Name: rapid and robust analysis of cellular and molecular polarization induced by chemokine signaling
Uploaded: 2014-12-12T14:00:00.000+00:00
Duration: 10 min 3 s
Description: Watch this Scientific Journal Video about Rapid and Robust Analysis of Cellular and Molecular Polarization Induced by Chemokine Signaling at JoVE.com

The authors greatly acknowledge Pierre Bourdoncle, Thomas Guilbert and Louise Rimbault of the Cochin Imaging Facility. This work was supported by Inserm, CNRS and Ligue Nationale contre le Cancer (Equipe labellis&#233;e).

1. Preparation of T Lymphocytes
<ol>
	<li>Prepare primary mouse or human T cells as described10,11.</li>
	<li>Cultivate human T cells in complete RPMI medium with 10% human serum AB at a density of 2 - 3 x 106 cells/ml. 
	NOTE: The use of fetal calf serum (FCS) instead of human serum can elicit spontaneous polarization of a large fraction of human T cells in culture. Keep these cells in culture for 4 - 5 days and further process them at any time during this period.</li>
	<li>Maintain mouse T cells in complete RPMI medium supplemented with 10% FCS at a similar cell density. Use right away or the next day, after an O/N culture at 37 &#176;C in the presence of 10 ng/ml IL7.</li>
	<li>Cultivate the CEM human T cell line in complete RPMI supplemented with 10% FCS.</li>
</ol>
2. Chemokine Stimulation
<ol>
	<li>Wash 5 x 105 cells per experimental condition in warm HBSS medium supplemented with 10 mM Hepes. For some experiments, co-transfect primary human T cells the day before with 2 &#181;g pmaxGFP and 8 &#181;g pcDNA3.1+ (empty vector, control), PKC&#950; kinase dead, or N-terminal Par6 plasmids.</li>
	<li>Resuspend the cell pellet in warm HBSS-Hepes medium (use 0.3 ml x number of experimental conditions).</li>
	<li>Distribute the cells in 1.5 ml microcentrifuge tubes. 
	NOTE: Therefore, one tube corresponding to a single experimental condition will contain 5 x 105 cells in 0.3 ml HBSS-Hepes medium. For some experiments, add 500 nM Latrunculin A or vehicle (DMSO) and incubate the cells for 30 min before chemokine stimulation.</li>
	<li>Add 10 to 500 ng/ml CCL19 or CXCL12 chemokine in each tube. 
	NOTE: We usually use 10 - 200 ng/ml chemokine for human T cells. CEM cells do not express the CCR7 receptor that binds CCL19. Therefore, CEM cells will only be able to respond to a CXCL12 stimulation. Moreover, use higher chemokine concentrations (300 - 500 ng/ml) to polarize mouse T cells.</li>
	<li>Flip the tubes several times and incubate them in a 37 &#176;C water bath for 8 or 10 min for primary T cells or CEM, respectively.</li>
	<li>Stop the polarization process by adding to each tube 0.3 ml of a warm solution containing 2% paraformaldehyde (PFA) and 10 mM Hepes in PBS. Flip the tubes and incubate them at 37 &#176;C for 5 min.</li>
</ol>
3. Stainings
<ol>
	<li>Transfer the cells from the microcentrifuge tubes to flow cytometry tubes.</li>
	<li>Fill the tubes completely with a RT solution containing 1% bovine serum albumin (BSA), 0.5 mM EDTA and 10 mM Hepes in PBS.</li>
	<li>Centrifuge the tubes at 460 x g for 4 min.</li>
	<li>Discard the supernatant and resuspend the cells in 100 &#181;l of a RT solution containing 5% FCS in PBS.</li>
	<li>Add 5 &#181;l of FITC-anti-HLA-ABC in each tube, vortex them, and incubate them for 30 min at RT, away from light.</li>
	<li>Wash cells once with PBS containing 5% FCS, and once with PBS only.</li>
	<li>At RT: add 500 &#181;l 1% PFA, incubate for 10 min, then wash cells with a solution containing 1% BSA, 0.5 mM EDTA and 10 mM HEPES in PBS.</li>
	<li>Discard the supernatant, fill the tubes completely with a solution of PBS containing 0.2% BSA, 0.1% saponin, 0.5 mM EDTA and 10 mM Hepes (permeabilization buffer).</li>
	<li>Wash cells twice in this medium.</li>
	<li>Flip the tubes to remove the medium and vortex them to dissociate the cell pellet.</li>
	<li>Add 0.25 &#181;g/ml TRITC-Phalloidin and/or a 1:100 dilution of anti-P-ERM antibody to each tube, vortex them and incubate for 30 min at RT.</li>
	<li>Wash cells with the permeabilization buffer. Incubate with a fluorescent secondary antibody if necessary.</li>
	<li>Resuspend the cells in 200 &#181;l PBS and transfer them to microcentrifuge tubes. 
	NOTE: Cells are ready for acquisition. Alternatively, while keeping a maximum total volume of 200 &#181;l per tube, add concentrated PFA to a final 1% concentration in order to preserve the stainings if the cells are not to be used the same day for further processing.</li>
</ol>
4. Images Acquisition and Analysis
<ol>
	<li>Switch on the apparatus (see Table of Specific Reagents/Equipment) and let it calibrate itself according to the manufacturer&#8217;s instructions. 
	NOTE: The INSPIRE software was used with a 40X objective (0.75 NA). The IDEAS 3.0 software was used for all the reported quantifications.</li>
	<li>Prepare a series of acquisition windows which can be saved in a template for future experiments. Draw histograms that quantify the RMS gradient values. From the &#34;In Focus&#34; population, selected on the RMS gradient histogram, delimitate the &#34;Single cell&#34; population on a histogram of the Area. Once the microcentrifuge tube has been inserted in the machine, adjust the laser power, gate on individual cells and acquire 5,000 T lymphocytes.</li>
	<li>In the Ideas software, open the acquisition file and create a histogram that will show the value of the gradient RMS value for bright field images (Channel 1) obtained for each individual cell. Draw a gate on the RMS gradient histogram that considers cells exhibiting RMS gradient value above 57. 
	NOTE: The RMS gradient allows taking into account in the analysis only the T lymphocytes that are in the focal plane. We have determined empirically that individual cells exhibiting a RMS gradient value superior to 57 are in the focal plane, and can be accurately considered.</li>
	<li>In the Analysis/Masks menu, create a new mask, called Erode(M01,2) from the morphology mask on the brightfield images M01, eroded of 2 pixels. Then, in the Analysis/Features menu, create a new feature of the Area, calculated on the Erode(M01,2) mask. From the cells selected in the previous gate, open a histogram showing the Area of cells using this newly created mask. 
	NOTE: The morphology masks that are available by default are much bigger than the actual size of the cell. Thus, it is more precise to erode it up to 2 pixels.</li>
	<li>Draw a gate on the individual T cells, excluding the calibration beads and debris (small Area) and the doublets (large Area). Adjust this gate at each acquisition. 
	NOTE: Variations in cell size will affect the position of the gate. As mouse T cells are smaller than human T cells which are themselves smaller than CEM cells, the area of each cell type will be proportional to its size.</li>
	<li>Considering the single, in-focus cells that were gated at the previous steps, open a dot plot consisting of the Raw Max Pixel on the HLA-ABC staining (Channel 2, x axis) as a function of the Raw Max Pixel on the phalloidin staining (Channel 4, y axis). Create a gate to exclude the unstained or saturated fluorescent events. Open two histograms showing the Raw Max Pixel for HLA-ABC (Channel 2) and phalloidin (Channel 4) stainings.</li>
	<li>In the Analysis/Masks menu, create a new mask, called Erode(M02,2) from the morphology mask of the HLA-ABC stained cells (Channel 2), eroded of 2 pixels. Then, in the Analysis/Features menu, create a new feature consisting of the Circularity parameter, calculated on the Erode(M02,2). 
	NOTE: This parameter measures the deviation of the cell shape from a circle. Therefore, a perfectly round T cell will have a high circularity value whereas elongated polarized cells will exhibit a low circularity index.</li>
	<li>Subsequently, create another histogram that will report the values of the Circularity feature from the previously gated cells. Use this histogram to directly plot the distribution of an individual, in-focus cell population according to the value of the Circularity for each individual cell.</li>
	<li>Looking at the shape of the histogram for non-stimulated cells, draw a gate for polarized cells, starting at the lowest circularity value up to the circularity limit value where most of the non-stimulated cells are plotted. Look at the statistics display for the percentage of polarized cells among the gated population (%Gated). 
	NOTE: We have set this gate for Circularity index values below 13.</li>
	<li>In order to look at the polarization of the actin staining in the cells, plot a histogram for the Bright Detail Similarity R3 value, comparing the HLA-ABC staining (Channel 2) and the phalloidin staining (Channel 4). 
	NOTE: The bigger the value of this feature, the more superimposed the two stainings are.</li>
	<li>Using the same gating strategy as before, plot a gate on the non-stimulated cells for the segregated staining that shows the percentage of cells with polarized actin staining.</li>
	<li>When completed, the percentage of cells exhibiting a segregation in the distribution of the MHC Class I and phalloidin stainings, the percentage of polarized cells together with the mean values of the Circularity and Similarity indexes of all the cells &#177; SD are shown in the corresponding statistics panels.</li>
</ol>

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	<li>Rossi, D., Zlotnik, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+biology+of+chemokines+and+their+receptors.">The biology of chemokines and their receptors.</a> Annu Rev Immunol. 18, 217-242 (2000).</li><li>Thelen, M., Stein, J. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+chemokines+invite+leukocytes+to+dance.">How chemokines invite leukocytes to dance.</a> Nat Immunol. 9 (9), 953-959 (2008).</li><li>Rougerie, P., Rho Delon, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GTPases:+masters+of+T+lymphocyte+migration+and+activation.">GTPases: masters of T lymphocyte migration and activation.</a> Immunol Lett. 142 (1-2), 1-13 (2012).</li><li>Sanchez-Madrid, F., del Pozo, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leukocyte+polarization+in+cell+migration+and+immune+interactions.">Leukocyte polarization in cell migration and immune interactions.</a> Embo J. 18 (3), 501-511 (1999).</li><li>Adams, D. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hepatocyte+growth+factor+and+macrophage+inflammatory+protein+1+beta:+structurally+distinct+cytokines+that+induce+rapid+cytoskeletal+changes+and+subset-preferential+migration+in+T+cells.">Hepatocyte growth factor and macrophage inflammatory protein 1 beta: structurally distinct cytokines that induce rapid cytoskeletal changes and subset-preferential migration in T cells.</a> Proc Natl Acad Sci U S A. 91 (15), 7144-7148 (1994).</li><li>Rougerie, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fam65b+is+a+new+transcriptional+target+of+FOXO1+that+regulates+RhoA+signaling+for+T+lymphocyte+migration.">Fam65b is a new transcriptional target of FOXO1 that regulates RhoA signaling for T lymphocyte migration.</a> J Immunol. 190 (2), 748-7455 (2013).</li><li>Real, E., Faure, S., Donnadieu, E., Delon, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cutting+edge:+Atypical+PKCs+regulate+T+lymphocyte+polarity+and+scanning+behavior.">Cutting edge: Atypical PKCs regulate T lymphocyte polarity and scanning behavior.</a> J Immunol. 179 (9), 5649-5652 (2007).</li><li>Negulescu, P. 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The authors declare that they have no competing financial interests.

Using a recent technology of imaging flow cytometry, a rapid and informative gating strategy to analyze cellular and molecular events induced by chemokine stimulation is presented. From a single experiment, one can obtain two main types of information: the changes in cell morphology induced by chemokine stimulation and the subcellular distribution of different proteins during the polarization process. Interestingly, evidence is also provided for the possibility to analyze a large number of cells, which allows statistical...

Chemokines are small soluble proteins that attract cells to specialized locations1. Therefore, they participate in the correct positioning of cells in tissues, a crucial function in development and physiology. The immune system is no exception to this rule as it relies on the action of many different cell types which act in concert to mount an effective immune response. By controlling the specific location of one immune cell type in a given state, chemokines are pre-required before foreign antigens can be detected and neutralized.
In T lymphocytes in particular, chemokines bind to specific surface receptors which, upon engagement, elicit many intracellular signals (calcium rise, ERK phosphorylation, Rho GTPases activation, increase in integrins affinity and cytoskeletal alterations) that favor T cell motility2,3. At the cellular level, one can observe morphological alterations elicited upon chemokine stimulation. These changes in cell shapes are especially dramatic in T cells: resting T cells have a bead-like round morphology when travelling in the blood stream. However, the sensing of the presence of chemokines in inflammatory sites or at proximity of lymphoid organs is going to change the shape of T cells which now adopt a typical &#8220;hand-mirror&#8221; morphology consisting of a bipolar form: a leading edge at the front and a trailing edge, or uropod, at the back4. In addition, intracellular components can segregate into these two opposite regions of a polarized T cell to sustain migration. For example, actin filaments polymerization increases upon chemokine stimulation5 and polymerized actin accumulates at the front of a polarized T cell2. On the other hand, several proteins, such as phosphorylated proteins of the Ezrin-Radixin-Moesin (ERM) family which link the plasma membrane to the cortical F-actin cytoskeleton, re-localize at the uropod of polarized T cells6. Interestingly, we and others have shown that this polarization process is required for T cell migration. Indeed, any treatment that interferes with polarization will inhibit cellular motility. For instance, inhibition of the activity of the members of the atypical protein kinases C (PKC) family, PKC&#950; and PKC&#953; blocks T cell polarization and their migratory scanning process of dendritic cells7. T cell polarization is also regulated by Rho GTPases. We have shown that the modulation of RhoA activity by the recently described Fam65b protein interferes with T cell changes in morphology and their capacity to migrate in a Transwell assay6. As polarization is a prerequisite step for cellular motility, it is thus crucial to be able to quantify it as a main readout of chemokine responses. Cell shape alterations were previously measured manually8. However, this kind of quantification is very time-consuming, so that usually only a few tens of cells are taken into account.
Here, a new method is presented to rapidly quantify the degree of shape alterations of T lymphocytes exposed to chemokine stimulation. An imaging flow cytometry technology (see Table of Specific Reagents/Equipment) is used, which combines the advantages of a flow cytometer and a microscope9 to quantify efficiently the amount of polarized cells in different conditions of chemokine stimulation. In addition to the quantification of the morphological alterations that one can measure robustly with this technology, it is also possible to evaluate changes in the subcellular localization of some proteins upon chemokine signaling.

<table><tbody><tr><td>RPMI</td><td>Gibco</td><td>61870-010</td><td></td></tr><tr><td>Human serum AB</td><td>PAA</td><td>C11-021</td><td>Pre-heat to inactivate the complement.</td></tr><tr><td>Fetal calf serum</td><td>PAN Biotech</td><td>P30-3300</td><td>Pre-heat to inactivate the complement.</td></tr><tr><td>Human T cell nucleofactor kit</td><td>Lonza</td><td>VCA-1002</td><td></td></tr><tr><td>Murine IL7</td><td>Peprotech</td><td>217-17</td><td></td></tr><tr><td>HBSS</td><td>Gibco</td><td>14025-050</td><td>Warm in 37 &amp;deg;C water bath before use.</td></tr><tr><td>Hepes</td><td>Gibco</td><td>15630-056</td><td></td></tr><tr><td>Murine CCL19</td><td>Peprotech</td><td>250-27B</td><td>Aliquots are thawed on ice before adding the chemokine to the cells.</td></tr><tr><td>Human CCL19</td><td>Peprotech</td><td>300-29B</td><td>Aliquots are thawed on ice before adding the chemokine to the cells.</td></tr><tr><td>Human CXCL12</td><td>Peprotech</td><td>300-28A</td><td>Aliquots are thawed on ice before adding the chemokine to the cells. This chemokine can also be used on mouse T cells.</td></tr><tr><td>PFA</td><td>Electron Microscopy Sciences</td><td>157-8-100</td><td>This is a 8% PFA solution in water. Mix volume to volume with 2x PBS to obtain a 4% PFA solution in PBS.</td></tr><tr><td>BSA</td><td>Sigma</td><td>A3059</td><td></td></tr><tr><td>Saponin</td><td>Fluka</td><td>84510</td><td></td></tr><tr><td>Alexa Fluor 594 phalloidin</td><td>Invitrogen</td><td>A12381</td><td></td></tr><tr><td>FITC-anti-HLA-ABC antibody</td><td>Beckman Coulter</td><td>IM1838</td><td>clone B9.12.1</td></tr><tr><td>Anti-P-ERM antibody</td><td>Cell Signaling Technology</td><td>3149P</td><td></td></tr><tr><td>ImageStream&lt;sup&gt;x&lt;/sup&gt; Mark II</td><td>Amnis</td><td></td><td></td></tr></tbody></table>

rapid and robust analysis of cellular and molecular polarization induced by chemokine signaling

Cells respond to chemokine stimulation by losing their round shape in a process called polarization, and by altering the subcellular localization of many proteins. Classic imaging techniques have been used to study these phenomena. However, they required the manual acquisition of many cells followed by time consuming quantification of the morphology and the co-localization of the staining of tens of cells. Here, a rapid and powerful method is described to study these phenomena on samples consisting of several thousands of cells using an imaging flow cytometry technology that combines the advantages of a microscope with those of a cytometer. Using T lymphocytes stimulated with CCL19 and staining for MHC Class I molecules and filamentous actin, a gating strategy is presented to measure simultaneously the degree of shape alterations and the extent of co-localization of markers that are affected by CCL19 signaling. Moreover, this gating strategy allowed us to observe the segregation of filamentous actin (at the front) and phosphorylated Ezrin-Radixin-Moesin (phospho-ERM) proteins (at the rear) in polarized T cells after CXCL12 stimulation. This technique was also useful to observe the blocking effect on polarization of two different elements: inhibition of actin polymerization by a pharmacological inhibitor and expression of mutants of the Par6/atypical PKC signaling pathway. Thus, evidence is shown that this technique is useful to analyze both morphological alterations and protein redistributions.

The first example chosen here concerns the use of human primary T lymphocytes stimulated with CCL19. However, the same strategy can be used with primary mouse T cells, T cell lines or any other cell type responsive to chemokine stimulation. The gating strategy presented here includes a series of windows that select the focused events, then the single cells. Finally the range of fluorescence intensity is followed here as an example on two markers: the MHC Class I HLA-ABC and filamentous actin for resting (Figure 1...

Watch this Scientific Journal Video about Rapid and Robust Analysis of Cellular and Molecular Polarization Induced by Chemokine Signaling at JoVE.com

Rapid and Robust Analysis of Cellular and Molecular Polarization Induced by Chemokine Signaling

Chemokine signaling elicits marked alterations of cellular morphology and some important redistributions of intracellular proteins. Here, a rapid and detailed protocol is provided to study these events.

Cells respond to chemokine stimulation by losing their round shape in a process called polarization, and by altering the subcellular localization of many ...

rapid-robust-analysis-cellular-molecular-polarization-induced

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Cell Polarization and Migration

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8.0K Views.  Institut Cochin. Chemokine signaling elicits marked alterations of cellular morphology and some important redistributions of intracellular proteins. Here, a rapid and detailed protocol is provided to study these events.

Video: Rapid and Robust Analysis of Cellular and Molecular Polarization Induced by Chemokine Signaling

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 ...

Planar Gradient Diffusion System to Investigate Chemotaxis in a 3D Collagen Matrix

The importance of cell migration can be seen through the development of human life. When cells migrate, they generate forces and transfer these forces to their surrounding area, leading to cell movement and migration. In order to understand the mechanisms that can alter and/or affect cell migration, one can study these forces. In theory, understanding the fundamental mechanisms and forces underlying cell migration holds the promise of effective approaches for treating diseases and promoting cellular transplantation. Unfortunately, modern chemotaxis chambers that have been developed are usually restricted to two dimensions (2D) and have complex diffusion gradients that make the experiment difficult to interpret. To this end, we have developed, and describe in this paper, a direct-viewing chamber for chemotaxis studies, which allows one to overcome modern chemotaxis chamber obstacles able to measure cell forces and specific concentration within the chamber in a 3D environment to study cell 3D migration. More compelling, this approach allows one to successfully model diffusion through 3D collagen matrices and calculate the coefficient of diffusion of a chemoattractant through multiple different concentrations of collagen, while keeping the system simple and user friendly for traction force microscopy (TFM) and digital volume correlation (DVC) analysis.

Cell migration is an important part of human development and life. In order to understand the mechanisms that can alter cell migration, we present a planar gradient diffusion system to investigate chemotaxis in a 3D collagen matrix, which allows one to overcome modern diffusion chamber limitations of existing assays.

The importance of cell migration can be seen through the development of human life. When cells migrate, they generate forces and transfer these forces to ...

Bioengineering

Polydimethylsiloxane-polycarbonate Microfluidic Devices for Cell Migration Studies Under Perpendicular Chemical and Oxygen Gradients

This paper reports a microfluidic device made of polydimethylsiloxane (PDMS) with an embedded polycarbonate (PC) thin film to study cell migration under combinations of chemical and oxygen gradients. Both chemical and oxygen gradients can greatly affect cell migration in vivo; however, due to technical limitations, very little research has been performed to investigate their effects in vitro. The device developed in this research takes advantage of a series of serpentine-shaped channels to generate the desired chemical gradients and exploits a spatially confined chemical reaction method for oxygen gradient generation. The directions of the chemical and oxygen gradients are perpendicular to each other to enable straightforward migration result interpretation. In order to efficiently generate the oxygen gradients with minimal chemical consumption, the embedded PC thin film is utilized as a gas diffusion barrier. The developed microfluidic device can be actuated by syringe pumps and placed into a conventional cell incubator during cell migration experiments to allow for setup simplification and optimized cell culture conditions. In cell experiments, we used the device to study migrations of adenocarcinomic human alveolar basal epithelial cells, A549, under combinations of chemokine (stromal cell-derived factor, SDF-1&#945;) and oxygen gradients. The experimental results show that the device can stably generate perpendicular chemokine and oxygen gradients and is compatible with cells. The migration study results indicate that oxygen gradients may play an essential role in guiding cell migration, and cellular behavior under combinations of gradients cannot be predicted from those under single gradients. The device provides a powerful and practical tool for researchers to study interactions between chemical and oxygen gradients in cell culture, which can promote better cell migration studies in more in vivo-like microenvironments.

The control of chemical and oxygen gradients is essential for cell cultures. This paper reports a polydimethylsiloxane-polycarbonate (PDMS-PC) microfluidic device capable of reliably generating combinations of chemical and oxygen gradients for cell migration studies, which can be practically utilized in biological labs without sophisticated instrumentation.

This paper reports a microfluidic device made of polydimethylsiloxane (PDMS) with an embedded polycarbonate (PC) thin film to study cell migration under ...

3D Analysis of Multi-cellular Responses to Chemoattractant Gradients

Various limitations of 2D cell culture systems have sparked interest in 3D cell culture and analysis platforms, which would better mimic the spatial and chemical complexity of living tissues and mimic in vivo tissue functions. Recent advances in microfabrication technologies have facilitated the development of 3D in vitro environments in which cells can be integrated into a well-defined extracellular matrix (ECM) and a defined set of soluble or matrix associated biomolecules. However, technological barriers have limited their widespread use in research laboratories. Here, we describe a method to construct simple devices for 3D culture and experimentation with cells and multicellular organoids in 3D microenvironments with a defined chemoattractant gradient. We illustrate the use of this platform for analysis of the response of epithelial cells and organoids to gradients of growth factors, such as epidermal growth factor (EGF). EGF gradients were stable in the devices for several days leading to directed branch formation in breast organoids. This analysis allowed us to conclude that collective gradient sensing by groups of cells is more sensitive vs. single cells. We also describe the fabrication method, which does not require photolithography facilities nor advanced soft lithography techniques. This method will be helpful to study 3D cellular behaviors in the context of the analysis of development and pathological states, including cancer.

We describe a method to construct devices for 3D culture and experimentation with cells and multicellular organoids. This device allows analysis of cellular responses to soluble signals in 3D microenvironments with defined chemoattractant gradients. Organoids are better than single cells at detection of weak noisy inputs.

Various limitations of 2D cell culture systems have sparked interest in 3D cell culture and analysis platforms, which would better mimic the spatial and ...

Imaging G-protein Coupled Receptor (GPCR)-mediated Signaling Events that Control Chemotaxis of Dictyostelium Discoideum

Many eukaryotic cells can detect gradients of chemical signals in their environments and migrate accordingly 1. This guided cell migration is referred as chemotaxis, which is essential for various cells to carry out their functions such as trafficking of immune cells and patterning of neuronal cells 2, 3. A large family of G-protein coupled receptors (GPCRs) detects variable small peptides, known as chemokines, to direct cell migration in vivo 4. The final goal of chemotaxis research is to understand how a GPCR machinery senses chemokine gradients and controls signaling events leading to chemotaxis. To this end, we use imaging techniques to monitor, in real time, spatiotemporal concentrations of chemoattractants, cell movement in a gradient of chemoattractant, GPCR mediated activation of heterotrimeric G-protein, and intracellular signaling events involved in chemotaxis of eukaryotic cells 5-8. The simple eukaryotic organism, Dictyostelium discoideum, displays chemotaxic behaviors that are similar to those of leukocytes, and D. discoideum is a key model system for studying eukaryotic chemotaxis. As free-living amoebae, D. discoideum cells divide in rich medium. Upon starvation, cells enter a developmental program in which they aggregate through cAMP-mediated chemotaxis to form multicullular structures. Many components involved in chemotaxis to cAMP have been identified in D. discoideum. The binding of cAMP to a GPCR (cAR1) induces dissociation of heterotrimeric G-proteins into G&gamma; and G&beta;&gamma; subunits 7, 9, 10. G&beta;&gamma; subunits activate Ras, which in turn activates PI3K, converting PIP2 into PIP3 on the cell membrane 11-13. PIP3 serve as binding sites for proteins with pleckstrin Homology (PH) domains, thus recruiting these proteins to the membrane 14, 15. Activation of cAR1 receptors also controls the membrane associations of PTEN, which dephosphorylates PIP3 to PIP2 16, 17. The molecular mechanisms are evolutionarily conserved in chemokine GPCR-mediated chemotaxis of human cells such as neutrophils 18. We present following methods for studying chemotaxis of D. discoideum cells. 1. Preparation of chemotactic component cells. 2. Imaging chemotaxis of cells in a cAMP gradient. 3. Monitoring a GPCR induced activation of heterotrimeric G-protein in single live cells. 4. Imaging chemoattractant-triggered dynamic PIP3 responses in single live cells in real time. Our developed imaging methods can be applied to study chemotaxis of human leukocytes.

Imaging G-protein Coupled Receptor GPCR-mediated Signaling Events that Control Chemotaxis of Dictyostelium Discoideum

Here, we describe detailed live cell imaging methods for investigating chemotaxis. We present fluorescence microscopic methods to monitor spatiotemporal dynamics of signaling events in migrating cells. Measurement of signaling events permits us to further understand how a GPCR-signaling network achieves gradient sensing of chemoattractants and controls directional migration of eukaryotic cells.

Many eukaryotic cells can detect gradients of chemical signals in their environments and migrate accordingly 1.  This guided cell migration is referred as ...

Biology

Measurement of Cellular Chemotaxis with ECIS/Taxis

Cellular movement in response to external stimuli is fundamental to many cellular processes including wound healing, inflammation and the response to infection. A common method to measure chemotaxis is the Boyden chamber assay, in which cells and chemoattractant are separated by a porous membrane. As cells migrate through the membrane toward the chemoattractant, they adhere to the underside of the membrane, or fall into the underlying media, and are subsequently stained and visually counted 1. In this method, cells are exposed to a steep and transient chemoattractant gradient, which is thought to be a poor representation of gradients found in tissues 2.
Another assay system, the under-agarose chemotaxis assay, 3, 4 measures cell movement across a solid substrate in a thin aqueous film that forms under the agarose layer. The gradient that develops in the agarose is shallow and is thought to be an appropriate representation of naturally occurring gradients. Chemotaxis can be evaluated by microscopic imaging of the distance traveled. Both the Boyden chamber assay and the under-agarose assay are usually configured as endpoint assays.
The automated ECIS/Taxis system combines the under-agarose approach with Electric Cell-substrate Impedance Sensing (ECIS) 5, 6. In this assay, target electrodes are located in each of 8 chambers. A large counter-electrode runs through each of the 8 chambers (Figure 2). Each chamber is filled with agarose and two small wells are the cut in the agarose on either side of the target electrode. One well is filled with the test cell population, while the other holds the sources of diffusing chemoattractant (Figure 3). Current passed through the system can be used to determine the change in resistance that occurs as cells pass over the target electrode. Cells on the target electrode increase the resistance of the system 6. In addition, rapid fluctuations in the resistance represent changes in the interactions of cells with the electrode surface and are indicative of ongoing cellular shape changes. The ECIS/Taxis system can measure movement of the cell population in real-time over extended periods of time, but is also sensitive enough to detect the arrival of a single cell at the target electrode. 
Dictyostelium discoidium is known to migrate in the presence of a folate gradient 7, 8 and its chemotactic response can be accurately measured by ECIS/Taxis 9. Leukocyte chemotaxis, in response to SDF1&alpha; and to chemotaxis antagonists has also been measured with ECIS/Taxis 10, 11. An example of the leukocyte response to SDF1&alpha; is shown in Figure 1.

The ECIS/Taxis system is an automated, real-time assay that measures cellular chemotaxis. In this assay, cells move beneath a layer of agarose to arrive at a target electrode. Cellular movement is measured by the onset of resistance to AC current 0.

Cellular movement in response to external stimuli is fundamental to many cellular processes including wound healing, inflammation and the response to ...

Assessment of Lymphocyte Migration in an Ex Vivo Transmigration System

Herein, we present an efficient method that can be executed with basic laboratory skills and materials to assess lymphocyte chemokinetic movement in an ex vivo transmigration system. Group 2 innate lymphoid cells (ILC2) and CD4+ T helper cells were isolated from spleens and lungs of chicken egg ovalbumin (OVA)-challenged BALB/c mice. We confirmed the expression of CCR4 on both CD4+ T cells and ILC2, comparatively. CCL17 and CCL22 are the known ligands for CCR4; therefore, using this ex vivo transmigration method we examined CCL17- and CCL22-induced movement of CCR4+ lymphocytes. To establish chemokine gradients, CCL17 and CCL22 were placed in the bottom chamber of the transmigration system. Isolated lymphocytes were then added to top chambers and over a 48 h period the lymphocytes actively migrated through 3 &#181;m pores towards the chemokine in the bottom chamber. This is an effective system for determining the chemokinetics of lymphocytes, but, understandably, does not mimic the complexities found in the in vivo organ microenvironments. This is one limitation of the method that can be overcome by the addition of in situ imaging of the organ and lymphocytes under study. In contrast, the advantage of this method is that is can be performed by an entry-level technician at a much more cost-effective rate than live imaging. As therapeutic compounds become available to enhance migration, as in the case of tumor infiltrating cytotoxic immune cells, or to inhibit migration, perhaps in the case of autoimmune diseases where immunopathology is of concern, this method can be used as a screening tool. In general, the method is effective if the chemokine of interest is consistently generating chemokinetics at a statistically higher level than the media control. In such cases, the degree of inhibition/enhancement by a given compound can be determined as well.

In this protocol, lymphocytes are placed in the top chamber of a transmigration system, separated from the bottom chamber by a porous membrane. Chemokine is added to the bottom chamber, which induces active migration along a chemokine gradient. After 48 h, lymphocytes are counted in both chambers to quantitate transmigration.

Herein, we present an efficient method that can be executed with basic laboratory skills and materials to assess lymphocyte chemokinetic movement in an ex ...

Time-lapse Imaging of Mouse Macrophage Chemotaxis

Chemotaxis is receptor-mediated guidance of cells along a chemical gradient, whereas chemokinesis is the stimulation of random cell motility by a chemical. Chemokinesis and chemotaxis are fundamental for the mobilization and deployment of immune cells. For example, chemokines (chemotactic cytokines) can rapidly recruit circulating neutrophils and monocytes to extravascular sites of inflammation. Chemoattractant receptors belong to the large family of G protein-coupled receptors. How chemoattractant (i.e., ligand) gradients direct cell migration via G protein-coupled receptor signaling is not yet fully understood. In the field of immunology, neutrophils are popular model cells for studying chemotaxis in vitro. Here we describe a real-time two-dimensional (2D) chemotaxis assay tailored for mouse resident macrophages, which have traditionally been more difficult to study. Macrophages move at a slow pace of ~1 &#181;m/min on a 2D surface and are less well suited for point-source migration assays (e.g., migration towards the tip of a micropipette filled with chemoattractant) than neutrophils or Dictyostelium discoideum, which move an order of magnitude faster. Widely used Transwell assays are useful for studying the chemotactic activity of different substances, but do not provide information on cell morphology, velocity, or chemotactic navigation. Here we describe a time-lapse microscopy-based macrophage chemotaxis assay that allows quantification of cell velocity and chemotactic efficiency and provides a platform to delineate the transducers, signal pathways, and effectors of chemotaxis.

Here we describe methods using time-lapse, phase-contrast microscopy to image mouse resident peritoneal macrophages in a chemotactic complement C5a gradient. The protocols can be extended to other immune cells.

Chemotaxis is receptor-mediated guidance of cells along a chemical gradient, whereas chemokinesis is the stimulation of random cell motility by a ...

Imaging G Protein-coupled Receptor-mediated Chemotaxis and its Signaling Events in Neutrophil-like HL60 Cells

Eukaryotic cells sense and move towards a chemoattractant gradient, a cellular process referred as chemotaxis. Chemotaxis plays critical roles in many physiological processes, such as embryogenesis, neuron patterning, metastasis of cancer cells, recruitment of neutrophils to sites of inflammation, and the development of the model organism Dictyostelium discoideum. Eukaryotic cells sense chemo-attractants using G protein-coupled receptors. Visual chemotaxis assays are essential for a better understanding of how eukaryotic cells control chemoattractant-mediated directional cell migration. Here, we describe detailed methods for: 1) real-time, high-resolution monitoring of multiple chemotaxis assays, and 2) simultaneously visualizing the chemoattractant gradient and the spatiotemporal dynamics of signaling events in neutrophil-like HL60 cells.

Visual chemotaxis assays are essential for a better understanding of how eukaryotic cells control chemoattractant-mediated directional cell migration. Here, we describe detailed methods for: 1) real-time, high-resolution monitoring of multiple chemotaxis assays, and 2) simultaneously visualizing the chemoattractant gradient and the spatiotemporal dynamics of signaling events in neutrophil-like HL60 cells.

Eukaryotic cells sense and move towards a chemoattractant gradient, a cellular process referred as chemotaxis. Chemotaxis plays critical roles in many ...

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

Chemotaxis, or migration up a gradient of a chemoattractant, is the best understood mode of directed migration. Studies using social amoeba Dictyostelium discoideum revealed that a complex signal transduction network of parallel pathways amplifies the response to chemoattractants, and leads to biased actin polymerization and protrusion of a pseudopod in the direction of a gradient. In contrast, molecular mechanisms driving other types of directed migration, for example, due to exposure to shear flow or electric fields, are not known. Many regulators of chemotaxis exhibit localization at the leading or lagging edge of a migrating cell, as well as show transient changes in localization or activation following global stimulation with a chemoattractant. To understand the molecular mechanisms of other types of directed migration we developed a method that allows examination of cellular response to acute mechanical stimulation based on brief (2 - 5 s) exposure to shear flow. This stimulation can be delivered in a channel while imaging cells expressing fluorescently-labeled biosensors to examine individual cell behavior. Additionally, cell population can be stimulated in a plate, lysed, and immunoblotted using antibodies that recognize active versions of proteins of interest. By combining both assays, one can examine a wide array of molecules activated by changes in subcellular localization and/or phosphorylation. Using this method we determined that acute mechanical stimulation triggers activation of the chemotactic signal transduction and actin cytoskeleton networks. The ability to examine cellular responses to acute mechanical stimulation is important for understanding the initiating events necessary for shear flow-induced motility. This approach also provides a tool for studying the chemotactic signal transduction network without the confounding influence of the chemoattractant receptor.

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation

Here we describe methods for assessing cellular response to acute mechanical stimulation. In the microscopy-based assay, we examine localization of fluorescently-labeled biosensors following brief stimulation with shear flow. We also test activation of various proteins of interest in response to acute mechanical stimulation biochemically.

Chemotaxis, or migration up a gradient of a chemoattractant, is the best understood mode of directed migration. Studies using social amoeba Dictyostelium ...

Rapid and Robust Analysis of Cellular and Molecular Polarization Induced by Chemokine Signaling

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Chapters in this video

Investigation of Macrophage Polarization Using Bone Marrow Derived Macrophages

Planar Gradient Diffusion System to Investigate Chemotaxis in a 3D Collagen Matrix

Polydimethylsiloxane-polycarbonate Microfluidic Devices for Cell Migration Studies Under Perpendicular Chemical and Oxygen Gradients

3D Analysis of Multi-cellular Responses to Chemoattractant Gradients

Imaging G-protein Coupled Receptor (GPCR)-mediated Signaling Events that Control Chemotaxis of Dictyostelium Discoideum

Measurement of Cellular Chemotaxis with ECIS/Taxis

Assessment of Lymphocyte Migration in an Ex Vivo Transmigration System

Time-lapse Imaging of Mouse Macrophage Chemotaxis

Imaging G Protein-coupled Receptor-mediated Chemotaxis and its Signaling Events in Neutrophil-like HL60 Cells

Assessment of Dictyostelium discoideum Response to Acute Mechanical Stimulation