* CLONING FACT SHEET
http://www.genome.gov/25020028
What is cloning?
The term cloning describes a number of different processes that can be used to produce genetically identical copies of a biological
entity. The copied material, which has the same genetic makeup as the original, is referred to as a clone.
Researchers have cloned a wide range of biological materials, including genes, cells, tissues and even entire organisms, such as a
sheep.
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Do clones ever occur naturally?
Yes. In nature, some plants and single-celled organisms, such as bacteria, produce genetically identical offspring through a process
called asexual reproduction. In asexual reproduction, a new individual is generated from a copy of a single cell from the parent
organism.
Natural clones, also known as identical twins, occur in humans and other mammals. These twins are produced when a fertilized egg
splits, creating two or more embryos that carry almost identical DNA. Identical twins have nearly the same genetic makeup as each
other, but they are genetically different from either parent.
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What are the types of artificial cloning?
There are three different types of artificial cloning: gene cloning, reproductive cloning and therapeutic cloning.
Gene cloning produces copies of genes or segments of DNA. Reproductive cloning produces copies of whole animals. Therapeutic
cloning produces embryonic stem cells for experiments aimed at creating tissues to replace injured or diseased tissues.
Gene cloning, also known as DNA cloning, is a very different process from reproductive and therapeutic cloning. Reproductive and
therapeutic cloning share many of the same techniques, but are done for different purposes.
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What sort of cloning research is going on at NHGRI?
Gene cloning is the most common type of cloning done by researchers at the National Human Genome Research Institute (NHGRI).
NHGRI researchers have not cloned any mammals and NHGRI does not clone humans.
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How are genes cloned?
Researchers routinely use cloning techniques to make copies of genes that they wish to study. The procedure consists of inserting a
gene from one organism, often referred to as "foreign DNA," into the genetic material of a carrier called a vector. Examples of vectors
include bacteria, yeast cells, viruses or plasmids, which are small DNA circles carried by bacteria. After the gene is inserted, the
vector is placed in laboratory conditions that prompt it to multiply, resulting in the gene being copied many times over.
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How are animals cloned?
The technique used to clone whole animals, such as sheep, is referred to as reproductive cloning.
In reproductive cloning, researchers remove a mature somatic cell, such as a skin cell or an udder cell, from an animal that they wish
to copy. They then transfer the DNA of the donor animal's somatic cell into an egg cell, or oocyte, that has had its own DNAcontaining nucleus removed.
Researchers can add the DNA from the somatic cell to the empty egg in two different ways. In the first method, they remove the
DNA-containing nucleus of the somatic cell and inject it into the empty egg. In the second approach, they use an electrical current to
fuse the entire somatic cell with the empty egg.
In both processes, the egg is allowed to develop into an early-stage embryo in the test-tube and then is implanted into the womb of an
adult female animal. Ultimately, the adult female gives birth to an animal that has the same genetic make up as the animal that donated
the somatic cell. This young animal is referred to as a clone. Reproductive cloning may require the use of a surrogate mother to allow
development of the cloned embryo, as was the case for the most famous cloned organism, Dolly the sheep.
Reproductive cloning may require the use of a surrogate mother to allow development of the cloned embryo, as was the case for the
most famous cloned organism, Dolly the sheep.
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What animals have been cloned?
Over the last 50 years, scientists have conducted cloning experiments in a wide range of animals using a variety of techniques. In
1979, researchers produced the first genetically identical mice by splitting mouse embryos in the test tube and then implanting the
resulting embryos into the wombs of adult female mice. Shortly after that, researchers produced the first genetically identical cows,
sheep and chickens by transferring the nucleus of a cell taken from an early embryo into an egg that had been emptied of its nucleus.
It was not until 1996, however, that researchers succeeded in cloning the first mammal from a mature (somatic) cell taken from an
adult animal. After 276 attempts, Scottish researchers finally produced Dolly, the lamb from the udder cell of a 6-year-old sheep. Two
years later, researchers in Japan cloned eight calves from a single cow, but only four survived.
Besides cattle and sheep, other mammals that have been cloned from somatic cells include: cat, deer, dog, horse, mule, ox, rabbit and
rat. In addition, a rhesus monkey has been cloned by embryo splitting.
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Have humans been cloned?
Despite several highly publicized claims, human cloning still appears to be fiction. There currently is no solid scientific evidence that
anyone has cloned human embryos.
In 1998, scientists in South Korea claimed to have successfully cloned a human embryo, but said the experiment was interrupted very
early when the clone was just a group of four cells. In 2002, Clonaid, part of a religious group that believes humans were created by
extraterrestrials, held a news conference to announce the birth of what it claimed to be the first cloned human, a girl named Eve.
However, despite repeated requests by the research community and the news media, Clonaid never provided any evidence to confirm
the existence of this clone or the other 12 human clones it purportedly created.
In 2004, a group led by Woo-Suk Hwang of Seoul National University in South Korea published a paper in the journal Science in
which it claimed to have created a cloned human embryo in a test tube. However, an independent scientific committee later found no
proof to support the claim and, in January 2006, Science announced that Hwang's paper had been retracted.
From a technical perspective, cloning humans and other primates is more difficult than in other mammals. One reason is that two
proteins essential to cell division, known as spindle proteins, are located very close to the chromosomes in primate eggs.
Consequently, removal of the egg's nucleus to make room for the donor nucleus also removes the spindle proteins, interfering with cell
division. In other mammals, such as cats, rabbits and mice, the two spindle proteins are spread throughout the egg. So, removal of the
egg's nucleus does not result in loss of spindle proteins. In addition, some dyes and the ultraviolet light used to remove the egg's
nucleus can damage the primate cell and prevent it from growing.
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Do cloned animals always look identical?
No. Clones do not always look identical. Although clones share the same genetic material, the environment also plays a big role in
how an organism turns out.
For example, the first cat to be cloned, named Cc, is a female calico cat that looks very different from her mother. The explanation for
the difference is that the color and pattern of the coats of cats cannot be attributed exclusively to genes. A biological phenomenon
involving inactivation of the X chromosome (See sex chromosome) in every cell of the female cat (which has two X chromosomes)
determines which coat color genes are switched off and which are switched on. The distribution of X inactivation, which seems to
occur randomly, determines the appearance of the cat's coat.
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What are the potential applications of cloned animals?
Reproductive cloning may enable researchers to make copies of animals with the potential benefits for the fields of medicine and
agriculture.
For instance, the same Scottish researchers who cloned Dolly have cloned other sheep that have been genetically modified to produce
milk that contains a human protein essential for blood clotting. The hope is that someday this protein can be purified from the milk
and given to humans whose blood does not clot properly. Another possible use of cloned animals is for testing new drugs and
treatment strategies. The great advantage of using cloned animals for drug testing is that they are all genetically identical, which
means their responses to the drugs should be uniform rather than variable as seen in animals with different genetic make-ups.
After consulting with many independent scientists and experts in cloning, the U.S. Food and Drug Administration (FDA) decided in
January 2008 that meat and milk from cloned animals, such as cattle, pigs and goats, are as safe as those from non-cloned animals.
The FDA action means that researchers are now free to using cloning methods to make copies of animals with desirable agricultural
traits, such as high milk production or lean meat. However, because cloning is still very expensive, it will likely take many years until
food products from cloned animals actually appear in supermarkets.
Another application is to create clones to build populations of endangered, or possibly even extinct, species of animals. In 2001,
researchers produced the first clone of an endangered species: a type of Asian ox known as a guar. Sadly, the baby guar, which had
developed inside a surrogate cow mother, died just a few days after its birth. In 2003, another endangered type of ox, called the
Banteg, was successfully cloned. Soon after, three African wildcats were cloned using frozen embryos as a source of DNA. Although
some experts think cloning can save many species that would otherwise disappear, others argue that cloning produces a population of
genetically identical individuals that lack the genetic variability necessary for species survival.
Some people also have expressed interest in having their deceased pets cloned in the hope of getting a similar animal to replace the
dead one. But as shown by Cc the cloned cat, a clone may not turn out exactly like the original pet whose DNA was used to make the
clone.
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What are the potential drawbacks of cloning animals?
Reproductive cloning is a very inefficient technique and most cloned animal embryos cannot develop into healthy individuals. For
instance, Dolly was the only clone to be born live out of a total of 277 cloned embryos. This very low efficiency, combined with
safety concerns, presents a serious obstacle to the application of reproductive cloning.
Researchers have observed some adverse health effects in sheep and other mammals that have been cloned. These include an increase
in birth size and a variety of defects in vital organs, such as the liver, brain and heart. Other consequences include premature aging and
problems with the immune system. Another potential problem centers on the relative age of the cloned cell?s chromosomes. As cells
go through their normal rounds of division, the tips of the chromosomes, called telomeres, shrink. Over time, the telomeres become so
short that the cell can no longer divide and, consequently, the cell dies. This is part of the natural aging process that seems to happen
in all cell types. As a consequence, clones created from a cell taken from an adult might have chromosomes that are already shorter
than normal, which may condemn the clones' cells to a shorter life span. Indeed, Dolly, who was cloned from the cell of a 6-year-old
sheep, had chromosomes that were shorter than those of other sheep her age. Dolly died when she was six years old, about half the
average sheep's 12-year lifespan.
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What is therapeutic cloning?
Therapeutic cloning involves creating a cloned embryo for the sole purpose of producing embryonic stem cells with the same DNA as
the donor cell. These stem cells can be used in experiments aimed at understanding disease and developing new treatments for disease.
To date, there is no evidence that human embryos have been produced for therapeutic cloning.
The richest source of embryonic stem cells is tissue formed during the first five days after the egg has started to divide. At this stage of
development, called the blastocyst, the embryo consists of a cluster of about 100 cells that can become any cell type. Stem cells are
harvested from cloned embryos at this stage of development, resulting in destruction of the embryo while it is still in the test tube.
In November 2007, using a new cloning method that removes the egg's nucleus without dyes or ultraviolet light, researchers produced
the first primate embryonic stem cells. The work involved transferring the nucleus of a skin cell from a male rhesus monkey into the
nucleus-free egg of a female rhesus monkey. These embryonic stem cells did not develop into a whole monkey, and researchers said
their work was aimed at therapeutic applications. However, the research shows that, with some adjustments, the techniques used to
make whole copies of other animals may also work in primates.
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What are the potential applications of therapeutic cloning?
Researchers hope to use embryonic stem cells, which have the unique ability to generate virtually all types of cells in an organism, to
grow tissues in the laboratory that can be used to grow healthy tissue to replace injured or diseased tissues. In addition, it may be
possible to learn more about the molecular causes of disease by studying embryonic stem cell lines from cloned embryos derived from
the cells of animals or humans with different diseases.
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What are the potential drawbacks of therapeutic cloning?
Many researchers think it is worthwhile to explore the use of embryonic stem cells as a path for treating human diseases. However,
some experts are concerned about the striking similarities between stem cells and cancer cells. Both cell types have the ability to
proliferate indefinitely and some studies show that after 60 cycles of cell division, stem cells can accumulate mutations that could lead
to cancer. Therefore, the relationship between stem cells and cancer cells needs to be more clearly understood if stem cells are to be
used to treat human disease.
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What are some of the ethical issues related to cloning?
Gene cloning is a carefully regulated technique that is largely accepted today and used routinely in many labs worldwide. However,
both reproductive and therapeutic cloning raise important ethical issues, especially as related to the potential use of these techniques in
humans.
Reproductive cloning would present the potential of creating a human that is genetically identical to another person who has
previously existed or who still exists. This may conflict with long-standing religious and societal values about human dignity, possibly
infringing upon principles of individual freedom, identity and autonomy. However, some argue that reproductive cloning could help
sterile couples fulfill their dream of parenthood. Others see human cloning as a way to avoid passing on a deleterious gene that runs in
the family without having to undergo embryo screening or embryo selection.
Therapeutic cloning, while offering the potential for treating humans suffering from disease or injury, would require the destruction of
human embryos in the test tube. Consequently, opponents argue that using this technique to collect embryonic stem cells is wrong,
regardless of whether such cells are used to benefit sick or injured people.
* Stem Cell Debate: Is it Over?
http://learn.genetics.utah.edu/content/tech/stemcells/scissues/
Both human embryonic stem (hES) cells and induced pluripotent stem (iPS) cells are pluripotent: they can become any type of cell in
the body. While hES cells are isolated from an embryo, iPS cells can be made from adult cells.
Stem cell therapies are not new. Doctors have been performing bone marrow stem cell transplants for decades. But when scientists
learned how to remove stem cells from human embryos in 1998, both excitement and controversy ensued.
The excitement was due to the huge potential these cells have in curing human disease. The controversy centered on the moral
implications of destroying human embryos. Political leaders began to debate over how to regulate and fund research involving human
embryonic stem (hES) cells.
New breakthroughs may soon bring this debate to an end. Scientists have learned how to stimulate a patient's own cells to behave like
embryonic stem cells. These so-called induced pluripotent stem (iPS) cells are reducing the need for human embryos in research and
opening up exciting new possibilities for stem cell therapies.
The Ethical Questions
Until recently, the only way to get pluripotent stem cells for research was to remove the inner cell mass of an embryo and put it in a
dish. The thought of destroying a human embryo can be unsettling, even if it is only five days old.
Stem cell research thus raised difficult questions:
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Does life begin at fertilization, in the womb, or at birth?
Is a human embryo equivalent to a human child?
Does a human embryo have any rights?
Might the destruction of a single embryo be justified if it provides a cure for a countless number of patients?
Since ES cells can grow indefinitely in a dish and can, in theory, still grow into a human being, is the embryo really
destroyed?
IPS Cells: Problem Solved?
With iPS cells now available as an alternative to hES cells, the debate over stem cell research is becoming increasingly irrelevant. But
ethical questions regarding hES cells may not entirely go away.
Inevitably, some human embryos will still be needed for research. iPS cells are not exactly the same as hES cells, and hES cells still
provide important controls: they are a gold standard against which the "stemness" of iPS cells is measured.
Some experts believe it's wise to continue the study of all stem cell types, since we're not sure yet which one will be the most useful
for cell replacement therapies.
An additional ethical consideration is that iPS cells have the potential to develop into a human embryo, in effect producing a clone of
the donor. Many nations are already prepared for this, having legislation in place that bans human cloning.
Stem Cell Research Legislation
Governments around the globe have passed legislation to regulate stem cell research. In the United States, laws prohibit the creation of
embryos for research purposes. Scientists instead receive "leftover" embryos from fertility clinics with consent from donors. Most
people agree that these guidelines are appropriate.
Disagreements surface, however, when political parties debate about how to fund stem cell research. The federal government allocates
billions of dollars each year to biomedical research. But should taxpayer dollars be used to fund embryo and stem cell research when
some believe it to be unethical? Legislators have had the unique challenge of encouraging advances in science and medicine while
preserving a respect for life.
U.S. President Bush, for example, limited federal funding to a study of 70 or so hES cell lines back in 2001. While this did slow the
destruction of human embryos, many believe the restrictions set back the progress of stem cell research.
President Obama overturned Bush's stem cell policy in 2009 to expand the number of stem cell lines available to researchers. Policy-
makers are now grappling with a new question: Should the laws that govern iPS cells differ from those for hES cells? If so, what new
legislation is needed?
Regulations and policies change frequently to keep up with the pace of research, as well as to reflect the views of different political
parties. Here President Obama signs an executive order on stem cells, reversing some limits on federal research funding. (White
House photo by Chuck Kennedy)
*How Stem Cells Work
http://science.howstuffworks.com/life/cellular-microscopic/stem-cell6.htm
How Stem Cells Work
by Stephanie Watson and Craig Freudenrich, Ph.D.
Stem Cell Research Advocates
Since 1991, when he was diagnosed with Parkinson's disease (a degenerative brain disorder that affects movement), actor Michael J.
Fox has been a vocal proponent for stem cell research. His foundation has donated more than $205 million to help fund Parkinson's
research [source: Michael J. Fox Foundation]. Fox and his foundation are hoping that scientists will one day be able to coax stem cells
into producing dopamine, a chemical in the body that is deficient in patients with Parkinson's disease.
Former first lady Nancy Reagan also became an advocate for stem cell research when her husband, former President Ronald Reagan,
was stricken with Alzheimer's, another degenerative brain disease. He died of Alzheimer's in the summer of 2004.
Stem Cell Research Controversy
Stem cell research has become one of the biggest issues dividing the scientific and religious communities around the world. At the
core of the issue is one central question: When does life begin? At this time, to get stem cells that are reliable, scientists either have to
use an embryo that has already been conceived or else clone an embryo using a cell from a patient's body and a donated egg. Either
way, to harvest an embryo's stem cells, scientists must destroy it. Although that embryo may only contain four or five cells, some
religious leaders say that destroying it is the equivalent of taking a human life. Inevitably, this issue entered the political arena.
In 1996, Congress passed a rider to the federal appropriations bill called the Dickey-Wicker amendment. Representatives Jay Dickey
and Roger Wicker proposed banning the use of federal monies for any research in which a human embryo is created or destroyed.
Federal monies are a primary source of funding for stem cell research. The amendment has been renewed every year since that time.
In 2001, President George W. Bush further restricted federal stem cell research. In an executive order, Bush stated that federal funds
could only be used for research on human embryonic stem cell lines that had already been established (only 22 cell lines). This
prevented researchers from creating more embryonic stem cell lines for research.
In 2009, President Barack Obama issued an executive order to expand embryonic stem cell research. Obama's administration allowed
federal funding of embryonic stem cell research if the following conditions applied:
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The cell line was one of the 22 in existence during the Bush administration or was created from
embryos that had been discarded after in vitro fertilization procedures.
The donors of the embryos were not paid in any way.
The donors clearly knew that the embryos would be used for research purposes prior to giving
consent.
According to the administration, the new policy did not violate the Dickey-Wicker amendment because the money did not finance the
creation of new embryos (they had already been created by private means) and did not finance the destruction of them.
In 2009, two researchers from Boston, Dr. James Sherley of the Boston Biomedical Research Institute and Dr. Theresa Deisher of the
Ava Maria Biotechnology Company, and other agencies filed a lawsuit against the government. Initially, the lawsuit was dismissed
because the judge ruled that the plaintiffs had no legal standing (i.e. they were not affected materially by the new rules). However, a
court of appeals overturned the initial ruling. The two scientists remained plaintiffs. The scientists claimed that, because they used
adult stem cells exclusively in their research, the new rules would increase competition for federal research dollars, thereby affecting
their ability to obtain funding. Federal Judge Royce Lamberth upheld the appeals court ruling. He placed an injunction preventing the
new rules from going into place. He claimed that the rules violated the Dickey-Wicker amendment because embryos must be
destroyed in the process of creating embryonic stem cell lines.
In September 2010, The New York Times reported that the U.S. Court of Appeals ruled that federal funding of embryonic stem cell
research could continue under the new rules while the court considers Judge Lamberth's ruling [source: New York Times]. This ruling
allows researchers to continue feeding embryonic stem cell cultures, experimenting with mice, and other research activities until this
court rules, the U.S. Supreme Court weighs in, or Congress passes legislation that clarifies the issues. In the meantime, stem cell
research and the careers of stem cell researchers hang on a legal roller coaster. Although stem cells have great potential for treating
diseases, much work on the science, ethical and legal fronts remains.
Stem Cell Basics
A stem cell is essentially the building block of the human body. Stem cells are capable of dividing for long periods of time, are
unspecialized, but can develop into specialized cells. The earliest stem cells in the human body are those found in the human embryo.
The stem cells inside an embryo will eventually give rise to every cell, tissue and organ in the fetus's body. Unlike a regular cell,
which can only replicate to create more of its own kind of cell, a stem cell is pluripotent. When it divides, it can make any one of the
220 different cells in the human body. Stem cells also have the capability to self-renew -- they can reproduce themselves many times
over.
There are several types of stem cells, including:
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Embryonic stem cells - Embryonic stem cells include those found within the embryo, the fetus or
the umbilical cord blood. Depending upon when they are harvested, embryonic stem cells can give
rise to just about any cell in the human body.
Adult stem cells - Adult stem cells can be found in infants, children and adults. They reside in
already developed tissues such as those of the heart, brain and kidney. They usually give rise to
cells within their resident organs.
Induced pluripotent stem cells (IPSC)- These stem cells are adult, differentiated cells that have
been experimentally "reprogrammed" into a stem cell-like state.
Embryonic Stem Cells
Once an egg cell is fertilized by a sperm, it will divide and become an embryo. In the embryo, there are stem cells that are capable of
becoming all of the various cell types of the human body. For research, scientists get embryos in two ways. Many couples conceive by
the process of in vitro fertilization. In this process, a couple's sperm and eggs are fertilized in a culture dish. The eggs develop into
embryos, which are then implanted in the female. However, more embryos are made than can be implanted. So, these embryos are
usually frozen. Many couples donate their unused embryos for stem cell research.
The second way in which scientists get embryos is therapeutic cloning. This technique merges a cell (from the patient who needs the
stem cell therapy) with a donor egg. The nucleus is removed from the egg and replaced with the nucleus of the patient's cell. (For a
detailed look at the process, see How Cloning Works) This egg is stimulated to divide either chemically or with electricity, and the
resulting embryo carries the patient's genetic material, which significantly reduces the risk that his or her body will reject the stem
cells once they are implanted.
Both methods -- using existing fertilized embryos and creating new embryos specifically for research purposes -- are controversial.
But before we get into the controversy, let's find out how scientists get stem cells to replicate in a laboratory setting in order to study
them.
When an embryo contains about eight cells, the stem cells are totipotent - they can develop into all cell types. At three to five days,
the embryo develops into a ball of cells called a blastocyst. A blastocyst contains about 100 cells total and the stem cells are inside. At
this stage, the stem cells are pluripotent - they can develop into almost any cell type.
HowStuffWorks / Lee Dempsey
To grow the stem cells, scientists remove them from the blastocyst and culture them (grow them in a nutrient-rich solution) in a Petri
dish in the laboratory. The stem cells divide several times and scientists divide the population into other dishes. After several months,
there are millions of stem cells. If the cells continue to grow without differentiating, then the scientists have a stem cell line. Cell lines
can be frozen and shared between laboratories. As we will see later, stem cell lines are necessary for developing therapies.
Today, many expectant mothers are asked about umbilical cord banking -- the process of storing umbilical cord blood after giving
birth. Why would someone want to do that? Once a mother gives birth, the umbilical cord and remaining blood are often discarded.
However, this blood also contains stem cells from the fetus. Umbilical cord blood can be harvested and the embryonic stem cells
grown in culture. Unlike embryonic stem cells from earlier in development, fetal stem cells from umbilical cord blood are
multipotent - they can develop into a limited number of cell types.
Adult Stem Cells
You can think of adult stem cells as our built-in repair kits, regenerating cells damaged by disease, injury and everyday wear and tear.
These undifferentiated cells reside among other differentiated cells in a tissue or organ; they divide and become specialized to repair
or replace the surrounding differentiated cells. A common example of adult stem cells is hemopoietic stem cells, which are found in
red bone marrow. These stem cells differentiate into various blood cells (red blood cells, lymphocytes, platelets-- see How Blood
Works for more information). For example, red blood cells are not capable of reproducing and survive for about 28 days. To replace
worn-out red blood cells, hemopoietic stem cells in the bone marrow divide and differentiate into new red blood cells.
Bone marrow also contains a second type of adult stem cell known as a stromal or mesenchymal stem cell. Stromal stem cells
become bone, cartilage, fat and connective tissues found in bone. Adult stem cells have also been found in many other tissues such as
the brain, skeletal muscle, blood vessels, skin, liver, teeth and the heart. Regardless of the source, adult stem cells are multipotent they can develop into a limited number of cell types.
Although adult stem cells exist in many tissues, their numbers are small, perhaps one adult stem cell for every 100,000 surrounding
cells. These stem cells look like the surrounding cells, so it's difficult to tell them apart. But researchers have developed an interesting
way to identify them by "lighting them up." All cells have unique proteins on their surface called receptors. Receptors bind chemical
messages from other cells as part of cell-to-cell communication. Researchers use these receptors -- or markers -- to identify and
isolate adult stem cells by "tagging" the chemical messages that bind to those specific receptors on the stem cell with fluorescent
molecules. Once the fluorescent chemical message binds to the receptor on the surface of the stem cell, the stem cell will "light up"
under fluorescent light. The "lighted" stem cell can then be identified and isolated.
Like embryonic stem cells, adult stem cells can be grown in culture to establish stem cell lines.
Adult stem cells were once believed to be more limited than embryonic stem cells, only giving rise to the same type of tissue from
which they originated. But new research suggests that adult stem cells may have the potential to generate other types of cells, as well.
For example, liver cells may be coaxed to produce insulin, which is normally made by the pancreas. This capability is known as
plasticity or transdifferentiation
It used to be believed that there were only two types of stem cells -- embryonic and adult -- but there's another kid on the stem cell
block. Keep reading to learn about this "new" type: the induced pluripotent stem cell.
Using Stem Cells to Treat Disease
The first step in using stem cells for disease treatment is to establish stem cell lines, which researchers have accomplished. Next,
scientists must be able to turn on specific genes within the stem cells so that the stem cells will differentiate into any cell they wish.
But scientists have not learned how to do this yet; so, studying stem cell differentiation is an active area of research. Once scientists
can create differentiated cells from stem cells, then there are many possibilities for their use, such as drug testing and cell-based
therapies. For example, let's say you want to test new drugs to treat heart diseases. Currently, new drugs must be tested on animals.
The data from animal research must be interpreted and then extrapolated to humans prior to human clinical trials. But suppose you
could test them directly on human heart cells. To do this, human stem cell lines could be treated to differentiate into human heart cells
in a dish. The potential drugs could be tested on those cells and the data would be directly applicable to humans. This use could save
vast amounts of time and money in bringing new drugs to market.
Stem-cell-based therapies are not new. The first stem-cell-based therapy was a bone marrow transplant used to treat leukemia. In this
procedure, the patient's existing bone marrow is destroyed by radiation and/or chemotherapy. Donor bone marrow is injected into the
patient and the bone marrow stem cells establish themselves in the patient's bones. The donor bone marrow cells differentiate into
blood cells that the patient needs. Often, the patient must take drugs to prevent his or her immune system from rejecting the new bone
marrow. But this procedure uses existing hemopoietic stem cells. How would you use stem cell lines? Let's look at how stem cells
might be used to treat heart failure.
Ideally, to treat a failing heart, scientists could stimulate stem cells to differentiate into heart cells and inject them into the patient's
damaged heart. There, the new heart cells could grow and repair the damaged tissue. Although scientists cannot yet direct stem cells to
differentiate into heart cells, they have tested this idea in mice. They have injected stem cells (adult, embryonic) into mice with
damaged hearts. The cells grew in the damaged heart cells and the mice showed improved heart function and blood flow.
In these experiments, exactly how the stem cells improved heart function remains controversial. They may have directly regenerated
new muscle cells. Alternatively, they may have stimulated the formation of new blood vessels into the damaged areas. And the new
blood flow may have stimulated existing heart stem cells to differentiate into new heart muscle cells. These experiments are currently
being evaluated.
One major obstacle in stem cell use is the problem of rejection. If a patient is injected with stem cells taken from a donated embryo,
his or her immune system may see the cells as foreign invaders and launch an attack against them. Using adult stem cells or IPSCs
could overcome this problem somewhat, since stem cells taken from the patient would not be rejected by his or her immune system.
But adult stem cells are less flexible than embryonic stem cells and are harder to manipulate in the lab. And IPSC technology is too
new for transplantation work.
Finally, by studying how stem cells differentiate into specialized cells, the information gained can be used to understand how birth
defects occur and possibly, how to treat them.
Stem Cell Research Controversy
Stem cell research has become one of the biggest issues dividing the scientific and religious communities around the world. At the
core of the issue is one central question: When does life begin? At this time, to get stem cells that are reliable, scientists either have to
use an embryo that has already been conceived or else clone an embryo using a cell from a patient's body and a donated egg. Either
way, to harvest an embryo's stem cells, scientists must destroy it. Although that embryo may only contain four or five cells, some
religious leaders say that destroying it is the equivalent of taking a human life. Inevitably, this issue entered the political arena.
In 1996, Congress passed a rider to the federal appropriations bill called the Dickey-Wicker amendment. Representatives Jay Dickey
and Roger Wicker proposed banning the use of federal monies for any research in which a human embryo is created or destroyed.
Federal monies are a primary source of funding for stem cell research. The amendment has been renewed every year since that time.
In 2001, President George W. Bush further restricted federal stem cell research. In an executive order, Bush stated that federal funds
could only be used for research on human embryonic stem cell lines that had already been established (only 22 cell lines). This
prevented researchers from creating more embryonic stem cell lines for research.
In 2009, President Barack Obama issued an executive order to expand embryonic stem cell research. Obama's administration allowed
federal funding of embryonic stem cell research if the following conditions applied:



The cell line was one of the 22 in existence during the Bush administration or was created from
embryos that had been discarded after in vitro fertilization procedures.
The donors of the embryos were not paid in any way.
The donors clearly knew that the embryos would be used for research purposes prior to giving
consent.
According to the administration, the new policy did not violate the Dickey-Wicker amendment because the money did not finance the
creation of new embryos (they had already been created by private means) and did not finance the destruction of them.
In 2009, two researchers from Boston, Dr. James Sherley of the Boston Biomedical Research Institute and Dr. Theresa Deisher of the
Ava Maria Biotechnology Company, and other agencies filed a lawsuit against the government. Initially, the lawsuit was dismissed
because the judge ruled that the plaintiffs had no legal standing (i.e. they were not affected materially by the new rules). However, a
court of appeals overturned the initial ruling. The two scientists remained plaintiffs. The scientists claimed that, because they used
adult stem cells exclusively in their research, the new rules would increase competition for federal research dollars, thereby affecting
their ability to obtain funding. Federal Judge Royce Lamberth upheld the appeals court ruling. He placed an injunction preventing the
new rules from going into place. He claimed that the rules violated the Dickey-Wicker amendment because embryos must be
destroyed in the process of creating embryonic stem cell lines.
In September 2010, The New York Times reported that the U.S. Court of Appeals ruled that federal funding of embryonic stem cell
research could continue under the new rules while the court considers Judge Lamberth's ruling [source: New York Times]. This ruling
allows researchers to continue feeding embryonic stem cell cultures, experimenting with mice, and other research activities until this
court rules, the U.S. Supreme Court weighs in, or Congress passes legislation that clarifies the issues. In the meantime, stem cell
research and the careers of stem cell researchers hang on a legal roller coaster. Although stem cells have great potential for treating
diseases, much work on the science, ethical and legal fronts remains.