Stem cell derived cultures harbor tremendous potential to model infectious diseases. Here, the culture of mouse and human gastric organoids derived from adult stem cells is described. The organoids are microinjected with the gastric pathogen Helicobacter pylori.
Recently infection biologists have employed stem cell derived cultures to answer the need for new and better models to study host-pathogen interactions. Three cellular sources have been used: Embryonic stem cells (ESC), induced pluripotent stem cells (iPSC) or adult stem cells. Here, culture of mouse and human gastric organoids derived from adult stem cells is described and used for infection with the gastric pathogen Helicobacter pylori. Human gastric glands are isolated from resection material, seeded in a basement matrix and embedded in medium containing growth factors epidermal growth factor (EGF), R-spondin, Noggin, Wnt, fibroblast growth factor (FGF) 10, gastrin and transforming growth factor (TGF) beta inhibitor. In these conditions, gastric glands grow into 3-dimensional organoids containing 4 lineages of the stomach. The organoids expand indefinitely and can be frozen and thawed similarly as cell lines. For infection studies, bacteria are microinjected into the lumen of the organoids. Infected organoids are processed for imaging. The described methods can be adapted to other organoids and infections with other bacteria, viruses or parasites. This allows the study of infection-induced changes in primary cells.
The study of pathogens relies on adequate model systems to mimic the in vivo infection. For some infective agents, adequate model systems are lacking while some of the used systems are far from optimal. One example is the gastric bacterium Helicobacter pylori (H. pylori), which is causally related to development of gastric cancer. Yet in absence of a more suitable cell culture system, many studies that aim to analyze the molecular mechanisms underlying cancer development use cancer cell lines, which represent the endpoint of the cancerous cascade. Primary, non-transformed cells would be a better model for these studies. However, primary cells are only available from a small number of donors and cannot be cultured over longer periods of time. In recent years, stem cell research has made significant progress to provide new sources for primary cell cultures for the study of infection biology.
Cultures from three stem cell sources have been used: Embryonic stem cells (ESC), induced pluripotent stem cells (iPSC) or adult stem cells. They have been used to model infections with viruses, such as Cytomegalovirus1,2 or Hepatitis C Virus3–7, parasites, such as Plasmodium falciparum8 or Toxoplasma gondii9, and bacteria, such as Bacterioides thetaiotaomicron10 or Salmonella enterica11. Most recently, several approaches have been published to model infection with H. pylori with organoids derived from ESC or iPS cells12, mouse adult stem cells21,22 or human adult stem cells13–15.
The development of organoid cultures from adult stem cells originated from a study, in which single stem cells isolated from murine intestinal epithelium were seeded into a 3-dimensional matrix and embedded in medium that mimicked the environment of the intestinal stem cells containing EGF as mitogen, R-spondin to enhance Wnt signalling and Noggin to inhibit bone morphogenic protein (BMP) signalling16. Notably these cultures do not require co-culture with mesenchymal cells. In these conditions, the stem cells proliferate and form small structures with domains harboring cells of the intestinal crypts, and domains that contain the cells of the intestinal villus. The organoids thus self-organize to mimic the in vivo situation. Today, adult stem cells from many murine and humane tissues can be grown in vitro and self-organize into organoids that resemble their in vivo counterpart, such as small intestine and colon17, stomach13,18, liver19,20, pancreas21 and prostate22.
Here we provide a video protocol to culture mouse or human gastric organoids from adult stem cells and microinject them with H. pylori. This protocol is based on previous reports13,18. This method can be adapted for culturing and infecting other organoid cultures such as intestinal organoids.
1. Establishment of Gastric Organoid Culture
Note: This protocol can be used for the isolation of gastric glands from mouse or human tissue. It is advised to use tissue of approximately 1 cm². Human tissue can be obtained from gastric resections or biopsies.
2. Passage of Gastric Organoid Culture Before Microinjection.
Note: Every type of organoid culture has its own doubling time. Mouse intestinal as well as gastric cultures are usually split 1:5 every 5-7 days. Human intestinal cultures are split 1:5 every 10-12 days. Human gastric cultures are split 1:5 every 14 days. If initiated from single cells, human gastric organoids may also take 20 days to form properly. It is a good sign if budding structures surround the central lumen. In this protocol, organoids are split in 4 well plates for microinjection. Maintenance of organoids follows the same protocol, but can use any other cell culture plate, such as standard 24 well cell culture plates.
3. Microinjection of Organoid Culture.
Note: This protocol can be used to microinject bacteria into organoids. It may be helpful to start the injection with organoids that are more permissive to microinjection. For example, mouse gastric organoids can grow into very large cystic organoids that are easy to target.
This protocol allows isolation of gastric glands (Figure 2). Glands are seeded into basement matrix, which solidifies as drop within a well, providing a 3 dimensional framework rich in laminin and collagen to allow the glands grow into organoids (Figure 3). Organoids typically start as small cysts and within 12-16 days, they expand into spheres with a diameter of 50-300 µm (Figure 4). Some organoids will stay cystic, some will develop small buddings. The latter is usually a sign of a healthy growing culture. In this protocol one well of a 24 well plate is used for 100 glands, 50 µl of basement matrix and 500 µl of medium. However, this can be up- or downscaled.
The success of the microinjection can readily be observed under the stereomicroscope as the cloudy, bacterial solution fills the organoid (Figure 5). After adequate incubation time, organoids can be processed for any analysis method desired. For example, organoids can be embedded in paraffin, sections can be cut and stained using standard immunohistochemistry techniques. Microscopic analysis of immunostained organoids demonstrate successful injection of the bacteria (Figure 6).
Figure 1. Image of Pasteur pipette used for passage of organoids. In each panel, the upper pipette is before, the lower pipette after narrowing by fire. Scale in upper and right panels is cm and mm. Please click here to view a larger version of this figure.
Figure 2. Representative image of isolated human gastric glands. Scale bar 100 µm. Please click here to view a larger version of this figure.
Figure 3. Scheme of wells and representative image of human gastric organoids. Isolated human gastric glands were dispensed in basement matrix and placed as drops into wells of a 24 well plate. Lower left: Overview of a representative well 11 days after seeding. Lower right: Enlargement of the indicated area. Scale bar 100 µm. Gastric mouse organoids expand faster18. Please click here to view a larger version of this figure.
Figure 4. Typical growth of human gastric organoids. Glands were seeded into basement matrix and images of the same organoid were taken over a period of 12 days. Scale bar 100 µm Please click here to view a larger version of this figure.
Figure 5. Microinjection of gastric organoids. Stereoscope images of a gastric organoid before (left) and during (right) microinjection of bacteria into the lumen. Bacteria are visible as cloud inside the organoid. Scale bar 200 µm. Please click here to view a larger version of this figure.
Figure 6. Immunostained organoids. Human gastric organoids were microinjected with H. pylori. After 4 hr, organoids were fixed in paraformaldehyde and embedded in paraffin. Sections were stained using antibodies targeting the bacterial protein Cytotoxicity associated gene A (CagA) according to standard histology methods25. Upper left: Image of a representative organoid. Lower panel: Higher magnification of the boxed area. Upper right: Higher magnification of the boxed area with a single bacterium close to the epithelial cells. Please click here to view a larger version of this figure.
This protocol describes the use of ever-expanding, untransformed primary organoids from adult stem cells for infection biology. Critical steps are i) the isolation of viable glands, ii) expansion of organoids and iii) the microinjection. Below are some suggestions for modifications, troubleshooting and technical considerations.
Compared to other isolation methods, which use vigorous shaking or pipetting to release glands and can be equally successful, the technique presented here has the advantage, that the release of the glands from the tissue can directly be observed under the microscope (step 1.2.14.). If glands are not released, incubation in EDTA can be varied (see step 1.2.9.). If preferred, try to isolate glands using vigorous shaking and control the presence of glands in the supernatant under the microscope as described for mouse intestinal crypts26. It is not critical, if isolated glands disintegrate during the washing steps. Organoids will still initiate from fragments or even single stem cells, as demonstrated previously13,18, 27.
When glands have been isolated and seeded, but organoids are not expanding as expected, troubleshooting should start with testing activity of Wnt and R-spondin. These factors are crucial for expansion of the organoids and it is advised to test the functionality of these two factors by an in vitro assay, for example the TOP flash reporter construct using Luciferase28. It is important that all growth factors are diluted and handled following manufacturers’ recommendation and kept in small aliquots to avoid freeze-thaw cycles.
The microinjection into organoids is comparable to injection of fish eggs or murine oocytes. Needles are pulled from glass capillaries and can be broken using tweezers directly before use to result in a tip end of about 10 µm. Smaller tips penetrate the organoids more easily but they also bear the risk that bacterial accumulations may clog the needle. For micromanipulation, different systems have specific advantages and limitations. It is practical to use a 3- dimensional manipulator instead of a 2 dimensional manipulator to allow maximal flexibility to reach into the wells. Oil-based microinjectors (such as Celltram, or IM-5B) provide a finer and slower manual control compared to air-based microinjectors (such as FemtoJet11, or Nanojet microinjector10). In turn, the latter have the important advantage that a precise injection volume can be programmed. If microinjection is initially difficult, it may be helpful practice with large mouse gastric organoids and a dye. With practice, also smaller organoids such as mouse intestinal organoids are amenable to microinjection.
Microinjection of organoids is technically limited to a small experimental size because every organoid has to be targeted manually. Positioning or size may not render all organoids equally amenable to injection, thus the technique is limited to applications that can tolerate some heterogeneity in a well. Reflux from the injection hole is minimal10,11, but should also be considered.
Comparing the different sources for new gastric stem cell derived cell cultures, it is evident that each of the systems has its own advantages. iPSC have been used to generate antral gastric organoids and allow following of the developmental steps towards the antral gastric lineages12. The cultures described here can be derived from antrum or corpus. While long-term corpus cultures as described here do not contain parietal cells13, very early passages as well as co-cultures with mesenchymal cells have been reported to contain parietal cells15,29.
The protocol described here has been developed for optimal long-term culture and allows unlimited maintenance of organoids (1 year tested). The organoids have typical advantages of cell lines: They can be expanded to allow larger experiments (split 1:5 every 2 weeks for human, every week for mouse organoids). They can be frozen and thawed. Human gastric organoids contain stem cells next to differentiated cells that express markers of mucous pit cells, mucous neck cells, chief cells and enteroendocrine cells. Differentiation to the lineages can be directed using Wnt and Nicotinamide. It is also possible to generate organoids from biopsies of cancers and thus organoids from healthy and cancerous tissue can be compared13,21,33. Generally, organoids are also amenable to genetic modification and intestinal or gastric organoids have been genetically modified using bacterial artificial chromosomes (BAC) transgenes30, retrovirus26,31, lentivirus14 and clustered regularly interspaced short palindromic repeats (CRISPR)/Cas932. Organoids have been used for various imaging techniques13,14,29, RNA analysis13, Western Blot33, Immunoprecipitation34 and drug screening33.
In summary, organoids grown from adult stem cells provide a valuable new tool for infection biology. The here provided protocol for gastric organoids may serve as basis to establish other new infection models.
The authors have nothing to disclose.
This work was supported by EU Marie Curie Fellowship (EU/300686-InfO) to S.B. and a Research Prize from the United European Gastroenterology Foundation to H.C. We would like to thank Harry Begthel, Jeroen Korving and the Hubrecht Imaging Center for technical assistance, Meritxell Huch for help with initial organoid culture and Yana Zavros for discussion.
Medium | |||
HEPES | Invitrogen | 15630-056 | |
Advanced DMEM/F12 | Invitrogen | 12634-028 | |
Matrigel, GFR, phenol free | BD | 356231 | |
GlutaMAX | Invitrogen | 35050-079 | Stock concentration 200 mM, final concentration 2 mM |
B27 | Invitrogen | 17504-044 | Stock concentration 50 x, final concentration 1x |
N-Acetylcysteine | Sigma-Aldrich | A9165-5G | Stock concentration 500 mM, final concentration 1 mM |
Murine recombinant EGF | Invitrogen | PMG8043 | Stock concentration 500 µg/mL, final concentration 50 ng/mL |
Human recombinant FGF10 | Peprotech | 100-26 | Stock concentration 100 µg/mL, final concentration 200 ng/mL |
TGFβi A-83-01 | Tocris | 2939 | Stock concentration 500 µM, final concentration 2 µM |
Nicotinamide | Sigma-Aldrich | N0636 | Stock concentration 1 M, final concentration 10 mM |
[Leu15]-Gastrin | Sigma-Aldrich | G9145 | Stock concentration 100 µM, final concentration 1 nM |
RHOKi Y-27632 | Sigma-Aldrich | Y0503 | Stock concentration 10 mM, final concentration 10 µM |
Wnt3A conditioned medium | Stable cell line generated in the Clevers Lab. Final concentration 50%. Cells can be obtained from Hans Clevers. | ||
R-spondin1 conditioned medium | Stable cell line generated in the Kuo Lab. Final concentration 10%. Cell line can be obtained from Calvin Kuo, Stanford. | ||
Noggin conditioned medium | Stable cell line generated in the Clevers Lab. Final concentration 10%. Cells can be obtained from Hans Clevers. | ||
R-spondin3 | R&D | 3500-RS/CF | Alternative source for R-spondin. This has been tested on human intestine organoids (1 µg/mL), but not yet on gastric organoids. |
Noggin | Peprotech | 120-10 | Alternative source for noggin. This has been tested on human intestine organoids (100 ng/mL), but not yet on gastric organoids. |
TrypLE express | Life Technologies | 12605036 | Enzymatic dissociation solution |
CoolCell® Alcohol-Free Cell Freezing Containers | biocision | BCS-405 | |
Recovery Cell Culture Freezing Medium | Invitrogen | 12648-010 | |
Antibiotics | |||
Primocin | Invivogen | ant-pm-1 | An antibiotics composition agains bacteria and fungi. It is helpful after initiation of a culture. For long term culture you can switch to other antibiotics or none. |
Penicillin/Streptomycin | Invitrogen | 15140-122 | Stock concentration 10000/10000 U/mL, final concentration 100/100 U/mL. Can be used alternatively to Primocin in long term culture. |
Outro | |||
Tweezers | Neolabs | 2-1033 | Tweezers with fine tips are helpful for the removal of muscle layer from the tissue. |
4 Well Multidishes | Thermo Scientific | 144444 | You can use other Multidishes. These were particularly helpful for microinjections because they have a low outer rim and allow more mobility for the manipulator. |
Micromanipulator | Narishige | M-152 | |
Microinjector | Narishige | IM-5B | |
Stereomicroscope | Leica | MZ75 | |
Workbench | Clean Air | Custom made to fit the stereomicroscope in ML2 condition | |
Cappillaries | Harvard Apparatus | GC100T-10 | 1 mm outer diameter, 0,78 mm inner diameter. |
Micropipette Puller | Sutter Instruments | Flaming Brown Micropipette Puller | |
anti Cag A antibody | Santa Cruz | sc-25766 |