Robo4/Magic Roundabout Is a Novel Surface Marker for Murine and Human Hematopoietic Stem Cells.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 682-682
Author(s):  
Fumi Shibata ◽  
Yuko Goto-Koshino ◽  
Miyuki Ito ◽  
Yumi Fukuchi ◽  
Yoshihiro Morikawa ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Cell Surface ◽  
Hematopoietic Stem Cells ◽  
Surface Markers ◽  
Hematopoietic Stem ◽  
Hematopoietic System ◽  
Cd34 Cells ◽  
Human Hscs

Abstract A variety of cell surface markers such as c-Kit, Sca-1, CD34 and Flt-3 have been utilized to prospectively isolate murine or human hematopoietic stem cells (HSCs). While murine HSCs were shown to be highly enriched in CD34−c-Kit+Sca-1+Lineage- (CD34−KSL) fraction, this population is still not homogeneous for long-term HSCs. In human, CD34+ cells are regarded as crude HSC fraction and used for clinical applications. However, quiescent human HSCs are also found in CD34− fraction, indicating that CD34 is not a bona fide marker for human HSC. Thus, novel surface markers that can be used to purify human or murine HSCs to homogeneity need to be identified. Roundabout (Robo) family proteins are immunoglobulin-type cell surface receptors that are predominantly expressed in nervous system. Slit2, a ligand for Robo, is a large leucine-rich repeat-containing secreted protein that is also expressed in brain. By binding with Robo, Slit2 acts as a repellant for axon guidance of developing neurons and they are critical for correct wiring of neuronal network. Robo family comprises four family members, Robo1 – Robo4, and Robo4 is distinct in that it is expressed specifically in endothelial cells, but not in brain. In this study, we investigated Robo4 for its possible application for HSC identification in murine and human hematopoietic system. By RT-PCR, Robo4 was specifically expressed in murine KSL fraction, and was not expressed in lineage positive cells and various progenitors such as common myeloid progenitor (CMP), granulocyte-monocyte progenitor (GMP), megakaryocyte/erythroid progenitor (MEP) and common lymphoid progenitor (CLP). Moreover, the expression of Robo4 was highest in side population of KSL cells (KSL-SP), and moderate in KSL-main population (KSL-MP) cells. Monoclonal antibody raised against Robo4 identified its high expression in KSL cells by FACS. FACS analysis of human cord blood cells revealed that Robo4 is highly expressed in CD34+ cells, and CD34+Robo4high population fell into CD38− fraction, which enriches human HSCs. Bone marrow transplantation experiments revealed that Robo4+ fraction of murine KSL cells had long-term repopulating activity, while Robo4−KSL cells not. Although both Robo4+ and Robo4− CD34−KSL cells repopulated murine hematopoietic system for long-term, Robo4+CD34−KSL cells achieved higher chimerism after repopulation compared with Robo4−CD34−KSL. To investigate the physiological role of Robo4 in HSC homeostasis, we next examined the expression of Slit2 in hematopoietic system. Interestingly, Slit2 is specifically expressed in bone marrow stromal cells, but not in hematopoietic cells. Moreover, Slit2 is induced in osteoblasts, a critical cellular component composing HSC niche, in response to myelosuppressive stress such as 5FU treatment. These results indicate that Robo4 is expressed in murine and human hematopoietic HSCs and useful for HSC purification, and Robo4 - Slit2 system may play a role in HSC physiology in niche environment under hematopoietic stress.

Reversibility of CD34 expression on human hematopoietic stem cells that retain the capacity for secondary reconstitution

Blood ◽  
2003 ◽  
Vol 101 (1) ◽  
pp. 112-118 ◽  
Author(s):  
Mo A. Dao ◽  
Jesusa Arevalo ◽  
Jan A. Nolta
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Cell Surface ◽  
Hematopoietic Stem Cells ◽  
Progenitor Cells ◽  
Hematopoietic Stem ◽  
Human Cd34 ◽  
Cd34 Cells ◽  
Cd34 Expression

Abstract The cell surface protein CD34 is frequently used as a marker for positive selection of human hematopoietic stem/progenitor cells in research and in transplantation. However, populations of reconstituting human and murine stem cells that lack cell surface CD34 protein have been identified. In the current studies, we demonstrate that CD34 expression is reversible on human hematopoietic stem/progenitor cells. We identified and functionally characterized a population of human CD45+/CD34− cells that was recovered from the bone marrow of immunodeficient beige/nude/xid (bnx) mice 8 to 12 months after transplantation of highly purified human bone marrow–derived CD34+/CD38− stem/progenitor cells. The human CD45+ cells were devoid of CD34 protein and mRNA when isolated from the mice. However, significantly higher numbers of human colony-forming units and long-term culture-initiating cells per engrafted human CD45+ cell were recovered from the marrow of bnx mice than from the marrow of human stem cell–engrafted nonobese diabetic/severe combined immunodeficient mice, where 24% of the human graft maintained CD34 expression. In addition to their capacity for extensive in vitro generative capacity, the human CD45+/CD34− cells recovered from thebnx bone marrow were determined to have secondary reconstitution capacity and to produce CD34+ progeny following retransplantation. These studies demonstrate that the human CD34+ population can act as a reservoir for generation of CD34− cells. In the current studies we demonstrate that human CD34+/CD38− cells can generate CD45+/CD34− progeny in a long-term xenograft model and that those CD45+/CD34− cells can regenerate CD34+ progeny following secondary transplantation. Therefore, expression of CD34 can be reversible on reconstituting human hematopoietic stem cells.

scholarly journals CD150− side population cells represent a functionally distinct population of long-term hematopoietic stem cells

Blood ◽  
2008 ◽  
Vol 111 (4) ◽  
pp. 2444-2451 ◽  
Author(s):  
David C. Weksberg ◽  
Stuart M. Chambers ◽  
Nathan C. Boles ◽  
Margaret A. Goodell
Keyword(s):  
Stem Cells ◽  
Cell Surface ◽  
Hematopoietic Stem Cells ◽  
Cell Biology ◽  
Side Population ◽  
Surface Markers ◽  
Cell Surface Markers ◽  
Hematopoietic Stem ◽  
Slam Family

Hematopoietic stem cells (HSCs) are a self-renewing population of bone marrow cells that replenish the cellular elements of blood throughout life. HSCs represent a paradigm for the study of stem-cell biology, because robust methods for prospective isolation of HSCs have facilitated rigorous characterization of these cells. Recently, a new isolation method was reported, using the SLAM family of cell-surface markers, including CD150 (SlamF1), to offer potential advantages over established protocols. We examined the overlap between SLAM family member expression with an established isolation scheme based on Hoechst dye efflux (side population; SP) in conjunction with canonical HSC cell-surface markers (Sca-1, c-Kit, and lineage markers). Importantly, we find that stringent gating of SLAM markers is essential to achieving purity in HSC isolation and that the inclusion of canonical HSC markers in the SLAM scheme can greatly augment HSC purity. Furthermore, we observe that both CD150+ and CD150− cells can be found within the SP population and that both populations can contribute to long-term multilineage reconstitution. Thus, using SLAM family markers to isolate HSCs excludes a substantial fraction of the marrow HSC compartment. Interestingly, these 2 subpopulations are functionally distinct, with respect to lineage output as well as proliferative status.

Expression of Endomucin, a CD34-Like Sialomucin, Marks Definitive Hematopoietic Stem Cells throughout Development.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 563-563
Author(s):  
Azusa Maeda ◽  
Atsushi Iwama ◽  
Koji Eto ◽  
Hideo Ema ◽  
Toshio Kitamura ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Cell Surface ◽  
Hematopoietic Stem Cells ◽  
Signal Sequence ◽  
High Yield ◽  
Specific Gene ◽  
Mouse Bone Marrow ◽  
Hematopoietic Stem ◽  
Cd34 Cells

Abstract In order to identify cell surface molecules specific to hematopoietic stem cells (HSCs), a modified signal sequence trap was applied to mouse bone marrow (BM) CD34− c-Kit+ sca-1+ lineage− (CD34−KSL) cells which is highly enriched for HSCs. Among the identified genes, mRNA expression of Endomucin, an endothelium-specific gene encoding a CD34-like sialomucin, appeared highly specific to CD34-KSL HSCs. To further investigate the expression of Endomucin, we generated two rat anti-mouse Endomucin monoclonal antibodies that recognize different epitopes (AE2D4, AE7F2). Taking advantage of these and another monoclonal antibody, V7c7 (1999, Blood, 93; 1; 165), detailed expression analysis was performed. Endomucin expression was largely confined to lineage markers-negative (Lin−) cells. Approximately 7 % of Lin− cells were Endomucin-positive. Cells strongly expressing Endomucin represented 30% of c-kit+ sca-1+ cells. Gating out CD34+ cells from Lin− Endomucin+ population resulted in high yield of KSL cells. High correlation between Lin− Endomucin+CD34− cells and KSL cells was confirmed by in vivo bone marrow transplantation. When Lin− cells were fractionated by their expression of CD34 and Endomucin, only Lin− Endomucin+CD34− cells contributed to long-term repopulation (LTR), and as few as 100 cells were enough to obtain engraftment. Furthermore, the majority of CD34−KSL cells were Endomucin+, and again, only CD34−KSL-Endomucin+ cells had LTR activity. These data indicate two facts: 1) A single positive marker, Endomucin can substitute for c-kit+ sca-1+, 2) All LTR -HSCs express Endomucin. We then analyzed the expression of Endomucin during embryonic development of the hematopoietic system. Definitive HSCs arise from the hemogenic endothelium lining the wall of the dorsal aorta in embryonic aorta-gonads-mesonephros (AGM) region, then seed to the fetal liver. E10.5 AGM CD45− cells were segregated into subpopulations by their expression of Endomucin and CD41, an early marker of embryonic hematopoiesis. In vitro coculture system with a stromal cell line, OP9, was applied to detect the ability of hematopoietic potential. Hematopoietic activity was exclusively found in the CD41+Endomucin+ population, that represents 24% of CD41+ cells. Taken together, these data indicate that Endomucin marks both embryonic and adult HSCs, providing a novel useful cell surface marker for definitive HSCs throughout development. Figure Figure

Plxdc2 Marks Hematopoietic Stem Cells and Th2 Cytokine-Producing Innate Lymphocytes in Adult Bone Marrow

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1278-1278
Author(s):  
Yasushi Kubota ◽  
Ivo Lieberam ◽  
Shinya Kimura ◽  
Thomas M Jessell ◽  
Shin-Ichi Nishikawa
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
T Cell ◽  
Cell Surface ◽  
Hematopoietic Stem Cells ◽  
Cell Population ◽  
Specific Marker ◽  
Simple Method ◽  
Hematopoietic Stem

Abstract Abstract 1278 Hematopoietic stem cells (HSCs) have been highly enriched using combinations of more than 10 surface markers. However the simple method using a few positive markers is preferable to identify HSCs location in tissue section. We performed a stringent comparative gene expression profiling analysis to find genes preferentially expressed in the HSC population, and identified a total of 63 genes that are highly expressed in HSC among various hematopoietic cell population. In order to find HSC-specific marker we focused on genes encoding cell surface protein, and found that plexin domain containing 2 (Plxdc2) is highly expressed in CD34—c-Kit+Sca-1+Lineage−(CD34−KSL) HSC population using Plxdc2::GFP knock-in mice. Only 0.2% of whole bone marrow cells were Plxdc2+, and competitive repopulation assay clearly showed that all HSCs are included in the Plxdc2+ fraction. These results identify Plxdc2 as a new marker of HSCs. Plxdc2+ population contain not only HSCs but uncharacterized c-Kitlow/−Sca-1+Lineage−cells. To further purify HSCs, we investigated the additional positive marker. Throughout the screening of various known HSC-related marker, CD150 was selected. CD150 is already recognized as a positive HSC marker (Kiel, et al. Cell 2005). The Plxdc2+CD150+ fraction represented only 0.1%±0.002% in whole bone marrow, and 6% in c-Kit+Sca-1+Lineage− cells, respectively. To test whether the combination of Plxdc2 and CD150 with or without other markers can highly enrich long-term HSCs, we competitively reconstituted irradiated mice with single Plxdc2+CD150+ cells or single Plxdc2+CD150+c-Kit+Sca-1+Lineage− cells. One out of every 4.6 Plxdc2+CD150+ cells (22%), and one out of 2.2 Plxdc2+CD150+c-Kit+Sca-1+Lineage− cells (44%) engrafted and gave long-term multi-lineage reconstitution. The simple combination of Plxdc2 and CD150 significantly increased HSC purity. In addition, we found robust levels of PLXDC2 transcripts in purified human cord blood CD34+ HSCs. Next, we attempted to characterize the another Plxdc2+ fraction which is c-Kitlow/−Sca-1+Lineage−. Multicolor flowcytometric analysis revealed that Plxdc2+c-Kitlow/−Sca-1+Lineage− cells uniformly express CD45, IL7Rα, Thy-1.2, CD27, T1/ST2 (IL1RL1, a subunit of IL33R) and CD25. These cell surface phenotype indicated that this population is probably of lymphoid lineage. However, culturing Plxdc2+ c-Kit low/−Sca-1+Lineage− cells on OP9-DL1, which supports the development of T-cell progenitors to mature T-cells, did not induce T-cell differentiation. Plxdc2+c-Kitlow/−Sca-1+Lineage−cells also did not differentiate into B cells when co-cultured with OP9 stroma cell line. Furthermore Plxdc2+c-Kitlow/−Sca-1+Lineage− cells produce IL-5 and IL-13 in response to IL-33 or a combination of IL-2 and IL-25. These characteristics resemble that of “natural helper (NH) cells”, a recently identified cell population capable of producing large amounts of Th2 cytokines in fat-associated lymphoid clusters (Moro, et al. Nature 2010). Immunohistochemical staining of bone section to detect HSCs, and functional analyses to clarify why Plxdc2 specifically express in HSCs and bone marrow “NH cells” using Plxdc2-deficient mice are our ongoing tasks. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Long-term repopulation of irradiated mice with limiting numbers of purified hematopoietic stem cells: in vivo expansion of stem cell phenotype but not function

Blood ◽  
1995 ◽  
Vol 85 (4) ◽  
pp. 1006-1016 ◽  
Author(s):  
GJ Spangrude ◽  
DM Brooks ◽  
DB Tumas
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Cell Surface ◽  
Hematopoietic Stem Cells ◽  
Peripheral Blood ◽  
Antigen Expression ◽  
Hematopoietic Stem ◽  
Surface Antigen Expression

Hematopoietic stem cells were isolated from normal adult mouse bone marrow based on surface antigen expression (Thy-1.1(low)Lin(neg)Ly- 6A/E+) and further selected for low retention of rhodamine 123. This population of cells (Rh-123low) could mediate radioprotection and long- term (greater than 12 months) repopulation after transplantation of as few as 25 cells. Transfer of five genetically marked Rh-123low cells in the presence of 10(5) normal bone marrow cells resulted in reconstitution of peripheral blood by greater than 10% donor cells in 64% (30 of 47) of recipient mice. Of 46 animals surviving after 24 weeks, 10 had over 50% donor-derived cells in peripheral blood. Two general patterns of long-term reconstitution were observed: one in which many donor-derived cells were observed 5 to 6 weeks after reconstitution and another in which donor-derived cells were rare initially but expanded with time. This result suggests that two classes of long-term repopulating hematopoietic stem cells exist, differing in their ability to function early in the course of transplantation. Alternatively, distinct anatomic sites of engraftment may dictate these two outcomes from a single type of cell. As an approach to measure the extent of self-renewal by the injected cells, recipients of five or 200 stem cells were killed 8 to 13 months after the transplants, and Thy- 1.1(low)Lin(neg)Ly-6A/E+ progeny of the original injected cells were isolated for a second transplant. While a numerical expansion of cells expressing the cell surface phenotype of stem cells was observed, along with activity in the colony-forming unit-spleen assay, the expanded cells were vastly inferior in radioprotection and long-term reconstitution assays when compared with cells freshly isolated from normal animals. This result demonstrates that in stem cell expansion experiments, cell surface antigen expression is not an appropriate indicator of stem cell function.

scholarly journals CD66e Enrichment Enhances Repopulation of Human Long-Term Hematopoietic Stem Cells

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 2156-2156
Author(s):  
Kuiying Ma ◽  
Riguo Fang ◽  
Lingling Yu ◽  
Yongjian Zhang ◽  
Chao Li ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Surface Markers ◽  
Post Transplantation ◽  
Hematopoietic Stem ◽  
Differentiation Pattern ◽  
Human Hscs

Abstract Gene-modified hematopoietic stem cells (HSCs) therapy has demonstrated remarkable success for the treatment of inherited blood disorders. As the origin of hematologic hierarchy, HSCs play an essential role in sustaining life-long hematopoiesis. HSCs identification via reliable and robust bio-markers could facilitate the development of HSC gene therapy. Previous studies showed that long-term hematopoietic stem cells (LT-HSCs) were enriched in the Lin -CD34 +CD38 -CD45RA -CD90 +CD49f + population which could support long-term hematopoietic reconstitution. However, several of these surface markers proved to be unreliable when ex vivo culturing, such as CD38 and CD49f. Thus, HSCs characterization is still hindered by lacking bona-fide bio-markers, and consequently identification of long-term HSCs still needs time-consuming in vivo transplantation. To this end, we performed in vitro screening and comprehensive functional evaluation to identify a novel surface marker of human HSCs. During initial screening, a cell surface antigen screen panel (including 242 human cell surface markers) and human CD34 and CD90 antibodies were used to perform flow cytometry analysis on CD34 + HSPCs enriched from umbilical cord blood. Compared with CD34 + cell population, we found that CD66 (a,c,d,e), CD200 and CD48 positive cells were more enriched in CD34 +CD90 + subset. Previous studies indicated that HSCs cannot be maintained during in vitro culturing. By tracking these candidate surface markers based on this principle, CD66e was selected as the potential HSCs bio-marker. Next, we examined the in vivo hematologic repopulating potential of HSCs by limiting dilution assay (LDA) on immune-deficient mouse model. We sorted CD66e + and CD66e - subsets from CD34 +CD90 +CD45RA - subpopulation, and transplanted into irradiated NOD-scid Il2rg −/− (NPG) mice respectively. At week16 post-transplantation, in contrast to the CD66e - group, CD66e + cells exhibited significantly higher reconstitution in peripheral blood (PB), bone marrow (BM) and spleen. Engraftment dynamics revealed that the CD66e - group were only capable of reconstitution 4 weeks post transplantation, even at the highest initial cell dose. Moreover, the CD66e - group displayed impaired multi-lineage differentiation pattern, especially in PB and BM samples, while the CD66e + group presented a robust multi-lineage reconstitution. Notably, LDA results showed that the CD66e + cells within CD34 +CD90 +CD45RA - population contained 1 out of 529 SCID repopulating cells (SRC), almost 60-fold greater than the CD66e - fraction. To further investigate the long-term repopulating potential of the CD66e + cells, we performed the secondary transplantation collected from the BM cells of primary recipients. CD66e + cells presented significant higher repopulating activity than CD66e- subset in the secondary recipients. These findings reveal that the major cells with homing and long-term reconstitution capacity among CD34 +CD90 +CD45RA - cells were CD66e positive. In order to determine the transcriptional profile of CD66e + cells, we performed RNA-sequencing analysis using the population of CD34 + cells, CD34 +CD90 +CD45RA - cells, CD66e + and CD66e - cells within CD34 +CD90 +CD45RA - subset. Remarkably, compared with other groups, the CD66e + cells displayed a bias toward the signature of HSC and early progenitors such as LMPP and CLP. Moreover, gene set enrichment analysis showed that hematopoietic lineage and long-term potentiation-related genes were highly enriched in the CD66e + cells. Further qRT-PCR experiment confirmed that several HSC-related genes were significantly higher expressed in CD34 +CD90 +CD45RA -CD66e + cells, compared to CD66e - population or CD34 + HSPCs, suggesting that the gene expression profile of CD66e + cells is reminiscent of HSC signature. Altogether, we demonstrate that CD66e is a robust functional HSC bio-marker that CD66e-positive population among CD34 +CD90 +CD45RA - cells exhibit typical HSC signature, enhanced in vivo engraftment potential and robust multilineage differentiation pattern, which will provide an invaluable tool to investigate the origin of human HSCs, paving the way for the therapeutic application. Figure 1 Figure 1. Disclosures Fang: EdiGene, Inc.: Current Employment.

scholarly journals Etoposide-Initiated MLL Rearrangements Detected at High Frequency in Human Primitive Hematopoietic Stem Cells with In Vitro and In Vivo Long-Term Repopulating Potential.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 98-98 ◽  
Author(s):  
Jolanta Libura ◽  
Marueen Ward ◽  
Grzegorz Przybylski ◽  
Christine Richardson
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Scid Mouse ◽  
P Value ◽  
Hematopoietic Stem ◽  
Cd34 Cells

Abstract Rearrangements involving the MLL gene locus at chromosome band 11q23 are observed in therapy-related acute myeloid leukemia and myelodysplastic syndromes following treatment with topoisomerase II (topoII) inhibitors including etoposide. We have shown that one hour of etoposide exposure (20–50 μM) stimulates stable MLL rearrangements in primary human CD34+ cells and that the spectrum of repair products within MLL gene is broader than so far described (Libura et al, Blood, 2005). Clinical data suggest that MLL-associated malignant leukemias originate within primitive hematopietic stem cells capable of differentiation into all hematopoietic lineages and repopulation of myelo-ablated hosts. These cells can be analyzed using the in vivo NOD-SCID mouse model as well as the in vitro long-term culture initiating cell (LTC-IC) assay. We adopted our in vitro CD34+ cell culture model to investigate the impact of etoposide exposure on the most primitive hematopoietic stem cells using parallel assays for LTC-IC and NOD-SCID Repopulating Cells (SRC). Following etoposide exposure (20–50 μM for 1 hour), and 48–96 hours recovery in vitro, untreated control and etoposide-treated CD34+ cells were either seeded in LTC-IC with a supportive feeder layer (Stem Cell Technologies, Inc.), or injected into NOD-SCID mice (0.1–1.5x106 cells per mouse). After 12 weeks, both LTC-IC cultures and bone marrow cells from NOD-SCID mice were seeded in methylcellulose media supplemented with growth factors that promote only human cell colony formation. An increased number of colonies in etoposide-treated samples was obtained from LTC-IC cultures in 3 out of 5 experiments (p value<0.05). This increase in colony number was more dramatic in etoposide-treated samples from NOD-SCID bone marrow (57 versus 0, 8 versus 0). These data demonstrate that etoposide exposure can significantly alter the potential of early hematopoietic stem cells to survive and proliferate both in vitro and in vivo. Injection of as few as 3x105 CD34+ cells into a NOD-SCID mouse was sufficient to obtain methylcellulose colonies, suggesting that this method can be used for the analysis of cells obtained from a single patient sample. Mutation analysis of human methylcellulose colonies derived from both LTC-IC and NOD-SCID was performed by inverse PCR and ligation-mediated PCR followed by sequencing. This analysis revealed that rearrangements originating within the MLL breakpoint cluster region (bcr) were present in 12 out of 29 colonies from etoposide-treated samples versus 5 out of 39 colonies from control samples (p value <0.01), demonstrating that etoposide exposure promotes stable rearrangements within a hematopoietic stem cell compartment with significant proliferative potential. Eight of the 17 events were sequenced, and showed 6 MLL tandem duplications within intron 8, one complex translocation between MLL and chr.15 and tandem duplication, and one event with foreign sequence of unknown origin. Our data are the first report of the spectrum and frequency of MLL rearrangements following topo II inhibitor exposure in a cell population thought to be the target for recombinogenic events leading to therapy-related leukemias.

Role of Protection of Telomeres 1A (Pot1a) In the Regulation of Hematopoietic Stem Cells.

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2617-2617
Author(s):  
Fumio Arai ◽  
Kentaro Hosokawa ◽  
Yumiko Nojima ◽  
Toshio Suda
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Telomerase Activity ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Cd34 Cells

Abstract Abstract 2617 Hematopoietic stem cells (HSCs) undergo self-renewing cell divisions and maintain blood cell production throughout the lifetime. Appropriate control of HSC self-renewal is critical for the maintenance of hematopoietic homeostasis. Telomeres are nucleoprotein structures that cap the ends of eukaryotic chromosomes, and shelterin is required for the stability of telomeres. It is known that HSCs have telomerase activity and maintains telomere lengths longer than those of differentiated cells. The accelerated telomere erosion reduces the long-term repopulating capacity of HSCs in mutant mice, suggesting that keeping the telomerase activity and telomere structures is critical for the maintenance of HSCs. On the other hand, it has been shown that the maintenance of cell cycle quiescence and self-renewal activity of HSCs largely depend on the interaction with the bone marrow niches. We previously reported that the interaction of Tie2 in HSCs with its ligand angiopietin-1 (Ang-1) in niche cells in bone marrow (BM) endosteum is critical for the maintenance of HSC quiescence (Arai 2004). In this study, we found that Ang-1 upregulated the expression of protection of telomeres 1A (Pot1a) in side-population (SP) cells within Lin–Sca-1+c-Kit+ (LSK) fraction, and further investigated the role of Pot1a in the regulation of HSCs. Pot1 has been proposed to form a part of the six-protein shelterin complex at telomeres. In mice, there are two genes encoding Pot1-related proteins, Pot1a and Pot1b. Knockout of Pot1a results in early embryonic lethality, whereas mice lacking Pot1b are alive and fertile, suggesting that Pot1a is essential for mouse development. We found that long-term HSC population, LSK-CD34– cells, expressed higher levels of Pot1a than short-term HSCs population, LSK-CD34+ cells, both in transcriptional and protein level. To analyze the function of Pot1a in the maintenance of HSCs, we transduced Pot1a in LSK cells and examined the colony formation and long-term BM reconstitution capacities. Overexpression of Pot1a increased the size of colonies compared to control. In addition, the number of high proliferative potential colony-forming cells (HPP-CFC) was increased by the overexpression of Pot1a after long-term culture. There was no significant difference in long-tern reconstitution capacity after the primary bone marrow transplantation (BMT) between Pot1a-transduced LSK cells and control. After the secondary BMT, however, Pot1a-transduced LSK cells showed higher reconstitution activity than control. Moreover, Pot1a-transduced cells increased the frequency of Ki67-negative cells after the primary and the secondary BMT compared with control. Next, we transduced Pot1a shRNA into LSK cells and examined the effect of Pot1a-knockdown on the regulation of HSCs. The number of colonies derived from Pot1a-knockdown LSK cells was significantly decreased compared to control. In addition, knockdown of Pot1a significantly reduced long-term reconstitution activity of LSK cells after BMT. These data suggest that Pot1a plays a critical role in the maintenance of self-renewal activity and cell cycle quiescence of HSCs. We will also discuss about the dependence of the Pot1a function in HSCs on the telomerase activity. Disclosures: No relevant conflicts of interest to declare.

Human CD34+ hematopoietic stem cells capable of multilineage engrafting NOD/SCID mice express flt3: distinct flt3 and c-kit expression and response patterns on mouse and candidate human hematopoietic stem cells

Blood ◽  
2003 ◽  
Vol 102 (3) ◽  
pp. 881-886 ◽  
Author(s):  
Ewa Sitnicka ◽  
Natalija Buza-Vidas ◽  
Staffan Larsson ◽  
Jens M. Nygren ◽  
Karina Liuba ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Cord Blood ◽  
Severe Combined Immunodeficiency ◽  
Scid Mice ◽  
Striking Difference ◽  
Hematopoietic Stem ◽  
Human Hscs

Abstract The cytokine tyrosine kinase receptors c-kit and flt3 are expressed and function in early mouse and human hematopoiesis. Through its ability to promote ex vivo expansion and oncoretroviral transduction of primitive human hematopoietic progenitors, the flt3 ligand (FL) has emerged as a key stimulator of candidate human hematopoietic stem cells (HSCs). However, recent studies in the mouse suggest that though it is present on short-term repopulating cells, flt3 is not expressed on bone marrow long-term reconstituting HSCs, the ultimate target for the development of cell replacement and gene therapy. Herein we demonstrate that though only a fraction of human adult bone marrow and cord blood CD34+long-term culture-initiating cells (LTC-ICs) express flt3, most cord blood lymphomyeloid HSCs capable of in vivo reconstituting nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice are flt3+. The striking difference in flt3 and c-kit expression on mouse and candidate human HSCs translated into a corresponding difference in flt3 and c-kit function because FL was more efficient than SCF at supporting the survival of candidate human HSCs. In contrast, SCF is far superior to FL as a viability factor for mouse HSCs. Thus, the present data provide compelling evidence for a contrasting expression and response pattern of flt3 and c-kit on mouse and human HSCs.

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