What is the role of fish intestine as environment-organism barrier? Mechanistic investigations using fish intestinal cells on a chip

The gut of fish belongs to the most essential barriers that mark the border between the organism and its surrounding environment. The pivotal barrier function, allowing to absorb nutrients from the diet while simultaneously protecting the organism from pathogens and contaminants, is accomplished by a single layer of epithelial cells lining the intestinal lumen. In vitro, this barrier has been mimicked by culturing fish epithelial intestinal cells on conventional permeable membranes within a two-chamber system, which creates an upper and a lower compartment representing the intestinal lumen and blood circulation respectively. This simplified approach, however, has at least three important limitations: The first being restricted diffusion through the several micrometer thick commercial membranes, which moreover have quite limited porosity. The second being a lack of interaction with other intestinal cell types and the third being absence of mechanical stimulation, such as shear forces from fluid flow to better simulate the physiology of the intestine. To overcome these limitations, this thesis focuses on the recreation of the piscine intestinal microenvironment by combining cells derived from the intestine of fish, precisely epithelial and fibroblast cell lines from rainbow trout (Oncorhynchus mykiss), with engineered microsystems. The applied stepwise approach encompasses the development of an ultrathin permeable membrane as novel support for barrier forming cells, followed by combining epithelial cells and fibroblasts for intestinal architecture reconstruction, and exposure to fluid flow to mimic the mechanical forces occurring on the epithelial-lumen interface.