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Ciorba MA, Konnikova L, Hirota SA, Lucchetta EM, Turner JR, Slavin A, Johnson K, Condray CD, Hong S, Cressall BK, Pizarro TT, Hurtado-Lorenzo A, Heller CA, Moss AC, Swantek JL, Garrett WS. Challenges in IBD Research 2024: Preclinical Human IBD Mechanisms. Inflamm Bowel Dis 2024; 30:S5-S18. [PMID: 38778627 DOI: 10.1093/ibd/izae081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Indexed: 05/25/2024]
Abstract
Preclinical human inflammatory bowel disease (IBD) mechanisms is one of 5 focus areas of the Challenges in IBD Research 2024 document, which also includes environmental triggers, novel technologies, precision medicine, and pragmatic clinical research. Herein, we provide a comprehensive overview of current gaps in inflammatory bowel diseases research that relate to preclinical research and deliver actionable approaches to address them with a focus on how these gaps can lead to advancements in IBD interception, remission, and restoration. The document is the result of multidisciplinary input from scientists, clinicians, patients, and funders and represents a valuable resource for patient-centric research prioritization. This preclinical human IBD mechanisms section identifies major research gaps whose investigation will elucidate pathways and mechanisms that can be targeted to address unmet medical needs in IBD. Research gaps were identified in the following areas: genetics, risk alleles, and epigenetics; the microbiome; cell states and interactions; barrier function; IBD complications (specifically fibrosis and stricturing); and extraintestinal manifestations. To address these gaps, we share specific opportunities for investigation for basic and translational scientists and identify priority actions.
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Affiliation(s)
- Matthew A Ciorba
- Inflammatory Bowel Diseases Center, Division of Gastroenterology, Washington University in St. Louis, Saint Louis, MO, USA
| | - Liza Konnikova
- Departments of Pediatrics, Immunobiology, and Obstetric, Gynecology and Reproductive Sciences, Yale School of Medicine, New Haven, CT, USA
| | - Simon A Hirota
- Snyder Institute for Chronic Diseases, Dept. of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Elena M Lucchetta
- The Leona M. and Harry B. Helmsley Charitable Trust, New York, NY, USA
| | - Jerrold R Turner
- Departments of Pathology and Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | | | | | - Cass D Condray
- Patient Representative for the Crohn's & Colitis Foundation, New York, NY, USA
| | - Sungmo Hong
- Patient Representative for the Crohn's & Colitis Foundation, New York, NY, USA
| | - Brandon K Cressall
- Patient Representative for the Crohn's & Colitis Foundation, New York, NY, USA
| | - Theresa T Pizarro
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | | | - Caren A Heller
- Research Department, Crohn's & Colitis Foundation, New York, NY, USA
| | - Alan C Moss
- Research Department, Crohn's & Colitis Foundation, New York, NY, USA
| | | | - Wendy S Garrett
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, MA, USA
- The Harvard T. H. Chan Microbiome in Public Health Center, Boston, MA, USA
- Kymera Therapeutics, Watertown, MA, USA
- The Broad Institute of MIT and Harvard, Cambridge, MA, USA
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, USA
- Department of Medicine, Harvard Medical School, Boston, MA, USA
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Song Z, Li X, Xie J, Han F, Wang N, Hou Y, Yao J. Associations of inflammatory cytokines with inflammatory bowel disease: a Mendelian randomization study. Front Immunol 2024; 14:1327879. [PMID: 38288119 PMCID: PMC10822978 DOI: 10.3389/fimmu.2023.1327879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Accepted: 12/27/2023] [Indexed: 01/31/2024] Open
Abstract
Objectives Previous studies have confirmed a link between specific inflammatory cytokines and inflammatory bowel disease (IBD), but the causal relationship between them is not completely clear. This Mendelian Randomization (MR) study aims to evaluate the causal relationship between 18 inflammatory cytokines and inflammatory bowel disease. Method Two-sample Mendelian randomization utilized genetic variances associated with IBD from two extensive publicly available genome-wide association studies (GWAS) (Crohn's Disease (CD): 12,194 cases and 28,072 controls; Ulcerative Colitis (UC): 12,336 cases and 33,609 controls). The data of inflammatory cytokines was acquired from a GWAS including 8,293 healthy participants. We used inverse variance weighted method, MR-Egger, weighted median, simple model and weighted model to evaluate the causal relationship between inflammatory cytokines and IBD. Sensitivity analysis includes heterogeneity and pleiotropy analysis to evaluate the robustness of the results. Results The findings indicated suggestive positive associations between Interleukin-13 (IL-13) and macrophage migration inhibitory factor (MIF) with CD (odds ratio, OR: 1.101, 95%CI: 1.021-1.188, p = 0.013; OR: 1.134, 95%CI: 1.024-1.255, p = 0.015). IL-13 also displayed a significant positive correlation with UC (OR: 1.099, 95%CI: 1.018-1.186, p = 0.016). Stem cell factor (SCF) was suggested to be associated with the development of both CD and UC (OR: 1.032, 95%CI: 0.973-1.058, p = 0.012; OR: 1.038, 95%CI: 1.005-1.072, p = 0.024). Conclusion This study proposes that IL-13 may be a factor correlated with the etiology of IBD (CD and UC), while MIF just be specifically associated with CD. Additionally, SCF appears more likely to be involved in the downstream development of IBD (CD and UC).
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Affiliation(s)
| | | | | | | | | | | | - Jianning Yao
- Department of Gastroenterology, The First Affiliated Hospital of Zhengzhou University, ZhengZhou, China
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Anandabaskaran S, Hanna L, Iqbal N, Constable L, Tozer P, Hart A. Where Are We and Where to Next?-The Future of Perianal Crohn's Disease Management. J Clin Med 2023; 12:6379. [PMID: 37835022 PMCID: PMC10573672 DOI: 10.3390/jcm12196379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Revised: 09/26/2023] [Accepted: 09/27/2023] [Indexed: 10/15/2023] Open
Abstract
Perianal fistulizing Crohn's Disease (pCD) affects about 25% of patients with Crohn's Disease (CD). It remains a difficult entity to manage with a therapeutic ceiling of treatment success despite improving medical and surgical management. The refractory nature of the disease calls for an imminent need to better understand its immunopathogenesis and classification to better streamline our treatment options. In this article, we overview the current state of pCD management and discuss where the future of its management may lie.
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Affiliation(s)
- Sulak Anandabaskaran
- Department of Metabolism, Digestion and Reproduction, Faculty of Medicine, Hammersmith Campus, Imperial College London, London W12 0NN, UK
- Robin Phillip’s Fistula Research Unit, St Mark’s Hospital and Academic Institute, London HA1 3UJ, UK
- Faculty of Medicine, St Vincent’s Clinical School, University of New South Wales, 390 Victoria Street, Darlinghurst, NSW 2010, Australia
| | - Luke Hanna
- Department of Metabolism, Digestion and Reproduction, Faculty of Medicine, Hammersmith Campus, Imperial College London, London W12 0NN, UK
- Robin Phillip’s Fistula Research Unit, St Mark’s Hospital and Academic Institute, London HA1 3UJ, UK
| | - Nusrat Iqbal
- Robin Phillip’s Fistula Research Unit, St Mark’s Hospital and Academic Institute, London HA1 3UJ, UK
- Department of Surgery and Cancer, South Kensington Campus, Imperial College London, London SW7 2BX, UK
| | - Laura Constable
- Department of Metabolism, Digestion and Reproduction, Faculty of Medicine, Hammersmith Campus, Imperial College London, London W12 0NN, UK
| | - Phil Tozer
- Robin Phillip’s Fistula Research Unit, St Mark’s Hospital and Academic Institute, London HA1 3UJ, UK
- Department of Surgery and Cancer, South Kensington Campus, Imperial College London, London SW7 2BX, UK
| | - Ailsa Hart
- Robin Phillip’s Fistula Research Unit, St Mark’s Hospital and Academic Institute, London HA1 3UJ, UK
- Department of Surgery and Cancer, South Kensington Campus, Imperial College London, London SW7 2BX, UK
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Management of Pelvic Pain in Patients with Crohn's Disease-Current Overview. J Clin Med 2023; 12:jcm12020526. [PMID: 36675454 PMCID: PMC9862261 DOI: 10.3390/jcm12020526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 12/29/2022] [Accepted: 01/04/2023] [Indexed: 01/11/2023] Open
Abstract
Crohn's disease (CD) is a subtype of chronic inflammatory bowel diseases (IBD) with characteristic skip lesions and transmural inflammation that may affect the entire gastrointestinal tract from the mouth to the anus. Persistent pain is one of the main symptoms of CD. This pain has multifactorial pathogenesis, but most often arises from intestinal inflammation itself, as well as from gut distention or partial intestinal obstruction. Some current evidence also suggests sensitization of sensory pathways, as well as modulation of those signals by the central nervous system, which highlights the impact of biopsychosocial factors. To date, most studies have focused only on the pain located in the abdomen, while pelvic pain has rarely been explored, despite it being a common symptom. The aim of this study is to provide an abbreviated summary of the current state of knowledge on the origins and treatment of pelvic pain in CD.
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Crohn's Disease-Associated and Cryptoglandular Fistulas: Differences and Similarities. J Clin Med 2023; 12:jcm12020466. [PMID: 36675403 PMCID: PMC9860571 DOI: 10.3390/jcm12020466] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 01/01/2023] [Accepted: 01/04/2023] [Indexed: 01/09/2023] Open
Abstract
Perianal fistulas are defined as pathological connections between the anorectal canal and the perianal skin. Most perianal fistulas are cryptoglandular fistulas, which are thought to originate from infected anal glands. The remainder of the fistulas mainly arises as complications of Crohn's disease (CD), trauma, or as a result of malignancies. Fistulas in CD are considered as a consequence of a chronic and transmural inflammatory process in the distal bowel and can, in some cases, even precede the diagnosis of CD. Although both cryptoglandular and CD-associated fistulas might look similar macroscopically, they differ considerably in their complexity, treatment options, and healing rate. Therefore, it is of crucial importance to differentiate between these two types of fistulas. In this review, the differences between CD-associated and cryptoglandular perianal fistulas in epidemiology, pathogenesis, and clinical management are discussed. Finally, a flow chart is provided for physicians to guide them when dealing with patients displaying their first episode of perianal fistulas.
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Pathogenesis of Fistulating Crohn's Disease: A Review. Cell Mol Gastroenterol Hepatol 2022; 15:1-11. [PMID: 36184031 PMCID: PMC9667304 DOI: 10.1016/j.jcmgh.2022.09.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 09/20/2022] [Accepted: 09/20/2022] [Indexed: 12/10/2022]
Abstract
Sustained, transmural inflammation of the bowel wall may result in the development of a fistula in Crohn's disease (CD). Fistula formation is a recognized complication and cause of morbidity, occurring in 40% of patients with CD. Despite advanced treatment, one-third of patients experience recurrent fistulae. Development of targeting treatment for fistulae will be dependent on a more in depth understanding of its pathogenesis. Presently, pathogenesis of CD-associated fistulae remains poorly defined, in part due to the lack of accepted in vitro tissue models recapitulating the pathogenic cellular lesions linked to fistulae and limited in vivo models. This review provides a synthesis of the existing knowledge of the histopathological, immune, cellular, genetic, and microbial contributions to the pathogenesis of CD-associated fistulae including the widely accredited contribution of epithelial-to-mesenchymal transition, upregulation of matrix metalloproteinases, and overexpression of invasive molecules, resulting in tissue remodeling and subsequent fistula formation. We conclude by exploring how we might utilize advancing technologies to verify and broaden our current understanding while exploring novel causal pathways to provide further inroads to future therapeutic targets.
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Mamie C, Bruckner RS, Lang S, Shpigel NY, Turina M, Rickenbacher A, Cabalzar-Wondberg D, Chvatchko Y, Rogler G, Scharl M. MMP9 expression in intestinal fistula from patients with fistulizing CD and from human xenograft mouse model. Tissue Barriers 2022; 10:1994350. [PMID: 34709129 PMCID: PMC9067458 DOI: 10.1080/21688370.2021.1994350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 10/07/2021] [Accepted: 10/10/2021] [Indexed: 10/20/2022] Open
Abstract
Fistula treatment represents a major unmet medical need in the therapy of Crohn's disease (CD). Current medical therapies, such as anti-TNF antibody treatments, are often insufficient and do not achieve permanent fistula closure. Previously published data point toward a critical role for metalloproteinase-9 (MMP-9)/gelatinase B in fistula pathogenesis. The aim of this project was to investigate in detail MMP-9 expression in different fistula types and to confirm that MMP-9 is a potential target for fistula therapy in CD patients.Immunohistochemistry for total and active MMP-9, Cytokeratin 8 (CK-8) and co-staining of active MMP-9/CK-8 was performed in specimen derived from perianal fistulas, entero-enteric fistulas and fistulas from patients not responding to anti-TNF therapy. In addition, fistulas from the xenograft mouse model (anti-TNF treated or untreated) were analyzed.Total and active MMP-9 protein was detectable in cells lining the tracts of perianal and entero-enteric fistulas. Of note, total and active MMP-9 was also expressed in fistulas of CD patients non-responding to anti-TNF treatment. Interestingly, we detected considerable co-staining of active MMP-9 and CK-8 in particular in cells lining the fistula tract and in transitional cells around the fistulas. Furthermore, total and active MMP-9 are detectable in both anti-TNF treated and untreated xenograft fistulas.Taken together, our data suggest that MMP-9 is involved in fistula pathogenesis in CD patients, in fistulas of different origins and particularly in patients non-responding to anti-TNF therapy. Our xenograft fistula model is suitable for in vivo studies investigating a possible therapeutic role for MMP-9 targeting as fistula therapy.
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Affiliation(s)
- Céline Mamie
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Ramona S. Bruckner
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Silvia Lang
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Nahum Y. Shpigel
- Koret School of Veterinary Medicine, Hebrew University of Jerusalem, Rehovot, Israel
| | - Matthias Turina
- Department of Visceral and Transplantation Surgery, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Andreas Rickenbacher
- Department of Visceral and Transplantation Surgery, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Daniela Cabalzar-Wondberg
- Department of Visceral and Transplantation Surgery, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | | | - Gerhard Rogler
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Michael Scharl
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
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Ayoub F, Odenwald M, Micic D, Dalal SR, Pekow J, Cohen RD, Rubin DT, Sakuraba A. Vedolizumab for perianal fistulizing Crohn's disease: systematic review and meta-analysis. Intest Res 2022; 20:240-250. [PMID: 35124951 PMCID: PMC9081994 DOI: 10.5217/ir.2021.00091] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 09/08/2021] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND/AIMS Perianal fistulas are a debilitating manifestation of Crohn's disease (CD). Despite the advent of anti-tumor necrosis factor (anti-TNF) therapy, the medical management of fistulizing CD continues to be challenged by unmet needs. We conducted a systematic review and meta-analysis of the effectiveness of vedolizumab for the management of perianal fistulizing CD. METHODS A search of PubMed, EMBASE and the Cochrane Library was performed from inception to June 2020 for studies reporting rates of perianal fistula healing in CD patients treated with vedolizumab. The primary outcome of interest was complete healing of perianal fistulas and the secondary outcome was partial healing. The pooled fistula healing rates with 95% confidence intervals (CI) were calculated utilizing a random effects model. RESULTS A total of 74 studies were initially identified, 4 of which met the inclusion criteria. A total of 198 patients with active perianal fistulas were included, 87% of whom had failed previous anti-TNF therapy. The pooled complete healing rate was 27.6% (95% CI, 18.9%-37.3%) with moderate heterogeneity (I2=49.4%) and the pooled partial healing rate was 34.9% (95% CI, 23.2%-47.7%) with high heterogeneity (I2=67.1%). CONCLUSIONS In a meta-analysis of 4 studies that included 198 patients with perianal fistulizing CD, the majority of whom had failed previous anti-TNF therapy, vedolizumab treatment led to healing of perianal fistulas in nearly one-third of the patients. The lack of high-quality data and significant study heterogeneity underscores the need for future prospective studies of fistula healing in patients receiving anti-integrin therapy.
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Affiliation(s)
- Fares Ayoub
- Inflammatory Bowel Disease Center, Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, IL, USA
| | - Matthew Odenwald
- Inflammatory Bowel Disease Center, Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, IL, USA
| | - Dejan Micic
- Inflammatory Bowel Disease Center, Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, IL, USA
| | - Sushila R. Dalal
- Inflammatory Bowel Disease Center, Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, IL, USA
| | - Joel Pekow
- Inflammatory Bowel Disease Center, Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, IL, USA
| | - Russell D. Cohen
- Inflammatory Bowel Disease Center, Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, IL, USA
| | - David T. Rubin
- Inflammatory Bowel Disease Center, Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, IL, USA
| | - Atsushi Sakuraba
- Inflammatory Bowel Disease Center, Section of Gastroenterology, Hepatology, and Nutrition, University of Chicago, Chicago, IL, USA
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Bruckner RS, Spalinger MR, Barnhoorn MC, Feakins R, Fuerst A, Jehle EC, Rickenbacher A, Turina M, Niechcial A, Lang S, Hawinkels LJAC, van der Meulen-de Jong AE, Verspaget HW, Rogler G, Scharl M. Contribution of CD3+CD8- and CD3+CD8+ T Cells to TNF-α Overexpression in Crohn Disease-Associated Perianal Fistulas and Induction of Epithelial-Mesenchymal Transition in HT-29 Cells. Inflamm Bowel Dis 2021; 27:538-549. [PMID: 33146394 DOI: 10.1093/ibd/izaa240] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Indexed: 12/12/2022]
Abstract
BACKGROUND Fistulas represent a frequent and severe complication in patients with Crohn disease (CD). Tumor necrosis factor-alpha (TNF-α), transforming growth factor-beta, and interleukin (IL)-13 are known to trigger epithelial-mesenchymal transition (EMT), promoting fistula formation. Here, we investigated the role of T-lymphocytes (T cells) in fistula pathogenesis. METHODS CD3+CD8-, CD3+CD8+, or CD45+CD3- cells from healthy volunteers, patients with CD, and patients with CD with perianal fistula were co-cultured with HT-29 cells. The EMT, cytokine production, and mRNA expression were analyzed. Perianal CD fistula specimens were immunohistochemically stained for cytokines and their receptors. The effect of cytokines on EMT induction was investigated using an EMT spheroid model. RESULTS Patients with CD with fistula revealed more CD3+CD8- and less CD3+CD8+ T cells in blood than healthy control patients and patients with CD without fistula. In perianal fistula specimens, CD4+ cells-and to a lesser extent CD8+ cells-were highly present around fistula tracts. When co-cultured with HT-29 cells, both cell subsets promoted EMT-related gene expression and TNF-α production in a time-dependent manner. The CD3+CD8- T cells from patients with CD with fistula also produced higher amounts of IL-13 than cells from healthy control patients or patients with CD without a fistula. We found that IL-22 and IL-22Rα1 were highly expressed in perianal CD fistula specimens and that IL-22 cotreatment potentiated TNF-α-induced EMT in HT-29 spheroids. CONCLUSIONS Our data indicate that both CD3+CD8- and CD3+CD8+ T cells play an important role in the pathogenesis of perianal CD fistulas by the secretion of TNF-α. Our data support clinical evidence indicating that anti-TNF-α therapy is effective in fistula treatment and identify IL-13 and IL-22 as possible novel therapeutic targets for fistula therapy.
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Affiliation(s)
- Ramona S Bruckner
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.,Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Marianne R Spalinger
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Marieke C Barnhoorn
- Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Roger Feakins
- Department of Histopathology, Royal Free Hospital, London, United Kingdom
| | - Alois Fuerst
- Department of Surgery, Caritas-Krankenhaus St. Josef, Regensburg, Germany
| | | | - Andreas Rickenbacher
- Department of Surgery, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Matthias Turina
- Department of Surgery, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Anna Niechcial
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Silvia Lang
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Lukas J A C Hawinkels
- Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, The Netherlands
| | | | - Hein W Verspaget
- Department of Gastroenterology and Hepatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Gerhard Rogler
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Michael Scharl
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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10
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Wajant H, Beilhack A. Targeting Regulatory T Cells by Addressing Tumor Necrosis Factor and Its Receptors in Allogeneic Hematopoietic Cell Transplantation and Cancer. Front Immunol 2019; 10:2040. [PMID: 31555271 PMCID: PMC6724557 DOI: 10.3389/fimmu.2019.02040] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 08/12/2019] [Indexed: 12/15/2022] Open
Abstract
An intricate network of molecular and cellular actors orchestrates the delicate balance between effector immune responses and immune tolerance. The pleiotropic cytokine tumor necrosis factor-alpha (TNF) proves as a pivotal protagonist promoting but also suppressing immune responses. These opposite actions are accomplished through specialist cell types responding to TNF via TNF receptors TNFR1 and TNFR2. Recent findings highlight the importance of TNFR2 as a key regulator of activated natural FoxP3+ regulatory T cells (Tregs) in inflammatory conditions, such as acute graft-vs.-host disease (GvHD) and the tumor microenvironment. Here we review recent advances in our understanding of TNFR2 signaling in T cells and discuss how these can reconcile seemingly conflicting observations when manipulating TNF and TNFRs. As TNFR2 emerges as a new and attractive target we furthermore pinpoint strategies and potential pitfalls for therapeutic targeting of TNFR2 for cancer treatment and immune tolerance after allogeneic hematopoietic cell transplantation.
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Affiliation(s)
- Harald Wajant
- Division of Molecular Internal Medicine, Department of Internal Medicine II, University Hospital Würzburg, Würzburg, Germany
| | - Andreas Beilhack
- Department of Internal Medicine II, University Hospital Würzburg, Würzburg, Germany.,Center for Interdisciplinary Clinical Research, University of Würzburg, Würzburg, Germany.,Else-Kröner-Forschungskolleg Würzburg, Würzburg University Hospital, Würzburg University, Würzburg, Germany
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11
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Bislenghi G, Wolthuis A, Van Assche G, Vermeire S, Ferrante M, D'Hoore A. Cx601 (darvadstrocel) for the treatment of perianal fistulizing Crohn's disease. Expert Opin Biol Ther 2019; 19:607-616. [PMID: 31121104 DOI: 10.1080/14712598.2019.1623876] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Introduction: Given the well-documented difficulty to treat perianal fistulizing Crohn's disease (pCD), with 40% of patients experiencing recurrence even after reiterative surgery and advanced medical therapy, research in this field has focused on the role of mesenchymal stem cells (MSC). Areas covered: The aim of this article is to furnish an overview of the pathogenetic mechanisms, clinical applications and evidences for the use of MSC for pCD with particular focus on adipose-derived allogenic MSC including darvadstrocel. Expert Opinion: The effect of MSC on fistula healing is probably mediated by their anti-inflammatory properties more than by their ability to engraft and trans-differentiate in the healthy tissue. A holistic treatment of pCD, addressing different pathophysiological factors, may represent the key for an improvement in the healing rate. In this setting, MSC might play a role as 'augmentation' therapy in combination with more conventional treatments. Whether MSC have benefit in non-complex fistula in biological naïve patients, in complex fistula with many tracts and/or in rectovaginal fistulas, are unexplored fields that need further investigation. A central registry of pCD patients undergoing treatment with MSC should be created in order to elucidate the efficacy, safety and costs of stem cells treatment on long term follow up.
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Affiliation(s)
- G Bislenghi
- a Department of Abdominal Surgery , University Hospitals Leuven, KU Leuven , Leuven , Belgium
| | - A Wolthuis
- a Department of Abdominal Surgery , University Hospitals Leuven, KU Leuven , Leuven , Belgium
| | - G Van Assche
- b Department of Gastroenterology and Hepatology , University Hospitals Leuven, KU Leuven , Leuven , Belgium
| | - S Vermeire
- b Department of Gastroenterology and Hepatology , University Hospitals Leuven, KU Leuven , Leuven , Belgium
| | - M Ferrante
- b Department of Gastroenterology and Hepatology , University Hospitals Leuven, KU Leuven , Leuven , Belgium
| | - A D'Hoore
- a Department of Abdominal Surgery , University Hospitals Leuven, KU Leuven , Leuven , Belgium
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12
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Leutenegger M, Bruckner R, Spalinger MR, Lang S, Rogler G, Scharl M. Eribulin Does Not Prevent Epithelial-to-Mesenchymal Transition in HT-29 Intestinal Epithelial Cells. Inflamm Intest Dis 2018; 2:211-218. [PMID: 30221148 DOI: 10.1159/000490052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 05/10/2018] [Indexed: 12/19/2022] Open
Abstract
Background Fistula formation affects up to 50$ of Crohn's disease (CD) patients and causes considerable morbidity. Current pharmacological management mainly includes antibiotics, immunosuppressives, and anti-TNF antibodies. CD fistulas develop from intestinal epithelial cells undergoing epithelial-to-mesenchymal transition (EMT). TGFβ, the most important inducer of EMT, is detectable around CD fistula tracts and induces expression of the EMT-associated transcription factors SNAIL1 and SLUG as well as of IL-13. Conversely, together with TNF, IL-13 induces the expression of the transcription factor Ets-1 and β6-integrin, which are associated with cell invasiveness. Eribulin is a synthetic derivative of halichondrin B, a large polyether macrolide, which reverses EMT in triple-negative breast cancer (TNBC) cells. Here, we investigated whether Eribulin might be a potential therapeutic option for CD fistulas via the inhibition of EMT. Summary Chronic treatment with high concentrations of Eribulin (> 5 ng/ml) is toxic for intestinal epithelial cells (IEC), and Eribulin treatment does not decrease the mRNA expression of EMT markers in HT-29 monolayers nor prevent EMT in HT-29 spheroids. Together with TNF, Eribulin induces the expression of vimentin and SLUG mRNA in HT-29 spheroids but concomitantly also promotes E-cadherin expression. Key Messages Our data suggest that the previously reported antimetastatic effect of Eribulin in TNBC by reversing EMT does not apply to IEC. Interestingly, Eribulin promotes E-cadherin expression, suggesting an additional mechanism. The increase of E-cadherin might point towards the described role for Eribulin in reversing EMT. Taken together, our data do not support a role for Eribulin as treatment option for CD-associated fistulas.
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Affiliation(s)
- Martin Leutenegger
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Ramona Bruckner
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Marianne R Spalinger
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Silvia Lang
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Gerhard Rogler
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Michael Scharl
- Department of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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Epithelial-mesenchymal transition in Crohn's disease. Mucosal Immunol 2018; 11:294-303. [PMID: 29346350 DOI: 10.1038/mi.2017.107] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 11/06/2017] [Indexed: 02/06/2023]
Abstract
Crohn's disease (CD) is often accompanied by the complications of intestinal strictures and fistulas. These complications remain obstacles in CD treatment. In recent years, the importance of epithelial-mesenchymal transition in the pathogenesis of CD-associated fistulas and intestinal fibrosis has become apparent. Epithelial-mesenchymal transition refers to a dynamic change, wherein epithelial cells lose their polarity and adherence and acquire migratory function and fibroblast features. During formation of CD-associated fistulas, intestinal epithelial cells dislocate from the basement membrane and migrate to the lining of the fistula tracts, where they convert into transitional cells as a compensatory response under the insufficient wound healing condition. In CD-associated intestinal fibrosis, epithelial-mesenchymal transition may serve as a source of new fibroblasts and consequently lead to overproduction of extracellular matrix. In this review, we present current knowledge of epithelial-mesenchymal transition and its role in the pathogenesis of CD in order to highlight new therapy targets for the associated complications.
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Abstract
Perianal fistulizing Crohn's disease has a major negative effect on patient quality of life and is a predictor of poor long-term outcomes. Factors involved in the pathogenesis of perianal fistulizing Crohn's disease include an increased production of transforming growth factor β, TNF and IL-13 in the inflammatory infiltrate that induce epithelial-to-mesenchymal transition and upregulation of matrix metalloproteinases, leading to tissue remodelling and fistula formation. Care of patients with perianal Crohn's disease requires a multidisciplinary approach. A complete assessment of fistula characteristics is the basis for optimal management and must include the clinical evaluation of fistula openings, endoscopic assessment of the presence of proctitis, and MRI to determine the anatomy of fistula tracts and presence of abscesses. Local injection of mesenchymal stem cells can induce remission in patients not responding to medical therapies, or to avoid the exposure to systemic immunosuppression in patients naive to biologics in the absence of active luminal disease. Surgery is still required in a high proportion of patients and should not be delayed when criteria for drug failure is met. In this Review, we provide an up-to-date overview on the pathogenesis and diagnosis of fistulizing Crohn's disease, as well as therapeutic strategies.
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Abstract
Fistulas still represent one of the most important complications in patients with Crohn’s disease (CD). At least one third of CD patients suffer from fistulas during their disease course and amongst them longstanding remission of complex fistulas occurs only in about one third. So far, fistula pathogenesis is only partially understood. From a histopathological view, a fistula is a tube covered by flat epithelial cells. Current research suggests that the driving force for fistula development is epithelial-to-mesenchymal transition (EMT). Around the fistula, high levels of tumor necrosis factor (TNF), IL-13, and TGFβ can be detected and recent studies indicated an involvement of the intestinal microbiota. Fistula diagnosis requires clinical and surgical assessment, radiologic investigations, e.g., magnet resonance imaging and endoscopy. Routine medical treatment of fistulas includes antibiotics, immunosuppressives, and anti-TNF antibodies. There is no well-established role for calcineurin inhibitors in fistula treatment, corticosteroids appear to be even contra-productive. A promising novel approach might be the application of adipose tissue-derived or bone marrow-derived mesenchymal stem cells that have been studied recently. Due to insufficient efficacy of medical treatment and recurrence of fistulas, surgical interventions are frequently necessary. Further research is needed to better understand fistula pathogenesis aiming to develop novel treatment option for our patients.
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Zeitz J, Fournier N, Labenz C, Biedermann L, Frei P, Misselwitz B, Scharl S, Vavricka SR, Sulz MC, Fried M, Rogler G, Scharl M. Risk Factors for the Development of Fistulae and Stenoses in Crohn Disease Patients in the Swiss Inflammatory Bowel Disease Cohort. Inflamm Intest Dis 2017; 1:172-181. [PMID: 29922674 DOI: 10.1159/000458144] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 01/19/2017] [Indexed: 12/14/2022] Open
Abstract
Background Fistulae and stenoses represent frequent and severe complications in patients with Crohn disease (CD). Our study aimed to identify risk factors for fistula and stenosis formation in CD patients. Summary We retrieved data of 1,600 CD patients from the nationwide Swiss Inflammatory Bowel Disease Cohort Study (SIBDCS). The risk for fistulae and stenoses in relation to gender, age at diagnosis, smoking status at diagnosis, and ileal involvement at diagnosis were analyzed. In the multivariate analysis, female gender showed a lower risk for developing perianal and any fistula (risk ratio [RR] 0.721, 95% confidence interval [CI] 0.582-0.893, p = 0.003 and RR 0.717, 95% CI 0.580-0.888, p = 0.002, respectively), and older age at diagnosis showed a lower risk for developing perianal fistula (RR 0.661, 95% CI 0.439-0.995, p = 0.047). Furthermore, ileal involvement was associated with a lower risk for perianal fistula (RR 0.713, 95% CI 0.561-0.906, p = 0.006), a lower risk for any fistula (RR 0.709, 95% CI 0.558-0.901, p = 0.005), and a higher risk for stenosis (RR 2.170, 95% CI 1.728-2.725, p < 0.001). Key Messages In the nationwide SIBDCS, younger age at diagnosis and male gender were risk factors for developing perianal and nonperianal fistulae. Additionally, ileal involvement was revealed to be a potent risk factor (RR 2.170) for developing a stenosis.
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Affiliation(s)
- Jonas Zeitz
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Nicolas Fournier
- Institute of Social and Preventive Medicine, Université de Lausanne, Lausanne, Switzerland
| | - Christian Labenz
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.,Department of Internal Medicine, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany
| | - Luc Biedermann
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Pascal Frei
- Department of Gastroenterology, Gastroenterology Bethanien, University of Zurich, Zurich, Switzerland
| | - Benjamin Misselwitz
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Sylvie Scharl
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Stephan R Vavricka
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.,Department of Gastroenterology, Triemli Spital, Zurich, Switzerland
| | - Michael C Sulz
- Department of Gastroenterology and Hepatology, Kantonsspital St. Gallen, St. Gallen, Switzerland
| | - Michael Fried
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Gerhard Rogler
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
| | - Michael Scharl
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland
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Bai JA, jie H, wei S, Wang S, Guo H, Tang Q. GART mediates the renewal of intestinal epithelial barrier via p38/p53/PUMA cascade in colitis. Apoptosis 2016; 21:1386-1397. [DOI: 10.1007/s10495-016-1301-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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18
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Scharl M, Bruckner RS, Rogler G. The two sides of the coin: Similarities and differences in the pathomechanisms of fistulas and stricture formations in irritable bowel disease. United European Gastroenterol J 2016; 4:506-14. [PMID: 27536360 PMCID: PMC4971795 DOI: 10.1177/2050640616635957] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 01/27/2016] [Indexed: 12/11/2022] Open
Abstract
Fistulas and fibrosis or strictures represent frequent complications in irritable bowel disease (IBD) patients. To date, treatment options for fistulas are limited and surgery is often required. Similarly, no preventive treatment for fibrosis and stricture formation has been established. Frequently, stricture formation and fibrosis precede fistula formation, indicating that both processes may be connected or interrelated. Knowledge about the pathology of both processes is limited. A crucial role for the epithelial-to-mesenchymal transition (EMT) in fistula development has been demonstrated. Of note, EMT also plays a major role in the pathogenesis of fibrosis in many organs, and most likely also plays that role in the intestine. In addition, aberrant matrix remodeling, as well as soluble factors such as tumor necrosis factor (TNF), interleukin 13 (IL-13) and tumor growth factor beta (TGFβ) were involved, both in the onset of the fistula and fibrosis formation. Both fistulas and fibrosis may occur due to deregulated wound healing mechanisms from chronic and severe intestinal inflammation; however, further research is required to obtain a better understanding of the complex pathophysiology of fistula and intestinal fibrosis formation, to allow the development of new and more effective preventive treatment options for those important disease complications.
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Affiliation(s)
- Michael Scharl
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Ramona S Bruckner
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Gerhard Rogler
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
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Siegmund B, Feakins RM, Barmias G, Ludvig JC, Teixeira FV, Rogler G, Scharl M. Results of the Fifth Scientific Workshop of the ECCO (II): Pathophysiology of Perianal Fistulizing Disease. J Crohns Colitis 2016; 10:377-86. [PMID: 26681764 PMCID: PMC4946764 DOI: 10.1093/ecco-jcc/jjv228] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Accepted: 12/08/2015] [Indexed: 12/19/2022]
Abstract
The fifth scientific workshop of the European Crohn's and Colitis Organization (ECCO) focused on the relevance of fistulas to the disease course of patients with Crohn's disease (CD). The objectives were to reach a better understanding of the pathophysiological mechanisms underlying the formation of CD fistulas; to identify future topics in fistula research that could provide insights into pathogenesis; to develop novel therapeutic approaches; and to review current therapeutic strategies (with clarification of existing approaches to prevention, diagnosis and treatment). The results of the workshop are presented in two separate manuscripts. This manuscript describes current state-of-the-art knowledge about fistula pathogenesis, including the roles of epithelial-to-mesenchymal transition and cytokine matrix remodelling enzymes, and highlights the common association between fistulas and stenosis in CD. The review also considers the possible roles that genetic predisposition and intestinal microbiota play in fistula development. Finally, it proposes future directions and needs for fistula research that might substantially increase our understanding of this complex condition and help unravel novel therapeutic strategies and specific targets for treatment. Overall, it aims to highlight unanswered questions in fistula research and to provide a framework for future research work.
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Affiliation(s)
- Britta Siegmund
- Department of Medicine (Gastroenterology, Infectious Diseases, Rheumatology), Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Roger M Feakins
- Department of Histopathology, Royal London Hospital, London, UK
| | - Giorgos Barmias
- Academic Department of Gastroenterology, Ethnikon and Kapodistriakon University of Athens, Laikon Hospital, Athens, Greece
| | - Juliano Coelho Ludvig
- ESADI Clinic and Gastroenterology Unit, Santa Isabel Hospital, Blumenau, Santa Catarina, Brazil
| | - Fabio Vieira Teixeira
- Colorectal Unit, Gastrosaude Clinic, Marilia, Sao Paulo, Brazil Department of Surgery, UNESP Botucatu, Sao Paulo, Brazil
| | - Gerhard Rogler
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
| | - Michael Scharl
- Division of Gastroenterology and Hepatology, University Hospital Zurich, University of Zurich, Zurich, Switzerland
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20
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Abstract
Mast cells (MCs) are tissue-resident immune cells that carry out protective roles against pathogens. In disease states, such as inflammatory bowel disease, these granulocytes release a diverse array of mediators that contribute to inflammatory processes. They also participate in wound repair and tissue remodeling. In this review, the composition of MCs and how their phenotypes can be altered during inflammation of the gastrointestinal tract is detailed. Animal and human clinical studies that have implicated the participation of MCs in inflammatory bowel disease are reviewed, including the contribution of the cell's mediators to clinical symptoms, stress-triggered inflammation, and fistula and strictures. Studies that have focused on negating the proinflammatory roles of MCs and their mediators in animal models suggest new targets for therapies for patients with inflammatory bowel disease.
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21
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Scharl M, Rogler G. Pathophysiology of fistula formation in Crohn's disease. World J Gastrointest Pathophysiol 2014; 5:205-212. [PMID: 25133023 PMCID: PMC4133520 DOI: 10.4291/wjgp.v5.i3.205] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 04/04/2014] [Accepted: 05/29/2014] [Indexed: 02/06/2023] Open
Abstract
Fistulae represent an important complication in patient suffering from Crohn’s disease (CD). Cumulative incidence of fistula formation in CD patients is 17%-50% and about one third of patients suffer from recurring fistulae formation. Medical treatment options often fail and also surgery frequently is not successful. Available data indicate that CD-associated fistulae originate from an epithelial defect that may be caused by ongoing inflammation. Having undergone epithelial to mesenchymal transition (EMT), intestinal epithelial cells (IEC) penetrate into deeper layers of the mucosa and the gut wall causing localized tissue damage formation of a tube like structure and finally a connection to other organs or the body surface. EMT of IEC may be initially aimed to improve wound repair mechanisms since “conventional” wound healing mechanisms, such as migration of fibroblasts, are impaired in CD patients. EMT also enhances activation of matrix remodelling enzymes such as matrix metalloproteinase (MMP)-3 and MMP-9 causing further tissue damage and inflammation. Finally, soluble mediators like TNF and interleukin-13 further induce their own expression in an autocrine manner and enhance expression of molecules associated with cell invasiveness aggravating the process. Additionally, pathogen-associated molecular patterns also seem to play a role for induction of EMT and fistula development. Though current knowledge suggests a number of therapeutic options, new and more effective therapeutic approaches are urgently needed for patients suffering from CD-associated fistulae. A better understanding of the pathophysiology of fistula formation, however, is a prerequisite for the development of more efficacious medical anti-fistula treatments.
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