This work was supported by a start-up funding of Cincinnati Children&#8217;s Research Foundation and a University of Cincinnati Pilot Translational grant to M.N.&#160;We would like to thank the Cincinnati Children&#8217;s Hospital Research Flow Cytometry Core for their services.

Mouse blood collection should be conducted with appropriate institutional animal care and use committee approval.
NOTE: The platelet purification protocol is described in a flow diagram in Figure 1.
1. Collection of Blood
<ol>
	<li>Add 25 &#181;L of 3.2% sodium citrate (pH 7.2) as an anti-coagulant and 0.4 mM of Gly-Pro-Arg-Pro (GPRP) in a polypropylene tube.</li>
	<li>Collect approximately 200 &#181;L of blood from the C57BL/6 mouse using retro-orbital bleeding. 
	NOTE: Blood can be collected from any type of mouse strain regardless of age or gender.
	<ol>
		<li>Use 2 mL of isoflurane in any type of chamber to anesthetize the mouse. 
		NOTE: Depth of anesthesia is checked by signs of increased respiration and decreased movement. The mouse should not respond to movement of the anesthesia chamber, or to being handled. If the mouse is responsive to movement or handling, then it requires more time to keep in the anesthesia chamber.</li>
		<li>1.2.2 Open either right or left eyelid of the mouse and insert a 7.5 cm (0.12 cm diameter) capillary tube into the vascular plexus of the eye.</li>
		<li>Twist the capillary tube one half turn while applying pressure to the capillary tube to break the vessels and initiate blood flow. Hold the animal upside down over the collection vial to be filled by capillary action.</li>
		<li>Once the appropriate volume of blood is collected, remove the capillary tube and close the eye by applying mild pressure for 30 s on the eyelid with gauze. Once bleeding is stopped, return the mouse to its cage and monitor for bleeding.</li>
		<li>Check eyes for trauma 1-2 days after retro-orbital bleeding. Remove any mouse from the study showing signs of significant trauma to the eye as a result of the procedure and euthanize. 
		NOTE: The mouse should not undergo any kind of treatment which can inhibit platelets for at least two weeks before blood collection. The blood sample must be used for platelet purification within one hour of bleeding the mouse.</li>
	</ol>
	</li>
</ol>
2. Platelet Purification
NOTE: Platelet purification should be carried out at room temperature to prevent their degradation. Make sure that temperature of the reagents and instruments are between 18 to 22 &#176;C. To prevent platelet degradation, fast pipetting and vigorous shaking should be avoided during the procedure.
<ol>
	<li>Add 600 &#181;L of iohexol gradient medium (12% iohexol powder in 0.85% sodium chloride, 5 mM Tricine, pH 7.2)11 into an 1.5 mL tube.</li>
	<li>Add 200 &#181;L of blood sample slowly down the side of the tube on top of the gradient medium with a wide bore pipette tip so that blood and iohexol medium do not mix (Figure 2A).</li>
	<li>Centrifuge the sample containing tube at 400 x g for 20 min at 20 &#176;C in a swinging bucket rotor with slow acceleration and deceleration.</li>
	<li>Collect most of the platelet-rich layer and a small fraction of platelet-poor layer (total 300 to 400 &#181;L) using a wide bore pipette tip without disturbing the RBC and WBC layers (Figure 2B). Transfer the platelet sample to a new tube. 
	NOTE: If the platelet count is less in the blood or a smaller volume of blood is used, the platelet-rich layer and platelet-poor layer can be seen as a single layer.</li>
	<li>Add 1 mL of PBS to the platelet sample, mix by inverting, and centrifuge at 800 x g for 10 min at 20 &#176;C in a swinging bucket rotor. Discard the solution completely and add 200 &#181;L of PBS to resuspend the platelets with mild pipetting. 
	NOTE: This step is optional, as it removes the gradient medium and plasma proteins and increases the sensitivity of platelets to agonists such as thrombin. Since different centrifuges have different programs, the slow acceleration/deceleration can be determined by reading the user manual of the centrifuge.</li>
	<li>Transfer 30 &#181;L of this sample into a new tube to count platelets. The remaining platelets can be used for biochemical and physiological assays such as platelet activation, aggregation, granule release, etc.</li>
	<li>For RNA or protein extraction, centrifuge the platelet sample at 800 x g for 10 min to pellet the platelets. Discard supernatant completely without disturbing the pellet. Add the desired volume of RNA or protein lysis buffer to lyse the platelets.</li>
</ol>
3. Counting the Platelets
<ol>
	<li>Count the whole blood cells without dilution and purified platelets (diluted 2 to 5-fold with PBS) using an automated cell analyzer. Use 30 to 50 &#181;L samples for counting.</li>
	<li>Calculate the total number of platelets by multiplying by the volume of the sample.</li>
	<li>Calculate the percentage of yield/recovery of purified platelets.</li>
	<li>Count the RBC and WBC in the purified platelet sample (diluted 50 to 100-fold with PBS) with a hemocytometer and microscope.</li>
</ol>
4. Platelet Activation
<ol>
	<li>In a tube, add 1 to 2 million purified platelets in up to 100 &#181;L of staining buffer (PBS with 2% fetal bovine serum, FBS).</li>
	<li>For multiple number of samples, make a master mix of antibodies with 1 &#181;L (0.5 mg/mL) of the following: PE-Cy7 rat anti-mouse TER 119, PE rat anti-mouse CD45, FITC rat anti-mouse CD41, and APC rat anti-mouse/human CD62P (P-selectin) to detect RBC, WBC, platelets, and activated platelets, respectively. Add the master mix to the tubes for staining the cells. Do not add thrombin.</li>
	<li>In another tube, add 1 to 2 million of purified platelets in up to 100 &#181;L of staining buffer, and 0.4 mM GPRP peptide. Add thrombin to activate the platelets and stain the cells following step 4.2. 
	NOTE: GPRP should be added to the sample before adding thrombin to prevent aggregate or clot formation through platelet activation. Thrombin concentration should be optimized to obtain good activation of platelets. After platelet activation, event counts are decreased during acquisition of samples by flow cytometry.</li>
	<li>As a positive control, add 1 &#181;L of whole blood in up to 100 &#181;L staining buffer in a tube and 0.4 mM GPRP peptide. Add thrombin to activate platelets. As a negative control, add 1 &#181;L of whole blood in up to 100 &#181;L of staining buffer. Do not add thrombin in negative control sample. Stain the cells following step 4.2.</li>
	<li>For flow cytometry isotype control, label 5 tubes with unstained, PE-Cy7, PE, FITC, and APC. Add 100 &#181;L of staining buffer, 1 &#181;L of blood, and 1 &#181;L of the respective antibody to the labeled tubes to stain the cells.</li>
	<li>Incubate samples to stain for 30 min at room temperature in the dark.</li>
	<li>Wash the samples by adding 1 mL of staining buffer to each tube. Centrifuge at 800 x g for 5 min at room temperature. Discard the staining buffer carefully without dislodging the pellet.</li>
	<li>Add 300 &#181;L of staining buffer to each tube, mix mildly, and transfer to a FACS tube. Store the stained samples in the dark until analyzed with a flow cytometer.</li>
</ol>
5. Flow Cytometry Analyses of Platelets
<ol>
	<li>Create a new experiment and generate log forward scatter vs log side scatter dot plots and assign gates for Ter119 PE-Cy7 (RBC), CD45 PE (WBC), CD41 FITC (platelets), and CD62P APC (activated platelets) populations according to the gating strategy chosen for the experiment in the FACS DIVA software.
	<ol>
		<li>Open the population hierarchy by choosing Show Population Hierarchy under the Populations tab. Edit the population hierarchy by checking the gating strategy and properly renaming the gates.</li>
		<li>Open statistics view by choosing Create Statistics View. Edit statistics view according to user preferences by right clicking the statistics view and selecting Edit Statistics View.</li>
		<li>Choose a color for each gate that enhances the visual aspect of the layout by double clicking on the box corresponding to the population.</li>
	</ol>
	</li>
	<li>In the Cytometer window, click on the Parameters tab and adjust the voltages for parameters to visualize the population of interest on the plots.</li>
	<li>Adjust voltages for each of the parameters so that the negative population can be distinguished from the positive population. Before recording the samples for the compensation control, check that the single-stained positive controls are on scale (ensure that the positive peaks are visible and not too far to the right). 
	NOTE: If the positive peaks are off scale, the voltages should be adjusted to see the positive populations.</li>
	<li>Record the single-color stained cells for compensation controls (unstained, PE-Cy7, PE, FITC, and APC).</li>
	<li>If the positive control gates are not set up properly, adjust them by changing voltages.</li>
	<li>Go to Experiment &#62; Compensation Setup &#62; Calculate Compensation. Choose Apply Only in the resulting window.</li>
	<li>Switch to the global worksheet by clicking on the toggle button in the top, left of the worksheet window.</li>
	<li>Load the positive control sample and acquire enough cells to adjust the compensation and the gates.</li>
	<li>Load the sample again and check that each plot shows the expected cell population based on the fluorochrome stained antibody. Acquire and record 100,000 events for whole blood samples and 10,000 events for purified platelets. Load the samples one by one until acquisition is completed.</li>
	<li>Analyze the flow cytometry data with the software with appropriate plots and gates (Figure 3)</li>
</ol>

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	<li>de Witt, S. M., Verdoold, R., Cosemans, J. M., Heemskerk, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Insights+into+platelet-based+control+of+coagulation.">Insights into platelet-based control of coagulation.</a> Thrombosis Research. 133, S139-S148 (2014).</li><li>Machlus, K. R., Thon, J. N., Italiano, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Interpreting+the+developmental+dance+of+the+megakaryocyte:+a+review+of+the+cellular+and+molecular+processes+mediating+platelet+formation.">Interpreting the developmental dance of the megakaryocyte: a review of the cellular and molecular processes mediating platelet formation.</a> British Journal of Haematology. 165 (2), 227-236 (2014).</li><li>Weyrich, A. S., Zimmerman, G. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Platelets:+signaling+cells+in+the+immune+continuum.">Platelets: signaling cells in the immune continuum.</a> Trends in Immunology. 25 (9), 489-495 (2004).</li><li>Nami, N., 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=Crosstalk+between+platelets+and+PBMC:+New+evidence+in+wound+healing.">Crosstalk between platelets and PBMC: New evidence in wound healing.</a> Platelets. 27 (2), 143-148 (2016).</li><li>Mancuso, M. E., Santagostino, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Platelets:+much+more+than+bricks+in+a+breached+wall.">Platelets: much more than bricks in a breached wall.</a> British Journal of Haematology. 178 (2), 209-219 (2017).</li><li>Hampton, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Platelets'+Role+in+Adaptive+Immunity+May+Contribute+to+Sepsis+and+Shock.">Platelets' Role in Adaptive Immunity May Contribute to Sepsis and Shock.</a> Journals of the American Medical Association. 319 (13), 1311-1312 (2018).</li><li>Sabrkhany, S., Griffioen, A. W., Oude Egbrink, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+blood+platelets+in+tumor+angiogenesis.">The role of blood platelets in tumor angiogenesis.</a> Biochimica et Biophysica Acta (BBA) - Reviews on Cancer. 1815 (2), 189-196 (2011).</li><li>Menter, D. G., 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=Platelet+&amp;#34;first+responders&amp;#34;+in+wound+response,+cancer,+and+metastasis.">Platelet &amp;#34;first responders&amp;#34; in wound response, cancer, and metastasis.</a> Cancer and Metastasis Reviews. 36 (2), 199-213 (2017).</li><li>Fink, 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=Characterization+of+platelet-specific+mRNA+by+real-time+PCR+after+laser-assisted+microdissection.">Characterization of platelet-specific mRNA by real-time PCR after laser-assisted microdissection.</a> Thrombosis and Haemostasis. 90 (4), 749-756 (2003).</li><li>Trichler, S. A., Bulla, S. C., Thomason, J., Lunsford, K. V., Bulla, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultra-pure+platelet+isolation+from+canine+whole+blood.">Ultra-pure platelet isolation from canine whole blood.</a> BioMed Central Veterinary Research. 9, 144 (2013).</li><li>Ford, T. C., Graham, J., Rickwood, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new,+rapid,+one-step+method+for+the+isolation+of+platelets+from+human+blood.">A new, rapid, one-step method for the isolation of platelets from human blood.</a> Clinica Chimica Acta. 192 (2), 115-119 (1990).</li><li>Noisakran, S., 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=Infection+of+bone+marrow+cells+by+dengue+virus+in+vivo.">Infection of bone marrow cells by dengue virus in vivo.</a> Experimental Hematolology. 40 (3), 250-259 (2012).</li><li>Rickwood, D., Ford, T., Graham, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nycodenz:+a+new+nonionic+iodinated+gradient+medium.">Nycodenz: a new nonionic iodinated gradient medium.</a> Analytical Biochemistry. 123 (1), 23-31 (1982).</li><li>Graham, J. M., Ford, T., Rickwood, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+the+major+subcellular+organelles+from+mouse+liver+using+Nycodenz+gradients+without+the+use+of+an+ultracentrifuge.">Isolation of the major subcellular organelles from mouse liver using Nycodenz gradients without the use of an ultracentrifuge.</a> Analytical Biochemistry. 187 (2), 318-323 (1990).</li><li>Milligan, G. N., 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+lethal+model+of+disseminated+dengue+virus+type+1+infection+in+AG129+mice.">A lethal model of disseminated dengue virus type 1 infection in AG129 mice.</a> Journal of General Virology. 98 (10), 2507-2519 (2017).</li><li>Strassel, C., 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=Lentiviral+gene+rescue+of+a+Bernard-Soulier+mouse+model+to+study+platelet+glycoprotein+Ibbeta+function.">Lentiviral gene rescue of a Bernard-Soulier mouse model to study platelet glycoprotein Ibbeta function.</a> Journal of Thrombosis and Haemostasis. 14 (7), 1470-1479 (2016).</li><li>Bergmeier, W., Boulaftali, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adoptive+transfer+method+to+study+platelet+function+in+mouse+models+of+disease.">Adoptive transfer method to study platelet function in mouse models of disease.</a> Thrombosis Research. 133, S3-S5 (2014).</li><li>Bakchoul, T., 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=Recommendations+for+the+use+of+the+non-obese+diabetic/severe+combined+immunodeficiency+mouse+model+in+autoimmune+and+drug-induced+thrombocytopenia:+communication+from+the+SSC+of+the+ISTH.">Recommendations for the use of the non-obese diabetic/severe combined immunodeficiency mouse model in autoimmune and drug-induced thrombocytopenia: communication from the SSC of the ISTH.</a> Journal of Thrombosis and Haemostasis. 13 (5), 872-875 (2015).</li><li>Aurbach, K., Spindler, M., Haining, E. J., Bender, M., Pleines, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blood+collection,+platelet+isolation+and+measurement+of+platelet+count+and+size+in+mice-a+practical+guide.">Blood collection, platelet isolation and measurement of platelet count and size in mice-a practical guide.</a> Platelets. , 1-10 (2018).</li><li>Jirouskova, M., Shet, A. S., Johnson, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+guide+to+murine+platelet+structure,+function,+assays,+and+genetic+alterations.">A guide to murine platelet structure, function, assays, and genetic alterations.</a> Journal of Thrombosis and Haemostasis. 5 (4), 661-669 (2007).</li><li>Birschmann, I., 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=Use+of+functional+highly+purified+human+platelets+for+the+identification+of+new+proteins+of+the+IPP+signaling+pathway.">Use of functional highly purified human platelets for the identification of new proteins of the IPP signaling pathway.</a> Thrombosis Research. 122 (1), 59-68 (2008).</li></ol>

The authors declare no conflict of interest.

Commonly, platelets are isolated by low-speed centrifugation which yields platelet-rich plasma that contains a significant number of blood cells, cellular debris, and plasma proteins which can interfere with the biochemical and physiological assays and needs further purification21. Therefore, it is important to use a rapid and simple method which can yield pure platelets without major contaminants. The protocol presented here describes the purification of platelets from mouse blood using a gradien...

Platelets are a component of blood that functions as an initiator of blood clotting in response to damage in the blood vessel. They gather at the site of injury to plug the vessel wall1. Platelets are anucleate fragments of cytoplasm derived from the megakaryocytes of the bone marrow under the influence of thrombopoietin and enter the circulation2. They are considered as metabolically active and capable of sensing extracellular environment by activating intracellular signaling cascades that result in platelet spreading, aggregation, and hemostatic plug formation1,3. Besides hemostasis/thrombosis and wound healing4, platelets play an important role in host inflammatory responses, angiogenesis, and metastatis3,5,6,7,8.
Platelets are purified from blood to study their biochemical and physiological properties, which should be free from other blood components. Since red blood cells (RBC) and white blood cells (WBC) contain significantly more RNA and proteins than platelets9,10, the presence of even a small number of these cells can interfere with transcriptomic and proteomic analyses of RNA and proteins derived from platelets. We found that purified platelets activated with thrombin bind antibody such as anti-GPIIb/IIIa (JON/A) and anti-P-selectin more efficiently than whole blood platelets.
Since platelets are fragile, it is important to treat the samples as mildly as possible. If the platelets are activated, they release their granule contents and ultimately degrade. Therefore, to keep the platelets&#8217; functional properties intact, it is important to maintain platelet quiescence during isolation. Several protocols have described isolation of platelets from human, dog, rat, and non-human primate by various methods1,10,11,12. Some of the methods require multiple steps such as collection of platelet-rich plasma by centrifugation, filtration by separation column, negative selection of platelets with RBC- and WBC-specific antibody conjugated to magnetic beads, and so on, which are time-consuming and may degrade platelets and their contents.
Ford and his colleagues described platelet purification from human blood using iohexol medium11. This method uses a similar volume of blood sample and medium during purification. Since humans yield a higher volume of blood, it is relatively easy to purify the platelets.
Iohexol is a universal density gradient inert medium that is freely soluble in water and used in the fractionation of nucleic acids, proteins, polysaccharides, and nucleoproteins13,14. It has low osmolality and is non-toxic, thus making it an ideal medium for purification of intact living cells11. It is a non-particulate medium; therefore, the distribution of cells in a gradient can be determined using hemocytometer, flow cytometer, or spectrophotometer. It does not interfere with most of the enzymatic or chemical reaction of the cells or cellular fragments after dilution.
The mouse serves as an important animal model for many human diseases15,16,17,18. There are a few published articles that describe purification of mouse platelets19,20. However, the mouse yields a relatively smaller volume of blood, which makes it difficult to purify platelets. If the same small volume of gradient medium and blood samples is used, the platelet layer cannot be clearly separated from RBC-WBC layer after centrifugation. In this article, we have described a quick and simple method of mouse platelet purification with three-fold more iohexol gradient medium relative to the blood sample volume and low speed centrifugation. We have also activated the purified platelets with thrombin and investigated their quality with flow cytometry and microscopy.

<table>
	<tbody>
		<tr>
			<td>APC rat anti-mouse/human CD62P (P-selectin)</td>
			<td>Thermoscientific</td>
			<td>17-0626-82</td>
			<td>Platelets activation marker</td>
		</tr>
		<tr>
			<td>Eppendorf tube</td>
			<td>Fisher Scientific</td>
			<td>14-222-166</td>
			<td>Tube for centifuge</td>
		</tr>
		<tr>
			<td>FACS DIVA software</td>
			<td>BD Biosciences</td>
			<td>Non-catalog item</td>
			<td>Analysis of platelets and whole blood</td>
		</tr>
		<tr>
			<td>FACS tube</td>
			<td>Fisher Scientific</td>
			<td>352008</td>
			<td>Tubes for flow cytomtery</td>
		</tr>
		<tr>
			<td>Fetal bovine serum (FBS)</td>
			<td>Invitrogen</td>
			<td>26140079</td>
			<td>Ingredient for staining buffer</td>
		</tr>
		<tr>
			<td>FITC rat anti-mouse CD41</td>
			<td>BD Biosciences</td>
			<td>553848</td>
			<td>Platelets marker</td>
		</tr>
		<tr>
			<td>Flow cytometer</td>
			<td>BD Biosciences</td>
			<td>Non-catalog item</td>
			<td>Analysis of platelets and whole blood</td>
		</tr>
		<tr>
			<td>FlowJo software</td>
			<td>FlowJo, Inc.</td>
			<td>Non-catalog item</td>
			<td>Analysis of platelets and whole blood</td>
		</tr>
		<tr>
			<td>Gly-Pro-Arg-Pro (GPRP)</td>
			<td>EMD Millipore</td>
			<td>03-34-0001</td>
			<td>Prevent platelet clot formation</td>
		</tr>
		<tr>
			<td>Hematocrit Capillary tube</td>
			<td>Fisher Scientific</td>
			<td>22-362566</td>
			<td>Blood collection capillary tube</td>
		</tr>
		<tr>
			<td>Hemavet</td>
			<td>Drew Scientific</td>
			<td>Non-catalog item</td>
			<td>Blood cell analyzer</td>
		</tr>
		<tr>
			<td>Hemocytometer</td>
			<td>Hausser Scientific</td>
			<td>3100</td>
			<td>Cell counting chamber</td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Baxter</td>
			<td>1001936040</td>
			<td>Use to Anesthetize mouse</td>
		</tr>
		<tr>
			<td>Microscope (Olympus CKX41)</td>
			<td>Olympus</td>
			<td>Non-catalog item</td>
			<td>Cell monitoring and counting</td>
		</tr>
		<tr>
			<td>Nycodenz (Histodenz)</td>
			<td>Sigma-Aldrich</td>
			<td>D2158</td>
			<td>Gradient medium</td>
		</tr>
		<tr>
			<td>PE rat anti-mouse CD45</td>
			<td>BD Biosciences</td>
			<td>561087</td>
			<td>WBC marker</td>
		</tr>
		<tr>
			<td>PE-Cy7 rat anti-mouse TER 119</td>
			<td>BD Biosciences</td>
			<td>557853</td>
			<td>RBC marker</td>
		</tr>
		<tr>
			<td>Pipet tips 200 &#181;L, wide-bore</td>
			<td>ThermoFisher Scientific</td>
			<td>21-236-1A</td>
			<td>Transferring blood and platelet samples</td>
		</tr>
		<tr>
			<td>Pipet tips 1000 &#181;L, wide-bore</td>
			<td>ThermoFisher Scientific</td>
			<td>21-236-2C</td>
			<td>Transferring blood and platelet samples</td>
		</tr>
		<tr>
			<td>Phosphate buffured saline (PBS)</td>
			<td>ThermoFisher Scientific</td>
			<td>14040-117</td>
			<td>Buffer for washing and dilution</td>
		</tr>
		<tr>
			<td>Sodium chloride</td>
			<td>Sigma-Aldrich</td>
			<td>S7653</td>
			<td>Physiological saline</td>
		</tr>
		<tr>
			<td>Sodium citrate</td>
			<td>Fisher Scientific</td>
			<td>02-688-26</td>
			<td>Anti-coagulant</td>
		</tr>
		<tr>
			<td>Staining buffer</td>
			<td>In-house</td>
			<td>Non-catalog item</td>
			<td>Wash and dilution buffer</td>
		</tr>
		<tr>
			<td>Steile water</td>
			<td>In-house</td>
			<td>Non-catalog item</td>
			<td>Solvent</td>
		</tr>
		<tr>
			<td>Table top centrifuge</td>
			<td>ThermoFisher Scientific</td>
			<td>75253839/433607</td>
			<td>Swinging bucket rotor centrifuge</td>
		</tr>
		<tr>
			<td>Thrombin</td>
			<td>Enzyme Research Laboratoty</td>
			<td>HT 1002a</td>
			<td>Platelet activation agonist</td>
		</tr>
		<tr>
			<td>Tricine</td>
			<td>Sigma-Aldrich</td>
			<td>T0377</td>
			<td>Buffer for Nycodenz medium</td>
		</tr>
	</tbody>
</table>

purification of platelets from mouse blood

Platelets are purified from whole blood to study their functional properties, which should be free from red blood cells (RBC), white blood cells (WBC), and plasma proteins. We describe here purification of platelets from mouse blood using three-fold more iohexol gradient medium relative to blood sample volume and centrifugation in a swinging bucket rotor at 400 x g for 20 min at 20 &#176;C. The recovery/yield of the purified platelets were 18.2-38.5%, and the purified platelets were in a resting state, which did not contain any significant number of RBC and WBC. The purified platelets treated with thrombin showed up to 93% activation, indicating their viability. We confirmed that the purified platelets are sufficiently pure using flow cytometric and microscopic evaluation. These platelets can be used for gene expression, activation, granule release, aggregation, and adhesion assays. This method can be used for purification of platelets from the blood of other species as well.

The summary of platelet purification is described in a flow diagram (Figure 1). Steps include collection of blood from mouse using retro-orbital bleeding in the presence of an anticoagulant, addition of blood sample onto the iohexol gradient medium, centrifugation in a swinging bucket rotor at 400 x g for 20 min at 20 &#176;C. The quality of the purified platelets was evaluated with microscopy and flow cytometry after staining with antibody to detect any contaminating cells and acti...

Watch this Scientific Journal Video about Purification of Platelets from Mouse Blood at JoVE.com

Purification of Platelets from Mouse Blood

Here, mouse blood was collected in the presence of an anti-coagulant. The platelets were purified by iohexol gradient medium using low speed centrifugation. The platelets were activated with thrombin to investigate if they were viable. The quality of the purified platelets was analyzed by flow cytometry and microscopy.

Platelets are purified from whole blood to study their functional properties, which should be free from red blood cells (RBC), white blood cells (WBC), ...

purification-of-platelets-from-mouse-blood

Research

JoVE Journal

Biology

21.5K Views.  Cincinnati Children's Hospital Medical Center. Here, mouse blood was collected in the presence of an anti-coagulant. The platelets were purified by iohexol gradient medium using low speed centrifugation. The platelets were activated with thrombin to investigate if they were viable. The quality of the purified platelets was analyzed by flow cytometry and microscopy.

Video: Purification of Platelets from Mouse Blood

Isolation of CD4+ T cells from Mouse Lymph Nodes Using Miltenyi MACS Purification

Isolation of cells from the primary source is a necessary step in many more complex protocols. Miltenyi offers kits to isolate cells from several organisms including humans, non-human primates, rat and, as we describe here, mice. Magnetic bead-based cell separation allows for either positive selection (or cell depletion) as well as negative selection. Here, we demonstrate negative selection of untouched or na ve CD4+ helper T cells. Using this standard protocol we typically purify cells that are &#8805; 96% pure CD4+/CD3+. This protocol is used in conjunction with the protocol Dissection and 2-Photon Imaging of Peripheral Lymph Nodes in Mice published in issue 7 of JoVE, for purification of T cells and other cell types to adoptively transfer for imaging purposes. Although we did not demonstrate FACS analysis in this protocol video, it is highly recommended to check the overall purity of isolated cells using the appropriate antibodies via FACS. In addition, we demonstrate the non-sterile method of T cell isolation. If sterile cells are needed for your particular end-user application, be sure to do all of the demonstrated procedures in the tissue culture hood under standard sterile conditions. Thank you for watching and good luck with your own experiments!

Isolation of lymphocytes using the Miltenyi MACs kit is a reliable way to purify cells from whole lymphoid tissue homogenates. Cells purified using the Miltenyi system are typically &#8805; 96% pure. Here, we demonstrate the steps taken to isolate CD4+ T cells, one of the many kits offered by Miltenyi.

Isolation of cells from the primary source is a necessary step in many more complex protocols. Miltenyi offers kits to isolate cells from several ...

Staining of Proteins in Gels with Coomassie G-250 without Organic Solvent and Acetic Acid

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents (Methanol, Ethanol or 2-Propanol) and acetic acid are used for fixation, staining and destaining of proteins in a gel after SDS-PAGE. To speed up the procedure, heating the staining solution in the microwave oven for a short time is frequently used. This usually results in evaporation of toxic or hazardous Methanol, Ethanol or 2-Propanol and a strong smell of acetic acid in the lab which should be avoided due to safety considerations. In a protocol originally published in two patent applications by E.M. Wondrak (US2001046709 (A1), US6319720 (B1)), an alternative composition of the staining solution is described in which no organic solvent or acid is used. The CBB is dissolved in bidistilled water (60-80mg of CBB G-250 per liter) and 35 mM HCl is added as the only other compound in the staining solution. The CBB staning of the gel is done after SDS-PAGE and thorough washing of the gel in bidistilled water. By heating the gel during the washing and staining steps, the process can be finished faster and no toxic or hazardous compunds are evaporating. The staining of proteins occurs already within 1 minute after heating the gel in staining solution and is fully developed after 15-30 min with a slightly blue background that is destained completely by prolonged washing of the stained gel in bidistilled water, without affecting the stained protein bands.

A short protocol for protein staining with Coomassie Brilliant Blue (CBB) G-250 in polyacrylamide gels is described without using organic solvents or acetic acid as in the classical staining procedures with CBB.

In classical protein staining protocols using Coomassie Brilliant Blue (CBB), solutions with high contents of toxic and flammable organic solvents ...

Purification of Mitochondria from Yeast Cells

Mitochondria are the main site of ATP production during aerobic metabolism in eukaryotic non-photosynthetic cells1. These complex organelles also play essential roles in apoptotic cell death2, cell survival3, mammalian development4, neuronal development and function4, intracellular signalling5, and longevity regulation6. Our understanding of these complex biological processes controlled by mitochondria relies on robust methods for assessing their morphology, their protein and lipid composition, the integrity of their DNA, and their numerous vital functions. The budding yeast Saccharomyces cerevisiae, a genetically and biochemically manipulable unicellular eukaryote with annotated genome and well-defined proteome, is a valuable model for studying the molecular and cellular mechanisms underlying essential biological functions of mitochondria. For these types of studies, it is crucial to have highly pure mitochondria. Here we present a detailed description of a rapid and effective method for purification of yeast mitochondria. This method enables the isolation of highly pure mitochondria that are essentially free of contamination by other organelles and retain their structural and functional integrity after their purification. Mitochondria purified by this method are suitable for cell-free reconstitution of essential mitochondrial processes and can be used for the analysis of mitochondrial structure and functions, mitochondrial proteome and lipidome, and mitochondrial DNA.

We describe a rapid and effective method for purification of mitochondria from the yeast Saccharomyces cerevisiae. This method enables the high-yield isolation of pure mitochondria that are essentially free of contamination by other organelles and retain their structural and functional integrity after their purification.

Mitochondria are the main site of ATP production during aerobic metabolism in eukaryotic non-photosynthetic cells1. These complex organelles also play ...

Isolation and Culture of Pulmonary Endothelial Cells from Neonatal Mice

Endothelial cells provide a useful research model in many areas of vascular biology. Since its first isolation 1, human umbilical vein endothelial cells (HUVECs) have shown to be convenient, easy to obtain and culture, and thus are the most widely studied endothelial cells. However, for research focused on processes like angiogenesis, permeability or many others, microvascular endothelial cells (ECs) are a much more physiologically relevant model to study 2. Furthermore, ECs isolated from knockout mice provide a useful tool for analysis of protein function ex vivo. Several approaches to isolate and culture microvascular ECs of different origin have been reported to date 3-7, but consistent isolation and culture of pure ECs is still a major technical problem in many laboratories. Here, we provide a step-by-step protocol on a reliable and relatively simple method of isolating and culturing mouse lung endothelial cells (MLECs). In this approach, lung tissue obtained from 6- to 8-day old pups is first cut into pieces, digested with collagenase/dispase (C/D) solution and dispersed mechanically into single-cell suspension. MLECS are purified from cell suspension using positive selection with anti-PECAM-1 antibody conjugated to Dynabeads using a Magnetic Particle Concentrator (MPC). Such purified cells are cultured on gelatin-coated tissue culture (TC) dishes until they become confluent. At that point, cells are further purified using Dynabeads coupled to anti-ICAM-2 antibody. MLECs obtained with this protocol exhibit a cobblestone phenotype, as visualized by phase-contrast light microscopy, and their endothelial phenotype has been confirmed using FACS analysis with anti-VE-cadherin 8 and anti-VEGFR2 9 antibodies and immunofluorescent staining of VE-cadherin. In our hands, this two-step isolation procedure consistently and reliably yields a pure population of MLECs, which can be further cultured. This method will enable researchers to take advantage of the growing number of knockout and transgenic mice to directly correlate in vivo studies with results of in vitro experiments performed on isolated MLECs and thus help to reveal molecular mechanisms of vascular phenotypes observed in vivo.

Here, we describe a protocol for isolation and culture of murine pulmonary endothelial cells. This method comprises mechanic and enzymatic lung tissue dissociation as well as a 2-step purification process using anti-PECAM-1 and anti-ICAM-2 antibodies conjugated to magnetic beads, which produces a pure endothelial cell population of mostly microvascular origin.

Endothelial cells provide a useful research model in many areas of vascular biology. Since its first isolation 1, human umbilical vein endothelial cells ...

Purification of Progenitors from Skeletal Muscle

Skeletal muscle contains multiple progenitor populations of distinct embryonic origins and developmental potential. Myogenic progenitors, usually residing in a "satellite cell position" between the myofiber plasma membrane and the laminin-rich basement membrane that ensheaths it, are self-renewing cells that are solely committed to the myogenic lineage1,2. We have recently described a second class of vessel associated progenitors that can generate myofibroblasts and white adipocytes, which responds to damage by efficiently entering proliferation and provides trophic support to myogenic cells during tissue regeneration3,4. One of the most trusted assays to determine the developmental and regenerative potential of a given cell population relies on their isolation and transplantation5-7. To this end we have optimized protocols for their purification by flow cytometry from enzymatically dissociated muscle, which we will outline in this article. The populations obtained using this method will contain either myogenic or fibro/adipogenic colony forming cells: no other cell types are capable of expanding in vitro or surviving in vivo delivery. However, when these populations are used immediately after the sort for molecular analysis (e.g qRT-PCR) one must keep in mind that the freshly sorted subsets may contain other contaminant cells that lack the ability of forming colonies or engrafting recipients.

Method for the enzymatic dissociation, surface labeling and purification by flow cytometry of fibro/adipogenic and myogenic progenitors from murine skeletal muscle.

Skeletal muscle contains multiple progenitor populations of distinct embryonic origins and developmental potential. Myogenic progenitors, usually residing ...

Generation of Mice Derived from Induced Pluripotent Stem Cells

The production of induced pluripotent stem cells (iPSCs) from somatic cells provides a means to create valuable tools for basic research and may also produce a source of patient-matched cells for regenerative therapies. iPSCs may be generated using multiple protocols and derived from multiple cell sources. Once generated, iPSCs are tested using a variety of assays including immunostaining for pluripotency markers, generation of three germ layers in embryoid bodies and teratomas, comparisons of gene expression with embryonic stem cells (ESCs) and production of chimeric mice with or without germline contribution2. Importantly, iPSC lines that pass these tests still vary in their capacity to produce different differentiated cell types2. This has made it difficult to establish which iPSC derivation protocols, donor cell sources or selection methods are most useful for different applications.
The most stringent test of whether a stem cell line has sufficient developmental potential to generate all tissues required for survival of an organism (termed full pluripotency) is tetraploid embryo complementation (TEC)3-5. Technically, TEC involves electrofusion of two-cell embryos to generate tetraploid (4n) one-cell embryos that can be cultured in vitro to the blastocyst stage6. Diploid (2n) pluripotent stem cells (e.g. ESCs or iPSCs) are then injected into the blastocoel cavity of the tetraploid blastocyst and transferred to a recipient female for gestation (see Figure 1). The tetraploid component of the complemented embryo contributes almost exclusively to the extraembryonic tissues (placenta, yolk sac), whereas the diploid cells constitute the embryo proper, resulting in a fetus derived entirely from the injected stem cell line.
Recently, we reported the derivation of iPSC lines that reproducibly generate adult mice via TEC1. These iPSC lines give rise to viable pups with efficiencies of 5-13%, which is comparable to ESCs3,4,7 and higher than that reported for most other iPSC lines8-12. These reports show that direct reprogramming can produce fully pluripotent iPSCs that match ESCs in their developmental potential and efficiency of generating pups in TEC tests. At present, it is not clear what distinguishes between fully pluripotent iPSCs and less potent lines13-15. Nor is it clear which reprogramming methods will produce these lines with the highest efficiency. Here we describe one method that produces fully pluripotent iPSCs and "all- iPSC" mice, which may be helpful for investigators wishing to compare the pluripotency of iPSC lines or establish the equivalence of different reprogramming methods.

Generating induced pluripotent stem cell (iPSC) lines produces lines of differing developmental potential even when they pass standard tests for pluripotency. Here we describe a protocol to produce mice derived entirely from iPSCs, which defines the iPSC lines as possessing full pluripotency1.

The production of induced pluripotent stem cells (iPSCs) from somatic cells provides a means to create valuable tools for basic research and may also ...

Purification and microRNA Profiling of Exosomes Derived from Blood and Culture Media

Stable miRNAs are present in all body fluids and some circulating miRNAs are protected from degradation by sequestration in small vesicles called exosomes. Exosomes can fuse with the plasma membrane resulting in the transfer of RNA and proteins to the target cell. Their biological functions include immune response, antigen presentation, and intracellular communication. Delivery of miRNAs that can regulate gene expression in the recipient cells via blood has opened novel avenues for target intervention. In addition to offering a strategy for delivery of drugs or RNA therapeutic agents, exosomal contents can serve as biomarkers that can aid in diagnosis, determining treatment options and prognosis.	Here we will describe the procedure for quantitatively analyzing miRNAs and messenger RNAs (mRNA) from exosomes secreted in blood and cell culture media. Purified exosomes will be characterized using western blot analysis for exosomal markers and PCR for mRNAs of interest. Transmission electron microscopy (TEM) and immunogold labeling will be used to validate exosomal morphology and integrity. Total RNA will be purified from these exosomes to ensure that we can study both mRNA and miRNA from the same sample. After validating RNA integrity by Bioanalyzer, we will perform a medium throughput quantitative real time PCR (qPCR) to identify the exosomal miRNA using Taqman Low Density Array (TLDA) cards and gene expression studies for transcripts of interest.	
 These protocols can be used to quantify changes in exosomal miRNAs in patients, rodent models and cell culture media before and after pharmacological intervention. Exosomal contents vary due to the source of origin and the physiological conditions of cells that secrete exosomes. These variations can provide insight on how cells and systems cope with stress or physiological perturbations. Our representative data show variations in miRNAs present in exosomes purified from mouse blood, human blood and human cell culture media.	
 Here we will describe the procedure for quantitatively analyzing miRNAs and messenger RNAs (mRNA) from exosomes secreted in blood and cell culture media. Purified exosomes will be characterized using western blot analysis for exosomal markers and PCR for mRNAs of interest. Transmission electron microscopy (TEM) and immunogold labeling will be used to validate exosomal morphology and integrity. Total RNA will be purified from these exosomes to ensure that we can study both mRNA and miRNA from the same sample. After validating RNA integrity by Bioanalyzer, we will perform a medium throughput quantitative real time PCR (qPCR) to identify the exosomal miRNA using Taqman Low Density Array (TLDA) cards and gene expression studies for transcripts of interest.
 These protocols can be used to quantify changes in exosomal miRNAs in patients, rodent models and cell culture media before and after pharmacological intervention. Exosomal contents vary due to the source of origin and the physiological conditions of cells that secrete exosomes. These variations can provide insight on how cells and systems cope with stress or physiological perturbations. Our representative data show variations in miRNAs present in exosomes purified from mouse blood, human blood and human cell culture media

The presence of stable microRNAs (miRNAs) in exosomes has generated immense interest as a novel mode of intercellular communication, for their potential utility as biomarkers and as a route for therapeutic intervention. Here we demonstrate exosome purification from blood and culture media followed by quantitative PCR to identify miRNAs being transported.

Stable miRNAs are present in all body fluids and some circulating miRNAs  are protected from degradation by sequestration in small vesicles called  ...

Cell Surface Marker Mediated Purification of iPS Cell Intermediates from a Reprogrammable Mouse Model

Mature cells can be reprogrammed to a pluripotent state. These so called induced pluripotent stem (iPS) cells are able to give rise to all cell types of the body and consequently have vast potential for regenerative medicine applications. Traditionally iPS cells are generated by viral introduction of transcription factors Oct-4, Klf-4, Sox-2, and c-Myc (OKSM) into fibroblasts. However, reprogramming is an inefficient process with only 0.1-1% of cells reverting towards a pluripotent state, making it difficult to study the reprogramming mechanism. A proven methodology that has allowed the study of the reprogramming process is to separate the rare intermediates of the reaction from the refractory bulk population. In the case of mouse embryonic fibroblasts (MEFs), we and others have previously shown that reprogramming cells undergo a distinct series of changes in the expression profile of cell surface markers which can be used for the separation of these cells. During the early stages of OKSM expression successfully reprogramming cells lose fibroblast identity marker Thy-1.2 and up-regulate pluripotency associated marker Ssea-1. The final transition of a subset of Ssea-1 positive cells towards the pluripotent state is marked by the expression of Epcam during the late stages of reprogramming. Here we provide a detailed description of the methodology used to isolate reprogramming intermediates from cultures of reprogramming MEFs. In order to increase experimental reproducibility we use a reprogrammable mouse strain that has been engineered to express a transcriptional transactivator (m2rtTA) under control of the Rosa26 locus and OKSM under control of a doxycycline responsive promoter. Cells isolated from these mice are isogenic and express OKSM homogenously upon addition of doxycycline. We describe in detail the establishment of the reprogrammable mice, the derivation of MEFs, and the subsequent isolation of intermediates during reprogramming into iPS cells via fluorescent activated cells sorting (FACS).

Mouse embryonic fibroblast can be reprogrammed into induced pluripotent stem cells at low efficiency by the forced expression of transcription factors Oct-4, Sox-2, Klf-4, c-Myc. The rare intermediates of the reprogramming reaction are FACS isolated via labeling with antibodies against cell surface makers Thy-1.2, Ssea-1, and Epcam.

Mature cells can be reprogrammed to a pluripotent state. These so called induced pluripotent stem (iPS) cells are able to give rise to all cell types of ...

Trans-inner Cell Mass Injection of Embryonic Stem Cells Leads to Higher Chimerism Rates

In an effort to increase efficiency in the creation of genetically modified mice via ES Cell methodologies, we present an adaptation to the current blastocyst injection protocol. Here we report that a simple rotation of the embryo, and injection through Trans-Inner cell mass (TICM) increased the percentage of chimeric mice from 31% to 50%, with no additional equipment or further specialized training. 26 different inbred clones, and 35 total clones were injected over a period of 9 months. There was no significant difference in either pregnancy rate or recovery rate of embryos between traditional injection techniques and TICM. Therefore, without any major alteration in the injection process and a simple positioning of the blastocyst and injecting through the ICM, releasing the ES cells into the blastocoel cavity can potentially improve the quantity of chimeric production and subsequent germline transmission.

Here we present a protocol to increase chimera production without the use of new equipment. A simple orientation change of the embryo for injection can increase the number of embryos produced, and potentially reduce the timeline to germline transmission.

In an effort to increase efficiency in the creation of genetically modified mice via ES Cell methodologies, we present an adaptation to the current ...

A High Output Method to Isolate Cerebral Pericytes from Mouse

In recent years, cerebral pericytes have become the focus of extensive research in vascular biology and pathology. The importance of pericytes in blood brain barrier formation and physiology is now demonstrated but its molecular basis remains largely unknown. As the pathophysiological role of cerebral pericytes in neurological disorders is intriguing and of great importance, the in vitro models are not only sufficiently appropriate but also able to incorporate different techniques for these studies. Several methods have been proposed as in vitro models for the extraction of cerebral pericytes, although an antibiotic-free protocol with high output is desirable. Most importantly, a method that has increased output per extraction reduces the usage of more animals.
Here, we propose a simple and efficient method for extracting cerebral pericytes with sufficiently high output. The mouse brain tissue homogenate is mixed with a BSA-dextran solution for the separation of the tissue debris and microvascular pellet. We propose a three-step separation followed by filtration to obtain a microvessel rich filtrate. With this method, the quantity of microvascular fragments obtained from 10 mice is sufficient to seed 9 wells (9.6 cm2 each) of a 6-well plate. Most interestingly with this protocol, the user can obtain 27 pericyte rich wells (9.6 cm2 each) in passage 2. The purity of the pericyte cultures are confirmed with the expression of classical pericyte markers: NG2, PDGFR-&#946; and CD146. This method demonstrates an efficient and feasible in vitro tool for physiological and pathophysiological studies on pericytes.

We present a protocol for the extraction of murine cerebral pericytes. Based on an antibiotic-free enrichment oriented pericyte extraction, this protocol is a valuable tool for in vitro studies providing high purity and high yield, thus decreasing the number of experimental animals used.

In recent years, cerebral pericytes have become the focus of extensive research in vascular biology and pathology. The importance of pericytes in blood ...

Methods Article

Purification of Platelets from Mouse Blood