correlation between tissue structure and the mechanical behaviour of the urinary bladder

The mechanical properties of the urinary bladder wall are important to understand its filling-voiding cycle in health and disease. However, much remains unknown about its mechanical properties, especially regarding regional heterogeneities and wall microstructure. The present study aimed to assess the regional differences in the mechanical properties and microstructure of the urinary bladder wall. Ninety (n=90) samples of porcine urinary bladder wall (ten samples from nine different locations) were mechanically and histologically analysed. Half of the samples (n=45) were equibiaxially tested within physiological conditions, and the other half, matching the sample location of the mechanical tests, was frozen, cryosectioned, and stained with Picro-Sirius red to differentiate smooth muscle cells, extracellular matrix, and fat. The bladder wall shows a non-linear stress-stretch relationship with hysteresis and softening effects. Regional differences were found in the mechanical response and in the microstructure. The trigone region presents higher peak stresses and thinner muscularis layer compared to the rest of the bladder. Furthermore, the ventral side of the bladder presents anisotropic characteristics, whereas the dorsal side features perfect isotropic behaviour. This response matches the smooth muscle fibre bundle orientation within the tunica muscularis. This layer, comprising approximately 78% of the wall thickness, is composed of two fibre bundle arrangements that are cross-oriented, one with respect to the other, varying the angle between them across the organ. That is, the ventral side presents a 60°/120° cross-orientation structure, while the muscle bundles were oriented perpendicular in the dorsal side.

STATEMENT OF SIGNIFICANCE

In the present study, we demonstrate that the mechanical properties and the microstructure of the urinary bladder wall are heterogeneous across the organ. The mechanical properties and the microstructure of the urinary bladder wall within nine specific locations matching explicitly the mechanical and structural variations have been examined. On the one hand, the results of this study contribute to the understanding of bladder mechanics and thus to their functional understanding of bladder filling and voiding. On the other hand, they are relevant to the fields of constitutive formulation of bladder tissue, whole bladder mechanics, and bladder-derived scaffolds i.e., tissue-engineering grafts.

Late toxicity after post-prostatectomy intensity modulated radiation therapy: Evaluating normal-tissue sparing guidelines

Purpose

Dose-volume histogram (DVH) toxicity relationships are poorly defined in men who receive radiation after radical prostatectomy (RP). We evaluated Radiation Therapy Oncology Group (RTOG) study 0534 and institutional intact normal-tissue sparing guidelines, as well as dose to bladder trigone, for ability to minimize late toxicity.

Methods and materials

164 men received intensity modulated radiation therapy (RT) to a median prostate bed dose of 66.6 Gy at a median of 22 months after RP. 46% of men were prescribed androgen deprivation therapy and pelvic lymph node irradiation to a median dose of 50.4 Gy. DVH relationships for the rectum, bladder, trigone, and bladder excluding the clinical target volume (bladder-CTV) were analyzed against the Common Terminology Criteria for Adverse Events late grade 2 + (G2+) gastrointestinal (GI) and genitourinary (GU) toxicity by log-rank test. RTOG 0534 (rectum V65, 40 Gy ≤35, 55%, and bladder-CTV V65, 40 ≤50, 70%) and intact prostate RT institutional guidelines (rectum V70, 65, 40 ≤20, 40, 80% and bladder V70, 65, 40 ≤30, 60, 80%, respectively) guidelines were evaluated.

Results

With a median follow-up time of of 33 months, the 4-year freedom from G2 + GI and GU toxicity were both 91%. G2 + GI (n = 12) and GU (n = 15) toxicity included 4% diarrhea (n = 6), 4% hemorrhage (n = 6), 1% proctitis (n = 1), and 4% urinary frequency (n = 7), 1% obstructive (n = 2), 2% cystitis (n = 3), and 3% incontinence (n = 5), respectively. RTOG 0534 rectum and bladder goals were not achieved in 65% and 41% of cases, while the institutional intact prostate goals were not achieved in 21% and 25% of cases, respectively. Neither dose to the bladder trigone nor any of the proposed normal tissue goals were associated with late toxicity (P > .1). In the univariate analysis, age, pelvic RT, RT dose, anticoagulation use, androgen deprivation therapy, time from RP to RT, and tobacco history were not associated with toxicity.

Conclusions

More than 90% of men were free from late G2 + toxicity 4 years after post-RP intensity modulated RT. No tested parameters were associated with late toxicity. In the absence of established normal-tissue DVH guidelines in the postoperative setting, the use of intact guidelines is reasonable.

Adreno-muscarinic synergy in the male human urinary outflow tract

AIM

To examine putative interaction between adrenergic and muscarinic contractile activation in the human urinary outflow tract.

METHODS

Tissue from the trigone and prostatic urethra was obtained from 12 cystectomy and 16 prostatectomy specimen. Contractions were elicited by exposure to exogenous agonists before and after inhibition of Rho kinase and protein kinase c (PKC). Immunofluorescence and Western-blot studies were performed using antibodies to muscarinic M3-receptors (M3-R) and alpha1A-adrenoreceptors (alpha1A-AR). The study is registered with ClinicalTrials.gov, number NCT01227447.

RESULTS

There was strong co-localization of M3-R and alpha1A-AR on trigonal and urethral myocytes. Western blot analysis revealed a significantly higher expression of alpha1A-AR in the superficial than in the deep trigone. Phenylephrine (PE, 1 μm) augmented contractions induced by carbachol (CA, 3 μm) to more than threefold control in the male superficial trigone, and to about sevenfold control in the proximal urethra. No such potentiation could be detected in female bladder outlet. Both PKC inhibitor GF 109203X and Rho kinase inhibitor Y-27632 reduced responses to 1 μM PE as well as to 3 μM CA significantly. However, the synergistic effect of the combined intervention remained proportionally unaffected.

CONCLUSIONS

Muscarinic and adrenergic receptor activation exerts a strong synergistic effect in the male human bladder trigone and proximal urethra.

PRISMA-combined α-blockers and antimuscarinics for ureteral stent-related symptoms: A meta-analysis

BACKGROUND

As a monotherpay, a-blockers and anti-muscarinics are both efficacy for ureteral stent-related symptoms (SRS). The aim of the study was to systematically evaluate their efficacy of a combination therapy for SRS.

METHODS

Relevant studies investigating α-blockers and/or anti-muscarinics for SRS were identified though searching online databases including PubMed, EMBASE, Cochrane Library, and other sources up to March 2016. The RevMan software was used for data analysis, and senesitivity analysis and inverted funnel plot were also adopted.

RESULTS

Seven randomized controlled trials (RCTs) and 1 prospective controlled trial including 545 patients were selected. Compared with α-blockers, the combination group achieved significant improvements in total International Prostate Symptom Score (IPSS) [-3.93 (2.89, 4.96), P < 0.00001], obstructive subscore [-1.29 (0.68, 1.89), P < 0.0001], irritative subscore [-2.93 (2.18, 3.68), P < 0.00001], and quality of life score [-0.99 (0.42, 1.55), P < 0.001]. Compared with antimuscarinics, there were also significant differences in total IPSS [-3.49 (2.43, 4.55), P < 0.00001], obstructive subscore [-1.40 (0.78, 2.01), P < 0.00001], irritative subscore [-2.10 (1.30, 2.90), P < 0.00001], and quality of life score [-1.18 (0.58, 1.80), P < 0.001] in favor of combination group. No significant difference was found in the visual analog pain score and the urinary symptoms score in Ureteral Stent Symptom Questionnaire (USSQ). No significant difference in complications was found.

CONCLUSIONS

Current analysis shows significant advantages of combination therapy compared with monotherapy of α-blockers or antimuscarinics alone mainly based on IPSS. More RCTs adopting validated USSQ as outcome measures are warranted to support the finding.

Dose to the bladder neck is the most important predictor for acute and late toxicity after low-dose-rate prostate brachytherapy: implications for establishing new dose constraints for treatment planning

PURPOSE

To identify an anatomic structure predictive for acute (AUT) and late (LUT) urinary toxicity in patients with prostate cancer treated with low-dose-rate brachytherapy (LDR) with or without external beam radiation therapy (EBRT).

METHODS AND MATERIALS

From July 2002 to January 2013, 927 patients with prostate cancer (median age, 66 years) underwent LDR brachytherapy with Iodine 125 (n=753) or Palladium 103 (n=174) as definitive treatment (n=478) and as a boost (n=449) followed by supplemental EBRT (median dose, 50.4 Gy). Structures contoured on the computed tomographic (CT) scan on day 0 after implantation included prostate, urethra, bladder, and the bladder neck, defined as 5 mm around the urethra between the catheter balloon and the prostatic urethra. AUT and LUT were assessed with the Common Terminology Criteria for Adverse Events, version4. Clinical and dosimetric factors associated with AUT and LUT were analyzed with Cox regression and receiver operating characteristic analysis to calculate area under the receiver operator curve (ROC) (AUC).

RESULTS

Grade ≥2 AUT and grade ≥2 LUT occurred in 520 patients (56%) and 154 patients (20%), respectively. No grade 4 toxicities were observed. Bladder neck D2cc retained a significant association with AUT (hazard ratio [HR], 1.03; 95% confidence interval [CI], 1.03-1.04; P<.0001) and LUT (HR, 1.01; 95% CI, 1.00-1.03; P=.014) on multivariable analysis. In a comparison of bladder neck with the standard dosimetric variables by use of ROC analysis (prostate V100 >90%, D90 >100%, V150 >60%, urethra D20 >130%), bladder neck D2cc >50% was shown to have the strongest prognostic power for AUT (AUC, 0.697; P<.0001) and LUT (AUC, 0.620; P<.001).

CONCLUSIONS

Bladder neck D2cc >50% was the strongest predictor for grade ≥2 AUT and LUT in patients treated with LDR brachytherapy. These data support inclusion of bladder neck constraints into brachytherapy planning to decrease urinary toxicity.

Central role of the BK channel in urinary bladder smooth muscle physiology and pathophysiology

The physiological functions of the urinary bladder are to store and periodically expel urine. These tasks are facilitated by the contraction and relaxation of the urinary bladder smooth muscle (UBSM), also known as detrusor smooth muscle, which comprises the bladder wall. The large-conductance voltage- and Ca(2+)-activated K(+) (BK, BKCa, MaxiK, Slo1, or KCa1.1) channel is highly expressed in UBSM and is arguably the most important physiologically relevant K(+) channel that regulates UBSM function. Its significance arises from the fact that the BK channel is the only K(+) channel that is activated by increases in both voltage and intracellular Ca(2+). The BK channels control UBSM excitability and contractility by maintaining the resting membrane potential and shaping the repolarization phase of the spontaneous action potentials that determine UBSM spontaneous rhythmic contractility. In UBSM, these channels have complex regulatory mechanisms involving integrated intracellular Ca(2+) signals, protein kinases, phosphodiesterases, and close functional interactions with muscarinic and β-adrenergic receptors. BK channel dysfunction is implicated in some forms of bladder pathologies, such as detrusor overactivity, and related overactive bladder. This review article summarizes the current state of knowledge of the functional role of UBSM BK channels under normal and pathophysiological conditions and provides new insight toward the BK channels as targets for pharmacological or genetic control of UBSM function. Modulation of UBSM BK channels can occur by directly or indirectly targeting their regulatory mechanisms, which has the potential to provide novel therapeutic approaches for bladder dysfunction, such as overactive bladder and detrusor underactivity.

Impact of dose to the bladder trigone on long-term urinary function after high-dose intensity modulated radiation therapy for localized prostate cancer

PURPOSE

To determine the potential association between genitourinary (GU) toxicity and planning dose-volume parameters for GU pelvic structures after high-dose intensity modulated radiation therapy in localized prostate cancer patients.

METHODS AND MATERIALS

A total of 268 patients who underwent intensity modulated radiation therapy to a prescribed dose of 86.4 Gy in 48 fractions during June 2004-December 2008 were evaluated with the International Prostate Symptom Score (IPSS) questionnaire. Dose-volume histograms of the whole bladder, bladder wall, urethra, and bladder trigone were analyzed. The primary endpoint for GU toxicity was an IPSS sum increase ≥10 points over baseline. Univariate and multivariate analyses were done by the Kaplan-Meier method and Cox proportional hazard models, respectively.

RESULTS

Median follow-up was 5 years (range, 3-7.7 years). Thirty-nine patients experienced an IPSS sum increase ≥10 during follow-up; 84% remained event free at 5 years. After univariate analysis, lower baseline IPSS sum (P=.006), the V90 of the trigone (P=.006), and the maximal dose to the trigone (P=.003) were significantly associated with an IPSS sum increase ≥10. After multivariate analysis, lower baseline IPSS sum (P=.009) and increased maximal dose to the trigone (P=.005) remained significantly associated. Seventy-two patients had both a lower baseline IPSS sum and a higher maximal dose to the trigone and were defined as high risk, and 68 patients had both a higher baseline IPSS sum and a lower maximal dose to the trigone and were defined as low risk for development of an IPSS sum increase ≥10. Twenty-one of 72 high-risk patients (29%) and 5 of 68 low-risk patients (7%) experienced an IPSS sum increase ≥10 (P=.001; odds ratio 5.19).

CONCLUSIONS

The application of hot spots to the bladder trigone was significantly associated with relevant changes in IPSS during follow-up. Reduction of radiation dose to the lower bladder and specifically the bladder trigone seems to be associated with a reduction in late GU toxicity.

T-type Ca2+ channels and the urinary and male genital tracts

T-type Ca(2+) channels are widely expressed throughout the urinary and male genital tracts, generally alongside L-type Ca(2+) channels. The use of pharmacological blockers of these channels has suggested functional roles in all regions, with the possible exception of the ureter. Their functional expression is apparent not just in smooth muscle cells but also in interstitial cells that lie in close proximity to muscle, nerve and epithelial components of these tissues. Thus, T-type Ca(2+) channels can contribute directly to modulation of muscle function and indirectly to changes of epithelial and nerve function. T-type Ca(2+) channel activity modulates phasic contractile activity, especially in conjunction with Ca(2+)-activated K(+) channels, and also to agonist-dependent responses in different tissues. Upregulation of channel density occurs in pathological conditions associated with enhanced contractile responses, e.g. overactive bladder, but it is unclear if this is causal or a response to the pathological state. Moreover, T-type Ca(2+) channels may have a role in the development of prostate tumours regulating the secretion of mitogens from neuroendocrine cells. Although a number of selective channel blockers exist, their relative selectivity over L-type Ca(2+) channels is often low and makes evaluation of T-type Ca(2+) channel function in the whole organism difficult.

Low concentrations of niflumic acid enhance basal spontaneous and carbachol-induced contractions of the detrusor

PURPOSE

The urinary bladder expresses Ca(2+)-activated Cl(-) channels (CACC), but its physiological role in governing contractility remains to be defined. The CACC modulator niflumic acid (NFA) is widely used despite the variable results arisen from different drug concentrations used. This study was designed to examine the effects of NFA at low concentrations on detrusor strip contractility.

METHODS

Rat detrusor strips with mucosa-intact (+MU) and mucosa-denuded (-MU) were prepared in transverse (Tr) and longitudinal (Lg) with respect to the bladder orientation. Isometric force measurements were made at baseline (for spontaneous phasic contractile activity) and during drug stimulation (by carbachol, CCh) with and without NFA.

RESULTS

NFA (1 and 10 μmol/L) pretreatment enhanced CCh-induced contractions more in +MU than -MU strips with no selectivity on contractile direction. For spontaneous phasic contractions, NFA-treated strips in the Tr direction showed increased phasic amplitude, while phasic frequency was unchanged.

CONCLUSIONS

The findings suggest low concentrations of NFA having a potentiating effect on detrusor contractions that was sensitive to the MU and contractile direction.

Therapeutic effects of connexin inhibitors on detrusor overactivity induced by bladder outlet obstruction in rats

OBJECTIVES

To investigate the alterations in Connexin 43 (Cx43) and connexin 26 (Cx26) levels in the bladder outlet obstruction (BOO)-induced detrusor overactivity and examine the effect of connexin inhibitors on this condition.

METHODS

Fifty Sprague-Dawley rats were divided into 4 groups: sham-operated control group (n = 10), BOO group (n = 10), and 2 groups that were administered connexin inhibitors. The first of these 2 groups was administered 18β-glycyrrhetinic acid (BOO-18β-GA group, n = 15) and the second group was given oleamide (BOO-oleamide group, n = 15). Cystometrogram was performed in all groups after 2 weeks of obstruction. The expression levels of Cx26 and Cx43 were analyzed using immunohistochemical staining and Western blot.

RESULTS

The intercontraction interval was markedly shorter in the BOO group compared with the control group (P <.05). Intercontraction intervals in the BOO-18β-GA and BOO-oleamide groups at 2 weeks were significantly longer than that observed for the BOO group (P <.05). The expression of Cx43 and Cx26 were increased in the BOO group. After administration of connexin inhibitors, downregulation of Cx43 and Cx26 was noted.

CONCLUSIONS

These results suggest that upregulation of Cx43 and Cx26 induce detrusor overactivity after BOO, and connexin inhibitors may have some role in relieving BOO-induced detrusor overactivity in rats.

Is the urothelium intelligent?

The urothelium separates the urinary tract lumen from underlying tissues of the tract wall. Previously considered as merely an effective barrier between these two compartments it is now recognized as a more active tissue that senses and transduces information about physical and chemical conditions within the urinary tract, such as luminal pressure, urine composition, etc. To understand this sensory function it is useful to consider the urothelium and suburothelium as a functional unit; containing uroepithelial cells, afferent and efferent nerve fibers and suburothelial interstitial cells. This structure responds to alterations in its external environment through the release of diffusible agents, such as ATP and acetylcholine, and eventually modulates the activity of afferent nerves and underlying smooth muscles. This review considers different stresses the urothelium/suburothelium responds to; the particular chemicals released; the cellular receptors that are consequently affected; and how nerve and muscle function is modulated. Brief consideration is also to regional differences in the urothelium/suburothelium along the urinary tract. The importance of different pathways in relaying sensory information in the normal urinary tract, or whether they are significant only in pathological conditions is also discussed. An operational definition of intelligence is used, whereby a system (urothelium/suburothelium) responds to external changes, to maximize the possibility of the urinary tract achieving its normal function. If so, the urothelium can be regarded as intelligent. The advantage of this approach is that input-output functions can be mathematically formulated, and the importance of different components contributing to abnormal urinary tract function can be calculated.