Dissection of Barrier Dysfunction in Organoid-Derived Human Intestinal Epithelia Induced by Giardia duodenalis

The pathogenic responses elicited during exposure of human intestinal cell line with Giardia duodenalis excretory-secretory products and the potential attributed endocytosis mechanism

Giardia duodenalis, an important zoonotic protozoan parasite, adheres to host intestinal epithelial cells (IECs) via the ventral disc and causes giardiasis characterized mainly by diarrhea. To date, it remains elusive how excretory-secretory products (ESPs) of Giardia enter IECs and how the cells respond to the entry. Herein, we initially demonstrated that ESPs evoked IEC endocytosis in vitro. We indicated that ESPs contributed vitally in triggering intrinsic apoptosis, pro-inflammatory responses, tight junction (TJ) protein expressional changes, and autophagy in IECs. Endocytosis was further proven to be implicated in those ESPs-triggered IEC responses. Ten predicted virulent excretory-secretory proteins of G. duodenalis were investigated for their capability to activate clathrin/caveolin-mediated endocytosis (CME/CavME) in IECs. Pyridoxamine 5'-phosphate oxidase (PNPO) was confirmed to be an important contributor. PNPO was subsequently verified as a vital promoter in the induction of giardiasis-related IEC apoptosis, inflammation, and TJ protein downregulation. Most importantly, this process seemed to be involved majorly in PNPO-evoked CME pathway, rather than CavME. Collectively, this study identified Giardia ESPs, notably PNPO, as potentially important pathogenic factors during noninvasive infection. It was also noteworthy that ESPs-evoked endocytosis might play a role in triggering giardiasis-inducing cellular regulation. These findings would deepen our understanding about the role of ESPs, notably PNPO, in the pathogenesis of giardiasis and the potential attributed endocytosis mechanism.

Organoids as a tool to study the impact of heterogeneity in gastrointestinal epithelium on host-pathogen interactions

The epithelium of the gastrointestinal (GI) tract has been extensively characterized using advanced histological and RNA sequencing techniques, which has revealed great cellular diversity. Pathogens, such as viruses and bacteria, are highly adapted to their host and often exhibit not only species-specificity but also a preference or tropism for specific GI segments or even cell types-some of these preferences are so specific, that these pathogens still cannot be cultured invitro. Organoid technology now provides a tool to generate human cell types, which enables the study of host cell tropism. Focussing on the GI tract, we provide an overview about cellular differentiation in vivo and in organoids and how differentiation in organoids and their derived models is used to advance our understanding of viral, bacterial, and parasitic infection. We emphasize that it is central to understand the composition of the model, as the alteration of culture conditions yields different cell types which affects infection. We examine future directions for wider application of cellular heterogeneity and potential advanced model systems for GI tract infection studies.

Inhibition of ADAM17 increases the cytotoxic effect of cisplatin in cervical spheroids and organoids

Introduction

Cervical cancer represents one of the main causes of female, cancer-related mortality worldwide. The majority of cancers are caused by human papillomaviruses such as HPV16 and HPV18. As chemotherapeutic resistance to first-line platinum treatment is still a predominant clinical challenge in advanced cervical cancer, novel treatment options including combinatorial therapies are urgently required to overcome chemotherapeutic resistance. Inhibition of A Disintegrin And Metalloproteinase (ADAM)-family members, heavily involved in tumour progression of a vast range of solid tumours, strongly improved response to chemotherapeutic treatment in other tumour entities including ovarian cancer.

Methods

We established two- and three-dimensional models derived from three traditional cervical cancer cell lines and ectocervical cancer-derived organoids. Following characterisation, these models were used to investigate their response to cisplatin treatment in the absence and presence of ADAM inhibitors using viability assays and automated live cell imaging.

Results

The pivotal role of the metalloprotease ADAM17 driving chemotherapy resistance was detectable in all ectocervical cultures irrespective of the model system used, whereas ADAM10 inhibition was predominantly effective only in loosely aggregated spheroids. We showed prominent differences regarding treatment responses between 2D monolayers compared to 3D spheroid and 3D organoid model systems. Particularly, the organoid system, regarded as the closest representation of primary tumours, exhibited reliably the combinatorial effect of ADAM17 inhibition and cisplatin in all three individual donors.

Discussion

As two- and three-dimensional models of the same cell lines differ in their responses to chemotherapy it is essential to validate treatment strategies in more advanced model systems representing the patient situation more realistically. Ectocervical organoids showed reliable results regarding treatment responses closely mimicking the primary tumours and could therefore serve as an important tool for personalized medicine in cervical cancer. These findings strengthen the role of ADAM17 as a potential novel target for combinatorial treatments to overcome chemoresistance in cervical cancer.

A long journey to the colon: The role of the small intestine microbiota in intestinal disease

The small intestine represents a complex and understudied gut niche with significant implications for human health. Indeed, many infectious and non-infectious diseases center within the small intestine and present similar clinical manifestations to large intestinal disease, complicating non-invasive diagnosis and treatment. One major neglected aspect of small intestinal diseases is the feedback relationship with the resident collection of commensal organisms, the gut microbiota. Studies focused on microbiota-host interactions in the small intestine in the context of infectious and non-infectious diseases are required to identify potential therapeutic targets dissimilar from those used for large bowel diseases. While sparsely populated, the small intestine represents a stringent commensal bacterial microenvironment the host relies upon for nutrient acquisition and protection against invading pathogens (colonization resistance). Indeed, recent evidence suggests that disruptions to host-microbiota interactions in the small intestine impact enteric bacterial pathogenesis and susceptibility to non-infectious enteric diseases. In this review, we focus on the microbiota's impact on small intestine function and the pathogenesis of infectious and non-infectious diseases of the gastrointestinal (GI) tract. We also discuss gaps in knowledge on the role of commensal microorganisms in proximal GI tract function during health and disease.

Giardia intestinalis extracellular vesicles induce changes in gene expression in human intestinal epithelial cells in vitro

Giardiasis is a common waterborne zoonotic disease caused by Giardia intestinalis. Upon infection, Giardia releases excretory and secretory products (ESPs) including secreted proteins (SPs) and extracellular vesicles (EVs). Although the interplay between ESPs and intestinal epithelial cells (IECs) has been previously described, the functions of EVs in these interactions and their differences from those of SPs require further exploration. In the present study, EVs and EV-depleted SPs were isolated from Giardia ESPs. Proteomic analyses of isolated SPs and EVs showed 146 and 91 proteins, respectively. Certain unique and enriched proteins have been identified in SPs and EVs. Transcriptome analysis of Caco-2 cells exposed to EVs showed 96 differentially expressed genes (DEGs), with 56 upregulated and 40 downregulated genes. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Gene Set Enrichment Analysis (GSEA) indicated that Caco-2 genes related to metabolic processes, the HIF-1 signaling pathway, and the cAMP signaling pathway were affected. This study provides new insights into host-parasite interactions, highlighting the potential significance of EVs on IECs during infections.

Culture media and format alter cellular composition and barrier integrity of porcine colonoid-derived monolayers

Intestinal organoid technology has revolutionized our approach to in vitro cell culture due in part to their three-dimensional structures being more like the native tissue from which they were derived with respect to cellular composition and architecture. For this reason, organoids are becoming the new gold standard for undertaking intestinal epithelial cell research. Unfortunately, their otherwise advantageous three-dimensional geometry prevents easy access to the apical epithelium, which is a major limitation when studying interactions between dietary or microbial components and host tissues. To overcome this problem, we developed porcine colonoid-derived monolayers cultured on both permeable Transwell inserts and tissue culture treated polystyrene plates. We found that seeding density and culture format altered the expression of genes encoding markers of specific cell types (stem cells, colonocytes, goblets, and enteroendocrine cells), and barrier maturation (tight junctions). Additionally, we found that changes to the formulation of the culture medium altered the cellular composition of colonoids and of monolayers derived from them, resulting in cultures with an increasingly differentiated phenotype that was similar to that of their tissue of origin.

Three-Dimensional Scaffolds for Intestinal Cell Culture: Fabrication, Utilization, and Prospects

The intestine is a visceral organ that integrates absorption, metabolism, and immunity, which is vulnerable to external stimulus. Researchers in the fields such as food science, immunology, and pharmacology have committed to developing appropriate in vitro intestinal cell models to study the intestinal absorption and metabolism mechanisms of various nutrients and drugs, or pathogenesis of intestinal diseases. In the past three decades, the intestinal cell models have undergone a significant transformation from conventional two-dimensional cultures to three-dimensional (3D) systems, and the achievements of 3D cell culture have been greatly contributed by the fabrication of different scaffolds. In this review, we first introduce the developing trend of existing intestinal models. Then, four types of scaffolds, including Transwell, hydrogel, tubular scaffolds, and intestine-on-a-chip, are discussed for their 3D structure, composition, advantages, and limitations in the establishment of intestinal cell models. Excitingly, some of the in vitro intestinal cell models based on these scaffolds could successfully mimic the 3D structure, microenvironment, mechanical peristalsis, fluid system, signaling gradients, or other important aspects of the original human intestine. Furthermore, we discuss the potential applications of the intestinal cell models in drug screening, disease modeling, and even regenerative repair of intestinal tissues. This review presents an overview of state-of-the-art scaffold-based cell models within the context of intestines, and highlights their major advances and applications contributing to a better knowledge of intestinal diseases. Impact statement The intestine tract is crucial in the absorption and metabolism of nutrients and drugs, as well as immune responses against external pathogens or antigens in a complex microenvironment. The appropriate experimental cell model in vitro is needed for in-depth studies of intestines, due to the limitation of animal models in dynamic control and real-time assessment of key intestinal physiological and pathological processes, as well as the "R" principles in laboratory animal experiments. Three-dimensional (3D) scaffold-based cell cultivation has become a developing tendency because of the superior cell proliferation and differentiation and more physiologically relevant environment supported by the customized 3D scaffolds. In this review, we summarize four types of up-to-date 3D cell culture scaffolds fabricated by various materials and techniques for a better recapitulation of some essential physiological and functional characteristics of original intestines compared to conventional cell models. These emerging 3D intestinal models have shown promising results in not only evaluating the pharmacokinetic characteristics, security, and effectiveness of drugs, but also studying the pathological mechanisms of intestinal diseases at cellular and molecular levels. Importantly, the weakness of the representative 3D models for intestines is also discussed.

Organoids to Remodel SARS-CoV-2 Research: Updates, Limitations and Perspectives

The novel COVID-19 pneumonia caused by the SARS-CoV-2 virus poses a significant threat to human health. Scientists have made significant efforts to control this virus, consequently leading to the development of novel research methods. Traditional animal and 2D cell line models might not be suitable for large-scale applications in SARS-CoV-2 research owing to their limitations. As an emerging modelling method, organoids have been applied in the study of various diseases. Their advantages include their ability to closely mirror human physiology, ease of cultivation, low cost, and high reliability; thus, they are considered to be a suitable choice to further the research on SARS-CoV-2. During the course of various studies, SARS-CoV-2 was shown to infect a variety of organoid models, exhibiting changes similar to those observed in humans. This review summarises the various organoid models used in SARS-CoV-2 research, revealing the molecular mechanisms of viral infection and exploring the drug screening tests and vaccine research that have relied on organoid models, hence illustrating the role of organoids in remodelling SARS-CoV-2 research.

Critical Signaling Transduction Pathways and Intestinal Barrier: Implications for Pathophysiology and Therapeutics

The intestinal barrier is a sum of the functions and structures consisting of the intestinal mucosal epithelium, mucus, intestinal flora, secretory immunoglobulins, and digestive juices. It is the first-line defense mechanism that resists nonspecific infections with powerful functions that include physical, endocrine, and immune defenses. Health and physiological homeostasis are greatly dependent on the sturdiness of the intestinal barrier shield, whose dysfunction can contribute to the progression of numerous types of intestinal diseases. Disorders of internal homeostasis may also induce barrier impairment and form vicious cycles during the response to diseases. Therefore, the identification of the underlying mechanisms involved in intestinal barrier function and the development of effective drugs targeting its damage have become popular research topics. Evidence has shown that multiple signaling pathways and corresponding critical molecules are extensively involved in the regulation of the barrier pathophysiological state. Ectopic expression or activation of signaling pathways plays an essential role in the process of shield destruction. Although some drugs, such as molecular or signaling inhibitors, are currently used for the treatment of intestinal diseases, their efficacy cannot meet current medical requirements. In this review, we summarize the current achievements in research on the relationships between the intestinal barrier and signaling pathways. The limitations and future perspectives are also discussed to provide new horizons for targeted therapies for restoring intestinal barrier function that have translational potential.

Organoids as a novel tool in modelling infectious diseases

Infectious diseases worldwide affect human health and have important societal impacts. A better understanding of infectious diseases is urgently needed. In vitro and in vivo infection models have brought notable contributions to the current knowledge of these diseases. Organoids are multicellular culture systems resembling tissue architecture and function, recapitulating many characteristics of human disease and elucidating mechanisms of host-infectious agent interactions in the respiratory and gastrointestinal systems, the central nervous system and the skin. Here, we discuss the applicability of the organoid technology for modeling pathogenesis, host response and features, which can be explored for the development of preventive and therapeutic treatments.

Regulatory Functions of Hypoxia in Host-Parasite Interactions: A Focus on Enteric, Tissue, and Blood Protozoa

Body tissues are subjected to various oxygenic gradients and fluctuations and hence can become transiently hypoxic. Hypoxia-inducible factor (HIF) is the master transcriptional regulator of the cellular hypoxic response and is capable of modulating cellular metabolism, immune responses, epithelial barrier integrity, and local microbiota. Recent reports have characterized the hypoxic response to various infections. However, little is known about the role of HIF activation in the context of protozoan parasitic infections. Growing evidence suggests that tissue and blood protozoa can activate HIF and subsequent HIF target genes in the host, helping or hindering their pathogenicity. In the gut, enteric protozoa are adapted to steep longitudinal and radial oxygen gradients to complete their life cycle, yet the role of HIF during these protozoan infections remains unclear. This review focuses on the hypoxic response to protozoa and its role in the pathophysiology of parasitic infections. We also discuss how hypoxia modulates host immune responses in the context of protozoan infections.

Trophozoite fitness dictates the intestinal epithelial cell response to Giardia intestinalis infection

Giardia intestinalis is a non-invasive, protozoan parasite infecting the upper small intestine of most mammals. Symptomatic infections cause the diarrhoeal disease giardiasis in humans and animals, but at least half of the infections are asymptomatic. However, the molecular underpinnings of these different outcomes of the infection are still poorly defined. Here, we studied the early transcriptional response to G. intestinalis trophozoites, the disease-causing life-cycle stage, in human enteroid-derived, 2-dimensional intestinal epithelial cell (IEC) monolayers. Trophozoites preconditioned in media that maximise parasite fitness triggered only neglectable inflammatory transcription in the IECs during the first hours of co-incubation. By sharp contrast, "non-fit" or lysed trophozoites induced a vigorous IEC transcriptional response, including high up-regulation of many inflammatory cytokines and chemokines. Furthermore, "fit" trophozoites could even suppress the stimulatory effect of lysed trophozoites in mixed infections, suggesting active G. intestinalis suppression of the IEC response. By dual-species RNA-sequencing, we defined the IEC and G. intestinalis gene expression programs associated with these differential outcomes of the infection. Taken together, our results inform on how G. intestinalis infection can lead to such highly variable effects on the host, and pinpoints trophozoite fitness as a key determinant of the IEC response to this common parasite.

Murine colon organoids as a novel model to study Trypanosoma cruzi infection and interactions with the intestinal epithelium

Chagas disease (CD) is a life-threatening illness caused by the parasite Trypanosoma cruzi (T. cruzi). With around seven million people infected worldwide and over 50,000 deaths per year, CD is a major public health issue in Latin America. The main route of transmission to humans is through a triatomine bug (vector-borne), but congenital and oral transmission have also been reported. The acute phase of CD presents mild symptoms but may develop into a long-lasting chronic illness, characterized by severely impaired cardiac, digestive, and neurological functions. The intestinal tissue appears to have a key role during oral transmission and chronic infection of CD. In this immune-privileged reservoir, dormant/quiescent parasites have been suggested to contribute to disease persistence, infection relapse, and treatment failure. However, the interaction between the intestinal epithelium and T. cruzi has not been examined in depth, in part, due to the lack of in vitro models that approximate to the biological and structural complexity of this tissue. Therefore, to understand the role played by the intestinal tissue during transmission and chronic infection, physiological models resembling the organ complexity are needed. Here we addressed this issue by establishing and characterizing adult stem cell-derived colonoid infection models that are clinically relevant for CD. 3D and 2D systems of murine intestinal organoids infected with T. cruzi Dm28c (a highly virulent strain associated with oral outbreaks) were analyzed at different time points by confocal microscopy. T. cruzi was able to invade and replicate in intestinal epithelial primary cells grown as intact organoids (3D) and monolayers (2D). The permissiveness to pathogen infection differed markedly between organoids and cell lines (primate and intestinal human cell lines). So far, this represents the first evidence of the potential that these cellular systems offer for the study of host-pathogen interactions and the discovery of effective anti-chagasic drugs.

Giardia and growth impairment in children in high-prevalence settings: consequence or co-incidence?

PURPOSE OF REVIEW

Giardia is a common intestinal parasite worldwide, and infection can be associated with clear, and sometimes persistent symptomatology. However, in children in high-prevalence settings, it is most often not associated with or is perhaps even protective against acute diarrhea. Nonetheless, recent longitudinal studies in high-prevalence settings increasingly identify an association with long-term outcomes that has been difficult to discern.

RECENT FINDINGS

Recent studies have made progress in disentangling this apparent paradox. First, prospective, well characterized cohort studies have repeatedly identified associations between Giardia infection, gut function, and child growth. Second, experimental animal and in-vitro models have further characterized the biological plausibility that Giardia could impair intestinal function and subsequently child development through different pathways, depending upon biological and environmental factors. Finally, new work has shed light on the potential for Giardia conspiring with specific other gut microbes, which may explain discrepant findings in the literature, help guide future higher resolution analyses of this pathogen, and inform new opportunities for intervention.

SUMMARY

Recent prospective studies have confirmed a high, if not universal, prevalence of persistent Giardia infections in low-and-middle income countries associated with child-growth shortfalls and altered gut permeability. However, the predominance of subclinical infections limits understanding of the true clinical impact of endemic pediatric giardiasis, and global disease burdens remain uncalculated. Integrating the role of Giardia in multipathogen enteropathies and how nutritional, microbial, metabolic, and pathogen-strain variables influence Giardia infection outcomes could sharpen delineations between pathogenic and potentially beneficial attributes of this enigmatic parasite.

Organoids in gastrointestinal diseases: from experimental models to clinical translation

We are entering an era of medicine where increasingly sophisticated data will be obtained from patients to determine proper diagnosis, predict outcomes and direct therapies. We predict that the most valuable data will be produced by systems that are highly dynamic in both time and space. Three-dimensional (3D) organoids are poised to be such a highly valuable system for a variety of gastrointestinal (GI) diseases. In the lab, organoids have emerged as powerful systems to model molecular and cellular processes orchestrating natural and pathophysiological human tissue formation in remarkable detail. Preclinical studies have impressively demonstrated that these organs-in-a-dish can be used to model immunological, neoplastic, metabolic or infectious GI disorders by taking advantage of patient-derived material. Technological breakthroughs now allow to study cellular communication and molecular mechanisms of interorgan cross-talk in health and disease including communication along for example, the gut-brain axis or gut-liver axis. Despite considerable success in culturing classical 3D organoids from various parts of the GI tract, some challenges remain to develop these systems to best help patients. Novel platforms such as organ-on-a-chip, engineered biomimetic systems including engineered organoids, micromanufacturing, bioprinting and enhanced rigour and reproducibility will open improved avenues for tissue engineering, as well as regenerative and personalised medicine. This review will highlight some of the established methods and also some exciting novel perspectives on organoids in the fields of gastroenterology. At present, this field is poised to move forward and impact many currently intractable GI diseases in the form of novel diagnostics and therapeutics.

Human duodenal organoid-derived monolayers serve as a suitable barrier model for duodenal tissue

Usually, duodenal barriers are investigated using intestinal cell lines like Caco-2, which in contrast to native tissue are limited in cell-type representation. Organoids can consist of all intestinal cell types and are supposed to better reflect the in vivo situation. Growing three-dimensionally, with the apical side facing the lumen, application of typical physiological techniques to analyze the barrier is difficult. Organoid-derived monolayers (ODMs) were developed to overcome this. After optimizing culturing conditions, ODMs were characterized and compared to Caco-2 and duodenal tissue. Tight junction composition and appearance were analyzed, and electrophysiological barrier properties, like paracellular and transcellular barrier function and macromolecule permeability, were evaluated. Furthermore, transcriptomic data were analyzed. ODMs had tight junction protein expression and paracellular barrier properties much more resembling the originating tissue than Caco-2. Transcellular barrier was similar between ODMs and native tissue but was increased in Caco-2. Transcriptomic data showed that Caco-2 expressed fewer solute carriers than ODMs and native tissue. In conclusion, while Caco-2 cells differ mostly in transcellular properties, ODMs reflect trans- and paracellular properties of the originating tissue. If cultured under optimized conditions, ODMs possess reproducible functionality, and the variety of different cell types makes them a suitable model for human tissue-specific investigations.

CFTR and Gastrointestinal Cancers: An Update

Cystic Fibrosis (CF) is a disease caused by mutations in the CFTR gene that severely affects the lungs as well as extra-pulmonary tissues, including the gastrointestinal (GI) tract. CFTR dysfunction resulting from either mutations or the downregulation of its expression has been shown to promote carcinogenesis. An example is the enhanced risk for several types of cancer in patients with CF, especially cancers of the GI tract. CFTR also acts as a tumor suppressor in diverse sporadic epithelial cancers in many tissues, primarily due to the silencing of CFTR expression via multiple mechanisms, but especially due to epigenetic regulation. This review provides an update on the latest research linking CFTR-deficiency to GI cancers, in both CF patients and in sporadic GI cancers, with a particular focus on cancer of the intestinal tract. It will discuss changes in the tissue landscape linked to CFTR-deficiency that may promote cancer development such as breakdowns in physical barriers, microbial dysbiosis and inflammation. It will also discuss molecular pathways and mechanisms that act upstream to modulate CFTR expression, such as by epigenetic silencing, as well as molecular pathways that act downstream of CFTR-deficiency, such as the dysregulation of the Wnt/β-catenin and NF-κB signaling pathways. Finally, it will discuss the emerging CFTR modulator drugs that have shown promising results in improving CFTR function in CF patients. The potential impact of these modulator drugs on the treatment and prevention of GI cancers can provide a new example of personalized cancer medicine.

Porcine Intestinal Organoids: Overview of the State of the Art

The intestinal tract is a crucial part of the body for growth and development, and its dysregulation can cause several diseases. The lack of appropriate in vitro models hampers the development of effective preventions and treatments against these intestinal tract diseases. Intestinal organoids are three-dimensional (3D) polarized structures composed of different types of cells capable of self-organization and self-renewal, resembling their organ of origin in architecture and function. Porcine intestinal organoids (PIOs) have been cultured and are used widely in agricultural, veterinary, and biomedical research. Based on the similarity of the genomic sequence, anatomic morphology, and drug metabolism with humans and the difficulty in obtaining healthy human tissue, PIOs are also considered ideal models relative to rodents. In this review, we summarize the current knowledge on PIOs, emphasizing their culturing, establishment and development, and applications in the study of host-microbe interactions, nutritional development, drug discovery, and gene editing potential.

Dual RNA Sequencing Reveals Key Events When Different Giardia Life Cycle Stages Interact With Human Intestinal Epithelial Cells In Vitro

Giardia intestinalis is a protozoan parasite causing diarrheal disease, giardiasis, after extracellular infection of humans and other mammals’ intestinal epithelial cells (IECs) of the upper small intestine. The parasite has two main life cycle stages: replicative trophozoites and transmissive cysts. Differentiating parasites (encysting cells) and trophozoites have recently been shown to be present in the same regions of the upper small intestine, whereas most mature cysts are found further down in the intestinal system. To learn more about host-parasite interactions during Giardia infections, we used an in vitro model of the parasite’s interaction with host IECs (differentiated Caco-2 cells) and Giardia WB trophozoites, early encysting cells (7 h), and cysts. Dual RNA sequencing (Dual RNAseq) was used to identify differentially expressed genes (DEGs) in both Giardia and the IECs, which might relate to establishing infection and disease induction. In the human cells, the largest gene expression changes were found in immune and MAPK signaling, transcriptional regulation, apoptosis, cholesterol metabolism and oxidative stress. The different life cycle stages of Giardia induced a core of similar DEGs but at different levels and there are many life cycle stage-specific DEGs. The metabolic protein PCK1, the transcription factors HES7, HEY1 and JUN, the peptide hormone CCK and the mucins MUC2 and MUC5A are up-regulated in the IECs by trophozoites but not cysts. Cysts specifically induce the chemokines CCL4L2, CCL5 and CXCL5, the signaling protein TRKA and the anti-bacterial protein WFDC12. The parasite, in turn, up-regulated a large number of hypothetical genes, high cysteine membrane proteins (HCMPs) and oxidative stress response genes. Early encysting cells have unique DEGs compared to trophozoites (e.g. several uniquely up-regulated HCMPs) and interaction of these cells with IECs affected the encystation process. Our data show that different life cycle stages of Giardia induce different gene expression responses in the host cells and that the IECs in turn differentially affect the gene expression in trophozoites and early encysting cells. This life cycle stage-specific host-parasite cross-talk is an important aspect to consider during further studies of Giardia’s molecular pathogenesis.

What Do In Vitro and In Vivo Models Tell Us about Anisakiasis? New Tools Still to Be Explored

Anisakiasis is a zoonosis caused by the ingestion of raw or undercooked seafood infected with third-stage larvae (L3) of the marine nematode Anisakis. Based on L3 localization in human accidental hosts, gastric, intestinal or ectopic (extra-gastrointestinal) anisakiasis can occur, in association with mild to severe symptoms of an allergic nature. Given the increasing consumption of fish worldwide, the European Food Safety Authority declared Anisakis as an emerging pathogen. Despite its importance for public health and economy, the scientific literature is largely characterized by taxonomic, systematic and ecological studies, while investigations on clinical aspects, such as the inflammatory and immune response during anisakiasis, using a proper model that simulates the niche of infection are still very scarce. The aims of this review are to describe the clinical features of anisakiasis, to report the main evidence from the in vivo and in vitro studies carried out to date, highlighting limitations, and to propose future perspectives in the study field of anisakiasis.

From 3D to 2D: Harmonization of Protocols for Two-dimensional Cultures on Cell Culture Inserts of Intestinal Organoids from Various Species

In the expanding field of intestinal organoid research, various protocols for three- and two-dimensional organoid-derived cell cultures exist. Two-dimensional organoid-derived monolayers are used to overcome some limitations of three-dimensional organoid cultures. They are increasingly used also in infection research, to study physiological processes and tissue barrier functions, where easy experimental access of pathogens to the luminal and/or basolateral cell surface is required. This has resulted in an increasing number of publications reporting different protocols and media compositions for organoid manipulation, precluding direct comparisons of research outcomes in some cases. With this in mind, here we describe a protocol aimed at the harmonization of seeding conditions for three-dimensional intestinal organoids of four commonly used research species onto cell culture inserts, to create organoid-derived monolayers that form electrophysiologically tight epithelial barriers. We give an in-depth description of media compositions and culture conditions for creating these monolayers, enabling also the less experienced researchers to obtain reproducible results within a short period of time, and which should simplify the comparison of future studies between labs, but also encourage others to consider these systems as alternative cell culture models in their research. Graphic abstract: Schematic workflow of organoid-derived monolayer generation from intestinal spheroid cultures. ECM, extracellular matrix; ODM, organoid-derived monolayer.