Welcome back to our blog! This week, let’s turn our attention to the gut.
Why study gut tissue?
The main function of the gastrointestinal tract is to take in food, digest it so that nutrients and energy can be absorbed by the body, and expel remaining waste as feces. The gastrointestinal tract includes the mouth, esophagus, stomach, small intestines, and large intestines. Here, we’ll be discussing tissues of the large intestines.
There are two principle inflammatory diseases of the large intestines: Crohn’s disease and ulcerative colitis (Figure 1). Together, these disorders make up inflammatory bowel disease (IBD), which affects about 1.6 million Americans. As many as 70,000 new cases of IBD are diagnosed in the United States each year. Thus, studies on gut tissue would make a significant impact for discovering new drugs and diagnostics to treat these conditions.
Precision-cut intestinal slices (PCIS)
When it comes to testing the efficacy of drugs for preclinical investigation, we need a model to study the absorption, distribution, metabolism, excretion, and toxicity of drugs. Because the intestines are heavily involved in all of these mechanisms, the development of precision-cut intestinal slices (PCIS) has allowed scientists to study cell metabolism and drug processing in the ex vivo gut tissues (Figure 2).
Initially, the precision-cut technique was only applied to solid organs such as the liver and kidney. Acute slicing of brain tissue was also performed for electrophysiology studies. But because the gut is a long, soft, hollow organ, it was more difficult to slice and incubate.
With the Compresstome, we have developed a method using our agarose-embedding technique for cutting healthy precision-cut intestinal slices. To do this, we found that the following steps work best to produce viable PCIS for metabolic studies (Figure 3):
- Dissect out the section of intestinal tissue to be sectioned. Using a small syringe filled with PBS, flush out all fecal material from the intestinal lumen.
- Using 2% agarose in a small syringe, inject agarose into the intestinal lumen.
- Embed the intestinal tissue into a Compresstome specimen tube, and embed the entire specimen in 2% agarose.
- Slice the tissue on a Compresstome to obtain longitudinal slices.
Having the same concentration of agarose both inside and outside of the intestinal lumen allows for greater stability during cutting. This is an improve technique for obtaining PCIS, and can be applied to various animal models (mouse, rat, human, etc).
Ongoing PCIS studies
Current studies using precision-cut intestinal slices include experiments on intestinal fibrosis, which is a major complication of inflammation bowel disease. Studies of intestinal cancers can also be done in the lab with gut slices. Drug development and testing is a major component of using PCIS. Overall, precision-cut intestinal slices are a simple and reliable method for ex vivo studies of intestinal disorders and the impact of drugs on intestinal tissues.