Recent progress in organoid culture to model intestinal epithelial barrier functions.

The intestinal epithelium not only acts as the physical structure that separates the intestinal lumen from the body but also actively participates in intestinal barrier functions. In the past decade, significant progress has been made in the development of culture technologies to maintain intestinal epithelial cells (IECs) as various forms of intestinal organoids. As these organoids allow for restoration of the physiological composition of IECs, they represent suitable models to study the mechanisms of development and differentiation or the molecular basis of functions in specific types of IECs, such as goblet cells, Paneth cells, tuft cells and M cells. In addition, intestinal organoids are now widely used as model systems to investigate the dynamic processes occurring at the host-microbe interface and the mutual interactions between IECs and the cells involved in the maintenance of local immune homeostasis. In this review article, I showcase recent work that has utilized intestinal organoids to study various aspects of intestinal epithelial barrier functions.