Testing Epithelial Permeability in Fetal Tissue-Derived Enteroids.

Human fetal tissue-derived enteroids are emerging as a promising in vitro model to study intestinal injuries in preterm infants. Enteroids exhibit polarity, consisting of a lumen with an apical border, tight junctions, and a basolateral outer layer exposed to growth media. The consequences of intestinal injuries include mucosal inflammation and increased permeability. Testing intestinal permeability in vulnerable preterm human subjects is often not feasible. Thus, an in vitro fetal tissue-derived intestinal model is needed to study intestinal injuries in preterm infants. Enteroids can be used to test changes in epithelial permeability regulated by tight junction proteins. In enteroids, intestinal stem cells differentiate into all epithelial cell types and form a three-dimensional structure on a basement membrane matrix secreted by mouse sarcoma cells. In this article, we describe the methods used for establishing enteroids from fetal intestinal tissue, characterizing the enteroid tight junction proteins with immunofluorescent imaging, and testing epithelial permeability. As gram-negative dominant bacterial dysbiosis is a known risk factor for intestinal injury, we used lipopolysaccharide (LPS), an endotoxin produced by gram-negative bacteria, to induce permeability in the enteroids. Fluorescein-labeled dextran was microinjected into the enteroid lumen, and serial dextran concentrations leaked into the culture media were measured to quantify the changes in paracellular permeability. The experiment showed that apical exposure to LPS induces epithelial permeability in a concentration-dependent manner. These findings support the hypothesis that gram-negative dominant dysbiosis contributes to the mechanism of intestinal injury in preterm infants.