Article

The hematopoietic stem cell in its place.

Center for Regenerative Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
Nature Immunology (Impact Factor: 24.97). 05/2006; 7(4):333-7. DOI: 10.1038/ni1331
Source: PubMed

ABSTRACT A signature characteristic of stem cells is their ability to self-renew, affording a theoretically limitless ability to produce daughter cells and their descendents. This near-timeless dimension of stem cell function is not free of the constraints of place. The idea that highly specialized 'microenvironmental' cues participate in the regulation of stem cells has evidence in classic embryology and more recently in adult stem cells through the use of model organisms. There is now ample evidence that an anatomically defined, specifically constituted place represents the niche for hematopoietic and other tissue-specific stem cells. This review provides a conceptual framework and detailed account of the hematopoietic stem cell niche as defined at present. The components are assembling into a more complex view of the niche and may now be amenable to examination as a system and possibly to alteration to affect outcomes in immune regeneration.

Download full-text

Full-text

Available from: Gregor B. Adams, Jun 08, 2015
0 Followers
 · 
121 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Tumor initiation, growth and relapse after therapy are thought to be driven by a population of cells with stem cell characteristics, named cancer stem cells (CSC). The regulation of their radiation resistance and their maintenance is poorly understood. CSC are believed to reside preferentially in special microenvironmental niches located within tumor tissues. The features of these niches are of crucial importance for CSC self-renewal, metastatic potential and therapy resistance. One of the characteristics of solid tumors is occurrence of less oxygenated (hypoxic regions), which are believed to serve as so-called hypoxic niches for CSC. Purpose: The purpose of this review is the critical discussion of the supportive role of hypoxia and hypoxia-related pathways during cancer progression and radiotherapy resistance and the relevance for therapeutic implications in the clinic. Conclusion: It is generally known since decades that hypoxia inside solid tumors impedes chemo- and radiotherapy. However, there is limited evidence to date that targeting hypoxic regions during conventional therapy is effective. Nonetheless improved hypoxia-imaging technologies and image guided individualized hypoxia targeted therapy in conjunction with the development of novel molecular targets may be able to challenge the protective effect on the tumor provided by hypoxia.
    International Journal of Radiation Biology 05/2014; DOI:10.3109/09553002.2014.916841 · 1.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In patients with multiple myeloma (MM), the bone marrow (BM) contains hematopoietic stem cells (HSCs) and non-hematopoietic cells. HSCs are able to give rise to all types of mature blood cells, while the non hematopoietic component includes mesenchymal stem cells (MSCs), fibroblasts, osteoblasts, osteoclasts, chondroclasts, endothelial cells, endothelial progenitor cells (EPCs), B and T lymphocytes, NK cells, erythrocytes, megakaryocytes, platelets, macrophages and mast cells. All of these cells form specialized "niches" in the BM microenvironment which are close to the vasculature ("vascular niche") or to the endosteum ("osteoblast niche"). The "vascular niche" is rich in blood vessels where endothelial cells and mural cells (pericytes and smooth muscle cells) create a microenvironment that affects the behavior of several stem and progenitor cells. The vessel wall serves as an independent niche for the recruitment of endothelial progenitor cells, MSCs and HSCs. The activation by angiogenic factors and inflammatory cytokines switch the "vascular niche" to promote MM tumor growth and spread. This review will focus on the mechanisms involved in the generation of signals released by endothelial cells in the "vascular niche" that promote tumor growth and spread in MM. © 2014 Elsevier Ltd. All rights reserved.
    Thrombosis Research 05/2014; 133 Suppl 2:S102-6. DOI:10.1016/S0049-3848(14)50017-5 · 2.43 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Reactive oxygen species (ROS), generated as a result of various reactions, control an array of cellular processes. The role of ROS during megakaryocyte (MK) development has been a subject of interest and research. The bone marrow niche is a site of MK differentiation and maturation. In this environment, a gradient of oxygen tension, from normoxia to hypoxia results in different levels of ROS, impacting cellular physiology. This article provides an overview of major sources of ROS, their implication in different signaling pathways, and their effect on cellular physiology, with a focus on megakaryopoiesis. The importance of ROS-generating oxidases in MK biology and pathology, including myelofibrosis, is also described.
    Journal of Cellular Physiology 10/2012; 227(10):3355-62. DOI:10.1002/jcp.24071 · 3.87 Impact Factor