A Millifluidic Perfusion Cassette for Studying the Pathogenesis of Enteric Infections Using Ex-Vivo Organoids

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.

Investigating nanoplastics toxicity using advanced stem cell-based intestinal and lung in vitro models

Plastic particles in the nanometer range-called nanoplastics-are environmental contaminants with growing public health concern. As plastic particles are present in water, soil, air and food, human exposure via intestine and lung is unavoidable, but possible health effects are still to be elucidated. To better understand the Mode of Action of plastic particles, it is key to use experimental models that best reflect human physiology. Novel assessment methods like advanced cell models and several alternative approaches are currently used and developed in the scientific community. So far, the use of cancer cell line-based models is the standard approach regarding in vitro nanotoxicology. However, among the many advantages of the use of cancer cell lines, there are also disadvantages that might favor other approaches. In this review, we compare cell line-based models with stem cell-based in vitro models of the human intestine and lung. In the context of nanoplastics research, we highlight the advantages that come with the use of stem cells. Further, the specific challenges of testing nanoplastics in vitro are discussed. Although the use of stem cell-based models can be demanding, we conclude that, depending on the research question, stem cells in combination with advanced exposure strategies might be a more suitable approach than cancer cell lines when it comes to toxicological investigation of nanoplastics.

Microfluidic Device to Manipulate 3D Human Epithelial Cell-Derived Intestinal Organoids

In this study, we propose a microfluidic organoid-trapping device used to immobilize human intestinal organoids and apply fluidic stimuli to them. The proposed device has a microchannel with a trapping region with wall gaps between the channel walls and the bottom surface, and a constriction to clog the organoids in the channel. Since the introduced culture medium escapes from the gap, organoids can be cultured without excessive deformation by hydrostatic pressure. Owing to the characteristics of the organoid-trapping device, we succeeded in trapping human intestinal organoids in the channel. Furthermore, to demonstrate the applicability of the device for culturing intestinal organoids, we induced organoid fusion to form large organoids by aligning the organoids in the channel and applying fluidic shear stress to the organoids to regulate their surface structures. Therefore, we believe that organoid-trapping devices will be useful for investigating organoids aligned or loaded with fluidic stimulation.

Organoids to Dissect Gastrointestinal Virus-Host Interactions: What Have We Learned?

Historically, knowledge of human host-enteric pathogen interactions has been elucidated from studies using cancer cells, animal models, clinical data, and occasionally, controlled human infection models. Although much has been learned from these studies, an understanding of the complex interactions between human viruses and the human intestinal epithelium was initially limited by the lack of nontransformed culture systems, which recapitulate the relevant heterogenous cell types that comprise the intestinal villus epithelium. New investigations using multicellular, physiologically active, organotypic cultures produced from intestinal stem cells isolated from biopsies or surgical specimens provide an exciting new avenue for understanding human specific pathogens and revealing previously unknown host-microbe interactions that affect replication and outcomes of human infections. Here, we summarize recent biologic discoveries using human intestinal organoids and human enteric viral pathogens.

Experimental Methods to Study the Pathogenesis of Human Enteric RNA Viruses

Every year, millions of children are infected with viruses that target the gastrointestinal tract, causing acute gastroenteritis and diarrheal illness. Indeed, approximately 700 million episodes of diarrhea occur in children under five annually, with RNA viruses norovirus, rotavirus, and astrovirus serving as major causative pathogens. Numerous methodological advancements in recent years, including the establishment of novel cultivation systems using enteroids as well as the development of murine and other animal models of infection, have helped provide insight into many features of viral pathogenesis. However, many aspects of enteric viral infections remain elusive, demanding further study. Here, we describe the different in vitro and in vivo tools available to explore different pathophysiological attributes of human enteric RNA viruses, highlighting their advantages and limitations depending upon the question being explored. In addition, we discuss key areas and opportunities that would benefit from further methodological progress.