scholarly journals Fibronectin and Its Receptors in Hematopoiesis

Cells ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 2717
Author(s):  
Franziska Wirth ◽  
Alexander Lubosch ◽  
Stefan Hamelmann ◽  
Inaam A. Nakchbandi
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Matrix Protein ◽  
Cell Types ◽  
Extracellular Matrix Protein ◽  
In Vivo Models ◽  
Hematopoietic Stem ◽  
Almost All

Fibronectin is a ubiquitous extracellular matrix protein that is produced by many cell types in the bone marrow and distributed throughout it. Cells of the stem cell niche produce the various isoforms of this protein. Fibronectin not only provides the cells a scaffold to bind to, but it also modulates their behavior by binding to receptors on the adjacent hematopoietic stem cells and stromal cells. These receptors, which include integrins such as α4β1, α9β1, α4β7, α5β1, αvβ3, Toll-like receptor-4 (TLR-4), and CD44, are found on the hematopoietic stem cell. Because the knockout of fibronectin is lethal during embryonal development and because fibronectin is produced by almost all cell types in mammals, the study of its role in hematopoiesis is difficult. Nevertheless, strong and direct evidence exists for its stimulation of myelopoiesis and thrombopoiesis using in vivo models. Other reviewed effects can be deduced from the study of fibronectin receptors, which showed their activation modifies the behavior of hematopoietic stem cells. Erythropoiesis was only stimulated under hemolytic stress, and mostly late stages of lymphocytic differentiation were modulated. Because fibronectin is ubiquitously expressed, these interactions in health and disease need to be taken into account whenever any molecule is evaluated in hematopoiesis.

scholarly journals Integrin-αvβ3 regulates thrombopoietin-mediated maintenance of hematopoietic stem cells

Blood ◽  
2012 ◽  
Vol 119 (1) ◽  
pp. 83-94 ◽  
Author(s):  
Terumasa Umemoto ◽  
Masayuki Yamato ◽  
Jun Ishihara ◽  
Yoshiko Shiratsuchi ◽  
Mika Utsumi ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Matrix Protein ◽  
Ex Vivo ◽  
Extracellular Matrix Protein ◽  
Αvβ3 Integrin ◽  
Hematopoietic Stem ◽  
Β3 Integrin ◽  
Ex Vivo Culture

AbstractThroughout life, one's blood supply depends on sustained division of hematopoietic stem cells (HSCs) for self-renewal and differentiation. Within the bone marrow microenvironment, an adhesion-dependent or -independent niche system regulates HSC function. Here we show that a novel adhesion-dependent mechanism via integrin-β3 signaling contributes to HSC maintenance. Specific ligation of β3-integrin on HSCs using an antibody or extracellular matrix protein prevented loss of long-term repopulating (LTR) activity during ex vivo culture. The actions required activation of αvβ3-integrin “inside-out” signaling, which is dependent on thrombopoietin (TPO), an essential cytokine for activation of dormant HSCs. Subsequent “outside-in” signaling via phosphorylation of Tyr747 in the β3-subunit cytoplasmic domain was indispensable for TPO-dependent, but not stem cell factor-dependent, LTR activity in HSCs in vivo. This was accompanied with enhanced expression of Vps72, Mll1, and Runx1, 3 factors known to be critical for maintaining HSC activity. Thus, our findings demonstrate a mechanistic link between β3-integrin and TPO in HSCs, which may contribute to maintenance of LTR activity in vivo as well as during ex vivo culture.

scholarly journals Clonal-level lineage commitment pathways of hematopoietic stem cells in vivo

2019 ◽  
Vol 116 (4) ◽  
pp. 1447-1456 ◽  
Author(s):  
Rong Lu ◽  
Agnieszka Czechowicz ◽  
Jun Seita ◽  
Du Jiang ◽  
Irving L. Weissman
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Hematopoietic Stem Cell ◽  
Lineage Commitment ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Hematopoietic System ◽  
Different Levels

While the aggregate differentiation of the hematopoietic stem cell (HSC) population has been extensively studied, little is known about the lineage commitment process of individual HSC clones. Here, we provide lineage commitment maps of HSC clones under homeostasis and after perturbations of the endogenous hematopoietic system. Under homeostasis, all donor-derived HSC clones regenerate blood homogeneously throughout all measured stages and lineages of hematopoiesis. In contrast, after the hematopoietic system has been perturbed by irradiation or by an antagonistic anti-ckit antibody, only a small fraction of donor-derived HSC clones differentiate. Some of these clones dominantly expand and exhibit lineage bias. We identified the cellular origins of clonal dominance and lineage bias and uncovered the lineage commitment pathways that lead HSC clones to different levels of self-renewal and blood production under various transplantation conditions. This study reveals surprising alterations in HSC fate decisions directed by conditioning and identifies the key hematopoiesis stages that may be manipulated to control blood production and balance.

Clonal Level Lineage Commitment of Mouse Hematopoietic Stem Cells in Vivo

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 27-27
Author(s):  
Rong Lu ◽  
Agnieszka Czechowicz ◽  
Jun Seita ◽  
Irving L. Weissman
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Cellular Proliferation ◽  
Population Level ◽  
Cell Types ◽  
Lineage Commitment ◽  
Hematopoietic Stem ◽  
Clonal Level ◽  
Hsc Niche

Abstract Abstract 27 Hematopoietic stem cells (HSCs) sustain the blood and immune systems through a complex differentiation process. This process involves several steps of lineage commitment and forms a paradigm for understanding cellular development, differentiation, and malignancy. While this step-wise differentiation has been extensively studied at the population level, little is known about the lineage commitment of individual HSC clones. The importance of understanding HSC differentiation at the clonal level has been raised by several recent studies suggesting that individual HSCs differentially contribute to various blood cell types and that the aggregate HSC differentiation at the population level is an amalgamation of the diverse lineage commitments of individual HSC clones. The distinct differentiation of individual HSCs may also be accentuated by their regulatory microenvironments, HSC niche. HSC niche may not affect all HSCs in an organism equally, and may instead act directly on resident HSC clones through direct contact or by tuning local cytokine concentrations. Knowledge of HSC clonal level lineage commitment will reveal new insights into HSC regulatory mechanisms and will improve our understanding of aging, immune deficiency, and many hematopoietic disorders involving an unbalanced hematopoietic system. Here, we provide a comprehensive map of in vivo HSC clonal development in mice. The clonal map was derived from the simultaneous tracking of hundreds of individual mouse HSCs in vivo using genetic barcodes. These unique barcodes were delivered into HSCs using a lentiviral vector to obtain a one-to-one mapping between barcodes and HSCs. Barcoded HSCs were then transplanted into recipient mice using standard procedures. Genetic barcodes from donor derived HSCs and their progenies were examined twenty-two weeks after transplantation using high-throughput sequencing. We found that the dominant differentiation of HSC clones is always present in pre-conditioned mice. In these recipients, a small fraction of engrafted HSCs become dominantly abundant at the intermediate progenitor stages, but not at the HSC stage. Thus, clonal dominance is a characteristic of HSC differentiation but not of HSC self-renewal. Additionally, the dominant differentiation of HSC clones exhibits distinct expansion patterns through various stages of hematopoiesis. We provide evidence that observed HSC lineage bias arises from dominant differentiation at distinct lineage commitment steps. In particular, myeloid bias arises from dominant differentiation at the first lineage commitment step from HSC to MPP, whereas lymphoid bias arises from dominant differentiation at the last lineage commitment step from CLP to B cells. We also show that dominant differentiation and lineage bias are interrelated and together delineate discrete HSC lineage commitment pathways. These pathways describe how individual HSC clones produce differential blood quantities and cell types. Multiple clonal differentiation pathways can coexist simultaneously in a single organism, and mutually compensate to sustain overall blood production. Thus, the distinct HSC differentiation characteristics uncovered by clonal analysis are not evident at the population level. We have also identified the lineage commitment profiles of HSC clones belonging to each pathway. These profiles elucidate the cellular proliferation and development of HSCs at the clonal level and demonstrate that distinct modes of HSC regulation exist in vivo. In summary, our in vivo clonal mapping reveals discrete clonal level HSC lineage commitment pathways. We have identified the cellular origins of clonal dominance and lineage bias, which may be the key hematopoietic stages where blood production and balance can be manipulated. These discoveries based on clonal level analysis are unexpected and unobtainable from conventional studies at the population level. Together, they open new avenues of research for studying hematopoiesis. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Life span of multipotential hematopoietic stem cells in vivo.

1990 ◽  
Vol 171 (5) ◽  
pp. 1407-1418 ◽  
Author(s):  
G Keller ◽  
R Snodgrass
Keyword(s):  
Stem Cells ◽  
Gene Therapy ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Strong Evidence ◽  
Stem Cell Population ◽  
Hematopoietic Stem ◽  
Somatic Tissues ◽  
Exogenous Factors

The findings reported in this study highlight several important features of the development of hematopoietic stem cells after transplantation into irradiated recipients. First, they demonstrate the existence of a class of primitive multipotential stem cells that can function for a significant portion of the lifetime of a mouse (15 mo). In addition, they clearly show that these primitive stem cells can be infected with recombinant retroviruses and thus would be appropriate targets for gene therapy in somatic tissues. Second, our data indicate that the progeny of some, but not all, of the primitive stem cells have fully expanded into the various hematopoietic lineages by 2 mo after reconstitution. Finally, our analysis of the secondary recipients provides strong evidence suggesting that the primitive stem cell population can actually clonally expand. Our current experiments are aimed at determining the extent to which this expansion can occur and whether or not this expansion can be influenced by exogenous factors.

scholarly journals Native associations of early hematopoietic stem cells and stromal cells isolated in bone marrow cell aggregates

Blood ◽  
1994 ◽  
Vol 83 (2) ◽  
pp. 361-369 ◽  
Author(s):  
PE Funk ◽  
PW Kincade ◽  
PL Witte
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Hematopoietic Cells ◽  
Hematopoietic Stem ◽  
Factor C

In suspensions of murine bone marrow, many stromal cells are tightly entwined with hematopoietic cells. These cellular aggregations appear to exist normally within the marrow. Previous studies showed that lymphocytes and stem cells adhered to stromal cells via vascular cell adhesion molecule 1 (VCAM1). Injection of anti-VCAM1 antibody into mice disrupts the aggregates, showing the importance of VCAM1 in the adhesion between stromal cells and hematopoietic cells in vivo. Early hematopoietic stem cells were shown to be enriched in aggregates by using a limiting-dilution culture assay. Myeloid progenitors responsive to WEHI-3CM in combination with stem cell factor (c-kit ligand) and B220- B-cell progenitors responsive to insulin-like growth factor-1 in combination with interleukin-7 are not enriched. We propose a scheme of stromal cell-hematopoietic cell interactions based on the cell types selectively retained within the aggregates. The existence of these aggregates as native elements of bone marrow organization presents a novel means to study in vivo stem cell-stromal cell interaction.

scholarly journals Canonical Notch Signaling Is Dispensable for the Maintenance of Adult Hematopoietic Stem Cells.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 267-267 ◽  
Author(s):  
Ivan Maillard ◽  
Seth E. Pross ◽  
Olga Shestova ◽  
Hong Sai ◽  
Jon C. Aster ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Notch Signaling ◽  
Transcriptional Activation ◽  
Cell Function ◽  
Fetal Life ◽  
Hematopoietic Stem

Abstract Canonical Notch signaling operates through a highly conserved pathway that regulates the differentiation and homeostasis of hematopoietic cells. Ligand-receptor binding initiates proteolytic release of the Notch intracellular domain (ICN) which migrates to the nucleus, binds the transcription factor CSL/RBPJk and activates target genes through the recruitment of transcriptional coactivators of the Mastermind-like family (MAML). Notch signaling is essential for the emergence of hematopoietic stem cells (HSCs) during fetal life, but its effects on adult HSCs are controversial. In gain-of-function experiments, activation of Notch signaling in adult HSCs increased their self-renewal potential in vitro and in vivo. However, loss-of-function studies have provided conflicting results as to the role of physiological Notch signaling in HSC maintenance and homeostasis. To address this question, we expressed DNMAML1, a GFP-tagged pan-inhibitor of Notch signaling, in mouse HSCs. We have shown previously that DNMAML1 interferes with the formation of the ICN/CSL/MAML transcriptional activation complex and blocks signaling from all four Notch receptors (Notch1-4) (Maillard, Blood 2004). Transfer of DNMAML1-transduced bone marrow (BM) as compared to control GFP-transduced BM into lethally irradiated recipients gave rise to similar long-term stable expression of GFP for at least 6 months after transplant. DNMAML1 and GFP-transduced cells contributed equally to all hematopoietic lineages, except to the T cell and marginal zone B cell lineages, which are Notch-dependent. Expression of DNMAML1 did not affect the size of the BM progenitor compartment (Lin negative, Sca-1 positive, c-Kit high, or LSK cells), or the proportion of LSK cells that were negative for Flt3 and L-Selectin expression (containing long-term HSCs). The stem cell function of DNMAML1-transduced LSK cells was further assessed with in vivo competitive repopulation assays in lethally irradiated recipients. DNMAML1 and GFP-transduced LSK cells competed equally well with wild-type BM, as judged by their contribution to the myeloid lineage up to 4 months post-transplant, through two successive rounds of transplantation. Our data indicate that canonical Notch signaling is dispensable for the maintenance of stem cell function in adult HSCs.

In Vivo Fate Tracing Studies Using the SCL Stem Cell Enhancer: Embryonic Hematopoietic Stem Cells Significantly Contribute to Adult Hematopoiesis.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 559-559
Author(s):  
Joachim R. Gothert ◽  
Sonja E. Gustin ◽  
Mark A. Hall ◽  
Anthony R. Green ◽  
Berthold Gottgens ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
De Novo ◽  
Genetic Manipulation ◽  
Fetal Liver ◽  
Hematopoietic Stem ◽  
Reporter Mice ◽  
First Time

Abstract Evidence for the direct lineage relationship between embryonic and adult hematopoietic stem cells (HSCs) in the mouse is primarily indirect. In order to study this relationship in a direct manner we expressed the tamoxifen-inducible Cre-ERT-recombinase under the control of the SCL-stem-cell-enhancer in transgenic mice (HSC-SCL-Cre-ERT). To determine functionality, HSC-SCL-Cre-ERT transgenics were bred with the Cre-reporter-mice ROSA26R and R26R-EYFP. Flow-cytometric and transplantation studies revealed tamoxifen-dependent recombination occurring in more than 90% of adult long-term HSCs, whereas the targeted proportion within mature progenitor populations was significantly lower. Moreover, the transgene was able to irreversibly tag embryonic HSCs on days 10 and 11 of gestation. These cells contributed to bone marrow hematopoiesis five months later. In order to investigate whether the de novo HSC-generation is completed during embryogenesis, HSC-SCL-Cre-ERT marked fetal liver cells were transplanted into adult recipients. Strikingly, the proportion of marked cells within the transplanted and the in vivo-remaining HSC-compartment was not different, implying that no further HSC-generation occurred during late fetal and neonatal stages of development. These data demonstrate for the first time the direct lineage relationship between mid-gestation embryonic and adult HSCs in the mouse. Additionally, the HSC-SCL-Cre-ERT mice will provide a valuable tool to achieve temporally controlled genetic manipulation of HSCs.

In Vitro and In Vivo Evidence That Umbilical Cord Blood (UCB)-Derived CD45-/SSEA-4+/OCT-4+/CD133+/CXCR4+/Lin- Very Small Embryonic/Epiblast Like Stem Cells (VSELs) Do Not Contain Clonogenic Hematopoietic Progenitors but Are Highly Enriched in More Primitive Stem Cells - Novel View On Hierarchy of UCB Stem Cell Compartment.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 35-35 ◽  
Author(s):  
Ewa K. Zuba-Surma ◽  
Izabela Klich ◽  
Marcin Wysoczynski ◽  
Nicholas J Greco ◽  
Mary J. Laughlin ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Cord Blood ◽  
Umbilical Cord ◽  
Umbilical Cord Blood ◽  
Hematopoietic Stem ◽  
Hematopoietic Activity

Abstract Abstract 35 Recently, we identified in umbilical cord blood (UCB) a population of very small embryonic/epiblast-like (VSEL) stem cells (Leukemia 2007;21:297–303) that are i) smaller than erythrocytes, ii) SSEA-4+/Oct-4+/CD133+/CXCR4+/Lin−/CD45−, iii) respond to SDF-1 gradient and iv) possess large nuclei containing primitive euchromatin. We have demonstrated in vitro that UCB-derived VSELs did not reveal hematopoietic activity freshly after isolation, but grow hematopoietic colonies following co-culture/activation over OP-9 cells. To investigate the hierarchy of UCB-derived, CD45 negative VSELs, we employed staining with Aldefluor - detecting aldehyde dehydrogenase (ALDH), the enzyme expressed in primitive hematopoietic cells. Subsequently, we sorted CD45−/CD133+/ALDHhigh and CD45−/CD133+/ALDHlow sub-fractions of VSELs from UCB samples and established that freshly sorted from UCB VSELs in contrast to sorted CD45+/ CD133+/ALDHhigh and CD45+/CD133+/ALDHlow hematopoietic stem cells (HSC) did not grow colonies in vitro. However, when CD45− VSELs were activated/expanded over OP-9 stroma cells, they exhibit hematopoietic potential and grew in routine methylcellulose cultures hematopoietic colonies composed of CD45+ cells. Interestingly, while CD45−/CD133+/ALDHhigh VSELs gave raise to hematopoietic colonies after the first replating, the formation of colonies by CD45−/CD133+/ALDHlow VSELs was somehow delayed, what suggest that they needed more time to acquire hematopoietic commitment. Thus our in vitro data indicate that both populations of CD45− cells may acquire hematopoietic potential; however hematopoietic specification is delayed for CD45−/CD133+/ALDHlow cells, suggesting their more primitive nature. In parallel, real time PCR analysis confirmed that while freshly isolated CD45−/CD133+/ALDHhigh VSELs express more hematopoietic transcripts (e.g., c-myb, 80.2±27.4 fold difference), CD45−/CD133+/ALDHlow exhibit higher levels of pluripotent stem cell markers (e.g., Oct-4, 119.5±15.5 fold difference as compared to total UCB mononuclear cells) (Figure 1 panel A). Next hematopoietic potential of UCB-derived VSELs was tested in vivo after transplantation into NOD/SCID mice (Figure 1 panel B and C). We noticed that both CD45−/CD133+/ALDHhigh and CD45−/CD133+/ALDHlow VSELs, give rise to human lympho-hematopoietic chimerism in lethally irradiated NOD/SCID mice as assayed 4–6 weeks after transplantation. The level of human hematopoietic CD45+ cells in murine peripheral blood (PB), bone marrow (BM) and spleen (SP) were comparable for both transplanted UCB-VSELs fractions - 7.1±2.9% (PB), 23.2±0.2% (SP) and 25.2±1.0% (BM). In conclusion, our data suggest that freshly isolated very small CD45 negative UCB-VSELs are depleted from clonogeneic progenitors, however they are highly enriched for primitive HSC. Based on our in vitro and in vivo data we postulate following hierarchy of hematopoietic stem cells in UCB (from most primitive to more differentiated) i) CD45−/CD133+/ALDHlow, ii) CD45−/CD133+/ALDHhigh , iii) CD45+/CD133+/ALDHlow and iv) CD45−/CD133+/ALDHhigh. We also postulate that as we have already shown for murine BM-derived VSELs, human UCB-derived CD45 negative VSELs correspond to a population of most primitive long term repopulating HSC (LT-HSC). Of note, we also found that currently employed, routine UCB processing strategies may lead up to ∼50% unwanted loss of these small cells that are endowed with such remarkable hematopoietic activity! Disclosures: No relevant conflicts of interest to declare.

Heterogeneity Of Leukemic Stem Cell Capacity Of BCR-ABL+ Long-Term Hematopoietic Stem cells In CML Is Associated With Variability In MPL Expression

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 516-516
Author(s):  
Bin Zhang ◽  
Yin Wei Ho ◽  
Wei Tong ◽  
Ling Li ◽  
Ravi Bhatia
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Cell Growth ◽  
Hematopoietic Stem Cells ◽  
Myelogenous Leukemia ◽  
Hematopoietic Stem ◽  
Nsg Mice ◽  
Donor Cells

Abstract In chronic myelogenous leukemia (CML), in vivo long-term repopulating and leukemia stem cell (LSC) capacity is restricted to a small population of BCR-ABL+ long-term hematopoietic stem cells (LTHSC). Using an inducible transgenic SCL-tTA/BCR-ABL mouse model of CML, we have shown that leukemic cells with long-term repopulating and leukemia-initiating capacity have the Lin-Sca-1+Kit+Flt3-CD150+CD48- phenotype, also characteristic of normal LTHSC. Limiting dilution transplantation studies show that frequency of cells with LTHSC phenotype with long-term engraftment capacity (1:6) is considerably higher than those with leukemia-initiating capacity (1:80) suggesting that only some LTHSC may have LSC capacity (Cancer Cell 21:577, 2012). To further evaluate the basis for heterogeneity in LSC potential of BCR-ABL+ LTHSC, SCL-tTA/BCR-ABL mice were crossed with GFP expressing mice to allow tracking of donor cells, and a cohort of mice were transplanted with limiting numbers of GFP+LTHSC (200 per mouse) and followed for engraftment of GFP+ cells and development of CML (WBC>10,000/ul). Only 11 of 20 mice developed CML, whereas 9 mice showed long term engraftment without development of CML. GFP+ LTHSC selected from primary recipients were transplanted into secondary recipients (200 per mouse). Seven of 17 mice receiving cells from mice with CML also developed CML after the second transplant, whereas none of the mice receiving cells from non-CML mice developed CML, suggesting the distinction between leukemogenic versus non-leukemogenic LTHSC was maintained after transplantation. LTHSC isolated from primary recipients were also analyzed for expression of several HSC-regulatory genes by multiplex Q-PCR using the Fluidigm system. On hierarchical clustering, LTHSC from mice developing CML clustered separately from LTHSC from mice without CML. Amongst cell surface expressed genes, expression of the thrombopoietin (TPO) receptor MPL (p=0.006) and CD47 (p=0.006) was significantly increased in LTHSC from mice developing CML. We did not see significant differences in BCR-ABL expression in LTHSC from mice with or without CML. We further analyzed the relationship of MPL expression with CML LTHSC function. CML LTHSC (n=6) expressing high levels of MPL (MPLhi, top 10% based on MPL expression) showed significantly increased cell growth (p<0.0001) and CFC potential (p=0.0007) when cultured with TPO (10ng/ml) compared to LTHSC expressing low levels of MPL (MPLlo, lowest 10% based on MPL expression), as well as significantly increased cell growth (p=0.005) and CFC (p=0.03) compared to normal MPLhi LTHSC. Following transplantation, MPLhi LTHSC (200 per mouse) generated significantly higher short-term (4 wks, p=0.008) and long-term (16 wks, p=0.003) engraftment of donor cells compared to MPLlo LTHSC. Seven of 16 mice receiving MPLhi LTHSC developed CML compared to only 1 out of 17 mice receiving MPLlo LTHSC. We next evaluated heterogeneity of MPL expression in LTHSC (CD34+CD38-CD90+ cells) from CML patients and normal subjects. As was seen in murine studies, human CML MPLhi LTHSC cultured with TPO (10ng/ml) showed increased cell growth (p<0.0001) and CFC frequency (p=0.02) compared to CML MPLlo LTHSC, and significantly increased cell growth (p<0.0001) and CFC generation (p=0.02) compared to normal MPLhi LTHSC. Both baseline and TPO stimulated p-Stat3/5 levels were significantly higher in human CML MPLhi LTHSC compared with MPLlo LTHSC (p<0.0001), and in CML compared to normal MPLhi LTHSC. Interestingly p-Stat5 response peaked at 1 hour in CML LTHSC compared to 20 minutes in normal LTHSC, further indicating alterations in MPL signaling in CML LTHSC. Transplantation of CML MPLhi LTHSC (3x104 cells/mouse) into NSG mice resulted in higher engraftment of human myeloid cells in BM at both 4 and 16 weeks (p<0.05) compared with MPLlo LTHSC. Normal MPLhi LTHSC also showed higher engraftment in NSG mice at 4 and 16 weeks compared with MPLlo cells. Our studies indicate that CML LTHSC represent a heterogeneous population with varying LSC capacity. Heterogeneity in LSC capacity is associated with variability in expression of MPL. Higher levels of MPL expression in CML LTHSC are associated with significantly increased Stat3/5 signaling, in vitro and in vivo growth, and LSC capacity. These results identify MPL as a key regulator of LSC potential of BCR-ABL+ LTHSC and a potential target for LSC-directed therapeutics. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Native associations of early hematopoietic stem cells and stromal cells isolated in bone marrow cell aggregates

Blood ◽  
1994 ◽  
Vol 83 (2) ◽  
pp. 361-369 ◽  
Author(s):  
PE Funk ◽  
PW Kincade ◽  
PL Witte
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Stromal Cells ◽  
Stromal Cell ◽  
Hematopoietic Cells ◽  
Hematopoietic Stem ◽  
Factor C

Abstract In suspensions of murine bone marrow, many stromal cells are tightly entwined with hematopoietic cells. These cellular aggregations appear to exist normally within the marrow. Previous studies showed that lymphocytes and stem cells adhered to stromal cells via vascular cell adhesion molecule 1 (VCAM1). Injection of anti-VCAM1 antibody into mice disrupts the aggregates, showing the importance of VCAM1 in the adhesion between stromal cells and hematopoietic cells in vivo. Early hematopoietic stem cells were shown to be enriched in aggregates by using a limiting-dilution culture assay. Myeloid progenitors responsive to WEHI-3CM in combination with stem cell factor (c-kit ligand) and B220- B-cell progenitors responsive to insulin-like growth factor-1 in combination with interleukin-7 are not enriched. We propose a scheme of stromal cell-hematopoietic cell interactions based on the cell types selectively retained within the aggregates. The existence of these aggregates as native elements of bone marrow organization presents a novel means to study in vivo stem cell-stromal cell interaction.

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