| 1. |
- Eliasson, Pernilla, et al.
(författare)
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Hypoxia mediates low cell-cycle activity and increases the proportion of long-term reconstituting hematopoietic stem cells during in vitro culture
- 2010
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Ingår i: Experimental Hematology. - : Elsevier. - 0301-472X .- 1873-2399. ; 38:4, s. 301-310
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Recent evidence suggests that hematopoietic stem cells (HSCs) in the bone marrow (BM) are located in areas where the environment is hypoxic. Although previous studies have demonstrated positive effects by hypoxia, its role in HSC maintenance has not been fully elucidated, neither has the molecular mechanisms been delineated. Here, we have investigated the consequence of in vitro incubation of HSCs in hypoxia prior to transplantation and analyzed the role of hypoxia-inducible factor (HIF)-1 alpha. Materials and Methods. HSC and progenitor populations isolated from mouse BM were cultured in 20% or 1% O-2, and analyzed for effects on cell cycle, expression of cyclin-dependent kinase inhibitors genes, and reconstituting ability to lethally irradiated mice. The involvement of HIF-1 alpha was studied using methods of protein stabilization and gene silencing. Results. When long-term FLT3(-)CD34(-)Lin(-)Sca-1(+)c-Kit(+) (LSK) cells were cultured in hypoxia, cell numbers were significantly reduced in comparison to normoxia. This was due to a decrease in proliferation and more cells accumulating in G(0). Moreover, the proportion of HSCs with long-term engraftment potential was increased. Whereas expression of the cyclin-dependent kinase inhibitor genes p21(cip1), p27(Kip1), and p57(Kip2) increased in LSK cells by hypoxia, only p21(cip1) was upregulated in FLT3(-)CD34(-)LSK cells. We could demonstrate that expression of p27(KiP1) and p57(Kip2) was dependent of HIF-1 alpha. Surprisingly, overexpression of constitutively active HIF-1 alpha or treatment with the HIF stabilizer agent FG-4497 led to a reduction in HSC reconstituting ability. Conclusions. Our results imply that hypoxia, in part via HIF-1 alpha, maintains HSCs by decreasing proliferation and favoring quiescence.
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| 2. |
- Eriksson, Matilda, et al.
(författare)
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Cats and owners interact more with each other after a longer duration of separation
- 2017
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about the cat's (Felis silvestris catus) need for human contact, although it is generally believed that cats are more independent pets than e. g. dogs. In this study, we investigated the effect of time left alone at home on cat behaviour (e. g. social and distressrelated) before, during and after separation from their owner. Fourteen privately owned cats (single-housed) were each subjected to two treatments: the cat was left alone in their home environment for 30 min (T-0.5) and for 4 h (T-4). There were no differences between treatments in the behaviour of the cat (or owner) before owner departure, nor during the first 5 min of separation. During separation, cats were lying down resting proportionally less (T = 22.5, P = 0.02) in T-0.5 (0.27 +/- 0.1 (mean +/- SE)) compared to in T-4 (0.58 +/- 0.08), probably due to a similar duration of higher activity early in the separation phase in both treatments. Comparisons of the time interval (min 20 +/- 25) in both treatments indicated no differences across treatments, which supports such an explanation. Towards the end of the separation phase (the last two 5-min intervals of separation in both treatments), no differences were observed in the cats' behaviour, indicating that cats were unaffected by separation length. At reunion however, cats purred more (T = 10.5, P = 0.03) and stretched their body more (T = 17, P = 0.04) after a longer duration of separation (T4: 0.05 +/- 0.02; 0.03 +/- 0.01; T-0.5: 0.01 +/- 0.007; 0.008 +/- 0.003). Also, owners initiated more verbal contact (T = 33.5, P = 0.04) after 4 h (0.18 +/- 0.05) compared to after 30 min (0.12 +/- 0.03). There was no evidence of any correlations between the level of purring or body stretching by the cat and verbal contact by the owner implying that the behavioural expressions seen in the cats are independent of the owner's behaviour. Hence, it seemed as cats coped well with being left alone, but they were affected by the time they were left alone, since they expressed differences in behaviour when the owner returned home. The increased level of social contact initiated by the cats after a longer duration of separation indicates a rebound of contact-seeking behaviour, implying that the owner is an important part of the cat's social environment.
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| 3. |
- Knudsen, Kasper Jermiin, et al.
(författare)
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ERG promotes the maintenance of hematopoietic stem cells by restricting their differentiation.
- 2015
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Ingår i: Genes & Development. - : Cold Spring Harbor Laboratory. - 1549-5477 .- 0890-9369. ; 29:18, s. 1915-1929
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Tidskriftsartikel (refereegranskat)abstract
- The balance between self-renewal and differentiation is crucial for the maintenance of hematopoietic stem cells (HSCs). Whereas numerous gene regulatory factors have been shown to control HSC self-renewal or drive their differentiation, we have relatively few insights into transcription factors that serve to restrict HSC differentiation. In the present work, we identify ETS (E-twenty-six)-related gene (ERG) as a critical factor protecting HSCs from differentiation. Specifically, loss of Erg accelerates HSC differentiation by >20-fold, thus leading to rapid depletion of immunophenotypic and functional HSCs. Molecularly, we could demonstrate that ERG, in addition to promoting the expression of HSC self-renewal genes, also represses a group of MYC targets, thereby explaining why Erg loss closely mimics Myc overexpression. Consistently, the BET domain inhibitor CPI-203, known to repress Myc expression, confers a partial phenotypic rescue. In summary, ERG plays a critical role in coordinating the balance between self-renewal and differentiation of HSCs.
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| 4. |
- Miharada, Kenichi, et al.
(författare)
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Cripto Regulates Hematopoietic Stem Cells as a Hypoxic-Niche-Related Factor through Cell Surface Receptor GRP78.
- 2011
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Ingår i: Cell Stem Cell. - : Elsevier BV. - 1934-5909. ; 9:4, s. 330-344
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Tidskriftsartikel (refereegranskat)abstract
- Hematopoietic stem cells (HSCs) are maintained in hypoxic niches in endosteal regions of bones. Here we demonstrate that Cripto and its receptor GRP78 are important regulators of HSCs in the niche. Flow cytometry analyses revealed two distinct subpopulations of CD34(-)KSL cells based on the expression of GRP78, and these populations showed different reconstitution potential in transplantation assays. GRP78(+)HSCs mainly reside in the endosteal area, are more hypoxic, and exhibit a lower mitochondrial potential, and their HSC capacity was maintained in vitro by Cripto through induction of higher glycolytic activity. Additionally, HIF-1α KO mice have decreased numbers of GRP78(+)HSCs and reduced expression of Cripto in the endosteal niche. Furthermore, blocking GRP78 induced a movement of HSCs from the endosteal to the central marrow area. These data suggest that Cripto/GRP78 signaling is an important pathway that regulates HSC quiescence and maintains HSCs in hypoxia as an intermediary of HIF-1α.
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| 5. |
- Miharada, Kenichi, et al.
(författare)
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Hematopoietic stem cells are regulated by Cripto, as an intermediary of HIF-1α in the hypoxic bone marrow niche.
- 2012
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Ingår i: Annals of the New York Academy of Sciences. - : Wiley. - 0077-8923. ; 1266:1, s. 55-62
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Tidskriftsartikel (refereegranskat)abstract
- Cripto has been known as an embryonic stem (ES)- or tumor-related soluble/cell membrane protein. In this study, we demonstrated that Cripto has a role as an important regulatory factor for hematopoietic stem cells (HSCs). Recombinant Cripto sustained the reconstitution ability of HSCs in vitro. Flow cytometry analysis uncovered that GRP78, one of the candidate receptors for Cripto, was expressed on a subset of HSCs and could distinguish dormant/myeloid-biased HSCs and active/lymphoid-biased HSCs. Cripto is expressed in hypoxic endosteal niche cells where GRP78(+) HSCs mainly reside. Proteomics analysis revealed that Cripto-GRP78 binding stimulates glycolytic metabolism-related proteins and results in lower mitochondrial potential in HSCs. Furthermore, conditional knockout mice for HIF-1α, a master regulator of hypoxic responses, showed reduced Cripto expression and decreased GRP78(+) HSCs in the endosteal niche area. Thus, Cripto-GRP78 is a novel HSC regulatory signal mainly working in the hypoxic niche.
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| 6. |
- Pietras, Alexander, et al.
(författare)
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HIF-2 alpha maintains an undifferentiated state in neural crest-like human neuroblastoma tumor-initiating cells
- 2009
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 106:39, s. 16805-16810
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Tidskriftsartikel (refereegranskat)abstract
- High hypoxia-inducible factor-2 alpha (HIF-2 alpha) protein levels predict poor outcome in neuroblastoma, and hypoxia dedifferentiates cultured neuroblastoma cells toward a neural crest-like phenotype. Here, we identify HIF-2 alpha as a marker of normoxic neural crest-like neuroblastoma tumor-initiating/stem cells (TICs) isolated from patient bone marrows. Knockdown of HIF-2 alpha reduced VEGF expression and induced partial sympathetic neuronal differentiation when these TICs were grown in vitro under stem cell-promoting conditions. Xenograft tumors of HIF-2 alpha-silenced cells were widely necrotic, poorly vascularized, and resembled the bulk of tumor cells in clinical neuroblastomas by expressing additional sympathetic neuronal markers, whereas control tumors were immature, well-vascularized, and stroma-rich. Thus, HIF-2 alpha maintains an undifferentiated state of neuroblastoma TICs. Because low differentiation is associated with poor outcome and angiogenesis is crucial for tumor growth, HIF-2 alpha is an attractive target for neuroblastoma therapy.
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| 7. |
- Reckzeh, Kristian, et al.
(författare)
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Molecular and cellular effects of oncogene cooperation in a genetically accurate AML mouse model.
- 2012
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Ingår i: Leukemia. - : Springer Science and Business Media LLC. - 1476-5551 .- 0887-6924. ; 26:7, s. 1527-1536
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Tidskriftsartikel (refereegranskat)abstract
- Biallelic CEBPA mutations and FLT3 length mutations are frequently identified in human acute myeloid leukemia (AML) with normal cytogenetics. However, the molecular and cellular mechanisms of oncogene cooperation remain unclear due to a lack of disease models. We have generated an AML mouse model using knockin mouse strains to study cooperation of internal tandem duplication (ITD) mutation in the Flt3 gene with commonly observed C/EBPα mutations. This study provides evidence that FLT3 ITD cooperates in leukemogenesis by enhancing the generation of leukemia-initiating granulocyte-monocyte progenitors (GMP) otherwise prevented by a block in differentiation and skewed lineage priming induced by biallelic C/EBPα mutations. These cellular changes are accompanied by an upregulation of hematopoietic stem cell and STAT5 target genes. By gene expression analysis in premalignant populations we further show a role of FLT3 ITD in activating genes involved in survival/transformation and chemoresistance. Both multipotent progenitors (MPP) and GMP cells contain the potential to induce AML similar to corresponding cells in human AML samples showing that this model resembles human disease.Leukemia accepted article preview online, 9 February 2012; doi:10.1038/leu.2012.37.
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Rehn, Matilda, et al.
(författare)
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Hypoxic induction of vascular endothelial growth factor regulates erythropoiesis but not hematopoietic stem cell function in the fetal liver.
- 2014
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Ingår i: Experimental Hematology. - : Elsevier BV. - 1873-2399 .- 0301-472X. ; 42:11, s. 941-944
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Tidskriftsartikel (refereegranskat)abstract
- Hypoxia is an important factor in the hematopoietic stem cell (HSC) niche in the bone marrow, but whether it also plays a role in the regulation of fetal liver (FL) HSCs is unclear. Vascular endothelial growth factor A (VEGFA) is essential for adult HSC survival, and hypoxic induction of VEGFA in adult HSCs is required for proper function. Loss of hypoxia-regulated VEGFA expression increases the number of phenotypically defined hematopoietic stem and progenitor cells in the FL, but whether stem cell function is affected in FL HSCs has not, to our knowledge, been assessed. We show that fetal erythropoiesis is severely impaired when hypoxic induction of VEGFA is lacking. Fetal liver HSCs deficient for hypoxia-induced VEGFA expression have normal HSC function, arguing against a hypoxic FL HSC niche. However, after adaptation of FL HSCs to the bone marrow microenvironment, FL HSCs lose their function, as measured by serial transplantation.
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| 12. |
- Rehn, Matilda, et al.
(författare)
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Hypoxic induction of vascular endothelial growth factor regulates murine hematopoietic stem cell function in the low-oxygenic niche.
- 2011
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Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 118:6, s. 1534-1543
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Tidskriftsartikel (refereegranskat)abstract
- Hypoxia is emerging as an important characteristic of the hematopoietic stem cell (HSC) niche, but the molecular mechanisms contributing to quiescence, self-renewal, and survival remain elusive. Vascular endothelial growth factor A (VEGFA) is a key regulator of angiogenesis and hematopoiesis. Its expression is commonly regulated by hypoxia-inducible factors (HIF) that are functionally induced in low-oxygen conditions and that activate transcription by binding to hypoxia-response elements (HRE). Vegfa is indispensable for HSC survival, mediated by a cell-intrinsic, autocrine mechanism. We hypothesized that a hypoxic HSC microenvironment is required for maintenance or upregulation of Vegfa expression in HSCs and therefore crucial for HSC survival. We have tested this hypothesis in the mouse model Vegfa(δ/δ), where the HRE in the Vegfa promoter is mutated, preventing HIF binding. Vegfa expression was reduced in highly purified HSCs from Vegfa(δ/δ) mice, showing that HSCs reside in hypoxic areas. Loss of hypoxia-regulated Vegfa expression increases the numbers of phenotypically defined hematopoietic stem and progenitor cells. However, HSC function was clearly impaired when assessed in competitive transplantation assays. Our data provide further evidence that HSCs reside in a hypoxic microenvironment and demonstrate a novel way in which the hypoxic niche affects HSC fate, via the hypoxia-Vegfa axis.
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| 13. |
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| 14. |
- Rehn, Matilda
(författare)
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THE HYPOXIC HEMATOPOIETIC STEM CELL NICHE Consequences of Hypoxia-induced Transcription on Stem Cell Fate
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hematopoiesis is the process of blood formation that originates with the hematopoietic stem cell (HSC), a cell type that is responsible for the life-long supply of mature blood cells. HSCs are defined by their ability to self-renew as well as giving rise to differentiated cells of all blood lineages. Because of these features, HSCs are also the basis for bone marrow transplantation regimens for treatment of leukemia and various other hematopoietic disorders. HSCs reside in the bone marrow of adult mammals, in the so called niche. The HSC niche refers to the specific anatomical region where the stem cells reside, but also to the regulatory microenvironment consisting of adjacent cells and factors produced by these. An important feature of the HSC niche seems to be a relatively low level of oxygen: hypoxia. Hypoxia leads to activation of Hypoxia-Inducible Factors (HIF). We have investigated the role of hypoxia and HIFs in HSC biology. By in vitro hypoxic treatment, we could show that hypoxia leads to less proliferation of HSCs, with up-regulation of cell-cycle inhibitory genes, while full reconstitution potential of irradiated recipient mice is preserved. Ectopic activation of HIF, mediated by retroviral overexpression in hematopoietic stem and progenitor cells (HSPC), leads to even less proliferation and a disability to sustain hematopoiesis in vivo. The role of the HIF target gene Vegfa was studied in a mouse model where hypoxia-induced transcription of Vegfa is abrogated (Vegfaδ/δ). HSCs could be maintained under steady-state conditions without hypoxic induction of Vegfa. In transplantation assays however, we show that when Vegfa upregulation upon hypoxia is lacking, adult HSC function is clearly impaired. On the contrary, HSCs isolated from the fetal liver of developing Vegfaδ/δ mice had a normal function. Furthermore, we show that erythropoiesis during development and to a lesser extent in the adult involves hypoxic Vegfa expression. In summary, this thesis contributes new findings to the role of the hypoxic HSC niche. We show that hypoxia and HIFs are involved in regulating HSC proliferation. Furthermore, hypoxia-induced Vegfa is identified as an important player in HSCs.
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| 15. |
- Velasco, Talia, et al.
(författare)
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HIF-1α can act as a tumor suppressor gene in murine Acute Myeloid Leukemia.
- 2014
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Ingår i: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 124:24, s. 3597-3607
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Tidskriftsartikel (refereegranskat)abstract
- Self-renewal of hematopoietic stem cells (HSCs) and leukemia-initiating cells (LICs) has been proposed to be influenced by low oxygen tension (hypoxia). This signaling, related to the cellular localization inside the bone marrow niche and/or influenced by extrinsic factors, promotes the stabilization of hypoxia inducible factors (HIFs). Whether HIF-1α can be used as a therapeutic target in the treatment of myeloid malignancies remains unknown. We have used three different murine models to investigate the role of HIF-1α in acute myeloid leukemia (AML) initiation/progression and self-renewal of LICs. Unexpectedly, we failed to observe a delay or prevention of disease development from hematopoietic cells lacking Hif-1α. In contrast, deletion of Hif-1α resulted in faster development of the disease and an enhanced leukemia phenotype in some of the investigated models. Our results therefore warrant a reconsideration of the role of HIF-1α and, as a consequence, question its generic therapeutic usefulness in AML.
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