Functional, histological and molecular characteristics of human exstrophy detrusor

Innervation pattern of the unclosed detrusor muscle in classic bladder exstrophy: a study of patients with urothelial overexpression of nerve growth factor

PURPOSE

An overexpression of nerve growth factor (NGF) in the urothelium is discussed to lead to neuronal hyperinnervation of the bladder detrusor. The aim was to assess the sensory and sympathetic innervation of the detrusor in unclosed exstrophic bladders patients with known overexpression of NGF in the urothelium.

METHODS

Full-thickness bladder biopsies were prospectively obtained from 34 infants at delayed primary bladder closure between 01/2015 and 04/2020. The bladder biopsies were immunohistochemically stained with antibodies against S100, calcitonin gene-related peptide (anti-CGRP), Neurofilament 200 (anti-NF200), and tyrosine-hydroxylase (anti-TH). Specimens from 6 children with congenital vesicoureterorenal reflux (VUR) served as controls.

RESULTS

There was no statistically significant difference in nerve fiber density in any of the immunohistochemical assessments (anti-S100 [p = 0.210], anti-CGRP [p = 0.897], anti-NF200 [p = 0.897]), and anti-TH [p = 0.956]) between patients with BE and patients with VUR. However, we observed a trend toward lower nerve fiber densities in exstrophic detrusor.

CONCLUSION

Overall our results showed an unharmed innervation pattern in this cohort but a lower density of nerve fibers in the detrusor compared to controls. Further studies in patients after successful primary closure are needed to clarify the potential impact of the urothelial overexpression of NGF modulating the innervation pattern in exstrophic bladders.

Targeting neurotrophin and nitric oxide signaling to promote recovery and ameliorate neurogenic bladder dysfunction following spinal cord injury - Mechanistic concepts and clinical implications

This review summarizes the presentations made to a workshop entitled "Targeting Neurotrophin and Nitric Oxide Signaling to Promote Recovery and Ameliorate Neurogenic Bladder Dysfunction following Spinal Cord Injury - Mechanistic Concepts and Clinical Implications" at the International Continence Society (ICS) 2022 Vienna Meeting. Spinal cord injury (SCI; T8-T9 contusion/transection) causes impaired mobility, neurogenic detrusor overactivity (NDO), detrusor sphincter dyssynergia (DSD) and subsequent decreased quality of life. This workshop discussed the potential of future therapeutic agents that manage the lesion and its consequences, in particular possibilities to reduce the lesion itself and manage pathophysiological changes to the lower urinary tract (LUT). Attenuation of the spinal cord lesion itself was discussed with respect to the potential of a trio of agents: LM11A-3, a p75 neurotrophin receptor modulator to counter activation of local apoptotic pathways; LM22B-10 to promote neuronal growth by targeting tropomyosin-related kinase (Trk) receptors; and cinaciguat, a soluble guanylate cyclase (sGC) activator as an agent promoting angiogenesis at the injury site. The workshop also discussed targets on the bladder to block selectivity sites associated with detrusor overactivity and poor urinary filling profiles, such as purinergic pathways controlling excess contractile activity and afferent signaling, as well as excess fibrosis. Finally, the importance of increased mechanosensitive signaling as a contributor to DSD was considered, as well as potential drug targets. Overall, an emphasis was placed on targets that help restore function and reduce pathological LUT consequences, rather than downregulate normal function.

Inflammatory Expression Profiles in Bladder Exstrophy Smooth Muscle: Normalization Over Time

OBJECTIVE

To test the hypothesis that phenotypes in bladder exstrophy result from alterations in detrusor smooth muscle cell (SMC) gene expression.

METHODS

We generated primary human bladder smooth muscle cell lines from patients with classic bladder exstrophy (CBE) undergoing newborn closure (n = 6), delayed primary closure (n = 5), augmentation cystoplasty (n = 6), and non-CBE controls (n = 3). Gene expression profiles were then created using RNA sequencing and characterized using gene set enrichment analysis (GSEA).

RESULTS

We identified 308 differentially expressed genes in bladder exstrophy SMC when compared to controls, including 223 upregulated and 85 downregulated genes. Bladder exstrophy muscle cell lines from newborn closure and primary delayed closures shared expression changes in 159 genes. GSEA analysis revealed increased expression in the inflammatory response and alteration of genes for genitourinary development in newborn and delayed closure SMC. However, these changes were absent in SMC from older exstrophy patients after closure.

CONCLUSION

Bladder exstrophy SMC demonstrate gene expression changes in the inflammatory response and genitourinary development. However, gene expression profiles normalized in exstrophy SMC from older patients after closure, suggesting a normalization of exstrophy SMC over time. Our in vitro findings regarding the normalization of exstrophy SMC gene expression following bladder closure suggest that the development of poor detrusor compliance in bladder exstrophy has a complex multifactorial etiology. Taken together, our findings suggest that alterations in SMC gene expression may explain abnormalities in the exstrophy bladder seen prior to and immediately after closure and suggest that surgical closure may allow exstrophy SMC to normalize over time.

Frequency-dependent characteristics of nerve-mediated ATP and acetylcholine release from detrusor smooth muscle

NEW FINDINGS

The frequency-dependencies of acetylcholine (ACh) and ATP co-transmitter release are different. ACh release can be modelled to a one-compartment process, whereas ATP release requires a two-compartment model. Nerve-mediated release of ACh and ATP can be independently regulated, for example by the phosphodiesterase-type 5 inhibitor, sildenafil. What is the central question of this study? Is the frequency-dependency of co-transmitter release from postganglionic nerve fibres different for each transmitter? What is the main finding and its importance? Release of co-transmitters from the parasympathetic supply to detrusor smooth muscle can be independently regulated. This offers a targeted drug model to reduce selectively the release of transmitter associated with human pathologies (ATP) and may also be applicable to other smooth muscle-based disorders of visceral tissues.

ABSTRACT

Nerve-mediated contractions of detrusor smooth muscle are mediated by acetylcholine (ACh) and ATP release in most animals. However, with the normal human bladder only ACh is a functional transmitter but in benign pathologies such as overactive bladder (OAB), ATP re-emerges a secondary transmitter. The selective regulation of ATP release offers a therapeutic approach to manage OAB, in contrast to current primary strategies that target ACh actions. However, the release characteristics of nerve-mediated ACh and ATP are poorly defined and this study aimed to measure the frequency-dependence of ACh and ATP release and determine if selective regulation of ATP or ACh was possible. Experiments were carried out in vitro with mouse detrusor with nerve-mediated ATP and ACh release measured, simultaneously with tension recording. ATP was released in two frequency-dependent components, both at lower frequencies (mid-range 0.4 and 5.5 Hz stimulation) compared to a single compartment release of ACh at 14 Hz. Intervention with the phosphodiesterase type-5 inhibitor, sildenafil, attenuated ATP release, equally from both components, but had no effect on ACh release. These data demonstrate that nerve-mediated ACh and ATP release characteristics are distinct and may be separately manipulated. This offers a potential targeted drug model to manage benign lower urinary tract conditions such as OAB. This article is protected by copyright. All rights reserved.

Contractile and Structural Properties of Detrusor from Children with Neurogenic Lower Urinary Tract Dysfunction

Simple Summary

Disorders of bladder function can result from congenital spinal cord developmental defects and can remain in a significant number of patients despite surgical improvements to repair the primary defect. We studied the ability of bladder wall muscle from such patients to contract, a function essential to void collected urine and avoid urinary tract infections and potential damage to the kidneys. Tissue was taken when patients were several years old, at the time of surgical operations to improve bladder function. This tissue would otherwise have been discarded and was collected with the full ethical approval and consent of parents or guardians. We found that the ability of the bladder wall samples to contract was impaired and was generally stiffer; both of which would make it more difficult for the bladder to void urine. These functional changes were associated with a replacement of muscle with connective tissue (fibrosis). The experiments provide a pathway to devise strategies that might improve bladder function in these patients through reversal of the intrinsic tissue pathways that increase fibrosis.

Abstract

Neurogenic lower urinary tract (NLUT) dysfunction in paediatric patients can arise after congenital or acquired conditions that affect bladder innervation. With some patients, urinary tract dysfunction remains and is more difficult to treat without understanding the pathophysiology. We measured in vitro detrusor smooth muscle function of samples from such bladders and any association with altered Wnt-signalling pathways that contribute to both foetal development and connective tissue deposition. A comparator group was tissue from children with normally functioning bladders. Nerve-mediated and agonist-induced contractile responses and passive stiffness were measured. Histology measured smooth muscle and connective tissue proportions, and multiplex immunohistochemistry recorded expression of protein targets associated with Wnt-signalling pathways. Detrusor from the NLUT group had reduced contractility and greater stiffness, associated with increased connective tissue content. Immunohistochemistry showed no major changes to Wnt-signalling components except down-regulation of c-Myc, a multifunctional regulator of gene transcription. NLUT is a diverse term for several diagnoses that disrupt bladder innervation. While we cannot speculate about the reasons for these pathophysiological changes, their recognition should guide research to understand their ultimate causes and develop strategies to attenuate and even reverse them. The role of changes to the Wnt-signalling pathways was minor.

Neurophysiological control of urinary bladder storage and voiding-functional changes through development and pathology

The effective storage of urine and its expulsion relies upon the coordinated activity of parasympathetic, sympathetic, and somatic innervations to the lower urinary tract (LUT). At birth, all mammalian neonates lack the ability to voluntary regulate bladder storage or voiding. The ability to control urinary bladder activity is established as connections to the central nervous system (CNS) form through development. The neural regulation of the LUT has been predominantly investigated in adult animal models where comparatively less is known about the neonatal and postnatal neurophysiological development that facilitate urinary continence. Furthermore, congenital neurological or anatomical defects can adversely affect both storage and voiding functions through postnatal development and into adulthood, leading to secondary conditions including vesicoureteral reflux, chronic urinary tract infections, and end-stage renal disease. Therefore, the aim of the review is to provide the current knowledge available on neurophysiological regulation of the LUT through pre- to postnatal development of human and animal models and the consequences of congenital anomalies that can affect LUT neural function.

Antenatal biological models in the characterization and research of congenital lower urinary tract disorders

Congenital lower urinary tract disorders are a family of diseases affecting both urinary storage and voiding as well as upstream kidney function. Current treatments include surgical reconstruction but many children still fail to achieve urethral continence or progress to chronic kidney disease. New therapies can only be achieved through undertaking research studies to enhance our understanding of congenital lower urinary tract disorders. Animal models form a critical component of this research, a corner of the triangle composed of human in-vitro studies and clinical research. We describe the current animal models for two rare congenital bladder disorders, posterior urethral valves (PUV) and bladder exstrophy (BE). We highlight important areas for researchers to consider when deciding which animal model to use to address particular research questions and outline the strengths and weaknesses of current models available for PUV and BE. Finally, we present ideas for refining animal models for PUV and BE in the future to stimulate future researchers and help them formulate their thinking when working in this field.

Contractile function of detrusor smooth muscle from children with posterior urethral valves - The role of fibrosis

INTRODUCTION

Posterior urethral valves (PUV) is the most common cause of congenital bladder outflow obstruction with persistent lower urinary tract and renal morbidities. There is a spectrum of functional bladder disorders ranging from hypertonia to bladder underactivity, but the aetiology of these clinical conditions remains unclear.

AIMS AND OBJECTIVES

We tested the hypothesis that replacement of detrusor muscle with non-muscle cells and excessive deposition of connective tissue is an important factor in bladder dysfunction with PUV. We used isolated detrusor samples from children with PUV and undergoing primary or secondary procedures in comparison to age-matched data from children with functionally normal bladders. In vitro contractile properties, as well as passive stiffness, were measured and matched to histological assessment of muscle and connective tissue. We examined if a major pathway for fibrosis was altered in PUV tissue samples.

METHODS

Isometric contractions were measured in vitro in response to either stimulation of motor nerves to detrusor or exposure to cholinergic and purinergic receptor agonists. Passive mechanical stiffness was measured by rapid stretching of the tissue and recording changes to muscle tension. Histology measured the relative amounts of detrusor muscle and connective tissue. Multiplex quantitative immunofluorescence labelling using five epitope markers was designed to determine cellular pathways, in particular the Wnt-signalling pathway, responsible for any changes to excessive deposition of connective tissue.

RESULTS AND DISCUSSION

PUV tissue showed equally reduced contractile function to efferent nerve stimulation or exposure to contractile agonists. Passive muscle stiffness was increased in PUV tissue samples. The smooth muscle:connective tissue ratio was also diminished and mirrored the reduction of contractile function and the increase of passive stiffness. Immunofluorescence labelling showed in PUV samples increased expression of the matrix metalloproteinase, MMP-7; as well as cyclin-D1 expression suggesting cellular remodelling. However, elements of a fibrosis pathway associated with Wnt-signalling were either reduced (β-catenin) or unchanged (c-Myc). The accumulation of extracellular matrix, containing collagen, will contribute to the reduced contractile performance of the bladder wall. It will also increase tissue stiffness that in vivo would lead to reduced filling compliance.

CONCLUSIONS

Replacement of smooth muscle with fibrosis is a major contributory factor in contractile dysfunction in the hypertonic PUV bladder. This suggests that a potential strategy to restore normal contractile and filling properties is development of the effective use of antifibrotic agents.

New Insights on the Basic Science of Bladder Exstrophy-epispadias Complex

The exstrophy-epispadias complex is a rare congenital anomaly presenting as a wide spectrum of disorders. The complex nature of this malformation leads to continuous investigations of the basic science concepts behind it. Elucidating these concepts allows one to fully understand the mechanisms behind the disease in order to improve diagnosis, management, and treatment ultimately leading to improvement in patient quality of life. Multiple technological advancements within the last 10 years have been made allowing for new studies to be conducted. Herein, the authors conduct a literature review of studies from 2009 to 2019, considering novel theories regarding the genetics, embryology, bladder, bony pelvis, prostate, and genitalia of patients with bladder exstrophy-epispadias complex.

New targets for overactive bladder-ICI-RS 2109

AIM

To review evidence for novel drug targets that can manage overactive bladder (OAB) symptoms.

METHODS

A think tank considered evidence from the literature and their own research experience to propose new drug targets in the urinary bladder to characterize their use to treat OAB.

RESULTS

Five classes of agents or cellular pathways were considered. (a) Cyclic nucleotide-dependent (cyclic adenosine monophosphate and cyclic guanosine monophosphate) pathways that modulate adenosine triphosphate release from motor nerves and urothelium. (b) Novel targets for β3 agonists, including the bladder wall vasculature and muscularis mucosa. (c) Several TRP channels (TRPV1 , TRPV4 , TRPA1 , and TRPM4 ) and their modulators in affecting detrusor overactivity. (d) Small conductance Ca2+ -activated K+ channels and their influence on spontaneous contractions. (e) Antifibrosis agents that act to modulate directly or indirectly the TGF-β pathway-the canonical fibrosis pathway.

CONCLUSIONS

The specificity of action remains a consideration if particular classes of agents can be considered for future development as receptors or pathways that mediate actions of the above mentioned potential agents are distributed among most organ systems. The tasks are to determine more detail of the pathological changes that occur in the OAB and how the specificity of potential drugs may be directed to bladder pathological changes. An important conclusion was that the storage, not the voiding, phase in the micturition cycle should be investigated and potential targets lie in the whole range of tissue in the bladder wall and not just detrusor.

Stretch- and carbachol-induced ATP release from bladder wall preparations of young and aged mice

AIMS

Bladder wall stretch increases tissue tension and releases adenosine 5'-triphosphate (ATP) as part of a transduction process to sense bladder filling. Aging is associated with bladder fibrosis to produce a stiffer bladder wall: this may augment ATP release and contribute to age-dependent urgency. Muscarinic agonists also release ATP and present a potential target for antimuscarinic agents, but its age-dependency is unknown. This study aimed, in young and old mice, to: (a) quantify the relationship between bladder wall stiffness and stretch-dependent ATP release and; (b) characterize muscarinic agonist-dependent release.

METHODS

ATP release from young (9-12 weeks) and aged (24 months) mouse bladder wall was measured in vitro, with a luciferin-luciferase assay, after stretch or carbachol exposure. Bladder wall stiffness, measured simultaneously during stretch, was compared to histological proportions of connective tissue and detrusor muscle.

RESULTS

With young mice, stretch-activated ATP release required an intact mucosa and was positively associated with wall stiffness. ATP release by carbachol was about four-fold greater compared to stretch. With aged mice: ATP release varied a hundred-fold and no association with stiffness; carbachol release diminished; connective tissue and mucosa thickness increased.

CONCLUSIONS

With young mice, stretch, or muscarinic agonists potently induce bladder wall ATP release. Stretch-dependent release is proportional to bladder wall stiffness, independent of the extent of stretch. With aged mice dependence of stretch-activated ATP release with stiffness was lost. The huge variability of release suggests that aged mice do not form a homogenous cohort and may underlie the heterogeneity in bladder filling sensations.