Alex Tang
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Medical Students /Paediatric notes
Stem Cell Research
Dr Alex Tang
Embryonic and Adult Stem Cells
Embryonic stem cells are cells present in the embryo just before it begins to
differentiate. Hence stem cells have the potential to differentiate into any
tissue, organ or structure of the human body. When the embryo begins to develop,
each stem cell receives its instructions and follows its programming to develop
into the different parts of the human body.
After the spermatozoa enters the ovum and fertilises the egg, an embryo is
formed. This then begins to divide. When it reaches the 100 cells stage, it is
known as a blastocyte. The blastocyte is a circular mass of cells. When the
blastocyte is implanted onto a favourable environment such as the uterine wall,
it begins to differentiate. The outer wall of cells will differentiate into the
placenta and umbilical cord. The cells at the centre are the embryonic stem
cells or, to be more specific, human embryonic stem cells (hES). This is to
differentiate it from embryonic stem cells harvested from the gonadal ridge of
aborted foetus, which are termed human embryonic gonadal stem cells (hEG). This
discussion will centre on hES cells. In November 1998, researchers at the
University of Wisconsin and John Hopkins University in Baltimore found a way to
harvest the stem cells. Researchers have estimated that stem cells have the
potential to differentiate into 110 types of human cells, which can turn into
the different organs that make up our body.
It was discovered recently that contrary to decades of biological knowledge,
adult differentiated cells can also be stimulated to revert to its
undifferentiated state with the potential to develop into other tissues or
organs. The undifferentiated adult cells are called adult stem cells. While
there are possibilities that adult stem cells can be used, recent studies are
not too encouraging compared to the embryonic stem cells. The adult stem cells
are not so easily cultured and not so versatile in differentiation.
Embryonic stem cells are more versatile. It would solve a lot of ethical
problems if adult stem cells were equivalent to embryonic stem cells. As noted
earlier, embryonic stem cells are harvested by destroying an embryo or
blastocyte. Adult stem cells are obtained from cells from umbilical cord blood,
placenta, bone marrow, brain of cadavers and skin (fibroblasts).
Potential Applications of Stem Cell Research
Stem cell research offers a radical shift in the way research is conducted due
to the properties of the stem cells. Firstly, stem cells are pluripotent. This
means they are able to grow into any tissues in the human body. It is a matter
of programming the cell to differentiate into any one particular tissue.
Secondly, stem cells are immortal. With the right environment, they will
continue dividing forever without loss of their genetic structure. Thirdly, they
are malleable. This means they can be manipulated without losing their cell
functions. In animal experiments, stem cells can be inserted into an animal
blastocyte and they will continue to grow.
Stem cell research will make give significant contributions in the areas of
medical research. It can be used to identify potential teratogens. Pregnant
women are exposed to many agents that can kill or maim the growing foetus. The
horrors of thalidomide, a sedative given to pregnant women, producing babies
without limbs are one example. At this moment, there are not many ways to
determine which are the teratogens which are harmful to human foetus because
obviously no one will expose human foetuses to them to find out. Most of our
knowledge came from research on animals. Stem cell research offers a way to
identify and study the environmental toxins as well as drugs (medications)
directly harmful to a growing foetus. Exposing some stem cells to a suspected
teratogen and observing its development can give us information on its
harmfulness to a human foetus.
Secondly, one of the problems when developing new drugs or medication in the
pharmaceutical industry is drug toxicity. Now with the pharmaceutical industry
custom-designing the molecules of new drugs, they need a fast and safe way to
test these compounds. Stem cells offer such an avenue. For example, recently the
Food and Drug Administration (FDA) approved a drug for general use only to
withdraw it later after the discovery of liver toxicity in the drug. This was in
spite of human drug trials being carried out. With stem cells differentiated
into liver cells, it is possible to test these drugs for liver toxicity even
before human trials. This means that new drugs can be made available for general
use earlier. Normally, it takes about takes about five years for a new drug to
reach the general public. Animal trials are conducted first, then human drug
trials in multiple medical centres. With stem cells, it has been speculated that
a new drug may be made available as quickly as six months.
Thirdly, the present approach in medical care is mainly prevention and
limitation of damage in response to diseases. One example is myocardial
infarction or heart attack. A myocardial infarction occurs when blood flow to a
certain part of the heart is stopped, often the result of a blockage of one or
more of the coronary arteries. Without blood supply, oxygen and glucose, the
heart muscles die. The aim of medical treatment is to restore blood supply to
the affected part of the heart as soon as possible either by medication, balloon
angioplasty or open-heart surgery. When blood supply is restored, the patient
survives. Unfortunately, in the area where the heart muscles have died, new
muscles are not formed because heart muscles cannot divide to form new heart
muscles. They can only be replaced. Hence the functional tissue in this area is
replaced by non-functional scars or fibrous tissue. As a result, the functional
contractibility of the heart is compromised. Stem cell research holds the
promise of creating new heart muscles cells and introducing it into the damaged
portion of the heart to re-populate it. Similar procedures may be possible for
diseases like insulin dependent diabetes mellitus (growing new pancreatic islets
insulin-producing cells), stroke, Alzheimer’s disease and Parkinson’s disease.
Stem cells herald a new phase of medical care called regenerative medicine.
Stem Cell Research and Therapeutic Cloning
One potential of embryonic stem cell research is to grow entire organs. So far
scientists have been able to grow liver cells around a supportive structure.
Would it not be possible to grow a new kidney, liver or some other organs? Organ
transplantation has always been the last option. There is a long wait list for
patients requiring kidneys, liver or heart transplants. It is difficult to get
donors and even more difficult to get matching or compatible organs. Patients
who have received organ transplant will need life-long immunosuppressant drugs
to stop their bodies rejecting the donated organ. One result of this is that
most donated organs will have a lifespan of five to ten years after which
another organ will be needed. So it would be wonderful if an organ grown from
the person’s own stem cells was available for transplant. There would be no
problems with organ rejection. This sounds like science fiction at present but
the prospects are exciting. On 6 April 2006, the first stem cell surgery in the
world was performed in the Royal Melbourne Hospital in Australia. The patient
had lost a large segment of his leg bone in a motorcycle accident. Stem cells
harvested from his bone marrow were introduced to the gap in the bone to produce
new bones.
Therapeutic cloning is made possible by the process of nuclear transfer, the
nuclear coming from the recipient. Being of the same genetic material, there
will be no problem of organ rejection or incompatibility. The stem cells can
then be reprogrammed into replacement cells for the damaged body organ or even
grow into an organ itself.
The Current State of Embryonic Stem Cells Research
In 2004, South Korean scientists from Seoul national University announced that
they have cloned 30 human embryos. From these 30 cloned embryos, they have
managed to establish 11 cell lines. Cell lines are the culture of a colony of
cells from a single original cell.. Unfortunately it was later discovered that
Dr. Hwang had falsified his results and a Seoul National University Panel
concluded its investigation in December 2005 that all 11 stem cell lines were
forgeries. This was a major blow to stem cell research and to the reputation of
the objectivity of scientific research.
Two proposals in the UK for research using cloned human embryos to create stem
cells was submitted in 2004.. One is from the Newcastle Fertility Centre while
the other is from the Roslin Institute, famous for the cloning of Dolly the
sheep. The scientific focus for these proposals is for research on motor neurone
disease by the Roslin Institute and diabetes by the Newcastle Fertility Centre.
The Newcastle research proposal also cites that stem cell research will
eventually lead to therapeutic cloning.
Such research on human embryos is legal in the UK. The Donaldson Report from the
Ministry of Health in the UK in the year 2000 recommended extending the limits
of human embryo research to allow human embryos to be used as a source of stem
cells. It also called for the creation of cloned human embryos which could be
reprogrammed to become replacement body cells for a wide range of degenerative
diseases. It proposed research into mitochondrial disease using parts of the
cloning process.
While research using stem cells has been authorised in Britain, in the USA, it
was initially halted by President George W. Bush. In 2001, Bush allowed research
to resume in government labs, but restricted researchers to only 72 existing
lines of stem cells. In June 2003, the American Medical Association announced
its support for human cloning for research purposes. Later that year, the first
law in the USA permitting stem cell research was signed. Another bill was
simultaneously signed that bans reproductive cloning.
On both sides of the Atlantic, Christians are actively involved in the ethical
debate on cloning and stem cell research. The Church of Scotland has issued
several joint statements on the issue of stem cell research since 1996. The
Conference of European Churches calls for a ban on all cloned embryo research
until a ban on reproductive cloning is in place in the United Nations. These
concerned church leaders are not against therapeutic cloning but are fearful
that if cloning research on the whole is not banned, some maverick scientists
will proceed with reproductive cloning. The churches were also against creating
human embryos for harvesting of stem cells but would allow extra embryos created
for in-vitro fertilisation (IVF) to be harvested for stem cells. The
justification is that these extra human embryos are scheduled for destruction
anyway.
The Center for Bioethics and Human Dignity in the USA in its statement On Human
Embryos and Stem Cell Research concludes, “We call on Congress to (1) maintain
the existing ban against harmful federally-funded human embryo research and make
explicit its application to stem cell research requiring the destruction of
human embryos and (2) provide funding for the development of alternative
treatments which do not require the destruction of human embryonic life.”
The public reaction to these statements are mixed. Several surveys in the UK and
USA show that while many people are clear in their stand against reproductive
cloning, they are confused in their understanding of stem cells and therapeutic
cloning. Stem cell research is still a very new and developing field. In 1999,
stem cell research was named ‘Breakthrough of the Year’ by the prestigious
journal Science.
Christopher Reeves, the ‘Superman’ actor who became a paraplegic due to spinal
cord injury in 1995, said, “Stem cell research holds the promise of hope for 100
million people living with incurable diseases from diabetes to heart conditions
to Alzheimer’s to Parkinson’s, ALS, MS and spinal cord injury. It will affect
the entire American family. I believe this is why we find in surveys such strong
support from people with such diverse religious and ethical beliefs.”
Colleen Parro, spokesperson for the Republican National Coalition for Life said
in 2001, “We do not believe that human beings should ever be sacrificed for the
benefit of another. We thought we left that at Nuremberg more than fifty years
ago.”
Christopher Reeves and Colleen Parro are on opposite side of the wide spectrum
of views on stem cell research. Unfortunately Christopher Reeves died before any
of the research in stem cells bore fruit.
Some Christian Ethics Considerations
One of the key ethical concerns with respect to stem cell research is the human
embryo, which is a major source of stem cells. In this regard, there are two
opposing views. Those who hold that human embryos, especially ‘pre-implantation
embryos’, are nothing more than a mass of cells have no problems teasing these
mass of cells apart and using the core cells, which are the embryonic stem
cells, for research purposes. At the other end are those who hold to the
principle that all embryos are human beings and should be accorded the rights of
human beings. To them, breaking apart an embryo to harvest embryonic stem cells
would be equivalent to murder.
Then there are a number of intermediary positions. One is held by the Church of
Scotland, which in 1995 affirmed “the sanctity of the human embryo from
conception but granted that there are limited circumstances under which such
research might be reluctantly allowed prior to the ‘primitive streak’ stage,
bearing in mind the seriousness of certain medical conditions especially
infertility and genetically transmitted diseases.” Its think tank, The Society,
Religion and Technology Project and the Working Group on Bioethics and
Biotechnology of the Church and Society Commission of the Conference of European
Churches is against the creation of human embryos as a source of stem cells but
will allow extra embryos from IVF which are targeted for destruction to be used
as a source of stem cells. The argument is that these ‘left behind’ embryos are
destined to be discarded anyway. Some ‘parents’ of these embryos have since
completed their families and do not want them anymore. Other embryos can be
considered ‘orphaned’ as their parents had died. In Australia, according to The
Age newspaper (September 21, 2005), The National Health and Medical Research
Council has granted licences allowing research on 1731 ‘unwanted’ spare embryos
since the law was passed in 2002 allowing research on such embryos.This seems to
be a pragmatic approach to a bad situation. Is it then acceptable? If these
‘unwanted’ embryos are considered to have the status of human beings, then do we
have the right to experiment on them on the premise they will be destroyed
anyway? At this moment, we would not allow any human experimentation, even those
who are convinced criminals awaiting execution. One could extend this argument
to these ‘unwanted’ embryos.
There are other suggestions. One is to concentrate research on adult stem cells
so that these can be reprogrammed to be as versatile as the embryonic stem
cells. Nobody has any objection to the creation of adult stem cells from
differentiated adult cells so it is a non-issue. One novel suggestion, which is
being explored at this moment, is the creation of non-viable human embryos with
cow’s eggs. The idea is to transfer a human cell nucleus into a cow’s egg.
Passing an electric current will fuse the two and stimulate the human nucleus to
divide like an embryo. At the appropriate stage of the blastocyte, the embryonic
stem cell will then be harvested. This interesting idea avoids the creation of a
human embryo but opens a new frontier of concern: the formation of transgenic
animals with the mixing of human and animal genetic materials. Still another
novel alternative is to create human embryos for stem cell research by
pathogenesis. This involves chemically inducing an unfertilised human egg to
divide as if it was an embryo. These are then possible alternatives to using
cloned human embryos as a source of stem cells. Meanwhile, Christians should be
supporting research in finding and refining the production of adult stem cells.
There have been concerns that stem cell research is human experimentation. It
has been likened to experimentation on inmates of the concentration camps in
Nazi Germany during the Second World War. The analogy, however, may not hold.
The victims of the Nazi experiments were children and adults. Stem cells on the
other hand are clusters of cells. There is no comparison. Human experimentation
has always been done. Every new drug or medical treatment module has been
subjected to animal testing, and when found to be safe and effective, were tried
on humans (with the participants’ consent, of course). It is by this form of
human experimentation that we are able to enjoy the better healthcare we have
today. Christians, fulfilling the mandate to ‘love our neighbour’, should
consider supporting and even taking part in such clinical trials or human
experimentation because the data obtained will benefit humankind.
Another area of ethical concern is the patenting of human cells. Commercial
organisations are bound to patent their inventions or discoveries for monetary
profit. This is especially so in the pharmaceutical and biotechnological
companies. Patents have always been awarded for inventions. Whether a discovery
can be patented is questionable but the distinction has been blurred for some
time, again because of financial goals. Whether one can claim exclusive rights
to something natural is debatable. A USA patent has been granted to a company
for ‘cells which come from the early human embryo and are pluripotent’. What
this would mean is that in the USA, all embryonic stem cells are the monopoly of
one company! But it must be questioned whether anyone can patent a part of the
human body. The human body is God’s creation. This applies to stem cells which
are also part of the human body. That we know more about them and their
potential is a discovery, not an invention. One may patent the techniques of
nuclear transfer technology but can anyone patent stem cells?
The patenting of stem cells also creates another problem. It limits the
opportunities for other researchers to do stem cell research. Stem cell research
is in its infancy, so it is in the interest of humankind that as many
researchers and institutions as possible be given the freedom to be involved.
Finally the patenting of stem cells and its research will result in only the
rich reaping the benefits. Basic healthcare data and use should be available to
everybody. The Christian response should be to fight against such exploitation
and commercialisation of our natural resources. Even though some may not agree
with stem cell research, all must fight against the commercialisation of pure
science research.
Conclusion
Stem cell research is new and many people confuse the issues of stem cell
research with cloning. We should be able to differentiate between the two issues
and respond appropriately. The potential benefits from stem cell research are
enormous. Its clinical application through therapeutic cloning is even more
awesome. Doctors will be able to treat cell degeneration diseases with cell
replacements and circumvent organ donor rejection with the patient’s own cloned
tissue and organs. Most Christians would agree on the potential of the
applications of stem cell research. The main point of contention is the source
of stem cells. While there is room for a range of views on the source of stem
cells, depending on one’s belief on when human life begins, Christians should
continue to pray for adult stem cell research to advance rapidly to make adult
stem cells as pluripotent as embryonic stem cells.
The editors in their introduction to the book, The Embryonic Stem Cell Debate,
describe the contributors to the book, “All of them take the status of the
embryo as critically important, but some hold that status in tension with other
values such as the mandate to heal, whereas others maintain that a theological
view mandates particular commitment to the weak and vulnerable or to new
understanding of the origins or respect. Others, finally, believe that respect
must be nuanced according to the nature of what is being respected…it is, in
large part, a conversation about the ethical, scientific, philosophic, and
religious meaning of who we are as human beings and what our fate will be in the
new century.”
Soli Deo Gloria
|posted 10 June 2006|
