Paneth Cell Metaplasia Research Articles

Absence of Paneth Cell Metaplasia to Predict Clinical Relapse in Ulcerative Colitis with Endoscopically Quiescent Mucosa.

Paneth cells play multiple roles in maintaining intestinal homeostasis. However, the clinical role of Paneth cell metaplasia (PCM) in ulcerative colitis (UC) remains unclear. We aimed to investigate the relationship between PCM and relapse in patients with UC and compare the usefulness of PCM with other histological indexes, including mucin depletion (MD) and basal plasmacytosis (BP). Patients with UC in clinical remission (CR) who underwent colonoscopy to confirm a Mayo endoscopic subscore (MES) ≦1 with biopsies from the distal colon were enrolled into this retrospective cohort study. Biopsy samples were evaluated for histological findings of PCM, MD, and BP. Clinical relapse was defined as partial Mayo score ≧3 or medication escalation. Multivariate analysis was performed to determine independent predictors of relapse among the three histological findings, MES, and patient background, and relapse prediction models were generated. Eighty-three patients were enrolled in this study (MES 0, n = 47; MES 1, n = 36). The number of PCM cases was significantly higher in patients with prolonged CR than that in those with relapse (p = 0.01). Multivariate analysis showed that the absence of PCM and MD were related to relapse in all the patients. In patients with MES 1, the absence of PCM was the only risk factor significantly and independently associated with relapse (hazard ratio, 4.51 [1.15-17.7]; p = 0.03). The absence of PCM was a histological risk factor for relapse in patients with MES 1, implying a protective role for PCM in remission and a new index for mucosal healing.

Paneth cell differentiation associated with neoadjuvant therapy in esophageal adenocarcinoma.

Paneth cells and Paneth cell metaplasia are well-known in pathology as foundational components in the gastrointestinal system. When within malignant cells (Paneth cell differentiation [PCD]), however, the function and significance of these cells is less well understood. Here, we present findings from the first study focused on PCD in postneoadjuvant esophageal adenocarcinoma (EAC) resection specimens. Patients with EAC treated with neoadjuvant chemoradioation and followed by esophagectomy between 2012 and 2018 in our institution were retrospectively evaluated. A tissue microarray was constructed, and special and immunohistochemical stains were performed. A total of 64 cases were collected, of which 8 had PCD, as highlighted by periodic acid-Schiff with diastase staining. Adenocarcinomas with PCD were more commonly seen in patients 60 to 70 years of age and typically had a poorly differentiated morphology, observationally fewer stromal mucinous changes, and less lymph node metastasis. β-catenin activation induced by neoadjuvant therapy was more frequent in the PCD-positive cases. Patients with PCD-positive disease had low programmed cell death 1 ligand 1 levels, no positive or equivocal ERBB2 (HER2) expression, and low CD8-positive T-cell infiltration; they were also mismatch repair proficient. Patients with PCD-positive disease showed a survival pattern inferior to that of patients with PCD-negative disease. When induced by neoadjuvant therapy in EAC, PCD is associated with high β-catenin activation, less expression of targetable biomarkers, and a potentially worse clinical prognosis.

Ion Transport Basis of Diarrhea, Paneth Cell Metaplasia, and Upregulation of Mechanosensory Pathway in Anti-CD40 Colitis Mice.

Anti-Cluster of differentiation (CD)-40-induced colitis, driven by innate inflammatory responses in the intestine, is a potent animal model exhibiting IBD pathophysiology including diarrhea. However, the ion transport basis of diarrhea and some key mucosal pathways (Paneth cells, stem cell niche, and mechanosensory) in this model have not been investigated. Mucosal scrapings and intestinal tissue from control and CD40 antibody (150 µg) treated Rag2-/- mice were examined for gut inflammation, Paneth cell numbers, expression of key transporters, tight/adherens junction proteins, stem cell niche, and mechanosensory pathway via hematoxylin and eosin staining, quantitative polymerase chain reaction, and western blotting. Compared with control, anti-CD40 antibody treatment resulted in a significant loss of body weight (P < .05) and diarrhea at day 3 postinjection. Distal colonic tissues of anti-CD40 mice exhibited increased inflammatory infiltrates, higher claudin-2 expression, and appearance of Paneth cell-like structures indicative of Paneth cell metaplasia. Significantly reduced expression (P < .005) of downregulated in adenoma (key Cl- transporter), P-glycoprotein/multidrug resistantance-1 (MDR1, xenobiotic transporter), and adherens junction protein E-cadherin (~2-fold P < .05) was also observed in the colon of anti-CD40 colitis mice. Interestingly, there were also marked alterations in the stem cell markers and upregulation of the mechanosensory YAP-TAZ pathway, suggesting the activation of alternate regeneration pathway post-tissue injury in this model. Our data demonstrate that the anti-CD40 colitis model shows key features of IBD observed in the human disease, hence making it a suitable model to investigate the pathophysiology of ulcerative colitis (UC).

Histopathologic Features of Unmasked Inflammatory Bowel Disease Following Immune Checkpoint Inhibitor Therapy in Colon Biopsies

Typical immune checkpoint inhibitor-induced colitis (T-ICI) has significant histomorphologic overlap with inflammatory bowel disease (IBD), a distinction further complicated in ICI-treated patients with pre-existing inflammatory bowel disease (P-IBD) and those with potentially "unmasked" inflammatory bowel disease (U-IBD) after ICI therapy. This study describes histopathologic findings seen in U-IBD colonic biopsies and assesses for distinguishing features from T-ICI and P-IBD biopsies. Initial colon biopsies after symptom onset from 34 patients on ICI therapy were reviewed, and histopathologic features were tabulated. U-IBD patients were identified clinically based on rapid toxicity development post-ICI treatment with multiple recurrences after immune suppression, frequently with regional colitis (versus pancolitis). The study cohort was classified into T-ICI (n= 20), P-IBD (n= 9), and U-IBD (n= 5) groups. The predominant histological patterns were diffuse active colitis (35%) in the T-ICI, and chronic active colitis in both the P-IBD (67%) and U-IBD (60%) groups (overall P= .003, P > .05 between the two IBD groups). None of the T-ICI biopsies demonstrated chronicity features (ie, architectural distortion score 2, basal lymphoplasmacytosis, or Paneth cell metaplasia). Only U-IBD biopsies demonstrated basal lymphoplasmacytosis (60% vs 0% in T-ICI/P-IBD, P= .002). Among available follow-up biopsies, chronicity features were present in all (4/4) U-IBD patients, including those without chronicity seen in the initial biopsy, but none (0/7) of T-ICI patients. These early results show that no definite features of chronicity were seen in colon biopsies from T-ICI patients, suggesting that the presence of those features may be a clue to U-IBD in patients without a known IBD diagnosis. Frequent basal lymphoplasmacytosis seen in U-IBD may support a recent onset of mucosal injury and early architectural remodeling.

Interleukin-9 production by type 2 innate lymphoid cells induces Paneth cell metaplasia and small intestinal remodeling

Paneth cell metaplasia (PCM) typically arises in pre-existing gastrointestinal (GI) diseases; however, the mechanistic pathway that induces metaplasia and whether PCM is initiated exclusively by disorders intrinsic to the GI tract is not well known. Here, we describe the development of PCM in a murine model of chronic myelogenous leukemia (CML) that is driven by an inducible bcr-abl oncogene. Mechanistically, CML induces a proinflammatory state within the GI tract that results in the production of epithelial-derived IL-33. The binding of IL-33 to the decoy receptor ST2 leads to IL-9 production by type 2 innate lymphoid cells (ILC2) which is directly responsible for the induction of PCM in the colon and tissue remodeling in the small intestines, characterized by goblet and tuft cell hyperplasia along with expansion of mucosal mast cells. Thus, we demonstrate that an extra-intestinal disease can trigger an ILC2/IL-9 immune circuit, which induces PCM and regulates epithelial cell fate decisions in the GI tract.

P754 Beyond Paneth cell metaplasia: Small intestinal metaplasia of the sigmoid colon in patients with Inflammatory Bowel Disease

Abstract Background Paneth cells are normally found in the small intestine, and when found in the left colon, they represent Paneth cell metaplasia (PCM). This finding indicates a chronic inflammatory state and is seen in some patients with inflammatory bowel disease (IBD). However, small intestinal differentiation beyond PCM has not been reported. We report a broader range of small intestinal metaplasia in the sigmoid colon in patients with IBD, including loss of expression of the colonic marker SATB2, presence of a brush border and villous architecture, and gain of expression of the small intestinal markers CD10 and HepPar1. We perform a pilot study to investigate the frequency, staining patterns, and clinical correlates of this metaplastic phenomenon. Methods A database search for sigmoid biopsies for the words “Paneth cell metaplasia” from 2010-2018 returned 862 cases. The 100 most recent consecutive cases with a history of IBD were reviewed and confirmed to have PCM in non-neoplastic sigmoid biopsies in 96 cases. Of these, 94 blocks from 91 patients (age range 7-88, median age 43, 53% male, 74% ulcerative colitis (UC), 23% Crohn’s disease, 3% IBD) were on file. IHC staining for HepPar1, CD10, and SATB2 was performed on each case. Results Of the 94 cases, 13 (13.8%) had HepPar1 positivity, 5 (5.3%) had CD10 positivity, 2 (2.1%) had SATB2 loss, 1 (1.1%) had reduced SATB2 expression, and 2 showed villous architectural features. Extensive positivity for CD10 was seen in 3 (3.2%) cases, and one case showed all 3 IHC markers of small intestinal metaplasia. Of the CD10+ cases, there were 3 UC, 1 Crohn's, and 1 IBD (Table 1). The index case (sigmoid colon) showed a brush border (Figure 1) and intermixed small (Figure 2, red arrows) and large bowel (Figure 2, black arrows) differentiation. Conclusion A range of small intestinal differentiation may be seen in the left colon in IBD patients, including PCM, the presence of brush border, villous architecture, CD10 and HepPar1 positivity, and reduced or lost SATB2 expression. Since the frequency of HepPar1+&amp;gt;CD10+&amp;gt;SATB2 loss, there may be a sequence of small intestinal metaplasia, with PCM occurring first, and loss of SATB2 reflecting more advanced metaplasia. Previous studies suggest that SATB2 and HepPar1 are helpful in distinguishing between inflamed ileal pouch vs rectal cuff in patients with IBD, and that CD10 could be used to distinguish between ileum and colon in anastomoses, but our data refute these claims. SATB2 loss has been described in dysplastic lesions in patients with IBD, and thus these markers could serve as biomarkers of progression to dysplasia.

Paneth Cell Hyperplasia and Metaplasia in Hirschsprung-associated Enterocolitis in An Aganglionosis Rat Model

BACKGROUND: Many hypotheses regarding the pathophysiology of enterocolitis in aganglionic megacolon or Hirschsprung disease (HSCR) has been proposed. Paneth cells are columnar intestinal epithelial cells that have an important role in maintaining of intestinal homeostasis as a bactericide. Since enterocolitis in HSCR may have association with Paneth cells metaplasia and hyperplasia, current study investigated Paneth cells metaplasia and hyperplasia in the sigmoid colon of HSCR rat model and its products, namely a-defensins and IL-1b, in the sigmoid colon tissues.METHODS: Aganglionosis-induced and control Sprague-Dawley rats were euthanized on Day (D)-7, -14, -17, -19, -21, -23, -25, and -28. Sigmoid colon tissue was isolated at each time point, and degree of enterocolitis as well as Paneth cells metaplasia and hyperplasia were analyzed by Hematoxylin-eosin staining, then protein levels of a-defensins and interleukin (IL)-1b were determined by enzyme-linked immunosorbent assay (ELISA).RESULTS: Enterocolitis scores increased with time. The Paneth cells metaplasia and hyperplasia were observed on D14 until D28 (p&lt;0.01 vs. control group) followed by an increased in the levels of IL-1b. The levels of a-defensins protein expression were initially increased (D7-D14; p&lt;0.01 vs. control group) but then undergo reciprocal changes on D19 until D28 (p&lt;0.01 vs. D7 and D14). Positive correlations between the degree of enterocolitis and Paneth cells number were detected in the sigmoid colon (r=0.42).CONCLUSION: Paneth cells underwent metaplasia and hyperplasia in the sigmoid colon of HSCR rats corresponding to an increase in the degree of enterocolitis, but not followed by an increase in the level of a-defensins as well as IL-1b, suggesting that there is an involvement of Paneth cells in the pathophysiology of enterocolitis due to HSCR.KEYWORDS: Hirschsprung, enterocolitis, defensins; metaplasia, Paneth cell, animal model

Abstract B026: Implicating SATB2 loss in a metaplasia-dysplasia sequence in human inflammatory bowel disease

Abstract Epithelial metaplasia, or the histologically evident replacement of one differentiated somatic cell type with another, offers insights into mucosal homeostasis as an adaptation to diverse inflammatory pathogenic stimuli. The cellular framework for metaplasia can be created by coordination of tissue-specific transcription factors (TFs) with epigenetic regulators of chromatin remodeling, allowing altered TF binding of inflammation-associated exposed genomic loci. For example, intestinal metaplasia (aberrant goblet cell differentiation and CDX2 expression, a pan-intestinal TF) is a common metaplastic response to chronic injury in the upper gastrointestinal tract, associated with increased risk of epithelial dysplasia and cancer. Inflammatory bowel disease (IBD) is an etiologically complex chronic inflammatory disease characterized by relapsing cycles of intestinal injury and healing. IBD patients carry increased risk of colitis-associated dysplasia and colorectal cancer (CAC) proportional to disease duration, extent, and severity. SATB2, or special AT-rich binding protein 2, is a chromatin organizing protein with homeostatic roles in osteoblastic, neural, and colonic differentiation. Intriguingly, others have recently shown that SATB2 is uniquely lost in human IBD dysplasia and CAC, in contrast to sporadic CRC where its expression is typically retained. (By contrast, CDX2 shows retained expression in both CAC and CRC.) Other recent work has shown that colon-specific Satb2 knockout in mice results in conversion of colon to small intestine, including emergence of villi and Paneth cells. Colonic mucosal biopsies from chronic IBD patients show histologic features reminiscent of small intestine with so-called Paneth cell metaplasia (PCM) and villiform, distorted growth. The molecular mediators of this epithelial remodeling in IBD are unknown. We hypothesized that SATB2 loss could result in a form of “small intestinal metaplasia” in human IBD colon. To investigate this, we selected a cohort of 20 IBD distal colon mucosal biopsies with marked crypt architectural changes and PCM and performed SATB2 immunostaining (n=7 Crohn’s disease, n=13 ulcerative colitis). Indeed, 19 of 20 such samples showed striking evidence of SATB2 loss. The pattern of SATB2 loss was heterogeneous; some tissue fragments showed complete epithelial loss as expected in small intestine, whereas others showed patchy loss in alternating crypts, even some showing heterogeneous expression within the same crypt. As positive and negative controls, we included normal distal colon and terminal ileum samples, observing expected intact and negative SATB2 expression, respectively. Of note, CDX2 was strongly expressed across the entire cohort, even in IBD tissue with loss of SATB2 expression. We propose that SATB2 loss is a pre-neoplastic metaplastic response to chronic injury in human colon. Future work will investigate how SATB2 loss enables a plasticity state permissive for emergence of TP53 mutations, dysplasia, and CAC. Citation Format: Maged Zeineldin, Reem Abu-Shamma, Tatianna Larman. Implicating SATB2 loss in a metaplasia-dysplasia sequence in human inflammatory bowel disease [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr B026.

Single-cell Transcriptomics Reveals Early Molecular and Immune Alterations Underlying the Serrated Neoplasia Pathway Toward Colorectal Cancer

Approximately one-third of colorectal cancers develop from serrated lesions (SLs), including hyperplastic polyp (HP), sessile serrated lesion (SSL), traditional serrated adenoma (TSA), and SSL with dysplasia (SSLD) through the serrated neoplasia pathway, which progresses faster than the conventional adenoma-carcinoma pathway. We sought to depict the currently unclarified molecular and immune alterations by the single-cell landscape in SLs. We performed single-cell RNA sequencing of 16 SLs (including four proximal HPs, five SSLs, two SSLDs, and five TSAs) versus three normal colonic tissues. A total of 60,568 high-quality cells were obtained. Two distinct epithelial clusters with redox imbalance in SLs were observed, along with upregulation of tumor-promoting SerpinB6 that regulated ROS level. Epithelial clusters of SSL and TSA showed distinct molecular features: SSL-specific epithelium manifested overexpressed proliferative markers with Notch pathway activation, while TSA-specific epithelium showed Paneth cell metaplasia with aberrant lysozyme expression. As for immune contexture, enhanced cytotoxic activity of CD8+ T cells was observed in SLs; it was mainly attributable to increased proportion of CD103+CD8+ tissue-resident memory T cells, which might be regulated by retinoic acid metabolism. Microenvironment of SLs was generally immune-activated, while some immunosuppressive cells (regulatory T cells, anti-inflammatory macrophages, MDK+IgA+ plasma cells, MMP11-secreting PDGFRA+ fibroblasts) also emerged at early stage and further accumulated in SSLD. Epithelial, immune, and stromal components in the serrated pathway undergo fundamental alterations. Future molecular subtypes of SLs and potential immune therapy might be developed.

Gastrointestinal: Autoimmune enteropathy associated with thymoma.

A 50-year-old gentleman presented with 4 months of chronic watery, non-bloody diarrhea up to 10 times a day, and weight loss. He had a history of a thymoma first diagnosed 7 years earlier, which was resected with positive histological margins. There was no macroscopic residual disease or vascular invasion. He did not receive any adjuvant treatment and developed recurrent Masaoka-Koga stage IVa thymoma with pleural, pericardial, and lung invasion requiring further treatment with resection, chemotherapy (3 cycles of cisplatin, doxorubicin, and cyclophosphamide), and radiotherapy (54 Gy in 30 fractions). There was no mediastinal lymph node involvement or evidence of distant hematogenous metastasis. Histopathology demonstrated multiple nodules of mixed WHO type B1 and B2, but predominantly type B1 thymoma. His diarrhea commenced after his thymoma recurrence. He did not have any features suggesting other autoimmune diseases associated with thymoma including myasthenia gravis. Physical examination and initial laboratory investigations were unremarkable. Stool cultures were negative for bacterial, viral, and parasitic infections. A computed tomography (CT) scan of the abdomen revealed wall thickening and fat stranding affecting the small intestine and colon (Fig. 1a). Correspondingly, mild patchy erythematous colitis in the rectum and sigmoid colon was seen on colonoscopy (Fig. 1b). Histologically, colonic biopsies showed active colitis with prominent regenerative changes. Goblet cells were noticeably absent, and there was prominent apoptosis, features typical of autoimmune enteropathy (Fig. 1c). Patient serum was incubated with frozen sections of normal small intestinal mucosa, showing strong staining by immunofluorescence for human IgA and IgG with a goblet cell distribution (Fig. 2). A diagnosis of thymoma-associated autoimmune enteropathy was made, and the patient was commenced on a weaning dose of prednisone starting at 25 mg daily leading to resolution of his symptoms. Thymomas are associated with concomitant autoimmune diseases in up to 30% of patients, possibly due to defective immune regulation. Differentials for thymoma-associated autoimmune conditions causing diarrhea include autoimmune enteropathy and Good's syndrome (thymoma-associated hypogammaglobulinemia). Thymoma-associated autoimmune enteropathy is rare with only five reported cases in the literature. Proposed diagnostic criteria include chronic diarrhea lasting over 6 weeks, malabsorption, and abnormal histology of the small bowel (villous blunting, deep crypt lymphocytosis, minimal intraepithelial lymphocytosis, and increased crypt apoptotic bodies). A spectrum of changes can be seen in the colon including increased mononuclear inflammatory infiltrate, active inflammation including neutrophilic cryptitis and microabscesses, intraepithelial lymphocytosis, and increased crypt epithelial apoptosis. Changes of chronicity including crypt architectural distortion and Paneth cell metaplasia have also been described. The presence of anti-enterocyte or anti-goblet antibodies is supportive, but the sensitivity and specificity of these markers are unknown. Steroids are the first-line management for autoimmune enteropathy; however, further immunosuppression (azathioprine, cyclosporin, tacrolimus, or infliximab) may be required in up to 90% of cases. For patients with thymoma-associated autoimmune enteropathy, resection of the thymoma may also improve symptoms.

DOP55 Histopathological features at diagnosis to predict long-term disease course of Crohn’s Disease

Abstract Background Crohn’s disease (CD) is characterized by a heterogeneous disease course and treatment response. There is a clinical need to identify CD patients at diagnosis who are at risk for developing a severe disease course. Patient stratification using state-of-the-art clinical, serological or genetic markers does not predict disease course sufficiently to facilitate clinical decision making. The current study aimed to investigate the additive predictive value of histopathological features at diagnosis to discriminate between patients with a long-term mild and severe disease course. Methods Diagnostic biopsies from treatment-naïve CD patients with mild or severe disease courses in the first 10 years after diagnosis (i.e. based on the number of quarterly flares) were reviewed by two senior gastrointestinal pathologists after developing a standardized form comprising 15 histopathological features related to acute and chronic inflammation. Multivariable logistic regression models were built to identify predictive features and compute receiver operating characteristics (ROC) curves. Model 1 included clinically relevant baseline characteristics (Montreal classification, smoking status and gender). Next, histopathological were added by applying two different model-building strategies (forward selection and purposeful selection algorithm)(Model 2). Prediction models were internally validated using bootstrapping to obtain optimism-corrected performance estimates. Results In total, 817 biopsies from 137 CD patients (64 mild disease course, 73 severe disease course) were included. Based on clinical baseline characteristics alone, disease course could only be moderately predicted (Model 1 Area under ROC (AUROC): 0.738 (optimism 0.018), 95%CI 0.65–0.83, sensitivity 83.6%, specificity 53.1%). When adding histopathological features, in colonic, but not ileal, biopsies a combination of (1) basal plasmacytosis, (2) severe lymphocyte and plasma cell infiltration in the lamina propria, (3) Paneth cell metaplasia and (4) absence of ulcers were identified and resulted in significantly better prediction of a severe disease course (Model 2 AUROC: 0.883 (optimism 0.033), 95%CI 0.82–0.94, sensitivity 80.4%, specificity 84.2%, model 2 vs. model 1 AUROC p = 0.001)[Figure 1]. Conclusion In this first study investigating the additive predictive value of multiple histopathological features in biopsies at CD diagnosis, we found that certain features of chronic inflammation in colonic biopsies contributed to prediction of a severe disease course, thereby presenting a novel approach to improve stratification and facilitate clinical decision making.

Histopathological Features in Colonic Biopsies at Diagnosis Predict Long-term Disease Course in Patients with Crohn's Disease.

Background and AimsCrohn’s disease [CD] is characterised by a heterogeneous disease course. Patient stratification at diagnosis using clinical, serological, or genetic markers does not predict disease course sufficiently to facilitate clinical decision making. The current study aimed to investigate the additive predictive value of histopathological features to discriminate between a long-term mild and severe disease course.MethodsDiagnostic biopsies from treatment-naïve CD patients with mild or severe disease courses in the first 10 years after diagnosis were reviewed by two gastrointestinal pathologists after developing a standardised form comprising 15 histopathological features. Multivariable logistic regression models were built to identify predictive features and compute receiver operating characteristic [ROC] curves. Models were internally validated using bootstrapping to obtain optimism-corrected performance estimates.ResultsIn total, 817 biopsies from 137 patients [64 mild, 73 severe cases] were included. Using clinical baseline characteristics, disease course could only moderately be predicted (area under receiver operating characteristic curve [AUROC]: 0.738 [optimism 0.018], 95% confidence interval [CI] 0.65–0.83, sensitivity 83.6%, specificity 53.1%). When adding histopathological features, in colonic biopsies a combination of [1] basal plasmacytosis, [2] severe lymphocyte infiltration in lamina propria, [3] Paneth cell metaplasia, and [4] absence of ulcers were identified and resulted in significantly better prediction of a severe course (AUROC: 0.883 [optimism 0.033], 95% CI 0.82–0.94, sensitivity 80.4%, specificity 84.2%).ConclusionsIn this first study investigating the additive predictive value of histopathological features in biopsies at CD diagnosis, we found that certain features of chronic inflammation in colonic biopsies contributed to prediction of a severe disease course, thereby presenting a novel approach to improving stratification and facilitating clinical decision making.

Medication-specific variations in morphological patterns of injury in immune check-point inhibitor-associated colitis.

A varied spectrum of histopathological changes has been associated with immune checkpoint inhibitor (ICI) colitis. This study was performed to evaluate the prevalence of different histopathological patterns of injury in patients with ICI colitis and their association with specific immune check-point inhibitors. Biopsies from patients with clinically and histologically confirmed ICI colitis were reviewed blindly to determine the predominant pattern of injury and to quantitate discrete histological parameters using the Geboes score. Paneth cell metaplasia, intraepithelial lymphocytes, abnormal subepithelial collagen and degree of crypt epithelial apoptosis was also recorded. A total of 86 patients with ICI colitis (ipilimumab, n=14; ipilimumab+nivolumab, n=29; nivolumab, n=20 and pembrolizumab, n=23) were included. The patterns of injury identified included diffuse active colitis (n=22), chronic active colitis (n=22), lymphocytic colitis (LC, n=16), collagenous colitis (CC, n=14), graft-versus-host disease-like colitis (n=7) and mixed colitis (n=5). Patients on ipilimumab were more likely to have a diffuse active colitis pattern without features of chronicity (P<0.01) and less likely to have LC (P<0.05) compared to other ICIs. LC and CC were more common in patients on nivolumab and pembrolizumab relative to other groups (P<0.05). Chronic active colitis was most frequent in nivolumab patients (P<0.05), and these patients had received more ICI doses and had been on ICI treatment longer compared to other treatment groups. ICI colitis should be considered in the differential diagnosis of all the common inflammatory patterns of colitis and shows medication specific differences in patterns of injury.

Incidental morphological findings in colorectal adenomas.

Owing to a sharp increase in the frequency of diagnosis of colorectal adenomas in the current era of population screening, distinctive morphological features are increasingly being observed. These may present diagnostic challenges and cause clinical management issues. Paneth cell metaplasia is a more common occurrence, but the incidence rates of squamous metaplasia, clear cell metaplasia, osseous metaplasia, neuroendocrine differentiation and signet‐ring cell‐like lesion are low, and they can be seen in <1% of colorectal adenomas. Their histomorphological characteristics are quite unique; ancillary studies are not very helpful and often not needed. In this review, we give an overview and describe the potential clinical consequences of such incidental and special morphological findings in colorectal adenomas.

Segmental Diffuse Inflammatory Pseudopolyps Associated With Diverticulitis

Abstract Introduction/Objective Inflammatory pseudopolyps (IPs) often develop in response to chronic active inflammation in patients with inflammatory bowel disease (IBD). IPs can be diffuse and numerous in severe IBD. IPs can also occur from other chronic active injuries, such as ulcers, persistent infection, ischemic colitis, anastomotic site and diverticulitis. IPs arising from diverticulitis is uncommon and generally few in numbers. We report a rare case of a patient with segmental diffuse IPs associated with diverticulitis in the absence of IBD. Methods A 59-year-old male patient with a history of sigmoid diverticulitis presented with abdominal pain and was treated with antibiotics. Three months later he had severe recurrent diverticulitis. CT scan showed wall thickening of the sigmoid colon and multiple sigmoid diverticula. Colonoscopy showed extremely severe inflammatory colitis in the area of diverticulitis between 25.0 and 35.0 cm from the anal verge. Biopsies revealed cryptitis, crypt abscesses, crypt architecture distortion and Paneth cell metaplasia. The patient underwent laparoscopic left colectomy. Results The rectosigmoid colon specimen is 18.0 cm in length and 6.0 cm in diameter. There was a 7.5 cm segment with numerous polyps. Multiple diverticula with diverticulitis were also identified in this region. The rest of the colon was unremarkable. Microscopic examination revealed numerous IPs and multiple diverticulitis. No evidence of IBD was identified. Conclusion To our knowledge, this is the first time that segmental and diffuse IPs are described with associated diverticulitis in the absence of IBD. The pathogenesis of IPs in non-inflammatory bowel disease is not well described. Previously, it was reported that diverticulosis and subsequent diverticulitis has no significant impact on the development of IPs, and IPs may arise independent of location and time of diverticulitis. Sporadic IPs may also appear without any underlying pathology. In the current case, there were multiple diverticula and diffuse diverticulitis, which may have contributed to the diffuse IPs. Further clinical inquiries revealed no clinical signs and symptoms of IBD.

Contribution to histology of Paneth Cell Metaplasia from a feline (Felis catus domesticus) with colon adenomatous

The colon embryology in vertebrates recognizes the endoderm layer of the middle and caudal intestine as source of epithelium, and the surrounding lateral splanchnic mesoderm as a source of lamina propria, submucosa, muscular propria and adventitial or serosa tunic. The enterocytes, enteroendocrine cells and goblet cells of distal colon are generated by cranio-caudal expression of homeotic genes Hoxa13 and Hoxd13 both in the mesoderm and endoderm layer reported, and also spatially and temporally, everything under regulation of homeotic genes Cdx2. Concerning the Paneth Cell or PC, the endoderm layer is a source by sponsoring mesodermal layer related with lower expressions to Cdx2, leading to high expressions Hoxa13 and Hoxd13; and PC absence by high Cdx-2 expressions lead to lack of co-expression of same Hoxa genes. This case report contributes to the histology of PC from a domestic feline with a diagnosis of colon adenomatous, a species that does not normally express PC in the colon, reasonably proposing that PC metaplasia in feline adenomatous may imply expressive disabilities of Cdx-2 and / or Hoxa13 and Hoxd13 expressions

S2257 Immune Checkpoint Inhibitor-Induced Colitis or Ulcerative Colitis: A Histopathological Dilemma

INTRODUCTION: Immune checkpoint inhibitor (ICI) induced colitis occurs in 1-2% of treated patients. The onset of symptoms is usually between 6-18 weeks after therapy initiation. It can often appear endoscopically and histologically similar to ulcerative colitis (UC). It may also share similar pathological mechanisms of injury. We present a case of colitis that appears to have worsened with ICI therapy. CASE DESCRIPTION/METHODS: An 81 year old male with a history of stage 4 poorly differentiated non-small cell carcinoma (favoring adenocarcinoma) of the lung presented to our clinic for 7 months of diarrhea. Patient had a prior colonoscopy 6 months earlier for the same complaint with noted left sided diverticulitis and colitis. Pathology revealed erythematous tissue with shallow ulceration and friability without crypt abscesses, architectural distortion, granulomas, dysplasia, or malignancy. Mesalamine was started with mild improvement. After starting pembrolizumab he noted worsening diarrhea, at which time prednisone was prescribed, with partial improvement. However, even with loperamide use, he had numerous non-bloody diarrheal bowel movements daily. Sigmoidoscopy was performed, with colitis noted. Pathology of the sigmoid and rectum revealed cryptitis, focal crypt abscesses, and mild architectural distortion with focal paneth cell metaplasia and an increase in chronic inflammatory cells including lymphocytes, plasma cells and eosinophils within the lamina propria without dysplasia or malignancy. Budensonide was started with plans for potential institution of vedolizumab. DISCUSSION: After ruling out infection, the next step in diagnosing ICI mediated colitis is a colonoscopy. Endoscopy may reveal ulcers, erythema, and erosions. Microscopy may reveal crypt abscesses, neutrophilic infiltrate, or an increase in the number of cells within the lamina propria. Occasionally, chronic inflammatory findings such as crypt architecture alterations and lymphocyte predominant infiltrate may be seen. Differentiation with ulcerative colitis is done via clinical history. Treatment for ICI induced colitis is dependent on symptoms. For those with < 4 bowel movements daily (grade 1), symptomatic treatment only is reasonable. For those with 4-6 per day (grade 2), ICI therapy is withheld, and steroids utilized if diarrhea is not self-resolving after 1 week. For >7 stools daily (grade 3 or 4) therapy is discontinued permanently. In some cases, when patients are steroid refractory, infliximab and vedolizumab have been utilized.Image 1.: Colitis on endoscopy.Image 2.: Cryptitis with crypt abscesses along with lymphocytes, plasma cells, and eosinophils.Image 3.: Paneth cells.

S2316 Evaluating Bloody Diarrhea During the COVID-19 Pandemic in a 20-Year-Old Patient

INTRODUCTION: During the COVID-19 pandemic, differentiating between acute infectious diarrhea versus a chronic inflammatory bowel disease (IBD) presents a new challenge altering the way we approach the diagnosis and treatment of IBD. CASE DESCRIPTION/METHODS: A 20-year-old gentleman with no known past medical history presented to his PCP with 14 bloody bowel movements daily. He was started on a 5-day course of Azithromycin. Stool studies were sent and his C. Difficile stool antigen turned positive. He was switched to oral Vancomycin. He presented to the hospital 3 days later after no improvement. On presentation, patient was febrile with diffuse abdominal and rectal pain. Initial lab results revealed leukocytosis (29.5K) with elevated bands (35), CRP 127.3, Albumin 3.0, Ferritin 236, Procalcitonin 1.13, Fibrinogen 698, and D-Dimer 1.57. Repeat stool studies were negative. His SARS CoV-2 PCR was positive. Chest X-ray was unremarkable. CT abdomen revealed diffuse colonic wall thickening and peri-colonic inflammation consistent with pancolitis without intra-abdominal or pelvic abscess. Symptoms improved with antibiotics. Flexible sigmoidoscopy revealed diffuse, severely edematous and erythematous mucosa with granularity and discontinuous areas of ulcers of varying size and depth seen in descending colon. Ulcerations were superficial and circumferential. Due to severity of disease and contact bleeding, scope was not advanced beyond this point. The lumen became narrowed due to inflammation without overt stricture or obstructing lesions. The sigmoid colon and rectum, ulcerations became mixed with exudates and the area was generally less effected. Numerous biopsies were taken. Pathology showed severe chronic active colitis with ulceration. Histology showed frequent crypt abscesses, cystic crypt changes and basal lympho-plasmacytosis. There is no definite Paneth cell metaplasia, pseudomembranous or viral cytopathic changes. After multidisciplinary discussion, he was started on IV Solumedrol. 72 hours later patient reported near resolution in symptoms and was transitioned to oral Prednisone taper. He was started on Infliximab 10 mg/kg prior to discharge after a repeat COVID test was negative. Outpatient follow up was arranged for repeat testing and interval colonoscopy. DISCUSSION: The documentation of collective experiences with newly diagnosed IBD patients during the COVID pandemic presents a diagnostic and therapeutic dilemma possibly altering our decisions moving into a new era.Figure 1.: Descending colon images.Figure 2.: Sigmoid colon images.Figure 3.: Rectal images.

Paneth Cell-Derived Lysozyme Defines the Composition of Mucolytic Microbiota and the Inflammatory Tone of the Intestine

Paneth cells are the primary source of C-type lysozyme, a β-1,4-N-acetylmuramoylhydrolase that enzymatically processes bacterial cell walls. Paneth cells are normally present in human cecum and ascending colon, but are rarely found in descending colon and rectum; Paneth cell metaplasia in this region and aberrant lysozyme production are hallmarks of inflammatory bowel disease (IBD) pathology. Here, we examined the impact of aberrant lysozyme production in colonic inflammation. Targeted disruption of Paneth cell lysozyme (Lyz1) protected mice from experimental colitis. Lyz1-deficiency diminished intestinal immune responses to bacterial molecular patterns and resulted in the expansion of lysozyme-sensitive mucolytic bacteria, including Ruminococcus gnavus, a Crohn's disease-associated pathobiont. Ectopic lysozyme production in colonic epithelium suppressed lysozyme-sensitive bacteria and exacerbated colitis. Transfer of R.gnavus into Lyz1-/- hosts elicited a type 2 immune response, causing epithelial reprograming and enhanced anti-colitogenic capacity. In contrast, in lysozyme-intact hosts, processed R.gnavus drove pro-inflammatory responses. Thus, Paneth cell lysozyme balances intestinal anti- and pro-inflammatory responses, with implications for IBD.

Intestinal autophagy links psychosocial stress with gut microbiota to promote inflammatory bowel disease

Psychosocial stress is a critical inducing factor of inflammatory bowel diseases (IBD), while autophagy is a novel central issue of IBD development. The present study investigated the potential role of autophagy in stress-related IBD in patients and animal model. The correlation between psychosocial stress and intestinal autophagy was determined in 23 patients with IBD. Corticotropin-releasing hormone (CRH), a well-established inducer of psychosocial stress, was administrated in dextran sulfate sodium (DSS)-induced IBD mice and lipopolysaccharide (LPS)-stimulated bone marrow-derived macrophages (BMDM). In IBD patients, the autophagy markers beclin-1, LC3-II/I ratio, Atg16L1, and Atg4B were significantly enhanced. The psychosocial stress score was positively associated with the levels of beclin-1 and the LC3II/I ratio in intestinal biopsy specimens. In IBD mouse model, CRH significantly aggravated intestinal inflammation, increased Paneth cell metaplasia, and enhanced intestinal autophagy (beclin-1, Atg16L1, PIK3R4, and Atg4B upregulation; GAA, CTSD, and PPKAA1 downregulation). Additionally, the CRH-induced gut microbial dysbiosis was evidenced by a marked increase in the number of detrimental bacteria. In LPS-stimulated BMDM, CRH substantially increased M1/M2 polarization and thus promoted inflammation. In both IBD mice and LPS-treated BMDM, blockade of autophagy by chloroquine abrogated the unbeneficial effects of CRH, whereas autophagy inducer rapamycin resulted in a pronounced protective effect against IBD lesion. Our data demonstrate that psychosocial stress may link the enhanced intestinal autophagy by modulating gut microbiota and inflammation to aggravate IBD. These data indicate autophagy as a promising therapeutic target for psychosocial stress-related IBD.