Using Human Intestinal Organoids to Understand the Small Intestine Epithelium at the Single Cell Transcriptional Level

Summary

The protocol combines human intestinal organoid technology with single cell transcriptomic analysis to provide significant insight into previously unexplored intestinal biology.

Abstract

Single cell transcriptomics has revolutionized our understanding of the cell biology of the human body. State-of-the-art human small intestinal organoid cultures provide ex vivo model systems that bridge the gap between animal models and clinical studies. The application of single cell transcriptomics to human intestinal organoid (HIO) models is revealing previously unrecognized cell biology, biochemistry, and physiology of the GI tract. The advanced single cell transcriptomics platforms use microfluidic partitioning and barcoding to generate cDNA libraries. These barcoded cDNAs can be easily sequenced by next generation sequencing platforms and used by various visualization tools to generate maps. Here, we describe methods to culture and differentiate human small intestinal HIOs in different formats and procedures for isolating viable cells from these formats that are suitable for use in single-cell transcriptional profiling platforms. These protocols and procedures facilitate the use of small intestinal HIOs to obtain an increased understanding of the cellular response of human intestinal epithelium at the transcriptional level in the context of a variety of different environments.

Introduction

The small intestinal epithelium has two distinct zones: the crypt that houses the intestinal stem cell (ISC) and the villus, which is comprised of differentiated cells of the secretory and absorptive lineages. Adding to this complexity is the regional specificity of the epithelium that provides unique functional properties between the regions of the small intestine. Pioneering work established culture conditions in which both the human small intestinal crypt and villus zones can be generated ex vivo from surgical tissues or tissue biopsies¹. These cultures are bridging the gap between animal studies and clinical trials and are revealing previously unrecognized cell biology, biochemistry, and physiology of the gastrointestinal tract. The HIOs are propagated as 3D spherical structures using a media with growth factors that promote stem cell viability and extracellular support matrices. These conditions result in a crypt-like HIO model that consists mostly of progenitors and stem cells. Removal of the growth factors promotes ISC differentiation (villus-like model) and production of mature intestinal epithelial cells (goblet, enteroendocrine, tuft, enterocyte) in appropriate ratios along with cell proliferation and differentiation, polarization, barrier integrity, regional specific features, and appropriate physiological responses². HIO cultures are genetically stable and can be propagated indefinitely in their crypt-like state. Easy access to the apical surface of these cultures is provided by culture conditions that allow growth in a monolayer format³. HIOs also allow considerations of host individual variability such as genetics, age, sex, ethnicity, and disease status to be included in biological analyses. Analytic and functional assessment tools are identical to those used in approaches centered on transformed cell lines and include a variety of molecular techniques such as flow cytometry, microscopy, transcriptomics, proteomics, and metabolomics.

Single cell transcriptomics is revolutionizing our understanding of the biology and physiology of the small intestine by providing insight into the individual contributions of each cell type to a biological process. Pioneering work using this technology has provided a landscape of the cell types present in the native human intestine^4,5,6. Single cell transcriptional profiling platforms allow exploration of the transcriptional landscape of individual cells, allowing cell heterogeneity to come to the forefront of scientific exploration. In some single cell transcriptional profiling platforms, microfluidic partitioning and barcoding are used to generate cDNA libraries from cellular polyadenylated mRNAs obtained from up to 10,000 cells per sample. On this platform, droplets containing single cells, barcoded oligonucleotides, reverse transcription reagents, and oil form a reaction vesicle that results in all cDNAs from a single cell having the same barcode. The barcoded cDNAs can then be efficiently sequenced using next generation sequencing. Data generated can be handled through software and visualization tools, which convert the barcoded sequences into visualization maps and single cell transcriptional profiles. Cell populations can be identified using publicly available databases of human small intestinal epithelium^4,5,6. Although many studies have utilized this platform to interrogate murine intestinal organoids at the single cell level, the analysis of single cell transcriptional responses of HIOs has lagged behind^{7,8,9,10,11,12}.

Here, we provide a step-by-step guide to isolating viable cells from small intestinal HIOs for processing on single cell transcriptional profiling platforms (Figure 1). We provide culturing and differentiation guidelines along with media components that have been optimized for epithelial differentiation. We outline cell recovery methods for three different culture formats: three dimensional (3D) and monolayer cultures either on plastic or on membrane cell culture inserts. We provide sample clustering data obtained using open-source software to derive differentially expressed genes in each cluster.

Protocol

The organoid lines used here were obtained from the Texas Medical Center Digestive Disease Center GEMS Core. Briefly, to initially establish organoid lines, donor tissue samples were washed and enzymatically digested to release the intestinal crypts. Crypts were embedded in a basement membrane and cultured in a medium. The Institutional Review Board at Baylor College of Medicine approved the study protocol to obtain tissue samples from which organoid lines were established, and informed consent was obtained from all dono…

Representative Results

Single-cell suspensions were pooled from 2-3 wells of membrane cell culture insert, monolayer, and 3D HIOs to ensure sufficient cell yield and reduce well-to-well variation. Single cell libraries were prepared using reagents specific to the single cell transcriptional profiling platform. and sequenced with paired end reads on a next generation sequencing platform, 30,000 reads/cell. Reads were mapped, counted, and analyzed using analytical tools for single cell genomics. Low-quality cells with more than 20% mitochondrial…

Discussion

Using single cell genomics platforms, complex biological systems, such as tissue derived HIO cultures that model the intestinal epithelium, can be broken down to yield individual cellular contributions to overall biological response^4,5,6. Cellular heterogeneity and rare cell populations can also be identified and interrogated. Cellular input needs to be optimized to maximize output using single cell transcriptomic-based platform…

Materials

[Leu15]-Gastrin I	Sigma-Aldrich	G9145	10 nM
0.05% Trypsin-EDTA	Invitrogen	25300054
0.4% Trypan blue	Millipore-Sigma	T8154
0.5 M EDTA	Corning	46-034-CI
1x PBS Ca- Mg-	Corning	21-040-CM
24 mm Transwell	Costar	3412
24 well Nunclon delta surface tissue culture dish	Thermo Scientific	142475
40 µm cell strainer	Falcon	352340
40 µm Flowmi tip strainer	SP Bel-Art Labware	H13680-0040
70 µm Flowmi tip strainer	SP Bel-Art Labware	H13680-0070
96 well plate	Corning	3595
A-83-01	Tocris	2939	500 nM
Accutase	StemCell Technologies	7920
Advanced DMEM/F12	Invitrogen	12634-028
B27 supplement	Invitrogen	17504-044	1X
Chromium Next GEM Single Cell 3’ GEM, Library & Gel Bead Kit v3.1	10x Genomics	PN-1000128
Collagen IV	Sigma-Aldrich	C5533-5MG	33 µg/mL
Corning Cell Recovery Solution	VWR	354253
DPBS (Mg2-, Ca2-)	Invitrogen	14190-136	1X
GlutaMAX-I	Invitrogen	35050-061	2 mM
HEPES 1M	Invitrogen	15630-080	10 mM
L-WRN conditioned media	ATCC	CRL-3276
Matrigel, GFR, phenol free	Corning	356231
mouse recombinant EGF	Invitrogen	PMG8043	50 ng/mL
N2 supplement	Invitrogen	17502-048	1X
N-Acetylcysteine	Sigma-Aldrich	A9165-5G	500 µM
Nicotinamide	Sigma-Aldrich	N0636	10 mM
SB202190	Sigma-Aldrich	S7067	10 µM
Transwell	Corning	3413
Y27632	Stem Cell Technologies	72308	10 µM