Defining Parameters Attributing to the Role of Osteomacs in Regulating Stem Cell Function and the Hematopoietic Niche

Abstract Networking between hematopoietic stem cells (HSC) and cells of the hematopoietic niche is critical for the maintenance of stem cell renewal and function. HSC maintenance in the hematopoietic niche is considered to be the product of intimate interactions between cellular and soluble elements of the niche and stem cells. Among the cellular components of the niche participating in this function are a group of specialized bone-resident macrophages known as osteomacs (OM). Previously, we established the importance of osteoblasts (OB) in hematopoiesis and quite recently, we described the importance of OM and their interactions with OB and megakaryocytes (MK) in sustaining HSC function. We have also illustrated that CD166 is a critical functional marker of stem cell function and competence of the hematopoietic niche. Interestingly, immature OB which are CD166+ mediate the highest level of hematopoietic enhancing activity. We report here the importance of CD166 on calvarie-resident OM (identified as CD45+F4/80+ cells) and outline how these cells require cooperation from MK to increase CD166 expression and sustain HSC function. Bone resident-osteomacs, which are phenotypically similar but functionally different from bone marrow-derived macrophages, were collected by the enzymatic digestion of neonatal calvarial cells (NCC) or long bones of adult mice. Transplantation assays indicated that OM are relatively radioresistant and survive several weeks post lethal radiation. However, they eventually deplete and are replenished by progeny of donor HSC. To understand the importance of OM-OB-MK interactions in maintaining HSC function in the niche, we performed 3D cytometry on fixed and stained bone marrow sections that revealed intimate spatial interactions between OM, OB, MK and HSC. To assess changes in gene expression observed due to these interactions, we cultured NCC for 16hr in the absence or presence of MK prepared from fetal liver followed by sorting out OM from each group. These cells were then captured as single cells and sequenced to identify potential targets through which OM enhanced hematopoietic activity. Strikingly, several genes involved in the hematopoietic stem cell differentiation pathway including lmo2, fli1 and ikzf1 were upregulated in OM cultured in the presence of MK. Other genes that were upregulated were embigin and PF-4, both of which have been implicated in the maintenance of HSC function. Interestingly, OM express embigin, angiogenin and IL-18 mRNA similar to proximal osteolineage cells which we previously described as HSC regulators. To investigate changes at the translational level, we performed single cell proteomics using CyTOF. NCC were cultured for 2 days in the absence and presence of MK followed by staining for a panel of 29 surface and intracellular markers. Expression of markers such as CD166, embigin, mac-2 and STAT3 amongst others was elevated on OM cultured with MK compared to OM cultured without. These data informed our decision to focus our future investigations on CD166 and embigin. Next CD166+OM and CD166-OM were isolated by cell sorting and used in co-culture assays with OB to support the production of clonogenic cells in vitro. Only the CD166+ fraction of OM maintained hematopoietic activity similar to unsorted OM, implicating CD166 as one of the mediators of OM function. These results were validated using recombinant CD166 protein to substitute for OM function. Under these conditions, recombinant CD166 supported the hematopoietic enhancing activity of OB in the absence of OM. Recombinant Angiogenin and IL-18 were unable to augment the CD166-mediated support of hematopoiesis. Interestingly, CD166 knockout OM were unable to mediate the same hematopoietic enhancing activity observed with WT OM regardless of the presence or absence of MK in culture. In vivo transplantation studies to corroborate these findings have been initiated and are very early to yield meaningful conclusions. These data demonstrate that CD166 is one of the important mediators through which OM maintain HSC function. However, CD166-OM mediated HSC function is only maintained in conjunction with OB-MK interactions. Our data indicate the importance of crosstalk between OM, OB and MK which leads to the expression of novel mediators such as CD166 to support HSC function. Disclosures No relevant conflicts of interest to declare.

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In vivo and in vitro stem cell function of c-kit- and Sca-1-positive murine hematopoietic cells

Blood ◽

10.1182/blood.v80.12.3044.bloodjournal80123044 ◽

1992 ◽

Vol 80 (12) ◽

pp. 3044-3050 ◽

Cited By ~ 2

Author(s):

S Okada ◽

H Nakauchi ◽

K Nagayoshi ◽

S Nishikawa ◽

Y Miura ◽

...

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Stem Cell ◽

Hematopoietic Stem Cells ◽

Cell Function ◽

Bone Marrow Cells ◽

Synergistic Effects ◽

Single Cells ◽

Hematopoietic Stem

c-kit is expressed on hematopoietic stem cells and progenitor cells, but not on lymphohematopoietic differentiated cells. Lineage marker- negative, c-kit-positive (Lin-c-kit+) bone marrow cells were fractionated by means of Ly6A/E or Sca-1 expression. Lin-c-kit+Sca-1+ cells, which consisted of 0.08% of bone marrow nucleated cells, did not contain day-8 colony-forming units-spleen (CFU-S), but 80% were day-12 CFU-S. One hundred cells rescued the lethally irradiated mice and reconstituted hematopoiesis. On the other hand, 2 x 10(3) of Lin-c- kit+Sca-1- cells formed 20 day-8 and 11 day-12 spleen colonies, but they could not rescue the lethally irradiated mice. These data indicate that Lin-c-kit+Sca-1+ cells are primitive hematopoietic stem cells and that Sca-1-cells do not contain stem cells that reconstitute hematopoiesis. Lin-c-kit+Sca-1+ cells formed no colonies in the presence of stem cell factor (SCF) or interleukin-6 (IL-6), and only 10% of them formed colonies in the presence of IL-3. However, approximately 50% of them formed large colonies in the presence of IL-3, IL-6, and SCF. Moreover, when single cells were deposited into culture medium by fluorescence-activated cell sorter clone sorting system, 40% of them proliferated on a stromal cell line (PA-6) and proliferated for more than 2 weeks. In contrast, 15% of the Lin-c- kit+Sca-1-cells formed colonies in the presence of IL-3, but no synergistic effects were observed in combination with SCF plus IL-6 and/or IL-3. Approximately 10% proliferated on PA-6, but most of them degenerated within 2 weeks. The population ratio of c-kit+Sca-1+ to c-kit+Sca-1- increased 2 and 4 days after exposure to 5-fluorouracil (5-FU). These results are consistent with the relative enrichment of highly proliferative colony-forming cells by 5-FU. These data show that, although c-kit is found both on the primitive hematopoietic stem cells and progenitors, Sca-1+ cells are more primitive and respond better than Sca-1- cells to a combination of hematopoietic factors, including SCF and stromal cells.

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In vivo and in vitro stem cell function of c-kit- and Sca-1-positive murine hematopoietic cells

Blood ◽

10.1182/blood.v80.12.3044.3044 ◽

1992 ◽

Vol 80 (12) ◽

pp. 3044-3050 ◽

Cited By ~ 354

Author(s):

S Okada ◽

H Nakauchi ◽

K Nagayoshi ◽

S Nishikawa ◽

Y Miura ◽

...

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Stem Cell ◽

Hematopoietic Stem Cells ◽

Cell Function ◽

Bone Marrow Cells ◽

Synergistic Effects ◽

Single Cells ◽

Hematopoietic Stem

Abstract c-kit is expressed on hematopoietic stem cells and progenitor cells, but not on lymphohematopoietic differentiated cells. Lineage marker- negative, c-kit-positive (Lin-c-kit+) bone marrow cells were fractionated by means of Ly6A/E or Sca-1 expression. Lin-c-kit+Sca-1+ cells, which consisted of 0.08% of bone marrow nucleated cells, did not contain day-8 colony-forming units-spleen (CFU-S), but 80% were day-12 CFU-S. One hundred cells rescued the lethally irradiated mice and reconstituted hematopoiesis. On the other hand, 2 x 10(3) of Lin-c- kit+Sca-1- cells formed 20 day-8 and 11 day-12 spleen colonies, but they could not rescue the lethally irradiated mice. These data indicate that Lin-c-kit+Sca-1+ cells are primitive hematopoietic stem cells and that Sca-1-cells do not contain stem cells that reconstitute hematopoiesis. Lin-c-kit+Sca-1+ cells formed no colonies in the presence of stem cell factor (SCF) or interleukin-6 (IL-6), and only 10% of them formed colonies in the presence of IL-3. However, approximately 50% of them formed large colonies in the presence of IL-3, IL-6, and SCF. Moreover, when single cells were deposited into culture medium by fluorescence-activated cell sorter clone sorting system, 40% of them proliferated on a stromal cell line (PA-6) and proliferated for more than 2 weeks. In contrast, 15% of the Lin-c- kit+Sca-1-cells formed colonies in the presence of IL-3, but no synergistic effects were observed in combination with SCF plus IL-6 and/or IL-3. Approximately 10% proliferated on PA-6, but most of them degenerated within 2 weeks. The population ratio of c-kit+Sca-1+ to c-kit+Sca-1- increased 2 and 4 days after exposure to 5-fluorouracil (5-FU). These results are consistent with the relative enrichment of highly proliferative colony-forming cells by 5-FU. These data show that, although c-kit is found both on the primitive hematopoietic stem cells and progenitors, Sca-1+ cells are more primitive and respond better than Sca-1- cells to a combination of hematopoietic factors, including SCF and stromal cells.

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Effects of Sickle Cell Disease on Hematopoietic Stem Cell Function and the Bone Marrow Microenvironment.

Blood ◽

10.1182/blood.v108.11.1227.1227 ◽

2006 ◽

Vol 108 (11) ◽

pp. 1227-1227

Author(s):

Elisabeth H. Javazon ◽

Leslie S. Kean ◽

Jennifer Perry ◽

Jessica Butler ◽

David R. Archer

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Stem Cell ◽

Sickle Cell Disease ◽

Sickle Cell ◽

Cell Function ◽

Donor Cell ◽

Cell Disease ◽

Hematopoietic Stem ◽

Cell Engraftment

Abstract Gene therapy and stem cell transplantation are attractive potential therapies for sickle cell disease (SCD). Previous studies have shown that the sickle environment is highly enriched for reactive oxygen species (ROS), but have not addressed whether or not the increased ROS may alter the bone marrow (BM) microenvironment or affect stem cell function. Using the Berkeley sickle mouse model, we examined the effects of sickle cell disease on hematopoietic stem cell function and the bone marrow microenvironment. We transplanted C57BL/6 (control) BM into C57BL/6 and homozygous sickle mice. Recipients received 2 × 106 BM cells and a conditioning regimen consisting of busulfan, anti-asialo GM1, and co-stimulation blockade (anti-CD40L and CTLA4-Ig). Following transplantation, sickle mice demonstrated increased donor cell engraftment in the peripheral blood compared to normal mice (58.3% vs. 33.1%, respectively). Similarly, BMT in a fully allogeneic system also resulted in enhanced engraftment in sickle recipients. Next we analyzed whether or not engraftment defects exist within the BM stem cell population of sickle mice. In vitro colony forming assays showed a significant decrease in progenitor colony formation in sickle compared to control BM. By flow cytometry, we determined that there was a significant decrease in the KSL (c-Kit+, Sca-1+, Lineage−) progenitor population within the BM of sickle mice. Cell cycle analysis of the KSL population demonstrated that significantly fewer sickle KSL cells were in G0 phase compared to control, suggesting that there are fewer quiescent stem cells in the BM of sickle mice. To assess the potential role of ROS and glutathione depletion in sickle mice, we tested the engraftment efficiency of KSL cells from untreated and n-acetyl-cysteine (NAC) treated control, hemizygous sickle (hemi), and sickle mice in a competitive repopulation experiment. Peripheral chimerism showed an engraftment defect from both hemizygous and homozygous sickle mice such that control KSL cells engrafted > hemi > sickle at a ratio of 1 : 0.4 : 0.25. Treatment with NAC for four months prior to transplantation partially restored KSL engraftment (control : hemi : sickle; 1 : 0.97 : 0.56 ). We have demonstrated that congenic and allogeneic BMT into sickle mice result in increased donor cell engraftment in the sickle recipients. Both the decreased number of KSL cells and the decreased percentage of quiescent KSL cells in the sickle mice indicate that more stem cells in the transgenic sickle mouse model are mobilized from the BM environment. The engraftment defect of sickle KSL cells that was partially ameliorated by NAC treatment suggests that an altered redox environment in sickle mice may contribute to the engraftment deficiencies that we observed.

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Regulation of Hematopoietic Stem Cells by Interferons and by DNA Methylation: Implications for Bone Marrow Failure

Blood ◽

10.1182/blood.v124.21.sci-20.sci-20 ◽

2014 ◽

Vol 124 (21) ◽

pp. SCI-20-SCI-20

Author(s):

Margaret A. Goodell

Keyword(s):

Dna Methylation ◽

Stem Cells ◽

Bone Marrow ◽

Stem Cell ◽

Hematopoietic Stem Cells ◽

Bone Marrow Failure ◽

Stem Cell Differentiation ◽

Primary Myelofibrosis ◽

Differentiation Potential ◽

Hematopoietic Stem

Bone marrow failure (BMF), the inability to regenerate the differentiated cells of the blood, has a number of genetic and environmental etiologies, such as mutation of telomere-associated protein genes and immune-related aplastic anemia. Recently, mutations in DNA methyltransferase 3A (DNMT3A) have been found to be associated with approximately 15% of cases of primary myelofibrosis (MF), which can be a cause of BMF. The role of DNMT3A more broadly in hematopoiesis, and specifically in BMF, is currently poorly understood. DNMT3A is one of two de novo DNA methylation enzymes important in developmental fate choice. We showed that Dnmt3a is critical for normal murine hematopoiesis, as hematopoietic stem cells (HSCs) from Dnmt3a knockout (KO) mice displayed greatly diminished differentiation potential while their self-renewal ability was markedly increased1, in effect, leading to failure of blood regeneration or BMF. Combined with loss of Dnmt3b, HSCs exhibited a profound differentiation block, mediated in part by an increase of stabilized b-catenin. While we did not initially observe bone marrow pathology or malignancy development in mice transplanted with Dnmt3a KO HSCs, when we aged a large cohort of mice, all mice succumbed to hematologic disease within about 400 days. Roughly one-third of mice developed frank leukemia (acute lymphocytic leukemia or acute myeloid leukemia), one-third developed MDS, and the remainder developed primary myelofibrosis or chronic myelomonocytic leukemia. The pathological characteristics of the mice broadly mirror those of patients, suggesting the Dnmt3a KO mice can serve as a model for human DNMT3A-mutation associated disease. Strikingly, bone marrow of mice with different disease types exhibit distinct DNA methylation features. These will findings and the implications for disease development will be discussed. We are currently investigating the factors that drive different outcomes in the mice, including stressors such as exposure to interferons. We have hypothesized that HSC proliferation accelerates the Dnnmt3a-associated disease phenotypes. We have previously shown that interferons directly impinge on HSCs in the context of infections. Interferons activate HSCs to divide, generating differentiated progeny and cycling HSCs. Repeated interferon stimulation may permanently impair HSC function and bias stem cell output. When combined with loss of Dnmt3a, interferons may promote BMF. We will discuss broadly how external factors such as aging and infection may collaborate with specific genetic determinants to affect long-term hematopoiesis and malignancy development. Reference: Challen GA, Sun D, Jeong M, et al. Dnmt3a is essential for hematopoietic stem cell differentiation. Nat Genet 2012; 44: 23-31 Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

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Hematopoietic Expression of Hoxb4 Is Regulated in Normal and Leukemic Stem Cells through Transcriptional Activation of the Hoxb4 Promoter by Upstream Stimulating Factor (Usf)-1 and Usf-2

Journal of Experimental Medicine ◽

10.1084/jem.192.10.1479 ◽

2000 ◽

Vol 192 (10) ◽

pp. 1479-1490 ◽

Cited By ~ 36

Author(s):

Diane M. Giannola ◽

Warren D. Shlomchik ◽

Mithila Jegathesan ◽

David Liebowitz ◽

Charles S. Abrams ◽

...

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Stem Cell ◽

Luciferase Expression ◽

Regulatory Sequence ◽

Regulatory Sequences ◽

Cell Renewal ◽

Self Renewal ◽

Hematopoietic Stem ◽

Stimulating Factor

The homeobox genes encode a family of transcription factors that regulate development and postnatal tissue homeostasis. Since HOXB4 plays a key role in regulating the balance between hematopoietic stem cell renewal and differentiation, we studied the molecular regulation of HOXB4 expression in human hematopoietic stem cells. HOXB4 expression in K562 cells is regulated at the level of transcription, and transient transfection defines primary HOXB4 regulatory sequences within a 99-bp 5′ promoter. Culture of highly purified human CD34+ bone marrow cells in thrombopoietin/Flt-3 ligand/stem cell factor induced HOXB4 3–10-fold, whereas culture in granulocyte/macrophage colony-stimulating factor, only increased HOXB4/luciferase expression 20–50%. Mutations within the HOXB4 promoter identified a potential E box binding site (HOX response element [HXRE]-2) as the most critical regulatory sequence, and yeast one hybrid assays evaluating bone marrow and K562 libraries for HXRE-2 interaction identified upstream stimulating factor (USF)-2 and micropthalmia transcription factor (MITF). Electrophoretic mobility shift assay with K562 extracts confirmed that these proteins, along with USF-1, bind to the HOXB4 promoter in vitro. Cotransfection assays in both K562 and CD34+ cells showed that USF-1 and USF-2, but not MITF, induce the HOXB4 promoter in response to signals stimulating stem cell self-renewal, through activation of the mitogen-activated protein kinase pathway. Thus hematopoietic expression of the human HOXB4 gene is regulated by the binding of USF-1 and USF-2, and this process may be favored by cytokines promoting stem cell self-renewal versus differentiation.

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Emilin-2 is a component of bone marrow extracellular matrix regulating mesenchymal stem cell differentiation and hematopoietic progenitors

Stem Cell Research & Therapy ◽

10.1186/s13287-021-02674-2 ◽

2022 ◽

Vol 13 (1) ◽

Author(s):

Francesco Da Ros ◽

Luca Persano ◽

Dario Bizzotto ◽

Mariagrazia Michieli ◽

Paola Braghetta ◽

...

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Extracellular Matrix ◽

Stem Cell ◽

Mesenchymal Stem Cell ◽

Adipogenic Differentiation ◽

Stem Cell Differentiation ◽

Dependent Manner ◽

Hematopoietic Stem

Abstract Background Dissection of mechanisms involved in the regulation of bone marrow microenvironment through cell–cell and cell–matrix contacts is essential for the detailed understanding of processes underlying bone marrow activities both under physiological conditions and in hematologic malignancies. Here we describe Emilin-2 as an abundant extracellular matrix component of bone marrow stroma. Methods Immunodetection of Emilin-2 was performed in bone marrow sections of mice from 30 days to 6 months of age. Emilin-2 expression was monitored in vitro in primary and mesenchymal stem cell lines under undifferentiated and adipogenic conditions. Hematopoietic stem cells and progenitors in bone marrow of 3- to 10-month-old wild-type and Emilin-2 null mice were analyzed by flow cytometry. Results Emilin-2 is deposited in bone marrow extracellular matrix in an age-dependent manner, forming a meshwork that extends from compact bone boundaries to the central trabecular regions. Emilin-2 is expressed and secreted by both primary and immortalized bone marrow mesenchymal stem cells, exerting an inhibitory action in adipogenic differentiation. In vivo Emilin-2 deficiency impairs the frequency of hematopoietic stem/progenitor cells in bone marrow during aging. Conclusion Our data provide new insights in the contribution of bone marrow extracellular matrix microenvironment in the regulation of stem cell niches and hematopoietic progenitor differentiation.

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The bone marrow stem cell niche grows up: mesenchymal stem cells and macrophages move in

Journal of Experimental Medicine ◽

10.1084/jem.20110132 ◽

2011 ◽

Vol 208 (3) ◽

pp. 421-428 ◽

Cited By ~ 363

Author(s):

Armin Ehninger ◽

Andreas Trumpp

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Mesenchymal Stem Cells ◽

Stem Cell ◽

Cell Function ◽

Cell Types ◽

Nerve Fibers ◽

Hematopoietic Stem ◽

Sympathetic Nerve Fibers ◽

Cell Mobilization

Stem cell niches are defined as the cellular and molecular microenvironments that regulate stem cell function together with stem cell autonomous mechanisms. This includes control of the balance between quiescence, self-renewal, and differentiation, as well as the engagement of specific programs in response to stress. In mammals, the best understood niche is that harboring bone marrow hematopoietic stem cells (HSCs). Recent studies have expanded the number of cell types contributing to the HSC niche. Perivascular mesenchymal stem cells and macrophages now join the previously identified sinusoidal endothelial cells, sympathetic nerve fibers, and cells of the osteoblastic lineage to form similar, but distinct, niches that harbor dormant and self-renewing HSCs during homeostasis and mediate stem cell mobilization in response to granulocyte colony-stimulating factor.

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Hematopoiesis and Stem Cell Renewal in Long-Term Bone Marrow Cultures Containing Catalase.

Blood ◽

10.1182/blood.v104.11.371.371 ◽

2004 ◽

Vol 104 (11) ◽

pp. 371-371 ◽

Cited By ~ 1

Author(s):

Rashmi Gupta ◽

Simon Karpatkin ◽

Ross Basch

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Stem Cell ◽

Bone Marrow Cells ◽

Fold Increase ◽

Cell Renewal ◽

Hematopoietic Stem ◽

Stem Cell Renewal ◽

Bone Marrow Cultures

Abstract Many of the events that occur within the bone marrow can be modeled in long-term bone marrow cultures (LTBMC), which are capable of producing stem cells. Although the cultures faithfully replicate the differentiation of many hematopoietic lineages, they are relatively short-lived. The stem cell compartment is rapidly depleted and attempts to achieve expansion of hematopoietic cells in culture have met with limited success. These cultures accumulate large numbers of granulocytes and monocytes capable of producing significant levels of reactive oxygen species (ROS). It has recently become clear that some ROS, including H2O2 can play a critical role in intracellular signalling induced by various growth factors and cytokines. We therefore elected to test the effect of 2 different H2O2 scavenger catalases, (bovine or aspergillosis added on alternate days) on LTBMC hematopoiesis of mouse low density bone marrow cells on irradiated adherent preformed stromal monolayers. Dramatic alterations were noted with either catalase, whereas heat-inactivated catalase had no effect. Initially there is a 5–10 fold increase in the non-adherent granulocytes and their precursors. The increase is relatively short-lived at 3–4 weeks when catalase cultures contain 1/5 as many hematopoietic cells as controls. However these cells contain 5 times the number of myeloid clonal progenitors (CFU-c) than controls. After 4–5 weeks the catalase treated cells become quiescent. When catalase is removed hematopoiesis returns promptly, ruling out a catalase-induced toxic effect. By the 3rd week of catalase treatment >90% of non-adherent cells are Sca-1+ and 36% of them are Lin−. In absolute numbers the Sca-1+ and Lin− population increase 80 fold at 3 weeks. If losses induced by removal of half of the non-adherent cells with each weekly feeding are considered, the absolute increase is >500 fold. Virtually all of the Sca-1+, Lin− cells express C-Kit+. At 2–3 weeks, approximately 15% of cells recovered from the catalase cultures have this stem cell phenotype described for murine cells, which represents a 200 fold increase in stem cells compared to controls. These cells (20,000 Ly 5.1 cells) were then tested for their ability to sustain both short- and long-term hematopoiesis in lethally irradiated Ly 5.2 mice along with 30,000 freshly isolated Ly 5.2 bone marrow cells. The catalase-treated cells showed both short- and long-term repopulating activity. At 3,6 and 10 weeks sorted Sca-1+, Lin− catalase-treated Ly 5.1 cells were 14,20 and 39% respectively of host cells, compared to 1,3 and 5% of cells cultured without catalase. These catalase-treated cells underwent multilinege repopulation granulocytes (Gr-1+), monocytes (mac-1+), T-cells (CD3+) and B− cells (B-220+) in the Ly 5.2 host. Thus, peroxide-sensitive regulatory mechanisms play an important role in regulating hematopoietic stem cell renewal and differentiation. Protected from H2O2, hematopoietic progenitors multiply and become quiescent. These cells are 200–500 fold enriched with functional stem cells. Manipulation of peroxide levels in vitro can dramatically enhance the growth of self-renewing hematopoietic stem cells and may provide a unique source of undifferentiated hematopoietic progenitors.

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MT1-MMP Regulates Hematopoiesis Through HIF-Mediated Chemo-/Cytokine Release From the Bone Marrow Niche,

Blood ◽

10.1182/blood.v118.21.3409.3409 ◽

2011 ◽

Vol 118 (21) ◽

pp. 3409-3409

Author(s):

Chiemi Nishida ◽

Kaori Kusubata ◽

Yoshihiko Tashiro ◽

Ismael Gritli ◽

Aki Sato ◽

...

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Stem Cell ◽

Cell Fate ◽

Conflicts Of Interest ◽

Stem Cell Differentiation ◽

Cell Phenotype ◽

Bone Marrow Niche ◽

Matrix Remodeling ◽

Hematopoietic Stem

Abstract Abstract 3409 Stem cells reside in a physical niche, a particular microenvironment. The organization of cellular niches has been shown to play a key role in regulating normal stem cell differentiation, stem cell maintenance and regeneration. Various stem cell niches have been shown to be hypoxic, thereby maintaining the stem cell phenotype, e.g. for hematopoietic stem cells (HSCs) or cancer stem cells. The bone marrow (BM) niche is a rich reservoir for tissue-specific pluripotent HSCs. Proteases, such as matrix metalloproteinases (MMPs) can modulate stem cell fate due to their proteolytic or non-proteolytic functions (abilities). We have investigated the role of membrane-type1 matrix metalloproteinase (MT1-MMP), known for its role in pericellular matrix remodeling and cell migration, in hematopoiesis. MT1-MMP is highly expressed in HSCs and stromal cells. In MT1-MMP−/− mice, release of kit ligand (KitL), stromal cell derived factor-1 (SDF-1/CXCL12), erythropoietin (Epo) and interleukin-7 were impaired resulting in erythroid, myeloid and T and B lymphoid differentiation. Addition of exogenous rec. KitL and rec. SDF-1 restored hematopoiesis in vivo and in vitro. Further mechanistic studies revealed that MT1-MMP in a non-proteolytic manner activates the HIF-1 pathway, thereby inducing the transcription of the HIF-responsive genes KitL, SDF-1 and Epo. These results suggested MT1-MMP as a critical regulator of postnatal hematopoiesis, which as a modulator of the HIF pathway alters critical hematopoietic niche factors necessary for terminal differentiation and or migration. Thus, our results indicate that MT1-MMP as a key molecular link between hypoxia and the regulation of vital HSC niche factors. Disclosures: No relevant conflicts of interest to declare.

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Bone marrow clones representing an intermediate stage of development between hematopoietic stem cells and pro-T-lymphocyte or pro-B- lymphocyte progenitors

Blood ◽

10.1182/blood.v81.5.1222.bloodjournal8151222 ◽

1993 ◽

Vol 81 (5) ◽

pp. 1222-1238

Author(s):

R Palacios ◽

J Samaridis

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Stem Cell ◽

T Lymphocytes ◽

Progenitor Cells ◽

B Lymphocytes ◽

Stem Cell Differentiation ◽

Intermediate Stage ◽

Hematopoietic Stem ◽

Stage Of Development

We have established in culture several nontransformed bone marrow clones (called PR) that show phenotypic and genotypic characteristics that distinguish them from totipotent stem cells and lineage-restricted Pro-T lymphocytes, Pro-B lymphocytes, and myeloid cell progenitors. In vivo and/or in vitro the PR clones give rise to T lymphocytes, B lymphocytes, and some myeloid-lineage cells, but they appear not to be able to generate cells of the erythroid lineage, nor can they rescue mice from a lethal dose of irradiation. We conclude that the PR clones are precursor cells representing an intermediate stage of development between the totipotential stem cell and lineage-restricted progenitor cells. The results described here support a model of blood cell formation in which stem cell differentiation is a progressive process marked by the stepwise loss of self renewal and functional potential. In addition, they provide evidence that cytokines and specialized microenvironments can direct the fate of the developing multipotent progenitor cells.

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