Transcript Stem Cells in Biology

• Summer 2007 Workshop
• in Biology and Multimedia
• for High School Teachers
Life Sciences-HHMI Outreach. Copyright 2006 President and
Fellows of Harvard College.
Stem Cells in Biology
An Introduction to Stem Cells and
Stem Cell Applications for English
Learners
Andrew Creamer
Life Sciences-HHMI Outreach. Copyright 2006 President and
Fellows of Harvard College.
Objectives
• Define and describe the characteristics of
embryonic and adult stem cells
• Describe the origins of various stem cells
• Describe the debate surrounding and
identify misconceptions about stem cell
research
• Describe the present and future
applications for stem cell research
Life Sciences-HHMI Outreach. Copyright 2006 President and
Fellows of Harvard College.
What makes a cell a stem cell?
• Plasticity: A stem cell is plastic, meaning it
can develop into another type of cell.
• Differentiation: The process where a stem
cell specializes or develops into another
type of cell.
• Self-Renewal: a stem cell can divide (renew
itself) indefinitely (go through mitosis) and
without always developing into another cell.
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Stem Cell
Self-renewal
Differentiation
Stem Cell
differentiated
cell
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Differentiation
Qu i c k T i m e ™ a n d a
T I F F (U n c o m p re s s e d ) d e c o m p re s s o r
a re n e e d e d to s e e th is p i c t u re .
http://stemcells.nih.gov/info/basics/basics4.asp
"Image courtesy of NIH resource for stem cell research"
Life Sciences-HHMI Outreach. Copyright 2006 President and
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Major Types of Stem Cells
Embryonic Stem Cells
Adult Stem Cells
• Totipotent : cell can
• Multipotent: cell can
develop into all cell
develop into a few cell
types
types but not all
• “Immortal”: can selfrenew indefinitely
• Located in few organs
or may be unidentified
• Plentiful
• Hard to find
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Embryonic Stem cells
Embryos are formed
in labs that help
couples get pregnant.
An egg and sperm
fertilize a zygote and
are inserted into a
woman’s uterus to
develop into an
embryo and then
fetus.
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In Vitro Fertilization (IVF): a
sperm fertilizes an egg in a lab
dish creating the embryo.
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http://en.wikipedia.org/wiki/Image:Icsi.JPG
Embryonic Stem Cells
First stages of segmentation of a mammalian ovum. Semidiagrammatic. z.p. Zona striata.
p.gl. Polar bodies. a. Two-cell stage. b. Four-cell stage. c. Eight-cell stage. d, e. Morula
stage.
This process creates
multiple embryos that
will not be used to
make a baby. Many
donors wish to donate
these unused embryos
to scientific research
instead of having the
lab throw them away.
Life Sciences-HHMI Outreach. Copyright 2006 President and
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http://en.wikipedia.org/wiki/Polar_bodies
Embryonic Stem Cells
The embryo used in
research is 4-5 days old
and is a microscopic ball
of about 150 cells.
The ball as thick as a hair
is called a Blastocyst and
has three layers called
germ layers. Each layer
has special stem cells that
makes a part of the body.
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http://en.wikipedia.org/wiki/Image:Blastocyst.svg
Blastocyst:
Source of Embryonic Stem Cells
Blastocyst under the microscope
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http://en.wikipedia.org/wiki/Image:Blastocyst%2C_day_5.JPG
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Germ Layers
The embryo develops three germ
layers of cells called the
ectoderm, mesoderm and
endoderm
http://en.wikipedia.org/wiki/Image:Gastrulation.png
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Embryonic Stem Cell
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These embryos not used in
IVF will not grow into a
fetus or baby because an
embryo like the one in the
picture needs to be
implanted inside a
woman’s uterus to
develop into a human
fetus. Fetuses and babies
are not aborted for stem
cell research.
AuthorPhotograph by Ed Uthman, MD.PermissionPD Public domain
http://en.wikipedia.org/wiki/Image:Tubal_Pregnancy_with_embryo.jpg.
Life Sciences-HHMI Outreach. Copyright 2006 President and
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Embryonic Stem Cells
Embryos can also be used
for cloning research. The
process called Somatic
Nuclear Transfer (SNT)
removes an embryo’s
nucleus and replaces it
with another person’s
adult cell nucleus. The
embryo would then have
the ability to develop into
a clone or genetic copy of
the nucleus donor if the
embryo were implanted
into a woman’s uterus.
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Dolly the Sheep was first cloned
using SNT. An adult sheep body
cell nucleus was implanted into
an embryo and then implanted in
a mother sheep’s uterus.
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TIFF ( Unc ompres s ed) dec ompr ess or
are needed to s ee this pic ture.
http://en.wikipedia.org/wiki/Image:Dollyscotland.JPG
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Adult Stem Cells
Adult stem cells are called
somatic or body stem
cells. Some people call
these adult because they
are found after an embryo
develops into a fetus and
are no longer an
embryonic stem cell. Not
only adults have adult
stem cells! Some organs
are believed to lack stem
cells and these cells grow
and replace dead cells
with mitosis.
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http://en.wikipedia.org/wiki/Image:Mitosis-flourescent.jpg
Adult Stem Cells
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http://www.ulb.ac.be/sciences/biodic/homepage2.htm red corpuscles figurel
Adult stem cells develop
into a few cell types.
These multipotent cells
are used in bone-marrow
transplants and will
develop into all the blood
cells. These cells are
important, but some
organs may not have adult
stem cells and these cells
can be difficult to find.
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All Stem Cells Are Important
• All stem cells can help scientists learn how cells
regenerate or repair injured cells, tissues and
organs.
• Scientists need both types of stem cells for their
research.
• Each cell type can help inform scientists on how
we develop and how some diseases affect our
cells. Life Sciences-HHMI Outreach. Copyright 2006 President and
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Stem Cell Debate
Some people oppose stem cell research because
they believe that the 4-5 day old ball of cells is a
living human being. What some do not
understand is that unused embryos are trashed
regardless. Many people, religious and nonreligious, believe it is better to use these embryos
for research on how to cure human diseases rather
than to just trash them without purpose. The
underlying issue is the personal belief when life
actually begins.
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Misconceptions
• Pregnancy, fetuses or babies are aborted or
harmed in stem cell research.
Fact: Fertilized Blastocysts donated from IVF labs
are used and no pregnancy is aborted.
• The fertilized embryos are removed from women’s
bodies and used for research.
Fact: The embryos are left over from IVF and are
frozen and are not implanted for pregnancy.
Life Sciences-HHMI Outreach. Copyright 2006 President and
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Misconceptions
• A clone is grown in a lab without an embryo or
born from a mother and is the same age and
personality as you, and has no belly button.
Fact: a clone would need a fertilized embryo and
would have to be implanted in a woman’s uterus.
If you were cloned at 14, the clone would be 14
years younger than you (a baby you) and would
have to have a mother to be born, so yes, it would
have a belly button.
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http://en.wikipedia.org/wiki/Image:Femnavel.jpg
Misconceptions
• If the embryos were not used in stem cell research
they would have been used to make children.
Fact: The embryos left over from IVF are discarded.
• Men and women who donate their embryos do not
know that their embryos are used for research.
Fact: The embryos used in scientific research are
donated with written and informed consent
(permission) by the donors.
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Stem Cell Research
Some scientists want to identify the genes
and processes used in embryo development
to figure out how to make new cells in
damaged or diseased cells and organs or fix
old cells by reprogramming them to be
young cells again.
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Cell-Based Therapy
Qu i c k T i m e ™ a n d a
T I F F (Un c o m p re s s e d ) d e c o m p re s s o r
a re n e e d e d t o s e e t h i s p i c tu re .
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http://stemcells.nih.gov/info/basics/basics6.asp
Cell-Based Therapies
Science has known for a long time that certain
organisms and organs can regenerate or re-grow
themselves after being damaged or injured. For
example, planaria can regenerate after being cut
up into small pieces and certain lizards can
regenerate limbs and tails. Scientists want to know
“How do they do it?” and study these animals in
the lab. Using cells to medically regenerate or
replace dead or injured cells is an example of a
cell-based therapy.
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Planaria can regenerate lost cells
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Cell-Based Therapy
• If your skin was burned
in an accident, there
would be layers of skin
cells that die. Using stem
cell techniques, scientists
could take a skin cell from
another area on your body
or stem cell and grow new
plates of skin tissue in a
lab tissue culture dish to
regenerate new skin cells
for you.
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Future Applications
Stem Cells may one day help scientists to
regenerate cells lost in diseases like:
• Repair heart muscle after a heart attack
• Pancreas cells lost in diabetes
• Neurons lost in Alzheimer’s
• Retinal cells causing blindness
• Understand the cell growths of cancers
• Help organ transplantation
Life Sciences-HHMI Outreach. Copyright 2006 President and
Fellows of Harvard College.