Advanced Placement Biology
and
Stem Cells
Click on the cartoon above for a tutorial on
Stem Cells
Click on the cartoon above for a tutorial on
The Nature of Stem Cells and Embryology
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
Replace Skin
Click on the picture to watch a video on the skin shooter
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
EMBRYONIC STEM CELLS
Blastocyst
http://en.wikipedia.org/wiki/Image:Blastocyst_English.svg
http://stemcells.nih.gov/info/basics/
"Image courtesy of NIH resource for stem cell research"
Umbilical Cord Stem Cells
•
•
•
•
•
Also Known as Wharton’s Jelly
Adult stem cells of infant origin
Less invasive than bone marrow
Greater compatibility
Less expensive
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
Umbilical Cord Stem Cells
Three important functions:
1. Plasticity: Potential to change into
other cell types like nerve cells
2. Homing: To travel to the site of
tissue damage
3. Engraftment: To unite with other
tissues
STEM CELLS HAVE ALSO BEEN
FOUND IN “MATURE” ORGANS
Illustration by Matt Bohan, 2007
Differences between
embryonic stem cells and adult 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
– MULTIPOTENT
– EASY TO FIND
– ETHICAL ISSUES WHEN DOES LIFE
BEGIN?
• ADULT
– CELL LINES DO
NOT LAST
– NOT 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.
Extracting stem cells destroys the developing
blastocyst (embryo).
-Questions for ConsiderationIs an embryo a person?
Is it morally acceptable to use embryos for
research?
When do we become “human beings?”
People in the US affected by diseases that may be
helped by stem cell research
Condition
Number of Persons Affected
Cardiovascular diseases
58 Million
Autoimmune diseases
30 Million
Diabetes
16 Million
Osteoporosis
10 Million
Cancer
8.2 Million
Alzheimer's disease
4 Million
Parkinson's disease
1.5 Million
Burns (severe)
0.3 Million
Spinal cord injuries
0.25 Million
Birth defects
150,000 (per year)
Total
128.4 Million
-------------------------------------------------------------------------------------Data from the Patients' Coalition for Urgent Research, Washington, DC (according
to Perry, Ref. 267).
How can scientists ensure ethical conduct
in stem cell research
• Education for researchers
– Routine emphasis by principle investigators
– Emphasis by funding agencies
– Classes and seminars
• Education for the public
– Understand the importance of research
– Understand that scientists are under ethical guidance
• Communication and open dialogue
– Understand each others’ opinion
– Reach a rationale common ground.
• Last step: Legal reinforcement
Useful Resources
• National Institute of Health resource for stem cells
(http://stemcells.nih.gov)
• International Society for Stem Cell Research:
“Guidelines for the Conduct of Human Embryonic Stem Cell
Research (www.isscr.org)”
• National Academy of Science: “Guidelines for human
embryonic stem cell research”
(http://www.nap.edu/openbook.php?isbn=0309096537)