Assessment of colon and bladder crosstalk in an experimental colitis model using contrast-enhanced magnetic resonance imaging

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.

Visualising and quantifying intestinal permeability -where do we stand

Intestinal permeability is getting more and more attention in gastrointestinal research. Although well recognized, its exact role in health and disease is yet to be defined. There are many methods of quantifying intestinal permeability, but most of them fail to deliver tangible information about the morphological integrity of the intestinal barrier. In this review we aim to describe imaging options for the assessment of intestinal barrier integrity and their potential relevance for clinical practice. Our focus is on confocal laser endomicroscopy, which is at this time the only method for visualizing not only functional but also morphological aspects of the gut barrier in vivo.

Inhibition of CXCR4 in Spinal Cord and DRG with AMD3100 Attenuates Colon-Bladder Cross-Organ Sensitization

Background

Cross-sensitization of pelvic organs is one theory for why symptoms of gut sickness and interstitial cystitis/bladder pain syndrome overlap. Experimental colitis has been shown to trigger bladder hyperactivity and hyperalgesia in rats. The chemokine receptor CXCR4 plays a key role in bladder function and central sensitization. We aim to study the role of CXCR4 and its inhibitor AMD3100 in colon-bladder cross-organ sensitization.

Methods

The colitis model was established by rectal infusion of trinitrobenzene sulfonic acid. Western blot and immunofluorescence were used to assess the expression and distribution of CXCR4. Intrathecal injection of AMD3100 (a CXCR4 inhibitor) and PD98059 (an ERK inhibitor) were used to inhibit CXCR4 and downstream extracellular signal-regulated kinase (ERK) in the spinal cord and dorsal root ganglion (DRG). Intravesical perfusion of resiniferatoxin was performed to measure the pain behavior counts of rats, and continuous cystometry was performed to evaluate bladder voiding function.

Results

Compared to the control group, CXCR4 was expressed more in bladder mucosa and colon mucosa, L6-S1 dorsal root ganglion (DRG), and the corresponding segment of the spinal dorsal horn (SDH) in rats with colitis. Moreover, intrathecal injection of the AMD3100 suppressed bladder overactivity, bladder hyperalgesia, and mastocytosis symptoms caused by colitis. Furthermore, AMD3100 effectively inhibited ERK activation in the spinal cord induced by experimental colitis. Finally, treatment with PD98059 alleviated bladder overactivity and hyperalgesia caused by colitis.

Conclusion

Increased CXCR4 in the DRG and SDH contributes to colon inflammation-induced bladder overactivity and hyperalgesia partly via the phosphorylation of spinal ERK. Treatment targeting the CXCR4/ERK pathway might provide a potential new approach for the comorbidity between the digestive system and the urinary system.

MRI as a Tool to Assess Interstitial Cystitis Associated Bladder and Brain Pathologies

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic, often incapacitating condition characterized by pain seeming to originate in the bladder in conjunction with lower urinary tract symptoms of frequency and urgency, and consists of a wide range of clinical phenotypes with diverse etiologies. There are currently no diagnostic tests for IC/BPS. Magnetic resonance imaging (MRI) is a relatively new tool to assess IC/BPS. There are several methodologies that can be applied to assess either bladder wall or brain-associated alterations in tissue morphology and/or pain. IC/BPS is commonly associated with bladder wall hyperpermeability (BWH), particularly in severe cases. Our group developed a contrast-enhanced magnetic resonance imaging (CE-MRI) approach to assess BWH in preclinical models for IC/BPS, as well as for a pilot study for IC/BPS patients. We have also used the CE-MRI approach to assess possible therapies to alleviate the BWH in preclinical models for IC/BPS, which will hopefully pave the way for future clinical trials. In addition, we have used molecular-targeted MRI (mt-MRI) to quantitatively assess BWH biomarkers. Biomarkers, such as claudin-2, may be important to assess and determine the severity of BWH, as well as to assess therapeutic efficacy. Others have also used other MRI approaches to assess the bladder wall structural alterations with diffusion-weighted imaging (DWI), by measuring changes in the apparent diffusion coefficient (ADC), diffusion tensor imaging (DTI), as well as using functional MRI (fMRI) to assess pain and morphological MRI or DWI to assess anatomical or structural changes in the brains of patients with IC/BPS. It would be beneficial if MRI-based diagnostic tests could be routinely used for these patients and possibly used to assess potential therapeutics.

SuperGAG biopolymers for treatment of excessive bladder permeability

Few therapeutic options exist for treatment of IC/BPS. A novel high MW GAG biopolymer ("SuperGAG") was synthesized by controlled oligomerization of CS, purified by TFF and characterized by SEC-MALLS and 1H-NMR spectroscopy. The modified GAG biopolymer was tested in an OVX female rat model in which bladder permeability was induced by a 10-minute intravesicular treatment with dilute (1 mg/ml) protamine sulfate and measured by classical Ussing Chamber TEER measurements following treatment with SuperGAG, chondroitin sulfate, or saline. The effect on abrogating the abdominal pain response was assessed using von Frey filaments. The SuperGAG biopolymer was then investigated in a second, genetically modified mouse model (URO-MCP1) that increasingly is accepted as a model for IC/BPS. Permeability was induced with a brief exposure to a sub-noxious dose of LPS and was quantified using contrast-enhanced MRI (CE-MRI). The SuperGAG biopolymer restored impermeability to normal levels in the OVX rat model as measured by TEER in the Ussing chamber and reduced the abdominal pain response arising from induced permeability. Evaluation in the URO-MCP1 mouse model also showed restoration of bladder impermeability and showed the utility of CE-MRI imaging for evaluating the efficacy of agents to restore bladder impermeability. We conclude novel high MW SuperGAG biopolymers are effective in restoring urothelial impermeability and reducing pain produced by loss of the GAG layer on the urothelium. SuperGAG biopolymers could offer a novel and effective new therapy for IC/BPS, particularly if combined with MRI to assess the efficacy of the therapy.

Molecular pathogenesis of interstitial cystitis/bladder pain syndrome based on gene expression

Interstitial cystitis/painful bladder syndrome (IC/PBS) is a chronic bladder inflammation that leads to chronic bladder pain and urinary urgency and frequency. The presentation of IC/PBS is heterogeneous, and it is classified as ulcerative IC/PBS and nonulcerative IC/PBS. The main cause of IC/PBS is thought to be a persistent inflammatory condition in the bladder, though the actual pathophysiology has not been identified yet. Although the underlying pathophysiology of IC/PBS is not completely understood, several theories for the etiology of this syndrome have been suggested, including deficiency of the glycosaminoglycan covering urothelium surface that results in leaky urothelium infection, immunological etiology, activated mast cells, neural changes, and inflammation. In addition, there are no gold standards for the detection of this disorder to date. So, determination of gene expression and its role in different signaling pathways in the pathogenesis of this heterogeneous disorder contribute to the more efficient cognition of the pathophysiology of this disease and to the design of effective treatments and molecular diagnostic methods for IC/PBS.

Preclinical Animal Studies of Intravesical Recombinant Human Proteoglycan 4 as a Novel Potential Therapy for Diseases Resulting From Increased Bladder Permeability

OBJECTIVE

To test in an animal model the hypothesis that recombinant human proteoglycan 4 (rhPRG4; lubricin), a highly O-glycosylated mucin-like glycoprotein, may be a novel surface-active therapeutic for treating bladder permeability with comorbid bowel permeability. Previously we showed that inducing bladder permeability in rats with dilute protamine sulfate (PS) produced colonic permeability and visceral hypersensitivity, suggesting increased bladder permeability could represent an etiologic factor in both interstitial cystitis-bladder pain syndrome and irritable bowel syndrome.

METHODS

We used an animal model of catheterized ovariectomized female rats instilled intravesically with 1 mg/mL PS for 10 minutes that after 24 hours were treated with 1.2 mg/mL lubricin or with vehicle alone. After 24 hours the bladder and colon were removed and permeability assessed electrophysiologically with the Ussing chamber to measure the transepithelial electrical resistance. A second set of rats was treated identically, except permeability was assessed on day 3 and on day 5 using contrast-enhanced magnetic resonance imaging with gadolinium diethylenetriamine penta-acetic acid instilled into the bladder.

RESULTS

Intravesical lubricin reversed bladder permeability induced by PS and prevented the concomitant increase in permeability induced in the bowel (organ crosstalk). The protective effect was confirmed with magnetic resonance imaging, and because individual rats could be followed over time, the impermeability of the bladder restored by rhPRG4 remained for 5 days.

CONCLUSION

These data indicate that instillation of rhPRG4 into a permeable bladder can restore its normally impermeable state, and that the effect lasts for 5 days and also prevents bowel symptoms often comorbid with interstitial cystitis-bladder pain syndrome.