Stem Cells
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What is a Stem Cell?
General
Specific
 Unspecialized cells
 Self-Renewal
 Give rise to more than 250
 Differentiation
specialized cells in the
body
 Serve as the body’s repair
system
(specialization)
http://www.nih.gov/news/stemcell/figure5.jpg
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Two “types” of stem cells
•Embryonic (ES)
•Adult (non-embryonic) (AS)
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Stem Cells differ by
 Origin
 Embryonic
 Adult
Origin determines potential
 Different “potentials”
 Totipotent
 Pluripotent
 Multipotent
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Potentials
Totipotent - having unlimited capability.
Totipotent cells have the capacity to
specialize into extraembryonic membranes
and all cells of the embryo.
Pluripotent -capable of giving rise to most
tissues of an organism.
Multipotent -capable of giving rise to many
tissues of an organism.
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Definitions
 Stem cells – undifferentiated cells that have the
ability to:
 divide for indefinite periods in culture
 to become specialized cells
 Differentiation –
 the process whereby cells become specialized
 Produces stems cells with decreasing potential
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Derivation
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Embryonic Stem Cells (ESC)
1. Embryos are the result of In Vitro
Fertilization (IVF)
2. Cells are taken from the Inner Cell Mass
(ICM) of a blastocyst
3. ICM cells are nourished in a petri dish in an
incubator
4. Cells are given different types of
Factors/chemicals
These cells can give rise to most types of cells
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In Vitro Fertilization (IVF)
Eggs are removed from ovary of female
Sperm is obtained from male
Egg and sperm are combined in test tubes/Petri
dish
4. Fertilized eggs (zygotes) are allowed to divide for a
few days.
5. Blastocysts are then transferred to uterus of
woman
What happens to left over embryos?
1.
2.
3.


Frozen until used again
Discarded*
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In Vitro Fertilization
+
Fertilization
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The zygote divides
Each cell is totipotent
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Blastocyst formation
The 1st sign of differentiation
Blastocyst
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Blastocyst
Inner Cell Mass (ICM)
Trophoblast
These are
now
Pluripotent
stem cells
Gives rise to
an embryo
under proper
conditions
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Embryonic Stem Cells
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Cell differentiation
Can divide
Can divide
Differentiation
Can divide
Differentiation
Pluripotent
stem cell
Multipotent
stem cells
(Embryonic
stem cell)
(Adult stem cell)
Differentiated cells
(muscle, nerve, skin,
fibroblast, etc)
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Adult Stem Cells
 Adult tissues reported to contain stem
cells include: brain, bone marrow,
peripheral blood, blood vessels, skeletal
muscle, skin and liver.
 There are a very small number of stem
cells in each tissue
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Why is research
on embryonic
stem cells
important?
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Current Issues
 Derivation
 Induced-pluripotent
stem cells
 Ethics
 Challenges
 Controlling
specialization
 Donor acceptance
Importance of Stem Cells
 Perhaps the most important
potential application of human
stem cells is the generation of
cells and tissues that could be
used for cell-based therapies.
http://stemcells.nih.gov/index.asp
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Importance of Stem Cells
 Today, donated organs and tissues
are often used to replace ailing or
destroyed tissue, but the need
for transplantable tissues and
organs far outweighs the available
supply.
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Importance of Stem Cells
 Parkinson’s Disease
 Loss of dopaminergic
producing nerve cell in
substantia nigra
 Severe motor disturbance
 Fetal brain cells and iPS
(reprogramming)
 http://www.youtube.com/watch?v=1
yCgLythe00
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Importance of Stem Cells
Alzheimers Disease
 Dementia
 Death brain tissue, protein
placques, hippocampus
 http://www.youtube.com/watch?
v=zgvm_vvqq3I&feature=related
 http://www.youtube.com/watch?
v=TZA3QFliteA&feature=related
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Importance of Stem Cells
http://www.youtube.com/watch?v=vwCrxomPbtY
http://www.youtube.com/watch?v=ADchGO-0kGo&feature=related
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