Name: the ex vivo colon organ culture and its use in antimicrobial host defense studies
Uploaded: 2017-02-13T14:00:00
Description: Watch this Scientific Journal Video about The Ex Vivo Colon Organ Culture and Its Use in Antimicrobial Host Defense Studies at JoVE.com

This work was supported by funding from Crohn&#39;s and Colitis Foundation of America, (CCFA; 3711) Cancer Prevention and Research Institute of Texas (CPRIT; RP160169), and UT Southwestern Medical Center given to M.H.Z.

All experiments described here were performed using 6-8 weeks old male wild-type (C57BL6/J) mice maintained in a specific pathogen free (SPF) facility at the Animal Resource Center (ARC), UT Southwestern Medical Center. All studies were approved by the Institutional Animal Care and Use Committee (IACUC) and were conducted in accordance with the IACUC guidelines and the National Institutes of Health Guide for the Care and Use of Laboratory Animals.
1. Collection and Preparation of the Colon
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<ol>
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The intestinal epithelial cells are very sensitive in terms of their growth requirements and therefore difficult to culture. The epithelial cells isolated by EDTA treatment do not survive in conventional cell culture media such as DMEM8. Therefore, host-pathogen interaction studies using isolated crypt or primary epithelial cells are very challenging. Recently, Sato et al. described a crypt organoid culture system which is very promising and useful for studies related to intestinal pathophysiology...

The intestine represents a dynamic system that acts as a barrier for commensal microorganisms, fights against invading pathogens, and regulates the microbial composition1. The intestinal epithelial cells, consisting of enterocytes, goblet cells, Paneth cells and enteroendocrine cells, are the major cell populations that provide host defense responses against intestinal microbiota. The goblet cells produce mucins that create a demilitarized zone on the top of the epithelial layer2. The Paneth cells and enterocytes produce antimicrobial peptides, cytokines, and reactive oxygen and nitrogen species that constitute antimicrobial host defense responses and contribute to shaping the intestinal microbial composition3,4. In addition to epithelial cells, the immune cells including macrophages, dendritic cells, neutrophils, natural killer cells, lymphocytes, and innate lymphoid cells in the lamina propria and submucosa play a critical role in intestinal antimicrobial host defense responses by producing cytokines, chemokines, and other mediators5-7. In order to understand how the mucosal immune system regulates microbiota and provides protection against microbial infection, it is important to consider the complex interaction of the heterogeneous cell populations of the gut. However, an in vitro model that encompasses all of the features of the intestine is not available. Therefore, molecular studies on host-pathogen interaction in the intestine are highly challenging.
Over the past few years, several model systems that mimic aspects of the intestinal mucosa have been developed for investigating the pathophysiological processes involved in inflammatory bowel diseases (IBD) and other gastrointestinal disorders8-14. Immortalized intestinal epithelial cell lines are often used to study epithelial cell specific responses. However, because of differential gene expression and function in immortalized cells, the data obtained from using those cells do not often match with those observed in in vivo studies. Intestinal crypt organoid culture has recently emerged as a potential tool for assessing the response of the intestinal epithelium to different stimuli13. In this system, crypt stem cells are allowed to grow and develop a 3D organoid structure. While the organoid culture system is very useful for studying many aspects of the intestinal epithelium, it does not mimic the complex interaction of immune cells, epithelial cells and microbial products. The ex vivo culture of the intestinal tissue offers a better representation of in vivo host defense responses. In this method, a part of the intestine is cultured in a cell culture plate with appropriate media allowing the different types of cell populations in the intestine to be metabolically active for at least 48 h. Thus, an ex vivo culture of the organ can be used to measure the expression of antimicrobial genes and the host defense responses of the intestine to a particular stimulus.
Investigators have been using the ex vivo organ culture system to study host defense responses against microbial infection in the intestine15-21. We recently adopted the organ culture system to study the role of the inflammasome in antimicrobial host defense responses in mouse colons22. The inflammasome is a molecular platform for the activation of caspase-1, which is required for the production of matured IL-1&#946; and IL-18. We showed that IL-1&#946; and IL-18 induce antimicrobial peptides which effectively kill commensal pathobionts such as E. coli. This observation was consistent with increased E. coli burden in inflammasome-defective mouse colons22. This system therefore can be used to study the role of pattern recognition receptors (PRRs) and other innate immune molecules in intestinal antimicrobial host defense responses as well as pathogenesis of intestinal disorders such as inflammatory bowel disease (IBD) and colorectal cancer (CRC). There are more than 200 IBD susceptibility genes, and mutations in many of these genes are associated with altered microbial composition in the gut. It is of great clinical significance to determine the precise mechanism through which the IBD-susceptibility genes regulate gut microbiota. The overall goal of this method is to introduce a basic protocol of ex vivo colon organ culture and demonstrate how this culture method can be used to study antimicrobial host defense responses of the intestine.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Advanced DMEM/ F12</td>
			<td>Life Technologies</td>
			<td>12634-010</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s phosphate buffered saline, modified, w/o Calcium chloride &#38; Magnesium chloride</td>
			<td>Sigma</td>
			<td>5634</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS, heat inactivated</td>
			<td>Sigma</td>
			<td>F4135</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>Life Technologies</td>
			<td>15070063</td>
			<td></td>
		</tr>
		<tr>
			<td>Gentamicin solution</td>
			<td>Sigma</td>
			<td>G1272</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse IL-1b recombinan</td>
			<td>Reprokine</td>
			<td>RKP10749</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse IL-18 recombinant</td>
			<td>Reprokine</td>
			<td>RKP70380</td>
			<td></td>
		</tr>
		<tr>
			<td>TRIzol Reagent</td>
			<td>Thermo Fisher Scientific</td>
			<td>15596018</td>
			<td></td>
		</tr>
		<tr>
			<td>Difco Luria-Bertani Broth&#160;</td>
			<td>BD Bioscience</td>
			<td>244620</td>
			<td></td>
		</tr>
		<tr>
			<td>BD&#160;Difco Dehydrated Culture Media: MacConkey Agar</td>
			<td>Fisher Scientific</td>
			<td>DF0075-17-1</td>
			<td></td>
		</tr>
		<tr>
			<td>NanoDrop 1000 Spectrophotometer</td>
			<td>Thermo Scientific</td>
			<td></td>
			<td>Uded to measure RNA concentration</td>
		</tr>
		<tr>
			<td>UV/Vis Spectrophotometer</td>
			<td>BECKMAN</td>
			<td>DU 530</td>
			<td>Used to determine E. coli count</td>
		</tr>
		<tr>
			<td>iScript RT Supermix, 100 rxns</td>
			<td>Bio-Rad</td>
			<td>1708841</td>
			<td></td>
		</tr>
		<tr>
			<td>iTaq Univer SYBR Green Supermix&#160;</td>
			<td>Bio-Rad</td>
			<td>1725125&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Lysing Matrix S (1/8&#34;), 2 mL Tube</td>
			<td>MP Biomedicals</td>
			<td>116925500</td>
			<td>Used to homgenize colon organ for RNA isolation</td>
		</tr>
		<tr>
			<td>FastPrep-24 5G System</td>
			<td>Bio-Rad</td>
			<td>116005500</td>
			<td></td>
		</tr>
		<tr>
			<td>100x15 Petri Dish</td>
			<td>Falcon</td>
			<td>5687</td>
			<td></td>
		</tr>
		<tr>
			<td>Plate 6well ps TC CS100, Cellstar, 6w, tc, F-bottom (Flat), w/lid, sterile</td>
			<td>Cellstar</td>
			<td>5085</td>
			<td></td>
		</tr>
		<tr>
			<td>100 micron cell strainer</td>
			<td>Falcon</td>
			<td>5698</td>
			<td></td>
		</tr>
		<tr>
			<td>Sorvall Legend Micro 21R Centrifuge</td>
			<td>Thermo Fisher Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sorvall ST40R Centrifuge</td>
			<td>Thermo Fisher Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Forma Scientific orbital shaker</td>
			<td>Thermo Fisher Scientific</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

the ex vivo colon organ culture and its use in antimicrobial host defense studies

The intestine displays an architecture of repetitive crypt structures consisting of different types of epithelial cells, lamina propia containing immune cells, and stroma. All of these heterogeneous cells contribute to intestinal homeostasis and participate in antimicrobial host defense. Therefore, identifying a surrogate model for studying immune response and antimicrobial activity of the intestine in an in vitro setting is extremely challenging. In vitro studies using immortalized intestinal epithelial cell lines or even primary crypt organoid culture do not represent the exact physiology of normal intestine and its microenvironment. Here, we discuss a method of culturing mouse colon tissue in a culture dish and how this ex vivo organ culture system can be implemented in studies related to antimicrobial host defense responses. In representative experiments, we showed that colons in organ culture express antimicrobial peptides in response to exogenous IL-1&#946; and IL-18. Further, the antimicrobial effector molecules produced by the colon tissues in the organ culture efficiently kill Escherichia coli in vitro. This approach, therefore, can be utilized to dissect the role of pathogen- and danger-associated molecular patterns and their cellular receptors in regulating intestinal innate immune responses and antimicrobial host defense responses.

A representative picture of colons in organ culture is shown in Figure 1. The colon pieces in the culture remain metabolically and physiologically active. They respond efficiently to exogenous stimuli added to the culture media. A schematic work flow of the preparation of the colon tissue for ex vivo culture and stimulation with exogenous stimuli, e.g. IL-1&#946; and IL-18, is shown in Figure 2. The representative data in Figure ...

Watch this Scientific Journal Video about The Ex Vivo Colon Organ Culture and Its Use in Antimicrobial Host Defense Studies at JoVE.com

The Ex Vivo Colon Organ Culture and Its Use in Antimicrobial Host Defense Studies

The ex vivo organ culture allows investigation of biological processes in the context of the intact tissue architecture. Here, we introduce a method of ex vivo culture of the mouse colon, which can be used to study innate immunity and antimicrobial host defense in the intestine.

The Ex Vivo Colon Organ Culture and Its Use in Antimicrobial Host Defense Studies

The intestine displays an architecture of repetitive crypt structures consisting of different types of epithelial cells, lamina propia containing immune ...

The overall goal of this procedure is to use ex vivo cultured mouse intestinal tissue to study the role of pathogen associated molecular patterns and the pattern recognition receptors for intestinal antimicrobial host defense responses.This method can help answer how innate immune pathways regulate intestinal microbiota via regulation of antimicrobial peptides.The main advantage of this technique is that the intestinal architecture remains intact while measuring antimicrobial peptides ex vivo.After euthanizing a mouse according to the text protocol, place the animal dorsal side down on a pinning board and pin the limbs.Then use 70%ethanol to spray the mouse.With presterilized dissecting scissors and forceps, make a midline incision in the peritoneum of the abdomen.Then use forceps to open the abdomen by folding the peritoneum.With dissecting forceps and scissors, separate the colon from the small intestine by cutting at the bottom of the cecum, and the other end at the rectum.Place the colon in sterile Petri dish containing ice cold PBS, and then place it on a paper towel.Use the ice cold buffer and a 20 milliliter syringe, holding a 20g needle, or an oral gavage needle, to flush the contents of the lumen of the colon until the stool is completely removed.Using scissors, cut the colon longitudinally.Then wash the tissue by placing it into ice cold PBS in a sterile Petri dish and vigorously shaking.Repeat this wash three times.With a sterile scalpel or scissors, cut the colon tissue into pieces approximately one centimeter long, then record the weight of the colon pieces.To culture colon tissue, place a cell strainer on a six well cell culture plate.Then transfer all of the colon pieces collected from one mouse into the cell strainer.Add 5 milliliters of DMEM F12 medium containing 5%FBS, one x penicillin streptomycin, and 20 micrograms per milliliter of gentamycin, completely covering the colon pieces with the medium.Incubate the tissue at 37 degrees Celsius with 5%CO2 and 95%air for two hours.Then lift the cell strainer and aspirate the medium.Next, place the cell strainer back on the well and add five milliliters of fresh medium without antibiotics.Then lift the cell strainer and aspirate the medium.Repeat the wash two more times to remove all of the residual antibiotics.Transfer the colon pieces from a single cell strainer into a single well of a sterile 12 well cell culture plate.Add one milliliter of DMEM F12 medium containing 5%FBS per one milligram of tissue, then incubate the tissue at 37 degrees Celsius, injecting 5%CO2 and 95%air for 12 hours.Following the incubation, collect the culture supernatant in a sterile 1.5 milliliter tube.Centrifuge the sample at 12, 000 times g and four degrees Celsius for five minutes.Separate the supernatant into a new 1.5 milliliter tube for the use in the bacteria killing assay and/or other immune assays.Store the supernatant at minus 80 degrees Celsius until ready to perform the assay.To carry out an e.coli killing assay, inoculate e.coli into give milliliters of LB in a 15 milliliter tube.While keeping the cap on the culture tube slightly loose incubate the cell culture at 37 degrees C while shaking at 200 rpm overnight.Centrifuge the bacterial culture tube at 12, 000 times g and four degrees Celsius for 10 minutes.Then remove the supernatant and resuspend the bacterial pellet in five milliliters of ice cold PBS.Transfer one milliliter of the bacterial suspension into a cuvette and measure the optical density at 600 nanometers.Use a predetermined standard curve to calculate the colony forming units.In this experiment, assume that one optical density unit equals two times 10 to the ninth CFU per milliliter.Next, dilute the bacterial suspension to make a stock suspension of one times 10 to the fifth colony forming units per milliliter.Then transfer the previously collected colon organ culture supernatant and control media into duplicate wells of a 24 well cell culture plate.Add 10 microliters of e.coli culture into one well of the supernatant and control.Leave the duplicate wells without e.coli to confirm the colon organ culture supernatant is not contaminated.Incubate the culture at 37 degrees Celsius for one hour.After collecting colons from mice as demonstrated earlier in this video, place the colon on a sterile paper towel and use scissors to cut the colon longitudinally into three parts.Use ice cold PBS to wash each part of the colon.Then cut each part of the organ into small pieces and weigh.Transfer the colon pieces into three separate cell strainers placed on three wells of a six well cell culture plate.Add five milliliters of DMEM F12 medium containing 5%FBS, one x penicillin streptomycin, and 20 micrograms per milliliter gentamycin.Incubate the tissue at 37 degrees Celsius and 5%CO2 for two hours.After washing the colon pieces as demonstrated earlier in this video, transfer the tissue from a single cell strainer into a single well of a sterile 12 well cell culture plate.Designate the three wells as untreated, IL-1

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Immunology and Infection

In vivo Imaging of Transgenic Leishmania Parasites in a Live Host

Distinct species of Leishmania, a protozoan parasite of the family Trypanosomatidae, typically cause different human disease manifestations. The most common forms of disease are visceral leishmaniasis (VL) and cutaneous leishmaniasis (CL). Mouse models of leishmaniasis are widely used, but quantification of parasite burdens during murine disease requires mice to be euthanized at various times after infection. Parasite loads are then measured either by microscopy, limiting dilution assay, or qPCR amplification of parasite DNA. The in vivo imaging system (IVIS) has an integrated software package that allows the detection of a bioluminescent signal associated with cells in living organisms. Both to minimize animal usage and to follow infection longitudinally in individuals, in vivo models for imaging Leishmania spp. causing VL or CL were established. Parasites were engineered to express luciferase, and these were introduced into mice either intradermally or intravenously. Quantitative measurements of the luciferase driving bioluminescence of the transgenic Leishmania parasites within the mouse were made using IVIS. Individual mice can be imaged multiple times during longitudinal studies, allowing us to assess the inter-animal variation in the initial experimental parasite inocula, and to assess the multiplication of parasites in mouse tissues. Parasites are detected with high sensitivity in cutaneous locations. Although it is very likely that the signal (photons/second/parasite) is lower in deeper visceral organs than the skin, but quantitative comparisons of signals in superficial versus deep sites have not been done. It is possible that parasite numbers between body sites cannot be directly compared, although parasite loads in the same tissues can be compared between mice. Examples of one visceralizing species (L. infantum chagasi) and one species causing cutaneous leishmaniasis (L. mexicana) are shown. The IVIS procedure can be used for monitoring and analyzing small animal models of a wide variety of Leishmania species causing the different forms of human leishmaniasis.

In vivo Imaging of Transgenic Leishmania Parasites in a Live Host

An in vivo imaging system is used to generate quantitative measurements of murine infection with the Trypanosomatid protozoan Leishmania. This is a non-invasive and non-lethal method for detecting parasites expressing luciferase within many tissues throughout the course of chronic Leishmania spp. infection.

Distinct species of Leishmania, a protozoan parasite of the family Trypanosomatidae, typically cause different human disease manifestations. The most ...

The Ex Vivo Culture and Pattern Recognition Receptor Stimulation of Mouse Intestinal Organoids

Primary intestinal organoids are a valuable model system that has the potential to significantly impact the field of mucosal immunology. However, the complexities of the organoid growth characteristics carry significant caveats for the investigator. Specifically, the growth patterns of each individual organoid are highly variable and create a heterogeneous population of epithelial cells in culture. With such caveats, common tissue culture practices cannot be simply applied to the organoid system due to the complexity of the cellular structure. Counting and plating based solely on cell number, which is common for individually separated cells, such as cell lines, is not a reliable method for organoids unless some normalization technique is applied. Normalizing to total protein content is made complex due to the resident protein matrix. These characteristics in terms of cell number, shape and cell type should be taken into consideration when evaluating secreted contents from the organoid mass. This protocol has been generated to outline a simple procedure to culture and treat small intestinal organoids with microbial pathogens and pathogen associated molecular patterns (PAMPs). It also emphasizes the normalization techniques that should be applied when protein analysis are conducted after such a challenge.

The Ex Vivo Culture and Pattern Recognition Receptor Stimulation of Mouse Intestinal Organoids

Here, a protocol to harvest, maintain, and treat mouse small intestinal organoids with pathogen associated molecular patterns (PAMPs) and Listeria monocytogenes is described, as well as emphasis on gene expression and proper normalization techniques for protein.

Primary intestinal organoids are a valuable model system that has the potential to significantly impact the field of mucosal immunology. However, the ...

Human Placental and Decidual Organ Cultures to Study Infections at the Maternal-fetal Interface

The placenta shows a large degree of interspecies anatomic variability. To best understand biology and pathophysiology of the human placenta, it is imperative to design experiments using human cells and tissues. An advantage of organ culture is maintenance of three-dimensional (3D) structural organization and extracellular matrix. The goal of the method described here is successful establishment of ex vivo human gestational tissue organ cultures and their healthy culture maintenance for 72-96 hr. The protocol details the immediate processing of research-consented, placental and decidual specimens fresh from the operating suite. These are abundant specimens that would otherwise be discarded. Detailed instructions on the sterile collection of these samples, including morphologic details on how to select appropriate tissues to establish 3D organ cultures, is provided. Placental villous and decidual tissues are microdissected into 2-3 mm3 pieces and placed separately on matrix-lined transwell filters and cultured for several days. Villous and decidual organ cultures are well suited for the study of human host-pathogen interaction. As compared to other model organisms, these human cultures are particularly advantageous to examine mechanism of infection for pathogens that demonstrate variable patterns of host specificity. As an example, we demonstrate infection of placental and decidual organ cultures with the clinically relevant, facultative intracellular bacterial pathogen Listeria monocytogenes.

A simple method to establish primary human placental (villous) and decidual organ cultures is described. Villous and decidual organ cultures are invaluable tools for studying pathogenesis at the human maternal-fetal interface. Infection with the facultative intracellular bacterium Listeria monocytogenes is demonstrated.

The placenta shows a large degree of interspecies anatomic variability. To best understand biology and pathophysiology of the human placenta, it is ...

Noninvasive Sampling of Mucosal Lining Fluid for the Quantification of In Vivo Upper Airway Immune-mediator Levels

This protocol describes noninvasive sampling of undisturbed upper airway mucosal lining fluid. It also details the extraction procedure used prior to the analysis of immune mediators in fluid eluates for the study of the airway topical immune signature, without the need for stimulation procedures (often used by other techniques). The mucosal lining fluid is sampled on a strip of filter paper placed at the anterior part of the inferior turbinate and left for 2 min of absorption. Analytes are eluted from the filter papers, and the extracted protein-based eluates are analyzed by an electrochemiluminescence-based immunoassay, allowing for the high-sensitivity quantification of low- and high-level analytes in the same sample. We measured the in vivo levels of 20 preselected immune mediators related to specific immune signaling pathways in the upper airway mucosa, but the technique is not limited to that specific panel or sampling site. The technique was first implemented in 7-year-old children from the Copenhagen Prospective Studies on Asthma in Childhood2000 (COPSAC2000) cohort with allergic rhinitis. It was thereafter used in the longitudinal COPSAC2010 birth cohort, sampled at 1 month, 2 years, and 6 years of age and at instances of acute respiratory symptoms. We successfully obtained and analyzed samples from 620 (89%) of 700 1-month-old children; a few samples were below the assay detection limit (reported as the median (Inter-Quartile Range (IQR)). The number of samples below the detection limit (i.e.&#160;from 0 to the set point for the lower limit of detection) for each mediator was 29 (7.25 - 119.5). This technique enables the quantification of the in vivo airway mucosal immune profile from birth, can be applied longitudinally, and can be applied to studies on the effect of genetics and early-life environmental exposures, pathophysiology, endotyping, and monitoring of respiratory diseases, and development and evaluation of novel therapeutics.

Noninvasive Sampling of Mucosal Lining Fluid for the Quantification of In Vivo Upper Airway Immune-mediator Levels

This protocol describes a noninvasive technique for the sampling of undisturbed mucosal lining fluid from the upper airways. It can be used to perform the quantification of in vivo levels of protein mediators, such as cytokines and chemokines, in subjects of all ages.

This protocol describes noninvasive sampling of undisturbed upper airway mucosal lining fluid. It also details the extraction procedure used prior to the ...

An Ex Vivo Chicken Primary Bursal-cell Culture Model to Study Infectious Bursal Disease Virus Pathogenesis

Infectious bursal disease virus (IBDV) is a birnavirus of economic importance to the poultry industry. The virus infects B cells, causing morbidity, mortality, and immunosuppression in infected birds. In this study, we describe the isolation of chicken primary bursal cells from the bursa of Fabricius, the culture and infection of the cells with IBDV, and the quantification of viral replication. The addition of chicken CD40 ligand significantly increased cell proliferation fourfold over six days of culture and significantly enhanced cell viability. Two strains of IBDV, a cell-culture adapted strain, D78, and a very virulent strain, UK661, replicated well in the ex vivo cell cultures. This model will be of use in determining how cells respond to IBDV infection and will permit a reduction in the number of infected birds used in IBDV pathogenesis studies. The model can also be expanded to include other viruses and could be applied to different species of birds.

An Ex Vivo Chicken Primary Bursal-cell Culture Model to Study Infectious Bursal Disease Virus Pathogenesis

Here we describe the isolation of chicken primary bursal cells from the bursa of Fabricius, the culture and infection of the cells with infectious bursal disease virus, and the quantification of viral replication.

Infectious bursal disease virus (IBDV) is a birnavirus of economic importance to the poultry industry. The virus infects B cells, causing morbidity, ...

Optimization of the Cuff Technique for Murine Heart Transplantation

Murine cardiac transplantation has been performed for more than 40 years. With advancements in microsurgery, certain new techniques have been used to improve surgical efficiency. In our lab, we have optimized the cuff technique with two major steps. First, we used the inner tube technique to insert a temporary inner tube into the external jugular vein and carotid artery blood vessel to facilitate eversion of the vessel over the cuff. Second, we performed complete heterotopic cardiac transplantation through the collaboration of two experienced surgeons. These modifications effectively reduced the operation time to 25 minutes, with a success rate of 95%. In this report, we describe these procedures in detail and provide a supplemental video. We believe that this report on the improved cuff technique will offer practical guidance for murine heterotopic heart transplantation and will enhance the utility of this mouse model for basic research.

We introduce an inner tube approach to the cuff technique for mouse cervical heterotopic heart transplantation to help evert the vessel over the cuff. We found that cooperation between two experienced surgeons markedly shortens the operation time.

Murine cardiac transplantation has been performed for more than 40 years. With advancements in microsurgery, certain new techniques have been used to ...

Establishing a Porcine Ex Vivo Cornea Model for Studying Drug Treatments against Bacterial Keratitis

When developing novel antimicrobials, the success of animal trials is dependent on accurate extrapolation of antimicrobial efficacy from in vitro tests to animal infections in vivo. The existing in vitro tests typically overestimate antimicrobial efficacy as the presence of host tissue as a diffusion barrier is not accounted for. To overcome this bottleneck, we have developed an ex vivo porcine corneal model of bacterial keratitis using Pseudomonas aeruginosa as a prototypic organism. This article describes the preparation of the porcine cornea and protocol for establishment of the infection. Bespoke glass molds enable straightforward setup of the cornea for infection studies. The model mimics in vivo infection as bacterial proliferation is dependent on the ability of the bacterium to damage corneal tissue. Establishment of infection is verified as an increase in the number of colony forming units assessed via viable plate counts. The results demonstrate that infection can be established in a highly reproducible fashion in the ex vivo corneas using the method described here. The model can be extended in the future to mimic keratitis caused by microorganisms other than P. aeruginosa. The ultimate aim of the model is to investigate the effect of antimicrobial chemotherapy on the progress of bacterial infection in a scenario more representative of in vivo infections. In so doing, the model described here will reduce the use of animals for testing, improve success rates in clinical trials and ultimately enable rapid translation of novel antimicrobials to the clinic.

This article describes a step-by-step protocol to set up an ex vivo porcine model of bacterial keratitis. Pseudomonas aeruginosa is used as a prototypic organism. This innovative model mimics in vivo infection as bacterial proliferation is dependent on the ability of the bacterium to damage corneal tissue.

When developing novel antimicrobials, the success of animal trials is dependent on accurate extrapolation of antimicrobial efficacy from in vitro tests to ...

An Ex vivo Assay to Study Candida albicans Hyphal Morphogenesis in the Gastrointestinal Tract

Candida albicans hyphal morphogenesis in the gastrointestinal (GI) tract is tightly controlled by various environmental signals, and plays an important role in the dissemination and pathogenesis of this opportunistic fungal pathogen. However, methods to visualize fungal hyphae in the GI tract in vivo are challenging which limits the understanding of environmental signals in controlling this morphogenesis process. The protocol described here demonstrates a novel ex vivo method for visualization of hyphal morphogenesis in gut homogenate extracts. Using an ex vivo assay, this study demonstrates that cecal contents from antibiotic treated mice, but not from untreated control mice, promote C. albicans hyphal morphogenesis in the gut content. Further, adding back specific groups of gut metabolites to the cecal contents from antibiotic-treated mice differentially regulates hyphal morphogenesis ex vivo. Taken together, this protocol represents a novel method to identify and investigate the environmental signals that control C. albicans hyphal morphogenesis in the GI tract.

An Ex vivo Assay to Study Candida albicans Hyphal Morphogenesis in the Gastrointestinal Tract

The ex vivo assay described in this study using gut homogenate extracts and immunofluorescence staining represents a novel method to examine the hyphal morphogenesis of Candida albicans in the GI tract. This method can be utilized to investigate the environmental signals regulating morphogenetic transition in the gut.

Candida albicans hyphal morphogenesis in the gastrointestinal (GI) tract is tightly controlled by various environmental signals, and plays an important ...

Antibiotic Efficacy Testing in an Ex vivo Model of Pseudomonas aeruginosa and Staphylococcus aureus Biofilms in the Cystic Fibrosis Lung

The effective prescription of antibiotics for the bacterial biofilms present within the lungs of individuals with cystic fibrosis (CF) is limited by a poor correlation between antibiotic susceptibility testing (AST) results using standard diagnostic methods (e.g., broth microdilution, disk diffusion, or Etest) and clinical outcomes after antibiotic treatment. Attempts to improve AST by the use of off-the-shelf biofilm growth platforms show little improvement in results. The limited ability of in vitro biofilm systems to mimic the physicochemical environment of the CF lung and, therefore bacterial physiology and biofilm architecture, also acts as a brake on the discovery of novel therapies for CF infection. Here, we present a protocol to perform AST of CF pathogens grown as mature, in vivo-like biofilms in an ex vivo CF lung model comprised of pig bronchiolar tissue and synthetic CF sputum (ex vivo&#160;pig lung, EVPL).
Several in vitro&#160;assays exist for biofilm susceptibility testing, using either standard laboratory medium or various formulations of synthetic CF sputum in microtiter plates. Both growth medium and biofilm substrate (polystyrene plate vs. bronchiolar tissue) are likely to affect biofilm antibiotic tolerance. We show enhanced tolerance of clinical Pseudomonas aeruginosa and Staphylococcus aureus isolates in the ex vivo model; the effects of antibiotic treatment of biofilms is not correlated with the minimum inhibitory concentration (MIC) in standard microdilution assays or a sensitive/resistant classification in disk diffusion assays.
The ex vivo platform could be used for bespoke biofilm AST of patient samples and as an enhanced testing platform for potential antibiofilm agents during pharmaceutical research and development. Improving the prescription or acceleration of antibiofilm drug discovery through the use of more in vivo-like testing platforms could drastically improve health outcomes for individuals with CF, as well as reduce the costs of clinical treatment and discovery research.

Antibiotic Efficacy Testing in an Ex vivo Model of Pseudomonas aeruginosa and Staphylococcus aureus Biofilms in the Cystic Fibrosis Lung

This workflow can be used to perform antibiotic susceptibility testing using an established&#160;ex vivo model of bacterial biofilm in the lungs of individuals with cystic fibrosis. Use of this model could enhance the clinical validity of MBEC (minimal biofilm eradication concentration) assays.

The effective prescription of antibiotics for the bacterial biofilms present within the lungs of individuals with cystic fibrosis (CF) is limited by a ...

Analysis of SAMHD1 Restriction by Flow Cytometry in Human Myeloid U937 Cells

Sterile &#945;-motif/histidine-aspartate domain-containing protein 1 (SAMHD1) inhibits replication of HIV-1 in quiescent myeloid cells. U937 cells are widely used as a convenient cell system for analyzing SAMHD1 activity due to a low level of SAMHD1 RNA expression, leading to undetectable endogenous protein expression. Based on similar assays developed in the Stoye laboratory to characterize other retroviral restriction factors, the Bishop lab developed a two-color restriction assay to analyze SAMHD1 in U937 cells. Murine Leukaemia Virus-like particles expressing SAMHD1, alongside YFP expressed from an IRES, are used to transduce U937 cells. Cells are then treated with phorbol myristate acetate to induce differentiation to a quiescent phenotype. Following differentiation, cells are infected with HIV-1 virus-like particles expressing a fluorescent reporter. After 48 h, cells are harvested and analyzed by flow cytometry. The proportion of HIV-infected cells in the SAMHD1-expressing population is compared to that in internal control cells lacking SAMHD1. This comparison reveals a restriction ratio. SAMHD1 expression leads to a five-fold reduction in HIV infection, corresponding to a restriction ratio of 0.2. Our recent substitution of RFP for the original GFP as the reporter gene for HIV infection has facilitated flow cytometry analysis.
This assay has been successfully used to characterize the effect of amino acid substitutions on SAMHD1 restriction by transducing with viruses encoding altered SAMHD1 proteins, derived from site-directed mutagenesis of the expression vector. For example, the catalytic site substitutions HD206-7AA show a restriction phenotype of 1, indicating a loss of restriction activity. Equally, the susceptibility of different tester viruses can be determined. The assay can be further adapted to incorporate the effect of differentiation status, metabolic status, and SAMHD1 modifiers to better understand the relationship between SAMHD1, cell metabolic state, and viral restriction.

Described here is an established method to determine the extent of HIV-1 restriction by the cellular inhibitory protein SAMHD1. Human myeloid lineage U937 cells are transduced with a SAMHD1 expression vector co-expressing YFP, differentiated and then challenged with HIV-RFP. The level of restriction is determined by flow cytometry analysis.

Sterile &#945;-motif/histidine-aspartate domain-containing protein 1 (SAMHD1) inhibits replication of HIV-1 in quiescent myeloid cells. U937 cells are ...