Hematopoetic stem cells

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IDENTIFICATION ISOLATION OF HEMATOPOIETIC STEM
CELLS

• BY,
• PRANAV NAKHATE
• ABHIJEET KAMBLE

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STEM CELLS-

• Cells having potential to develop themselves
  through mitotic cell division into diverse range
  of specialized cell types.
• PROPERTIES-
• Self-renewal
• Potency
• Totipotency/ Pluripotency
• Multipotency / Unipotency

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• TYPES-
• Two broad types-
• 1.Embryonic stem cells-
• Found in inner cell mass of blastocyst.
• Can differentiate into all of the specialized
  embryonic tissues.
• 2.Adult stem cells-
• Found in adult tissue
• They generate same type of tissue in which they
  reside.

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HEMATOPOIETIC STEM CELL

• The stem cells that form blood and immune cells
  are known as HSCs.
• Responsible for Immunity.
• Isolated from Blood or Bone Marrow of long
  bones.
  
• Ultimately responsible for the constant renewal
  of blood.
• Can undergo programmed cell death

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HEMATOPOIETIC STEM CELL DIFFERENTIATION-
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• SOURCES
• 1.Bone marrow.
  
  
  2.Peripheral blood.
  
  
  
  3.Ubilical cord blood.
  
  
  4.Fetal hematopoietic system.
  
  
  5.Embryonic stem germ
  cells.
• USES-
• 1.In treatment of cancer of blood-LEUKEMIA
  LYMPHOMA.
• 2Inherited blood disorder.
• 3.Rescue in cancer chemotherapy.
• 4.Graft-versus-tumor treatment of cancer.
• 5.Diabetes.

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IDENTIFICATION PROBLEMS-

• 1. Rare long-term replicating ability.
• 
  
• 2. Multiple types of stem cells present.
• 3. HSCs look like many other blood or bone marrow
  cells, like WBCs.
• 
  

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STEM CELL MARKERS-

• In 1992, Irving Weissman proposed a comparable
  set of markers for the human stem cell.
• Proteins coating the stem cell surface, are
  receptors.
• These receptors are nothing but stem cell
  markers.
• They have capability of selectively binding to
  signaling molecule.

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HSCs IDENTIFYING MARKERS
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HSCs IDENTIFYING MARKERS

• CD34-
• It is found on a small fraction of human bone
  Marrow cells.
• Considered to be the most critical marker for
  hematopoietic stem cells.
• Its expression on primitive cells is
  down-regulated.
• It plays a significant role in early
  hematopoiesis.
• Its precise function is still unknown.

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• Irving Weissman proposes the closest markers for
  mouse and human HSCs.
• Mouse HSC  CD34lo/-, SCA-1 , Thy1.1/lo, CD38,
  C-kit, lin-
• Human HSC  CD34, CD59, Thy1/CD90,CD38lo/-,
  C-kit/CD117, lin-

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TECHNIQUES FOR ISOLATION-

• Signaling molecule selectively adhering to the
  receptors.
• Tool for identifying the stem cells.
• Molecules having ability to emit light can also
  be attached to signaling molecules.

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Approaches/Techniques

• The combination of fluorescence and unique
  receptor patterns on cell surface give two
  approaches to identify hematopoetic stem cells.
• 1st approach
• Stem cell markers are research tools.
• FACS (Fluorescence Activated Cell Sorting)
  technique

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• 2nd approach
• To visually assess the cells as they exist in
  tissue.
• Use of microscope rather than FACS instrument.
• Thin slice of tissue is prepared.
• Fluorescent tagging of stem cell markers.
• Activation of fluorescent tag by light energy or
  chemical reaction.

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Genetic and molecular biology techniques

• These are extensively used to study how cells
  become specialized in the organism's development.
• polymerase chain reaction (PCR) to detect the
  presence of genes that are active.
• PCR play a role guiding the specialization of a
  cell.
• PCR technique can be used for DNA Sequencing,
  Genetic Fingerprinting Cloning Genes .

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Genetic engineering approach

• It uses fluorescent tag, but isn't dependent on
  cell surface markers.
• It allows the tracking of stem cells as they
  differentiate or become specialized.
• Insertion of reporter gene green fluorescent
  protein (GFP) which "reports" when cells are
  undifferentiated and turned off once they are
  specialized.

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LIMITATIONS-

• A single marker identifying pluripotent stem
  cells, has yet to be found.
• Researchers cant distinguish the long-term from
  the short-term cells when they are removed from
  the bloodstream or The bone marrow.
• Impact of Hepatitis B virus (HBV) infection on
  hematopoietic stem cell transplantation.
• Hence , markers are useful but not perfect tools
  for the research laboratory.

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References

• Jacobsen LO, Marks EK, Gaston EO, Zirkle RE.
  Effect of spleen protection on mortality
  following X-irradiation. J Lab Clin Med.
• Lorenz E, Uphoff ED, Reid TR, Shelton E.
  Modification of acute irradiation injury in mice
  and guinea pigs by bone marrow injection.
  Radiology.
• Sieburg, HB, Muller-Sieburg, CE. Classification
  of short kinetics by shape. In Silico Biol.
• Team C. S. Swapnil Mohite , Modification of
  HSCs vol 14