Toll-like receptor 4 and comorbid pain in Interstitial Cystitis/Bladder Pain Syndrome: a multidisciplinary approach to the study of chronic pelvic pain research network study

Widespread pain phenotypes impact treatment efficacy results in randomized clinical trials for interstitial cystitis/bladder pain syndrome: a Multidisciplinary Approach to the Study of Chronic Pelvic Pain network study

ABSTRACT

Pain clinical trials are notoriously complex and often inefficient in demonstrating efficacy, even for known efficacious treatments. A major issue is the difficulty in the a priori identification of specific phenotypes to include in the study population. Recent work has identified the extent of widespread pain as an important determinant of the likelihood of response to therapy, but it has not been tested in clinical trials for the treatment of interstitial cystitis/bladder pain syndrome (IC/BPS). We explored this hypothesis using data from 3 previously published trials testing treatments for IC/BPS, which suggested modest benefits but did not meet a priori primary outcome statistical significance criteria. Importantly, these studies also collected symptom questionnaire data that allowed us to retrospectively identify participants with and without widespread pain. Analyzing the treatment by the degree of widespread pain revealed a difference in outcome and statistical significance level for each trial. Participants with predominately local pain (ie, limited widespread pain symptoms) responded to therapy targeting local symptoms, whereas those with widespread pain did not. Alternatively, participants with widespread pain beyond their local pelvic pain responded to more centrally acting treatments. Our results suggest that differentiating patients based on widespread vs more localized pain is a key consideration for designing future clinical trials for conditions with variable pain profiles, such as IC/BPS and potentially other pain-based syndromic disorders.

Brain predicted age in chronic pelvic pain: a study by the Multidisciplinary Approach to the Study of Chronic Pelvic Pain Research Network

ABSTRACT

The effect of chronic pain on brain-predicted age is unclear. We performed secondary analyses of a large cross-sectional and 3-year longitudinal data set from the Multidisciplinary Approach to the Study of Chronic Pelvic Pain Research Network to test the hypothesis that chronic pelvic pain accelerates brain aging and brain aging rate. Brain-predicted ages of 492 chronic pelvic pain patients and 72 controls were determined from T1-weighted MRI scans and used to calculate the brain-predicted age gap estimation (brainAGE; brain-predicted - chronological age). Separate regression models determined whether the presence of chronic pelvic pain could explain brainAGE and brain aging rate when accounting for covariates. We performed secondary analyses to understand whether brainAGE was associated with factors that subtype chronic pelvic pain patients (inflammation, widespread pain, and psychological comorbidities). We found a significant association between chronic pelvic pain and brainAGE that differed by sex. Women with chronic pelvic pain had higher brainAGE than female controls, whereas men with chronic pelvic pain exhibited lower brainAGE than male controls on average-however, the effect was not statistically significant in men or women when considered independently. Secondary analyses demonstrated preliminary evidence of an association between inflammatory load and brainAGE. Further studies of brainAGE and inflammatory load are warranted.

Nociplastic pain mechanisms and toll-like receptors as promising targets for its management

ABSTRACT

Nociplastic pain, characterized by abnormal pain processing without an identifiable organic cause, affects a significant portion of the global population. Unfortunately, current pharmacological treatments for this condition often prove ineffective, prompting the need to explore new potential targets for inducing analgesic effects in patients with nociplastic pain. In this context, toll-like receptors (TLRs), known for their role in the immune response to infections, represent promising opportunities for pharmacological intervention because they play a relevant role in both the development and maintenance of pain. Although TLRs have been extensively studied in neuropathic and inflammatory pain, their specific contributions to nociplastic pain remain less clear, demanding further investigation. This review consolidates current evidence on the connection between TLRs and nociplastic pain, with a specific focus on prevalent conditions like fibromyalgia, stress-induced pain, sleep deprivation-related pain, and irritable bowel syndrome. In addition, we explore the association between nociplastic pain and psychiatric comorbidities, proposing that modulating TLRs can potentially alleviate both pain syndromes and related psychiatric disorders. Finally, we discuss the potential sex differences in TLR signaling, considering the higher prevalence of nociplastic pain among women. Altogether, this review aims to shed light on nociplastic pain, its underlying mechanisms, and its intriguing relationship with TLR signaling pathways, ultimately framing the potential therapeutic role of TLRs in addressing this challenging condition.

Divergent histopathological and molecular patterns in chemically induced interstitial cystitis/bladder pain syndrome rat models

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a complex chronic pain disorder with an elusive etiology and nonspecific symptoms. Although numerous animal models with phenotypes similar to human disease have been established, no available regimen can consistently alleviate clinical symptoms. This dilemma led us to question whether current animal models adequately represent IC/BPS. We compared four commonly used IC/BPS rat models to determine their diverse histopathological and molecular patterns. Female rats were given single treatments with hydrochloric acid (HCL), acetic acid (AA), protamine sulfate plus lipopolysaccharide (PS + LPS), or cyclophosphamide (CYP) to induce IC/BPS. Bladder sections were stained for histopathologic evaluation, and mRNA expression profiles were examined using next-generation sequencing and gene set analyses. Mast cell counts were significantly higher in the HCL and AA groups than in the PS + LPS, CYP, and control groups, but only the AA group showed significant collagen accumulation. The models differed substantially in terms of their gene ontology and Kyoto encyclopedia of genes and genomes pathways. Our observations suggest that none of these rat models fully reflects the complexity of IC/BPS. We recommend that future studies apply and compare multiple models simultaneously to fully replicate the complicated features of IC/BPS.

Deciphering nociplastic pain: clinical features, risk factors and potential mechanisms

Nociplastic pain is a mechanistic term used to describe pain that arises or is sustained by altered nociception, despite the absence of tissue damage. Although nociplastic pain has distinct pathophysiology from nociceptive and neuropathic pain, these pain mechanisms often coincide within individuals, which contributes to the intractability of chronic pain. Key symptoms of nociplastic pain include pain in multiple body regions, fatigue, sleep disturbances, cognitive dysfunction, depression and anxiety. Individuals with nociplastic pain are often diffusely tender - indicative of hyperalgesia and/or allodynia - and are often more sensitive than others to non-painful sensory stimuli such as lights, odours and noises. This Review summarizes the risk factors, clinical presentation and treatment of nociplastic pain, and describes how alterations in brain function and structure, immune processing and peripheral factors might contribute to the nociplastic pain phenotype. This article concludes with a discussion of two proposed subtypes of nociplastic pain that reflect distinct neurobiological features and treatment responsivity.

Evaluation of Central Sensitisation in Bladder Pain Syndrome: A Systematic Review

INTRODUCTION AND HYPOTHESIS

Bladder pain syndrome (BPS) is a debilitating condition characterised by exaggerated bladder sensations and altered bladder function. It is still unknown whether the condition is a peripheral sensory problem or due to abnormal central sensory processing as seen in central sensitisation. This systematic review, which followed a published and Prospective Register of Systematic Reviews-registered protocol (CRD42021229962), is aimed at establishing the scope of central sensitisation in patients with BPS to aid optimal management and treatment.

METHODS

Four databases were searched, and appraisal of the identified studies was conducted by two independent reviewers based on eligibility criteria: patients with BPS being investigated for central sensitisation with or without comparison of controls, English-language articles, full text and publication in a peer-reviewed journal. The Methodological Index for non-Randomised Studies was used to determine study quality. We identified 763 papers in total, with 15 studies included in the final analysis. All studies were observational and had a low risk of bias. Measures included in the evaluation of CS were questionnaires, urodynamics, and quantitative sensory testing methods.

RESULTS

There was evidence of central sensitisation in patients with BPS in all papers evaluated (15 out of 15). In addition, more significant central sensitisation correlated with severe disease presentation (3 out of 3 papers) and concomitant chronic pain conditions (5 out of 5 papers).

CONCLUSIONS

Central sensitisation plays an integral role in BPS patient pathology. Many secondary measures are used to evaluate this condition. Stratification of patients based on their pathology (peripheral, central or a combination of the two) will aid in implementing an individualised management strategy.

Pain mechanisms for the practicing rheumatologist

Pain in rheumatic diseases transcends the traditional nociceptive paradigm, incorporating complex interactions between nociceptive, neuropathic, and nociplastic mechanisms, as well as significant psychosocial factors. Advances in understanding chronic pain highlight the role of peripheral and central sensitization, and the emergence of nociplastic pain-a result of altered central nervous system processing. This modern perspective acknowledges the influence of mood disorders, environmental stressors, and cognitive patterns like catastrophizing, revealing the intricate interplay between biological, psychological, and social determinants of pain. Research emphasizes the brain's pivotal role in pain perception, underscoring the importance of comprehensive approaches that integrate medical, psychological, and social interventions to address the multifaceted nature of chronic pain in rheumatic diseases effectively.

Links between brain neuroimaging and blood inflammatory markers in urological chronic pelvic pain syndrome

Urological chronic pelvic pain syndrome (UCPPS) is a debilitating painful condition with unclear etiology. Prior researchers have indicated that compared to healthy controls, patients with UCPPS demonstrated altered brain activity. Researchers have also shown that in UCPPS, several blood inflammatory markers relate to clinical variables of pain, fatigue, and pain widespreadness. However, how altered brain function in patients with UCPPS relates to blood inflammation remains unknown. To extend and connect prior findings of altered brain function and inflammatory factors in UCPPS, we conducted a secondary analysis of data from a cohort of UCPPS patients (N = 29) and healthy controls (N = 31) who provided both neuroimaging and blood data (National Institute of Health MAPP Research Network publicly available dataset). In our present study, we aimed to evaluate relationships between a priori-defined brain neuroimaging markers and inflammatory factors of interest and their relationships to pain-psychological variables. We hypothesized that two brain alterations of interest (i.e., PCC - left hippocampus functional connectivity and PCC - bilateral amygdala functional connectivity) would be correlated with four cytokine markers of interest: interleukin (IL) - 6, tumor necrosis factor-alpha (TNF-a), IL-8, and granulocyte-macrophage colony-stimulating factor (GM-CSF). In the UCPPS cohort, we identified a significant PCC - left hippocampus functional connectivity relationship with IL-6 (p = 0.0044). Additionally, in the UCPPS cohort, we identified a PCC - amygdala functional connectivity relationship with GM-CSF which did not meet our model's threshold for statistical significance (p = 0.0665). While these data are preliminary and cross-sectional, our findings suggest connections between brain function and levels of low-grade systemic inflammation in UCPPS. Thus, while further study is needed, our data indicate the potential for advancing the understanding of how brain functional circuits may relate to clinical symptoms and systemic inflammation.

The Impact of Stress, Microbial Dysbiosis, and Inflammation on Necrotizing Enterocolitis

Necrotizing enterocolitis (NEC) is the leading cause of intestinal morbidity and mortality in neonates. A large body of work exists; however, the pathogenesis of NEC remains poorly understood. Numerous predictors have been implicated in the development of NEC, with relatively less emphasis on maternal factors. Utilizing human tissue plays a crucial role in enhancing our comprehension of the underlying mechanisms accountable for this devastating disease. In this review, we will discuss how maternal stress affects the pathogenesis of NEC and how changes in the intestinal microbiome can influence the development of NEC. We will also discuss the results of transcriptomics-based studies and analyze the gene expression changes in NEC tissues and other molecular targets associated with the pathogenesis of NEC.

Early and recent exposure to adversity, TLR-4 stimulated inflammation, and diurnal cortisol in women with interstitial cystitis/bladder pain syndrome: A MAPP research network study

Both early (ELA) and recent life adversity (RLA) have been linked with chronic pain conditions and persistent alterations of neuroendocrine and inflammatory responses. Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS) is a chronic urologic disorder characterized by bladder and/or pelvic pain, and excessive urinary frequency and/or urgency. IC/BPS has been associated with high levels of ELA as well as a distinct inflammatory signature. However, associations between ELA and RLA with inflammatory mechanisms in IC/BPS that might underlie the link between adversity and symptoms have not been examined. Here we investigated ELA and RLA in women with IC/BPS as potential risk factors for inflammatory processes and hypothalamic-pituitaryadrenal (HPA) abnormalities using data from the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network. Women with IC/BPS and healthy controls (n = 154 and 32, respectively) completed surveys, collected salivary cortisol at awakening and bedtime for 3 days, and gave a blood sample which was analyzed for 7 LPS-stimulated cytokines and chemokines (IL-6, TNFα, IL-1β, MIP1α, MCP1, IL-8, and IL-10). Two cytokine/chemokine composites were identified using principal components analysis. Patients with greater exposure to RLA or cumulative ELA and RLA of at least moderate severity showed elevated levels of a composite of all cytokines, adjusting for age, body mass index, and study site. Furthermore, there was a trending relationship between ELA and the pro-inflammatory composite score. Nocturnal cortisol and cortisol slope were not associated with ELA, RLA, or inflammation. The present findings support the importance of adverse events in IC/BPS via a biological mechanism and suggest that ELA and RLA should be assessed as risk factors for inflammation as part of a clinical workup for IC/BPS.

Stimulated whole-blood cytokine/chemokine responses are associated with interstitial cystitis/bladder pain syndrome phenotypes and features of nociplastic pain: a multidisciplinary approach to the study of chronic pelvic pain research network study

ABSTRACT

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a common and debilitating disease with poor treatment outcomes. Studies from the multidisciplinary approach to the study of chronic pelvic pain research network established that IC/BPS patients with chronic overlapping pain conditions (COPCs) experience poorer quality of life and more severe symptoms, yet the neurobiological correlates of this subtype are largely unknown. We previously showed that ex vivo toll-like receptor 4 (TLR4) cytokine/chemokine release is associated with the presence of COPCs, as well as widespread pain and experimental pain sensitivity women with IC/BPS. Here, we attempt to confirm these findings in the multisite multidisciplinary approach to the study of chronic pelvic pain Symptom Patterns Study using TLR4-stimulated whole blood (female IC/BPS patients with COPC n = 99; without n = 36). Samples were collected in tubes preloaded with TLR4 agonist, incubated for 24 hours, and resulting supernatant assayed for 7 cytokines/chemokines. These were subject to a principal components analysis and the resulting components used as dependent variables in general linear models. Controlling for patient age, body mass index, and site of collection, we found that greater ex vivo TLR4-stimulated cytokine/chemokine release was associated with the presence of COPCs ( P < 0.01), extent of widespread pain ( P < 0.05), but not experimental pain sensitivity ( P > 0.05). However, a second component of anti-inflammatory, regulatory, and chemotactic activity was associated with reduced pain sensitivity ( P < 0.01). These results confirm that the IC/BPS + COPCs subtype show higher levels of ex vivo TLR4 cytokine/chemokine release and support a link between immune priming and nociplastic pain in IC/BPS.

One immune system plays many parts: The dynamic role of the immune system in chronic pain and opioid pharmacology

The transition from acute to chronic pain is an ongoing major problem for individuals, society and healthcare systems around the world. It is clear chronic pain is a complex multidimensional biological challenge plagued with difficulties in pain management, specifically opioid use. In recent years the role of the immune system in chronic pain and opioid pharmacology has come to the forefront. As a highly dynamic and versatile network of cells, tissues and organs, the immune system is perfectly positioned at the microscale level to alter nociception and drive structural adaptations that underpin chronic pain and opioid use. In this review, we highlight the need to understand the dynamic and adaptable characteristics of the immune system and their role in the transition, maintenance and resolution of chronic pain. The complex multidimensional interplay of the immune system with multiple physiological systems may provide new transformative insight for novel targets for clinical management and treatment of chronic pain. This article is part of the Special Issue on "Opioid-induced changes in addiction and pain circuits".

Decreased autophagic activity of detrusor cells is involved in the inflammatory response of interstitial cystitis/bladder pain syndrome

INTRODUCTION AND HYPOTHESIS

Genome-wide association studies suggest that autophagy plays an important regulatory role in inflammatory and autoimmune diseases. Inflammation and immune regulation disorders are involved in the occurrence and development of interstitial cystitis/bladder pain syndrome (IC/BPS). However, the changes and roles of autophagy in IC/BPS have not been reported. Therefore, this study aimed to investigate bladder autophagy and inflammation changes in patients with IC/BPS.

METHODS

Bladder specimens (n = 5) from patients with cystectomy due to end-stage IC/BPS were collected. The bladder samples of the control group (n = 5) were derived from the normal area bladder tissue after radical cystectomy. H&E and toluidine blue staining were used for histological evaluation. The co-location of LC3, alpha-smooth muscle actin (α-SMA), and autophagosome was investigated with double-labeled immunofluorescence and transmission electron microscopy (TEM). The expression of IL-6, TNF-α, Bax, caspase-3, and BCL-2 in the detrusor layer was analyzed using immunohistochemistry (IHC) and Western blot (WB).

RESULTS

Compared with the control group, bladder tissue from IC/BPS patients revealed thinner and edematous epithelium with many mast cells (P < 0.05) infiltrating into the muscle layer. By using TEM (P < 0.05), double-labeled immunofluorescence (P < 0.05), and Western blot (P < 0.05) in IC/BPS patients, autophagy was also found and was significantly increased in detrusor myocytes. IHC and WB indicate the expression of BCL-2 (P < 0.05) was decreased, while IL-6, TNF-α, Bax, and caspase-3 expression was elevated (P < 0.05).

CONCLUSIONS

The number of autophagosomes in detrusor cells was increased in IC/BPS. However, autophagy of detrusor muscle cells may not have sufficient phagocytic activity to effectively remove damaged proteins and mitochondria, which may lead to the continued deterioration of IC/BPS inflammation and apoptosis.

Widespread Pain Phenotypes Impact Treatment Efficacy Results in Randomized Clinical Trials for Interstitial Cystitis/Bladder Pain Syndrome: A MAPP Network Study

Clinical trials of pain are notoriously difficult and inefficient in demonstrating efficacy even for known efficacious treatments. Determining the appropriate pain phenotype to study can be problematic. Recent work has identified the extend of widespread pain as an important factor in the likelihood of response to therapy, but has not been tested in clinical trials. Using data from three previously published negative studies of the treatment of interstitial cystitis/ bladder pain with data on the extent of widespread pain, we examined the response of patients to different therapies base on the amount of pain beyond the pelvis. Participants with predominately local but not widespread pain responded to therapy targeting local symptoms. Participants with widespread and local pain responded to therapy targeting widespread pain. Differentiating patients with and without widespread pain phenotypes may be a key feature of designing future pain clinical trials to demonstrate treatments that are effective versus not.

Lysophosphatidylcholine: Potential Target for the Treatment of Chronic Pain

The bioactive lipid lysophosphatidylcholine (LPC), a major phospholipid component of oxidized low-density lipoprotein (Ox-LDL), originates from the cleavage of phosphatidylcholine by phospholipase A2 (PLA2) and is catabolized to other substances by different enzymatic pathways. LPC exerts pleiotropic effects mediated by its receptors, G protein-coupled signaling receptors, Toll-like receptors, and ion channels to activate several second messengers. Lysophosphatidylcholine (LPC) is increasingly considered a key marker/factor positively in pathological states, especially inflammation and atherosclerosis development. Current studies have indicated that the injury of nervous tissues promotes oxidative stress and lipid peroxidation, as well as excessive accumulation of LPC, enhancing the membrane hyperexcitability to induce chronic pain, which may be recognized as one of the hallmarks of chronic pain. However, findings from lipidomic studies of LPC have been lacking in the context of chronic pain. In this review, we focus in some detail on LPC sources, biochemical pathways, and the signal-transduction system. Moreover, we outline the detection methods of LPC for accurate analysis of each individual LPC species and reveal the pathophysiological implication of LPC in chronic pain, which makes it an interesting target for biomarkers and the development of medicine regarding chronic pain.

Study protocol: an observational study of distress, immune function and persistent pain in HIV

INTRODUCTION

Many people with HIV report both distress and pain. The relationship between distress and pain is bidirectional, but the mechanisms by which distress exacerbates pain are unclear. The inflammatory response to challenge (inflammatory reactivity, IR) may be a partial mediator, given that neuroimmune interactions provide a substrate for IR to also influence neurological reactivity and, thus, pain-related neural signalling. This prospective, observational, case-control study will characterise the relationships between distress, IR, pain-related signalling as captured by induced secondary hyperalgesia (SH), and pain, in people with HIV who report persistent pain (PP) (cases) or no pain (controls).

METHODS AND ANALYSIS

One hundred people with suppressed HIV, reporting either PP or no pain, will be assessed two or four times over 6 months. The primary outcomes are distress (Hopkins 25-item symptom checklist), IR (multiplex assay after LPS challenge), and PP (Brief Pain Inventory), assessed at the baseline timepoint, although each will also be assessed at follow-up time points. Induced SH will be assessed in a subsample of 60 participants (baseline timepoint only). To test the hypothesis that IR partly mediates the relationship between distress and pain, mediation analysis will use the baseline data from the PP group to estimate direct and indirect contributions of distress and IR to pain. To test the hypothesis that IR is positively associated with SH, data from the subsample will be analysed with generalised mixed effects models to estimate the association between IR and group membership, with SH as the dependent variable.

ETHICS AND DISSEMINATION

Information obtained from this study will be published in peer-reviewed journals and presented at scientific meetings. The study has been approved by the Human Research Ethics Committee of the University of Cape Town (approval number: 764/2019) and the City of Cape Town (ref: 24699).

TRIAL REGISTRATION NUMBER

NCT04757987.

Tibetan Herbal Pain-Relieving Plaster for Chronic Musculoskeletal Pain Among Cancer Survivors: Study Protocol of a Randomized, Double-Blind, Placebo-Controlled Trial

Chronic pain is common and debilitating in cancer survivors. Tibetan herbal pain-relieving plaster is used as an external analgesic to treat musculoskeletal pain in China; however, its safety and efficacy have not been evaluated via clinical trials in cancer survivors. We designed this Phase II randomized, double-blind, placebo-controlled trial (ClinicalTrials.gov Identifier: NCT04916249) to assess the efficacy and safety of the pain-relieving plaster for temporary pain relief among cancer survivors with chronic musculoskeletal pain. Under ethical approval from the Institutional Review Board at the Memorial Sloan Kettering Cancer Center, we will enroll eligible cancer survivors who have a clinical diagnosis of moderate to severe chronic musculoskeletal pain in this study. We use a central randomization system to allocate the eligible participants to either the treatment or the control group in a 1:1 ratio, with stratification by baseline opioid use. We will instruct the participants to apply the herbal patch (Tibetree Pain-Relieving Plaster, Tibet Cheezheng Tibetan Medicine Co. Ltd., Tibet, China) or placebo patch daily at the focal area with worst pain for 14 consecutive days. Study physician, participant, outcome assessor, and biostatistician are blinded to the group allocation. The primary outcome is pain severity measured by the Brief Pain Inventory on Days 2–7. Secondary outcomes include changes in insomnia, anxiety, depression, fatigue, pressure pain threshold, pain medication use, and global impression of change. We will also monitor the adverse events throughout the study period. Statistical analysis will follow the intention-to-treat principle and linear mixed modeling will be used. With rigorous design and implementation, this randomized, placebo-controlled trial will provide the initial evidence on the efficacy and safety of the pain-relieving plaster for pain relief among cancer survivors with chronic musculoskeletal pain.

Individuals with both higher recent negative affect and physical pain have higher levels of C-reactive protein

Conceptualizing physical pain and negative affect as potentially interactive, we hypothesized that higher levels of peripheral inflammatory markers would be observed consistently only among individuals with both higher negative affect and pain symptomatology. Participants were generally healthy midlife adults from the Bronx, NY (N ​= ​212, M_age ​= ​46.77; 60.8% Black, 25.5% Hispanic/Latina/o) recruited as part of a larger study. Key measures were: reported pain intensity and pain interference at baseline, recent negative affect averaged from self-reports 5x/day for 7 days, and peripheral inflammatory markers (C-reactive protein [CRP] and a composite cytokine measure based on seven cytokines). Controlling for age, BMI, gender, and education, recent negative affect significantly interacted with both pain variables to explain variance in CRP, with higher CRP levels observed only in individuals with both higher negative affect and either higher pain intensity or pain interference. These findings contribute to an emerging literature suggesting that negative affect, pain, and inflammation are related in important and complex ways.

Multi-Site Observational Study to Assess Biomarkers for Susceptibility or Resilience to Chronic Pain: The Acute to Chronic Pain Signatures (A2CPS) Study Protocol

Chronic pain has become a global health problem contributing to years lived with disability and reduced quality of life. Advances in the clinical management of chronic pain have been limited due to incomplete understanding of the multiple risk factors and molecular mechanisms that contribute to the development of chronic pain. The Acute to Chronic Pain Signatures (A2CPS) Program aims to characterize the predictive nature of biomarkers (brain imaging, high-throughput molecular screening techniques, or "omics," quantitative sensory testing, patient-reported outcome assessments and functional assessments) to identify individuals who will develop chronic pain following surgical intervention. The A2CPS is a multisite observational study investigating biomarkers and collective biosignatures (a combination of several individual biomarkers) that predict susceptibility or resilience to the development of chronic pain following knee arthroplasty and thoracic surgery. This manuscript provides an overview of data collection methods and procedures designed to standardize data collection across multiple clinical sites and institutions. Pain-related biomarkers are evaluated before surgery and up to 3 months after surgery for use as predictors of patient reported outcomes 6 months after surgery. The dataset from this prospective observational study will be available for researchers internal and external to the A2CPS Consortium to advance understanding of the transition from acute to chronic postsurgical pain.

Biomarkers in Interstitial Cystitis/Bladder Pain Syndrome with and without Hunner Lesion: A Review and Future Perspectives

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a debilitating urinary bladder condition that presents with a wide variety of clinical phenotypes. It is commonly characterized by persistent pelvic pain and lower urinary tract symptoms, such as urinary frequency and urgency. Current clinicopathological and genomic evidence has indicated that IC/BPS with Hunner lesions is a clinically relevant distinct subtype with proven bladder pathology of subepithelial chronic inflammatory changes that are characterized by enhanced local immune responses and epithelial denudation. However, other forms of IC/BPS lacking Hunner lesions are a symptom syndrome complex of non-inflammatory conditions with little evidence of bladder etiology, characterized by aberrant neural activity in neurotransmission systems which leads to central nervous sensitization with potential involvement of urothelial malfunction, or clinical presentation of somatic and/or psychological symptoms beyond the bladder. Given such distinct potential pathophysiology between IC/BPS subtypes, disease biomarkers of IC/BPS should be provided separately for subtypes with and without Hunner lesions. Tailored approaches that target characteristic immunological inflammatory processes and epithelial denudation for IC/BPS with Hunner lesions, or the sensitized/altered nervous system, urothelial malfunction, association with other functional somatic syndromes, and psychosocial problems for IC/BPS without Hunner lesions, are essential to identify optimal and reliable disease-specific IC/BPS biomarkers.

"The Urinary Proteomic Profile Implicates Key Regulators for Urologic Chronic Pelvic Pain Syndrome (UCPPS): A MAPP Research Network Study"

Urologic chronic pelvic pain syndrome (UCPPS) is a condition of unknown etiology characterized by pelvic pain and urinary frequency and/or urgency. As the proximal fluid of this syndrome, urine is an ideal candidate sample matrix for an unbiased study of UCPPS. In this study, a large, discovery-phase, TMT-based quantitative urinary proteomics analysis of 244 participants was performed. The participants included patients with UCPPS (n = 82), healthy controls (HC) (n = 94), and disparate chronic pain diseases, termed positive controls (PC) (n = 68). Using training and testing cohorts, we identified and validated a small and distinct set of proteins that distinguished UCPPS from HC (n = 9) and UCPPS from PC (n = 3). The validated UCPPS: HC proteins were predominantly extracellular matrix/extracellular matrix modifying or immunomodulatory/host defense in nature. Significantly varying proteins in the UCPPS: HC comparison were overrepresented by the members of several dysregulated biological processes including decreased immune cell migration, decreased development of epithelial tissue, and increased bleeding. Comparison with the PC cohort enabled the evaluation of UCPPS-specific upstream regulators, contrasting UCPPS with other conditions that cause chronic pain. Specific to UCPPS were alterations in the predicted signaling of several upstream regulators, including alpha-catenin, interleukin-6, epidermal growth factor, and transforming growth factor beta 1, among others. These findings advance our knowledge of the etiology of UCPPS and inform potential future clinical translation into a diagnostic panel for UCPPS.

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The proteomics of urinary chronic pelvic pain syndrome (UCPPS) found altered pathways.

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Key changes among the extracellular matrix and inflammatory response proteins were found.

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Several of these pathways and proteins were exclusively altered in UCPPS.

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These findings may have diagnostic and/or therapeutic potential in the future.

The Relationship Between Androgens and Days per Month of Period Pain, Pelvic Pain, Headache, and TLR4 Responsiveness of Peripheral Blood Mononuclear Cells in Young Women with Dysmenorrhoea

Purpose

Women bear a disproportionate burden of persistent pain conditions when compared to men. To determine whether the hormonal environment affects the clinical experience of pain, as measured by the days per month of pelvic pain (DPelvicPM), period pain (DPeriodPM), headache (DHeadachePM) or the in vitro EC₅₀ for Interleukin-1β (IL-1β) release following TLR4 stimulation with Lipopolysaccharide from Peripheral Blood Mononuclear Cells (PBMCs). Findings were stratified according to use or non-use of the oral contraceptive pill.

Patients and Methods

Fifty-six women aged 16–35 years, with minimal or severe dysmenorrhea, and use or non-use of the OC, were enrolled. Blood was collected on two occasions in a single menstrual cycle: Days 1–2 and Days 7–10. Hormonal analysis for testosterone, dihydrotestosterone, dehydroepiandrosterone, Androstenedione, 3α-Androstanediol, 3β-androstanediol, estradiol, estrone, 17α-hydroxyprogesterone, progesterone, cortisol and sex-hormone binding globulin was undertaken using ultra-sensitive Liquid Chromatography Mass–Spectrometry (LC-MS). PBMCs were exposed to lipopolysaccharide (LPS) and the resulting Interleukin-1β output was determined.

Results

Non-users of the OC showed a strongly inverse correlation between a reducing free androgen index (FAI) and increasing DPelvicPM (p=0.0032), DPeriodPM (p=0.013), DHeadachePM (p=0.041). Non-users of the OC showed a significant increase in DPelvicPM (p=0.049) on Days 7–10. Modestly significant associations were found between reduced androgens and potentiated LPS-induced IL-1β (lower EC₅₀).

Conclusion

This is the first study to investigate the relationship between the hormonal environment and activation of the immune system in young women with dysmenorrhoea-related pain conditions. Low androgen levels were consistently associated with increased pain. Translational implications for the findings are discussed.

Relationship Between Blood Cytokine Levels, Psychological Comorbidity, and Widespreadness of Pain in Chronic Pelvic Pain

Background: Low-grade inflammation has been implicated in the etiology of depression, long-term fatigue and chronic pain. TNFα and IL-6 are perhaps the most studied pro-inflammatory cytokines in the field of psychoneuroimmunology. The purpose of our study was to further investigate these relationships in patients with chronic pelvic pain specifically. Using plasma samples from a large, well-described cohort of patients with pelvic pain and healthy controls via the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network, we examined the relationship between TNFα and IL-6 and comorbid psychological symptoms. We also investigated the relationship between IL-8 and GM-CSF, and widespreadness of pain. Methods: We included baseline blood samples in the analyses, 261 patients (148 women) and 110 healthy controls (74 women). Fourteen pro- and anti-inflammatory or regulatory cytokines were analyzed in a Luminex^® xMAP^® high-sensitivity assay. We used regression models that accounted for known factors associated with the outcome variables to determine the relationship between cytokine levels and clinical measures. Results: There were no statistical differences in cytokine levels between patients and healthy controls when controlling for age. In patients, TNFα was significantly associated with levels of fatigue (p = 0.026), but not with pain intensity or depression. IL-6 was not significantly related to any of the outcome variables. Women with pelvic pain showed a negative relationship between IL-8 and widespreadness of pain, while men did not (p = 0.003). For both sexes, GM-CSF was positively related to widespreadness of pain (p = 0.039). Conclusion: Our results do not suggest low-grade systemic inflammation in chronic pelvic pain. Higher TNFα blood levels were related to higher fatigue ratings, while higher systemic GM-CSF levels predicted more widespread pain. Our study further suggests a potentially protective role of IL-8 with regard to with regard to the widepreadness of pain in the body, at least for women.

Cognitive behavioral therapy for the treatment of chronic pelvic pain

Chronic pelvic pain (CPP) in women is defined as noncyclical and persistent pain lasting more than six months perceived to be related to the pelvis. There are many etiologies that can cause CPP, including gynecologic, urologic, gastrointestinal, musculoskeletal, neurologic, and psychosocial. There is a strong association between psychological factors and CPP. It has been noted that almost half of women being treated for CPP report a history of sexual, physical, or emotional trauma. Women with CPP have been noted to have higher rates of psychological disorders in comparison to their peers. For men, the most common etiology for CPP is chronic prostatitis and there are also correlations with psychological disorders. There are many different treatment options for CPP: surgical, pharmacological, and non-pharmacological (alternative therapies). Cognitive-behavioral therapy may be another option when treating chronic pelvic pain syndrome and should be considered.

Phenotypes of BPS/IC

Purpose of Review

The aim of this review is to summarise the latest research related to different phenotypes of BPS/IC, addressing the evidence for current well-defined phenotypes as well as identifying novel potential phenotypes and highlighting areas for future study.

Recent Findings

Two distinct phenotypes of BPS/IC are well-recognised: Hunner’s lesion disease and non-Hunner’s lesion BPS/IC. Recent studies have shown these phenotypes exhibit distinct clinical, pathological and cystoscopic features, and targeted treatment to Hunner’s lesions can prove effective. Recent studies have also identified new potential phenotypes based on biochemical, molecular and histological markers, pathophysiological mechanisms of disease, clinical features, cystoscopic findings, radiological features and urodynamic factors. This evidence has improved our understanding of the underlying mechanism of disease and may enable more personalised and targeted therapy in the future.

Summary

Novel phenotypes of BPS/IC relate to the presence of certain biomarkers, alterations in the urinary microbiome, the characteristics of pain and presence of co-existing somatic and psychosocial conditions, altered patterns of brain white matter changes and urodynamic features. Further study is required to evaluate whether these potential phenotypes are clinically useful based on their ability to guide treatment selection and predict outcome from therapy, and therefore optimise therapeutic outcomes.

The Multidisciplinary Approach to The Study of Chronic Pelvic Pain (MAPP) Research Network*: Design and implementation of the Symptom Patterns Study (SPS)

AIMS

The Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network initiated a second observational cohort study-the Symptom Patterns Study (SPS)-to further investigate the underlying pathophysiology of Urologic Chronic Pelvic Pain Syndrome (UCPPS) and to discover factors associated with longitudinal symptom changes and responses to treatments.

METHODS

This multisite cohort study of males and females with UCPPS features a run-in period of four weekly web-based symptom assessments before a baseline visit, followed by quarterly assessments up to 36 months. Controls were also recruited and assessed at baseline and 6 months. Extensive clinical data assessing urological symptoms, nonurological pain, chronic overlapping pain syndromes, and psychosocial factors were collected. Diverse biospecimens for biomarker and microbiome studies, quantitative sensory testing (QST) data under multiple stimuli, and structural and functional neuroimaging scans were obtained under a standardized protocol.

RESULTS

Recruitment was initiated (July 2015) and completed (February 2019) at six discovery sites. A total of 620 males and females with UCPPS and 73 Controls were enrolled, including 83 UCPPS participants who re-enrolled from the first MAPP Network cohort study (2009-2012). Baseline neuroimaging scans, QST measures, and biospecimens were obtained on 578 UCPPS participants. The longitudinal follow-up of the cohort is ongoing.

CONCLUSIONS

This comprehensive characterization of a large UCPPS cohort with extended follow-up greatly expands upon earlier MAPP Network studies and provides unprecedented opportunities to increase our understanding of UCPPS pathophysiology, factors associated with symptom change, clinically relevant patient phenotypes, and novel targets for future interventions.

Quantitative assessment of nonpelvic pressure pain sensitivity in urologic chronic pelvic pain syndrome: a MAPP Research Network study

Experimental pain sensitivity was assessed in individuals with urologic chronic pelvic pain syndrome (UCPPS) as part of the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network. A series of computer-controlled pressure stimuli were delivered to the thumbnail bed, an asymptomatic site distant from the area of UCPPS pain that is considered to be indicative of overall body pain threshold. Stimuli were rated according to a standardized magnitude estimation protocol. Pain sensitivity in participants with UCPPS was compared with healthy controls and a mixed pain group composed of individuals with other chronic overlapping pain conditions, including fibromyalgia, chronic fatigue, and irritable bowel syndromes. Data from 6 participating MAPP testing sites were pooled for analysis. Participants with UCPPS (n = 153) exhibited an intermediate pain sensitivity phenotype: they were less sensitive relative to the mixed pain group (n = 35) but significantly more sensitive than healthy controls (n = 100). Increased pain sensitivity in patients with UCPPS was associated with both higher levels of clinical pain severity and more painful body areas outside the pelvic region. Exploratory analyses in participants with UCPPS revealed that pain sensitivity increased during periods of urologic symptom flare and that less pressure pain sensitivity at baseline was associated with a greater likelihood of subsequent genitourinary pain improvement 1 year later. The finding that individuals with UCPPS demonstrate nonpelvic pain hypersensitivity that is related to clinical symptoms suggests that central nervous system mechanisms of pain amplification contribute to UCPPS.

Pressure Pain Tolerance Predicts the Success of Emotional Awareness and Expression Therapy in Patients With Fibromyalgia

OBJECTIVES

Quantitative sensory testing may help predict treatment responses in individuals with chronic pain. Our objective was to determine whether evoked pain sensitivity at baseline predicted preferential treatment responses to either emotional awareness and expression therapy (EAET) or cognitive behavioral therapy (CBT) in individuals with fibromyalgia (FM).

METHODS

This was a secondary analysis of a previous randomized clinical trial, in which individuals with FM were randomized to EAET, CBT, or Education as a control intervention. Only females who completed baseline and post-treatment assessments were analyzed (n=196). The primary outcome was change in overall clinical pain severity from pretreatment to posttreatment, and the primary predictor of interest was pressure pain tolerance at baseline.

RESULTS

Among patients with low pain tolerance at baseline (n=154), both EAET and CBT led to small but significant improvements in clinical pain severity (CBT mean=0.66, 95% confidence interval [0.24-1.07]; EAET mean=0.76 [0.34-1.17]). Conversely, in patients with normal pain tolerance (n=42), there was no significant improvement in clinical pain after CBT (0.13 [-0.88 to 1.14]), a small improvement after FM Education (0.81 [0.14-1.48]), but a much larger and statistically significant improvement after EAET (2.14 [1.23-3.04]).

DISCUSSION

Normal levels of pressure pain tolerance at baseline predicted greater improvement in clinical pain severity after EAET than CBT. Quantitative sensory testing may provide insights about individual responses to psychologically based therapies for individuals with chronic pain.

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.

Toll-Like Receptor Responsiveness of Peripheral Blood Mononuclear Cells in Young Women with Dysmenorrhea

PURPOSE

Dysmenorrhea is a common disorder that substantially disrupts the lives of young women. To determine whether there is evidence of activation of the innate immune system in dysmenorrhea and whether the degree of activation may be used as a biomarker for pain, we compared the responsiveness of peripheral blood mononuclear cells (PBMCs) to toll-like receptor (TLR) 2 or 4 stimulation. We also investigated whether this effect is modulated by the use of the oral contraceptive pill (OC).

PATIENTS AND METHODS

Fifty-six women aged 16-35 years, with either severe or minimal dysmenorrhea, and use or non-use of the OC, were enrolled. PBMCs were collected on two occasions in a single menstrual cycle: the menstrual phase and the mid-follicular phase. PBMCs were exposed to lipopolysaccharide (LPS), a TLR4 agonist, and PAM3CSK4 (PAM), a TLR2 agonist, and the resulting interleukin-1beta (IL-1β) output was determined. Statistical analysis compared the EC50 between groups as a measure of TLR responsiveness of PBMCs.

RESULTS

The key finding following LPS stimulation was a pain effect of dysmenorrhea (p=0.042) that was independent of use or non-use of OC, and independent of day of testing. Women with dysmenorrhea showed a large 2.15-fold (95% CI -4.69, -0.09) increase in IL-1β release when compared with pain-free participants across both days.

CONCLUSION

This is the first study to demonstrate an ex vivo immune relationship in women with dysmenorrhea-related pelvic pain. It provides evidence for the potential of immune modulation as a novel pharmacological target for future drug development in the management of dysmenorrhea.

Urologic chronic pelvic pain syndrome: insights from the MAPP Research Network

Urologic chronic pelvic pain syndrome (UCPPS), which encompasses interstitial cystitis/bladder pain syndrome and chronic prostatitis/chronic pelvic pain syndrome, is characterized by chronic pain in the pelvic region or genitalia that is often accompanied by urinary frequency and urgency. Despite considerable research, no definite aetiological risk factors or effective treatments have been identified. The Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network uses a novel integrated strategy to characterize UCPPS as a systemic disorder that potentially involves multiple aetiologies. The first phase, MAPP I, included >1,000 participants who completed an intensive baseline assessment followed by a 12-month observational follow-up period. MAPP I studies showed that UCPPS pain and urinary symptoms co-vary, with only moderate correlation, and should be evaluated separately and that symptom flares are common and can differ considerably in intensity, duration and influence on quality of life. Longitudinal clinical changes in UCPPS correlated with structural and functional brain changes, and many patients experienced global multisensory hypersensitivity. Additionally, UCPPS symptom profiles were distinguishable by biological correlates, such as immune factors. These findings indicate that patients with UCPPS have objective phenotypic abnormalities and distinct biological characteristics, providing a new foundation for the study and clinical management of UCPPS.

Chemotherapy-induced peripheral neuropathy (CIPN) in breast cancer survivors: a comparison of patient-reported outcomes and quantitative sensory testing

PURPOSE

CIPN is a common, debilitating, and dose-limiting side effect of chemotherapy. Here, we describe characteristics of patients with CIPN using both patient-reported outcomes (PRO) and quantitative sensory testing (QST).

METHODS

Breast cancer survivors with persistent moderate to severe CIPN defined by a rating of 4 or greater on a 0-10 Numeric Rating Scale (NRS) from two ongoing clinical trials were included. PROs included the Neuropathic Pain Scale (NPS) and Functional Assessment of Cancer Therapy-Gynecologic Oncology Group/Neurotoxicity (FACT/GOG-Ntx). QST included tactile and vibration detection threshold measurements. Data were analyzed using descriptive statistics and Spearman correlation coefficients.

RESULTS

49 female patients with a mean age of 61 years were assessed; 63% were Caucasian. Mean NRS scores were 4.2, 5.7, and 4.3 on 0-10 scale for pain, numbness, and tingling, respectively. Mean NPS score was 41.0 on a 0-100 scale, and the mean FACT/GOG-Ntx score was 25.8 on a 0-44 scale. QST showed mild to moderate impairments in tactile and vibration perception. The FACT/GOG-Ntx subscale for numbness was negatively correlated with tactile and vibration thresholds in both hands and feet (both p < 0.05). NPS was positively correlated with tactile thresholds in the hands and feet (p < 0.05).

CONCLUSION

Patients with moderate to severe CIPN report moderate pain, numbness, and tingling, and exhibit reduced tactile and vibration perception on QST. Weak to moderate correlations were observed between PRO and QST. These data suggest that QST outcomes are associated with CIPN symptoms and may be useful in helping monitor and manage CIPN treatment.

Adverse Childhood Experiences and Symptoms of Urologic Chronic Pelvic Pain Syndrome: A Multidisciplinary Approach to the Study of Chronic Pelvic Pain Research Network Study

Background

Adverse Childhood Experiences (ACEs) such as sexual and physical violence, serious illness, and bereavement have been linked to number of chronic pain conditions in adulthood, and specifically to urologic chronic pelvic pain syndrome (UCPPS).

Purpose

We sought to characterize the prevalence of ACEs in UCPPS using a large well-characterized cohort in comparison with a group of healthy controls. We also sought to determine the association of ACE severity with psychological factors known to impact pain and to determine whether ACEs are associated with patterns of improvement or worsening of symptom over a year of naturalistic observation.

Methods

For longitudinal analyses we used functional clusters identifying broad classes of (a) improved, (b) worsened, and (c) stable groups for genitourinary pain and urinary symptoms. We employed a mediation/path analysis framework to determine whether ACEs influenced 1 year outcomes directly, or indirectly through worse perceptions of physical well-being.

Results

ACE severity was elevated in UCPPS (n = 421) participants compared with healthy controls (n = 414; p < .001), and was most strongly associated with factors associated with complex chronic pain, including more diffuse pain, comorbid functional symptoms/syndromes, and worse perceived physical well-being (all p < .001). Finally, worse physical well-being mediated the relationship between ACE severity and less likelihood of painful symptom improvement (OR = .871, p = .007)) and a greater likelihood of painful symptom worsening (OR = 1.249, p = .003) at 1 year.

Conclusions

These results confirm the association between ACEs and UCPPS symptoms, and suggest potential targets for therapeutic interventions in UCPPS.

Clinical Trial registration

NCT01098279.

Psychology of Chronic Pelvic Pain: Prevalence, Neurobiological Vulnerabilities, and Treatment

Patients with pelvic pain suffer from psychological conditions at a disproportionately high rate compared with their peers. We review environmental, genetic, inflammatory, and neurobiological factors that increase vulnerability to developing both of these conditions. We review treatment strategies for chronic pelvic pain in patients who have comorbid psychological conditions, including both nonpharmacologic and pharmacologic options.

Cystitis-induced bladder pain is Toll-like receptor 4 dependent in a transgenic autoimmune cystitis murine model: a MAPP Research Network animal study

Altered Toll-like receptor (TLR)4 activation has been identified in several chronic pain conditions but has not been well studied in interstitial cystitis/bladder pain syndrome (IC/BPS). Our previously published human studies indicated that patients with IC/BPS present altered systemic TLR4-mediated inflammatory responses, which were significantly correlated with reported pain severity. In the present study, we sought to determine whether altered TLR4 activation plays a role in pelvic/bladder pain seen in patients with IC/BPS using our validated IC/BPS-like transgenic autoimmune cystitis model (URO-OVA). URO-OVA mice developed responses consistent with pelvic and bladder pain after cystitis induction, which was associated with increased splenocyte production of TLR4-mediated proinflammatory cytokines IL-1β, IL-6, and TNF-α. Increased spinal expression of mRNAs for proinflammatory cytokines IL-6 and TNF-α, glial activation markers CD11b and glial fibrillary acidic protein, and endogenous TLR4 ligand high mobility group box 1 was also observed after cystitis induction. Compared with URO-OVA mice, TLR4-deficient URO-OVA mice developed significantly reduced nociceptive responses, although similar bladder inflammation and voiding dysfunction, after cystitis induction. Intravenous administration of TAK-242 (a TLR4-selective antagonist) significantly attenuated nociceptive responses in cystitis-induced URO-OVA mice, which was associated with reduced splenocyte production of TLR4-mediated IL-1β, IL-6, and TNF-α as well as reduced spinal expression of mRNAs for IL-6, TNF-α, CD11b, glial fibrillary acidic protein, and high mobility group box 1. Our results indicate that altered TLR4 activation plays a critical role in bladder nociception independent of inflammation and voiding dysfunction in the URO-OVA model, providing a potential mechanistic insight and therapeutic target for IC/BPS pain.

Neuroimmune modulation of pain across the developmental spectrum

Today's treatment for chronic pain is inadequate, and novel targets need to be identified. This requires a better understanding of the mechanisms involved in pain sensitization and chronification. In this review, we discuss how peripheral inflammation, as occurs during an infection, modulates the central pain system. In rodents, neonatal inflammation leads to increased pain sensitivity in adulthood by priming immune components both peripherally and centrally. The excitability of neurons in the spinal cord is also altered by neonatal inflammation and may add to pain sensitization later in life. In adult humans, inflammation modulates pain sensitivity as well, partly by affecting the activity in brain areas that process and regulate pain signals. Low-grade inflammation is common in clinical populations both peripherally and centrally, and priming of the immune system has also been suggested in some pain populations. The nociceptive and immune systems are primed by infections and inflammation. The early life programming of nociceptive responses following exposure to infections or inflammation will define individual differences in adult pain perception. Immune-to-brain mechanisms and neuroimmune pathway need further investigation as they may serve both as predictors and therapeutic targets in chronic pain.

The LURN Research Network Neuroimaging and Sensory Testing (NIST) Study: Design, protocols, and operations

The Neuroimaging and Sensory Testing (NIST) Study of the Symptoms of Lower Urinary Tract Dysfunction Research Network (LURN) is a cross-sectional, case-control study designed to investigate whether disrupted brain connectivity and sensory processing are associated with abnormal lower urinary tract symptoms (LUTS) in patients with overactive bladder syndrome (OAB). The NIST Study tests the hypotheses that patients with urinary urgency will demonstrate: (1) abnormal functional and structural connectivity of brain regions involved in urinary sensation on magnetic resonance imaging (MRI), and (2) hypersensitivity to painful (pressure) and non-painful (auditory) sensory stimuli on quantitative sensory testing (QST), compared to controls. Male and female adults (18 years or older) who present at one of the six participating LURN clinical centers for clinical care of their LUTS, with symptoms of urinary urgency with or without urgency urinary incontinence, are eligible to participate. The NIST Study is the largest MRI and QST study of its kind, yielding a neuroimaging and sensory testing dataset unprecedented in OAB research. Advanced multi-modal techniques are used to understand brain functional and structural connectivity, including gray matter volume, and sensory function. Unlike previous MRI studies which involved invasive catheterization and repeated cycles of non-physiologic bladder filling and emptying via a catheter, we use a water ingestion protocol to mimic more physiological bladder filling through natural diuresis. Furthermore, these data will be used in concert with other phenotyping data to improve our understanding of clinically meaningful subtypes of patients with LUTS in order to improve patient care and management outcomes.

Sensory sensitivity and symptom severity represent unique dimensions of chronic pain: a MAPP Research Network study

Chronic overlapping pain conditions (COPCs) are characterized by aberrant central nervous system processing of pain. This "centralized pain" phenotype has been described using a large and diverse set of symptom domains, including the spatial distribution of pain, pain intensity, fatigue, mood imbalances, cognitive dysfunction, altered somatic sensations, and hypersensitivity to external stimuli. Here, we used 3 cohorts, including patients with urologic chronic pelvic pain syndrome, a mixed pain cohort with other COPCs, and healthy individuals (total n = 1039) from the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network to explore the factor structure of symptoms of centralized pain. Using exploratory and confirmatory factor analysis, we identified 2 general factors in all 3 cohorts, one characterized by a broad increased sensitivity to internal somatic sensations,environmental stimuli, and diffuse pain, termed Generalized Sensory Sensitivity, and one characterized by constitutional symptoms-Sleep, Pain, Affect, Cognition, Energy (SPACE). Longitudinal analyses in the urologic chronic pelvic pain syndrome cohort found the same 2-factor structure at month 6 and 1 year, suggesting that the 2-factor structure is reproducible over time. In secondary analyses, we found that Generalized Sensory Sensitivity particularly is associated with the presence of comorbid COPCs, whereas SPACE shows modest associations with measures of disability and urinary symptoms. These factors may represent an important and distinct continuum of symptoms that are indicative of the centralized pain phenotype at high levels. Future research of COPCs should accommodate the measurement of each factor.

Phenotypic Features of Central Sensitization

PURPOSE

The current manuscript reviews approaches for phenotyping central sensitization (CS).

METHODS

The manuscript covers the concept of diagnostic phenotyping, use of endophenotypes, biomarkers, and symptom clusters. Specifically, the components of CS that include general sensory sensitivity (assessed by quantitative sensory testing) and a symptom cluster denoting sleep difficulties, pain, affect, cognitive difficulties, and low energy (S.P.A.C.E.).

RESULTS

Each of the assessment domains are described with reference to CS and their presence in chronic overlapping pain conditions (COPCs) - conditions likely influenced by CS.

CONCLUSIONS

COPCs likely represent clinical diagnostic phenotypes of CS. Components of CS can also be assessed using QST or self-report instruments designed to assess single elements of CS or more general composite indices.

Spinal Glial Adaptations Occur in a Minimally Invasive Mouse Model of Endometriosis: Potential Implications for Lesion Etiology and Persistent Pelvic Pain

Glial adaptations within the central nervous system are well known to modulate central sensitization and pain. Recently, it has been suggested that activity of glial-related proinflammatory cytokines may potentiate peripheral inflammation, via central neurogenic processes. However, a role for altered glial function has not yet been investigated in the context of endometriosis, a chronic inflammatory condition in women associated with peripheral lesions, often manifesting with persistent pelvic pain. Using a minimally invasive mouse model of endometriosis, we investigated associations between peripheral endometriosis-like lesions and adaptations in central glial reactivity. Spinal cords (T13-S1) from female C57BL/6 mice with endometriosis-like lesions (ENDO) were imaged via fluorescent immunohistochemistry for the expression of glial fibrillary acidic protein (GFAP; astrocytes) and CD11b (microglia) in the dorsal horn (n = 5). Heightened variability ( P = .02) as well as an overall increase ( P = .04) in the mean area of GFAP immunoreactivity was found in ENDO versus saline-injected control animals. Interestingly, spinal levels showing the greatest alterations in GFAP immunoreactivity appeared to correlate with the spatial location of lesions within the abdominopelvic cavity. A subtle but significant increase in the mean area of CD11b immunostaining was also observed in ENDO mice compared to controls ( P = .02). This is the first study to describe adaptations in nonneuronal, immune-like cells of the central nervous system attributed to the presence of endometriosis-like lesions.

Deletion or pharmacological blockade of TLR4 confers protection against cyclophosphamide-induced mouse cystitis

Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS) is a chronic inflammatory disease without consistently effective treatment. We investigate the role of toll-like receptor 4 (TLR4) on voiding dysfunction and inflammation in the cyclophosphamide (CYP)-induced mouse cystitis. Male C57BL/6 [wild-type, (WT)] and/or TLR4 knockout (TLR4^-/-) mice were treated with an injection of CYP (300 mg/kg, 24 h) or saline (10 ml/kg). The pharmacological blockade of the TLR4 by resatorvid (10 mg/kg) was also performed 1 h prior CYP-injection in WT mice. Urodynamic profiles were assessed by voiding stain on filter paper and filling cystometry. Contractile responses to carbachol were measured in isolated bladders. In CYP-exposed WT mice, mRNA for TLR4, myeloid differentiation primary response 88, and TIR-domain-containing adapter-inducing interferon-β increased by 45%, 72%, and 38%, respectively ( P < 0.05). In free-moving mice, CYP-exposed mice exhibited a higher number of urinary spots and smaller urinary volumes. Increases of micturition frequency and nonvoiding contractions, concomitant with decreases of intercontraction intervals and capacity, were observed in the filling cystometry of WT mice ( P < 0.05). Carbachol-induced bladder contractions were significantly reduced in the CYP group, which was paralleled by reduced mRNA for M2 and M3 muscarinic receptors. These functional and molecular alterations induced by CYP were prevented in TLR4^-/- and resatorvid-treated mice. Additionally, the increased levels of inflammatory markers induced by CYP exposure, myeloperoxidase activity, interleukin-6, and tumor necrosis factor-alpha were significantly reduced by resatorvid treatment. Our findings reveal a central role for the TLR4 signaling pathway in initiating CYP-induced bladder dysfunction and inflammation and thus emphasize that TLR4 receptor blockade may have clinical value for IC/BPS treatment.

Current best practice management of interstitial cystitis/bladder pain syndrome

Introduction

Over the last 100 years, the terminology and diagnosis criteria for interstitial cystitis have evolved. Many therapeutic options have changed, but others have endured. This article will review the idea of separating 'classic' Hunner lesion interstitial cystitis (HL IC) from non-Hunner lesion interstitial cystitis and bladder pain syndrome (N-HL IC/BPS) and their respective treatment algorithms.

Methods/Results

A literature search was performed to identify articles and research on HL IC and N-HL IC/BPS including definitions, etiological theories, and treatments. This article is an overview of the existing literature. We also offer insight into how HL IC and N-HL IC/BPS are approached at our tertiary referral center. Additionally, American Urological Association guidelines have been integrated and newer treatment modalities and research will be introduced at the conclusion.

Conclusion

The AUA guidelines have mapped out a stepwise fashion to treat IC/BPS; at our institution we separate patients with HL IC from those with N-HL IC/BPS prior to them entering a treatment pathway. We identify the rarer patient with HL as having classic 'IC'; this cystoscopic finding is critical in guiding treatment. We believe HL IC is a distinct disease from N-HL IC/BPS and therapy should focus on the bladder. The vast majority of patients with N-HL IC/BPS need management of their pelvic floor muscles as the primary therapy, complemented by bladder-directed therapies as needed as well as a multidisciplinary team to manage a variety of other regional/systemic symptoms. Ongoing research into IC/BPS will help us better understand the pathophysiology and phenotypes of this complex disease while exciting and novel research studies are developing promising treatments.

RNA-seq of spinal cord from nerve-injured rats after spinal cord stimulation

Spinal cord stimulation has become an important modality in pain treatment especially for neuropathic pain conditions refractory to pharmacotherapy. However, the molecular control of inhibitory and excitatory mechanisms observed after spinal cord stimulation are poorly understood. Here, we used RNA-seq to identify differences in the expression of genes and gene networks in spinal cord tissue from nerve-injured rats with and without repetitive conventional spinal cord stimulation treatment. Five weeks after chronic constrictive injury to the left sciatic nerve, male and female rats were randomized to receive repetitive spinal cord stimulation or no treatment. Rats receiving spinal cord stimulation underwent epidural placement of a miniature stimulating electrode and received seven sessions of spinal cord stimulation (50 Hz, 80% motor threshold, 0.2 ms, constant current bipolar stimulation, 120 min/session) over four consecutive days. Within 2 h after the last spinal cord stimulation treatment, the L4-L6 spinal segments ipsilateral to the side of nerve injury were harvested and used to generate libraries for RNA-seq. Our RNA-seq data suggest further increases of many existing upregulated immune responses in chronic constrictive injury rats after repetitive spinal cord stimulation, including transcription of cell surface receptors and activation of non-neuronal cells. We also demonstrate that repetitive spinal cord stimulation represses transcription of several key synaptic signaling genes that encode scaffold proteins in the post-synaptic density. Our transcriptional studies suggest a potential relationship between specific genes and the therapeutic effects observed in patients undergoing conventional spinal cord stimulation after nerve injury. Furthermore, our results may help identify new therapeutic targets for improving the efficacy of conventional spinal cord stimulation and other chronic pain treatments.

Identification of novel non-invasive biomarkers of urinary chronic pelvic pain syndrome: findings from the Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network

OBJECTIVE

To examine a series of candidate markers for urological chronic pelvic pain syndrome (UCPPS), selected based on their proposed involvement in underlying biological processes so as to provide new insights into pathophysiology and suggest targets for expanded clinical and mechanistic studies.

METHODS

Baseline urine samples from Multidisciplinary Approach to the Study of Chronic Pelvic Pain (MAPP) Research Network study participants with UCPPS (n = 259), positive controls (PCs; chronic pain without pelvic pain, n = 107) and healthy controls (HCs, n = 125) were analysed for the presence of proteins that are suggested in the literature to be associated with UCPPS. Matrix metalloproteinase (MMP)-2, MMP-9, MMP-9/neutrophil gelatinase-associated lipocalin (NGAL) complex (also known as Lipocalin 2), vascular endothelial growth factor (VEGF), VEGF receptor 1 (VEGF-R1) and NGAL were assayed and quantitated using mono-specific enzyme-linked immunosorbent assays for each protein. Log-transformed concentration (pg/mL or ng/mL) and concentration normalized to total protein (pg/μg) values were compared among the UCPPS, PC and HC groups within sex using the Student's t-test, with P values adjusted for multiple comparisons. Multivariable logistic regression and receiver-operating characteristic curves assessed the utility of the biomarkers in distinguishing participants with UCPPS and control participants. Associations of protein with symptom severity were assessed by linear regression.

RESULTS

Significantly higher normalized concentrations (pg/μg) of VEGF, VEGF-R1 and MMP-9 in men and VEGF concentration (pg/mL) in women were associated with UCPPS vs HC. These proteins provided only marginal discrimination between UCPPS participants and HCs. In men with UCCPS, pain severity was significantly positively associated with concentrations of MMP-9 and MMP-9/NGAL complex, and urinary severity was significantly positively associated with MMP-9, MMP-9/NGAL complex and VEGF-R1. In women with UCPPS, pain and urinary symptom severity were associated with increased normalized concentrations of MMP-9/NGAL complex, while pain severity alone was associated with increased normalized concentrations of VEGF, and urinary severity alone was associated with increased normalized concentrations of MMP-2. Pain severity in women with UCPPS was significantly positively associated with concentrations of all biomarkers except NGAL, and urinary severity with all concentrations except VEGF-R1.

CONCLUSION

Altered levels of MMP-9, MMP-9/NGAL complex and VEGF-R1 in men, and all biomarkers in women, were associated with clinical symptoms of UCPPS. None of the evaluated candidate markers usefully discriminated UCPPS patients from controls. Elevated VEGF, MMP-9 and VEGF-R1 levels in men and VEGF levels in women may provide potential new insights into the pathophysiology of UCPPS.

Pharmacologic attenuation of cross-modal sensory augmentation within the chronic pain insula

Supplemental Digital Content is Available in the Text.

Sensitivity to visual stimuli is increased in patients with fibromyalgia and improved with administration of pregabalin.

Pain can be elicited through all mammalian sensory pathways yet cross-modal sensory integration, and its relationship to clinical pain, is largely unexplored. Centralized chronic pain conditions such as fibromyalgia are often associated with symptoms of multisensory hypersensitivity. In this study, female patients with fibromyalgia demonstrated cross-modal hypersensitivity to visual and pressure stimuli compared with age- and sex-matched healthy controls. Functional magnetic resonance imaging revealed that insular activity evoked by an aversive level of visual stimulation was associated with the intensity of fibromyalgia pain. Moreover, attenuation of this insular activity by the analgesic pregabalin was accompanied by concomitant reductions in clinical pain. A multivariate classification method using support vector machines (SVM) applied to visual-evoked brain activity distinguished patients with fibromyalgia from healthy controls with 82% accuracy. A separate SVM classification of treatment effects on visual-evoked activity reliably identified when patients were administered pregabalin as compared with placebo. Both SVM analyses identified significant weights within the insular cortex during aversive visual stimulation. These data suggest that abnormal integration of multisensory and pain pathways within the insula may represent a pathophysiological mechanism in some chronic pain conditions and that insular response to aversive visual stimulation may have utility as a marker for analgesic drug development.