Treatments for Crohn's Disease-Associated Bowel Damage: A Systematic Review

Emerging strategy towards mucosal healing in inflammatory bowel disease: what the future holds?

For decades, the therapeutic goal of conventional treatment among inflammatory bowel disease (IBD) patients is alleviating exacerbations in acute phase, maintaining remission, reducing recurrence, preventing complications, and increasing quality of life. However, the persistent mucosal/submucosal inflammation tends to cause irreversible changes in the intestinal structure, which can barely be redressed by conventional treatment. In the late 1990s, monoclonal biologics, mainly anti-TNF (tumor necrosis factor) drugs, were proven significantly helpful in inhibiting mucosal inflammation and improving prognosis in clinical trials. Meanwhile, mucosal healing (MH), as a key endoscopic and histological measurement closely associated with the severity of symptoms, has been proposed as primary outcome measures. With deeper comprehension of the mucosal microenvironment, stem cell niche, and underlying mucosal repair mechanisms, diverse potential strategies apart from monoclonal antibodies have been arising or undergoing clinical trials. Herein, we elucidate key steps or targets during the course of MH and review some promising treatment strategies capable of promoting MH in IBD.

Hepatic Abscess in Inflammatory Bowel Disease: A Systematic Scoping Review of an Overlooked Entity

Background

Liver abscess is one of the hepatobiliary manifestations of inflammatory bowel disease (IBD) that has been scarcely described in the literature.

Objectives

To conduct a scoping review to provide a detailed description of the occurrence of hepatic abscess in patients with IBD and summarize the observed clinical features.

Methodology

Searches were carried out using relevant keywords in Medline (via PubMed) and Web of Science from inception until June 13, 2022. Only articles that reported the occurrence of hepatic abscess in patients with IBD were included.

Results

Forty-eight publications (40 case reports and 8 case series) were included, representing 73 patients with IBD who were radiologically or intraoperatively diagnosed with hepatic abscess. Patients with Crohn's disease were more predisposed to developing hepatic abscess than patients with ulcerative colitis (79.5% vs. 20.5%, respectively). Furthermore, pyogenic liver abscess was found to be more prevalent (57.9%) compared with aseptic (38.7%) and amebic (3.2%) abscesses. No clear relation was found between death or prolonged hospital stay in terms of the clinical presentation or management plan, as mortality was reported in different age groups with different managements.

Conclusion

To date, there is no consensus regarding the appropriate management of hepatic abscess as an extraintestinal manifestation of IBD. However, the condition shares several features with liver abscess diagnosed among the general population.

Mucosal healing and inflammatory bowel disease: Therapeutic implications and new targets

Mucosal healing (MH) is vital in maintaining homeostasis within the gut and protecting against injury and infections. Multiple factors and signaling pathways contribute in a dynamic and coordinated manner to maintain intestinal homeostasis and mucosal regeneration/repair. However, when intestinal homeostasis becomes chronically disturbed and an inflammatory immune response is constitutively active due to impairment of the intestinal epithelial barrier autoimmune disease results, particularly inflammatory bowel disease (IBD). Many proteins and signaling pathways become dysregulated or impaired during these pathological conditions, with the mechanisms of regulation just beginning to be understood. Consequently, there remains a relative lack of broadly effective therapeutics that can restore MH due to the complexity of both the disease and healing processes, so tissue damage in the gastrointestinal tract of patients, even those in clinical remission, persists. With increased understanding of the molecular mechanisms of IBD and MH, tissue damage from autoimmune disease may in the future be ameliorated by developing therapeutics that enhance the body’s own healing response. In this review, we introduce the concept of mucosal healing and its relevance in IBD as well as discuss the mechanisms of IBD and potential strategies for altering these processes and inducing MH.

Autologous Bioactive Compound Concentrated Growth Factor Ameliorates Fistula Healing of Anal Fistula in a Pig Model and Promotes Proliferation and Migration of Human Skin Fibroblasts via Regulating the MEK/ERK Pathway

Recent evidence suggested that autologous concentrated growth factor (CGF), a new bioactive compound from autologous blood is used widely as an ingenious biomaterial in tissue regeneration with anti-inflammatory properties. This study investigated whether CGF could be involved in the treatment of fistula healing in the anal fistula. For this purpose, the porcine anal fistula model was conducted using the rubber band ligation method and collected pig autogenic CGF to treat the fistulas. CGF treatment promoted fistula healing, which was reflected in the downregulation of inflammatory factors, upregulation of growth factors, and promoted epithelial-mesenchymal transition with increased collagen synthesis. Besides, 16S rRNA gene sequencing analysis of fistula tissues between the control and CGF groups showed that the microbial populations exhibiting significant differences were VadinCA02, Blastomonas, Deinococcus, Devosia, Sphingomonas, Rubrobacteria, and GW_34. CGF of volunteers were collected to process small interfering RNA- (siRNA-) ERK or siRNA-negative control transfected human skin fibroblasts (HSF). The results showed that CGF also promoted the proliferation and extracellular matrix-related functions in HSF, as well as activated the MEK/ERK pathway in vitro and in vivo. Finally, knockdown ERK reversed the effects of CGF in promoting wound healing in HSF. Collectively, our results suggest that the CGF as the bioactive compound from autologous blood exhibited great potential for repairing fistulas as well as promoting the proliferation and migration of human skin fibroblasts by triggering MEK/ERK signaling. These findings provided a fresh perspective for understanding the role of CGF in the management of fistulas.

Large-scale sequencing identifies multiple genes and rare variants associated with Crohn's disease susceptibility

Genome-wide association studies (GWASs) have identified hundreds of loci associated with Crohn's disease (CD). However, as with all complex diseases, robust identification of the genes dysregulated by noncoding variants typically driving GWAS discoveries has been challenging. Here, to complement GWASs and better define actionable biological targets, we analyzed sequence data from more than 30,000 patients with CD and 80,000 population controls. We directly implicate ten genes in general onset CD for the first time to our knowledge via association to coding variation, four of which lie within established CD GWAS loci. In nine instances, a single coding variant is significantly associated, and in the tenth, ATG4C, we see additionally a significantly increased burden of very rare coding variants in CD cases. In addition to reiterating the central role of innate and adaptive immune cells as well as autophagy in CD pathogenesis, these newly associated genes highlight the emerging role of mesenchymal cells in the development and maintenance of intestinal inflammation.

CD147 Targeting by AC-73 Induces Autophagy and Reduces Intestinal Fibrosis Associated with TNBS Chronic Colitis

BACKGROUND AND AIMS

Intestinal fibrosis is a common complication of inflammatory bowel diseases. Medical treatment of intestinal fibrosis is an unmet therapeutic need. CD147 overexpression can induce myofibroblast differentiation associated with extracellular matrix deposition, favouring the development of fibrosis. To understand whether CD147 may promote intestinal fibrosis, we analysed its expression and blocked its function by using its specific inhibitor AC-73 [3-{2-[([1,1'-biphenyl]-4-ylmethyl) amino]-1-hydroxyethyl} phenol] in the murine TNBS [trinitrobenzenesulfonic acid]-chronic colitis model associated with intestinal fibrosis.

METHODS

TNBS chronic colitis was induced by weekly intrarectal administration of escalating doses of TNBS. Ethanol-treated and untreated mice were used as controls. Separated groups of TNBS, ethanol-treated or untreated mice received AC-73 or vehicle administered intraperitoneally from day 21 to day 49. At day 49, mice were killed, and colons collected for histological analysis, protein and RNA extraction. CD147, α-SMA and activated TGF-β1 protein levels, CD147/ERK/STAT3 signalling pathway and autophagy were assessed by Western blot, collagen and inflammatory/fibrogenic cytokines mRNA tissue content by quantitative PCR.

RESULTS

In mice with chronic TNBS colitis, CD147 protein level increased during fibrosis development in colonic tissue, as compared to control mice. CD147 inhibition by AC-73 treatment reduced intestinal fibrosis, collagen and cytokine mRNA tissue content, without significant modulation of activated TGF-β1 protein tissue content. AC-73 inhibited CD147/ERK1/2 and STAT3 signalling pathway activation and induced autophagy.

CONCLUSIONS

CD147 is a potential new target for controlling intestinal fibrosis and its inhibitor, AC-73, might represent a potential new anti-fibrotic therapeutic option in IBD.

Constrictive and Hypertrophic Strictures in Ileal Crohn's Disease

BACKGROUND & AIMS

Strictures in Crohn's disease (CD) are classically attributed to fibromuscular hypertrophy of the intestinal wall. We have identified and characterized CD-related ileal strictures that result instead from mural constriction (ie, reduced external circumference).

METHODS

Twenty-four strictures and internal controls from 17 adults with obstructive CD were analyzed by cross-sectional morphometry.

RESULTS

The stricture-to-control circumference ratios (CRs) ranged from 0.53 to 1.7. Six strictures with CR ≥1.0, designated hypertrophic, had concentrically thickened walls, mean 3-fold increases in cross-sectional area and stainable fibromucular tissue, and high transmural inflammation scores. In contrast, 18 strictures with CR <1.0, designated constrictive, had thin, pliant walls, cross-sectional areas and stainable fibromuscular tissue comparable with control values, and low transmural inflammation scores. Eight mildly constrictive strictures also showed mild fibromuscular mural expansion that fell short of statistical significance. Twelve of 18 constrictive strictures (67%) occurred multiply (2-4 strictures per specimen) in contrast with hypertrophic strictures, all of which occurred singly (P = .01). Constriction correlated quantitatively with circumferential serosal fat wrapping (P = .003) and was associated with myenteric lymphocytic plexitis (P = .02). Disease duration was shortest among subjects with constrictive strictures and correlated with increasing circumference (CR ≤0.8, 6.3 ± 6.2 years; CR >0.8, 8.7 ± 6.4 years; and CR ≥1.00, 13.7 ± 5.0 years, respectively; P = .03).

CONCLUSIONS

Constrictive ileal strictures in CD differ pathologically and clinically from hypertrophic strictures, featuring little or no fibromuscular mural expansion, frequent multiplicity, and earlier onset. Mesenteric fat wrapping and myenteric plexitis may contribute to their pathogenesis. Pathologic manifestations of constriction and hypertrophy can coexist, suggesting that stricture heterogeneity may be shaped in part by the dynamics of constrictive and hypertrophic processes.

How Gut Bacterial Dysbiosis Can Promote Candida albicans Overgrowth during Colonic Inflammation

Candida albicans is a commensal opportunistic yeast, which is capable of colonising many segments of the human digestive tract. Excessive C. albicans overgrowth in the gut is associated with multiple risk factors such as immunosuppression, antibiotic treatment associated with changes to the gut microbiota and digestive mucosa that support C. albicans translocation across the digestive intestinal barrier and haematogenous dissemination, leading to invasive fungal infections. The C. albicans cell wall contains mannoproteins, β-glucans, and chitin, which are known to trigger a wide range of host cell activities and to circulate in the blood during fungal infection. This review describes the role of C. albicans in colonic inflammation and how various receptors are involved in the immune defence against C. albicans with a special focus on the role of mannose-binding lectin (MBL) and TLRs in intestinal homeostasis and C. albicans sensing. This review highlights gut microbiota dysbiosis during colonic inflammation in a dextran sulphate sodium (DSS)-induced colitis murine model and the effect of fungal glycan fractions, in particular β-glucans and chitin, on the modification of the gut microbiota, as well as how these glycans modulate the immuno-inflammatory response of the host.

Review article: distinctions between ileal and colonic Crohn's disease: from physiology to pathology

BACKGROUND

Ileal and colonic Crohn's disease seem to be two separate entities.

AIMS

To describe the main physiological distinctions between the small and the large intestine and to analyse the differences between ileal and colonic Crohn's disease.

METHODS

The relevant literature was critically examined and synthesised.

RESULTS

The small and large intestine have fundamental distinctions (anatomy, cellular populations, immune defence, microbiota). The differences between ileal and colonic Crohn's disease are highlighted by a heterogeneous body of evidence including clinical features (natural history of the disease, efficacy of treatments, and monitoring), epidemiological data (smoking status, age, gender) and biological data (genetics, microbiota, immunity, mesenteric fat). However, the contribution of these factors to disease location remains poorly understood.

CONCLUSION

The classification of ileal and colonic Crohn's disease as distinct subphenotypes is well supported by the literature. Understanding of these differences could be exploited to develop more individualised patient care.

Clinical Use of Schistosoma mansoni Antigens as Novel Immunotherapies for Autoimmune Disorders

The hygiene hypothesis states that improved hygiene and the resulting disappearance of once endemic diseases is at the origin of the enormous increase in immune related disorders such as autoimmune diseases seen in the industrialized world. Helminths, such as Schistosoma mansoni, are thought to provide protection against the development of autoimmune diseases by regulating the host's immune response. This modulation primarily involves induction of regulatory immune responses, such as generation of tolerogenic dendritic cells and alternatively activated macrophages. This points toward the potential of employing helminths or their products/metabolites as therapeutics for autoimmune diseases that are characterized by an excessive inflammatory state, such as multiple sclerosis (MS), type I diabetes (T1D) and inflammatory bowel disease (IBD). In this review, we examine the known mechanisms of immune modulation by S. mansoni, explore preclinical and clinical studies that investigated the use of an array helminthic products in these diseases, and propose that helminthic therapy opens opportunities in the treatment of chronic inflammatory disorders.

Differential regulation of JAK/STAT-signaling in patients with ulcerative colitis and Crohn’s disease

In 2018, the pan-Janus kinase (JAK) inhibitor tofacitinib was launched for the treatment of ulcerative colitis (UC). Although tofacitinib has proven efficacious in patients with active UC, it failed in patients with Crohn’s disease (CD). This finding strongly hints at a different contribution of JAK signaling in both entities. Here, we review the current knowledge on the interplay between the JAK/signal transducer and activator of transcription (STAT) pathway and inflammatory bowel diseases (IBD). In particular, we provide a detailed overview of the differences and similarities of JAK/STAT-signaling in UC and CD, highlight the impact of the JAK/STAT pathway in experimental colitis models and summarize the published evidence on JAK/STAT-signaling in immune cells of IBD as well as the genetic association between the JAK/STAT pathway and IBD. Finally, we describe novel treatment strategies targeting JAK/STAT inhibition in UC and CD and comment on the limitations and challenges of the new drug class.

Mucosal healing in Crohn's disease: new insights

INTRODUCTION

Traditional management of patients with Crohn's disease includes symptoms and quality of life improvement. With the advent of biological agents, mucosal healing has become an achievable goal, documented through endoscopy. However, due to the transmural nature of inflammation, the prevention of bowel damage should be included in the aims of a targeted therapeutic strategy.

AREAS COVERED

Updated literature has been searched in PubMed from 2008 to 2020. This review focuses on the state of the art in the innovative therapeutic goals in Crohn's disease, also considering still controversial aspects and future research topics in the management of Crohn's disease.

EXPERT OPINION

Although a widely agreed view supports the notion that mucosal healing and bowel damage control may promote beneficial outcomes (i.e. reduction in hospitalization and surgical rates, avoidance of steroids), long-term robust data are still missing. On the other hand, the development of -omics techniques has expanded our knowledge of the pathogenetic mechanism underlying inflammatory bowel disease and opened up new horizons in precision or personalized medicine.

Succinate Activates EMT in Intestinal Epithelial Cells through SUCNR1: A Novel Protagonist in Fistula Development

The pathogenesis of Crohn’s disease-associated fibrostenosis and fistulas imply the epithelial-to-mesenchymal transition (EMT) process. As succinate and its receptor (SUCNR1) are involved in intestinal inflammation and fibrosis, we investigated their relevance in EMT and Crohn’s disease (CD) fistulas. Succinate levels and SUCNR1-expression were analyzed in intestinal resections from non-Inflammatory Bowel Disease (non-IBD) subjects and CD patients with stenosing-B2 or penetrating-B3 complications and in a murine heterotopic-transplant model of intestinal fibrosis. EMT, as increased expression of Snail1, Snail2 and vimentin and reduction in E-cadherin, was analyzed in tissues and succinate-treated HT29 cells. The role played by SUCNR1 was studied by silencing its gene. Succinate levels and SUCNR1 expression are increased in B3-CD patients and correlate with EMT markers. SUCNR1 is detected in transitional cells lining the fistula tract and in surrounding mesenchymal cells. Grafts from wild type (WT) mice present increased succinate levels, SUCNR1 up-regulation and EMT activation, effects not observed in SUCNR1^−/− tissues. SUCNR1 activation induces the expression of Wnt ligands, activates WNT signaling and induces a WNT-mediated EMT in HT29 cells. In conclusion, succinate and its receptor are up-regulated around CD-fistulas and activate Wnt signaling and EMT in intestinal epithelial cells. These results point to SUCNR1 as a novel pharmacological target for fistula prevention.

Fibrostenotic strictures in Crohn's disease

The use of biologic agents including anti-tumor necrosis factor monoclonal antibodies followed by anti-integrins and anti-interleukins has drastically changed the treatment paradigm of Crohn’s disease (CD) by improving clinical symptoms and mucosal healing. However, up to 70% of CD patients still eventually undergo surgery mainly due to fibrostenotic strictures. There are no specific anti-fibrotic drugs yet. This review comprehensively addresses the mechanism, prediction, diagnosis and treatment of the fibrostenotic strictures in CD. We also introduce promising anti-fibrotic agents which may be available in the near future and summarize challenges in developing novel therapies to treat fibrostenotic strictures in CD.

Proteomics Highlights Common and Distinct Pathophysiological Processes Associated with Ileal and Colonic Ulcers in Crohn's Disease

BACKGROUND AND AIMS

Based on genetics and natural history, Crohn's disease can be separated into two entities, an ileal and a colonic disease. Protein-based approaches are needed to elucidate whether such subphenotypes are related to distinct pathophysiological processes.

METHODS

The proteome of ulcer edges was compared with that of paired control tissue samples [n = 32 biopsies] by differential proteomics in the ileum and the colon of Crohn's disease patients [n = 16]. The results were analysed using a hypothesis-driven approach [based on the literature] and a hypothesis-free approach [pathway enrichment analyses] to determine common and segment-specific pathophysiological processes associated with ileal and colonic CD ulcer edges. To confirm the involvement of a key pathway highlighted by proteomics, two proteins were also studied by immunochemistry.

RESULTS

In the ileum and the colon, 4428 and 5204 proteins, respectively, were identified and quantified. Ileal and colonic ulcer edges differed in having a distinct distribution of proteins associated with epithelial-mesenchymal transition, neutrophil degranulation, and ribosomes. Ileal and colonic ulcer edges were similarly characterized by an increase in the proteins implicated in the endoplasmic reticulum protein-processing pathway and a decrease in mitochondrial proteins. Immunochemistry confirmed the presence of endoplasmic reticulum stress in the mucosa of ileal and colonic ulcer edges.

CONCLUSION

This study provides protein-based evidence for partially distinct pathophysiological processes being associated with ileal and colonic ulcer edges in Crohn's disease patients. This could constitute a first step toward the development of gut segment-specific diagnostic markers and therapeutics.

Natural history, diagnosis and treatment approach to fibrostenosing Crohn's disease

Stricturing Crohn's disease (CD) is a significant clinical problem. The presence of a stricture may be suggested by clinical symptoms. Cross-sectional imaging using computed tomography or magnetic resonance enterography is essential in diagnosing strictures as it allows further characterization and evaluation for complications such as abscess, fistulizing disease or malignancy. Managing small bowel stricturing CD should be approached in a multidisciplinary fashion. Medical therapy can be considered in strictures which are not associated with complications, with most of the data supporting anti-TNF strategies in this setting. If the disease is refractory to medical therapy, endoscopic therapy or surgery should be performed. Endoscopic balloon dilation (EBD) is an option for short, uncomplicated and straight strictures that are within reach of a colonoscope. Although EBD has good short-term outcomes, repeat dilation is often required. Surgical options mainly include resection and strictureplasty. Strictures refractory to medical therapy, not amenable or refractory to EBD, or associated with complications or malignancy should be managed surgically. However, surgery may also be considered at an earlier stage depending on disease characteristics and patient preference. Postoperative recurrence is common, highlighting the importance of careful monitoring of the patient postoperatively and optimization of medical management accordingly. There is a pressing need to develop anti-fibrotics for the treatment of stricturing CD. This requires the development of standardized diagnostic criteria, patient-reported outcome measures and validation of endpoints in fibrostenotic CD. The STAR consortium is pioneering this effort in order to allow development and testing of anti-fibrotics in future clinical trials.

Concentrates of two subsets of extracellular vesicles from cow's milk modulate symptoms and inflammation in experimental colitis

Extracellular vesicles (EVs) are involved in cell-to-cell communication and modulation of numerous physiological and pathological processes. EVs are found in large quantities in milk and contain several inflammation- and immunity-modulating proteins and microRNAs, through which they exert beneficial effects in several inflammatory disease models. Here, we investigated the effects of two EV subsets, concentrated from commercial cow's milk, on a murine model of colitis induced with dextran sodium sulfate (DSS). P35K EVs, isolated by ultracentrifugation at 35,000 g, and P100K EVs, isolated at 100,000 g, were previously characterized and administered by gavage to healthy and DSS-treated mice. P35K EVs and, to a lesser extent, P100K EVs improved several outcomes associated to DSS-induced colitis, modulated the gut microbiota, restored intestinal impermeability and replenished mucin secretion. Also, P35K EVs modulated innate immunity, while P100K EVs decreased inflammation through the downregulation of colitis-associated microRNAs, especially miR-125b, associated with a higher expression of the NFκB inhibitor TNFAIP3 (A20). These results suggest that different milk EV subsets may improve colitis outcomes through different, and possibly complementary, mechanisms. Further unveiling of these mechanisms might offer new opportunities for improving the life of patients with colitis and be of importance for milk processing, infant milk formulation and general public health.

Image-Guided Transarterial Directed Delivery of Human Mesenchymal Stem Cells for Targeted Gastrointestinal Therapies in a Swine Model

PURPOSE

To evaluate the feasibility of catheter-directed intra-arterial stem cell delivery of human mesenchymal stem cells (MSCs) to the small bowel in a porcine model.

MATERIALS AND METHODS

The cranial mesenteric artery of 6 Yucatan minipigs was selectively catheterized under fluoroscopic guidance following cut-down and carotid artery access. A proximal jejunal branch artery was selectively catheterized for directed delivery of embolic microspheres (100-300 μm) or MSCs (0.1-10 million cells). The pigs were euthanized after 4 hours and specimens collected from the proximal duodenum and the targeted segment of the jejunum. The Chiu/Park system for scoring intestinal ischemia was used to compare hematoxylin and eosin-stained sections of jejunum and duodenum.

RESULTS

Successful delivery of microspheres or MSCs in a proximal jejunal branch artery of the cranial mesenteric artery was achieved in all subjects. Radiopaque microspheres and post-delivery angiographic evidence of stasis in the targeted vessels were observed on fluoroscopy after delivery of embolics. Preserved blood flow was observed after MSC delivery in the targeted vessel. The Chiu/Park score for intestinal ischemia in the targeted proximal jejunal segments were similar for microspheres (4, 4; n = 2) and MSCs (4, 4, 4, 3; n = 4), indicating moderate ischemic effects that were greater than for control duodenal tissue (3, 1; 0, 0, 3, 3).

CONCLUSIONS

Selective arteriographic deployment of MSCs in swine is feasible for study of directed intestinal stem cell delivery. In this study, directed therapy resulted in intestinal ischemia.