Stem Cells

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What is a Stem Cell?What is a Stem Cell?

General Specific

Unspecialized cells Give rise to more

than 250 specialized cells in the body

Serve as the body’s repair system

Self-Renewal Differentiation

(specialization)

4http://www.nih.gov/news/stemcell/figure5.jpg

Two “types” of stem cellsTwo “types” of stem cells

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•Embryonic (ES)

•Adult (non-embryonic) (AS)

Stem Cells differ byStem Cells differ by

Origin Embryonic Adult

Different “potentials” Totipotent Pluripotent Multipotent

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Origin determines potential

PotentialsPotentials

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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.

DefinitionsDefinitions

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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

Derivation

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Embryonic Stem Cells Embryonic Stem Cells (ESC)(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 In Vitro Fertilization (IVF)(IVF)1. Eggs are removed from ovary of female 2. Sperm is obtained from male3. Egg and sperm are combined in test

tubes/Petri dish4. Fertilized eggs (zygotes) are allowed to

divide for a few days.5. Blastocysts are then transferred to uterus

of womanWhat happens to left over embryos?

Frozen until used again Discarded*

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In Vitro FertilizationIn Vitro Fertilization

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Fertilization

+

The zygote dividesThe zygote divides

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Each cell is totipotent

Blastocyst formationBlastocyst formation

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The 1st sign of differentiation

Blastocyst

BlastocystBlastocyst

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Inner Cell Mass (ICM)

Trophoblast

Gives rise to an embryo under proper conditionsThese are

now Pluripotent stem cells

Embryonic Stem CellsEmbryonic Stem Cells

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Cell differentiationCell differentiation

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Pluripotent stem cell

(Embryonic stem cell)

Multipotent stem cells

(Adult stem cell)

Differentiated cells(muscle, nerve,

skin, fibroblast, etc)

Differen

tiation

Differentiation

Can divide

Differentiation

Differentiation

Can divide

Can divide

Adult Stem CellsAdult 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 Why is research on embryonic stem embryonic stem cells important?cells important?

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Current IssuesCurrent Issues

Derivation Induced-

pluripotent stem cells

Ethics Challenges

Controlling specialization

Donor acceptance

Importance of Stem CellsImportance 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.

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http://stemcells.nih.gov/index.asp

Importance of Stem CellsImportance 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 CellsImportance 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=1yCgLythe00

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Importance of Stem CellsImportance 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 CellsImportance of Stem Cells

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http://www.youtube.com/watch?v=vwCrxomPbtY

http://www.youtube.com/watch?v=ADchGO-0kGo&feature=related