The endometrium, which is of crucial importance for reproduction, undergoes dynamic cyclic tissue remodeling. Knowledge of its molecular and cellular regulation is poor, primarily owing to a lack of study models. Here, we have established a novel and promising organoid model from both mouse and human endometrium. Dissociated endometrial tissue, embedded in Matrigel under WNTactivating conditions, swiftly formed organoid structures that showed long-term expansion capacity, and reproduced the molecular and histological phenotype of the tissue's epithelium. The supplemented WNT level determined the type of mouse endometrial organoids obtained: high WNT yielded cystic organoids displaying a more differentiated phenotype than the dense organoids obtained in low WNT. The organoids phenocopied physiological responses of endometrial epithelium to hormones, including increased cell proliferation under estrogen and maturation upon progesterone. Moreover, the human endometrial organoids replicated the menstrual cycle under hormonal treatment at both the morpho-histological and molecular levels. Together, we established an organoid culture system for endometrium, reproducing tissue epithelium physiology and allowing long-term expansion. This novel model provides a powerful tool for studying mechanisms underlying the biology as well as the pathology of this key reproductive organ.

Infection with the gastric bacterial pathogen Helicobacter pylori is typically contracted in early childhood and often persists for decades. The immunomodulatory properties of H. pylori that allow it to colonize humans persistently are believed to also account for H. pylori's protective effects against allergic and chronic inflammatory diseases. H. pylori infection efficiently reprograms dendritic cells (DCs) toward a tolerogenic phenotype and induces regulatory T cells (Tregs) with highly suppressive activity in models of allergen-induced asthma. We show here that two H. pylori virulence determinants, the γ-glutamyl transpeptidase GGT and the vacuolating cytotoxin VacA, contribute critically and nonredundantly to H. pylori's tolerizing effects on murine DCs in vitro and in vivo. The tolerancepromoting effects of both factors are independent of their described suppressive activity on T cells. Isogenic H. pylori mutants lacking either GGT or VacA are incapable of preventing LPS-induced DC maturation and fail to drive DC tolerization as assessed by induction of Treg properties in cocultured naive T cells. The Δggt and ΔvacA mutants colonize mice at significantly reduced levels, induce stronger T-helper 1 (Th1) and T-helper 17 (Th17) responses, and/or trigger more severe gastric pathology. Both factors promote the efficient induction of Tregs in vivo, and VacA is required to prevent allergen-induced asthma. The defects of the Δggt mutant in vitro and in vivo are phenocopied by pharmacological inhibition of the transpeptidase activity of GGT in all readouts. In conclusion, our results reveal the molecular players and mechanistic basis for H. pyloriinduced immunomodulation, promoting persistent infection and conferring protection against allergic asthma.bacterial virulence factors | hygiene hypothesis | persistent bacterial infection | human microbiota | persistence strategies T he bacterial pathogen Helicobacter pylori persistently colonizes the gastric mucosa of humans. It is typically acquired in early childhood (1) and, in the absence of antibiotic therapy, may persist for the entire lifespan of the host (2, 3). The extraordinary ability of H. pylori to resist a vigorous adaptive immune response driven in large part by T-helper 1 (Th1) and/or T-helper 17 (Th17)-polarized effector T cells (4, 5) has been attributed to its perfect adaptation to-and manipulation of-the human innate and adaptive immune systems (6). H. pylori has colonized its human host for at least 60,000 y (7) and during this long period of coevolution has evolved elaborate ways to systemically manipulate adaptive immune responses and to promote its persistence through the preferential induction of regulatory T-cell (Treg) over T-effector cell responses. Treg-predominant responses are characteristic of heavily colonized but asymptomatic carriers (4) and of children with particularly mild forms of Helicobacter-associated gastritis (8). Several recent functional studies using experimentally infected animals have implicated Tregs and dendritic cells (...

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Determining the exact pathogenesis of chronic gastrointestinal diseases remains difficult due to the complex in vivo environment. In this review we give an overview of the available epithelial cell culture systems developed to investigate pathophysiology of gastrointestinal diseases. Traditionally used two-dimensional (2D) immortalised (tumour) cell lines survive long-term, but are not genetically stable nor represent any human in particular. In contrast, primary cultures are patient unique, but short-lived. Three-dimensional (3D) organoid cultures resemble the crypt-villus domain and contain all cell lineages, are long-lived and genetically stable. Unfortunately, manipulation of the 3D organoid system is more challenging. Combining the 3D and 2D technologies may overcome limitations and offer the formation of monolayers on permeable membranes or flow-chambers. Determining the right model to use will depend on the pathology of interest and the focus of the research, defining which cell types need to be included in the model.

We developed and validated an ex vivo intestinal epithelial cell culture system and showed that patients with more ER stress and autophagy risk alleles have augmented epithelial ER stress responses. We thus presented a personalised approach whereby patient-specific defects can be identified, which in turn could help in selecting tailored therapies.