Human Leukocyte Antigen Signatures as Pathophysiological Discriminants of Microscopic Colitis Subtypes.

BACKGROUND AND AIMS: Microscopic colitis [MC] is currently regarded as an inflammatory bowel disease that manifests as two subtypes: collagenous colitis [CC] and lymphocytic colitis [LC]. Whether these represent a clinical continuum or distinct entities is, however, an open question. Genetic investigations may contribute important insight into their respective pathophysiologies. METHODS: We conducted a genome-wide association study [GWAS] meta-analysis in 1498 CC, 373 LC patients, and 13 487 controls from Europe and the USA, combined with publicly available MC GWAS data from UK Biobank and FinnGen [2599 MC cases and 552 343 controls in total]. Human leukocyte antigen [HLA] alleles and polymorphic residues were imputed and tested for association, including conditional analyses for the identification of key causative variants and residues. Genetic correlations with other traits and diagnoses were also studied. RESULTS: We detected strong HLA association with CC, and conditional analyses highlighted the DRB1*03:01 allele and its residues Y26, N77, and R74 as key to this association (best p = 1.4 × 10-23, odds ratio [OR] = 1.96). Nominally significant genetic correlations were detected between CC and pneumonia [rg = 0.77; p = 0.048] and oesophageal diseases [rg = 0.45, p = 0.023]. An additional locus was identified in MC GWAS analyses near the CLEC16A and RMI2 genes on chromosome 16 [rs35099084, p = 2.0 × 10-8, OR = 1.31]. No significant association was detected for LC. CONCLUSION: Our results suggest CC and LC have distinct pathophysiological underpinnings, characterised by an HLA predisposing role only in CC. This challenges existing classifications, eventually calling for a re-evaluation of the utility of MC umbrella definitions.

Pomegranate Extract Affects Gut Biofilm Forming Bacteria and Promotes Intestinal Mucosal Healing Regulating the Crosstalk between Epithelial Cells and Intestinal Fibroblasts.

Background: Pomegranate (Punica granatum) can be used to prepare a bioactive extract exerting anti-inflammatory activities. Clinical studies demonstrated an improvement in clinical response in inflammatory bowel disease (IBD) patients when pomegranate extract (PG) was taken as a complement to standard medications. However, the molecular mechanisms underlying its beneficial effects are still scarcely investigated. This study investigates the effect of PG on bacterial biofilm formation and the promotion of mucosal wound healing. Methods: The acute colitis model was induced in C57BL/6N mice by 3% dextran sodium sulfate administration in drinking water for 5 days. During the recovery phase of colitis, mice received saline or PG (200 mg/kg body weight) by oral gavage for 11 days. Colitis was scored daily by evaluating body weight loss, bleeding, and stool consistency. In vivo intestinal permeability was evaluated by fluorescein isothiocyanate-conjugated dextran assay, bacterial translocation was assessed by fluorescence in situ hybridization on tissues, whereas epithelial and mucus integrity were monitored by immunostaining for JAM-A and MUC-2 markers. Bacterial biofilm formation was assessed using microfluidic devices for 24 or 48 h. Primary fibroblasts were isolated from healthy and inflamed areas of 8 IBD patients, and Caco-2 cells were stimulated with or without PG (5 µg/mL). Inflammatory mediators were measured at the mRNA and protein level by RT-PCR, WB, or Bio-plex multiplex immunoassay, respectively. Results: In vivo, PG boosted the recovery phase of colitis, promoting a complete restoration of the intestinal barrier with the regeneration of the mucus layer, as also demonstrated by the absence of bacterial spread into the mucosa and the enrichment of crypt-associated fibroblasts. Microfluidic experiments did not highlight a specific effect of PG on Enterobacterales biofilm formation, even though Citrobacter freundii biofilm was slightly impaired in the presence of PG. In vitro, inflamed fibroblasts responded to PG by downregulating the release of metalloproteinases, IL-6, and IL-8 and upregulating the levels of HGF. Caco-2 cells cultured in a medium supplemented with PG increased the expression of SOX-9 and CD44, whereas in the presence of HGF or plated with a fibroblast-conditioned medium, they displayed a decrease in SOX-9 and CD44 expression and an increase in AXIN2, a negative regulator of Wnt signaling. Conclusions: These data provide new insight into the manifold effects of PG on promoting mucosal homeostasis in IBD by affecting pathogen biofilm formation and favoring the regeneration of the intestinal barrier through the regulation of the crosstalk between epithelial and stromal cells.

Dysfunctional Extracellular Matrix Remodeling Supports Perianal Fistulizing Crohn's Disease by a Mechanoregulated Activation of the Epithelial-to-Mesenchymal Transition.

BACKGROUND AND AIMS: Perianal fistula represents one of the most disabling manifestations of Crohn's disease (CD) due to complete destruction of the affected mucosa, which is replaced by granulation tissue and associated with changes in tissue organization. To date, the molecular mechanisms underlying perianal fistula formation are not well defined. Here, we dissected the tissue changes in the fistula area and addressed whether a dysregulation of extracellular matrix (ECM) homeostasis can support fistula formation. METHODS: Surgical specimens from perianal fistula tissue and the surrounding region of fistulizing CD were analyzed histologically and by RNA sequencing. Genes significantly modulated were validated by real-time polymerase chain reaction, Western blot, and immunofluorescence assays. The effect of the protein product of TNF-stimulated gene-6 (TSG-6) on cell morphology, phenotype, and ECM organization was investigated with endogenous lentivirus-induced overexpression of TSG-6 in Caco-2 cells and with exogenous addition of recombinant human TSG-6 protein to primary fibroblasts from region surrounding fistula. Proliferative and migratory assays were performed. RESULTS: A markedly different organization of ECM was found across fistula and surrounding fistula regions with an increased expression of integrins and matrix metalloproteinases and hyaluronan (HA) staining in the fistula, associated with increased newly synthesized collagen fibers and mechanosensitive proteins. Among dysregulated genes associated with ECM, TNFAI6 (gene encoding for TSG-6) was as significantly upregulated in the fistula compared with area surrounding fistula, where it promoted the pathological formation of complexes between heavy chains from inter-alpha-inhibitor and HA responsible for the formation of a crosslinked ECM. There was a positive correlation between TNFAI6 expression and expression of mechanosensitive genes in fistula tissue. The overexpression of TSG-6 in Caco-2 cells promoted migration, epithelial-mesenchymal transition, transcription factor SNAI1, and HA synthase (HAs) levels, while in fibroblasts, isolated from the area surrounding the fistula, it promoted an activated phenotype. Moreover, the enrichment of an HA scaffold with recombinant human TSG-6 protein promoted collagen release and increase of SNAI1, ITGA4, ITGA42B, and PTK2B genes, the latter being involved in the transduction of responses to mechanical stimuli. CONCLUSIONS: By mediating changes in the ECM organization, TSG-6 triggers the epithelial-mesenchymal transition transcription factor SNAI1 through the activation of mechanosensitive proteins. These data point to regulators of ECM as new potential targets for the treatment of CD perianal fistula.

New Insights into Bile Acids Related Signaling Pathways in the Onset of Colorectal Cancer.

Colorectal cancer (CRC) ranks as the second among the causes of tumor death worldwide, with an estimation of 1.9 million new cases in 2020 and more than 900,000 deaths. This rate might increase by 60% over the next 10 years. These data are unacceptable considering that CRC could be successfully treated if diagnosed in the early stages. A high-fat diet promotes the hepatic synthesis of bile acids (BAs) increasing their delivery to the colonic lumen and numerous scientific reports correlate BAs, especially secondary BAs, with CRC incidence. We reviewed the physicochemical and biological characteristics of BAs, focusing on the major pathways involved in CRC risk and progression. We specifically pointed out the role of BAs as signaling molecules and the tangled relationships among their nuclear and membrane receptors with the big bang of molecular and cellular events that trigger CRC occurrence.

Ileal Pouch-Anal Anastomosis and Pouchitis: The Role of the Microbiota in the Pathogenesis and Therapy.

Inflammatory bowel diseases, Crohn's disease and ulcerative colitis, are life-long disorders characterized by the chronic relapsing inflammation of the gastrointestinal tract with the intermittent need for escalation treatment and, eventually, even surgery. The total proctocolectomy with ileal pouch-anal anastomosis (IPAA) is the surgical intervention of choice in subjects affected by ulcerative colitis (UC). Although IPAA provides satisfactory functional outcomes, it can be susceptible to some complications, including pouchitis as the most common. Furthermore, 10-20% of the pouchitis may develop into chronic pouchitis. The etiology of pouchitis is mostly unclear. However, the efficacy of antibiotics in pouchitis suggests that the dysbiosis of the IPAA microbiota plays an important role in its pathogenesis. We aimed to review the role of the microbiota in the pathogenesis and as a target therapy in subjects who develop pouchitis after undergoing the surgical intervention of total proctocolectomy with IPAA reconstruction.

Endoscopic Surveillance in Inflammatory Bowel Diseases: Selecting a Suitable Technology.

In the treat-to-target era, endoscopy has become the backbone of the assessment of remission, defined as mucosal healing, in inflammatory bowel disease (IBD) patients. Current recommendations indicate that endoscopic procedures should be performed with high-definition white-light endoscopy (HD-WLE), as it guarantees the best possible visualization of the mucosa. With respect to endoscopic surveillance, the preventive strategy for dysplasia and colorectal cancer (CRC) in long-standing IBD, is the use of dye-chromoendoscopy (DCE), which enhances the mucosal pattern of the colonic walls. DCE has been established as the gold standard for dysplasia detection and is at present incorporated in all international guidelines. Over the past years, novel technologies, such as high-definition endoscopic imaging, and optical and digital enhancement tools have revolutionized the quality and level of fine details of vascular and mucosal patterns. These endoscopic images have the ambition to reflect histological changes for suspected neoplastic lesions and inflammation or healing and are emerging as potential alternatives to DCE. Indeed, the comparison of DCE with high-definition imaging is an open issue that deserves further investigation. We aimed to examine and summarize the technical aspects and the current evidence on endoscopic technologies with a specific focus on the surveillance in IBD patients.

Therapeutic drug monitoring of biologics in inflammatory bowel disease: unmet needs and future perspectives.

Therapeutic drug monitoring (TDM) has emerged as a useful tool for optimising the use of biologics, and in particular anti-tumour necrosis factor (anti-TNF) therapy, in inflammatory bowel disease (IBD). However, challenges remain and are hindering the widespread implementation of TDM in clinical practice. These barriers include identification of the optimal drug concentration to target, the lag time between sampling and results, and the proper interpretation of anti-drug antibody titres among different assays. Solutions to overcome these barriers include the harmonisation of TDM assays and the use of point-of-care testing. Other unmet needs include well designed prospective studies and randomised controlled trials focusing on proactive TDM, particularly during induction therapy. Future studies should also investigate the utility of TDM for biologics other than anti-TNF therapies in both IBD and other immune-mediated inflammatory diseases such as rheumatoid arthritis and psoriasis, and the use of pharmacokinetic modelling dashboards and pharmacogenetics towards individual personalised medicine.

Baseline Histological Findings Do Not Predict the Risk of Subsequent Extension in Patients with Limited Ulcerative Colitis.

BACKGROUND: Among patients with limited ulcerative colitis (UC), 30% ultimately extend to pancolitis and are at increased risk of adverse clinical outcomes. Risk of endoscopic extension has been found to correlate with clinical features such as early age of onset. AIMS: We sought to determine whether histologic features correlate with disease extension. METHODS: The study population consisted of 40 patients with UC from two large academic centers diagnosed between 2006 and 2017. Eligible cases had a diagnosis of endoscopically limited UC (Montreal E1 or E2) at baseline and ≥ 2 subsequent endoscopic examinations with biopsies. Severity of inflammation was scored using both the Mount Sinai Activity Index and Nancy Histological Index. RESULTS: Patients were divided into two cohorts: those who progressed to pancolitis (Montreal E3) were defined as "Extenders" (n = 21), whereas "Non-extenders" (n = 19) were cases without progression in the follow-up period. The median follow-up time was 58.4 months. The histologic scores in the endoscopically involved mucosa of the index biopsies were not associated with subsequent extension of disease, overall. However, among extender cohort, the index histology scores correlated with biopsy scores at extension (r = 0.455, P = 0.044) and index severity was associated with a shorter time to extension (r = - 0.611, P = 0.003). Furthermore, female patients had a shorter time to extension (P = 0.013). CONCLUSIONS: Histological severity of limited UC is not an independent predictor of extension in UC. However, among patients who subsequently extend, severe inflammation at baseline correlates with shorter progression time and severe inflammation when extension occurs. Patients with limited UC but severe histologic inflammation may warrant more frequent endoscopic surveillance.

Diversion proctocolitis and the problem of the forgotten rectum in inflammatory bowel diseases: A systematic review.

BACKGROUND AND AIMS: Diversion proctocolitis (DP) is a non-specific mucosal inflammation arising in the defunctionalized colon and/or rectum following faecal diversion (colostomy, ileostomy). Differential diagnosis of DP from the underlying disease in patients with inflammatory bowel diseases (IBD) is often unclear. As a result, it might be difficult to undertake any specific treatment. We aimed to systematically review the literature evidence on DP in IBD patients. METHODS: For this qualitative systematic review, we searched PubMed, EMBASE and Scopus to identify all studies published until July 2021 including IBD patients affected by DP. RESULTS: Overall, 37 papers published between 1982 and 2021 were included. A total of 1.211 IBD patients were included: 613 UC (50.6%), 524 CD (43.3%), 66 IBD-unclassified (IBD-U) (5.4%), 8 unspecified patients (0.7%). Most patients with DP are asymptomatic, although inflammation is detectable in almost all patients with a rectal stump. Reduced short-chain fatty acids and an altered microbiome, may trigger mucosal inflammation and have been proposed as causing factors. An increased risk of developing cancer on DP has been reported in patients with a history of previous dysplasia/cancer. CONCLUSIONS: The etiopathogenesis of DP is still unknown. The efficacy of mesalamine, corticosteroids or short-chain fatty acids has not been proven by randomized trials yet. Since the incidence of cancer of the rectal stump can reach 4.5 per 1.000 diverted patients-year, IBD patients undergoing subtotal colectomy with end-ileostomy should undergo close endoscopic surveillance, being eventually counseled for surgery with or without the restoration of the intestinal continuity.

The IL23-IL17 Immune Axis in the Treatment of Ulcerative Colitis: Successes, Defeats, and Ongoing Challenges.

Ulcerative colitis (UC) is a chronic relapsing disorder of the colonic tract, characterized by a dysregulated innate and adaptive immune response to gut microbiota that contributes to the perpetuation of intestinal inflammatory processes. The Interleukin (IL) 23/IL17 axis has been reported to play a key role in UC pathogenesis promoting Th17 cells and cytokines-related immune response. Recently, the blockade of IL23/IL17 pathways has been raised enormous interest in the treatment o several chronic inflammatory disorders. In this review, we summarize the emerging results from clinical trials that evoked both promise and discouragement in IL23/IL17 axis in the treatment of UC. Targeting IL23 p40 through Ustekinumab results safe and effective to induce and maintain clinical remission, low inflammatory indexes, mucosal healing, and a better quality of life. Studies targeting IL23 p19 through Mirikizumab, Risankizumab, Brazikumab and Guselkumab are still ongoing. To date, no clinical studies targeting IL17 pathway are ongoing in UC. IL-17 targeting is thought to have a context-dependent biological effect, based on whether cytokine is selectively targeted or if its function is dampened by the upstream block of IL23.

TL1A: A New Potential Target in the Treatment of Inflammatory Bowel Disease.

Inflammatory bowel diseases (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), are chronic inflammatory diseases of the gastrointestinal tract. In the last few years, the development of biological agents targeting cytokines and receptors involved in IBD pathogenesis has led to better outcomes and has improved the course of the disease. Despite their effectiveness, drugs such as tumor necrosis factor (TNF) inhibitors, anti-Interleukin-12/23 and anti-integrins, do not induce a response in about one-third of patients, and 40% of patients lose response over time. Therefore, more efficient therapies are required. Recent studies showed that TL1A (Tumor necrosis factor-like cytokine 1A) acts as a regulator of mucosal immunity and participates in immunological pathways involved in the IBD pathogenesis. In this review article, we analyze the role of TL1A as a new potential target therapy in IBD patients.

Fibrotic Strictures in Crohn's Disease: Mechanisms and Predictive Factors.

Fibrotic strictures are one of the most severe complications of Crohn's Disease (CD). They occur in about 50% of patients at five years and in 70% at ten years of the diagnosis. The only treatment available for symptomatic fibrotic strictures is surgical resection and endoscopic dilation. Both strategies are associated with a high rate of recurrence, and with multiple surgical resections, which pose the threat of surgical morbidity and short bowel syndrome. Therefore, it is crucial to identify, early, the patients more prone to develop intestinal fibrosis to intensify follow-ups, switch to more aggressive treatments, and suggest lifestyle modifications. Scarce data are available concerning biomarkers and genetic determinants to predict which patient will develop intestinal fibrosis. Biologic or clinical markers would be useful to determine this subgroup of CD patients and to predict the onset of intestinal fibrosis and, ideally, its severity. Furthermore, the identification of environmental risk factors may suggest lifestyle changes aimed at modifying the natural course, thus decreasing the risk of complicated CD. In this review, we will critically revise clinical, environmental, genetic, and serologic factors that have been associated with a complicated CD course with a particular focus on the fibrostenosing phenotype and their possible implications as predictive factors of intestinal fibrosis.

'Treat to Target' in Mild to Moderate Ulcerative Colitis: Evidence to Support this Strategy.

BACKGROUND: The management of chronic conditions, above all rheumatic disease and diabetes, now incorporates a "treat to target" strategy where treatment aims to achieve objective outcomes. This is applicable in ulcerative colitis (UC) as well. Targets are demonstrated to prevent endorgan dysfunction, specifically bowel damage and its complications, and lastly colorectal cancer. Recently, the scientific community has tried to define further targets beyond those currently recommended, namely mucosal healing and clinical remission. Studies that prospectively investigated this approach in UC are scanty and a treat-to-target (T2T) algorithm is not routinely used in daily clinical practice. OBJECTIVE: We aim to review current evidence on T2T in UC and discuss its adoption in routine clinical practice as well as in clinical trials. METHODS: A PubMed search was conducted in February 2020 to identify published papers investigating targets' achievement rates in UC. RESULTS: Different targets can be achieved through approved drugs for mild to moderate UC; histological remission is emerging as a robust target with respect to long-term outcomes. CONCLUSION: Further studies to compare a T2T strategy with the traditional care are needed, particularly in the mild to moderate spectrum of disease.

New Paradigms to Help Decisions in Treatment Choice: Head to Head Trial of Biological Therapies in Inflammatory Bowel Diseases.

The increasing armamentarium of drugs for inflammatory bowel disease (IBD) requires a direct comparison of different therapeutic options in order to guide physicians in the choice of the most appropriate treatment for their patients. Head-to-head trials, considered the gold standard in comparative research in IBD, allow to compare different therapies in the same population and setting, but also to evaluate different treatment strategies. Although head-to-head trials including biologics and immunosuppressive therapy in IBD have been performed decades ago, the interest in these direct comparisons is growing since the publication of the first randomized controlled trial directly comparing biologic agents with different molecular targets. This review provides an overview of the past and current IBD head-to-head trials, considering their respective strengths and limitations in a real-life setting.

Application of Ultrasound Elastography for Assessing Intestinal Fibrosis in Inflammatory Bowel Disease: Fiction or Reality?

BACKGROUND: Intestinal fibrosis and subsequent strictures represent an important burden in inflammatory bowel disease (IBD). Both the detection and evaluation of the degree of fibrosis in stricturing Crohn's disease (CD) are important when deciding the best therapeutic strategy (medical anti-inflammatory therapy, endoscopic dilation, surgery). Ultrasound elastography (USE) is a non-invasive technique that has been proposed in the field of IBD for evaluating intestinal stiffness as a biomarker of intestinal fibrosis. OBJECTIVE: The aim of this review is to discuss the ability and current role of ultrasound elastography in the assessment of intestinal fibrosis. RESULTS AND CONCLUSION: Data on USE in IBD are provided by pilot and proof-of-concept studies with small sample size. The first type of USE investigated was strain elastography, while shear wave elastography has been introduced recently. Despite the heterogeneity of the methods of the studies, USE has been proven to be able to assess intestinal fibrosis in patients with stricturing CD. However, before introducing this technique in current practice, further studies with larger sample sizes are needed. In addition, the use of homogeneous parameters, the assessment of reproducibility, and the identification of validated cut-off values are essential.

Validation of the Red Flags Index for Early Diagnosis of Crohn's Disease: A Prospective Observational IG-IBD Study Among General Practitioners.

INTRODUCTION: Diagnostic delay >12 months is frequent in Crohn's disease [CD]. Recently, the International Organization for Inflammatory Bowel Disease [IO-IBD] developed a tool to identify early CD and reduce diagnostic delay. Subjects with an index ≥8 are more likely to have suspected CD (odds ratio [OR] 205, p <0.0001). We aimed to validate this questionnaire at the community level in patients seen by the general practitioners [GPs] in two large areas of Lombardy, Italy. METHODS: Consecutive adult patients referring to the GP were screened. The GPs administered the Red Flags [RF] questionnaire to the eligible patients. All patients were referred to the nearest participating centre to confirm or exclude the diagnosis of CD. Sensitivity, specificity, and positive and negative predictive values [PPV, NPV] of the RF index [RFI] were calculated. Patients lost to follow-up after the first gastroenterological visit were analysed using a non-responder imputation, assuming they were negative for CD diagnosis. RESULTS: From November 2016 to November 2019, 112 patients were included. A total of 66 subjects [59%] completed the study after the first gastroenterological visit. The prevalence of CD was 3.6% in the study population [4/112]. The RF index had 50% sensitivity, 58% specificity, 4% PPV, and 97% NPV. A combined diagnostic strategy with faecal calprotectin [FC] [RFI ≥8 and/or FC >250 ng/g] resulted in significantly improved accuracy: sensitivity 100% [29-100%], specificity 72% [55-85%], PPV = 21% [5-51%], NPV = 100% [88-100%]. CONCLUSIONS: The RF Index combined with FC is a valid tool to identify patients with high probability of having CD at early stage.

Treat to target or 'treat to clear' in inflammatory bowel diseases: one step further?

INTRODUCTION: Inflammatory bowel diseases (IBD) are chronic and progressive diseases. Long-term complications are demolitive surgery and colon-rectal cancer. A 'treat to target' strategy, in which the treatment aims to achieve objective outcomes, has already been introduced in the management of chronic conditions as rheumatic diseases. This approach is emerging as suitable for ulcerative colitis and Crohn's disease. Targets are predefined therapeutic goals demonstrated to prevent end-organ dysfunction. An optimization or switch of therapy is considered depending on the target's achievement, with regular monitoring. AREAS COVERED: According to the Selecting Therapeutic Targets in Inflammatory Bowel Disease (STRIDE) indications, mucosal healing and clinical remission are the main targets in IBDs. Histological remission is increasingly being considered as a novel target and has given rise to the new concept of 'disease clearance' which includes clinical, endoscopic and microscopic remission. We aim to review current evidence on the treat-to-target strategy in comparison to a stricter treat-to-clear in the IBD field. EXPERT OPINION: Prospective studies on treat-to-target algorithm are sparse; a treat-to-clear approach is desirable but far from adoption in the daily practice and clinical trials. The ultimate goals of a treat-to-clear strategy differ in UC and in CD, including histological healing and transmural healing, respectively.

JAK selectivity: more precision less troubles.

INTRODUCTION: Janus kinases inhibitors (JAKi) are new small molecules recently introduced in the armamentarium of treatments for Inflammatory Bowel Disease (IBD). Janus Kinases (JAK) are tyrosine kinases that act by linkage with different intracellular receptors, regulating cytokines gene transcription implicated in the inflammatory burden seen in IBD patients. AREAS COVERED: A comprehensive literature search was performed to retrieve studies on JAKi and IBD to discuss the latest developments and how the selectivity of these drugs is changing the natural course of IBD. EXPERT OPINION: Available data on efficacy and safety of JAKi in IBD are highly encouraging and because of their selectivity, these drugs might become among the foremost options in the treatment algorithm.

Author Correction: Crohn's disease.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.