Lecture4 - Stem Cells Lisheng WANG Department of...

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Lisheng WANG Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine Stem Cells
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Lecture 4. Adult Stem Cells - Hematopoietic Stem Cells • HSC - hematopoiesis • Hematopoietic system • Hierarchy of hematopoietic cells • Embryonic hematopoiesis
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Hematopoiesis From Greek, hemato meaning blood and poiesis meaning make Hematopoiesis: Adult hematopoiesis Embryonic hematopoiesis What is hematopoiesis
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Hematopoietic system (mammalian) comprises cells and molecules generated in the adult bone marrow (BM) The cells of the hematopoietic system are divided into: myeloid (meaning derived from bone marrow) elements Red blood cells (erythrocytes) White blood cells (leukocytes) Platelets (megakaryocytes) lymphoid elements generated in the BM, spleen, thymus and lymph nodes: B and T cells (lymphocytes) Plasma cells Hematopoietic system – myeloid and lymphoid elements
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Peripheral Blood a: Erythrocytes (96% or ~5-million/ m l) b-d: Leukocytes e.g. b: neutrophil; c: eosinophil; d: lymphocyte (3% or 3,000-10,000/ m l) e: Platelets (<1%) Image adapted from Wikipedia.org “Blood”. Used with permission under GNU Free Documentation License e Hematopoietic system – peripheral blood smear
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Hematopoietic system – bone marrow smear Normal bone marrow. MGG stain. Norm: normoblast; Gran: granulocyte; My: myelocyte; PC: plasma cell; Meta: metamyelocyte. www.hmds.org.uk/insets/normal_bm.htm
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(Immunity 2007;26:669) CFU-s, colony-forming unit-spleen; CMP, common myeloid progenitor; CLP, common lymphoid progenitor, MEP, megakaryocyte- erythroid progenitor; GMP, granulocyte- macrophage progenitor; BFU-E, burst- forming unit-erythroid; Meg, megakaryocyte; Eo, eosinophil; G, granulocyte; and M, macrophage. Hierarchy of adult hematopoiesis Hematopoiesis - after born
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Specific Functions of Matured Blood Cells Erythrocytes Hemoglobin-containing blood cells that transport oxygen and carbon dioxide to and from tissues Leukocytes Identify, engulf and destroy pathogens (bacteria, viruses). Classified according to whether they contain granules (granulocytes) or not (lymphocytes, monocytes). Granulocytes are further subdivided based on their staining properties (neutrophils, eosinophils, basophils) Platelets Small cytoplasmic fragments that break off from megakaryocytes and prevent bleeding by forming clots Mature Blood Cells
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Limited Lifespan of Blood Cells (requiring hematopoietic stem cells to replenish them) Erythrocytes: ~120 days Leukocytes: ~1-2 days Platelets: ~8 days In order to replace the billions of blood cells that are lost each day, hematopoietic stem cells (HSC) that reside in the bone marrow become activated and proliferate Bone marrow is a highly organized matrix of hematopoietic and supportive cells (“microenvironment”) located in the ends of the long bones, pelvis, vertebrae, ribs, sternum and skull The bone marrow takes over from the fetal liver as the primary site of hematopoiesis just prior to birth Mature Blood Cells
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Properties of Committed Progenitor Cells (Daughters of HSC) Restricted to differentiate into only one or two lineages: i.e.
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This note was uploaded on 12/18/2011 for the course BCH 4122 taught by Professor Ilonaskerjanc during the Spring '11 term at University of Ottawa.

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Lecture4 - Stem Cells Lisheng WANG Department of...

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