Breast Milk Enhances Growth of Enteroids: An Ex Vivo Model of Cell Proliferation
Summary
This protocol describes how to establish an enteroid culture system from neonatal mouse or premature human intestine as well as an efficient method to collect milk from mice.
Abstract
Human small intestinal enteroids are derived from the crypts and when grown in a stem cell niche contain all of the epithelial cell types. The ability to establish human enteroid ex vivo culture systems are important to model intestinal pathophysiology and to study the particular cellular responses involved. In recent years, enteroids from mice and humans are being cultured, passaged, and banked away for future use in several laboratories across the world. This enteroid platform can be used to test the effects of various treatments and drugs and what effects are exerted on different cell types in the intestine. Here, a protocol for establishing primary stem cell-derived small intestinal enteroids derived from neonatal mice and premature human intestine is provided. Moreover, this enteroid culture system was utilized to test the effects of species-specific breast milk. Mouse breast milk can be obtained efficiently using a modified human breast pump and expressed mouse milk can then be used for further research experiments. We now demonstrate the effects of expressed mouse, human, and donor breast milk on the growth and proliferation of enteroids derived from neonatal mice or premature human small intestine.
Introduction
Necrotizing enterocolitis (NEC) is the leading cause of death from gastrointestinal disease in premature infants, affecting nearly 1 in 10 infants born before 29 weeks gestation1,2,3. Half of the infants with NEC progress to the most severe form, where survival is only 10 – 30%4,5. In the United States, an estimated 2 – 3 billion USD/year are spent treating infants with NEC6,7, yet neither the survival rate nor therapy has changed over the past 30 years. The pathogenesis of NEC is characterized by intestinal injury and impaired mucosal healing8,9,10,11, however, the signaling pathways leading to an exacerbated inflammatory response and mechanisms to reverse the inflammation remain incompletely understood.
The administration of human breast milk has been found to be the only protective strategy against NEC for premature infants. We have previously shown that breast milk protects against NEC development through inhibition of the innate immune receptor toll-like receptor 4 (TLR4) in the intestinal epithelium via the epidermal growth factor receptor (EGFR) signaling pathway11. Supplementation of breast milk to an experimental NEC formula attenuated the inflammatory response seen in NEC as demonstrated by inhibition of enterocyte apoptosis and restoration of enterocyte proliferation in a manner that was dependent on epidermal growth factor (EGF) and EGFR11. In another study, it was shown that nitrate, another component of breast milk, contributes to its protective nature by modulating intestinal perfusion, as compared to infant formula, which is lacking nitrate and may contribute to the increased frequency of NEC in formula fed infants12,13. Other compounds present in breast milk that have been shown to be involved in the protection against NEC include human milk oligosaccharides, L-arginine, glutamine, and lactoferrin14,15,16,17,18,19. These beneficial elements of breast milk reveal the necessity of its use in the prevention of NEC, but also stress the importance of studying the mechanisms, signaling pathways, and cellular effects involved in how breast milk is mediating the protection against NEC.
In order to further study the protective properties of breast milk in a mouse model of NEC, we developed a novel, easy to use technique by which mouse breast milk can be extracted from an anesthetized dam using an electric human breast pump11,12. This strategy of acquiring mouse breast milk is advantageous, not only because human breast pumps are readily available and efficient in the procurement of breast milk, but also because this method allows for species-specific breast milk analyses. As a result, we can compare the effects of mouse breast milk with those of expressed human breast milk as well as pasteurized human donor milk from a milk bank in species-specific models. This technique allows for the study of breast milk components in relation to their contribution towards NEC prevention. Other investigators have developed breast milk extraction methods, however, these techniques are manual and typically require more than one lab member20,21,22. Here an easy technique that can be utilized by modifying a human electric breast pump to collect milk from a mouse is presented. This technique can also be applied to other species.
To adequately interrogate the signaling pathways involved with NEC, model systems are needed to evaluate all of the different cell types known to be affected in the disease process. Here, we discuss one such model system – enteroids – and their establishment from mouse and human small intestine. Human intestinal enteroids (HIEs) in particular provide significant promise, because they offer an innovative, genetically diverse ex vivo human model to aid in the study of pathophysiological processes that take place in the gastrointestinal tract23. Enteroids have been found to be cultured long-term and can be frozen for later use23, and unlike Human Intestinal Organoids (HIOs), whose cultures are developed from inducible pluripotent stem cells, enteroids are generated from stem cells within isolated intestinal crypts24. Enteroids require less maintenance, can be infected quickly25, and can be established easily since intestinal crypts are more differentiated than HIOs23. Therefore, HIEs offer many advantages over existing techniques because they can be developed to exhibit region-specific compositional and functional properties of the human gastrointestinal epithelium23. The use of enteroids is a highly effective choice when in need of a human model of the intestine, with adherence to region-specific limitations and ease-of-use. Here we demonstrate the technique of isolating and maintaining primary stem cell-derived small intestinal enteroids from mice and premature human infants.
Protocol
Representative Results
Discussion
The intestinal epithelium is comprised of many cellular subtypes that are responsible for providing host defense against pathogens, maintaining gut barrier integrity, and can be breached in the pathogenesis of several diseases. While animal models can recapitulate some facets of the disease, the ex vivo model of enteroids derived from the small intestine of mice and humans provides a platform to test effects of various treatments. The significance of the enteroid model allows researchers to culture and different…
Divulgaciones
The authors have nothing to disclose.
Acknowledgements
MG is supported by grants K08DK101608 and R03DK111473 from the National Institutes of Health, March of Dimes Foundation Grant No. 5-FY17-79, the Children's Discovery Institute of Washington University and St. Louis Children's Hospital and the Department of Pediatrics at Washington University School of Medicine, St. Louis. CJL is supported by R01DK104946 (PI: Silverman), the Children's Discovery Institute of Washington University and St. Louis Children's Hospital.
Materials
| Dulbecco's Modified Eagle's Medium (DMEM) with 4.5 g/L Glucose and L-Glutamine | Lonza | 12-604F | |
| Fetal Bovine Serum (FBS) | Gibco | 26140-079 | |
| Penicillin-Streptomycin | Gibco | 15140-122 | |
| Humulin N (Insulin) | Eli Lilly And Company | 0002-8315 | |
| 1x Dulbecco's Phosphate-Buffered Saline (DPBS) | Sigma-Aldrich | D8537 | |
| Gentamicin | Gibco | 15750-060 | |
| Amphotericin B | Gibco | 15290-026 | |
| 0.5 M Ethylenediaminetetraacetic acid (EDTA), pH 8.0 | Invitrogen | 15575-020 | |
| 1x Advanced DMEM/F-12 | Invitrogen | 12634-028 | |
| 200 mM L-Glutamine | Gibco | 25030-081 | |
| 1 M N-2-Hydroxyethylpiperazine-N-2-Ethane Sulfonic Acid (HEPES) | Sigma-Aldrich | H3537 | |
| N-Acetylcysteine | Sigma-Aldrich | A9165 | |
| 100x N-2 Supplement | Gibco | 17502-048 | |
| 50x B-27 Supplement Minus Vitamin A | Gibco | 08-0085SA | |
| 100x ROCK Inhibitor Y-27632, Dihydrochloride | Sigma-Aldrich | Y0503 | |
| Recombinant Mouse Wnt3a Protein | R&D Systems | 1324-WN | |
| Murine Noggin | PeproTech | 250-38 | |
| Recombinant Mouse R-Spondin 1 | R&D Systems | 3474-RS | |
| Recombinant Murine Epidermal Growth Factor (EGF) | PeproTech | 315-09 | |
| Matrigel Growth Factor Reduced Basement Membrane Matrix | Corning | 356231 | |
| 35 x 10 mm Cell Culture Petri Dish | Eppendorf | 0030700112 | |
| 24-Well Cell Culture Plate | Eppendorf | 0030722116 | |
| 48-Well Cell Culture Plate | Eppendorf | 0030723112 | |
| 8-Well Nunc Lab-Tek II Chamber Slide System | Thermo Scientific | 154534 | |
| 50 mL Conical Tube | Corning | 352070 | |
| 100 μM Sterile Cell Strainer | Fisher Scientific | 22-363-549 | |
| 70 μM Sterile Cell Strainer | Fisher Scientific | 22-363-548 | |
| 1x Phosphate-Buffered Saline (PBS), pH 7.2 | Invitrogen | 20012-027 | |
| 16% Paraformaldehyde (PFA) | Electron Microscopy Sciences | 15710 | |
| Triton X-100 | Sigma-Aldrich | T8787 | |
| Tween 20 | Sigma-Aldrich | P1379 | |
| Normal Donkey Serum (NDS) | Sigma-Aldrich | D9663 | |
| 4',6-Diamidino-2-Phenylindole, Dihydrochloride (DAPI) | Invitrogen | D1306 | |
| Microscope Cover Glass | Fisher Scientific | 12-544-D | |
| Confocal Microscope Leica TCS SP8 X | Leica Microsystems | N/A | |
| Photoshop CS6 | Adobe Systems | N/A | |
| 18 G 1.5 Inch Needle | Becton Dickinson | 305196 | |
| Isoflurane | Sigma-Aldrich | 792632 | |
| Oxytocin | Sigma-Aldrich | O3251 | |
| Human Double Electric Breast Pump | Lansinoh | 044677530163 | |
| 5 mL Round Bottom Test Tube | Corning | 352058 | |
| Rubber Stoppers | Frey Scientific | 560761 | |
| Ki67 Antibody | Abcam | AB15580 | |
| Human Mki67 primer F: 5'-GACCTCAAACTGGCTCCTAATC-3' R: 5'-GCTGCCAGATAGAGTCAGAAAG-3' | Integrated DNA Technologies | N/A |
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