Past, Present and Future of Chemodenervation with Botulinum Toxin in the Treatment of Overactive Bladder

An overview on disease modifying and symptomatic drug treatments for multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is an inflammatory and degenerative autoimmune condition, resulting frequently in a disabling condition. Significant improvements of long-term prognosis have been recently achieved with an early and more aggressive use of disease modifying therapies (DMTs). Addressing the complexity of managing its progressive forms remains a significant challenge.

AREAS COVERED

This review provides an update on DMTs for relapsing-remitting MS (RRMS) and progressive MS and their efficacy, safety, and mechanism of action, emphasizing the critical role of biomarkers in optimizing treatment decisions. Moreover, some key information on drugs used to manage symptoms such as pain, fatigue, spasticity and urinary problems will be provided. The literature search was conducted using PubMed, Embase, and Cochrane Library databases covering the period from January 2000 to January 2024.

EXPERT OPINION

Major advances have been achieved in the treatment of RRMS. Treatment should start immediately as soon as the neurologist is confident with the diagnosis and its choice should be based on the prognostic profile and on the patient's propensity to accept drug-related risks. The therapeutic landscape for progressive MS is quite disappointing and necessitates further innovation. Personalized medicine, leveraging biomarker insights, holds promise for refining treatment efficacy and patient outcomes.

Treating Lower Urinary Tract Symptoms in Older Adults: Intravesical Options

This article provides an overview of the diagnosis and the treatment of lower urinary tract symptoms in older adults complicated by the neurodegenerative changes in the micturition reflex and further confounded by age-related decline in hepatic and renal clearance raising the propensity of adverse drug reactions. The first-line drug treatment for lower urinary tract symptoms, orally administered antimuscarinics, fails to reach the equilibrium dissociation constant of muscarinic receptors even at their maximum plasma concentration and tends to evoke a half-maximal response at a muscarinic receptor occupancy of just 0.206% in the bladder with a minimal difference from exocrine glands, which raises the adverse drug reaction risk. On the contrary, intravesical antimuscarinics are instilled at concentrations 1000-fold higher than the oral maximum plasma concentration and the equilibrium dissociation constant erects a downhill concentration gradient that drives passive diffusion and achieves a mucosal concentration around ten-fold lower than the instilled concentration for a long-lasting occupation of muscarinic receptors in mucosa and sensory nerves. A high local concentration of antimuscarinics in the bladder triggers alternative mechanisms of action and is supposed to engage retrograde transport to nerve cell bodies for neuroplastic changes that underlie a long-lasting therapeutic effect, while an intrinsically lower systemic uptake of the intravesical route lowers the muscarinic receptor occupancy of exocrine glands to lower the adverse drug reaction relative to the oral route. Thus, the traditional pharmacokinetics and pharmacodynamics of oral treatment are upended by intravesical antimuscarinics to generate a dramatic improvement (~ 76%) noted in a meta-analysis of studies enrolling children with neurogenic lower urinary tract symptoms on the primary endpoint of maximum cystometric bladder capacity as well as the secondary endpoints of filling compliance and uninhibited detrusor contractions. The therapeutic success of intravesical multidose oxybutynin solution or oxybutynin entrapped in the polymer for sustained release in the pediatric population bodes well for patients with lower urinary tract symptoms at the other extreme of the age spectrum. Though generally used to predict oral drug absorption, Lipinski's rule of five can also explain the ten-fold lower systemic uptake from the bladder of positively charged trospium over oxybutynin, a tertiary amine. Chemodenervation by an intradetrusor injection of onabotulinumtoxinA is merited for patients with idiopathic overactive bladder discontinuing oral treatment because of a lack of efficacy. However, age-related peripheral neurodegeneration potentiates the adverse drug reaction risk of urinary retention that motivates the quest of liquid instillation, delivering larger fraction of onabotulinumtoxinA to the mucosa as opposed to muscle by an intradetrusor injection can also probe the neurogenic and myogenic predominance of idiopathic overactive bladder. Overall, the treatment paradigm of lower urinary tract symptoms in older adults should be tailored to individual's overall health status and the risk tolerance for adverse drug reactions.

Perioperative Techniques for the Use of Botulinum Toxin in Overactive Bladder: Results of a Multinational Online Survey of Urogynecologists in Germany, Austria, and Switzerland

INTRODUCTION AND HYPOTHESIS

Botulinum toxin (BoNT) is a widely used treatment for overactive bladder (OAB). Despite its common use, no standardized treatment regimen exists so far. The aim of this survey was to evaluate the variation in perioperative treatment strategies among members of the German-speaking urogynecologic societies.

MATERIALS AND METHODS

A clinical practice online survey was carried out between May 2021 and May 2022, and all members of the German, Swiss, and Austrian urogynecologic societies were invited to participate. Participants were grouped in two ways. First, they were grouped into (1) urogynecologists with board certification and (2) non-board-certified general obstetricians and gynecologists (OBGYNs). Second, we set a cut-off at 20 transurethral BoNT procedures per year to differentiate between (1) high- and (2) low-volume surgeons.

RESULTS

One hundred and six completed questionnaires were received. Our results demonstrated that BoNT is mostly used as a third-line treatment (93%, n = 98/106), while high-volume surgeons used it significantly more often as a first/second-line treatment (21% vs. 6%, p = 0.029). Large variations existed in the use of perioperative antibiotics, preferred sites of injection, the number of injections, and the timing of the measurement of the postvoid residual volume (PVRV). Forty percent of participants did not offer outpatient treatment to patients. Local anesthesia (LA) was mostly used by board-certified urogynecologists (49% vs. 10%, p < 0.001) and high-volume surgeons (58% vs. 27%, p = 0.002). Injections into the trigone were also more often performed by board-certified urogynecologists and high-volume surgeons (22% vs. 3% (p = 0.023) and 35% vs. 6% (p < 0.001), respectively). PVRV was controlled between weeks 1 and 4 by only 54% of participants (n = 57/106). Clean intermittent self-catheterization (CISC) was infrequently taught (26%).

CONCLUSIONS

Our survey confirmed that BoNT is widely used by urogynecologists in the three German-speaking countries, but practice patterns vary widely, and no standardized method could be detected, despite interviewing urogynecologic experts. These results clearly demonstrate that there is a need for studies to define standardized treatment strategies for the best perioperative and surgical approach regarding the use of BoNT in patients with OAB.

Long-Term Surveillance and Management of Urological Complications in Chronic Spinal Cord-Injured Patients

Bladder dysfunction is a common complication after chronic spinal cord injury (SCI). Patients may experience renal function loss, urinary tract infection (UTI), urolithiasis, bladder cancer, and even life-threatening events such as severe sepsis or renal failure. Suitable patient care may prevent UTI and urinary incontinence, decrease medication use, and preserve renal function. As the primary goal is to preserve renal function, management should be focused on facilitating bladder drainage, the avoidance of UTI, and the maintenance of a low intravesical pressure for continence and complete bladder emptying. Currently, several bladder management options are available to SCI patients: (1) reflex voiding; (2) clean intermittent catheterization; (3) indwelling catheterization. The target organ may be the bladder or the bladder outlet. The purposes of intervention include the following: (1) increasing bladder capacity and/or decreasing intravesical pressure; (2) increasing bladder outlet resistance; (3) decreasing bladder outlet resistance; (4) producing detrusor contractility; (5) urinary diversion. Different bladder management methods and interventions may have different results depending on the patient's lower urinary tract dysfunction. This review aims to report the current management options for long-term bladder dysfunction in chronic SCI patients. Furthermore, we summarize the most suitable care plans for improving the clinical outcome of SCI patients.

Intravesical Botulinum toxin-A injection in pediatric overactive neurogenic bladder with Detrusor overactivity: Radiologic and clinical outcomes

Objective:

The neurogenic bladder is one of the most serious and painful disorders seen in pediatric urology clinics. The upper urinary tract can be impaired by increased bladder pressure. Botulinum toxin-A (BTX-A) is one of the new therapeutic interventions for this disease. Thus, this research was designed to determine the clinical as well as radiological outcomes intravesical BTX-A injections in patients with overactive neurogenic bladder with Detrusor over activity.

Patients and methods:

From March 2012 to March 2019, this cohort study was conducted at Shahid Labbafinejad hospital in Tehran, Iran. Thirty-five pediatric patients with a neurogenic bladder and Detrusor overactivity who fulfilled the eligibility criteria received BTX-A injections. Demographic data, including spinal cord lesions or congenital malformations, upper and lower urinary tract nuclear scans, evidence of vesicoureteral reflux (VUR) and its severity, and hydronephrosis and 72 h voiding diary before and after intervention were all recorded.

Results:

The mean ± standard deviation age of participants was 9.47 ± 4.61 years. After injection, nocturia and urination frequency as general symptoms of the overactive neurogenic bladder improved ( p < 0.05). Also, the severity of hydronephrosis was decreased in 33% of patients following injection. In our study, 32 out of 35 patients had vesicoureteral reflux. Of those, there was complete resolution and downgrading of VUR in 17 (53.12%) and 13 (40.62%) respectively. Seventeen patients (53.12%) had complete recovery post-injection from VUR.

Conclusion:

In the evaluation of voiding cystourethrography (VCUG) before and after the injection, downgrading of VUR was seen in 53% of the cases. In the 99mTc-DMSA nuclear scan before and after the injection, the appearance of a new parenchymal scar and uptake reduction was not observed, which indicates the cessation of scar formation in all patients. Although Enuresis, Urgency, Frequency, Nocturia, and UUI significantly improved after injection.

Nanotechnology as a tool to advance research and treatment of non-oncologic urogenital diseases

Nanotechnology represents an expanding area of research and innovation in almost every field of science, including Medicine, where nanomaterial-based products have been developed for diagnostic and therapeutic applications. Because of their small, nanoscale size, these materials exhibit unique physical and chemical properties that differ from those of each component when considered in bulk. In Nanomedicine, there is an increasing interest in harnessing these unique properties to engineer nanocarriers for the delivery of therapeutic agents. Nano-based drug delivery platforms have many advantages over conventional drug administration routes as this technology allows for local and transdermal applications of therapeutics that can bypass the first-pass metabolism, improves drug efficacy through encapsulation of hydrophobic drugs, and allows for a sustained and controlled release of encapsulated agents. In Urology, nano-based drug delivery platforms have been extensively investigated and implemented for cancer treatment. However, there is also great potential for use of nanotechnology to treat non-oncologic urogenital diseases. We provide an update on research that is paving the way for clinical translation of nanotechnology in the areas of erectile dysfunction (ED), overactive bladder (OAB), interstitial cystitis/bladder pain syndrome (IC/BPS), and catheter-associated urinary tract infections (CAUTIs). Overall, preclinical and clinical studies have proven the utility of nanomaterials both as vehicles for transdermal and intravesical delivery of therapeutic agents and for urinary catheter formulation with antimicrobial agents to treat non-oncologic urogenital diseases. Although clinical translation will be dependent on overcoming regulatory challenges, it is inevitable before there is universal adoption of this technology to treat non-oncologic urogenital diseases.

Excitatory effect of acotiamide on rat and human bladder: Implications for underactive bladder treatment

OBJECTIVE

To evaluate whether approved gastroprokinetic agent, acotiamide exerts a direct excitatory effect on bladder to help explain the reported meaningful reduction of post-void residual urine volume (PVR) in detrusor underactivity (DU) patients after thrice daily oral intake of acotiamide 100 mg for 2 weeks.

METHODS

Effect of acotiamide [1-16 μM] was assessed on nerve-mediated contractions evoked by electrical field stimulation (EFS) for 5 s with 5 ms pulse trains of 10 V in longitudinal, mucosa intact rat and human bladder strips to construct frequency response curve (1-32 Hz) and repeat 10 Hz stimulation at 60s interval. Effect of acotiamide 2 μM on spontaneous and carbachol evoked contractions was also assessed.

RESULTS

Acotiamide 2 μM significantly enhanced the Atropine and Tetrodotoxin (TTX)-sensitive EFS evoked contractions of rat and human bladder at 8-32 Hz (Two-way ANOVA followed Sidak's multiple comparison; *p < 0.01) and on repeat 10 Hz stimulation (Paired Student's t-test; *p < 0.05), while producing a modest effect on the spontaneous contractions and a negligible effect on the carbachol evoked contractions.

CONCLUSIONS

Enhancement of TTX-sensitive evoked contractions of rat and human bladder by acotiamide is consistent with the enhancement of excitatory neuro-effector transmission mainly through prejunctional mechanisms. Findings highlight immense therapeutic potential of antimuscarinics with low M3 receptor affinity like acotiamide in Underactive bladder (UAB)/DU treatment.

Current management of refractory overactive bladder

Overactive bladder (OAB) is a common condition affecting one-sixth to one-fifth of the global population. The treatment of refractory OAB remains a challenge for urologists. Current treatment options include the use of combination therapy with antimuscarinic agents and beta-3 adrenoceptor agonists, and treating underlying curable disorders. Intravesical botulinum toxin type A (BoNT-A) injection, percutaneous tibial nerve stimulation, and sacral nerve stimulation are third-line management therapies suggested by the American Urological Association/Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction (AUA/SUFU) guidelines. In rare cases, more invasive surgical interventions can be considered after explaining the benefits and risks to the patients. Augmentation cystoplasty has a high success rate; however, it has also been associated with a high complication rate. In contrast, detrusor myomectomy is an easy procedure, but the treatment outcome remains controversial. Liposome-encapsulated BoNT-A is administered via bladder instillation, and promising results have been obtained in preliminary studies. More therapies are currently being investigated, and transient receptor potential vanilloid 1 antagonists may be new type of medication. Radiofrequency ablation and other targets for neuromodulation have also been studied; however, more evidence is needed to confirm their efficacy.

Are 200 units of onabotulinumtoxin A sufficient for the suppression of neurogenic detrusor overactivity in individuals with established 300-unit botulinum toxin treatment? A retrospective cohort study

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To investigate the effects of 200-unit onabotulinumtoxin A detrusor injections on neurogenic detrusor overactivity (NDO) in patients who have previously been treated with 300-unit injections.

SETTING

Tertiary urologic referral center in Switzerland.

METHODS

The patient database was screened for patients with NDO as a result of chronic (≥ 12 months) spinal cord injury (SCI), who had been treated with 300- followed by 200-unit onabotulinumtoxin A detrusor injections. Patient characteristics, bladder management data and concurrent bladder medication as well as urodynamic data were collected. The percent changes in the urodynamic parameters from the 300- to the 200-unit treatment phase were calculated to test for non-inferiority of the 200-unit treatment.

RESULTS

The data of 61 individuals with a mean age of 44 ± 15 years (range 18-73 years) and a mean 13.2 ± 9.5 years (range 2-43 years) since SCI were analyzed. The 200-unit treatment was not inferior regarding the urodynamic parameters compared to the 300-unit treatment. Furthermore, the proportion of patients with urinary incontinence was similar for both doses. There was no significant difference in the number of daily bladder evacuations (p = 0.13) or used incontinence pads (p = 0.43) between the two dosage phases. Moreover, there was no significant (p = 0.19) increase in the use of concurrent NDO medication (antimuscarinics or mirabegron) during the 200-unit treatment.

CONCLUSIONS

The treatment of NDO with 200 units of onabotulinumtoxin A was not inferior to a 300-unit treatment regarding urodynamic parameters in patients with chronic SCI.

Botulinum toxin A for refractory OAB and idiopathic urinary retention: Can phenotyping improve outcome for patients: ICI-RS 2019?

AIMS

Botulinum toxin A (BTX-A) is a well-established treatment for refractory idiopathic overactive bladder (OAB). It has also been used with short-term success in treating idiopathic urinary retention. However, efficacy and complication rates are variable and predicting those likely to benefit most from treatment would enable personalization of therapy and optimization of outcomes. At the International Consultation on Incontinence-Research Society (ICI-RS) meeting in 2019 a Think Tank addressed the question of how we can improve the way we phenotype patients undergoing BTX-A treatment.

METHODS

The Think Tank conducted a literature review and expert consensus meeting focussing on how advances in basic science research of the mechanism of action of BTX-A, as well as assessment of psychological comorbidity, can be translated into clinical practice to improve patient selection for therapy.

RESULTS

Idiopathic OAB and idiopathic urinary retention are heterogenous conditions encompassing several phenotypes with multiple potential pathophysiological mechanisms. Animal models have demonstrated a central nervous system mechanism of action of intravesically injected BTX-A and this has been confirmed in human functional MRI studies, but whether this tool can be used to predict outcome from treatment remains to be determined. Phenotyping based on psychological comorbidity using validated screening tools should be studied as a way to potentially optimize patient selection for therapy.

CONCLUSIONS

Advances in basic science research into the mechanism of action of BTX-A have improved our understanding of the pathophysiology of OAB and may lead to novel ways to phenotype patients. Psychological assessment is another way in which phenotyping may be improved. Areas for further research are proposed.

Using electroacupuncture with optimized acupoint positioning to predict the efficacy of sacral neuromodulation of refractory overactive bladder: A case report

RATIONALE

Overactive bladder (OAB) is a common disease in the female urinary system. Refractory OAB is an indication for sacral neuromodulation (SNM) therapy, which was approved by the Food and Drug Administration (FDA) of the United States. However, SNM does not alleviate the clinical symptoms in all refractory OAB cases. Patients are required to undergo an SNM stage 1 operation, a traumatic and costly procedure, to evaluate the clinical efficacy of the treatment. If the procedure is predicted to likely be ineffective, the patient has to bear the physical and economic losses. Here, we report a patient with a 3-year course of refractory urge urinary incontinence who was treated with electroacupuncture according to traditional Chinese medicine (TCM).

PATIENT CONCERNS

The patient was 73 years old and had frequent urination and urge urinary incontinence for 3 years; she had 24 to 30 counts of urination per day and 7 to 9 counts of urge incontinence. The patient was treated with multiple TCM and Western medicines and therapies. The TCM treatment consisted of several patented Chinese medicines and TCM decoctions. The Western medication comprised mainly antibiotics, alpha receptor antagonists, and muscarinic receptor antagonists. The treatment effect was unsatisfactory, and there was no apparent alleviation of symptoms; therefore, she underwent electroacupuncture.

DIAGNOSIS

Refractory OAB.

INTERVENTIONS

The patient received 30 days of TCM-based electroacupuncture with optimized acupoint positioning, which comprised a total of 10 sessions (1 electroacupuncture session every 2 days) targeting the bilateral Zhongliao and Sanyinjiao acupoints. After treatment, the patient experienced a good therapeutic outcome.

OUTCOMES

After 30 days of electroacupuncture treatment, the average daily count of urination in 5 days decreased from 29.3 per day before treatment to 19.8 after treatment, and the average count of urge incontinence decreased from 9.3 before treatment to 5.8 after treatment. However, good prognosis was not stable. After careful consideration, the patient accepted SNM treatment, which greatly alleviated the symptoms of frequent urination and urge incontinence. The patient received follow-up visits for 2 years, during which she manifested stable curative effects.

LESSONS

The optimized positioning at the Zhongliao acupoint improves the accuracy of acupuncture. Accurate electroacupuncture alleviates the symptoms of refractory OAB by stimulating the Zhongliao and Sanyinjiao acupoints, as the underlying mechanisms are similar to those of SNM. Therefore, it is possible to use electroacupuncture to estimate the therapeutic effect of SNM, thereby providing a reference for patients and clinicians to determine whether SNM treatment will be effective.

Toxin-induced hormesis may restrain aging

Mild environmental stress might have beneficial effects in aging by activating maintenance and repair processes in cells and organs. These beneficial stress effects fit to the concept of hormesis. Prominent stressors acting in a hormetic way are physical exercises, fasting, cold and heat. This review will introduce some toxins, which have been found to induce hormetic responses in animal models of aging research. To highlight the molecular signature of these hormetic effects we will depict signaling pathways affected by low doses of toxins on cellular and organismic level. As prominent examples for signaling pathways involved in both aging processes as well as toxin responses, PI3K/Akt/mTOR- and AMPK-signal transduction will be described in more detail. Due to the striking overlap of signaling pathways mediating toxin induced responses and aging processes we propose considering the ability of low doses of toxins to slow down the rate of aging.

Current Therapeutic Strategies in Clinical Urology

The field of urology encompasses all benign and malignant disorders of the urinary tract and the male genital tract. Urological disorders convey a huge economic and patient quality-of-life burden. Hospital acquired urinary tract infections, in particular, are under scrutiny as a measure of hospital quality. Given the prevalence of these pathologies, there is much progress still to be made in available therapeutic options in order to minimize side effects and provide effective care. Current drug delivery mechanisms in urological malignancy and the benign urological conditions of overactive bladder (OAB), interstitial cystitis/bladder pain syndrome (IC/BPS), and urinary tract infection (UTI) will be reviewed herein. Both systemic and local therapies will be discussed including sustained release formulations, nanocarriers, hydrogels and other reservoir systems, as well as gene and immunotherapy. The primary focus of this review is on agents which have passed the preclinical stages of development.

Novel Applications of OnabotulinumtoxinA in Lower Urinary Tract Dysfunction

OnabotulinumtoxinA (BoNT-A) was first used to treat neurogenic lower urinary tract dysfunction (LUTD) 30 years ago. Recently, application of BoNT-A in LUTD have become more common since the approval of intravesical BoNT-A injection for patients with both overactive bladders (OAB) and neurogenic detrusor overactivity (NDO) by regulatory agencies in many countries. Although unlicensed, BoNT-A has been recommended to treat patients with interstitial cystitis/bladder pain syndrome (IC/BPS) under different guidelines. BoNT-A delivery with liposome-encapsulation and gelation hydrogel intravesical instillation provided a potentially less invasive and more convenient form of application for patients with OAB or IC/BPS. BoNT-A injections into the urethral sphincter for spinal cord injury patients with detrusor-sphincter dyssynergia have been used for a long time. New evidence revealed that it could also be applied to patients with non-neurogenic dysfunctional voiding. Previous studies and meta-analyses suggest that BoNT-A injections for patients with benign prostate hyperplasia do not have a better therapeutic effect than placebo. However, new randomized and placebo-controlled trials revealed intraprostatic BoNT-A injection is superior to placebo in specific patients. A recent trial also showed intraprostatic BoNT-A injection could significantly reduce pain in patients with chronic prostatitis. Both careful selection of patients and prudent use of urodynamic evaluation results to confirm diagnoses are essential for successful outcomes of BoNT-A treatment for LUTD.

The Expanding Therapeutic Utility of Botulinum Neurotoxins

Botulinum neurotoxin (BoNT) is a major therapeutic agent that is licensed in neurological indications, such as dystonia and spasticity. The BoNT family, which is produced in nature by clostridial bacteria, comprises several pharmacologically distinct proteins with distinct properties. In this review, we present an overview of the current therapeutic landscape and explore the diversity of BoNT proteins as future therapeutics. In recent years, novel indications have emerged in the fields of pain, migraine, overactive bladder, osteoarthritis, and wound healing. The study of biological effects distal to the injection site could provide future opportunities for disease-tailored BoNT therapies. However, there are some challenges in the pharmaceutical development of BoNTs, such as liquid and slow-release BoNT formulations; and, transdermal, transurothelial, and transepithelial delivery. Innovative approaches in the areas of formulation and delivery, together with highly sensitive analytical tools, will be key for the success of next generation BoNT clinical products.

Can bladder fibrosis in congenital urinary tract obstruction be reversed?

A variety of conditions exists in adults and children in which functional or anatomical urinary tract obstructions cause bladder fibrosis, which reduces the bladder's ability to store and empty urine. Current surgical procedures include removal of the obstructions to facilitate bladder emptying or prompt prenatal or postnatal spinal closure to prevent further neurogenic damage. Bladder fibrosis may occur, and it can get worse if a flow hindrance persists or deteriorates. Anti-fibrotic therapeutic strategies that target a variety of factors have been developed in animal models, but currently there are no anti-fibrotic therapies available for clinical use. This review examines the pathogenesis of bladder fibrosis that is caused by congenital obstructions of the lower urinary tract, and it focuses on the principal signalling factors and potential treatment modalities.

[Overactive bladder-which treatment when?]

The term OAB (overactive bladder) describes a symptom complex. Therefore, initial treatment should be based on clinical symptoms and the results of basic diagnostics. Patient preference is essential for the choice of the initial treatment. Behavioural therapy, electrostimulation and medical treatment are available treatment options. If these are not effective, extended diagnostic examinations should be performed prior to minimally invasive treatments, like onabotulinumtoxin injections in the detrusor or sacral neuromodulation. Surgical interventions like augmentation cystoplasty are rarely required today.

MicroRNAs as potential biomarkers to predict the risk of urinary retention following intradetrusor onabotulinumtoxin-A injection

AIMS

MicroRNAs (miRs) control post-transcriptional gene expression, and this is relevant in understanding better chronic diseases and treatment outcomes. The role of miRs in the pathology and treatment outcomes of overactive bladder (OAB) is unknown. In this study, we assessed the differential expression of miRs in OAB patients responding with either normal or elevated post-void residual volumes (PVRs) ≥200 mL following intradetrusor injection of onabotulinumtoxin-A (onaBoNT-A).

METHODS

Female OAB patients refractory to OAB drugs were consented for this study. Cystoscopic-guided punch bladder biopsy was obtained at the time of injection of onaBoNT-A 100 units. The expression of 13 miR species, selected for their known effect on neurotrophin expression and smooth muscle function, was measured. PVRs and urine nerve growth factor (NGF) levels were measured at baseline and at the follow-up visit.

RESULTS

Fourteen patients with mean age of 66 years were consented. Of these patients, nine maintained PVRs <200 mL after onaBoNT-A injection to comprise the low PVR group. The other five patients with PVRs ≥200 mL comprised the high PVR group. The expression of miR221 and miR125b was upregulated by 11- and 2-fold, respectively, in patients who responded with low PVRs after onaBoNT-A (P < 0.05). Urine NGF levels at baseline were not different between the two groups.

CONCLUSIONS

This study suggests that deficiency in the pretreatment expression of miR221 and miR125b may predispose OAB patients to high PVRs following intradetrusor onaBoNT-A. Additional studies are needed to better understand the role of miRs in OAB.