Muscular hyperplasia in Crohn's disease strictures: through thick and thin.

Fibrostenosing Crohn's disease (CD) represents a challenging clinical condition characterized by the development of symptomatic strictures within the gastrointestinal tract. Despite therapeutic advancements in managing inflammation, the progression of fibrostenotic complications remains a significant concern, often necessitating surgical intervention. Recent investigations have unveiled the pivotal role of smooth muscle cell hyperplasia in driving luminal narrowing and clinical symptomatology. Drawing parallels to analogous inflammatory conditions affecting other organs, such as the airways and blood vessels, sheds light on common underlying mechanisms of muscular hyperplasia. This review synthesizes current evidence to elucidate the mechanisms underlying smooth muscle cell proliferation in CD-associated strictures, offering insights into potential therapeutic targets. By highlighting the emerging significance of muscle thickening as a novel therapeutic target, this review aims to inform future research endeavors and clinical strategies with the goal to mitigate the burden of fibrostenotic complications in CD and other conditions.

Fibrosis-Related microRNAs in Crohn's Disease with Fibrostenosis and Inflammatory Stenosis.

Crohn's disease (CD) is frequently complicated by strictures that can be either inflammatory or fibrostenotic. This distinction is important for deciding the best treatment course, but it can be difficult to determine clinically, sometimes even by advanced imaging techniques. We performed miRNA PCR panel screening on pooled samples of ileum with CD fibrostenosis or inflammatory stenosis. Eight miRNAs with profibrotic (miR-93-5p, miR-376c-3p and miR-424-5p), or fibroprotective (miR-133a-3p, miR-133b, miR-193a-5p, miR-335-5p and miR-378a-3p) functions described in the literature were selected for validation on 20 samples each of CD with fibrostenosis or inflammatory stenosis, with a separate sampling of the submucosa and subserosa. The results showed significant differences between the groups in subserosal samples, with upregulation of profibrotic miRNAs and downregulation of fibroprotective miRNAs in fibrostenosis compared to inflammatory stenosis. Only miR-424-5p showed a significant difference in the submucosa. There were significant differences in miRNA expression between subserosa and submucosa. Our results provide further evidence that the major differences between fibrostenosis and inflammatory stenosis are located in the subserosa, which is inaccessible to endoscopic sampling, highlighting the need for cross-sectional imaging or serological markers. We identify several miRNAs previously not connected to fibrosis in CD, which could potentially serve as biomarkers of fibrostenosis.

Esophageal Distensibility Defines Fibrostenotic Severity in Pediatric Eosinophilic Esophagitis.

BACKGROUND & AIMS: Identification of fibrosis in pediatric eosinophilic esophagitis (EoE) relies on symptom assessment and endoscopy. Symptoms are highly variable, and early fibrotic remodeling may go undetected on endoscopy yet contribute to esophageal dysfunction. We aimed to assess whether esophageal distensibility has utility in defining fibrostenotic severity in a cohort of pediatric patients with EoE with symptoms of esophageal dysfunction. METHODS: We analyzed a prospectively recruited a cohort of children ages 9 to 21 years undergoing upper endoscopy and Endoscopic Functional Lumen Imaging Probe (EndoFLIP) for suspected or previously diagnosed EoE. Esophageal distensibility was evaluated by the distensibility index (DI) and esophageal diameter at the distensibility plateau. The association of esophageal distensibility to clinical, endoscopic, and histologic parameters of disease severity was assessed. Receiver operating characteristic analysis was performed to determine the utility of distensibility in defining esophageal rigidity in pediatric EoE. RESULTS: We identified 59 pediatric patients with EoE undergoing endoscopy and EndoFLIP at a single pediatric tertiary referral center. DI (mm2/mmHg) was significantly lower in patients with fibrotic as compared with inflammatory features on endoscopy (median, 3.3; interquartile range, 2.3-4.4) vs median, 5.5; interquartile range, 4.1-6.0; P = .02) and showed no correlation with eosinophil count. DI <4.5 mm2/mmHg predicted grade 2 rings on endoscopy with area under the curve of 0.81 (P = .0004). DI predicted food impaction in both unadjusted and adjusted models (fully adjusted odds ratio, 1.44; 95% confidence interval, 1.02-2.14; P = .0486). CONCLUSION: Esophageal distensibility determined by EndoFLIP is a measure of fibrostenotic severity that can be used to clinically phenotype pediatric EoE. We propose parameters of DI <4.5 mm2/mmHg for defining esophageal rigidity in pediatric patients with EoE ages 9 years and older.

NR4A1 modulates intestinal smooth muscle cell phenotype and dampens inflammation-associated intestinal remodeling.

Stricture formation is a common complication of Crohn's disease (CD), driven by enhanced deposition of extracellular matrix (ECM) and expansion of the intestinal smooth muscle layers. Nuclear receptor subfamily 4 group A member 1 (NR4A1) is an orphan nuclear receptor that exhibits anti-proliferative effects in smooth muscle cells (SMCs). We hypothesized that NR4A1 regulates intestinal SMC proliferation and muscle thickening in the context of inflammation. Intestinal SMCs isolated from Nr4a1+/+ and Nr4a1-/- littermates were subjected to shotgun proteomic analysis, proliferation, and bioenergetic assays. Proliferation was assessed in the presence and absence of NR4A1 agonists, cytosporone-B (Csn-B) and 6-mercaptopurine (6-MP). In vivo, we compared colonic smooth muscle thickening in Nr4a1+/+ and Nr4a1-/- mice using the chronic dextran sulfate sodium (DSS) model of colitis. Second, SAMP1/YitFc mice (a model of spontaneous ileitis) were treated with Csn-B and small intestinal smooth muscle thickening was assessed. SMCs isolated from Nr4a1-/- mice exhibited increased abundance of proteins related to cell proliferation, metabolism, and ECM production, whereas Nr4a1+/+ SMCs highly expressed proteins related to the regulation of the actin cytoskeleton and contractile processes. SMCs isolated from Nr4a1-/- mice exhibited increased proliferation and alterations in cellular metabolism, whereas activation of NR4A1 attenuated proliferation. In vivo, Nr4a1-/- mice exhibited increased colonic smooth muscle thickness following repeated cycles of DSS. Activating NR4A1 with Csn-B, in the context of established inflammation, reduced ileal smooth muscle thickening in SAMP1/YitFc mice. Targeting NR4A1 may provide a novel approach to regulate intestinal SMC phenotype, limiting excessive proliferation that contributes to stricture development in CD.

Biomarkers for the Prediction and Diagnosis of Fibrostenosing Crohn's Disease: A Systematic Review.

BACKGROUND AND AIMS: Intestinal strictures are a common complication of Crohn's disease (CD). Biomarkers of intestinal strictures would assist in their prediction, diagnosis, and monitoring. Herein we provide a comprehensive systematic review of studies assessing biomarkers that may predict or diagnose CD-associated strictures. METHODS: We performed a systematic review of PubMed, EMBASE, ISI Web of Science, Cochrane Library, and Scopus to identify citations pertaining to biomarkers of intestinal fibrosis through July 6, 2020, that used a reference standard of full-thickness histopathology or cross-sectional imaging or endoscopy. Studies were categorized based on the type of biomarker they evaluated (serum, genetic, histopathologic, or fecal). RESULTS: Thirty-five distinct biomarkers from 3 major groups were identified: serum (20 markers), genetic (9 markers), and histopathology (6 markers). Promising markers include cartilage oligomeric matrix protein, hepatocyte growth factor activator, and lower levels of microRNA-19-3p (area under the curves were 0.805, 0.738, and 0.67, respectively), and multiple anti-flagellin antibodies (A4-Fla2 [odds ratio, 3.41], anti Fla-X [odds ratio, 2.95], and anti-CBir1 [multiple]). Substantial heterogeneity was observed and none of the markers had undergone formal validation. Specific limitations to acceptance of these markers included failure to use a standardized definition of stricturing disease, lack of specificity, and insufficient relevance to the pathogenesis of intestinal strictures or incomplete knowledge regarding their operating properties. CONCLUSIONS: There is a lack of well-defined studies on biomarkers of intestinal stricture. Development of reliable and accurate biomarkers of stricture is a research priority. Biomarkers can support the clinical management of CD patients and aid in the stratification and monitoring of patients during clinical trials of future antifibrotic drug candidates.

Computed tomography and magnetic resonance enterography findings in Crohn's disease: what does the clinician need to know from the radiologist?

The purpose of this pictorial essay was to discuss and illustrate computed tomography and magnetic resonance enterography findings in patients with Crohn's disease. These noninvasive and easily performed methods for the evaluation of Crohn's disease are useful for differentiating between active and fibrotic bowel disease, and can help to guide treatment (medical vs surgical). Although inflammatory and fibrostenotic findings of Crohn's disease may overlap, computed tomography and magnetic resonance enterography can help to identify the presence, extent, and severity of active inflammation that may respond to medical therapy, and the existence of fistulas and fibrostenosis that may benefit from surgical management.

Radiomics to Detect Inflammation and Fibrosis on Magnetic Resonance Enterography in Stricturing Crohn's Disease.

BACKGROUND & AIMS: Non-invasive cross-sectional imaging via magnetic resonance enterography (MRE) offers excellent accuracy for the diagnosis of stricturing complications in Crohn's disease (CD) but is limited in determining the degrees of fibrosis and inflammation within a stricture. We developed and validated a radiomics-based machine-learning model for separately characterizing the degree of histopathologic inflammation and fibrosis in CD strictures and compared it to centrally read visual radiologist scoring of MRE. METHODS: This single center, cross-sectional study, included 51 CD patients (n=34 for discovery; n=17 for validation) with terminal ileal strictures confirmed on diagnostic MRE within 15 weeks of resection. Histopathological specimens were scored for inflammation and fibrosis and spatially linked with corresponding pre-surgical MRE sequences. Annotated stricture regions on MRE were scored visually by radiologists as well as underwent 3D radiomics-based machine learning analysis; both evaluated against histopathology. RESULTS: Two distinct sets of radiomic features capturing textural heterogeneity within strictures were linked with each of severe inflammation or severe fibrosis across both discovery (area under the curve (AUC)=0.69, 0.83) and validation (AUCs=0.67,0.78) cohorts. Radiologist visual scoring had an AUC=0.67 for identifying severe inflammation and AUC=0.35 for severe fibrosis. Use of combined radiomics and radiologist scoring robustly augmented identification of severe inflammation (AUC=0.79) and modestly improved assessment of severe fibrosis (AUC=0.79 for severe fibrosis) over individual approaches. CONCLUSIONS: Radiomic features of CD strictures on MRE can accurately identify severe histopathologic inflammation and severe histopathologic fibrosis, as well as augment performance of radiologist visual scoring in stricture characterization.

Thrombospondin 2, matrix Gla protein and digital analysis identified distinct fibroblast populations in fibrostenosing Crohn's disease.

Fibrosis is an important complication in inflammatory bowel diseases. Previous studies suggest an important role of matrix Gla protein (MGP) and thrombospondin 2 (THBS2) in fibrosis in various organs. Our aim was to analyse their expression together with regulatory miRNAs in submucosal and subserosal fibroblasts in ulcerative colitis (UC) and Crohn's disease (CD) using immunohistochemistry and qPCR. Digital pathology was used to compare collagen fibre characteristics of submucosal and subserosal fibrosis. Immunohistochemistry showed expression of MGP, but not THBS2 in submucosa in UC and CD. In the subserosa, there was strong staining for both proteins in CD but not in UC. qPCR showed significant upregulation of THBS2 and MGP genes in CD subserosa compared to the submucosa. Digital pathology analysis revealed higher proportion of larger and thicker fibres that were more tortuous and reticulated in subserosal fibrosis compared to submucosal fibrosis. These results suggest distinct fibroblast populations in fibrostenosing CD, and are further supported by image analysis showing significant differences in the morphology and architecture of collagen fibres in submucosal fibrosis in comparison to subserosal fibrosis. Our study is the first to describe differences in submucosal and subserosal fibroblast populations, contributing to understanding of the pathogenesis of fibrostenosis in CD.

Nutritional interventions in adult fibrostenotic Crohn's disease: A systematic review.

Background: Management of Crohn's disease (CD) using dietary interventions has become an area of increased research interest. There is a lack of specific research exploring if diet and nutrition interventions are beneficial in patients with strictures, as current dietary recommendations in fibrostenotic CD are often based on clinical judgment. The aim of this systematic review was to assess the impact of dietary interventions in fibrostenotic CD on medical and surgical outcomes. Methods: A systematic search of MEDLINE (Ovid), EMBASE (Ovid), CINAHL (EBSCO), and Cochrane Central Register of Controlled Trials (Ovid) was conducted. Studies reporting dietary interventions or nutritional factors in fibrostenotic CD were included. Outcomes for studies assessing dietary interventions such as enteral nutrition were evaluated as changes in (1) CD symptoms (CD Activity Index), (2) stricture parameters on diagnostic imaging, and (3) rates of surgical or medical intervention following dietary interventions. Results: Five studies were included in this review. Three studies assessed exclusive enteral nutrition (EEN), one evaluated total parenteral nutrition (TPN), and one studied a liquid diet. All included studies evaluated symptoms as an outcome, while diagnostic imaging parameters and surgical outcomes in the studies were either absent or too heterogeneous to appraise improvement post dietary intervention. Included EEN studies displayed similar efficacy, with approximately 60% of patients having symptom improvement. The included TPN study also reported 75% of patients with symptom improvement, while the liquid diet did not. Conclusion: Exclusive enteral nutrition and total parental nutrition may provide benefit for use as a dietary intervention for fibrostenotic CD. There remains a need for high-quality controlled trials which utilize standardized definitions of strictures.

Downregulation of Heat Shock Protein 72 Contributes to Fibrostenosis in Crohn's Disease.

Background/Aims: Crohn's disease (CD) with recurrent inflammation can cause intestinal fibrostenosis due to dysregulated deposition of extracellular matrix. However, little is known about the pathogenesis of fibrostenosis. Here, we performed a differential proteomic analysis between normal, inflamed, and fibrostenotic specimens of patients with CD and investigated the roles of the candidate proteins in myofibroblast activation and fibrosis. Methods: We performed two-dimensional difference gel electrophoresis and identified candidate proteins using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and orbitrap liquid chromatography-mass spectrometry. We also verified the levels of candidate proteins in clinical specimens and examined their effects on 18Co myofibroblasts and Caco-2 intestinal epithelial cells. Results: We identified five of 30 proteins (HSP72, HSPA5, KRT8, PEPCK-M, and FABP6) differentially expressed in fibrostenotic CD. Among these proteins, the knockdown of heat shock protein 72 (HSP72) promoted the activation and wound healing of myofibroblasts. Moreover, knockdown of HSP72 induced the epithelial-mesenchymal transition of intestinal epithelial cells by reducing E-cadherin and inducing fibronectin and α-smooth muscle actin, which contribute to fibrosis. Conclusions: HSP72 is an important mediator that regulates myofibroblasts and epithelial-mesenchymal transition in fibrosis of CD, suggesting that HSP72 can serve as a target for antifibrotic therapy.

Epidemiology of fibrostenosing inflammatory bowel disease.

Fibrostenosis occurs in both Crohn's disease (CD) and ulcerative colitis (UC). Up to 21% of patients with CD present with strictures at diagnosis, while the rate of stenosis varies from 1% to 11% in UC. Despite the increasing use of immunomodulators and biologics in treatment, there has been no decrease in the rate of progression from inflammatory to complicated disease phenotypes (either stricturing or penetrating). The presence of stenosis is an independent risk factor for surgery in patients with CD, who are at a risk of postoperative recurrence at a rate of up to 55% at 10 years after surgery. Patients with inflammatory bowel disease (IBD) strictures are at risk of malignant transformation. Thus, surveillance colonoscopy should be offered to this group of patients. Several risk factors for the development of stricture have been identified. In CD, patients aged less than 40-years old, with perianal disease at diagnosis, who need steroids at the first flare up or have ileal disease are at the risk of developing strictures; while in UC, patients with extensive colitis and long-standing disease are at risk. Recently, microbiota signatures have also been identified as markers for stricture development. The presence of Ruminococcus spp. is associated with the development of stricture in pediatric patients with CD. In this review, we highlight the epidemiology, risk factors and natural history of fibrostenosing IBD.

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.

Gene expression-phenotype associations in adults with eosinophilic esophagitis.

BACKGROUND: Gene expression patterns have not been extensively examined in the context of clinical features of eosinophilic esophagitis (EoE). AIMS: To assess whether gene expression is associated with clinically defined phenotypes in adults with EoE. METHODS: This was an analysis of prospectively collected esophageal biopsies in newly diagnosed EoE patients. We determined differential gene expression with a 94 gene panel in relation to clinical features and phenotypes. These included: endoscopic findings of esophageal rings, stricture, narrowing, linear furrows, exudates, edema, and dilation; an allergic phenotype; an inflammatory phenotype, and a fibrostenotic phenotype. RESULTS: In 89 EoE cases analyzed, patients with exudates on endoscopy had multiple differences in gene expression compared to patients without exudates, though patients with exudates also had higher eosinophil counts (172 vs 106eos/hpf; p=.01). Genes associated with esophageal narrowing included CCL26 (q-value=0.028), ALOX15 (q=0.011), GRK5 (q=0.029), CPA3 (q=0.012), and TRIM2 (q=0.0027). TRIM2 was also associated with the fibrostenotic phenotype (q=0.0051). No genes were associated with the inflammatory or atopic phenotypes, or with dilation. CONCLUSIONS: Multiple genes are associated with exudates, possibly related to higher eosinophil counts. However, a number of genes, including those related to both inflammation and remodelling, are associated with esophageal narrowing. In particular, TRIM2 is associated with clinical fibrotic phenotypes.

Smooth Muscle Hyperplasia/Hypertrophy is the Most Prominent Histological Change in Crohn's Fibrostenosing Bowel Strictures: A Semiquantitative Analysis by Using a Novel Histological Grading Scheme.

BACKGROUND: The simplistically and ambiguously termed 'fibrostenosis' of bowel is a hallmark of severe Crohn's disease [CD] and a major contributor to medical treatment failure. Non-invasive imaging assessment and novel medical therapy targeting this condition are under investigation, which particularly requires a better understanding of the underlying histological basis. METHODS: We analysed 48 patients with stricturing Crohn's ileitis or/and colitis that required surgical resection. The most representative sections of the fibrostenotic, non-stenotic and uninvolved regions were reviewed for histological analysis. For each layer of bowel wall (mucosa including muscularis mucosae [MU], submucosa [SM], muscularis propria [MP], subserosal adventitia [SS]), histological abnormalities were evaluated individually, including active and chronic inflammation, fibrosis, smooth muscle hyperplasia or hypertrophy, neuronal hypertrophy and adipocyte proliferation. A novel semiquantitative histological grading scheme was created. RESULTS: The most significant histopathological features characterizing the stricturing intestines were smooth muscle hyperplasia of SM, hypertrophy of MP and chronic inflammation. The muscular alteration was predominant in all layers. The overall muscular hyperplasia/hypertrophy was positively correlated with chronic inflammation and negatively correlated with fibrosis, whereas SM muscular hyperplasia was also associated with MU active inflammation. Similar changes, to a lesser extent, occurred in the adjacent non-stenotic inflamed bowel as well. CONCLUSIONS: In CD-associated 'fibrostenosis', it is the smooth muscle hyperplasia/hypertrophy that contributes most to the stricturing phenotype, whereas fibrosis is less significant. The 'inflammation-smooth muscle hyperplasia axis' may be the most important in the pathogenesis of Crohn's strictures.

The Role of Cytokines in the Fibrotic Responses in Crohn's Disease.

Crohn's disease is an idiopathic disorder of the gut thought to be caused by a combination of environmental and genetic factors in susceptible individuals. It is characterized by chronic transmural inflammation of the terminal ileum and colon, with typical transmural lesions. Complications, including fibrosis, mean that between 40 and 70% of patients require surgery in the first 10 years after diagnosis. Presently, there is no evidence that the current therapies which dampen inflammation modulate or reverse intestinal fibrosis. In this review, we focus on cytokines that may lead to fibrosis and stenosis and the contribution of experimental models for understanding and treatment of gut fibrosis.

Enfermedad de Crohn fibroestenótica en íleon medio como manifestación inicial de la enfermedad. Reporte de un caso / A Case Report of Fibro-Stenotic Crohn's Disease in the Middle Ileum as the Initial Manifestation

Resumen La enfermedad de Crohn (EC) es una enfermedad inflamatoria intestinal que puede afectar todo el tracto gastrointestinal; el intestino delgado es el segmento afectado en cerca del 50% de los pacientes, en los cuales el íleon terminal es el área más comúnmente comprometida por la enfermedad. Las estenosis intestinales son una complicación frecuente en la EC y aproximadamente 30% a 50% de los pacientes presentan estenosis o lesiones penetrantes al momento del diagnóstico. Las técnicas endoscópicas convencionales no permiten evaluar las lesiones del intestino delgado; es por esto que se desarrollaron técnicas como la enteroscopia y la videocápsula endoscópica, teniendo cada una de ellas sus ventajas e indicaciones. Se presenta un caso de un paciente con EC con fibroestenosis localizada en el íleon medio. No es una localización frecuente para este tipo de lesiones.

Abstract Crohn's disease (CD) is an inflammatory bowel disease that can affect the entire gastrointestinal tract. The small intestine is affected in about 50% of patients among whom the terminal ileum is the area most commonly affected. Intestinal stenosis is a common complication in CD and approximately 30% to 50% of patients present stenosis or penetrating lesions at the time of diagnosis. Because conventional endoscopic techniques do not allow evaluation of small bowel lesions, techniques such as enteroscopy and endoscopic video-capsule were developed. Each has advantages and indications. We present the case of a patient with CD with localized fibrostenosis in the middle ileum which is not a frequent site for this type of lesion.