Development of a chicken ileal explant culture model for measurement of gut inflammation induced by lipopolysaccharide
Gut mucosa holds a single layer of epithelial cells and the largest mass of lymphoid tissue in the body. Although the epithelial cell culture model is widely used to assess intestinal barrier function, it has limitations for studying cellular interactions, in particular those of the immune system. In this study, a chicken ileal explant culture model was developed for investigating short-term gut inflammatory and secretory responses in an ex vivo environment. Initially, ileal explants from broilers at 21 d of age were cultured ex vivo up to 6 h. Explants cultured for a maximum of 2 h remained over 90% viable, based on lactate dehydrogenase (LDH) release assay. Morphologically, explants cultured for 2 h displayed normal morphology compared to those cultured longer, further confirming that short-term culture for up to 2 h duration is an acceptable model for studying ex vivo regulation of inflammation. Subsequently, lipopolysaccharide (LPS) dose-related responses were determined for explants cultured for 2 h. Results from LDH activity assay showed that the viability of explants was decreased (P ≤ 0.05) at an LPS dose higher than 50 μg/mL. A significant (P ≤ 0.05) nitric oxide release was observed at LPS concentrations of 10 and 20 μg/mL. In addition, the highest inflammatory and secretory responses were detected at 20 μg/mL LPS based on gene expression of TLR-4, IL-1β, IL-8, MUC2, IgA, and pIgR (P ≤ 0.05). However, the gene expression of claudin-1 and claudin-4 were not increased at the determined LPS concentrations (P > 0.05). These results demonstrated the potential usefulness of this intestinal explant culture model for short-term study of biological factors in gut inflammatory and secretory responses, but not a sufficient duration for evaluation of tight junction responsiveness.