Neuroimmune interactions at different intestinal sites are related to abdominal pain symptoms in children with IBS

Navigating through 65 years of insights: lessons learned on functional abdominal pain in children

In 1958, Apley and Naish authored a groundbreaking paper in Archives of Disease in Childhood, elucidating the epidemiology and risk factors of recurrent abdominal pain in children-a subject that had confounded clinicians of their time. Surprisingly, even after 65 years, there are several unanswered questions regarding the etiology, pathophysiology, and management of pediatric abdominal pain. Contrary to the prevailing notion that children naturally outgrow functional abdominal pain, compelling evidence suggests it's possible these children develop a number of clinically significant psychological issues that could profoundly impact their quality of life and, consequently, future health and educational outcomes. In this light, we aimed to comprehensively review the current literature to update the knowledge of practicing clinicians on functional abdominal pain, summarizing the evidence from the last 65 years.Conclusion: The enduring unanswered questions surrounding childhood abdominal pain continue to challenge clinicians, resulting in unnecessary investigations, thereby contributing to substantial healthcare expenditures. It is also evident that children with long-standing symptoms would progress to adulthood with the potential to develop irritable bowel syndrome and many psychological disturbances. Several key interventions using pharmacological agents, such as amitriptyline, showed that some of these drugs are no more effective than the placebo in clinical trials. Several research during the recent past suggest that psychological interventions such as gut-directed hypnotherapy alleviate symptoms and ensure better prognosis in the long run. Therefore, clinicians and researchers must join hands to explore the pathophysiological mechanisms underpinning functional abdominal pain and novel therapeutic strategies to ensure the well-being of these children. What is Known: • Functional abdominal pain disorders are common among children, with a worldwide prevalence of 13.5% of children suffering from at least one of these disorders • These disorders contribute to a significant reduction in the quality of life of affected children and their families and lead to an array of psychological problems What is New: • The biological basis of functional abdominal pain is becoming more explicit, including complex interactions between altered microbiome, deranged motility, and psychological dysfunction with gut-brain interactions • Novel approaches giving minimal emphasis on pharmacological interventions and exploring psychological interventions are showing promising results.

Palmitoylethanolamide and polydatin in pediatric irritable bowel syndrome: A multicentric randomized controlled trial

OBJECTIVE

This study aimed to evaluate the efficacy and safety of co-micronized palmitoylethanolamide (PEA)/polydatin (PD) in the treatment of abdominal pain symptoms in pediatric patients with irritable bowel syndrome (IBS).

METHODS

This was a multicenter trial conducted at three Italian pediatric gastroenterology centers, employing a double-blind, placebo-controlled, parallel-arm design. Participants were ages 10 to 17 y and met Rome IV criteria for pediatric IBS. They were randomly allocated to receive either co-micronized PEA/PD or placebo, administered three times daily in a 1:1 ratio, over a 12-wk period. The study assessed baseline severity using the IBS-Severity Scoring System (IBS-SSS) at enrollment and after 4, 8, and 12 wk of treatment. Abdominal pain frequency was assessed on a scale from 1 to 7 d/wk, while stool consistency was classified using the Bristol Stool Scale (BSS) to categorize various IBS subtypes. The primary outcome was the percentage of patients who achieved complete remission, defined as IBS-SSS score <75 points after 12 wk of therapy.

RESULTS

The study involved 70 children with IBS. Of the participants, 34 received co-micronized PEA/PD, and 36 received a placebo. As compared with the placebo group, the co-micronized therapy group had significantly more patients achieving complete remission after 12 wk (P = 0.015), with particular benefit in the IBS-diarrhea subtype (P = 0.01). The treatment group also experienced a significant reduction in abdominal pain intensity and frequency compared with the placebo group. No adverse events were recorded during the study period.

CONCLUSIONS

Co-micronized PEA/PD is a safe and effective treatment to treat abdominal pain symptoms in pediatric IBS.

Italian guidelines for the management of irritable bowel syndrome in children and adolescents : Joint Consensus from the Italian Societies of: Gastroenterology, Hepatology and Pediatric Nutrition (SIGENP), Pediatrics (SIP), Gastroenterology and Endoscopy (SIGE) and Neurogastroenterology and Motility (SINGEM)

The irritable bowel syndrome (IBS) is a functional gastrointestinal disorder (FGID), whose prevalence has widely increased in pediatric population during the past two decades. The exact pathophysiological mechanism underlying IBS is still uncertain, thus resulting in challenging diagnosis and management. Experts from 4 Italian Societies participated in a Delphi consensus, searching medical literature and voting process on 22 statements on both diagnosis and management of IBS in children. Recommendations and levels of evidence were evaluated according to the grading of recommendations, assessment, development, and evaluation (GRADE) criteria. Consensus was reached for all statements. These guidelines suggest a positive diagnostic strategy within a symptom-based approach, comprehensive of psychological comorbidities assessment, alarm signs and symptoms' exclusion, testing for celiac disease and, under specific circumstances, fecal calprotectin and C-reactive protein. Consensus also suggests to rule out constipation in case of therapeutic failure. Conversely, routine stool testing for enteric pathogens, testing for food allergy/intolerance or small intestinal bacterial overgrowth are not recommended. Colonoscopy is recommended only in patients with alarm features. Regarding treatment, the consensus strongly suggests a dietary approach, psychologically directed therapies and, in specific conditions, gut-brain neuromodulators, under specialist supervision. Conditional recommendation was provided for both probiotics and specific fibers supplementation. Polyethylene glycol achieved consensus recommendation for specific subtypes of IBS. Secretagogues and 5-HT4 agonists are not recommended in children with IBS-C. Certain complementary alternative therapies, antispasmodics and, in specific IBS subtypes, loperamide and rifaximin could be considered.

Mast Cell Disorders of the Gastrointestinal Tract: Clarity out of Chaos

Pathologists are increasingly asked to evaluate mast cell infiltrates in the gastrointestinal tract when there is clinical concern for systemic mastocytosis or a variety of functional disorders, including irritable bowel syndrome and mast cell activation syndrome. Neoplastic mast cells have established quantitative, morphologic, and immunohistochemical features that facilitate their identification in gastrointestinal mucosal biopsies. Specific qualitative and quantitative findings are lacking for inflammatory mast cell-mediated disorders. This review covers histopathologic features of mast cell disorders that affect the gastrointestinal tract and offers practical guidance for their assessment in mucosal biopsies.

Causal associations of 25-hydroxyvitamin D with functional gastrointestinal disorders: a two-sample Mendelian randomization study

BACKGROUND

Previous observational studies have shown associations between vitamin Ds and FGIDS[Including irritable bowel syndrome(IBS) and functional dyspepsia(FD)]. However, the association is controversial and the causality remains unknown. In this study, two-sample MR was cited to explore the causal effect on FGIDS caused by vitamin D level and serum 25-hydroxyvitamin D.

METHOD

The GWASs of vitaminD and 25-hydroxyvitamin D, with 57-99 strongly related SNPs were all obtained from UK biobank. The GWASs of IBS and FD were obtained from FinnGen biobank with respectively 187,028 and 194,071 participants involved. Fixed-effect inverse variance weighted regression was used to evaluate causal estimates. Other statistical methods such as MR Egger, weighted median estimation, maximum likelihood estimation and penalty-weighted median estimation are also used to verify the accuracy of the main results.

RESULTS

Measuring by the IVW method, our research indicated that no causal relationship was detected between vitamin D intake and Functional gastrointestinal disorders [IVW, OR(vitamin D-IBS) = 0.909, 95% CI 0.789-1.053, p = 0.2017); OR(vitamin D-FD) = 1.0662, 95% CI 0.9182-1.2380, p = 0.4000]. As for serum 25-hydroxyvitamin D, no causal relationship was detected on FD(IVW, OR(25-hydroxyvitamin D-FD) = 0.9635, 95% CI 0.8039-1.1546, p = 0.6869). Nevertheless, a negative causal relationship was revealed between 25-hydroxyvitamin D and IBS(IVW, OR(25-hydroxyvitamin D-IBS) = 0.832, 95% CI 0.696-0.995, p = 0.0436). Sensitive analysis supported the main findings but did not suggest bias due to pleiotropy.

CONCLUSIONS

Our Mendelian randomization analyses suggest a negative causal relationship between 25-hydroxyvitamin D and IBS. For each additional SD increase of genetically determined 25-hydroxyvitamin D levels, the risk of IBS decreased by 16.8%.

Impact of auricular percutaneous electrical nerve field stimulation on gut microbiome in adolescents with irritable bowel syndrome: A pilot study

OBJECTIVES

Percutaneous electrical nerve field stimulation (PENFS) has documented efficacy for irritable bowel syndrome (IBS) via plausible vagal neuromodulation effects. The vagus nerve may affect gut microbiome composition via brain-gut-microbiome signaling. We aimed to investigate gut microbiome alterations by PENFS therapy in adolescent IBS patients.

METHODS

A prospective study of females with IBS aged 11-18 years receiving PENFS therapy for 4 weeks with pre- and post-intervention stool sampling was conducted. Outcome surveys completed pre-therapy, weekly, and post-therapy included IBS-Severity Scoring System (IBS-SSS), Visceral Sensitivity Index (VSI), Functional Disability Inventory (FDI), and the global symptom response scale (SRS). Bacterial DNA was extracted from stool samples followed by 16S rRNA amplification and sequencing. QIIME 2 (version 2022.2) was used for analyses of α and β diversity and differential abundance by group.

RESULTS

Twenty females aged 15.6 ± 1.62 years were included. IBS-SSS, VSI, and FDI scores decreased significantly after PENFS therapy (P < 0.0001, P = 0.0003, P = 0.0004, respectively). No intra- or interindividual microbiome changes were noted pre- versus post-therapy or between responders and non-responders. When response was defined by 50-point IBS-SSS score reduction, α diversity was higher in responders compared with non-responders at week 4 (P = 0.033). There was higher abundance of Blautia in excellent responders versus non-responders.

CONCLUSIONS

There were no substantial microbial diversity alterations with PENFS. Subjects with excellent therapeutic response showed an enrichment of relative abundance of Blautia, which may indicate that patients with specific microbial signature have a more favorable response to PENFS.

Role of inflammation in pediatric irritable bowel syndrome

BACKGROUND

IBS affects a large number of children throughout the world and is thought to be the result of disturbed neuroimmune function along with the brain-gut axis. Although the underlying pathophysiologic mechanisms are not clear, the role of low-grade inflammation and mucosal immune activation in IBS symptom generation has become evident also in subsets of pediatric patients. Animal models provided meaningful insight in the causal relationship between abnormal mucosal immune activation and changes in gastrointestinal (GI) sensory-motor function. Likewise, the development of long-standing GI symptoms fulfilling the current criteria for functional GI disorders after infection gastroenteritis and in patients with IBD or celiac disease in remission further supports this hypothesis. Immune activation, its impact on gut sensory-motor function, and potential implications for symptom generation emerged in both children and adults with IBS.

PURPOSE

The aim of this review is to summarize the main evidence on the presence of low-grade inflammation and immune activation in children with IBS, its possible role in symptom generation, and its potential implication for new therapeutic strategies.

Mast cell presence in tendon sheaths of trigger fingers: implications on pathogenesis and clinical presentation

Trigger finger is a common hand disorder; however, its pathogenesis remains unknown. In this study, we aimed to investigate mast cells, fibroblast activators that synthesize collagen, in the tendon sheaths of trigger fingers. We investigated the presence of mast cells and their association with changes in the collagen content of the tendon sheath and clinical data. We performed a multicenter prospective study of 77 adult patients with trigger finger who had undergone resection of the first annular pulley between August 2012 and January 2020. The tendon sheath was immunostained with an anti-tryptase antibody to confirm mast cell presence. The percentage of collagen in the tendon sheath was determined by picrosirius red staining observed through a polarization microscope. The clinical data, including the duration from symptom onset to surgery, severity, pain numerical rating scale, and Hand20 scores, were evaluated. Tryptase-positive mast cells were recognized in 83.5% of all specimens. The mast cell presence group (Group P) had a significantly higher percentage of type-3 collagen in the tendon sheath than the non-mast cell presence group (Group N) (Group P, 15.6%; Group N, 12.7%; p = 0.03). Moreover, Group P had significantly higher pain numerical rating scale (Group P; 5, Group N; 3, p = 0.04) and Hand20 (Group P; 35.5, Group N; 13.0, p = 0.01) scores than Group N. These findings suggest that mast cell presence in the tendon sheath of the trigger finger is related to the pathology and clinical symptoms of trigger finger.

Identifying Mast Cells in Gastrointestinal Biopsies in Pediatric Irritable Bowel Patients

OBJECTIVES

Mast cells (MCs) have been proposed to be involved in the pathophysiology of irritable bowel syndrome (IBS). Nonetheless, the quantity and distribution of MCs in the gastrointestinal tract of pediatric patients with IBS are not well defined. This study aimed to compare the number of MCs in children with and without IBS and to establish histopathological reference values in pediatrics.

METHODS

Forty-nine participants with IBS were prospectively enrolled and classified into IBS with atopy (n = 29) and IBS without atopy (n = 20). As our retrospective control group, we selected 42 individuals with a history of polyposis syndrome or gastroesophageal reflux disease with normal histopathology. Retrospective selection of the control cohort was performed in a manner similar to previously published adult and pediatric studies. MCs were prospectively stained immunohistochemically on specimens from the stomach, duodenum, terminal ileum, and descending colon of both groups.

RESULTS

The IBS group showed significantly more MCs per high-power field (MCs/HPF) in the stomach, duodenum, terminal ileum, and descending colon ( P < 0.001), irrespective of their atopic status. Optimal MC cutoff values for IBS are ≥20.5 MCs/HPF in the stomach (area under the curve [AUC] = 0.84); ≥23.0 MCs/HPF in the duodenum (AUC = 0.79); ≥33.5 MCs/HPF in the terminal ileum (AUC = 0.82); and ≥22.5 MCs/HPF in the descending colon (AUC = 0.86).

CONCLUSIONS

Pediatric patients with IBS showed increased numbers of MCs in the stomach, duodenum, terminal ileum, and descending colon when compared with controls. Further trials are needed to explain the role of MCs in pediatric IBS, which might facilitate the development of targeted therapeutic interventions.

Mast cell mediation of visceral sensation and permeability in irritable bowel syndrome

Abnormalities of mast cell structure or function may play prominent roles in irritable bowel syndrome (IBS) symptom genesis. Mast cells show close apposition to sensory nerves and release bioactive substances in response to varied stimuli including infection, stress, and other neuroendocrine factors. Most studies focus on patients who develop IBS after enteric infection or who report diarrhea-predominant symptoms. Three topics underlying IBS pathogenesis have been emphasized in recent investigations. Visceral hypersensitivity to luminal stimulation is found in most IBS patients and may contribute to abdominal pain. Mast cell dysfunction also may disrupt epithelial barrier function which alters mucosal permeability potentially leading to altered bowel function and pain. Mast cell products including histamine, proteases, prostaglandins, and cytokines may participate in hypersensitivity and permeability defects, especially with diarrhea-predominant IBS. Recent experimental evidence indicates that the pronociceptive effects of histamine and proteases are mediated by the generation of prostaglandins in the mast cell. Enteric microbiome interactions including increased mucosal bacterial translocation may activate mast cells to elicit inflammatory responses underlying some of these pathogenic effects. Therapies to alter mast cell activity (mast cell stabilizers) or function (histamine antagonists) have shown modest benefits in IBS. Future investigations will seek to define patient subsets with greater potential to respond to therapies that address visceral hypersensitivity, epithelial permeability defects, and microbiome alterations secondary to mast cell dysfunction in IBS.

Brain to Belly: Abdominal Variants of Migraine and Functional Abdominal Pain Disorders Associated With Migraine

Migraine is one of the most frequent causes of primary headache and 9% of children suffer from migraines. Most children will continue to experience migraine attacks as adults, therefore it is imperative that we have a thorough understanding of this major health issue. This article considers the so-called abdominal variants of migraine, which are more commonly seen in children rather than adults: abdominal migraine, cyclic vomiting syndrome, and infantile colic. Other functional abdominal pain disorders such as irritable bowel syndrome and functional dyspepsia have also been linked to migraine in clinical studies. The common pathophysiological root of these diseases seems to be the gut-brain axis mechanism. Abdominal variants of migraine are considered pediatric precursors of migraine whereas the functional abdominal pain disorders related to migraine seem to share a pathophysiological root with no temporarily link as for today. In this review we aim to describe the epidemiological background, the current pathophysiological theories and the relationship of each disease to migraine. This review is the first to compile abdominal variants of migraine and functional abdominal pain disorders associated with migraine and we endeavor to elucidate the broad spectrum of migraine-related episodes in children.

Activation of the Innate Immune System in Children With Irritable Bowel Syndrome Evidenced by Increased Fecal Human β-Defensin-2

BACKGROUND & AIMS

The role of the innate immune system in functional gastrointestinal pain disorders is unclear. We investigated the role of β-defensin-2 and gut permeability in childhood irritable bowel syndrome (IBS) and functional abdominal pain (FAP) symptom generation.

METHODS

Fecal β-defensin-2 (and in a subset, gut permeability) was measured in children with IBS (n = 116), FAP (n = 33), and healthy control (HC) children (n = 72). IBS and FAP patients were recruited from tertiary and primary care, and HCs were recruited from primary care.

RESULTS

β-defensin-2 concentration was greater in children with IBS (P = .003) and FAP (P = .03) than in HCs. β-defensin-2 was greater in girls with IBS than female HCs (P = .007) and in girls with IBS vs boys with IBS (P = .036). There was no difference by sex in the FAP and HC groups. For the entire cohort, β-defensin-2 correlated with multiple pain symptoms. In the IBS group, β-defensin-2 correlated with pain interference (P = .014). No correlation with pain was found in the FAP or HC group. Gut permeability was greater in the IBS vs the FAP and HC groups (P = .038). For the entire cohort, permeability correlated with the number of pain episodes (P = .041) and interfering pain episodes (P = .049). For the entire cohort there was a correlation between β-defensin-2 and permeability (P = .003), with borderline correlation in the IBS group (P = .086). For the cohort and IBS and HC groups, the number of bowel movements was modestly inversely related to fecal β-defensin-2 concentrations.

CONCLUSIONS

Increased fecal β-defensin-2 concentration in children with IBS suggests activation of the innate immune system in some, which, along with increased gut permeability, appears related to abdominal pain symptoms. Sex is an important variable in interpreting β-defensin-2 concentration in children with IBS.

A Survey of Methodologies for Assessing Mast Cell Density and Activation in Patients with Functional Abdominal Pain Disorders

The aim was to assess methods utilized in assessing mast cell involvement in functional abdominal pain disorders (FAPDs), specifically to describe variability in methods utilized to assess both mast cell density and activation and determine if a consensus exists. After a literature search identified 70 manuscripts assessing mast cell density, data were extracted including FAPD diagnosis, site of biopsy, selection of microscopic fields analyzed, selection of mucosal region analyzed, method of mast cell identification, method to assess mast cell density, and if performed, method to assess mast cell activation. There appears to be some consensus favoring inmmunohistochemical stains over histochemical stains for identifying mast cells. Otherwise, considerable variability exists in methodology for assessing mast cell density and activation. Regardless of method, approximately 80% of studies found increased mast cell density and/or activation in comparison to controls with no method being superior. A wide variety of methods have been employed to assess mast cell density and activation with no well-established consensus and inadequate data to recommend specific approaches. The current methodology providing physiologic information needs to be translated to a standard methodology providing clinical information with the development of criteria establishing abnormal density and/or activation, and more importantly, predicting treatment response.

Allergy-related diseases in childhood and risk for abdominal pain-related functional gastrointestinal disorders at 16 years-a birth cohort study

BACKGROUND

Studies on allergy-related diseases in relation to abdominal pain-related functional gastrointestinal disorders (AP-FGIDs) in children are few and results are contradictory. We examined the associations between childhood allergy-related diseases and adolescent AP-FGIDs in general and irritable bowel syndrome (IBS) in particular.

METHOD

Prospective population-based birth cohort study of 4089 children born in Sweden 1994-1996. We analysed data from 2949 children with complete follow-up at 16 years (y) and no diagnosis of inflammatory bowel disease or coeliac disease at 12y or 16y. Asthma, rhinitis, eczema, and food hypersensitivity (FH) were assessed through questionnaires at 1-2y, 4y, 8y, 12y, and 16y. AP-FGIDs and IBS were assessed through questionnaires at 16y and defined according to the Rome III criteria. Associations between childhood allergy-related diseases and any AP-FGID and IBS and 16y respectively were examined using binomial generalized linear models with a log link function and described as relative risk with 95% confidence intervals.

RESULTS

The prevalence of any AP-FGID and IBS at 16y were 12.0% and 6.0% respectively. Eczema at 1-2y, 4y, and 8y, and FH at 12y and 16y were associated with an increased risk for any AP-FGID at 16y. Asthma and FH at 12y and 16y were associated with an increased risk for IBS at 16y. The relative risk for IBS at 16y increased with increasing number of concurrent allergy-related diseases at 16y, but linear trend for relative risk was only borderline statistically significant (P for trend = 0.05).

CONCLUSIONS

This prospective population-based study demonstrated positive associations between childhood allergy-related diseases and adolescent AP-FGIDs, including IBS, implicating shared pathophysiology among these disorders.

Involvement of Mast Cells in the Pathophysiology of Pain

Mast cells (MCs) are immune cells and are widely distributed throughout the body. MCs are not only classically viewed as effector cells of some allergic diseases but also participate in host defense, innate and acquired immunity, homeostatic responses, and immunoregulation. Mounting evidence indicates that activation of MCs releasing numerous vasoactive and inflammatory mediators has effects on the nervous system and has been involved in different pain conditions. Here, we review the latest advances made about the implication of MCs in pain. Possible cellular and molecular mechanisms regarding the crosstalk between MC and the nervous system in the initiation and maintenance of pain are also discussed.

Differential mRNA Expression in Ileal Mucosal Biopsies of Patients With Diarrhea- or Constipation-Predominant Irritable Bowel Syndrome

INTRODUCTION

Previous studies in patients with irritable bowel syndrome (IBS) showed immune activation, secretion, and barrier dysfunction in duodenal, jejunal, or colorectal mucosa. This study aimed to measure ileal mucosal expression of genes and proteins associated with mucosal functions.

METHODS

We measured by reverse transcription polymerase chain reaction messenger RNA (mRNA) expression of 78 genes (reflecting tight junction proteins, chemokines, innate immunity, ion channels, and transmitters) and 5 proteins (barrier, bile acid receptor, and ion exchanger) in terminal ileal mucosa from 11 patients with IBS-diarrhea (IBS-D), 17 patients with IBS-constipation (IBS-C), and 14 healthy controls. Fold changes in mRNA were calculated using 2(-Δ, ΔCT) formula. Group differences were measured using analysis of variance. Protein ratios relative to healthy controls were based on Western blot analysis. Nominal P values (P < 0.05) are reported.

RESULTS

In ileal mucosal biopsies, significant differences of mRNA expression in IBS-D relative to IBS-C were upregulation of barrier proteins (TJP1, FN1, CLDN1, and CLDN12), repair function (TFF1), and cellular functions. In ileal mucosal biopsies, mRNA expression in IBS-C relative to healthy controls was reduced GPBAR1 receptor, myosin light chain kinase (MYLK in barrier function), and innate immunity (TLR3), but increased mRNA expression of cadherin cell adhesion mechanisms (CTNNB1) and transport genes SLC9A1 (Na-H exchanger [NHE1]) and INADL (indirect effect on ion transport).

DISCUSSION

These data support a role of ileal mucosal dysfunction in IBS, including barrier dysfunction in IBS-D and alterations in absorption/secretion mechanisms in IBS-C.

The Use of Fecal Calprotectin Testing in Paediatric Disorders: A Position Paper of the European Society for Paediatric Gastroenterology and Nutrition Gastroenterology Committee

OBJECTIVES

The aim of the study was to review the evidence regarding the clinical use and value of fecal calprotectin (FC) measurements in different gastrointestinal disorders in children.

METHODS

A literature search was conducted in the PubMed, MEDLINE, EMBASE, and Cochrane databases until October 31, 2019. Subtopics were identified and each assigned to individual authors.

RESULTS

A total of 28 recommendations were voted on using the nominal voting technique. Recommendations are given related to sampling, measurement methods, and results interpretation. The 14 authors anonymously voted on each recommendation using a 9-point scale (1 strongly disagree to 9 fully agree). Consensus was considered achieved if at least 75% of the authors voted 6, 7, 8, or 9.

CONCLUSIONS

Consensus was reached for all recommendations. Limitations for the use of FC in clinical practice include variability in extraction methodology, performance of test kits as well as the need to establish local reference ranges because of the influence of individual factors, such as age, diet, microbiota, and drugs. The main utility of FC measurement at present is in the diagnosis and monitoring of inflammatory bowel disease (IBD) as well as to differentiate it from functional gastrointestinal disorders (FAPDs). FC, however, has neither utility in the diagnosis of infantile colic nor to differentiate between functional and organic constipation. A rise in FC concentration, may alert to the risk of developing necrotizing enterocolitis and help identifying gastrointestinal involvement in children with Henoch-Schönlein purpura. FC measurement is of little value in Cow's Milk Protein Allergy, coeliac disease (CD), and cystic fibrosis. FC does neither help to distinguish bacterial from viral acute gastroenteritis (AGE), nor to diagnose Helicobacter Pylori infection, small intestinal bacterial overgrowth (SIBO), acute appendicitis (AA), or intestinal polyps.

The role of intestinal mast cell infiltration in irritable bowel syndrome

As an essential part of the immune system, mast cells (MCs) play an important role in the pathogenesis of irritable bowel syndrome (IBS). Accumulating evidence has identified altered MC count and density in intestinal mucosa of patients with IBS; however, conflicting findings yield inconsistent conclusions. Currently, most studies have suggested intestinal MC infiltration in IBS patients. Considering the pivotal role of MCs in IBS, it is necessary to achieve a better understanding about the pathological changes in the intestine. The risk factors for IBS, including dietary habits, psychological factors, infection, and dysbiosis, are implicated to induce intestinal MC infiltration. Mechanistically, food may trigger immune-related allergic reactions and affect the intestinal microbiota activity. Some exogenous pathogens and altered profile of commensal bacteria promote intestinal MC recruitment through promoted release of chemokines from epithelial cells or direct activation of the immune system. In addition, psychological factors may affect the microenvironment where MCs live. MCs have been proven to interact with the enteric neurons and other immunocytes, evidenced by the close proximity of MCs to neurons and regional altered immune system components. A variety of mediators released by the enteric neurons, immunocytes, and MCs per se, such as neurotrophins, neuropeptides, cytokines, and chemokines, may have stimulant effects on MCs by modulating the survival, proliferation, and recruitment process of MCs in the intestine. In this review, the associations between IBS and intestinal MC density and the underlying mechanisms are discussed.

Scientific Evidence for the Treatment of Children with Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most common functional gastro-intestinal disorders which significantly impacts the quality of life of affected children. Abdominal pain improved by defecation, associated with a change in stool form and frequency, represents its specific clinical marker. Even if a number of potential patho-physiological mechanisms have been described, the exact underlying etiology of IBS is so far unclear. Likewise, no optimal treatment has ever been found neither for adult nor for pediatric patients. Current therapeutic options include drugs, dietary interventions and biopsychosocial therapies. The present review aims at evaluating the scientific evidence supporting the efficacy of these treatments for children with IBS.

Paediatric functional abdominal pain disorders

Paediatric functional abdominal pain disorders, currently referred to as disorders of gut-brain interaction, comprise irritable bowel syndrome, functional dyspepsia, abdominal migraine and functional abdominal pain not otherwise specified, as defined by the Rome IV diagnostic criteria. Functional abdominal pain disorders are common disorders with a prevalence of 3-16% depending on country, age and sex. A greater understanding of aetiopathogenesis and pathophysiology is emerging and includes intestinal components (inflammation, motility and the microbiota), central factors (psychological aspects, sensitization and/or differences in connectivity or activity of certain brain regions) as well as extrinsic factors (infections). In particular, the timing of disruption of the microbiota-gut-brain axis seems to be important. Diagnosis is challenging but is primarily based on clinical symptoms and exclusion of other organic causes, with an emphasis on avoiding unnecessary invasive diagnostic procedures. The available pharmacological interventions are limited in children and, therefore, management has focused on combined approaches, including mind-targeted interventions (hypnotherapy and cognitive behavioural therapy), diet (probiotics) and percutaneous electrical nerve field stimulation. The evidence for their clinical efficacy, although limited, is favourable, with positive impacts on symptoms and overall quality of life. The coming decades hold promise for improved understanding and management of these enigmatic disorders.

The relationship between mucosal inflammatory cells, specific symptoms, and psychological functioning in youth with irritable bowel syndrome

Both mucosal inflammation and psychologic dysfunction have been implicated in irritable bowel syndrome (IBS). While some relationships between inflammation (mast cells and eosinophils) and depression have been reported in adults with IBS, relationships between inflammation and psychologic function have not been studied in children and adolescents. The aims of the current study were to: (1) assess densities of colonic mast cells, eosinophils, and TH17 cells in youth with IBS; and, (2) explore relationships between these cells and specific IBS symptoms and psychologic functioning. Utilizing previously obtained biopsies from the descending and rectosigmoid colons, densities were determined for mast cells, eosinophils, and TH17 cells, respectively, in 37 youth with IBS and 10 controls. In IBS patients, densities were assessed in relation to specific IBS symptoms and in relation to self-report anxiety and depression scores. In both the descending and rectosigmoid colons, densities of mast cells, eosinophils, and TH17 cells were higher in IBS patients as compared to controls. In IBS patients, rectosigmoid mast cell density was higher in those reporting pain relief with defecation. Also, in IBS patients, rectosigmoid eosinophilia was associated with higher anxiety scores and eosinophil density correlated with depression scores. In the descending colon, eosinophil and mast cell densities both correlated with depression scores. In conclusion, mucosal inflammation (mast cells and eosinophils) is associated with pain relief with defecation and with anxiety and depression in youth with IBS.

Mast cells are increased in the small intestinal mucosa of patients with irritable bowel syndrome: A systematic review and meta-analysis

BACKGROUND

Colonic mast cells have been proposed to be related to the pathophysiology of irritable bowel syndrome (IBS). Whether mast cell counts are altered in the small intestine, a less-explored region in patients with IBS is not completely clear.

METHODS

PubMed and EMBASE were searched for case-control studies on mast cell count/density in the small intestine of patients with IBS vs controls through February 2019. Mast cell counts were separately analyzed in the duodenum, jejunum, and ileum. Data were pooled using the standardized mean difference (SMD) method. When zero was not within the 95% confidence interval (CI), the SMD was considered significant.

KEY RESULTS

Data from 344 patients with IBS and 229 healthy controls from three studies in the duodenum, six in the jejunum, and five in the ileum were pooled in this meta-analysis. The number of mast cells was significantly higher in the ileum (SMD: 1.78 [95% CI: 0.89, 2.66]) of patients with IBS. Mast cell counts were not significantly different in the duodenum (SMD: 0.81 [-0.06, 1.67]) or the jejunum (SMD: 0.58 [-0.03, 1.19]) of patients with IBS vs healthy controls.

CONCLUSIONS AND INFERENCES

Mast cells are increased in the small intestine of IBS vs controls, mainly in the ileum. Future studies should address whether such findings are IBS subtype or gender-dependent. Methodological variations, single-center bias, and the limited number of studies included in this meta-analysis may affect the final results.

Is fecal calprotectin always normal in children with irritable bowel syndrome?

Background/Aims

Fecal calprotectin (FC) is a marker of intraluminal intestinal inflammation. Intestinal inflammation may contribute to the pathophysiology of irritable bowel syndrome (IBS). This study evaluated FC levels in children with IBS and differences in FC levels in children stratified by IBS subtype and healthy controls (HCs).

Methods

A total of 157 children with IBS and 56 HCs aged 4–16 years (119 boys, 94 girls, mean age of 9.48 years) were included in this prospective study. Children with IBS were diagnosed using the Rome III criteria and classified into 4 subtypes: IBS with constipation (IBS-C, n=37), IBS with diarrhea (IBS-D, n=54), IBS with alternating constipation and diarrhea (IBS-M, n=49), and IBS unsubtyped (IBS-U, n=17); postinfectious IBS (PI-IBS) was also considered. The FC concentration in stool samples was analyzed using an enzyme-linked immunosorbent assay. All participants answered a questionnaire regarding several demographic and clinical characteristics.

Results

Children with IBS had significantly higher levels of FC than the HCs (88.71 μg/g vs. 17.77 μg/g). Among the 4 IBS subtypes, the FC concentration was highest in children with IBS-D, followed by those with IBS-M, IBS-C, and IBS-U (169.94 μg/g vs. 45.04, 31.22, and 33.52 μg/g, respectively), and these differences were statistically significant. For PI-IBS, 90% of cases were in the IBS-D group.

Conclusions

The FC level was significantly higher in children with IBS than in HCs and differed depending on the IBS subtype, supporting the notion that IBS is a type of low-grade bowel inflammation.

Secretion of Mast Cell Inflammatory Mediators Is Enhanced by CADM1-Dependent Adhesion to Sensory Neurons

Neuroimmune interactions are important in the pathophysiology of many chronic inflammatory diseases, particularly those associated with alterations in sensory processing and pain. Mast cells and sensory neuron nerve endings are found in areas of the body exposed to the external environment, both are specialized to sense potential damage by injury or pathogens and signal to the immune system and nervous system, respectively, to elicit protective responses. Cell adhesion molecule 1 (CADM1), also known as SynCAM1, has previously been identified as an adhesion molecule which may couple mast cells to sensory neurons however, whether this molecule exerts a functional as well as structural role in neuroimmune cross-talk is unknown. Here we show, using a newly developed in vitro co-culture system consisting of murine bone marrow derived mast cells (BMMC) and adult sensory neurons isolated from dorsal root ganglions (DRG), that CADM1 is expressed in mast cells and adult sensory neurons and mediates strong adhesion between the two cell types. Non-neuronal cells in the DRG cultures did not express CADM1, and mast cells did not adhere to them. The interaction of BMMCs with sensory neurons was found to induce mast cell degranulation and IL-6 secretion and to enhance responses to antigen stimulation and activation of FcεRI receptors. Secretion of TNFα in contrast was not affected, nor was secretion evoked by compound 48/80. Co-cultures of BMMCs with HEK 293 cells, which also express CADM1, while also leading to adhesion did not replicate the effects of sensory neurons on mast cells, indicative of a neuron-specific interaction. Application of a CADM1 blocking peptide or knockdown of CADM1 in BMMCs significantly decreased BMMC attachment to sensory neurites and abolished the enhanced secretory responses of mast cells. In conclusion, CADM1 is necessary and sufficient to drive mast cell-sensory neuron adhesion and promote the development of a microenvironment in which neurons enhance mast cell responsiveness to antigen, this interaction could explain why the incidence of painful neuroinflammatory disorders such as irritable bowel syndrome (IBS) are increased in atopic patients.

The role of mast cells in pediatric gastrointestinal disease

Mast cells are granulocytes derived from CD34+ pluripotent progenitor cells that demonstrate plasticity in their development, leaving the bone marrow and differentiating in the tissue where they ultimately reside. They are best known for their role in the allergic response, but also play a prominent immunoregulatory role in other processes, including immune tolerance, the innate immune response, angiogenesis, wound healing and tissue remodeling. Mast cells are found throughout the gastrointestinal tract; their metabolic products influence and regulate intestinal epithelial and endothelial function, gastrointestinal secretion, intestinal motility and absorption, and contribute to host defense. They also play an important role in the development of visceral hypersensitivity through bidirectional interaction with the enteric nervous system. Mast cells have been found to have an increasingly important role in the pathophysiology of a number of pediatric gastrointestinal diseases. This review summarizes the current understanding of the role that mast cells play in the development of pediatric gastrointestinal disorders, including eosinophilic esophagitis, functional dyspepsia, irritable bowel syndrome, celiac disease, inflammatory bowel disease, histologically negative appendicitis, Hirschsprung’s disease, intestinal neuronal dysplasia, and food protein-induced enterocolitis syndrome.

Evidence of increased fecal granins in children with irritable bowel syndrome and correlates with symptoms

BACKGROUND

Granins have been implicated in the pathophysiology of irritable bowel syndrome (IBS) in adults. We sought to determine whether fecal granins are altered in children with IBS and associated with symptoms.

METHODS

Children (7-12 years of age) with IBS and healthy controls (HC) kept daily pain and stool diaries for 2 weeks. Stool samples were analyzed for chromogranins A and B (CgA, CgB) and secretogranins II and III (SgII, SgIII). Children also completed psychological measures to assess anxiety, depression, somatization, and internalizing symptoms.

KEY RESULTS

Fecal CgB and SgIII concentrations were higher in all the boys (IBS plus HC, n = 48) than in all the girls (IBS plus HC, n = 75) (P = 0.02 and P = 0.046, respectively). CgA and SgIII were greater in children with IBS (n = 52) vs HC (n = 69) (P = 0.01, P = 0.017, respectively). CgB and SgII did not differ between groups. In children with IBS, the number of pain episodes per week and mean daily pain rating correlated positively with all four granins. The number of stools per day correlated positively with CgB and SgII, and the percent of diarrheal stools (6 or 7 on the Bristol Scale) correlated inversely with all four granins in boys but not in girls. Fecal granins did not correlate with psychological measures.

CONCLUSIONS AND INFERENCES

As measured by fecal granins, there is evidence of neuroimmune activation in children with IBS. Granins are related to abdominal pain symptoms, stooling frequency, and stool form in children with IBS. Sex influences the fecal concentration of CgB and SgIII.

Update on Dietary Management of Childhood Functional Abdominal Pain Disorders

Diet plays a significant role for children with functional abdominal pain disorders. A large majority of these children identify at least 1 food that exacerbates their symptoms. Malabsorbed carbohydrates may have both direct and microbiome-mediated physiologic effects. There are several factors associated with carbohydrate symptom generation, including (1) the amount ingested, (2) ingestion with a meal, (3) small intestinal enzymatic activity, (4) consuming the carbohydrate with microorganisms capable of breaking down the carbohydrate, (5) the gut microbiome, and (6) host factors. Therapies include carbohydrate (single and/or comprehensive) restriction, selective prebiotic and/or enzyme supplementation. Fiber supplementation may also be beneficial.

Pharmacokinetic drug evaluation of rifaximin for treatment of diarrhea-predominant irritable bowel syndrome

INTRODUCTION

Rifaximin is a poorly absorbable antibiotic with a broad-spectrum activity against both Gram-negative and -positive bacteria. It is active in the small intestine due to its high bile solubility, whereas in the aqueous environment of the colon, it shows limited efficacy against highly susceptible bacteria. These unique pharmacokinetic properties limit its systemic effects and can correct gut microflora imbalances. Thus, rifaximin has become a major therapeutic agent in several gastrointestinal diseases in which an imbalance in gut microflora may play a role, including diarrhea predominant irritable bowel syndrome (IBS-D). Area covered: This is an up-to-date review focusing on the efficacy of rifaximin in the treatment of IBS-D in both adult and pediatric populations. We will review the pharmacokinetic properties of rifaximin, including its absorption in health and disease, mechanisms of action, and interactions with other drugs. Expert opinion: Given its safety profile and its negligible absorption, rifaximin is a suitable treatment for IBS-D, in both adults and children. The possibility of modulating gut microbiota composition without side effects has made this drug an appealing therapeutic agent in highly prevalent gastrointestinal diseases. However, to date, monitoring for the development of resistant bacterial strains during long-term rifaximin use is still lacking.

Mast cell-nerve interaction in the colon of Trypanosoma cruzi-infected individuals with chagasic megacolon

Chagas disease is an infection caused by the parasite Trypanosoma cruzi that affects millions of people worldwide and is endemic in Latin America. Megacolon is the most frequent complication of the digestive chronic form and happens due to lesions of the enteric nervous system. The neuronal lesions seem to initiate in the acute phase and persist during the chronic phase, albeit the mechanisms involved in this process are still debated. Among the cells of the immune system possibly involved in this pathological process is the mast cell (MC) due to its well-known role in the bi-directional communication between the immune and nervous systems. Using ultrastructural analysis, we found an increased number of degranulated MCs in close proximity to nerve fibers in infected patients when compared with uninfected controls. We also immunostained MCs for the two pro-inflammatory molecules tryptase and chymase, the first being also important in neuronal death. The number of MCs immunostained for tryptase or chymase was increased in patients with megacolon, whereas increased tryptase staining was additionally observed in patients without megacolon. Moreover, we detected the expression of the tryptase receptor PAR2 in neurons of the enteric nervous system, which correlated to the tryptase staining results. Altogether, the data presented herein point to the participation of MCs on the denervation process that occurs in the development of T. cruzi-induced megacolon.

Colonic immune cells in irritable bowel syndrome: A systematic review and meta-analysis

BACKGROUND & AIMS

Increases in mucosal immune cells have frequently been observed in irritable bowel syndrome (IBS) patients. However, this finding is not completely consistent between studies, possibly due to a combination of methodological variability, population differences and small sample sizes. We performed a meta-analysis of case-control studies that compared immune cell counts in colonic biopsies of IBS patients and controls.

METHODS

PubMed and Embase were searched in February 2017. Results were pooled using standardized mean difference (SMD) and were considered significant when zero was not within the 95% confidence interval (CI). Heterogeneity was assessed based on I² statistics where I²  ≤ 50% and I²  > 50% indicated fixed and random effect models, respectively.

KEY RESULTS

Twenty-two studies on 706 IBS patients and 401 controls were included. Mast cells were increased in the rectosigmoid (SMD: 0.38 [95% CI: 0.06-0.71]; P = .02) and descending colon (SMD: 1.69 [95% CI: 0.65-2.73]; P = .001) of IBS patients. Increased mast cells were observed in both constipation (IBS-C) and diarrhea predominant IBS (IBS-D). CD3⁺ T cells were increased in the rectosigmoid (SMD: 0.53 [95% CI: 0.21-0.85]; P = .001) and the descending colon of the IBS patients (SMD: 0.79, 95% CI [0.28-1.30]; P = .002). This was possibly in relation to higher CD4⁺ T cells in IBS (SMD: 0.33 [95% CI: 0.01-0.65]; P = .04) as there were no differences in CD8⁺ T cells.

CONCLUSIONS & INFERENCES

Mast cells and CD3⁺ T cells are increased in colonic biopsies of patients with IBS vs non-inflamed controls. These changes are segmental and sometimes IBS-subtype dependent. The diagnostic value of the quantification of colonic mucosal cells in IBS requires further investigation.

Effect of combined consumption of Lactobacillus brevis KB290 and β-carotene on minor diarrhoea-predominant irritable bowel syndrome-like symptoms in healthy subjects: a randomised, double-blind, placebo-controlled, parallel-group trial

People with non-pathological diarrhoea-predominant irritable bowel syndrome (IBS-D)-like symptoms are present at a significant level even in healthy populations, but established prophylaxis is lacking. Previously, we have found that co-administration of Lactobacillus brevis KB290 (KB290) and β-carotene (βC) attenuated murine colitis (potential cause of IBS-D-like symptoms) significantly. Here, we investigated the effect of KB290 and βC on minor IBS-D-like symptoms in healthy volunteers. After a 4-week run-in period, subjects received a KB290 + βC or placebo capsule for 12 weeks, followed by a 4-week washout period. The KB290 + βC group showed a significant improvement in intensity of abdominal pain and stool frequency compared with the placebo group. The KB290 + βC group showed a significantly higher serum concentration of anti-inflammatory cytokine, interleukin-10, compared with the placebo group. In conclusion, we demonstrated that consumption of KB290 + βC improves minor IBS-D-like symptoms and inflammatory status in healthy volunteers. (UMIN000018002).

Gender Differences in Serotonin Signaling in Patients with Diarrhea-predominant Irritable Bowel Syndrome

Objective Gender differences, including differences in the prevalence, subtypes and the effectiveness of treatment, are generally recognized in irritable bowel syndrome (IBS). Although serotonin type 3 receptor (5-HT3R) antagonists appear to be more effective in women with diarrhea predominant IBS (IBS-D) than they are in men, the mechanisms underlying these effects remain unclear. The aim of the present was to investigate the gender differences in 5-HT signaling. Methods The subjects were selected from outpatients with IBS-D and healthy controls. Their rectal mucosal S100A, tryptophan hydroxylase (TPH) and 5-HT transporter (5-HTT, SERT, SLC6A4) mRNA expression levels were measured. Clinical symptoms were evaluated using the gastrointestinal symptom rating scale (GSRS) and the self-rating depression scale (SDS). Results The study population of 100 subjects included 47 IBS-D patients and 53 age- and gender-matched healthy controls. The S100A9 (5.20 vs. 1.90, p=0.001) and SLC6A4 (2.00 vs. 1.00, p=0.019) mRNA levels in the rectal mucosa of women with IBS-D were significantly higher than those in men. Among the healthy controls, the S100A10 expression levels in men were higher than those in women (1.33 vs. 0.82, p=0.005). The S100A8 and S100A10 expression levels in women with IBS-D were positively correlated with their diarrhea scores (r=0.55 and 0.58, p<0.05). Conclusion 5-HT signaling might be a major contributor to the symptoms of IBS in men, and the differences may be associated with the effectiveness of 5-HT3R antagonists.

The Role of Mast Cells in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, but its treatment is unsatisfactory as its pathophysiology is multifactorial. The putative factors of IBS pathophysiology are visceral hypersensitivity and intestinal dysmotility, also including psychological factors, dysregulated gut-brain axis, intestinal microbiota alterations, impaired intestinal permeability, and mucosal immune alterations. Recently, mucosal immune alterations have received much attention with the role of mast cells in IBS. Mast cells are abundant in the intestines and function as intestinal gatekeepers at the interface between the luminal environment in the intestine and the internal milieu under the intestinal epithelium. As a gatekeeper at the interface, mast cells communicate with the adjacent cells such as epithelial, neuronal, and other immune cells throughout the mediators released when they themselves are activated. Many studies have suggested that mast cells play a role in the pathophysiology of IBS. This review will focus on studies of the role of mast cell in IBS and the limitations of studies and will also consider future directions.

Underlying molecular and cellular mechanisms in childhood irritable bowel syndrome

Irritable bowel syndrome (IBS) affects a large number of children throughout the world. The symptom expression of IBS is heterogeneous, and several factors which may be interrelated within the IBS biopsychosocial model play a role. These factors include visceral hyperalgesia, intestinal permeability, gut microbiota, psychosocial distress, gut inflammation, bile acids, food intolerance, colonic bacterial fermentation, and genetics. The molecular and cellular mechanisms of these factors are being actively investigated. In this mini-review, we present updates of these mechanisms and, where possible, relate the findings to childhood IBS. Mechanistic elucidation may lead to the identification of biomarkers as well as personalized childhood IBS therapies.

Early life adversity in piglets induces long-term upregulation of the enteric cholinergic nervous system and heightened, sex-specific secretomotor neuron responses

BACKGROUND

Early life adversity (ELA) is a risk factor for the later-life onset of gastrointestinal (GI) diseases such as irritable bowel syndrome (IBS); however, the mechanisms are poorly understood. Here, we utilized a porcine model of ELA, early weaning stress (EWS), to investigate the influence of ELA on the development and function of the enteric nervous system (ENS).

METHODS

Female and castrated male (Male-C) piglets were weaned from their sow either at 15 days of age (EWS) or 28 days of age (late weaning control, LWC). At 60 and 170 days of age, ileal mucosa-submucosa preparations were mounted in Ussing chambers and veratridine- and corticotropin releasing factor (CRF)-releasing factor-evoked short circuit current (Isc ) responses were recorded as indices of secretomotor neuron function. Enteric neuron numbers and the expression of select neurotransmitters and their receptors were also measured.

KEY RESULTS

Compared with LWC pigs, female, but not Male-C EWS, pigs exhibited heightened veratridine-induced Isc responses at 60 and 170 days of age that were inhibited with tetrodotoxin and atropine. Ileum from EWS pigs had higher numbers of enteric neurons that were choline acetyltransferase positive. Markers of increased cholinergic signaling (increased acetylcholinesterase) and downregulated mucosal muscarinic receptor 3 gene expression were also observed in EWS pigs.

CONCLUSIONS & INFERENCES

This study demonstrated that EWS in pigs induces lasting and sex-specific hypersensitivity of secretomotor neuron function and upregulation of the cholinergic ENS. These findings may represent a mechanistic link between ELA and lifelong susceptibility to GI diseases such as IBS.

Mast cell activation disease and the modern epidemic of chronic inflammatory disease

A large and growing portion of the human population, especially in developed countries, suffers 1 or more chronic, often quite burdensome ailments which either are overtly inflammatory in nature or are suspected to be of inflammatory origin, but for which investigations to date have failed to identify specific causes, let alone unifying mechanisms underlying the multiple such ailments that often afflict such patients. Relatively recently described as a non-neoplastic cousin of the rare hematologic disease mastocytosis, mast cell (MC) activation syndrome-suspected to be of greatly heterogeneous, complex acquired clonality in many cases-is a potential underlying/unifying explanation for a diverse assortment of inflammatory ailments. A brief review of MC biology and how aberrant primary MC activation might lead to such a vast range of illness is presented.

Early life programming of pain: focus on neuroimmune to endocrine communication

Chronic pain constitutes a challenge for the scientific community and a significant economic and social cost for modern societies. Given the failure of current drugs to effectively treat chronic pain, which are based on suppressing aberrant neuronal excitability, we propose in this review an integrated approach that views pain not solely originating from neuronal activation but also the result of a complex interaction between the nervous, immune, and endocrine systems. Pain assessment must also extend beyond measures of behavioural responses to noxious stimuli to a more developmentally informed assessment given the significant plasticity of the nociceptive system during the neonatal period. Finally integrating the concept of perinatal programming into the pain management field is a necessary step to develop and target interventions to reduce the suffering associated with chronic pain. We present clinical and animal findings from our laboratory (and others) demonstrating the importance of the microbial and relational environment in programming pain responsiveness later in life via action on hypothalamo-pituitary adrenal (HPA) axis activity, peripheral and central immune system, spinal and supraspinal mechanisms, and the autonomic nervous system.

Persistent visceral allodynia in rats exposed to colorectal irradiation is reversed by mesenchymal stromal cell treatment

Each year, millions of people worldwide are treated for primary or recurrent pelvic malignancies, involving radiotherapy in almost 50% of cases. Delayed development of visceral complications after radiotherapy is recognized in cancer survivors. Therapeutic doses of radiation may lead to the damage of healthy tissue around the tumor and abdominal pain. Because of the lack of experimental models, the underlying mechanisms of radiation-induced long-lasting visceral pain are still unknown. This makes managing radiation-induced pain difficult, and the therapeutic strategies proposed are mostly inefficient. The aim of our study was to develop an animal model of radiation-induced visceral hypersensitivity to (1) analyze some cellular and molecular mechanisms involved and (2) to test a therapeutic strategy using mesenchymal stromal cells (MSCs). Using a single 27-Grays colorectal irradiation in rats, we showed that such exposure induces a persistent visceral allodynia that is associated with an increased spinal sensitization (enhanced p-ERK neurons), colonic neuroplasticity (as increased density of substance P nerve fibers), and colonic mast cell hyperplasia and hypertrophy. Mast cell stabilization by ketotifen provided evidence of their functional involvement in radiation-induced allodynia. Finally, intravenous injection of 1.5 million MSCs, 4 weeks after irradiation, induced a time-dependent reversion of the visceral allodynia and a reduction of the number of anatomical interactions between mast cells and PGP9.5+ nerve fibers. Moreover, unlike ketotifen, MSC treatment has the key advantage to limit radiation-induced colonic ulceration. This work provides new insights into the potential use of MSCs as cellular therapy in the treatment of pelvic radiation disease.

The role of mast cells in functional GI disorders

Functional gastrointestinal disorders (FGIDs) are characterized by chronic complaints arising from disorganized brain-gut interactions leading to dysmotility and hypersensitivity. The two most prevalent FGIDs, affecting up to 16-26% of worldwide population, are functional dyspepsia and irritable bowel syndrome. Their etiopathogenic mechanisms remain unclear, however, recent observations reveal low-grade mucosal inflammation and immune activation, in association with impaired epithelial barrier function and aberrant neuronal sensitivity. These findings come to challenge the traditional view of FGIDs as pure functional disorders, and relate the origin to a tangible organic substrate. The mucosal inflammatory infiltrate is dominated by mast cells, eosinophils and intraepithelial lymphocytes in the intestine of FGIDs. It is well established that mast cell activation can generate epithelial and neuro-muscular dysfunction and promote visceral hypersensitivity and altered motility patterns in FGIDs, postoperative ileus, food allergy and inflammatory bowel disease. This review will discuss the role of mucosal mast cells in the gastrointestinal tract with a specific focus on recent advances in disease mechanisms and clinical management in irritable bowel syndrome and functional dyspepsia.

Irritable Bowel Syndrome: A Review for General Pediatricians

Irritable bowel syndrome (IBS) is a prevalent gastrointestinal disorder characterized by abdominal pain or discomfort and altered bowel habits. The bothersome and chronic nature of IBS symptoms negatively affects patients' activity level and quality of life, imparting an economic burden on the patient, the family, and the health care system. Research is still trying to elicit a clear pathophysiologic mechanism for IBS, and its clinical presentation and manifestations vary from patient to patient. The importance of a comprehensive history and physical examination cannot be emphasized enough in the diagnosis of IBS, as to date there are no specific laboratory studies that will confirm the diagnosis. There is currently no cure for IBS, and treatments range from a broad range of medications, to cognitive-behavioral therapy, to hyponotherapy. This review highlights recent advances in research on the epidemiology, pathophysiology, clinical manifestations, evaluation, and management of IBS.

Mast Cell-Mediated Mechanisms of Nociception

Mast cells are tissue-resident immune cells that release immuno-modulators, chemo-attractants, vasoactive compounds, neuropeptides and growth factors in response to allergens and pathogens constituting a first line of host defense. The neuroimmune interface of immune cells modulating synaptic responses has been of increasing interest, and mast cells have been proposed as key players in orchestrating inflammation-associated pain pathobiology due to their proximity to both vasculature and nerve fibers. Molecular underpinnings of mast cell-mediated pain can be disease-specific. Understanding such mechanisms is critical for developing disease-specific targeted therapeutics to improve analgesic outcomes. We review molecular mechanisms that may contribute to nociception in a disease-specific manner.

Neuroimmune pharmacological approaches

Intestinal inflammation is a major health problem which impairs the quality of life, impacts mental health and is exacerbated by stress and psychiatric disturbances which, in turn, can affect disease prognosis and response to treatment. Accumulating evidence indicates that the immune system is an important interface between intestinal inflammation and the enteric, sensory, central and autonomic nervous systems. In addition, the neuroimmune interactions originating from the gastrointestinal tract are orchestrated by the gut microbiota. This article reviews some major insights into this complex homeostatic network that have been achieved during the past two years and attempts to put these advances into perspective with novel opportunities of pharmacological intervention.

Role of mast cells in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder characterized by high prevalence and recurrence rates, which contribute to the patient's poor quality of life and an economic burden to the society and family for substantial costs. Multiple factors (e.g., stress, infection, and food allergy) can induce IBS via the neuro-endocrine-immune system. Abdominal pain, a hallmark symptom of IBS, correlates with visceral hypersensitivity. In recent years, the immune-associated mechanism for IBS has received more and more attention. Mast cells (MCs) are important immune cells in the intestine. The changes in the number, degranulation and interaction of MCs with the nerve play an important role in the development of IBS. This paper reviews the association between mast cells and the onset of IBS.

Measuring the symptoms of pediatric constipation and irritable bowel syndrome with constipation: expert commentary and literature review

BACKGROUND

Symptom measurement in pediatric chronic idiopathic constipation (CIC) and irritable bowel syndrome with constipation (IBS-C) trials requires appropriately developed clinical outcome assessments (COAs).

METHODS

Literature was reviewed to identify symptom COAs meeting regulatory standards. Searches were conducted in Pubmed/Medline, EMBASE, and PsychINFO. Title/abstracts were reviewed to identify qualitative studies and those using COAs to measure pediatric CIC/IBS symptoms. Pediatric functional gastrointestinal experts provided input on relevant symptom-concepts to measure.

RESULTS

Review of 1,105 abstracts identified 1 relevant qualitative article and 113 articles including COAs. Symptoms most frequently measured in CIC studies were frequency of bowel movements, fecal incontinence/encopresis, abdominal pain, stool consistency, and painful defecation. Symptoms most frequently measured in IBS were abdominal pain, abdominal distention/bloating, stool consistency, frequency of bowel movements, and gas. Evidence of development/validity of COAs was limited. Expert feedback was broadly consistent with the literature.

CONCLUSION

Findings demonstrate consistency in the literature on key CIC/IBS symptoms to measure in pediatric trials, but existing COAs do not meet regulatory standards.

Crosstalk at the mucosal border: importance of the gut microenvironment in IBS

The aetiology and pathology of IBS, a functional bowel disorder thought to lack an organic cause, is largely unknown. However, studies suggest that various features, such as altered composition of the gut microbiota, together with increased intestinal permeability, a changed balance in the enteroendocrine system and a dysregulated immune system in the gut, most likely have an important role in IBS. Exactly how these entities act together and give rise to symptoms is still unknown, but an altered gut microbiota composition could lead to dysregulation of the intestinal barrier as well as the enteroendocrine and the immune systems, which (through interactions with the nervous system) might generate symptoms. This Review highlights the crosstalk between the gut microbiota, the enteroendocrine system, the immune system and the role of intestinal permeability in patients with IBS.

Using human intestinal biopsies to study the pathogenesis of irritable bowel syndrome

BACKGROUND

Although animal models of the irritable bowel syndrome (IBS) have provided important insights, there are no models that fully express the features of this complex condition. One alternative approach is the use of human intestinal biopsies obtained during endoscopic procedures to examine peripheral mechanisms in this disorder. These studies have served to confirm the existence of peripheral pathways in humans with IBS and have provided many new mechanistic insights. Two general approaches have been employed; one approach has been to examine the biological activity of mediators within the mucosal tissue of IBS patients and the other has been to examine changes in the structural properties of key signaling pathways contained within the biopsies. Using these approaches, important changes have been discovered involving the enteric nervous system and the extrinsic sensory pathway (dorsal root ganglia neurons), the immune system, and epithelial signaling in IBS patients compared to healthy subjects.

PURPOSE

This review will systematically explore these mechanistic pathways, highlight the implications of these novel findings and discuss some of the important limitations of this approach.