Assessing Intestinal Health. In Vitro and Ex vivo Gut Barrier Models of Farm Animals: Benefits and Limitations

Abstract

Animal performance is determined by the functionality and health of the gastrointestinal tract (GIT). Complex mechanisms and interactions are involved in the regulation of GIT functionality and health. The understanding of these relationships could be crucial for developing strategies to improve animal production yields. The concept of "gut health" is not well defined, but this concept has begun to play a very important role in the field of animal science. However, a clear definition of GIT health and the means by which to measure it are lacking. In vitro and ex vivo models can facilitate these studies, creating well-controlled and repeatable conditions to understand how to improve animal gut health. Over the years, several models have been developed and used to study the beneficial or pathogenic relationships between the GIT and the external environment. This review aims to describe the most commonly used animals' in vitro or ex vivo models and techniques that are useful for better understanding the intestinal health of production animals, elucidating their benefits and limitations.

Keywords: ex vivo model; farm animal; gut barrier; in vitro model; intestinal health.

Figure 1

The figure represents the different cell sources for in vitro studies. Epithelial cells can derive directly from intestinal tissue or from tumors. The intestine allows the isolations of primary cells or stem cells to produce enteroids and organoids. On the other hand, intestinal tumors generate continuous cell cultures. These can also be obtained by immortalization techniques of primary cells. Cells can be seeded on specific inserts, alone or in co-culture with other cell types to create either monolayers or a more representative intestinal barrier model, respectively. Created with BioRender.com.

Figure 2

The figure represents the different ex vivo models. The Using chamber or the inTESTine™ system works by removing a segment of intestinal mucosa from an animal, which is then mounted between two halves of a chamber filled with physiological buffer to simulate the mucosal and basolateral passage flow. In everted intestinal rings, the animal's intestine is cut into ring slices and transferred into oxygenated culture media. This model is a useful tool for investigating uptake into intestinal cells and metabolism in different regions of the intestine—Created with BioRender.com.