Integrated mRNA-miRNA transcriptome analysis of bladder biopsies from patients with bladder pain syndrome identifies signaling alterations contributing to the disease pathogenesis.

BACKGROUND: Interstitial cystitis, or bladder pain syndrome (IC/BPS), is a chronic bladder disorder characterized by lower abdominal pain associated with the urinary bladder and accompanied by urinary frequency and urgency in the absence of identifiable causes. IC/PBS can be separated into the classic Hunner's ulcerative type and the more prevalent non-ulcerative disease. Our aim was to unravel the biological processes and dysregulated cell signaling pathways leading to the bladder remodeling in non-ulcerative bladder pain syndrome (BPS) by studying the gene expression changes in the patients' biopsies. METHODS: We performed paired microRNA (miRNA) and mRNA expression profiling in the bladder biopsies of BPS patients with non-Hunner interstitial cystitis phenotype, using comprehensive Next-generation sequencing (NGS) and studied the activated pathways and altered biological processes based on the global gene expression changes. Paired mRNA-miRNA transcriptome analysis delineated the regulatory role of the dysregulated miRNAs by identifying their targets in the disease-induced pathways. RESULTS: EIF2 Signaling and Regulation of eIF4 and p70S6K Signaling, activated in response to cellular stress, were among the most significantly regulated processes during BPS. Leukotriene Biosynthesis nociceptive pathway, important in inflammatory diseases and neuropathic pain, was also significantly activated. The biological processes identified using Gene Ontology over-representation analysis were clustered into six main functional groups: cell cycle regulation, chemotaxis of immune cells, muscle development, muscle contraction, remodeling of extracellular matrix and peripheral nervous system organization and development. Compared to the Hunner's ulcerative type IC, activation of the immune pathways was modest in non-ulcerative BPS, limited to neutrophil chemotaxis and IFN-γ-mediated signaling. We identified 62 miRNAs, regulated and abundant in BPS and show that they target the mRNAs implicated in eIF2 signalling pathway. CONCLUSIONS: The bladders of non-ulcerative BPS patients recruited in this study had alterations consistent with a strong cell proliferative response and an up-regulation of smooth muscle contractility, while the contribution of inflammatory processes was modest. Pathway analysis of the integrated mRNA-miRNA NGS dataset pinpointed important regulatory miRNAs whose dysregulation might contribute to the pathogenesis. Observed molecular changes in the peripheral nervous system organization and development indicate the potential role of local bladder innervation in the pain perceived in this type of BPS.

[BLADDER PAIN SYNDROME - DOES DETRUSOR MASTOCYTOSIS PREDICT SYMPTOMATIC IMPROVEMENT FOLLOWING BLADDER HYDRODISTENTION UNDER ANESTHESIA?]

INTRODUCTION: Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic, debilitating syndrome involving bladder pain and lower urinary tract symptoms (LUTS), with a substantial effect on patients' quality of life. IC/BPS poses a diagnostic challenge, and its available treatment options remain only moderately effective. Bladder-wall biopsies from IC/BPS patients commonly uncover mastocytosis. While mast-cells are suspected as pivotal in disease pathogenesis, the clinical significance of their presence remains unclear. Clinical guidelines differ on whether or not bladder biopsies should be a part of routine IC/BPS workup. AIMS: To determine whether detrusor mastocytosis can serve as a prognostic marker for treatment response and improvement duration. METHODS: We retrospectively collected patient data for IC/BPS patients who underwent bladder hydrodistension under anesthesia. We used statistical modelling to determine the effect of mastocystosis and other possible predictive factors - age, comorbidity, Hunner lesions - on the presence and duration of symptom improvement. RESULTS: A total of 35 patients (89% female, median age 63.5 [IQR 48.8-73.6] years) underwent hydrodistension, of whom 28 (89% female, median age 63.0 [44.8-73.1] years) had bladder biopsies; 11 (39%) of them had mastocystosis. Within a median follow-up of 8.8 [1.7-24.2] months, 11 (100%) of the patients with mastocytosis and 9 (53%) of the patients without it, experienced symptomatic improvement (p=0.007). Improvement duration was 8 months longer (p=0.006) in those with mastocystosis. Univariate logistic regression models were used to estimate odds ratios (OR). Mastocytosis (p=0.004) and Charlson Comorbidity score were the only variables with a statistically significant OR. Univariate survival models were fitted, and improvement duration was estimated to be longer in patients with mastocystosis (p=0.01). A multivariate Cox regression model found no variable to be statistically significant, though mastocystosis was borderline significant (p=0.055). CONCLUSIONS: Mastocystosis defines a discernible phenotype of IC/BPS, which exhibits higher rates and longer duration of hydrodistention treatment response. DISCUSSION: Notwithstanding limitations of sample size and retrospective study design, we were able to demonstrate that mastocystosis can serve as a prognostic factor for symptom improvement after hydrodistension in IC/BPS patients. Prospective studies are required to validate this finding and to investigate the mechanisms involved.

High-Density Surface Electromyography Assessment of Pelvic Floor Dysfunction in Women with Interstitial Cystitis/Bladder Pain Syndrome.

PURPOSE: Up to 85% of women with interstitial cystitis/bladder pain syndrome have pelvic floor dysfunction and hypertonicity. Current evaluation methodologies lack objective measures of pelvic floor muscle activity. We examined the ability of using intravaginal high-density surface electromyography to quantitatively, objectively and noninvasively map pelvic floor muscle activity and innervation zone locations in patients with interstitial cystitis/bladder pain syndrome. MATERIALS AND METHODS: Fifteen women with interstitial cystitis/bladder pain syndrome and 15 controls underwent 2 sessions of digital pelvic examinations and high-density surface electromyography assessments. The root mean squared amplitude of high-density surface electromyography was first calculated, and the resting root mean squared ratio was then calculated by normalizing the resting electromyography root mean squared to the peak electromyography amplitude reached during maximum voluntary contraction. Innervation zone distributions were obtained from decomposed high-density surface electromyography signals. The correlation between the root mean squared ratio and interstitial cystitis/bladder pain syndrome symptom scores and pelvic floor muscle alignment were investigated in patients with interstitial cystitis/bladder pain syndrome and healthy controls. RESULTS: Women with interstitial cystitis/bladder pain syndrome demonstrated significantly increased resting root mean squared ratios compared to controls (0.155±0.048 vs 0.099±0.041, p=0.0019). Significant correlations were found between resting root mean squared ratio and patient reported pain (rs=0.523, p=0.003), interstitial cystitis symptom (rs=0.521, p=0.003) and problem indices (rs=0.60, p <0.001). In addition, women with interstitial cystitis/bladder pain syndrome were more likely to have shortened pelvic floor muscles (80%, 12 vs 13.3%, 2, p <0.01). Women with shortened pelvic floor muscles demonstrated significantly higher resting root mean squared ratio compared to those with normal pelvic floor muscle length (0.155±0.046 vs 0.107±0.040, p=0.0058). CONCLUSIONS: Intravaginal high-density surface electromyography offers an objective and quantitative strategy to noninvasively assess pelvic floor muscle dysfunction in women with interstitial cystitis/bladder pain syndrome. Abundant spatiotemporal muscle activity information captured by high-density surface electromyography allows for mapping innervation zone distributions for major pelvic floor muscles.

Microbiota: a novel regulator of pain.

Among the various regulators of the nervous system, the gut microbiota has been recently described to have the potential to modulate neuronal cells activation. While bacteria-derived products can induce aversive responses and influence pain perception, recent work suggests that "abnormal" microbiota is associated with neurological diseases such as Alzheimer's, Parkinson's disease or autism spectrum disorder (ASD). Here we review how the gut microbiota modulates afferent sensory neurons function and pain, highlighting the role of the microbiota/gut/brain axis in the control of behaviors and neurological diseases. We outline the changes in gut microbiota, known as dysbiosis, and their influence on painful gastrointestinal disorders. Furthermore, both direct host/microbiota interaction that implicates activation of "pain-sensing" neurons by metabolites, or indirect communication via immune activation is discussed. Finally, treatment options targeting the gut microbiota, including pre- or probiotics, will be proposed. Further studies on microbiota/nervous system interaction should lead to the identification of novel microbial ligands and host receptor-targeted drugs, which could ultimately improve chronic pain management and well-being.

HMGB1 and its membrane receptors as therapeutic targets in an intravesical substance P-induced bladder pain syndrome mouse model.

HMGB1, a nuclear protein, once released to the extracellular space, promotes somatic and visceral pain signals. We thus analyzed the role of HMGB1 in an intravesical substance P-induced bladder pain syndrome (BPS) mouse model. Intravesical administration of substance P caused referred hyperalgesia/allodynia in the lower abdomen and hindpaw without producing severe urothelial damage, which was prevented by an anti-HMGB1-neutralizing antibody, thrombomodulin α capable of inactivating HMGB1 and antagonists of RAGE or CXCR4. The HMGB1 inactivation or RAGE blockade also reversed the established bladder pain symptoms. HMGB1 and RAGE are thus considered to serve as therapeutic targets for BPS.

Does weather trigger urologic chronic pelvic pain syndrome flares? A case-crossover analysis in the multidisciplinary approach to the study of the chronic pelvic pain research network.

BACKGROUND: To investigate whether meteorological factors (temperature, barometric pressure, relative humidity, ultraviolet index [UVI], and seasons) trigger flares in male and female urologic chronic pelvic pain patients. METHODS: We assessed flare status every 2 weeks in our case-crossover study of flare triggers in the Multidisciplinary Approach to the Study of Chronic Pelvic Pain 1-year longitudinal study. Flare symptoms, flare start date, and exposures in the 3 days preceding a flare or the date of questionnaire completion were assessed for the first three flares and at three randomly selected nonflare times. We linked these data to daily temperature, barometric pressure, relative humidity, and UVI values by participants' first 3 zip code digits. Values in the 3 days before and the day of a flare, as well as changes in these values, were compared to nonflare values by conditional logistic regression. Differences in flare rates by astronomical and growing seasons were investigated by Poisson regression in the full study population. RESULTS: A total of 574 flare and 792 nonflare assessments (290 participants) were included in the case-crossover analysis, and 966 flare and 5389 nonflare (409 participants) were included in the full study analysis. Overall, no statistically significant associations were observed for daily weather, no patterns of associations were observed for weather changes, and no differences in flare rates were observed by season. CONCLUSIONS: We found minimal evidence to suggest that weather triggers flares, although we cannot rule out the possibility that a small subset of patients is susceptible.

Interstitial cystitis/bladder pain syndrome: The evolving landscape, animal models and future perspectives.

Interstitial cystitis/bladder pain syndrome is a debilitating condition of unknown etiology characterized by persistent pelvic pain with lower urinary tract symptoms and comprises a wide variety of potentially clinically useful phenotypes with different possible etiologies. Current clinicopathological and genomic evidence suggests that interstitial cystitis/bladder pain syndrome should be categorized by the presence or absence of Hunner lesions, rather than by clinical phenotyping based on symptomatology. The Hunner lesion subtype is a distinct inflammatory disease with proven bladder etiology characterized by epithelial denudation and enhanced immune responses frequently accompanied by clonal expansion of infiltrating B cells, with potential engagement of infection. Meanwhile, the non-Hunner lesion subtype is a non-inflammatory disorder with little evidence of bladder etiology. It is potentially associated with urothelial malfunction and neurophysiological dysfunction, and frequently presents with somatic and/or psychological symptoms, that commonly result in central nervous sensitization. Animal models of autoimmune cystitis and neurogenic sensitization might serve as disease models for the Hunner lesion and non-Hunner lesion subtypes, respectively. Here, we revisit the taxonomy of interstitial cystitis/bladder pain syndrome according to current research, and discuss its potential pathophysiology and representative animal models. Categorization of interstitial cystitis/bladder pain syndrome based on cystoscopy is mandatory to design optimized treatment and research strategies for each subtype. A tailored approach that specifically targets the characteristic inflammation and epithelial denudation for the Hunner lesion subtype, or the urothelial malfunction, sensitized/altered nervous system and psychosocial problems for the non-Hunner lesion subtype, is essential for better clinical management and research progress in this complex condition.

[A new approach to understanding the pathogenesis and treatment of infectious and inflammatory diseases of the urogenital tract].

The current trends in understanding the pathogenesis of infectious and inflammatory urogenital disorders are highlighted in the review. The etiological and pathogenetic significance of increased intestinal permeability for pathogens in the development of various diseases has been convincedly proved. There is no doubt about the pathogenetic role of increased permeability of the bladder mucosa, which can result in interstitial cystitis (IC). The association of intestinal diseases with IC has been established. In rats, the induction of intestinal inflammation may cause increased permeability of the bladder mucosa. In the postoperative period, bacteria are translocated from the gastrointestinal tract to the urinary tract, which is associated with stress. Particular attention is paid to the therapy based on new knowledge about the pathogenesis of infectious and inflammatory diseases of the urogenital tract. Possibilities of decreasing intestinal and bladder permeability using rebamipide are described. Various therapeutic mechanisms of action made it possible to use this drug in endoscopy, ophthalmology, chemotherapy and rheumatology. The antioxidant and anti-inflammatory properties of rebamipide has been shown in-vitro. Intravesical instillation of rebamipide accelerates the recovery of damaged urothelium and its barrier function, and also influences on bladder hyperactivity. Thus, the first results of using rebamipide in urology are encouraging; however, further researches are required.

Is bladder blood flow an etiologic factor for the bladder pain syndrome?

AIM: Bladder pain syndrome (BPS) is a complex disease which causes cognitive, behavioral, sexual, and emotional problems. Vascular factors related to bladder blood supply may be one of the etiologic cause of BPS. This study aims to investigate the bladder blood flow and internal iliac artery resistive indices of patients with BPS. METHODS: A total of 30 female patients with the diagnosis of BPS and 30 female as control group were enrolled in the study. Bilateral internal iliac arterial blood flow distal to uterine arteries were examined as the primary source of vesical arterial blood supply. Peak systolic velocities, end diastolic velocities, resistive indices, and flow volumes of internal iliac arteries were measured by color Doppler ultrasonography in a single-blind fashion. RESULTS: The blood flows volume of the right and left internal iliac arteries during empty and full bladder were significantly lower at BPS group compared with control (P < 0.05). Although the difference was not significant, the mean resistive index of right and left internal iliac arteries were lower at the control group ( P > 0.05). Aging decreased the bladder blood volume and both BPS and control group internal iliac artery blood volume decreased by aging. The decrease was more significant at the control group, but the internal iliac artery blood volume was still lower at patients with BPS compared with the control group. CONCLUSION: Arterial blood flow of bladder was lower at patients with BPS compared with the control group. The decrease in the vascular supply of bladder might be one of the related factors for the BPS etiology.

Small fiber polyneuropathy as a potential therapeutic target in interstitial cystitis/bladder pain syndrome.

INTRODUCTION AND HYPOTHESIS: Interstitial cystitis/bladder pain syndrome (IC/BPS) and fibromyalgia (FM) are frequently co-occurring medical diagnoses in patients referred to the urology clinic for secondary and tertiary treatment options. METHODS: Abundant literature has shown that many patients with FM have small fiber polyneuropathy (SFPN) that can be confirmed via skin punch biopsy and immunological staining to measure nerve density. RESULTS AND CONCLUSIONS: This finding of SFPN provides a therapeutic target for FM and in this article we hypothesize and provide rationale for the idea that this same phenomenon (SFPN) might explain, in some IC/BPS patients, the finding of widespread pain and likewise provide a therapeutic target for these patients.

Variations in bladder pain syndrome/interstitial cystitis (IC) definitions, pathogenesis, diagnostics and treatment: a systematic review and evaluation of national and international guidelines.

INTRODUCTION AND HYPOTHESIS: Interstitial cystitis (IC) and bladder pain syndrome (BPS) are challenging and encompassing hypersensitivity disorders of the lower urinary tract. A variety of national and international guidelines have been published including guidance on nomenclature, definitions, etiopathology, diagnostics and treatment. A lack of universally established clinical guidance is apparent. The aim of this review is to evaluate key guidelines on this area of practice, identify variations, compare their recommendations and grade them using AGREE II. METHODS: Literature searches were performed using the PUBMED and CINAHL database from January 1, 1983, to December 1, 2018, referring to the search strategy of AUA. Ten national and international guidelines were included into the analysis. We assessed the guidelines with the updated AGREE II. RESULTS: Symptoms congruent in all guidelines are: pain, pressure, discomfort and frequency, urgency and nocturia. Urinalysis is a prerequisite for diagnostics, cystoscopy for most and urodynamics not part of the routine assessment. Treatment options are recommended stepwise. The highest level of evidence and consensus was identified for oral therapies. Nine guidelines had an overall quality score ≥ 50% and three scored ≥ 70% (AUA, GG, RCOG). CONCLUSIONS: The guidelines are congruent in symptom reporting, quite congruent in diagnostics and vary to a high degree on treatment recommendations. The complexity of BPS and emerging evidence indicate the need for regular updating of the guidelines and a wider consensus.

Endometriosis increased the risk of bladder pain syndrome/interstitial cystitis: A population-based study.

OBJECTIVE: Previous studies have suggested an association between bladder pain syndrome/interstitial cystitis (BPS/IC) and endometriosis. However, no nation-wide population study has yet reported an association between them. In this study, we examined the risk of BPS/IC among subjects with endometriosis during a 3-year follow-up in Taiwan using a population-based dataset. STUDY DESIGN: This study comprised 9191 subjects with endometriosis, and 27 573 subjects randomly selected as controls. We individually followed-up each subject (n = 36 764) for a 3-year period to identify subjects subsequently diagnosed with BPS/IC. A Cox proportional hazards regression model was employed to estimate the risk of subsequent BPS/IC following a diagnosis of endometriosis. RESULTS: Incidences of BPS/IC during the 3-year follow-up period was 0.2% and 0.05% for subjects with and without endometriosis, respectively. The hazard ratio for developing BPS/IC over a 3-year period for subjects with endometriosis compared to subjects without endometriosis was 4.43 (95% CI: 2.13-9.23). After adjusting for co-morbidities like diabetes, hypertension, coronary heart disease, obesity, hyperlipidemia, chronic pelvic pain, irritable bowel syndrome, fibromyalgia, chronic fatigue syndrome, depression, panic disorder, migraines, sicca syndrome, allergies, endometriosis, asthma, tobacco use, and alcohol abuse, the Cox proportional hazards regressions revealed that the hazard ratio for BPS/IC among subjects with endometriosis was 3.74 (95% CI = 1.76-7.94, P < 0.001) compared to that in controls. CONCLUSIONS: This study provides epidemiological evidence of an association between endometriosis and a subsequent diagnosis of BPS/IC.

Interstitial Cystitis: An uncommon revelation in primitive Sjögren syndrome.

Interstitial cystitis is an exceptional entity during primary Sjögren's syndrome. In this regard, we report the case of a 67-year-old patient in whom initially idiopathic interstitial cystitis revealed primary Sjögren's syndrome after 5 years of evolution in front of xerostomiaa, xerophtalmia and bilateral parotid hypertrophy with histological confirmation at the biopsy of accessory salivary glands.

Sjogren's syndrome: Clinical aspects.

Sjogren's syndrome (SS) is the 2nd most common chronic autoimmune rheumatic disease and associated with a high burden of illness. Morbidity arises not only from untreated xerostomia and keratoconjunctivitis sicca but also from extra-glandular manifestations including the development of non-Hodgkin's B cell lymphomas. Proper diagnosis of SS requires objective evidence of dry eyes and/or objective evidence of dry mouth as well as proof of autoimmunity. The recent development of new international classification criteria and clinical practice guidelines for SS should not only enhance the existing standards of care but also facilitate further studies to improve future diagnosis and outcomes.

Etiology, pathophysiology and biomarkers of interstitial cystitis/painful bladder syndrome.

PURPOSE: Interstitial cystitis/painful bladder syndrome (IC/PBS) is a chronic pain syndrome and a chronic inflammatory condition prevalent in women that leads to urgency, sleep disruption, nocturia and pain in the pelvic area, to the detriment of the sufferer's quality of life. The aim of this review is to highlight the newest diagnostic strategies and potential therapeutic techniques. METHODS: A comprehensive literature review was performed on MEDLINE, PubMed, and Cochrane databases gathering all literature about "Interstitial cystitis" and "Painful Bladder Syndrome". Visual analogue scales, epidemiological strategies, pain questionnaires and similar techniques were not included in this literature survey. RESULTS: The etiology, exact diagnosis and epidemiology of IC/PBS are still not clearly understood. To date, its prevalence is estimated to be in the range of 45 per 100,000 women and 8 per 100,000 men, whereas joint prevalence in both sexes is 10.6 cases per 100,000. There are no "gold standards" in the diagnosis or detection of IC/PBS, therefore, several etiological theories were investigated, such as permeability, glycosaminoglycans, mast cell, infection and neuroendocrine theory to find new diagnostic strategies and potential biomarkers. CONCLUSION: Due to the fact that this disease is of an intricate nature, and that many of its symptoms overlap with other concomitant diseases, it could be suggested to classify the patients with emphasis on the phenotype, as well as their symptom clusters, to tailor the diagnostic and management choices according to the observed biomarkers.

Intravesical liposome therapy for interstitial cystitis.

Over the past two decades, there has been lot of interest in the use of liposomes as lipid-based biocompatible carriers for drugs administered by the intravesical route. The lipidic bilayer structure of liposomes facilitates their adherence to the apical membrane surface of luminal cells in the bladder, and their vesicular shape allows them to co-opt the endocytosis machinery for bladder uptake after instillation. Liposomes have been shown to enhance the penetration of both water-soluble and insoluble drugs, toxins, and oligonucleotides across the bladder epithelium. Empty liposomes composed entirely of the endogenous phospholipid, sphingomyelin, could counter mucosal inflammation and promote wound healing in patients suffering from interstitial cystitis. Recent clinical studies have tested multilamellar liposomes composed entirely of sphingomyelin as a novel intravesical therapy for interstitial cystitis. In addition, liposomes have been used as a delivery platform for the instillation of botulinum toxin in overactive bladder patients. The present review discusses the properties of liposomes that are important for their intrinsic therapeutic effect, summarizes the recently completed clinical studies with intravesical liposomes and covers the latest developments in this field.

Liposome Based Intravesical Therapy Targeting Nerve Growth Factor Ameliorates Bladder Hypersensitivity in Rats with Experimental Colitis.

PURPOSE: Pelvic organ cross sensitization is considered to contribute to overlapping symptoms in chronic pelvic pain syndrome. Nerve growth factor over expression in the bladder is reportedly involved in the symptom development of bladder pain syndrome/interstitial cystitis. We examined whether a reduction of over expressed nerve growth factor in the bladder by intravesical treatment with liposome and oligonucleotide conjugates would ameliorate bladder hypersensitivity in a rat colitis model. MATERIALS AND METHODS: Adult female rats were divided into 1) a control group, 2) a colitis-oligonucleotide group with intracolonic TNBS (2,4,6-trinitrobenzene sulfonic acid) enema and intravesical liposome-oligonucleotide treatments, 2) a colitis-saline group with intracolonic TNBS and intravesical saline treatments, 4) a sham oligonucleotide group with intravesical liposome-oligonucleotide treatment without colitis and 5) a sham-saline group with intravesical saline treatment without colitis. Liposomes conjugated with nerve growth factor antisense oligonucleotide or saline solution were instilled in the bladder and 24 hours later colitis was induced by TNBS enema. Effects of nerve growth factor antisense treatment were evaluated by pain behavior, cystometry, molecular analyses and immunohistochemistry 10 days after TNBS treatment. RESULTS: In colitis-oligonucleotide rats nerve growth factor antisense treatment ameliorated pain behavior and decreased a reduction in the intercontraction interval in response to acetic acid stimulation as well as nerve growth factor expression in the bladder mucosa. All were enhanced in colitis-saline rats compared to sham rats. CONCLUSIONS: Nerve growth factor over expression in the bladder mucosa and bladder hypersensitivity induced after colitis were decreased by intravesical application of liposome-oligonucleotide targeting nerve growth factor. This suggests that local antinerve growth factor therapy could be effective treatment of bladder symptoms in chronic pelvic pain syndrome.

Underlying Mechanisms and Optimal Treatment for Interstitial Cystitis: A Brief Overview.

The intention of this article is to present a brief overview of the etiology, diagnosis, and treatment modalities of interstitial cystitis for primary care clinicians. While very succinct, it encapsulates the condition with clear and precise definition.

Role of urinary cations in the aetiology of bladder symptoms and interstitial cystitis.

OBJECTIVES: To identify and characterise urinary cationic metabolites, defined as toxic factors, in patients with interstitial cystitis (IC) and in control subjects. To evaluate the cytotoxicity of the urinary cationic metabolite fraction of patients with IC vs control subjects and of individual metabolites in cultured urothelial cells. SUBJECTS AND METHODS: Cationic fractions (CFs) were isolated from the urine specimens of 62 patients with IC and 33 control subjects by solid-phase extraction. CF metabolites were profiled using C18 reverse-phase high performance liquid chromatography (RP-HPLC) with UV detection, quantified by area-under-the-peaks using known standards, and normalized to creatinine. RP-HPLC and liquid chromatography (LC)-mass spectrometry (MS)/tandem MS (MS/MS) were used to identify major CF peaks. HTB-4 urothelial cells were used to determine the cytotoxicity of CFs and of individual metabolites with and without Tamm-Horsfall protein (THP). RESULTS: RP-HPLC analysis showed that metabolite quantity was twofold higher in patients with IC compared with control subjects. The mean (SEM) for control subjects vs patients was 3.1 (0.2) vs 6.3 (0.5) mAU*min/µg creatinine (P < 0.001). LC-MS identified 20 metabolites. Patients with IC had higher levels of modified nucleosides, amino acids and tryptophan derivatives compared with control subjects. The CF cytotoxicity was higher for patients with IC compared with control subjects. The mean (SEM) for control subjects vs patients was -2.3 (2.0)% vs 36.7 (2.7)% (P < 0.001). A total of 17 individual metabolites were tested for their cytotoxicity. Cytotoxicity data for major metabolites were all significant (P < 0.001): 1-methyladenosine (51%), 5-methylcytidine (36%), 1-methyl guanine (31%), N(4)-acetylcytidine (24%), N(7)-methylguanosine (20%) and L-Tryptophan (16%). These metabolites were responsible for higher toxicity in patients with IC. The toxicity of all metabolites was significantly lower in the presence of control THP (P < 0.001). CONCLUSIONS: Major urinary cationic metabolites were characterised and found to be present in higher amounts in patients with IC compared with control subjects. The cytotoxicity of cationic metabolites in patients with IC was significantly higher than in control subjects, and control THP effectively lowered the cytotoxicity of these metabolites. These data provide new insights into toxic factor composition as well as a framework in which to develop new therapeutic strategies to sequester their harmful activity, which may help relieve the bladder symptoms associated with IC.