Structures involved in Parkinson's disease. Basal ganglia affect movement;
substantia nigra produces the neurotransmitter dopamine, which sends messages
that control muscles. The globus pallidus is part of a larger structure
connected to the substantia nigra affecting movement, balance and walking.
The thalamus is a relay station for brain impulses, and the cerebellum
affects muscle coordination.
FDA.
Eliezer Masliah, of the University of California, San Diego got a grant
from the Michael J. Fox Foundation to research a cure for Parkinson's
disease, a debilitating neurological disorder that affects 1.5 million
Americans.
© UCSD
Health Sciences Communications.
If reproductive cloning has few friends -- aside from some renegade scientists and cultists who insist they'll use it to help infertile couples -- a related technology poses much tougher ethical questions.
Therapeutic cloning does not strive to make whole humans. Instead, it makes embryos as a source of embryonic stem cells for therapeutic purposes. Because embryonic stem cells can grow into any body cell, they might be cultured into nerve cells, skin cells, even hair follicles for the bald. The obvious use of therapeutic cloning would be treating deadly diseases like diabetes and Parkinson's, where a specific type of cell has died. It's a good bet that replacing those cells would restore health.
Therapeutic cloning research would end in this country, however, if restrictive
legislation passes the Senate. Sen. Sam Brownback, for example, writes that "The prospect of creating
new human life solely to be exploited and destroyed in this way has been
condemned on moral grounds by many as displaying a profound disrespect
for life."
But society is already willing to tolerate the death of lab-created embryos during in-vitro fertilization, says medical ethicist Dan Wikler. "Anyone who would says we should not embark on this kind of therapeutic cloning would, on pain of inconsistency, be opposed to routine IVF, where embryo are created in advance, with big chance of being destroyed as surplus."
Wikler maintains that the quest to save existing lives deserves moral standing. "Anyone who would says that the chance to save a life through therapeutic cloning is wrong, would have to explain why they have not been upset by the practices that go on under IVF, which is basically the same thing."
The middle ground?
But is therapeutic cloning so close to fruition as to require immediate human research?
No, says Alexander Capron, professor of law and medicine at the University of Southern California. He favors a "temporary moratorium" on cloning research, on the grounds that the potential benefits don't measure up to the risks, at least right now.
Even
if therapeutic cloning did not lead to reproductive cloning (which he
also opposes), he says therapeutic cloning research should be opposed
"on the grounds of the risk of misuse." Fertility clinics, which use IVF
to create babies, have been charged with such abuses as selling embryos
without the approval of their biological parents.
If, as it presumably would, therapeutic cloning increased knowledge of how to do reproductive cloning, the potential for abuse is just too great, he says.
Were that risk counterbalanced by a convincing case that therapeutic cloning research is necessary for curing disease, he might favor further research, but he does not think that argument has been made. "At the moment, I think delay has a very small price," Capron says.
Answers wanted
Capron says several issues must be resolved before therapeutic cloning research
becomes necessary.
What is causing the disease? Therapies depending on
cells or tissues derived from embryonic stem cells, Capron says, "Require
us to understand what is the cause of the underlying disease." Diseases
like juvenile diabetes are caused by immune attack, and he thinks adding
new cells would probably not "make a difference because they will be attacked
too," (see "Doctors Advance" in the bibliography).
However, notes Green, many diseases that might be treated with stem cells,
like burns, heart attacks, don't involve immune attack. " Most illness
or disease is caused by cell death, and this truly a promising research
direction," he says.
How do we program stem cells? To create tissues (like muscle for an ailing heart)
or organs (a kidney) in the lab and transplant them whole, Capron says, "You need to do a
lot of work on how you signal cells to differentiate and grow in normal fashion. None of that
work requires cloned embryos, it all can be done with existing or newly created cell lines."
How do we control stem cells? Stem-cell therapy also requires that embryonic
stem cells be taught to behave correctly -- to reach the proper part of the body and
assume the proper, mature form. While there is some indication that stem cells are
influenced by surrounding tissue to assume the correct role, that remains unproven,
Capron says.
More hurdles
Were therapeutic cloning to emerge as the most promising
line of therapy, Capron says he would reconsider his opposition. But therapeutic
cloning has another potential drawback: if you get your own cells back
in an attempt to repair a disease with genetic roots, you would only be
restoring the same disease.
Capron
also argues that existing lines of embryonic stem cells might have an
advantage over those custom-designed through therapeutic cloning, since
they would be available faster. And while therapeutic cloned embryonic
stem cells would be tailored to the patient's immune system, they would
be much more expensive.
Until these questions are answered (a project that many scientists say requires further research into therapeutic cloning), Capron maintains that some pro-cloning forces are overstating their case. "The kind of suggestion that Michael West [CEO of Advanced Cell Technology] has made in Congressional testimony, that any delay in making or attempting to make cloned human embryos, in effect puts the weight of tens or hundreds of thousands of deaths on the shoulders of the people who are causing the delay, is either hyperbole or some form of salesmanship, or is a dreadful slander."
Dolly's getting old, he said sheepishly.
There are 1 2
3 4 5 pages
in this feature.
Bibliography | Credits
| Feedback | Search
©2002, University of Wisconsin, Board of Regents.