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Transcript of Hemopoiesis. http://en.wikipedia.org/wiki/Haematopoiesis.

  • Slide 1
  • Hemopoiesis
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  • http://en.wikipedia.org/wiki/Haematopoiesis
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  • Haematopoiesis (from Ancient Greek: , "blood"; "to make") (or hematopoiesis in American English; sometimes also haemopoiesis or hemopoiesis) is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. In a healthy adult person, approximately 10 11 10 12 new blood cells are produced daily in order to maintain steady state levels in the peripheral circulation. [1][2]bloodhaematopoietic stem cells [1][2] http://en.wikipedia.org/wiki/Haematopoiesis
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  • Nagasawa Nature Reviews Immunology 6, 107116 (February 2006) | doi:10.1038/nri1780
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  • All blood cells are divided into three lineages Erythroid cells are the oxygen carrying red blood cells. Both reticulocytes and erythrocytes are functional and are released into the blood. In fact, a reticulocyte count estimates the rate of erythropoiesis. Erythroidred blood cellsreticulocyteserythrocyteserythropoiesis Lymphocytes are the cornerstone of the adaptive immune system. They are derived from common lymphoid progenitors. The lymphoid lineage is primarily composed of T-cells and B-cells (types of white blood cells). This is lymphopoiesis. LymphocytesT-cellsB-cellswhite blood cellslymphopoiesis Myelocytes, which include granulocytes, megakaryocytes and macrophages and are derived from common myeloid progenitors, are involved in such diverse roles as innate immunity, adaptive immunity, and blood clotting. This is myelopoiesis. Myelocytesgranulocytesmegakaryocytesmacrophagesinnate immunityadaptive immunityblood clottingmyelopoiesis Granulopoiesis (or granulocytopoiesis) is haematopoiesis of granulocytes. Granulopoiesisgranulocytes Megakaryocytopoiesis is haematopoiesis of megakaryocytes. Megakaryocytopoiesismegakaryocytes http://en.wikipedia.org/wiki/Haematopoiesis
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  • Multipotency and self-renewal As stem cells, HSC are defined by their ability to replenish all blood cell types (Multipotency) and their ability to self-renew. It is known that a small number of HSCs can expand to generate a very large number of daughter HSCs. This phenomenon is used in bone marrow transplantation, when a small number of HSCs reconstitute the hematopoietic system. This process indicates that, subsequent to bone marrow transplantation, symmetrical cell divisions into two daughter HSCs must occur.bone marrow transplantation Stem cell self-renewal is thought to occur in the stem cell niche in the bone marrow, and it is reasonable to assume that key signals present in this niche will be important in self-renewal.stem cell niche There is much interest in the environmental and molecular requirements for HSC self-renewal, as understanding the ability of HSC to replenish themselves will eventually allow the generation of expanded populations of HSC in vitro that can be used therapeutically.
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  • There are various kinds of colony-forming units: Colony-forming unit lymphocyte (CFU-L)lymphocyte Colony-forming unit erythrocyte (CFU-E)erythrocyte Colony-forming unit granulo-monocyte (CFU-GM)monocyte Colony-forming unit megakaryocyte (CFU-Me)megakaryocyte Colony-forming unit Basophil (CFU-B)Basophil Colony-forming unit Eosinophil (CFU-Eo)Eosinophil The above CFUs are based on the lineage. Another CFU, the colony- forming unitspleen (CFUS) was the basis of an in vivo clonal colony formation, which depends on the ability of infused bone marrow cells to give rise to clones of maturing hematopoietic cells in the spleens of irradiated mice after 8 to 12 days. It was used extensively in early studies, but is now considered to measure more mature progenitor or Transit Amplifying Cells rather than stem cells.
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  • Haematopoietic stem cells (HSCs) reside in the medulla of the bone (bone marrow) and have the unique ability to give rise to all of the different mature blood cell types and tissues. Haematopoietic stem cellsbone marrow HSCs are self-renewing cells: when they proliferate, at least some of their daughter cells remain as HSCs, so the pool of stem cells does not become depleted. The other daughters of HSCs (myeloid and lymphoid progenitor cells), however can commit to any of the alternative differentiation pathways that lead to the production of one or more specific types of blood cells, but cannot self-renew. This is one of the vital processes in the body. http://en.wikipedia.org/wiki/Haematopoiesishttp://en.wikipedia.org/wiki/Haematopoiesis and Hematopoietic_stem_cell
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  • HSCs are also found in umbilical cord blood and, in small numbers, in peripheral blood. Stem and progenitor cells can be taken from the pelvis, at the iliac crest, using a needle and syringe. The cells can be removed a 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).umbilical cordperipheral blood In order to harvest stem cells from the circulating peripheral, blood donors are injected with a cytokine, such as granulocyte-colony stimulating factor (G-CSF), that induce 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. [2]Aorta-gonad-mesonephros [2] http://en.wikipedia.org/wiki/Haematopoiesishttp://en.wikipedia.org/wiki/Haematopoiesis and Hematopoietic_stem_cell
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  • http://en.wikipedia.org/wiki/Haematopoiesis
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  • In developing embryos, blood formation occurs in aggregates of blood cells in the yolk sac, called blood islands.blood islands As development progresses, blood formation occurs in the spleen, liver and lymph nodes.spleenliverlymph nodes When bone marrow develops, it eventually assumes the task of forming most of the blood cells for the entire organism.bone marrow Maturation, activation, and some proliferation of lymphoid cells occurs in secondary lymphoid organs (spleen, thymus, and lymph nodes).thymus In children, haematopoiesis occurs in the marrow of the long bones such as the femur and tibia. In adults, it occurs mainly in the pelvis, cranium, vertebrae, and sternum. In some cases, the liver, thymus, and spleen may resume their haematopoietic function. This is called extramedullary haematopoiesis. During fetal development, since bones and thus the bone marrow develop later, the liver functions as the main haematopoetic organ. Therefore, the liver is enlarged during development.extramedullary haematopoiesis http://en.wikipedia.org/wiki/Haematopoiesis blood island
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  • Cell Morphology Exercise http://www.dartmouth.edu/~anatomy/Histo/lab_4/bonemarrow/DMS104/popup.html http://www.anatomyatlases.org/MicroscopicAnatomy/Section04/Plate0458.shtml
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  • Erythropoiesis
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  • Granulopoiesis
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  • The determinism theory of haematopoiesis, saying that colony stimulating factors and other factors of the haematopoietic microenvironment determine the cells to follow a certain path of cell differentiation. This is the classical way of describing haematopoiesis. The ability of the bone marrow to regulate the quantity of different cell types to be produced is more accurately explained by astochastic theory. Undifferentiated blood cells are determined to specific cell types by randomness. The haematopoietic microenvironment prevails upon some of the cells to survive and some, on the other hand, to perform apoptosis and die.apoptosis http://en.wikipedia.org/wiki/Haematopoiesis Cell Differentiation
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  • Transcription factors Growth factors initiate signal transduction pathways, altering transcription factors, that, in turn activate genes that determine the differentiation of blood cells.signal transductiontranscription factors The early committed progenitors express low levels of transcription factors that may commit them to discrete cell lineages. Which cell lineage is selected for differentiation may depend both on chance and on the external signals received by progenitor cells. Several transcription factors have been isolated that regulate differentiation along the major cell lineages. PU.1 commits cells to the myeloid lineage GATA-1 has an essential role in erythropoietic and megakaryocytic differentiation.GATA-1 The Ikaros, Aiolos and Helios transcription factors play a major role in lymphoid development. [5] [5] http://en.wikipedia.org/wiki/Haematopoiesis
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  • The proliferation and self-renewal of these cells depend on stem cell factor (SCF). Glycoprotein growth factors regulate the proliferation and maturation of the cells that enter the blood from the marrow, and cause cells in one or more committed cell lines to proliferate and mature.stem cell factorGlycoprotein Three more factors that stimulate the production of committed stem cells are called colony-stimulating factors (CSFs) and include granulocyte-macrophage CSF (GM-CSF), granulocyte CSF (G-CSF) and macrophage CSF (M-CSF). These stimulate much granulocyte formation and are active on either progenitor cells or end product cells.committed stem cellscolony-stimulating factorsgranulocyte-macrophage CSFgranulocyte CSFmacrophage CSFgranulocyteprogenitor cells Erythropoietin is required for a myeloid prog