The authors acknowledge the group of Dr John Dick for previous work on this method, and Monica Doedens for training. We are grateful to the Cambridge Blood and Stem Cell Biobank (CBSB), specifically Dr. Joanna Baxter and the team of CBSB nurses who consented and collected cord blood samples; our sample donors; the University Biomedical Service, specifically Nicolas Lumley and staff at The Anne McLaren Building for maintenance of our mice strains and support of our in vivo experiments; Shaaezmeen Basheer for editing of the manuscript.
E.L. is funded by a Sir Henry Dale Fellowship jointly funded by the Wellcome Trust and the Royal Society (107630/Z/15/A). L.M. is supported by Sofinter - HR Welfare Program. This research was funded in whole, or in part, by the Wellcome Trust (203151/Z/16/Z, 203151/A/16/Z, 215116/Z/18/Z) and the UKRI Medical Research Council (MC_PC_17230). For the purpose of open access, the author has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission.

All animal research presented here adheres to the Animals (Scientific Procedures) Act 1986 Amendment Regulations 2012 and was performed after ethical review and approval by the University of Cambridge Animal Welfare and Ethical Review Body (AWERB). Female NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice, aged between 12 and 16 weeks (~21-30 g), bred in-house and maintained in a Specific-Pathogen-Free animal facility, were used for intrafemoral injections. De-identified CB samples were collected from healt...

Injecting Human HSPCs into the Femur of Sub-Lethally Irradiated Mice

<ol>
	<li>Dancey, J. T., Deubelbeiss, K. A., Harker, L. A., Finch, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neutrophil+kinetics+in+man.">Neutrophil kinetics in man.</a> J Clin Invest. 58 (3), 705-715 (1976).</li><li>Purton, L. E., Scadden, D. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Limiting+factors+in+murine+hematopoietic+stem+cell+assays.">Limiting factors in murine hematopoietic stem cell assays.</a> Cell Stem Cell. 1 (3), 263-270 (2007).</li><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>Cosgrove, J., Hustin, L. S. P., de Boer, R. J., Peri&#233;, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hematopoiesis+in+numbers.">Hematopoiesis in numbers.</a> Trends Immunol. 42 (12), 1100-1112 (2021).</li><li>Mazurier, F., Doedens, M., Gan, O. I., Dick, 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=Rapid+myeloerythroid+repopulation+after+intrafemoral+transplantation+of+NOD-SCID+mice+reveals+a+new+class+of+human+stem+cells.">Rapid myeloerythroid repopulation after intrafemoral transplantation of NOD-SCID mice reveals a new class of human stem cells.</a> Nat Med. 9 (7), 959-963 (2003).</li><li>McKenzie, J. L., Gan, O. I., Doedens, M., Dick, 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=Human+short-term+repopulating+stem+cells+are+efficiently+detected+following+intrafemoral+transplantation+into+NOD/SCID+recipients+depleted+of+CD122++cells.">Human short-term repopulating stem cells are efficiently detected following intrafemoral transplantation into NOD/SCID recipients depleted of CD122+ cells.</a> Blood. 106 (4), 1259-1261 (2005).</li><li>Notta, F., 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+of+single+human+hematopoietic+stem+cells+capable+of+long-term+multilineage+engraftment.">Isolation of single human hematopoietic stem cells capable of long-term multilineage engraftment.</a> Science. 333 (6039), 218-221 (2011).</li><li>Belluschi, 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=Myelo-lymphoid+lineage+restriction+occurs+in+the+human+haematopoietic+stem+cell+compartment+before+lymphoid-primed+multipotent+progenitors.">Myelo-lymphoid lineage restriction occurs in the human haematopoietic stem cell compartment before lymphoid-primed multipotent progenitors.</a> Nat Commun. 9 (1), 4100 (2018).</li><li>McDermott, S. P., Eppert, K., Lechman, E. R., Doedens, M., Dick, 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=Comparison+of+human+cord+blood+engraftment+between+immunocompromised+mouse+strains.">Comparison of human cord blood engraftment between immunocompromised mouse strains.</a> Blood. 116 (2), 193-200 (2010).</li><li>Billerbeck, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+human+CD4+FoxP3++regulatory+T+cells+in+human+stem+cell+factor-,+granulocyte-macrophage+colony-stimulating+factor-,+and+interleukin-3-expressing+NOD-SCID+IL2R&#947;(null)+humanized+mice.">Development of human CD4+FoxP3+ regulatory T cells in human stem cell factor-, granulocyte-macrophage colony-stimulating factor-, and interleukin-3-expressing NOD-SCID IL2R&#947;(null) humanized mice.</a> Blood. 117 (11), 3076-3086 (2011).</li><li>Rongvaux, 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=Development+and+function+of+human+innate+immune+cells+in+a+humanized+mouse+model.">Development and function of human innate immune cells in a humanized mouse model.</a> Nat Biotechnol. 32 (4), 364-372 (2014).</li><li>McIntosh, B. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nonirradiated+NOD,B6.SCID+Il2r&#947;&#8722;/&#8722;+KitW41/W41+(NBSGW)+Mice+support+multilineage+engraftment+of+human+hematopoietic+cells.">Nonirradiated NOD,B6.SCID Il2r&#947;&#8722;/&#8722; KitW41/W41 (NBSGW) Mice support multilineage engraftment of human hematopoietic cells.</a> Stem Cell Reports. 4 (2), 171-180 (2015).</li><li>Notta, F., Doulatov, S., Dick, 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=Engraftment+of+human+hematopoietic+stem+cells+is+more+efficient+in+female+NOD/SCID/IL-2Rgc-null+recipients.">Engraftment of human hematopoietic stem cells is more efficient in female NOD/SCID/IL-2Rgc-null recipients.</a> Blood. 115 (18), 3704-3707 (2010).</li><li>Futrega, K., Lott, W. B., Doran, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+bone+marrow+HSC+transplantation+enhances+local+engraftment+at+the+expense+of+systemic+engraftment+in+NSG+mice.">Direct bone marrow HSC transplantation enhances local engraftment at the expense of systemic engraftment in NSG mice.</a> Sci Rep. 6, 23886 (2016).</li><li>Mende, 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=Unique+molecular+and+functional+features+of+extramedullary+hematopoietic+stem+and+progenitor+cell+reservoirs+in+humans.">Unique molecular and functional features of extramedullary hematopoietic stem and progenitor cell reservoirs in humans.</a> Blood. 139 (23), 3387-3401 (2022).</li><li>Medyouf, 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=Myelodysplastic+cells+in+patients+reprogram+mesenchymal+stromal+cells+to+establish+a+transplantable+stem+cell+niche+disease+unit.">Myelodysplastic cells in patients reprogram mesenchymal stromal cells to establish a transplantable stem cell niche disease unit.</a> Cell Stem Cell. 14 (6), 824-837 (2014).</li><li>Eppert, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stem+cell+gene+expression+programs+influence+clinical+outcome+in+human+leukemia.">Stem cell gene expression programs influence clinical outcome in human leukemia.</a> Nat Med. 17 (9), 1086-1093 (2011).</li><li>Sanchez, P. 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=A+robust+xenotransplantation+model+for+acute+myeloid+leukemia.">A robust xenotransplantation model for acute myeloid leukemia.</a> Leukemia. 23 (11), 2109-2117 (2009).</li><li>Li, J., Chen, H., Zhao, S., Wen, D., Bi, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patient-derived+intrafemoral+orthotopic+xenografts+of+peripheral+blood+or+bone+marrow+from+acute+myeloid+and+acute+lymphoblastic+leukemia+patients:+clinical+characterization,+methodology,+and+validation.">Patient-derived intrafemoral orthotopic xenografts of peripheral blood or bone marrow from acute myeloid and acute lymphoblastic leukemia patients: clinical characterization, methodology, and validation.</a> Clin Exp Med. 23 (4), 1293-1306 (2023).</li><li>Dobson, S. M., 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=Relapse-fated+latent+diagnosis+subclones+in+acute+B+lineage+leukemia+are+drug+tolerant+and+possess+distinct+metabolic+programs.">Relapse-fated latent diagnosis subclones in acute B lineage leukemia are drug tolerant and possess distinct metabolic programs.</a> Cancer Discov. 10 (4), 568-587 (2020).</li><li>Marktel, 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=Intrabone+hematopoietic+stem+cell+gene+therapy+for+adult+and+pediatric+patients+affected+by+transfusion-dependent+&#223;-thalassemia.">Intrabone hematopoietic stem cell gene therapy for adult and pediatric patients affected by transfusion-dependent &#223;-thalassemia.</a> Nat Med. 25 (2), 234-241 (2019).</li></ol>

Intrafemoral injections are a useful tool in xenotransplantation when only a small number of HSPCs are available, providing improved engraftment compared to intravenous injections. However, the technique requires dexterity and training. When practicing, we would recommend using fresh cadavers of the correct weight range (see below) and injecting a colored dye (such as trypan blue) so that upon dissection, it is clear if the injection went into the femur and was restricted to it (no dye should be observed in the muscles)....

Blood has one of the highest regeneration rates in the human body, producing 1 &#215; 1012 cells per day in the adult human bone marrow1. Hematopoietic stem cells (HSCs) guarantee blood production over the lifespan by the process of hematopoiesis and are defined by their capacity to produce all blood cell types (multipotentiality) while maintaining themselves (self-renewal). Historically, the gold standard for testing the function of an HSC has always relied on transplantation, testing the ability of a donor population to reconstitute all blood lineages of a mouse long-term (commonly defined as a minimum of 20 weeks)2. A large body of functional work spanning several decades has demonstrated that the HSC compartment is heterogeneous in both lineage output and long-term reconstitution. The toolkit to study hematopoiesis has expanded considerably over the years, with many new techniques, including in vitro single-cell functional assays, single-cell -omics approaches, and lineage tracing3. The latter have conclusively demonstrated that the contributions of HSC and multipotent progenitors largely differ in native hematopoiesis and under the stress imposed by transplantation. All these techniques complement transplantation assays, which remain important to assess the long-term repopulation capacity of HSCs. In the context of the study of human hematopoiesis, xenotransplantation provides the only method to experimentally assess self-renewal in a whole-organism setting.
Xenotransplantation of HSCs is commonly performed using intravenous injection of cells into immunocompromised mice. However, HSCs are rare4 and access to human samples containing HSCs is limited. In 2003, the group of John Dick adapted a protocol for bone marrow aspiration and intrafemorally injected non-obese diabetic/severe combined immunodeficiency (NOD-SCID) mice with Lin&#8722;CD34+ umbilical cord blood (CB) cells5. To our knowledge, there has been no reported formal comparison of intravenous versus intrafemoral injections in long-term and serial transplantation outcomes. However, compared directly with intravenous injections, intrafemoral injections provide larger graft sizes with the same number of transplanted cells6, at least in the short term. In addition, engraftment can be detected with many fewer hematopoietic stem and progenitor cells (HSPCs) transplanted. This is thought to be because intrafemoral delivery bypasses the need for HSCs to home to the bone marrow, which in the xenograft context is limiting due to a lack of cross-species reactivity for a number of receptors and cytokines. Via the use of intrafemoral injections, Notta and colleagues were the first to transplant single human HSCs7, though extra considerations need to be taken, as described in their methods. Intrafemoral delivery of HSPCs also has limitations. The injection itself disrupts and destroys part of the bone marrow, and therefore is not indicated for studies of the crosstalk between HSCs and their bone marrow microenvironment. Additionally, the maximum number of cells is limited by the volume of that bone cavity and that may be too few for some applications. As with every technique, its application in a specific experiment needs to be weighed up based on the benefits/disadvantages and the question being asked. In the context of xenotransplantation, if the aim of the experiment is to test the engraftment of a low number of human HSPCs with no assessment of microenvironment, intrafemoral delivery is usually preferred over intravenous injection.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.5 mL Insulin Syringe with 29 G x 12.7 mm Needle</td>
			<td>BD</td>
			<td>324892</td>
			<td></td>
		</tr>
		<tr>
			<td>1 mL Insulin Syringe with 29 G x 0.5&#34; Needle</td>
			<td>BD</td>
			<td>324827</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 mL tube</td>
			<td>Fisherbrand</td>
			<td>509-GRD-PFB</td>
			<td></td>
		</tr>
		<tr>
			<td>3 mL syringe&#160;</td>
			<td>HENKE SASS WOLF GMBH</td>
			<td>4020.000V0</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL Round Bottom Polystyrene Test Tube with Cell Strainer Cap 12 x 75 mm</td>
			<td>Falcon</td>
			<td>352235</td>
			<td>FACS tube</td>
		</tr>
		<tr>
			<td>5 mL Round Bottom Polystyrene Test Tube with Snap Cap 12 x 75 mm</td>
			<td>Falcon</td>
			<td>352058</td>
			<td>FACS tube</td>
		</tr>
		<tr>
			<td>27 G 1/2&#34; needle&#160;</td>
			<td>BD&#160;</td>
			<td>300635</td>
			<td></td>
		</tr>
		<tr>
			<td>40 &#181;m cell strainer for 50 mL tube</td>
			<td>Greiner Bio-one</td>
			<td>542040</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL tube</td>
			<td>Sarstedt Ltd</td>
			<td>62.547.254</td>
			<td></td>
		</tr>
		<tr>
			<td>96 well round-bottom plate&#160;</td>
			<td>Falcon</td>
			<td>351177</td>
			<td></td>
		</tr>
		<tr>
			<td>Alcohol Swab</td>
			<td>VITREX MEDICAL A/S</td>
			<td>520213</td>
			<td></td>
		</tr>
		<tr>
			<td>BD LSR Fortessa X-20 Cell Analyzer&#160;</td>
			<td>BD</td>
			<td></td>
			<td>flow cytometer</td>
		</tr>
		<tr>
			<td>Buphrenorphine</td>
			<td>Animalcare</td>
			<td>XVD190</td>
			<td></td>
		</tr>
		<tr>
			<td>CD14/PECy7 (Clone M5E2)</td>
			<td>biolegend</td>
			<td>301814</td>
			<td>Used at 1 in 1000</td>
		</tr>
		<tr>
			<td>CD19/Alexa 700 (Clone HIB19)</td>
			<td>biolegend</td>
			<td>302226</td>
			<td>Used at 1 in 300</td>
		</tr>
		<tr>
			<td>CD19/FITC (Clone HIB19)</td>
			<td>biolegend</td>
			<td>302206</td>
			<td>Used at 1 in 200</td>
		</tr>
		<tr>
			<td>CD3/APCCy7&#160;(Clone HIT3a)</td>
			<td>biolegend</td>
			<td>300318</td>
			<td>Used at 1 in 100</td>
		</tr>
		<tr>
			<td>CD33/APC (Clone P67.6)</td>
			<td>BD</td>
			<td>345800</td>
			<td>Used at 1 in 200</td>
		</tr>
		<tr>
			<td>CD45/BV510 (Clone HI30)</td>
			<td>biolegend</td>
			<td>304036</td>
			<td>Used at 1 in 500</td>
		</tr>
		<tr>
			<td>CD45/PECy5 (Clone 2D1)</td>
			<td>biolegend</td>
			<td>368526</td>
			<td>Used at 1 in 300</td>
		</tr>
		<tr>
			<td>CompBeads Anti-Mouse Ig, &#954;/Negative Control Compensation Particles Set</td>
			<td>BD</td>
			<td>552843</td>
			<td></td>
		</tr>
		<tr>
			<td>Dnase 1</td>
			<td>Worthington Biochemical</td>
			<td>LS002139</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>PAN-Biotech</td>
			<td>P40-37500</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycophorin A (GlyA)/PE (Clone GA-R2)</td>
			<td>BD</td>
			<td>340947</td>
			<td>Used at 1 in 1000</td>
		</tr>
		<tr>
			<td>Iscove Modified Dulbecco Media (IMDM)</td>
			<td>PAN-Biotech</td>
			<td>P04-20250</td>
			<td></td>
		</tr>
		<tr>
			<td>Isoflurane (IsoFlo 100% w/w Inhalation Vapor, liquid)</td>
			<td>Zoetis</td>
			<td>115095</td>
			<td></td>
		</tr>
		<tr>
			<td>Microvette&#160;300 Lithium heparin LH, 300 &#181;L</td>
			<td>Sarstedt Ltd</td>
			<td>20.1309</td>
			<td>Mouse blood collection tube</td>
		</tr>
		<tr>
			<td>NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice&#160;</td>
			<td>Charles River&#160;</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pancoll human, Density: 1.077 g/mL</td>
			<td>PAN-Biotech</td>
			<td>P04-60500</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin&#160;</td>
			<td>Gibco</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate Buffered Saline (PBS)</td>
			<td>Gibco</td>
			<td>14190169</td>
			<td></td>
		</tr>
	</tbody>
</table>

intrafemoral injection of human hematopoietic stem and progenitor cells into immunocompromised mice 

Hematopoietic stem cells (HSCs) are defined by their lifelong ability to produce all blood cell types. This is operationally tested by transplanting cell populations containing HSCs into syngeneic or immunocompromised mice. The size and multilineage composition of the graft is then measured over time, usually by flow cytometry. Classically, a population containing HSCs is injected into the circulation of the animal, after which the HSCs home to the bone marrow, where they lodge and begin blood production. Alternatively, HSCs and/or progenitor cells (HSPCs) can be placed directly in the bone marrow cavity. 
This paper describes a protocol for intrafemoral injection of human HSPCs into immunodeficient mice. In short, preconditioned mice are anesthetized, and a small hole is drilled through the knee into the femur using a needle. Using a smaller insulin needle, cells are then injected directly into the same conduit created by the first needle. This method of transplantation can be applied in varied experimental designs, using either mouse or human cells as donor cells. It has been most widely used for xenotransplantation, because in this context, it is thought to provide improved engraftment over intravenous injections, therefore improving statistical power and reducing the number of mice to be used.

Author Spotlight: Exploring the Lifespan Dynamics of Healthy Human Hematopoiesis

Intrafemoral Injection of Human Hematopoietic Stem and Progenitor Cells into Immunocompromised Mice 

Our interest is studying healthy human hematopoiesis across a whole lifetime from the fetus to the elderly. For example, we study the liver in the fetus and the bone marrow and peripheral blood in the adult. We think it is important to study the healthy context to help us understand what goes wrong in disease.There are many single cell Onyx approaches that have advanced the field in recent years, but these work alongside rather than replace transplantation experiments that test the function of stem cells. By injecting blood stem and progenitor cells directly into the femur, we bypass the homing phase of intravenous injections. The cells are already in their natural environment, and therefore we often have much higher engraftment.We want to provide a quantitative view of how blood stem cells evolve over human life, how they are affected by events such as inflammation or infections, and finally, how mutations accumulate with age, how they reshape blood stem cell function, and how this predisposes us to age-related disease.

The engraftment of the intrafemorally injected cells can be assessed at any time point from 24 h onwards depending on the experimental design. At the end time point, IF, BM, PB, and spleens may be collected. These can be processed, and the level of engraftment assessed via flow cytometry. To robustly call human engraftment even at low levels, we stained with two distinct antibodies against human CD45 (clone HI30 and clone 2D1). Only cells positive for both antibodies (CD45++) were considered of human origin. T...

Read this Scientific Article Protocol about Author Spotlight: Exploring the Lifespan Dynamics of Healthy Human Hematopoiesis at JoVE.com

Intrafemoral injections allow for the engraftment of a small number of hematopoietic stem and progenitor cells (HSPCs), by placing the cells directly in the bone marrow cavity. Here we describe an experimental protocol of intrafemoral injection of human HSPCs into immunodeficient mice.

Hematopoietic stem cells (HSCs) are defined by their lifelong ability to produce all blood cell types. This is operationally tested by transplanting cell ...

intrafemoral-injection-human-hematopoietic-stem-progenitor-cells-into