STEM CELLS MARKERS

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STEM CELLS MARKERS

• By
• Salwa Hassan Teama
• M.D. Clinical Pathology Oncolgic laboratory
  Medicine (N.C.I)
• Fellow Ain Shams University

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STEM CELLS

• A stem cell is a cell that has the ability to
  divide (self replicate) for indefinite
  periodsoften throughout the life of the
  organism. Under the right conditions, or given
  the right signals, stem cells can give rise
  (differentiate) to the many different cell types
  that make up the organism. That is, stem cells
  have the potential to develop into mature cells
  that have characteristic shapes and specialized
  functions, such as heart cells, skin cells, or
  nerve cells.

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STEM CELLS

• Stem cells that have unique capabilities to
  self-renew, grow indefinitely, and differentiate
  or develop into multiple types of cells and
  tissues. Researchers now know that many different
  types of stem cells exist but they all are found
  in very small populations in the human body, in
  some cases 1 stem cell in 100,000 cells in
  circulating blood.

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STEM CELLS

• Pluripotent to describe stem cells that can
  give rise to cells derived from all three
  embryonic germ layersmesoderm, endoderm, and
  ectoderm. These three germ layers are the
  embryonic source of all cells of the body. All of
  the many different kinds of specialized cells
  that make up the body are derived from one of
  these germ layers.

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STEM CELLS

• The embryonic stem cell is defined by its
  originthat is from one of the earliest stages of
  the development of the embryo, called the
  blastocyst. Specifically, embryonic stem cells
  are derived from the inner cell mass of the
  blastocyst at a stage before it would implant in
  the uterine wall. The embryonic stem cell can
  self-replicate and is pluripotentit can give
  rise to cells derived from all three germ layers.

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• The adult stem cell is an undifferentiated
  (unspecialized) cell that is found in a
  differentiated (specialized) tissue it can renew
  itself and become specialized to yield all of the
  specialized cell types of the tissue from which
  it originated. Adult stem cells are capable of
  self-renewal for the lifetime of the organism.
  Sources of adult stem cells have been found in
  the bone marrow, blood stream, cornea and retina
  of the eye, the dental pulp of the tooth, liver,
  skin, gastrointestinal tract, and pancreas.

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STEM CELLS

• Unipotent stem cell, a term that is usually
  applied to a cell in adult organisms, the cells
  in question are capable of differentiating along
  only one lineage. Also, it may be that the adult
  stem cells in many differentiated, undamaged
  tissues are typically unipotent and give rise to
  just one cell type under normal conditions. This
  process would allow for a steady state of
  self-renewal for the tissue.

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STEM CELLS

• However, if the tissue becomes damaged and the
  replacement of multiple cell types is required,
  pluripotent stem cells may become activated to
  repair the damage.

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STEM CELLS MARKERS

• Coating the surface of every cell in the body
  are specialized proteins, called receptors, that
  have the capability of selectively binding or
  adhering to other "signaling" molecules.

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STEM CELLS MARKERS

• There are many different types of receptors
  that differ in their structure and affinity for
  the signaling molecules. Normally, cells use
  these receptors and the molecules that bind to
  them as a way of communicating with other cells
  and to carry out their proper functions in the
  body. These same cell surface receptors are the
  stem cell markers.

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STEM CELLS MARKERS

• Each cell type, for example a liver cell, has a
  certain combination of receptors on their surface
  that makes them distinguishable from other kinds
  of cells.

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STEM CELLS MARKERS

• The signaling molecules that selectively adhere
  to the receptors on the surface of the cell as a
  tool that allows them to identify stem cells.
  Many years ago, a technique was developed to
  attach to the signaling molecule another molecule
  (or the tag) that has the ability to fluoresce or
  emit light energy when activated by an energy
  source such as an ultraviolet light or laser
  beam.

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• Fluorescent
• tags with
• emitted light
• that differ
• in color and
• intensity.

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STEM CELLS MARKERS

• Genetic and molecular biology techniques are
  extensively used to study how cells become
  specialized in the organism's development. Genes
  and transcription factors (proteins found within
  cells that regulate a gene's activity) that are
  unique in stem cells.
• Polymerase chain reaction (PCR) to detect the
  presence of genes that are "active" and play a
  role guiding the specialization of a cell. This
  technique has is helpful to identify "genetic
  markers" that are characteristic of stem cells.

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STEM CELLS MARKERS

• For example, a gene marker called PDX-1 is
  specific for a transcription factor protein that
  initiates activation of the insulin gene, this
  marker to identify cells that are able to develop
  islet cells in the pancreas.

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STEM CELLS MARKERS

• Recently, Genetic engineering approach that
  uses fluorescence, but isn't dependent on cell
  surface markers. The importance of this new
  technique is that it allows the tracking of stem
  cells as they differentiate or become
  specialized. A stem cell a "reporter gene" called
  green fluorescent protein or GFP. The gene is
  only activated or "reports" when cells are
  undifferentiated and is turned off once they
  become specialized. Once activated, the gene
  directs the stem cells to produce a protein that
  fluoresces in a brilliant green color Researchers
  are now coupling this reporting method with the
  FACS and microscopic methods to sort cells,
  identify them in tissues, and now, track them as
  they differentiate or become specialized.

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(Figure E.i.3. Microscopic Image of
Fluorescent-Labeled Stem Cell).
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STEM CELLS MARKERS

• For example, a special type of hematopoietic
  stem cell from blood and bone marrow called "side
  population" or "SP" is described as (CD34-/low,
  c-Kit, Sca-1).

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