Experimentally Induced Bladder Permeability Evokes Bladder Afferent Hypersensitivity in the Absence of Inflammation

Preparation and characterization of a novel composite acellular matrix/hyaluronic acid thermosensitive hydrogel for interstitial cystitis/bladder pain syndrome

Bladder mucosa damage that causes harm to the interstitium is a recognized pathogenesis of interstitial cystitis/bladder pain syndrome (IC/BPS). The intravesical instillation of drugs is an important second-line therapy, but it is often necessary to use drugs repeatedly in the clinic because of their short residence time in the bladder cavity, which alters the therapeutic effect. To overcome this drawback, this study developed a novel composite acellular matrix/hyaluronic acid (HA) thermosensitive hydrogel (HA-Gel) using rabbit small intestinal submucosa extracellular matrix (ECM) as the thermosensitive material and HA as the drug component and examined its composition, microstructure, thermodynamic properties, temperature sensitivity, rheological properties, biocompatibility, drug release, hydrogel residue, and bacteriostatic properties. The study showed HA-Gel was liquid at temperatures of 15-37.5°C and solid at 37.5-50°C, its swelling rate decreased with increasing temperature, and its lower critical solution temperature occurred at approximately 37.5°C. This property made the hydrogel liquid at room temperature convenient for intravesical perfusion and turned into a solid about 1 min after entering the body and rising to body temperature to increase its residence time. Subsequent experiments also proved that the gel residue time of HA-Gel in vivo and the drug release time of HA in vivo could reach more than 5 days, which was significantly higher than that of HA alone, and it had good biocompatibility and antibacterial properties. Therefore, this hydrogel possesses the proper characteristics to possibly make it an ideal dosage form for IC/BPS intravesical instillation therapy.

BCG induced lower urinary tract symptoms during treatment for NMIBC-Mechanisms and management strategies

Non-muscle invasive bladder cancer (NMIBC) accounts for ~70-75% of total bladder cancer tumors and requires effective early intervention to avert progression. The cornerstone of high-risk NMIBC treatment involves trans-urethral resection of the tumor followed by intravesical Bacillus Calmette-Guerin (BCG) immunotherapy. However, BCG therapy is commonly accompanied by significant lower urinary tract symptoms (LUTS) including urinary urgency, urinary frequency, dysuria, and pelvic pain which can undermine treatment adherence and clinical outcomes. Despite this burden, the mechanisms underlying the development of BCG-induced LUTS have yet to be characterized. This review provides a unique perspective on the mechanisms thought to be responsible for the development of BCG-induced LUTS by focussing on the sensory nerves responsible for bladder sensory transduction. This review focuses on how the physiological response to BCG, including inflammation, urothelial permeability, and direct interactions between BCG and sensory nerves could drive bladder afferent sensitization leading to the development of LUTS. Additionally, this review provides an up-to-date summary of the latest clinical data exploring interventions to relieve BCG-induced LUTS, including therapeutic targeting of bladder contractions, inflammation, increased bladder permeability, and direct inhibition of bladder sensory signaling. Addressing the clinical burden of BCG-induced LUTS holds significant potential to enhance patient quality of life, treatment compliance, and overall outcomes in NMIBC management. However, the lack of knowledge on the pathophysiological mechanisms that drive BCG-induced LUTS has limited the development of novel and efficacious therapeutic options. Further research is urgently required to unravel the mechanisms that drive BCG-induced LUTS.

Antinociceptive Effects of an Anti-CGRP Antibody in Rat Models of Colon-Bladder Cross-Organ Sensitization

Irritable bowel syndrome (IBS) and bladder pain syndrome/interstitial cystitis (BPS/IC) are comorbid visceral pain disorders seen commonly in women with unknown etiology and limited treatment options and can involve visceral organ cross-sensitization. Calcitonin gene-related peptide (CGRP) is a mediator of nociceptive processing and may serve as a target for therapy. In three rodent models, we employed a monoclonal anti-CGRP F(ab')2 to investigate the hypothesis that visceral organ cross-sensitization is mediated by abnormal CGRP signaling. Visceral organ cross-sensitization was induced in adult female rats via transurethral infusion of protamine sulfate (PS) into the urinary bladder or infusion into the colon of trinitrobenzene sulfonic acid (TNBS). Colonic sensitivity was assessed via the visceromotor response to colorectal distension (CRD). Bladder sensitivity was assessed as the frequency of abdominal withdrawal reflexes to von Frey filaments applied to the suprapubic region. PS- or TNBS-induced changes in colonic and bladder permeability were investigated in vitro via quantification of transepithelial electrical resistance (TEER). Peripheral administration of an anti-CGRP F(ab')2 inhibited PS-induced visceral pain behaviors and colon hyperpermeability. Similarly, TNBS-induced pain behaviors and colon and bladder hyperpermeability were attenuated by anti-CGRP F(ab')2 treatment. PS into the bladder or TNBS into the colon significantly increased the visceromotor response to CRD and abdominal withdrawal reflexes to suprapubic stimulation and decreased bladder and colon TEER. These findings suggest an important role of peripheral CGRP in visceral nociception and organ cross-sensitization and support the evaluation of CGRP as a therapeutic target for visceral pain in patients with IBS and/or BPS/IC. SIGNIFICANCE STATEMENT: A monoclonal antibody against calcitonin gene-related peptide (CGRP) was found to reduce concomitant colonic and bladder hypersensitivity and hyperpermeability. The results of this study suggest that CGRP-targeting antibodies, in addition to migraine prevention, may provide a novel treatment strategy for multiorgan abdominopelvic pain following injury or inflammation.

Animal models of interstitial cystitis/bladder pain syndrome

Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS) is a chronic disorder characterized by pelvic and/or bladder pain, along with lower urinary tract symptoms that have a significant impact on an individual's quality of life. The diverse range of symptoms and underlying causes in IC/BPS patients pose a significant challenge for effective disease management and the development of new and effective treatments. To facilitate the development of innovative therapies for IC/BPS, numerous preclinical animal models have been developed, each focusing on distinct pathophysiological components such as localized urothelial permeability or inflammation, psychological stress, autoimmunity, and central sensitization. However, since the precise etiopathophysiology of IC/BPS remains undefined, these animal models have primarily aimed to replicate the key clinical symptoms of bladder hypersensitivity and pain to enhance the translatability of potential therapeutics. Several animal models have now been characterized to mimic the major symptoms of IC/BPS, and significant progress has been made in refining these models to induce chronic symptomatology that more closely resembles the IC/BPS phenotype. Nevertheless, it's important to note that no single model can fully replicate all aspects of the human disease. When selecting an appropriate model for preclinical therapeutic evaluation, consideration must be given to the specific pathology believed to underlie the development of IC/BPS symptoms in a particular patient group, as well as the type and severity of the model, its duration, and the proposed intervention's mechanism of action. Therefore, it is likely that different models will continue to be necessary for preclinical drug development, depending on the unique etiology of IC/BPS being investigated.

The T-type calcium channel Ca V 3.2 regulates bladder afferent responses to mechanical stimuli

ABSTRACT

The bladder wall is innervated by a complex network of afferent nerves that detect bladder stretch during filling. Sensory signals, generated in response to distension, are relayed to the spinal cord and brain to evoke physiological and painful sensations and regulate urine storage and voiding. Hyperexcitability of these sensory pathways is a key component in the development of chronic bladder hypersensitivity disorders including interstitial cystitis/bladder pain syndrome and overactive bladder syndrome. Despite this, the full array of ion channels that regulate bladder afferent responses to mechanical stimuli have yet to be determined. Here, we investigated the role of low-voltage-activated T-type calcium (Ca V 3) channels in regulating bladder afferent responses to distension. Using single-cell reverse-transcription polymerase chain reaction and immunofluorescence, we revealed ubiquitous expression of Ca V 3.2, but not Ca V 3.1 or Ca V 3.3, in individual bladder-innervating dorsal root ganglia neurons. Pharmacological inhibition of Ca V 3.2 with TTA-A2 and ABT-639, selective blockers of T-type calcium channels, dose-dependently attenuated ex-vivo bladder afferent responses to distension in the absence of changes to muscle compliance. Further evaluation revealed that Ca V 3.2 blockers significantly inhibited both low- and high-threshold afferents, decreasing peak responses to distension, and delayed activation thresholds, thereby attenuating bladder afferent responses to both physiological and noxious distension. Nocifensive visceromotor responses to noxious bladder distension in vivo were also significantly reduced by inhibition of Ca V 3 with TTA-A2. Together, these data provide evidence of a major role for Ca V 3.2 in regulating bladder afferent responses to bladder distension and nociceptive signalling to the spinal cord.

Urinary Tract Infection in Overactive Bladder: An Update on Pathophysiological Mechanisms

Overactive bladder (OAB) is a clinical syndrome defined by urinary urgency, increased daytime urinary frequency and/or nocturia, with or without urinary incontinence, that affects approximately 11% of the western population. OAB is accepted as an idiopathic disorder, and is charactersied clinically in the absence of other organic diseases, including urinary tract infection. Despite this, a growing body of research provides evidence that a significant proportion of OAB patients have active bladder infection. This review discusses the key findings of recent laboratory and clinical studies, providing insight into the relationship between urinary tract infection, bladder inflammation, and the pathophysiology of OAB. We summarise an array of clinical studies that find OAB patients are significantly more likely than control patients to have pathogenic bacteria in their urine and increased bladder inflammation. This review reveals the complex nature of OAB, and highlights key laboratory studies that have begun to unravel how urinary tract infection and bladder inflammation can induce urinary urgency and urinary frequency. The evidence presented in this review supports the concept that urinary tract infection may be an underappreciated contributor to the pathophysiology of some OAB patients.