Intestinal organoids as the model for pathogen-host interactions

The intestinal epithelium is an important barrier against pathogens in the lumen. Tight junctions between epithelial cells reduce the possibility of pathogens to pass through the mucosa and infect the host. A kind of specialized epithelial cell, known as microfold cells (M cells), can sample antigens from the lumen and transfer them to submucosal immune cells. This cell type initiates a specific immune response characterized by the secretion of sIgA. This thesis focuses more particularly on the interaction of the epithelium with porcine enteric viruses.
In the first part, we focused on establishing a new research model for enteric viruses based on intestinal organoids. In this study, intestinal organoids were differentiated from crypt stem cells of porcine small intestines. After 2-week culture in Matrigel, the organoids were collected and plated into suspension culture without Matrigel. In this way, apical-out organoids were generated. We then investigated the infection of the apical-out organoids by the Transmissible gastroenteritis virus (TGEV). The results show that apical-out organoids are a physiological model for virus-epithelium interaction research.
To better understand the mechanisms behind the differentiation of M cells, we investigated inflammation-related M cell differentiation. We found that both dextran sulphate sodium (DSS) treatment and Salmonella choleraesuis (S. choleraesuis) infection promotes transcription of M cells-related genes in mice. In the MyD88-/- mice, DSS failed to enhance the differentiation of M cells. We further demonstrate that receptor activator of NF-κB ligand (RANKL) can stimulate M cell differentiation in both wild type and MyD88-/- murine intestinal organoids. However, in MyD88-/- organoids, the RANKL-induced up-regulation of the M cell related gene is attenuated. These results suggest that MyD88 plays an essential role in regulating colitis-related and RANKL-induced M cell differentiation.
These studies indicate that intestinal organoids are a physiological model to investigate intestinal mucosal immunity. These results will provide data for further study on M cells’ function in enteric virus’ invasion.