Intestinal crypt organoids as experimental models

When it comes to studying the effect of food bioactives on gut health, one of the essential steps that needs to be assessed is characterizing specific effects of the bioactives on the physical barrier of the lumen, the gastrointestinal tissue. In addition to studying the effects on transport function (e.g. by using Ussing chambers or cell culture systems), it is of great interest to evaluate the effects on morphology, cell biology, gene expression, and relevant functions of different cell types that are resident in the gastrointestinal (GI) tract. An ideal near-physiological model should contain a mixture of different GI epithelial cells (e.g. Paneth cells, goblet cells, absorptive and hormone secretive epithelial cells), which can be cultured indefinitely. Recently, the culture and applications of long-term primary multi-cellular cluster structures gastrointestinal organoids (or enteroids) have been demonstrated, and within the last 5 years the number of researchers that commonly use this tissue culture model has increased rapidly. This multi-cellular system may be a promising addition for existing ex vivo and alternative for animal models for testing effects of food bioactives on the intestinal tissue, and could provide a model for pre-screening of compounds prior to moving to the large scale testing systems. Moreover, intestinal organoids can be cultured from different species (e.g. human, pig and mouse). In this chapter we will focus on organoids cultured from mouse and pig crypt cells. We will give a short overview on how to isolate, culture, incubate, and apply them in different research fields

Sustained in vitro intestinal epithelial culture within a Wnt-dependent stem cell niche

The in vitro analysis of intestinal epithelium has been hampered by a lack of suitable culture systems. Here we describe robust long-term methodology for small and large intestinal culture, incorporating an air-liquid interface and underlying stromal elements. These cultures showed prolonged intestinal epithelial expansion as sphere-like organoids with proliferation and multilineage differentiation. The Wnt growth factor family positively regulates proliferation of the intestinal epithelium in vivo. Accordingly, culture growth was inhibited by the Wnt antagonist Dickkopf-1 (Dkk1) and markedly stimulated by a fusion protein between the Wnt agonist R-spondin-1 and immunoglobulin Fc (RSpo1-Fc). Furthermore, treatment with the gamma-secretase inhibitor dibenzazepine and neurogenin-3 overexpression induced goblet cell and enteroendocrine cell differentiation, respectively, consistent with endogenous Notch signaling and lineage plasticity. Epithelial cells derived from both leucine-rich repeat-containing G protein-coupled receptor-5-positive (Lgr5(+)) and B lymphoma moloney murine leukemia virus insertion region homolog-1-positive (Bmi1(+)) lineages, representing putative intestinal stem cell (ISC) populations, were present in vitro and were expanded by treatment with RSpo1-Fc; this increased number of Lgr5(+) cells upon RSpo1-Fc treatment was subsequently confirmed in vivo. Our results indicate successful long-term intestinal culture within a microenvironment accurately recapitulating the Wnt- and Notch-dependent ISC niche