We thank the WIMM Flow Cytometry Core for flow cytometry access, and the WIMM Virus Screening Core for lentiviral vector generation. This work was funded by the Kay Kendall Leukaemia Fund and the UK Medical Research Council.

All animal procedures, including breeding and euthanasia, must be performed within institutional and national guidelines. The experiments detailed below were approved by the UK Home Office. See the Table of Materials for a list of all materials, reagents, and equipment used in this protocol.
1. Preparing stock solutions
<ol>
	<li>PVA stock solution
	<ol>
		<li>Take 50 mL of tissue culture quality water in a small glass bottle (suitable for autoclaving). Warm...

<ol>
	<li>Laurenti, E., G&#246;ttgens, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=From+haematopoietic+stem+cells+to+complex+differentiation+landscapes.">From haematopoietic stem cells to complex differentiation landscapes.</a> Nature. 553 (7689), 418-426 (2018).</li><li>Eaves, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hematopoietic+stem+cells:+concepts,+definitions,+and+the+new+reality.">Hematopoietic stem cells: concepts, definitions, and the new reality.</a> Blood. 125 (17), 2605-2613 (2015).</li><li>Wilkinson, A. C., Igarashi, K. J., Nakauchi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Haematopoietic+stem+cell+self-renewal+in+vivo+and+ex+vivo.">Haematopoietic stem cell self-renewal in vivo and ex vivo.</a> Nature Reviews Genetics. 21 (9), 541-554 (2020).</li><li>Crane, G. M., Jeffery, E., Morrison, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adult+haematopoietic+stem+cell+niches.">Adult haematopoietic stem cell niches.</a> Nature Reviews Immunology. 17 (9), 573-590 (2017).</li><li>Osawa, M., Hanada, K., Hamada, H., Nakauchi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+lymphohematopoietic+reconstitution+by+a+single+CD34-low/negative+hematopoietic+stem+cell.">Long-term lymphohematopoietic reconstitution by a single CD34-low/negative hematopoietic stem cell.</a> Science. 273 (5272), 242-245 (1996).</li><li>Granot, N., Storb, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=History+of+hematopoietic+cell+transplantation:+challenges+and+progress.">History of hematopoietic cell transplantation: challenges and progress.</a> Haematologica. 105 (12), 2716-2729 (2020).</li><li>Wilkinson, A. C., Nakauchi, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stabilizing+hematopoietic+stem+cells+in+vitro.">Stabilizing hematopoietic stem cells in vitro.</a> Current Opinion in Genetics &amp; Development. 64, 1-5 (2020).</li><li>Wilkinson, A. 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=Long-term+ex+vivo+haematopoietic-stem-cell+expansion+allows+nonconditioned+transplantation.">Long-term ex vivo haematopoietic-stem-cell expansion allows nonconditioned transplantation.</a> Nature. 571 (7763), 117-121 (2019).</li><li>Nishimura, 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=Use+of+polyvinyl+alcohol+for+chimeric+antigen+receptor+T-cell+expansion.">Use of polyvinyl alcohol for chimeric antigen receptor T-cell expansion.</a> Experimental Hematology. 80, 16-20 (2019).</li><li>Becker, H. J., 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+single+cell+cloning+platform+for+gene+edited+functional+murine+hematopoietic+stem+cells.">A single cell cloning platform for gene edited functional murine hematopoietic stem cells.</a> bioRxiv. , (2022).</li><li>Kobayashi, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Environmental+optimization+enables+maintenance+of+quiescent+hematopoietic+stem+cells+ex+vivo.">Environmental optimization enables maintenance of quiescent hematopoietic stem cells ex vivo.</a> Cell Reports. 28 (1), 145-158 (2019).</li><li>Kobayashi, H., Takubo, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+culture+method+to+maintain+quiescent+human+hematopoietic+stem+cells.">A culture method to maintain quiescent human hematopoietic stem cells.</a> Journal of Visualized Experiments. (171), e61938 (2021).</li><li>Aal Wilson, ., 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=Hematopoietic+stem+cells+reversibly+switch+from+dormancy+to+self-renewal+during+homeostasis+and+repair.">Hematopoietic stem cells reversibly switch from dormancy to self-renewal during homeostasis and repair.</a> Cell. 135 (6), 1118-1129 (2008).</li><li>Ochi, K., Morita, M., Wilkinson, A. C., Iwama, A., Yamazaki, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-conditioned+bone+marrow+chimeric+mouse+generation+using+culture-based+enrichment+of+hematopoietic+stem+and+progenitor+cells.">Non-conditioned bone marrow chimeric mouse generation using culture-based enrichment of hematopoietic stem and progenitor cells.</a> Nature Communications. 12 (1), 3568 (2021).</li><li>Wilkinson, A. 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=Cas9-AAV6+gene+correction+of+beta-globin+in+autologous+HSCs+improves+sickle+cell+disease+erythropoiesis+in+mice.">Cas9-AAV6 gene correction of beta-globin in autologous HSCs improves sickle cell disease erythropoiesis in mice.</a> Nature Communications. 12 (1), 686 (2021).</li><li>Haney, M. 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=Large-scale+in+vivo+CRISPR+screens+identify+SAGA+complex+members+as+a+key+regulators+of+HSC+lineage+commitment+and+aging.">Large-scale in vivo CRISPR screens identify SAGA complex members as a key regulators of HSC lineage commitment and aging.</a> bioRxiv. , (2022).</li><li>Che, J. L. 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=Identification+and+characterization+of+in+vitro+expanded+hematopoietic+stem+cells.">Identification and characterization of in vitro expanded hematopoietic stem cells.</a> EMBO Reports. 23 (10), e55502 (2022).</li><li>Zhang, Q., Konturek-Ciesla, A., Yuan, O., Bryder, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+expansion+potential+of+murine+hematopoietic+stem+cells:+a+rare+property+only+partially+predicted+by+phenotype.">Ex vivo expansion potential of murine hematopoietic stem cells: a rare property only partially predicted by phenotype.</a> bioRxiv. , (2022).</li><li>Schindele, P., Wolter, F., Puchta, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CRISPR+guide+RNA+design+guidelines+for+efficient+genome+editing.">CRISPR guide RNA design guidelines for efficient genome editing.</a> Methods in Molecular Biology. 2166, 331-342 (2020).</li><li>Hanna, R. E., Doench, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+and+analysis+of+CRISPR-Cas+experiments.">Design and analysis of CRISPR-Cas experiments.</a> Nat Biotechnol. 38 (7), 813-823 (2020).</li><li>Wilkinson, A. C., Ishida, R., Nakauchi, H., Yamazaki, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+ex+vivo+expansion+of+mouse+hematopoietic+stem+cells.">Long-term ex vivo expansion of mouse hematopoietic stem cells.</a> Nature Protocols. 15 (2), 628-648 (2020).</li><li>Ieyasu, 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=An+all-recombinant+protein-based+culture+system+specifically+identifies+hematopoietic+stem+cell+maintenance+factors.">An all-recombinant protein-based culture system specifically identifies hematopoietic stem cell maintenance factors.</a> Stem Cell Reports. 8 (3), 500-508 (2017).</li></ol>

We hope that this protocol provides a useful approach to investigate HSC biology, hematopoiesis, and hematology more generally. Since the initial development of the PVA-based culture method for FACS-purified HSCs8, the method has been extended. For example, the method has been shown to work with c-Kit enriched with bone marrow and with negative surface charged plates14. Its compatibility with transduction and electroporation has also been demonstrated14</s...

The hematopoietic system supports a range of essential processes in mammals, from oxygen supply to fighting pathogens, through specialized blood and immune cell types. Continuous blood production (hematopoiesis) is required to support blood system homeostasis, which is sustained by hematopoietic stem and progenitor cells (HSPCs)1. The most primitive hematopoietic cell is the hematopoietic stem cell (HSC), which has unique capacities for self-renewal and multilineage differentiation2,3. This is a rare cell population, mainly found in the adult bone marrow4, where they occur at a frequency of just approximately one every 30,000 cells. HSCs are thought to support life-long hematopoiesis and help to re-establish hematopoiesis following hematological stress. These capacities also allow HSCs to stably reconstitute the entire hematopoietic system following transplantation into an irradiated recipient5. This represents the functional definition of an HSC and also forms the scientific basis for HSC transplantation therapy, a curative treatment for a range of blood and immune diseases6. For these reasons, HSCs are a major focus of experimental hematology.
Despite a large focus of research, it has remained challenging to stably expand HSCs ex vivo7. We recently developed the first long-term ex vivo expansion culture system for mouse HSCs8. The approach can expand transplantable HSCs by 234-899-fold over a 4 week culture. In comparison to alternative approaches, the major change in the protocol was the removal of serum albumin and its replacement with a synthetic polymer. Polyvinyl alcohol (PVA) was identified as an optimal polymer for the mouse HSC cultures8, which has now also been used to culture other hematopoietic cell types9. However, another polymer called Soluplus (a polyvinyl caprolactam-acetate-polyethylene glycol graft copolymer) has also recently been identified, which appears to improve clonal HSC expansion10. Prior to the use of polymers, serum albumin in the form of fetal bovine serum, bovine serum albumin fraction V, or recombinant serum albumin were used, but these had limited support for HSC expansion and only supported short-term (~1 week) ex vivo culture7. However, it should be noted that HSC culture protocols that retain HSCs in a quiescent state can support a longer ex vivo culture time11,12.
In comparison with other culture methods, a major advantage of PVA-based cultures is the number of cells that can be generated and the length of time the protocol can be used to track HSCs ex vivo. This overcomes several barriers in the field of experimental hematology, such as the low numbers of HSCs isolatable per mouse (only a few thousand) and the difficulty to track HSCs over time in vivo. However, it is important to remember that these cultures stimulate HSC proliferation, while the in vivo HSC pool is predominantly quiescent at a steady state13. Additionally, although the cultures are selective for HSCs, additional cell types do accumulate with the cultures over time, and transplantable HSCs only represent approximately one in 34 cells after 1 month. Myeloid hematopoietic progenitor cells appear to be the major contaminating cell type in these HSC cultures8. Nevertheless, we can use these cultures to enrich for HSCs from heterogeneous cell populations (e.g., c-Kit+ bone marrow HSPCs14). It also supports transduction or electroporation of HSCs for genetic manipulation14,15,16. To help identify HSCs from the heterogeneous cultured HSPC population, CD201 (EPCR) has recently been identified as a useful ex vivo HSC marker10,17,18, with transplantable&#160;HSCs restricted to the CD201+CD150+c-Kit+Sca1+Lineage- fraction.
This protocol describes methods to initiate, maintain, and assess PVA-based mouse HSC expansion cultures, as well as protocols for genetic manipulation within these cultures using electroporation or lentiviral vector transduction. These methods are expected to be useful for a range of experimental hematologists.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dissection kit</td>
			<td>Fisher Scientific</td>
			<td>12764416</td>
			<td></td>
		</tr>
		<tr>
			<td>Hemocytometer</td>
			<td>Appleton Woods Ltd</td>
			<td>HC002</td>
			<td></td>
		</tr>
		<tr>
			<td>P3 Primary Cell 4D-Nucleofector X Kit</td>
			<td>Lonza&#160;</td>
			<td>V4XP-3024</td>
			<td></td>
		</tr>
		<tr>
			<td>Pestle and mortar</td>
			<td>Scientific Laboratory Supplies Limited</td>
			<td>X18000</td>
			<td></td>
		</tr>
		<tr>
			<td>QuadroMACS separator</td>
			<td>Miltenyi Biotec</td>
			<td>130-090-976</td>
			<td></td>
		</tr>
		<tr>
			<td>Materials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL syringe</td>
			<td>VWR International Ltd</td>
			<td>720-2519</td>
			<td></td>
		</tr>
		<tr>
			<td>19 G needle</td>
			<td>VWR International Ltd</td>
			<td>613-5394</td>
			<td></td>
		</tr>
		<tr>
			<td>50 &#956;m cell strainer</td>
			<td>Sysmex</td>
			<td>04-004-2317</td>
			<td></td>
		</tr>
		<tr>
			<td>70 &#956;m cell strainer</td>
			<td>Corning</td>
			<td>431751</td>
			<td></td>
		</tr>
		<tr>
			<td>Kimtech wipes</td>
			<td>VWR International Ltd</td>
			<td>115-2075</td>
			<td></td>
		</tr>
		<tr>
			<td>LS MACS column</td>
			<td>Miltenyi Biotec</td>
			<td>130-042-401</td>
			<td></td>
		</tr>
		<tr>
			<td>Reagents</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Alt-R S.p. Cas9 Nuclease V3, 100 &#956;g</td>
			<td>IDT&#160;</td>
			<td>1081058</td>
			<td></td>
		</tr>
		<tr>
			<td>Animal free recombinant mouse stem cell factor&#160;</td>
			<td>Peprotech</td>
			<td>AF-250-03</td>
			<td></td>
		</tr>
		<tr>
			<td>Animal free recombinant mouse thrombopoietin</td>
			<td>Peprotech</td>
			<td>AF-315-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD117 APC (clone: 2B8)</td>
			<td>ThermoFisher</td>
			<td>17-1171-83</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD117 BV421 (clone: 2B8)</td>
			<td>Biolegend</td>
			<td>105828</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD127&#160;APC/Cy7 (clone: A7R34)</td>
			<td>Biolegend</td>
			<td>135040</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD127 biotin (clone: A7R34)</td>
			<td>Biolegend</td>
			<td>135006</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD150 PE/Cy7 (clone: TC15-12F12.2)</td>
			<td>Biolegend</td>
			<td>115914</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD201&#160;APC (clone: eBio1560)</td>
			<td>ThermoFisher</td>
			<td>17-2012-82</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD34 FITC (clone: RAM34)</td>
			<td>ThermoFisher</td>
			<td>11-0341-85</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD4&#160;APC/Cy7 (clone: RM4-5)</td>
			<td>Biolegend</td>
			<td>100526</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD4 biotin (clone: RM4-5)</td>
			<td>Biolegend</td>
			<td>100508</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD45R&#160;APC/Cy7 (clone: RA3-6B2)</td>
			<td>Biolegend</td>
			<td>103224</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD45R biotin (clone: RA3-6B2)</td>
			<td>Biolegend</td>
			<td>103204</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD48 BV421 (clone: HM48-1)</td>
			<td>Biolegend</td>
			<td>103428</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD8 biotin (clone: 53-6.7)</td>
			<td>Biolegend</td>
			<td>100704</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse CD8a&#160;APC/Cy7 (clone: 53-6.7)</td>
			<td>Biolegend</td>
			<td>100714</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse Ly6G/Ly6C&#160;APC/Cy7 (clone: RB6-8C5)</td>
			<td>Biolegend</td>
			<td>108424</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse Ly6G/Ly6C biotin (clone: RB6-8C5)</td>
			<td>Biolegend</td>
			<td>108404</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse Sca1 PE (clone: D7)</td>
			<td>Biolegend</td>
			<td>108108</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse Ter119&#160;APC/Cy7 (clone: TER-119)</td>
			<td>Biolegend</td>
			<td>116223</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-mouse Ter119 biotin (clone: TER-119)</td>
			<td>Biolegend</td>
			<td>116204</td>
			<td></td>
		</tr>
		<tr>
			<td>CellBIND plates, 24-well</td>
			<td>Corning</td>
			<td>3337</td>
			<td>negative surface charged</td>
		</tr>
		<tr>
			<td>CellBIND plates, 96-well&#160;</td>
			<td>Corning</td>
			<td>3330</td>
			<td>negative surface charged</td>
		</tr>
		<tr>
			<td>Custom synthetic sgRNA&#160;</td>
			<td>Synthego, Sigma Aldrich, IDT</td>
			<td>Custom order</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>Merck Life Science UK Limited</td>
			<td>F7524-50ML</td>
			<td></td>
		</tr>
		<tr>
			<td>Fibronectin Coated plates, 96-well</td>
			<td>BD Biosciences</td>
			<td>354409</td>
			<td></td>
		</tr>
		<tr>
			<td>Ham&#39;s F-12 Nutrient Mix</td>
			<td>Gibco</td>
			<td>11765054</td>
			<td></td>
		</tr>
		<tr>
			<td>Insulin-Transferrin-Selenium-X (100x)</td>
			<td>Gibco</td>
			<td>51500.056</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffered saline</td>
			<td>Alfa Aesar</td>
			<td>J61196.AP</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyvinyl alcohol</td>
			<td>Sigma Aldrich</td>
			<td>P8136</td>
			<td></td>
		</tr>
		<tr>
			<td>Propidium Iodide</td>
			<td>Enzo Life Sciences (UK) Ltd</td>
			<td>EXB-0018</td>
			<td></td>
		</tr>
		<tr>
			<td>Streptavidin APC/Cy7</td>
			<td>Biolegend</td>
			<td>405208</td>
			<td></td>
		</tr>
		<tr>
			<td>T&#252;rks&#8217; solution</td>
			<td>Sigma Aldrich</td>
			<td>109277</td>
			<td></td>
		</tr>
		<tr>
			<td>Virkon</td>
			<td>Mettler-Toledo Ltd</td>
			<td>95015662</td>
			<td></td>
		</tr>
	</tbody>
</table>

ex vivo expansion and genetic manipulation of mouse hematopoietic stem cells in polyvinyl alcohol-based cultures

Self-renewing&#160;multipotent&#160;hematopoietic stem cells (HSCs) are an important cell type due to their abilities to support hematopoiesis throughout life and reconstitute the entire blood system following transplantation. HSCs are used clinically in stem cell transplantation therapies, which represent curative treatment for a range of blood diseases. There is substantial interest in both understanding the mechanisms that regulate HSC activity and hematopoiesis, and developing new HSC-based therapies. However, the stable culture and expansion of HSCs ex vivo has been a major barrier in studying these stem cells in a tractable ex vivo system. We recently developed a polyvinyl alcohol-based culture system that can support the long-term and large-scale expansion of transplantable mouse HSCs and methods to genetically edit them. This protocol describes methods to culture and genetically manipulate mouse HSCs via electroporation and lentiviral transduction. This protocol is expected to be useful to a wide range of experimental hematologists interested in HSC biology and hematopoiesis.

For the FACS purification of HSCs, we expect that within the c-Kit-enriched bone marrow, ~0.2% of the cells are the CD150+CD34-c-Kit+Sca1+Lineage- population for young (8-12-week-old) C57BL/6 mice (Figure 1). However, it is likely that transgenic mice or mice of different ages display differing HSC frequencies. After 4 weeks of culture, we expect the CD201+CD150+c-Kit+Sca1+Lineage- f...

Watch this Scientific Journal Video about Ex Vivo Expansion and Genetic Manipulation of Mouse Hematopoietic Stem Cells in Polyvinyl Alcohol-Based Cultures at JoVE.com

Ex Vivo Expansion and Genetic Manipulation of Mouse Hematopoietic Stem Cells in Polyvinyl Alcohol-Based Cultures

Presented here is a protocol to initiate, maintain, and analyze mouse hematopoietic stem cell cultures using ex vivo polyvinyl alcohol-based expansion, as well as methods to genetically manipulate them by lentiviral transduction and electroporation.

Ex Vivo Expansion and Genetic Manipulation of Mouse Hematopoietic Stem Cells in Polyvinyl Alcohol-Based Cultures

Self-renewing&#160;multipotent&#160;hematopoietic stem cells (HSCs) are an important cell type due to their abilities to support hematopoiesis throughout ...

This protocol permits the expansion and genetic manipulation of functional mouse hematopoietic stem cells, allowing a deeper understanding of hematopoietic stem cell biology and hematopoiesis. The advantage of this technique is that it can support hematopoietic stem cells in long-term ex vivo culture and permit genetic manipulation to interrogate the genetics of hematopoiesis. This culture system provides a platform technology for various studies into hematopoietic stem cell biology and hematopoiesis, including genetic, molecular, and biochemical studies.The troubleshooting table lists the causes and solutions for the common struggles encountered with this technique. It's much easier and more effective to show how to correctly extract bone marrow cells and perform complete media changes rather than read about it. To begin hematopoietic stem cell, or HSC, extraction, use lint-free delicate task wipes to clean the bones freshly isolated from properly euthanized mice.Remove muscles and spinal cord from the bones before adding them to a mortar containing approximately three milliliters of PBS. Using a pestle, crush the bones without grinding them to minimize shearing forces. Then, using a 19-gauge needle attached to a 5-milliliter syringe, break up the large bone marrow fragments released into the PBS and transfer the suspension through a 70-micron filter into a 50-milliliter conical tube.Once the suspension has been transferred, repeat the process with fresh PBS until the bones are bleached. Aim for an end volume of approximately 30 milliliters per mouse and 50 milliliters for two mice to bleach the bones until no more marrow is visible. Prepare for column enrichment by placing a magnetic filtration column into the magnet of a magnetic column separator with a 50-micron filter on top and a 15 milliliter conical tube below.Next, after treating the cells with allophycocyanin anti-c-Kit antibody and allophycocyanin magnetic microbeads, run three milliliters of sterile PBS through the 50-micron filter and the filtration column. Once the PBS has run through, pass the cell suspension through the column, followed by three washes of three milliliters of cold PBS each time. After each wash, wait for the column to stop dripping before adding PBS for the next wash.Next, remove the column from the magnet and place it on top of a fresh 15-milliliter tube and add five milliliters of cold PBS into the column before fitting the column plunger onto it and eluting the cells by pushing the plunger. Follow the protocol described in the text to prepare enough HSC medium for the desired number of cells or wells to seed 0.5 to 1 million cells per milliliter. Then spin down the c-Kit-enriched hematopoietic stem and progenitor cells, or HSPCs, and resuspend the pellet in the freshly prepared HSC medium at the desired cell density.Transfer the cells to fibronectin-coated or negative surface charged plates, maintaining appropriate volume. Place the cells in a tissue culture incubator at 37 degrees Celsius and 5%carbon dioxide. After gently removing the plate from the tissue culture incubator without disturbing the cell cultures, use a pipette or vacuum pump to slowly aspirate approximately 90 to 95%of the medium from the liquid meniscus of each well.Avoid drawing up medium from the base of the well. Then add one milliliter of fresh medium prewarmed to 37 degrees Celsius into the well. Return the plate to the tissue culture incubator, and change media every two to three days until the experiment requires.After resuspending the cells in nucleofection buffer, immediately transfer the cell suspension into the PCR tube containing the complexed ribonucleoprotein, and gently mix by pipetting up and down slowly. Now transfer the mixture into an electroporation cuvette of appropriate volume very slowly, maintaining a continuous fluid motion to avoid forming air bubbles inside the cuvette. Then, on the electroporator, select the position of the wells being electroporated.Using the touchscreen, select the cell type program as CD34-positive human or type in the pulse code EO100, and then press the OK button. Transfer the cuvette to the electroporator and press the Start button on the touchscreen to initiate electroporation. Immediately after electroporation, add five times the reaction volume of the culture medium to the cuvette.Now gently transfer the cells to the prepared plate, and place the plate back in the tissue culture incubator. After performing a medium change as demonstrated previously, collect 10 microliters of the cells and count them using Turk's solution at a dilution of 1:2 with a hemocytometer. Replate the required dose of cells in fibronectin-coated plates for transduction, and separately, plate the un-transduced negative control cells.Then add the lentiviral vector to each well containing cells, maintaining a dose of 20 transduction units per cell to achieve around 30%transduction efficiency. However, determine the lentiviral vector dose empirically depending on the experimental requirements. Finally, return the cells to the tissue culture incubator for six hours.Perform a medium change as described previously. The fluorescence-activated cell sorting of the c-Kit-enriched HSCs yielded approximately 0.2%of the cells that were CD150-positive, CD34-negative, c-Kit-positive, Sca1-positive, and lineage-negative. After four weeks of HSPC culture, the CD201-positive, CD150-positive, c-Kit-positive, Sca1-positive, and lineage-negative fractions was found to be about 10%Following transduction with a GFP-expressing lentiviral vector, the GFP-positive cells were approximately 30%When confluent, the expected density of the cultures was around 2 million cells per milliliter.Approximately 50%cell death was observed within the first 24 to 48 hours before the first medium change was performed. After one week, however, cell numbers returned to 80 to 100%of the seeded cell number. Accurate media changes using fresh and prewarmed media are critical for the long-term stability of this HSC culture method.Since the original method was published in 2019, the field has begun to use it in different ways to study HSC biology.

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