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Animal-Human Hybrids Spark Controversy
http://news.nationalgeographic.com/news/2005/01/0125_050125_chimeras_2.html
 Animal-Human
Hybrids Spark Controversy
Maryann Mott
National Geographic News
January 25, 2005
Scientists have begun blurring the line between
human and animal by producing chimeras—a
hybrid creature that's part human, part animal.
Chinese scientists at the Shanghai Second Medical
University in 2003 successfully fused human cells
with rabbit eggs. The embryos were reportedly
the first human-animal chimeras successfully created.
They were allowed to develop for several days
in a laboratory dish before the scientists destroyed
the embryos to harvest their stem cells.
In Minnesota last year researchers at the Mayo
Clinic created pigs with human blood flowing through
their bodies.
And at Stanford University in California an experiment
might be done later this year to create mice with
human brains.
Scientists feel that, the more humanlike the animal,
the better research model it makes for testing
drugs or possibly growing "spare parts,"
such as livers, to transplant into humans.
Watching how human cells mature and interact in
a living creature may also lead to the discoveries
of new medical treatments.
But creating human-animal chimeras—named
after a monster in Greek mythology that had a
lion's head, goat's body, and serpent's tail—has
raised troubling questions: What new subhuman
combination should be produced and for what purpose?
At what point would it be considered human? And
what rights, if any, should it have?
There are currently no U.S. federal laws that
address these issues.
Ethical Guidelines
The National Academy of Sciences, which advises
the U.S. government, has been studying the issue.
In March it plans to present voluntary ethical
guidelines for researchers.
A chimera is a mixture of two or more species
in one body. Not all are considered troubling,
though.
For example, faulty human heart valves are routinely
replaced with ones taken from cows and pigs. The
surgery—which makes the recipient a human-animal
chimera—is widely accepted. And for years
scientists have added human genes to bacteria
and farm animals.
What's caused the uproar is the mixing of human
stem cells with embryonic animals to create new
species.
Biotechnology activist Jeremy Rifkin is opposed
to crossing species boundaries, because he believes
animals have the right to exist without being
tampered with or crossed with another species.
He concedes that these studies would lead to some
medical breakthroughs. Still, they should not
be done.
"There are other ways to advance medicine
and human health besides going out into the strange,
brave new world of chimeric animals," Rifkin
said, adding that sophisticated computer models
can substitute for experimentation on live animals.
"One doesn't have to be religious or into
animal rights to think this doesn't make sense,"
he continued. "It's the scientists who want
to do this. They've now gone over the edge into
the pathological domain."
David Magnus, director of the Stanford Center
for Biomedical Ethics at Stanford University,
believes the real worry is whether or not chimeras
will be put to uses that are problematic, risky,
or dangerous.
Human Born to Mice Parents?
For example, an experiment that would raise concerns,
he said, is genetically engineering mice to produce
human sperm and eggs, then doing in vitro fertilization
to produce a child whose parents are a pair of
mice.
"Most people would find that problematic,"
Magnus said, "but those uses are bizarre
and not, to the best of my knowledge, anything
that anybody is remotely contemplating. Most uses
of chimeras are actually much more relevant to
practical concerns."
Last year Canada passed the Assisted Human Reproduction
Act, which bans chimeras. Specifically, it prohibits
transferring a nonhuman cell into a human embryo
and putting human cells into a nonhuman embryo.
Cynthia Cohen is a member of Canada's Stem Cell
Oversight Committee, which oversees research protocols
to ensure they are in accordance with the new
guidelines.
She believes a ban should also be put into place
in the U.S.
Creating chimeras, she said, by mixing human and
animal gametes (sperms and eggs) or transferring
reproductive cells, diminishes human dignity.
"It would deny that there is something distinctive
and valuable about human beings that ought to
be honored and protected," said Cohen, who
is also the senior research fellow at Georgetown
University's Kennedy Institute of Ethics in Washington,
D.C.
But, she noted, the wording on such a ban needs
to be developed carefully. It shouldn't outlaw
ethical and legitimate experiments—such
as transferring a limited number of adult human
stem cells into animal embryos in order to learn
how they proliferate and grow during the prenatal
period.
Irv Weissman, director of Stanford University's
Institute of Cancer/
Stem Cell Biology and Medicine in California,
is against a ban in the United States.
"Anybody who puts their own moral guidance
in the way of this biomedical science, where they
want to impose their will—not just be part
of an argument—if that leads to a ban or
moratorium. … they are stopping research
that would save human lives," he said.
Mice With Human Brains
Weissman has already created mice with brains
that are about one percent human.
Later this year he may conduct another experiment
where the mice have 100 percent human brains.
This would be done, he said, by injecting human
neurons into the brains of embryonic mice.
Before being born, the mice would be killed and
dissected to see if the architecture of a human
brain had formed. If it did, he'd look for traces
of human cognitive behavior.
Weissman said he's not a mad scientist trying
to create a human in an animal body. He hopes
the experiment leads to a better understanding
of how the brain works, which would be useful
in treating diseases like Alzheimer's or Parkinson's
disease.
The test has not yet begun. Weissman is waiting
to read the National Academy's report, due out
in March.
William Cheshire, associate professor of neurology
at the Mayo Clinic's Jacksonville, Florida, branch,
feels that combining human and animal neurons
is problematic.
"This is unexplored biologic territory,"
he said. "Whatever moral threshold of human
neural development we might choose to set as the
limit for such an experiment, there would be a
considerable risk of exceeding that limit before
it could be recognized."
Cheshire supports research that combines human
and animal cells to study cellular function. As
an undergraduate he participated in research that
fused human and mouse cells.
But where he draws the ethical line is on research
that would destroy a human embryo to obtain cells,
or research that would create an organism that
is partly human and partly animal.
"We must be cautious not to violate the integrity
of humanity or of animal life over which we have
a stewardship responsibility," said Cheshire,
a member of Christian Medical and Dental Associations.
"Research projects that create human-animal
chimeras risk disturbing fragile ecosystems, endanger
health, and affront species integrity."
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