Name: extracellular vesicle uptake assay via confocal microscope imaging analysis
Uploaded: 2022-02-14T13:00:00
Description: Watch this Scientific Journal Video about Extracellular Vesicle Uptake Assay via Confocal Microscope Imaging Analysis at JoVE.com

This work was supported by NCI grant nos. U54CA143803, CA163124, CA093900, and CA143055 to K. J. P. This research was supported by a grant of the Korea Health Technology R&#38;D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health &#38; Welfare, Republic of Korea (grant number: HI19C1122). Work by J. Kim and Y.-K. Cho was supported by Institute for Basic Science (IBS-R020-D1), funded by the Korean Government. The authors thank the current and past members of the Brady Urological Institute, especially members of the Pienta-Amend laboratory, for the critical reading of the manuscript.

1. EV isolation and on-chip immuno-fluorescent EV labeling
<ol>
	<li>Collection of cell culture media (CCM) and pre-processing of CCM for EV isolation
	<ol>
		<li>Seed PC3 cells at 30% confluency in a 75 cm2 cell culture flask. Allow control cells to grow to 90% confluency (~48 h) in standard media and cell-line-specific supplements. 
		NOTE: To prevent EV-containing components from affecting cellular uptake (i.e., fetal bovine serum), use exosome-depleted media and supplements.</li>
		<li>Harvest the C...

<ol>
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S. <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,+function,+and+biomedical+applications+of+exosomes.">The biology, function, and biomedical applications of exosomes.</a> Science. 367 (6478), (2020).</li><li>Mathieu, M., Martin-Jaular, L., Lavieu, G., Th&#233;ry, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Specificities+of+secretion+and+uptake+of+exosomes+and+other+extracellular+vesicles+for+cell-to-cell+communication.">Specificities of secretion and uptake of exosomes and other extracellular vesicles for cell-to-cell communication.</a> Nature Cell Biology. 21 (1), 9-17 (2019).</li><li>Bonsergent, E., 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=Quantitative+characterization+of+extracellular+vesicle+uptake+and+content+delivery+within+mammalian+cells.">Quantitative characterization of extracellular vesicle uptake and content delivery within mammalian cells.</a> Nature Communications. 12, 1864 (2021).</li><li>Mulcahy, L. 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K., 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=Exodisc+for+Rapid,+Size-Selective,+and+Efficient+Isolation+and+Analysis+of+Nanoscale+Extracellular+Vesicles+from+Biological+Samples.">Exodisc for Rapid, Size-Selective, and Efficient Isolation and Analysis of Nanoscale Extracellular Vesicles from Biological Samples.</a> ACS Nano. 11 (2), 1360-1370 (2017).</li><li>Kim, T. -. 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=FAST:+Size-Selective,+Clog-Free+Isolation+of+Rare+Cancer+Cells+from+Whole+Blood+at+a+Liquid-Liquid+Interface.">FAST: Size-Selective, Clog-Free Isolation of Rare Cancer Cells from Whole Blood at a Liquid-Liquid Interface.</a> Analytical Chemistry. 89 (2), 1155-1162 (2017).</li><li>Joshi, B. S., De Beer, M. A., Giepmans, B. N. G., Zuhorn, I. 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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=A+live+cell+reporter+of+exosome+secretion+and+uptake+reveals+pathfinding+behavior+of+migrating+cells.">A live cell reporter of exosome secretion and uptake reveals pathfinding behavior of migrating cells.</a> Nature Communications. 11, 2092 (2020).</li><li>Heusermann, W., 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=Exosomes+surf+on+filopodia+to+enter+cells+at+endocytic+hot+spots,+traffic+within+endosomes,+and+are+targeted+to+the+ER.">Exosomes surf on filopodia to enter cells at endocytic hot spots, traffic within endosomes, and are targeted to the ER.</a> Journal of Cell Biology. 213 (2), 173-184 (2016).</li><li>Reclusa, 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=Improving+extracellular+vesicles+visualization:+From+static+to+motion.">Improving extracellular vesicles visualization: From static to motion.</a> Scientific Reports. 10, 6494 (2020).</li><li>Verweij, F. 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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=Visualization+and+tracking+of+tumour+extracellular+vesicle+delivery+and+RNA+translation+using+multiplexed+reporters.">Visualization and tracking of tumour extracellular vesicle delivery and RNA translation using multiplexed reporters.</a> Nature Communications. 6, 7029 (2015).</li><li>Durak-Kozica, M., Baster, Z., Kubat, K., St&#281;pie&#324;, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+visualization+of+extracellular+vesicle+uptake+by+endothelial+cells.">3D visualization of extracellular vesicle uptake by endothelial cells.</a> Cellular &amp; Molecular Biology Letters. 23, 57 (2018).</li><li>Sunkara, V., 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=Fully+Automated,+Label-Free+Isolation+of+Extracellular+Vesicles+from+Whole+Blood+for+Cancer+Diagnosis+and+Monitoring.">Fully Automated, Label-Free Isolation of Extracellular Vesicles from Whole Blood for Cancer Diagnosis and Monitoring.</a> Theranostics. 9 (7), 1851-1863 (2019).</li><li>Li, 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=Internalization+of+trophoblastic+small+extracellular+vesicles+and+detection+of+their+miRNA+cargo+in+P-bodies.">Internalization of trophoblastic small extracellular vesicles and detection of their miRNA cargo in P-bodies.</a> Journal of Extracellular Vesicles. 9 (1), 1812261 (2020).</li><li>Dong, L., 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=Comprehensive+evaluation+of+methods+for+small+extracellular+vesicles+separation+from+human+plasma,+urine+and+cell+culture+medium.">Comprehensive evaluation of methods for small extracellular vesicles separation from human plasma, urine and cell culture medium.</a> Journal of Extracellular Vesicles. 10, 12044 (2020).</li></ol>

An EV uptake assay based on 3D fluorescence imaging via confocal microscopy provides an efficient methodology and sensitive analysis. This fluorescent EV labeling facilitates the visualization of EVs and successfully performs a precise EV uptake assay. Previous methods for labeling EVs and removing the residual dye have been reported by removing precipitation using ultracentrifugation (UC); however, UC may co-precipitate EVs, and the immobilized dye may lead to a false-positive signal12<s...

Extracellular vesicles (EVs) are nano-sized, lipid membrane-bound particles that are categorized by their sizes: ectosomes (100-500 nm) and exosomes (50-150 nm)1. EVs contain various biomolecules, such as proteins, nucleic acids, and lipids. These biomolecules originate from the cells before being encapsulated as cargo and released into the extracellular space via EVs1,2,3.
Due to the variety of their cargo, EVs are believed to play an active role in intercellular communication. The release and uptake of EVs by cells allow the transfer of biomolecules between the cells4,5. The introduction of EV cargo to a cell may alter the recipient cell&#39;s functions and homeostatic state4,5,6. EVs are internalized through multiple pathways; however, the exact mechanisms have not been accurately demonstrated.
The majority of the EV uptake assays, such as genetic tagging, fluorescently label individual EVs7. The resulting signal can be measured by microplate photometer, flow cytometry, or microscopy, with each technology having substantial limitations. Microplate photometers, flow cytometry, or standard two-dimensional (2D) microscopy cannot distinguish between internalized and superficially attached EVs8,9. Additionally, the necessary sample preparation for each of these techniques may introduce additional issues to EV uptake evaluation. For example, lifting adhered cells with trypsin before EV uptake analysis may cleave some superficially attached EVs on the cell&#39;s surface10,11. Trypsin may also interact with the cell surface, affecting cell and EV phenotype. Additionally, trypsin may not detach superficial EVs entirely, skewing isolated populations.
To accurately label EVs with fluorescent dyes, additional wash steps are required to remove the residual dye7. Accepted isolation techniques can also contribute to false-positive signals due to coagulation that occurs during EV isolation. For example, serial ultracentrifugation (UC) is widely used to isolate EVs and remove the immobilized dye. However, UC may co-precipitate EVs, and the residual dye may lead to a false-positive signal12,13. Other nano-filtration methods, such as column-based filtration, are also widely used for non-immobilized dye removal. The complex nature of EVs and dye interacting within the column matrix may lead to incomplete removal of residual dye due to the molecular cut-off of the column being altered by the complex input14,15,16.
The current protocol proposes a nano-filtration-based microfluidic device to isolate and wash fluorescently labeled isolated EVs. The nano-filtration-based microfluidic device can provide efficient filtration via fluid-assisted separation technology (FAST)17,18. FAST reduces the pressure drop across the filter, thus reducing potential aggregation between EVs and dyes. By efficiently removing residual dye, it is possible to enhance the quality of fluorescently labeled EVs and the assay&#39;s specificity.
Confocal microscopy can distinguish between internalized and superficially attached EVs on the cell surface and comprehensively investigate the cellular mechanisms of EV uptake in a spatiotemporal resolution19,20,21,22,23,24,25. For example, Sung et al. described the visualization of the exosome lifecycle using their developed live-cell reporter. The location of the internalized EVs was detected and analyzed using a confocal microscope in three-dimension (3D) and post-image processing tools20. Although the size of small EVs (40-200 nm) is below the resolution limit of the optical microscope, the fluorescently labeled EVs can be detected by confocal microscopy since the photodetector can detect the enhanced fluorescence emission. Therefore, the subcellular localization of the fluorescently labeled EVs within a cell can be precisely determined by acquiring multiple z-stacked images of the EVs and the surrounding cellular organelles.
Additionally, 3D reconstruction and post-data processing can provide further insight into the positioning of the internalized, superficial, and free-floating EVs. By utilizing these processes in conjunction with the time-lapse live-cell imaging offered by confocal microscopy, the level of EV uptake can be precisely evaluated, and the real-time tracking of EV uptake is also possible. Further, EV trafficking analysis can be performed using confocal microscopy by assessing the co-localization of EVs with organelles, a first step to determine how internalized EVs are involved in the intracellular function. This protocol describes the methodology for performing an EV uptake assay using the nano-filtration-based microfluidic device17,26, confocal microscopy, and post-image analysis.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Alexa Fluor 488 anti-human CD63 Antibody</td>
			<td>Biolegend</td>
			<td>353038</td>
			<td>Fluorescent dye conjugated EV-specific antibody</td>
		</tr>
		<tr>
			<td>CellTracker Orange CMTMR Dye</td>
			<td>Thermo Fisher Scientific</td>
			<td>C2927</td>
			<td>Live cell (cytoplasm) fluoresent labeling reagent</td>
		</tr>
		<tr>
			<td>CFI Apo Lambda S 40XC WI</td>
			<td>Nikon</td>
			<td>MRD77400</td>
			<td>Objective for confocal imaging, NA=1.25</td>
		</tr>
		<tr>
			<td>CFI Plan Apo VC 20X</td>
			<td>Nikon</td>
			<td>MRD70200</td>
			<td>Objective for confocal imaging, NA=0.75</td>
		</tr>
		<tr>
			<td>Exodisc</td>
			<td>Labspinner Inc.</td>
			<td>EX-D1001</td>
			<td>A nano-filtration based microfluidic device for EV isolation</td>
		</tr>
		<tr>
			<td>ExoDiscovery</td>
			<td>Labspinner Inc.</td>
			<td>EX-R1001</td>
			<td>Operation device for Exodisc</td>
		</tr>
		<tr>
			<td>Exosome-depleted FBS</td>
			<td>Thermo Fisher Scientific</td>
			<td>A2720801</td>
			<td>Nutrient of cell culture media for PC3 cell line derived EV collection</td>
		</tr>
		<tr>
			<td>Fetal bovine serum (FBS)</td>
			<td>VWR</td>
			<td>1500-500</td>
			<td>Nutrient for cell cultivation</td>
		</tr>
		<tr>
			<td>Goat Anti-Mouse IgG H&#38;L preadsorbed</td>
			<td>abcam</td>
			<td>&#160;ab7063</td>
			<td>Mouse IgG antibody for negatvie control of EV labeling</td>
		</tr>
		<tr>
			<td>Ibidi USA&#160;U DISH &#956;-Dish 35 mm</td>
			<td>Ibidi</td>
			<td>81156</td>
			<td>Culture dish for confocal imaging</td>
		</tr>
		<tr>
			<td>Imaris 9.7.1</td>
			<td>Oxford Instruments</td>
			<td>9.7.1</td>
			<td>Post-image processing software</td>
		</tr>
		<tr>
			<td>Incubator System+ CO2/O2/N2 gas mixer</td>
			<td>Live Cell Instrument</td>
			<td>TU-O-20</td>
			<td>Incubator system for live cell imaging</td>
		</tr>
		<tr>
			<td>Nikon A1 HD25 / A1R HD25 camera</td>
			<td>Nikon</td>
			<td>NA</td>
			<td>Camera for confocal imaging</td>
		</tr>
		<tr>
			<td>Nikon Eclipse Ti microscope</td>
			<td>Nikon</td>
			<td>NA</td>
			<td>Inverted microscope for confocal imaging</td>
		</tr>
		<tr>
			<td>NIS-Elements AR 4.50.00</td>
			<td>Nikon</td>
			<td>4.50.00</td>
			<td>Image processing software for Nikon microscope</td>
		</tr>
		<tr>
			<td>NTA, NanoSight NS500</td>
			<td>Malvern Panalytical</td>
			<td>NS500</td>
			<td>Measurement device for EV concentration</td>
		</tr>
		<tr>
			<td>OriginPro 2020</td>
			<td>OriginLab</td>
			<td>9.7.0.185</td>
			<td>Graphing software</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>Thermo Fisher Scientific</td>
			<td>15140122</td>
			<td>Antibiotics for cell cultivation</td>
		</tr>
		<tr>
			<td>RPMI 1640</td>
			<td>Thermo Fisher Scientific</td>
			<td>21875034</td>
			<td>Cell culture media for PC3 cell line cultivation</td>
		</tr>
		<tr>
			<td>SYTO RNASelect Green Fluorescent cell Stain - 5 mM Solution in DMSO</td>
			<td>Thermo Fisher Scientific</td>
			<td>S32703</td>
			<td>RNA staining fluorescent dye for the EV labeling</td>
		</tr>
	</tbody>
</table>

extracellular vesicle uptake assay via confocal microscope imaging analysis

There is a need for practical assays to visualize and quantify the cells' extracellular vesicle (EV) uptake. EV uptake plays a role in intercellular communication in various research fields; cancer biology, neuroscience, and drug delivery. Many EV uptake assays have been reported in the literature; however, there is a lack of practical, detailed experimental methodology. EV uptake can be assessed by fluorescently labeling EVs to detect their location within cells. Distinguishing between internalized EVs in cells and the superficial EVs on cells is difficult, yet critical, to accurately determine the EV uptake. Therefore, an assay that efficiently quantifies EV uptake through three-dimensional (3D) fluorescence confocal microscopy is proposed in this work. Fluorescently labeled EVs were prepared using a nano-filtration-based microfluidic device, visualized by 3D confocal microscopy, and then analyzed through advanced image-processing software. The protocol provides a robust methodology for analyzing EVs on a cellular level and a practical approach for efficient analysis.

Using a nano-filtration-based microfluidic device, EVs were isolated from PC3 CCM and labeled with a fluorophore-conjugated EV-specific (CD63) antibody (Figure 1). The labeled EVs were successfully visualized by the 3D confocal microscopy (Figure 2). The labeled EVs were incubated with cells for several hours in exosome-depleted media. Following incubation, cells were washed with exosome depleted media. The remaining EVs were internalized or adhered to cells dur...

Watch this Scientific Journal Video about Extracellular Vesicle Uptake Assay via Confocal Microscope Imaging Analysis at JoVE.com

Extracellular Vesicle Uptake Assay via Confocal Microscope Imaging Analysis

Extracellular vesicles (EVs) contribute to cellular biology and intercellular communications. There is a need for practical assays to visualize and quantify EVs uptake by the cells. The current protocol proposes the EV uptake assay by utilizing three-dimensional fluorescence imaging via confocal microscopy, following EV isolation by a nano-filtration-based microfluidic device.

Extracellular Vesicle Uptake Assay via Confocal Microscope Imaging Analysis

There is a need for practical assays to visualize and quantify the cells' extracellular vesicle (EV) uptake. EV uptake plays a role in intercellular ...

This protocol provides a robust methodology for analyzing EVs at a cellular level, and a practical approach for efficient EV uptake and EV tracking analysis. This method of EV labeling eliminates co-precipitation of EVs and dye, thus enhancing the EV signals. EV uptake is measured by volumetric analysis to distinguish the internalized EVs from the superficial EVs.EVs are active cargo, thus, their uptake allows the transfer of biochemical molecules. For research on EV-based drug delivery and cancer therapy, this technique can be an assessment tool. EV uptake plays a role in intercellular communication and is investigated in various research fields, such as cancer biology, neuroscience, and drug delivery.This protocol potentially facilitates efficient EV uptake assay. For isolation of extracellular vesicles, or EVs, inject one milliliter of pre-processed cell culture media into the sample chamber of the nanofiltration-based microfluidic device. To operate the device, spin the device in the benchtop spinning machine at 3000 RPM for 10 minutes.After spinning, remove the fluid from the waste chamber by pipetting or aspirating, then repeat this procedure twice for processing an additional two milliliters of the cell culture media. Next, to wash the isolated EVs, inject one milliliter of PBS into the sample chamber and spin the device in the benchtop spinning machine. For immunofluorescent labeling of the EVs, inject one microgram per milliliter of the EV-specific antibody into the elution hole of the device containing 100 microliters of isolated EVs.Then incubate for one hour in the dark on a plate shaker to ensure the even distribution of the antibody across the sample. Next, attach an adhesive tape to the elution hole. Inject one milliliter of PBS into the sample chamber to wash out residual antibodies, then spin the device until the sample chamber is empty.Repeat the wash by injecting another milliliter of PBS into the sample chamber, and spinning the device as demonstrated previously. After removing the residual fluid from the chamber, pipette the fluorescently-labeled EVs from the membrane chamber into an amber tube or micro tube. Protect the tube from light until use.Seed four times 10 to the fourth PC3 cells into a 35-milliliter dish with one milliliter media. Allow the cells to adhere overnight in optimal cell culture conditions. The following day, wash the adhered cells twice with exosome-depleted media.After diluting the fluorescently-labeled EVs to the appropriate concentration using exosome-depleted media, add the diluted EVs to the adhered target cells and incubate for the desired experimental time. After removing non-internalized EVs by washing the cells thrice with exosome-free media, label the cytoplasm of the adhered cells with one microgram per milliliter of CMTMR, and incubate in optimal cell culture conditions. For live cell imaging, place the prepared cells in the onstage incubator.After setting the imaging parameters based on control samples, determine the depth of the target cells and the range of stacking size in the Z direction to acquire 3D confocal images, then set the image acquisition to multiple Z-stacked images of both cell-specific dye and EV-specific dye simultaneously. For image processing, utilize automatic image processing software. To build virtual surfaces of the cells, click on Add new Surfaces.To configure the virtual cell surfaces, click the Add button and select Quality as the filter type. Threshold the appropriate value for the low limit by visual inspection, set the maximum value for the upper limit, and click the Finish button Next, to build the virtual dots of the EVs, click the button Add new Spots. Under Algorithm Settings, select Different Spot Sizes and Shortest Distance Calculation, then click Next and select Channel 1 Alexa Fluor 488 as the source channel.Enter the appropriate value for the estimated XY diameter under Spot Detection and click Next. To configure the virtual EV dots, click the Add button and select Quality as the filter type. Set the lower threshold by a visual inspection and click Next For the Spot Regions Type, select Absolute Intensity, then click Next.To threshold the region of EV dots, enter the appropriate value for Region Threshold by visual inspection. Select Diameter From under Region Volume and click Finish. To split the grouped spots inside the built surface, click on the Build Spots and go into Filters.Next click the Add button and select Shortest Distance to Surfaces, Surfaces Surface 1 as the filter type. After setting the lowest threshold for the low limit and the appropriate value for the upper limit, click the Duplicate Section to the new Spots button. For automatic counting of EVs inside the cells, click the Built Spots 1 selection, go to Statistics, and export the value from the Total Number of Spots.To obtain the number of cells, click the Built Surfaces 1, then go to Statistics and export the value of Total Number of Surfaces from Overall. Finally, go to the Detailed tab under Statistics to export the volume. EVs isolated from PC3 cell culture media using a nanofiltration-based microfluidic device were labeled with a fluoro-4-conjugated EV-specific antibody, and visualized using 3D confocal microscopy.The internalized EVs were visualized as puncta and an individual EV.Post-processing of these images allows the visualization and quantification of EV internalization into the cells. The EV uptake assay results indicate that the level of EV uptake depends on the length of the incubation period. The number of internalized EVs can be normalized to the recipient cell volume to determine the actual rate of EV uptake for the specified cell.This procedure allows for the systematic exclusion of non-internalized EVs to precisely measure the number of internalized EVs. The size distribution of internalized EV dots is shown here. So the key steps are the utilization of the microfluidic device for EV labeling, the minimization of background fluorescence when visualizing fluorescent EVs, and then the post-imaging analysis to determine internalized versus superficial EVs.So intracellular EV tracking can be performed in real time on a 3D plane, and additionally, EV trafficking analysis on spatial/temporal resolutions and the co-localization of EVs with subcellular organelles can be achieved. So we believe this technique provides an easier, more efficient way to investigate EVs within the intra-and extracellular matrices for researchers within the cellular communication field for EVs.

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Unit 1

Endocytosis and Exocytosis

SCIENTISTS IN ACTION

Proper Care and Cleaning of the Microscope

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a microscope causes reduction in contrast and resolution. DIC is especially sensitive to contamination and scratches on the lens surfaces. This protocol details the procedure for keeping the microscope clean.

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a microscope causes reduction in contrast and resolution. DIC is especially sensitive to contamination and scratches on the lens surfaces. This protocol details the procedure for keeping the microscope clean.

Keeping the microscope optics clean is important for high-quality imaging. Dust, fingerprints, excess immersion oil, or mounting medium on or in a ...

Major Components of the Light Microscope

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for different applications, and how it should be maintained as required to obtain maximum image-forming capacity and resolution. The components of the microscope are described in detail here.

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for different applications, and how it should be maintained as required to obtain maximum image-forming capacity and resolution. The components of the microscope are described in detail here.

The light microscope is a basic tool for the cell biologist, who should have a thorough understanding of how it works, how it should be aligned for ...

A Neuronal and Astrocyte Co-Culture Assay for High Content Analysis of Neurotoxicity

High Content Analysis (HCA) assays combine cells and detection reagents with automated imaging and powerful image analysis algorithms, allowing measurement of multiple cellular phenotypes within a single assay. In this study, we utilized HCA to develop a novel assay for neurotoxicity. Neurotoxicity assessment represents an important part of drug safety evaluation, as well as being a significant focus of environmental protection efforts. Additionally, neurotoxicity is also a well-accepted in vitro marker of the development of neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Recently, the application of HCA to neuronal screening has been reported. By labeling neuronal cells with &beta;III-tubulin, HCA assays can provide high-throughput, non-subjective, quantitative measurements of parameters such as neuronal number, neurite count and neurite length, all of which can indicate neurotoxic effects. However, the role of astrocytes remains unexplored in these models. Astrocytes have an integral role in the maintenance of central nervous system (CNS) homeostasis, and are associated with both neuroprotection and neurodegradation when they are activated in response to toxic substances or disease states. GFAP is an intermediate filament protein expressed predominantly in the astrocytes of the CNS. Astrocytic activation (gliosis) leads to the upregulation of GFAP, commonly accompanied by astrocyte proliferation and hypertrophy. This process of reactive gliosis has been proposed as an early marker of damage to the nervous system. The traditional method for GFAP quantitation is by immunoassay. This approach is limited by an inability to provide information on cellular localization, morphology and cell number. We determined that HCA could be used to overcome these limitations and to simultaneously measure multiple features associated with gliosis - changes in GFAP expression, astrocyte hypertrophy, and astrocyte proliferation - within a single assay. In co-culture studies, astrocytes have been shown to protect neurons against several types of toxic insult and to critically influence neuronal survival. Recent studies have suggested that the use of astrocytes in an in vitro neurotoxicity test system may prove more relevant to human CNS structure and function than neuronal cells alone. Accordingly, we have developed an HCA assay for co-culture of neurons and astrocytes, comprised of protocols and validated, target-specific detection reagents for profiling &beta;III-tubulin and glial fibrillary acidic protein (GFAP). This assay enables simultaneous analysis of neurotoxicity, neurite outgrowth, gliosis, neuronal and astrocytic morphology and neuronal and astrocytic development in a wide variety of cellular models, representing a novel, non-subjective, high-throughput assay for neurotoxicity assessment. The assay holds great potential for enhanced detection of neurotoxicity and improved productivity in neuroscience research and drug discovery.

This article describes a novel protocol and reagent set designed for sensitive measurement of neurotoxic effects of compounds and treatments on co-cultures of neurons and astrocytes using high content analysis. Results demonstrate that high content analysis represents an exciting novel technology for neurotoxicity assessment.

High Content Analysis (HCA) assays combine cells and detection reagents with automated imaging and powerful image analysis algorithms, allowing ...

Fluorescence-based Measurement of Store-operated Calcium Entry in Live Cells: from Cultured Cancer Cell to Skeletal Muscle Fiber

Store operated Ca2+ entry (SOCE), earlier termed capacitative Ca2+ entry, is a tightly regulated mechanism for influx of extracellular Ca2+ into cells to replenish depleted endoplasmic reticulum (ER) or sarcoplasmic reticulum (SR) Ca2+ stores1,2. Since Ca2+ is a ubiquitous second messenger, it is not surprising to see that SOCE plays important roles in a variety of cellular processes, including proliferation, apoptosis, gene transcription and motility. Due to its wide occurrence in nearly all cell types, including epithelial cells and skeletal muscles, this pathway has received great interest3,4. However, the heterogeneity of SOCE characteristics in different cell types and the physiological function are still not clear5-7.
The functional channel properties of SOCE can be revealed by patch-clamp studies, whereas a large body of knowledge about this pathway has been gained by fluorescence-based intracellular Ca2+ measurements because of its convenience and feasibility for high-throughput screening. The objective of this report is to summarize a few fluorescence-based methods to measure the activation of SOCE in monolayer cells, suspended cells and muscle fibers5,8-10. The most commonly used of these fluorescence methods is to directly monitor the dynamics of intracellular Ca2+ using the ratio of F340nm and F380nm (510 nm for emission wavelength) of the ratiometric Ca2+ indicator Fura-2. To isolate the activity of unidirectional SOCE from intracellular Ca2+ release and Ca2+ extrusion, a Mn2+ quenching assay is frequently used. Mn2+ is known to be able to permeate into cells via SOCE while it is impervious to the surface membrane extrusion processes or to ER uptake by Ca2+ pumps due to its very high affinity with Fura-2. As a result, the quenching of Fura-2 fluorescence induced by the entry of extracellular Mn2+ into the cells represents a measurement of activity of SOCE9. Ratiometric measurement and the Mn+2 quenching assays can be performed on a cuvette-based spectrofluorometer in a cell population mode or in a microscope-based system to visualize single cells. The advantage of single cell measurements is that individual cells subjected to gene manipulations can be selected using GFP or RFP reporters, allowing studies in genetically modified or mutated cells. The spatiotemporal characteristics of SOCE in structurally specialized skeletal muscle can be achieved in skinned muscle fibers by simultaneously monitoring the fluorescence of two low affinity Ca2+ indicators targeted to specific compartments of the muscle fiber, such as Fluo-5N in the SR and Rhod-5N in the transverse tubules9,11,12.

The extent of store-operated Ca2+ entry (SOCE) can be monitored using fluorescent Ca2+ indicators. Mn2+ quenching of such indicators assays SOCE in cultured cells and skeletal muscle fibers. A technique allowing spatial and temporal resolution of SOCE by confocal imaging of mechanically skinned muscle fibers is also described.

Store operated Ca2+ entry (SOCE), earlier termed capacitative Ca2+ entry, is a tightly regulated mechanism for influx of extracellular Ca2+ into cells to ...

LDL Cholesterol Uptake Assay Using Live Cell Imaging Analysis with Cell Health Monitoring

The regulation of LDL cholesterol uptake through LDLR-mediated endocytosis is an important area of study in various major pathologies including metabolic disorder, cardiovascular disease, and kidney disease. Currently, there is no available method to assess LDL uptake while simultaneously monitoring for health of the cells. The current study presents a protocol, using a live cell imaging analysis system, to acquire serial measurements of LDL influx with concurrent monitoring for cell health. This novel technique is tested in three human cell lines (hepatic, renal tubular epithelial, and coronary artery endothelial cells) over a four-hour time course. Moreover, the sensitivity of this technique is validated with well-known LDL uptake inhibitors, Dynasore and recombinant PCSK9 protein, as well as by an LDL uptake promoter, Simvastatin. Taken together, this method provides a medium-to-high throughput platform for simultaneously screening pharmacological activity as well as monitoring of cell morphology, hence cytotoxicity of compounds regulating LDL influx. The analysis can be used with different imaging systems and analytical software.

This protocol provides an efficient approach to measuring LDL cholesterol uptake with real time influx rates using a live cell imaging system in various cell types. This technique provides a platform to screen the pharmacological activity of compounds affecting LDL influx while monitoring for cell morphology and hence potential cytotoxicity.

The regulation of LDL cholesterol uptake through LDLR-mediated endocytosis is an important area of study in various major pathologies including metabolic ...

Single Extracellular Vesicle Transmembrane Protein Characterization by Nano-Flow Cytometry

Single particle characterization has become increasingly relevant for research into extracellular vesicles, progressing from bulk analysis techniques and first-generation particle analysis to comprehensive multi-parameter measurements such as nano-flow cytometry (nFCM). nFCM is a form of flow cytometry that utilizes instrumentation specifically designed for nano-particle analysis, allowing for thousands of EVs to be characterized per minute both with and without the use of staining techniques. High resolution side scatter (SS) detection allows for size and concentration to be determined for all biological particles larger than 45 nm, while simultaneous fluorescence (FL) detection identifies the presence of labeled markers and targets of interest. Labeled subpopulations can then be described in quantitative units of particles/mL or as a percentage of the total particles identified by side scatter.
Here, EVs derived from conditioned cell culture media (CCM) are labeled with both a lipid dye, to identify particles with a membrane, and antibodies specific for CD9, CD63, and CD81 as common EV markers. Measurements of comparison material, a concentration standard and a size standard of silica nanospheres, as well as labeled sample material are analyzed in a 1-minute analysis. The software is then used to measure the concentration and size distribution profile of all particles, independent of labeling, before determining the particles that are positive for each of the labels.
Simultaneous SS and FL detection can be utilized flexibly with many different EV sources and labeling targets, both external and internal, describing EV samples in a comprehensive and quantitative manner.

The latest generation of EV characterization tools are capable of single EV analysis across multiple parameters simultaneously. Nano-flow cytometry measures all biological particles larger than 45 nm without labeling and identifies specific characteristics of subpopulations by a variety of fluorescent labeling techniques.

Single particle characterization has become increasingly relevant for research into extracellular vesicles, progressing from bulk analysis techniques and ...

Analysis of Extracellular Vesicle-Mediated Vascular Calcification Using In Vitro and In Vivo Models

Cardiovascular disease is the leading cause of death in the world, and vascular calcification is the most significant predictor of cardiovascular events; however, there are currently no treatment or therapeutic options for vascular calcification. Calcification begins within specialized extracellular vesicles (EVs), which serve as nucleating foci by aggregating calcium and phosphate ions. This protocol describes methods for obtaining and assessing calcification in murine aortas and analyzing the associated extracted EVs. First, gross dissection of the mouse is performed to collect any relevant organs, such as the kidneys, liver, and lungs. Then, the murine aorta is isolated and excised from the aortic root to the femoral artery. Two to three aortas are then pooled and incubated in a digestive solution before undergoing ultracentrifugation to isolate the EVs of interest. Next, the mineralization potential of the EVs is determined through incubation in a high-phosphate solution and measuring the light absorbance at a wavelength of 340 nm. Finally, collagen hydrogels are used to observe the calcified mineral formation and maturation produced by the EVs in vitro.

Analysis of Extracellular Vesicle-Mediated Vascular Calcification Using In Vitro and In Vivo Models

This paper presents the methodology for obtaining and assessing vascular calcification by isolating murine aortas followed by extracting calcified extracellular vesicles to observe the mineralization potential.

Cardiovascular disease is the leading cause of death in the world, and vascular calcification is the most significant predictor of cardiovascular events; ...

Multimodal Analytical Platform on a Multiplexed Surface Plasmon Resonance Imaging Chip for the Analysis of Extracellular Vesicle Subsets

Extracellular vesicles (EVs) are membrane-derived, tiny vesicles produced by all cells that range from 50 to several hundreds of nanometers in diameter and are used as a means of intercellular communication. They are emerging as promising diagnostic and therapeutic tools for a variety of diseases. There are two main biogenesis processes used by cells to produce EVs with differences in size, composition, and content. Due to their high complexity in size, composition, and cell origin, their characterization requires a combination of analytical techniques. This project involves the development of a new generation of multiparametric analytical platforms with increased throughput for the characterization of subpopulations of EVs. To achieve this goal, the work starts from the nanobioanalytical platform (NBA) established by the group, which allows an original investigation of EVs based on a combination of multiplexed biosensing methods with metrological and morphomechanical analyses by atomic force microscopy (AFM) of vesicular targets trapped on a microarray biochip. The objective was to complete this EV investigation with a phenotypic and molecular analysis by Raman spectroscopy. These developments enable the proposal of a multimodal and easy-to-use analytical solution for the discrimination of EV subsets in biological fluids with clinical potential

This paper proposes a new generation of multiparametric analytical platforms with increased throughput for the characterization of extracellular vesicle subsets. The method is based on a combination of multiplexed biosensing methods with metrological and morphomechanical analyses by atomic force microscopy, coupled with Raman spectroscopy, to qualify vesicular targets trapped on a microarray biochip.

Extracellular vesicles (EVs) are membrane-derived, tiny vesicles produced by all cells that range from 50 to several hundreds of nanometers in diameter ...

Imaging of Mitochondrial Peroxide in Living Yeast Cells Using mtHyper7

Imaging of mtHyPer7, a Ratiometric Biosensor for Mitochondrial Peroxide, in Living Yeast Cells

Mitochondrial dysfunction, or functional alteration, is found in many diseases and conditions, including neurodegenerative and musculoskeletal disorders, cancer, and normal aging. Here, an approach is described to assess mitochondrial function in living yeast cells at cellular and subcellular resolutions using a genetically encoded, minimally invasive, ratiometric biosensor. The biosensor, mitochondria-targeted HyPer7 (mtHyPer7), detects hydrogen peroxide (H2O2) in mitochondria. It consists of a mitochondrial signal sequence fused to a circularly permuted fluorescent protein and the H2O2-responsive domain of a bacterial OxyR protein. The biosensor is generated and integrated into the yeast genome using a CRISPR-Cas9 marker-free system, for&#160;more consistent expression compared to plasmid-borne constructs.
mtHyPer7 is quantitatively targeted to mitochondria, has no detectable effect on yeast growth rate or mitochondrial morphology, and provides a quantitative readout for mitochondrial H2O2 under normal growth conditions and upon exposure to oxidative stress. This protocol explains how to optimize imaging conditions using a spinning-disk confocal microscope system and perform quantitative analysis using freely available software. These tools make it possible to collect rich spatiotemporal information on mitochondria both within cells and among cells in a population. Moreover, the workflow described here can be used to validate other biosensors.

Author Spotlight: Advancing Mitochondrial Research - mtHyper7 Biosensor for Subcellular Analysis 

Hydrogen peroxide (H2O2) is both a source of oxidative damage and a signaling molecule. This protocol describes how to measure mitochondrial H2O2 using mitochondria-targeted HyPer7 (mtHyPer7), a genetically encoded ratiometric biosensor, in living yeast. It details how to optimize imaging conditions and perform quantitative cellular and subcellular analysis using freely available software.

Mitochondrial dysfunction, or functional alteration, is found in many diseases and conditions, including neurodegenerative and musculoskeletal disorders, ...

Intravital Imaging Using an Inverted Microscope to Track Skin Cell Dynamics

Streamlined Intravital Imaging Approach for Long-Term Monitoring of Epithelial Tissue Dynamics on an Inverted Confocal Microscope

Understanding normal and aberrant in vivo cell behaviors is necessary to develop clinical interventions to thwart disease initiation and progression. It is therefore critical to optimize imaging approaches that facilitate the observation of cell dynamics in situ, where tissue structure and composition remain unperturbed. The epidermis is the body&#39;s outermost barrier, as well as the source of the most prevalent human cancers, namely cutaneous skin carcinomas. The accessibility of skin tissue presents a unique opportunity to monitor epithelial and dermal cell behaviors in intact animals using noninvasive intravital microscopy. Nevertheless, this sophisticated imaging approach has primarily been achieved using upright multiphoton microscopes, which represent a significant barrier for entry for most investigators. This study presents a custom-designed, 3D-printed microscope stage insert suitable for use with inverted confocal microscopes, streamlining the long-term intravital imaging of ear skin in live transgenic mice. We believe this versatile invention, which may be customized to fit the inverted microscope brand and model of choice and adapted to image additional organ systems, will prove invaluable to the greater scientific research community by significantly enhancing the accessibility of intravital microscopy. This technological advancement is critical for bolstering our understanding of live cell dynamics in normal and disease contexts.

Author Spotlight: Developing a Tool for Using Inverted Confocal Microscopes for In Vivo Intravital Imaging 

The protocol presents a new tool to simplify intravital imaging using inverted confocal microscopy.

Understanding normal and aberrant in vivo cell behaviors is necessary to develop clinical interventions to thwart disease initiation and progression. It ...