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I-SIS Report 23 Jan. 2001
The Unnecessary Evil of ‘Therapeutic’ Human
Cloning
The United Kingdom House of Lords voted last night by an overwhelming
majority to allow the creation of human embryos to provide embryonic stem
cells that can be used for cell and tissue replacement. Britain stands out
as the only country in the European Union to approve of this so-called
therapeutic human cloning. Drs. Mae-Wan Ho and Joe Cummins
explain why ‘therapeutic’ human cloning is both morally
unacceptable and scientifically unjustifiable.
What are stem cells?
Stems cells are cells in mammals including human beings that have the
ability to divide and give rise to specialized, differentiated cells. The
fertilized egg cell possesses this ability to the highest degree, for it
has the potential to divide and develop into the entire organism with the
full complement of cell types. The fertilized egg cell is totipotent.
Totipotency is retained as the egg divides into two and even four cells,
so that each cell, when separated, is capable of developing into a
complete foetus. That is how twins, triplets and quadruplets come about;
they are natural human clones with identical genetic and
cytoplasmic makeup.
When the embryo is four days old, and after several rounds of cell
division, a hollow sphere is formed, called a blastocyst, within
which is a cluster of cells called the inner cell mass. The outer
layer is destined to form the placenta and other supporting tissues needed
for the development of the foetus in the womb. The inner cell mass will go
on to become all the tissues of the foetus’ body. These cells are no
longer totipotent, but pluripotent, ie, they can give rise to many
types of cells, but not all of the ones required for foetal development.
As development proceeds, the inner cell mass divides further and become
more restricted in the range of cells they will become. For example, blood
stem cells will eventually give rise to red blood cells, white blood cells
and platelets, and skin stem cells will give rise to all the various types
of skin cells. These more specialized stem cells are said to be multipotent.
Pluripotent and multipotent stem cells in the embryo came to be known as
embryonic stem cells or ES cells.
Stem cells are also found in children and adults, these are known as
adult stem cells. Blood stem cells, for example, are found in the
bone marrow of every child and adult, and in very small numbers, also in
the blood stream; they continually replace the supply of blood cells
throughout life. Recently, adult stem cells have also been found in brain
as well as muscle, liver, skin and other tissues.
One of the main arguments used in favour of ‘therapeutic’
human embryo cloning is that adult stem cells are much more restricted in
their potential to become different cell types than ES cells. However, it
is beginning to appear that adult stem cells have the potential to give
rise to a far greater range of cell types than previously imagined, and
stunning results have been obtained. Furthermore, there are ways to obtain
ES cells other than human cloning.
Embryonic stem cells are not all equal
There are three kinds of ES cells. The first is derived from the inner
cell mass, a procedure pioneered in Dr. James Thomson’s laboratory in
the University of Wisconsin using ‘excess’ embryos from in
vitro fertilization clinics. The second, embryonic germ cells, is
isolated from the regions of the embryo destined to become ovaries or
testes. This was first carried out by Dr. John Gearhart’s group in
John Hopkins’ University, using foetuses from terminated pregnancies.
The cells resulting from the two laboratories appear to be very similar.
The third kind of ES cells involves somatic cell nuclear transfer, the
technique that created Dolly, the lamb cloned from a cell of an adult
sheep. Researchers take a normal human (or animal) unfertilised egg and
remove the nucleus, replacing it with the nucleus from a somatic cell of a
human donor. The perceived advantage of this procedure is that the somatic
cell donor could be the patient requiring tissue replacement, thus
avoiding problems associated with immune rejection of transplanted cells
or tissues that are foreign to the body.
As is clear from the description, the first two categories of ES cells
do not involve the creation of human embryos, and research on those ES
cells has already been going on for the past two years. Many people may
find research on those stem cells morally acceptable, though it will be
difficult to justify research on those cells in view of the latest
discoveries on the enormous developmental potentials of adult cells (see
below), which make ES cells completely redundant.
It is research on ES cells obtained by nuclear transfer that raises
the most serious moral concerns, for it requires the creation of embryos
specifically for providing ES cells, the embryos being destroyed in the
process.
In December 1998, researchers in the Infertility Clinic at Kyeonghee
University in Korea announced that they had successfully cloned a human
embryo by transferring the nucleus from the somatic cell of a 30 year old
woman into one of her unfertilized eggs. This embryo was reported to have
developed to the fourth cell division stage, when it would have been
implanted. But it was destroyed on ethical considerations. Meanwhile,
researchers in the United States and Australia have created ‘human’
embryos by transferring the nucleus of human cells into the eggs of the
cow and the pig. It is of course questionable whether the embryos created
by such procedures are human, and whether they are justifiable on moral
grounds. These were destroyed at day 14. It was not clear, however,
whether ES cells have been extracted from the embryos before they were
destroyed.
Proponents claim that one of the major advantage of ES cells is that
established cell lines can be obtained only from ES cells and not adult
stem cells; though this may no longer be true (see below).
ES cells carry health risks, and there are major technical difficulties
in creating them with nuclear transplant cloning techniques.
- ES cells can give rise to teratomas – malignant tumours
(cancers) consisting of a disorganized mass of differentiated cells –
on being transplanted.
- Nuclear transplant cloning is a very inefficient process with massive
failure rates, requiring a large number of donor eggs.
- Nuclear transplant clones created by transferring human nuclei into
cow and pig egg carry even greater risks, as it is well-known that such
interspecific nuclear-cytoplasmic hybrids fail to develop normally.
ES stem cell research serves commercial interests, not public good
There are powerful commercial interests in ES stem cells. Geron
Corporation of Menlo Park California gained first rights to exploit cells
commercially, and also funded the isolation of embryonic germ cells. A
total of ten companies were involved in exploiting stem cell technology
and stem cells in 2000. Geron already owns dozens of patents on ES cells.
Companies investing in adult stem cell technology include Nexell
Therapeutics of Irvine California and Anastrom Biosciences of Ann Arbor.
Osiris Therapeutics of Baltimore identified mesenchyme stem in the
supportive tissue that surrounds the bone marrow, and has patented systems
for isolating and producing those cells, and launched two clinical trials.
Mesenchyme cells can differentiate into cartilage, muscle and even
neurons. Neural stem cells came on the scene later, but already clinical
trials have begun.
It is clear that the major impetus for both ES and adult stem cell
research is coming from the biotech companies and scientists working with
them. Therapy is likely to be very costly on account of the multiple
license fees that have to be paid, not only on cells and cell lines but on
isolation procedures.
Public opposition to ‘therapeutic’ human embryo cloning has
been fierce. Apart from the moral objection to the creation of human
embryos that are destined to be destroyed, many groups feel that ‘therapeutic’
human cloning is a slippery slope to reproductive cloning and the
re-emergence of eugenics. The Clinton administration had forbidden such
research in federally funded projects; and no European Government, with
the exception of the United Kingdom, is in favour of such research.
The British government first announced plans to relax the law on human
embryo cloning to allow the creation of human embryos up to 14 days to
provide ES cells. Parliament voted in favour of the new law in December,
against the advice of the European Group of Ethics in Science and New
Technologies (EGE). The House of Lords endorsed Parliament’s decision
with an overwhelming majority last night.
The EGE had warned that the creation of embryos by somatic cell nuclear
transfer (‘therapeutic cloning’) for research on stem cell
therapy would be premature", drawing attention to the rapidly
developing research in adult stem cells. The EGE recommended that the EU
should set up a budget to explore non-cloning sources of stem cells,
especially adult tissue, and to enable the results of such research to be
"widely disseminated."
Promises of adult stem cells
Mammals appear to contain some 20 major types of somatic stem cells.
Stem cells have been described that can generate all the cells in the
brain, the liver, pancreas, bone and cartilage. These adult stem cells are
increasingly found to have the potential to become practically as many
different cell types as ES cells. Furthermore, it appears that
differentiated adult cells can be made to revert to cells remarkably
similar to stem cells, and to have the ability to multiply for long
periods in cell culture. Some of the findings are highlighted below.
- Mouse bone marrow stem cells can give rise to skeletal muscle and
brain cells. Liver /pancreas stem cells can give rise to blood cells and
brain cells. Brain cells can give rise to all previous cells types
including the peripheral nervous system and smooth muscle. Brain cells
have been found to differentiate to muscle, blood, instestine, liver and
heart.
- Catherine Verfaillie of the University of Minnesota in Minneapolis is
reported to have isolated bone marrow cells from children and adults
that can become brain, liver, and muscle cells as well. These were found
in adults between 45 and 50 years old. This research has not yet
appeared in print.
- Scientists from the National Neurological Institute and Stem Cell
Research Institute in Milan, Italy, succeeded in growing skeletal muscle
from stem cells originating from an adult brain, both in culture and in
animals receiving the transplanted stem cells (Galli, R. et al (2000)
Nature Neuroscience 3, 986-991).
- A researcher in Britain, Dr. Ilham Abuljadaye, has just announced an
efficient method for creating large quantities of adult stem cells from
white blood cells, and her findings have been independently replicated,
though not yet published. The method involves inducing the white blood
cells to de-differentiate in the test-tube into stem cells ("Stem
cell discovery reverses time" The Times, 15 Jan 2001,
http://www.thetimes.co.uk/article).
That means it will be feasible to prepare stem cells from the patient
who is in need of cell or tissue transplant, greatly simplifying the
procedure, avoiding immune reactions and reducing cost.
- Two research teams at University College London found that adult rat
cells can be made to divide hundreds of times when provided with the
right mixture of nutrients, and without taking on the undesirable
characteristics of cancer cells, such as uncontrollable growth (Cohen,
P. (2001). New Scientist 18 Jan.
latestnews@newscientist.com).
Adult human cells may have the same capacity.
- Another possibility is that the patient’s own stem cells could
be stimulated to multiply and replace cells and tissues within the body
itself (McKay, R. (2000). Nature 406,361-364.)
Conclusion
We reject research on ES cells created by human ‘therapeutic’
cloning on the following grounds.
- It is totally unnecessary, given the promise of adult stem cells and
adult cells from the patients themselves, which can be most effectively
used for cell and tissue replacement.
- It is morally unacceptable to create human embryos for providing ES
cells.
- It is a slippery slope to human reproductive cloning.
- Nuclear transplant cloning has very low success rates and generates
many abnormalities.
- Cloning procedures involving transplanting human nuclei into animal
eggs carry even greater risks.
- ES cells are already available using ‘excess’ embryos from
in vitro fertilization clinics and aborted fetuses.
- ES cells carry cancer risks on being transplanted.
- ES cells are subject to multiple patents, on cloning and isolation
procedures as well as on the cells themselves; this will make their use
in cell or tissue replacement therapy very costly.
- Adult stem cells are already showing great promise in cell and tissue
replacement; and are likely to be much less costly.
‘Therapeutic’ human cloning is an unnecessary evil. We call on
the UK Government to reject it in line with the other EU countries, and to
support research into non-cloning sources of stem cells, especially adult
cells, with special emphasis on methods that do not involve patented
procedures and cell lines.
General References
European Union (EU) ethics panel report and press release on embryo
cloning
http://europa.eu.int/comm/secretariat_general/sgc/ethics/en/opinions.htm
Greenwood, D. (1998). The First Derivation of Human Embryonic Stem
Cells. Geron Corporation info@geron.com
Press release 5 November 1998.
Human Cloning: Ethical aspects
www.religioustolerance.org/cloning.htm
Stem Cells, Science volume 278, 25 February, 2000.
Stem Cells: A Primer, National Institutes of Health, May 2000.
Dr. Mae-Wan Ho
Director
Institute of Science in Society
m.w.ho@onetel.net
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