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Hematopoietic stem cells (HSCs) are the stem cells that give rise to all the other blood cells through the process of haematopoiesis. They are derived from mesoderm and located in the red bone marrow, which is contained in the core of most bones. They give rise to both the myeloid and lymphoid lineages of blood cells. (Myeloid cells include monocytes, macrophages, neutrophils, basophils, eosinophils, erythrocytes, dendritic cells, and megakaryocytes or platelets. Lymphoid cells include T cells, B cells, and natural killer cells.) The definition of hematopoietic stem cells has changed in the last two decades. The hematopoietic tissue contains cells with long-term and short-term regeneration capacities and committed multipotent, oligopotent, and unipotent progenitors. HSCs constitute 1:10.000 of cells in myeloid tissue. HSCs are a heterogeneous population. The third category consists of the balanced (Bala) HSC, whose L/M ratio is between 3 and 10. Only the myeloid-biased and -balanced HSCs have durable self-renewal properties. In addition, serial transplantation experiments have shown that each subtype preferentially re-creates its blood cell type distribution, suggesting an inherited epigenetic program for each subtype. HSC studies through much of the past half century have led to a much deeper understanding. More recent advances have resulted in the use of HSC transplants in the treatment of cancers and other immune system disorders.〔"5. Hematopoietic Stem Cells." Stem Cell Information. National Institutes of Health, U.S. Department of Health and Human Services, 17 Jun 2011. Web. 9 Nov 2013. ==Sources== HSCs are found in the bone marrow of adults, specially in the pelvis, femur, and sternum. They are also found in umbilical cord blood and, in small numbers, in peripheral blood.〔http://cordadvantage.com/cord-blood-101/hematopoietic-stem-cell〕 Stem and progenitor cells can be taken from the pelvis, at the iliac crest, using a needle and syringe.〔(【引用サイトリンク】url=http://www.mayoclinic.org/departments-centers/transplant-center/bone-marrow-transplant/preparing/process )〕 The cells can be removed as liquid (to perform a smear to look at the cell morphology) or they can be removed via a core biopsy (to maintain the architecture or relationship of the cells to each other and to the bone). In order to harvest stem cells from the circulating peripheral blood, blood donors are injected with a cytokine, such as granulocyte-colony stimulating factor (G-CSF), that induces cells to leave the bone marrow and circulate in the blood vessels. In mammalian embryology, the first definitive HSCs are detected in the AGM (aorta-gonad-mesonephros), and then massively expanded in the fetal liver prior to colonising the bone marrow before birth.〔Dzierzak & Speck, Of lineage and legacy: the development of mammalian hematopoietic stem cells, Nature Immunology, 2008〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hematopoietic stem cell」の詳細全文を読む スポンサード リンク
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