Name: fabricating optical-quality glass surfaces to study macrophage fusion
Uploaded: 2018-03-14T12:30:00
Description: Watch this Scientific Journal Video about Fabricating Optical-quality Glass Surfaces to Study Macrophage Fusion at JoVE.com

We wish to thank members of the Ugarova laboratory and investigators in the Center for Metabolic and Vascular Biology for helpful discussion of this work. James Faust wishes to express his gratitude to the instructors at the European Molecular Biology Laboratory Super Resolution Microscopy course in 2015. We wish to thank Satya Khuon at Janelia for help with sample preparation for LLSM. During the review and filming portions of this work James Faust was supported by a T32 Fellowship (5T32DK007569-28). The Lattice Light Sheet component of this work was supported by HHMI and the Betty and Gordon Moore Foundation. T.U. is funded by NIH grant HL63199.

Procedures that utilize animals were approved by the Animal Care and Use Committees at Mayo Clinic, Janelia Research Campus, and Arizona State University.
1. Preparing Acid-cleaned Cover Glass
NOTE: Cover glass purchased from many manufacturers may not be as clean as expected. Consider routinely cleaning batches of cover glass before any procedure where microscopy is involved.
<ol>
	<li>Purchase high stringency cover glass. Take special care to choose the correct ...

<ol>
	<li>McNally, A. K., Anderson, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interleukin-4+induces+foreign+body+giant+cells+from+human+monocytes/macrophages.+Differential+lymphokine+regulation+of+macrophage+fusion+leads+to+morphological+variants+of+multinucleated+giant+cells.">Interleukin-4 induces foreign body giant cells from human monocytes/macrophages. Differential lymphokine regulation of macrophage fusion leads to morphological variants of multinucleated giant cells.</a> Am J Pathol. 147 (5), 1487 (1995).</li><li>Helming, L., Gordon, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+mediators+of+macrophage+fusion.">Molecular mediators of macrophage fusion.</a> Trends Cell Biol. 19 (10), 514-522 (2009).</li><li>Podolnikova, N. P., Kushchayeva, Y. S., Wu, Y., Faust, J., Ugarova, T. 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The need to identify and subsequently develop optical-quality glass surfaces that promote macrophage fusion stemmed from the fact that until recently no published study directly visualized macrophage fusion in the context of living specimens3,4. This is due to the fact that fusogenic plastic surfaces that are commonly used require LWD objectives and are largely limited to phase contrast optics. These barriers were overcome by engineering an optical-quality glass ...

The formation of MGCs accompanies a number of pathological states in the human body distinguished by chronic inflammation1. Despite agreement that mononucleated macrophages fuse to form MGCs2, surprisingly few studies have shown fusion in context with living specimens3,4. This is because clean glass surfaces that are required for most imaging techniques do not promote macrophage fusion when induced by inflammatory cytokines5. Indeed, if clean glass is used as a substrate for macrophage fusion, then low to intermediate magnification objectives (i.e., 10 - 20X) and more than 15 h of continuous imaging are often required to observe a single fusion event.
On the other hand, fusogenic plastic surfaces (e.g., permanox) or bacteriological grade plastic promote fusion2. However, imaging through plastic is problematic because the substrate is thick and scatters light. This complicates imaging since long working distance (LWD) objectives are required. However, LWD objectives usually have low light gathering capacity compared to their coverslip-corrected counterpart. Further, techniques that exploit changes in the polarity of light passing through the specimen such as differential interference contrast are impossible since plastic is birefringent. The barriers associated with the use of plastic are further underscored by the fact that it is impossible to predict where macrophage fusion/MGC formation will occur on the surface. Together, these limitations restrict the visualization of macrophage fusion to phase contrast optics, extended total imaging durations (&#62;15 continuous hours), and low resolution.
We recently identified a highly fusogenic glass surface while conducting single-molecule super resolution microscopy with fixed macrophages/MGCs4. This observation was surprising because clean glass surfaces promote fusion at the very low rate of ~ 5% after 24 h in the presence of interleukin-4 (IL-4) as determined by the fusion index4. We found that the capacity to promote fusion was due to oleamide contamination. Adsorption of oleamide or other compounds that similarly contained long-chain hydrocarbons made the glass fusogenic. The most fusogenic compound (paraffin wax) was micropatterned, and it imparted a high degree of spatiotemporal control over macrophage fusion and a 2-fold increase in the number of fusion events observed within the same amount of time compared to permanox. These optical-quality surfaces provided the first glimpse into the morphological features and kinetics that govern the formation of MGCs in living specimens.
In this protocol we describe the fabrication of a variety of glass surfaces that can be used to monitor the formation of MGCs from living specimens. In addition, we show that these surfaces are amenable to far-field super-resolution techniques. Surface fabrication is dependent on the goal of the experiment, and each surface is described with related examples in the proceeding text.

<table border="0" cellpadding="0" cellspacing="0" width="1000">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:160px;">Plasma cleaner</td>
			<td style="width:240px;">Harrick Plasma</td>
			<td style="width:129px;">PCD-32G</td>
			<td style="width:471px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Finder grid</td>
			<td>Electron microscopy sciences</td>
			<td>G400F1-Au</td>
			<td>any gold TEM grid will work</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cover glass (22x22 mm)</td>
			<td>Thor Labs</td>
			<td>CG15CH</td>
			<td>use only high stringency cover glass</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Paraffin wax</td>
			<td>Sigma Aldrich</td>
			<td>17310</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Petrolatum</td>
			<td>Sigma Aldrich</td>
			<td>16415</td>
			<td>must be &#945;-tocopherol-free if substituted</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Oleamide</td>
			<td>Sigma Aldrich</td>
			<td>O2136</td>
			<td>prepare fresh</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Isopropanol</td>
			<td>Sigma Aldrich</td>
			<td>278475</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Toluene</td>
			<td>Sigma Aldrich</td>
			<td>244511</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Acetone</td>
			<td>VWR International</td>
			<td>BDH1101</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethanol</td>
			<td>Electron microscopy sciences</td>
			<td>15050</td>
			<td>use low dissolved solids ethanol</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hydrochloric acid</td>
			<td>Fischer Scientific</td>
			<td>A144C-212</td>
			<td>use to acid wash cover glass</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Slyguard 184</td>
			<td>VWR International</td>
			<td>102092-312</td>
			<td>mix in a 1:10 ratio and cure at 50 &#176;C for 4 h</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">35 mm petri dish</td>
			<td>Santa Cruz Biotech</td>
			<td>sc-351864</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dumont no. 5 forceps</td>
			<td>Electron microscopy sciences</td>
			<td>72705</td>
			<td>ideal for removing TEM grid in section 3.5</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FBS</td>
			<td>Atlanta Biological</td>
			<td>S11550</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DMEM:F12</td>
			<td>Corning</td>
			<td>10-092</td>
			<td>contains 15 mM HEPES</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Pen/Strept</td>
			<td>Corning</td>
			<td>30-002-Cl</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">HBSS</td>
			<td>Corning</td>
			<td>21-023</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">BSA solution</td>
			<td>Sigma Aldrich</td>
			<td>A9576</td>
			<td>use at 0.1% in HBSS to wash non-adherent macrophages</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">IL-4</td>
			<td>Genscript</td>
			<td>Z02996</td>
			<td>aliquot at 10 &#956;g/mL and store at -20 &#176;C</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">C57BL/6J</td>
			<td>Jackson Laboratory</td>
			<td>000664</td>
			<td>use for fixed samples or techniques that do not require contrast agents</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">eGFP-LifeAct mice</td>
			<td>n/a</td>
			<td>n/a</td>
			<td>use for live fluorescence imaging</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Kimwipe</td>
			<td>Kimberly Clark&#160;</td>
			<td>34155</td>
			<td>use to polish hydrocarbon adsorbed surfaces</td>
		</tr>
	</tbody>
</table>

fabricating optical-quality glass surfaces to study macrophage fusion

Visualizing the formation of multinucleated giant cells (MGCs) from living specimens has been challenging due to the fact that most live imaging techniques require propagation of light through glass, but on glass macrophage fusion is a rare event. This protocol presents the fabrication of several optical-quality glass surfaces where adsorption of compounds containing long-chain hydrocarbons transforms glass into a fusogenic surface. First, preparation of clean glass surfaces as starting material for surface modification is described. Second, a method is provided for the adsorption of compounds containing long-chain hydrocarbons to convert non-fusogenic glass into a fusogenic substrate. Third, this protocol describes fabrication of surface micropatterns that promote a high degree of spatiotemporal control over MGC formation. Finally, fabricating glass bottom dishes is described. Examples of use of this in vitro cell system as a model to study macrophage fusion and MGC formation are shown.

Physicochemical parameters of materials have dramatic effects on the extent of macrophage fusion7,8,9,10. Moreover, surface contaminants are known to promote macrophage fusion11. Therefore, it is important to start with clean cover glass as a negative control for macrophage fusion. When cleaned as described in protocol 1, the cover glass ...

Watch this Scientific Journal Video about Fabricating Optical-quality Glass Surfaces to Study Macrophage Fusion at JoVE.com

Fabricating Optical-quality Glass Surfaces to Study Macrophage Fusion

This protocol describes the fabrication of optical-quality glass surfaces adsorbed with compounds containing long-chain hydrocarbons that can be used to monitor macrophage fusion of living specimens and enables super-resolution microscopy of fixed specimens.

Visualizing the formation of multinucleated giant cells (MGCs) from living specimens has been challenging due to the fact that most live imaging ...

The overall goal of this protocol is to transform non-fusogenic cover glass into a fusogenic surface that can be used to study macrophage fusion using any form of optical microscopy. This method can help to answer the fundamental questions related to the molecular mechanism of macrophage fusion. The main advantage of this procedure is that any microscope technique, particularly live imaging, can be used to study macrophage fusion.Demonstrating the procedure will be James Faust, third fellow, and Arnat Balabiyev, a graduate student from my laboratory. To begin, in a well-ventilated chemical fume hood incubate high-stringency cover glass in 12-molar hydrochloric acid with sonication for one hour. Repeat the step two additional times with fresh 12-molar HCL.Fill a separate beaker with ultrapure water, and add the cover glass. Then sonicate the cover glass for five to 10 minutes. Next, incubate the cover glass in pure acetone for 30 minutes with sonication.Repeat the step two additional times. Then fill a separate beaker with sterile ultrapure water, and add the cover glass. Sonicate the cover glass for five to 10 minutes.Incubate the cover glass in 100%ethyl alcohol for 30 minutes with sonication. Repeat this step two additional times. For longterm storage, place the acid-cleaned cover glass in a container willed with pure ethyl alcohol.Alternatively, dry the cover glass with nitrogen gas, and store in a vacuum desiccator. Dissolve DMSO-free high-melting-point paraffin wax in ultrapure toluene. Using a glass pipette, apply enough paraffin working solution to a dry acid-cleaned cover glass to evenly coat the glass surface.Decant the excess solution, and with nitrogen gas or air, dry the cover glass. With a lint-free wipe, polish the cover glass using three strokes along the X axis, then three strokes along the Y axis. Immediately before the experiment is conducted, use sterile ultrapure water to wash the cover glass, and subsequently sterilize it with ultraviolet light in a biological safety hood for 15 to 30 minutes.Dry the acid-cleaned cover glass, and immobilize the glass on a flat surface. Using forceps, carefully immerse a gold transmission electron microscopy finder grid in a working solution of a hydrocarbon compound. Wick away excess solution by gently tapping the grid on filter paper, then immediately place the grid in the center of the cover glass.Allow the toluene to dry for two minutes. Make sure the grid is bonded to the glass by gently inverting the glass. If the grid detaches, repeat the bonding using a new acid-washed cover glass.After removing the TEM grid, examine the continuity of the micro pattern with low magnification. The micro pattern should appear continuous, but the material should not extend beyond the margins of the pattern. Next, use a plasma cleaner with vacuum-gas plasma to clean the cover glass according to the text protocol.Then, using fine-tip forceps, carefully remove the grid from the glass surface to expose the micro pattern. With a step drill bit, drill a six to 10 millimeter circular hole with smooth edges in the bottom of a 35-millimeter plastic petri dish. Carefully mix and degas silicon elastomer according to the manufacturer's instructions.Apply a thin coating of elastomer just proximate to the edge of the hole in the petri dish. The elastomer should appear as a continuous thin band surrounding the hole. Gently apply either a fusogenic or the dry acid-cleaned cover glass to the dish in order to cover the hole surrounded by elastomer.Ensure that the cover glass appears flush with the bottom of the dish and extends beyond the diameter of the hole so that a substantial portion of the glass is in contact with the plastic. Cure the elastomer by baking it at 50 degrees Celsius for two to three hours. Inject eight-week-old C57 black-6 mice with 0.5 milliliters of a sterile solution of 4%Brewer's Thioglycolate as outlined in the text protocol.72 hours later, after euthanizing the animal according to approved animal care and use guidelines, collect macrophage by interperitoneal lavage using ice-cold PBS supplemented with five-millimolar EDTA. Centrifuge the macrophages at 300 times G for three minutes, and resuspend the cell pellet in one milliliter of DMEM/F-12 supplemented with 15 millimolar heaps 10%FBS and 1%antibiotics. After counting and diluting the cells and applying them to the surfaces for 30 minutes, use HBSS 0.1%BSA to wash the surfaces, and replace the culture medium.Then return the cultures to the incubator. Two hours later, aspirate the medium, and replace it with culture medium supplemented with 10 nanograms per milliliter of IL4 before imaging the cells. When cleaned as described in this video, the cover glass is exceptionally flat with no obvious surface features;whereas the absorption of long-chain hydrocarbons followed by surface polishing creates a degree of nanotopography seen here.On clean cover-glass surfaces macrophages fuse at a very low rate. In contrast, after 24 hours in the presence of IL4, the macrophages applied to surfaces adsorbed with compounds containing long-chain hydrocarbons undergo robust fusion. Further, absorption of solvent alone does not make glass a fusogenic surface.Here, full width at half maximum, or FWHM, of structures smaller than the diffraction limit of the light microscope is used to quantitatively assess the potential differences in resolution. Importantly, there is no apparent difference in FWHM of 100-nanometer fluorescent beads among the various surfaces, suggesting that the characteristics of glass required for fluorescence imaging were sufficiently preserved. In this experiment macrophages were applied to the surfaces containing long-chain hydrocarbons.Then a form of super-resolution microscopy called 3D Direct Stochastic Optical Reconstruction Microscopy was carried out. These videos demonstrate that a variety of live-imaging techniques are feasible when macrophages are applied to the surfaces. Once mastered, modifying the glass to make the surface fusogenic can be done in half an hour if it is properly done.While attempting this procedure it is important to remember to follow it carefully. Following this procedure, other methods, like fluorescence microscopy, can be performed in order to obtain views of fusion with molecule-specific contrast. This will enable experiments designed to identify proteins directly involved at the time of fusion.After its development, this technique paved the way for investigators to acquire time-resolved views of macrophage fusion. In the future, this will help us to better understand the mechanism of macrophage fusion. After watching this video, you should be able to modify cover glass to study macrophage fusion.Please don't forget that working with acid and toluene can be extremely hazardous, and PPE and proper ventilation should always be used while performing this procedure.

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Research

JoVE Journal

Immunology and Infection

Glass Wool Filters for Concentrating Waterborne Viruses and Agricultural Zoonotic Pathogens

The key first step in evaluating pathogen levels in suspected contaminated water is concentration. Concentration methods tend to be specific for a particular pathogen group, for example US Environmental Protection Agency Method 1623 for Giardia and Cryptosporidium1, which means multiple methods are required if the sampling program is targeting more than one pathogen group. Another drawback of current methods is the equipment can be complicated and expensive, for example the VIRADEL method with the 1MDS cartridge filter for concentrating viruses2. In this article we describe how to construct glass wool filters for concentrating waterborne pathogens. After filter elution, the concentrate is amenable to a second concentration step, such as centrifugation, followed by pathogen detection and enumeration by cultural or molecular methods. The filters have several advantages. Construction is easy and the filters can be built to any size for meeting specific sampling requirements. The filter parts are inexpensive, making it possible to collect a large number of samples without severely impacting a project budget. Large sample volumes (100s to 1,000s L) can be concentrated depending on the rate of clogging from sample turbidity. The filters are highly portable and with minimal equipment, such as a pump and flow meter, they can be implemented in the field for sampling finished drinking water, surface water, groundwater, and agricultural runoff. Lastly, glass wool filtration is effective for concentrating a variety of pathogen types so only one method is necessary. Here we report on filter effectiveness in concentrating waterborne human enterovirus, Salmonella enterica, Cryptosporidium parvum, and avian influenza virus.

Glass wool filters have been used to concentrate waterborne viruses by a number of research groups around the world. Here we show a simple approach for constructing glass wool filters and demonstrate the filters are also effective in concentrating waterborne viral, bacterial and protozoan pathogens.

The key first step in evaluating pathogen levels in suspected contaminated water is concentration.  Concentration methods tend to be specific for a ...

Chemoselective Modification of Viral Surfaces via Bioorthogonal Click Chemistry

The modification of virus particles has received a significant amount of attention for its tremendous potential for impacting gene therapy, oncolytic applications and vaccine development.1,2,3 Current approaches to modifying viral surfaces, which are mostly genetics-based, often suffer from attenuation of virus production, infectivity and cellular transduction.4,5 Using chemoselective click chemistry, we have developed a straightforward alternative approach which sidesteps these issues while remaining both highly flexible and accessible.1,2
The goal of this protocol is to demonstrate the effectiveness of using bioorthogonal click chemistry to modify the surface of adenovirus type 5 particles. This two-step process can be used both therapeutically1 or analytically,2,6 as it allows for chemoselective ligation of targeting molecules, dyes or other molecules of interest onto proteins pre-labeled with azide tags. The three major advantages of this method are that (1) metabolic labeling demonstrates little to no impact on viral fitness,1,7 (2) a wide array of effector ligands can be utilized, and (3) it is remarkably fast, reliable and easy to access.1,2,7
In the first step of this procedure, adenovirus particles are produced bearing either azidohomoalanine (Aha, a methionine surrogate) or the unnatural sugar O-linked N-azidoacetylglucosamine (O-GlcNAz), both of which contain the azide (-N3) functional group. After purification of the azide-modified virus particles, an alkyne probe containing the fluorescent TAMRA moiety is ligated in a chemoselective manner to the pre-labeled proteins or glycoproteins. Finally, an SDS-PAGE analysis is performed to demonstrate the successful ligation of the probe onto the viral capsid proteins. Aha incorporation is shown to label all viral capsid proteins (Hexon, Penton and Fiber), while O-GlcNAz incorporation results in labeling of Fiber only.
In this evolving field, multiple methods for azide-alkyne ligation have been successfully developed; however only the two we have found to be most convenient are demonstrated herein &#x2013; strain-promoted azide-alkyne cycloaddition (SPAAC) and copper-catalyzed azide-alkyne cycloaddition (CuAAC) under deoxygenated atmosphere.

Adenovirus particles are engineered to contain either the unnatural amino acid analogue azidohomoalanine or the azido sugar O-GlcNAz. The azide group of each is chemoselectively ligated via "click" chemistry reactions as a means of viral surface modification.

The modification of virus particles has received a significant amount of attention for its tremendous potential for impacting gene therapy, oncolytic ...

Investigation of Macrophage Polarization Using Bone Marrow Derived Macrophages

The article describes a readily easy adaptive in vitro model to investigate macrophage polarization. In the presence of GM-CSF/M-CSF, hematopoietic stem/progenitor cells from the bone marrow are directed into monocytic differentiation, followed by M1 or M2 stimulation. The activation status can be tracked by changes in cell surface antigens, gene expression and cell signaling pathways.

The article describes a readily easy adaptive in vitro model to investigate macrophage polarization. In the presence of GM-CSF/M-CSF, hematopoietic stem/progenitor cells from the bone marrow are directed into monocytic differentiation, followed by M1 or M2 stimulation. The activation status can be tracked by changes in cell surface antigens, gene expression and cell signaling pathways.

The article describes a readily easy adaptive in vitro model to investigate macrophage polarization. In the presence of GM-CSF/M-CSF, hematopoietic ...

An In vitro Model to Study Heterogeneity of Human Macrophage Differentiation and Polarization

Monocyte-derived macrophages represent an important cell type of the innate immune system. Mouse models studying macrophage biology suffer from the phenotypic and functional differences between murine and human monocyte-derived macrophages. Therefore, we here describe an in vitro model to generate and study primary human macrophages. Briefly, after density gradient centrifugation of peripheral blood drawn from a forearm vein, monocytes are isolated from peripheral blood mononuclear cells using negative magnetic bead isolation. These monocytes are then cultured for six days under specific conditions to induce different types of macrophage differentiation or polarization. The model is easy to use and circumvents the problems caused by species-specific differences between mouse and man. Furthermore, it is closer to the in vivo conditions than the use of immortalized cell lines. In conclusion, the model described here is suitable to study macrophage biology, identify disease mechanisms and novel therapeutic targets. Even though not fully replacing experiments with animals or human tissues obtained post mortem, the model described here allows identification and validation of disease mechanisms and therapeutic targets that may be highly relevant to various human diseases.

An In vitro Model to Study Heterogeneity of Human Macrophage Differentiation and Polarization

Monocyte-derived macrophages are important cells of the innate immune system. Here, we describe an easy to use in vitro model to generate these cells. Using gradient centrifugation, negative bead isolation and specific cell culture conditions, monocyte-derived macrophages can be generated for phenotypic and functional studies.

Monocyte-derived macrophages represent an important cell type of the innate immune system. Mouse models studying macrophage biology suffer from the ...

Bone Marrow-derived Macrophage Production

Macrophages are critical components of the innate and adaptive immune responses, and they are the first line of defense against foreign invaders because of their powerful microbicidal activities. Macrophages are widely distributed throughout the body and are present in the lymphoid organs, liver, lungs, gastrointestinal tract, central nervous system, bone, and skin. Because of their repartition, they participate in a wide range of physiological and pathological processes. Macrophages are highly versatile cells that are able to recognize microenvironmental alterations and to maintain tissue homeostasis. Numerous pathogens have evolved mechanisms to use macrophages as Trojan horses to survive, replicate in, and infect both humans and animals and to propagate throughout the body. The recent explosion of interest in evolutionary, genetic, and biochemical aspects of host-pathogen interactions has renewed scientific attention regarding macrophages. Here, we describe a procedure to isolate and cultivate macrophages from murine bone marrow that will provide large numbers of macrophages for studying host-pathogen interactions as well as other processes.

Macrophages have long been recognized as a critical component of the innate and adaptive immune responses. The recent explosion of knowledge pertaining to evolutionary, genetic, and biochemical aspects of the interaction between macrophages and microbes has renewed scientific attention to macrophages. This article describes a method to differentiate macrophages from mouse bone marrow.

Macrophages are critical components of the innate and adaptive immune responses, and they are the first line of defense against foreign invaders because ...

RNA Purification from Intracellularly Grown Listeria monocytogenes in Macrophage Cells

Analysis of the transcriptome of bacterial pathogens during mammalian infection is a valuable tool for studying genes and factors that mediate infection. However, isolating bacterial RNA from infected cells or tissues is a challenging task, since mammalian RNA mostly dominates the lysates of infected cells. Here we describe an optimized method for RNA isolation of Listeria monocytogenes bacteria growing within bone marrow derived macrophage cells. Upon infection, cells are mildly lysed and rapidly filtered to discard most of the host proteins and RNA, while retaining intact bacteria. Next, bacterial RNA is isolated using hot phenol-SDS extraction followed by DNase treatment. The extracted RNA is suitable for gene transcription analysis by multiple techniques. This method is successfully employed in our studies of Listeria monocytogenes gene regulation during infection of macrophage cells 1-4. The protocol can be easily modified to study other bacterial pathogens and cell types.

RNA Purification from Intracellularly Grown Listeria monocytogenes in Macrophage Cells

Here we describe a method for bacterial RNA isolation from Listeria monocytogenes bacteria growing inside murine macrophages. This technique can be used with other intracellular pathogens and mammalian host cells.

Analysis of the transcriptome of bacterial pathogens during mammalian infection is a valuable tool for studying genes and factors that mediate infection. ...

A High-throughput Compatible Assay to Evaluate Drug Efficacy against Macrophage Passaged Mycobacterium tuberculosis

The early drug development process for anti-tuberculosis drugs is hindered by the inefficient translation of compounds with in vitro activity to effectiveness in the clinical setting. This is likely due to a lack of consideration for the physiologically relevant cellular penetration barriers that exist in the infected host. We recently established an alternative infection model that generates large macrophage aggregate structures containing densely packed M. tuberculosis (Mtb) at its core, which was suitable for drug susceptibility testing. This infection model is inexpensive, rapid, and most importantly BSL-2 compatible. Here, we describe the experimental procedures to generate Mtb/macrophage aggregate structures that would produce macrophage-passaged Mtb for drug susceptibility testing. In particular, we demonstrate how this infection system could be directly adapted to the 96-well plate format showing throughput capability for the screening of compound libraries against Mtb. Overall, this assay is a valuable addition to the currently available Mtb drug discovery toolbox due to its simplicity, cost effectiveness, and scalability.

A High-throughput Compatible Assay to Evaluate Drug Efficacy against Macrophage Passaged Mycobacterium tuberculosis

New models and assays that would improve the early drug development process for next-generation anti-tuberculosis drugs are highly desirable. Here, we describe a quick, inexpensive, and BSL-2 compatible assay to evaluate drug efficacy against Mycobacterium tuberculosis that can be easily adapted for high-throughput screening.

The early drug development process for anti-tuberculosis drugs is hindered by the inefficient translation of compounds with in vitro activity to ...

Visualizing Macrophage Extracellular Traps Using Confocal Microscopy

A primary method used to define the presence of neutrophil extracellular traps (NETs) is confocal microscopy. We have modified established confocal microscopy methods to visualize macrophage extracellular traps (METs). These extracellular traps are defined by the presence of extracellular chromatin with co-expression of other components such as granule proteases, citrullinated histones, and peptidyl arginase deiminase (PAD). The expression of METs is generally measured after exposure to a stimulus and compared to un-stimulated samples. Samples are also included for background and isotype control. Cells are analyzed using well-defined image analysis software. Confocal microscopy may be used to define the presence of METs both in vitro and in vivo in lung tissue.

Macrophage extracellular traps are a newly described entity. This article will concentrate on confocal microscopy methods and how they are visualized in vitro and in vivo from lung samples.

A primary method used to define the presence of neutrophil extracellular traps (NETs) is confocal microscopy. We have modified established confocal ...

A High-throughput Cre-Lox Activated Viral Membrane Fusion Assay to Identify Inhibitors of HIV-1 Viral Membrane Fusion

This assay is designed to specifically report on HIV-1 fusion via the expression of green fluorescent protein (GFP) detectable by flow cytometry or fluorescence microscopy. An HIV-1 reporter virus (HIV-1 Gag-iCre) is generated by inserting Cre recombinase into the HIV-1 genome between the matrix and the capsid proteins of the Gag polyprotein. This results in a packaging of Cre recombinase into virus particles, which is then released into a target cell line stably expressing a Cre recombinase-activated red fluorescent protein (RFP) to GFP switch cassette. In the basal state, this cassette expresses RFP only. Following the delivery of Cre recombinase into the target cell, the RFP, flanked by loxP sites, excises, resulting in GFP expression. This assay can be used to test any inhibitors of viral entry (specifically at the fusion step) in cell-free and cell-to-cell infection systems and has been used to identify a class of purinergic receptor antagonists as novel inhibitors of HIV-1 viral membrane fusion.

We describe a cell-based assay to report on HIV-1 fusion via the expression of green fluorescent protein detectable by flow cytometry or fluorescence microscopy. It can be used to test inhibitors of viral entry (specifically at the fusion step) in cell-free and cell-to-cell infection systems.

This assay is designed to specifically report on HIV-1 fusion via the expression of green fluorescent protein (GFP) detectable by flow cytometry or ...

An Immunohistopathologic Study to Profile the Folate Receptor Beta Macrophage and Vascular Immune Microenvironment in Giant Cell Arteritis

Giant cell arteritis (GCA) is a chronic immune-mediated disease of medium-to-large sized arteries that affects older adults. GCA manifests with arthritis and occlusive symptoms of headaches, stroke or vision loss. Macrophages and T-helper lymphocytes infiltrate the vascular wall and produce a pro-inflammatory response that lead to vessel damage and ischemia. To date, there is no GCA biomarker that can monitor disease activity and guide therapeutic response.
Folate receptor beta (FRB) is a glycosylphosphatidylinositol protein that is anchored on cell membranes and normally expressed in the myelomonocytic lineage and in the majority of myeloid leukemia cells as well as in tumor and rheumatoid synovial macrophages, where its expression correlates with disease severity. The ability of FRB to bind folate compounds, folic acid-conjugates and antifolate drugs has made it a druggable target in cancer and inflammatory disease research. This report describes the histopathologic and immunohistochemical methods used to assess expression and distribution of FRB in relation to GCAimmunopathology.
Formalin-fixed and paraffin-embedded temporal artery biopsies from GCA and normal controls were stained with Hematoxylin and Eosin to review tissue histology and identify pathognomonic features.Immunohistochemistry was used to detect FRB, CD68 and CD3 expression. A microscopic analysis was performed to quantify the number of positively stained cells on 10 selected high-power-field sections and their respective locations in the arterial wall.
Lymphohistiocytic (LH) inflammation accompanied by intimal hyperplasia and disrupted elastic lamina was seen in GCA with none found in controls. The LH infiltrate was composed of approximately 60% lymphocytes and 40% macrophages. FRB expression was restricted to macrophages, comprising 31% of the total CD68+ macrophage population and localized to the media and adventitia. No FRB was seen in controls.
This protocol demonstrated a distinct numerical and spatial pattern of the FRB macrophage relative to the vascular immune microenvironment in GCA.

The protocol illustrates the use of histopathologic examination and immunohistochemistry to profile the folate receptor beta macrophage and its relationship with the total immune cell infiltrate in temporal artery biopsies in giant cell arteritis.

Giant cell arteritis (GCA) is a chronic immune-mediated disease of medium-to-large sized arteries that affects older adults. GCA manifests with arthritis ...