Distinct profiles of effector cytokines mark the different phases of Crohn's disease

Targeting CD4+ T cells through gut microbiota: therapeutic potential of traditional Chinese medicine in inflammatory bowel disease

Inflammatory Bowel Disease (IBD) is an autoimmune disease characterized by chronic relapsing inflammation of the intestinal tract. Gut microbiota (GM) and CD4+T cells are important in the development of IBD. A lot of studies have shown that GM and their metabolites like short-chain fatty acids, bile acids and tryptophan can be involved in the differentiation of CD4+T cells through various mechanisms, which in turn regulate the immune homeostasis of the IBD patients. Therefore, regulating CD4+T cells through GM may be a potential therapeutic direction for the treatment of IBD. Many studies have shown that Traditional Chinese Medicine (TCM) formulas and some herbal extracts can affect CD4+T cell differentiation by regulating GM and its metabolites. In this review, we mainly focus on the role of GM and their metabolites in regulating the differentiation of CD4+T cells and their correlation with IBD. We also summarize the current research progress on the regulation of this process by TCM.

Immunohistochemistry Analysis in Inflammatory Bowel Disease-Should We Bring to Light Interleukin-10?

Background/Objectives: Inflammatory bowel diseases (IBDs) are chronic intestinal disorders with an unpredictable course. In parallel with the advent of new biologic therapies targeting specific interleukin pathways, end-point targets have become more stringent, aiming for mucosal and even histologic healing. Methods: We conducted a prospective study assessing immunohistochemical (IHC) parameters in 46 IBD patients treated with biologic therapy. A similar IHC analysis was performed for comparison with a cohort of 10 "non-IBD" patients. Results: The highest integrated optical density (IOD) of TNF-α was observed in patients with dysplasia, abscesses, mucin depletion and basal plasmacytosis. Non-responders had higher pre- and post-treatment TNF-α expression in both UC and CD compared to responders. On the contrary, the same analysis conducted in the subpopulation treated with anti-TNF-α therapy (Infliximab and Adalimumab) did not reveal a substantial difference in TNF-α expression between responders and non-responders. High pre-treatment interleukin-10 expression was associated with biologic therapy failure, histological inflammatory activity and longer disease duration. Conclusions: Pre-treatment assessment of IL-10 might be a useful tool for identifying a high-risk subset of IBD patients and determining a more aggressive therapy and intensive monitoring strategy.

Biomarkers for Personalizing IBD Therapy: The Quest Continues

Despite recent advances in the understanding of the pathogenesis of inflammatory bowel diseases (IBD) and advent of multiple targeted therapies, approximately one-third of patients are primary non-responders to initiated treatment, and half of patients lose response over time. There is currently a lack of available biomarkers that would prognosticate therapeutic effectiveness of these advanced therapies. This is partly explained by insufficient characterization of the functional roles assumed by the chosen molecular targets during disease treatment. There is a dire need for validated objective biomarkers, which could be indicators of a biological process, that can be applied in clinical practice to assist us in assigning therapies to patients with the highest probability of response. An appropriate molecular and cellular characterization that accounts for the interindividual differences in drug efficacy and potential side effects would help to guide clinicians in the management of patients with IBD and represent a major step to tailor a more personalized approach to treatment. An appropriate combination of complementing biomarkers should ideally incorporate a multimodal analysis in which genetic, microbial, transcriptional, proteomic, metabolic, and immunologic data are combined to enable a truly personalized approach. This would classify patients into disease subgroups according to molecular characteristics, which would enable us to initiate the most appropriate therapeutic substance. Emergence of single-cell technologies to map the intestinal cellular landscape and multiomic approaches have helped to further dissect the pathogenic mechanisms of mucosal inflammation, but the clinical translation of potential biomarkers remains cumbersome, and an ongoing concerted effort by the IBD community is required.

Management of Post-Operative Crohn's Disease: Knowns and Unknowns

Crohn's disease (CD) is a chronic inflammatory disorder of the gastrointestinal tract characterized by relapsing-remission phases. CD often requires surgical intervention during its course, mainly ileo-cecal/ileo-colonic resection. However, surgery in CD is not curative and post-operative recurrence (POR) can happen. The management of CD after surgery presents challenges. Ensuring timely, effective, and safe therapy to prevent POR is essential but difficult, considering that approximately 20-30% of subjects may not experience endoscopic POR and that 40-50% will only exhibit intermediate lesions, which carry a low risk of mid- and long-term clinical and surgical POR. Currently, there are two accepted intervention strategies: early post-operative prophylactic therapy (systematically or based on the patient's risk of recurrence) or starting therapy after confirming endoscopic POR 6-12 months after surgery (endoscopy-driven prophylactic therapy). The risk of overtreatment lies in exposing patients to undesired adverse events, along with the costs associated with medications. Conversely, undertreatment may lead to missed opportunities to prevent bowel damage and the necessity for additional surgery. This article aims to perform a comprehensive review regarding the optimal strategy to reduce the risk of POR in CD patients and the current therapeutic options.

Comparing the Effects of Anti-TNF Agent and Ustekinumab on Small Bowel Inflammation in Crohn's Disease: Inverse Probability Weighting With Stabilized Weights of Propensity Scores

Background

Endoscopic mucosal healing serves as a critical predictor for achieving long-term remission in Crohn's disease treatment. Recent data indicate that the effectiveness of healing varies based on the location of gastrointestinal inflammation. Additionally, reports suggest that antitumor necrosis factor-α (anti-TNF-α) agents exhibit reduced efficacy in treating small intestinal inflammation compared to colorectal inflammation. Conversely, limited research exists regarding the impact of the anti-IL12/23 agent ustekinumab (UST) on small intestinal inflammation. This study aimed to compare the effects of anti-TNF-α agents and UST on small intestinal inflammation using propensity score analysis.

Methods

This retrospective observational study involved 70 patients with Crohn's disease who had inflammation in the small intestine and had initiated treatment with either anti-TNF agents or UST between March 2015 and August 2021. Endoscopic findings were evaluated before treatment commencement and at 1-2 years post-treatment initiation. The propensity score was employed to compare the efficacy of TNF agents and UST on small bowel inflammation.

Results

Ustekinumab exhibited greater improvement in the small intestinal endoscopy score than anti-TNF-α antibodies according to the propensity score analysis (inverse probability weighting; P = .0448). However, no significant disparity was observed in the overall improvement of endoscopic scores between UST and anti-TNF-α antibodies (P = .5938).

Conclusions

This study suggests that UST might be more effective than anti-TNF-α agents in treating small intestinal inflammation in Crohn's disease.

ATP citrate lyase (ACLY)-dependent immunometabolism in mucosal T cells drives experimental colitis in vivo

OBJECTIVE

Mucosal T cells play a major role in inflammatory bowel disease (IBD). However, their immunometabolism during intestinal inflammation is poorly understood. Due to its impact on cellular metabolism and proinflammatory immune cell function, we here focus on the enzyme ATP citrate lyase (ACLY) in mucosal T cell immunometabolism and its relevance for IBD.

DESIGN

ACLY expression and its immunometabolic impact on colitogenic T cell function were analysed in mucosal T cells from patients with IBD and in two experimental colitis models.

RESULTS

ACLY was markedly expressed in colon tissue under steady-state conditions but was significantly downregulated in lamina propria mononuclear cells in experimental dextran sodium sulfate-induced colitis and in CD4+ and to a lesser extent in CD8+ T cells infiltrating the inflamed gut in patients with IBD. ACLY-deficient CD4+ T cells showed an impaired capacity to induce intestinal inflammation in a transfer colitis model as compared with wild-type T cells. Assessment of T cell immunometabolism revealed that ACLY deficiency dampened the production of IBD-relevant cytokines and impaired glycolytic ATP production but enriched metabolites involved in the biosynthesis of phospholipids and phosphatidylcholine. Interestingly, the short-chain fatty acid butyrate was identified as a potent suppressor of ACLY expression in T cells, while IL-36α and resolvin E1 induced ACLY levels. In a translational approach, in vivo administration of the butyrate prodrug tributyrin downregulated mucosal infiltration of ACLYhigh CD4+ T cells and ameliorated chronic colitis.

CONCLUSION

ACLY controls mucosal T cell immunometabolism and experimental colitis. Therapeutic modulation of ACLY expression in T cells emerges as a novel strategy to promote the resolution of intestinal inflammation.

Coexisting Th1 and Th2 cytokines in patients with collagenous gastritis and implications for its pathogenesis

OBJECTIVES

Collagenous gastritis (CG) is a rare cause of refractory dyspepsia and anemia that frequently affects children and young adults and whose histological hallmark is chronic mucosal inflammation with a subepithelial collagen band. The etiology remains obscure, and no established treatments exist. We investigated the pathogenesis of CG by determining the expression profiles of genes related to immunity and inflammation in index biopsies.

METHODS

Gastric biopsies from 10 newly diagnosed patients with CG were evaluated using the NanoString nCounter assay. Gastric biopsies from 14 normal individuals served as controls. The gene expression ratios for CG versus controls were determined in pooled samples and confirmed in individual samples by quantitative reverse transcription polymerase chain reaction. The results were compared with previously reported expression data from a cohort of patients with collagenous colitis, a colonic disorder with similar morphology, including subepithelial collagen band.

RESULTS

CG biopsies featured enhanced expression of key genes encoding both Th1 (IFNγ, TNF-α, IL-2, IL-10, IL-12A, IL-12B, and IL-18) and Th2 cytokines (IL-3, IL-4, IL-5, IL-6, and IL-13). In contrast, biopsies from patients with CC exhibited upregulated Th1 cytokines only.

CONCLUSIONS

We show in this first published gene expression profiling study that CG involves simultaneous upregulation of Th1 and Th2 cytokines. This finding is unique, contrasting with other types of chronic gastritis as well as with collagenous colitis, which shares the presence of a collagen band. Involvement of Th2 immunity in CG would support further investigation of potential dietary, environmental, or allergic factors to guide future therapeutic trials.

TGF-β1 signaling and Smad7 control T-cell responses in health and immune-mediated disorders

Transforming growth factor (TGF)-β1, a member of the TGF-β superfamily, is produced by many immune and nonimmune cells and has pleiotropic effects on both innate and adaptive immunity, especially in the control of T-cell differentiation and function. Consistently, loss of TGF-β1 function is associated with exacerbated T-cell-dependent inflammatory responses that culminate in pathological processes in allergic and immune-mediated diseases. In this review, we highlight the roles of TGF-β1 in immunity, focusing mainly on its ability to promote differentiation of regulatory T cells, T helper (Th)-17, and Th9 cells, thus contributing to amplifying or restricting T-cell responses in health and human diseases (e.g., inflammatory bowel diseases, type 1 diabetes, asthma, and MS). In addition, we discuss the involvement of Smad7, an inhibitor of TGF-β1 signaling, in immune-mediated disorders (e.g., psoriasis, rheumatoid arthritis, MS, and inflammatory bowel diseases), as well as the discordant results of clinical trials with mongersen, an oral pharmaceutical compound containing a Smad7 antisense oligonucleotide, in patients with Crohn's disease. Further work is needed to ascertain the reasons for such a discrepancy as well as to identify better candidates for treatment with Smad7 inhibitors.

Immune-mediated inflammatory diseases: Common and different pathogenic and clinical features

The term "immune-mediated inflammatory diseases (IMIDs)" refers to several inflammatory pathologies of multifactorial etiology and involving either simultaneously or sequentially more organs. IMIDs share some common pathogenic mechanisms, which account for some similarities in the clinical course and the impact that these diseases may have on other organs and systems of the body. However, there are some differences in the IMID-associated pathological process, including the synthesis and function of multiple inflammatory cytokines, which are supposed to perpetuate the tissue-damaging inflammation. This justifies the different indications and responsiveness to corticosteroids, immunosuppressors, small molecules, and biologics. Many individuals with IMIDs are, however, intolerant, or unresponsive to the current drugs, thus suggesting the necessity of novel therapeutic approaches, such as the combination of compounds that either inhibit more immuno-inflammatory networks selectively or simultaneously suppress inflammatory signals and activate counter-regulatory pathways. In this article, we highlight the most relevant features of IMIDs and discuss how clinicians can combat the detrimental immune response in such disorders.

The role of upadacitinib in the treatment of ulcerative colitis

The JAK signaling pathway plays a major role in the immunopathology of autoimmune diseases, including inflammatory bowel disease. JAK enzymes provide novel targets for rapidly effective inflammatory bowel disease therapy, particularly in ulcerative colitis. Upadacitinib is a targeted JAK1 inhibitor. In multiple phase III clinical trials, upadacitinib has demonstrated significant improvement in clinical and endoscopic outcomes and quality of life for patients with moderate-to-severe ulcerative colitis. In this drug evaluation we describe the role of the JAK signaling pathway in ulcerative colitis, the mechanism of action of upadacitinib and the current clinical evidence for its use in ulcerative colitis; we also review its safety and tolerability, including for special populations.

CD4 T-Cell Subsets and the Pathophysiology of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an umbrella term for the chronic immune-mediated idiopathic inflammation of the gastrointestinal tract, manifesting as Crohn's disease (CD) or ulcerative colitis (UC). IBD is characterized by exacerbated innate and adaptive immunity in the gut in association with microbiota dysbiosis and the disruption of the intestinal barrier, resulting in increased bacterial exposure. In response to signals from microorganisms and damaged tissue, innate immune cells produce inflammatory cytokines and factors that stimulate T and B cells of the adaptive immune system, and a prominent characteristic of IBD patients is the accumulation of inflammatory T-cells and their proinflammatory-associated cytokines in intestinal tissue. Upon antigen recognition and activation, CD4 T-cells differentiate towards a range of distinct phenotypes: T helper(h)1, Th2, Th9, Th17, Th22, T follicular helper (Tfh), and several types of T-regulatory cells (Treg). T-cells are generated according to and adapt to microenvironmental conditions and participate in a complex network of interactions among other immune cells that modulate the further progression of IBD. This review examines the role of the CD4 T-cells most relevant to IBD, highlighting how these cells adapt to the environment and interact with other cell populations to promote or inhibit the development of IBD.

Retreatment with anti-tumor necrosis factor therapy in combination with an immunomodulator for recurrence of Crohn's disease after ileocecal resection results in prolonged continuation as compared to anti-tumor necrosis factor monotherapy

BACKGROUND

A considerable proportion of Crohn's disease patients that undergo ileocecal resection (ICR) have failed anti-tumor necrosis factor (TNF) therapy preoperatively. This study aimed to assess the effectiveness of retreatment of anti-TNF therapy in patients with postoperative recurrence.

METHODS

A real-world cohort study was performed on Crohn's disease patients who underwent primary ICR after anti-TNF therapy failure, and who were retreated with anti-TNF therapy for postoperative symptomatic Crohn's disease. The primary outcome was treatment failure (the need for (re)introduction of corticosteroids, immunosuppressants, or biologicals or the need for re-resection). Sub-analyses were performed on the nature of preoperative anti-TNF failure (primary non-response, secondary loss of response, intolerance), indication for ICR (refractory, stricturing, penetrating disease), combination therapy with immunomodulators, retreatment with the same anti-TNF agent and preoperative exposure to 1 vs. >1 anti-TNF agents.

RESULTS

In total, 66 of 364 patients retreated with anti-TNF therapy following ICR. Cumulative rates of treatment failure at 1 and 2 years were 28% and 47%. Treatment failure rate at 2 years was significantly lower in patients receiving combination therapy as compared to anti-TNF monotherapy (30% vs. 49%, P = 0.02). No difference in treatment failure was found with regards to the nature of preoperative anti-TNF failure (P = 0.76), indication for ICR (P = 0.88) switch of anti-TNF agent (P = 0.55) agent, and preoperative exposure to 1 vs. >1 anti-TNF agents (P = 0.88).

CONCLUSION

Retreatment with anti-TNF therapy for postoperative Crohn's disease recurrence is a valid strategy after preoperative failure. Combination therapy is associated with a lower rate of treatment failure.

A scoping review on early inflammatory bowel disease: definitions, pathogenesis, and impact on clinical outcomes

Background

Crohn's disease (CD) and ulcerative colitis (UC) arise from a dysregulation of the balance between commensal microbiota and mucosal-associated immune system, in patients with genetic and environmental predisposition. Different pathophysiological mechanisms have been reported to influence disease history, with impact on disease phenotype and risk of complications.

Objectives

This review aims to summarize the definitions of early CD and UC, analyze the underlying immunological mechanisms, and evaluate the impact of recognizing and treating early inflammatory bowel disease (IBD) on patients' prognosis (short- and long-term outcomes).

Design

To address this issue, we have performed a scoping review.

Data sources and methods

Three online databases (MEDLINE, Web of Science, and ScienceDirect) were searched and the results were independently screened by two reviewers.

Results

From 683 records identified, 42 manuscripts evaluating early IBD in adult patients were included. The 'early CD' concept was first described in 2008. Four years later, an international consensus proposed the definition of diagnosis up to 18 months, in patients without previous or current need for disease-modifying therapies. Several other definitions have been proposed; the '2 years since diagnosis' is the most used, regardless of disease characteristics or medication. The amount of evidence on early UC is lower and more recent. Regarding early disease pathogenesis, most theories emphasize the prominent role of innate immunity, followed by early-Th1 adaptive response.

Conclusion

The treatment of early CD seems to be crucial for the management of CD patients, impacting short-, medium-, and long-term outcomes. On the other hand, the early treatment of UC appears to be less advantageous, yet evidence comes from only a few retrospective studies.

Intra-abdominal septic complications after ileocolic resection increases risk for endoscopic and surgical postoperative Crohn's disease recurrence

BACKGROUND

Postoperative recurrence [POR] of Crohn's disease following ileocolonic resection is common. The impact of immediate postoperative intra-abdominal septic complications [IASC] on endoscopic and surgical recurrence has not been elucidated.

AIMS

To evaluate if IASC is associated with an increased risk for endoscopic and surgical POR.

METHODS

This was a retrospective study of adult Crohn's disease patients undergoing ileocolonic resection with primary anastomosis between 2009 and 2020. IASC was defined as anastomotic leak or intra-abdominal abscess within 90 days of the date of surgery. Multivariable logistic and Cox proportional hazard modelling were performed to assess the impact of IASC on endoscopic POR [modified Rutgeerts' score ≥ i2b] at index postoperative ileocolonoscopy and long-term surgical recurrence.

RESULTS

In 535 Crohn's disease patients [median age 35 years, 22.1% active smokers, 35.7% one or more prior resection] had an ileocolonic resection with primary anastomosis. A minority of patients [N = 47; 8.8%] developed postoperative IASC. In total, 422 [78.9%] patients had one or more postoperative ileocolonoscopies, of whom 163 [38.6%] developed endoscopic POR. After adjusting for other risk factors for postoperative recurrence, postoperative IASC was associated with significantly greater odds (adjusted odds ratio [aOR]: 2.45 [1.23-4.97]; p = 0.01) and decreased time (adjusted hazards ratio [aHR]: 1.60 [1.04-2.45]; p = 0.03] to endoscopic POR. Furthermore, IASC was associated with increased risk (aOR: 2.3 [1.04-4.87] p = 0.03) and decreased survival-free time [aHR: 2.53 [1.31-4.87]; p = 0.006] for surgical recurrence.

CONCLUSION

IASC is associated with an increased risk for endoscopic and surgical POR of Crohn's disease. Preoperative optimization to prevent IASC, in addition to postoperative biological prophylaxis, may help reduce the risk for endoscopic and surgical POR.

Fecal Stream Diversion Changes Intestinal Environment, Modulates Mucosal Barrier, and Attenuates Inflammatory Cells in Crohn's Disease

BACKGROUND

The intestinal environment plays important roles in mucosal barrier homeostasis and intestinal inflammation, as clarified in studies using experimental animals but not in humans.

AIMS

We investigated whether environmental changes in the fecal stream cause phenotypic changes in the human mucosal barrier.

METHODS

We obtained human ileal samples after fecal stream diversions in patients with rectal cancer or Crohn's disease. We investigated the bacterial load and diversity in the human defunctioned ileum, defined as the anal side of the ileum relative to the ileostomy. We also examined the epithelium and lamina propria cell phenotypes in the defunctioned ileum.

RESULTS

After fecal stream diversion, bacterial loads decreased significantly in the defunctioned ileum. Based on the Chao1, Shannon, and observed species indices, the diversity of mucosa-associated microbiota was lower in the defunctioned ileum than in the functional ileum. Moreover, the healthy defunctioned ileum showed reductions in villous height, goblet cell numbers, and Ki-67⁺ cell numbers. Additionally, interferon-γ⁺, interleukin-17⁺, and immunoglobulin A⁺ cell abundance in the lamina propria decreased. After the intestinal environment was restored with an ileostomy closure, the impaired ileal homeostasis recovered. The defunctioned ileum samples from patients with Crohn's disease also showed reductions in interferon-γ⁺ and interleukin-17⁺ cell numbers.

CONCLUSIONS

Fecal stream diversion reduced the abundance and diversity of intestinal bacteria. It also altered the intestinal mucosal barrier, similar to the alterations observed in germ-free animals. In patients with Crohn's disease, Th1 and Th17 cell numbers were attenuated, which suggests that the host-microbiome interaction is important in disease pathogenesis.

IL-23 Blockade in Anti-TNF Refractory IBD: From Mechanisms to Clinical Reality

Increasing insights into the immunopathogenesis of inflammatory bowel diseases [IBD] have led to the advent of targeted therapies that inhibit crucial mediators of the inflammatory process, thereby widening our available therapeutic armamentarium. Anti-tumour necrosis factor [anti-TNF] agents are still a mainstay of our therapeutic endeavours and the introduction of corresponding biosimilars has further widened their use. Nevertheless, only a subgroup of treated patients benefit from the initiated treatment and there is secondary non-response in the course of therapy. Initiation of subsequent therapy often poses a challenge to the treating physician, as non-response to primary anti-TNF treatment generally characterizes a patient group that is more treatment-resistant, which may be due to the immunological impregnation by prior anti-TNF exposure. At present, there is currently no guidance for the most appropriate second-line therapy after anti-TNF failure. Here, we review the efficacy of secondary biological therapy in anti-TNF-treated patients. We focus on and assess available clinical trial data of the emerging substance class of IL-23p19 inhibitors, which have demonstrated remarkable efficacy not only in anti-TNF-naïve but also refractory patients. We present molecular mechanisms that drive IL-23-mediated resistance to ongoing anti-TNF therapy and discuss the dynamic fluidity of the mucosal cytokine network in the course of therapy that perpetuates the mucosal inflammatory reaction. Translation of these findings into clinical practice might finally lead to initiation of the most appropriate therapy at the right time of the individual disease course, which would have important implications for the patient's probability of response to treatment.

Interleukin-34 Mediates Cross-Talk Between Stromal Cells and Immune Cells in the Gut

Initially known as a cytokine produced by and regulating the function of monocytes and macrophages, interleukin-34 (IL-34) can be synthesized by many cell types and interacts with receptors expressed by multiple immune and non-immune cells. IL-34 is constitutively expressed in the healthy human small intestine and colon and its production is markedly increased in damaged gut of patients with Crohn's disease and patients with ulcerative colitis, the main forms of chronic inflammatory bowel diseases (IBD) in human beings. Circumstantial evidence suggests that, in these pathologies, IL-34 plays a crucial role in mediating cross-talk between immune cells and stromal cells, thereby promoting activation of signalling pathways, which amplify the ongoing mucosal inflammation as well as production of fibrogenic molecules. In this article, we summarize the available data supporting the multiple effects of IL-34 in human IBD with particular attention to the role of the cytokine in immune and stromal cell interactions.

Novel trends with biologics in inflammatory bowel disease: sequential and combined approaches

Inflammatory bowel disease (IBD) management has changed dramatically over the past 20 years, after the introduction of targeted biological therapies. However, the impact of these new drugs in changing the natural history of disease is still under debate. Recent evidence seems to suggest that the extent of their efficacy might be, at least partially, dependent on the timing of their introduction and on the subsequent management strategy. In this complex landscape, the potential role for a more dynamic approach with treatments based on sequencing and combining targeted therapies has been explored only minimally so far. In this review, we aim to explore the potential biological rationale behind the use of sequential and combination therapies in IBD, to summarise the current knowledge on this topic and to propose a management algorithm that combines these notions.

Precision Medicine in Inflammatory Bowel Diseases

During the last decades, a better understanding of the mechanisms sustaining the pathogenic process in inflammatory bowel diseases (IBD) has contributed to expand the therapeutic armamentarium for patients with these disorders. Alongside with traditional therapies, monoclonal antibodies against tumor necrosis factor-α, the interleukin (IL)-12/IL-23 p40 subunit and the α4β7 integrin, and tofacitinib, a small molecule inhibiting intracellular pathways downstream to cytokine receptors, have entered into the clinic. However, these drugs are not effective in all patients and some responders can lose response over time. Such a therapeutic failure is, at least in part, dependent on the fact that, in IBD, the tissue damage is driven by simultaneous activation of multiple and distinct immune-inflammatory signals and the detrimental mucosal immune response changes over time even in the same patient. Therefore, personalized approaches aimed at identifying which patient should be treated with a specific drug at a precise time point are worth pursuing. A such approach has the advantage to improve efficacy of the drug and limit adverse reactions, thereby improving quality of the life of the patients and reducing costs. In this review, we summarize all the available evidence about the possible role of precision medicine in IBD.

Personalized Clinical Phenotyping through Systems Medicine and Artificial Intelligence

Personalized Medicine (PM) has shifted the traditional top-down approach to medicine based on the identification of single etiological factors to explain diseases, which was not suitable for explaining complex conditions. The concept of PM assumes several interpretations in the literature, with particular regards to Genetic and Genomic Medicine. Despite the fact that some disease-modifying genes affect disease expression and progression, many complex conditions cannot be understood through only this lens, especially when other lifestyle factors can play a crucial role (such as the environment, emotions, nutrition, etc.). Personalizing clinical phenotyping becomes a challenge when different pathophysiological mechanisms underlie the same manifestation. Brain disorders, cardiovascular and gastroenterological diseases can be paradigmatic examples. Experiences on the field of Fondazione Policlinico Gemelli in Rome (a research hospital recognized by the Italian Ministry of Health as national leader in "Personalized Medicine" and "Innovative Biomedical Technologies") could help understanding which techniques and tools are the most performing to develop potential clinical phenotypes personalization. The connection between practical experiences and scientific literature highlights how this potential can be reached towards Systems Medicine using Artificial Intelligence tools.

Role of the IL23/IL17 Pathway in Crohn's Disease

Crohn's disease (CD) is a chronic relapsing disorder of the gastrointestinal tract and represents one of the main entities of inflammatory bowel disease (IBD). CD affects genetically susceptible patients that are influenced by environmental factors and the intestinal microbiome, which results in excessive activation of the mucosal immune system and aberrant cytokine responses. Various studies have implicated the pro-inflammatory cytokines IL17 and IL23 in the pathogenesis of CD. IL23 is a member of the IL12 family of cytokines and is able to enhance and affect the expansion of pathogenic T helper type 17 (Th17) cells through various mechanisms, including maintenance of Th17 signature genes, upregulation of effector genes or suppression of repressive factors. Moreover, IL17 and IL23 signaling is able to induce a cascade of pro-inflammatory molecules like TNF, IFNγ, IL22, lymphotoxin, IL1β and lipopolysaccharide (LPS). Here, IL17A and TNF are known to mediate signaling synergistically to drive expression of inflammatory genes. Recent advances in understanding the immunopathogenetic mechanisms underlying CD have led to the development of new biological therapies that selectively intervene and inhibit inflammatory processes caused by pro-inflammatory mediators like IL17 and IL23. Recently published data demonstrate that treatment with selective IL23 inhibitors lead to markedly high response rates in the cohort of CD patients that failed previous anti-TNF therapy. Macrophages are considered as a main source of IL23 in the intestine and are supposed to play a key role in the molecular crosstalk with T cell subsets and innate lymphoid cells in the gut. The following review focuses on mechanisms, pathways and specific therapies in Crohn's disease underlying the IL23/IL17 pathway.

Predictors and Early Markers of Response to Biological Therapies in Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) are chronic conditions that primarily affect the gastrointestinal tract, with a complex pathogenesis; they are characterized by a significant heterogeneity of clinical presentations and of inflammatory pathways that sustain intestinal damage. After the introduction of the first biological therapies, the pipeline of therapies for IBD has been constantly expanding, and a significant number of new molecules is expected in the next few years. Evidence from clinical trials and real-life experiences has taught us that up to 40% of patients do not respond to a specific drug. Unfortunately, to date, clinicians lack a valid tool that can predict each patient’s response to therapies and that could help them in choosing what drug to administer. Several candidate biomarkers have been investigated so far, with conflicting results: clinical, genetic, immunological, pharmacokinetic and microbial markers have been tested, but no ideal marker has been identified so far. Based on recent evidence, multiparametric models seemingly hold the greatest potential for predicting response to therapy. In this narrative review, we aim to summarize the current knowledge on predictors and early markers of response to biological therapies in IBD.

The Role of Inflammation in Crohn's Disease Recurrence after Surgical Treatment

Introduction

Postoperative recurrence after surgery for Crohn's disease (CD) is virtually inevitable, and its mechanism is poorly known.

Aim

To review the numerous factors involved in CD postoperative recurrence (POR) pathogenesis, focusing on single immune system components as well as the immune system as a whole and highlighting the clinical significance in terms of preventive strategies and future perspectives.

Methods

A systematic literature search on CD POR, followed by a review of the main findings.

Results

The immune system plays a pivotal role in CD POR, with many different factors involved. Memory T-lymphocytes retained in mesenteric lymph nodes seem to represent the main driving force. New pathophysiology-based preventive strategies in the medical and surgical fields may help reduce POR rates. In particular, surgical strategies have already been developed and are currently under investigation.

Conclusions

POR is a complex phenomenon, whose driving mechanisms are gradually being unraveled. New preventive strategies addressing these mechanisms seem promising.

High Smad7 in the early post-operative recurrence of Crohn's disease

Background

In Crohn’s disease (CD), one of the major inflammatory bowel disease (IBD) in human beings, there is over-expression of Smad7, an intracellular inhibitor of the suppressive cytokine TGF-β1. The aim of this study was to assess whether Smad7 over-expression occurs in the early and/or late phases of CD.

Methods

Mucosal samples were taken from the neo-terminal ileum of CD patients undergoing ileocolonic resection, with or without (early CD) post-operative endoscopic recurrence, and terminal ileum of CD patients with long-standing disease undergoing intestinal resection (late CD). Smad7 was examined by immunohistochemistry and cytokine expression was analysed by flow-cytometry.

Results

Before the appearance of endoscopic lesions, the mucosa of the neo-terminal ileum contained high number of Smad7-expressing cells in both the epithelial and lamina propria compartments. Transition from this stage to endoscopic recurrence was marked by persistence of high number of Smad7-positive cells, which reduced significantly in the late stages of the disease, where Smad7 expression remained, however, greater than that seen in normal controls. In samples with early lesions, Smad7 expression positively correlated with the number of interferon-γ-secreting cells.

Conclusions

Smad7 induction is an early event in the inflammatory sequence occurring in CD, thus suggesting that knockdown of Smad7 can help prevent post-operative recurrence.

Early Intervention in Ulcerative Colitis: Ready for Prime Time?

Growing evidence shows that ulcerative colitis (UC) is a progressive disease similar to Crohn’s disease (CD). The UC-related burden is often underestimated by physicians and a standard step-up therapeutic approach is preferred. However, in many patients with UC the disease activity is not adequately controlled by current management, leading to poor long-term prognosis. Data from both randomized controlled trials and real-world studies support early intervention in CD in order to prevent disease progression and irreversible bowel damage. Similarly, an early disease intervention during the so-called “window of opportunity” could lead to better outcomes in UC. Here, we summarize the literature evidence on early intervention in patients with UC, highlighting strengths and limitations of this approach.

Role of Interleukin-17 in Pathogenesis of Intestinal Fibrosis in Mice

BACKGROUND

The level of interleukin (IL)-17 is commonly increased in serum and intestinal mucosa of patients with inflammatory bowel disease, especially Crohn's disease with intestinal stricture. However, the role of IL-17 in the pathogenesis of intestinal fibrosis and the effect of anti-IL-17 treatment on intestinal fibrosis remain unclear; these issues are studied in vivo in this study.

METHOD

A total of 24 wild female Balb/c mice (18-22 g) were randomly divided into three groups: (1) control group, (2) 2,4,6-trinitrobenzenesulfonic acid (TNBS) + immunoglobulin G (IgG) group, and (3) TNBS + anti-IL-17 group. The levels of IL-17, IL-1β, transforming growth factor (TGF)-β1, and tumor necrosis factor (TNF)-α in blood and of collagen 3 and IL-17 in gut were measured by enzyme-linked immunosorbent assay (ELISA). The messenger RNA (mRNA) levels of collagen 3, IL-17, TNF-α, tissue inhibitor of metalloproteinase (TIMP)-1, and matrix metalloproteinase (MMP)-2 in gut were measured by reverse-transcription polymerase chain reaction. The protein expression of IL-17, collagen 3, TNF-α, TIMP-1, and MMP-2 were measured by immunoblot analysis. Collagen deposition was evaluated by standard hematoxylin and eosin and Masson's trichrome staining.

RESULTS

The profibrogenic cytokines IL-17, IL-1β, TGF-β1, and TNF-α in serum, mRNA levels of collagen 3, IL-17, TNF-α, TIMP-1, and MMP-2, and protein levels of IL-17, collagen 3, TNF-α, TIMP-1, and MMP-2 in gut were upregulated in TNBS-induced intestinal fibrosis mice. Treatment with anti-IL-17 antibody significantly alleviated intestinal fibrosis and reduced both mRNA and protein levels of collagen 3, TNF-α, TIMP-1, and MMP-2. The levels of profibrogenic cytokines IL-1β, TGF-β1, and TNF-α were also decreased in mice treated with anti-IL-17 antibody.

CONCLUSIONS

IL-17 contributes to the pathogenesis of intestinal fibrosis, and anti-IL-17 therapy may weaken this effect by downregulating expression of profibrogenic cytokines and disturbing the MMP/TIMPs balance.

JAK-STAT pathway targeting for the treatment of inflammatory bowel disease

Cytokines are involved in intestinal homeostasis and pathological processes associated with inflammatory bowel disease (IBD). The biological effects of cytokines, including several involved in the pathology of Crohn's disease and ulcerative colitis, occur as a result of receptor-mediated signalling through the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) DNA-binding families of proteins. Although therapies targeting cytokines have revolutionized IBD therapy, they have historically targeted individual cytokines, and an unmet medical need exists for patients who do not respond to or lose response to these treatments. Several small-molecule inhibitors of JAKs that have the potential to affect multiple pro-inflammatory cytokine-dependent pathways are in clinical development for the treatment of IBD, with one agent, tofacitinib, already approved for ulcerative colitis and several other agents with demonstrated efficacy in early phase trials. This Review describes the current understanding of JAK-STAT signalling in intestinal homeostasis and disease and the rationale for targeting this pathway as a treatment for IBD. The available evidence for the efficacy, safety and pharmacokinetics of JAK inhibitors in IBD as well as the potential approaches to optimize treatment with these agents, such as localized delivery or combination therapy, are also discussed.

Impact of smoking cigarette on the mRNA expression of cytokines in mucosa of inflammatory bowel disease

It is well known that smoking is the risk factor in the development and clinical course of Crohn s disease (CD), but on the other hand, smoking is a protective factor against ulcerative colitis (UC). The pathways that are influenced by smoking in CD and UC are poorly understood. The aim of our study was to analyse the influence of smoking on the mRNA expression of cytokines in mucosa in patients with CD and UC. We performed a cross-sectional study. The cohort consisted of 86 IBD patients (48 CD patients and 38 UC patients) and took place at the IBD Centre at the University Hospital Bratislava-Ružinov. We took the demographic and clinical data of each patient, including information about their smoking habits. We performed a colonoscopy on each patient and took biopsies from both inflamed and non-inflamed sigma (CD, UC) and terminal ileum (CD). mRNA was extracted from mucosal biopsy samples for each cytokine and was normalized to a housekeeping gene (GAPDH). Finally, we compared the mRNA expression of target cytokines in the mucosa of smokers and non-smokers in IBD patients. Smokers with Crohn s disease have a significantly higher mRNA expression of pro-inflammatory cytokine TNF ? (p=0.003) in inflamed mucosa in sigma compared with non-smokers. In smokers with ulcerative colitis, we observed significantly higher mRNA expression of anti-inflammatory cytokine IL 10 (p=0.022) in non-inflamed mucosa of sigma. Similarly, smokers with UC have a significantly decreased mRNA expression of cytokine TLR 2 (p=0.024) and CCR1 (p=0.049) in non-inflamed mucosa of sigma. Based on our results, smoking has a positive influence on cessation and the clinical course of UC due to the stimulation of anti-inflammatory cytokine IL 10 in mucosa. On the other hand, smokers with CD have a higher expression of pro-inflammatory cytokine TNF ?, which could be associated with a worsening of the disease and response to therapy.

Inflammatory bowel disease pathobiology: the role of the interferon signature

The pathogenesis of inflammatory bowel disease (IBD) is still unclear, but includes both inflammatory and autoimmune reactions. Current methodological approaches could better elucidate the cytokine pathways and the genetics involved in the etiopathogenesis of this disease. Interferons (IFNs) are cytokines that play a key role in autoimmune/inflammatory disorders because of their pro- and anti-inflammatory properties as well as their immunoregulatory functions. An increased expression of IFN-regulated genes, widely known as an IFN signature, has been reported in blood and tissue from patients with autoimmune disorders. In this review, we present the function as well as the clinical and therapeutic potential of the IFN signature. Current data demonstrate that the IFN signature can be used as a biomarker that defines disease activity in autoimmune diseases, although this has not been thoroughly studied in IBD. Consequently, further investigation of the IFN signature in IBD would be essential for a better understanding of its actions.

Role of innate lymphoid cells in chronic colitis during anti-IL-17A therapy

IL-17A is an important cytokine in intestinal inflammation. However, anti-IL-17A therapy does not improve clinical outcomes in patients with Crohn's disease. We aimed to evaluate the role of RORγt+ innate lymphoid cells (ILCs) in murine colitis models in the absence of IL-17A. An acute colitis model was induced with either dextran sulfate sodium (DSS) or trinitrobenzenesulfonic acid (TNBS) and a chronic colitis model was induced by CD4+CD45RBhi T cell transfer from either wild-type C57BL/6 or Il17a-/- mice. An anti-IL-17A antibody, secukinumab, was also used to inhibit IL-17A function in the colitis model. Flow cytometry was performed to analyze the population of RORγt+ ILCs in the colonic lamina propria of mice with chronic colitis. Acute intestinal inflammation due to DSS and TNBS was attenuated in IL-17A knockout mice, whereas chronic colitis was not relieved by T cell transfer from Il17a-/- mice (% of original body weight: wild-type mice vs. Il17a-/- mice, 81.9% vs. 82.2%; P = 0.922). However, the mean proportion of Lin-RORγt+ lymphocytes was higher after T cell transfer from Il17a-/- mice than that after T cell transfer from wild-type mice (28.8% vs. 18.5%). The proportion of Lin-RORγt+ was also increased in Rag2-/- mice that received T cell transfer from wild-type mice when anti-IL-17A antibody was administered (31.7%). Additionally, Il6 and Il22 tended to be highly expressed after T cell transfer from Il17a-/- mice. In conclusion, RORγt+ ILCs may have an important role in the pathogenesis of chronic colitis in the absence of IL-17A. Blocking the function of IL-17A may upregulate Il6 and recruit RORγt+ ILCs in chronic colitis, thereby upregulating IL-22 and worsening the clinical outcomes of patients with Crohn's disease.

Mucosal microbial load in Crohn's disease: A potential predictor of response to faecal microbiota transplantation

BACKGROUND

The remission of Crohn's disease (CD) can be accomplished by faecal microbiota transplantation (FMT). However, this procedure has a low success rate, which could be attributed to mis-communication between recipient intestinal mucosa and donor microbiota.

METHODS

Here we used a human explant tissue model and an in vivo mouse model to examine changes in recipient intestinal mucosa upon contact with a faecal suspension (FS) obtained from a healthy donor. CD patients provided resected inflamed and non-inflamed mucosal tissues, whereas control colonic mucosa samples were collected from colorectal cancer patients. For the models, mucosal microbiome composition and tissue response were evaluated.

FINDINGS

We show that cytokine release and tissue damage were significantly greater in inflamed compared to non-inflamed CD tissues. Moreover, mucosal samples harbouring an initial low microbial load presented a shift in composition towards that of the FS, an increase in the relative count of Faecalibacterium prausnitzii, and a higher secretion of anti-inflammatory cytokine IL-10 compared to those with a high microbial load.

INTERPRETATION

Our results indicate that FMT during active inflammatory disease can compromise treatment outcome. We recommend the stratification of FMT recipients on the basis of tissue microbial load as a strategy to ensure successful colonization.

FUNDING

This study was supported by grants from the Instituto de Salud Carlos III/FEDER (PI17/00614), the European Commission: (INCOMED-267128) and PERIS (SLT002/16). K.M. is a postdoctoral fellow and S.V. a senior clinical investigator of the Fund for Scientific Research Flanders, Belgium (FWO-Vlaanderen).

Dissecting the Heterogeneity in T-Cell Mediated Inflammation in IBD

Infiltration of the lamina propria by inflammatory CD4+ T-cell populations is a key characteristic of chronic intestinal inflammation. Memory-phenotype CD4+ T-cell frequencies are increased in inflamed intestinal tissue of IBD patients compared to tissue of healthy controls and are associated with disease flares and a more complicated disease course. Therefore, a tightly controlled balance between regulatory and inflammatory CD4+ T-cell populations is crucial to prevent uncontrolled CD4+ T-cell responses and subsequent intestinal tissue damage. While at steady state, T-cells display mainly a regulatory phenotype, increased in Th1, Th2, Th9, Th17, and Th17.1 responses, and reduced Treg and Tr1 responses have all been suggested to play a role in IBD pathophysiology. However, it is highly unlikely that all these responses are altered in each individual patient. With the rapidly expanding plethora of therapeutic options to inhibit inflammatory T-cell responses and stimulate regulatory T-cell responses, a crucial need is emerging for a robust set of immunological assays to predict and monitor therapeutic success at an individual level. Consequently, it is crucial to differentiate dominant inflammatory and regulatory CD4+ T helper responses in patients and relate these to disease course and therapy response. In this review, we provide an overview of how intestinal CD4+ T-cell responses arise, discuss the main phenotypes of CD4+ T helper responses, and review how they are implicated in IBD.

Should We Divide Crohn's Disease Into Ileum-Dominant and Isolated Colonic Diseases?

Crohn's disease (CD) is an inflammatory bowel disease that can involve any region of the gastrointestinal tract. First described in 1932 as terminal ileitis or regional enteritis, it predominately involves the ileum with or without colonic involvement. Isolated colonic CD was first described in 1960 and since then the phenotypic classification of CD has evolved to stratify patients into isolated ileal, ileocolonic, or isolated colonic involvement. In the current review we evaluate the published literature regarding differences in epidemiology, natural history, pathogenesis, response to therapy, and disease monitoring, when stratified by disease location. Based on the available evidence consideration could be given to a new classification for CD, which splits it into ileum dominant (isolated ileal and ileocolonic) and isolated colonic disease. This may allow for a more optimized approach to clinical care and scientific research for CD.

The Role of Early Biologic Therapy in Inflammatory Bowel Disease

The goals for treatment of inflammatory bowel diseases (IBDs) are changing from elimination of symptoms toward complete disease control-a process that demands both clinical and endoscopic remission. This new IBD treatment paradigm has been shifting from a conventional "step-up" approach toward a more "top-down" early intervention treatment strategy. Recent studies suggest that the use of biologic agents, specifically those targeting tumor necrosis factor alpha, earlier in the treatment course improves patient outcomes and can prevent progression to irreversible bowel damage. Although the strategy of early intervention has accumulating evidence in Crohn's disease, there is less evidence supporting its impact in ulcerative colitis.

Macrophages Inability to Mediate Adherent-Invasive E. coli Replication is Linked to Autophagy in Crohn's Disease Patients

The macrophages from Crohn’s Disease (CD) patients are defective to control the replication of CD-associated adherent-invasive E. coli (AIEC). We aimed to identify the host factors associated with AIEC replication focusing on polymorphisms related to autophagy. Peripheral blood monocyte-derived macrophages (MDM), obtained from 95 CD patient, 30 ulcerative colitis (UC) patients and 15 healthy subjects, were genotyped for several CD-associated polymorphisms. AIEC bacteria survival increased within MDM from CD patients compared to UC (p = 0.0019). AIEC bacteria survival increased in patients with CD-associated polymorphism IRGM (p = 0.05) and reduced in those with CD-associated polymorphisms XBP-1 (p = 0.026) and ULK-1 (p = 0.033). AIEC infection led to an increase of pro-inflammatory cytokines IL-1β (p < 0.0001) and TNF-α (p < 0.0001) in CD macrophages. ULK-1 expression increased in AIEC-infected MDM from CD patients compared to MDM from UC patients or healthy subjects (p = 0.0056) and correlated with AIEC survival (p = 0.0013). Moreover, the expression of ULK-1 phosphorylation on Serine 757 decreased following to AIEC infection (p < 0.0001). Short-term silencing of ULK-1 and IRGM genes restricted and promote, respectively, AIEC survival within MDM (p = 0.0018 and p = 0.0291). In conclusion, the macrophage defect to mediate AIEC clearance in CD patients is linked to polymorphisms related to autophagy such as IRGM and ULK-1.

Shorter Disease Duration Is Associated With Higher Rates of Response to Vedolizumab in Patients With Crohn's Disease But Not Ulcerative Colitis

BACKGROUND & AIMS

Patients with Crohn's disease (CD), but not ulcerative colitis (UC), of shorter duration have higher rates of response to tumor necrosis factor (TNF) antagonists than patients with longer disease duration. Little is known about the association between disease duration and response to other biologic agents. We aimed to evaluate response of patients with CD or UC to vedolizumab, stratified by disease duration.

METHODS

We analyzed data from a retrospective, multicenter, consortium of patients with CD (n = 650) or UC (n = 437) treated with vedolizumab from May 2014 through December 2016. Using time to event analyses, we compared rates of clinical remission, corticosteroid-free remission (CSFR), and endoscopic remission between patients with early-stage (≤2 years duration) and later-stage (>2 years) CD or UC. We used Cox proportional hazards models to identify factors associated with outcomes.

RESULTS

Within 6 months initiation of treatment with vedolizumab, significantly higher proportions of patients with early-stage CD, vs later-stage CD, achieved clinical remission (38% vs 23%), CSFR (43% vs 14%), and endoscopic remission (29% vs 13%) (P < .05 for all comparisons). After adjusting for disease-related factors including previous exposure to TNF antagonists, patients with early-stage CD were significantly more likely than patients with later-stage CD to achieve clinical remission (adjusted hazard ratio [aHR], 1.59; 95% CI, 1.02-2.49), CSFR (aHR, 3.39; 95% CI, 1.66-6.92), and endoscopic remission (aHR, 1.90; 95% CI, 1.06-3.39). In contrast, disease duration was not a significant predictor of response among patients with UC.

CONCLUSIONS

Patients with CD for 2 years or less are significantly more likely to achieve a complete response, CSFR, or endoscopic response to vedolizumab than patients with longer disease duration. Disease duration does not associate with response vedolizumab in patients with UC.

Mucosal and Systemic Immune Profiles Differ During Early and Late Phases of the Disease in Patients With Active Ulcerative Colitis

BACKGROUND AND AIMS

Alterations in the immunopathogenesis in ulcerative colitis [UC] during the disease course have been proposed. We therefore aimed to determine mucosal and systemic immune profiles in individual patients at the time of diagnosis [early disease] and after 10 years [late disease].

METHODS

Patients with UC provided serum and mucosal biopsies during a flare in early and in late disease. Serum samples were analysed using the Olink Proseek Inflammation panel. mRNA gene expression of biopsies was analysed using the Qiagen RT2 Profiler PCR Arrays Antibacterial response and T Helper Cell Differentiation.

RESULTS

Orthogonal projections to latent structures discriminant analyses [OPLS-DA] demonstrated that the profile of 15 serum proteins discriminated in early and late disease [R2 = 0.84, Q2 = 0.65] in 15 UC patients. Eight of these proteins were differently expressed between the groups [Q <0.05]. Further, OPLS-DA of the mRNA profiles in biopsies strongly discriminated early and late disease with high predictability [R2 = 0.96, Q2 = 0.89]; 42 genes were differently expressed at the two time points [Q <0.05]. Finally, principal component analysis showed that T helper [Th] 1- and Th2-related genes were associated with early disease and late disease, respectively, and hierarchical cluster analysis was able to cluster patients with early from late disease with only minor overlap.

CONCLUSIONS

Mucosal and systemic immune profiles differ between early and late disease in patients with active UC, with a transition from a Th1- to a Th2-driven disease in the intestine. Improved understanding of the variation in immunopathogenesis during the disease course in UC is important to guide individualised treatment decision making.

A Nomogram Combining Fecal Calprotectin Levels and Plasma Cytokine Profiles for Individual Prediction of Postoperative Crohn's Disease Recurrence

BACKGROUND

The aims of this study were to characterize the immune response profile in patients with Crohn's disease (CD) and early postoperative recurrence (POR), to identify predictive biomarkers, and to develop a noninvasive predictive tool for individual estimation of POR risk.

METHODS

Sixty-one patients who had undergone ileocolonic resection for CD were prospectively included and followed up for 24 months. Fecal calprotectin (FC), analytical parameters, and plasma cytokines were obtained before surgery and at various time points during postoperative follow-up. Morphological recurrence was assessed by ileocolonoscopy or magnetic resonance enterography within 6-12 months after surgery. Clinical activity was scored using the Harvey-Bradshaw Index.

RESULTS

Twenty-seven patients (44.3%) had morphological recurrence during follow-up. Fecal calprotectin values were significantly associated with POR risk over time. The receiver operating characteristic curve for FC provided an area under the curve (AUC) of 0.88 (95% confidence interval, 0.75-0.96), and morphological recurrence was best predicted by FC ≥160 μg/g at 6 months after surgery (85% sensitivity, 70% specificity, 26% predictive positive value, 98% negative predictive value [NPV]). The plasma cytokine profile showed higher presurgery interleukin (IL)-13 plasma levels and higher IL-6 and interferon (IFN)-γ levels at 6 months after surgery in patients with POR compared with patients without recurrence. The combination of FC, IL-6, and IFN-γ values at 6 months gave an AUC of 0.90 for predicting an early recurrence.

CONCLUSIONS

FC values <160 μg/g at 6 months have a high NPV to rule out early lesions. Combined values of FC, IL-6, and IFN-γ levels at 6 months postsurgery constitute a prognostic index with a high predictive capacity to assess the risk of early POR.

Inflammatory cytokines: from discoveries to therapies in IBD

Introduction: Although the etiology of inflammatory bowel diseases (IBD) remains unknown, accumulating evidence suggests that the intestinal tissue damage in these disorders is due to a dynamic interplay between immune cells and non-immune cells, which is mediated by cytokines produced within the inflammatory microenvironment. Areas covered: We review the available data about the role of inflammatory cytokines in IBD pathophysiology and provide an overview of the therapeutic options to block the function of such molecules. Expert opinion: Genome studies, in vitro experiments with patients' samples and animal models of colitis, have largely advanced our understanding of how cytokines modulate the ongoing mucosal inflammation in IBD. However, not all the cytokines produced within the damaged gut seem to play a major role in the amplification and perpetuation of the IBD-associated inflammatory cascade. Indeed, while some of the anti-cytokine compounds are effective in some subgroups of IBD patients, others have no benefit. In this complex scenario, a major unmet need is the identification of biomarkers that can predict response to therapy and facilitate a personalized therapeutic approach, which maximizes the benefits and limits the adverse events.

Temporally Distinct Functions of the Cytokines IL-12 and IL-23 Drive Chronic Colon Inflammation in Response to Intestinal Barrier Impairment

Epithelial barrier defects are implicated in the pathogenesis of inflammatory bowel disease (IBD); however, the role of microbiome dysbiosis and the cytokine networks orchestrating chronic intestinal inflammation in response to barrier impairment remain poorly understood. Here, we showed that altered Schaedler flora (ASF), a benign minimal microbiota, was sufficient to trigger colitis in a mouse model of intestinal barrier impairment. Colitis development required myeloid-cell-specific adaptor protein MyD88 signaling and was orchestrated by the cytokines IL-12, IL-23, and IFN-γ. Colon inflammation was driven by IL-12 during the early stages of the disease, but as the mice aged, the pathology shifted toward an IL-23-dependent inflammatory response driving disease chronicity. These findings reveal that IL-12 and IL-23 act in a temporally distinct, biphasic manner to induce microbiota-driven chronic intestinal inflammation. Similar mechanisms might contribute to the pathogenesis of IBD particularly in patients with underlying intestinal barrier defects.

Expansion of IL-23 receptor bearing TNFR2+ T cells is associated with molecular resistance to anti-TNF therapy in Crohn's disease

OBJECTIVE

Anti-tumour necrosis factor (TNF) antibodies are successfully used for treatment of Crohn's disease. Nevertheless, approximately 40% of patients display failure to anti-TNF therapy. Here, we characterised molecular mechanisms that are associated with endoscopic resistance to anti-TNF therapy.

DESIGN

Mucosal and blood cells were isolated from patients with Crohn's disease prior and during anti-TNF therapy. Cytokine profiles, cell surface markers, signalling proteins and cell apoptosis were assessed by microarray, immunohistochemistry, qPCR, ELISA, whole organ cultures and FACS.

RESULTS

Responders to anti-TNF therapy displayed a significantly higher expression of TNF receptor 2 (TNFR2) but not IL23R on T cells than non-responders prior to anti-TNF therapy. During anti-TNF therapy, there was a significant upregulation of mucosal IL-23p19, IL23R and IL-17A in anti-TNF non-responders but not in responders. Apoptosis-resistant TNFR2+IL23R+ T cells were significantly expanded in anti-TNF non-responders compared with responders, expressed the gut tropic integrins α4β7, and exhibited increased expression of IFN-γ, T-bet, IL-17A and RORγt compared with TNFR2+IL23R- cells, indicating a mixed Th1/Th17-like phenotype. Intestinal TNFR2+IL23R+ T cells were activated by IL-23 derived from CD14+ macrophages, which were significantly more present in non-responders prior to anti-TNF treatment. Administration of IL-23 to anti-TNF-treated mucosal organ cultures led to the expansion of CD4+IL23R+TNFR2+ lymphocytes. Functional studies demonstrated that anti-TNF-induced apoptosis in mucosal T cells is abrogated by IL-23.

CONCLUSIONS

Expansion of apoptosis-resistant intestinal TNFR2+IL23R+ T cells is associated with resistance to anti-TNF therapy in Crohn's disease. These findings identify IL-23 as a suitable molecular target in patients with Crohn's disease refractory to anti-TNF therapy.

Mechanisms of molecular resistance and predictors of response to biological therapy in inflammatory bowel disease

Biological therapy has led to marked improvements in treatment of patients with inflammatory bowel disease, and an increasing number of drugs has been approved for treatment. However, only a subgroup of patients responds to therapy, highlighting the need to identify biomarkers for therapeutic response to allow personalised medicine in inflammatory bowel disease. Potential markers of response to biological therapy have been identified; however, studies also suggest that changes in the composition of immune cell infiltrates in response to therapeutic pressure lead to molecular resistance to these drugs. For instance, the cytokine interleukin 23 has been identified as a driver of evasion of apoptosis in response to anti-tumour necrosis factor drugs in patients with Crohn's disease, leading to expansion of apoptosis-resistant T cells and drug resistance. In this Review, we examine the concept of molecular resistance to biological therapy and discuss implications for future therapy.

Mechanisms by Which the Gut Microbiota Influences Cytokine Production and Modulates Host Inflammatory Responses

The gastrointestinal tract encounters a wide variety of microorganisms, including beneficial symbionts, pathobionts, and pathogens. Recent evidence has shown that the gut microbiota, directly or indirectly through its components, such as metabolites, actively participates in the host inflammatory response by cytokine-microbiota or microbiota-cytokine modulation interactions, both in the gut and systemically. Therefore, further elucidation of host cytokine molecular pathways and microbiota components will provide a novel and promising therapeutic approach to control or prevent inflammatory disease and to maintain host homeostasis. The purpose of this review is to summarize well-established scientific findings and provide an updated overview regarding the direct and indirect mechanisms by which the gut microbiota can influence the inflammatory response by modulating the host's cytokine pathways that are mostly involved, but not exclusively so, with gut homeostasis. In addition, we will highlight recent results from our group, which suggest that the microbiota promotes cytokine release from inflammatory cells though activation of microbial metabolite sensor receptors that are more highly expressed on inflammatory and intestinal epithelial cells.

Intestinal Organoids as a Novel Complementary Model to Dissect Inflammatory Bowel Disease

Inflammatory bowel diseases (IBDs) include colitis ulcerosa and Crohn's disease, besides the rare microscopic colitis. Both diseases show a long-lasting, relapsing-remitting, or even chronic active course with tremendous impact on quality of life. IBDs frequently cause disability, surgical interventions, and high costs; as in other autoimmune diseases, their prevalent occurrence at an early phase of life raises the burden on health care systems. Unfortunately, our understanding of the pathogenesis is still incomplete and treatment therefore largely focuses on suppressing the resulting excessive inflammation. One obstacle for deciphering the causative processes is the scarcity of models that parallel the development of the disease, since intestinal inflammation is mostly induced artificially; moreover, the intestinal epithelium, which strongly contributes to IBD pathogenesis, is difficult to assess. Recently, the development of intestinal epithelial organoids has overcome many of those problems. Here, we give an overview on the current understanding of the pathogenesis of IBDs with reference to the limitations of previous well-established experimental models. We highlight the advantages and detriments of recent organoid-based experimental setups within the IBD field and suggest possible future applications.

IL-12, IL-23 and IL-17 in IBD: immunobiology and therapeutic targeting

IL-12 and IL-23 are closely related cytokines with important roles in the regulation of tissue inflammation. Converging evidence from studies in mice, human observational studies and population genetics supports the importance of these cytokines in the regulation of mucosal inflammation in the gut in particular. Ustekinumab, a therapeutic antibody targeting both cytokines is now widely licensed for the treatment of Crohn's disease, including in Europe, the USA, Canada and Japan, whilst agents targeting IL-23 specifically are in late-phase clinical trials. We review the emerging understanding of the biology of IL-12 and IL-23, as well as that of their major downstream cytokines, including IL-17. In particular, we discuss how their biology has influenced the development of clinical trials and therapeutic strategies in IBD, as well as how findings from clinical trials, at times surprising, have in turn refocused our understanding of the underlying biology.

Causes of Treatment Failure in Children With Inflammatory Bowel Disease Treated With Infliximab: A Pharmacokinetic Study

OBJECTIVES

Anti-tumor necrosis factor antibodies have led to a revolution in the treatment of inflammatory bowel diseases (IBD); however, a sizable proportion of patients does not respond to therapy. There is increasing evidence suggesting that treatment failure may be classified as mechanistic (pharmacodynamic), pharmacokinetic, or immune-mediated. Data regarding the contribution of these factors in children with IBD treated with infliximab (IFX) are still incomplete. The aim was to assess the causes of treatment failure in a prospective cohort of pediatric patients treated with IFX.

METHODS

This observational study considered 49 pediatric (median age 14.4) IBD patients (34 Crohn disease, 15 ulcerative colitis) treated with IFX. Serum samples were collected at 6, 14, 22 and 54 weeks, before IFX infusions. IFX and anti-infliximab antibodies (AIA) were measured using enzyme linked immunosorbent assays. Disease activity was determined by Pediatric Crohn's Disease Activity Index or Pediatric Ulcerative Colitis Activity Index.

RESULTS

Clinical remission, defined as a clinical score <10, was obtained by 76.3% of patients at week 14 and by 73.9% at week 54. Median trough IFX concentration was higher at all time points in patients achieving sustained clinical remission. IFX levels during maintenance correlated also with C-reactive protein, albumin, and fecal calprotectin. After multivariate analysis, IFX concentration at week 14 >3.11 μg/mL emerged as the strongest predictor of sustained clinical remission. AIA concentrations were correlated inversely with IFX concentrations and directly with adverse reactions.

CONCLUSIONS

Most cases of therapeutic failure were associated with low serum drug levels. IFX trough levels at the end of induction are associated with sustained long-term response.

Defective IgA response to atypical intestinal commensals in IL-21 receptor deficiency reshapes immune cell homeostasis and mucosal immunity

Despite studies indicating the effects of IL-21 signaling in intestinal inflammation, its roles in intestinal homeostasis and infection are not yet clear. Here, we report potent effects of commensal microbiota on the phenotypic manifestations of IL-21 receptor deficiency. IL-21 is produced highly in the small intestine and appears to be critical for mounting an IgA response against atypical commensals such as segmented filamentous bacteria and Helicobacter, but not to the majority of commensals. In the presence of these atypical commensals, IL-21R-deficient mice exhibit reduced numbers of germinal center and IgA⁺ B cells and expression of activation-induced cytidine deaminase in Peyer's patches as well as a significant decrease in small intestine IgA⁺ plasmablasts and plasma cells, leading to higher bacterial burdens and subsequent expansion of Th17 and Treg cells. These microbiota-mediated secondary changes in turn enhance T cell responses to an oral antigen and strikingly dampen Citrobacter rodentium-induced immunopathology, demonstrating a complex interplay between IL-21-mediated mucosal immunity, microbiota, and pathogens.

IL-17A Promotes Initiation and Development of Intestinal Fibrosis Through EMT

BACKGROUND

Intestinal fibrosis is a common complication of Crohn's disease (CD). Its exact mechanism is still unclear, and effective treatments to control or reverse the fibrosis process are unavailable. Epithelial-mesenchymal transition (EMT) may promote intestinal fibrosis by increasing deposition of extracellular matrix protein. IL-17A is a pro-inflammatory cytokine, and it has been shown as a profibrotic factor as its association with fibrosis of multiple organs was reported.

AIMS

To assess the roles of IL-17A and EMT in the initiation and development of intestinal fibrosis and to verify the potential inductive effect of IL-17A on EMT.

METHODS

In this study, we evaluated the expression of IL-17A and EMT-related genes in colonic mucosal biopsy tissues of CD patients and control individuals. Then, we examined the changes of EMT-related genes and fibrosis-related genes of IEC-6 cells which cultured for 72 h under increasing concentrations of IL-17A or with TGF-β1, to verify the potential inductive effect of IL-17A on EMT in vitro. We blocked the IL-17A of the mouse model of TNBS-induced experimental intestinal colitis and fibrosis to further verify the potential inductive effect of IL-17A on EMT in vivo.

RESULTS

We found the occurrence of EMT and high-level expression of IL-17A in intestinal mucosa of CD patients. Using IEC-6 cells, we showed that IL-17A may induce EMT in intestinal epithelial cells that come with reduced E-cadherin expression and increased expression of vimentin, snail, and α-SMA. We further found that anti-IL-17A treatment alleviated intestinal fibrosis through reducing EMT in mouse intestine.

CONCLUSIONS

Our study confirmed the involvement of IL-17A in the development of intestinal fibrosis through inducing EMT.