bluuebunny/crossref_metadata_2025 huggingface dataset:
A12 ROLE OF INTESTINAL EPITHELIAL HNF4A IN PROTECTING AGAINST ACUTE INFLAMMATORY STIMULI
Authors: Pupo Gómez D , Reyes Nicolas V , Marrero Cofino G , Perreault N , Menendez A , Boudreau F
Published: February 2024

Background

Inflammatory bowel disease is a group of chronic resulting from complex interactions between host susceptibility genes, the host microbiome, the immune system, and environmental triggers. The gastrointestinal epithelium acts as a barrier against harmful stimuli, and defects in its integrity are a precursor for the development of IBD. Our laboratory has shown that the conditional deletion of Hnf4a in the mouse intestinal epithelium leads to chronic intestinal inflammation. However, the functional role of HNF4A on epithelial barrier integrity is still controversial.

Aims

To evaluate the impact of Hnf4a deletion on barrier integrity during acute inflammation.

Methods

We used a tamoxifen-inducible CreER-loxP system to delete Hnf4a in the adult intestinal epithelium (Hnf4aΔIEC-ind). Intestinal permeability was assessed in Hnf4aΔIEC-ind and control mice in the collected serum after oral gavage of FITC-dextran. Mice were infected with an invasion-attenuated strain of Salmonella Typhimurium (SB103). S. Typhimurium loads were scored in the feces, liver, and spleen tissue. Histological analysis was carried out by various staining. Also, we used a model of T-cell-induced enteropathy triggered by a T-cell activating monoclonal anti-CD3ε Ab (145-2C11). Mice were assessed for clinical signs of enteropathy and sacrificed 1-, 3-, and 5 days post-injection. Gene expression of selected targets was studied by RT-qPCR.

Results

FITC-dextran assay showed a significant increase of the intestinal permeability in uninfected mutant mice compared to controls. In contrast, an oral infection with an invasion-deficient S. Typhimurium strain did not differentially impact in tissue bacterial loads or epithelial damage between groups. Likewise, the loss of epithelial HNF4A led to increased Muc2 transcripts expression in the ileum of infected mutant mice but not in the colon. Histological examinations at four days post-infection showed an elevated number and size of goblet cells in the ileal crypts of mutant mice. Bacterial localization using the general bacterial probe EUB388-cy3 (red) staining showed that infected mutant mice tended to enhance barrier mucus layer thickness compared to the controls. On the contrary, acute T cell activation with anti-CD3 mAb induced a significant increase of mRNA expression of Cxcl1 in the small intestine of mutant mice. H&E staining showed elongated ileal crypts in mutant mice compared to controls after anti-CD3 injection.

Conclusions

Altogether, these results support that HNF4A could play a crucial adaptive role in modulating the small intestine epithelial barrier function and controlling the immune system during acute inflammatory stress.

Funding Agencies

CCC, CIHR
A13 MICROBIOTA FROM PATIENTS WITH INFLAMMATORY BOWEL DISEASE (IBD) INDUCE ALTERED BEHAVIOUR AND VISCERAL HYPERSENSITIVITY IN MICROBIOTA-HUMANIZED MICE
Authors: Vicentini F A , Pujo J , Rueda G H , Nardelli A , De Palma G , Verdu E , Collins S , Bercik P
Published: February 2024

Background

IBD is characterized by relapsing episodes of tissue-damaging inflammation in the gastrointestinal tract. Abdominal pain is common in IBD and often persists in the absence of overt inflammation. The treatment has limited efficacy, in part due to our partial understanding of its pathophysiology, and thus commonly leads to dependency on opioids. Moreover, patients with IBD are more likely to develop psychiatric comorbidities (anxiety and depression), further impairing the disease course and quality of life. The gut microbiota has been shown to modulate pain, mood, and anxiety. Gut bacterial composition and function are altered in patients with IBD. However, whether IBD microbiota affects pain perception and emotional behaviour is unknown.

Aims

To determine whether microbiota from patients with IBD contributes to visceral hypersensitivity and behavioural abnormalities in a microbiota-humanized mouse model.

Methods

Adult germ-free C57BL/6 mice (n=65) of both sexes were colonized with fecal microbiota from 7 patients with IBD (Crohn’s Disease n=5, Ulcerative Colitis n=2) and 3 healthy controls (HC). Mice were fed with a human-like (Western) diet. Behavioural tests (light preference, open field, and tail suspension tests) were employed to assess anxiety- and depression-like behaviour. Visceral sensitivity was assessed by measuring visceromotor responses to colorectal distension.

Results

Compared to mice with HC microbiota, mice with IBD microbiota had reduced body weight gain. However, no differences in colon length were found, suggesting that IBD microbiota did not induce overt colonic inflammation. Mice with IBD microbiota displayed a reduced preference for the light chamber and increased immobility in the tail suspension test compared to HC mice, suggestive of anxiety- and depression-like behaviour, respectively. Importantly, no differences in overall locomotion were observed, thus ruling out sickness-like behaviour. When subjected to colorectal distension, mice with IBD microbiota had an overall higher visceromotor response (area under the curve) compared to HC mice. Furthermore, they displayed increased responses to non-noxious stimuli (100 μL distension), suggestive of visceral allodynia.

Conclusions

Our data demonstrate that microbiota from patients with IBD negatively affects the gut-brain axis, by inducing changes in emotionality-related behaviour and triggering visceral hypersensitivity. Uncovering the microbial products and molecular mechanisms underlying these abnormalities will guide the development of novel microbiota-based therapies for patients with IBD.

Funding Agencies

CCC, CIHRCrohn's and Colitis Foundation (USA)
A17 COMPARING ENDOSCOPIST DIAGNOSIS OF COLORECTAL POLYPS ASSISTED BY ARTIFICIAL INTELLIGENCE (CADX) VS CADX WITHOUT ENDOSCOPIST INPUT: A RANDOMIZED CONTROLLED TRIAL
Authors: Djinbachian R , Haumesser C , Taghiakbari M , Alj A , Barkun A , Liu J , Panzini B , Sidani S , von Renteln D
Published: February 2024

Background

Artificial intelligence-based optical diagnosis systems (CADx) have been developped to assist in eliminating the need for histologic diagnosis of diminutive colorectal polyps (resect-and-discard and diagnose-and-leave strategies). However, these systems have not yet been implemented in routine clinical practice.

Aims

We were interested in evaluating the performance of CADx without human input to diagnoses performed by endoscopists assisted by CADx.

Methods

We performed a randomized clinical trial of patients undergoing elective colonoscopies at the CHUM. Patients were randomized into two arms: 1) optical diagnosis of colorectal polyps using CADx without human input; 2) endoscopists performed optical diagnosis after consulting a real-time CADx diagnosis (Human in the Loop [HiL]). Primary outcome was accuracy in optical diagnosis for both arms.

Results

467 patients were randomized (229 in the CADx group, 238 in the HiL group). Overall accuracy for optical diagnosis was 76.3% in the CADx group and 70.5% in the HiL group (p=0.19). Sensitivity, specificity, PPV and NPV for adenoma diagnosis were 89.7%, 58.4%, 82.2%, and 72.5% respectively in the CADx group vs 85.3%, 69.6%, 81.8%, and 74.8% in the HiL group. Sensitivity, specificity, PPV and NPV did not differ significantly between the two groups.

Conclusions

Optical diagnosis of colorectal polyps had similar accuracy when using CADx without human input compared to endoscopist-based diagnosis assisted by CADx. Resect and discard and diagnose and leave strategies can therefore potentially be implemented without need for endoscopist optical diagnosis.

Funding Agencies

CAGFujifilm
A21 EFFECTS OF LYOPHILIZED FECAL FILTRATE COMPARED TO LYOPHILIZED DONOR STOOL IN THE TREATMENT OF RECURRENT CLOSTRIDIOIDES DIFFICILE INFECTION: A MULTI-CENTER RANDOMIZED TRIAL
Authors: Kao D , Wong K , Lee C , Steiner T , Franz R , McDougall C , Silva M , Yaskina M , Walter J , Loo V , Loebenberg R , Xu H , Louie T
Published: February 2024

Background

Fecal microbiota transplantation (FMT) is the most effective therapy in the treatment of recurrent Clostridioides difficile infection (rCDI), and can be offered in fresh, frozen or lyophilized formulation with similar efficacy. Microbial engraftment is thought to be one of the mechanisms mediating its efficacy. However, the importance of microbes has been questioned by two small preliminary clinical studies that showed sterile fecal filtrate could prevent C. difficile recurrence.

Aims

To establish whether lyophilized sterile fecal filtrate (LSFF) is noninferior to lyophilized FMT (LFMT) in efficacy

Methods

In this double-blind, non-inferiority study conducted in 4 academic centers in Alberta and British Columbia, we randomized rCDI patients with ≥ 3 CDI episodes to either LSFF or LFMT at a 1:1 ratio between 2019 and 2023.The non inferiority margin was 10%. Each treatment dose consisted of 15 oral capsules. Participants who failed the assigned treatments were offered open-label LFMT. An interim analysis was planned after reaching 50% of recruitment target (124/248 participants). Primary outcome was the proportion of participants without CDI recurrence 8 weeks following assigned treatment. Secondary outcomes included 1) the proportion of participants without CDI recurrence 24 weeks following assigned treatment, 2) serious adverse events (mortality, hospitalization and infections related to treatments), and 3) minor adverse events (nausea, vomiting, abdominal pain and fever). Exploratory outcomes included changes in quality of life, stool microbial composition analyses, as well as patient preferences.

Results

137 participants were randomized (mean [SD] age, 61.2 [18.6] years; 89 women [65.4%]; mean CDI episodes 3.8) to LFMT group (66 participants) and LSFF (71 participants) group. In per-protocol analysis, prevention of rCDI 8 weeks after assigned treatment was achieved in 63.8% of participants in LSFF group and 86.9% in LFMT group (difference, -23.1%), resulting in trial termination. Serious adverse events were infrequent: 4 hospitalizations deemed not related and 1 hospitalization possibly related, and 1 death from COVID deemed not related to assigned treatment. Minor adverse events were self-limited and infrequent: nausea (6), vomiting (2), abdominal discomfort (15) and fever (2).

Conclusions

Among adults with rCDI, LSFF was inferior to LFMT by oral capsules in preventing recurrent infection over 8 weeks. The result emphasizes the importance of microbes in mediating FMT efficacy. Preserving microbial viability in future development of microbial therapeutics is paramount.

Funding Agencies

CIHR
A23 IMPAIRMENT OF INTESTINAL CRYPTAL STEM CELL CYCLE AND PANETH CELL PROLIFERATION BY CHRONIC STRESS
Authors: Bai X , Ihara E , Ogawa Y
Published: February 2024

Background

The small intestine’s epithelial barrier is essential for intestinal homeostasis and host defense. It consists of epithelial cells that are constantly renewed by crypt stem cells and their progeny, which have different functions in the gut. Chronic stress can impair the barrier by modulating the gut-brain axis, which involves the hypothalamic-pituitary-adrenal (HPA) axis, the vagus nerve, and the immune system. Chronic stress can also alter the gut microbiota, which can further influence the barrier and immune system.

Aims

The present study examines how chronic stress affects the crypt stem cell niche and function in the small intestine.

Methods

Restraint stress was applied to 6-8 weeks old mice in a plastic container for 1 hour daily for 7 days. The dark/light transition box test was used to evaluate the stress-induced behavior change. The Ussing chamber technique was used to assess the paracellular permeability of the small intestine. RNA was extracted from the mucosa and submucosa layers of the small intestine, after removing the muscle layer, and RNA sequencing analysis was performed. Immunofluorescence analysis was also performed on the small intestinal tissues to detect the expression of various markers. To assess the in vivo effect of cortisol, dexamethasone (a synthetic steroid activating same receptors as cortisol), or metyrapone (an 11β-hydroxylation blocker to inhibit cortisol production), was applied to the mice.

Results

We found that restraint stress induced anxiety-like behavior, increased small intestinal epithelial permeability, and reduced villus and crypt length in mice. RNA sequencing analysis revealed that restraint stress upregulated steroid-driven pathways and downregulated cell cycle and cell mitosis pathways in the small intestinal mucosa, suggesting increased cortisol production and decreased stem cell activity. Immunofluorescence analysis confirmed that restraint stress reduced the expression of stem cell marker Olfm-4 and proliferation markers Ki-67 and p-H3 in the small intestinal crypts. Dexamethasone, a synthetic glucocorticoid, mimicked the effects of restraint stress on crypt stem cell proliferation, while metyrapone, a steroid synthesis inhibitor, attenuated the effects of restraint stress on crypt stem cell proliferation. Restraint stress and dexamethasone also reduced Paneth cell RNA expression and marker in the small intestine.

Conclusions

Chronic stress induces anxiety, barrier dysfunction, and epithelial shortening. Chronic stress also alters crypt stem cell and Paneth cell expression. These findings show how chronic stress impacts intestinal epithelial renewal and differentiation, which may affect intestinal health and disease.

Funding Agencies

JSPS
A24 AN ULCERATIVE COLITIS-ISOLATED PATHOBIONT CAN DEGRADE MUCUS PRODUCED BY UC PATIENT-DERIVED COLONOIDS
Authors: Gilliland A , Chen Y , Tertigas D , Surette M , Bressler B , Vallance B
Published: February 2024

Background

Inflammatory bowel disease (IBD) pathobionts are commensal microbes with pathogenic potential that may cause or exacerbate IBD symptoms. Some pathobionts (ex. Escherichia coli) reside at low levels in the lumen of a healthy gut but can rapidly grow in the inflamed colons of ulcerative colitis (UC) patients. To promote disease, these pathobionts must cross the colonic mucus barrier (comprised of MUC2) that separates the epithelium from luminal microbes. It is currently unclear how bacterial pathobionts cross the mucus barrier of UC patients.

Aims

Using healthy and UC patient biopsy-derived colonic organoids (colonoids) and an air liquid interface (ALI) monolayer model, we investigated how the UC-isolated E. coli pathobiont p19A crosses the mucus barrier.

Methods

Apical out healthy and UC patient biopsy-derived colonoids were infected with p19A to confirm this pathobiont exerts direct cytopathic effects on human colonocytes. Sequencing p19A’s genome, we found it contains two mucus degrading proteins (mucinases). Healthy human and UC colonoids, as well as mouse colonoids, were used to generate mucus-producing ALI monolayers. To detect p19A-mediated mucus degradation, concentrated p19A supernatant was incubated with ALI-derived mucus and degraded MUC2 proteins were detected by protein gel and MUC2 Western blot. MUC2 glycosylation was analyzed by protein gel and PAS staining. ALI monolayers were infected with p19A to evaluate mucus degradation and p19A localization by immunostaining.

Results

The UC-isolated pathobiont p19A infected and exerted cytotoxic effects on apical out healthy and UC patient colonoids. By day 14, ALI monolayers were differentiated and covered by a thick mucus layer as assessed using brightfield microscopy. Mucus removed for mucinase assays was replenished within 7 days. p19A harbours proteins capable of degrading human ALI-, but not mouse ALI-derived mucus, in vitro, suggesting the presence of host-specific mucinases. Mucus produced by UC ALI monolayers showed reduced glycosylation and increased degradation both over time and by p19A proteins. Day 21 ALI-monolayers infected with p19A for 18 hours exhibited overt mucus degradation allowing p19A to infect the underlying epithelium.

Conclusions

Patient-derived ALI monolayers produce a thick mucus layer that can be used to study pathobiont-mucus interactions. The UC pathobiont p19A disrupts apical out organoids and produces proteins that degrade ALI-derived mucus in vitro, with UC mucus being more susceptible to degradation than mucus from healthy controls. The results from our model suggest a potential mechanism for pathobiont-mediated mucosal barrier disruption in UC patients.

Patient-derived ALI monolayer (blue/white) produces a thick mucus layer (green) that can be degraded by the pathobiont p19A (red).

Funding Agencies

CCC, CIHR
A25 DETECTION OF BACTERIAL ADP-HEPTOSE BY INTESTINAL STEM CELLS DRIVES EPITHELIAL REGENERATION FROM PANETH CELL DEDIFFERENTIATION
Authors: Goyal S , Gray-Owen S , Girardin S E
Published: February 2024

NOT PUBLISHED AT AUTHOR’S REQUEST

Please acknowledge all funding agencies listed below

Funding Agencies

CCC, CIHR
A27 ROLE OF HIPPO SIGNALING EFFECTORS YAP & TAZ IN GASTRIC METAPLASIA AND TUMORIGENESIS
Authors: Ju Z , Farag M , Haddad M , Fiset P , Lorenzo L , Gregorieff A
Published: February 2024

NOT PUBLISHED AT AUTHOR’S REQUEST

Please acknowledge all funding agencies listed below

Funding Agencies

CIHR
A28 A SERUM REDOX STATUS-RELATED INDICATOR IS ASSOCIATED WITH THE RISK OF ONSET OF CROHN'S DISEASE
Authors: Mu K , Xue M , Turpin W , Croitoru K
Published: February 2024

Background

Crohn's disease (CD) is a gastrointestinal disorder characterized by chronic inflammation. While increased oxidative stress is observed in established CD patients, it remains unknown whether a shift in redox status is present before the diagnosis of CD and whether it is correlated with changes in immune response and microbial composition. Our hypothesis is that oxidative stress plays a role in the development of CD, and it could be detected before the diagnosis of CD. Furthermore, it is likely to be correlated with systemic inflammation and alterations in gut microbiota composition.

Aims

We aimed to assess the relationship between the serum redox status-related indicators, specifically amino acids ratios, with risk of CD onset and if this is further association with systemic inflammation marker, and gut microbiota composition.

Methods

In the Genetic Environment Microbial Project (CCC-GEM), a cohort of first-degree relatives (FDRs) of CD patients was prospectively followed. Among them, we identified subjects who later developed CD, defined as pre-CD (n=69), and matched them at a 1:4 ratio with FDRs who remained disease-free (n=276). Serum levels at enrollment of cysteineglycine (reduced form) and cystineglycine (oxidized form) were quantified by mass spectrometry, and the cysteineglycine/cystineglycine ratio was used as an indicator of redox status. Conditional logistic regression assessed the association with CD, while partial Spearman regression evaluated its correlation with systemic inflammation, as indicated by c-reactive protein (CRP), and gut microbiota composition (determined by fecal 16S rRNA sequencing).

Results

A decrease in the ratio indicates a shift in redox status toward oxidative stress. The cysteineglycine/cystineglycine ratio was negatively associated with the likelihood of developing CD (coefficient = -0.6188; p =0.0146), and it was also negatively correlated with CRP levels (coefficient = -0.177; p =0.00095). A list of taxa belonging to the phyla Firmicutes and Actinobacteriota were positively correlated with cysteineglycine/cystineglycine ratio (p≤0.05).

Conclusions

This study is the first to report that when redox status shifts towards oxidative stress, as indicated by the cysteineglycine/cystineglycine ratio, the likelihood of CD increases. Furthermore, these markers also correlate with CRP levels and gut microbiota composition, indicating a loss of various taxa when the redox status shifts towards oxidative stress.

Submitted on behalf of the CCC-GEM consortium.

Funding Agencies

CCC, CIHRHCT
A29 INVESTIGATING THE IMPACT OF PARKINSON’S DISEASE-ASSOCIATED GENES ON INTESTINAL HOMEOSTASIS
Authors: Pei J , Recinto S , MacDonald A , Kazanova A , Gavino C , Trudeau L , Desjardins M , Stratton J , Gruenheid S
Published: February 2024

Background

Intestinal epithelial cells (IECs) provide an essential physical barrier between harsh luminal contents and underlying host tissue. The maintenance of intestinal homeostasis must be intricately regulated through the proliferation and differentiation of intestinal stem cells (ISCs). Dysregulation of this system results in the loss of barrier function, causing pathologies in both intestinal and extra-intestinal diseases. While Parkinson’s Disease (PD) is primarily a neurodegenerative disorder, there is increasing evidence linking PD progression and gastrointestinal (GI) dysfunction. Constipation and increased bowel permeability are often observed years prior to development of motor dysfunction in PD, and people with inflammatory bowel disease are more likely to develop PD. Our group developed a model to investigate the role of the gut in PD, demonstrating that mice with genetic ablation of the PD-associated gene Pink1 exhibited motor phenotypes only when previously infected with Gram-negative Citrobacter rodentium intestinal bacteria. As Pink1 and other PD-associated genes are expressed in IECs, we hypothesize that PD-associated gene mutations directly affect the epithelium and impact early PD pathophysiology.

Aims

1. Determine how Pink1 mutation affects the transcriptional profiles in IECs at steady state and in vivo C. rodentium infection.

2. Use colonoid systems to study the effect of Pink1 mutation on epithelial activity.

Methods

ScRNAseq was performed on IECs isolated from uninfected and infected Pink1 WT and KO mice, sacrificed at day 7 and 14 (early and peak infection) to elucidate transcriptional differences between epithelial lineages of each genotype. Additionally, colonoids were derived from primary mouse tissue and treated with lipopolysaccharide (LPS) to determine how Pink1 KO affects the inflammatory response of the epithelium.

Results

Our data revealed that Pink1 KO profoundly affected several epithelial lineages. ISCs from infected Pink1 KO mice had dysregulated cell cycle genes, transit amplifying cells showed dysregulated expression of tight junction genes, and enterocytes displayed dysregulation in oxidative damage and apoptotic genes. Preliminary data from colonoids showed that Pink1 KO mice, when stimulated with LPS, had altered pro-inflammatory cytokine gene expression. We are also evaluating colon motility differences between genotypes through transit time assays, counting fecal pellets per hour, and fecal water content.

Conclusions

In Pink1 KO IECs, there is indeed an altered cellular response upon infection, but more information is needed to decern the mechanistic role of IECs in PD. By investigating the role of PD genes in the GI tract, these studies carry important implications for understanding the initiation and progression of PD.

Funding Agencies

CIHR
A30 MICROBIOTA AND NOD2 REGULATE SMALL INTESTINAL RESTITUTION THROUGH FETAL-LIKE INTESTINAL STEM CELLS
Authors: Tsang D , Maisonneuve C , Ayyaz A , Foerster E , Nissan M , Baerg L , Trcka D , Streutker C , Wrana J L , Girardin S E , Philpott D
Published: February 2024

Background

Inflammatory bowel disease is characterized by chronic inflammation of the gastrointestinal tract, resulting in recurrent injury to the intestinal epithelium. Restitution of the small intestinal epithelium is a coordinated response that involves the dedifferentiation of epithelial cell lineages, proliferation of Lgr5+ intestinal stem cells, and fetal-like stem cell reversion. While gut microbiota are critical mediators of intestinal inflammation, their impact on epithelial restitution remains unclear.

Aims

We aim to identify the how microbes regulate small intestinal epithelial restitution following damage. Our hypothesis is that gut microbiota accelerate restitution through pattern recognition receptor-driven signals following fetal-like stem cell reversion.

Methods

Irradiation (IR, 12Gγ) was used to induce a synchronized small intestinal epithelial restitution response in mice. Intestinal restitution kinetics were assessed transcriptionally (scRNA-Seq, qPCR) and histologically. Small intestinal organoids were used to assess epithelial restitution kinetics in vitro.

Results

ScRNA-Seq of small intestinal epithelial cells following IR from germ-free mice (GF), and specific pathogen-free mice (SPF) mice revealed that microbiota induced greater expression of fetal-like stem cell reversion markers, Ly6a and Clu, and greater expression of the proliferation marker, Pcna. These results were supported histologically as irradiated SPF mice observed an increase in fetal-like stem cells marked by Ly6a and Clu and an increase BrdU+ proliferating cells. ScRNA-seq and in situ hybridization highlighted that fetal-like intestinal stem cells upregulate expression of Nod2, a bacterial pattern recognition receptor. Using intestinal organoids to assess the function of Nod2, we observed that muramyl dipeptide driven Nod2-signlaing potentiates an interferon gene signature following IFNγ and TNFα co-stimulation. Further supporting the role for Nod2 in intestinal restitution, intestinal epithelium specific Nod2KO mice decreased BrdU+ proliferating cells post-IR compared to littermate controls.

Conclusions

Microbiota promote small intestinal restitution following IR through Nod2-signaling in fetal-like intestinal stem cells.

Funding Agencies

CIHR
A31 DYSPLASIA IN COLONIC POLYPS: PREPARING FOR A RESECT AND DISCARD STRATEGY IN CANADA
Authors: Patel V , Bechara R , Rai M S
Published: February 2024

Background

While diminutive colorectal polyps have a negligible cancer risk, current management involves resecting and submitting all polyps for histological assessment. This is a substantial burden and cost to the healthcare system. The European Society of Gastrointestinal Endoscopy (ESGE) has recommended a “resect-and-discard strategy” without histological evaluation as an acceptable strategy when high-confidence endoscopic characterization of colorectal polyps is achieved. However, a resect and discard strategy has not been adopted yet in Canada.

Aims

The objective of this study was to determine the prevalence and characteristics of polyps removed at our center based on size.

Methods

We retrospectively reviewed colonoscopies and pathology reports at Kingston Health Sciences Center from January to December 2020. Based on the pathology report, polyps were classified as diminutive (1-5mm), small (6-9mm) or large (ampersand:003E or = 10mm). We recorded histology and the presence of high-grade dysplasia (HGD) or cancer.

Results

Out of 2218 colonoscopies, 2945 polyps were removed. 1703 (57.8%) polyps were diminutive with only two (0.1%) having focal HGD and none having cancer. 699 (23.7%) polyps were classified as small with three (0.4%) having HGD and none having cancer. The large polyp group had 543 (18.4%) polyps, of which 87 (16%) showed HGD and 15 (2.8%) exhibited cancer. The specific histologic findings are shown in Table 1. Endoscopy reports specifically mentioned concern of dysplasia in one out of the five polyps with HGD in the diminutive and small groups.

Conclusions

As expected, most polyps were either diminutive or small (81.5%). Neither of these groups had cancer and only 5 had HGD. Adopting a resect and discard strategy at our center for diminutive polyps has the potential for significant cost savings with negligible risk of missing a high-risk polyp. The next steps would involve assessing optical diagnosis sensitivity and specificity for diminutive and small polyps.

Histological characterization of polyps within each size range

Funding Agencies

None
A32 CATHELICIDIN REGULATES GOBLET CELL MUCUS SECRETION DURING CITROBACTER RODENTIUM-INDUCED COLITIS
Authors: Cobo E R , Blyth G , Fiorani F , Lahiri P , Herik A , Dufour A , Chadee K
Published: February 2024

Background

Colonic goblet cells by secreting Muc2 mucin and specific proteins is critical for physically entrapping and expelling invading enteropathogens. Thus, is not surprising that Muc2-/- littermates exhibit increased susceptibility to attaching/effacing Citrobacter rodentium colonization. The colonic epithelium also secretes small cathelicidin peptide, which potentially interacts intimately with goblet cells and was presumed to accumulate within the sterile inner mucus layer as a simple antimicrobial peptide defense.

Aims

To determine the effects of cathelicidin on mucin secretion in goblet cells during C. rodentium-induced colitis and the impact on the mucus barrier defense.

Methods

We used cathelicidin-deficient (Camp-/-) mice, mouse colonoids and human colonic LS174T like-goblet epithelial cells to elucidate the mechanisms by which cathelicidin regulates goblet cell secretions.

Results

Camp -/- littermates infected with C. rodentium displayed increased fecal shedding and epithelial colonization. Camp-/- littermates at the peak of C. rodentium infection (7 dpi) showed a deficient mucin layer with fewer Alcian blue/PAS filled goblet cells and a reduction in fucose (UEA-1+) and N-acetylglucosamine (WGA+) glycoproteins. By transmission electron microscopy (TEM), goblet cells in Camp-/- colons were swollen and retained a large number of mucus granules during C. rodentium infection. C. rodentium infected Camp-/- littermates showed impaired reactive oxygen species (ROS) production and a transcriptomic profiling associated with decreased ROS biosynthesis and an increase in ROS negative regulators. In mucin producing LS174T colonic epithelial cells, human cathelicidin LL-37 promptly induced the secretion of goblet cell-associated TFF3 and RELMβ, via a ROS-dependent mechanism.

Conclusions

These findings revealed that mice lacking cathelicidin (Camp-/-) were more susceptible to C. rodentium colonization caused by defective goblet cell mucus and mucin-associated protein secretion via a ROS-dependent mechanism. Importantly, cathelicidin regulated mucus secretion revealing a non microbicidal action of this peptide with homeostatic properties on the colonic mucus barrier, critical in excluding luminal microbiota away from the epithelia to clear bacterial infections and restore gut homeostasis.

Funding Agencies

NSERC
A33 EOSINOPHILS PROMOTE SALMONELLA TYPHIMURIUM COLONIZATION IN THE MURINE SMALL INTESTINE
Authors: FitzPatrick R D , Noone J R , Cartwright R A , Gatti D M , Brosschot T , Lane J M , Zafarullah M , Kroker Kimber I , Reynolds L
Published: February 2024

Background

During inflammatory bowel disease (IBD) both the number of intestinal eosinophils and susceptibility to enteric bacterial infections can drastically increase. It is unknown, however, whether eosinophils recruited to the tissues lining the gastrointestinal (GI) tract during severe disease help to control pathogenic bacterial colonization or whether their presence promotes bacterial infection. No studies to date have examined the role of eosinophils during an acute bacterial infection in the small intestine.

Aims

Our research aims to uncover the role of eosinophils during an enteric Salmonella infection in mice and we hypothesize that eosinophils undergo phenotypic changes in the presence of Salmonella and aid in the clearance of this enteric bacterial pathogen.

Methods

To assess how the presence of Salmonella impacts the frequency and phenotype of eosinophils we performed flow cytometry on eosinophils isolated from mice 3-days post-oral infection with Salmonella enterica serovar Typhimurium and compared these findings to naïve BALB/c controls. To determine if eosinophils are essential for controlling Salmonella infection we quantified levels of Salmonella colonization along the GI tract, liver and spleen of wild-type and eosinophil-deficient (ΔdblGATA) littermate mice by plating homogenized tissues on LB agar.

Results

Following an oral Salmonella infection we found higher frequencies of eosinophils in the gut-draining mesenteric lymph nodes compared to uninfected mice. Intestinal lamina propria-resident eosinophils in the small intestine and colon displayed altered phenotypes following infection in an intestinal-region specific manner: during infection, in the small intestine eosinophils increased their expression of MHCII, and in the colon eosinophils displayed elevated granularity. When wild-type and ΔdblGATA mice were pre-treated with the antibiotic streptomycin 1-day prior to infection to confer robust Salmonella burdens in the small intestine we found a significant reduction in Salmonella colonization in the ileum of the small intestine in ΔdblGATA mice compared to their wild-type littermates. These data suggest eosinophils have a role in promoting colonization by this enteric bacterial pathogen.

Conclusions

Our data contribute to the growing evidence that microbes can influence the phenotype of intestinal eosinophils and demonstrate that the influence of and requirements for eosinophils during bacterial infection is highly context-dependent. We found that eosinophils are not essential for controlling an acute enteric Salmonella infection and instead they promote Salmonella colonization in the small intestine.

Funding Agencies

CIHRTRIANGLE
A35 INTESTINAL REGENERATION IS IMPAIRED IN HIRSCHSPRUNG-ASSOCIATED ENTEROCOLITIS
Authors: Li B , Zhang Z , Lee D , Lee C , Jiang Q , Pierro A
Published: February 2024

NOT PUBLISHED AT AUTHOR’S REQUEST

Please acknowledge all funding agencies listed below.

Funding Agencies

NFRF
A36 EFFECT OF FIBRE SUPPLEMENTATION IN CELIAC DISEASE: IMPLICATIONS FOR MUCOSAL HEALING
Authors: Wulczynski M , Blom J , Rueda G H , Pinto-Sanchez M , Constante M , Rahmani S , Murray J , Armstrong D , Galipeau H , Verdu E
Published: February 2024

Background

Celiac disease (CeD) is a T-cell mediated enteropathy driven by gluten in genetically susceptible individuals. Mucosal inflammation persists for years even when treated with a gluten-free diet (GFD). Although patients may be advised to increase dietary fibre, some fibres are poorly tolerated leading, potentially, to suboptimal fibre intake and hampering dietary recommendations.

Aims

Our project aims to investigate whether and how the supplementation of two fibre types with distinct functional profiles affects the recovery of gluten-immunopathology in a mouse model of gluten-sensitivity. We hypothesize that: (1) HylonVII, but not inulin, accelerates mucosal recovery by increasing microbial carbolytic activity and production of short-chain fatty acids (SCFA); (2) fibre intake is decreased in CeD patients, leading to decreased SCFA production.

Methods

NOD-DQ8 mice were immunized to gliadin and then placed on a gluten-containing diet. Three weeks later, mice were returned to GFD supplemented with or without HylonVII or inulin to 15% total fibre, for 6, 10, or 12 weeks. Recovery from gluten-induced pathology was evaluated by counting CD3+ intraepithelial lymphocytes (IELs) in villi tips and measuring villus-to-crypt (V/C) ratios in the small intestine. Adult CeD patients (newly diagnosed n=6 and GFD-treated n=7) and healthy controls (n=5) completed a food frequency questionnaire (Victoria DQES v2) and provided fecal samples for evaluation of SCFA production. Fecal SCFA were measured with targeted single ion monitoring gas-chromatography/mass-spectrometry (Agilent) as markers of fibre metabolism.

Results

In gluten immunized mice, 3 weeks of wheat diet led to increased CD3+ IEL counts and decreased V/C ratios (pampersand:003C0.01), which remained abnormal after 6 weeks of GFD. Mice consuming GFD+inulin, but not HylonVII, normalized CD3+ IELs and V/C ratios, had higher fecal SCFAs (pampersand:003C0.05) (primarily acetate), and a higher carbolytic-proteolytic metabolite ratio (pampersand:003C0.05) compared with mice consuming a GFD alone for six weeks. Only 1/7 patients with CeD on GFD met the minimum recommendation for fibre intake (25 g/day, Health Canada), compared with 5/11 participants on gluten-containing diets. SCFA production was impaired in active but not in treated CeD patients (2563 vs 3744 μg/g, pampersand:003C0.01).

Conclusions

In gluten-immunized NOD-DQ8 mice, GFD+inulin accelerates mucosal recovery, which is associated with increased fecal SCFA. In our pilot clinical data, patients on a GFD did not meet the recommendation for fibre intake although they were capable of metabolizing fibre to produce SCFA that could facilitate mucosal recovery. Together these results suggest that CeD on GFD may benefit from increasing fibre, such as inulin, during the GFD.

Funding Agencies

CIHRCeliac Canada
A37 POSTBIOTIC BACTERIAL MEMBRANE VESICLES FROM B. SUBTILIS DELIVER NOD2 LIGANDS AND PROMOTE IN VITRO WOUND RE-EPITHLIALIZATION THROUGH RIPK2 SIGNALING
Authors: Baerg L , Philpott D , Mahadevan R
Published: February 2024

Background

Bacterial membrane vesicles (MVs) are bilipid nanoparticles secreted as a conserved method of intercellular communication. MVs from Gram-positive bacteria carry diverse bacterial products and represent a unique opportunity in the growing field of postbiotics. This native machinery for mediating microbe-host interactions makes MVs a promising tool for intestinal drug delivery in the context of Crohn’s disease (CD). CD is a chronic inflammatory bowel disease characterized by relapsing inflammation of the digestive tract. CD is associated with (1) loss of function mutations in the host gene encoding the nuclear-binding oligomerization domain 2 (NOD2) pattern recognition receptor and (2) a gut microbiome with reduced capabilities to generate NOD2 stimulating muropeptides from peptidoglycan. Nod2-/- mice have decreased barrier integrity and impaired epithelial restitution upon challenge. However, there are currently no therapeutic strategies targeting NOD2 for CD management.

Aims

The aims of this study were to (1) leverage MVs as a biological system for NOD2 ligand delivery to intestinal epithelial cells and (2) determine the roll of probiotic MVs and bacterial ligand synergy in wound re-epithelialization.

Methods

MVs were purified from B. subtilis through filtration and ultracentrifugation. MVs were characterized through nanoparticle tracking analysis using NanoSight300. WT and NOD2-/- HCT116 cells, a human colorectal carcinoma cell line, were utilized for IL-8 secretion quantification by ELISA, gene expression by qPCR, and in vitro scratch wound assay by Incucyte quantification.

Results

Here, we demonstrate for the first time that MVs from B. subtilis deliver NOD2 ligands in vitro. Treatment with isolated MVs induces IL8 secretion and CXCL1 expression in a NOD2-dependent manner. Furthermore, MVs promote re-epithelialization after in vitro scratch wounding. This effect was completely blunted by the addition of an inhibitor for RIPK2, a downstream transducer required for NOD2 signaling. Through bacterial pathogen-associated molecular patterns (PAMPs) screening, we found that wound re-epithelialization is promoted by PAMP synergy but dependent on RIPK2 signaling.

Conclusions

This work suggests that delivery of muropeptides by probiotic-derived MVs is a promising strategy to promote epithelial regeneration during injury through targeting NOD2. Future directions will work towards validating these findings in human ileal primary cells and murine models of intestinal injury.

Funding Agencies

CIHRMedicine by Design
A38 EXPLORING HOW BOWEL PREPARATION CAN AFFECT INFLAMMATORY BOWEL DISEASE VIA THE GUT MICROBIOTA
Authors: Clayton C , Ng K , Tropini C
Published: February 2024

Background

Inflammatory bowel disease (IBD) is a debilitating disorder that targets the gastrointestinal (GI) tract. Although its causes remain unknown, recent studies have identified changes to the gut microbiota associated with IBD. While most gut bacteria are essential for GI health, pathobionts are bacteria that are prevalent in IBD patients and that can act as pathogens and induce inflammation. IBD patients undergo routine endoscopies which require the administration of laxative-based bowel prep to clear out the luminal contents of the GI for the endoscope. It has been found that after bowel prep some IBD patients experience inflammatory flareups. IBD patients may experience adverse reactions following bowel prep, including increased inflammation, emergency room visits, and medication adjustments. Importantly, bowel prep perturbs the gut microbiota, depleting beneficial microorganisms, while allowing pathobiont strains to thrive, which could be the cause for worsened symptoms post-bowel prep in some patients.

Aims

We hypothesize that the altered intestinal microenvironment during bowel prep causes commensal bacteria depletion and favours osmotolerant pathogenic species that lead to increased inflammation in two systems: 1) in a model disease-causing microorganism, Salmonella enterica 2) in an IBD microbiota.

Methods

To investigate pathogen expansion after bowel prep a Salmonella mouse model was established. Microbiota changes were determined by 16S rRNA sequencing and spot plating. Changes to the gut environment and the mechanism for pathogen colonization were characterized using Salmonella mutants and confocal imaging. To identify changes to the IBD microbiota, a humanized mouse model was established, and microbiota changes were investigated as done in the Salmonella model. IBD-associated pathobiont growth was also characterized in in vitro conditions that were identified in our in vivo model.

Results

We have demonstrated that bowel prep increases GI osmolality and leads to increased Salmonella colonization in the gut and systemic organs following bowel prep unlike mice treated with vehicle, supporting our hypothesis. We then explored the effects of bowel prep in a humanized mouse model of IBD, which showed increased translocation of bacteria from the gut to internal organs post-prep. Additionally, IBD-associated pathobionts were able to grow much greater than commensal strains highlighting that IBD pathobionts can persist in the gut after bowel prep.

Conclusions

Our study highlights that bowel prep disrupts the gut microbiota and the intestinal environment allowing for pathogen colonization and bacterial translocation. Therefore, bacterial translocation could provide mechanistic insight for inflammatory flareups following bowel prep. Ultimately, our research underscores the importance of the gut environment in facilitating pathobiont exacerbation of IBD.

Funding Agencies

CIHR
A40 THE ROLE OF HYPOXIA-INDUCIBLE FACTOR IN CELLULAR METABOLIC ADAPTATION UPON GIARDIA INFECTION
Authors: DeMichele E R , Sosnowski O , Allain T , Buret A G
Published: February 2024

Background

Recent findings have highlighted the integral role of oxygen tension in gastrointestinal (GI) homeostasis. During hypoxia when oxygen supply is limited, mammalian cells utilize the Hypoxia-Inducible Factor (HIF) complex to activate genes that promote cell survival and alter glucose metabolism. The GI system exists in a state of physiologic hypoxia, subject to further alterations by pathogens. Although tissue and blood parasites are known to influence tissue oxygen tension, little is known regarding the modulation of hypoxia and HIF by enteric parasites.

Aims

This project aims to characterize the effect of Giardia duodenalis, a common enteric protozoan that perturbs gastrointestinal function leading to diarrheal disease, on the cellular hypoxic response. We hypothesize that hypoxia-associated genes are activated upon Giardia infection, leading to an adaptive metabolic response with increased glycolytic flux to maintain cellular bioenergetic homeostasis.

Methods

Caco-2 colonic epithelial cells were infected with Giardia isolate GS/M (MOI 10) for 1.5 or 4.5 hours to capture early and peak HIF activation, under normoxic (21% O2) or hypoxic (1%O2, STEMCELL hypoxia incubator) conditions. RNA was extracted for RT-qPCR to assess transcriptional changes of known HIF-target genes. Intracellular metabolite analysis via liquid-chromatography mass-spectrometry (hydrophilic-interaction chromatography method) was performed to assess HIF-mediated metabolic changes in uninfected and Giardia-infected cells (MOI 10) exposed to the hypoxia mimetic DMOG or the HIF inhibitor PX-478.

Results

Under normoxic conditions, genes associated with compensatory cellular stress responses such as VEGFA, ANKRD37, GADD45A, and glycolysis-associated genes HK2, and LDHA are upregulated in Giardia-infected cells in a time-dependent manner (pampersand:003C0.05). Under hypoxic conditions, fewer HIF-target genes are upregulated (e.g., VEGFA, GADD45A, PGK1; pampersand:003C0.05), suggesting Giardia-infected cells behave similarly to uninfected cells with constant HIF activation. Analysis of the Caco-2 intracellular metabolome indicates HIF-dependent changes in amino acid (e.g., glycine, threonine) and nucleic acid (e.g., guanosine, inosine, uracil) metabolism. DMOG treatment altered the production of glycolytic intermediates (e.g., DHAP, PEP), confirming the promotion of glycolytic flux by HIF.

Conclusions

Both cell-stress-related and glucose-metabolism HIF target genes are activated upon Giardia infection. As well, some metabolic changes are dependent on HIF activation. These novel findings indicate Giardia promotes a hypoxic state in human intestinal cells, highlighting a metabolic cell rescue mechanism in response to enteropathogens. Furthermore, understanding the role of hypoxia in enteric parasitic infections will shed light on the potential of HIF as a therapeutic target.

Funding Agencies

Natural Sciences and Engineering Research Council of Canada (NSERC)