Human intestinal organoids as models to study enteric bacteria and viruses

The 3C (Cell Culture, Computer Simulation, Clinical Trial) Solution for Optimizing the 3R (Replace, Reduction, Refine) Framework during Preclinical Research Involving Laboratory Animals

Preclinical research has traditionally utilized laboratory animals to elucidate the safety, tolerability, pharmacokinetics, and pharmacodynamics of new chemical entities prior to human trials. The use of animal models has been pivotal in advancing scientific knowledge and medical breakthroughs, contributing significantly to our understanding of the complex biological processes and human diseases. However, many promising treatments that have demonstrated efficacy in animal studies have failed to translate to human subjects during clinical trials. Consequently, animal testing faces ethical concerns and criticism regarding its predictive reliability for human responses. This has led to the development of 3R principles (Replacement, Reduction, Refinement), introduced in 1959, advocating for alternative methods and improved animal welfare in research. Furthermore, regulatory frameworks and recent legislation, such as the 2022 FDA Modernisation Act, emphasize modern scientific alternatives to traditional animal testing. Emerging approaches, known as the 3Cs-cell culture, computer simulation, and phase 0 clinical trials-offer promising nonanimal solutions that could accelerate drug development and address ethical concerns, potentially rendering preclinical research more humane and efficient.

Intestinal organoid coculture systems: current approaches, challenges, and future directions

The intestinal microenvironment represents a complex and dynamic ecosystem, comprising a diverse range of epithelial and nonepithelial cells, a protective mucus layer, and a diverse community of gut microbiota. Understanding the intricate interplay between these components is essential for uncovering the mechanisms underlying intestinal health and disease. The development of intestinal organoids, three-dimensional (3-D) mini-intestines that closely mimic the architecture, cellular diversity, and functionality of the intestine, offers a powerful platform for investigating different aspects of intestinal physiology and pathology. However, current intestinal organoid models, mainly adult stem cell-derived organoids, lack the nonepithelial and microbial components of the intestinal microenvironment. As such, several coculture systems have been developed to coculture intestinal organoids with other intestinal elements including microbes (bacteria and viruses) and immune, stromal, and neural cells. These coculture models allow researchers to recreate the complex intestinal environment and study the intricate cross talk between different components of the intestinal ecosystem under healthy and pathological conditions. Currently, there are several approaches and methodologies to establish intestinal organoid cocultures, and each approach has its own strengths and limitations. This review discusses the existing methods for coculturing intestinal organoids with different intestinal elements, focusing on the methodological approaches, strengths and limitations, and future directions.

Applying 3D cultures and high-throughput technologies to study host-pathogen interactions

Recent advances in cell culturing and DNA sequencing have dramatically altered the field of human microbiome research. Three-dimensional (3D) cell culture is an important tool in cell biology, in cancer research, and for studying host-microbe interactions, as it mimics the in vivo characteristics of the host environment in an in vitro system, providing reliable and reproducible models. This work provides an overview of the main 3D culture techniques applied to study interactions between host cells and pathogenic microorganisms, how these systems can be integrated with high-throughput molecular methods, and how multi-species model systems may pave the way forward to pinpoint interactions among host, beneficial microbes and pathogens.

Virulence expression difference to intestinal cells of different pathogenic Listeria monocytogenes contaminating sausages after simulated digestive tract

This study investigated the difference in survival among Listeria monocytogenes (LM) 10403S (highly pathogenic strain) and M7 (low pathogenic strain) in sausage under a simulated digestive environment, and established intestinal organoids and macrophages co-culture model to further explore the virulence expression difference to intestinal cells between LM 10403S and M7 after in vitro gastrointestinal digestion. Results showed that, compared with LM M7, LM 10403S exhibited a high survival rate during in vitro digestion, which may be due to the increased expression of stress response-related genes. In addition, the expression of virulence genes in LM 10403S was significantly higher than in LM M7 under the gastrointestinal environment. Furthermore, in the intestinal organoids and macrophages co-culture model infected by LM 10403S and M7 after in vitro gastrointestinal digestion, results showed that, compared with the LM M7 group, the LM 10403S group had significantly lower budding rate and significantly higher mortality of organoids. Also, the significantly increased LDH release and inflammatory factors (TNF-α and IL-1β) in the LM 10403S group were observed, and the main virulence genes (iap, inlA, inlB, actA, hly, plcA, and plcB) of 10403S were significantly highly expressed than LM M7 during the cell infection. These results reflected that the reason for the different pathogenicity between LM 10403S and M7 may be due to the high tolerance and the expression of virulence genes than LM M7 during gastrointestinal digestion and cell infection, which would be expected to provide a better understanding of the infection mechanisms among different pathogenic strains of L. monocytogenes in food.

Reverse Genetics of Murine Rotavirus: A Comparative Analysis of the Wild-Type and Cell-Culture-Adapted Murine Rotavirus VP4 in Replication and Virulence in Neonatal Mice

Small-animal models and reverse genetics systems are powerful tools for investigating the molecular mechanisms underlying viral replication, virulence, and interaction with the host immune response in vivo. Rotavirus (RV) causes acute gastroenteritis in many young animals and infants worldwide. Murine RV replicates efficiently in the intestines of inoculated suckling pups, causing diarrhea, and spreads efficiently to uninoculated littermates. Because RVs derived from human and other non-mouse animal species do not replicate efficiently in mice, murine RVs are uniquely useful in probing the viral and host determinants of efficient replication and pathogenesis in a species-matched mouse model. Previously, we established an optimized reverse genetics protocol for RV and successfully generated a murine-like RV rD6/2-2g strain that replicates well in both cultured cell lines and in the intestines of inoculated pups. However, rD6/2-2g possesses three out of eleven gene segments derived from simian RV strains, and these three heterologous segments may attenuate viral pathogenicity in vivo. Here, we rescued the first recombinant RV with all 11 gene segments of murine RV origin. Using this virus as a genetic background, we generated a panel of recombinant murine RVs with either N-terminal VP8* or C-terminal VP5* regions chimerized between a cell-culture-adapted murine ETD strain and a non-tissue-culture-adapted murine EW strain and compared the diarrhea rate and fecal RV shedding in pups. The recombinant viruses with VP5* domains derived from the murine EW strain showed slightly more fecal shedding than those with VP5* domains from the ETD strain. The newly characterized full-genome murine RV will be a useful tool for dissecting virus-host interactions and for studying the mechanism of pathogenesis in neonatal mice.