Polarised epithelial monolayers of the gastric mucosa reveal insights into mucosal homeostasis and defence against infection

Propheter D.C., Chara A.L., Harris T.A., Ruhn K.A., Hooper L.V.

Significance The mammalian gastrointestinal tract is home to diverse communities of bacteria that contribute to the metabolic health of their hosts. The epithelial lining of the intestine produces a diverse repertoire of antimicrobial proteins that limit the ability of these microorganisms to enter host tissues and cause disease. We have discovered that resistin-like molecule β (RELMβ) is a previously unknown member of the intestine's antibacterial arsenal. RELMβ is secreted from the intestinal surface and kills Gram-negative bacteria by damaging their membranes, thereby preventing these bacteria from coming into close contact with host tissues. Our findings reveal a new family of endogenous antibiotic proteins and contribute to the understanding of how mammals maintain mutually beneficial relationships with complex communities of intestinal bacteria.

Gall A., Gaudet R.G., Gray-Owen S.D., Salama N.R.

ABSTRACT Helicobacter pylori is a bacterial pathogen that colonizes the human stomach, causing inflammation which, in some cases, leads to gastric ulcers and cancer. The clinical outcome of infection depends on a complex interplay of bacterial, host genetic, and environmental factors. Although H. pylori is recognized by both the innate and adaptive immune systems, this rarely results in bacterial clearance. Gastric epithelial cells are the first line of defense against H. pylori and alert the immune system to bacterial presence. Cytosolic delivery of proinflammatory bacterial factors through the cag type 4 secretion system ( cag -T4SS) has long been appreciated as the major mechanism by which gastric epithelial cells detect H. pylori . Classically attributed to the peptidoglycan sensor NOD1, recent work has highlighted the role of NOD1-independent pathways in detecting H. pylori ; however, the bacterial and host factors involved have remained unknown. Here, we show that bacterially derived heptose-1,7-bisphosphate (HBP), a metabolic precursor in lipopolysaccharide (LPS) biosynthesis, is delivered to the host cytosol through the cag -T4SS, where it activates the host tumor necrosis factor receptor-associated factor (TRAF)-interacting protein with forkhead-associated domain (TIFA)-dependent cytosolic surveillance pathway. This response, which is independent of NOD1, drives robust NF-κB-dependent inflammation within hours of infection and precedes NOD1 activation. We also found that the CagA toxin contributes to the NF-κB-driven response subsequent to TIFA and NOD1 activation. Taken together, our results indicate that the sequential activation of TIFA, NOD1, and CagA delivery drives the initial inflammatory response in gastric epithelial cells, orchestrating the subsequent recruitment of immune cells and leading to chronic gastritis. IMPORTANCE H. pylori is a globally prevalent cause of gastric and duodenal ulcers and cancer. H. pylori antibiotic resistance is rapidly increasing, and a vaccine remains elusive. The earliest immune response to H. pylori is initiated by gastric epithelial cells and sets the stage for the subsequent immunopathogenesis. This study revealed that host TIFA and H. pylori -derived HBP are critical effectors of innate immune signaling that account for much of the inflammatory response to H. pylori in gastric epithelial cells. HBP is delivered to the host cell via the cag -T4SS at a time point that precedes activation of the previously described NOD1 and CagA inflammatory pathways. Manipulation of the TIFA-driven immune response in the host and/or targeting of ADP-heptose biosynthesis enzymes in H. pylori may therefore provide novel strategies that may be therapeutically harnessed to achieve bacterial clearance.

Zimmermann S., Pfannkuch L., Al-Zeer M.A., Bartfeld S., Koch M., Liu J., Rechner C., Soerensen M., Sokolova O., Zamyatina A., Kosma P., Mäurer A.P., Glowinski F., Pleissner K., Schmid M., et. al.

Summary Activation of transcription factor NF-κB is a hallmark of infection with the gastric pathogen Helicobacter pylori , associated with inflammation and carcinogenesis. Genome-wide RNAi screening revealed numerous host factors involved in H. pylori-, but not IL-1β- and TNF-α-dependent NF-κB regulation. Pathway analysis including CRISPR/Cas9-knockout and recombinant protein technology, immunofluorescence microscopy, immunoblotting, mass spectrometry, and mutant H. pylori strains identified the  H. pylori metabolite D- glycero -β-D- manno -heptose 1,7-bisphosphate (βHBP) as a cag PAI type IV secretion system (T4SS)-dependent effector of NF-κB activation in infected cells. Upon pathogen-host cell contact, TIFA forms large complexes (TIFAsomes) including interacting host factors, such as TRAF2. NF-κB activation, TIFA phosphorylation, and TIFAsome formation depend on a functional ALPK1 kinase, highlighting the ALPK1-TIFA axis as a core innate immune pathway. ALPK1-TIFA-mediated NF-κB activation was independent of CagA protein translocation, indicating that CagA translocation and HBP delivery to host cells are distinct features of the pathogen's T4SS.

Sigal M., Logan C.Y., Kapalczynska M., Mollenkopf H., Berger H., Wiedenmann B., Nusse R., Amieva M.R., Meyer T.F.

Myofibroblast-derived R-spondin 3 orchestrates regeneration of antral stomach epithelium via Wnt signalling in Axin2+ stem cells. Regeneration of the stomach epithelium is thought to be driven by long-lived stem cells residing in a niche that is yet to be defined and which can be activated in response to gastric pathogens, such as Helicobacter pylori, through an unknown mechanism. Thomas Meyer and colleagues now show that Wnt target gene expression is constrained to a restricted region of the stomach encompassing Lgr5+ stem cells. The myofibroblasts adjacent to this region provide R-spondin 3 to the stem cell compartment. R-spondin 3 is able to convert Lgr5− cells to Lgr5+ cells. The authors also find that Helicobacter pylori infection stimulates the expression of R-spondin 3 in myofibroblasts. This control of epithelial stem cell dynamics by stromal niche cells illustrates the sophisticated mechanism behind epithelial regeneration. The constant regeneration of stomach epithelium is driven by long-lived stem cells1,2,3, but the mechanism that regulates their turnover is not well understood. We have recently found that the gastric pathogen Helicobacter pylori can activate gastric stem cells and increase epithelial turnover4, while Wnt signalling is known to be important for stem cell identity and epithelial regeneration in several tissues5. Here we find that antral Wnt signalling, marked by the classic Wnt target gene Axin2, is limited to the base and lower isthmus of gastric glands, where the stem cells reside. Axin2 is expressed by Lgr5+ cells, as well as adjacent, highly proliferative Lgr5− cells that are able to repopulate entire glands, including the base, upon depletion of the Lgr5+ population. Expression of both Axin2 and Lgr5 requires stroma-derived R-spondin 3 produced by gastric myofibroblasts proximal to the stem cell compartment. Exogenous R-spondin administration expands and accelerates proliferation of Axin2+/Lgr5− but not Lgr5+ cells. Consistent with these observations, H. pylori infection increases stromal R-spondin 3 expression and expands the Axin2+ cell pool to cause hyperproliferation and gland hyperplasia. The ability of stromal niche cells to control and adapt epithelial stem cell dynamics constitutes a sophisticated mechanism that orchestrates epithelial regeneration and maintenance of tissue integrity.

Gudipaty S.A., Rosenblatt J.

To remove dying or unwanted cells from an epithelium while preserving the barrier function of the layer, epithelia use a unique process called cell extrusion. To extrude, the cell fated to die emits the lipid Sphingosine 1 Phosphate (S1P), which binds the G-protein-coupled receptor Sphingosine 1 Phosphate receptor 2 (S1P2) in the neighboring cells that activates Rho-mediated contraction of an actomyosin ring circumferentially and basally. This contraction acts to squeeze the cell out apically while drawing together neighboring cells and preventing any gaps to the epithelial barrier. Epithelia can extrude out cells targeted to die by apoptotic stimuli to repair the barrier in the face of death or extrude live cells to promote cell death when epithelial cells become too crowded. Indeed, because epithelial cells naturally turn over by cell death and division at some of the highest rates in the body, epithelia depend on crowding-induced live cell extrusion to preserve constant cell numbers. If extrusion is defective, epithelial cells rapidly lose contact inhibition and form masses. Additionally, because epithelia act as the first line of defense in innate immunity, preservation of this barrier is critical for preventing pathogens from invading the body. Given its role in controlling constant cell numbers and maintaining barrier function, a number of different pathologies can result when extrusion is disrupted. Here, we review mechanisms and signaling pathways that control epithelial extrusion and discuss how defects in these mechanisms can lead to multiple diseases. We also discuss tactics pathogens have devised to hijack the extrusion process to infect and colonize epithelia.

Bartfeld S.

Advances in stem cell research have allowed the development of 3-dimensional (3D) primary cell cultures termed organoid cultures, as they closely mimic the in vivo organization of different cell lineages. Bridging the gap between 2-dimensional (2D) monotypic cancer cell lines and whole organisms, organoids are now widely applied to model development and disease. Organoids hold immense promise for addressing novel questions in host-microbe interactions, infectious diseases and the resulting inflammatory conditions. Researchers have started to use organoids for modeling infection with pathogens, such as Helicobacter pylori or Salmonella enteritica , gut-microbiota interactions and inflammatory bowel disease. Future studies will broaden the spectrum of microbes used and continue to establish organoids as a standard model for human host-microbial interactions. Moreover, they will increasingly exploit the unique advantages of organoids, for example to address patient-specific responses to microbes. • Organoids are now used widely to study infection biology, interaction with the microbiota and associated diseases such as IBD. • Organoids contain differentiated host cells crucial for interaction with microorganisms. • Organoids provide host cells for microorganisms which were previously difficult to culture. • Simplified 2D layers and engineered tissues complete the spectrum of new model systems.

Ma B., Hottiger M.O.

Besides its important role in embryonic development and homeostatic self-renewal in adult tissues, Wnt/β-catenin signaling exerts both anti-inflammatory and pro-inflammatory functions. This is, at least partially, due to either repressing or enhancing the NF-κB pathway. Similarly, the NF-κB pathway either positively or negatively regulates Wnt/β-catenin signaling. Different components of the two pathways are involved in this crosstalk, forming a complex regulatory network. This review summarizes our current understanding of the molecular mechanisms underlying the cross-regulation between the two pathways and discusses their involvement in inflammation and inflammation-associated diseases such as cancer.

Neumann L., Mueller M., Moos V., Heller F., Meyer T.F., Loddenkemper C., Bojarski C., Fehlings M., Doerner T., Allers K., Aebischer T., Ignatius R., Schneider T.

Abstract The mucosal immune system is relevant for homeostasis, immunity, and also pathological conditions in the gastrointestinal tract. Inducible NO synthase (iNOS)–dependent production of NO is one of the factors linked to both antimicrobial immunity and pathological conditions. Upregulation of iNOS has been observed in human Helicobacter pylori infection, but the cellular sources of iNOS are ill defined. Key differences in regulation of iNOS expression impair the translation from mouse models to human medicine. To characterize mucosal iNOS-producing leukocytes, biopsy specimens from H. pylori–infected patients, controls, and participants of a vaccination trial were analyzed by immunohistochemistry, along with flow cytometric analyses of lymphocytes for iNOS expression and activity. We newly identified mucosal IgA-producing plasma cells (PCs) as one major iNOS+ cell population in H. pylori–infected patients and confirmed intracellular NO production. Because we did not detect iNOS+ PCs in three distinct infectious diseases, this is not a general feature of mucosal PCs under conditions of infection. Furthermore, numbers of mucosal iNOS+ PCs were elevated in individuals who had cleared experimental H. pylori infection compared with those who had not. Thus, IgA+ PCs expressing iNOS are described for the first time, to our knowledge, in humans. iNOS+ PCs are induced in the course of human H. pylori infection, and their abundance seems to correlate with the clinical course of the infection.

Birchenough G.M., Nyström E.E., Johansson M.E., Hansson G.C.

Mounting the intestinal barricades Gut microbiota are important for health and well-being, but they need to be kept under control and prevented from doing any harm. Birchenough et al. investigated the microbial molecules that trigger protective mucus secretion from a class of goblet cells in the colon. Once the molecules are detected, an alarm signal is transmitted from these cells via innate immune signal mediators and inflammasome components to adjacent cells, generating more mucus and repelling the invaders. Subsequently, the sentinel goblet cells are expelled from the epithelium and their remains may also add to the protective barricade. Science , this issue p. 1535

Mejías-Luque R., Zöller J., Anderl F., Loew-Gil E., Vieth M., Adler T., Engler D.B., Urban S., Browning J.L., Müller A., Gerhard M., Heikenwalder M.

Objective Lymphotoxin β receptor (LTβR) signalling has been implicated in inflammation-associated tumour development in different tissues. We have analysed the role of LTβR and alternative NF-κB signalling in Helicobacter pylori-mediated gastric inflammation and pathology.Design We analysed several ligands and receptors of the alternative NF-κB pathway, RelB, p52 nuclear translocation and target genes in tissue samples of H. pylori-infected patients with different degrees of gastritis or early gastric tumours by in situ hybridisation, immunohistochemistry, Western blot and real-time PCR analyses. Molecular mechanisms involved in LTβR activation by H. pylori were assessed in vitro using human gastric cancer cell lines and distinct H. pylori isolates. The effects of blocking or agonistically activating LTβR on gastric pathology during challenge with a human pathogenic H. pylori strain were studied in a mouse model.Results Among the tested candidates, LT was significantly increased and activated alternative NF-κB signalling was observed in the gastric mucosa of H. pylori-infected patients. H. pyloriinduced LTβR–ligand expression in a type IV secretion system-dependent but CagA-independent manner, resulting in activation of the alternative NF-κB pathway, which was further enhanced by blocking canonical NF-κB during infection. Blocking LTβR signalling in vivo suppressed H. pylori-driven gastritis, whereas LTβR activation in gastric epithelial cells of infected mice induced a broadened pro-inflammatory chemokine milieu, resulting in exacerbated pathology.Conclusions LTβR-triggered activation of alternative NF-κB signalling in gastric epithelial cells executes H. pylori-induced chronic gastritis, representing a novel target to restrict gastric inflammation and pathology elicited by H. pylori, while exclusively targeting canonical NF-κB may aggravate pathology by enhancing the alternative pathway.

Clevers H., Bartfeld S.

Hartung M., Gruber D., Koch K., Grüter L., Rehrauer H., Tegtmeyer N., Backert S., Müller A.

The human bacterial pathogen Helicobacter pylori exhibits genotoxic properties that promote gastric carcinogenesis. H. pylori introduces DNA double strand breaks (DSBs) in epithelial cells that trigger host cell DNA repair efforts. Here, we show that H. pylori-induced DSBs are repaired via error-prone, potentially mutagenic non-homologous end-joining. A genome-wide screen for factors contributing to DSB induction revealed a critical role for the H. pylori type IV secretion system (T4SS). Inhibition of transcription, as well as NF-κB/RelA-specific RNAi, abrogates DSB formation. DSB induction further requires β1-integrin signaling. DSBs are introduced by the nucleotide excision repair endonucleases XPF and XPG, which, together with RelA, are recruited to chromatin in a highly coordinated, T4SS-dependent manner. Interestingly, XPF/XPG-mediated DNA DSBs promote NF-κB target gene transactivation and host cell survival. In summary, H. pylori induces XPF/XPG-mediated DNA damage through activation of the T4SS/β1-integrin signaling axis, which promotes NF-κB target gene expression and host cell survival.

Huang J., Sweeney E., Sigal M., Zhang H.C., Remington S. ., Cantrell M., Kuo C., Guillemin K., Amieva M.

The gastric pathogen Helicobacter pylori interacts intimately with the gastric mucosa to avoid the microbicidal acid in the stomach lumen. The cues H. pylori senses to locate and colonize the gastric epithelium have not been well defined. We show that metabolites emanating from human gastric organoids rapidly attract H. pylori. This response is largely controlled by the bacterial chemoreceptor TlpB, and the main attractant emanating from epithelia is urea. Our previous structural analyses show that TlpB binds urea with high affinity. Here we demonstrate that this tight binding controls highly sensitive responses, allowing detection of urea concentrations as low as 50 nM. Attraction to urea requires that H. pylori urease simultaneously destroys the signal. We propose that H. pylori has evolved a sensitive urea chemodetection and destruction system that allows the bacterium to dynamically and locally modify the host environment to locate the epithelium.

Koeppel M., Garcia-Alcalde F., Glowinski F., Schlaermann P., Meyer T.

Infection with the human pathogen Helicobacter pylori (H. pylori) is a major risk factor for gastric cancer. Since the bacterium exerts multiple genotoxic effects, we examined the circumstances of DNA damage accumulation and identified regions within the host genome with high susceptibility to H. pylori-induced damage. Infection impaired several DNA repair factors, the extent of which depends on a functional cagPAI. This leads to accumulation of a unique DNA damage pattern, preferentially in transcribed regions and proximal to telomeres, in both gastric cell lines and primary gastric epithelial cells. The observed pattern correlates with focal amplifications in adenocarcinomas of the stomach and partly overlaps with known cancer genes. We thus demonstrate an impact of a bacterial infection directed toward specific host genomic regions and describe underlying characteristics that make such regions more likely to acquire heritable changes during infection, which could contribute to cellular transformation.

Sigal M., Rothenberg M.E., Logan C.Y., Lee J.Y., Honaker R.W., Cooper R.L., Passarelli B., Camorlinga M., Bouley D.M., Alvarez G., Nusse R., Torres J., Amieva M.R.

Background & Aims Helicobacter pylori infection is the main risk factor for gastric cancer. We characterized the interactions of H pylori with gastric epithelial progenitor and stem cells in humans and mice and investigated how these interactions contribute to H pylori–induced pathology. Methods We used quantitative confocal microscopy and 3-dimensional reconstruction of entire gastric glands to determine the localizations of H pylori in stomach tissues from humans and infected mice. Using lineage tracing to mark cells derived from leucine-rich repeat-containing G-protein coupled receptor 5–positive (Lgr5+) stem cells (Lgr5-eGFP-IRES-CreERT2/Rosa26-TdTomato mice) and in situ hybridization, we analyzed gastric stem cell responses to infection. Isogenic H pylori mutants were used to determine the role of specific virulence factors in stem cell activation and pathology. Results H pylori grow as distinct bacterial microcolonies deep in the stomach glands and interact directly with gastric progenitor and stem cells in tissues from mice and humans. These gland-associated bacteria activate stem cells, increasing the number of stem cells, accelerating Lgr5+ stem cell proliferation, and up-regulating expression of stem cell–related genes. Mutant bacteria with defects in chemotaxis that are able to colonize the stomach surface but not the antral glands in mice do not activate stem cells. In addition, bacteria that are unable to inject the contact-dependent virulence factor CagA into the epithelium colonized stomach glands in mice, but did not activate stem cells or produce hyperplasia to the same extent as wild-type H pylori. Conclusions H pylori colonize and manipulate the progenitor and stem cell compartments, which alters turnover kinetics and glandular hyperplasia. Bacterial ability to alter the stem cells has important implications for gastrointestinal stem cell biology and H pylori–induced gastric pathology.

Kahlert S., Nossol C., Krüger M., Kopp S., Grimm D., Wuest S.L., Rothkötter H.

The impact of gravity is a basic force determining our existence on Earth. Changes in orientation with respect to the gravity vector trigger alternating mechanical forces on organisms, organs, and cells. In the intestines of mammals, epithelial cells are continuously exposed to changed orientations to gravity. In this study, we employed dynamic cultivation systems to mimic the load changes and the resulting mechanical forces. The morphological and functional response of non-cancer-derived porcine epithelial cell lines IPEC-1 and IPEC-J2 was analyzed. We found that dynamic growth conditions affect morphology in the enterocyte model IPEC-1 but not in IPEC-J2. Changes in IPEC-1 were accompanied by modifications of the distribution and structure of the F-actin cytoskeleton rather than the amount. The structure of the apical brush border and the tight junction system seemed to be largely unaffected; however, a robust decrease in transepithelial resistance was found in IPEC-1 and partially in IPEC-J2. We further detected an increase in Ki67, pointing towards accelerated proliferation. In line with this finding, we detected a doubling of cellular mitochondrial respiration, which was not linked to a general increase in the respiratory chain capacity. Dynamic cultivation of confluent epithelial cell layers did not evoke signs of senescence. In summary, we identified the mechanical load cycle as a relevant parameter for the modulation of the morphological structure and physiological behaviour of intestinal epithelial cells.

Hofer M., Kim Y., Broguiere N., Gorostidi F., Klein J.A., Amieva M.R., Lutolf M.P.

Jiang X., Zhang L., Liu Z., Zhou T., Li W., Liu W., Zhang L., You W., Zhang Y., Pan K.

AbstractGastric microbiota and metabolites may interact and play collaborative roles in the carcinogenesis process. This study aims to investigate differential metabolites and microbes, as well as the possible roles of microbe‐metabolite interactions in gastric cancer (GC) development. Targeted metabolomics assays and 16S rRNA sequencing were performed to compare metabolic and microbial profiles in gastric tissues from subjects with superficial gastritis/chronic atrophic gastritis (SG/CAG), intestinal metaplasia/low‐grade intraepithelial neoplasia (IM/LGIN) and GC. Significant differences were found in metabolic and microbial profiles between the GC and SG/CAG or IM/LGIN groups, respectively (all p < .05). By comparing GC with the other lesions, 69 differential metabolites mainly comprised triglycerides and phosphatidylcholines, and 21 differential microbes included Peptostreptococcus, Lactobacillus, Dialister, Helicobacter pylori, and Streptococcus anginosus (all p < .05). The altered metabolites and microbes in GC were both significantly enriched in the glycerophospholipid metabolism pathway, in which the predicted down‐regulation of phospholipase C (plc) and up‐regulation of 1‐acyl‐sn‐glycerol‐3‐phosphate acyltransferase (plsC) by microbiota may affect phosphatidylcholine hydrolysis and triglyceride biosynthesis modules. More and stronger microbe‐metabolite correlations in GC compared to the other lesion group further supported the potential microbial regulations to the important metabolites in gastric carcinogenesis, such as Lactobacillus and phosphatidylcholines (.32 ≤ r ≤ .57, all p < .05), Peptostreptococcus (.36 ≤ r ≤ .60, all p < .05) or Dialister (.36 ≤ r ≤ .62, all p < .05) and triglycerides. We simultaneously identified differential metabolites and microbes and their altered correlations between GC and gastric lesions. The main GC‐associated phosphatidylcholines and triglycerides may be affected by gastric microbes, which provides new perspectives on the microbiota‐metabolite interactions during the development of GC.

Wizenty J., Sigal M.

Micati D., Hlavca S., Chan W.H., Abud H.E.

AbstractRepresentative models of intestinal diseases are transforming our knowledge of the molecular mechanisms of disease, facilitating effective drug screening and avenues for personalised medicine. Despite the emergence of 3D in vitro intestinal organoid culture systems that replicate the genetic and functional characteristics of the epithelial tissue of origin, there are still challenges in reproducing the human physiological tissue environment in a format that enables functional readouts. Here, we describe the latest platforms engineered to investigate environmental tissue impacts, host-microbe interactions and enable drug discovery. This highlights the potential to revolutionise knowledge on the impact of intestinal infection and inflammation and enable personalised disease modelling and clinical translation.

Moskal K., Khurana N., Siegert L., Lee Y.S., Clevers H., Elinav E., Puschhof J.

AbstractThe biology of cancer is characterized by an intricate interplay of cells originating not only from the tumor mass, but also its surrounding environment. Different microbial species have been suggested to be enriched in tumors and the impacts of these on tumor phenotypes is subject to intensive investigation. For these efforts, model systems that accurately reflect human–microbe interactions are rapidly gaining importance. Here we present a guide for selecting a suitable in vitro co‐culture platform used to model different cancer–microbiome interactions. Our discussion spans a variety of in vitro models, including 2D cultures, tumor spheroids, organoids, and organ‐on‐a‐chip platforms, where we delineate their respective advantages, limitations, and applicability in cancer microbiome research. Particular focus is placed on methodologies that facilitate the exposure of cancer cells to microbes, such as organoid microinjections and co‐culture on microfluidic devices. We highlight studies offering critical insights into possible cancer–microbe interactions and underscore the importance of in vitro models in those discoveries. We anticipate the integration of more complex microbial communities and the inclusion of immune cells into co‐culture systems to more accurately simulate the tumor microenvironment. The advent of ever more sophisticated co‐culture models will aid in unraveling the mechanisms of cancer‐microbiome interplay and contribute to exploiting their potential in novel diagnostic and therapeutic strategies.

Yang N., Li Y., Cai Y., Liu Y., Zhang Y., Fu Y., Tan C., Willems L., Liu G.

The mucus layer provides the first defense that keeps the epithelium free from microorganisms. However, the effect of the small intestinal mucus layer on pathogen invasion is still poorly understood, especially for swine enteric coronavirus. To better understand virus‒mucus layer‒intestinal epithelium interactions, here, we developed a porcine intestinal organoid mucus‒monolayer model under air‒liquid interface (ALI) conditions. We successfully established a differentiated intestinal organoid monolayer model comprising various differentiated epithelial cell types and a mucus layer under ALI conditions. Mass spectrometry analysis revealed that the mucus derived from the ALI monolayer shared a similar composition to that of the native small intestinal mucus. Importantly, our results demonstrated that the ALI monolayer exhibited lower infectivity of both TGEV and PEDV than did the submerged monolayer. To further confirm the impact of ALI mucus on coronavirus infection, mucus was collected from the ALI monolayer culture system and incubated with the viruses. These results indicated that ALI mucus treatment effectively reduced the infectivity of TGEV and PEDV. Additionally, Mucin 2 (Muc2), a major component of native small intestinal mucus, was found to be abundant in the mucus derived from the ALI monolayer, as determined by mass spectrometry analysis. Our study confirmed the potent antiviral activity of Muc2 against TGEV and PEDV infection. Considering the sialylation of Muc2 and the known sialic acid-binding activity of coronavirus, further investigations revealed that the sialic acid residues of Muc2 play a potential role in inhibiting coronavirus infection. We established the porcine intestinal organoid mucus monolayer as a novel and valuable model for confirming the pivotal role of the small intestinal mucus layer in combating pathogen invasion. In addition, our findings highlight the significance of sialic acid modification of Muc2 in blocking coronavirus infections. This discovery opens promising avenues for the development of tailor-made drugs aimed at preventing porcine enteric coronavirus invasion.

Hofer M., Duque-Correa M.A., Lutolf M.P.

Organoids for modelling the physiology and pathology of gastrointestinal tissues are constrained by a poorly accessible lumen. Here we report the development and applicability of bilaterally accessible organoid-derived patterned epithelial monolayers that allow the independent manipulation of their apical and basal sides. We constructed gastric, small-intestinal, caecal and colonic epithelial models that faithfully reproduced their respective tissue geometries and that exhibited stem cell regionalization and transcriptional resemblance to in vivo epithelia. The models’ enhanced observability allowed single-cell tracking and studies of the motility of cells in immersion culture and at the air–liquid interface. Models mimicking infection of the caecal epithelium by the parasite Trichuris muris allowed us to live image syncytial tunnel formation. The enhanced observability of bilaterally accessible organoid-derived gastrointestinal tissue will facilitate the study of the dynamics of epithelial cells and their interactions with pathogens. The enhanced observability of bilaterally accessible gastrointestinal organoid-derived monolayers facilitates the study of parasite infection of the gut.

Neuper T., Frauenlob T., Dang H., Krenn P.W., Posselt G., Regl C., Fortelny N., Schäpertöns V., Unger M.S., Üblagger G., Neureiter D., Mühlbacher I., Weitzendorfer M., Singhartinger F., Emmanuel K., et. al.

Vllahu M., Voli A., Licursi V., Zagami C., D’Amore A., Traulsen J., Woelffling S., Schmid M., Crickley R., Lisle R., Link A., Tosco A., Meyer T.F., Boccellato F.

Arai J., Hayakawa Y., Tateno H., Fujiwara H., Kasuga M., Fujishiro M.

AbstractGastric mucins serve as a protective barrier on the stomach's surface, protecting from external stimuli including gastric acid and gut microbiota. Their composition typically changes in response to the metaplastic sequence triggered by Helicobacter pylori infection. This alteration in gastric mucins is also observed in cases of gastric cancer, although the precise connection between mucin expressions and gastric carcinogenesis remains uncertain. This review first introduces the relationship between mucin expressions and gastric metaplasia or cancer observed in humans and mice. Additionally, we discuss potential pathogenic mechanisms of how aberrant mucins and their glycans affect gastric carcinogenesis. Finally, we summarize challenges to target tumor‐specific glycans by utilizing lectin‐drug conjugates that can bind to specific glycans. Understanding the correlation and mechanism between these mucin expressions and gastric carcinogenesis could pave the way for new strategies in gastric cancer treatment.

Canadas-Ortega M., Mühlbacher I., Posselt G., Diechler S., Ferner C.D., Boccellato F., Koch O.O., Neureiter D., Weitzendorfer M., Emmanuel K., Wessler S.

Impaired E-cadherin (Cdh1) functions are closely associated with cellular dedifferentiation, infiltrative tumor growth and metastasis, particularly in gastric cancer. The class-I carcinogen Helicobacter pylori (H. pylori) colonizes gastric epithelial cells and induces Cdh1 shedding, which is primarily mediated by the secreted bacterial protease high temperature requirement A (HtrA). In this study, we used human primary epithelial cell lines derived from gastroids and mucosoids from different healthy donors to investigate HtrA-mediated Cdh1 cleavage and the subsequent impact on bacterial pathogenesis in a non-neoplastic context. We found a severe impairment of Cdh1 functions by HtrA-induced ectodomain cleavage in 2D primary cells and mucosoids. Since mucosoids exhibit an intact apico-basal polarity, we investigated bacterial transmigration across the monolayer, which was partially depolarized by HtrA, as indicated by microscopy, the analyses of the transepithelial electrical resistance (TEER) and colony forming unit (cfu) assays. Finally, we investigated CagA injection and observed efficient CagA translocation and tyrosine phosphorylation in 2D primary cells and, to a lesser extent, similar effects in mucosoids. In summary, HtrA is a crucially important factor promoting the multistep pathogenesis of H. pylori in non-transformed primary gastric epithelial cells and organoid-based epithelial models.

Liu S., Wen H., Li F., Xue X., Sun X., Li F., Hu R., Xi H., Boccellato F., Meyer T.F., Mi Y., Zheng P.

Abstract Background Gastric intestinal metaplasia (GIM) is an essential precancerous lesion. Although the reversal of GIM is challenging, it potentially brings a state-to-art strategy for gastric cancer therapeutics (GC). The lack of the appropriate in vitro model limits studies of GIM pathogenesis, which is the issue this work aims to address for further studies. Method The air-liquid interface (ALI) model was adopted for the long-term culture of GIM cells in the present work. This study conducted Immunofluorescence (IF), quantitative real-time polymerase chain reaction (qRT-PCR), transcriptomic sequencing, and mucoproteomic sequencing (MS) techniques to identify the pathways for differential expressed genes (DEGs) enrichment among different groups, furthermore, to verify novel biomarkers of GIM cells. Result Our study suggests that GIM-ALI model is analog to the innate GIM cells, which thus can be used for mucus collection and drug screening. We found genes MUC17, CDA, TRIM15, TBX3, FLVCR2, ONECUT2, ACY3, NMUR2, and MAL2 were highly expressed in GIM cells, while GLDN, SLC5A5, MAL, and MALAT1 showed down-regulated, which can be used as potential biomarkers for GIM cells. In parallel, these genes that highly expressed in GIM samples were mainly involved in cancer-related pathways, such as the MAPK signal pathway and oxidative phosphorylation signal pathway. Conclusion The ALI model is validated for the first time for the in vitro study of GIM. GIM-ALI model is a novel in vitro model that can mimic the tissue micro-environment in GIM patients and further provide an avenue for studying the characteristics of GIM mucus. Our study identified new markers of GIM as well as pathways associated with GIM, which provides outstanding insight for exploring GIM pathogenesis and potentially other related conditions.

Liu Y., Wu D., Chen J., Tang Y., Jiang F.

Gastric organoids are models created in the laboratory using stem cells and sophisticated three-dimensional cell culture techniques. These models have shown great promise in providing valuable insights into gastric physiology and advanced disease research. This review comprehensively summarizes and analyzes the research advances in culture methods and techniques for adult stem cells and induced pluripotent stem cell-derived organoids, and patient-derived organoids. The potential value of gastric organoids in studying the pathogenesis of stomach-related diseases and facilitating drug screening is initially discussed. The construction of gastric organoids involves several key steps, including cell extraction and culture, three-dimensional structure formation, and functional expression. Simulating the structure and function of the human stomach by disease modeling with gastric organoids provides a platform to study the mechanism of gastric cancer induction by Helicobacter pylori . In addition, in drug screening and development, gastric organoids can be used as a key tool to evaluate drug efficacy and toxicity in preclinical trials. They can also be used for precision medicine according to the specific conditions of patients with gastric cancer, to assess drug resistance, and to predict the possibility of adverse reactions. However, despite the impressive progress in the field of gastric organoids, there are still many unknowns that need to be addressed, especially in the field of regenerative medicine. Meanwhile, the reproducibility and consistency of organoid cultures are major challenges that must be overcome. These challenges have had a significant impact on the development of gastric organoids. Nonetheless, as technology continues to advance, we can foresee more comprehensive research in the construction of gastric organoids. Such research will provide better solutions for the treatment of stomach-related diseases and personalized medicine.

Cai P.C., Braunreuther M., Shih A., Spakowitz A.J., Fuller G.G., Heilshorn S.C.

Intestinal health heavily depends on establishing a mucus layer within the gut with physical properties that strike a balance between being sufficiently elastic to keep out harmful pathogens yet viscous enough to flow and turnover the contents being digested. Studies investigating dysfunction of the mucus layer in the intestines are largely confined to animal models, which require invasive procedures to collect the mucus fluid. In this work, we develop a nondestructive method to study intestinal mucus. We use an air–liquid interface culture of primary human intestinal epithelial cells that exposes their apical surface to allow in situ analysis of the mucus layer. Mucus collection is not only invasive but also disrupts the mucus microstructure, which plays a crucial role in the interaction between mucus and the gut microbiome. Therefore, we leverage a noninvasive rheology technique that probes the mechanical properties of the mucus without removal from the culture. Finally, to demonstrate biomedical uses for this cell culture system, we characterize the biochemical and biophysical properties of intestinal mucus due to addition of the cytokine IL-13 to recapitulate the gut environment of Nippostrongylus brasiliensis infection.