Computer Science 129

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Computer Science 129

• Stem Cells

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Stem Cells

• There are two types of stem cells
• Embryonic Stem Cells
• Adult Stem Cells
• To figure out where they come from we need to
  understand a little embryology

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Stem Cells

• http//www.youtube.com/watch?vrN3lep6roRI
• Watch the above video until part 5 (watch the
  first 16 minutes)

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Stem Cells
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Stem Cells

• Cells from a morula are considered totipotent
  they can develop into anything embryonic or
  extra-embryonic
• Cells from the inner cell mass are called
  pluripotent they can be anything except
  trophoblast cells
• Once a cell has differentiated they are
  multipotent ex. Ectoderm can become skin, brain
  or nervous tissue multiple things

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Stem Cells
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Stem Cells

• Fertilization occurs in the fallopian tubes of a
  woman (uterine tubes)
• When the sperm combines with the ovum, we have a
  zygote
• The zygote undergoes cell division and we end up
  with a ball of cells called the morula
• The morula develops into a blastocyst with the
  inner cell mass inside

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Stem Cells

• The cells on the outside of the blastocyst are
  called trophoblasts. These cells protect the
  inner cell mass, which is the developing embryo,
  from the mothers immune system (the mothers
  immune system views the developing embryo as
  foreign since half of it is from the father
  actually it is 51 mom and 49 dad because of the
  mitochondrial DNA from mom makes it a little more
  mom than dad)

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Stem Cells

• The inner cell mass, which is developed at around
  day 7-10, is where scientists harvest embryonic
  stem cells
• These cells have not differentiated, or become
  determined at this point. When cells become
  determined, it is determined what they will
  become when they grow up.
• The cells will become endoderm, mesoderm or
  ectoderm

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Stem Cells

• The following table indicates the type of cells
  that each of the germ layers will ultimately
  develop into

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Stem Cells
Germ Layer Structures they become
Ectoderm Epidermis outer layer of skin Brain, spinal cord, nerves
Mesoderm Bones, muscle, dermis-lower layers of skin, blood, connective tissue, reproductive tissue, urinary tissue (basically everything else that is not from endoderm or ectoderm)
Endoderm Linings of the guts and associated organs and linings of lungs and respiratory tissues
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Stem Cells

• Once a cell has become determined, or become a
  germ layer, they will continue to develop into
  those tissue types. You can not make an endoderm
  cell become brain tissue or mesoderm become guts
  and so on.
• If a cell is gotten before it is determined, it
  can be forced to become any tissue. They are
  metabolically more active as well.

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Stem Cells

• It is no longer legal to make embryos for the
  purpose of destroying the embryo to do stem cell
  work. Where do scientists get them then?
• Unused embryos from fertility clinics
• Whartons jelly on the placenta

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Stem Cells

• Use of stem cells from Whartons jelly is ideal
  since there is no destruction of an embryo
  involved.

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Stem Cells

• What about Adult Stem Cells? Where can we
  harvest those?
• Adipose tissue (fat)
• Skin
• Spinal fluid
• Heart cells
• Liver cells
• Brain
• Bone marrow
• Teeth