To clone or not to cloneMICHAEL COOK
Whether or not embryos should be cloned and then destroyed for their stem cells has been one of the hottest issues in science this year. James Sherley, a professor at MIT, says that the use of cells from cloned embryos is scientifically and ethically dubious.
Whether or not embryos
should be cloned and then and destroyed for their stem cells has been one of the
hottest issues in science this year. MercatorNet asked James
Sherley, an associate professor of biological engineering at the
Massachusetts Institute of Technology, to give his views.
Professor Sherley, you have been outspoken in your opposition to therapeutic
cloning. What’s wrong with destroying a human embryo, especially if this
research might benefit people with terrible diseases?
Sherley: Despite the confusion that some like to create on the
questions of “are embryos human beings?” and “when does a human
life begin?”, both scientists and physicians know very well that human embryos
are alive and human. A human life begins when a diploid complement of human DNA
is initiated to begin human development. Therefore, a life can be initiated by
the fusion of sperm and egg or by the introduction of a diploid nucleus into an
enucleated egg (ie, “cloning”).
Given that embryos are
human beings, they have a right to self and a right to life. Exploiting their
parts (ie, cells) or killing them for research is moral trespass that society
should not allow. Even if the research might, and let’s be clear, might
benefit others, this trespass is not justified.
But can you distinguish between a human life and a human being?
A human life is the experience of a human being until its death. It begins
with a single cell that has a diploid complement of human DNA, programmed for
What are the scientific drawbacks of using human embryonic stem cells in clinical
applications and in research?
The most profound drawback, which has not been adequately disclosed, is
that they cannot be used directly to treat mature tissues and organs. The tissues
and organs of the body undergo constant cell turnover. Cells are born by cell
division, they turn into functional cells (ie, “differentiate”), they
function, they get old, they die, and finally they are lost or removed from their
tissue or organ. So, to treat mature tissues and organs by giving mature cells
produced from embryonic stem cells is not enough. The cells that normally sustain
cell turnover are adult stem cells that reside in every tissue and organ which
has this cell turnover process, and that is nearly all tissues. This means that,
in order to use embryonic stem cells for diseases in mature tissues, they must
be turned into adult stem cells.
Another reason that embryonic stem
cells cannot be used directly is that they form tumours when transplanted into
mature tissues. Knowing these facts, it is pure scientific folly to place such
emphasis on embryonic stem cells research to the exclusion of support for adult
stem cell research. No matter what the hurdles are for success with adult stem
cell-based therapy development, embryonic stem cell research faces the same hurdles
Many supporters of embryo research are aware of possible drawbacks
to using HESCs, but say that it would be wrong to ignore an avenue that might
lead to cures. What is your opinion of two-track research?
I would agree, if it did not require that human beings be exploited and killed.
Nearly every researcher advocating therapeutic cloning also decries
reproductive cloning because it is unsafe. Does that seem contradictory to you?
Yes, amazingly so! See my October
2004 Boston Globe op-ed. But as I like to say, “If a position
seems illogical or contradictory, look for a hidden agenda.” Proponents
of therapeutic cloning have set up reproductive cloning as the greater of two
evils and then insisted that the public must choose one. This leaves the public
with therapeutic cloning as the lesser evil. In fact, we can decide to reject
them both as evils, but I see reproductive cloning as the lesser of the two presented
evils. Instead of promoting deaths, it promotes life; although, of course, the
nature of cloned lives raise many deep concerns and fears.
Your rejection of therapeutic cloning must be a lonely stand, especially
in Cambridge, where therapeutic cloning is championed by several eminent researchers
at MIT and Harvard. Why do you think most scientists back it?
I don’t know that they are doing anything more than protecting their
own turf and promoting their own goals with a variety of motivations, including,
in some cases, the best intentions of doing public good. However, they can often
turn an amazingly blind eye to the contradictions in their position on therapeutic
cloning. For example, the same scientists who argue that reproductive cloning
would produce disease-ridden individuals insist that tissues created from therapeutic
cloning will function normally! Illogical position, hidden agenda.
Do you think that most stem cell scientists have an open mind towards
adult stem cell research?
It’s rather hard to know what most stem cell scientists or cell biologists
in general, for that matter, think about these issues. I have asked the leaderships
of both the American Society for Cell Biology and the International Society for
Stem Cell Research to conduct anonymous on-line polls of their membership regarding
their views on human embryo research. Neither has been willing to do so. Many
scientists who do not support human embryo research are afraid to speak out because
of possible reprisals from powerful scientists who can affect grant success, publication
acceptances, tenure promotion, and employment.
Do adult stem cells have advantages over HESCs?
Yes. The main advantage is that adult stem cells are already programmed
for function in adult tissues and organs. In addition, they do not form tumours
when transplanted from one person to another.
Is it true that it is impossible to propagate and grow adult stem cells
in quantities sufficient for clinical applications?
Impossible is not true. Challenging is true. We have recently
published a report
of a successful approach to multiplying adult stem cells from rat liver and
we have a patent application pending for the adaptation of the method to human
adult liver stem cells. Each adult stem cell is unique, and this requires development
of somewhat unique methods for the growth of each type. Every adult stem cell
has an intrinsic property to multiply itself, but this process is highly restricted
in some tissues. As research elucidates the basis for these restrictions, more
adult stem cells will become available for therapeutic development.
What about tissues like the heart, pancreas and the brain which apparently
do not have adult stem cells? Will embryonic stem cells be needed to provide transplant
Yes, the heart is tough one. It’s on my list of organs with little
evidence of cell turnover, and therefore unlikely to have stem cells, though this
is not certain yet. This being said, embryonic stem cells are not likely to be
able to impact heart muscle significantly either and their tumour risk in the
heart and after migration to other sites is likely to be prohibitive. We need
to stay sober. The belief that stem cell therapy will be a panacea is naïve
and greatly misguided. There is still a lot of other disease research that we
should continue to support, as the cures for heart disease may lie in a non-stem
There is good evidence for adult stem cells in the brain.
However, it is unclear how these cells normally function in the brain and what
are all of the regions of the brain that they might supply with young cells. For
brain diseases that primarily affect motor or sensory function, these cells may
have applications down the road.
The recent report concluding that
there were no adult stem cells in the pancreas from the Melton lab at Harvard
had several shortcomings in logic and experimental analysis and did not evaluate
the human pancreas. This conclusion has been used as a basis of persuasion that
we must conduct human embryo research in order to cure diabetes. Illogical position,
How long do you think it will be before adult stem cells are used as
medicines in American hospitals?
First it should be noted that preparations of adult stem cells are already
used as medicines in hospitals worldwide. Bone marrow transplantation, immobilized
peripheral blood stem cell transfusions, and cord blood cell transplants in children
are all examples of standard medical therapy with hematopoietic stem cells, which
are the adult stem cells responsible for blood cell formation. There is still
much work to be done to improve the effectiveness of these treatments by developing
methods that increase the number of stem cells in the donor cell preparations.
the future is always difficult to do when a field is still in primarily a research
phase. By the very nature of the research it is difficult to predict when discoveries
that will lead practical applications will occur, even though there is a high
probability of success. If we can breach the adult stem cell multiplication barrier
in liver, skin, hair follicle, pancreas, and skeletal muscle-derived cells, we
will move these adult stem cell types into a phase of development that may allow
more faithful prediction of the beginning of the era of adult stem cell-based
Michael Cook. "To clone or not to clone." MercatorNet
This article reprinted with permission from the author, Michael
Michael Cook is
the editor of MercatorNet, a new web magazine. He also edits a newsletter on developments
in bioethics and writes on bioethical issues for Australian and American newspapers
and magazines. He lives in Melbourne.
Copyright © 2005 MercatorNet