scholarly journals Immature human cord blood progenitors engraft and proliferate to high levels in severe combined immunodeficient mice

Blood ◽  
1994 ◽  
Vol 83 (9) ◽  
pp. 2489-2497 ◽  
Author(s):  
J Vormoor ◽  
T Lapidot ◽  
F Pflumio ◽  
G Risdon ◽  
B Patterson ◽  
...  
Keyword(s):  
Cord Blood ◽  
Dna Analysis ◽  
Hematopoietic Cells ◽  
In Vivo Model ◽  
Erythroid Progenitors ◽  
Human Cord Blood ◽  
Immunodeficient Mice ◽  
High Level

Unseparated or Ficoll-Hypaque (Pharmacia, Piscataway, NJ)--fractionated human cord blood cells were transplanted into sublethally irradiated severe combined immunodeficient (SCID) mice. High levels of multilineage engraftment, including myeloid and lymphoid lineages, were obtained with 80% of the donor samples as assessed by DNA analysis, fluorescence-activated cell sorting (FACS), and morphology. In contrast to previous and concurrent studies with adult human bone marrow (BM), treatment with human cytokines was not required to establish high-level human cell engraftment, suggesting that neonatal cells either respond differently to the murine microenvironment or they provide their own cytokines in a paracrine fashion. Committed and multipotential myelo- erythroid progenitors were detected using in vitro colony assays and FACS analysis of the murine BM showed the presence of immature CD34+ cells. In addition, human hematopoiesis was maintained for at least 14 weeks providing further evidence that immature hematopoietic precursors had engrafted the murine BM. This in vivo model for human cord blood- derived hematopoiesis will be useful to gain new insights into the biology of neonatal hematopoietic cells and to evaluate their role in gene therapy. There is growing evidence that there are ontogeny-related changes in immature human hematopoietic cells, and therefore, the animal models we have developed for adult and neonatal human hematopoiesis provide useful tools to evaluate these changes in vivo.

scholarly journals Immature human cord blood progenitors engraft and proliferate to high levels in severe combined immunodeficient mice

Blood ◽  
1994 ◽  
Vol 83 (9) ◽  
pp. 2489-2497 ◽  
Author(s):  
J Vormoor ◽  
T Lapidot ◽  
F Pflumio ◽  
G Risdon ◽  
B Patterson ◽  
...  
Keyword(s):  
Cord Blood ◽  
Dna Analysis ◽  
Hematopoietic Cells ◽  
In Vivo Model ◽  
Erythroid Progenitors ◽  
Human Cord Blood ◽  
Immunodeficient Mice ◽  
High Level

Abstract Unseparated or Ficoll-Hypaque (Pharmacia, Piscataway, NJ)--fractionated human cord blood cells were transplanted into sublethally irradiated severe combined immunodeficient (SCID) mice. High levels of multilineage engraftment, including myeloid and lymphoid lineages, were obtained with 80% of the donor samples as assessed by DNA analysis, fluorescence-activated cell sorting (FACS), and morphology. In contrast to previous and concurrent studies with adult human bone marrow (BM), treatment with human cytokines was not required to establish high-level human cell engraftment, suggesting that neonatal cells either respond differently to the murine microenvironment or they provide their own cytokines in a paracrine fashion. Committed and multipotential myelo- erythroid progenitors were detected using in vitro colony assays and FACS analysis of the murine BM showed the presence of immature CD34+ cells. In addition, human hematopoiesis was maintained for at least 14 weeks providing further evidence that immature hematopoietic precursors had engrafted the murine BM. This in vivo model for human cord blood- derived hematopoiesis will be useful to gain new insights into the biology of neonatal hematopoietic cells and to evaluate their role in gene therapy. There is growing evidence that there are ontogeny-related changes in immature human hematopoietic cells, and therefore, the animal models we have developed for adult and neonatal human hematopoiesis provide useful tools to evaluate these changes in vivo.

scholarly journals In Vivo Analysis of PML-RARA in a Humanized Mouse Model

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 1020-1020
Author(s):  
Hiromichi Matsushita ◽  
Takashi Yahata ◽  
Yin Sheng ◽  
Yoshihiko Nakamura ◽  
Yukari Muguruma ◽  
...  
Keyword(s):  
Cord Blood ◽  
Conflicts Of Interest ◽  
Nuclear Bodies ◽  
Leukemic Cells ◽  
Human Cord Blood ◽  
Immunodeficient Mice ◽  
Cd34 Cells ◽  
Nog Mice

Abstract Acute promyelocytic leukemia (APL) is a subtype of acute myeloid leukemia (AML) characterized by the formation of a PML-RARa fusion protein, which leads to the accumulation of abnormal promyelocytes. Xenograft mouse models with human leukemic cells have advantages for analyzing the human leukemias in vivo, especially for genetic analyses. However, human primary APL cells are difficult to engraft even in very severely immunodeficient mice, such as NOD/shi-SCID IL2Rg-/- (NOG) mice. In order to understand the mechanisms involved in human APL leukemogenesis, we established a humanized in vivo APL model using the transplantation of PML-RARA-transduced CD34+ cells from human cord blood into NOG mice. The expression of PML-RARa in the CD34+ cells disrupted the nuclear bodies in vitro. The clonogenic assay showed that PML-RARa inhibited the total colony formation, but favored the growth of myeloid colonies. When CD34+ cells with PML-RARA were transplanted, they proliferated in the NOG mice for more than three to four months after transplantation (in 24 out of the 34 mice). All 16 mice with more than 3,000 PML-RARA-transduced CD34+ cells were engrafted, while the engraftment was only detected in eight out of 18 mice when the cell density used for transplantation was less than 3,000 cells. These cells possessed abundant azurophilic abnormal granules in the cytoplasm, and some of them had bundles of Auer rods. They expressed CD13, CD33 and CD117, but not HLA-DR or CD34. In addition, the gene expression analysis revealed that these cells and human primary APL were clustered together among various types of AML, suggesting that these induced APL cells well recapitulated human primary APL. Similar to human primary APL, the induced APL cells possessed the ability for myeloid differentiation after treatment with all-trans retinoic acid in vitro and in vivo, and a very low potential for re-transplantation, which was similarly observed in both unsorted induced APL cells and the CD34- fraction. When human cord blood was fractionated before the PML-RARA transduction, the CD34+/CD38+ cells and common myeloid progenitors (CMP) in the CD34+/CD38+ cells led to the efficient development of APL in vivo. These findings demonstrate that CMP is a target for PML-RARA in APL, whereas the resultant CD34- APL cells may share the ability to maintain the leukemia. Disclosures No relevant conflicts of interest to declare.

Human Cord Blood Cells with Rapid In Vivo Platelet Regenerating Activity in NOD/SCID-IL-2Rγc-/- Mice Show Variable Aldehyde Dehydrogenase Activity.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2429-2429
Author(s):  
Alice M.S. Cheung ◽  
Connie J. Eaves
Keyword(s):  
Cord Blood ◽  
Dehydrogenase Activity ◽  
Aldehyde Dehydrogenase ◽  
Hematopoietic Cells ◽  
Scid Mice ◽  
Human Cord Blood ◽  
Post Transplant ◽  
Aldehyde Dehydrogenase Activity

Abstract Abstract 2429 Poster Board II-406 Human cord blood (CB) has emerged as an attractive source of hematopoietic cells for patients lacking a suitable donor. However, marked delays in platelet and immune recovery pose significant challenges to the use of CB cells as transplants for either children or adult patients. These difficulties in the use of CB have been attributed to low absolute numbers of repopulating cells (RCs) in most CB units which is not readily overcome by simply combining multiple units. Xenotransplantation of human hematopoietic cells into highly immunodeficient sublethally irradiated NOD/SCID mice has proven to be a powerful approach to characterize different types of primitive human hematopoietic cells with repopulating potential. However, the residual NK activity intrinsic to NOD/SCID mice poses a significant barrier to the engraftment of intermediate types of repopulating human cells and also to the terminal stages of their differentiation, as shown by recent studies using more immunodeficient mice as hosts. Nevertheless, the cells responsible for early platelet recovery post-transplant and factors that regulate their activity remain largely unknown. To address this issue, we have developed a quantitative and sensitive assay for characterizing the phenotypes of human CB cells that regenerate mature platelets detectable in the blood of NOD/SCID-IL-2Rγc-/- mice 3-6 weeks post-transplant. Lineage marker-negative (Lin-) human CB cells were stained with Aldefluor and then those with low light side-scattering properties were further separated by FACS according to whether they displayed aldehyde dehydrogenase activity above (ALDH+) or below (ALDH-) that detected in the presence of an ALDH inhibitor. Assays of different pooled human CB preparations showed that the most primitive class of in vitro megakaryocyte (Mk) colony-forming cells and cells responsible for rapid human platelet production in NOD/SCID-IL-2Rγc-/- mice were variably and comparably distributed between the small ALDH+ and prevalent ALDH- fractions. From 3 experiments, the following values were obtained for the ALDH+ and ALDH- subsets, respectively; ALDH+ - mature CFU-Mk = 47.8±21.3% of the total Lin- fraction, intermediate CFU-Mk = 66.3±25.4%, primitive CFU-Mk = 75.5±14.0%, 3-week platelet-producing STRC = 63.8±12.3%, 6-week platelet-producing STRC = 81.5±5.8%; and ALDH- - mature CFU-Mk = 52.2±21.3% of the total Lin- fraction, intermediate CFU-Mk = 33.7±25.4%, primitive CFU-Mk = 24.5±14.0%, 3-week platelet-producing STRC = 36.2±12.3%, 6-week platelet-producing STRC = 18.5±5.8%. Limiting dilution assays revealed 1 in 830 Lin-ALDH+ CB cells to be a cell that can produce detectable platelets in vivo within 3 weeks (95% CI = 1 in 534 to 1 in 1290) but only 1 in 1996 (95% CI = 1 in 1226 to 1 in 3247) within 6 weeks. The present study demonstrates the feasibility of using NOD/SCID-IL-2Rγc-/- mice for the sensitive detection of human CB cells with in vivo platelet regenerating activity and suggests that these may be closely related to primitive cells with in vitro Mk clonogenic activity (>50 Mk per colony). Biologically important platelet progenitors may thus be heterogeneous with respect to ALDH+ activity. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Primitive Human Hematopoietic Cells Are Enriched in Cord Blood Compared With Adult Bone Marrow or Mobilized Peripheral Blood as Measured by the Quantitative In Vivo SCID-Repopulating Cell Assay

Blood ◽  
1997 ◽  
Vol 89 (11) ◽  
pp. 3919-3924 ◽  
Author(s):  
Jean C.Y. Wang ◽  
Monica Doedens ◽  
John E. Dick
Keyword(s):  
Bone Marrow ◽  
Cord Blood ◽  
Peripheral Blood ◽  
Hematopoietic Cells ◽  
Allogeneic Transplantation ◽  
Functional Assay ◽  
Hematopoietic Stem ◽  
Mobilized Peripheral Blood

Abstract We have previously reported the development of in vivo functional assays for primitive human hematopoietic cells based on their ability to repopulate the bone marrow (BM) of severe combined immunodeficient (SCID) and nonobese diabetic/SCID (NOD/SCID) mice following intravenous transplantation. Accumulated data from gene marking and cell purification experiments indicate that the engrafting cells (defined as SCID-repopulating cells or SRC) are biologically distinct from and more primitive than most cells that can be assayed in vitro. Here we demonstrate through limiting dilution analysis that the NOD/SCID xenotransplant model provides a quantitative assay for SRC. Using this assay, the frequency of SRC in cord blood (CB) was found to be 1 in 9.3 × 105 cells. This was significantly higher than the frequency of 1 SRC in 3.0 × 106 adult BM cells or 1 in 6.0 × 106 mobilized peripheral blood (PB) cells from normal donors. Mice transplanted with limiting numbers of SRC were engrafted with both lymphoid and multilineage myeloid human cells. This functional assay is currently the only available method for quantitative analysis of human hematopoietic cells with repopulating capacity. Both CB and mobilized PB are increasingly being used as alternative sources of hematopoietic stem cells in allogeneic transplantation. Thus, the findings reported here will have important clinical as well as biologic implications.

scholarly journals Hematopoietic stem/progenitor cells, generation of induced pluripotent stem cells, and isolation of endothelial progenitors from 21- to 23.5-year cryopreserved cord blood

Blood ◽  
2011 ◽  
Vol 117 (18) ◽  
pp. 4773-4777 ◽  
Author(s):  
Hal E. Broxmeyer ◽  
Man-Ryul Lee ◽  
Giao Hangoc ◽  
Scott Cooper ◽  
Nutan Prasain ◽  
...  
Keyword(s):  
Stem Cells ◽  
Cord Blood ◽  
Progenitor Cells ◽  
Proliferative Potential ◽  
Hematopoietic Stem ◽  
Immunodeficient Mice ◽  
Induced Pluripotent

Abstract Cryopreservation of hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) is crucial for cord blood (CB) banking and transplantation. We evaluated recovery of functional HPC cryopreserved as mononuclear or unseparated cells for up to 23.5 years compared with prefreeze values of the same CB units. Highly efficient recovery (80%-100%) was apparent for granulocyte-macrophage and multipotential hematopoietic progenitors, although some collections had reproducible low recovery. Proliferative potential, response to multiple cytokines, and replating of HPC colonies was extensive. CD34+ cells isolated from CB cryopreserved for up to 21 years had long-term (≥ 6 month) engrafting capability in primary and secondary immunodeficient mice reflecting recovery of long-term repopulating, self-renewing HSCs. We recovered functionally responsive CD4+ and CD8+ T lymphocytes, generated induced pluripotent stem (iPS) cells with differentiation representing all 3 germ cell lineages in vitro and in vivo, and detected high proliferative endothelial colony forming cells, results of relevance to CB biology and banking.

scholarly journals Macrophages prevent human red blood cell reconstitution in immunodeficient mice

Blood ◽  
2011 ◽  
Vol 118 (22) ◽  
pp. 5938-5946 ◽  
Author(s):  
Zheng Hu ◽  
Nico Van Rooijen ◽  
Yong-Guang Yang
Keyword(s):  
Fetal Liver ◽  
In Vivo Model ◽  
Thymic Tissue ◽  
Immunodeficient Mice ◽  
Human Erythropoietin ◽  
Human Cd34 ◽  
Biologic Function ◽  
Human Rbcs

Abstract An animal model supporting human erythropoiesis will be highly valuable for assessing the biologic function of human RBCs under physiologic and disease settings, and for evaluating protocols of in vitro RBC differentiation. Herein, we analyzed human RBC reconstitution in NOD/SCID or NOD/SCID/γc−/− mice that were transplanted with human CD34+ fetal liver cells and fetal thymic tissue. Although a large number of human CD45−CD71+ nucleated immature erythroid cells were detected in the bone marrow, human RBCs were undetectable in the blood of these mice. Human RBCs became detectable in blood after macrophage depletion but disappeared again after withdrawal of treatment. Furthermore, treatment with human erythropoietin and IL-3 significantly increased human RBC reconstitution in macrophage-depleted, but not control, humanized mice. Significantly more rapid rejection of human RBCs than CD47-deficient mouse RBCs indicates that mechanisms other than insufficient CD47-SIRPα signaling are involved in human RBC xenorejection in mice. All considered, our data demonstrate that human RBCs are highly susceptible to rejection by macrophages in immunodeficient mice. Thus, strategies for preventing human RBC rejection by macrophages are required for using immunodeficient mice as an in vivo model to study human erythropoiesis and RBC function.

scholarly journals Differential Effects of Platelets Selectively Activated by Protease-Activated Receptors on Meniscal Cells

2019 ◽  
Vol 48 (1) ◽  
pp. 197-209 ◽  
Author(s):  
Hongyao Xu ◽  
Xiangjie Zou ◽  
Pengcheng Xia ◽  
Mohammad Ahmad Kamal Aboudi ◽  
Ran Chen ◽  
...  
Keyword(s):  
In Vivo Model ◽  
Enzyme Linked Immunosorbent Assay ◽  
Protease Activated Receptors ◽  
Activated Platelets ◽  
Meniscal Tissue ◽  
Vitro Model ◽  
High Level ◽  
Meniscal Cells

Background: Meniscal injury is very common, and injured meniscal tissue has a limited healing ability because of poor vascularity. Platelets contain both pro- and anti-angiogenic factors, which can be released by platelet selective activation. Hypothesis: Platelets release a high level of vascular endothelial growth factor (VEGF) when they are activated by protease-activated receptor 1 (PAR1), whereas the platelets release endostatin when they are activated by protease-activated receptor 4 (PAR4). The PAR1-treated platelets enhance the proliferation of meniscal cells in vitro and promote in vivo healing of wounded meniscal tissue. Study Design: Controlled laboratory study. Method: Platelets were isolated from human blood and activated with different reagents. The released growth factors from the activated platelets were determined by immunostaining and enzyme-linked immunosorbent assay. The effects of the platelets with different treatments on meniscal cells were tested by an in vitro model of cell culture and an in vivo model of wounded meniscal healing. Results: The results indicated that platelets contained both pro- and antiangiogenic factors including VEGF and endostatin. In unactivated platelets, VEGF and endostatin were contained inside of the platelets. Both VEGF and endostatin were released from the platelets when they were activated by thrombin. However, only VEGF was released from the platelets when they were activated by PAR1, and only endostatin was released from the platelets when they were activated by PAR4. The rat meniscal cells grew much faster in the medium that contained PAR1-activated platelets than in the medium that contained either PAR4-activated platelets or unactivated platelets. The wounds treated with PAR1-activated platelets healed faster than those treated with either PAR4-activated platelets or unactivated platelets. Many blood vessel–like structures were found in the wounded menisci treated with PAR1-activated platelets. Conclusion: The PAR1-activated platelets released high levels of VEGF, which increased the proliferation of rat meniscal cells in vitro, enhanced the vascularization of menisci in vivo, and promoted healing of wounded menisci. Clinical Relevance: Our results suggested that selective activated platelets can be used clinically to enhance healing of wounded meniscal tissue.

Unique Differentiation Programs of Human Fetal Liver Stem Cells Shown Both In Vitro and In Vivo in NOD/SCID Mice

Blood ◽  
1999 ◽  
Vol 94 (8) ◽  
pp. 2686-2695 ◽  
Author(s):  
Franck E. Nicolini ◽  
Tessa L. Holyoake ◽  
Johanne D. Cashman ◽  
Pat P.Y. Chu ◽  
Karen Lambie ◽  
...  
Keyword(s):  
Cord Blood ◽  
Fetal Liver ◽  
Scid Mice ◽  
Human Cord Blood ◽  
Human Fetal Liver ◽  
Human Erythropoietin ◽  
Erythroid Precursors ◽  
Lower Ratio

Comparative measurements of different types of hematopoietic progenitors present in human fetal liver, cord blood, and adult marrow showed a large (up to 250-fold), stage-specific, but lineage-unrestricted, amplification of the colony-forming cell (CFC) compartment in the fetal liver, with a higher ratio of all types of CFC to long-term culture-initiating cells (LTC-IC) and a lower ratio of total (mature) cells to CFC. Human fetal liver LTC-IC were also found to produce more CFC in LTC than cord blood or adult marrow LTC-IC, and more of the fetal liver LTC-IC–derived CFC were erythroid. Human fetal liver cells regenerated human multilineage hematopoiesis in NOD/SCID mice with the same kinetics as human cord blood and adult marrow cells, but sustained a high level of terminal erythropoiesis not seen in adult marrow-engrafted mice unless exogenous human erythropoietin (Epo) was injected. This may be due to a demonstrated 10-fold lower activity of murine versus human Epo on human cells, sufficient to distinguish between a differential Epo sensitivity of fetal and adult erythroid precursors. Examination of human LTC-IC, CFC, and erythroblasts generated either in NOD/SCID mice and/or in LTC showed the types of cells and hemoglobins produced also to reflect their ontological origin, regardless of the environment in which the erythroid precursors were generated. We suggest that ontogeny may affect the behavior of cells at many stages of hematopoietic cell differentiation through key changes in shared signaling pathways.

High GATA-2 expression inhibits human hematopoietic stem and progenitor cell function by effects on cell cycle

Blood ◽  
2009 ◽  
Vol 113 (12) ◽  
pp. 2661-2672 ◽  
Author(s):  
Alex J. Tipping ◽  
Cristina Pina ◽  
Anders Castor ◽  
Dengli Hong ◽  
Neil P. Rodrigues ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cord Blood ◽  
Cell Function ◽  
Ki 67 ◽  
Human Cord Blood ◽  
Hematopoietic Stem ◽  
Cord Blood Cells ◽  
Low Efficiency

Abstract Evidence suggests the transcription factor GATA-2 is a critical regulator of murine hematopoietic stem cells. Here, we explore the relation between GATA-2 and cell proliferation and show that inducing GATA-2 increases quiescence (G0 residency) of murine and human hematopoietic cells. In human cord blood, quiescent fractions (CD34+CD38−HoechstloPyronin Ylo) express more GATA-2 than cycling counterparts. Enforcing GATA-2 expression increased quiescence of cord blood cells, reducing proliferation and performance in long-term culture-initiating cell and colony-forming cell (CFC) assays. Gene expression analysis places GATA-2 upstream of the quiescence regulator MEF, but enforcing MEF expression does not prevent GATA-2–conferred quiescence, suggesting additional regulators are involved. Although known quiescence regulators p21CIP1 and p27KIP1 do not appear to be responsible, enforcing GATA-2 reduced expression of regulators of cell cycle such as CCND3, CDK4, and CDK6. Enforcing GATA-2 inhibited human hematopoiesis in vivo: cells with highest exogenous expression (GATA-2hi) failed to contribute to hematopoiesis in nonobese diabetic–severe combined immunodeficient (NOD-SCID) mice, whereas GATA-2lo cells contributed with delayed kinetics and low efficiency, with reduced expression of Ki-67. Thus, GATA-2 activity inhibits cell cycle in vitro and in vivo, highlighting GATA-2 as a molecular entry point into the transcriptional program regulating quiescence in human hematopoietic stem and progenitor cells.

Identification of a New Population of Human Cord Blood Cells with Lymphoid-Restricted Reconstituting Potential in Sublethally Irradiated Immunodeficient Mice.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3213-3213
Author(s):  
Oliver Christ ◽  
Clayton Smith ◽  
Karen Leung ◽  
Melisa Hamilton ◽  
Connie J. Eaves
Keyword(s):  
Cord Blood ◽  
Blood Cells ◽  
Adult Life ◽  
Lymphoid Cells ◽  
Human Cord Blood ◽  
Immunodeficient Mice ◽  
Post Transplant ◽  
Cord Blood Cells

Abstract Throughout adult life, human hematopoiesis is sustained by the activity of a small compartment of pluripotent stem cells with extensive self-renewal potential. Available evidence suggests that these cells undergo a process of progressive lineage restriction similar to that described for murine hematopoietic cells, although many of the intermediate stages of human hematopoiesis have not yet been characterized. In human hematopoietic tissues, cells with short-term (<4 months) as well as long term (>4 months) repopulating activity (termed STRCs and LTRCs, respectively) are distinguished by their differential ability to engraft sublethally irradiated NOD/SCID-β2microglobulin null mice as well as their transient versus sustained output of differentiated cells. In previous studies, both a myeloid-restricted type of human STRC (STRC-M) and a type of STRC with lymphoid as well as myeloid potential (STRC-ML) have been identified. STRC-Ms are CD34+CD38+ and produce mainly erythroid progeny for the first 3–4 weeks post-transplant. In contrast, STRC-MLs are CD34+CD38− and produce progeny only between weeks 5 and 12 post-transplant which consist mainly of B-lymphoid cells plus some granulopoietic cells. We show here that both STRC-MLs and STRC-Ms are similarly distributed among lin- cord blood cells with intermediate to high levels of aldehyde dehydrogenase activity (ALDH-int/hi) as evidenced by staining with the fluorescent dye BAAA. In addition, BAAA-staining has allowed a previously undescribed primitive cell with low ALDH activity (ALDH-lo) and lymphoid-restricted repopulating activity to be identified. Assessment of NOD/SCID-β2microglobulin null mice transplanted with various subsets of cord blood cells further demonstrated that these “STRC-Ls” are CD38− and 10-fold more prevalent in the CD133+ subset of the low-density SSC-low ALDH-lo/neg population but, numerically, are equally distributed between the CD133+ and CD133− fractions because of the proportionately larger size of the CD133− subpopulation. Phenotype analysis of CD34+CD38− cord blood cells revealed a small and distinct ALDH-lo subset that expressed 10-fold higher levels of CD7 than any other CD34+CD38− cells. However, transplantation of this small CD7++ subset into NOD/SCID- β2microglobulin null mice revealed that they accounted for very few of the ALDH-lo STRC-Ls. The discovery of a CD38− ALDH-lo population of lymphoid-restricted human cells with in vivo reconstituting activity identifies a key step in the process of human hematopoietic cell lineage determination and the ability to prospectively isolate these progenitors separately from other types of short- and long-term repopulating cells present in normal human hematopoietic tissues should greatly facilitate future analysis of the mechanisms regulating their normal differentiation or malignant transformation.

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