The ISSCR is an independent, nonprofit organization providin.docx

The ISSCR is an independent, nonprofit
organization providing a global forum for
stem cell research and regenerative medicine.
Stem Cell
Facts
What are stem cells?
Stem cells are the foundation cells for every organ and
tissue in our bodies. The highly specialized cells that make
up these tissues originally came from an initial pool of stem
cells formed shortly after fertilization. Throughout our lives,
we continue to rely on stem cells to replace injured tissues
and cells that are lost every day, such as those in our skin,
hair, blood and the lining of our gut. Stem cells have two
key properties: 1) the ability to self-renew, dividing in a
way that makes copies of themselves, and 2) the ability to
differentiate, giving rise to the mature types of cells that
make up our organs and tissues.
Tissue-specific stem cells
Tissue-specific stem cells, which are sometimes referred to
as “adult” or “somatic” stem cells, are already somewhat
specialized and can produce some or all of the mature
cell types found within the particular tissue or organ in
which they reside. Because of their ability to generate
multiple, organ-specific, cell types, they are described as
“multipotent.” For example, stem cells found within the
adult brain are capable of making neurons and two types of
glial cells, astrocytes and oligodendrocytes.

Tissue-specific stem cells have been found in several organs
that need to continuously replenish themselves, such as the
blood, skin and gut and have even been found in other, less
regenerative, organs such as the brain. These types of stem
cells represent a very small population and are often buried
deep within a given tissue, making them difficult to identify,
isolate and grow in a laboratory setting.
Neuron – Dr. Gerry Shaw, EnCor Biotechnology Inc.
Astrocyte – Abcam Inc.
Oligodendrocyte – Dhaunchak and Nave (2007).
Proc Natl Acad Sci USA 104:17813-8
www.isscr.org
Embryonic stem cells
Embryonic stem cells have been derived from a variety
of species, including humans, and are described as
“pluripotent,” meaning that they can generate all the
different types of cells in the body. Embryonic stem cells
can be obtained from the blastocyst, a very early stage
of development that consists of a mostly hollow ball of
approximately 150-200 cells and is barely visible to the
naked eye. At this stage, there are no organs, not even
blood, just an “inner cell mass” from which embryonic stem
cells can be obtained. Human embryonic stem cells are
derived primarily from blastocysts that were created by
in vitro fertilization (IVF) for assisted reproduction but
were no longer needed.
The fertilized egg and the cells that immediately arise in the
first few divisions are “totipotent.” This means that, under
the right conditions, they can generate a viable embryo

(including support tissues such as the placenta). Within a
matter of days, however, these cells transition to become
pluripotent. None of the currently studied embryonic stem
cell lines are alone capable of generating a viable embryo
(i.e., they are pluripotent, not totipotent).
Why are embryonic stem cells
so valuable?
Unlike tissue-specific (adult) stem cells, embryonic stem
cells have the potential to generate every cell type found
in the body. Just as importantly, these cells can, under the
right conditions, be grown and expanded indefinitely in
this unspecialized or “undifferentiated” state. These cells
help researchers learn about early human developmental
processes that are otherwise inaccessible, study diseases and
establish strategies that could ultimately lead to therapies
designed to replace or restore damaged tissues.
Induced pluripotent stem cells
One of the hottest topics in stem cell research today is the
study of induced pluripotent stem cells (iPS cells). These
are adult cells (e.g., skin cells) that are engineered, or
“reprogrammed,” to become pluripotent, i.e., behave like
an embryonic stem cell. While these iPS cells share many of
the same characteristics of embryonic stem cells, including
the ability to give rise to all the cell types in the body, it is
important to understand that they are not identical.
The original iPS cells were produced by using viruses to
insert extra copies of three to four genes known to be
important in embryonic stem cells into the specialized cell.
It is not yet completely understood how these three to four
“reprogramming” genes are able to induce pluripotency;
this question is the focus of ongoing research. In addition,

recent studies have focused on alternative ways of
reprogramming cells using methods that are safer for use
in clinical settings.
Disease- or patient-specific
pluripotent stem cells
One of the major advantages of iPS cells, and one of the
reasons that researchers are very interested in studying
them, is that they are a very good way to make pluripotent
stem cell lines that are specific to a disease or even to an
individual patient. Disease-specific stem cells are powerful
tools for studying the cause of a particular disease and
then for testing drugs or discovering other approaches to
treat or cure that disease. The development of patient-
specific stem cells is also very attractive for cell therapy, as
these cell lines are from the patient themselves and may
minimize some of the serious complications of rejection and
immunosuppression that can occur following transplants
from unrelated donors.
Moving stem cells into the clinic
Clinical translation is the process used to turn scientific
knowledge into real world medical treatments. Researchers
take what they have learned about how a tissue usually
works and what goes wrong in a particular disease or injury
and use this information to develop new ways to diagnose,
stop or fix what goes wrong. Before being marketed or
adopted as standard of care, most treatments are tested
through clinical trials. Sometimes, in attempting new surgical
techniques or where the disease or condition is rare and
does not have a large enough group of people to form a
clinical trial, certain treatments might be tried on one or
two people, a form of testing sometimes referred to as
innovative medicine.

For more information on how science becomes medicine,
please visit www.closerlookatstemcells.org.
Current therapies
Blood stem cells are currently the most frequently used stem
cells for therapy. For more than 50 years, doctors have been
using bone marrow transplants to transfer blood stem cells
to patients, and more advanced techniques for collecting
blood stem cells are now being used to treat leukemia,
lymphoma and several inherited blood disorders. Umbilical
cord blood, like bone marrow, is often collected as a source
of blood stem cells and in certain cases is being used as an
alternative to bone marrow transplantation.
Additionally, some bone, skin and corneal diseases or injuries
can be treated by grafting tissues that are derived from or
maintained by stem cells. These therapies have also been
shown to be safe and effective.
Potential therapies
Other stem cell treatments, while promising, are still at very
early experimental stages. For example, the mesenchymal
stem cell, found throughout the body including in the
bone marrow, can be directed to become bone, cartilage,
fat and possibly even muscle. In certain experimental
models, these cells also have some ability to modify immune
functions. These abilities have created considerable interest
in developing ways of using mesenchymal stem cells to treat
a range of musculoskeletal abnormalities, cardiac disease
and some immune abnormalities such as graft-versus-host
disease following bone marrow transplant.
Remaining challenges

Despite the successes we have seen so far, there are several
major challenges that must be addressed before stem cells
can be used as cell therapies to treat a wider range of
diseases.
First, we need to identify an abundant source of stem cells.
Identifying, isolating and growing the right kind of stem
cell, particularly in the case of rare adult stem cells, are
painstaking and difficult processes. Pluripotent stem cells,
such as embryonic stem cells, can be grown indefinitely in
the lab and have the advantage of having the potential to
become any cell in the body, but these processes are again
very complex and must be tightly controlled. iPS cells, while
promising, are also limited by these concerns. In both cases,
considerable work remains to be done to ensure that these
cells can be isolated and used safely and routinely.
Second, as with organ transplants, it is very important
to have a close match between the donor tissue and the
recipient; the more closely the tissue matches the recipient,
the lower the risk of rejection. Being able to avoid the life-
long use of immunosuppressants would also be preferable.
The discovery of iPS cells has opened the door to developing
patient-specific pluripotent stem cell lines that can later
be developed into a needed cell type without the problems
of rejection and immunosuppression that occur from
transplants from unrelated donors.
Third, a system for delivering the cells to the right part of
the body must be developed. Once in the right location,
the new cells must then be encouraged to integrate and
function together with the body’s other cells.
www.isscr.org

Glossary
Blastocyst
A very early embryo that has the shape of a ball and consists
of approximately 150-200 cells. It contains the inner cell
mass, from which embryonic stem cells are derived, and
an outer layer of cells called the trophoblast that forms the
placenta.
Cell line
Cells that can be maintained and grown in a dish outside of
the body.
Clinical translation
The process of using scientific knowledge to design, develop
and apply new ways to diagnose, stop or fix what goes
wrong in a particular disease or injury.
Differentiation
The process of development with an increase in the level of
organization or complexity of a cell or tissue, accompanied
by a more specialized function.
Embryo
The early developing organism; this term denotes the period of
development between the fertilized egg and the fetal stage.
Embryonic stem cell
Cells derived from very early in development, usually the
inner cell mass of a developing blastocyst. These cells are
self-renewing (can replicate themselves) and pluripotent
(can form all cell types found in the body).
Induced pluripotent stem (iPS) cell
Induced pluripotent cells (iPS cells) are stem cells that
were engineered (“induced”) from non-pluripotent cells

to become pluripotent. In other words, a cell with a
specialized function (for example, a skin cell) that has been
“reprogrammed” to an unspecialized state similar to that of
an embryonic stem cell.
Innovative medicine
Treatments that are performed on a small number of people
and are designed to test a novel technique or treat a rare
disease. These are done outside of a typical clinical trial
framework.
In vitro fertilization
A procedure in which an egg cell and sperm cells are
brought together in a dish to fertilize the egg. The fertilized
egg will start dividing and, after several divisions, forms the
embryo that can be implanted into the womb of a woman
and give rise to pregnancy.
Mesenchymal stem cells
Mesenchymal stem cells were originally discovered in the
bone marrow, but have since been found throughout the
body and can give rise to a large number of connective
tissue types such as bone, cartilage and fat.
Multipotent stem cells
Stem cells that can give rise to several different types of
specialized cells, but in contrast to a pluripotent stem cell,
are restricted to a certain organ or tissue types. For example,
blood stem cells are multipotent cells that can produce all
the different cell types that make up the blood but not the
cells of other organs such as the liver or brain.
Pluripotent stem cells
Stem cells that can become all the cell types that are found

in an implanted embryo, fetus or developed organism.
Embryonic stem cells are pluripotent stem cells.
Self-renewal
The process by which a cell divides to generate another cell
that has the same potential.
Stem cells
Cells that have both the capacity to self-renew (make more
stem cells by cell division) and to differentiate into mature,
specialized cells.
Tissue-specific stem cells
(also known as adult or somatic stem cells)
Stem cells found in different tissues of the body that can give
rise to some or all of the mature cell types found within the
particular tissue or organ from which they came, i.e., blood
stem cells can give rise to all the cells that make up the blood,
but not the cells of organs such as the liver or brain.
Totipotent stem cells
Stem cells that, under the right conditions, are wholly
capable of generating a viable embryo (including the
placenta) and, for humans, exist until about four days
after fertilization, prior to the blastocyst stage from which
embryonic stem cells are derived.
International Society for Stem Cell Research
111 Deer Lake Road, Suite 100 | Deerfield, IL 60015 | USA
[email protected] | www.isscr.org
© 2011 International Society for Stem Cell Research
http://www.isscr.org/ForThePublic.htm

National Academy of Sciences
National Academy of Engineering
Institute of Medicine
National Research Council
Over the past decade, stem cells have gained a place in most
Americans’ vocabularies—
discussions of them appear on TV and radio news programs, in
newspapers and mag-
azines, and even in political campaigns across the country. As
stem cells have come to
the forefront of medical research, the ethical controversies over
embryonic stem cells
have become prominent. This booklet is designed to provide
basic knowledge to facil-
itate thinking about and understanding the scientific and ethical
issues surrounding
stem cells. It is intended to help readers more easily interpret
news about stem cells, as
the science advances or new controversies develop.

WHAT IS A STEM CELL? 3
TYPES OF STEM CELLS 4
WORKING WITH STEM CELLS 9
WHY STEM CELL RESEARCH IS BEING PURSUED 13
ETHICS, Moral values, AND U.S. LAW 19
I N T H I S B O O K L E T. . .
F
or centuries, scientists have
known that certain animals
can regenerate missing parts
of their bodies. Humans actually
share this ability with animals like the
starfish and the newt. Although we can’t replace a
missing leg or a finger, our bodies are
constantly regenerating blood, skin,
and other tissues. The identity of
the powerful cells that allow us
to regenerate some tissues was
first revealed when experiments
with bone marrow in the 1950s

established the existence of stem
cells in our bodies and led to the develop-
ment of bone marrow transplantation, a therapy
now widely used in medicine. This discovery raised
hope in the medical potential of regeneration. For
the first time in history, it became possible for physi-
cians to regenerate a damaged tissue with a new
supply of healthy cells by drawing on the unique
ability of stem cells to create many of the
body’s specialized cell types.
Once they had recognized the medical
potential of regeneration through the suc-
cess of bone marrow transplants, scientists
sought to identify similar cells within the
embryo. Early studies of human development had
demonstrated that the cells of the embryo were
capable of producing every cell type in the human
body. Scientists were able to extract embryonic stem

cells from mice in the 1980s, but it wasn’t until 1998
that a team of scientists from the University of
Wisconsin–Madison became the first group to iso-
late human embryonic stem cells and keep them
alive in the laboratory. The team knew that they had
in fact isolated stem cells because the cells could
remain unspecialized for long periods of time, yet
maintained the ability to transform into a vari-
ety of specialized cell types, including nerve,
gut, muscle, bone, and cartilage cells.
Stem cell research is being pursued in the hope
of achieving major medical breakthroughs.
Scientists are striving to create therapies
that rebuild or replace damaged cells with
tissues grown from stem cells and offer
hope to people suffering from cancer, dia-
betes, cardiovascular disease, spinal-cord
injuries, and many other disorders. Both adult

and embryonic stem cells may also provide a route
for scientists to develop valuable new methods of
drug discovery and testing. They are also powerful
tools for doing the research that leads to a better
understanding of the basic biology of the human
body. By drawing on expert scientists,
doctors, bioethicists, and others, the National
Academies have examined the potential of stem
cell technologies for medicine and provided a forum
for discussing the ethical implications and moral
dilemmas of stem cell research.
2
3
Ultimately, every cell in the human
body can be traced back to a fertilized egg that came into
existence from the union of egg and sperm. But the body
is made up of over 200 different types of cells, not just

one. All of these cell types come from a pool of stem
cells in the early embryo. During early development, as
well as later in life, various
types of stem cells give rise to
the specialized or differentiat-
ed cells that carry out the spe-
cific functions of the body,
such as skin, blood, muscle,
and nerve cells.
Over the past two decades, sci-
entists have been gradually deci-
phering the processes by which
unspecialized stem cells become
the many specialized cell types
in the body. Stem cells can
regenerate themselves or produce specialized cell types.
This property makes stem cells appealing for scientists
seeking to create medical treatments that replace lost or

damaged cells.
WHAT IS A STEM CELL?
4
Stem cells are found in all of us,
from the early stages of human development to the end of
life. All stem cells may prove useful for medical research,
but each of the different types has both promise and
limitations. Embryonic stem cells, which can be derived
from a very early stage in human development, have the
potential to produce all of the body’s cell types. Adult
stem cells, which are found in certain tissues in fully
developed humans, from babies to adults, may be lim-
ited to producing only certain types of specialized cells.
Recently, scientists have also identified stem cells in
umbilical cord blood and the placenta that can give rise
to the various types of blood cells.
Embryonic Stem Cells
A blastocyst (BLAST-oh-sist), is a pre-implantation

embryo that develops 5 days after the fertilization of an
egg by a sperm. It contains all the material necessary for
the development of a complete human being. The blasto-
cyst is a mostly hollow sphere of cells that is smaller than
the period at the end of this sentence. In its interior is the
inner cell mass, which is composed of 30-34 cells that are
referred to by scientists as pluripotent because they can
differentiate into all of the cell types of the body. In
comon usage, “embryo” can refer to all stages of devel-
opment from fertilization until a somewhat ill-defined
stage when it is called a fetus. Scientists use terms such as
“morula” and “blastocyst” to refer to precise, specific
stages of pre-implantation development. In order to be as
precise as possible, this booklet uses the scientific terms
when describing scientific concepts but uses the term
“embryo” where more precision seemed likely to con-
fuse rather than clarify.
TYPES OF STEM CELLS

Embryonic
stem cells
are derived
from the inner
cell mass
of the
blastocyst.
In culture,
they can
self-replicate
or produce
specialized
cell types.
TYPES OF STEM CELLS
5
In normal development, the blastocyst would implant
in the wall of the uterus to become the embryo and
continue developing into a mature organism. Its outer
cells would begin to form the placenta and the inner
cell mass would begin to differentiate into the pro-
gressively more specialized cell types of the body.
When the blastocyst is used for stem cell research,
scientists remove the inner cell mass and place these

cells in a culture dish with a nutrient-rich liquid
where they give rise to embryonic stem cells.
Embryonic stem cells seem to be more flexible than
stem cells found in adults, because they have the
potential to produce every cell type in the human
body. They are also generally easier to collect, purify
and maintain in the laboratory than adult stem cells.
Scientists can induce embryonic stem cells to repli-
cate themselves in an undifferentiated state for very
long periods of time before stimulating them to cre-
ate specialized cells. This means that just a few
embryonic stem cells can build a large bank of stem
cells to be used in experiments. However, such
undifferentiated stem cells could not be used direct-
ly for tissue transplants because they can cause a
type of tumor called a teratoma. To be used for ther-
apies, embryonic stem cells would first need to be
differentiated into specialized cell types.

Some find embryonic stem cell research to be morally
objectionable, because when scientists remove the
inner cell mass, the blastocyst no longer has the poten-
tial to become a fully developed human being.
Sources of Embryonic Stem Cells
In Vitro Fertilization: The largest potential
source of blastocysts for stem cell research is from in
vitro fertilization (IVF) clinics. The process of IVF
requires the retrieval of a woman’s eggs via a surgical
procedure after undergoing an intensive regimen of
“fertility drugs,” which stimulate her ovaries to pro-
duce multiple mature eggs. When IVF is used for
reproductive purposes, doctors typically fertilize all of
the donated eggs in order to maximize their chance of
producing a viable blastocyst that can be implanted in
the womb. Because not all the fertilized eggs are
implanted, this has resulted in a large bank of
“excess” blastocysts that are currently stored in freez-
ers around the country. The blastocysts stored in IVF

clinics could prove to be a major source of embryon-
A human blastocyst,
which is produced
about 5 days after
fertilization, is smaller
than the period at
the end of this sen-
tence. NIH/Mr. J.
Conaghan.
ic stem cells for use in medical research. However,
because most of these blastocysts were created before
the advent of stem cell research, most donors were not
asked for their permission to use these left-over blas-
tocysts for research.
The in vitro fertilization (IVF) technique could poten-
tially also be used to produce blastocysts specifically
for research purposes. This would facilitate the isola-
tion of stem cells with specific genetic traits necessary
for the study of particular diseases. For example, it
may be possible to study the origins of an inherited
disease like cystic fibrosis using stem cells made from

egg and sperm donors who have this disease. The cre-
ation of stem cells specifically for research using IVF
is, however, ethically problematic for some people
because it involves intentionally creating a blastocyst
that will never develop into a human being.
Nuclear Transfer: The process called nuclear
transfer offers another potential way to produce
embryonic stem cells. In animals, nuclear transfer
has been accomplished by inserting the nucleus of
an already differentiated adult cell—for example,
a skin cell—into a donated egg that has had its
nucleus removed. This egg, which now contains the
genetic material of the skin cell, is then stimulated to
form a blastocyst from which embryonic stem cells
can be derived. The stem cells that are created in this
way are therefore copies or “clones” of the original
adult cell because their nuclear DNA matches that
of the adult cell.

As of the summer of 2006, nuclear transfer has not
been successful in the production of human embryon-
ic stem cells,1 but progress in animal research suggests
that scientists may be able to use this technique to
develop human stem cells in the future.
6
TYPES OF STEM CELLS
Through nuclear transfer, scientists could produce a blastocyst
by
inserting the nucleus from an adult cell (for example, a skin
cell)
into an egg without a nucleus. All the stem cells derived from
this
blastocyst are genetically matched to the adult cell.
1Claims by Korean scientists of successful derivation of human
embryonic stem cells using nuclear transfer have been found to
be invalid
and were retracted.
Scientists believe that if they are able to use nuclear
transfer to derive human stem cells, it could allow
them to study the development and progression of
specific diseases by creating stem cells containing

the genes responsible for certain disorders. In the
future, scientists may also be able to create “person-
alized” stem cells that contain only the DNA of
a specific patient. The embryonic stem cells created
by nuclear transfer would be genetically matched to
a person needing a transplant, making it far less
likely that the patient’s body would reject the new
cells than it would be with traditional tissue trans-
plant procedures.
Although using nuclear transfer to produce stem
cells is not the same as reproductive cloning, some
are concerned about the potential misapplication of
the technique for reproductive cloning purposes.
Other ethical considerations include egg donation,
which requires informed consent, and the possible
destruction of blastocysts.
Adult Stem Cells
Adult stem cells are hidden deep within organs,

surrounded by millions of ordinary cells, and may
help replenish some of the body’s cells when needed.
In fact, some adult stem cells are currently being
used in therapies. They have been found in several
7
TYPES OF STEM CELLSProducing Embryonic Stem Cells
Using Nuclear Transfer Is Not the
Same as Reproductive Cloning
The use of nuclear transfer to develop disease-specific
stem cells can be called research cloning, and the use
of this technique for personalized tissue transplants is
sometimes called therapeutic cloning. These terms must
be carefully distinguished from reproductive cloning,
in which the intent is to implant a cloned embryo in a
female’s womb and allow it to develop fully into
an individual. This was the technique by which Dolly the
sheep was made and is now widely used for reproductive
cloning in animals. In humans, however, reproductive
cloning has been actively discouraged by most in the
scientific community. The National Academies conclud-

ed, “Human reproductive cloning should not now be
practiced. It is dangerous and likely to fail” in the
2002 report Scientific and Medical Aspects of Human
Reproductive Cloning.
Some of
the known
sources of
adult stem
cells.
8
TYPES OF STEM CELLS
organs that need a constant supply of cells, such as
the blood, skin, and lining of the gut, and have also
been found in surprising places like the brain, which
is not known to readily replenish its cells. Unlike
embryonic stem cells, adult stem cells are already
somewhat specialized. For example, blood stem
cells normally only give rise to the many types of
blood cells, and nerve stem cells can only make the

various types of brain cells. Recent research however,
suggests that some adult stem cells might be more
flexible than previously thought, and may be made
to produce a wider variety of cell types. For example,
some experiments have suggested that blood stem cells
isolated from adult mice may also be able to produce
liver, muscle, and skin cells, but these results are not
yet proven and have not been demonstrated with
human cells. Nevertheless, scientists are working on
finding a way to stimulate adult stem cells, or even
other types of adult cells, to be more versatile. If
they succeed, it could provide another source of
unspecialized stem cells.
Attributes
Limitations
Ethical
Concerns
In Vitro Fertilization
• can produce all cell types

• relatively easy to identify,
isolate, maintain, and
grow in the laboratory
• large source of “excess”
blastocysts from IVF clinics
• limited number of cell
lines available for federally
funded research
• risk of creating teratomas
(tumors) from implanting
undifferentiated stem cells
• destruction of human
blastocysts
• donation of blastocysts
requires informed consent
Nuclear Transfer
• can produce all cell types
• relatively easy to identify,
isolate, maintain, and grow
in the laboratory
• stem cells may be genetically
matched to patient
• not yet achieved with human cells
• risk of creating teratomas

(tumors) from implanting
undifferentiated stem cells
• destruction of human
blastocysts
• donation of eggs requires
informed consent
• concern about misapplication
for reproductive cloning
Adult Tissues
• demonstrated success in
some treatments
• stem cells may be genetically
matched to patient
• produce limited number of
cell types
• not found in all tissues
• difficult to identify, isolate,
maintain, and grow in the
laboratory
• no major ethical concerns
have been raised
COMPARISON OF THE DIFFERENT SOURCES OF STEM
CELLS
Embryonic Stem Cells Adult Stem Cells

The day-to-day work that goes
on in the laboratories across the country studying
stem cells begins with developing ways to identify
stem cells, culture cell lines, and stimulate stem cells to
differentiate. Once these first steps have been
achieved, work on animals plays an important role in
furthering basic research and developing medical
applications. This work is necessary to form the foun-
dation of knowledge that will point the way to med-
ical advances.
Identifying Stem Cells
As early as 1961, scientists knew that adult bone mar-
row contained cells that could make all of the blood
cell types. But it wasn’t until 1988 that those stem cells
were isolated as pure populations. Why did it take so
long? The techniques for identifying stem cells have
only recently been developed. Partly, this is because
adult stem cells are, by their very nature, inconspicu-

ous in shape, size, and function. They also tend to hide
deep in tissues and are present only in very low num-
bers, making their identification and isolation like
finding a needle in a haystack.
How do scientists know when they have found a stem
cell? Every cell displays an array of proteins on its sur-
face; different cell types have different proteins.
Scientists can use these surface proteins as “markers”
that characterize individual cell types—a type of
“molecular ID.” For example, using molecules that
recognize and attach to specific surface proteins and
that can fluoresce under certain wavelengths of light,
scientists can visually tell the difference between a
blood stem cell and a mature white blood cell.
Unfortunately, not all stem cells can now be identified
in this manner because scientists have not yet identi-
fied markers for all stem cell types. Scientists also iden-
tify stem cells by observing their behavior in the

laboratory: stem cells must be able to remain unspe-
cialized and self-renew for long periods of time.
9
WORKING WITH
STEM CELLS
Fluorescent markers can be used to identify stem cells
hidden among ordinary adult cells. Here, human
embryonic stem cells are recognized by the marker
proteins they express (green). Courtesy of Paul J. Tesar,
Laboratory of Molecular Biology, NINDS and the NIH
Stem Cell Unit.
Scientists believe that there might be more types of
adult stem cells than the handful that have already
been identified, but finding them is a difficult process.
Culturing Cell Lines and
Stimulating Stem Cells to
Differentiate
Cell culture is a term that refers to the growth and
maintenance of cells in a controlled environment out-
side of an organism. A successful stem cell culture is
one that keeps the cells healthy, dividing, and unspe-

cialized. The culturing of stem cells is the first step in
establishing a stem cell line—a propagating collection
of genetically identical cells. Cell lines are important
because they provide a long-term supply of multiply-
ing cells that can be shared among scientists for
research and therapy development. The National
Academies report Stem Cells and the Future of
Regenerative Medicine (2001) described some of the
challenges of maintaining cell lines: “Over time, all
cell lines…change, typically accumulating harmful
genetic mutations. There is no reason to expect stem
cell lines to behave differently. While there is much
that can be learned using existing stem cell lines…such
concerns necessitate continued monitoring of these
cells as well as the development of new stem cell lines
in the future.”
Once they have established a stable stem cell line, sci-
entists start the process of causing the stem cells to dif-

ferentiate into specialized cell types. The cellular envi-
ronment in which stem cells naturally reside pro-
vides scientists with clues about how to make
them differentiate in a culture dish. For example,
in the bone marrow, where blood stem cells
reside, bone cells send physical and chemical sig-
nals that tell the blood stem cells when to differ-
entiate. Scientists are just beginning to under-
stand these signals and have developed ways to
mimic the natural processes in cell cultures.
Usually, the technology involves adding certain
proteins to the cell culture and, in some cases,
introducing specific genes into the stem cells.
It will be essential that scientists are sure that
stem cells have fully differentiated before they
can use them for medical applications. If
completely undifferentiated stem cells (such as
embryonic stem cells) are implanted directly into

an organism, they can cause a type of tumor
called a teratoma, which scientists have observed
in experiments using mice. Semi-specialized
adult stem cells and differentiated cells derived
from embryonic stem cells are unlikely to cause
teratomas.
The Role of Animals in Stem
Cell Research
For medical research, as well as for research that
explores the basic processes in the development
of organisms and diseases, scientists often rely on
animals. Implanting human cells into animals
10
WORKING WITH STEM CELLS
Center Photo: Scientists can test whether they have successfully
caused embryonic stem cells to differentiate by
labeling for specific marker proteins found in specialized cells.
Courtesy of Dr. Daniel Anderson, MIT.
such as mice has long been common practice in
order to test the safety and effectiveness of new

drugs, procedures, and medical devices before
clinical testing in human volunteers. For stem
cell research, scientists use animals to make sure
the stem cells are able to incorporate into the tis-
sue, do not cause any harmful consequences,
and function in concert with the rest of the body.
For example, before using stem cells to replace
the pancreatic cells that are destroyed by type I
diabetes in humans, scientists will transplant
human stem cells into a mouse to see whether
the stem cells yield healthy, insulin-producing
cells. If their methods prove successful in mice,
scientists may eventually apply the technology to
developing treatments for diabetes in humans.
Animal studies can also reveal how human
cells differentiate during normal development.
For example, scientists may implant human
stem cells into a developing mouse to observe

the processes involved in building and organ-
izing the different tissue types that make up
the human body. Scientists can also trace the
development and progression of certain dis-
eases within an animal. By implanting human
stem cells that lead to a particular disease into
a mouse blastocyst, scientists can observe
when and how the afflicted cells begin to show
signs of disease and can test drugs that might
prevent that process.
Organisms that contain cells or tissues from another
individual of the same or a different species are
called chimeras. A common example of a chimera is
a mouse that has been injected with some human
cells so that it can be used for studying a human dis-
ease or testing a new drug. A person who has had a
blood transfusion or a person who has received a
heart valve transplant from a pig is technically a

chimera, as well. The making of chimeras for research
has unique ethical implications that have been the
topic of discussions among scientists, ethicists and the
public, especially when the chimeras contain both
human and animal cells.
11
Many research
mice are chimeras
because they
contain both
human and mouse
cells. Courtesy of
Advanced Cell
Technology, Inc.,
Alameda, CA.
Alternatives to Using Embryos
in Stem Cell Research
To address ethical concerns about the destruction of
blastocysts, scientists are trying to find new ways of
obtaining stem cells that behave like embryonic

stem cells but that don’t require harming a blasto-
cyst. As the science progresses, ethical issues sur-
rounding these alternatives may also arise. Some
possible alternatives include:
• Cells collected from the
morula (MOR-yoo-la), the
developmental stage prior
to the blastocyst. The
morula, a solid ball of
about 16–30 cells, seems
able to sustain the loss of a
few cells without developmental damage so that
the remaining cells can continue to develop.
Cell extraction from the morula is already being
used in some clinics to screen for genetic
disorders in embryos produced by in vitro
fertilization. Researchers have recently shown
that cells isolated from a mouse morula can give
rise to embryonic stem cells while the remaining
morula cells develop into a healthy mouse.
However, this process may still be morally objec-
tionable to some because of the chance of harm
to the morula, and because the long-term effects
of removing cells from a morula are not yet
known.
• The creation of embryonic stem cells through a
process called altered nuclear transfer (ANT).
In this variation of the nuclear transfer technique,
scientists create a blastocyst whose genetic

material has been changed so that further
development and implantation into the uterus
is not possible. It aims to create embryo-like
entities that are not truly embryos but that can be
a source of pluripotent stem cells. ANT, so far only
tested with mouse blastocysts, could allow the
creation of embryonic stem cells without destroy-
ing a viable human blastocyst. Some who object to
embryonic stem cell research support ANT
because the resulting blastocyst could never
develop into a full human being and therefore
would not have the moral status of a human
embryo. However, this procedure is objectionable
to some because they believe that it involves the
creation of an imperfect blastocyst that is designed
to be destroyed.
• Causing an adult cell to act like an embryonic
stem cell. During development, as cells become
more and more specialized, they gradually lose the
ability to turn on the genes that allow embryonic
stem cells to be so versatile. The silencing of
these genes seems to be responsible for keeping
specialized cells specialized and limiting the
differentiation capacities of adult stem cells. By
“reprogramming” adult stem cells so that they can
turn on the genes that allow versatility,

scientists hope to cause them to revert to a more
flexible state. It is even possible that scientists
could one day “reprogram” any cell, not only
stem cells. However, research in this area is in the
early stages and scientists may be many years
away from making an adult cell as versatile as an
embryonic stem cell.
12
C
o
u
rt
e
sy
o
f
Le
o
n
a

rd
I
.
Zo
n
13
Right now, only a few diseases
are treatable with stem cell therapies because scientists
can only regenerate a few types of tissues. However,
the success of the most established stem cell-based
therapies—blood and skin transplants—gives hope
that someday stem cells will allow scientists to
develop therapies for a variety of diseases previous-
ly thought to be incurable. Many major diseases are
caused by the loss of a single type of cell or tissue.
For example, type I diabetes (juvenile-onset) is
caused by the loss of the insulin-producing cells of
the pancreas, and its treatment is limited to merely
alleviating the symptoms. Finding a cure for such

diseases would be much easier if scientists could
simply re-grow the missing or damaged cells and
implant them into patients.
Blood Stem Cells
After scraping a knee or donating blood, the body
replenishes the blood cells that are lost by drawing on
a small number of semi-specialized hematopoietic
(heem-AT-oh-poh-EH-tik) stem cells contained in the
blood and bone marrow. For decades, scientists have
been using this type of adult stem cell to treat patients
with diseases such as leukemia, sickle cell anemia,
bone marrow damage, and some metabolic disorders
and immunodeficiencies where the body has lost its
ability to replenish its own set of healthy blood cells.
Hematopoietic stem cells give rise to all the blood cell
types, from infection-fighting white blood cells to
blood-clotting platelets. Preliminary results have sug-
gested that they may also be able to produce other cell
types not found in blood, but this is not yet proven.

WHY STEM CELL RESEARCH
IS BEING PURSUED
In the past, the only way to use hematopoietic stem
cells for therapies was through bone marrow trans-
plants. Extracting bone marrow is an uncomfortable
and invasive procedure, and in order for a transplant
to work, the donor and recipient must be genetically
similar. If they are too genetically different, the
blood cells produced from the transplanted marrow
may recognize the patient’s body as foreign and
fight against the patient’s own cells and organs.
Additionally, the patient’s immune system may
reject the transplant, causing a dangerous “war”
within the patient’s body.
More recently, scientists have developed ways to
derive hematopoietic stem cells from the blood con-
tained in the umbilical cord and placenta at birth.

The stem cells isolated from a person’s own umbili-
cal cord blood and placenta, if used for therapies
later in life, would be less likely to cause an “inter-
nal war” within the recipient’s body. They are also
more accessible than the stem cells in bone marrow
because the extraction of this blood poses no risk to
the mother or infant.
The Changed Face of Skin Grafts
For many years, scientists have been harnessing the
regenerative capabilities of human skin to treat vic-
tims of severe burns using skin transplants. Skin
transplants are possible because of the existence of
stem cells located just under the top layer of skin.
Every day, thousands of new skin cells are produced
to replace those that have been shed. When someone
suffers severe burns that destroy the source of these
stem cells, their skin can no longer regenerate on its
own. Traditionally, doctors treated severe burns by
transplanting sections of skin from undamaged

areas of the body onto the burned areas, but if doc-
tors could not find enough unharmed skin to cover
the burned areas, the patient could die. Now, scien-
tists can grow vast sheets of new skin by culturing
the stem cells from small pieces of healthy skin.
This practice, which is a type of tissue engineering,
has become routine for treating burn victims over
the past 20 years. Recently, scientists have identi-
fied other types of stem cells in hair follicles and
deeper layers of the skin. The inclusion of these new
stem cells into engineered skin should help create
more natural-looking skin transplants in the future.
14
WHY STEM CELL RESEARCH IS BEING PURSUED
Stem Cells Found in Umbilical Cord Blood
In 2005, the National Academies issued a report, Cord Blood:
Establishing a National Hematopoietic
Stem Cell Bank Program, which recommended that a national
cord blood “bank” be established to

harness the medical potential of this source of stem cells. Such
a bank would not only benefit the
people from whom the blood was collected but anyone in need
of blood transplants. As with blood
banks for blood transfusions, scientists could screen the bank to
find the best match for each
patient, providing a safer, more personalized living-cell
therapy.
Possible Future Treatment for
Parkinson’s Disease?
When most people reach for a pen, their body acts in
one smooth and controlled movement. This is
because the instant a person thinks of grabbing the
pen, a series of nerve cells fire in an orchestrated sym-
phony from the brain to the muscles responsible for
that action. For the movement to be precise and
smooth, all the nerve cells in the “grabbing-the-pen
network” must function properly, including cells that
tell unneeded muscles to stay still. In Parkinson’s dis-
ease, the brain cells responsible for keeping unneed-

ed muscles from moving degenerate and die. This
results in progressively more dramatic and uncon-
trolled movements, tremors, and spasms. To date,
there is no cure for Parkinson’s disease because no
one has figured out a way to bring back the special-
ized nerve cells that have died.
Are the Promises of Stem Cell
Therapies Realistic?
The list of medical achievements stem cells could
offer seems to be expanding at an incredible pace.
The role of stem cells in medicine is already very
real, but there is a danger of exaggerating the
promise of new medical developments. What tend
to be “over-promised” are not only the potential out-
comes of both embryonic and adult stem cell
research, but also the time scales that are involved.
The basic research needed to develop viable thera-
peutic options is a lengthy process that may extend

over many years and decades. Even after science
has moved from basic research to developing med-
ical applications, it still takes many years to thor-
oughly test those applications and demonstrate that
they are safe to prescribe for patients. This is true for
all medical treatments, including the development
of new drugs, procedures, and medical equipment,
and is not specific to the living cell therapies made
possible by stem cell research.
There are also many legal and social questions that
must be addressed before stem cell-based therapies
become clinically available. Legal issues that will
affect stem cell applications include how to address
intellectual property concerns and how to apply
and enforce diverse and sometimes conflicting state
and national laws. Social issues include concerns
about the destruction of embryos, the distribution of
the benefits of the research, and the protection of

both physical and privacy interests of egg and
sperm donors and clinical research subjects.
15
Parkinson’s disease is caused by the loss of a single
type of nerve cell. These brain scans show the difference
between a normal brain (left) and the brain of a
Parkinson’s patient (right). Courtesy of Dr. David A.
Rottenberg, Professor of Neurology and Radiology,
University of Minnesota.
1956
First successful
bone marrow
transplant
1981
Embryonic stem
cells are isolated
from mouse
blastocysts
1988
Hematopoietic
(blood) stem
cells from adult

mice are
purified and
characterized
1992
Stem cells are
identified in the
adult human
brain
1998
The first human
embryonic
stem cells are
isolated
Because Parkinson’s disease results from the loss of
one specific type of nerve cell, stem cells offer a very
tangible possibility for treatment. Researchers have
recently learned how to differentiate embryonic
stem cells into the specific type of brain cell that is
lost in Parkinson’s disease. They have also success-
fully transplanted adult nerve stem cells into rat
brains. When this technique is proven to be effec-
tive and safe, transplantation of stem cells into the

brains of patients may one day allow doctors to
reverse the burden of Parkinson’s disease and
restore control of movement. Another strategy cur-
rently under study is the addition of chemicals or
growth factors that aim to induce the patient’s own
stem cells to repair the damaged nerves without
needing to grow and transplant stem cells.
Possible Fix for Diabetes?
In people who suffer from type I diabetes, the beta
cells of the pancreas that normally produce insulin are
destroyed by the patient’s overactive immune system.
Without insulin, the cells of the body cannot take up
glucose and they starve. Patients with type I diabetes
16
S T E M C E L L T I M E L I N E
require insulin injections several times a day for their

entire lives. The only current cure is a pancreatic
transplant from a recently deceased donor, but the
demand for transplants far outweighs the supply.
While adult stem cells have not yet been found in
the pancreas, scientists have made progress trans-
forming embryonic stem cells into insulin-producing
cells. Combining beta-cell transplants with methods
to “fix” the patient’s immune system—including
chemotherapy to destroy malfunctioning immune-
system cells and blood transplants to replenish healthy
white blood cells—could offer great hope for the
many Americans suffering with type I diabetes.
Cancer: Getting to the Root
of the Problem
Why are some cancers so hard to eliminate, even after
many rounds of chemotherapy? The answer may lie in
a few abnormal stem cells. Cancerous stem cells were
first identified in 1997 when a research group from
the University of Toronto transferred a few blood

stem cells from human leukemia patients into mice
and watched leukemia develop in the mice. Stem cell-
like cells have also recently been found in breast and
brain tumors. Like normal stem cells, tumor stem
cells exist in very low numbers, but they can replicate
and give rise to a multitude of cells. Unlike normal
stem cells, however, cancerous stem cells lack the
controls that tell them when to stop dividing.
Traditional chemotherapy kills off the majority of
the tumor cells, but if any of the cancerous stem
cells survive the treatment, the cancer may return.
Research into the differences in gene expression
between normal and tumor stem cells may lead to
treatments where the root of the problem—the can-
cer stem cell—is targeted.
Stem cell research continues to advance. Preliminary results
from
recent studies support the promise of stem cells for conducting
basic

research that may eventually lead to medical achievements. For
example, in 2005, human embryonic stem cells were shown to
differentiate into active functioning nerve cells when placed in
mouse
brains. Scientists also made significant progess in deriving
pancreatic
cells from adult stem cells. In 2006, scientists were able to
derive
embryonic stem cells from the morula of a mouse, and
embryonic
stem cells were first grown without animal products in the
culture.
Results of these and other recent experiments must be replicated
and consistently demonstrated by other researchers before they
become generally accepted by the scientific community.
2001
Mouse
embryonic stem
cells are created
by nuclear
transfer
2002

Pancreatic cells
derived from
mouse embry-
onic stem cells
cure diabetes
in mice
2004
The type of
nerve cell lost
in Parkinson’s
disease is
produced from
human
embryonic
stem cells
17
Stem cells offer opportunities for scientific advances
that go far beyond regenerative medicine. They
offer a window for addressing many of biology’s
most fundamental questions. Watching embryonic
stem cells give rise to specialized cells is like peeking
into the earliest development of the many tissues
and organs of the human body. Stem cell research

may help clarify the role genes play in human
development and how genetic mutations affect nor-
mal processes. They can be used to study how infec-
tious agents invade and attack human cells, to
investigate the genetic and environmental factors
that are involved in cancer and other diseases, and
to decipher what happens during aging.
Stem cells may also revolutionize tradi-
tional chemical medicine. Because
embryonic stem cells can continue to
divide for long periods of time and pro-
duce a variety of cell types, they could
provide a valuable source of human
cells for testing drugs or measuring the
effects of toxins on normal tissues with-
out risking the health of a single human
volunteer. In the future, thousands of
compounds could be quickly tested on

a wide assortment of cell types derived
from stem cells, making drug discovery
more efficient and cost effective.
Using nuclear transfer to produce stem cells could
be particularly useful for testing drugs for disorders
that are of genetic origin. For example, it is difficult
to study the progression of Alzheimer’s and
Parkinson’s diseases in the brains of live patients—
but by using the cells of an Alzheimer’s patient to
create stem cell lines with nuclear transfer, scientists
could trace the development of the disease in a
culture dish and test drugs that regenerate lost
nerve cells with no danger to the patient.
Stem cells may also help scientists calculate the
effects of toxic substances in drugs, food, and the
environment.
18
Courtesy of Dr. Leonard I. Zon.

The Role of Stem Cells in Basic Research
Scientists and society as a whole
must consider the ethical implications of stem cell
research. As discussed throughout this booklet, differ-
ent ethical issues are raised by the wide range of stem
cell research activities. In 2005, the National
Academies published guidelines for scientists who do
research with human embryonic stem cells to encour-
age responsible and ethically sensitive conduct in their
work. Although the guidelines are not expressly legal-
ly binding, many researchers have voluntarily adopted
them as a guide to what constitutes appropriate con-
duct in human embryonic stem cell research. Yet for
some people, such guidelines are inadequate because
they aim to govern a practice that they see as intrinsi-
cally unethical.
As the science advances, it is essential that scientists;

religious, moral, and political leaders; and society as a
whole continue to evaluate and communicate about
the ethical implications of stem cell research.
Is an Embryo a Person?
The controversy over embryonic stem cell research
touches on some of the same fundamental questions
that society has grappled with in the debates over con-
traception, abortion, and in vitro fertilization. The
questions at the center of the controversy concern the
nature of early human life and the legal and moral sta-
tus of the human embryo. Embryonic stem cell
research often involves removing the inner cell mass
from “excess” blastocysts that are unneeded by cou-
ples who have completed their fertility treatment. This
prevents those blastocysts from continuing to develop.
Although such blastocysts would likely be discarded
(and thus destroyed) by the clinics in any case, some
believe that this does not make it morally acceptable

19
E T H I C S , M O R A L VA L U E S ,
A N D U . S . L AW
The National Academies published the Guidelines for Human
Embryonic Stem Cell Research in 2005. Here, members of the
committee present at a report briefing.
to use them for research or therapeutic purposes. They
believe that the life of a human being begins at the
moment of conception and that society undermines a
commitment to human equality and to the protection
of vulnerable individuals if blastocysts are used for
such purposes. Some cultures and religious traditions
oppose the use of human life as a means to some other
end, no matter how noble that end might be. Other
traditions support embryonic stem cell research
because they believe that the embryo gains the moral
status of a human being only after a few weeks or
months of development. Many traditions emphasize
obligations to heal the sick and ease suffering—goals

for which embryonic stem cell research holds great
potential—and favor embryonic stem cell research for
this reason. Several religious groups are currently
involved in internal discussions about the status of the
human embryo and have not yet established official
opinions on the matter. Public opinion polls suggest
that the majority of both religious and non-religious
20
ETHICS, MORAL VALUES, AND U.S. LAW
The National Academies’ Guidelines for
Human Embryonic Stem Cell Research
In order to provide all scientists—those working in universities
and pri-
vate companies and with both public and private funding—with
a
common set of scientific and ethical guidelines, the National
Academies published the Guidelines for Human Embryonic
Stem Cell
Research in 2005. The report outlines the need for institutional
over-

sight mechanisms for monitoring all human embryonic stem cell
research and provides specific guidance regarding the derivation
of
new stem cell lines. Under the guidelines, certain activities,
such as
experimenting on human embryos by inserting stem cells into
them,
are not permitted. The guidelines also require that all egg,
sperm, and blastocyst donations follow appropriate
informed consent and confidentiality procedures. Because the
ethical and technical questions associated with
human embryonic stem cell research are likely to change as
science advances, in 2006, the National Academies
established a panel of experts to monitor and review scientific
developments and changing ethical, legal, and policy
issues and to prepare periodic reports to update the guidelines
as needed. For more information on the guidelines,
please visit www.nationalacademies.org/stemcells.
Americans support embryonic stem cell research,
although public opinion seems divided about the cre-
ation or use of human blastocysts solely for research.

The Relationship of Stem Cell
Research to Reproductive
Cloning
Although cloning and stem cell research are often
lumped together in the context of ethical debates, the
goals and results of the two are very different. The
common factor between current attempts at repro-
ductive cloning and stem cell research is a laboratory
technique called nuclear transfer. Using nuclear trans-
fer, scientists can create blastocysts containing stem
cells that are “clones” of a single adult cell by insert-
ing the genetic material from an adult cell (for exam-
ple, a skin cell) into an egg whose nucleus has been
removed (this process is described in more detail on
page 6). Scientists hope that they could derive stem
cells from the cells inside such blastocysts and grow
replacement tissues that are genetically matched to
specific patients, thus offering patients a safer alterna-
tive to traditional tissue transplants.
Reproductive cloning, such as the process that was

used to create Dolly the sheep, also uses the nuclear
transfer technique. However, instead of removing
the inner cell mass to derive a stem cell line, the blas-
tocyst is implanted into the uterus and allowed to
develop fully. In 2002, the National Academies
issued the report Scientific and Medical Aspects of
Human Reproductive Cloning, which concluded
“Human reproductive cloning should not now be
practiced. It is dangerous and likely to fail.”
The Ethics of Human-Animal
Chimeras
Chimeras are organisms composed of cells or tissues
from more than one individual. Chimeras have been
produced for research for many years, but when
human and animal cells are mixed in the laboratory,
there is a clear need for heightened ethical considera-
tion. Cells from different organisms can be combined
either in the early developmental stages (for example,
introducing human cells into a mouse blastocyst to

observe certain developmental processes) or after an
individual is fully developed (for example, implanting
21
ETHICS, moral values, AND U.S. LAW
“Human reproductive
cloning should not
now be practiced.
It is dangerous
and likely to fail.”
—Scientific and Medical Aspects of
Human Reproductive Cloning,
National Academies Press, 2005
human stem cell-derived pancreatic cells into a mouse
to test their ability to function in a living body).
Chimeras are considered essential for advancing stem
cell research to viable therapies, since no therapy can
be tested in humans without research in animals first.

Some people believe that the creation of chimeras
involving human cells for medical research is moral-
ly acceptable as long as the chimera has no level of
human consciousness. Therefore, research in which
it is possible for human stem cells to produce part of
an animal’s brain should be conducted with great
care. The National Academies’ guidelines prohibit
the introduction of human cells into the blastocyst
of a non-human primate, or the introduction of any
animal or human cells into a human blastocyst. The
guidelines also prohibit the breeding of human-ani-
mal chimeras in the unlikely event that any human
genetic material would be contained in their repro-
ductive cells.
ETHICS, MORAL VALUES, AND U.S. LAW
Is it legal?
Currently, all forms of stem cell research in the U.S. are legal at
the federal level. That is, it is not illegal to make or work with
new

embryonic stem cell lines. However, the use of federal funds for
human embryonic stem cell research is restricted to the cell
lines that were available as of August 9, 2001. Therefore, the
derivation of new embryonic stem cell lines can only occur
when scientists are working with non-federal funding. Some
states and private foundations have been supporting this work.
Some requirements of federal law, such as human
subjects protections, apply to state- and privately funded stem
cell research. For a complete discussion of the mechanisms
for oversight of stem cell research, see the National Academies’
report Guidelines for Human Embryonic Stem Cell Research.
It is legal to conduct research using blastocysts and to derive
new cell lines in most states, with some exceptions. Because
stem cell legislation is an area of active debate, please
visit the National Conference of State Legislatures at
http://www.ncsl.org/programs/health/genetics/embfet.htm
to learn about the laws in a particular state.

ABOUT THE NATIONAL ACADEMIES
The National Academies are private, nonprofit organizations
that were set up to provide independent sci-
entific and technological advice to the U.S. government and
nation. The National Academies includes
three honorary societies that elect new members to their ranks
each year—the National Academy of
Sciences, National Academy of Engineering, and Institute of
Medicine—and the National Research Council,
the operating arm that conducts the bulk of the institution’s
science policy and technical work. The
Academies enlist committees of the nation’s top scientists,
engineers, and other experts, all of whom vol-
unteer their time to study specific issues and concerns.
RELATED REPORTS FROM THE NATIONAL ACADEMIES
Stem Cells and the Future of
Regenerative Medicine (2001).
http://www.nap.edu/catalog/10195.html
Guidelines for Human
Embryonic Stem Cell Research (2005).
(free download is available)
These and other National Academies reports are available from
the National Academies Press,

500 Fifth Street, NW, Washington, DC 20001; 800-624-6242;
http://www.nap.edu. Reports are available
online in a fully searchable format.
23
Scientific and Medical Aspects of
Human Reproductive Cloning (2002).
Cord Blood: Establishing a National
Hematopoietic Stem Cell Bank
Program (2005).
This booklet and other information about activities related to
stem cells at the National Academies are
available at www.nationalacademies.org/stemcells.
For more information, contact the Board on Life Sciences at
[email protected] or visit www.nationalacade-
mies.org/bls. This brochure was prepared by National Research
Council staff Anne Jurkowski, Giovanna
Guerrero, Fran Sharples, and Adam Fagen in collaboration with
Bruce Altevogt and Andrew Pope of the
Institute of Medicine’s Health Sciences Policy Board. It was
designed by Michele de la Menardiere.
Division on Earth and Life Studies

Subscribe to the Earth and Life Studies Gateway at
http://dels.nas.edu to receive notification of report
releases, events, and news about stem cells or other specific
areas of interest.
Sign up to receive IOM News, a free, bi-monthly e-mail
newsletter that announces new IOM publications,
upcoming events, and new online content. See
www.iom.edu/subscribe. To visit the Health Sciences Policy
Board, see http://iom.edu/hsp.
PHOTO CREDITS
Cover images: (top) Nerve cells derived from human embryonic
stem cells. PNAS 101(34):12543, Copyright
2004, National Academy of Sciences, U.S.A. (bottom) Nerve
cells derived from human embryonic stem cells
in the laboratory of Professor Su-Chun Zhang at the University
of Wisconsin–Madison. Used with permission
from the University of Wisconsin’s Board of Regents. (inside
front and back cover) Neural progenitor cell
isolated from human embryonic stem cells. Nat. Biotech. 18:399
(2000). Image Courtesy of Martin Pera.
Page 2: (left and right) Nerve cells derived from human
embryonic stem cells. PNAS 101(34):12543, Copyright
2004, National Academy of Sciences, U.S.A. (middle) Nerve
cells derived from human embryonic stem cells
in the laboratory of Professor Su-Chun Zhang at the University
of Wisconsin–Madison. Used with permission
from the University of Wisconsin’s Board of Regents.

(left) NIH/Mr. J. Conaghan. (middle) Kitai Kim,
Children’s Hospital. (right) Suslov, Oleg N. et al. PNAS
99:14506. Copyright 2002, The National Academy of Sciences,
U.S.A.
24
National Academy of Sciences
National Academy of Engineering
National Research Council
Over the past decade, stem cells have gained a place in most
Americans’ vocabularies—
discussions of them appear on TV and radio news programs, in
newspapers and mag-
azines, and even in political campaigns across the country. As
stem cells have come to
the forefront of medical research, the ethical controversies over
embryonic stem cells
have become prominent. This booklet is designed to provide
basic knowledge to facil-
itate thinking about and understanding the scientific and ethical
issues surrounding
stem cells. It is intended to help readers more easily interpret

news about stem cells, as
the science advances or new controversies develop.
Worksheet: The Therapeutic Value of Stem Cells
Student name:
Objective: To understand the therapeutic value of stem cells
About tissue stem cells
Stem cells are one of the most amazing types of cells because
they can (1) make copies of themselves and (2) make
specialized cells like skin cells, red blood cells or liver cells.
1. We need stem cells in our body. What would happen to you if
you didn’t have stem cells?
Tissue stem cells have the potential to make several types of
specialized cells, but not all. For example blood stem cells can
make all the different types of cells in your blood, but they
can’t make skin cells.
2. Add the following labels to the diagram:
a. specialized cells in blood; b. blood stem cell; c. make copies;
d. bone marrow.
Questions 1 and 2 used with permission of
www.eurostemcell.org (Creative Commons license)Therapeutic

value of stem cells
3. Read the article from US News and World Report:
http://www.usnews.com/news/articles/2013/06/05/scientists-
find-stem-cells-in-liposuctioned-fat
Scientists study stem cells for many reasons, for example to
better understand the cell cycle and
to develop and test new ways to treat patients.
4. Give one more reason why Dr Chazenbalk is doing this
research.
Scientists can now take a cell from a body, for example a skin
cell, and turn it into a cell that behaves like stem cells from an
embryo.
5. What are these special types of cells called?
6. Why is Dr Chazenbalk eager to use this technique to study
Parkinson's?
Found in:
Blood progenitor cells

The ISSCR is an independent, nonprofit organization providin.docx

Recommended

Recommended

More Related Content

Similar to The ISSCR is an independent, nonprofit organization providin.docx

Similar to The ISSCR is an independent, nonprofit organization providin.docx (16)

More from oreo10

More from oreo10 (20)

Recently uploaded

Recently uploaded (20)

The ISSCR is an independent, nonprofit organization providin.docx