A novel animal model of underactive bladder: Analysis of lower urinary tract function in a rat lumbar canal stenosis model

Wireless, Fully Implantable and Expandable Electronic System for Bidirectional Electrical Neuromodulation of the Urinary Bladder

Current standard clinical options for patients with detrusor underactivity (DUA) or underactive bladder─the inability to release urine naturally─include the use of medications, voiding techniques, and intermittent catheterization, for which the patient inserts a tube directly into the urethra to eliminate urine. Although those are life-saving techniques, there are still unfavorable side effects, including urinary tract infection (UTI), urethritis, irritation, and discomfort. Here, we report a wireless, fully implantable, and expandable electronic complex that enables elaborate management of abnormal bladder function via seamless integrations with the urinary bladder. Such electronics can not only record multiple physiological parameters simultaneously but also provide direct electrical stimulation based on a feedback control system. Uniform distribution of multiple stimulation electrodes via mesh-type geometry realizes low-impedance characteristics, which improves voiding/urination efficiency at the desired times. In vivo evaluations using live, free-moving animal models demonstrate system-level functionality.

Functional, morphological and molecular characteristics in a novel rat model of spinal sacral nerve injury-surgical approach, pathological process and clinical relevance

Spinal sacral nerve injury represents one of the most serious conditions associated with many diseases such as sacral fracture, tethered cord syndrome and sacral canal tumor. Spinal sacral nerve injury could cause bladder denervation and detrusor underactivity. There is limited clinical experience resolving spinal sacral nerve injury associated detrusor underactivity patients, and thus the treatment options are also scarce. In this study, we established a spinal sacral nerve injury animal model for deeper understanding and further researching of this disease. Forty 8 w (week) old Sprague Dawley rats were included and equally divided into sham (n = 20) and crush group (n = 20). Bilateral spinal sacral nerves of rats were crushed in crush group, and sham group received same procedure without nerve crush. Comprehensive evaluations at three time points (1 w, 4 w and 6 w) were performed to comprehend the nature process of this disease. According to urodynamic test, ultrasonography and retrograde urography, we could demonstrate severe bladder dysfunction after spinal sacral nerve injury along the observation period compared with sham group. These functional changes were further reflected by histological examination (hematoxylin-eosin and Masson's trichrome staining) of microstructure of nerves and bladders. Immunostaining of nerve/bladder revealed schwann cell death, axon degeneration and collagen remodeling of bladder. Polymerase Chain Reaction results revealed vigorous nerve inflammation and bladder fibrosis 1 week after injury and inflammation/fibrosis returned to normal at 4 w. The CatWalk gait analysis was performed and there was no obvious difference between two groups. In conclusion, we established a reliable and reproducible model for spinal sacral nerve injury, this model provided an approach to evaluate the treatment strategies and to understand the pathological process of spinal sacral nerve injuries. It allowed us to understand how nerve degeneration and bladder fibrosis changed following spinal sacral nerve injury and how recovery could be facilitated by therapeutic options for further research.

Pathogenesis evidence from human and animal models of detrusor underactivity

Detrusor underactivity (DU) is a common urodynamic diagnosis in patients with lower urinary tract symptoms and large post-voiding residual volume. Animal and human studies showed the possible etiologies of DU include central or peripheral nerve injury, bladder outlet obstruction, chronic ischemia, aging, diabetes mellitus, and sympathetic inhibition of micturition reflex. Evidence from animal and human DU studies with various etiologies revealed highly similar gross and histological characteristics in the bladders, including increased bladder weight, bladder wall thickening, inflammation, collagen deposition, and fibrosis. In electron microscopy, smooth muscle destruction, swollen mitochondria, decreased nerve innervation, caveolae, and umbrella cell fusiform vesicles were noted in the DU bladders. Most animal DU models demonstrate detrusor contractility changes from compensatory to the decompensatory stage, and the change was compatible with human DU observation. The cystometry in the DU animal studies is characterized by impaired contractility, prolong intercontraction interval, and hyposensation, while in vitro bladder muscle strips experiment may exhibit normal detrusor contractility. Decreased bladder blood flow and increased oxidative stress in bladders had been proved in different animal DU models, suggesting they should be important in the DU pathogenesis pathway. Sensory receptors mRNA and protein expression changes in DU bladders had been observed in both animal and human studies, including muscarinic receptors M2, M3, adrenergic receptor β3, purinergic receptor P2X1, P2X3, and transient receptor potential vanilloid (TRPV) 1 and TRPV4. Although some of the sensory receptors changes remain controversial, it might be the target for further pharmacologic treatments.

Understanding underactive bladder: a review of the contemporary literature

Underactive bladder (UAB) is characterized by prolonged voiding, hesitancy, and slow and/or intermittent stream with or without a sensation of incomplete bladder emptying. The overlap of UAB lower urinary tract symptoms with those of overactive bladder or bladder outlet obstruction, as well as its multifactorial etiology, make UAB study, as well as its diagnosis and management, a very arduous and challenging task. Therefore, despite its incidence and significant impact in the quality of life of both men and women, UAB remains a poorly understood urologic condition with insufficient and ineffective treatment options available. In this review, we will focus on the etiology theories that have been proposed and the animal models available to test those theories.

Anesthetic agents affect urodynamic parameters and anesthetic depth at doses necessary to facilitate preclinical testing in felines

Urodynamic studies, used to understand bladder function, diagnose bladder disease, and develop treatments for dysfunctions, are ideally performed with awake subjects. However, in small and medium-sized animal models, anesthesia is often required for these procedures and can be a research confounder. This study compared the effects of select survival agents (dexmedetomidine, alfaxalone, and propofol) on urodynamic (Δpressure, bladder capacity, bladder compliance, non-voiding contractions, bladder pressure slopes) and anesthetic (change in heart rate [∆HR], average heart rate [HR], reflexes, induction/recovery times) parameters in repeated cystometrograms across five adult male cats. The urodynamic parameters under isoflurane and α-chloralose were also examined in terminal procedures for four cats. Δpressure was greatest with propofol, bladder capacity was highest with α-chloralose, non-voiding contractions were greatest with α-chloralose. Propofol and dexmedetomidine had the highest bladder pressure slopes during the initial and final portions of the cystometrograms respectively. Cats progressed to a deeper plane of anesthesia (lower HR, smaller ΔHR, decreased reflexes) under dexmedetomidine, compared to propofol and alfaxalone. Time to induction was shortest with propofol, and time to recovery was shortest with dexmedetomidine. These agent-specific differences in urodynamic and anesthetic parameters in cats will facilitate appropriate study-specific anesthetic choices.

Modulation of Bladder Wall Micromotions Alters Intravesical Pressure Activity in the Isolated Bladder

Micromotions are phasic contractions of the bladder wall. During urine storage, such phasic activity has little effect on intravesical pressure, however, changed motile activity may underlie urodynamic observations such as detrusor overactivity. The potential for bladder motility to affect pressure reflects a summation of the overall movements, comprising the initiation, propagation, and dissipation components of micromotions. In this study, the influence of initiation of micromotions was investigated using calcium activated chloride channel blocker niflumic acid, and the effect of propagation using blockers of gap junctions. The overall bladder tone was modulated using isoprenaline. Isolated tissue strips and whole bladder preparations from juvenile rats were used. 18β-glycyrrhetinic acid was used to block gap junctions, reducing the amplitude and frequency of micromotions in in vitro and ex vivo preparations. Niflumic acid reduced the frequency of micromotions but had no effect on the amplitude of pressure fluctuations. Isoprenaline resulted in a reduction in pressure fluctuations and a decrease in pressure baseline. Using visual video data analysis, bladder movement was visible, irrespective of lack of pressure changes, which persisted during bladder relaxation. However, micromotions propagated over shorter distances and the overall bladder tone was reduced. All these results suggest that phasic activity of the bladder can be characterised by a combination of initiation and propagation of movement, and overall bladder tone. At any given moment, intravesical pressure recordings are an integration of these parameters. This synthesis gives insight into the limitations of clinical urodynamics, where intravesical pressure is the key indicator of detrusor activity.

Effect of TRPV4 activation in a rat model of detrusor underactivity induced by bilateral pelvic nerve crush injury

AIMS

To produce an animal model of peripheral neurogenic detrusor underactivity (DU) and to evaluate the effect of TRPV4 receptor activation in this DU model.

METHODS

In female Sprague-Dawley rats, bilateral pelvic nerve crush (PNC) was performed by using sharp forceps. After 10 days, awake cystometrograms (CMG) were recorded in sham and PNC rats. A TRPV4 agonist (GSK 1016790A) with or without a TRPV4 antagonist (RN1734) were administered intravesically and CMG parameters were compared before and after drug administration in each group. The TRPV4 transcript level in the bladder mucosa and histological changes were also evaluated.

RESULTS

In CMG, PNC rats showed significant increases in intercontraction intervals (ICI), number of non-voiding contractions (NVCs), baseline pressure, threshold pressure, bladder capacity, voided volumes, and post-void residual (PVR) compared to sham rats. Contraction amplitude and voiding efficiency were significantly decreased in PNC rats. In PNC rats, intravesical application of GSK1016790A (1.5 μM) significantly decreased ICI, bladder capacity, voided volume, and PVR without increasing NVCs, and these effects were blocked by RN1734 (5.0 μM). In contrast, 1.5 μM GSK1016790A had no significant effects on CMG parameters in normal rats. TRPV4 expression within the bladder mucosa of PNC rats was increased in association with urothelial thickening.

CONCLUSIONS

Rats with bilateral PNC showed characteristics of DU, and this model seems appropriate for further evaluation of peripheral neurogenic mechanisms of DU. Also, TRPV4 receptors, the activation of which reduced bladder capacity and PVR, could be a target for DU treatment.

TGF-β1 and connexin-43 expression in neurogenic bladder from rats with sacral spinal cord injury

AIMS

Sacral spinal cord injury (SCI) could induce underactive bladder (UAB). Malfunction of connexin 43 (CX43) regulated by TGF-β1 might involve in urinary bladder dysfunction. We studied the changes of CX43 and TGF-β1/Smad3 signaling in detrusor of neurogenic bladder (NB) in sacral SCI rats.

METHODS

Sacral SCI was produced by hemisection (SSCH) or transection (SSCT) of spinal cord between L4 and L5 in female Wistar rats. BBB scores, residual urine volume and bladder weight as well as characteristic cystometric parameters at 6th week were used to confirm the successful establishment of NB. Western blotting and qRT-PCR were used to exam the protein and mRNA expression levels of CX43, CX45, TGF-β1, and Smad3 in detrusor.

RESULTS

BBB scores were significantly decreased, with the lowest in SSCT rats (P < 0.01). The residual urine volume, mean bladder weight, and cystometric parameters were increased, with the highest in SSCT rats. CX43 and phospho-CX43 protein levels were significantly decreased, but those of TGF-β1, Smad3, and phospho-Smad3 were significantly increased. It was the protein and mRNA levels of CX43 but not those of CX45 which were decreased in negative accordance with those of TGF-β1 and Smad3. Those changes were more significant in SSCT than in SSCH rats.

CONCLUSIONS

This study indicates that voiding dysfunction is related to the decreased CX43 function in detrusor from NB. TGF-β1/Smad3 signaling might be involved in the down-regulation of CX43 in SCI rats. Early regulation of CX43 might be beneficial to patients with voiding dysfunction.

Intravesical Activation of the Cation Channel TRPV4 Improves Bladder Function in a Rat Model for Detrusor Underactivity

BACKGROUND

Improvement of bladder emptying by modulating afferent nerve activity is an attractive therapeutic strategy for detrusor underactivity. Transient receptor potential vanilloid 4 (TRPV4) is a sensory ion channel in urothelial cells that contribute to the detection of bladder filling.

OBJECTIVE

To investigate the potential benefit of intravesical TRPV4 agonists in a pelvic nerve injury rat model for detrusor underactivity.

DESIGN, SETTING, AND PARTICIPANTS

Female wild-type and Trpv4 knockout rats underwent sham surgery or bilateral pelvic nerve injury (bPNI). Four weeks later, rats underwent cystometry with infusion of the TRPV4 agonist GSK1016790A. Bladders were harvested for in vitro pharmacological studies, quantitative reverse polymerase chain reaction and immunohistochemistry.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Data are expressed as median ± interquartile range. Statistical comparisons were made using the Mann-Witney U test and Wilcoxon signed rank test as appropriate.

RESULTS AND LIMITATIONS

Rats with bPNI showed a phenotype characteristic of detrusor underactivity with lower-amplitude voiding contractions, decreased voiding frequency, and increased postvoid residual. Intravesical application of GSK1016790A increased voiding frequency and reduced postvoid residual in wild-type, but not Trpv4^-/-, rats. In isolated bladder strips, GSK1016790A did not induce relevant contractions, indicating that the observed improvements in bladder function are the result of increased afferent signalling through TRPV4 activation, rather than a local effect on the detrusor. The altered urinary phenotype of Trpv4^-/- mice was not apparent in the Trpv4^-/- rat model, suggesting species-related functional variations. Our results are limited to the preclinical setting in rodents.

CONCLUSIONS

Intravesical activation of TRPV4 improves bladder dysfunction after bPNI by increasing afferent signalling.

PATIENT SUMMARY

We demonstrate that the sensory protein transient receptor potential vanilloid 4 (TRPV4) can be targeted to improve bladder function in animals that have iatrogenic injury to the nerves innervating the bladder. Further research is required to determine whether these results can be translated to patients with an underactive bladder.

Pathophysiology of the underactive bladder

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

Effects of an EP2 and EP3 Receptor Dual Agonist, ONO-8055, on a Radical Hysterectomy-Induced Underactive Bladder Model in Monkeys

OBJECTIVES

The objective was to develop an underactive bladder (UAB) model in primates and to evaluate the potential of prostanoid EP2 and EP3 receptor dual agonist ONO-8055 to become a therapeutic agent for UAB.

METHODS

A surgical procedure resembling radical hysterectomy was performed on female cynomolgus monkeys. Subsequently, in vitro muscle strip studies were performed using bladder muscle strips from normal monkeys and monkeys that underwent surgery. In addition, uroflowmetric data were obtained at specified days after the surgery. To evaluate the effects of ONO-8055 and distigmine (DIS) on voiding function in the UAB monkey model, uroflowmetry was performed approximately 1 week after the surgery, before and after the cumulative intravenous administration of the compounds at 2 h intervals.

RESULTS

In the bladder muscle strip studies, the responses to potassium chloride at 2 months, and carbachol and electrical field stimulation from 2 weeks decreased significantly. Voided volume (VV), maximum flow rate (Qmax), and average flow rate (Qave) decreased after surgery, while voiding time (VT) increased. In this model, ONO-8055 and DIS significantly increased VV and Qmax. DIS prolonged VT, while ONO-8055 had no effect. The results also showed that ONO-8055 increased Qave.

CONCLUSIONS

We developed a neurogenic UAB model in primates. As ONO-8055 improved voiding function in this model to at least the same degree as DIS, this EP2 and EP3 receptor dual agonist has the potential to be a candidate for neurogenic UAB pharmacotherapy.

Addressing challenges in underactive bladder: recommendations and insights from the Congress on Underactive Bladder (CURE-UAB)

Underactive bladder (UAB) is an expanding troublesome health issue, exerting a major influence on the health and independence of older people with a disproportionally low level of attention received. The 2nd International Congress on Underactive Bladder (CURE-UAB 2) convened in Denver, CO on December 3 and 4, 2015, and comprised of top clinicians, scientists, and other stakeholders to address the challenges in UAB. A series of workshops aimed to define UAB and its phenotype, define detrusor underactivity (DU) and create a subtyping of DU, evaluate existing animal models for DU, and lastly to establish research priorities for UAB.

The potential role of unregulated autonomous bladder micromotions in urinary storage and voiding dysfunction; overactive bladder and detrusor underactivity

The isolated bladder shows autonomous micromotions, which increase with bladder distension, generate sensory nerve activity, and are altered in models of urinary dysfunction. Intravesical pressure resulting from autonomous activity putatively reflects three key variables; the extent of micromotion initiation, distances over which micromotions propagate, and overall bladder tone. In vivo, these variables are subordinate to the efferent drive of the central nervous system. In the micturition cycle storage phase, efferent inhibition keeps autonomous activity generally at a low level, where it may signal 'state of fullness', whilst maintaining compliance. In the voiding phase, mass efferent excitation elicits generalised contraction (global motility initiation). In lower urinary tract dysfunction, efferent control of the bladder can be impaired, for example due to peripheral 'patchy' denervation. In this case, loss of efferent inhibition may enable unregulated micromotility, and afferent stimulation, predisposing to urinary urgency. If denervation is relatively slight, the detrimental impact on voiding may be low, as the adjacent innervated areas may be able to initiate micromotility synchronous with the efferent nerve drive, so that even denervated areas can contribute to the voiding contraction. This would become increasingly inefficient the more severe the denervation, such that ability of triggered micromotility to propagate sufficiently to engage the denervated areas in voiding declines, so the voiding contraction increasingly develops the characteristics of underactivity. In summary, reduced peripheral coverage by the dual efferent innervation (inhibitory and excitatory) impairs regulation of micromotility initiation and propagation, potentially allowing emergence of overactive bladder and, with progression, detrusor underactivity.

Estimating postvoid residual volume without measuring residual bladder volume during serial cystometrograms

The postvoid residual volume (PVR) is a common urodynamic parameter used to quantify the severity of lower urinary tract dysfunction. However, the serial cystometrograms that are typically used to assess bladder function in animal models make measuring PVR very difficult. Current approaches are to either remove PVR after each void to measure it, which is disruptive to the bladder, or to neglect the unknown contribution to PVR from ureter flow, which results in inaccurate estimates. We propose a procedure to estimate PVR during a serial cystometrogram that requires only a single measurement, rather than measuring after each void. Moreover, this measurement can occur at the end of the experiment such that it does not affect the bladder during data collection. We mathematically express PVR for all voids during a serial cystometrogram using a linear recurrence equation and use this equation to build an estimation procedure for PVR. Using in vivo measurements in urethane anesthetized rats and computer simulations we show that the estimation procedure is at least as accurate in determining PVR as the traditional method of measuring PVR after each void. Furthermore, we demonstrate the adverse effects of repeated PVR measurements in a common animal model of cystitis. Using the proposed procedure can increase the efficiency and accuracy of determining PVR for a serial cystometrogram and is less disruptive to the system under study. This, in turn, allows the calculation of other urodynamic parameters that are critical for research studies, including voiding efficiency and bladder capacity.

Promising Effects of a Novel EP2 and EP3 Receptor Dual Agonist, ONO-8055, on Neurogenic Underactive Bladder in a Rat Lumbar Canal Stenosis Model

PURPOSE

We investigated whether the novel EP (prostaglandin E2) receptor agonist ONO-8055 would improve the lower urinary tract dysfunction of neurogenic underactive bladder in a rat lumbar spinal canal stenosis model.

MATERIALS AND METHODS

First, we studied the agonistic effect of ONO-8055 on EP receptors in EP receptor expressing CHO (Chinese hamster ovary) cells using the increase in the intracellular calcium level and intracellular cAMP (cyclic adenosine monophosphate) production as indicators of receptor activation. The effects of ONO-8055 on bladder and urethral strips from normal rats were then investigated. Finally, the effects of ONO-8055 on bladder and urethral function in rats with lumbar spinal canal stenosis were evaluated by awake cystometry and intraurethral perfusion pressure, respectively. The effects of tamsulosin and distigmine on urethral pressure were also evaluated.

RESULTS

ONO-8055 is a highly potent and selective agonist for EP2 and EP3 receptors on CHO cells. While this compound contracted bladder strips, it relaxed urethral strips. Awake cystometry showed that ONO-8055 significantly decreased bladder capacity, post-void residual urine and voiding pressure. Compared with vehicle, tamsulosin and ONO-8055 significantly decreased urethral pressure.

CONCLUSIONS

ONO-8055 decreased post-void residual urine, probably by decreasing bladder capacity. The decrease in voiding pressure probably resulted from the lowered urethral pressure due to relaxation of the urethra. Thus, the novel EP2 and EP3 receptor dual agonist ONO-8055 has the potential to improve neurogenic underactive bladder.

Translational approaches to the treatment of benign urologic conditions in elderly women

PURPOSE OF REVIEW

Stress urinary incontinence, overactive bladder, interstitial cystitis/painful bladder syndrome, and underactive bladder are highly prevalent among elderly women, and have significant impact on quality of life; however, existing treatments are limited and are not always successful for all patients. Researchers are investigating a multitude of new therapies to treat these conditions. This review will summarize the recent literature on investigative therapies for these conditions.

RECENT FINDINGS

Multiple new treatments are being developed for lower urinary tract dysfunction. Some of these treatments, including balloon therapy and muscle-derived stem cells for stress urinary incontinence, could provide alternatives to existing therapies. Others require further research before being used in patients, such as pudendal nerve stimulation for overactive bladder and intravesical liposomes for drug delivery in interstitial cystitis/painful bladder syndrome.

SUMMARY

Multiple new therapies are being investigated that could provide clinicians with additional tools to treat lower urinary tract disorders in millions of elderly women.

Defining and advancing education and conservative therapies of underactive bladder

In contrast to other forms of voiding dysfunction, underactive bladder (UAB) has traditionally received little research or educational attention. This is changing as our understanding of the underlying mechanisms of detrusor dysfunction and other forms of underactive bladder improves. In addition, the impact of UAB on patient symptoms, general and health-related quality of life, and caregiver burden are becoming more recognized. However, there remains a paucity of data on the subject, and an extensive need for additional research and education on the topic. This paper explores the current state of knowledge about UAB with an emphasis on education regarding the condition and conservative methods of assessment and treatment. Recommendations for future work in this area are considered.

Pathophysiology and animal modeling of underactive bladder

While the symptomology of underactive bladder (UAB) may imply a primary dysfunction of the detrusor muscle, insights into pathophysiology indicate that both myogenic and neurogenic mechanisms need to be considered. Due to lack of proper animal models, the current understanding of the UAB pathophysiology is limited, and much of what is known about the clinical etiology of the condition has been derived from epidemiological data. We hereby review current state of the art in the understanding of the pathophysiology of and animal models used to study the UAB.

Detrusor underactivity: Pathophysiological considerations, models and proposals for future research. ICI-RS 2013

AIMS

Detrusor underactivity, resulting in either prolonged or inefficient voiding, is a common clinical problem for which treatment options are currently limited. The aim of this report is to summarize current understanding of the clinical observation and its underlying pathophysiological entities.

METHODS

This report results from presentations and subsequent discussion at the International Consultation on Incontinence Research Society (ICI-RS) in Bristol, 2013.

RESULTS AND CONCLUSIONS

The recommendations made by the ICI-RS panel include: Development of study tools based on a system's pathophysiological approach, correlation of in vitro and in vivo data in experimental animals and humans, and development of more comprehensive translational animal models. In addition, there is a need for longitudinal patient data to define risk groups and for the development of screening tools. In the near-future these recommendations should lead to a better understanding of detrusor underactivity and its pathophysiological background. Neurourol. Urodynam. 33:591-596, 2014. © 2014 Wiley Periodicals, Inc.