Genetic Influences on the Development of Fibrosis in Crohn's Disease

Fibrostenosing Crohn's Disease: Pathogenetic Mechanisms and New Therapeutic Horizons

Bowel strictures are well recognized as one of the most severe complications in Crohn's disease, with variable impacts on the prognosis and often needing surgical or endoscopic treatment. Distinguishing inflammatory strictures from fibrotic ones is of primary importance due to the different therapeutic approaches required. Indeed, to better understand the pathogenesis of fibrosis, it is crucial to investigate molecular processes involving genetic factors, cytokines, alteration of the intestinal barrier, and epithelial and endothelial damage, leading to an increase in extracellular matrix synthesis, which ultimately ends in fibrosis. In such a complex mechanism, the gut microbiota also seems to play a role. A better comprehension of molecular processes underlying bowel fibrosis, in addition to radiological and histopathological findings, has led to the identification of high-risk patients for personalized follow-up and testing of new therapies, primarily in preclinical models, targeting specific pathways involving Transforming Growth Factor-β, interleukins, extracellular matrix balance, and gut microbiota. Our review aims to summarize current evidence about molecular factors involved in intestinal fibrosis' pathogenesis, paving the way for potential diagnostic biomarkers or anti-fibrotic treatments for stricturing Crohn's disease.

NOD2 and Crohn's Disease Clinical Practice: From Epidemiology to Diagnosis and Therapy, Rewired

Crohn's disease (CD) is a chronic inflammatory bowel disease with a multifactorial pathogenesis involving environmental and genetic factors. Since the late 20th century, the discovery of the first susceptibility gene (NOD2, previously referred to as CARD15) for CD has paved the way for further investigations into the correlations between clinical features and genetics, and its potential impact on clinical practice has fueled the research in the last 2 decades. Recent therapeutic advancements involving novel biologic drugs and small molecules have shifted inflammatory bowel disease management from a disease-centered to a patient-centric approach. To date, the role of NOD2 has not been fully understood yet. Recent data suggest that its clinical impact may be greater than currently recognized. This review overviews the most common NOD2 variants' role in real-life clinical practice. These genetic variants increase the risk of developing the disease and can aid in tailoring diagnosis and treatment. They are associated with the stricturing phenotype and ileal involvement and increase the risk of steroid refractoriness. In the meantime, limited and inconclusive evidence exists regarding their predictive role in response to azathioprine, biologic drugs, and small molecules. Eventually, their role in increasing the risk for surgery is evident, especially in those with the L1007fs variant. If further trials will support the initial evidence reported so far, NOD2 genetic variants will emerge as possible candidates for developing precision medicine in CD.

Results of the Eighth Scientific Workshop of ECCO: Pathophysiology and Risk Factors of Postoperative Crohn's Disease Recurrence after an Ileocolonic Resection

Postoperative recurrence [POR] after an ileocolonic resection with ileocolonic anastomosis is frequently encountered in patients with Crohn's disease. The 8th Scientific Workshop of ECCO reviewed the available evidence on the pathophysiology and risk factors for POR. In this paper, we discuss published data on the role of the microbiome, the mesentery, the immune system and the genetic background. In addition to investigating the causative mechanisms of POR, identification of risk factors is essential to tailor preventive strategies. Potential clinical, surgical and histological risk factors are presented along with their limitations. Emphasis is placed on unanswered research questions, guiding prevention of POR based on individual patient profiles.

The Role of Genetic and Epigenetic Regulation in Intestinal Fibrosis in Inflammatory Bowel Disease: A Descending Process or a Programmed Consequence?

Inflammatory bowel diseases (IBDs) are a group of chronic diseases characterized by recurring periods of exacerbation and remission. Fibrosis of the intestine is one of the most common complications of IBD. Based on current analyses, it is evident that genetic factors and mechanisms, as well as epigenetic factors, play a role in the induction and progression of intestinal fibrosis in IBD. Key genetic factors and mechanisms that appear to be significant include NOD2, TGF-β, TLRs, Il23R, and ATG16L1. Deoxyribonucleic acid (DNA) methylation, histone modification, and ribonucleic acid (RNA) interference are the primary epigenetic mechanisms. Genetic and epigenetic mechanisms, which seem to be important in the pathophysiology and progression of IBD, may potentially be used in targeted therapy in the future. Therefore, the aim of this study was to gather and discuss selected mechanisms and genetic factors, as well as epigenetic factors.

Health Benefits of Dietary Fiber for the Management of Inflammatory Bowel Disease

Crohn's disease (CD) and ulcerative colitis (UC), two components of inflammatory bowel disease (IBD), are painful conditions that affect children and adults. Despite substantial research, there is no permanent cure for IBD, and patients face an increased risk of colon cancer. Dietary fiber's health advantages have been thoroughly investigated, and it is recommended for its enormous health benefits. This review article discusses the importance of appropriate fiber intake in managing IBD, emphasizing how optimal fiber consumption can significantly help IBD patients.

From single-target to cellular niche targeting in Crohn's disease: intercepting bad communications

The mainstay of moderate to severe Crohn's disease (CD), anti-TNF treatment, shows no clinical benefit in ∼40% of patients, likely due to incomplete cellular targeting and delayed treatment institution. While single-target therapeutics have been highly effective for some CD patients, substantial limitations with respect to safety, efficacy, and long-term, complete remission remain. Deconvolution of the cellular and molecular circuitry of tissue lesions underscores the importance of combinatorial strategies targeting cellular niches. This review aims to evaluate current therapeutic approaches used to manage CD, and highlight recent advances to our cellular, genetic, and molecular understanding of mechanisms driving pathogenic niche activation in CD. We propose new frameworks outlining that combinatorial therapies, along with serial tissue sampling and studies guided by genetics and genomics, can advance on current treatment approaches and will inform newer strategies upon which we can move towards precision therapeutics in IBD.

Crohn's disease-related single nucleotide polymorphisms are associated with ileal pouch afferent limb stenosis

BACKGROUND

Ileal pouch-anal anastomosis (IPAA) is a common surgical treatment for ulcerative colitis. Afferent limb stenosis is an infrequent complication following IPAA, suggesting underlying Crohn's disease (CD). We hypothesized that CD-related single nucleotide polymorphisms (SNPs) are associated with afferent limb stenosis.

METHODS

Afferent limb stenosis and CD control group patients were recruited from a prospective institutional inflammatory bowel disease database and associated biobank. Patient demographics, Montreal classification, and medication use were recorded. Ten SNPs associated with stricturing Crohn's disease were examined in genomic DNA and compared among afferent limb stenosis, stricturing CD, and non-stricturing CD controls.

RESULTS

Twenty-seven afferent limb stenosis and 162 CD control group patients (108 stricturing, 54 non-stricturing) were identified. Patients were gender and race matched. Afferent limb stenosis and stricturing CD controls were younger at diagnosis (Montreal A1/A2 vs. A3) compared to non-stricturing CD controls (both p < 0.05). The majority of afferent limb stenosis patients were non-smokers compared to CD controls (74% vs. 36%, p < 0.01) and did not use biologic therapies (4% vs. 37%, p < 0.001). The FUT2 G allele was more frequent in afferent limb stenosis and stricturing CD controls compared to non-stricturing CD controls (both p < 0.05). The NOD2 T allele was more frequent in stricturing CD controls compared to afferent limb stenosis and non-stricturing CD controls (both p < 0.05).

CONCLUSION

Afferent limb stenosis patients are phenotypically similar to stricturing CD controls, but differ with lower smoking rates and lower NOD2 allele frequency. Such differences could contribute to the presentation delay with a stricturing phenotype. Selective SNP assessment may help categorize patients likely to develop afferent limb stenosis.

A myeloid-stromal niche and gp130 rescue in NOD2-driven Crohn's disease

Crohn's disease is a chronic inflammatory intestinal disease that is frequently accompanied by aberrant healing and stricturing complications. Crosstalk between activated myeloid and stromal cells is critical in the pathogenicity of Crohn's disease^1,2, and increases in intravasating monocytes are correlated with a lack of response to anti-TNF treatment³. The risk alleles with the highest effect on Crohn's disease are loss-of-function mutations in NOD2^4,5, which increase the risk of stricturing⁶. However, the mechanisms that underlie pathogenicity driven by NOD2 mutations and the pathways that might rescue a lack of response to anti-TNF treatment remain largely uncharacterized. Here we use direct ex vivo analyses of patients who carry risk alleles of NOD2 to show that loss of NOD2 leads to dysregulated homeostasis of activated fibroblasts and macrophages. CD14⁺ peripheral blood mononuclear cells from carriers of NOD2 risk alleles produce cells that express high levels of collagen, and elevation of conserved signatures is observed in nod2-deficient zebrafish models of intestinal injury. The enrichment of STAT3 regulation and gp130 ligands in activated fibroblasts and macrophages suggested that gp130 blockade might rescue the activated program in NOD2-deficient cells. We show that post-treatment induction of the STAT3 pathway is correlated with a lack of response to anti-TNF treatment in patients, and demonstrate in vivo in zebrafish the amelioration of the activated myeloid-stromal niche using the specific gp130 inhibitor bazedoxifene. Our results provide insights into NOD2-driven fibrosis in Crohn's disease, and suggest that gp130 blockade may benefit some patients with Crohn's disease-potentially as a complement to anti-TNF therapy.

Personalised medicine in Crohn's disease

Similar to many immune-mediated diseases, Crohn's disease follows a relapsing-remitting pattern, with a variable disease course and heterogeneous clinical outcomes. Frequency of flare-ups, development of complications, and response to treatment collectively determine the effect on a patient's quality of life, which can vary from minimal disruption to profound disability or death. Despite recent advances in the understanding of complex disease pathogenesis, including for Crohn's disease, management decisions are still typically made using a one-size-fits-all approach. Indeed, the inability to reliably predict clinical outcomes in a way that could guide future therapy represents a major unmet need. Recently, several important insights have been made into the biology underlying outcomes in Crohn's disease. In this Review, we will summarise these insights and discuss how greater understanding of these disease mechanisms can be used to develop clinically useful biomarkers, identify novel approaches to optimise disease control, and help deliver the goal of personalised medicine.

Genetic Sequencing of Pediatric Patients Identifies Mutations in Monogenic Inflammatory Bowel Disease Genes that Translate to Distinct Clinical Phenotypes

OBJECTIVES

Monogenic inflammatory bowel disease (IBD) comprises rare Mendelian causes of gut inflammation, often presenting in infants with severe and atypical disease. This study aimed to identify clinically relevant variants within 68 monogenic IBD genes in an unselected pediatric IBD cohort.

METHODS

Whole exome sequencing was performed on patients with pediatric-onset disease. Variants fulfilling the American College of Medical Genetics criteria as "pathogenic" or "likely pathogenic" were assessed against phenotype at diagnosis and follow-up. Individual patient variants were assessed and processed to generate a per-gene, per-individual, deleteriousness score.

RESULTS

Four hundred one patients were included, and the median age of disease-onset was 11.92 years. In total, 11.5% of patients harbored a monogenic variant. TRIM22-related disease was implicated in 5 patients. A pathogenic mutation in the Wiskott-Aldrich syndrome (WAS) gene was confirmed in 2 male children with severe pancolonic inflammation and primary sclerosing cholangitis. In total, 7.3% of patients with Crohn's disease had apparent autosomal recessive, monogenic NOD2-related disease. Compared with non-NOD2 Crohn's disease, these patients had a marked stricturing phenotype (odds ratio 11.52, significant after correction for disease location) and had undergone significantly more intestinal resections (odds ratio 10.75). Variants in ADA, FERMT1, and LRBA did not meet the criteria for monogenic disease in any patients; however, case-control analysis of mutation burden significantly implicated these genes in disease etiology.

DISCUSSION

Routine whole exome sequencing in pediatric patients with IBD results in a precise molecular diagnosis for a subset of patients with IBD, providing the opportunity to personalize therapy. NOD2 status informs risk of stricturing disease requiring surgery, allowing clinicians to direct prognosis and intervention.

Inflammatory bowel disease: long-term therapeutic challenges

Introduction: Long-term, sustained, remission is the ultimate goal of contemporary inflammatory bowel disease (IBD) therapy. Avoiding complications, surgery and malignancy, alongside minimizing the side effects of medications are vital. However, the reality of treatment involves patients losing response to therapy, or developing complications requiring cessation of medication. The reasons underlying this are numerous and include medication and host-related influences. Underpinning the response to medication, long-term outcomes and loss of response are individual etiological factors including the molecular cause of disease and individual pharmacogenomic influences.Areas covered: In this review, we discuss the long-term outcome of IBD, with a focus on pediatric-onset illness and discuss the factors leading to loss of treatment response whilst briefly considering the future of personalized therapy as a strategy to improve long-term outcomes.Expert opinion: Research findings are now moving toward clinical translation, including application of novel medications targeting new pathways. The integration of biological and multiomic data to predict disease outcome will provide personalized therapeutic management.

Among autophagy genes, ATG16L1 but not IRGM is associated with Crohn's disease in Iranians

BACKGROUND

The prevalence of inflammatory bowel diseases is uprising in countries like Iran. Genetic predisposing elements play prominent role in the pathogenesis of Crohn's disease. In this study we studied the role of autophagy genes like IRGM (Immunity related GTPase M) and ATG16L1 (Autophagy related 16 like 1) in the pathogenesis of Crohn's Disease in Iranian patients.

METHODS

One hundred thirty-eight patients and 99 normal controls were recruited in this study. Polymorphisms in -1644 and -308 upstream of IRGM gene were studied by PCR-sequencing and 20 kb CNVdel/insertion was studied by specific PCR. Rs10065171, rs4958847 in IRGM gene and rs2241880 in ATG16L1 were studied by Taqman genotyping assays.

RESULTS

None of the so-called predisposing alleles of IRGM gene predispose Iranians to Crohn's disease while the prevalence of some of them like CNV deletion was higher in normal controls. Surprisingly all the so-called predisposing alleles in IRGM were linked to each other (especially rs4958847 with rs10065172 and polymorphisms in -308 region with rs4958847). Patients harboring A allele in rs4958847 site showed higher ratio of fibrostenotic type of disease while in patients with C/T genotype in rs4958847, colonic involvement was seen more frequently. G allele in ATG16L1 was associated with Crohn's disease though it was not associated with any phenotypic manifestation.

CONCLUSION

In our study the association of ATG16L1 to Crohn's disease in Iranian patients was confirmed while it was shown that the studied polymorphisms in IRGM was not associated with Crohn's disease. Therefore in order to have a better picture about the genetics of Crohn's disease in Iranian patients, it is recommended to study other clinically effective polymorphisms in IRGM and ATG16L1 in addition to other genes which are responsible for the process of autophagy.