A reliable, nondestructive animal model for interstitial cystitis: intravesical low-dose protamine sulfate combined with physiological concentrations of potassium chloride

Preclinical models of endometriosis and interstitial cystitis/bladder pain syndrome: an Innovative Medicines Initiative-PainCare initiative to improve their value for translational research in pelvic pain

ABSTRACT

Endometriosis (ENDO) and interstitial cystitis/bladder pain syndrome (IC/BPS) are chronic pain conditions for which better treatments are urgently needed. Development of new therapies with proven clinical benefit has been slow. We have conducted a review of existing preclinical in vivo models for ENDO and IC/BPS in rodents, discussed to what extent they replicate the phenotype and pain experience of patients, as well as their relevance for translational research. In 1009 publications detailing ENDO models, 41% used autologous, 26% syngeneic, 18% xenograft, and 11% allogeneic tissue in transplantation models. Intraperitoneal injection of endometrial tissue was the subcategory with the highest construct validity score for translational research. From 1055 IC/BPS publications, most interventions were bladder centric (85%), followed by complex mechanisms (8%) and stress-induced models (7%). Within these categories, the most frequently used models were instillation of irritants (92%), autoimmune (43%), and water avoidance stress (39%), respectively. Notably, although pelvic pain is a hallmark of both conditions and a key endpoint for development of novel therapies, only a small proportion of the studies (models of ENDO: 0.5%-12% and models of IC/BPS: 20%-44%) examined endpoints associated with pain. Moreover, only 2% and 3% of publications using models of ENDO and IC/BPS investigated nonevoked pain endpoints. This analysis highlights the wide variety of models used, limiting reproducibility and translation of results. We recommend refining models so that they better reflect clinical reality, sharing protocols, and using standardized endpoints to improve reproducibility. We are addressing this in our project Innovative Medicines Initiative-PainCare/Translational Research in Pelvic Pain.

Comparison of 5 Different Rat Models to Establish a Standard Animal Model for Research Into Interstitial Cystitis

Purpose

We evaluated 5 different rat models using different agents in order to establish a standard animal model for interstitial cystitis (IC) in terms of the functional and pathologic characteristics of the bladder.

Methods

Five IC models were generated in 8-week-old female Sprague-Dawley rats via transurethral instillation of 0.1M hydrogen chloride (HCl) or 3% acetic acid (AA), intraperitoneal injection of cyclophosphamide (CYP) or lipopolysaccharide (LPS), or subcutaneous injection of uroplakin II (UPK2). After generating the IC models, conscious cystometry was performed on days 3, 7, and 14. All rats were euthanized on day 14 and their bladders were obtained for histological and pro-inflammatory-related gene expression analysis.

Results

In the cystometric analysis, all experimental groups showed significantly decreased intercontraction intervals compared with the control group on day 3, but only the LPS and UPK groups maintained significantly shorter intercontraction intervals than the control group on day 14. The histological analysis revealed that areas with severe urothelial erosion (HCl, AA, and UPK) and hyperplasia (CYP and LPS), particularly in the UPK-treated bladders, showed a markedly increased infiltration of toluidine blue-stained mast cells and increased tissue fibrosis. In addition, significantly elevated expression of interleukin-1b, interleukin-6, myeloperoxidase, monocyte chemotactic protein 1, and Toll-like receptors 2 and 4 was observed in the UPK group compared to the other groups.

Conclusions

Among the 5 different agents, the injection of UPK generated the most effective IC animal model, showing consequent urothelial barrier loss, inflammatory reaction, tissue fibrosis stimulation, and persistent hyperactive bladder.

The water avoidance stress induces bladder pain due to a prolonged alpha1A adrenoceptor stimulation

Bladder Pain Syndrome/Interstitial Cystitis (BPS/IC) remains an elusive disease with the cause for the pain unclear. BPS/IC patients present increased sympathetic activity and high levels of urinary noradrenaline. At the experimental level, it has been shown that chronic adrenergic stimulation produces pain and bladder changes through an alpha 1A adrenoceptor mediated mechanism. Water avoidance stress (WAS) in rodents reproduces signs of nociception and bladder changes seen in BPS/IC patients. In this study, we explore the possible role of alpha 1A adrenoceptor in bladder pain and morphological changes. WAS was induced in a group of female Wistar rats. A separate WAS group received 0.2 mg/kg day silodosin (WAS + S). Lower abdominal pain was determined by performing sensitivity to Von Frey filaments. Bladder reflex activity was determined by cystometry in anaesthetised animals. Urine was collected for noradrenaline quantification by HPLC. Bladders were harvested and stained with Haematoxylin-eosin (to analyse urothelial morphology and to determine the disruption of surface umbrella cells) or with Toluidine Blue 0.1% to analyse mast cell infiltration. WAS increased urinary noradrenaline level and bladder frequency and decreased mechanical pain threshold, which was reversed by silodosin. WAS induced lymphocytic and mast cells infiltration in the mucosa and mild urothelial disruption, which was absent in WAS + S group. Alpha 1A adrenoceptor stimulation has an important role in the appearance of bladder pain in rats. Since BPS/IC patients present high levels of noradrenaline, alpha 1A stimulation may be an additional trigger for bladder dysfunction presented by these patients. Further studies will determine the clinical relevance of this finding in the treatment of BPS/IC patients.

Angiogenic factors, bladder neuroplasticity and interstitial cystitis-new pathobiological insights

Vascular endothelial growth factor (VEGF) is essential for normal embryonic development, and maintenance of adult vascular function. Originally described as a vascular permeability factor, VEGF alters tight cell junctions and contributes to maintenance of bladder permeability. VEGF and its receptors are not only expressed in bladder blood vessels but also in apical cells and intramural ganglia. VEGF receptors are fundamentally altered by inflammation and bladder diseases such as interstitial cystitis (IC). Experimental results indicate that VEGF exerts direct effects on bladder nerve density and function. Regardless of the etiology or initiating cause for IC, it is hypothesized that the urinary bladder responds to injury by increasing the production of VEGF that acts initially as a survival mechanism. However, VEGF also has the capacity to increase vascular permeability leading to glomerulations, edema, and inflammation. Moreover, due to elevated numbers of VEGF receptors in the urothelium, the increased levels of VEGF further increase bladder permeability and establish a vicioCus cycle of disease pathophysiology.

A mouse model for interstitial cystitis/painful bladder syndrome based on APF inhibition of bladder epithelial repair: a pilot study

BACKGROUND

Interstitial cystitis/painful bladder syndrome (IC/PBS) is a chronic bladder disorder with bladder epithelial thinning or ulceration, pain, urinary frequency and urgency. There is no reliably effective therapy for IC/PBS, and no generally accepted animal model for the disorder in which potential therapies can be tested. Bladder epithelial cells from IC/PBS patients make a small glycopeptide antiproliferative factor or "APF" that inhibits proliferation, decreases tight junction protein expression, increases paracellular permeability, and induces changes in gene expression of bladder epithelial cells in vitro that mimic abnormalities in IC/PBS patient biopsy specimens in vivo. We therefore determined the ability of a synthetic APF derivative to inhibit bladder epithelial repair in mice.

METHODS

The bladder epithelium of female CBA/J mice was stripped by transurethral infusion of 3% acetic acid, and mice were subsequently treated daily with one of three intravesical treatments [synthetic as-APF, inactive unglycosylated control peptide, or phosphate buffered saline carrier (PBS)] for 1-21 days. Fixed bladder sections were either stained with haematoxylin and eosin for determination of epithelial area by image analysis, or incubated with anti-uroplakin III (UPIII) or anti-zonula occludens type 1 (ZO-1) antibodies for immunofluorescence microscopy. Epithelial measurement data were analyzed by a two-way analysis of variance (ANOVA); post hoc comparisons of multiple groups were carried out using the Tukey-Kramer method.

RESULTS

Bladder epithelial repair was significantly attenuated in as-APF-treated mice as compared to control mice on days 3-21 (p < 0.05); the mean epithelial/total area over all measured days was also significantly lower in as-APF-treated mice vs. mice in either control group by post hoc analysis (p < 0.0001 for both comparisons). UPIII and ZO-1 expression was also decreased in as-APF-treated mice as compared to mice in either control group by day 7 (UPIII) or day 14 (ZO-1).

CONCLUSIONS

This model demonstrates in vivo effects of as-APF which abrogates bladder epithelial repair and expression of UPIII and ZO-1 in CBA/J mice following transurethral acetic acid infusion. As bladder epithelial thinning, decreased UPIII expression, and decreased ZO-1 expression are histopathologic features of IC/PBS patient biopsies, this model may be useful for studying the pathophysiology of IC/PBS and the effect of potential therapies.

[A new experimental model for inducing interstitial cystitis by oxidative stress using bladder instillation of a nitric oxide donor gel]

PURPOSE

The aim of this study is to develop a new experimental model of inducing interstitial cystitis (IC) through vesical instillation of a polymeric solution containing the NO donor S-nitrousglutathione (GSNO) and to compare it to the experimental interstitial cystitis induced by vesical instillation of protamine and potassium chloride.

MATERIAL AND METHOD

For that purpose 40 female Wistar rats were used, divided in four groups: 1. saline solution + GSNO; 2. saline solution + polymeric solution (without GNSO); 3. protamine sulphate + KCl; 4. protamine sulphate + GSNO. The rats received one application (5 animals) or 3 applications (5 animals) of the corresponding substance through intravesical instillation, and after 6 days (5 animals) or 9 days (5 animals) they were euthanized and their bladders were removed for macroscopic evaluation and histological study.

RESULTS

In the macroscopic evaluation we observed edema and hyperemia of the mucosa in 2 (22%) of the animals in group 1, in 0 (0%) of the animals in group 2, in 10 (100%) of the animals in group 3, and in 5 (50%) of the animals in group 4. In the protamine + KCl group and in saline + GSNO similar effects were observed on the bladder wall. The animals in group 2 (saline + polymeric) showed vascular congestion, significantly smaller than the rest after 9 days instillations (p=0.0035). Significant increased fibrosis was observed after instillations in groups 3 and 4, after 6 days (p=0.3781) and 9 days (p=0.0459) respectively, when compared to control (group 2). All groups presented neutrophilic infiltrate of variable intensity 6 days after instillations (p=0.7277). After 9 days, there was a regression of the infiltrate, with no evidence of accentuated neutrophilic reaction in all the groups (p=0.2301).

CONCLUSION

The inflammatory response to bladder instillation of an aqueous solution of S-nitrousglutathione was very similar to that induced by bladder instillation of protamine and KCl. Instillation of an aqueous solution of GSNO can be considered a new model for experimental induction of interstitial cystitis.

A new experimental model for inducing interstitial cystitis by oxidative stress using intravesical instillation of a nitric oxide donor gel

OBJECTIVE

The aim of this study was to develop an experimental model of inducing interstitial cystitis through intravesical instillation of a polymeric solution containing the NO donor S-nitrousglutathione (GSNO) and to compare it to the experimental interstitial cystitis induced by vesical instillation of protamine and potassium chloride.

METHODS

A total of 40 female Wistar rats were used and divided into four groups: 1 - ten rats treated with saline solution + GSNO; 2 - ten rats treated with saline solution + polymeric solution (without GNSO); 3 - ten rats treated with protamine sulphate + KCl; 4 - ten rats treated with protamine sulphate + GSNO. The rats received one application (five animals in each group) or three applications (five animals in each group) of the corresponding substance through intravesical instillation, and after six days (five animals in each group) or nine days (five animals in each group) they were euthanized and their bladders were removed for macroscopic evaluation and histological study.

RESULTS

In the macroscopic evaluation edema and hyperemia of the mucosa were observed in 2 (22%) animals in Group 1, in no (0%) animal in Group 2, in 10 (100%) animals in Group 3, and in 5 (50%) animals in Group 4. In the protamine + KCl group and in saline + GSNO, similar effects were observed in the bladder wall. The animals in Group 2 (saline + polymeric solution) showed significantly less vascular congestion compared to the other groups after 9 days of the instillation (p = 0.0035). Significant fibrosis was observed in Groups 3 and 4, 6 days (p = 0.3781) and 9 days (p = 0.0459) after instillations, when compared to controls (Group 2). All groups presented neutrophilic infiltrate of variable intensity, 6 days after instillations (p = 0.7277). After 9 days, there was a regression of the infiltrate, with no evidence of accentuated neutrophilic reaction in all the groups (p = 0.2301).

CONCLUSIONS

The inflammatory response to bladder instillation with an aqueous solution of S-nitrousglutathione was very similar to that induced by bladder instillation of protamine and KCl. Instillation of an aqueous solution of S-nitrousglutathione can be considered a new model for experimental induction of interstitial cystitis.

Urinary glycosaminoglycans excretion and the effect of dimethyl sulfoxide in an experimental model of non-bacterial cystitis

PURPOSE

We reproduced a non-bacterial experimental model to assess bladder inflammation and urinary glycosaminoglycans (GAG) excretion and examined the effect of dimethyl sulfoxide (DMSO).

MATERIALS AND METHODS

Female rats were instilled with either protamine sulfate (PS groups) or sterile saline (control groups). At different days after the procedure, 24 h urine and bladder samples were obtained. Urinary levels of hyaluronic acid (HA) and sulfated glycosaminoglycans (S-GAG) were determined. Also to evaluate the effect of DMSO animals were instilled with either 50% DMSO or saline 6 hours after PS instillation. To evaluate the effect of DMSO in healthy bladders, rats were instilled with 50% DMSO and controls with saline.

RESULTS

In the PS groups, bladder inflammation was observed, with polymorphonuclear cells during the first days and lymphomononuclear in the last days. HA and S-GAG had 2 peaks of urinary excretion, at the 1st and 7th day after PS injection. DMSO significantly reduced bladder inflammation. In contrast, in healthy bladders, DMSO produced mild inflammation and an increase in urinary HA levels after 1 and 7 days and an increase of S-GAG level in 7 days. Animals instilled with PS and treated with DMSO had significantly reduced levels of urinary HA only at the 1st day. Urinary S-GAG/Cr levels were similar in all groups.

CONCLUSIONS

Increased urinary levels of GAG were associated with bladder inflammation in a PS-induced cystitis model. DMSO significantly reduced the inflammatory process after urothelial injury. Conversely, this drug provoked mild inflammation in normal mucosa. DMSO treatment was shown to influence urinary HA excretion.

Nicotinic signaling ameliorates acute bladder inflammation induced by protamine sulfate or cyclophosphamide

PURPOSE

Nicotinic afferent pathways may be involved in the regulation of bladder inflammation. Based on that hypothesis we investigated the role of nicotinic signaling in a comparative analysis of 2 models of experimental bladder inflammation using protamine sulfate and cyclophosphamide.

MATERIALS AND METHODS

Protamine sulfate and cyclophosphamide were used to induce acute bladder inflammation. Nicotinic agonists and antagonists were given concomitant to the bladder inflammatory agents. Changes in bladder inflammation were measured histologically by a pathologist and through the expression of inflammatory genes.

RESULTS

Histologically cyclophosphamide induced more inflammatory changes than protamine sulfate during acute bladder inflammation. Antagonizing nicotinic signaling with mecamylamine induced further inflammatory changes on histology when used with cyclophosphamide but not with protamine sulfate. However, antagonizing nicotinic signaling in combination with protamine sulfate induced greater increases in mRNA expression of the inflammatory cytokine interleukin-6 compared to cyclophosphamide and mecamylamine combination treatments. The activation of nicotinic signaling attenuated acute bladder inflammation by protamine sulfate and cyclophosphamide independently through the down-regulation of increased interleukin-6 expression.

CONCLUSIONS

Acutely cyclophosphamide treatment results in a greater frank bladder inflammation model in mice than protamine sulfate. However, cholinergic signaling can inhibit inflammation by either mechanism of induced bladder injury. Interleukin-6 gene expression is present and it can be regulated by afferent neuronal signaling even in the absence of observed histological changes in acute bladder inflammatory models.

A model of neural cross-talk and irritation in the pelvis: implications for the overlap of chronic pelvic pain disorders

BACKGROUND & AIMS

Irritable bowel syndrome, interstitial cystitis, and other chronic pelvic pain (CPP) disorders often occur concomitantly. Neural cross-talk may play a role in the overlap of CPP disorders via the convergence of pelvic afferents. We investigated the hypothesis that afferent irritation of one pelvic organ may adversely influence and sensitize another via neural interactions.

METHODS

We measured pelvic organ smooth muscle and striated muscle reflexes during micturition and colorectal distention (CRD) in urethane-anesthetized rats. The effects of acute cystitis on distal colonic sensory thresholds to CRD and the effects of acute colonic irritation on micturition parameters were assessed.

RESULTS

External urethral sphincter (EUS) electromyography (EMG) was typical for the rat, with phasic firing during micturition. External anal sphincter EMG also showed phasic firing during micturition in synchrony with EUS activity but, in addition, showed both tonic bursts and phasic firing independent of EUS activity. Before bladder irritation, graded CRDs to 40 cm H2O produced no notable changes in abdominal wall EMG activity. Following acute bladder irritation, dramatic increases in abdominal wall EMG activity in response to CRD were observed at much lower distention pressures, indicating colonic afferent sensitization. Analogously, following acute colonic irritation, bladder contraction frequency increased 66%, suggesting sensitization of lower urinary tract afferents.

CONCLUSIONS

We report compelling evidence of bidirectional cross-sensitization of the colon and lower urinary tract in a novel experimental model. This cross-sensitization may account for the substantial overlap of CPP disorders; however, further studies are needed to fully characterize these pathways.