| 1. |
- Attema, Joanne, et al.
(author)
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Hematopoietic stem cell ageing is uncoupled from p16 INK4A-mediated senescence
- 2009
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In: Oncogene. - : Nature Publishing Group. - 0950-9232 .- 1476-5594. ; 28:22, s. 2238-2243
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Journal article (peer-reviewed)abstract
- Somatic stem cells are ultimately responsible for mediating appropriate organ homeostasis and have therefore been proposed to represent a cellular origin of the ageing process-a state often characterized by inappropriate homeostasis. Specifically, it has been suggested that ageing stem cells might succumb to replicative senescence by a mechanism involving the cyclin-dependent kinase inhibitor p16(INK4A). Here, we tested multiple functional and molecular parameters indicative of p16(INK4A) activity in primary aged murine hematopoietic stem cells (HSCs). We found no evidence that replicative senescence accompanies stem cell ageing in vivo, and in line with p16(INK4A) being a critical determinant of such processes, most aged HSCs (>99%) failed to express p16(INK4A) at the mRNA level. Moreover, whereas loss of epigenetically guided repression of the INK4A/ARF locus accompanied replicative senescent murine embryonic fibroblasts, such repression was maintained in aged stem cells. Taken together, these studies indicate that increased senescence as mediated by the p16(INK4A) tumor suppressor has only a minor function as an intrinsic regulator of steady-state HSC ageing in vivo.
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| 2. |
- Breitbach, Martin, et al.
(author)
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Potential risks of bone marrow cell transplantation into infarcted hearts
- 2007
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In: Blood. - Washington, DC : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 110:4, s. 1362-1369
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Journal article (peer-reviewed)abstract
- Cellular replacement therapy has emerged as a novel strategy for the treatment of heart failure. The aim of our study was to determine the fate of injected mesenchymal stem cells (MSCs) and whole bone marrow (BM) cells in the infarcted heart. MSCs were purified from BM of transgenic mice and characterized using flow cytometry and in vitro differentiation assays. Myocardial infarctions were generated in mice and different cell populations including transgenic MSCs, unfractionated BM cells, or purified hematopoietic progenitors were injected. Encapsulated structures were found in the infarcted areas of a large fraction of hearts after injecting MSCs (22 of 43, 51.2%) and unfractionated BM cells (6 of 46, 13.0%). These formations contained calcifications and/or ossifications. In contrast, no pathological abnormalities were found after injection of purified hematopoietic progenitors (0 of 5, 0.0%), fibroblasts (0 of 5, 0.0%), vehicle only (0 of 30, 0.0%), or cytokine-induced mobilization of BM cells (0 of 35, 0.0%). We conclude that the developmental fate of BM-derived cells is not restricted by the surrounding tissue after myocardial infarction and that the MSC fraction underlies the extended bone formation in the infarcted myocardium. These findings seriously question the biologic basis and clinical safety of using whole BM and in particular MSCs to treat nonhematopoietic disorders.
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| 3. |
- Buza-Vidas, Natalija, et al.
(author)
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Cytokines regulate postnatal hematopoietic stem cell expansion : Opposing roles of thrombopoietin and LNK
- 2006
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In: Genes & Development. - Woodbury, NY, USA : Cold Spring Harbor Laboratory Press (CSHL). - 0890-9369 .- 1549-5477. ; 20:15, s. 2018-2023
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Journal article (peer-reviewed)abstract
- The role of cytokines as regulators of hematopoietic stem cell (HSC) expansion remains elusive. Herein, we identify thrombopoietin (THPO) and the cytokine signaling inhibitor LNK, as opposing physiological regulators of HSC expansion. Lnk(-/-) HSCs continue to expand postnatally, up to 24-fold above normal by 6 mo of age. Within the stem cell compartment, this expansion is highly selective for self-renewing long-term HSCs (LT-HSCs), which show enhanced THPO responsiveness. Lnk(-/-) HSC expansion is dependent on THPO, and 12-wk-old Lnk(-/-)Thpo(-/-) mice have 65-fold fewer LT-HSCs than Lnk(-/-) mice. Expansions of multiple myeloid, but not lymphoid, progenitors in Lnk(-/-) mice also proved THPO-dependent.
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| 4. |
- Kolossov, Eugen, et al.
(author)
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Engraftment of engineered ES cell-derived cardiomyocytes but not BM cells restores contractile function to the infarcted myocardium
- 2006
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In: Journal of Experimental Medicine. - New York, USA : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 203:10, s. 2315-2327
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Journal article (peer-reviewed)abstract
- Cellular cardiomyoplasty is an attractive option for the treatment of severe heart failure. It is, however, still unclear and controversial which is the most promising cell source. Therefore, we investigated and examined the fate and functional impact of bone marrow (BM) cells and embryonic stem cell (ES cell)-derived cardiomyocytes after transplantation into the infarcted mouse heart. This proved particularly challenging for the ES cells, as their enrichment into cardiomyocytes and their long-term engraftment and tumorigenicity are still poorly understood. We generated transgenic ES cells expressing puromycin resistance and enhanced green fluorescent protein cassettes under control of a cardiac-specific promoter. Puromycin selection resulted in a highly purified (>99%) cardiomyocyte population, and the yield of cardiomyocytes increased 6-10-fold because of induction of proliferation on purification. Long-term engraftment (4-5 months) was observed when co-transplanting selected ES cell-derived cardiomyocytes and fibroblasts into the injured heart of syngeneic mice, and no teratoma formation was found (n = 60). Although transplantation of ES cell-derived cardiomyocytes improved heart function, BM cells had no positive effects. Furthermore, no contribution of BM cells to cardiac, endothelial, or smooth muscle neogenesis was detected. Hence, our results demonstrate that ES-based cell therapy is a promising approach for the treatment of impaired myocardial function and provides better results than BM-derived cells.
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| 5. |
- Nygren, Jens Martin, 1976-, et al.
(author)
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A novel assay to trace proliferation history in vivo reveals that enhanced divisional kinetics accompany loss of hematopoietic stem cell self-renewal
- 2008
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In: PLOS ONE. - San Francisco : Public Library of Science. - 1932-6203. ; 3:11, s. art. no. e3710-
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Journal article (peer-reviewed)abstract
- BACKGROUND: The maintenance of lifelong blood cell production ultimately rests on rare hematopoietic stem cells (HSCs) that reside in the bone marrow microenvironment. HSCs are traditionally viewed as mitotically quiescent relative to their committed progeny. However, traditional techniques for assessing proliferation activity in vivo, such as measurement of BrdU uptake, are incompatible with preservation of cellular viability. Previous studies of HSC proliferation kinetics in vivo have therefore precluded direct functional evaluation of multi-potency and self-renewal, the hallmark properties of HSCs. METHODOLOGY/PRINCIPAL FINDINGS: We developed a non-invasive labeling technique that allowed us to identify and isolate candidate HSCs and early hematopoietic progenitor cells based on their differential in vivo proliferation kinetics. Such cells were functionally evaluated for their abilities to multi-lineage reconstitute myeloablated hosts. CONCLUSIONS: Although at least a few HSC divisions per se did not influence HSC function, enhanced kinetics of divisional activity in steady state preceded the phenotypic changes that accompanied loss of HSC self-renewal. Therefore, mitotic quiescence of HSCs, relative to their committed progeny, is key to maintain the unique functional and molecular properties of HSCs.
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| 6. |
- Nygren, Jens Martin, 1976-, et al.
(author)
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Implications of Developmental Switches for Hematopoietic Stem Cell Aging
- 2009
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In: Handbook on Immunosenescence. - Dordrecht : Springer Science+Business Media B.V.. - 9781402090622 - 9781402090639 ; , s. 589-611
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Book chapter (peer-reviewed)abstract
- Each of the different hematopoietic cell types has their own properties and function, but only when they all act in tight synergy are they able to constitute a highly specific and efficient immune defense capable of efficient protection from invading pathogens and appropriate maintenance of blood clotting and oxygen transport functions. All blood cell types are continuously produced in the bone-marrow by rare hematopoietic stem cells that persist throughout the life of the organism. These stem cells are influenced by their environment and developmental history and experience a range of cell intrinsic changes that over time alter their functional properties. These timed changes include alterations in fundamental processes such as self-renewal, proliferation, differentiation and gene expression, thereby being crucial for both normal maturation as well as hematopoietic aging.
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| 7. |
- Nygren, Jens Martin, 1976-, et al.
(author)
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Myeloid and lymphoid contribution to non-haematopoietic lineages through irradiation-induced heterotypic cell fusion
- 2008
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In: Nature Cell Biology. - London : Nature Publishing Group. - 1465-7392 .- 1476-4679. ; 10:5, s. 584-92
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Journal article (peer-reviewed)abstract
- Recent studies have suggested that regeneration of non-haematopoietic cell lineages can occur through heterotypic cell fusion with haematopoietic cells of the myeloid lineage. Here we show that lymphocytes also form heterotypic-fusion hybrids with cardiomyocytes, skeletal muscle, hepatocytes and Purkinje neurons. However, through lineage fate-mapping we demonstrate that such in vivo fusion of lymphoid and myeloid blood cells does not occur to an appreciable extent in steady-state adult tissues or during normal development. Rather, fusion of blood cells with different non-haematopoietic cell types is induced by organ-specific injuries or whole-body irradiation, which has been used in previous studies to condition recipients of bone marrow transplants. Our findings demonstrate that blood cells of the lymphoid and myeloid lineages contribute to various non-haematopoietic tissues by forming rare fusion hybrids, but almost exclusively in response to injuries or inflammation.
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| 8. |
- Nygren, Jens Martin, 1976-, et al.
(author)
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Prolonged cell cycle transit is a defining and developmentally conserved hemopoietic stem cell property
- 2006
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In: Journal of Immunology. - Bethesda, USA : American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 177:1, s. 201-208
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Journal article (peer-reviewed)abstract
- Adult mouse hemopoietic stem cells (HSCs) are typically quiescent and enter and progress through the cell cycle rarely in steady-state bone marrow, but their rate of proliferation can be dramatically enhanced on demand. We have studied the cell cycle kinetics of HSCs in the developing fetal liver at a stage when they expand extensively. Despite that 100% of fetal liver HSCs divide within a 48-h period, their average cell cycle transit time (10.6 h) is twice that of their downstream progenitors, translating into a prolonged G(1) transit and a period of relative quiescence (G(0)). In agreement with their prolonged G(1) transit when compared with hemopoietic progenitors, competitive transplantation experiments demonstrate that fetal HSCs are highly enriched in G(1) but also functional in S-G(2)-M. This observation combined with experimental data demonstrating that adult HSCs forced to expand ex vivo also sustain a uniquely prolonged cell cycle and G(1) transit, demonstrate at least in part why purified HSCs at any state of development or condition are highly enriched in the G(0)-G(1) phases of the cell cycle. We propose that a uniquely prolonged cell cycle transit is a defining stem cell property, likely to be critical for their maintenance and self-renewal throughout development.
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| 9. |
- Sitnicka Quinn, Ewa, et al.
(author)
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Critical role of FLT3 ligand in IL-7 receptor-independent T lymphopoiesis and regulation of lymphoid-primed multipotent progenitors
- 2007
-
In: Blood. - Washington, DC : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 110:8, s. 2955-2964
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Journal article (peer-reviewed)abstract
- The molecular pathways regulating lymphoid priming, fate, and development of multipotent bone marrow (BM) stem/progenitor cells that continuously replace thymic progenitors remain largely unknown. Herein, we show that fms-like tyrosine kinase 3 (Flt3) ligand (Fl)-deficient mice have distinct reductions in the earliest thymic progenitors in fetal, postnatal, and adult thymus. A critical role of FL in thymopoiesis was particularly evident in the absence of interleukin-7 receptor alpha (IL-7Ralpha) signaling. Fl-/-Il-7r-/- mice have extensive reductions in fetal and postnatal thymic progenitors that result in a loss of active thymopoiesis in adult mice, demonstrating an indispensable role of FL in IL-7Ralpha-independent fetal and adult T lymphopoiesis. Moreover, we establish a unique and critical role of FL, distinct from that of IL-7Ralpha, in regulation of the earliest lineage-negative (Lin(-)) Lin(-)SCA1+KIT+ (LSK) FLT3(hi) lymphoid-primed multipotent progenitors in BM, demonstrating a key role of FLT3 signaling in regulating the very earliest stages of lymphoid progenitors.
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| 10. |
- Taneera, Jalal, et al.
(author)
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Failure of Transplanted Bone Marrow Cells to Adopt a Pancreatic β-Cell Fate
- 2006
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In: Diabetes. - Alexandria, USA : American Diabetes Association. - 0012-1797 .- 1939-327X. ; 55:2, s. 290-296
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Journal article (peer-reviewed)abstract
- Recent studies in normal mice have suggested that transplanted bone marrow cells can transdifferentiate into pancreatic beta-cells at relatively high efficiency. Herein, adopting the same and alternative approaches to deliver and fate map-transplanted bone marrow cells in the pancreas of normal as well as diabetic mice, we further investigated the potential of bone marrow transplantation as an alternative approach for beta-cell replacement. In contrast to previous studies, transplanted bone marrow cells expressing green fluorescence protein (GFP) under the control of the mouse insulin promoter failed to express GFP in the pancreas of normal as well as diabetic mice. Although bone marrow cells expressing GFP under the ubiquitously expressed beta-actin promoter efficiently engrafted the pancreas of normal and hyperglycemic mice, virtually all expressed CD45 and Mac-1/Gr-1, demonstrating that they adopt a hematopoietic rather than beta-cell fate, a finding further substantiated by the complete absence of GFP(+) cells expressing insulin and the beta-cell transcription factors pancreatic duodenal homeobox factor-1 and homeodomain protein. Thus, transplanted bone marrow cells demonstrated little, if any, capacity to adopt a beta-cell fate.
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