The Endothelial Antigen ESAM Marks Hematopoietic Stem Cells throughout Life

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 727-727 ◽  
Author(s):  
Takafumi Yokota ◽  
Kenji Oritani ◽  
Stefan Butz ◽  
Koichi Kokame ◽  
Paul W Kincade ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Endothelial Cell ◽  
Hematopoietic Stem Cells ◽  
Blood Cells ◽  
Fetal Liver ◽  
Side Population ◽  
Expression Profiles ◽  
Hematopoietic Stem

Abstract Hematopoietic stem cells (HSC) are an important cell type with the capacity for self-renewal as well as differentiation into multi-lineage blood cells, maintaining the immune system throughout life. Many studies have attempted to identify unique markers associated with these extremely rare cells. In bone marrow of adult mice, the Lin-c-kitHi Sca1+ CD34−/Lo Thy1.1Lo subset is known to include HSC with long-term repopulating capacity. However, several of these parameters differ between strains of mice, change dramatically during developmental age and/or are expressed on many non-HSC during inflammation. Efficient HSC-based therapies and the emerging field of regenerative medicine will benefit from learning more about what defines stem cells. We previously determined that the most primitive cells with lymphopoietic potential first develop in the paraaortic splanchnopleura/aorta-gonad-mesonephros (AGM) region of embryos using Rag1/GFP knock-in mice. We also reported that Rag1/GFP-c-kitHi Sca1+ cells derived from E14.5 fetal liver (FL) reconstituted lympho-hematopoiesis in lethally irradiated adults, while Rag1/GFPLo c-kitHi Sca1+ cells transiently contributed to T and B lymphopoiesis. To extend those findings, microarray analyses were conducted to search for genes that characterize the initial transition of fetal HSC to primitive lymphopoietic cells. The comparisons involved mRNA from Rag1Lo ckitHi Sca1+, early lymphoid progenitors (ELP) and the HSC-enriched Rag1-ckitHi Sca1+ fraction isolated from E14.5 FL. While genes potentially related to early lymphopoiesis were discovered, our screen also identified genes whose expression seemed to correlate with HSC. Among those, endothelial cell-selective adhesion molecule (ESAM) attracted attention because of its conspicuous expression in the HSC fraction and sharp down-regulation on differentiation to ELP. ESAM was originally identified as an endothelial cell-specific protein, but expression on megakaryocytes and platelets was also reported (J. Biol. Chem., 2001, 2002). Flow cytometry analyses with anti-ESAM antibodies showed that the HSC-enriched Rag1-c-kitHi Sca1+ fraction could be subdivided into two on the basis of ESAM levels. The subpopulation with the high density of ESAM was enriched for c-kitHi Sca1Hi cells, while ones with negative or low levels of ESAM were found in the c-kitHi Sca1Lo subset. Among endothelial-related antigens on HSC, CD34 and CD31/PECAM1 were uniformly present on Rag1-c-kitHi Sca1+ cells in E14.5 FL and neither resolved into ESAMHi and ESAM−/Lo fractions. Expression profiles of Endoglin and Tie2 partially correlate with ESAM. The primitive ESAMHi fraction uniformly expressed high levels of Endoglin and Tie2, but many of the more differentiated ESAM−/Lo cells still retained the two markers. ESAM expression correlated well with HSC activity. Cells in the ESAMHi Rag1-ckitHi Sca1+ fraction formed more and larger colonies than those in the ESAM-/Lo Rag1-ckitHi Sca1+ fraction. Particularly, most CFU-Mix, primitive progenitors with both myeloid and erythroid potential, were found in the ESAMHi fraction. In limiting dilution stromal cell co-cultures, we found that 1 in 2.1 ESAMHi Rag1-ckitHi Sca1+ cells and 1 in 3.5 ESAM−/Lo Rag1-ckitHi Sca1+ cells gave rise to blood cells. However, while only 1 in 125 ESAM−/Lo Rag1-ckitHi Sca1+ cells were lymphopoietic under these conditions, 1 in 8 ESAMHi Rag1-ckitHi Sca1+ cells produced CD19+ B lineage cells. In long-term reconstituting assays, ESAMHi Rag1-ckitHi Sca1+ cells contributed highly to the multi-lineage recovery of lympho-hematopoiesis in recipients, but no chimerism was detected in mice transplanted with ESAM−/Lo Rag1-ckitHi Sca1+ cells. These results suggested that HSC in E14.5 FL are exclusively present in the ESAMHi fraction. Tie2+ c-kit+ lympho-hematopoietic cells of E10.5 AGM also expressed high levels of ESAM. Furthermore, ESAM expression in adult bone marrow was detected on primitive progenitors and cells in the side population within the Lin-ckitHi Sca1+ fraction. Interestingly, the expression was up-regulated in aged mice. Based on these observations, we conclude that ESAM marks HSC throughout life in mice. We also observed that many of human cord blood CD34+ CD38− cells express ESAM, suggesting potential application for the purification of human HSC.

Mesenchymal Stem Cells from the Wharton’s Jelly of Umbilical Cord Segments Support the Maintenance of Long Term Culture-Initiating Cells from Cord Blood.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 3650-3650
Author(s):  
Kent W. Christopherson ◽  
Tiki Bakhshi ◽  
Shamanique Bodie ◽  
Shannon Kidd ◽  
Ryan Zabriskie ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Mesenchymal Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Cord Blood ◽  
Umbilical Cord ◽  
Blood Cells ◽  
Hematopoietic Stem ◽  
Cord Blood Cells

Abstract Hematopoietic Stem Cells (HSC) are routinely obtained from bone marrow, mobilized peripheral blood, and umbilical Cord Blood. Traditionally, adult bone marrow has been utilized as a source of Mesenchymal Stem Cells (MSC). Bone marrow derived MSC (BM-MSC) have previously been shown to maintain the growth of HSC obtained from cord blood and have been utilized for cord blood expansion purposes. However, the use of a mismatched BM-MSC feeder stromal layer to support the long term culture of cord blood HSC is not ideal for transplant purposes. The isolation of MSC from a novel source, the Wharton’s Jelly of Umbilical Cord segments, was recently reported (Romanov Y, et al. Stem Cells.2003; 21: 105–110) (Lee O, et al. Blood.2004; 103: 1669–1675). We therefore hypothesized that Umbilical Cord derived MSC (UC-MSC) have the ability to support the long term growth of cord blood derived HSC similar to that previously reported for BM-MSC. To test this hypothesis, MSC were isolated from the Wharton’s Jelly of Umbilical Cord segments and defined morphologically and by cell surface markers. UC-MSC were then tested for their ability to support the growth of pooled CD34+ cord blood cells in long term culture - initiating cell (LTC-IC) assays as compared to BM-MSC. We observed that like BM-MSC, CB-MSC express a defined set of cell surface markers. By flow cytometry we determined that that both UC-MSC and BM-MSC are positive for CD29, CD44, CD73, CD90, CD105, CD166, HLA-A and negative for CD45, CD34, CD38, CD117, HLA-DR expression. Utilizing Mitomycin C treated (200 μM, 15 min.) UC-MSC from multiple donors as a feeder layer we observed that UC-MSC have the ability to support the maintenance of long term hematopoiesis during the LTC-IC assay. Specifically, UC-MSC isolated from separate umbilical cord donors support the growth of 69.6±11.9 (1A), 31.7±3.9 (2B), 67.0±13.5 (3A), and 38.5±13.7 (3B) colony forming cells (CFC) per 1×104 CD34+ cord blood cells as compared to 64.0±4.2 CFC per 1×104 CD34+ cord blood cells supported by BM-MSC (Mean±SEM, N=4 separate segments from three different donors). Thus, Umbilical Cord derived Mesenchymal Stem Cells, a recently described novel source of MSC, have the ability to support long term maintenance of Hematopoietic Stem Cells, as defined by the LTC-IC assay. These results may have potential therapeutic application with respect to ex vivo stem cell expansion of Cord Blood Hematopoietic Stem Cells utilizing a Mesenchymal Stem Cell stromal layer. In addition, these data suggest the possibility of co-transplantation of matched Mesenchymal and Hematopoietic Stem Cells from the same umbilical cord and cord blood donor respectively. Lastly, these results describe a novel model system for the future study of the interaction between Cord Blood Hematopoietic Stem Cells and the appropriate supportive microenvironment represented by the Umbilical Cord - Mesenchymal Stem Cells.

Thrombopoietin Administration Alleviates Hematopoietic Stem Cells Intrinsic Long Term Ionizing Radiation Damages. Identification of Preferential Cellular Expansion Sites

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2441-2441
Author(s):  
Diana Tronik-Le Roux ◽  
Johnny Nehme ◽  
Arthur Simonnet ◽  
Pierre Vaigot ◽  
Marie Anne Nicola ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Ionizing Radiation ◽  
Hematopoietic Stem Cells ◽  
Cellular Response ◽  
Side Population ◽  
Hematopoietic Stem ◽  
Functional Changes ◽  
Progenitor Compartment

Abstract Hematopoietic stem cells (HSC) are indispensable for the integrity of complex and long-lived organisms since they can reconstitute the hematopoietic system for life and achieve long term repopulation of lethally irradiated mice. Exposure of an organism to ionizing radiation (IR) causes dose dependant bone marrow suppression and challenge the replenishment capacity of HSC. Yet, the precise damages that are generated remain largely unexplored. To better understand these effects, phenotypic and functional changes in the stem/progenitor compartments of sublethally irradiated mice were monitored over a ten week period after radiation exposure. We report that shortly after sublethal IR-exposure, HSC, defined by their repopulating ability, still segregate in the Hoechst dye excluding side population (SP); yet, their Sca-1 (S) and c-Kit (K) expression levels are increased and severely reduced, respectively, with a concurrent increase in the proportion of SPSK cells positive for established indicators of HSC presence: CD150+/CD105+ and Tie2+. Virtually all HSCs quickly but transiently mobilize to replenish the bone marrow of myelo-ablated mice. Ten weeks after, whereas bone marrow cellularity has recovered and hematopoietic homeostasis is restored, major phenotypic modifications can be observed within the c-Kit+ Sca-1+ Lin−/low (KSL) stem/progenitor compartment: CD150+/Flk2− and Flk2+ KSL cell frequencies are increased and dramatically reduced, respectively. CD150+ KSL cells also show impaired reconstitution capacity, accrued γ-H2AX foci and increased tendency to apoptosis. This demonstrates that the KSL compartment is not properly restored 10 weeks after sublethal exposure, and that long-term IR-induced injury to the bone marrow proceeds, at least partially, through direct damage to the stem cell pool. Since thrombopoietin (TPO) has been shown to reduce haematopoietic injury when administered immediately after exposure to radiations, we asked whether TPO could restore the permanent IR-induced damage we observed in the HSC compartment. We first found in competitive transplant experiments that a single TPO administration rescued the impaired reconstitution capacity of HSC’s from animals exposed to sublethal IR. In addition, we observed that TPO injection right after irradiation considerably attenuates IR-induced long-term injury to the stem/progenitor compartment. Finally, the use of marrow cells from transgenic ubiquitous luciferase-expressing donors combined with bioluminescence imaging technology provided a valuable strategy that allowed visualizing HSC homing improvements of TPO-treated compared to untreated irradiated donors, and enabled the identification of a preferential cellular expansion sites which were inaccessible to investigation in most studies. Electronic microscopy analysis revealed that these sites show also differential activity of megakaryocytopoiesis with marked differences in the proplatelets reaching the vascular sinus. Altogether, our data provide novel insights in the cellular response of HSC to IR and the beneficial effects of TPO administration to these cells.

scholarly journals Development of adult bone marrow stem cells in H-2-compatible and -incompatible mouse fetuses.

1984 ◽  
Vol 159 (3) ◽  
pp. 731-745 ◽  
Author(s):  
R A Fleischman ◽  
B Mintz
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Fetal Liver ◽  
Donor Strain ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Adult Bone Marrow ◽  
Adult Bone

Bone marrow of normal adult mice was found, after transplacental inoculation, to contain cells still able to seed the livers of early fetuses. The recipients' own hematopoietic stem cells, with a W-mutant defect, were at a selective disadvantage. Progression of donor strain cells to the bone marrow, long-term self-renewal, and differentiation into myeloid and lymphoid derivatives was consistent with the engraftment of totipotent hematopoietic stem cells (THSC) comparable to precursors previously identified (4) in normal fetal liver. More limited stem cells, specific for the myeloid or lymphoid cell lineages, were not detected in adult bone marrow. The bone marrow THSC, however, had a generally lower capacity for self-renewal than did fetal liver THSC. They had also embarked upon irreversible changes in gene expression, including partial histocompatibility restriction. While completely allogeneic fetal liver THSC were readily accepted by fetuses, H-2 incompatibility only occasionally resulted in engraftment of adult bone marrow cells and, in these cases, was often associated with sudden death at 3-5 mo. On the other hand, H-2 compatibility, even with histocompatibility differences at other loci, was sufficient to ensure long-term success as often as with fetal liver THSC.

scholarly journals Neogenin-1 distinguishes between myeloid-biased and balancedHoxb5+mouse long-term hematopoietic stem cells

2019 ◽  
Author(s):  
Gunsagar S. Gulati ◽  
Monika Zukowska ◽  
Joseph Noh ◽  
Allison Zhang ◽  
Rahul Sinha ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Blood Cells ◽  
Surface Marker ◽  
Cycle Phase ◽  
Hematopoietic Stem ◽  
Prospective Isolation

ABSTRACTHematopoietic stem cells (HSCs) self-renew and generate all blood cells. Recent studies with single-cell transplants (1–3) and lineage tracing (4, 5) suggest that adult HSCs are diverse in their reconstitution and lineage potentials. However, prospective isolation of these subpopulations has remained challenging. Here, we identify Neogenin-1 (NEO1) as a unique surface marker on a fraction of mouse HSCs labeled withHoxb5, a specific reporter of long-term HSCs (LT-HSCs) (6). We show that NEO1+Hoxb5+LT-HSCs expand with age and respond to myeloablative stress, while NEO1−Hoxb5+LT-HSCs exhibit no significant change in number. NEO1+Hoxb5+LT-HSCs are more often in the G2/S cell cycle phase compared to NEO1−Hoxb5+LT-HSCs in both young and old bone marrow. Upon serial transplantation, NEO1+Hoxb5+LT-HSCs exhibit myeloid-biased differentiation and reduced reconstitution, while NEO1−Hoxb5+LT-HSCs are lineage-balanced and stably reconstitute recipients. Gene expression comparison reveals increased expression of cell cycle genes and evidence of lineage-priming in the NEO1+fraction. Finally, transplanted NEO1+Hoxb5+LT-HSCs rarely generate NEO1−Hoxb5+LT-HSCs, while NEO1−Hoxb5+LT-HSCs repopulate both LT-HSC fractions. This supports a model in which dormant, balanced, NEO1−Hoxb5+LT-HSCs can hierarchically precede active, myeloid-biased NEO1+Hoxb5+LT-HSCs.SIGNIFICANCE STATEMENTHematopoietic stem cells (HSCs) are rare cells that have the unique ability to regenerate themselves and produce all blood cells throughout life. However, HSCs are functionally heterogeneous and several studies have shown that HSCs can differ in their contribution to major blood lineages. In this study, we discovered that the surface marker, Neogenin-1, can divide mouse HSCs into two subpopulations—one that is more active but biased towards producing myeloid cells and another that is more dormant and capable of equally producing all blood lineages. Neogenin-1 reveals the diversity and hierarchical relationship of HSCs in the mouse bone marrow, enables the prospective isolation of myeloid-biased and balanced HSCs, and opens opportunities to do the same in humans.

Tet2 Uniquely Regulates Self-Renewal and Long Term Repopulating Capacity of Fetal Liver and Bone Marrow Hematopoietic Stem Cells

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 4739-4739
Author(s):  
Hiroyoshi Kunimoto ◽  
Yumi Fukuchi ◽  
Masatoshi Sakurai ◽  
Daichi Abe ◽  
Ken Sadahira ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Peripheral Blood ◽  
Fetal Liver ◽  
Hematologic Malignancies ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Serial Transplantation

Abstract Abstract 4739 Ten-eleven-translocation 2 (TET2) gene is one of the frequent targets of mutation in various hematologic malignancies. These observations suggest critical roles of TET2 dysfunction in their molecular pathogenesis. To investigate physiological roles of TET2 in hematopoiesis, we previously analyzed fetal liver (FL) hematopoiesis of Tet2 gene-trap (Tet2gt) mice and showed that Tet2gt/gt FL cells displayed enhanced self-renewal and long term repopulating (LTR) capacity with expansion of Lineage(−)Sca-1(+)c-Kit(+) (LSK) and common myeloid progenitor (CMP) fractions. However, there remain several questions unanswered. First, self-renewal capacity was examined only by using bulk FL cells and therefore effects of Tet2 loss on purified cell populations such as hematopoietic stem cells (HSCs) or hematopoietic progenitor cells (HPCs) remain elusive. Second, because other groups have reported myeloid transformation in Tet2 conditional knockout mice, it is possible that Tet2 loss confers self-renewal capacity to non-self-renewing myeloid progenitors such as CMPs. Third, effects of Tet2 haploinsufficiency on adult hematopoiesis was not examined using purified HSCs or HPCs. To address these issues, we analyzed E14.5 FL and adult bone marrow (BM) cells from Tet2gt mice. We first performed serial replating assay of FL-LSK cells in methylcellulose containing interleukin (IL)-3, IL-6, stem cell factor (SCF) and erythropoietin (Epo). In this assay, Tet2gt/gt FL-LSK cells showed significantly higher replating capacity as compared to that of WT cells. Interestingly, Tet2gt/gt FL-LSK cells formed various types of colonies including granulocyte-macrophage (GM) and erythrocyte-megakaryocyte (EM) colonies, whereas WT FL-LSK cells generated only GM colonies at the second time of replating, showing that multipotent differentiation capacity was maintained in Tet2gt/gt cells even in the presence of lineage-acting cytokines. Next we examined the self-renewal capacity of highly purified FL-HSCs (CD34+LSK or CD150+LSK cells) by competitive repopulation assay. As expected, the recipients of Tet2gt/gt CD34+LSK cells showed significantly higher donor chimerism in peripheral blood as compared to those receiving WT cells. Furthermore, CD150+LSK cells from Tet2+/gt and Tet2gt/gt FLs demonstrated higher peripheral blood repopulation in the secondary and tertiary recipient mice as compared to that of WT recipients in serial transplantation assay. These results indicate that the enhanced self-renewal and LTR capacity of Tet2-mutant FL cells was uniquely associated with highly purified HSCs. This conclusion also applied to the BM LSK cells from adult mice, since Tet2+/gt BM LSK cells also showed significantly higher peripheral blood contribution compared to the WT cells in serial transplantation assays. This result demonstrates that Tet2 haploinsufficiency is sufficient to confer the enhanced self-renewal and LTR capacity to HSCs in adult hematopoiesis. Lastly, we examined self-renewal capacity of FL CMPs by serial replating assay. Interestingly, Tet2gt/gt FL CMP cells displayed increased replating capacity as compared to WT cells. However, in vivo repopulation assay using Tet2+/+, Tet2+/gt, and Tet2gt/gt FL CMP cells showed no significant difference in peripheral blood chimerism among these recipients. Taken together, enhanced self-renewal and LTR capacity by Tet2 ablation is uniquely associated with HSCs in FL and adult BM, but not with myeloid progenitors, indicating that Tet2 regulates self-renewal program intrinsic to HSCs. In addition, Tet2 haploinsufficiency is sufficient to enhance self-renewal and LTR capacity of HSCs, which explains pathological relation between high incidence of heterozygous TET2 mutations and hematologic malignancies. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Expression of murine CD38 defines a population of long-term reconstituting hematopoietic stem cells

Blood ◽  
1996 ◽  
Vol 87 (10) ◽  
pp. 4057-4067 ◽  
Author(s):  
TD Randall ◽  
FE Lund ◽  
MC Howard ◽  
IL Weissman
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Bone Marrow Cells ◽  
Fetal Liver ◽  
Mouse Strains ◽  
Hematopoietic Stem ◽  
Adult Bone Marrow ◽  
Adult Bone

Using a monoclonal antibody to murine CD38, we showed that a population of adult bone marrow cells that expressed the markers Sca-1 and c-kit but lacked the lineage markers Mac-1, GR-1, B220, IgM, CD3, CD4, CD8 and CD5 could be subdivided by the expression of CD38. We showed that CD38high c-kit+ Sca-1+, linlow/-cells sorted from adult bone marrow cultured with interleukin-3 (IL-3), IL-6, and kit-L produced much larger colonies in liquid culture at a greater frequency than their CD38low/- counterparts. In addition, we found that CD36low/ - cells contained most of the day-12 colony-forming units-spleen (CFU-S) but were not long-term reconstituting cells, whereas the population that expressed higher levels of CD38 contained few, but significant, day-12 CFU-S and virtually all the long-term reconstituting stem cells. Interestingly, the CD38high Sca-1+ c-kit+ linlow/- cells isolated from day-E14.5 fetal liver were also found to be long-term reconstituting stem cells. This is in striking contrast to human hematopoietic progenitors in which the most primitive hematopoietic cells from fetal tissues lack the expression of CD38. Furthermore, because antibodies to CD38 could functionally replace antibodies to Thy-1.1 in a stem cell purification procedure, the use of anti-CD38 may be more generally applicable to the purification of hematopoietic stem cells from mouse strains that do not express the Thy-1.1 allele.

Cultivation of aorta-gonad-mesonephros–derived hematopoietic stem cells in the fetal liver microenvironment amplifies long-term repopulating activity and enhances engraftment to the bone marrow

Blood ◽  
2002 ◽  
Vol 99 (4) ◽  
pp. 1190-1196 ◽  
Author(s):  
Masaki Takeuchi ◽  
Takashi Sekiguchi ◽  
Takahiko Hara ◽  
Taisei Kinoshita ◽  
Atsushi Miyajima
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Developmental Process ◽  
Fetal Liver ◽  
Hematopoietic Cells ◽  
Hematopoietic Stem ◽  
Hematopoietic Organ ◽  
Coculture System

During mammalian development, definitive hematopoietic stem cells (HSCs) arise in the aorta-gonad-mesonephros (AGM) region and colonize the fetal liver (FL) before hematopoiesis occurs in the bone marrow. The FL is a unique hematopoietic organ where both HSCs and mature blood cells are actively generated along with functional maturation of hepatic cells as a metabolic organ. To characterize HSCs and FL microenvironments during development, this study establishes a coculture system composed of AGM-originated HSCs and FL nonhematopoietic cells. The results demonstrate that FL cells support significant expansion of lineage-committed hematopoietic cells as well as immature progenitors. More important, long-term repopulating activity was amplified from AGM-originated HSCs in this coculture system. Engraftment of HSCs to the bone marrow was strongly enhanced by coculture. In addition, AGM HSCs produced significantly more hematopoietic cells than E14.5 and E18.5 FL HSCs in vitro. These results suggest that the FL microenvironment not only stimulates expansion of the hematopoietic system, but also possibly modifies the characteristics of AGM HSCs. Thus, this coculture system recapitulates the developmental process of HSCs and the FL microenvironment and provides a novel means to study the development of hematopoiesis.

Murine Hematopoietic Stem Cells Require Akt1 and Akt2 for Long-Term Self-Renewal

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 502-502
Author(s):  
Marisa M. Juntilla ◽  
Vineet Patil ◽  
Rohan Joshi ◽  
Gary A. Koretzky
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Fetal Liver ◽  
Akt Signaling ◽  
Self Renewal ◽  
Hematopoietic Stem

Abstract Murine hematopoietic stem cells (HSCs) rely on components of the Akt signaling pathway, such as FOXO family members and PTEN, for efficient self-renewal and continued survival. However, it is unknown whether Akt is also required for murine HSC function. We hypothesized that Akt would be required for HSC self-renewal, and that the absence of Akt would lead to hematopoietic failure resulting in developmental defects in multiple lineages. To address the effect of Akt loss in HSCs we used competitive and noncompetitive murine fetal liver-bone marrow chimeras. In short-term assays, Akt1−/−Akt2−/− fetal liver cells reconstituted the LSK compartment of an irradiated host as well or better than wildtype cells, although failed to generate wildtype levels of more differentiated cells in multiple lineages. When placed in a competitive environment, Akt1−/−Akt2−/− HSCs were outcompeted by wildtype HSCs in serial bone marrow transplant assays, indicating a requirement for Akt1 and Akt2 in the maintainance of long-term hematopoietic stem cells. Akt1−/−Akt2−/− LSKs tend to remain in the G0 phase of the cell cycle compared to wildtype LSKs, suggesting the failure in serial transplant assays may be due to increased quiesence in the absence of Akt1 and Akt2. Additionally, the intracellular content of reactive oxygen species (ROS) in HSCs is dependent on Akt signaling because Akt1−/−Akt2−/− HSCs have decreased ROS levels. Furthermore, pharmacologic augmentation of ROS in the absence of Akt1 and Akt2 results in an exit from quiescence and rescue of differentiation both in vivo and in vitro. Together, these data implicate Akt1 and Akt2 as critical regulators of long-term HSC function and suggest that defective ROS homeostasis may contribute to failed hematopoiesis.

scholarly journals The repopulation potential of fetal liver hematopoietic stem cells in mice exceeds that of their liver adult bone marrow counterparts

Blood ◽  
1996 ◽  
Vol 87 (8) ◽  
pp. 3500-3507 ◽  
Author(s):  
VI Rebel ◽  
CL Miller ◽  
CJ Eaves ◽  
PM Lansdorp
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Blood Cells ◽  
Fetal Liver ◽  
Hematopoietic Stem ◽  
Adult Bone Marrow ◽  
Significant Difference ◽  
Adult Bone ◽  
Marrow Cells

Varying, limiting numbers of unseparated or purified cells (Ly-5.1), either from 14.5-day-old fetal liver (FL) or from adult bone marrow (BM) were coinjected with 10(5) unseparated BM cells (Ly-5.2) into lethally irradiated adult C57B1/6 recipients (Ly-5.2). The kinetics of donor cell repopulation of the lymphoid and myeloid compartments by Ly- 5.1+ donor hematopoietic stem cells (ie, competitive repopulation units [CRU]) were monitored at various time points after the transplantation by Ly-5 analysis of the peripheral white blood cells (WBC). Recipients that had received on average less than 2 adult BM or FL CRU did not show a significant difference in the level of donor-reconstitution when analyzed 4 weeks after the transplantation, However, at 8 and 16 weeks, the FL recipients showed a significantly higher percentage of donor- derived nucleated peripheral blood cells than did the recipients of adult BM cells. Analysis of individual mice showed that approximately 80% of the recipients of FL CRU showed an increase in mature WBC output between 4 and 8 weeks after transplantation, whereas this occurred in less than 40% in the recipients of adult BM cells. In addition to this effect on mature cell output, the cellularity of the reconstituted BM was significantly higher in recipients of FL CRU than in recipients of adult BM CRU, even at 7 to 9 months after transplantation, which is consistent with an increased clonal expansion of FL CRU. When marrow cells from primary recipients of FL CRU were injected into secondary recipients, a significantly higher percentage of these mice showed donor-reconstitution of their lymphoid and myeloid compartments (P < .01) and to a greater extent (P < .008) as compared with mice that had received marrow cells from primary recipients of similar numbers of adult BM CRU. Taken together, these results show that individual FL CRU exhibit a greater proliferative activity in vivo than similar cells from adult BM that is accompanied by a greater production of daughter CRU.

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