Name: p. aeruginosa infected 3d co-culture of bronchial epithelial cells and macrophages at air-liquid interface for preclinical evaluation of anti-infectives
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Description: Watch this Scientific Journal Video about P. aeruginosa Infected 3D Co-Culture of Bronchial Epithelial Cells and Macrophages at Air-Liquid Interface for Preclinical Evaluation of Anti-Infectives at Jo

This work received funding from the European Union&#8217;s HORIZON 2020 Program for research, technological development, and demonstration under grant agreement no. 642028 H2020-MSCA-ITN-2014, NABBA - Design, and Development of advanced Nanomedicines to overcome Biological Barriers and to treat severe diseases. We thank Dr. Ana Costa and Dr. Jenny Juntke for the great support on the development of the co-culture, Olga Hartwig, for the scientific illustration, Anja Honecker, for ELISA assays, Petra K&#246;nig, Jana Westhues and Dr. Chiara De Rossi for the support on cell culture, analytics, and microscopy. We also thank Chelsea Thorn for proofreading our manuscript.

1. Growth and differentiation of cells in permeable support inserts
<ol>
	<li>Cultivate CFBE41o- in a T75 flask with 13 mL of minimum essential medium (MEM) containing 10% fetal calf serum (FCS), 1% non-essential amino acids and 600 mg/L glucose at 37 &#176;C with 5 % CO2 atmosphere. Add fresh medium to the cells every 2&#8211;3 days.
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		<li>Detach the cells after reaching 70% confluence&#160;in the flask with 3 mL of trypsin- Ethylenediaminetetraacetic acid (EDTA) at 37&#176;C for 15&#160;mi...

<ol>
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This paper describes a protocol for a 3D co-culture of the infected airways, constituted by the human cystic fibrosis bronchial epithelial cell line CFBE41o- and the human monocyte-derived macrophage cell line THP-1. The protocol allows the assessment of epithelial barrier integrity, macrophage transmigration, bacteria survival, and inflammation, which are important parameters when testing drug efficacy and host-responses simultaneously. The novelty in the model lies within the incorporation of epithelial cells (i.e.&#16...

Pseudomonas aeruginosa is a relevant pathogen in cystic fibrosis (CF) that contributes to lung tissue impairment1. The production of polysaccharides, such as alginate and other mucoid exopolysaccharides, coordinates the progress of the disease, which leads to tenacious bacterial adherence, limits the delivery of antibiotics to bacteria and protects the bacteria against the host immune system2. The transition of P. aeruginosa from the planktonic stage to biofilm formation is a critical issue in this context, also facilitating the occurrence of antibiotic tolerance.
In the context of CF, the mouse has primarily been used as a model. Mice, however, do not spontaneously develop this disease with the introduction of CF mutations3. Most of the bacterial biofilm development and drug susceptibility studies have been performed on abiotic surfaces, such as Petri dishes. However, this approach does not represent the in vivo complexity. For instance, important biological barriers are absent, including immune cells as well as the mucosal epithelium. Though P. aeruginosa is quite toxic to epithelial cells, some groups&#160;have managed to co-cultivate an earlier P. aeruginosa biofilm with human bronchial cells. These cells originated from cystic fibrosis patients with CFTR mutation (CFBE41o- cells)4 and allowed to assess antibiotic efficacy5 or assess the correction of the CFTR protein during infection6. Such a model was shown to improve the predictability of drug efficacy, in addition to enabling characterization of issues with drugs that failed in later phases of drug development7.
However, in the lung, the mucosal epithelium is exposed to air. Moreover, immune cells present in the airways, like tissue macrophages, play an essential role against inhaled pathogens or particles8. Macrophages migrate through the different cell layers to reach the bronchial lumen and fight the infection. Furthermore, inhaled drugs also have to cope with the presence of mucus as an additional non-cellular element of the pulmonary air-blood barrier9. Indeed, several complex three-dimensional (3D) in vitro models have been developed, aiming to increase the in vivo relevance. Co-culture systems not only increase the complexity of in vitro systems for drug discovery but also enable to study cell-cell interactions. Such complexity has been addressed in studies about macrophage migration10, the release of antimicrobial peptides by neutrophils11, the role of mucus in infection9, and the epithelial cell reaction to excessive damage12. However, a reliable CF-infected in vitro model that features the genetic mutation in CF, that is exposed to the air (increased&#160;physiological condition), and integrates immune cells is still lacking.
To bridge this gap, we describe a protocol for stable human 3D co-culture of the infected airways. The model is constituted of human CF bronchial epithelial cells and macrophages, infected with P. aeruginosa and capable of representing both a diffusional and immunological barrier. With the goal of testing anti-infectives at reasonably high throughput, this co-culture was established on the permeable filter membrane of well plate inserts, using two human cell lines: CFBE41o- and THP-1 monocyte-derived macrophages. Moreover, to eventually study the deposition of aerosolized anti-infectives13, the model was established at the air-liquid interface (ALI) rather than liquid covered conditions (LCC).
As we report here, this model allows assessing not only bacterial survival upon an antibiotic treatment but also cell cytotoxicity, epithelial barrier integrity, macrophage transmigration, and inflammatory responses, which are essential parameters for drug development.
This protocol combines two relevant cell types for inhalation therapy of the pulmonary airways: macrophages and CF bronchial epithelium. These cells are seeded on opposite sides of permeable support inserts, allowing cell exposure to air (called the air-liquid interface (ALI) conditions). This co-culture of host cells is subsequently infected with P. aeruginosa. Both host cell lines are of human origin: the epithelial cells represent the cystic fibrosis bronchial epithelium, with a mutation on the CF channel (CFBE41o-), and the THP-114 cells are a well-characterized macrophage-like cell line. A confluent epithelial layer is first allowed to form on the upper side of well plate inserts before the macrophage-like cells are added to the opposite compartment. Once the co-culture is established at ALI, the system is inoculated with P. aeruginosa at the apical side. This infected co-culture system is then used to assess the efficacy of an antibiotic, e.g.&#160;tobramycin. The following end-points are analyzed: epithelial barrier integrity in terms of transepithelial electrical resistance (TEER), visualization of cell-cell and cell-bacteria interactions by confocal laser scanning microscopy (CLSM), bacterial survival by counting of colony-forming units (CFU), host cell survival (cytotoxicity) and cytokine release.

<table border="0" cellpadding="0" cellspacing="0" style="width:1308px;" width="1306">
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		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:515px;">Accutase</td>
			<td style="width:525px;">Accutase</td>
			<td style="width:205px;">AT104</td>
			<td style="width:63px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ampicillin</td>
			<td>Carl Roth, Germany</td>
			<td>HP62.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CASY TT Cell Counter and Analyzer</td>
			<td>OLS Omni Life Sciences</td>
			<td>-</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">CellTrace Far Red</td>
			<td>Thermo Fischer</td>
			<td>C34564</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Centrifuge Universal 320R</td>
			<td>Hettich, Germany</td>
			<td>1406</td>
			<td></td>
		</tr>
		<tr height="33">
			<td height="33" style="height:33px;">CFBE41o- cells</td>
			<td style="width:525px;">1. Gruenert Cell Line Distribution Program 
			2. Sigma-Aldrich</td>
			<td style="width:205px;">1. gift from Dr. Dieter C. Gruenert 
			2. SCC151</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Chopstick Electrode Set for EVOM2, 4mm</td>
			<td>World Precision Instruments, Sarasota, USA</td>
			<td>STX2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Confocal Laser-Scanning Microscope CLSM</td>
			<td>Leica, Mannheim, Germany</td>
			<td>TCS SP 8</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cytokines ELISA Ready-SET-Go kits</td>
			<td>Affymetrix eBioscience, USA</td>
			<td>15541037</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cytokines Panel I and II</td>
			<td>LEGENDplex Immunoassay (Biolegend, USA).</td>
			<td>740102</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cytotoxicity Detection Kit (LDH)</td>
			<td>Roche</td>
			<td>11644793001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">D-(+) Glucose</td>
			<td>Merck</td>
			<td>47829</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dako Fluorescence Mounting Medium</td>
			<td>DAKO</td>
			<td>S3023</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DAPI (4&#8242;,6-diamidino-2-phenylindole)</td>
			<td>Thermo Fischer</td>
			<td>D1306</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Epithelial voltohmmeter</td>
			<td>World Precision Instruments, Sarasota, USA</td>
			<td>EVOM2</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Falcon Permeable Support for 12 Well Plate with 3.0&#956;m Transparent PET Membrane, Sterile</td>
			<td>Corning, Amsterdam, Netherlands</td>
			<td>353181</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fetal calf serum</td>
			<td>Lonza, Basel, Switzerland</td>
			<td>DE14-801F</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Goat anti-mouse (H+L) Cross-adsorbed secondary Antibody, Alexa Fluor 633</td>
			<td>Invitrogen</td>
			<td>A-21050</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">L-Lactate Dehydrogenase (LDH), rabbit muscle</td>
			<td>Roche, Mannheim, Germany</td>
			<td>10127230001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">LB broth</td>
			<td>Sigma-Aldrich, Germany</td>
			<td>L2897-1KG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">MEM (Minimum Essential Medium)</td>
			<td>Gibco Thermo Fisher Scientific Inc.</td>
			<td>11095072</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Non-Essential Amino Acids Solution (100X)</td>
			<td>Gibco Thermo Fisher Scientific Inc.</td>
			<td>11140050</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">P. aeruginosa strain PAO1</td>
			<td>American Type Culture Collection</td>
			<td>47085</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">P. aeruginosa strain PAO1-GFP</td>
			<td>American Type Culture Collection</td>
			<td>10145GFP</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Paraformaldehyde Aqueous Solution -16%</td>
			<td>EMS DIASUM</td>
			<td>15710-S</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Phosphate buffer solution buffer</td>
			<td>Thermo Fischer</td>
			<td>10010023</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Petri dishes</td>
			<td>Greiner</td>
			<td>664102</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Phorbol 12-myristate 13-acetate (PMA)</td>
			<td>Sigma, Germany</td>
			<td>P8139-1MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Precision Cover Glasses</td>
			<td>ThorLabs</td>
			<td>CG15KH</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Purified Mouse anti-human ZO-1 IgG antibody</td>
			<td>BD Transduction Laboratories</td>
			<td>610966</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Roswell Park Memorial Institute (RPMI) 1640 medium</td>
			<td>Gibco by Lifetechnologies, Paisley, UK</td>
			<td>11875093</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Soda-lime glass Petri dish, 50 x 200 mm (height x outside diameter)</td>
			<td>Normax, Portugal</td>
			<td>5058561</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Saponin</td>
			<td>Sigma-Aldrich, Germany</td>
			<td>S4521</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">T75 culture flasks</td>
			<td>Thermo Fischer</td>
			<td>156499</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">THP-1 cells</td>
			<td>Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSMZ; Braunschweig, Germany)</td>
			<td>No. ACC-16</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tobramycin sulfate salt</td>
			<td>Sigma</td>
			<td>T1783-500MG</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Trypsin-EDTA 0.05%</td>
			<td>Thermo Fischer</td>
			<td>25300054</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tween80</td>
			<td>Sigma-Aldrich, Germany</td>
			<td>P1754</td>
			<td></td>
		</tr>
	</tbody>
</table>

p. aeruginosa infected 3d co-culture of bronchial epithelial cells and macrophages at air-liquid interface for preclinical evaluation of anti-infectives

fDrug research for the treatment of lung infections is progressing towards predictive in vitro models of high complexity. The multifaceted presence of bacteria in lung models can re-adapt epithelial arrangement, while immune cells coordinate an inflammatory response against the bacteria in the microenvironment. While in vivo models have been the choice for testing new anti-infectives in the context of cystic fibrosis, they still do not accurately mimic the in vivo conditions of such diseases in humans and the treatment outcomes. Complex in vitro models of the infected airways based on human cells (bronchial epithelial and macrophages) and relevant pathogens could bridge this gap and facilitate the translation of new anti-infectives into the clinic. For such purposes, a co-culture model of the human cystic fibrosis bronchial epithelial cell line CFBE41o- and THP-1 monocyte-derived macrophages has been established, mimicking an infection of the human bronchial mucosa by P. aeruginosa at air-liquid interface (ALI) conditions. This model is set up in seven days, and the following parameters are simultaneously assessed: epithelial barrier integrity, macrophage transmigration, bacterial survival, and inflammation. The present protocol describes a robust and reproducible system for evaluating drug efficacy and host responses that could be relevant for discovering new anti-infectives and optimizing their aerosol delivery to the lungs.

Figure 1A shows the morphology of the resulting co-culture of human bronchial epithelial cells and macrophages after growing both for 24 h on the apical and basolateral side of permeable supports, respectively. The epithelial barrier integrity is shown by higher TEER (834 &#8486;&#215;cm2) and CLSM by immunostaining for the tight junction protein ZO-1 (Figure 1B). The same results observed in terms of barrier integrity of uninfected CFBE41o-</sup...

Watch this Scientific Journal Video about P. aeruginosa Infected 3D Co-Culture of Bronchial Epithelial Cells and Macrophages at Air-Liquid Interface for Preclinical Evaluation of Anti-Infectives at Jo

P. aeruginosa Infected 3D Co-Culture of Bronchial Epithelial Cells and Macrophages at Air-Liquid Interface for Preclinical Evaluation of Anti-Infectives

We describe a protocol for a three-dimensional co-culture model of infected airways, using CFBE41o- cells, THP-1 macrophages, and Pseudomonas aeruginosa, established at the air-liquid interface. This model provides a new platform to simultaneously test antibiotic efficacy, epithelial barrier function, and inflammatory markers.

P. aeruginosa Infected 3D Co-Culture of Bronchial Epithelial Cells and Macrophages at Air-Liquid Interface for Preclinical Evaluation of Anti-Infectives

fDrug research for the treatment of lung infections is progressing towards predictive in vitro models of high complexity. The multifaceted presence of ...

So when we are evaluating novel anti-infectives, we have to address two things. One side is the bacteria. If they are planktonic or informed biofilms, the other side is the presence of host cells, especially epithelial host cells, which form tight biological barriers.If these barriers are effected, how the monological response might be, and with this new model, we can actually monitor both parameters at the same time. When treating bacterial infections, we have to realize what organ is affected. For instance, if it is the lung, we can take advantage, and topically administer the drug as an aerosol.However, if we want to have a model for studying this, we need a model that also allows the position of aerosols which is the case in our model. The other advantage is that it's based on human cells, so that we can avoid problems due to differences to animals and species differences. This system could give you more insight to the field of infection research by shedding light on molecular and cellular events during the interaction of host cells and bacteria.When attempting this protocol for the first time, remember to check the cell medium for sterility and cell morphology and to be careful when handling the permeable supports. Cultivate CFBE41 O minus cells in a T 75 flask with minimum essential medium containing 10%FCS, 1%non-essential amino acids, and 600 milligrams per liter glucose at 37 degrees Celsius with 5%carbon dioxide. Add fresh medium to the cells every two to three days.After the cells reached 70%confluency, wash them with 10 milliliters of PBS and detach with three milliliters of trypsin EDTA at 37 degrees Celsius for 15 minutes. Then, add seven milliliters of fresh MEM and centrifuge the cells at 300 times G for four minutes. After discarding the supernatant, at 10 milliliters of MEM, while disrupting the clumps with gentle pipetting.Count the cells with an automated cell counter or Hemocytometer chamber, then dilute them to a concentration of 200, 000 cells per 500 microliters for seeding in 12 well plates with permeable supports. Add 500 microliters of the cell suspension per well to the apical side of the permeable support. Then add 1.5 milliliters of fresh medium to the basal lateral side.Incubate the cells at 37 degrees Celsius and 5%carbon dioxide for 72 hours. On the third day after seeding, create an air liquid interface by removing the medium from the basal lateral side first then from the apical side. Add 500 microliters of fresh MEM to the basal lateral side and change the medium every second day until cells form a confluent monolayer.To assess the epithelial barrier properties of the cells, add 500 microliters of cell medium to the apical side, and 1.5 milliliters to the basal lateral side, then returned the plate to the incubator for an hour. Measure the transit material electrical resistance or TEER with ann STX2 chopstick electrode and an epithelial volt ohm meter. To cultivate THP1 cells, grow them in the T 75 flask using RPMI 1640 medium, supplemented with 10%FCS at 37 degrees Celsius and 5%carbon dioxide.Split the cells every second day by seeding 2 million cells per milliliter in a new T75 flask. To differentiate the THP1 cells, centrifuge the contents of the flask at 300 times G for four minutes, discard the supernatant. Resuspend the pellet in fresh medium and put in a new T75 flask.Add 10 nanograms per milliliter PMA to the cells and return them to the incubator. To detach the macrophage like cells, wash them once with PBS at 37 degrees Celsius, and incubate them with three milliliters of cell detachment solution containing 0.5 millimolar EDTA for 10 minutes at room temperature. Check for cell detachment under an inverted microscope.When the cells have detached, add seven milliliters of fresh medium and centrifuge them at 300 times G for four minutes. After removing the supernatant, resuspend the macrophage cells in three milliliters of THP1 medium in a 15 milliliter conical tube, count the cells, and incubate them for a maximum of one hour before setting up the co-culture. To establish an epithelial macrophage co-culture, remove the medium from the lower chamber of the CFBE41 O minus monolayers and carefully invert the support inside a sterile glass Petri dish, use a cell scraper to remove the cells overgrown through the membrane pores.Place 200, 000 THP1 macrophages in 200 microliters of RPMI on the basal lateral side of the inverted insert in each well, close the Petri dishes, and incubate them for two hours. Then place the inserts back into the 12 well micro plates and add 500 microliters of MEM medium to the basal lateral side of the permeable insert. Inoculate 15 milliliters of lb supplemented with 300 micrograms per milliliter ampicillin with a single colony of P aeruginosa, PAO1GFP, incubate the bacteria for 18 hours at 37 degrees Celsius, while shaking at 180 RPM.After the incubation, transfer the bacteria to a 50 milliliter conical tube, and centrifuges at 3, 850 times G for five minutes. Discard the supernatant and add 10 milliliters of sterile PBS that has been preheated to 37 degrees Celsius. Measure optical density at 600 nanometers and adjust the concentration of bacteria with the cell culture medium to a final concentration of 200, 000 colony forming units per milliliter, which corresponds to a multiplicity of infection of one bacterium per epithelial cell.Add 100 microliters of bacterial suspension to the apical side of the permeable support and incubate the plate at 37 degrees Celsius and 5%carbon dioxide for one hour to allow bacteria to attach to the cells, then carefully remove apical liquid with a pipette to restore ALI conditions. For experiments with drug treatment, add 500 microliters of a drug solution diluted in cell medium to the apical side. Then add 1.5 milliliters of cell medium to the basal lateral side.Collect 500 microliters of the atypical and basal lateral medium and pool them to assess CFU of non-attached bacteria. To assess survival of attached or internalized bacteria, add 500 microliters of sterile deionized cold water to each compartment of the permeable support, and incubate the cells for 30 minutes at room temperature. If assessing CFU from frozen samples, thaw them at 37 degrees Celsius for 10 minutes.Then use pipette tips to scrape the membrane surface taking care to not put too much pressure on the wells. Pipette up and down to remove all adhered content. With the bacterial suspension from both fractions, make a one to 10 serial dilution with PBS tween and plate the bacteria on lb agar plates.Incubate the agar plates at 30 degrees Celsius for 16 to 72 hours, then count the colonies and calculate CFU. The morphology of the resulting co-culture of human bronchial epithelial cells and macrophages on the apical and basil lateral side of the permeable supports are shown here. A higher TEER measurement and immunostaining for the tight junction proteins ZO1, proved epithelial barrier integrity.To model a bacterial infection, P aeruginosa was inoculated on CFBE41 o minus cells. Macrophages were observed on the apical side of the co-culture six hours after infection. The TEER dropped to 250 ohm per centimeter squared, indicating a compromised epithelial barrier, which was also suggested by ZO1 staining.Macrophage trans migration through the permeable filter pores and bacteria uptake by THP-1 cells on the apical side is shown here. In the THP-1 monocultures, macrophage migration as early as one hour post-infection. Meanwhile the migration was seen after three hours post-infection in the co-culture.Infected co-cultures treated with tobramycin for six or 20 hours were imaged with confocal scanning laser microscopy. Without treatment, either the epithelial cells or macrophages died after 20 hours of infection. Despite being seen after six hours of treatment in the microscopy pictures, a CFU assay demonstrated that the bacteria did not proliferate.Nevertheless, the bacteria recovered their proliferation capability after the 20 hour treatment. TEER of monocultures and co cultures were also measured. The co-culture of CFBE41 o minus cells with THP-1 did not induce any changes in the epithelial barrier integrity compared to the monoculture.Upon infection, the TEER value dropped. when performing this procedure, it's crucial to ensure that the cells are seated properly and the filter membrane is not disrupted. Therefore the cell seeding steps need to be performed carefully.In addition to this protocol, nebulization of antibiotics on the inserts would make it possible to see if bacteria survival changes compared to submersed conditions.

p-aeruginosa-infected-3d-co-culture-bronchial-epithelial-cells

Research

JoVE Journal

Immunology and Infection

Co-culture Models of Pseudomonas aeruginosa Biofilms Grown on Live Human Airway Cells

Bacterial biofilms have been associated with a number of different human diseases, but biofilm development has generally been studied on non-living surfaces. In this paper, we describe protocols for forming Pseudomonas aeruginosa biofilms on human airway epithelial cells (CFBE cells) grown in culture. In the first method (termed the Static Co-culture Biofilm Model), P. aeruginosa is incubated with CFBE cells grown as confluent monolayers on standard tissue culture plates. Although the bacterium is quite toxic to epithelial cells, the addition of arginine delays the destruction of the monolayer long enough for biofilms to form on the CFBE cells. The second method (termed the Flow Cell Co-culture Biofilm Model), involves adaptation of a biofilm flow cell apparatus, which is often used in biofilm research, to accommodate a glass coverslip supporting a confluent monolayer of CFBE cells. This monolayer is inoculated with P. aeruginosa and a peristaltic pump then flows fresh medium across the cells. In both systems, bacterial biofilms form within 6-8 hours after inoculation. Visualization of the biofilm is enhanced by the use of P. aeruginosa strains constitutively expressing green fluorescent protein (GFP). The Static and Flow Cell Co-culture Biofilm assays are model systems for early P. aeruginosa infection of the Cystic Fibrosis (CF) lung, and these techniques allow different aspects of P. aeruginosa biofilm formation and virulence to be studied, including biofilm cytotoxicity, measurement of biofilm CFU, and staining and visualizing the biofilm.

Co-culture Models of Pseudomonas aeruginosa Biofilms Grown on Live Human Airway Cells

This paper describes different methods of growing Pseudomonas aeruginosa biofilms on cultured human airway epithelial cells. These protocols can be adapted to study different aspects of biofilm formation, including visualization of the biofilm, staining of the biofilm, measuring the colony forming units (CFU) of the biofilm, and studying biofilm cytotoxicity.

Bacterial biofilms have been associated with a number of different human diseases, but biofilm development has generally been studied on non-living ...

Application of a Mouse Ligated Peyer&#x2019;s Patch Intestinal Loop Assay to Evaluate Bacterial Uptake by M cells

The inside of our gut is inhabited with enormous number of commensal bacteria. The mucosal surface of the gastrointestinal tract is continuously exposed to them and occasionally to pathogens. The gut-associated lymphoid tissue (GALT) play a key role for induction of the mucosal immune response to these microbes1, 2. To initiate the mucosal immune response, the mucosal antigens must be transported from the gut lumen across the epithelial barrier into organized lymphoid follicles such as Peyer's patches. This antigen transcytosis is mediated by specialized epithelial M cells3, 4. M cells are atypical epithelial cells that actively phagocytose macromolecules and microbes. Unlike dendritic cells (DCs) and macrophages, which target antigens to lysosomes for degradation, M cells mainly transcytose the internalized antigens. This vigorous macromolecular transcytosis through M cells delivers antigen to the underlying organized lymphoid follicles and is believed to be essential for initiating antigen-specific mucosal immune responses. However, the molecular mechanisms promoting this antigen uptake by M cells are largely unknown. We have previously reported that glycoprotein 2 (Gp2), specifically expressed on the apical plasma membrane of M cells among enterocytes, serves as a transcytotic receptor for a subset of commensal and pathogenic enterobacteria, including Escherichia coli and Salmonella enterica serovar Typhimurium (S. Typhimurium), by recognizing FimH, a component of type I pili on the bacterial outer membrane 5. Here, we present a method for the application of a mouse Peyer's patch intestinal loop assay to evaluate bacterial uptake by M cells. This method is an improved version of the mouse intestinal loop assay previously described 6, 7. The improved points are as follows: 1. Isoflurane was used as an anesthetic agent. 2. Approximately 1 cm ligated intestinal loop including Peyer's patch was set up. 3. Bacteria taken up by M cells were fluorescently labeled by fluorescence labeling reagent or by overexpressing fluorescent protein such as green fluorescent protein (GFP). 4. M cells in the follicle-associated epithelium covering Peyer's patch were detected by whole-mount immunostainig with anti Gp2 antibody. 5. Fluorescent bacterial transcytosis by M cells were observed by confocal microscopic analysis. The mouse Peyer's patch intestinal loop assay could supply the answer what kind of commensal or pathogenic bacteria transcytosed by M cells, and may lead us to understand the molecular mechanism of how to stimulate mucosal immune system through M cells.

Application of a Mouse Ligated Peyer&#8217;s Patch Intestinal Loop Assay to Evaluate Bacterial Uptake by M cells

M cells in a specialized follicle-associated epithelium covering Peyer&#x2019;s patches play an important role for the mucosal immunosurveillance in gut-associated lymphoid tissue. Here we described the evaluation method for bacterial transcytosis by M cells in vivo. This method provides a method to understand M-cell function in the immune system.

The inside of our gut is inhabited with enormous number of commensal bacteria. The mucosal surface of the gastrointestinal tract is continuously exposed ...

Affinity Purification of Influenza Virus Ribonucleoprotein Complexes from the Chromatin of Infected Cells

Like all negative-strand RNA viruses, the genome of influenza viruses is packaged in the form of viral ribonucleoprotein complexes (vRNP), in which the single-stranded genome is encapsidated by the nucleoprotein (NP), and associated with the trimeric polymerase complex consisting of the PA, PB1, and PB2 subunits. However, in contrast to most RNA viruses, influenza viruses perform viral RNA synthesis in the nuclei of infected cells. Interestingly, viral mRNA synthesis uses cellular pre-mRNAs as primers, and it has been proposed that this process takes place on chromatin1. Interactions between the viral polymerase and the host RNA polymerase II, as well as between NP and host nucleosomes have also been characterized1,2.
Recently, the generation of recombinant influenza viruses encoding a One-Strep-Tag genetically fused to the C-terminus of the PB2 subunit of the viral polymerase (rWSN-PB2-Strep3) has been described. These recombinant viruses allow the purification of PB2-containing complexes, including vRNPs, from infected cells. To obtain purified vRNPs, cell cultures are infected, and vRNPs are affinity purified from lysates derived from these cells. However, the lysis procedures used to date have been based on one-step detergent lysis, which, despite the presence of a general nuclease, often extract chromatin-bound material only inefficiently. 
Our preliminary work suggested that a large portion of nuclear vRNPs were not extracted during traditional cell lysis, and therefore could not be affinity purified. To increase this extraction efficiency, and to separate chromatin-bound from non-chromatin-bound nuclear vRNPs, we adapted a step-wise subcellular extraction protocol to influenza virus-infected cells. Briefly, this procedure first separates the nuclei from the cell and then extracts soluble nuclear proteins (here termed the "nucleoplasmic" fraction). The remaining insoluble nuclear material is then digested with Benzonase, an unspecific DNA/RNA nuclease, followed by two salt extraction steps: first using 150 mM NaCl (termed "ch150"), then 500 mM NaCl ("ch500") (Fig. 1). These salt extraction steps were chosen based on our observation that 500 mM NaCl was sufficient to solubilize over 85% of nuclear vRNPs yet still allow binding of tagged vRNPs to the affinity matrix.
After subcellular fractionation of infected cells, it is possible to affinity purify PB2-tagged vRNPs from each individual fraction and analyze their protein and RNA components using Western Blot and primer extension, respectively. Recently, we utilized this method to discover that vRNP export complexes form during late points after infection on the chromatin fraction extracted with 500 mM NaCl (ch500)3.

Influenza viruses replicate their RNA genome in association with host-cell chromatin. Here, we present a method to purify intact viral ribonucleoprotein complexes from the chromatin of infected cells. Purified viral complexes can be analyzed by both Western blot and primer extension of protein and RNA content, respectively.

Like all negative-strand RNA viruses, the genome of influenza viruses is packaged in the form of viral ribonucleoprotein complexes (vRNP), in which the ...

Determination of Tolerable Fatty Acids and Cholera Toxin Concentrations Using Human Intestinal Epithelial Cells and BALB/c Mouse Macrophages

The positive role of fatty acids in the prevention and alleviation of non-human and human diseases have been and continue to be extensively documented. These roles include influences on infectious and non-infectious diseases including prevention of inflammation as well as mucosal immunity to infectious diseases. Cholera is an acute intestinal illness caused by the bacterium Vibrio cholerae. It occurs in developing nations and if left untreated, can result in death. While vaccines for cholera exist, they are not always effective and other preventative methods are needed. We set out to determine tolerable concentrations of three fatty acids (oleic, linoleic and linolenic acids) and cholera toxin using mouse BALB/C macrophages and human intestinal epithelial cells, respectively. We solubilized the above fatty acids and used cell proliferation assays to determine the concentration ranges and specific concentrations of the fatty acids that are not detrimental to human intestinal epithelial cell viability. We solubilized cholera toxin and used it in an assay to determine the concentration ranges and specific concentrations of cholera toxin that do not statistically decrease cell viability in BALB/C macrophages. 
We found the optimum fatty acid concentrations to be between 1-5 ng/&mu;l, and that for cholera toxin to be &lt; 30 ng per treatment. This data may aid future studies that aim to find a protective mucosal role for fatty acids in prevention or alleviation of cholera infections.

We set out to determine tolerable concentrations of three fatty acids (oleic, linoleic and linolenic acids) and cholera toxin that did not significantly and adversely affect cell survival by solubilizing the fatty acids and the toxin and using them in cell survival assays.

The positive role of fatty acids in the prevention and alleviation of non-human and  human diseases have been and continue to be extensively documented. ...

Assessing the Innate Sensing of HIV-1 Infected CD4+ T Cells by Plasmacytoid Dendritic Cells Using an Ex vivo Co-culture System.

HIV-1 innate sensing requires direct contact of infected CD4+ T cells with plasmacytoid dendritic cells (pDCs). In order to study this process, the protocols described here use freshly isolated human peripheral blood mononuclear cells (PBMCs) or plasmacytoid dendritic cells (pDCs) to sense infections in either T cell line (MT4) or heterologous primary CD4+ T cells. In order to ensure proper sensing, it is essential that PBMC are isolated immediately after blood collection and that optimal percentage of infected T cells are used. Furthermore, multi-parametric flow cytometric staining can be used to confirm that PBMC samples contain the different cell lineages at physiological ratios. A number of controls can also be included to evaluate viability and functionality of pDCs. These include, the presence of specific surface markers, assessing cellular responses to known agonist of Toll-Like Receptors (TLR) pathways, and confirming a lack of spontaneous type-I interferon (IFN) production. In this system, freshly isolated PBMCs or pDCs are co-cultured with HIV-1 infected cells in 96 well plates for 18-22 hr. Supernatants from these co-cultures are then used to determine the levels of bioactive type-I IFNs by monitoring the activation of the ISGF3 pathway in HEK-Blue IFN-&#945;/&#946; cells. Prior and during co-culture conditions, target cells can be subjected to flow cytometric analysis to determine a number of parameters, including the percentage of infected cells, levels of specific surface markers, and differential killing of infected cells. Although, these protocols were initially developed to follow type-I IFN production, they could potentially be used to study other imuno-modulatory molecules released from pDCs and to gain further insight into the molecular mechanisms governing HIV-1 innate sensing.

Assessing the Innate Sensing of HIV-1 Infected CD4+ T Cells by Plasmacytoid Dendritic Cells Using an Ex vivo Co-culture System.

Unlike cell-free HIV-1 particles, infected CD4+ T cells are effectively sensed by plasmacytoid dendritic cells (pDCs). This manuscript describes a method where peripheral blood mononuclear cells (PBMCs) or isolated pDCs are co-cultured with HIV-1 infected T cells to evaluate innate sensing by pDCs as assessed by release of type-I IFN.

HIV-1 innate sensing requires direct contact of infected CD4+ T cells with plasmacytoid dendritic cells (pDCs). In order to study this process, the ...

Isolation of Human Monocytes by Double Gradient Centrifugation and Their Differentiation to Macrophages in Teflon-coated Cell Culture Bags

Human macrophages are involved in a plethora of pathologic processes ranging from infectious diseases to cancer. Thus they pose a valuable tool to understand the underlying mechanisms of these diseases. We therefore present a straightforward protocol for the isolation of human monocytes from buffy coats, followed by a differentiation procedure which results in high macrophage yields. The technique relies mostly on commonly available lab equipment and thus provides a cost and time effective way to obtain large quantities of human macrophages. Briefly, buffy coats from healthy blood donors are subjected to a double density gradient centrifugation to harvest monocytes from the peripheral blood. These monocytes are then cultured in fluorinated ethylene propylene (FEP) Teflon-coated cell culture bags in the presence of macrophage colony-stimulating factor (M-CSF). The differentiated macrophages can be easily harvested and used for subsequent studies and functional assays. Important methods for quality control and validation of the isolation and differentiation steps will be highlighted within the protocol. In summary, the protocol described here enables scientists to routinely and reproducibly isolate human macrophages without the need for cost intensive tools. Furthermore, disease models can be studied in a syngeneic human system circumventing the use of murine macrophages.

We present a simple and efficient protocol for the generation of human macrophages. Buffy coats are processed by double density gradient centrifugation and isolated monocytes are then differentiated to macrophages in Teflon-coated cell culture bags. This maximizes macrophage yields and facilitates cell harvesting for subsequent experiments.

Human macrophages are involved in a plethora of pathologic processes ranging from infectious diseases to cancer. Thus they pose a valuable tool to ...

Assessing Bacterial Invasion of Cardiac Cells in Culture and Heart Colonization in Infected Mice Using Listeria monocytogenes

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that is capable of causing serious invasive infections in immunocompromised patients, the elderly, and pregnant women. The most common manifestations of listeriosis in humans include meningitis, encephalitis, and fetal abortion. A significant but much less documented sequelae of invasive L. monocytogenes infection involves the heart. The death rate from cardiac illness can be up to 35% despite treatment, however very little is known regarding L. monocytogenes colonization of cardiac tissue and its resultant pathologies. In addition, it has recently become apparent that subpopulations of L. monocytogenes have an enhanced capacity to invade and grow within cardiac tissue. This protocol describes in detail in vitro and in vivo methods that can be used for assessing cardiotropism of L. monocytogenes isolates. Methods are presented for the infection of H9c2 rat cardiac myoblasts in tissue culture as well as for the determination of bacterial colonization of the hearts of infected mice. These methods are useful not only for identifying strains with the potential to colonize cardiac tissue in infected animals, but may also facilitate the identification of bacterial gene products that serve to enhance cardiac cell invasion and/or drive changes in heart pathology. These methods also provide for the direct comparison of cardiotropism between multiple L. monocytogenes strains.

Assessing Bacterial Invasion of Cardiac Cells in Culture and Heart Colonization in Infected Mice Using Listeria monocytogenes

Listeria monocytogenes causes fetal infections in pregnant women and meningitis in susceptible populations. Subpopulations of bacteria can colonize cardiac tissue, causing myocarditis in patients and laboratory animals. Here we present a protocol that describes how to assess L. monocytogenes cardiac cell invasion in vitro and cardiac colonization in infected animals.

Listeria monocytogenes is a Gram-positive facultative intracellular pathogen that is capable of causing serious invasive infections in immunocompromised ...

Co-Culture of Murine Small Intestine Epithelial Organoids with Innate Lymphoid Cells

Complex co-cultures of organoids with immune cells provide a versatile tool for interrogating the bi-directional interactions that underpin the delicate balance of mucosal homeostasis. These 3D, multi-cellular systems offer a reductionist model for addressing multi-factorial diseases and resolving technical difficulties that arise when studying rare cell types such as tissue-resident innate lymphoid cells (ILCs). This article describes a murine system that combines small intestine organoids and small intestine lamina propria derived helper-like type-1 ILCs (ILC1s), which can be readily extended to other ILC or immune populations. ILCs are a tissue-resident population that is particularly enriched in the mucosa, where they promote homeostasis and rapidly respond to damage or infection. Organoid co-cultures with ILCs have already begun shedding light on new epithelial-immune signaling modules in the gut, revealing how different ILC subsets impact intestinal epithelial barrier integrity and regeneration. This protocol will enable further investigations into reciprocal interactions between epithelial and immune cells, which hold the potential to provide new insights into the mechanisms of mucosal homeostasis and inflammation.

This protocol offers detailed instructions for establishing murine small intestine organoids, isolating type-1 innate lymphoid cells from the murine small intestine lamina propria, and establishing 3-dimensional (3D) co-cultures between both cell types to study bi-directional interactions between intestinal epithelial cells and type-1 innate lymphoid cells.

Complex co-cultures of organoids with immune cells provide a versatile tool for interrogating the bi-directional interactions that underpin the delicate ...

Canine Intestinal Organoids in a Dual-Chamber Permeable Support System

The permeable support system is typically used in conjunction with traditional two-dimensional (2D) cell lines as an in vitro tool for evaluating the oral permeability of new therapeutic drug candidates. However, the use of these conventional cell lines has limitations, such as altered expression of tight junctions, partial cell differentiation, and the absence of key nuclear receptors. Despite these shortcomings, the Caco-2 and MDCK models are widely accepted and validated for the prediction of human in vivo oral permeability.
Dogs are a relevant translational model for biomedical research due to their similarities in gastrointestinal anatomy and intestinal microflora with humans. Accordingly, and in support of parallel drug development, the elaboration of an efficient and accurate in vitro tool for predicting in vivo drug permeability characteristics both in dogs and humans is highly desirable. Such a tool could be the canine intestinal organoid system, characterized by three-dimensional (3D), self-assembled epithelial structures derived from adult stem cells.
The (1) Permeable Support Seeding Protocol describes the experimental methods for dissociating and seeding canine organoids in the inserts. Canine organoid isolation, culture, and harvest have been previously described in a separate set of protocols in this special issue. Methods for general upkeep of the canine intestinal organoid monolayer are discussed thoroughly in the (2) Monolayer Maintenance Protocol. Additionally, this protocol describes methods to assess the structural integrity of the monolayer via transepithelial electrical resistance (TEER) measurements and light microscopy. Finally, the (3) Permeability Experimental Protocol&#160;describes the tasks directly preceding an experiment, including in vitro validation of experimental results.
Overall, the canine organoid model, combined with a dual-chamber cell culture technology, overcomes limitations associated with 2D experimental models, thereby improving the reliability of predictions of the apparent oral permeability of therapeutic drug candidates both in the canine and human patient.

Here, we present a protocol describing the culture of canine intestinal organoids in a dual-chamber, permeable support system. Organoid seeding in the permeable supports, the monolayer maintenance, and subsequent drug permeability experiments are described.

The permeable support system is typically used in conjunction with traditional two-dimensional (2D) cell lines as an in vitro tool for evaluating the oral ...

Isolating Bronchial Epithelial Cells from Resected Lung Tissue for Biobanking and Establishing Well-Differentiated Air-Liquid Interface Cultures

The airway epithelial cell layer forms the first barrier between lung tissue and the outside environment and is thereby constantly exposed to inhaled substances, including infectious agents and air pollutants. The airway epithelial layer plays a central role in a large variety of acute and chronic lung diseases, and various treatments targeting this epithelium are administered by inhalation. Understanding the role of epithelium in pathogenesis and how it can be targeted for therapy requires robust and representative models. In vitro epithelial culture models are increasingly being used and offer the advantage of performing experiments in a controlled environment, exposing the cells to different kinds of stimuli, toxicants, or infectious agents. The use of primary cells instead of immortalized or tumor cell lines has the advantage that these cells differentiate in culture to a pseudostratified polarized epithelial cell layer with a better representation of the epithelium compared to cell lines.
Presented here is a robust protocol, that has been optimized over the past decades, for the isolation and culture of airway epithelial cells from lung tissue. This procedure allows successful isolation, expansion, culture, and mucociliary differentiation of primary bronchial epithelial cells (PBECs) by culturing at the air-liquid interface (ALI) and includes a protocol for biobanking. Furthermore, the characterization of these cultures using cell-specific marker genes is described. These ALI-PBEC cultures can be used for a range of applications, including exposure to whole cigarette smoke or inflammatory mediators, and co-culture/infection with viruses or bacteria. 
The protocol provided in this manuscript, illustrating the procedure in a step-by-step manner, is expected to provide a basis and/or reference for those interested in implementing or adapting such culture systems in their laboratory.

Presented here is a reproducible, affordable, and robust method for the isolation and expansion of primary bronchial epithelial cells for long-term biobanking and the generation of differentiated epithelial cells by culture at the air-liquid interface.

The airway epithelial cell layer forms the first barrier between lung tissue and the outside environment and is thereby constantly exposed to inhaled ...