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Adult Stem Cells Stem Cells, Bone Marrow and Blood

Adult Stem Cells Stem Cells, Bone Marrow and Blood. Potent Biology: Stem Cells, Cloning and Regeneration July 10-13, 2007. Stem Cells. Embryonic – undifferentiated cells from the embryo that have the potential to become a wide variety of specialized cell types Zygote (totipotent)

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Adult Stem Cells Stem Cells, Bone Marrow and Blood

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  1. Adult Stem CellsStem Cells, Bone Marrow and Blood Potent Biology: Stem Cells, Cloning and Regeneration July 10-13, 2007

  2. Stem Cells • Embryonic – undifferentiated cells from the embryo that have the potential to become a wide variety of specialized cell types • Zygote (totipotent) • Morula (totipotent-pluripotent) • Blastocyst (pluripotent) • Inner Cell Mass (ICM) (pluripotent) • Gastrula (multipotent)

  3. Adult Stem Cells • What are adult stem cells? • Somatic cells that are unspecialized • Depending on the tissue, the cells have different properties. • What is the role of adult stem cells? • Maintain and repair the bodies tissue • Stem cells share 2 characteristics • Proliferate - capable of long-term self-renewal • Differentiate into mature cells • Progenitor cells • Precursor cells

  4. Stem Cells • Where are they found? • Infants • Adults • Bone marrow (BM)

  5. Bone Marrow, Stem Cells and Blood • Hiroshima and Nagasaki 1943 • Radiation • Compromised hematopoietic system • Couldn’t produce white blood cells (WBC’s) • Couldn’t produce platelets • Mouse studies • Irradiation to whole body resulted in death of the mice • BM cells from normal mouse injected into lethally irradiated mice • Prevented death from bone marrow failure McColloch and Till; Radiation Research 13, 115-125; 1960

  6. Why Did This Bone Marrow Transplant Work? • Bone Marrow is the site of blood cell (red blood cells, white blood cells, and platelets) production… Hematopoiesis.

  7. Hematopoiesis: Stem Cell Hierarchy • Process begins with Hematopoietic Stem Cells (HSCs) capable of • Proliferation • Differentiation • Differentiation of HSCs follows 2 cell lines. • Myeloid • Lymphoid Hematopoietic Stem Cell

  8. Hematopoiesis: Stem Cell Hierarchy • Cells in either line differentiate along an irreversible succession or hierarchy of precursor cells • Each descendent cell has progressively limited potential.

  9. Hematopoiesis: Stem Cell Hierarchy • How do HSC’s know which pathway to follow or which cell to become? • Differentiation is directed by signal molecules (growth factors known as cytokines and interleukins) • Bone marrow stromal cells are the major source of these growth factors.

  10. Hematopoiesis: Stem Cell Hierarchy • Cytokines are a family of proteins that direct differentiation of a particular lineage. • Combinations of cytokines can stimulate • Proliferation and/or • Differentiation

  11. Hematopoiesis: Stem Cell Hierarchy http://www.biocarta.com/pathfiles/h_stemPathway.asp

  12. Summary • The development of different blood cell types from bone marrow stem cells is an example of how the body uses adult stem cells. • Different types of blood cells (RBC, WBC, platelets) have very different functions. • All types of human blood cells differentiate from bone marrow stem cells. • The differentiation of human blood cells is hierarchical and irreversible. • An early division in the differentiation of human blood cells is along two (myeloid and lymphoid) precursor stem cell lines. • Differentiation is directed by signaling molecules • The signaling molecule(s) to which a stem cell is exposed determines which blood cell it becomes.

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