Significant progress has also been made in the phenotypic characterization of human HSCs via flow cytometric analysis combined with in vivo transplantation assays in immune-deficient mice.[1,2] Of particular note, although murine HSCs can be characterized by the absence of CD34 expression on the cell surface, human HSCs are primarily enriched using CD34 surface expression, and this provides the basis for confirming sufficient HSC content to allow for successful hematopoietic cell transplantation in patients.[3,4] There is also some controversy in this area because some investigations have suggested that LT-HSCs can be isolated from CD34− human hematopoietic cells.[5–8] Of note, only a small percentage (less than 0.1%) of CD34+ human hematopoietic cells possess the capacity to engraft following intravenous injection into non obese diabetic/severe combined immune deficient (NOD/SCID) mice.[2,4] Further enrichment of human HSCs has been demonstrated via negative selection for surface expression of CD38 and depletion of lineage surface markers.[2,9,10] Thy-1 (CD90) surface expression also enriches for multilineage colony-forming ability and in vivo reconstituting capacity of human hematopoietic cells.[3,11] Majeti et al. showed that the Lin−CD34+CD38−CD45RA−Thy-1+ population in human CB was enriched at the level of one in 10 cells for LT-HSCs.[11] The authors also showed that candidate multipotent progenitor cells (MPPs) were demarcated by the Lin−CD34+CD38−CD45RA−Thy-1− population, suggesting that the loss of Thy-1 reflects the transition of LT-HSCs to short-term (ST)-HSCs/MPPs.[3,11]

CD49f+ Human Hematopoietic Stem Cells

Although it is possible to enrich murine BM HSCs to the level of nearly single-cell purity using various combinations of cell surface markers, isolation of human BM HSCs to the same level of purity has not been readily achieved.[12,13,14] However, Notta et al. demonstrated that intrafemoral injection of a fluorescence activated cell sorting (FACS)-purified population of human CB CD34+CD38−CD45RA−Thy-1+ cells that were additionally purified based on surface expression of the integrin α6 (CD49f) yielded 6.7 fold increased human donor chimerism at 20 weeks in NOD/SCID IL2Rγ−/− (NSG) mice compared with injection with the identical dose of CD34+CD38−CD45RA−Thy-1+CD49f− cells.[15] Only the Thy-1+CD49f+ cells could be serially transplanted in this study, and the enrichment for LT-HSCs via limiting dilution analysis was estimated to be approximately one in 11 CD34+CD38−CD45RA−Thy 1+CD49f+ cells.[15] Further purification of this population of cells using Rh123 dye demonstrated that single-cell transplantation of Thy-1+Rh123loCD49f+ cells yielded LT, multilineage engraftment in five of 18 transplanted recipients. Serial transplantation was also successful in two of four secondary mice, suggesting that at least some of the Thy-1+Rh123loCD49f+ cells undergo self-renewal.[15] Of note, because mice were transplanted via intrafemoral injection in these studies, it remained unknown whether this panel of markers equally identified human HSCs capable of homing properly to the BM after intravenous injection. Nonetheless, these studies revealed that the addition of CD49f+ to the panel of human LT-HSC markers provided an improved capability to isolate human HSCs at a level of purity that was comparable to that applied to murine HSC isolation.

Two additional novel cell surface markers for human HSCs are CD166 (activated leukocyte adhesion molecule) and protein tyrosine phosphatase-sigma (PTPσ).[16,17] Human Lin−CD34+CD38− CD49f+CD166+ cells engrafted in primary and secondary NSG mice at a significantly higher level than Lin−CD34+CD38−CD49f+CD166− cells.[16] Interestingly, CD166 is also expressed by BM osteoblasts and it was postulated that CD166 mediated HSC maintenance in vivo via homophilic interactions between CD166 expressed on HSCs and osteoblasts.[16] Quarmyne et al. reported that NSG mice transplanted with human CB Lin−CD34+CD38−CD45RA−PTPσ− cells displayed 15-fold higher human hematopoietic cell engraftment at 16 weeks compared to mice transplanted with Lin−CD34+CD38−CD45RA− cells or Lin−CD34+CD38−CD45RA−PTPσ+ cells.{17} Protein tyrosine phosphatase–sigma (PTPσ) was shown to negatively regulate both murine and human HSC repopulation following transplantation, via inhibition of the RhoGTPase, RAC1.[17] Subsequent studies showed that systemic administration of a small molecule, an allosteric inhibitor of PTPσ to irradiated- or chemotherapy-treated mice promoted the early regeneration of HSCs, white blood cells, and neutrophils in vivo, while ex vivo treatment of irradiated human CD34+ hematopoietic stem and progenitor cells (HSPCs) similarly promoted the rescue of human NSG mice repopulating cells.[18]

Advances in methods to perform single cell transcriptomic, genomic, and proteomic analysis have led to several studies characterizing the molecular profile of single human HSCs.[19–25] These studies have revealed remarkable heterogeneity within phenotypically identical human HSCs in steady state and in response to growth factor treatment and have shown that HSC fate determinations can be related directly to expression levels of lineage-specific transcription factors.[26,27] Single cell analysis of HSCs from aging donors revealed age-associated epigenetic reprogramming within cancer and developmental pathways, suggesting the basis for increased incidence of acute myeloid leukemia (AML) with aging.[28] Continued progress in the molecular and functional characterization of single human HSCs will undoubtedly lead to much improved definition of the human hematopoietic hierarchy and the more optimized selection of purified human HSCs for transplantation.

References

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[2] Bhatia M, Wang JC, Kapp U, et al. Purification of primitive human hematopoietic cells capable of repopulating immune-deficient mice. Proc Natl Acad Sci USA. 1997;94:5320–5325. https://doi.org/10.1073/pnas.94.10.5320.

[3] Terakura S, Azuma E, Murata M, et al. Hematopoietic engraftment in recipients of unrelated donor umbilical cord blood is affected by the CD34+ and CD8+ cell doses. Biol Blood Marrow Transplant. 2007;13:822-830. https://doi.org/10.1016/j.bbmt.2007.03.006.

[4] Civin CI, Strauss LC, Brovall C, et al. Antigenic analysis of hematopoiesis. III. A hematopoietic progenitor cell surface antigen defined by a monoclonal antibody raised against KG-1a cells. J Immunol. 1984;133:157–165.

[5] Bhatia M, Bonnet D, Murdoch B, et al. A newly discovered class of human hematopoietic cells with SCID-repopulating activity. Nat Med. 1998;4:1038–1045. https://doi.org/10.1038/2023.

[6] Goodell MA, Rosenzweig M, Kim H, et al. Dye efflux studies suggest that hematopoietic stem cells expressing low or undetectable levels of CD34 antigen exist in multiple species. Nat Med. 1997;3:1337–1345. https://doi.org/10.1038/nm1297-1337.

[7] Zanjani ED, Almeida-Porada G, Livingston AG, et al. Human bone marrow CD34- cells engraft in vivo and undergo multilineage expression that includes giving rise to CD34+ cells. Exp Hematol. 1998;26:353–360.

[8] Gao Z, Fackler MJ, Leung W, et al. Human CD34+ cell preparations contain over 100-fold greater NOD/SCID mouse engrafting capacity than do CD34- cell preparations. Exp Hematol. 2001;29:910–921. https://doi.org/10.1016/s0301-472x(01)00654-3.

[9] Baum CM, Weissman IL, Tsukamoto AS, et al. Isolation of a candidate human hematopoietic stem-cell population. Proc Natl Acad Sci USA. 1992;89:2804–2808. https://doi.org/10.1073/pnas.89.7.2804.

[10] Petzer AL, Zandstra PW, Piret JM, et al. Differential cytokine effects on primitive (CD34+CD38-) human hematopoietic cells: novel responses to Flt3-ligand and thrombopoietin. J Exp Med. 1996;183:2551–2558. https://doi.org/10.1084/jem.183.6.2551.

[11] Majeti R, Park CY, Weissman IL. Identification of a hierarchy of multipotent hematopoietic progenitors in human cord blood. Cell Stem Cell. 2007;1:635–645. https://doi.org/10.1016/j.stem.2007.10.001.

[12] McKenzie JL, Takenaka K, Gan OI, et al. Low rhodamine 123 retention identifies long-term human hematopoietic stem cells within the Lin−CD34+CD38- population. Blood. 2007;109:543–545. https://doi.org/10.1182/blood-2006-06-030270.

[13] Goodell MA, Brose K, Paradis G, et al. Isolation and functional properties of murine hematopoietic stem cells that are replicating in vivo. J Exp Med. 1996;183:1797–1806. https://doi.org/10.1084/jem.183.4.1797.

[14] Kiel MJ, Yilmaz OH, Iwashita T, et al. SLAM family receptors distinguish hematopoietic stem and progenitor cells and reveal endothelial niches for stem cells. Cell. 2005;121:1109–1121. https://doi.org/10.1016/j.cell.2005.05.026.

[15] Notta F, Doulatov S, Laurenti E, et al. Isolation of single human hematopoietic stem cells capable of long-term multilineage engraftment. Science. 2011;333:218–221. https://doi.org/10.1126/science.1201219.

[16] Chitteti BR, Kobayashi M, Cheng Y, et al. CD166 regulates human and murine hematopoietic stem cells and the hematopoietic niche. Blood. 2014;124:519–529. https://doi.org/10.1182/blood-2014-03-565721.

[17] Quarmyne M, Doan PL, Himburg HA, et al. Protein tyrosine phosphatase sigma regulates hematopoietic stem cell-repopulating capacity. J Clin Invest. 2015;125:177–182. https://doi.org/10.1172/JCI77866.

[18] Zang Y, Roos M, Himburg H, et al. PTPσ inhibitors promote hematopoietic stem cell regeneration. Nat Commun. 2019;10:3667. https://doi.org/10.1038/s41467-019-11490-5.

[19] Buenrostro J, Corces MR, Lareau C, et al. Integrated single-cell analysis maps the continuous regulatory landscape of human hematopoietic differentiation. Cell. 2018;173:1535–1548. https://doi.org/10.1016/j.cell.2018.03.074.

[20] Knapp D, Hammond C, Wang F, et al. A topological view of human CD34+ cell state trajectories from integrated single-cell output and proteomic data. Blood. 2019;133:927–939. https://doi.org/10.1182/blood-2018-10-878025.

[21] Moussy A, Cosette J, Parmentier R, et al. Integrated time-lapse and single cell transcription studies highlight the variable and dynamic nature of human hematopoietic cell fate commitment. PLoS Biol. 2017;15:e2001867. https://doi.org/10.1371/journal.pbio.2001867.

[22] Knapp D, Hammon C, Aghaeepour N, et al. Distinct signaling programs control human hematopoietic stem cell survival and proliferation. Blood. 2017;129:307–318. https://doi.org/10.1182/blood-2016-09-740654.

[23] Han X, Zhou Z, Fei L, et al. Construction of a human cell landscape at single-cell level. Nature. 2020;581:303–309. https://doi.org/10.1038/s41586-020-2157-4.

[24] Pellin D, Loperfido M, Baricordi C, et al. A comprehensive single cell transcriptional landscape of human hematopoietic progenitors. Nat Commun. 2019;10:2395. https://doi.org/10.1038/s41467-019-10291-0.

[25] Rodriguez-Fraticelli A, Camargo F. Systems analysis of hematopoiesis using single-cell lineage tracing. Curr Opin Hematol. 2021;28:18–27. https://doi.org/10.1097/MOH.0000000000000624.

[26] Pali C, Cheng Q, Gillespie M, et al. Single-cell proteomics reveal that quantitative changes in co-expressed lineage-specific transcription factors determine cell fate. Cell Stem Cell. 2019;24:812–820. https://doi.org/10.1016/j.stem.2019.02.006.

[27] Watcham S, Kucinski I, Gottgens B. New insights into hematopoietic differentiation landscapes from single-cell RNA sequencing. Blood. 2019;133:1415–1426. https://doi.org/10.1182/blood-2018-08-835355.

[28] Adelman E, Huang HT, Roisman A, et al. Aging human hematopoietic stem cells manifest profound epigenetic reprogramming of enhancers that may predispose to leukemia. Cancer Discovery. 2019;9:1080–1101. https://doi.org/10.1158/2159-8290.CD-18-1474.

اخر الاخبار

اخبار العتبة العباسية المقدسة

شعبة رعاية الحرم تُجري أعمال تنظيف مرقد أبي الفضل العباس (عليه السلام)

في موكب العتبتين المقدستين..المجمَع العلمي يقيم سلسلة محافل قرآنية على طريق زائري الأربعين

العتبة العباسية المقدسة تواصل إقامة مجلسها العزائي بذكرى أربعين الإمام الحسين (عليه السلام)

مشروع التبليغ الحوزوي يستضيف وفدًا أكاديميًّا من جامعة واسط

المزيد

الآخبار الصحية

حجم جزء محدد من الجسم يعكس الصحة العامة ومخاطر الأمراض

تفشي عدوى بكتيرية بفرنسا يحتمل ارتباطها بنوع من الجبن الطري

دراسة حديثة تكشف ما تفعله الشاشات بـ"قلوب الأطفال" !

متلازمة المبنى المريض.. هكذا يتحول تكييف الهواء إلى خطر صحي ؟؟

المزيد

الآخبار التكنلوجية

كيف تتعامل مع حرارة الطقس أثناء القيادة؟

لماذا يجب عليك إيقاف تكييف السيارة قبل إطفاء المحرك؟

دراسة تكشف سببا محتملا وراء زيادة خطر إصابة الأطفال بالتوحد

تشيلي.. العثور على متحجرة حيوان ثديي صغير من زمن الديناصورات

المزيد

مواضيع ذات صلة

Embryonic Origin of Hematopoietic Stem Cells

نقي العظم (النخاع العظمي) Bone marrow

تكوين الدم Haematopoiesis

Gastrointestinal decontamination

تطبيقات البرايون ودوره المثير في مفهوم العقيدة المركزية

تصوير الأوعية التاجية

أدواء البريونات

Stages of Neutrophil Differentiation

Types of Bone

Elements Comprising Bone Tissue

تخفيض مستوى الكولسترول يخفض الأزمات القلبية

تخطيط القلب الكهربائي أثناء الإجهاد