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Stem Cells
The process of cell differentiation
A primary goal of research on embryonic stem cells is to learn
how undifferentiated stem cells turn into differentiated stem
cells that form specific tissues and organs. Researchers are
also interested in figuring out how to control this process of
differentiation.
What is a Stem Cell?
• A cell that has the ability to continuously
divide and differentiate (develop) into
various other kind(s) of cells/tissues
• Stem cells are different from other cells of
the body in that they have the ability to
differentiate into other cell/tissue types.
• This ability allows them to replace cells
that have died. With this ability, they have
been used to replace defective
cells/tissues in patients who have certain
diseases or defects.
Stem Cell Applications
• Tissue repair
 nerve, heart, muscle, organ, skin
 Regenerate spinal cord, heart tissue or any
other major tissue in the body.
• Cancers
 Studies show leukemia patients treated with
stem cells emerge free of disease
 Injections of stem cells have also reduces
pancreatic cancers in some patients.
• Autoimmune diseases
 diabetes, rheumatoid arthritis, MS
Kinds of Stem Cells
Stem cell
type
Totipotent
Pluripotent
Multipotent
Description
Examples
Cells from early
Each cell can develop
(1-3 days)
into a new individual
embryos
Some cells of
Cells can form any (over
blastocyst (5 to 14
200) cell types
days)
Cells differentiated, but
can form a number of
other tissues
Fetal tissue, cord
blood, and adult
stem cells
Embryonic Stem cells are obtained from In-Vitro Fertilization embryos that were
not used - http://www.news.wisc.edu/packages/stemcells/illustration.html
Illustration by Matt Bohan, 2007
This cell
Can form the
Embryo and placenta
This cell
Can just form the
embryo
Fully mature
Adult Stem Cells
An undifferentiated cells found
among specialized or differentiated
cells in a tissue or organ after birth
•
•
•
•
•
Skin
Fat Cells
Bone marrow
Brain
Many other organs
& tissues
STEM CELLS HAVE ALSO BEEN
FOUND IN “MATURE” ORGANS
Illustration by Matt Bohan, 2007
Differences between
embryonic stem cells and adult/somatic stem cells
• They have different self-renewal capabilities
– Embryonic stem cells: near indefinite self-renewal
– Adult stem cells: limited self-renewal
•
They have different differentiation potentials
– .Embryonic stem cells: differentiate into all cell types in an
organism
– Adult stem cells: differentiate into restricted cells types.
• They differ in how they respond to external stimuli
– Embryonic stem cells are readily to change upon stimulation
– Adult cells emphasize on stability and need to be activated by
cues, e.g. injuries.
PROS AND CONS OF EACH TYPE
• EMBRYONIC
– CELL LINES LAST
AND LAST AND
LAST
– Pluripotent and
totipotent in an early
embryonic stage
– EASY TO FIND
– ETHICAL ISSUES
• ADULT
– CELL LINES DO
NOT LAST
– MULTIPOTENT
– HARD TO LOCATE
– NO ETHICAL
ISSUES
Why the Controversy Over Stem cells?
•
•
•
•
Embryonic Stem cells are derived from extra
blastocysts that would otherwise be discarded
following IVF( in vitro fertilisation)
Extracting stem cells destroys the developing
blastocyst (embryo).
-Questions for ConsiderationIs an embryo a person?
Is it morally acceptable to use embryos for
research?
Current medical application of human stem cell
research
-Grow new cells in a laboratory to replace damaged
organs or tissues
-Correct parts of organs that don’t work properly
-Research causes of genetic defects in cells
-Research how diseases occur or why certain cells
develop into cancer cells
-Test new drugs for safety and effectiveness
- Bone marrow transplantation
Cord blood stem cells and amniotic fluid stem cells
Cord blood stem cells are harvested from the umbilical
cord after childbirth. They can be frozen in cell banks for
use in the future. These cells have been successfully used
to treat children with blood cancers, such as leukemia,
and certain genetic blood disorders.
Dolly the Sheep. Dolly (July 5, 1996 - February 14,
2003), a ewe, was the first mammal to have been
successfully cloned from an adult cell. She was cloned
at theRoslin Institute in Midlothian, Scotland, and lived
there until her death when she was six years old