scholarly journals Osteopontin is a hematopoietic stem cell niche component that negatively regulates stem cell pool size

2005 ◽  
Vol 201 (11) ◽  
pp. 1781-1791 ◽  
Author(s):  
Sebastian Stier ◽  
Yon Ko ◽  
Randolf Forkert ◽  
Christoph Lutz ◽  
Thomas Neuhaus ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Stem Cell Niche ◽  
Regulatory Element ◽  
Cell Number ◽  
Hematopoietic Cell ◽  
Hematopoietic Stem ◽  
Cell Pool ◽  
Cell Niche ◽  
Stem Cell Pool

Stem cells reside in a specialized niche that regulates their abundance and fate. Components of the niche have generally been defined in terms of cells and signaling pathways. We define a role for a matrix glycoprotein, osteopontin (OPN), as a constraining factor on hematopoietic stem cells within the bone marrow microenvironment. Osteoblasts that participate in the niche produce varying amounts of OPN in response to stimulation. Using studies that combine OPN-deficient mice and exogenous OPN, we demonstrate that OPN modifies primitive hematopoietic cell number and function in a stem cell–nonautonomous manner. The OPN-null microenvironment was sufficient to increase the number of stem cells associated with increased stromal Jagged1 and Angiopoietin-1 expression and reduced primitive hematopoietic cell apoptosis. The activation of the stem cell microenvironment with parathyroid hormone induced a superphysiologic increase in stem cells in the absence of OPN. Therefore, OPN is a negative regulatory element of the stem cell niche that limits the size of the stem cell pool and may provide a mechanism for restricting excess stem cell expansion under conditions of niche stimulation.

Matrix Glycoprotein Osteopontin Is a Stem Cell Niche Constituent That Constrains the Hematopoietic Stem Cell Pool Size.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 664-664 ◽  
Author(s):  
Sebastian Stier ◽  
Yon Ko ◽  
Randolf Forkert ◽  
Christoph Lutz ◽  
Thomas Neuhaus ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Hematopoietic Stem Cell ◽  
Stem Cell Niche ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Hematopoietic Stem Cell Niche ◽  
Cell Niche ◽  
Stem Cell Pool

Abstract Stem cells reside in a physical niche where a balance of signals controls their growth, differentiation and death. Niche components have generally been defined in terms of cells and positive effects on stem cell maintenance or expansion. Here we define a role for a matrix glycoprotein that provides a constraining function in the hematopoietic stem cell niche. Osteopontin (OPN) is an abundant glycoprotein in bone that can function as either cytokine or cell adhesion mediator. It is known to be produced by multiple cells types including osteoblasts, cells recently defined to be a regulatory component of the hematopoietic stem cell niche. Using studies combining OPN deficient mice and exogenous OPN, we demonstrate that OPN modifies primitive hematopoietic cell numbers and function. In OPN deficient mice, increased primitive cell numbers were observed in vivo associated with reduced progenitors and reduced primitive cell apoptotic fraction. To determine whether the effect of OPN deficiency was stroma dependent, we performed in vitro stem cell assays on OPN−/− stroma and observed greater LTC-IC supportive capacity compared with wild type stroma. Furthermore, OPN−/− recipients showed a significantly higher proportion of hematopoietic stem cells after transplantation of OPN+/+ bone marrow in comparison to wild-type recipients, indicating that the OPN null microenvironment was sufficient to increase stem cell number. A reduction in apoptotic fraction was seen in primitive cells in the OPN−/− recipient marrows. A role for OPN in apoptosis was confirmed by exogenous OPN in in-vitro studies. Hypothesizing that OPN may serve as a physiologic constraint on stem cell pool size, we compared OPN−/− with wild type animals following parathyroid hormone activation of the stem cell niche. The expansion of stem cells by PTH was superphysiologic in the absence of OPN. Therefore, OPN is a restricting element of the stem cell niche, limiting the number of stem cells produced by niche activation. Extracellular matrix components such as OPN may serve as modulable, regulatory participants in the stem cell niche.

scholarly journals Understanding the Influence of Substrate When Growing Tumorspheres

2020 ◽  
Author(s):  
Lucía Benítez ◽  
Lucas Barberis ◽  
Luciano Vellón ◽  
Carlos Alberto Condat
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Growth Factors ◽  
Cell Growth ◽  
Cancer Stem Cells ◽  
Cancer Stem Cell ◽  
Stem Cell Niche ◽  
Cell Number ◽  
Hard Substrate ◽  
Cell Niche

Abstract Background: Cancer stem cells are important for the development of many solid tumors. These cells receive promoting and inhibitory signals that depend on the nature of their environment (their niche) and determine cell dynamics. Mechanical stresses are crucial to the initiation and interpretation of these signals. Methods: A two-population mathematical model of tumorsphere growth is used to interpret the results of a series of experiments recently carried out in Tianjin, China, and extract information about the intraspecific and interspecific interactions between cancer stem cell and differentiated cancer cell populations. Results: The model allows us to reconstruct the time evolution of the cancer stem cell fraction, which was not directly measured. We find that, in the presence of stem cell growth factors, the interspecific cooperation between cancer stem cells and differentiated cancer cells induces a positive feedback loop that determines growth, independently of substrate hardness. In a frustrated attempt to reconstitute the stem cell niche, the number of cancer stem cells increases continuously with a reproduction rate that is enhanced by a hard substrate. For growth on soft agar, intraspecific interactions are always inhibitory, but on hard agar the interactions between stem cells are collaborative while those between differentiated cells are strongly inhibitory. Evidence also suggests that a hard substrate brings about a large fraction of asymmetric stem cell divisions. In the absence of stem cell growth factors, the barrier to differentiation is broken and overall growth is faster, even if the stem cell number is conserved. Conclusions: Our interpretation of the experimental results validates the centrality of the concept of stem cell niche when tumor growth is fueled by cancer stem cells. Niche memory is found to be responsible for the characteristic population dynamics observed in tumorspheres. A specific condition for the growth of the cancer stem cell number is also obtained.

scholarly journals Hemmule: A Novel Structure with the Properties of the Stem Cell Niche

2020 ◽  
Vol 21 (2) ◽  
pp. 539
Author(s):  
Vitaly Vodyanoy ◽  
Oleg Pustovyy ◽  
Ludmila Globa ◽  
Randy J. Kulesza ◽  
Iryna Sorokulova
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Stem Cell ◽  
Stem Cell Niche ◽  
Hematopoietic Stem ◽  
Novel Structure ◽  
Hematopoietic Stem Cell Niches ◽  
Cell Niche ◽  
Stem Cell Niches ◽  
Rat Bone

Stem cells are nurtured and regulated by a specialized microenvironment known as stem cell niche. While the functions of the niches are well defined, their structure and location remain unclear. We have identified, in rat bone marrow, the seat of hematopoietic stem cells—extensively vascularized node-like compartments that fit the requirements for stem cell niche and that we called hemmules. Hemmules are round or oval structures of about one millimeter in diameter that are surrounded by a fine capsule, have afferent and efferent vessels, are filled with the extracellular matrix and mesenchymal, hematopoietic, endothelial stem cells, and contain cells of the megakaryocyte family, which are known for homeostatic quiescence and contribution to the bone marrow environment. We propose that hemmules are the long sought hematopoietic stem cell niches and that they are prototypical of stem cell niches in other organs.

scholarly journals Wnt-inhibitory factor 1 dysregulation of the bone marrow niche exhausts hematopoietic stem cells

Blood ◽  
2011 ◽  
Vol 118 (9) ◽  
pp. 2420-2429 ◽  
Author(s):  
Christoph Schaniel ◽  
Dario Sirabella ◽  
Jiajing Qiu ◽  
Xiaohong Niu ◽  
Ihor R. Lemischka ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Wnt Signaling ◽  
Cell Fate ◽  
Sonic Hedgehog ◽  
Hematopoietic Stem ◽  
Cell Fate Decisions ◽  
Cell Niche ◽  
Wnt Inhibitory Factor 1 ◽  
Stem Cell Pool

Abstract The role of Wnt signaling in hematopoietic stem cell fate decisions remains controversial. We elected to dysregulate Wnt signaling from the perspective of the stem cell niche by expressing the pan Wnt inhibitor, Wnt inhibitory factor 1 (Wif1), specifically in osteoblasts. Here we report that osteoblastic Wif1 overexpression disrupts stem cell quiescence, leading to a loss of self-renewal potential. Primitive stem and progenitor populations were more proliferative and elevated in bone marrow and spleen, manifesting an impaired ability to maintain a self-renewing stem cell pool. Exhaustion of the stem cell pool was apparent only in the context of systemic stress by chemotherapy or transplantation of wild-type stem cells into irradiated Wif1 hosts. Paradoxically this is mediated, at least in part, by an autocrine induction of canonical Wnt signaling in stem cells on sequestration of Wnts in the environment. Additional signaling pathways are dysregulated in this model, primarily activated Sonic Hedgehog signaling in stem cells as a result of Wif1-induced osteoblastic expression of Sonic Hedgehog. We find that dysregulation of the stem cell niche by overexpression of an individual component impacts other unanticipated regulatory pathways in a combinatorial manner, ultimately disrupting niche mediated stem cell fate decisions.

2011 - ENGINEERING A HEMATOPOIETIC STEM CELL NICHE BY REVITALIZING MESENCHYMAL STEM CELLS

2019 ◽  
Vol 76 ◽  
pp. S45
Author(s):  
Fumio Nakahara ◽  
Daniel Borger ◽  
Qiaozhi Wei ◽  
Sandra Pinho ◽  
Maria Maryanovich ◽  
...  
Keyword(s):  
Stem Cells ◽  
Mesenchymal Stem Cells ◽  
Stem Cell ◽  
Hematopoietic Stem Cell ◽  
Stem Cell Niche ◽  
Hematopoietic Stem ◽  
Hematopoietic Stem Cell Niche ◽  
Cell Niche

scholarly journals Upregulation of the Drosophila Friend of GATA Gene u-shaped by JAK/STAT Signaling Maintains Lymph Gland Prohemocyte Potency

2009 ◽  
Vol 29 (22) ◽  
pp. 6086-6096 ◽  
Author(s):  
Hongjuan Gao ◽  
Xiaorong Wu ◽  
Nancy Fossett
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Cell Fate ◽  
Stem Cell Niche ◽  
Lymph Gland ◽  
Hematopoietic Stem ◽  
Functional Conservation ◽  
Stat Signaling ◽  
Signaling Center ◽  
Cell Niche

ABSTRACT Studies using Drosophila melanogaster have contributed significantly to our understanding of the interaction between stem cells and their protective microenvironments or stem cell niches. During lymph gland hematopoiesis, the Drosophila posterior signaling center functions as a stem cell niche to maintain prohemocyte multipotency through Hedgehog and JAK/STAT signaling. In this study, we provide evidence that the Friend of GATA protein U-shaped is an important regulator of lymph gland prohemocyte potency and differentiation. U-shaped expression was determined to be upregulated in third-instar lymph gland prohemocytes and downregulated in a subpopulation of differentiating blood cells. Genetic analyses indicated that U-shaped maintains the prohemocyte population by blocking differentiation. In addition, activated STAT directly regulated ush expression as evidenced by results from loss- and gain-of-function studies and from analyses of the u-shaped hematopoietic cis-regulatory module. Collectively, these findings identify U-shaped as a downstream effector of the posterior signaling center, establishing a novel link between the stem cell niche and the intrinsic regulation of potency and differentiation. Given the functional conservation of Friend of GATA proteins and the role that GATA factors play during cell fate choice, these factors may regulate essential functions of vertebrate hematopoietic stem cells, including processing signals from the stem cell niche.

Does primary myelofibrosis involve a defective stem cell niche? From concept to evidence

Blood ◽  
2008 ◽  
Vol 112 (8) ◽  
pp. 3026-3035 ◽  
Author(s):  
Jean-Jacques Lataillade ◽  
Olivier Pierre-Louis ◽  
Hans Carl Hasselbalch ◽  
Georges Uzan ◽  
Claude Jasmin ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Cell Proliferation ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Stem Cell Niche ◽  
Primary Myelofibrosis ◽  
Hematopoietic Stem ◽  
Stem Cell Proliferation ◽  
Cell Niche

Abstract Primary myelofibrosis (PMF) is the rarest and the most severe Philadelphia-negative chronic myeloproliferative syndrome. By associating a clonal proliferation and a mobilization of hematopoietic stem cells from bone marrow to spleen with profound alterations of the stroma, PMF is a remarkable model in which deregulation of the stem cell niche is of utmost importance for the disease development. This paper reviews key data suggesting that an imbalance between endosteal and vascular niches participates in the development of clonal stem cell proliferation. Mechanisms by which bone marrow niches are altered with ensuing mobilization and homing of neoplastic hematopoietic stem cells in new or reinitialized niches in the spleen and liver are examined. Differences between signals delivered by both endosteal and vascular niches in the bone marrow and spleen of patients as well as the responsiveness of PMF stem cells to their specific signals are discussed. A proposal for integrating a potential role for the JAK2 mutation in their altered sensitivity is made. A better understanding of the cross talk between stem cells and their niche should imply new therapeutic strategies targeting not only intrinsic defects in stem cell signaling but also regulatory hematopoietic niche–derived signals and, consequently, stem cell proliferation.

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