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The introduction of tumor necrosis factor inhibitors has led to a paradigm shift in the management of inflammatory bowel disease (IBD). The subsequent introduction of both anti-integrins and cytokine blockers has since expanded the biologic armamentarium. However, immunogenicity, defined as the production of anti-drug antibodies (ADAs) to the prescribed biopharmaceutical, means a significant fraction of patients exposed to biologic agents will experience a secondary loss of response to one or more of the drugs. In clinical settings, immunogenicity may be caused by several factors, both patient related (e.g., underlying chronic disease, systemic immune burden, including previous biologic therapy failure, and [epi]genetic background) and treatment related (e.g., dose and administration regimens, drug physical structure, photostability, temperature, and agitation). Here, we outline these elements in detail to enhance biopharmaceutical delivery and therapy for patients with IBD. Moreover, concurrent immunomodulator medication may reduce the risks of ADA generation, especially when using the chimeric drug infliximab. Summarizing the latest developments and knowledge in the field, this review aims to provide strategies to prevent ADA production and information on managing non-responsiveness or loss of response to biologics. Better understanding of the molecular mechanisms underlying the formation of ADAs and the critical factors influencing the immunogenicity of biopharmaceuticals may lead to improved health outcomes in the IBD community that may benefit both the individual patient and society through lower healthcare expenses., Competing Interests: Declarations Funding The study was supported by a grant from the Memorial Foundation of Solveig Høymann Jacobsen. John Gubatan was supported by a Chan Zuckerberg Biohub Physician Scientist Scholar Award, National Institutes of Health (NIH) National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Loan Repayment Program (LRP) Award (L30 DK126220), and a Doris Duke Physician Scientist Fellowship Award (grant #2021091). The funding sources had no role in the design of the study or in the analysis or interpretation of data. Figures were created using Bio Render. Competing Interests Ole Haagen Nielsen, Alexander Hammerhøj, and John Gubatan declare no conflicts of interest. Mark Andrew Ainsworth has undertaken educational tasks for AbbVie, Janssen, and Takeda. Geert D’Haens has served as a consultant for AbbVie, AgomAb, Alimentiv, AstraZeneca, Bristol Myers Squibb, Boehringer Ingelheim, Celltrion, Eli Lilly, Exeliom Biosciences, Galapagos, Index Pharmaceuticals, GSK, Pfizer, Immunic, Johnson & Johnson, Merck, Pfizer, Polpharma, Procise Diagnostics, Prometheus Laboratories, Prometheus Biosciences, Progenity, Protagonist, and Ventyx and has received speakers bureau fees from AbbVie, Arena Pharmaceuticals, Galapagos, Gilead, Pfizer, Bristol Myers Squibb, and Takeda. Ole Haagen Nielsen is an Editorial Board member of Drugs. Ole Haagen Nielsen was not involved in the selection of peer reviewers for the manuscript or any of the subsequent editorial decisions. Ethics Approval Not applicable. Consent to Participate Not applicable. Consent for Publication Not applicable. Availability of Data and Material Not applicable. Code Availability Not applicable. Author Contributions O.H.N. conceived the idea for the article and wrote the first draft. All authors performed the literature review and participated in critical revisions of the data presented and approval of the final manuscript., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Metabolomics is an emerging field involving the systematic identification and quantification of numerous metabolites in biological samples. Precision medicine applies multiomics systems biology to individual patients for reliable diagnostic classification, disease monitoring, and treatment. Multiomics systems biology encompasses genomics, transcriptomics, proteomics, epigenomics, and metabolomics. Therefore, metabolomic techniques could be highly valuable for future clinical decision-making. This review provides a technical overview of two commonly used techniques for metabolomics measurements: mass spectrometry (MS) and proton nuclear magnetic resonance ( 1 H NMR) spectroscopy. We also discuss recent clinical advances in these techniques. Individuals with inflammatory bowel disease (IBD) exhibit significant variability in prognosis and response to treatment. Since both genetic predisposition and environmental factors contribute to this condition, targeting the metabolome may provide key insights for distinguishing and profiling patients with different clinical needs. Additionally, the considerable overlap in the clinical presentation of various disease subtypes emphasizes the need for enhanced diagnostic methods to improve patient care., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Currently, there are no reliable biomarkers for predicting treatment response in chronic inflammatory diseases (CIDs)., Objective: To determine whether serum microfibrillar-associated protein 4 (MFAP4) levels can predict the treatment response to biological therapy in patients with CIDs., Methods: The BELIEVE study was originally designed as a prospective, multi-center cohort study of 233 patients with either rheumatoid arthritis, psoriatic arthritis, psoriasis, axial spondyloarthritis, Crohn's disease, or ulcerative colitis, initiating treatment with a biologic agent (or switching to another). Clinical assessment and blood sample collection were performed at baseline and 14-16 weeks after treatment initiation. The primary analyses included participants with available blood samples at baseline; missing data were handled as non-responders. The patients were stratified into the upper tertile of serum MFAP4 (High MFAP4) versus a combined category of middle and lower tertiles (Other MFAP4). The primary outcome was the proportion of patients with clinical response to biologic therapy after 14-16 weeks., Results: 211 patients were included in the primary analysis population. The mean age was 43.7 (SD: 14.8) years, and 120 (59%) were female. Positive treatment response was observed in 41 (59%) and 69 (49%) for High MFAP4 and Other MFAP4, respectively. When adjusting for pre-specified variables (CID, age, sex, smoking status, and BMI), the adjusted OR was 2.28 (95% CI: 1.07 to 4.85) for a positive treatment outcome in the High MFAP4 group., Conclusion: A high MFAP4 status before initiating biological treatment is associated with a positive clinical response, when adjusting for confounding factors., (© 2024. The Author(s).)

Background and Aims: Epidemiological studies have shown that subnormal levels of vitamin D (25[OH]D) are associated with a more aggravated clinical course of ulcerative colitis [UC]. Despite an increased focus on the therapeutic importance of vitamin D and vitamin D receptor [VDR] signalling, the mechanisms underlying the effects of the vitamin D-VDR axis on UC remain elusive. Therefore, we aimed to investigate whether exposure to active vitamin D (1,25[OH]2D3/VDR) signalling in human organoids could influence the maintenance of the colonic epithelium., Methods: Intestinal VDR expression was studied by immunohistochemistry, RNA expression arrays, and single-cell RNA sequencing of colonic biopsy specimens obtained from patients with UC and healthy individuals. To characterise the functional and transcriptional effects of 1,25[OH]2D3, we used patient-derived colonic organoids. The dependency of VDR was assessed by knocking out the receptor with CRISPR/Cas9., Results: Our results suggest that 1,25[OH]2D3/VDR stimulation supports differentiation of the colonic epithelium and that impaired 1,25[OH]2D3/VDR signalling thereby may compromise the structure of the intestinal epithelial barrier, leading to flares of UC. Furthermore, a transcriptional response to VDR activity was observed primarily in fully differentiated cells at the top of the colonic crypt, and this response was reduced during flares of UC., Conclusions: We identified an important role of vitamin D signalling in supporting differentiated cell states in the human colonic epithelium, and thereby maintenance of the intestinal barrier integrity. This makes the vitamin D-VDR signalling axis an interesting target for therapeutic efforts to achieve and maintain remission in patients with UC., (© The Author(s) 2024. Published by Oxford University Press on behalf of European Crohn’s and Colitis Organisation.)

Importance: Immune checkpoint inhibitors (ICIs) improve outcomes in a wide range of cancers; however, serious adverse effects, including cardiovascular adverse effects (CVAEs), can occur., Objective: To determine the incidence of CVAEs and analyze data on the management of myocarditis in patients exposed to ICIs., Data Sources: PubMed, Embase, and Cochrane Central Register of Controlled Trials from inception were searched on April 4, 2023., Study Selection: Two separate studies were performed. Key inclusion criteria for study 1 were phases 1 to 4 trials involving adults with malignant neoplasms treated with an ICI and toxicity data; for study 2, publications (case reports and retrospective analyses) on clinical manifestations and treatment of patients with ICI-induced CVAEs. Studies with dose escalation or fewer than 11 patients in each group and all case reports, retrospective analyses, letters, reviews, and editorials were excluded from study 1. Studies not published in English were excluded from study 2., Data Extraction and Synthesis: The PRISMA guidelines and Cochrane Handbook for Systematic Reviews were followed. Data were extracted independently by 2 researchers. A meta-analysis of the incidence of CVAEs in clinical trials and a systematic review of the evidence for the management of myocarditis were performed. Data were pooled using a random-effects model., Main Outcomes and Measures: In study 1, the primary outcome was incidence CVAEs in clinical trials with ICIs and ICI combination therapies. Study 2 examined evidence supporting specific management strategies that may decrease the mortality rate of myocarditis. The primary outcomes were planned before data collection began., Results: In study 1, a total of 83 315 unique participants in 589 unique trials were included in the meta-analysis. Incidence of CVAEs induced by anti-programmed cell death 1 and/or programmed cell death ligand 1 was 0.80% (95% CI, 0%-1.66%) in clinical trials, with no differences between the compounds, except for cemiplimab, which was associated with a higher risk of CVAEs. Incidence of CVAEs following ipilimumab treatment was 1.07% (95% CI, 0%-2.58%). The incidence of myocarditis was significantly higher following treatment with dual ICIs. However, CVAE incidence was not higher with dual ICIs, ICI combination with chemotherapy, or tyrosine kinase inhibitors. Evidence from randomized clinical trials on recommended monitoring and treatment strategies for ICI-induced myocarditis was lacking. Study 2 showed that myocarditis-associated mortality occurred in 83 of 220 patients (37.7%). Prospective data from 40 patients with myocarditis indicated that systematic screening for respiratory muscle involvement, coupled with active ventilation, prompt use of abatacept, and the addition of ruxolitinib, may decrease the mortality rate., Conclusions and Relevance: Immune checkpoint inhibitor-induced CVAEs and/or myocarditis were recorded in 1.07% of patients in clinical trials. The CVAE mortality risk remains high, justifying the need for monitoring and management strategies for which evidence from randomized clinical trials is absent. Early recognition, ICI therapy cessation, prompt initiation of corticosteroid therapy, and escalation of therapy are all crucial elements for achieving optimal outcomes. Prospective clinical trials or at least prospective registration of treatments and outcomes are highly warranted.

Chronic inflammatory diseases (CIDs) pose a growing healthcare challenge, with a substantial proportion of patients showing inadequate response to biological treatment. There is renewed interest in dietary changes to optimize treatment regimens, with a growing body of evidence suggesting beneficial effects with adherence to a gluten-free diet. This study compared the likelihood of achieving clinical response to biological treatment after 14-16 weeks in patients with CID with high versus low-to-medium gluten intake. Secondary outcomes of interest included changes in disease activity, health-related quality of life and C-reactive protein. The study was a multicentre prospective cohort of 193 participants with a CID diagnosis (i.e. Crohn's Disease, Ulcerative Colitis, Rheumatoid Arthritis, Axial Spondyloarthritis, Psoriatic Arthritis or Psoriasis) who initiated biological treatment between 2017 and 2020. Participants were stratified based on their habitual gluten intake: the upper 33.3% (high gluten intake) and the remaining 66.6% (low-to-medium gluten intake). The proportion of patients achieving clinical response to biological treatment after 14-16 weeks was compared using logistic regression models. The median gluten intake differed significantly between groups (12.5 g/day vs. 5.9 g/day, standardized mean difference = 1.399). In total, 108 (56%) achieved clinical response to treatment, with no difference between 35 (55%) in the high gluten group and 73 (57%) in the medium-to-low gluten group (OR = 0.96 [0.51-1.79], p = 0.897). No differences were found with secondary outcomes. In conclusion, this study found no association between gluten intake and response to biological treatment in patients with CID., (© 2024 The Author(s). Scandinavian Journal of Immunology published by John Wiley & Sons Ltd on behalf of The Scandinavian Foundation for Immunology.)

The intestinal epithelium ensures uptake of vital nutrients and acts as a barrier between luminal contents and the underlying immune system. In inflammatory bowel diseases, such as ulcerative colitis (UC), this barrier is compromised, and patients experience debilitating symptoms. Here, we perform single-cell RNA profiling of epithelial cells and outline patterns of cell fate decisions in healthy individuals and UC patients. We demonstrate that patterns of hierarchical behavior are altered in UC patients and identify unique cellular states associated with Janus kinase/signal transducer and activator of transcription (JAK/STAT) activation in ulcerated and non-ulcerated areas of the colonic epithelium. These transcriptional changes could be recapitulated in human colonic organoids, wherein cytokine-mediated activation of JAK/STAT led to the emergence of cell populations with augmented regenerative properties. Altogether, our findings indicate that intricate relationships between epithelial and cytokine signaling regulate cell fate during epithelial tissue regeneration in humans and have important implications for the understanding of UC biology., Competing Interests: Declaration of interests T.S. is an inventor on several patents related to organoids., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Introduction: Rapidity of effect of advanced therapies for patients with Crohn's disease (CD) can be an essential decision parameter; however, comparative evaluation is lacking. We aimed to compare early response for advanced CD therapies in a network meta-analysis (NMA)., Methods: We searched systematically MEDLINE, Embase, and CENTRAL up to 19 February 2024, for randomised controlled trials. The co-primary outcomes were induction of clinical remission (Crohn's Disease Activity Index (CDAI) ≤150) and clinical response (≥100-point reduction in CDAI) within the first 6 weeks of treatment. We incorporated any assessment within this time point in a Bayesian random-effects NMA following PRISMA-NMA guidance (PROSPERO ID: CRD42022368509)., Results: Twenty-five studies, comprising 7414 patients, were included. Infliximab combined with azathioprine or monotherapy ranked highest for induction of clinical remission within 6 weeks and was significantly superior to certolizumab, ustekinumab, guselkumab, vedolizumab, and upadacitinib. However, superiority over risankizumab 600 mg and adalimumab 160/80 mg was non-significant. Accordingly, infliximab in combination with azathioprine and guselkumab 600 mg ranked highest in the corresponding analysis of clinical response with no statistical significance demonstrated. Among bio-exposed patients, none of whom received infliximab, upadacitinib, and risankizumab induced the highest clinical responses. On the other hand, vedolizumab, certolizumab, and ustekinumab ranked lowest across the analyses., Conclusions: We found infliximab to be ranked highest and superior to all other agents but risankizumab and adalimumab, demonstrating the highest probability of early induction of remission. Upadacitinib and risankizumab induced the highest clinical responses in bio-exposed patients. However, infliximab was not investigated in this population., (© 2024 John Wiley & Sons Ltd.)

Inflammatory bowel disease (IBD) is a chronic disorder with an increasing global prevalence. Managing disease activity relies on various pharmacological options. However, the effectiveness of current therapeutics is limited and not universally applicable to all patients and circumstances. Consequently, developing new management strategies is necessary. Recent advances in endoscopically obtained intestinal biopsy specimens have highlighted the potential of intestinal epithelial organoid transplantation as a novel therapeutic approach. Experimental studies using murine and human organoid transplantations have shown promising outcomes, including tissue regeneration and functional recovery. Human trials with organoid therapy have commenced; thus, this article provides readers with insights into the necessity and potential of intestinal organoid transplantation as a new regenerative therapeutic option in clinical settings and explores its associated challenges., Competing Interests: T.S. is an inventor of several patents related to organoid culture. The remaining authors disclose no conflicts of interests., (© 2024 The Author(s).)

Inflammatory bowel disease (IBD) affects reproductive planning due to psychological effects and mechanical problems related to surgery. Children of people with IBD have an increased risk of about 10% if one parent has IBD and up to 33% if both parents have IBD. The fertility of people with IBD is similar to the general population, but fertility might be reduced in individuals with active IBD, ileal pouch-anal anastomosis, or perianal Crohn's disease. Flaring disease during pregnancy increases complications, such as preterm birth. Thus, disease management with appropriate medications can optimise outcomes. As most medications have minimal fetal risks, people with IBD should be informed about the risks of stopping medications and the importance of maintaining remission. A period of disease remission is advisable before pregnancy and could reduce the risks for both the pregnant person and the fetus. Flexible endoscopy, intestinal ultrasound, and gadolinium-free magnetic resonance enterography are safe during pregnancy. We provide state-of-the-art knowledge on the basis of the latest evidence to ensure successful pregnancy outcomes in controlled IBD., Competing Interests: Declaration of interests SES holds stocks in Merk and Johnson & Johnson and is a consultant for Janssen, Takeda, Bristol Myers Squibb, Gilead, Prometheus, and Surrozen. All other authors declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The intestinal epithelium fulfills important physiological functions and forms a physical barrier to the intestinal lumen. Barrier function is regulated by several pathways, and its impairment contributes to the pathogenesis of inflammatory bowel disease (IBD), a chronic inflammatory condition affecting more than seven million people worldwide. Current treatment options specifically target inflammatory mediators and have led to improvement of clinical outcomes; however, a significant proportion of patients experience treatment failure. Pro-repair effects of inflammatory mediators on the epithelium are emerging. In this review we summarize current knowledge on involved epithelial pathways, identify open questions, and put recent findings into clinical perspective, and pro-repair effects. A detailed understanding of epithelial pathways integrating mucosal stimuli in homeostasis and inflammation is crucial for the development of novel, more targeted therapies., Competing Interests: Declaration of interests C.S. lectures for MSD and Janssen-Cilag. The remaining authors have no interests to declare., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Competing Interests: Declaration of interests No interests are declared.

Innate immune activity fuels intestinal inflammation in Crohn's disease (CD), an inflammatory bowel disease. Identification and targeting of new molecular regulators of the innate activity are warranted to control the disease. Inhibitor of apoptosis proteins (IAPs) regulate both cell survival and inflammatory signaling. We investigated the effects of IAP inhibition by second mitochondria-derived activator of caspases (SMAC) mimetics (SMs) on innate responses and cell death to pathogen-associated molecular patterns in peripheral blood mononuclear cells (PBMCs) and monocytes. IAPs inhibited lipopolysaccharide (LPS)-induced expression of proinflammatory interleukin (IL)-1β, IL-6. Likewise, LPS (but not muramyl dipeptide or Escherichia coli) induced TNF-α was inhibited in CD and control PBMCs. The SM effect was partially reversed by inhibition of receptor-interacting serine/threonine-protein kinase 1 (RIPK1). The effect was mainly cell death independent. Thus, IAP inhibition by SMs leads to reduced production of proinflammatory cytokines and may be considered in the efforts to develop new therapeutic strategies to control CD., (© The Author(s) 2023. Published by Oxford University Press on behalf of the British Society for Immunology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Microscopic colitis, a diagnosis under the umbrella term of inflammatory bowel disease, is a prevalent cause of watery diarrhea, often with symptoms of urgency and bloating, typically observed in older adults aged ≥ 60 years. Its incidence has been reported to exceed those of ulcerative colitis and Crohn's disease in some geographical areas. Although nonpathognomonic endoscopic abnormalities, including changes of the vascular mucosal pattern; mucosal erythema; edema; nodularity; or mucosal defects, e.g., "cat scratches" have been reported, a colonoscopy is typically macroscopically normal. As reliable biomarkers are unavailable, colonoscopy using random biopsies from various parts of the colon is compulsory. Based on the histological examination under a microscope, the disease is divided into collagenous (with a thickened subepithelial collagenous band) and lymphocytic (with intraepithelial lymphocytosis) colitis, although incomplete forms exist. In routine clinical settings, the disease has a high risk of being misdiagnosed as irritable bowel syndrome or even overlooked. Therefore, healthcare providers should be familiar with clinical features and rational management strategies. A 6-8-week oral budesonide treatment course (9 mg/day) is considered the first-line therapy, but patients often experience relapse when discontinued, or might become intolerant, dependent, or even fail to respond. Consequently, other therapeutic options (e.g., bismuth subsalicylate, biologics, loperamide, bile acid sequestrants, and thiopurines) recommended by available guidelines may be prescribed. Herein, clinically meaningful data is provided based on the latest evidence that may aid in reaching a diagnosis and establishing rational therapy in geriatric care to control symptoms and enhance the quality of life for those affected., (© 2024. The Author(s).)

Colorectal cancer is a known complication of chronic inflammation of the colon ("colitis-associated colon cancer"). Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract. Patients with IBD are at increased risk of colon cancer compared to the general population. Kinase signaling pathways play critical roles in both the inflammation and regulating cellular processes such as proliferation and survival that contribute to cancer development. Here we review the interplay of kinase signaling pathways (mitogen-activated protein kinases, cyclin-dependent kinases, autophagy-activated kinases, JAK-STAT, and other kinases) and their effects on colitis-associated colon cancer. We also discuss the role of JAK-STAT signaling in the pathogenesis of IBD and the therapeutic landscape of JAK inhibitors for the treatment of IBD.

Background & Aims: Studies evaluating reproductive outcomes among male patients with inflammatory bowel disease (IBD) are limited. We evaluated use of IBD medications and association with semen parameters, a proxy of male fertility, and adverse pregnancy outcomes (early pregnancy loss [EPL], preterm birth [PB], congenital malformations [CM])., Methods: We searched Medline, Embase, Scopus, and Web of Science (PROSPERO CRD42020197098) from inception to April 2022 for studies reporting semen parameters and adverse pregnancy outcomes among male patients exposed to biologics, thiopurine, or methotrexate. Standardized mean difference, prevalence, and odds ratios (ORs) of outcomes were pooled and analyzed using a random effects model., Results: Ten studies reporting semen parameters (268 patients with IBD) and 16 studies reporting adverse pregnancy outcomes (over 25,000 patients with IBD) were included. Biologic, thiopurine, or methotrexate use were not associated with decreased sperm count, motility, or abnormal morphology compared with nonexposed patients. The prevalence of adverse pregnancy outcomes with paternal biologic (5%), thiopurine (6%), or methotrexate (6%) exposure was comparable to nonexposed patients (5%). Biologic use was not associated with risk of EPL (OR, 1.26; I 2  = 0%; P = .12), PB (OR, 1.10; I 2  = 0%; P = .17), or CM (OR, 1.03; I 2  = 0%; P = .69). Thiopurine use was not associated with risk of EPL (OR, 1.31; I 2  = 19%; P = .17), PB (OR, 1.05; I 2  = 0%; P = .20), or CM (OR, 1.07; I 2  = 7%; P = .34). Methotrexate use was not associated with risk of PB (OR, 1.06; I 2  = 0%; P = .62) or CM (OR, 1.03; I 2  = 0%; P = .81)., Conclusions: Biologic, thiopurine, or methotrexate use among male patients with IBD are not associated with impairments in fertility or with increased odds of adverse pregnancy outcomes., (Copyright © 2023 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Inflammatory bowel diseases (IBD) are without cure and troublesome to manage because of the considerable diversity between patients and the lack of reliable biomarkers. Several studies have demonstrated that diet, gut microbiota, genetics and other patient factors are essential for disease occurrence and progression. Understanding the link between these factors is crucial for identifying molecular signatures that identify biomarkers to advance the management of IBD. Recent technological breakthroughs and data integration have fuelled the intensity of this research. This research demonstrates that the effect of diet depends on patient factors and gut microbial activity. It also identifies a range of potential biomarkers for IBD management, including mucosa-derived cytokines, gasdermins and neutrophil extracellular traps, all of which need further evaluation before clinical translation. This review provides an update on cutting-edge research in IBD that aims to improve disease management and patient quality of life.

Janus kinase (JAK) inhibitors, also known as jakinibs, are third-generation oral small molecules that have expanded the therapeutic options for the management of chronic inflammatory diseases, including inflammatory bowel disease (IBD). Tofacitinib, a pan-JAK inhibitor, has spearheaded the new JAK class for IBD treatment. Unfortunately, serious adverse effects, including cardiovascular complications such as pulmonary embolism and venous thromboembolism or even death from any cause, have been reported for tofacitinib. However, it is anticipated that next-generation selective JAK inhibitors may limit the development of serious adverse events, leading to a safer treatment course with these novel targeted therapies. Nevertheless, although this drug class was recently introduced, following the launch of second-generation biologics in the late 1990s, it is breaking new ground and has been shown to efficiently modulate complex cytokine-driven inflammation in both preclinical models and human studies. Herein, we review the clinical opportunities for targeting JAK1 signaling in the pathophysiology of IBD, the biology and chemistry underpinning these target-selective compounds, and their mechanisms of actions. We also discuss the potential for these inhibitors in efforts to balance their benefits and harms., Competing Interests: Declaration of Competing Interest The authors declare that there are no conflicts of interest., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Competing Interests: Declaration of interests No interests are declared.

Background: Onset of effect of advanced therapies is an important parameter due to symptom load and risk of disease complications in moderate-to-severe ulcerative colitis (UC), but comparative data are lacking. Therefore, we aimed to assess the comparative onset of efficacy of biological therapies and small molecules for this patient population., Methods: In this systematic review and network meta-analysis, we searched MEDLINE, Embase, and Cochrane Central Register of Controlled Trials from inception to 24 August 2022, for randomised controlled trials or open-label studies assessing the efficacy of biologics or small molecule drugs within the first six weeks of treatment in adults with UC. The co-primary outcomes were the induction of clinical response and clinical remission at week 2. Network meta-analyses was conducted under the Bayesian framework. This study is registered with PROSPERO: CRD42021250236., Findings: The systematic literature search identified 20,406 citations, of which 25 studies comprising 11,074 patients fulfilled the eligibility criteria. Upadacitinib ranked highest for induction of clinical response and clinical remission at week 2 and was significantly superior to all agents but tofacitinib, which ranked second highest. Although the rankings remained consistent, no differences between upadacitinib and biological therapies were demonstrated in the sensitivity analyses of partial Mayo clinic score response or resolution of rectal bleeding at week 2. Tumor necrosis factor-α (TNF) inhibitors were significantly superior to vedolizumab and ustekinumab for patient-reported outcome-2 (PRO-2) remission at week 2 in bio-naïve patients. Filgotinib 100 mg, ustekinumab, and ozanimod ranked lowest across all endpoints., Interpretation: In this network meta-analysis, we found upadacitinib to be significantly superior to all agents but tofacitinib for the induction of clinical response and clinical remission two weeks after treatment initiation. In contrast, ustekinumab and ozanimod ranked lowest. Our findings help to establish the evidence regarding the onset of efficacy of advanced therapies., Funding: None., Competing Interests: M.A.: None. E.K.D.: reports research grants from Takeda, paid speaker by MSD, Tillotts. J.B.: reports grants and personal fees from AbbVie, grants and personal fees from Janssen-Cilag, personal fees from Celgene, grants and personal fees from MSD, personal fees from Pfizer, grants and personal fees from Takeda, grants and personal fees from Tillots Pharma, personal fees from Samsung Bioepis, grants and personal fees from Bristol Myers Squibb, grants from Novo Nordisk, personal fees from Pharmacosmos, personal fees from Ferring, personal fees from Galapagos, outside the submitted work. J.G.: None. O.H.N.: None. J.B.S.: has received research grants from Takeda, Janssen, the Danish Research Council, and the Capital Region Denmark, and is national coordinator of studies from AbbVie, Arena Pharmaceuticals, Ely Lilly, and Boehringer Ingelheim. None of these pertain to the research submitted here., (© 2023 The Author(s).)

Background: Biologic disease-modifying drugs have revolutionised the treatment of a number of chronic inflammatory diseases (CID). However, up to 60% of the patients do not have a sufficient response to treatment and there is a need for optimization of treatment strategies., Objective: To investigate if the treatment outcome of biological therapy is associated with the habitual dietary intake of fibre and red/processed meat in patients with a CID., Methods: In this multicentre prospective cohort study, we consecutively enrolled 233 adult patients with a diagnosis of Crohn's Disease, Ulcerative Colitis, Rheumatoid Arthritis (RA), Axial Spondyloarthritis, Psoriatic Arthritis and Psoriasis, for whom biologic therapy was planned, over a 3 year period. Patients with completed baseline food frequency questionnaires were stratified into a high fibre/low red and processed meat exposed group (HFLM) and an unexposed group (low fibre/high red and processed meat intake = LFHM). The primary outcome was the proportion of patients with a clinical response to biologic therapy after 14-16 weeks of treatment., Results: Of the 193 patients included in our primary analysis, 114 (59%) had a clinical response to biologic therapy. In the HFLM group ( N = 64), 41 (64%) patients responded to treatment compared to 73 (56%) in the LFHM group ( N = 129), but the difference was not statistically significant (OR: 1.48, 0.72-3.05). For RA patients however, HFLM diet was associated with a more likely clinical response (82% vs. 35%; OR: 9.84, 1.35-71.56)., Conclusion: Habitual HFLM intake did not affect the clinical response to biological treatment across CIDs. HFLM diet in RA patients might be associated with better odds for responding to biological treatment, but this would need confirmation in a randomised trial., Trial Registration: (clinicaltrials.gov), identifier [NCT03173144]., Competing Interests: Author CH has received speaker fee from Takeda Pharma and Tillotts Pharma (unrelated to the present work). The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Overgaard, Sørensen, Munk, Nexøe, Glerup, Henriksen, Guldmann, Pedersen, Saboori, Hvid, Dahlerup, Hvas, Jawhara, Andersen, Pedersen, Nielsen, Bergenheim, Brodersen, Heitmann, Halldorsson, Holmskov, Bygum, Christensen, Kjeldsen, Ellingsen and Andersen.)

Background: Immune checkpoint inhibitors (ICIs) have improved cancer outcomes. However, immune-related adverse effects are common. The aim was to investigate the incidence of diarrhea and colitis of ICIs alone and in combination with chemotherapy or tyrosine kinase inhibitors (TKIs), histopathological findings, and management., Methods: Two separate studies, including meta-analyses, were performed. Key inclusion criteria were for Study I) phase I-IV trials, and data on diarrhea and/or colitis; for Study II) studies describing histopathologic and endoscopic findings and/or biologic treatment for ICI-induced colitis., Results: The incidence of anti-PD-1/PD-L1 antibody-induced diarrhea and colitis was 10% and 2%, respectively, with no clinically relevant differences between the compounds. The CTLA-4 inhibitor, ipilimumab, induced diarrhea and colitis in 33% and 7% of patients, respectively, whereas the incidence of diarrhea and colitis following ipilimumab combined with nivolumab was 21%-37% and 4%-8%, depending on regimen. The incidence of all-grade diarrhea following ICIs combined with chemotherapy or TKIs was high (17%-56%), whereas only 0.5% of patients developed severe (≥grade 3) colitis. The main patterns of histopathologic presentation after PD-1/CTLA-4 inhibitor mono- or combination therapy were acute and chronic active colitis and microscopic colitis-like. Infliximab and vedolizumab were equally effective against ICI-induced colitis., Conclusion: Expanding treatment options include combinations of ICIs and chemotherapy/TKI with a high incidence of diarrhea and a low incidence of colitis; thus, a potential risk of overtreatment with corticosteroids exists. We suggest a more tailored approach, particularly for the management of low-grade diarrhea. Prospective clinical trials are needed to refine management., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Background: Immune-related adverse events due to immune checkpoint inhibitors (ICIs) are not always effectively treated using glucocorticoids and it may negatively affect the antitumor efficacy of ICIs. Interventional studies of alternatives to glucocorticoids are lacking. We examined whether interleukin-6 blockade by tocilizumab reduced ICI-induced colitis and arthritis., Patients and Methods: Patients with solid cancer experiencing Common Terminology Criteria for Adverse Events (CTCAE v5.0) grade >1 ICI-induced colitis/diarrhea (n=9), arthritis (n=9), or both (n=2) were recruited and treated with tocilizumab (8 mg/kg) every 4 weeks until worsening or unacceptable toxicity. Patients were not allowed to receive systemic glucocorticoids and other immunosuppressive drugs within the 14-day screening period. The primary endpoint was clinical improvement of colitis and arthritis, defined as ≥1 grade CTCAE reduction within 8 weeks. Secondary endpoints were improvements and glucocorticoid-free remission at week 24; safety; radiologic, endoscopic, and histological changes; and changes in plasma concentrations of C reactive protein, cytokines (IL-6, IL-8, and IL-17), and YKL-40., Results: Nineteen patients were available for efficacy analysis; one patient was excluded due to pancreatic insufficiency-induced diarrhea. Patients received treatment with pembrolizumab (n=10) or nivolumab (n=4) as monotherapy or ipilimumab and nivolumab (n=5) combined. Seven patients had been initially treated with glucocorticoids, and two of them also received infliximab. Ten patients continued ICI therapy during tocilizumab treatment. The primary endpoint was achieved in 15 of 19 (79%) patients. Additional one patient had ≥1 grade reduction at week 10, and another patient had stabilized symptoms. At week 24, ongoing improvement without glucocorticoids (n=12), including complete remission (n=10), was noted. Five patients had grades 3-4 treatment-related adverse events, which were manageable and reversible., Conclusions: Tocilizumab showed promising clinical efficacy and a manageable safety profile in the treatment of ICI-induced colitis and arthritis. Our findings support the feasibility of randomized trials of immune-related adverse events., Trial Registration Number: NCT03601611., Competing Interests: Competing interests: All authors completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. RBH received speaking honoraria from BPNO. P. Vilmann reported a consulting relationship with MediGlobe GmbH, Grassau. JJ reported receiving research funding and hotel/airfare reimbursement to attend global health meetings from Roche, BMS, and Celgene. MKB reported receiving hotel/airfare reimbursement to attend global health meetings from Pfizer. RHLE received research funding from BMS and advisory relationship with Amgen. IMS has been principal investigator in BMS-supported trials and received honoraria from BMS for speaking and serving on an advisory board. IMC reported receiving research funding and hotel/airfare reimbursement to attend global health meetings from Roche, BMS, Celgene, Genis, and advisory relationship with Amgen. OHN, LBR, ST, SJ, and DLN had no disclosures., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Microscopic colitis is an inflammatory bowel disease divided into two subtypes: collagenous colitis and lymphocytic colitis. With an increasing incidence of microscopic colitis exceeding those of ulcerative and Crohn's disease among elderly people in some countries, microscopic colitis is a debilitating life experience. Therefore, physicians should be familiar with its clinical features and management strategies because the disease deserves the same attention as the classical inflammatory bowel diseases. Here, state-of-the-art knowledge of microscopic colitis is provided from a global perspective with reference to etiopathology and how to establish the diagnosis with the overall aim to create awareness and improve rational management in clinical practice. The immune system and a dysregulated immune response seem to play a key role combined with risk factors (e.g. cigarette smoking) in genetically predisposed individuals. The symptoms are characterized by recurrent or chronic nonbloody, watery diarrhea, urgency, weight loss, and a female preponderance. As biomarkers are absent, the diagnosis relies on colonoscopy with a histological assessment of biopsy specimens from all parts of the colon. Although the disease is not associated with a risk of colorectal cancer, a recent nationwide, population-based cohort study found an increased risk of lymphoma and lung cancer. Budesonide is the first-line therapy for management, whereas immunomodulatory drugs (including biologics) and drugs with antidiarrheal properties may be indicated in those failing, dependent, or intolerant to budesonide. In microscopic colitis induced by checkpoint inhibitors, a drug class used increasingly for a wide range of malignancies, a more aggressive therapeutic approach with biologics introduced early seems reasonable. However, particular attention needs to be drawn to the existence of incomplete forms of microscopic colitis with the risk of being overlooked in routine clinical settings., Competing Interests: ON, TS No competing interests declared, FF Research grant from Falk Pharma; Consulting fee from Tillotts and Biomedal; Lectures for General Electrics and Termo Fisher, and travel support from Tillotts, Ferring, and Janssen as listed in the ICMJE form, DP Grants from Atlantic, Finch, Salix, Janssen, Pfizer, Seres, Applied Molecular Transport, and Takeda; Consulting fees from Abbvie, Vedanta, Seres, Immunic, Merck, Otsuka, Ferring, Rise Therapeutics, Boehringer Ingelheim, and Summit Therapeutics as listed in the ICMJE form, (© 2022, Nielsen et al.)

The gut microbiome has increasingly been recognized as a critical and central factor in inflammatory bowel disease (IBD). Here, we review specific microorganisms that have been suggested to play a role in the pathogenesis of IBD and the current state of fecal microbial transplants as a therapeutic strategy in IBD. We discuss specific nutritional and dietary interventions in IBD and their effects on gut microbiota composition. Finally, we examine the role and mechanisms of the gut microbiome in mediating colitis-associated colon cancer.

The pathogenesis of inflammatory bowel diseases (IBD) involves genetic predisposition, environmental factors, and a broadly dysregulated intestinal immune response to the commensal intestinal microflora. The interface between genetic predisposition and environmental factors is reflected in the epigenetic regulation at the transcriptional level. Treatment targets now involve mucosal and histological healing, but the future might additionally include normalization of intestinal cellular functions also at the molecular level, for example comprising complete restoration of phenotypic, genotypic, and epigenetic states. Recent developments in patient-derived epithelial intestinal stem cell (ISC) organoid technologies have opened exciting new therapeutic opportunities to potentially attain molecular healing by combining stem cell therapy with molecular manipulations using (epi)drugs and/or CRISPR/Cas9 genome editing. Here, we are the first to discuss the possibility for phenotypic, genotypic, and epigenetic restoration via molecular manipulations and stem cell therapy in IBD from a clinical perspective., (© The Author(s) 2022. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Recent significant advances have been made in the treatment of chronic inflammatory diseases with initiation of the era of biologics. However, an unmet medical need still exists for novel targeted therapies. Compared with biologics, Janus kinase inhibitors (JAKis) are a new drug class of orally administered small molecules that have been shown to efficiently modulate complex cytokine-driven inflammation in preclinical models and human studies. Unfortunately, serious adverse effects have been reported with the first introduced pan-JAKi, tofacitinib. Here, we review tyrosine kinase 2 (TYK2) signaling in the pathophysiology of inflammatory bowel disease (IBD), examine mechanisms of action of selective TYK2 inhibitors (TYK2is), and discuss the potential for these inhibitors in efforts to balance benefits and harms., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Improving the long-term prognosis of ulcerative colitis (UC) requires sustained deep mucosal colonic healing with histologic remission, making the study of colonic tissue regeneration essential. In experimental colitis models, lipid metabolites are recognized as pivotal components of this process. This study aimed to describe the kinetics of wound healing and lipid metabolites engaged in regeneration in the normal colonic mucosa and how they are affected in UC to reveal new therapeutic targets. Experimental colonic wounds were created endoscopically in quiescent UC (n=21) and controls (n=9), and the healing process was surveilled by serial endoscopies and cross-sectional wound biopsies post-wounding. Biopsies were analyzed by liquid chromatography coupled with mass spectrometry. Endoscopic wound scores were significantly higher in UC at day two (p=0.001) and seven (p<0.0001) post-wounding, demonstrating a prolonged wound healing process. The wound scores were correlated with lipid mediators crucial for normal regeneration and sustained UC-specific changes in key phospholipids and eicosanoids, i.e., lysophosphatidylcholine, phosphatidylcholine, lysophosphatidic acid, phosphatidylglycerol, phosphatidylinositol, prostaglandin D 2 , and prostaglandin E 1 , were observed. A prolonged wound healing process is identified in quiescent UC with altered disease specific lipidomic trajectories providing potential novel therapeutic avenues for stimulating mucosal regeneration as an add-on to the traditional immune suppression treatment., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

The interests in intestinal epithelial tuft cells, their basic physiology, involvement in immune responses and relevance for gut diseases, have increased dramatically over the last fifteen years. A key discovery in 2016 of their close connection to helminthic and protozoan infection has further spurred the exploration of these rare chemosensory epithelial cells. Although very sparse in number, tuft cells are now known as important sentinels in the gastrointestinal tract as they monitor intestinal content using succinate as well as sweet and bitter taste receptors. Upon stimulation, tuft cells secrete a broad palette of effector molecules, including interleukin-25, prostaglandin E 2 and D 2 , cysteinyl leukotriene C 4 , acetylcholine, thymic stromal lymphopoietin, and β-endorphins, some of which with immunomodulatory functions. Tuft cells have proven indispensable in anti-helminthic and anti-protozoan immunity. Most studies on tuft cells are based on murine experiments using double cortin-like kinase 1 (DCLK1) as a marker, while human intestinal tuft cells can be identified by their expression of the cyclooxygenase-1 enzyme. So far, only few studies have examined tuft cells in humans and their relation to gut disease. Here, we present an updated view on intestinal epithelial tuft cells, their physiology, immunological hub function, and their involvement in human disease. We close with a discussion on how tuft cells may have potential therapeutic value in a clinical context., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Hendel, Kellermann, Hausmann, Bindslev, Jensen and Nielsen.)

Background & Aims: Biologics are used routinely in pregnant women with inflammatory bowel disease (IBD), but large-scale data reporting adverse pregnancy outcomes among biologic users are lacking. We sought to estimate the prevalence of adverse pregnancy outcomes in women with IBD on biologic therapies., Methods: We searched major databases from inception to June 2020 for studies estimating the prevalence of adverse pregnancy outcomes in IBD when using biologics (anti-tumor necrosis factor [TNF], anti-integrins, and anticytokines). Prevalence and relative risk (RR) were pooled using a random-effects model., Results: Forty-eight studies were included in the meta-analysis comprising 6963 patients. Biologic therapy in IBD pregnancies was associated with a pooled prevalence of 8% (95% CI, 6%-10%; I 2  = 87.4%) for early pregnancy loss, 9% (95% CI, 7%-11%; I 2  = 89.9%) for preterm birth, 0% (95% CI, 0%-0%; I 2  = 0%) for stillbirth, 8% (95% CI, 5%-10%; I 2  = 87.0%) for low birth weight, and 1% (95% CI, 1%-2%; I 2  = 78.3%) for congenital malformations. These rates are comparable with those published in the general population. In subgroup analyses of a small number of studies, the prevalence of early pregnancy loss and preterm birth were higher in vedolizumab vs anti-TNF users. Meta-regression did not show an association of disease activity or concomitant thiopurine on adverse outcomes. Continued TNF inhibitor use during the third trimester was not associated with risk of preterm birth (RR, 1.41; 95% CI, 0.77-2.60; I 2  = 0%), low birth weight (RR, 1.32; 95% CI, 0.80-2.18; I 2  = 0%), or congenital malformations (RR, 1.28; 95% CI, 0.47-3.49; I 2  = 0%)., Conclusions: Adverse pregnancy outcomes among pregnant IBD women using biologics are comparable with that of the general population. PROSPERO protocol #CRD42019135721., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Metabonomics in inflammatory bowel disease (IBD) characterizes the effector molecules of biological systems and thus aims to describe the molecular phenotype, generate insight into the pathology, and predict disease course and response to treatment. Nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry (MS), and integrated NMR and MS platforms coupled with multivariate analyses have been applied to create such metabolic profiles. Recent advances have identified quiescent ulcerative colitis as a distinct molecular phenotype and demonstrated metabonomics as a promising clinical tool for predicting relapse and response to treatment with biologics as well as fecal microbiome transplantation, thus facilitating much needed precision medicine. However, understanding this complex research field and how it translates into clinical settings is a challenge. This review aims to describe the current workflow, analytical strategies, and associated bioinformatics, and translate current IBD metabonomic knowledge into new potential clinically applicable treatment strategies, and outline future key translational perspectives., Competing Interests: Declaration of Competing Interest The authors have no interests to declare., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

During the COVID-19 pandemic, telemedicine and virtual consultations have been rapidly implemented in paediatrics all over the world. Previous and current studies have shown satisfaction with telemedicine, especially from a parental perspective. The largest barrier for implementation is technology. Some studies have found telemedicine equal to in-person visits. Only few studies have measured clinical outcomes, and the perspective of the child and adolescents as well as healthcare personal is rarely examined. There is a need of developing guidelines and education in paediatric telemedicine, as argued in this review.

Gut-associated lymphoid tissues (GALTs) comprise key intestinal immune inductive sites, including the Peyer's patches of the small intestine and different types of isolated lymphoid follicle (ILF) found along the length of the gut. Our understanding of human GALT is limited due to a lack of protocols for their isolation. Here we describe a technique that, uniquely among intestinal cell isolation protocols, allows identification and isolation of all human GALT, as well as GALT-free intestinal lamina propria (LP). The technique involves the mechanical separation of intestinal mucosa from the submucosa, allowing the identification and isolation of submucosal ILF (SM-ILF), LP-embedded mucosal ILF (M-ILF) and LP free of contaminating lymphoid tissue. Individual SM-ILF, M-ILF and Peyer's patch follicles can be subsequently digested for downstream cellular and molecular characterization. The technique, which takes 4-10 h, will be useful for researchers interested in intestinal immune development and function in health and disease.

Introduction: Biologics, such as tumor necrosis factor inhibitors, anti-integrins and anticytokines, are therapies for inflammatory bowel disease (IBD) that may increase the risk of infection. Most biologics undergo placental transfer during pregnancy and persist at detectable concentrations in exposed infants. Whether this is associated with an increased risk of infantile infections is controversial. We performed a systematic review and meta-analysis evaluating the risk of infantile infections after in utero exposure to biologics used to treat IBD., Methods: We searched PubMed, Embase, Scopus, Web of Science, and CENTRAL from inception to June 2020 to evaluate the association of biologic therapy during pregnancy in women with IBD and risk of infantile infections. Odds ratios of outcomes were pooled and analyzed using a random effects model., Results: Nine studies met the inclusion criteria comprising 8,013 women with IBD (5,212 Crohn's disease, 2,801 ulcerative colitis) who gave birth to 8,490 infants. Biologic use during pregnancy was not associated with an increased risk of all infantile infections (odds ratio [OR] 0.91, 95% confidence interval [CI] 0.73-1.14, I2 = 30%). In a subgroup analysis for the type of infection, biologic use was associated with increased infantile upper respiratory infections (OR 1.57, 95% CI 1.02-2.40, I2 = 4%). Biologic use during pregnancy was not associated with infantile antibiotic use (OR 0.91, 95% CI 0.73-1.14, I2 = 30%) or infection-related hospitalizations (OR 1.33, 95% CI 0.95-1.86, I2 = 26%)., Discussion: Biologics use during pregnancy in women with IBD is not associated with the overall risk of infantile infections or serious infections requiring antibiotics or hospitalizations but is associated with an increased risk of upper respiratory infections., (Copyright © 2020 by The American College of Gastroenterology.)

Intestinal organoids have widespread research and biomedical applications, such as disease modeling, drug testing and regenerative medicine. However, the transition towards clinical use has in part been hampered by the dependency on animal tumor-derived basement membrane extracts (BMEs), which are poorly defined and ill-suited for regulatory approval due to their origin and batch-to-batch variability. In order to overcome these limitations, and to enable clinical translation, we tested the use of a fully defined hydrogel matrix, QGel CN99, to establish and expand intestinal organoids directly from human colonic biopsies. We achieved efficient de novo establishment, expansion and organoid maintenance, while also demonstrating sustained genetic stability. Additionally, we were able to preserve stemness and differentiation capacity, with transcriptomic profiles resembling normal colonic epithelium. All data proved comparable to organoids cultured in the BME-benchmark Matrigel. The application of a fully defined hydrogel, completely bypassing the use of BMEs, will drastically improve the reproducibility and scalability of organoid studies, but also advance translational applications in personalized medicine and stem cell-based regenerative therapies., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Epidemiological studies have identified vitamin D (25(OH)D) deficiency to be highly prevalent among patients with inflammatory bowel disease (IBD), and low serum levels correlate with a higher disease activity and a more complicated disease course. The link to IBD pathogenesis has been subject of investigations, primarily due to the distinct immunological functions of vitamin D signaling, including anti-inflammatory and anti-fibrotic actions. Vitamin D is a pleiotropic hormone that executes its actions on cells through the vitamin D receptor (VDR). A leaky gut, i.e. an insufficient intestinal epithelial barrier, is thought to be central for the pathogenesis of IBD, and emerging data support the concept that vitamin D/VDR signaling in intestinal epithelial cells (IECs) has an important role in controlling barrier integrity. Here we review the latest evidence on how vitamin D promotes the interplay between IECs, the gut microbiome, and immune cells and thereby regulate the intestinal immune response. On the cellular level, vitamin D signaling regulates tight junctional complexes, apoptosis, and autophagy, leading to increased epithelial barrier integrity, and promotes expression of antimicrobial peptides as part of its immunomodulating functions. Further, intestinal VDR expression is inversely correlated with the severity of inflammation in patients with IBD, which might compromise the positive effects of vitamin D signaling in patients with flaring disease. Efforts to reveal the role of vitamin D in the pathophysiology of IBD will pave the road for the invention of more rational treatment strategies of this debilitating disease in the future., Competing Interests: Declaration of Competing Interest The authors have declared that no conflict of interest exists., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Germline telomere maintenance defects are associated with an increased incidence of inflammatory diseases in humans, yet whether and how telomere dysfunction causes inflammation are not known. Here, we show that telomere dysfunction drives pATM/c-ABL-mediated activation of the YAP1 transcription factor, up-regulating the major pro-inflammatory factor, pro-IL-18. The colonic microbiome stimulates cytosolic receptors activating caspase-1 which cleaves pro-IL-18 into mature IL-18, leading to recruitment of interferon (IFN)-γ-secreting T cells and intestinal inflammation. Correspondingly, patients with germline telomere maintenance defects exhibit DNA damage (γH2AX) signaling together with elevated YAP1 and IL-18 expression. In mice with telomere dysfunction, telomerase reactivation in the intestinal epithelium or pharmacological inhibition of ATM, YAP1, or caspase-1 as well as antibiotic treatment, dramatically reduces IL-18 and intestinal inflammation. Thus, telomere dysfunction-induced activation of the ATM-YAP1-pro-IL-18 pathway in epithelium is a key instigator of tissue inflammation.

The intestine contains some of the most diverse and complex immune compartments in the body. Here we describe a method for isolating human gut-associated lymphoid tissues (GALTs) that allows unprecedented profiling of the adaptive immune system in submucosal and mucosal isolated lymphoid follicles (SM-ILFs and M-ILFs, respectively) as well as in GALT-free intestinal lamina propria (LP). SM-ILF and M-ILF showed distinct patterns of distribution along the length of the intestine, were linked to the systemic circulation through MAdCAM-1 + high endothelial venules and efferent lymphatics, and had immune profiles consistent with immune-inductive sites. IgA sequencing analysis indicated that human ILFs are sites where intestinal adaptive immune responses are initiated in an anatomically restricted manner. Our findings position ILFs as key inductive hubs for regional immunity in the human intestine, and the methods presented will allow future assessment of these compartments in health and disease., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)