Suppression of detrusor-sphincter dyssynergia by immunoneutralization of nerve growth factor in lumbosacral spinal cord in spinal cord injured rats

Therapeutic effects of p38 mitogen-activated protein kinase inhibition on hyperexcitability of capsaicin sensitive bladder afferent neurons in mice with spinal cord injury

AIMS

Nerve growth factor (NGF) has been implicated as a key molecule of pathology-induced changes in C-fiber afferent nerve excitability, which contributes to the emergence of neurogenic detrusor overactivity due to spinal cord injury (SCI). It is also known that the second messenger signaling pathways activated by NGF utilize p38 Mitogen-Activated Protein Kinase (MAPK). We examined the roles of p38 MAPK on electrophysiological properties of capsaicin sensitive bladder afferent neurons with SCI mice.

MAIN METHODS

We used female C57BL/6 mice and transected their spinal cord at the Th8/9 level. Two weeks later, continuous administration of p38 MAPK inhibitor (0.51 μg/h, i.t. for two weeks) was started. Bladder afferent neurons were labelled with a fluorescent retrograde tracer, Fast-Blue (FB), injected into the bladder wall three weeks after SCI. Four weeks after SCI, freshly dissociated L6-S1 dorsal root ganglion neurons were prepared and whole cell patch clamp recordings were performed in FB-labelled neurons. After recording action potentials or voltage-gated K+ currents, the sensitivity of each neuron to capsaicin was evaluated.

KEY FINDINGS

In capsaicin-sensitive FB-labelled neurons, SCI significantly reduced the spike threshold and increased the number of action potentials during 800 ms membrane depolarization. Densities of slow-decaying A-type K+ (KA) and sustained delayed rectifier-type K+ (KDR) currents were significantly reduced by SCI. The reduction of KA, but not KDR, current density was reversed by the treatment with p38 MAPK inhibitor.

SIGNIFICANCE

P38 MAPK plays an important role in hyperexcitability of capsaicin-sensitive bladder afferent neurons due to the reduction in KA channel activity in SCI mice.

Assessing Neurogenic Lower Urinary Tract Dysfunction after Spinal Cord Injury: Animal Models in Preclinical Neuro-Urology Research

Neurogenic bladder dysfunction is a condition that affects both bladder storage and voiding function and remains one of the leading causes of morbidity after spinal cord injury (SCI). The vast majority of individuals with severe SCI develop neurogenic lower urinary tract dysfunction (NLUTD), with symptoms ranging from neurogenic detrusor overactivity, detrusor sphincter dyssynergia, or sphincter underactivity depending on the location and extent of the spinal lesion. Animal models are critical to our fundamental understanding of lower urinary tract function and its dysfunction after SCI, in addition to providing a platform for the assessment of potential therapies. Given the need to develop and evaluate novel assessment tools, as well as therapeutic approaches in animal models of SCI prior to human translation, urodynamics assessment techniques have been implemented to measure NLUTD function in a variety of animals, including rats, mice, cats, dogs and pigs. In this narrative review, we summarize the literature on the use of animal models for cystometry testing in the assessment of SCI-related NLUTD. We also discuss the advantages and disadvantages of various animal models, and opportunities for future research.

Molecular Mechanisms of Neurogenic Lower Urinary Tract Dysfunction after Spinal Cord Injury

This article provides a synopsis of current progress made in fundamental studies of lower urinary tract dysfunction (LUTD) after spinal cord injury (SCI) above the sacral level. Animal models of SCI allowed us to examine the effects of SCI on the micturition control and the underlying neurophysiological processes of SCI-induced LUTD. Urine storage and elimination are the two primary functions of the LUT, which are governed by complicated regulatory mechanisms in the central and peripheral nervous systems. These neural systems control the action of two functional units in the LUT: the urinary bladder and an outlet consisting of the bladder neck, urethral sphincters, and pelvic-floor striated muscles. During the storage phase, the outlet is closed, and the bladder is inactive to maintain a low intravenous pressure and continence. In contrast, during the voiding phase, the outlet relaxes, and the bladder contracts to facilitate adequate urine flow and bladder emptying. SCI disrupts the normal reflex circuits that regulate co-ordinated bladder and urethral sphincter function, leading to involuntary and inefficient voiding. Following SCI, a spinal micturition reflex pathway develops to induce an overactive bladder condition following the initial areflexic phase. In addition, without proper bladder-urethral-sphincter coordination after SCI, the bladder is not emptied as effectively as in the normal condition. Previous studies using animal models of SCI have shown that hyperexcitability of C-fiber bladder afferent pathways is a fundamental pathophysiological mechanism, inducing neurogenic LUTD, especially detrusor overactivity during the storage phase. SCI also induces neurogenic LUTD during the voiding phase, known as detrusor sphincter dyssynergia, likely due to hyperexcitability of Aδ-fiber bladder afferent pathways rather than C-fiber afferents. The molecular mechanisms underlying SCI-induced LUTD are multifactorial; previous studies have identified significant changes in the expression of various molecules in the peripheral organs and afferent nerves projecting to the spinal cord, including growth factors, ion channels, receptors and neurotransmitters. These findings in animal models of SCI and neurogenic LUTD should increase our understanding of pathophysiological mechanisms of LUTD after SCI for the future development of novel therapies for SCI patients with LUTD.

Consequences of spinal cord injury on the sympathetic nervous system

Spinal cord injury (SCI) damages multiple structures at the lesion site, including ascending, descending, and propriospinal axons; interrupting the conduction of information up and down the spinal cord. Additionally, axons associated with the autonomic nervous system that control involuntary physiological functions course through the spinal cord. Moreover, sympathetic, and parasympathetic preganglionic neurons reside in the spinal cord. Thus, depending on the level of an SCI, autonomic function can be greatly impacted by the trauma resulting in dysfunction of various organs. For example, SCI can lead to dysregulation of a variety of organs, such as the pineal gland, the heart and vasculature, lungs, spleen, kidneys, and bladder. Indeed, it is becoming more apparent that many disorders that negatively affect quality-of-life for SCI individuals have a basis in dysregulation of the sympathetic nervous system. Here, we will review how SCI impacts the sympathetic nervous system and how that negatively impacts target organs that receive sympathetic innervation. A deeper understanding of this may offer potential therapeutic insight into how to improve health and quality-of-life for those living with SCI.

Molecular Mechanism Operating in Animal Models of Neurogenic Detrusor Overactivity: A Systematic Review Focusing on Bladder Dysfunction of Neurogenic Origin

Neurogenic detrusor overactivity (NDO) is a severe lower urinary tract disorder, characterized by urinary urgency, retention, and incontinence, as a result of a neurologic lesion that results in damage in neuronal pathways controlling micturition. The purpose of this review is to provide a comprehensive framework of the currently used animal models for the investigation of this disorder, focusing on the molecular mechanisms of NDO. An electronic search was performed with PubMed and Scopus for literature describing animal models of NDO used in the last 10 years. The search retrieved 648 articles, of which reviews and non-original articles were excluded. After careful selection, 51 studies were included for analysis. Spinal cord injury (SCI) was the most frequently used model to study NDO, followed by animal models of neurodegenerative disorders, meningomyelocele, and stroke. Rats were the most commonly used animal, particularly females. Most studies evaluated bladder function through urodynamic methods, with awake cystometry being particularly preferred. Several molecular mechanisms have been identified, including changes in inflammatory processes, regulation of cell survival, and neuronal receptors. In the NDO bladder, inflammatory markers, apoptosis-related factors, and ischemia- and fibrosis-related molecules were found to be upregulated. Purinergic, cholinergic, and adrenergic receptors were downregulated, as most neuronal markers. In neuronal tissue, neurotrophic factors, apoptosis-related factors, and ischemia-associated molecules are increased, as well as markers of microglial and astrocytes at lesion sites. Animal models of NDO have been crucial for understanding the pathophysiology of lower urinary tract (LUT) dysfunction. Despite the heterogeneity of animal models for NDO onset, most studies rely on traumatic SCI models rather than other NDO-driven pathologies, which may result in some issues when translating pre-clinical observations to clinical settings other than SCI.

Current knowledge and novel frontiers in lower urinary tract dysfunction after spinal cord injury: Basic research perspectives

This review article aims to summarize the recent advancement in basic research on lower urinary tract dysfunction (LUTD) following spinal cord injury (SCI) above the sacral level. We particularly focused on the neurophysiologic mechanisms controlling the lower urinary tract (LUT) function and the SCI-induced changes in micturition control in animal models of SCI. The LUT has two main functions, the storage and voiding of urine, that are regulated by a complex neural control system. This neural system coordinates the activity of two functional units in the LUT: the urinary bladder and an outlet including bladder neck, urethra, and striated muscles of the pelvic floor. During the storage phase, the outlet is closed and the bladder is quiescent to maintain a low intravesical pressure and continence, and during the voiding phase, the outlet relaxes and the bladder contracts to promote efficient release of urine. SCI impairs voluntary control of voiding as well as the normal reflex pathways that coordinate bladder and sphincter function. Following SCI, the bladder is initially areflexic but then becomes hyperreflexic due to the emergence of a spinal micturition reflex pathway. However, the bladder does not empty efficiently because coordination between the bladder and urethral sphincter is lost. In animal models of SCI, hyperexcitability of silent C-fiber bladder afferents is a major pathophysiological basis of neurogenic LUTD, especially detrusor overactivity. Reflex plasticity is associated with changes in the properties of neuropeptides, neurotrophic factors, or chemical receptors of afferent neurons. Not only C-fiber but also Aδ-fiber could be involved in the emergence of neurogenic LUTD such as detrusor sphincter dyssynergia following SCI. Animal research using disease models helps us to detect the different contributing factors for LUTD due to SCI and to find potential targets for new treatments.

Overactive Bladder Symptoms Within Nervous System: A Focus on Etiology

Overactive bladder (OAB) is a common debilitating condition characterized by urgency symptoms with detrimental effects on the quality of life and survival. The exact etiology of OAB is still enigmatic, and none of therapeutic approaches seems curative. OAB is generally regarded as a separate syndrome, whereas in clinic, OAB symptoms could be found in numerous diseases of other non-urogenital systems, particularly nervous system. The OAB symptoms in neurological diseases are often poorly recognized and inadequately treated. This review provided a comprehensive overview of recent findings related to the neurogenic OAB symptoms. Relevant neurological diseases could be mainly divided into seven kinds as follows: multiple sclerosis and related neuroinflammatory disorders, Parkinson's diseases, multiple system atrophy, spinal cord injury, dementia, peripheral neuropathy, and others. Concurrently, we also summarized the hypothetical reasonings and available animal models to elucidate the underlying mechanism of neurogenic OAB symptoms. This review highlighted the close association between OAB symptoms and neurological diseases and expanded the current knowledge of pathophysiological basis of OAB. This may increase the awareness of urological complaints in neurological disorders and inspire robust therapies with better outcomes.

Dynamics of biomarkers across the stages of traumatic spinal cord injury - implications for neural plasticity and repair

BACKGROUND

Traumatic spinal cord injury (SCI) is a complex medical condition causing significant physical disability and psychological distress. While the adult spinal cord is characterized by poor regenerative potential, some recovery of neurological function is still possible through activation of neural plasticity mechanisms. We still have limited knowledge about the activation of these mechanisms in the different stages after human SCI.

OBJECTIVE

In this review, we discuss the potential role of biomarkers of SCI as indicators of the plasticity mechanisms at work during the different phases of SCI.

METHODS

An extensive review of literature related to SCI pathophysiology, neural plasticity and humoral biomarkers was conducted by consulting the PubMed database. Research and review articles from SCI animal models and SCI clinical trials published in English until January 2021 were reviewed. The selection of candidates for humoral biomarkers of plasticity after SCI was based on the following criteria: 1) strong evidence supporting involvement in neural plasticity (mandatory); 2) evidence supporting altered expression after SCI (optional).

RESULTS

Based on selected findings, we identified two main groups of potential humoral biomarkers of neural plasticity after SCI: 1) neurotrophic factors including: Brain derived neurotrophic factor (BDNF), Nerve growth factor (NGF), Neurotrofin-3 (NT-3), and Insulin-like growth factor 1 (IGF-1); 2) other factors including: Tumor necrosis factor-alpha (TNF-α), Matrix Metalloproteinases (MMPs), and MicroRNAs (miRNAs). Plasticity changes associated with these biomarkers often can be both adaptive (promoting functional improvement) and maladaptive. This dual role seems to be influenced by their concentrations and time-window during SCI.

CONCLUSIONS

Further studies of dynamics of biomarkers across the stages of SCI are necessary to elucidate the way in which they reflect the remodeling of neural pathways. A better knowledge about the mechanisms underlying plasticity could guide the selection of more appropriate therapeutic strategies to enhance positive spinal network reorganization.

Bladder and bowel responses to lumbosacral epidural stimulation in uninjured and transected anesthetized rats

Spinal cord epidural stimulation (scES) mapping at L5-S1 was performed to identify parameters for bladder and bowel inhibition and/or contraction. Using spinally intact and chronic transected rats of both sexes in acute urethane-anesthetized terminal preparations, scES was systematically applied using a modified Specify 5-6-5 (Medtronic) electrode during bladder filling/emptying cycles while recording bladder and colorectal pressures and external urethral and anal sphincter electromyography activity. The results indicate frequency-dependent effects on void volume, micturition, bowel peristalsis, and sphincter activity just above visualized movement threshold intensities that differed depending upon neurological intactness, with some sex-dependent differences. Thereafter, a custom-designed miniature 15-electrode array designed for greater selectivity was tested and exhibited the same frequency-dependent urinary effects over a much smaller surface area without any concurrent movements. Thus, select activation of autonomic nervous system circuitries with scES is a promising neuromodulation approach for expedient translation to individuals with SCI and potentially other neurologic disorders.

Role of p38 MAP kinase signaling pathways in storage and voiding dysfunction in mice with spinal cord injury

AIM

To investigate the role of p38 MAP kinase in lower urinary tract dysfunction in mice with spinal cord injury (SCI).

METHODS

Cystometry and external urethral sphincter-electromyography were performed under an awake condition in 4-week SCI female mice. Two weeks after SCI, a catheter connected to an osmotic pump filled with a p38 mitogen-activated protein kinase (MAPK) inhibitor or artificial cerebrospinal fluid (CSF) was implanted into the intrathecal space of L6-S1 spinal cord for continuous intrathecal instillation at infusion rate of 0.51 μL/h for 2 weeks before the urodynamic study. L6 dorsal root ganglia were then removed from CSF and p38 MAPK inhibitor-treated SCI mice as well as from CSF-treated normal (spinal intact) mice to evaluate the levels of transient receptor potential cation channel subfamily V member 1 (TRPV1), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase (iNOS) transcripts by real-time polymerase chain reaction.

RESULTS

In p38 MAPK inhibitor-treated SCI mice, nonvoiding contractions during bladder filling, bladder capacity, and post-void residual volume were significantly reduced while micturition pressure and voiding efficiency were significantly increased in comparison to these measurements in CSF-treated SCI mice. The expression of TRPV1, TNF-α, and iNOS messenger RNA was increased in SCI mice compared with expression in spinal intact mice and significantly decreased after p38 MAPK inhibitor treatment.

CONCLUSIONS

The p38 MAPK signaling pathway in bladder sensory neurons or in the spinal cord plays an important role in storage and voiding problems such as detrusor overactivity and inefficient voiding after SCI.

Effect of cerebrolysin on bladder function after spinal cord injury in female Wistar rats

OBJECTIVES

To study the effect of cerebrolysin on bladder function after spinal cord injury using functional measurements in rats.

METHODS

A total of 60 female rats were enrolled in this study. After induction of complete transection at T9-T10 spinal vertebrae, cerebrolysin was injected intraperitoneally, and daily in three dosages until 7 days (1 week) and continued until 28 days (4 weeks) in three groups to show the impact of that on the bladder function. Urodynamic parameters were measured in the different groups.

RESULTS

Cerebrolysin injection in a dose of 1 mL/kg for 1 week showed a slight improvement in urodynamic parameters. However, infusion of 2.5 and 5 mL/kg cerebrolysin for 1 week caused an elevation in contractions and a decrease in compliance. In long-term 2.5 mL/kg cerebrolysin injection, an improvement in compliance was observed, despite relative contractions. Furthermore, the bladder pressure pattern in the 2.5 mL/kg infused rats for 4 weeks was similar to the control group, but in the group receiving 5 mL/kg cerebrolysin for 4 weeks, reduced bladder contractions and function were observed.

CONCLUSIONS

Our findings suggest that cerebrolysin might be able to inhibit the emergence of neurogenic detrusor overactivity in spinal cord injured female rats.

Partners in Crime: NGF and BDNF in Visceral Dysfunction

Neurotrophins (NTs), particularly Nerve Growth Factor (NGF) and Brain-Derived Neurotrophic Factor (BDNF), have attracted increasing attention in the context of visceral function for some years. Here, we examined the current literature and presented a thorough review of the subject. After initial studies linking of NGF to cystitis, it is now well-established that this neurotrophin (NT) is a key modulator of bladder pathologies, including Bladder Pain Syndrome/Interstitial Cystitis (BPS/IC) and Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS. NGF is upregulated in bladder tissue and its blockade results in major improvements on urodynamic parameters and pain. Further studies expanded showed that NGF is also an intervenient in other visceral dysfunctions such as endometriosis and Irritable Bowel Syndrome (IBS). More recently, BDNF was also shown to play an important role in the same visceral dysfunctions, suggesting that both NTs are determinant factors in visceral pathophysiological mechanisms. Manipulation of NGF and BDNF improves visceral function and reduce pain, suggesting that clinical modulation of these NTs may be important; however, much is still to be investigated before this step is taken. Another active area of research is centered on urinary NGF and BDNF. Several studies show that both NTs can be found in the urine of patients with visceral dysfunction in much higher concentration than in healthy individuals, suggesting that they could be used as potential biomarkers. However, there are still technical difficulties to be overcome, including the lack of a large multicentre placebo-controlled studies to prove the relevance of urinary NTs as clinical biomarkers.

Effects of nerve growth factor neutralization on TRP channel expression in laser-captured bladder afferent neurons in mice with spinal cord injury

Nerve growth factor (NGF) is reportedly involved in the changes in C-fiber bladder afferent pathways that induce detrusor overactivity (DO) following spinal cord injury (SCI). This study examined the roles of NGF in TRP channel expression in bladder afferent neurons in mice with SCI using laser-capture microdissection (LCM) methods. Spinal intact (SI) and SCI mice were divided into 3 groups: (1) SI with vehicle treatment; (2) SCI with vehicle treatment; and (3) SCI with anti-NGF antibody. Two weeks after SCI, an osmotic pump was placed subcutaneously into the back of the mice and vehicle or anti-NGF antibody was administered at a rate of 10 μg/kg per hour for two weeks. Four weeks after SCI, the L6 dorsal root ganglia (DRG) were removed. Expression of the TRPV1, TRPC1, TRPC3, and TRPC6 genes was analyzed using real-time polymerase chain reaction (PCR) following LCM of the bladder afferent neurons, which were labeled by Fast Blue injected into the bladder wall 1 week prior to tissue removal. The mRNA expression of TRPV1 was found to be higher in vehicle-treated SCI mice than in SI mice. The expression level of TRPC3 and TRPC6 in vehicle-treated SCI mice was lower than in SI mice. However, in SCI mice treated with anti-NGF antibody, the mRNA expression of TRPV1 was lower, and the mRNA levels of TRPC3 and TRPC6 were higher than in vehicle-SCI mice. These results suggest that the NGF-dependent changes in specific TRP channel genes, such as TRPV1, TRPC3, and TRPC6, could be involved in SCI-induced afferent hyperexcitability and DO.

Nerve growth factor-dependent hyperexcitability of capsaicin-sensitive bladder afferent neurones in mice with spinal cord injury

NEW FINDINGS

What is the central question of this study? Nerve growth factor (NGF) is reportedly a mediator inducing urinary bladder dysfunction. Is NGF directly involved in hyperexcitability of capsaicin-sensitive C-fibre bladder afferent pathways after spinal cord injury (SCI)? What is the main finding and its importance? Neutralization of NGF by anti-NGF antibody treatment reversed the SCI-induced increase in the number of action potentials and the reduction in spike thresholds and A-type K⁺ current density in mouse capsaicin-sensitive bladder afferent neurones. Thus, NGF plays an important and direct role in hyperexcitability of capsaicin-sensitive C-fibre bladder afferent neurones attributable to the reduction in A-type K⁺ channel activity in SCI.

ABSTRACT

Nerve growth factor (NGF) has been implicated as an important mediator in the induction of C-fibre bladder afferent hyperexcitability, which contributes to the emergence of neurogenic lower urinary tract dysfunction after spinal cord injury (SCI). In this study, we determined whether NGF immunoneutralization using an anti-NGF antibody (NGF-Ab) normalizes the SCI-induced changes in electrophysiological properties of capsaicin-sensitive C-fibre bladder afferent neurones in female C57BL/6 mice. The spinal cord was transected at the Th8/Th9 level. Two weeks later, continuous administration of NGF-Ab (10 μg kg^-1  h^-1 , s.c. for 2 weeks) was started. Bladder afferent neurones were labelled with Fast-Blue (FB), a fluorescent retrograde tracer, injected into the bladder wall 3 weeks after SCI. Four weeks after SCI, freshly dissociated L6-S1 dorsal root ganglion neurones were prepared. Whole-cell patch-clamp recordings were then performed in FB-labelled neurones. After recording action potentials or voltage-gated K⁺ currents, the sensitivity of each neurone to capsaicin was evaluated. In capsaicin-sensitive FB-labelled neurones, SCI significantly reduced the spike threshold and increased the number of action potentials during membrane depolarization for 800 ms. These SCI-induced changes were reversed by NGF-Ab. Densities of slow-decaying A-type K⁺ (K_A ) and sustained delayed rectifier-type K⁺ currents were significantly reduced by SCI. The NGF-Ab treatment reversed the SCI-induced reduction in the K_A current density. These results indicate that NGF plays an important role in hyperexcitability of mouse capsaicin-sensitive C-fibre bladder afferent neurones attributable to a reduction in K_A channel activity. Thus, NGF-targeting therapies could be effective for treatment of afferent hyperexcitability and neurogenic lower urinary tract dysfunction after SCI.

Role of proNGF/p75 signaling in bladder dysfunction after spinal cord injury

Loss of bladder control is a challenging outcome facing patients with spinal cord injury (SCI). We report that systemic blocking of pro-nerve growth factor (proNGF) signaling through p75 with a CNS-penetrating small-molecule p75 inhibitor resulted in significant improvement in bladder function after SCI in rodents. The usual hyperreflexia was attenuated with normal bladder pressure, and automatic micturition was acquired weeks earlier than in the controls. The improvement was associated with increased excitatory input to the spinal cord, in particular onto the tyrosine hydroxylase-positive fibers in the dorsal commissure. The drug also had an effect on the bladder itself, as the urothelial hyperplasia and detrusor hypertrophy that accompany SCI were largely prevented. Urothelial cell loss that precedes hyperplasia was dependent on p75 in response to urinary proNGF that is detected after SCI in rodents and humans. Surprisingly, death of urothelial cells and the ensuing hyperplastic response were beneficial to functional recovery. Deleting p75 from the urothelium prevented urothelial death, but resulted in reduction in overall voiding efficiency after SCI. These results unveil a dual role of proNGF/p75 signaling in bladder function under pathological conditions with a CNS effect overriding the peripheral one.

The effect of neutralization of nerve growth factor (NGF) on bladder and urethral dysfunction in mice with spinal cord injury

AIMS

To investigate the role of nerve growth factor (NGF) in lower urinary tract dysfunction in mice with spinal cord injury (SCI).

METHODS

Using 4-week SCI mice, single-filling cystometry and external urethral sphincter (EUS)-electromyography were performed under an awake condition. In some SCI mice, anti-NGF antibodies (10 µg/kg/h) were administered for 1 or 2 weeks before the urodynamic study. NGF levels in the bladder and L6/S1 spinal cord were assayed by ELISA. The transcript levels of P2X receptors and TRP channels in L6/S1 dorsal root ganglia (DRG) were measured by RT-PCR.

RESULTS

In SCI mice, the area under the curve of non-voiding contractions (NVCs) during the storage phase was significantly decreased in both 1- and 2-week anti-NGF antibody-treated SCI groups. However, EUS-electromyogram parameters during voiding were not altered by the treatment. Bladder mucosal and spinal NGF levels were decreased after 2 weeks of anti-NGF antibody treatment. TRPA1 and TRPV1 transcripts in L6/S1 DRG were significantly decreased after 1- or 2-week anti-NGF treatment.

CONCLUSIONS

In SCI mice, NGF is involved in the emergence of NVCs in association with increased expression of TRP receptors that are predominantly found in C-fiber afferent pathways. Thus, NGF targeting treatments could be effective for treating storage problems such as detrusor overactivity after SCI.

Afferent Pathway-Mediated Effect of α1 Adrenergic Antagonist, Tamsulosin, on the Neurogenic Bladder After Spinal Cord Injury

Purpose

The functions of the lower urinary tract (LUT), such as voiding and storing urine, are dependent on complex central neural networks located in the brain, spinal cord, and peripheral ganglia. Thus, the functions of the LUT are susceptible to various neurologic disorders including spinal cord injury (SCI). SCI at the cervical or thoracic levels disrupts voluntary control of voiding and the normal reflex pathways coordinating bladder and sphincter functions. In this context, it is noteworthy that α1-adrenoceptor blockers have been reported to relieve voiding symptoms and storage symptoms in elderly men with benign prostatic hyperplasia (BPH). Tamsulosin, an α1-adrenoceptor blocker, is also considered the most effective regimen for patients with LUT symptoms such as BPH and overactive bladder (OAB).

Methods

In the present study, the effects of tamsulosin on the expression of c-Fos, nerve growth factor (NGF), and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) in the afferent micturition areas, including the pontine micturition center (PMC), the ventrolateral periaqueductal gray matter (vlPAG), and the spinal cord (L5), of rats with an SCI were investigated.

Results

SCI was found to remarkably upregulate the expression of c-Fos, NGF, and NADPH-d in the afferent pathway of micturition, the dorsal horn of L5, the vlPAG, and the PMC, resulting in the symptoms of OAB. In contrast, tamsulosin treatment significantly suppressed these neural activities and the production of nitric oxide in the afferent pathways of micturition, and consequently, attenuated the symptoms of OAB.

Conclusions

Based on these results, tamsulosin, an α1-adrenoceptor antagonist, could be used to attenuate bladder dysfunction following SCI. However, further studies are needed to elucidate the exact mechanism and effects of tamsulosin on the afferent pathways of micturition.

The role of capsaicin-sensitive C-fiber afferent pathways in the control of micturition in spinal-intact and spinal cord-injured mice

We examined bladder and urethral sphincter activity in mice with or without spinal cord injury (SCI) after C-fiber afferent desensitization induced by capsaicin pretreatment and changes in electrophysiological properties of mouse bladder afferent neurons 4 wk after SCI. Female C57BL/6N mice were divided into four groups: 1) spinal intact (SI)-control, 2) SI-capsaicin pretreatment (Cap), 3) SCI-control, and 4) SCI-Cap groups. Continuous cystometry and external urethral sphincter (EUS)-electromyogram (EMG) were conducted under an awake condition. In the Cap groups, capsaicin (25, 50, or 100 mg/kg) was injected subcutaneously 4 days before the experiments. In the SI-Cap group, 100 mg/kg capsaicin pretreatment significantly increased bladder capacity and decreased the silent period duration of EUS/EMG compared with the SI-control group. In the SCI-Cap group, 50 and 100 mg/kg capsaicin pretreatment decreased the number of nonvoiding contractions (NVCs) and the duration of reduced EUS activity during voiding, respectively, compared with the SCI-control group. In SCI mice, hexamethonium, a ganglionic blocker, almost completely blocked NVCs, suggesting that they are of neurogenic origin. Patch-clamp recordings in capsaicin-sensitive bladder afferent neurons from SCI mice showed hyperexcitability, which was evidenced by decreased spike thresholds and increased firing rate compared with SI mice. These results indicate that capsaicin-sensitive C-fiber afferent pathways, which become hyperexcitable after SCI, can modulate bladder and urethral sphincter activity in awake SI and SCI mice. Detrusor overactivity as shown by NVCs in SCI mice is significantly but partially dependent on capsaicin-sensitive C-fiber afferents, whereas the EUS relaxation during voiding is enhanced by capsaicin-sensitive C-fiber bladder afferents in SI and SCI mice.

Post-injury bladder management strategy influences lower urinary tract dysfunction in the mouse model of spinal cord injury

AIMS

To examine the effects of a different number of daily bladder squeezes on bladder dysfunction in mice with spinal cord injury (SCI).

METHODS

Spinal cord was transected at the Th8/9 in female C57BL/6N mice. Their bladders were manually squeezed to eliminate urine inside every day for 4 weeks. The mice were divided into three groups depending on the number of bladder squeezes; A: once daily, B: twice daily, C: three times daily. Four weeks after transection, single-filling cystometry were performed under an awake condition. NGF in the bladder mucosa and mRNA expression of P2X receptors and TRP channels in L6/S1 dorsal root ganglia (DRG) were measured.

RESULTS

Bladder weight in group C was less than that of group A. Bladder capacity, post-void residual, and the number of non-voiding contractions during the storage phase were significantly larger in group A compared to group B or C. The level of NGF in groups C were lower compared to group A or B. The expression of P2X3 and TRPA1 in groups B and C was decreased compared to group A. The expression of P2X2 was decreased in groups B compared to group A.

CONCLUSION

The post-injury bladder management after SCI with an increased number of daily bladder emptying improves the storage and voiding bladder dysfunction associated with the reduction of NGF in the bladder as well as P2X and TRP transcripts in lumbosacral DRG.

Pathophysiology, Clinical Importance, and Management of Neurogenic Lower Urinary Tract Dysfunction Caused by Suprasacral Spinal Cord Injury

Management of persistent lower urinary tract dysfunction resulting from severe thoracolumbar spinal cord injury can be challenging. Severe suprasacral spinal cord injury releases the spinal cord segmental micturition reflex from supraspinal modulation and increases nerve growth factor concentration in the bladder wall, lumbosacral spinal cord, and dorsal root ganglion, which subsequently activates hypermechanosensitive C-fiber bladder wall afferents. Hyperexcitability of bladder afferents and detrusor overactivity can cause urine leaking during the storage phase. During urine voiding, the loss of supraspinal control that normally coordinates detrusor contraction with sphincter relaxation can lead to spinal cord segmental reflex-mediated simultaneous detrusor and sphincter contractions or detrusor-sphincter dyssynergia, resulting in inefficient urine voiding and high residual volume. These disease-associated changes can impact on the quality of life and life expectancy of spinal-injured animals. Here, we discuss the pathophysiology and management considerations of lower urinary tract dysfunction as the result of severe, acute, suprasacral spinal cord injury. In addition, drawing from experimental, preclinical, and clinical medicine, we introduce some treatment options for neurogenic lower urinary tract dysfunction that are designed to: (1) prevent urine leakage arising because of detrusor overactivity during bladder filling, (2) preserve upper urinary tract integrity and function by reducing intravesical pressure and subsequent vesicoureteral reflux, and (3) prevent urinary tract and systemic complications by treating and preventing urinary tract infections.

Effects of Panax ginseng on the nerve growth factor expression in testosterone induced benign prostatic hyperplasia

The prostatic hyperplasia in benign prostatic hyperplasia (BPH) leads to obstructive micturition symptoms. Previous studies showed that pontine micturition center (PMC), ventrolateral periaqueductal gray (vlPAG), and medial preopticnucleus (MPA) regions in the brain have been known to regulate the urinary bladder function. The present study shows the influences of Panax ginseng on nerve growth factor (NGF) expressions in PMC, vlPAG, and MPA regions in the brain. Wistar rats were used for the present study. The rats split into four groups; 4 groups (n = 6) in control group, BPH-induced group, BPH-induced and P. ginseng-treated group, and BPH-induced and finasteride-treated group. BPH in rats was induced by testosterone and the animals were evaluated for NGF expression in PMC, vlPAG, and MPA regions in the brain. The NGF expression was identified using immunohistochemistry (IHC). The NGF expression by IHC showed spots with dark brown color. In our results, NGF expressions in PMC, vlPAG, and MPA regions in the brainstem of the BPH-induced group showed increase than the control animal. These increased NGF expressions in three regions were decreased using treatment with P. ginseng (200 mg/kg). These results suggest that P. ginseng has therapeutic effects on the symptoms of BPH and is associated with the regulation of NGF expression in the brain. In conclusion, the administration of P. ginseng helps nerve growth factor activation.

Constitutive expression Of NGF And P75(NTR) affected by bladder distension and NGF antisense treatment

AIMS

It is known that bladder exposure to noxious stimuli elicits nerve growth factor (NGF) expression with region wise differences. Here, we investigated the effect of bladder distension (cystometry) and bladder wall injection of NGF antisense oligonucleotide (ODN) together as well as separately on spontaneous (constitutive) expression of NGF and its cognate p75 neurotrophin receptor (p75(NTR)).

METHOD

Under isoflurane anesthesia, either 15μg of protamine sulfate (vehicle) alone or complexed with 1.5μg of NGF antisense or scrambled ODN was injected (10μL) at 4 sites in bladder wall of 24 adult female Sprague-Dawley rats and 6 rats were left untreated (n=30). Under urethane anesthesia, cystometry (CMG) was performed in treated and control rats. Fluorescent ODN and NGF/p75(NTR) expression was localized in harvested tissue.

KEY FINDINGS

Complexation of ODN with protamine was essential for the retention of ODN in bladder tissue as the uncomplexed ODN was untraceable after injection. Bladder distension from CMG raised the expression of NGF and p75(NTR) relative to CMG naïve rats. The groups treated with vehicle, scrambled and antisense ODN were indistinct with regard to CMG parameters, but the intense immunoreactivity of NGF and p75(NTR) seen in the vehicle and scrambled ODN groups was reduced following treatment with NGF antisense.

SIGNIFICANCE

The constitutive expression of NGF and p75(NTR) is responsive to bladder distension and administration of NGF antisense. Complexation with protamine reduces the clearance of ODN and demonstrates the potential of ODN nanoparticles as an option for reducing the inducible NGF expression in OAB patients following intradetrusor injection.

Anatomy and physiology of the lower urinary tract

Functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain, spinal cord, and peripheral autonomic ganglia that coordinates the activity of smooth and striated muscles of the bladder and urethral outlet. Neural control of micturition is organized as a hierarchic system in which spinal storage mechanisms are in turn regulated by circuitry in the rostral brainstem that initiates reflex voiding. Input from the forebrain triggers voluntary voiding by modulating the brainstem circuitry. Many neural circuits controlling the lower urinary tract exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. The major component of the micturition switching circuit is a spinobulbospinal parasympathetic reflex pathway that has essential connections in the periaqueductal gray and pontine micturition center. A computer model of this circuit that mimics the switching functions of the bladder and urethra at the onset of micturition is described. Micturition occurs involuntarily during the early postnatal period, after which it is regulated voluntarily. Diseases or injuries of the nervous system in adults cause re-emergence of involuntary micturition, leading to urinary incontinence. The mechanisms underlying these pathologic changes are discussed.

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.

Long-term anodal block stimulation at sacral anterior roots promoted recovery of neurogenic bladder function in a rabbit model of complete spinal cord injury

A complete spinal cord injury model was established in experimental rabbits using the spinal cord clip compression method. Urodynamic examination was performed 2 weeks later to determine neurogenic bladder status. The rabbits were treated with anodal block stimulation at sacral anterior roots for 4 weeks. Electrical stimulation of sacral anterior roots improved urodynamic parameters of neurogenic bladder in rabbit models of complete spinal cord injury, effectively promoted urinary function, and relieved urinary retention. Immunohistochemistry results showed that a balance was achieved among expression of muscarinic receptor subunits M2, M3, ATP-gated ion channel P2X3 receptors, and β2-adrenergic receptor, and nerve growth factor expression decreased. These results suggested that long-term sacral anterior root stimulation of anodal block could be used to treat neurogenic bladder in a rabbit model of complete spinal cord injury.

The role of brain-derived neurotrophic factor (BDNF) in the development of neurogenic detrusor overactivity (NDO)

Neurogenic detrusor overactivity (NDO) is a well known consequence of spinal cord injury (SCI), recognizable after spinal shock, during which the bladder is areflexic. NDO emergence and maintenance depend on profound plastic changes of the spinal neuronal pathways regulating bladder function. It is well known that neurotrophins (NTs) are major regulators of such changes. NGF is the best-studied NT in the bladder and its role in NDO has already been established. Another very abundant neurotrophin is BDNF. Despite being shown that, acting at the spinal cord level, BDNF is a key mediator of bladder dysfunction and pain during cystitis, it is presently unclear if it is also important for NDO. This study aimed to clarify this issue. Results obtained pinpoint BDNF as an important regulator of NDO appearance and maintenance. Spinal BDNF expression increased in a time-dependent manner together with NDO emergence. In chronic SCI rats, BDNF sequestration improved bladder function, indicating that, at later stages, BDNF contributes NDO maintenance. During spinal shock, BDNF sequestration resulted in early development of bladder hyperactivity, accompanied by increased axonal growth of calcitonin gene-related peptide-labeled fibers in the dorsal horn. Chronic BDNF administration inhibited the emergence of NDO, together with reduction of axonal growth, suggesting that BDNF may have a crucial role in bladder function after SCI via inhibition of neuronal sprouting. These findings highlight the role of BDNF in NDO and may provide a significant contribution to create more efficient therapies to manage SCI patients.

Neural control of the lower urinary tract

This article summarizes anatomical, neurophysiological, pharmacological, and brain imaging studies in humans and animals that have provided insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract. The functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain, spinal cord, and peripheral autonomic ganglia that coordinates the activity of smooth and striated muscles of the bladder and urethral outlet. The neural control of micturition is organized as a hierarchical system in which spinal storage mechanisms are in turn regulated by circuitry in the rostral brain stem that initiates reflex voiding. Input from the forebrain triggers voluntary voiding by modulating the brain stem circuitry. Many neural circuits controlling the lower urinary tract exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. The major component of the micturition switching circuit is a spinobulbospinal parasympathetic reflex pathway that has essential connections in the periaqueductal gray and pontine micturition center. A computer model of this circuit that mimics the switching functions of the bladder and urethra at the onset of micturition is described. Micturition occurs involuntarily in infants and young children until the age of 3 to 5 years, after which it is regulated voluntarily. Diseases or injuries of the nervous system in adults can cause the re-emergence of involuntary micturition, leading to urinary incontinence. Neuroplasticity underlying these developmental and pathological changes in voiding function is discussed.

Effects of lateral funiculus sparing, spinal lesion level, and gender on recovery of bladder voiding reflexes and hematuria in rats

Deficits in bladder function are complications following spinal cord injury (SCI), severely affecting quality of life. Normal voiding function requires coordinated contraction of bladder and urethral sphincter muscles dependent upon intact lumbosacral reflex arcs and integration of descending and ascending spinal pathways. We previously reported, in electrophysiological recordings, that segmental reflex circuit neurons in anesthetized male rats were modulated by a bilateral spino-bulbo-spinal pathway in the mid-thoracic lateral funiculus. In the present study, behavioral measures of bladder voiding reflexes and hematuria (hemorrhagic cystitis) were obtained to assess the correlation of plasticity-dependent recovery to the degree of lateral funiculus sparing and mid-thoracic lesion level. Adult rats received mid-thoracic-level lesions at one of the following severities: complete spinal transection; bilateral dorsal column lesion; unilateral hemisection; bilateral dorsal hemisection; a bilateral lesion of the lateral funiculi and dorsal columns; or a severe contusion. Voiding function and hematuria were evaluated by determining whether the bladder was areflexic (requiring manual expression, i.e., "crede maneuver"), reflexive (voiding initiated by perineal stroking), or "automatic" (spontaneous voiding without caretaker assistance). Rats with one or both lateral funiculi spared (i.e., bilateral dorsal column lesion or unilateral hemisection) recovered significantly faster than animals with bilateral lateral funiculus lesions, severe contusion, or complete transection. Bladder reflex recovery time was significantly slower the closer a transection lesion was to T10, suggesting that proximity to the segmental sensory and sympathetic innervation of the upper urinary tract (kidney, ureter) should be avoided in the choice of lesion level for SCI studies of micturition pathways. In addition, hematuria duration was significantly longer in males, compared to females, despite similar bladder reflex onset times. We conclude that the sparing of the mid-thoracic lateral funiculus on one side is required for early recovery of bladder reflex voiding function and resolution of hematuria.

Herpes simplex virus vector-mediated gene transfer of kynurenine aminotransferase improves detrusor overactivity in spinal cord-injured rats

Detrusor overactivity threatens the renal function of patients with spinal cord injury. Suppressing N-methyl-D-aspartate receptors is known to improve detrusor overactivity in rats with spinal cord injury, whereas kynurenic acid, the endogenous antagonist of N-methyl-D-aspartate receptors, is irreversibly synthesized by kynurenine aminotransferases (KATs). In this study, we investigated whether replication-defective herpes simplex virus vector-mediated gene transfer of human KAT II could treat detrusor overactivity by injecting the vectors into the rat bladder wall 1 week after spinal cord injury. Three weeks after injection, we evaluated the cystometry and gene expression of KAT II in L6-S1 dorsal root ganglia. The results showed that the vectors are transported to L6-S1 dorsal root ganglia and upregulate the expression of KAT II, and that they also improve the detrusor overactivity and voiding efficiency. We also proved that N-methyl-D-aspartate receptors were blocked by kynurenic acid in the extracellular solution or the vector-mediated gene transfer of KAT II in cultured rat neurons of L6-S1 dorsal root ganglia by whole-cell patch clamp to explore the mechanisms of gene therapy. Therefore, replication-defective herpes simplex virus vector-mediated KAT II inhibits detrusor overactivity in spinal cord-injured rats, possibly by suppressing N-methyl-D-aspartate receptors in bladder afferent pathways.

Neural mechanisms underlying lower urinary tract dysfunction

This article summarizes anatomical, neurophysiological, and pharmacological studies in humans and animals to provide insights into the neural circuitry and neurotransmitter mechanisms controlling the lower urinary tract and alterations in these mechanisms in lower urinary tract dysfunction. The functions of the lower urinary tract, to store and periodically release urine, are dependent on the activity of smooth and striated muscles in the bladder, urethra, and external urethral sphincter. During urine storage, the outlet is closed and the bladder smooth muscle is quiescent. When bladder volume reaches the micturition threshold, activation of a micturition center in the dorsolateral pons (the pontine micturition center) induces a bladder contraction and a reciprocal relaxation of the urethra, leading to bladder emptying. During voiding, sacral parasympathetic (pelvic) nerves provide an excitatory input (cholinergic and purinergic) to the bladder and inhibitory input (nitrergic) to the urethra. These peripheral systems are integrated by excitatory and inhibitory regulation at the levels of the spinal cord and the brain. Therefore, injury or diseases of the nervous system, as well as disorders of the peripheral organs, can produce lower urinary tract dysfunction, leading to lower urinary tract symptoms, including both storage and voiding symptoms, and pelvic pain. Neuroplasticity underlying pathological changes in lower urinary tract function is discussed.

Intravesical liposome and antisense treatment for detrusor overactivity and interstitial cystitis/painful bladder syndrome

Purpose. The following review focuses on the recent advancements in intravesical drug delivery, which brings added benefit to the therapy of detrusor overactivity and interstitial cystitis/painful bladder syndrome (IC/PBS). Results. Intravesical route is a preferred route of administration for restricting the action of extremely potent drugs like DMSO for patients of interstitial cystitis/painful bladder syndrome (IC/PBS) and botulinum toxin for detrusor overactivity. Patients who are either refractory to oral treatment or need to mitigate the adverse effects encountered with conventional routes of administration also chose this route. Its usefulness in some cases can be limited by vehicle (carrier) toxicity or short duration of action. Efforts have been underway to overcome these limitations by developing liposome platform for intravesical delivery of biotechnological products including antisense oligonucleotides. Conclusions. Adoption of forward-thinking approaches can achieve advancements in drug delivery systems targeted to future improvement in pharmacotherapy of bladder diseases. Latest developments in the field of nanotechnology can bring this mode of therapy from second line of treatment for refractory cases to the forefront of disease management.

Neurotrophins in bladder function: what do we know and where do we go from here?

AIMS

Neurotrophins (NTs) have attracted considerable attention in the urologic community. The reason for this resides in the recognition of their ability to induce plastic changes of the neuronal circuits that govern bladder function. In many pathologic states, urinary symptoms, including urgency and urinary frequency, reflect abnormal activity of bladder sensory afferents that results from neuroplastic changes. Accordingly, in pathologies associated with increased sensory input, such as the overactive bladder syndrome (OAB) or bladder pain syndrome/interstitial cystitis (BPS/IC), significant amounts of NTs have been found in the bladder wall.

METHODS

Here, current knowledge about the importance of NTs in bladder function will be reviewed, with a focus on the most well-studied NTs, nerve growth factor (NGF), and brain-derived neurotrophic factor (BDNF).

RESULTS

Both NTs are present in the bladder and regulate bladder sensory afferents and urothelial cells. Experimental models of bladder dysfunction show that upregulation of these NTs is strongly linked to bladder hyperactivity and, in some cases, pain. NT manipulation has been tested in animal models of bladder dysfunction, and recently, NGF downregulation, achieved by administration of a monoclonal antibody, has also been tested in patients with BPS/IC and chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS). NTs have also been found in high quantities in the urine of OAB and BPS/IC patients, raising the possibility of NTs serving as biomarkers.

CONCLUSIONS

Available data show that our knowledge of NTs has greatly increased in recent years and that some results may have future clinical application.

Nerve growth factor (NGF): a potential urinary biomarker for overactive bladder syndrome (OAB)?

WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: The search for a biomarker in overactive bladder syndrome (OAB) is an emerging field of interest, as bladder dysfunction is a common complaint that causes significant morbidity. A biomarker may give us insight as a diagnostic tool, and also inform us about how severe the condition is, how it may progress and how it may best be treated. The protein of interest here is nerve growth factor (NGF) and it has been shown to be a dynamic molecule in the bladder of patients with OAB. Urinary levels have been seen to rise in patients with OAB and fall in those who respond to treatment. However, there have also been many studies that examine this trend in numerous other conditions, e.g. interstitial cystitis, bladder outflow obstruction, renal stone disease and patients with neurological impairment after stroke. As a result the specificity of this as a potential urinary biomarker for OAB is questioned. This is a review of published studies, which discusses the pros and cons of NGF as a potential urinary biomarker. The evidence is examined and the studies are summarised together in a Table. Questions remain about the reliability, practicality and specificity of NGF as a biomarker for OAB. These questions need to be addressed by further studies that could clarify the points raised.

OBJECTIVE

To review the current literature on the use of urinary nerve growth factor (NGF) as a potential biomarker for overactive bladder syndrome (OAB).

METHOD

A comprehensive electronic literature search was conducted using the PubMed database to identify publications relating to urinary NGF.

RESULTS

There are a growing number of publications that have measured urinary NGF levels in different types of bladder dysfunction. These range from OAB, bladder pain syndrome, idiopathic and neurogenic detrusor overactivity, bladder oversensitivity and bladder outflow obstruction. Urinary NGF levels do appear to be raised in these pathological states when compared with healthy control samples. In patients with OAB, these raised urinary NGF levels appear to also reduce after successful treatment with antimuscarinics and botulinum toxin A, which indicates a potential use in monitoring responses to treatment. However, raised levels are not limited to OAB, which questions its specificity. Urinary NGF measurements are performed with an enzyme-linked immunosorbent assay using polyclonal antibodies to NGF. The technique requires standardisation, and the different antibodies to NGF require validating. Also a definition of what is the 'normal' range of NGF in urine is still required before it can be used as a diagnostic and prognostic tool.

CONCLUSIONS

Whilst the evidence for an increased urinary NGF in OAB appears convincing, many questions about its validity remain including: specificity, sensitivity, cost- and time-effectiveness. Many criteria for what constitutes a biomarker still need to be evaluated and met before this molecule can be considered for this role.

Organization of the neural switching circuitry underlying reflex micturition

The functions of the lower urinary tract to store and periodically eliminate urine are regulated by a complex neural control system in the brain and spinal cord that coordinates the activity of the bladder and urethral outlet. Experimental studies in animals indicate that urine storage is modulated by reflex mechanisms in the spinal cord, whereas voiding is mediated by a spinobulbospinal pathway passing through a coordination centre in the rostral brain stem. Many of the neural circuits controlling micturition exhibit switch-like patterns of activity that turn on and off in an all-or-none manner. This study summarizes the anatomy and physiology of the spinal and supraspinal micturition switching circuitry and describes a computer model of these circuits that mimics the switching functions of the bladder and urethra at the onset of micturition.

Multisystem neuroprosthetic training improves bladder function after severe spinal cord injury

Severe spinal cord injury leads to neurogenic bladder dysfunction. We recently developed a multisystem neuroprosthetic training program that promotes plastic changes capable of restoring refined locomotion in rats with severe spinal cord injury. We investigated whether multisystem neuroprosthetic training would influence the development of posttraumatic bladder dysfunction.

MATERIALS AND METHODS

Eight and 4 adult rats were randomly assigned to a spinal cord injury and an intact control group, respectively. Spinal cord injury consisted of 2 opposite lateral hemisections (T7 and T11), thus, interrupting all direct supraspinal input. After spinal cord injury 4 rats were subjected to a multisystem neuroprosthetic training program and 4 were not trained. At 8 weeks we performed urodynamics and evaluated kidney function using creatinine and cystatin C. Bladder investigation included morphological, histological and immunohistochemical evaluations.

RESULTS

Bladder capacity increased threefold in trained and sevenfold in nontrained rats compared to intact rats. During filling we found a mean ± SEM of 2.7 ± 1.1 vs 12.6 ± 5.2 nonvoiding contractions in trained vs nontrained rats. Bladder morphology was similar in trained and intact rats. Nontrained rats showed detrusor hypertrophy, characterized by increased detrusor thickness and a decreased connective tissue-to-smooth muscle ratio. As labeled with protein gene product 9.5, general nerve density was significantly increased in trained and significantly decreased in nontrained rats. The relative proportion of neurofilament 200 positive afferent nerves was significantly lower in trained than in intact and nontrained rats. Neuropeptide Y positive fibers showed significantly lower density in nontrained rats.

CONCLUSIONS

Multisystem neuroprosthetic training effectively counteracts the formation of neurogenic bladder dysfunction after severe spinal cord injury and might contribute to preserving bladder function and preventing long-term complications in patients with severe spinal cord injury.

Increased urine and serum nerve growth factor levels in interstitial cystitis suggest chronic inflammation is involved in the pathogenesis of disease

Objective

Interstitial cystitis/bladder pain syndrome (IC/BPS) is considered a bladder disorder due to localized chronic inflammation. This study investigated the nerve growth factor (NGF) levels in serum and urine in patients with IC/BPS.

Materials and Methods

Thirty patients with IC/BPS and 28 normal subjects without lower urinary tract symptoms were recruited from an outpatient clinic. IC/BPS was diagnosed by frequency, bladder pain, and the presence of glomerulations during cystoscopic hydrodistention. Serum and urine were collected before any treatment was given. Serum NGF and urinary NGF/Cr levels were compared between IC/BPS and the controls.

Results

Urinary NGF levels were significantly higher in patients with IC/PBS (26.3±11.2 pg/ml) than in controls (1.40±0.63 pg) (p = 0.014). After normalization, the urinary NGF/Cr levels were significantly greater in IC/BPS (0.69±0.38 pg/mg) than controls (0.20±0.01, p = 0.011). Relative to the levels in control subjects (1.90±0.38 pg/mL), the mean serum NGF levels were higher in patients IC/BPS patients (3.48±0.55 pg/mL) (p = 0.015). No significant correlation was found between the serum and urinary NGF levels in IC/BPS patients. However, the clinical characteristics and medical co-morbidities did not show significant difference between IC/BPS patients with a higher and lower serum NGF level.

Conclusions

Increased urinary NGF levels in IC/BPS patients suggest that chronic inflammation is involved in this bladder disorder. Increased circulating serum NGF levels were noted in over half of patients with IC/BPS, however, the urinary and serum NGF were not inter-correlated and elevated serum NGF did not relate with clinical features.

Do Sacral/Peripheral Lesions Contribute to Detrusor-Sphincter Dyssynergia?

OBJECTIVES

While detrusor-sphincter dyssynergia (DSD) occurs in conjunction with lesions between the brainstem and the sacral cord, it is not well known whether sacral/peripheral lesions contribute to DSD. We studied the relationship between DSD and sacral/peripheral lesions.

METHODS

One hundred and forty-four patients with diverse neurologic etiologies underwent urodynamic study and analysis of motor unit potentials in the external sphincter muscles, 117 of whom were able to void during a urodynamic test. Sacral/peripheral lesion (SPL) is defined as neurogenic change in motor unit potentials. Detrusor overactivity (DO) is defined as involuntary detrusor contractions during the filling phase, which commonly occurs in lesions above the sacral cord. We considered DO as a putative indicator of supra-sacral lesion.

RESULTS

DSD was found in 44 (30.6%), SPL in 71 (49.3%), and DO in 83 (57.6%) of 144 patients, respectively. The incidence of DSD was the same in the SPL positive group (31%) and the SPL negative group (30.1%). By contrast, within the subgroup of patients without DO, the incidence of DSD was significantly more common in the SPL positive group (41.4%) than in the SPL negative group (25.0%) (P < 0.05). In 53 of the SPL positive group who were able to void, postvoid residual >100 mL was more common in patients with DSD (not statistically significant).

CONCLUSION

The results of the present study suggest that not only suprasacral pathology, but also sacral/peripheral lesions can produce DSD. In light of the previous reports, DSD might also result from partial lesions in peripheral branches of the sphincter circuit.

Neurotrophins in the lower urinary tract: becoming of age

The lower urinary tract (LUT) comprises a storage unit, the urinary bladder, and an outlet, the urethra. The coordination between the two structures is tightly controlled by the nervous system and, therefore, LUT function is highly susceptible to injuries to the neuronal pathways involved in micturition control. These injuries may include lesions to the spinal cord or to nerve fibres and result in micturition dysfunction. A common trait of micturition pathologies, irrespective of its origin, is an upregulation in synthesis and secretion of neurotrophins, most notably Nerve Growth Factor (NGF) and Brain Derived Neurotrophic Factor (BDNF). These neurotrophins are produced by neuronal and non-neuronal cells and exert their effects upon binding to their high-affinity receptors abundantly expressed in the neuronal circuits regulating LUT function. In addition, NGF and BDNF are present in detectable amounts in the urine of patients suffering from various LUT pathologies, suggesting that analysis of urinary NGF and BDNF may serve as likely biomarkers to be studied in tandem with other factors when diagnosing patients. Studies with experimental models of bladder dysfunction using antagonists of NGF and BDNF receptors as well as scavenging agents suggest that those NTs may be key elements in the pathophysiology of bladder dysfunctions. In addition, available data indicates that NGF and BDNF might constitute future targets for designing new drugs for better treatment of bladder dysfunction.

The dark side of neuroplasticity

Whether dramatic or modest, recovery of neurological function after spinal cord injury (SCI) is greatly due to neuroplasticity--the process by which the nervous system responds to injury by establishing new synaptic connections or by altering the strength of existing synapses. However, the same neuroplasticity that allows locomotor function to recover also produces negative consequences such as pain and dysfunction of organs controlled by the autonomic nervous system. In this review we focus specifically on structural neuroplasticity (the growth of new synaptic connections) after SCI and on the consequent development of pain and autonomic dysreflexia, a condition of episodic hypertension. Neuroplasticity after SCI is stimulated by the deafferentation of spinal neurons below the lesion and by the expression of growth-promoting neurotrophins such as nerve growth factor (NGF). A broad range of therapeutic strategies that affect neuroplasticity is being developed for the treatment of SCI. At one end of the spectrum are therapeutic strategies that directly or indirectly increase NGF in the injured spinal cord, and have the most robust effects on neuroplasticity. At the other end of the spectrum are neuroprotective strategies focused on supporting and rescuing uninjured, or partially injured, axons; these might limit the deafferentation stimulus for neuroplasticity. In the middle of this spectrum are strategies that block axon growth inhibitors without necessarily providing a growth stimulus. The literature supports the view that the negative consequences of neuroplasticity develop more commonly with therapies that directly stimulate nerve growth than they develop in the untreated injured cord. Compared to these conditions, neuroplasticity with negative outcomes is less prevalent after treatments that that neutralize axon growth inhibitors, and least apparent after strategies that promote neuroprotection.

Sophisticated models and methods for studying neurogenic bladder dysfunction

AIM

To describe how the use of new and established animal models and methods can generate vital and far reaching experimental data in the study of mechanism underlying neurogenic bladder overactivity.

METHODS

Bladder and colonic irradiated mice and those with upper and lower motor neuron lesions were used to study neurogenic bladder overactivity. Methods included cystometry, tension measurements, afferent nerve recordings and optical mapping of action potentials and intracellular Ca(2+) transients. Recordings were made in a number of innovative preparations including in-line cultured cells, bladder-urethra sheets and cross-sections, spinal cord slices and the cerebral cortex.

RESULTS

The animal models and methods used allow for the study of peripheral and central mechanisms of neurogenic overactivity. While colonic irradiation results in solely neurogenic dysfunction, spinal cord lesions also induce non-neural changes resulting in increased spontaneous detrusor contractions that can directly stimulate afferent nerves. Imaging of cultured bladder interstitial cells reveals spontaneous firing that could contribute to detrusor overactivity, while optical imaging of the spinal cord and brain could identify changes in central pathways that underlie lower urinary tract dysfunction.

CONCLUSIONS

The animal models and methods described allow for the study of neurogenic overactivity at the peripheral, spinal and cortical levels. This may lead to greater understanding of sensory and motor mechanisms involved in incontinence, the contributions of interstitial cells and spontaneous detrusor contractions, and the involvement of the cortex.

Biomarkers in overactive bladder: a new objective and noninvasive tool?

Overactive bladder syndrome (OAB) is a highly prevalent urinary dysfunction, with considerable economic and human costs. Clinical diagnosis of OAB is still based on subjective symptoms. A new accurate, objective and noninvasive test to diagnose OAB and assess therapeutic outcome is lacking. Recent studies in lower urinary tract (LUT) dysfunctions, particularly in OAB patients, indicate that urinary proteins (neurotrophins, prostaglandins, and cytokines), serum C reactive protein, and detrusor wall thickness are altered, and such changes could be used as biomarkers of the disease. Nowadays, increasing emphasis has been given to the role of urinary neurotrophins, namely nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF), as key players in some urinary dysfunctions. Although recently considered to be a bladder dysfunction biomarker, urinary NGF presents low sensitivity and specificity. Preliminary results suggest that BDNF may serve as a more efficient biomarker. Even though we have to wait for future studies to confirm the potential role of NGF and BDNF as OAB biomarkers, it is already clear that neurotrophins will contribute to elucidate the physiopathological basis of OAB. Herein are reviewed the latest advances in this new and exciting field, the detection and clinical application of emerging OAB biomarkers.

Plasticity in reflex pathways to the lower urinary tract following spinal cord injury

The lower urinary tract has two main functions, storage and periodic expulsion of urine, that are regulated by a complex neural control system in the brain and lumbosacral spinal cord. This neural system coordinates the activity of two functional units in the lower urinary tract: (1) a reservoir (the urinary bladder) and (2) an outlet (consisting of bladder neck, urethra and striated muscles of the external urethra sphincter). During urine storage the outlet is closed and the bladder is quiescent to maintain a low intravesical pressure. During micturition the outlet relaxes and the bladder contracts to promote efficient release of urine. This reciprocal relationship between bladder and outlet is generated by reflex circuits some of which are under voluntary control. Experimental studies in animals indicate that the micturition reflex is mediated by a spinobulbospinal pathway passing through a coordination center (the pontine micturition center) located in the rostral brainstem. This reflex pathway is in turn modulated by higher centers in the cerebral cortex that are involved in the voluntary control of micturition. Spinal cord injury at cervical or thoracic levels disrupts voluntary control of voiding as well as the normal reflex pathways that coordinate bladder and sphincter function. Following spinal cord injury the bladder is initially areflexic but then becomes hyperreflexic due to the emergence of a spinal micturition reflex pathway. However the bladder does not empty efficiently because coordination between the bladder and urethral outlet is lost. Studies in animals indicate that dysfunction of the lower urinary tract after spinal cord injury is dependent in part on plasticity of bladder afferent pathways as well as reorganization of synaptic connections in the spinal cord. Reflex plasticity is associated with changes in the properties of ion channels and electrical excitability of afferent neurons and appears to be mediated in part by neurotrophic factors released in the spinal cord and/or the peripheral target organs.

Microsurgical anatomy of lumbosacral nerve rootlets for highly selective rhizotomy in chronic spinal cord injury

It is known that selective sacral roots rhizotomy is effective for relieving the neurogenic bladder associated with spinal cord injury. The goal of this study is to review the surgical anatomy of the lumbosacral nerve rootlets and to provide some morphological bases for highly selective sacral roots rhizotomy. Spinal cord dissections were performed on five cadavers under surgical microscope. At each spinal cord segment, we recorded the number, diameter and length of the rootlets, subbundles and bundles from the L1 to S2 spinal segments, and the length of the dorsal/ventral root entry zone. Peripheral nervous system myelin was examined by immunohistochemistry. We found: (1) the ventral or the dorsal root of the lumbosacral segment of the spinal cord was divided into one to three nerve bundles and each bundle was subdivided into one to three subbundles. Each subbundle further gave out two to three rootlets connected with the spinal cord; (2) there were no significant differences in the number of rootlets within the L1 to S2 segments, but the size of rootlets and the length of nerve roots varied (P < 0.05); and (3) the more myelinated fibers a rootlet contained, the larger transection area it had. The area of peripheral nervous system myelin positive cells and the total area of rootlets were correlated (P < 0.001). Thus, during highly selective sacral roots rhizotomy, the ventral and dorsal roots can be divided into several bundles of rootlets, and we could initially distinct the rootlets by their diameters.

Promise of Urinary Nerve Growth Factor for Assessment of Overactive Bladder Syndrome

Overactive bladder syndrome (OAB) is highly prevalent bladder disorder in men and women. About 10-15% of the population suffers from urgency frequency with or without urgency urinary incontinence. It is estimated that 50-75% of patients with OAB may have urodynamic detrusor overactivity (DO). Urodynamic study invasive and most of the OAB patients might not accept it as a routine assessment. Therefore, a more objective and non-invasive test for diagnosis and assessing DO from OAB patients is needed. Recently, urinary nerve growth factor (NGF) has gained great interest in detecting DO in patients with OAB. Urinary NGF level was found to increase in OAB and urodynamic DO. Urinary NGF levels correlated with severity of OAB symptoms. Patients with either idiopathic or neurogenic DO may have increased urinary NGF levels. Urinary NGF levels have been shown to decrease in patients with patients with OAB and DO who have been well treated with antimuscarinics or botulinum toxin injection, but not in those with persistent OAB after treatment. Not all patients with OAB can have an elevated urinary NGF level; it may also be increased in patients with interstitial cystitis/painful bladder syndrome and other lower urinary tract diseases, suggesting urinary NGF expression could be a product of bladder inflammation and a limited specificity of urinary NGF for diagnosing DO. The source of urinary NGF has not yet been fully explored yet. Nevertheless, urinary NGF level is likely to be a promising biomarker for diagnosis of DO from OAB patients, to monitor therapeutic outcome and predict disease progression.