Establishment of a system to evaluate the therapeutic effect and the dynamics of an investigational drug on ulcerative colitis using human colonic organoids

Harnessing 3D models to uncover the mechanisms driving infectious and inflammatory disease in the intestine

Representative 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.

Development of an Evaluation System Using Intestinal Organoids for Drug Efflux Transport Analysis by an Imaging Approach

There are several in vitro systems that enable evaluation of the absorption direction, but there are few quantitative systems that enable easy evaluation of the excretion direction. Enteroids, organoids derived from intestine, have been frozen and passaged for various research. But it is not clear how the freezing and passaging affect the expression and function of transporters. We investigated the effects of passage and cryopreservation of enteroids. We focused on P-gp (P-glycoprotein) and compared the transfer rates of rhodamine 123 (Rh123) into the lumen of enteroids with and without a P-gp inhibitor. mRNA expression levels did not change significantly before and after passage and cryopreservation. Accumulation of Rh123 in the lumen of enteroids was observed. With some P-gp inhibitors, excretion of Rh123 into the lumen of enteroids was inhibited and the nonexcreted Rh123 accumulated in enteroids epithelial cells. The transfer rate of Rh123 into the lumen of enteroids with a P-gp inhibitor was significantly decreased compared to that of without a P-gp inhibitor. Before and after passage and cryopreservation, the transfer rate was almost the same as that of primary cultured enteroids. We succeeded in easily evaluating whether a component is a substrate of P-gp using enteroids.

Gastrointestinal tract organoids as novel tools in drug discovery

Organoids, characterized by their high physiological attributes, effectively preserve the genetic characteristics, physiological structure, and function of the simulated organs. Since the inception of small intestine organoids, other organoids for organs including the liver, lungs, stomach, and pancreas have subsequently been developed. However, a comprehensive summary and discussion of research findings on gastrointestinal tract (GIT) organoids as disease models and drug screening platforms is currently lacking. Herein, in this review, we address diseases related to GIT organoid simulation and highlight the notable advancements that have been made in drug screening and pharmacokinetics, as well as in disease research and treatment using GIT organoids. Organoids of GIT diseases, including inflammatory bowel disease, irritable bowel syndrome, necrotizing enterocolitis, and Helicobacter pylori infection, have been successfully constructed. These models have facilitated the study of the mechanisms and effects of various drugs, such as metformin, Schisandrin C, and prednisolone, in these diseases. Furthermore, GIT organoids have been used to investigate viruses that elicit GIT reactions, including Norovirus, SARS-CoV-2, and rotavirus. Previous studies by using GIT organoids have shown that dasabuvir, gemcitabine, and imatinib possess the capability to inhibit viral replication. Notably, GIT organoids can mimic GIT responses to therapeutic drugs at the onset of disease. The GIT toxicities of compounds like gefitinib, doxorubicin, and sunset yellow have also been evaluated. Additionally, these organoids are instrumental for the study of immune regulation, post-radiation intestinal epithelial repair, treatment for cystic fibrosis and diabetes, the development of novel drug delivery systems, and research into the GIT microbiome. The recent use of conditioned media as a culture method for replacing recombinant hepatocyte growth factor has significantly reduced the cost associated with human GIT organoid culture. This advancement paves the way for large-scale culture and compound screening of GIT organoids. Despite the ongoing challenges in GIT organoid development (e.g., their inability to exist in pairs, limited cell types, and singular drug exposure mode), these organoids hold considerable potential for drug screening. The use of GIT organoids in this context holds great promises to enhance the precision of medical treatments for patients living with GIT diseases.

Identification and immunoinfiltration analysis of key genes in ulcerative colitis using WGCNA

Objective

Ulcerative colitis (UC) is a chronic non-specific inflammatory bowel disease characterized by an unclear pathogenesis. This study aims to screen out key genes related to UC pathogenesis.

Methods

Bioinformatics analysis was conducted for screening key genes linked to UC pathogenesis, and the expression of the screened key genes was verified by establishing a UC mouse model.

Results

Through bioinformatics analysis, five key genes were obtained. Subsequent infiltration analysis revealed seven significantly different immune cell types between the UC and general samples. Additionally, animal experiment results illustrated markedly decreased body weight, visible colonic shortening and damage, along with a significant increase in the DAI score of the DSS-induced mice in the UC group in comparison with the NC group. In addition, H&E staining results demonstrated histological changes including marked inflammatory cell infiltration, loss of crypts, and epithelial destruction in the colon mucosa epithelium. qRT-PCR analysis indicated a down-regulation of ABCG2 and an up-regulation of IL1RN, REG4, SERPINB5 and TRIM29 in the UC mouse model. Notably, this observed trend showed a significant dependence on the concentration of DSS, with the mouse model of UC induced by 7% DSS demonstrating a more severe disease state compared to that induced by 5% DSS.

Conclusion

ABCG2, IL1RN, REG4, SERPINB5 and TRIM29 were screened out as key genes related to UC by bioinformatics analysis. The expression of ABCG2 was down-regulated, and that of IL1RN, REG4, SERPINB5 and TRIM29 were up-regulated in UC mice as revealed by animal experiments.

Mechanism of Acupuncture and Moxibustion on Promoting Mucosal Healing in Ulcerative Colitis

The latest guideline about ulcerative colitis (UC) clinical practice stresses that mucosal healing, rather than anti-inflammation, is the main target in UC clinical management. Current mucosal dysfunction mainly closely relates to the endoscopic intestinal wall (mechanical barrier) injury with the imbalance between intestinal epithelial cells (IECs) regeneration and death, as well as tight junction (TJ) dysfunction. It is suggested that biological barrier (gut microbiota), chemical barrier (mucus protein layer, MUC) and immune barrier (immune cells) all take part in the imbalance, leading to mechanical barrier injury. Lots of experimental studies reported that acupuncture and moxibustion on UC recovery by adjusting the gut microbiota, MUC and immune cells on multiple targets and pathways, which contributes to the balance of IEC regeneration and death, as well as TJ structure recovery in animals. Moreover, the validity and superiority of acupuncture and moxibustion were also demonstrated in clinic. This study aims to review the achievements of acupuncture and moxibustion on mucosal healing and analyse the underlying mechanisms.

A multi-mineral intervention to counter pro-inflammatory activity and to improve the barrier in human colon organoids

Introduction: Ulcerative colitis is a chronic inflammatory condition, and continuous inflammatory stimulus may lead to barrier dysfunction. The goal of this study was to assess barrier proteomic expression by a red algae-derived multi-mineral intervention in the absence or presence of pro-inflammatory insult. Methods: Human colon organoids were maintained in a control culture medium alone or exposed to lipopolysaccharide with a combination of three pro-inflammatory cytokines [tumor necrosis factor-α, interleukin-1β and interferon-γ (LPS-cytokines)] to mimic the environment in the inflamed colon. Untreated organoids and those exposed to LPS-cytokines were concomitantly treated for 14 days with a multi-mineral product (Aquamin®) that has previously been shown to improve barrier structure/function. The colon organoids were subjected to proteomic analysis to obtain a broad view of the protein changes induced by the two interventions alone and in combination. In parallel, confocal fluorescence microscopy, tissue cohesion and transepithelial electrical resistance (TEER) measurements were used to assess barrier structure/function. Results: The LPS-cytokine mix altered the expression of multiple proteins that influence innate immunity and promote inflammation. Several of these were significantly decreased with Aquamin® alone but only a modest decrease in a subset of these proteins was detected by Aquamin® in the presence of LPS-cytokines. Among these, a subset of inflammation-related proteins including fibrinogen-β and -γ chains (FGB and FGG), phospholipase A2 (PLA2G2A) and SPARC was significantly downregulated in the presence of Aquamin® (alone and in combination with LPS-cytokines); another subset of proteins with anti-inflammatory, antioxidant or anti-microbial activity was upregulated by Aquamin® treatment. When provided alone, Aquamin® strongly upregulated proteins that contribute to barrier formation and tissue strength. Concomitant treatment with LPS-cytokines did not inhibit barrier formation in response to Aquamin®. Confocal microscopy also displayed increased expression of desmoglein-2 (DSG2) and cadherin-17 (CDH17) with Aquamin®, either alone or in the presence of the pro-inflammatory stimulus. Increased cohesion and TEER with Aquamin® (alone or in the presence of LPS-cytokines) indicates improved barrier function. Conclusion: Taken together, these findings suggest that multi-mineral intervention (Aquamin®) may provide a novel approach to combating inflammation in the colon by improving barrier structure/function as well as by directly altering the expression of certain pro-inflammatory proteins.

Organoids are not organs: Sources of variation and misinformation in organoid biology

In the past decade, the term organoid has moved from obscurity to common use to describe a 3D in vitro cellular model of a tissue that recapitulates structural and functional elements of the in vivo organ it models. The term organoid is now applied to structures formed as a result of two distinct processes: the capacity for adult epithelial stem cells to re-create a tissue niche in vitro and the ability to direct the differentiation of pluripotent stem cells to a 3D self-organizing multicellular model of organogenesis. While these two organoid fields rely upon different stem cell types and recapitulate different processes, both share common challenges around robustness, accuracy, and reproducibility. Critically, organoids are not organs. This commentary serves to discuss these challenges, how they impact genuine utility, and shine a light on the need to improve the standards applied to all organoid approaches.

Paeoniflorin promotes intestinal stem cell-mediated epithelial regeneration and repair via PI3K-AKT-mTOR signalling in ulcerative colitis

Ulcerative colitis (UC) is a chronic and immune-mediated inflammatory disorder characterized by abdominal pain, diarrhoea, and haematochezia. The goal of clinical therapy for UC is mucosal healing, accomplished by regenerating and repairing the intestinal epithelium. Paeoniflorin (PF) is a natural ingredient extracted from Paeonia lactiflora that has significant anti-inflammatory and immunoregulatory efficacy. In this study, we investigated how PF could regulate the renewal and differentiation of intestinal stem cells (ISCs) to improve the regeneration and repair of the intestinal epithelium in UC. Our experimental results showed that PF significantly alleviated colitis induced by dextran sulfate sodium (DSS) and ameliorated intestinal mucosal injury by regulating the renewal and differentiation of ISCs. The mechanism by which PF regulates ISCs was confirmed to be through PI3K-AKT-mTOR signalling. In vitro, we found that PF not only improved the growth of TNF-α-induced colon organoids but also increased the expression of genes and proteins related to the differentiation and regeneration of ISCs. Furthermore, PF promoted the repair ability of lipopolysaccharide (LPS)-induced IEC-6 cells. The mechanism by which PF regulates ISCs was further confirmed and was consistent with the in vivo results. Overall, these findings demonstrate that PF accelerates epithelial regeneration and repair by promoting the renewal and differentiation of ISCs, suggesting that PF treatment may be beneficial to mucosal healing in UC patients.

Comprehensive protocols for culturing and molecular biological analysis of IBD patient-derived colon epithelial organoids

There are many unanswered questions regarding responses to proinflammatory signals in intestinal epithelial cells (IECs). For example, chemokines secreted by IECs upon external stimuli play multifunctional roles in both homeostasis and during inflammation. Several chemokines are upregulated during active inflammatory bowel disease (IBD), which is associated with an increased influx of immune cells into the gut mucosa. Therefore, studies on how chemokines are regulated in the intestinal epithelium may identify putative treatment targets in IBD. More recently, patient-derived ex vivo models such as intestinal organoids have facilitated molecular analysis of epithelial alterations in IBD patients own cells. Here, we describe refined experimental protocols and methods for the generation and maintenance of IBD patient-derived colonic organoids (colonoids) culture. We also give detailed description of medium, and supplements needed for colonoid establishment, growth, and differentiation, including production of Wnt-3A and Rspondin1 enriched media. Further, we present protocols for RNA and protein isolation from human colonoids, and subsequent gene expression analysis and Western blotting for e.g., signal transduction studies. We also describe how to process colonoids for chemokine protein expression analysis such as immunostaining, confocal imaging, and detection of secreted chemokines by e.g., enzyme-linked immunosorbent assay (ELISA). As proof of principle, we give examples of how the chemoattractant CCL20 can be regulated and expressed in colonoids derived from IBD-patients and healthy controls upon ligands-driven inflammation.

Tumor-Derived Lysophosphatidic Acid Blunts Protective Type I Interferon Responses in Ovarian Cancer

Lysophosphatidic acid (LPA) is a bioactive lipid enriched in the tumor microenvironment of immunosuppressive malignancies such as ovarian cancer. Although LPA enhances the tumorigenic attributes of cancer cells, the immunomodulatory activity of this phospholipid messenger remains largely unexplored. Here, we report that LPA operates as a negative regulator of type I interferon (IFN) responses in ovarian cancer. Ablation of the LPA-generating enzyme autotaxin (ATX) in ovarian cancer cells reprogrammed the tumor immune microenvironment, extended host survival, and improved the effects of therapies that elicit protective responses driven by type I IFN. Mechanistically, LPA sensing by dendritic cells triggered PGE2 biosynthesis that suppressed type I IFN signaling via autocrine EP4 engagement. Moreover, we identified an LPA-controlled, immune-derived gene signature associated with poor responses to combined PARP inhibition and PD-1 blockade in patients with ovarian cancer. Controlling LPA production or sensing in tumors may therefore be useful to improve cancer immunotherapies that rely on robust induction of type I IFN.

SIGNIFICANCE

This study uncovers that ATX-LPA is a central immunosuppressive pathway in the ovarian tumor microenvironment. Ablating this axis sensitizes ovarian cancer hosts to various immunotherapies by unleashing protective type I IFN responses. Understanding the immunoregulatory programs induced by LPA could lead to new biomarkers predicting resistance to immunotherapy in patients with cancer. See related commentary by Conejo-Garcia and Curiel, p. 1841. This article is highlighted in the In This Issue feature, p. 1825.

Interleukin-27 Regulates the Function of the Gastrointestinal Epithelial Barrier in a Human Tissue-Derived Organoid Model

A treatment with direct healing effects on the gastrointestinal epithelial barrier is desirable for inflammatory bowel disease (IBD). Interleukin-27 (IL-27) is an immunoregulatory cytokine, and oral delivery is an effective treatment in murine models of IBD. We aimed to define IL-27 effects on the human gastrointestinal epithelial barrier. We characterised gene and protein expression of permeability mediators in a human colon-derived organoid model. Functional permeability was determined in an organoid-derived 2D monolayer by transepithelial electrical resistance. IL-27 effects on epithelial innate immune responses were assessed through expression of cytokines, anti-microbial peptides and MUC genes. IL-27 effects on wound healing and proliferation were determined in human colon epithelial cell lines. IL-27 led to restoration of permeability regulation following inflammatory cytokine insult (p = 0.001), associated with differential expression of tight junction mediators with decrease in claudin 2 (p = 0.024) and increase in claudin 4 (p < 0.001), E-cadherin (p < 0.001) and zona occludens (p = 0.0014). IL-27 evoked differential gene expression of epithelial-derived innate immune responses (reduced IL1B and IL18, and increased IL33, HBD1, MUC1 and MUC2; p < 0.012). IL-27 induced epithelial barrier wound healing through restitution (p < 0.001), and increased proliferation (p < 0.001) following injury. Overall, IL-27 provokes mucosal healing of the human gastrointestinal epithelial barrier.

Importance of Telomere Shortening in the Pathogenesis of Ulcerative Colitis: A New Treatment From the Aspect of Telomeres in Intestinal Epithelial Cells

BACKGROUND AND AIMS

Ulcerative colitis [UC] is a chronic inflammatory disease of the colon with frequent relapses. Telomere shortening in intestinal epithelial cells has been reported in severe or longstanding cases. However, its influence on UC pathogenesis remains unelucidated. To this end, we evaluated telomere shortening using a long-term organoid inflammation model that we had originally established.

METHODS

A UC model using human colon organoids was established to assess telomere changes chronologically. MST-312 was used for the telomerase inhibition assay. The potential of telomerase activators as a novel UC treatment was evaluated with an in vitro model, including microarray analysis, and histological changes were assessed using xenotransplantation into mouse colonic mucosa.

RESULTS

Our UC model reproduced telomere shortening in vitro, which was induced by the continuous suppression of telomerase activity via P53. MST-312-based analysis revealed that telomere shortening was involved in the pathogenesis of UC. Madecassoside [MD] improved the telomere length of the UC model and UC patient-derived organoids, which further promoted cell proliferation in vitro and improved the graft take-rate of xenotransplantation. Moreover, histological analysis revealed that MD induced normal crypt structure with abundant goblet cells.

CONCLUSIONS

This study is the first to reveal the mechanism and importance of telomere shortening in the pathogenesis of UC. MD could be a novel candidate for UC treatment beyond endoscopic mucosal healing.

Schlafen 11 Is a Novel Target for Mucosal Regeneration in Ulcerative Colitis

BACKGROUND AND AIMS

Ulcerative colitis [UC] is a chronic inflammatory disease of the colon with an intractable course. Although the goal of UC therapy is to achieve mucosal healing, the pathogenesis of mucosal injury caused by chronic inflammation remains unknown. We therefore aim to elucidate molecular mechanisms of mucosal injury by establishing in vitro and in vivo humanised UC-mimicking models.

METHODS

An in vitro model using human colon organoids was established by 60 weeks of inflammatory stimulation. The key gene for mucosal injury caused by long-term inflammation was identified by microarray analysis. An in vivo model was established by xenotransplantation of organoids into mouse colonic mucosa.

RESULTS

An in vitro model demonstrated that long-term inflammation induced irrecoverable changes in organoids: inflammatory response and apoptosis with oxidative stress and suppression of cell viability. This model also mimicked organoids derived from patients with UC at the gene expression and phenotype levels. Microarray analysis revealed Schlafen11 [SLFN11] was irreversibly induced by long-term inflammation. Consistently, SLFN11 was highly expressed in UC mucosa but absent in normal mucosa. The knockdown of SLFN11 [SLFN11-KD] suppressed apoptosis of intestinal epithelial cells [IECs] induced by inflammation. Moreover, SLFN11-KD improved the take rates of xenotransplantation and induced the regenerative changes of crypts observed in patients with UC in remission.

CONCLUSIONS

In vitro and in vivo UC-mimicking models were uniquely established using human colonic organoids. They revealed that SLFN11 is significant for mucosal injury in UC, and demonstrated its potential as a novel target for mucosal regeneration.

Biomaterials for intestinal organoid technology and personalized disease modeling

Recent advances in intestinal organoid technologies have paved the way for in vitro recapitulation of the homeostatic renewal of adult tissues, tissue or organ morphogenesis during development, and pathogenesis of many disorders. In vitro modelling of individual patient diseases using organoid systems have been considered key in establishing rational design of personalized treatment strategies and in improving therapeutic outcomes. In addition, the transplantation of organoids into diseased tissues represents a novel approach to treat currently incurable diseases. Emerging evidence from intensive studies suggests that organoid systems' development and functional maturation depends on the presence of an extracellular matrix with suitable biophysical properties, where advanced synthetic hydrogels open new avenues for theoretical control of organoid phenotypes and potential applications of organoids in therapeutic purposes. In this review, we discuss the status, applications, challenges and perspectives of intestinal organoid systems emphasising on hydrogels and their properties suitable for intestinal organoid culture. We provide an overview of hydrogels used for intestinal organoid culture and key factors regulating their biological activity. The comparison of different hydrogels would be a theoretical basis for establishing design principles of synthetic niches directing intestinal cell fates and functions. STATEMENT OF SIGNIFICANCE: Intestinal organoid is an in vitro recapitulation of the gut, which self-organizes from intestinal stem cells and maintains many features of the native tissue. Since the development of this technology, intestinal organoid systems have made significant contribution to rapid progress in intestinal biology. Prevailing methodology for organoid culture, however, depends on animal-derived matrices and suffers from variability and potential risk for contamination of pathogens, limiting their therapeutic application. Synthetic scaffold matrices, hydrogels, might provide solutions to these issues and deepen our understanding on how intestinal cells sense and respond to key biophysical properties of the surrounding matrices. This review provides an overview of developing intestinal models and biomaterials, thereby leading to better understanding of current intestinal organoid systems for both biologists and materials scientists.

An alternative approach to produce versatile retinal organoids with accelerated ganglion cell development

Genetically complex ocular neuropathies, such as glaucoma, are a major cause of visual impairment worldwide. There is a growing need to generate suitable human representative in vitro and in vivo models, as there is no effective treatment available once damage has occured. Retinal organoids are increasingly being used for experimental gene therapy, stem cell replacement therapy and small molecule therapy. There are multiple protocols for the development of retinal organoids available, however, one potential drawback of the current methods is that the organoids can take between 6 weeks and 12 months on average to develop and mature, depending on the specific cell type wanted. Here, we describe and characterise a protocol focused on the generation of retinal ganglion cells within an accelerated four week timeframe without any external small molecules or growth factors. Subsequent long term cultures yield fully differentiated organoids displaying all major retinal cell types. RPE, Horizontal, Amacrine and Photoreceptors cells were generated using external factors to maintain lamination.

Organoid Models of Colorectal Pathology: Do They Hold the Key to Personalized Medicine? A Systematic Review

BACKGROUND

Colorectal cancer and IBD account for a large portion of the practice of colorectal surgery. Historical research models have provided insights into the underlying causes of these diseases but come with many limitations.

OBJECTIVE

The aim of this study was to systematically review the literature regarding the advantage of organoid models in modeling benign and malignant colorectal pathology.

DATA SOURCES

Sources included PubMed, Ovid-Medline, and Ovid Embase STUDY SELECTION:: Two reviewers completed a systematic review of the literature between January 2006 and January of 2020 for studies related to colon and intestinal organoids. Reviews, commentaries, protocols, and studies not performed in humans or mice were excluded.

RESULTS

A total of 73 articles were included. Organoid models of colorectal disease have been rising in popularity to further elucidate the genetic, transcriptomic, and treatment response of these diseases at the individual level. Increasingly complex models utilizing coculture techniques are being rapidly developed that allow in vitro recapitulation of the disease microenvironment.

LIMITATIONS

This review is only qualitative, and the lack of well utilized nomenclature in the organoid community may have resulted in the exclusion of articles.

CONCLUSIONS

Historical disease models including cell lines, patient-derived tumor xenografts, and animal models have created a strong foundation for our understanding of colorectal pathology. Recent advances in 3-dimensional cell cultures, in the form of patient-derived epithelial organoids and induced human intestinal organoids have opened a new avenue for high-resolution analysis of pathology at the level of an individual patient. Recent research has shown the potential of organoids as a tool for personalized medicine with their ability to retain patient characteristics, including treatment response.

Enteroids Generated from Patients with Severe Inflammation in Crohn's Disease Maintain Alterations of Junctional Proteins

BACKGROUND

The mechanisms underlying loss of intestinal epithelial barrier [IEB] function in Crohn's disease [CD] are poorly understood. We tested whether human enteroids generated from isolated intestinal crypts of CD patients serve as an appropriate in vitro model to analyse changes of IEB proteins observed in patients' specimens.

METHODS

Gut samples from CD patients and healthy individuals who underwent surgery were collected. Enteroids were generated from intestinal crypts and analyses of junctional proteins in comparison to full wall samples were performed.

RESULTS

Histopathology confirmed the presence of CD and the extent of inflammation in intestinal full wall sections. As revealed by immunostaining and Western blot analysis, profound changes in expression patterns of tight junction, adherens junction and desmosomal proteins were observed in full wall specimens when CD was present. Unexpectedly, when enteroids were generated from specimens of CD patients with severe inflammation, alterations of most tight junction proteins and the majority of changes in desmosomal proteins but not E-cadherin were maintained under culture conditions. Importantly, these changes were maintained without any additional stimulation of cytokines. Interestingly, qRT-PCR demonstrated that mRNA levels of junctional proteins were not different when enteroids from CD patients were compared to enteroids from healthy controls.

CONCLUSIONS

These data indicate that enteroids generated from patients with severe inflammation in CD maintain some characteristics of intestinal barrier protein changes on a post-transcriptional level. The enteroid in vitro model represents an appropriate tool to gain further cellular and molecular insights into the pathogenesis of barrier dysfunction in CD.

Enhancing responsiveness of human jejunal enteroids to host and microbial stimuli

KEY POINTS

Enteroids are a physiologically relevant model to examine the human intestine and its functions. Previously, the measurable cytokine response of human intestinal enteroids has been limited following exposure to host or microbial pro-inflammatory stimuli. Modifications to enteroid culture conditions facilitated robust human cytokine responses to pro-inflammatory stimuli. This new human enteroid culture methodology refines the ability to study microbiome:human intestinal epithelium interactions in the laboratory.

ABSTRACT

The intestinal epithelium is the primary interface between the host, the gut microbiome and its external environment. Since the intestinal epithelium contributes to innate immunity as a first line of defence, understanding how the epithelium responds to microbial and host stimuli is an important consideration in promoting homeostasis. Human intestinal enteroids (HIEs) are primary epithelial cell cultures that can provide insights into the biology of the intestinal epithelium and innate immune responses. One potential limitation of using HIEs for innate immune studies is the relative lack of responsiveness to factors that stimulate epithelial cytokine production. We report technical refinements, including removal of extracellular antioxidants, to facilitate enhanced cytokine responses in HIEs. Using this new method, we demonstrate that HIEs have distinct cytokine profiles in response to pro-inflammatory stimuli derived from host and microbial sources. Overall, we found that host-derived cytokines tumour necrosis factor and interleukin-1α stimulated reactive oxygen species and a large repertoire of cytokines. In contrast, microbial lipopolysaccharide, lipoteichoic acid and flagellin stimulated a limited number of cytokines and histamine did not stimulate the release of any cytokines. Importantly, HIE-secreted cytokines were functionally active, as denoted by the ability of human blood-derived neutrophil to migrate towards HIE supernatant containing interleukin-8. These findings establish that the immune responsiveness of HIEs depends on medium composition and stimuli. By refining the experimental culture medium and creating an environment conducive to epithelial cytokine responses by human enteroids, HIEs can facilitate exploration of many experimental questions pertaining to the role of the intestinal epithelium in innate immunity.

Microphysiological systems for ADME-related applications: current status and recommendations for system development and characterization

Over the last decade, progress has been made on the development of microphysiological systems (MPS) for absorption, distribution, metabolism, and excretion (ADME) applications. Central to this progress has been proof of concept data generated by academic and industrial institutions followed by broader characterization studies, which provide evidence for scalability and applicability to drug discovery and development. In this review, we describe some of the advances made for specific tissue MPS and outline the desired functionality for such systems, which are likely to make them applicable for practical use in the pharmaceutical industry. Single organ MPS platforms will be valuable for modelling tissue-specific functions. However, dynamic organ crosstalk, especially in the context of disease or toxicity, can only be obtained with the use of inter-linked MPS models which will enable scientists to address questions at the intersection of pharmacokinetics (PK) and efficacy, or PK and toxicity. In the future, successful application of MPS platforms that closely mimic human physiology may ultimately reduce the need for animal models to predict ADME outcomes and decrease the overall risk and cost associated with drug development.

Intestinal enteroids/organoids: A novel platform for drug discovery in inflammatory bowel diseases

The introduction of biologics such as anti-tumor necrosis factor (TNF) monoclonal antibodies followed by anti-integrins has dramatically changed the therapeutic paradigm of inflammatory bowel diseases (IBD). Furthermore, a newly developed anti-p40 subunit of interleukin (IL)-12 and IL-23 (ustekinumab) has been recently approved in the United States for patients with moderate to severe Crohn’s disease who have failed treatment with anti-TNFs. However, these immunosuppressive therapeutics which focus on anti-inflammatory mechanisms or immune cells still fail to achieve long-term remission in a significant percentage of patients. This strongly underlines the need to identify novel treatment targets beyond immune suppression to treat IBD. Recent studies have revealed the critical role of intestinal epithelial cells (IECs) in the pathogenesis of IBD. Physical, biochemical and immunologic driven barrier dysfunctions of epithelial cells contribute to the development of IBD. In addition, the recent establishment of adult stem cell-derived intestinal enteroid/organoid culture technology has allowed an exciting opportunity to study human IECs comprising all normal epithelial cells. This long-term epithelial culture model can be generated from endoscopic biopsies or surgical resections and recapitulates the tissue of origin, representing a promising platform for novel drug discovery in IBD. This review describes the advantages of intestinal enteroids/organoids as a research tool for intestinal diseases, introduces studies with these models in IBD, and gives a description of the current status of therapeutic approaches in IBD. Finally, we provide an overview of the current endeavors to identify a novel drug target for IBD therapy based on studies with human enteroids/organoids and describe the challenges in using enteroids/organoids as an IBD model.