This work has been supported&#160;by ANR (Agence National de la Recherche) Grant ANR- 17-CE14-0001-1.

Control human samples were obtained from volonteer blood donors who gave written informed consent recruited by the blood transfusion center where the research was performed (Etablissement Fran&#231;ais du Sang-Grand Est). All procedures were registered and approved by the French Ministry of Higher Education and Research and registered under the number AC_2015_2371.The donors gave their approval in the CODHECO number AC- 2008 - 562 consent form, in order for the samples to be used for research purposes. Human studies were performed according to Helsinki declaration.
1. Extraction and selection of CD34+ cells (HP) from LRF
<ol>
	<li>Reagent&#39;s preparation (for one LRF)
	<ol>
		<li>Prepare 25 mL of filtered elution buffer: 21.25 mL of Phosphate Buffered Saline (PBS), 2.5 mL of Acid-Citrate-Dextrose (ACD) and 1.25 mL of decomplemented Fetal Bovine Serum (FBS). Filter on 0.22 &#181;m and place at 37 &#176;C.</li>
		<li>Prepare 500 mL of PBS with 2 mM of ethylenediaminetetraacetic-acid (EDTA).</li>
		<li>Dispose 25 mL of density gradient medium (DGM) (1.077 g/mL) in two 50 mL tubes.</li>
	</ol>
	</li>
	<li>LRF back-flushing modalities (Figure 1) 
	NOTE: This step requires a sterile tube welding machine, allowing sterile connection of thermoplastic tubing.
	<ol>
		<li>First, connect the LRF to an empty 600 mL transfer bag and the LRF to a tubing set (Figure 1A). Under the biosafety cabinet, inject the total volume of filtered and prepared elution buffer corresponding to the number of LRFs handled (xLRF x 25 mL) into the empty bag. Then, using a 30 mL syringe to gently aspirate the entire contents of the bag through the LRF, backflush and transfer the cells into a new 50 mL tube (Figure 1B).</li>
		<li>To the red blood cells sedimentation, dilute the cell suspension by half with Dextran 2% and mix well to aggregate red blood cells. Wait for 30 min at room temperature (RT).</li>
	</ol>
	</li>
</ol>
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/62499/62499fig01.jpg" /> 
Figure 1: LRF back flushing modalities. (A) Representative scheme of (i) the sterile connection of the transfer bag to the LRF and (ii) the tubing set to the LRF. (B) Representative scheme of the connection of the syringes for cell collection. <a href="https://www.jove.com/files/ftp_upload/62499/62499fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="3">
	<li>PBMC collection
	<ol>
		<li>Following the red blood cells sedimentation, remove and transfer the supernatant into a 50 mL tube and fill it with PBS-EDTA 2 mM. Gently overlay the supernatant onto the above-prepared DGM. Let the supernatant flow gently without breaking the surface plane of the density gradient. Centrifuge at 400 x g at RT for 30 min in brake off mode.</li>
		<li>Collect the PBMC layer with a disposable transfer pipette. Transfer the cells from each DGM tube into a new sterile 50 mL tube. Fill each tube with PBS-EDTA 2 mM and wash twice in 50 mL of PBS-EDTA 2 mM at 200 x g for 10 min at RT in brake on mode.</li>
		<li>Pipette off and pool the cell pellet with 50 mL PBS-EDTA 2 mM. 
		NOTE: There is a possibility to stop the procedure by maintaining the collected cells under agitation at 4 &#176;C during the night. Then, filter the suspension with a 40 &#181;m cell strainer to remove the aggregates formed.</li>
	</ol>
	</li>
	<li>CD34+ cells selection
	<ol>
		<li>Determine the cell number and centrifuge at 400 x g at room temperature for 10 min with the break on.</li>
		<li>Aspirate the supernatant completely and resuspend in the appropriate volume of PBS-EDTA 2 mM detailed by the manufacturer of the CD34 selection kit (300 &#181;L of PBS-EDTA for 108 cells). Add the FcR blocking Reagent and the CD34 Microbeads in the appropriate concentration (50 &#181;L for 108 cells).</li>
		<li>After 30 min at 4 &#176;C, wash the cell suspension and resuspend in the appropriate volume of PBS-EDTA 2 mM detailed by the manufacturer of the CD34 selection kit (500 &#181;L per 108 cells). 
		&#8203;NOTE: The selection is made on sorting columns for the passage of maximum 2 x 109 cells per column.</li>
		<li>Pass the sample over the wet column of the magnet. Wash twice with 3 mL of PBS-EDTA 2 mM and elute the cells with 5 mL of PBS-EDTA 2 mM. A second run on a new column following the same procedure is necessary to improve the purity of the sample. 
		NOTE: An expected number of 6.1 x 105 cells/LRF (Figure 2A). For higher LRF numbers, scale up reagents and methods accordingly.</li>
	</ol>
	</li>
	<li>Evaluation of CD34+ cell purity
	<ol>
		<li>Add to an aliquot of 100 &#181;L of suspension obtained after the CD34+ selection, 2 &#181;L of human CD34-PE antibody or 2 &#181;L of IgG - PE (control). Mix well and incubate for 15 min at 4 &#176;C.</li>
		<li>Wash cells by adding 2 mL of PBS and centrifuge at 400 x g for 5 min. Aspirate supernatant completely and resuspend in 200 &#181;L of PBS.</li>
		<li>Analyze the purity by flow cytometry as shown in Figure 2A and in the Discussion. 
		&#8203;NOTE: A purity of CD34+ cells above 90% is expected (Figure 2Bii).</li>
		<li>Use the CD34+ cells directly or freeze for further use.</li>
	</ol>
	</li>
	<li>CD34+ cells freezing 
	NOTE: CD34+ cells freezing is done at a density of 106 cells per mL.
	<ol>
		<li>Following the CD34+ cell number determination, prepare the following cryopreservation media: (1) 60% Stemspan + 40% FBS, (2) 40% Stemspan + 40% FBS + 20% Dimethyl Sulfoxide (DMSO) and allow cooling at 4 &#176;C.</li>
		<li>Centrifuge the CD34+ cells at 400 x g at room temperature for 5 min and resuspend the pellet in cold solution 1 and then immediately add to the cold solution 2 (v/v).</li>
		<li>Place the cryotubes immediately into a -80 &#176;C freezer for 24 h and then transfer cryotubes into the liquid nitrogen tank.</li>
	</ol>
	</li>
</ol>
2. Culture and differentiation of CD34+ cells to produce mature proplatelet-bearing megakaryocytes
NOTE: Cell culture protocol (Figure 3A), representative scheme of the cell culture procedure are detailed in this section.
<ol>
	<li>CD34+ cells thawing (if required)
	<ol>
		<li>Prepare the thawing solution: 13 mL of PBS-20% FBS and place at 37 &#176;C for 15 min. Quickly transfer the cryotubes to a 37 &#176;C water bath until only one small ice crystal. Under the biological culture cabinet, pipette the whole content, and slowly transfer in 13 mL of prewarmed thawing solution.</li>
		<li>Determine the cell number and cell viability.</li>
	</ol>
	</li>
	<li>Culture protocol, step 1: from day 0 to day 7 
	NOTE: Usually cultures are made in 24-well plates with 1 mL of medium per well at a density of 40,000 viable cells/mL, corresponding to 20,000 viable cells/cm2. It is crucial to respect this density if any scale up is planned.
	<ol>
		<li>Growth medium preparation : In serum-free hematopoietic cell expansion media (previously heated to 37 &#176;C) add Penicillin-Streptomycin-Glutamine (PSG) 1x, human Low-Density Lipoprotein (hLDL) at 20 &#181;g/mL, cytokine cocktail of megakaryocyte expansion 1x and Stemregenin 1 (SR1) at 1 &#181;M.</li>
		<li>Cell seeding : Centrifuge the thawed CD34+ cells at 400 x g at room temperature for 5 min. Thoroughly remove the supernatant and resuspend the cell pellet in 1 mL of culture media and performa cell numeration and viability to determine the appropriate volume to seed the cells.</li>
		<li>Centrifuge the cells 400 x g at room temperature for 5 min and resuspend the pellet in the appropriate volume of the warm growth medium. Incubate the cells at 37 &#176;C with 5% CO2 for 7 days.</li>
	</ol>
	</li>
	<li>Culture protocol, step 2: from day 7 to day 13 (Figure 3B, representative images at day 13) 
	NOTE: Usually cultures are made in 24-well plates with 1 mL of medium per well at a density of 50,000 viable cells/mL, corresponding to 25,000 viable cells/cm&#178;. It is crucial to respect this density if any scale up is planned.
	<ol>
		<li>Maturation medium preparation: In serum-free hematopoietic cell expansion media (previously heated to 37 &#176;C) add PSG 1x, hLDL at 20 &#181;g/mL, TPO at 50 ng/mL, and SR1 at 1 &#181;M.</li>
		<li>Examine the cells under the microscope. At day 7, cells display a round and homogeneous appearance by filling the wells or the flasks without being too confluent.</li>
		<li>Under a biosafety cabinet, gently transfer the cells in a 15 mL tube. Wash wells with PBS. Then, determine the number of cells and their viability to calculate the appropriate volume to seed the cells.</li>
		<li>Centrifuge the cells at 400 x g at room temperature for 5 min. Remove the supernatant and resuspend the cells in the appropriate volume of warm media calculated in the previous step. Incubate the cells at 37 &#176;C, 5% CO2 for 6 days.</li>
	</ol>
	</li>
	<li>Cultured platelet release at day 13
	<ol>
		<li>Add 0.5 &#181;M of prostaglandine I2 (PGI2) and 0.02 U/mL of apyrase to the culture and perform successive pipetting five times with a 1 mL pipette. 
		&#8203;NOTE: Platelets are now released into the medium.</li>
	</ol>
	</li>
</ol>
3. Flow cytometry analysis (MK phenotyping and cultured platelets count)
NOTE: This protocol can be applied to the phenotyping of the cells on the selected culture days. It also allows the determination of the number of the cultured platelet release (Figure 4A,B).
<ol>
	<li>Preparation for MK analysis
	<ol>
		<li>Label four sets of microcentrifuge tubes as follows: Unlabeled cells as control, cells + 5 &#181;L CD41 - Alexa Fluor 488, Cells + 5 &#181;L CD34 - PECy7, Cells + 5 &#181;L CD41 - Alexa Fluor 488 + 5 &#181;L CD34 - PECy7. Use a minimum of 1.105 cells per tube, do not exceed 1.106 cells per tube. Add to 100 &#181;L of cell suspension per cytometry tube and the different antibodies. Incubate in the dark for 30 min at 4 &#176;C.</li>
		<li>Then, add 2 mL of PBS-EDTA 2 mM per tube and centrifuge at 400 x g for 5 min at room temperature. During centrifugation, prepare a solution of PBS-EDTA 2 mM + 7-Aminoactinomycin-D (7AAD) (1/100), allow for 300 &#181;L solution per tube.</li>
		<li>Remove the supernatant and take up the pellet in 300 &#181;L of PBS-EDTA 2 mM with 7AAD. Run samples through the flow cytometer within 30 min. 
		NOTE: Analysis strategy for flow cytometry is shown in the Figure 3C and in the Discussion.</li>
	</ol>
	</li>
	<li>Tube preparation for cultured platelet analysis
	<ol>
		<li>Label four sets of microcentrifuge tubes as follows: Unlabeled cells as control, Cells + 5 &#181;L CD41 - Alexa Fluor 488, Cells + 20 &#181;L CD42a - PE, Cells + 5 &#181;L CD41 - Alexa Fluor 488 + 20 &#181;L CD42a - PE. Following five successive pipetting in culture well, transfer 300 &#181;L of the suspension in tube for cytometry containing a calibrated number of fluorescent beads.</li>
		<li>Add antibodies and incubate in the dark at RT for 30 min.</li>
		<li>Run the samples through the flow cytometer within 30 min and set the acquisition for the passage of 5,000 beads. 
		NOTE: Analysis strategy for flow cytometry is shown in the Figure 4B and in the Discussion.</li>
	</ol>
	</li>
</ol>

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H., Mangla, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> StatPearls. , (2020).</li><li>Strassel, C., Hechler, B., Bull, A., Gachet, C., Lanza, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studies+of+mice+lacking+the+GPIb-V-IX+complex+question+the+role+of+this+receptor+in+atherosclerosis.">Studies of mice lacking the GPIb-V-IX complex question the role of this receptor in atherosclerosis.</a> Journal of Thrombosis and Haemostasis. 7 (11), 1935-1938 (2009).</li><li>Delalat, B., 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=Isolation+and+ex+vivo+expansion+of+human+umbilical+cord+blood-derived+CD34++stem+cells+and+their+cotransplantation+with+or+without+mesenchymal+stem+cells.">Isolation and ex vivo expansion of human umbilical cord blood-derived CD34+ stem cells and their cotransplantation with or without mesenchymal stem cells.</a> Hematology. 14 (3), 125-132 (2009).</li><li>Yin, T., Li, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+stem+cell+niches+in+bone.">The stem cell niches in bone.</a> The Journal of Clinical Investigation. 116 (5), 1195-1201 (2006).</li><li>Salunkhe, V., Papadopoulos, P., Guti&#233;rrez, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Culture+of+megakaryocytes+from+human+peripheral+blood+mononuclear+cells.">Culture of megakaryocytes from human peripheral blood mononuclear cells.</a> Bio-protocol. 5 (21), 1639 (2015).</li><li>Peytour, Y., Villacreces, A., Chevaleyre, J., Ivanovic, Z., Praloran, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Discarded+leukoreduction+filters:+a+new+source+of+stem+cells+for+research,+cell+engineering+and+therapy.">Discarded leukoreduction filters: a new source of stem cells for research, cell engineering and therapy.</a> Stem Cell Research. 11 (2), 736-742 (2013).</li><li>Lapostolle, 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=Repopulating+hematopoietic+stem+cells+from+steady-state+blood+before+and+after+ex+vivo+culture+are+enriched+in+the+CD34(+)CD133(+)CXCR4(low)+fraction.">Repopulating hematopoietic stem cells from steady-state blood before and after ex vivo culture are enriched in the CD34(+)CD133(+)CXCR4(low) fraction.</a> Haematologica. 103 (10), 1604-1615 (2018).</li><li>Ivanovic, Z., 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=Whole-blood+leuko-depletion+filters+as+a+source+of+CD+34++progenitors+potentially+usable+in+cell+therapy.">Whole-blood leuko-depletion filters as a source of CD 34+ progenitors potentially usable in cell therapy.</a> Transfusion. 46 (1), 118-125 (2006).</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=Aryl+hydrocarbon+receptor-dependent+enrichment+of+a+megakaryocytic+precursor+with+a+high+potential+to+produce+proplatelets.">Aryl hydrocarbon receptor-dependent enrichment of a megakaryocytic precursor with a high potential to produce proplatelets.</a> Blood. 127 (18), 2231-2240 (2016).</li><li>Do Sacramento, 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=Functional+properties+of+human+platelets+derived+in+vitro+from+CD34(+)+cells.">Functional properties of human platelets derived in vitro from CD34(+) cells.</a> Scientific Reports. 10 (1), 914 (2020).</li><li>Blin, A., 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=Microfluidic+model+of+the+platelet-generating+organ:+beyond+bone+marrow+biomimetics.">Microfluidic model of the platelet-generating organ: beyond bone marrow biomimetics.</a> Scientific Reports. 6, 21700 (2016).</li><li>Ito, Y., 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=Turbulence+activates+platelet+biogenesis+to+enable+clinical+scale+ex+vivo+production.">Turbulence activates platelet biogenesis to enable clinical scale ex vivo production.</a> Cell. 174 (3), 636-648 (2018).</li><li>Pallotta, I., Lovett, M., Kaplan, D. 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The authors have nothing to disclose.

This protocol describes a method for producing MK capable of emitting proplatelets from blood-derived HP and to release platelets from the culture medium. HP are obtained from LRF, a by-product of the blood banks, used to remove contaminating leukocytes from cellular blood products and avoid adverse reactions. Although this method is relatively simple, a few points deserve special attention.
Deposition of the cell suspension on the density gradient medium (step 1.3.1) has to be performed gentl...

Blood platelets come from specialized large polyploid cells, the megakaryocytes (MK), that originate from a constant and fine-tuned production process known as megakaryopoiesis (MKP). At the apex of this process are hematopoietic stem cells which, in contact with the bone marrow environment (cytokines, transcription factors, hematopoietic niche), will be able to proliferate and differentiate into hematopoietic progenitors (HP) able to commit toward the megakaryocytic pathway, giving rise to immature MKs1. Under the influence of various cytokines, and in particular thrombopoietin (TPO), which is the major cytokine of MKP; the MK will then undergo two major stages of maturation: endomitosis and the development of demarcation membranes (DMS). This fully mature MK then appears close to a sinusoid vessel in which it can emit cytoplasmic extensions, the proplatelets, which will be released under the blood flow and subsequently remodeled into functional platelets2. The cloning of TPO in 19943 provided a boost in the study of MKP by accelerating the development of in vitro culture techniques allowing HP differentiation and MK maturation.
There are many pathologies affecting blood platelets, both in terms of platelet number (increase or decrease) and function4,5. Being able to recapitulate MKP in vitro from human HP could improve understanding of the molecular and cellular mechanisms underlying this process and ultimately the therapeutic management of patients.
Various sources of human HP are suitable: cord blood, bone marrow, and peripheral blood6,7,8. Harvesting HP from peripheral blood raises less logistical and ethical problems than their recovery from cord blood or the bone marrow. HP can be recovered from leukapheresis or buffy coat, but these sources are expensive and not always available in blood centers. Other protocols, less expensive and easier to perform, allow direct recovery of human peripheral blood mononuclear cells (PBMCs) without the need for prior CD34 driven isolation4,8. However, the purity of megakaryocytes is not satisfactory with this method and a selection of CD34+ cells from PBMC is recommended for optimal differentiation into MK. This led us to implement a HP purification from leukoreduction filters (LRF), routinely used in blood banks to remove white blood cells and thus avoid adverse immunological reactions9. Indeed, since 1998, platelet concentrates have been automatically leukodepleted in France. At the end of this process, LRF are discarded and all the cells retained in the LRF are destroyed. Cells in LRFs are, therefore, readily available at no additional cost. LRFs have a cellular content close to that obtained by leukapheresis or in buffy coats, notably in their composition of CD34+ HP making them a remarkably attractive source10. LRF as a human HP source has already been demonstrated to provide cells with intact functional capacities11. This source has the advantage of being abundant and affordable for laboratory research. In this context, this article describes successively: i) the extraction and selection of CD34+ HP from LRFs; ii) a two-phase optimized culture, which recapitulates the commitment of HP into the megakaryocytic pathway and the maturation of MK capable of emitting proplatelets; iii) a method for efficiently releasing platelets from these MK; and iv) a procedure for phenotyping MK and cultured platelets.

<table><tbody><tr><td>7-AAD</td><td>Biolegend</td><td>558819</td><td></td></tr><tr><td>ACD</td><td>EFS-Alsace</td><td>NA</td><td></td></tr><tr><td>Anti-CD34-PE&amp;nbsp;</td><td>Miltenyi biotec</td><td>130-081-002</td><td></td></tr><tr><td>Anti-CD34-PECy7</td><td>eBioscience</td><td>25-0349-42</td><td></td></tr><tr><td>Anti-CD41-Alexa Fluor 488</td><td>Biolegend</td><td>303724</td><td></td></tr><tr><td>Anti-CD42a-PE</td><td>BD Bioscience</td><td>559919</td><td></td></tr><tr><td>Apyrase</td><td>EFS-Alsace</td><td>NA</td><td></td></tr><tr><td>BD Trucount Tubes</td><td>BD Bioscience</td><td>340334</td><td></td></tr><tr><td>CD34 MicroBead Kit UltraPure, human&amp;nbsp;</td><td>Miltenyi biotec</td><td>130-100-453</td><td></td></tr><tr><td>Centrifuge</td><td>Heraeus</td><td>Megafuge 1.OR</td><td>Or equivalent material</td></tr><tr><td>Compteur ADAM&amp;nbsp;</td><td>DiagitalBio</td><td>NA</td><td>Or equivalent material</td></tr><tr><td>Cryotubes</td><td>Dutscher</td><td>55002</td><td>Or equivalent material</td></tr><tr><td>Dextran from leuconostoc spp&amp;nbsp;</td><td>Sigma</td><td>31392-50g</td><td>Or equivalent material</td></tr><tr><td>DMSO Hybri-max&amp;nbsp;</td><td>Sigma</td><td>D2650</td><td></td></tr><tr><td>EDTA 0.5 M&amp;nbsp;</td><td>Gibco</td><td>15575-039</td><td></td></tr><tr><td>Eppendorf 1,5 mL&amp;nbsp;</td><td>Dutscher</td><td>616201</td><td>Or equivalent material</td></tr><tr><td>Filtration unit Steriflip PVDF</td><td>Merck Millipore Ltd</td><td>SE1M179M6</td><td></td></tr><tr><td>Flow Cytometer</td><td>BD Bioscience</td><td>Fortessa</td><td></td></tr><tr><td>Human LDL</td><td>Stemcell technologies</td><td>#02698</td><td></td></tr><tr><td>ILOMEDINE 0,1 mg/1 mL</td><td>Bayer</td><td>MA038EX</td><td></td></tr><tr><td>Inserts</td><td>Fenwal</td><td>R4R1401</td><td>Or equivalent material</td></tr><tr><td>Laminar flow hood&amp;nbsp;</td><td>Holten</td><td>NA</td><td>Archived product</td></tr><tr><td>LS Columms&amp;nbsp;</td><td>Miltenyi Biotec</td><td>130-042-401&amp;nbsp;</td><td></td></tr><tr><td>Lymphoprep</td><td>Stemcell</td><td>7861</td><td></td></tr><tr><td>Pen Strep Glutamine (100x)</td><td>Gibco</td><td>10378-016</td><td></td></tr><tr><td>PBS (-)</td><td>Life Technologies</td><td>14190-169&amp;nbsp;</td><td>Or equivalent material</td></tr><tr><td>PGi2</td><td>Sigma</td><td>P6188</td><td></td></tr><tr><td>Poches de transferts 600ml&amp;nbsp;</td><td>Macopharma</td><td>VSE4001XA</td><td></td></tr><tr><td>Pre-Separation Filters (30&amp;micro;m)</td><td>Miltenyi Biotec</td><td>130-041-407</td><td></td></tr><tr><td>StemRegenin 1 (SR1)</td><td>Stemcell technologies</td><td>#72344</td><td></td></tr><tr><td>StemSpan Expansion Supplement (100x)</td><td>Stemcell technologies</td><td>#02696</td><td></td></tr><tr><td>StemSpan-SFEM&amp;nbsp;</td><td>Stemcell technologies</td><td>#09650</td><td></td></tr><tr><td>Stericup Durapore 0,22&amp;micro;m PVDF</td><td>Merck Millipore Ltd</td><td>SCGVU05RE</td><td></td></tr><tr><td>SVF Hyclone&amp;nbsp;</td><td>Thermos scientific</td><td>SH3007103</td><td></td></tr><tr><td>Syringues 30 mL&amp;nbsp;</td><td>Terumo</td><td>SS*30ESE1</td><td>Or equivalent material</td></tr><tr><td>Syringe filters Millex 0,22&amp;micro;M PVDF</td><td>Merck Millipore Ltd</td><td>SLGV033RB</td><td></td></tr><tr><td>TPO</td><td>Stemcell technologies</td><td>#02822</td><td></td></tr><tr><td>Tubes 50 mL</td><td>Sarstedt</td><td>62.548.004 PP</td><td>Or equivalent material</td></tr><tr><td>Tubes 15 mL&amp;nbsp;</td><td>Sarstedt</td><td>62.554.001 PP</td><td>Or equivalent material</td></tr><tr><td>Tubulures</td><td>B Braun</td><td>4055137</td><td>Or equivalent material</td></tr></tbody></table>

leukodepletion filters-derived cd34+ cells as a cell source to study megakaryocyte differentiation and platelet formation

The in vitro expansion and differentiation of human hematopoietic progenitors into megakaryocytes capable of elongating proplatelets and releasing platelets allows an in-depth study of the mechanisms underlying platelet biogenesis. Available culture protocols are mostly based on hematopoietic progenitors derived from bone marrow or cord blood raising a number of ethical, technical, and economic concerns. If there are already available protocols for obtaining CD34 cells from peripheral blood, this manuscript proposes a straightforward and optimized protocol for obtaining CD34+ cells from leukodepletion filters readily available in blood centers. These cells are isolated from leukodepletion filters used in the preparation of blood transfusion products, corresponding to eight blood donations. These filters are meant to be discarded. A detailed procedure to collect hematopoietic progenitors identified as CD34+ cells from these filters is described. The method to obtain mature megakaryocytes extending proplatelets while discussing their phenotypic evolution is also detailed. Finally, the protocol present a calibrated pipetting method, to efficiently release platelets that are morphologically and functionally similar to native ones. This protocol can serve as a basis for evaluating pharmacological compounds acting at various steps of the process to dissect the underlying mechanisms and approach the in vivo platelet yields.

Extraction and selection of CD34+ cells from LRFs 
Here, the method, derived from Peytour et al.9, describes the extraction and selection of CD34+ cells from discarded LRFs available in blood banks after leukocyte removal. Following the backflush procedure, usually 1.03 x 109 &#177;&#160;2.45 x 108 cells/LRF (Mean&#177;SEM; n = 155) are recovered with a viability of 94.88 &#177; 0.10% (Figure 2A i...

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Leukodepletion Filters-Derived CD34+ Cells As a Cell Source to Study Megakaryocyte Differentiation and Platelet Formation

This protocol describes in detail all the steps involved in obtaining leukofilter-derived CD34+ hematopoietic progenitors and their in vitro differentiation and maturation into proplatelet-bearing megakaryocytes that are able to release platelets in the culture medium. This procedure is useful for in-depth analysis of cellular and molecular mechanisms controlling megakaryopoiesis.

The in vitro expansion and differentiation of human hematopoietic progenitors into megakaryocytes capable of elongating proplatelets and releasing ...

leukodepletion-filters-derived-cd34-cells-as-cell-source-to-study

Research

JoVE Journal

Biology

3.9K Views.  Université de Strasbourg, INSERM, EFS Grand Est. This protocol describes in detail all the steps involved in obtaining leukofilter-derived CD34+ hematopoietic progenitors and their in vitro differentiation and maturation into proplatelet-bearing megakaryocytes that are able to release platelets in the culture medium. This procedure is useful for in-depth analysis of cellular and molecular mechanisms controlling megakaryopoiesis.

Video: Leukodepletion Filters-Derived CD34+ Cells As a Cell Source to Study Megakaryocyte Differentiation and Platelet Formation

Bioenergetics and the Oxidative Burst: Protocols for the Isolation and Evaluation of Human Leukocytes and Platelets

Mitochondrial dysfunction is known to play a significant role in a number of pathological conditions such as atherosclerosis, diabetes, septic shock, and neurodegenerative diseases but assessing changes in bioenergetic function in patients is challenging.&#160;Although diseases such as diabetes or atherosclerosis present clinically with specific organ impairment, the systemic components of the pathology, such as hyperglycemia or inflammation, can alter bioenergetic function in circulating leukocytes or platelets. This concept has been recognized for some time but its widespread application has been constrained by the large number of primary cells needed for bioenergetic analysis.&#160;This technical limitation has been overcome by combining the specificity of the magnetic bead isolation techniques, cell adhesion techniques, which allow cells to be attached without activation to microplates, and the sensitivity of new technologies designed for high throughput microplate respirometry.&#160;An example of this equipment is the extracellular flux analyzer. Such instrumentation typically uses oxygen and pH sensitive probes to measure rates of change in these parameters in adherent cells, which can then be related to metabolism. Here we detail the methods for the isolation and plating of monocytes, lymphocytes, neutrophils and platelets, without activation, from human blood and the analysis of mitochondrial bioenergetic function in these cells. In addition, we demonstrate how the oxidative burst in monocytes and neutrophils can also be measured in the same samples. Since these methods use only 8-20 ml human blood they have potential for monitoring reactive oxygen species generation and bioenergetics in a clinical setting.

Blood leukocytes and platelets can be used as a marker of overall bioenergetic health of an individual and so have the potential to monitor pathological processes and the impact of treatments. Here&#160;we describe a method to isolate and measure mitochondrial function and the oxidative burst in these cells.

Mitochondrial dysfunction is known to play a significant role in a number of pathological conditions such as atherosclerosis, diabetes, septic shock, and ...

Immunology and Infection

Pan-myeloid Differentiation of Human Cord Blood Derived CD34+ Hematopoietic Stem and Progenitor Cells

Ex vivo differentiation of human hematopoietic stem cells is a widely used model for studying hematopoiesis. The protocol described here is for cytokine induced differentiation of CD34+ hematopoietic stem and progenitor cells to the four myeloid lineage cells. CD34+ cells are isolated from human umbilical cord blood and co-cultured with MS-5 stromal cells in the presence of cytokines. Immunophenotypic characterization of the stem and progenitor cells, and the differentiated myeloid lineage cells are described. Using this protocol, CD34+ cells may be incubated with small molecules or transduced with lentiviruses to express myeloid disease mutations to investigate their impact on myeloid differentiation.

Pan-myeloid Differentiation of Human Cord Blood Derived CD34+ Hematopoietic Stem and Progenitor Cells

Here, we present a protocol for immunophenotypic characterization and cytokine induced differentiation of cord blood derived CD34+ hematopoietic stem and progenitor cells to the four myeloid lineages. The applications of this protocol include investigations on the effect of myeloid disease mutations or small molecules on myeloid differentiation of the CD34+ cells.

Ex vivo differentiation of human hematopoietic stem cells is a widely used model for studying hematopoiesis. The protocol described here is for cytokine ...

Developmental Biology

Megakaryocyte Differentiation and Platelet Formation from Human Cord Blood-derived CD34+ Cells

Platelet production occurs principally in the bone marrow in a process known as thrombopoiesis. During thrombopoiesis, hematopoietic progenitor cells differentiate to form platelet precursors called megakaryocytes, which terminally differentiate to release platelets from long cytoplasmic processes termed proplatelets. Megakaryocytes are rare cells confined to the bone marrow and are therefore difficult to harvest in sufficient numbers for laboratory use. Efficient production of human megakaryocytes can be achieved in vitro by culturing CD34+ cells under suitable conditions. The protocol detailed here describes isolation of CD34+ cells by magnetic cell sorting from umbilical cord blood samples. The necessary steps to produce highly pure, mature megakaryocytes under serum-free conditions are described. Details of phenotypic analysis of megakaryocyte differentiation and determination of proplatelet formation and platelet production are also provided. Effectors that influence megakaryocyte differentiation and/or proplatelet formation, such as anti-platelet antibodies or thrombopoietin mimetics, can be added to cultured cells to examine biological function.

Megakaryocyte Differentiation and Platelet Formation from Human Cord Blood-derived CD34+ Cells

A highly pure population of megakaryocytes can be obtained from cord blood-derived CD34+ cells. A method for CD34+ cell isolation and megakaryocyte differentiation is described here.

Platelet production occurs principally in the bone marrow in a process known as thrombopoiesis. During thrombopoiesis, hematopoietic progenitor cells ...

Lentiviral-mediated Knockdown During Ex Vivo Erythropoiesis of Human Hematopoietic Stem Cells

Erythropoiesis is a commonly used model system to study cell differentiation. During erythropoiesis, pluripotent adult human hematopoietic stem cells (HSCs) differentiate into oligopotent progenitors, committed precursors and mature red blood cells 1. This process is regulated for a large part at the level of gene expression, whereby specific transcription factors activate lineage-specific genes while concomitantly repressing genes that are specific to other cell types 2. Studies on transcription factors regulating erythropoiesis are often performed using human and murine cell lines that represent, to some extent, erythroid cells at given stages of differentiation 3-5. However transformed cell lines can only partially mimic erythroid cells and most importantly they do not allow one to comprehensibly study the dynamic changes that occur as cells progress through many stages towards their final erythroid fate. Therefore, a current challenge remains the development of a protocol to obtain relatively homogenous populations of primary HSCs and erythroid cells at various stages of differentiation in quantities that are sufficient to perform genomics and proteomics experiments.
Here we describe an ex vivo cell culture protocol to induce erythroid differentiation from human hematopoietic stem/progenitor cells that have been isolated from either cord blood, bone marrow, or adult peripheral blood mobilized with G-CSF (leukapheresis). This culture system, initially developed by the Douay laboratory 6, uses cytokines and co-culture on mesenchymal cells to mimic the bone marrow microenvironment. Using this ex vivo differentiation protocol, we observe a strong amplification of erythroid progenitors, an induction of differentiation exclusively towards the erythroid lineage and a complete maturation to the stage of enucleated red blood cells. Thus, this system provides an opportunity to study the molecular mechanism of transcriptional regulation as hematopoietic stem cells progress along the erythroid lineage. 
Studying erythropoiesis at the transcriptional level also requires the ability to over-express or knockdown specific factors in primary erythroid cells. For this purpose, we use a lentivirus-mediated gene delivery system that allows for the efficient infection of both dividing and non-dividing cells 7. Here we show that we are able to efficiently knockdown the transcription factor TAL1 in primary human erythroid cells. In addition, GFP expression demonstrates an efficiency of lentiviral infection close to 90%. Thus, our protocol provides a highly useful system for characterization of the regulatory network of transcription factors that control erythropoiesis.

Lentiviral-mediated Knockdown During Ex Vivo Erythropoiesis of Human Hematopoietic Stem Cells

An ex vivo protocol to generate mature human red blood cells from hematopoietic stem/progenitors is described. Additionally we describe an efficient lentiviral-delivery method to knockdown the transcription factor TAL1 in primary erythroid cells. The efficiency of lentivirus mediated gene delivery is demonstrated using GFP expressing viruses.

Erythropoiesis is a commonly used model system to study cell differentiation. During erythropoiesis, pluripotent adult human hematopoietic stem cells ...

Isolation of CD133+ Liver Stem Cells for Clonal Expansion

Liver stem cell, or oval cells, proliferate during chronic liver injury, and are proposed to differentiate into both hepatocytes and cholangiocytes. In addition, liver stem cells are hypothesized to be the precursors for a subset of liver cancer, Hepatocellular carcinoma. One of the primary challenges to stem cell work in any solid organ like the liver is the isolation of a rare population of cells for detailed analysis. For example, the vast majority of cells in the liver are hepatocytes (parenchymal fraction), which are significantly larger than non-parenchymal cells. By enriching the specific cellular compartments of the liver (i.e. parenchymal and non-parenchymal fractions), and selecting for CD45 negative cells, we are able to enrich the starting population of stem cells by over 600-fold.The proceduresdetailed in this report allow for a relatively rare population of cells from a solid organ to be sorted efficiently. This process can be utilized to isolateliver stem cells from normal murine liver as well as chronic liver injury models, which demonstrate increased liver stem cell proliferation. This method has clear advantages over standard immunohistochemistry of frozen or formalin fixed liver as functional studies using live cells can be performed after initial co-localization experiments. To accomplish the procedure outlined in this report, a working relationship with a research based flow-cytometry core is strongly encouraged as the details of FACS isolation are highly dependent on specialized instrumentation and a strong working knowledge of basic flow-cytometry procedures. The specific goal of this process is to isolate a population of liver stem cells that can be clonally expanded in vitro.

Here we describe the isolation of CD133 expressing liver stem cells and cancer stem cells from whole murine liver, a process that requires tissue digestion, cell enrichment, and flow cytometry isolation. We include methods for advanced single cell isolation and clonal expansion.

Liver stem cell, or oval cells, proliferate during chronic liver injury, and are proposed to differentiate into both hepatocytes and cholangiocytes. In ...

Identification and Isolation of Oligopotent and Lineage-committed Myeloid Progenitors from Mouse Bone Marrow

Myeloid progenitors that yield neutrophils, monocytes and dendritic cells (DCs) can be identified in and isolated from the bone marrow of mice for hematological and immunological analyses. For example, studies of the cellular and molecular properties of myeloid progenitor populations can reveal mechanisms underlying leukemic transformation, or demonstrate how the immune system responds to pathogen exposure. Previously described flow cytometry strategies for myeloid progenitor identification have enabled significant advances in many fields, but the fractions they identify are very heterogeneous. The most commonly used gating strategies define bone marrow fractions that are enriched for the desired populations, but also contain large numbers of &#34;contaminating&#34; progenitors. Our recent studies have resolved much of this heterogeneity, and the protocol we present here permits the isolation of 6 subpopulations of oligopotent and lineage-committed myeloid progenitors from 2 previously described bone marrow fractions. The protocol describes 3 stages: 1) isolation of bone marrow cells, 2) enrichment for hematopoietic progenitors by magnetic-activated cell sorting (lineage depletion by MACS), and 3) identification of myeloid progenitor subsets by flow cytometry (including fluorescence-activated cell sorting, FACS, if desired). This approach permits progenitor quantification and isolation for a variety of in vitro and in vivo applications, and has already yielded novel insight into pathways and mechanisms of neutrophil, monocyte, and DC differentiation.

We demonstrate how to identify and isolate 6 subsets of myeloid progenitors from murine bone marrow using a combination of magnetic and fluorescence sorting (MACS and FACS). This protocol can be used for in vitro culture assays (methylcellulose or liquid cultures), in vivo adoptive transfer experiments, and RNA/protein analyses.

Myeloid progenitors that yield neutrophils, monocytes and dendritic cells (DCs) can be identified in and isolated from the bone marrow of mice for ...

Phenotypic Analysis and Isolation of Murine Hematopoietic Stem Cells and Lineage-committed Progenitors

The bone marrow is the principal site where HSCs and more mature blood cells lineage progenitors reside and differentiate in an adult organism. HSCs constitute a minute cell population of pluripotent cells capable of generating all blood cell lineages for a life-time1. The molecular dissection of HSCs homeostasis in the bone marrow has important implications in hematopoiesis, oncology and regenerative medicine. We describe the labeling protocol with fluorescent antibodies and the electronic gating procedure in flow cytometry to score hematopoietic progenitor subsets and HSCs distribution in individual mice (Fig. 1). In addition, we describe a method to extensively enrich hematopoietic progenitors as well as long-term (LT) and short term (ST) reconstituting HSCs from pooled bone marrow cell suspensions by magnetic enrichment of cells expressing c-Kit. The resulting cell preparation can be used to sort selected subsets for in vitro and in vivo functional studies (Fig. 2).
Both trabecular osteoblasts2,3 and sinusoidal endothelium4 constitute functional niches supporting HSCs in the bone marrow. Several mechanisms in the osteoblastic niche, including a subset of N-cadherin+ osteoblasts3 and interaction of the receptor tyrosine kinase Tie2 expressed in HSCs with its ligand angiopoietin-15 concur in determining HSCs quiescence. "Hibernation" in the bone marrow is crucial to protect HSCs from replication and eventual exhaustion upon excessive cycling activity6. Exogenous stimuli acting on cells of the innate immune system such as Toll-like receptor ligands7 and interferon-&alpha;6 can also induce proliferation and differentiation of HSCs into lineage committed progenitors. Recently, a population of dormant mouse HSCs within the lin- c-Kit+ Sca-1+ CD150+ CD48- CD34- population has been described8. Sorting of cells based on CD34 expression from the hematopoietic progenitors-enriched cell suspension as described here allows the isolation of both quiescent self-renewing LT-HSCs and ST-HSCs9. A similar procedure based on depletion of lineage positive cells and sorting of LT-HSC with CD48 and Flk2 antibodies has been previously described10. In the present report we provide a protocol for the phenotypic characterization and ex vivo cell cycle analysis of hematopoietic progenitors, which can be useful for monitoring hematopoiesis in different physiological and pathological conditions. Moreover, we describe a FACS sorting procedure for HSCs, which can be used to define factors and mechanisms regulating their self-renewal, expansion and differentiation in cell biology and signal transduction assays as well as for transplantation.

A method to analyse the distribution of bone marrow hematopoietic progenitors in flow cytometry as well as to efficiently isolate highly purified hematopoietic stem cells (HSCs) is described. The isolation procedure is essentially based on magnetic enrichment of c-Kit+ cells and cell sorting to purify HSCs for cellular and molecular studies.

The bone marrow is the principal site where HSCs and more mature blood cells lineage progenitors reside and differentiate in an adult organism. HSCs ...

Isolation and Magnetic Separation of Murine CD34+ Stem Cells from the Vascular Wall

Immunomagnetic Isolation of the Vascular Wall-Resident CD34+ Stem Cells from Mice

Resident CD34+ vascular wall-resident stem and progenitor cells (VW-SCs) are increasingly recognized for their crucial role in regulating vascular injury and repair. Establishing a stable and efficient method to culture functional murine CD34+ VW-SCs is essential for further investigating the mechanisms involved in the proliferation, migration, and differentiation of these cells under various physiological and pathological conditions. The described method combines magnetic bead screening and flow cytometry to purify primary cultured resident CD34+ VW-SCs. The purified cells are then functionally identified through immunofluorescence staining and Ca2+ imaging. Briefly, vascular cells from the adventitia of the murine aorta and mesenteric artery are obtained through tissue block attachment, followed by subculturing until reaching a cell count of at least 1 &#215; 107. Subsequently, CD34+ VW-SCs are purified using magnetic bead sorting and flow cytometry. Identification of CD34+ VW-SCs involves cellular immunofluorescence staining, while functional multipotency is determined by exposing cells to a specific culture medium for oriented differentiation. Moreover, functional internal Ca2+ release and external Ca2+ entry is assessed using a commercially available imaging workstation in Fura-2/AM-loaded cells exposed to ATP, caffeine, or thapsigargin (TG). This method offers a stable and efficient technique for isolating, culturing, and identifying vascular wall-resident CD34+ stem cells, providing an opportunity for in vitro studies on the regulatory mechanisms of VW-SCs and the screening of targeted drugs.

Author Spotlight: Enhanced Isolation and Characterization of Vascular Wall Resident Murine CD34+ Stem Cells Using Magnetic Bead Screening-Coupled Flow Cytometry

This study has established a stable and efficient method for the isolation, culture, and functional determination of vascular wall-resident CD34+ stem cells (CD34+ VW-SCs). This easy-to-follow and time-effective isolation method can be utilized by other investigators to study the potential mechanisms involved in cardiovascular diseases.

Resident CD34+ vascular wall-resident stem and progenitor cells (VW-SCs) are increasingly recognized for their crucial role in regulating vascular injury ...

Medicine

Isolation of Mouse Megakaryocyte Progenitors

Bone marrow megakaryocytes are large polyploid cells that ensure the production of blood platelets. They arise from hematopoietic stem cells through megakaryopoiesis. The final stages of this process are complex and classically involve the bipotent Megakaryocyte-Erythrocyte Progenitors (MEP) and the unipotent Megakaryocyte Progenitors (MKp). These populations precede the formation of bona fide megakaryocytes and, as such, their isolation and characterization could allow for the robust and unbiased analysis of megakaryocyte formation. This protocol presents in detail the procedure to collect hematopoietic cells from mouse bone marrow, the enrichment of hematopoietic progenitors through magnetic depletion and finally a cell sorting strategy that yield highly purified MEP and MKp populations. First, bone marrow cells are collected from the femur, the tibia, and also the iliac crest, a bone that contains a high number of hematopoietic progenitors. The use of iliac crest bones drastically increases the total cell number obtained per mouse and thus contributes to a more ethical use of animals. A magnetic lineage depletion was optimized using 450 nm magnetic beads allowing a very efficient cell sorting by flow cytometry. Finally, the protocol presents the labeling and gating strategy for the sorting of the two highly purified megakaryocyte progenitor populations: MEP (Lin-Sca-1-c-Kit+CD16/32-CD150+CD9dim) and MKp (Lin- Sca-1-c-Kit+CD16/32-CD150+CD9bright). This technique is easy to implement and provides enough cellular material to perform i) molecular characterization for a deeper knowledge of their identity and biology, ii) in vitro differentiation assays, that will provide a better understanding of the mechanisms of maturation of megakaryocytes, or iii) in vitro models of interaction with their microenvironment.

This method describes the purification by flow cytometry of MEP and MKp from mice femurs, tibias, and pelvic bones.

Bone marrow megakaryocytes are large polyploid cells that ensure the production of blood platelets. They arise from hematopoietic stem cells through ...

Immunophenotyping and Cell Sorting of Human MKs from Human Primary Sources or Differentiated In Vitro from Hematopoietic Progenitors

Megakaryocyte (MK) differentiation encompasses a number of endomitotic cycles that result in a highly polyploid (reaching even&#160;&#62;64N) and extremely large cell (40-60 &#181;m). As opposed to the fast-increasing knowledge in megakaryopoiesis at the cell biology and molecular level, the characterization of megakaryopoiesis by flow cytometry is limited to the identification of mature MKs using lineage-specific surface markers, while earlier MK differentiation stages remain unexplored. Here, we present an immunophenotyping strategy that allows the identification of successive MK differentiation stages, with increasing ploidy status, in human primary sources or in vitro cultures with a panel integrating MK specific and non-specific surface markers. Despite its size and fragility, MKs can be immunophenotyped using the above-mentioned panel and enriched by fluorescence-activated cell sorting under specific conditions of pressure and nozzle diameter. This approach facilitates multi-Omics studies, with the aim to better understand the complexity of megakaryopoiesis and platelet production in humans. A better characterization of megakaryopoiesis may pose fundamental in the diagnosis or prognosis of lineage-related pathologies and malignancy.

Immunophenotyping and Cell Sorting of Human MKs from Human Primary Sources or Differentiated In Vitro from Hematopoietic Progenitors

Here, we present an immunophenotyping strategy for the characterization of megakaryocyte differentiation, and show how that strategy allows the sorting of megakaryocytes at different stages with a fluorescence-activated cell sorter. The methodology can be applied to human primary tissues, but also to megakaryocytes generated in culture in vitro.

Leukodepletion Filters-Derived CD34+ Cells As a Cell Source to Study Megakaryocyte Differentiation and Platelet Formation

Summary

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Megakaryocyte Differentiation and Platelet Formation from Human Cord Blood-derived CD34⁺ Cells

Lentiviral-mediated Knockdown During Ex Vivo Erythropoiesis of Human Hematopoietic Stem Cells

Isolation of CD133+ Liver Stem Cells for Clonal Expansion

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Phenotypic Analysis and Isolation of Murine Hematopoietic Stem Cells and Lineage-committed Progenitors

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Immunophenotyping and Cell Sorting of Human MKs from Human Primary Sources or Differentiated In Vitro from Hematopoietic Progenitors