April 29, 2005
Pedroncelli / AP
Sheep that have partially human livers, hearts, brains and other
are shown here at the
University of Nevada, in Sparks, Nev., on April 27.
On a farm about six miles outside
this gambling town, Jason Chamberlain looks over a flock of about 50
smelly sheep, many of them possessing partially human livers,
hearts, brains and other organs.
The University of Nevada-Reno researcher talks matter-of-factly
about his plans to euthanize one of the pregnant sheep in a nearby
lab. He can’t wait to examine the effects of the human cells he had
injected into the fetus’ brain about two months ago.
“It’s mice on a large scale,”
Chamberlain says with a shrug.
As strange as his work may sound, it
falls firmly within the
new 'ethics' guidelines the influential
National Academies issued this past week for stem cell research.
In fact, the Academies’ report endorses research that co-mingles
human and animal tissue as vital to ensuring that experimental drugs
and new tissue replacement therapies are safe for people.
Doctors have transplanted pig valves into human hearts for years,
and scientists have injected human cells into lab animals for even
mixing of species
But the biological co-mingling of animal and human is now evolving
into even more exotic and unsettling mixes of species, evoking the
Greek myth of the monstrous chimera, which was part lion, part goat
and part serpent.
In the past two years, scientists have created pigs with human
blood, fused rabbit eggs with
human DNA and injected human stem
cells to make paralyzed mice walk.
Particularly worrisome to some scientists are the nightmare
scenarios that could arise from the mixing of brain cells: What if a
human mind somehow got trapped inside a sheep’s head?
“The idea that human neuronal cells
might participate in 'higher order' brain functions in a
nonhuman animal, however unlikely that may be, raises concerns
that need to be considered,” the academies report warned.
In January, an informal ethics committee at Stanford University
endorsed a proposal to create mice with brains nearly completely
made of human brain cells.
Stem cell scientist Irving Weissman said
his experiment could provide unparalleled insight into how the human
brain develops and how degenerative brain diseases like Parkinson’s
We're about to see a body-language blitz: sweaty palms clasping
mouths in disbelief and - the sweetest Olympic pose - two fists
hoisted aloft in displays of golden bliss.
Scholars think body language likely
began eons ago, before language, so why do we still rely on it?
Stanford law professor Hank Greely, who chaired the ethics
committee, said the board was satisfied that the size and shape of
the mouse brain would prevent the human cells from creating any
traits of humanity. Just in case, Greely said, the committee
recommended closely monitoring the mice’s behavior and immediately
killing any that display human-like behavior.
The Academies’ report recommends that each institution involved in
stem cell research create a formal, standing committee to
specifically oversee the work, including experiments that mix human
and animal cells.
Weissman, who has already created mice with 1 percent human brain
cells, said he has no immediate plans to make mostly human mouse
brains, but wanted to get ethical clearance in any case.
Stanford committee that oversees research at the university would
also need to authorize the experiment.
human organs from sheep
Few human-animal hybrids are as advanced as the sheep created by
another stem cell scientist, Esmail Zanjani, and his team at
the University of Nevada-Reno.
They want to one day turn sheep into
living factories for human organs and tissues and along the way
create cutting-edge lab animals to more effectively test
Zanjani is most optimistic about the sheep that grow partially human
livers after human stem cells are injected into them while they are
still in the womb. Most of the adult sheep in his experiment contain
about 10 percent human liver cells, though a few have as much as 40
percent, Zanjani said.
Because the human liver regenerates, the research raises the
possibility of transplanting partial organs into people whose livers
Zanjani must first ensure no animal diseases would be passed on to
patients. He also must find an efficient way to completely separate
the human and sheep cells, a tough task because the human cells
aren’t clumped together but are rather spread throughout the sheep’s
Zanjani and other stem cell scientists defend their research and
insist they aren’t creating monsters - or anything remotely human.
“We haven’t seen them act as
anything but sheep,” Zanjani said.
Zanjani’s goals are many years from
He’s also had trouble raising funds, and the U.S. Department of
Agriculture is investigating the university over allegations made by
another researcher that the school mishandled its research sheep.
Zanjani declined to comment on that matter, and university officials
have stood by their practices.
Allegations about the proper treatment of lab animals may take on
strange new meanings as scientists work their way up the
evolutionary chart. First, human stem cells were injected into
bacteria, then mice and now sheep.
Such research blurs biological divisions
between species that couldn’t until now be breached.
monkeys and people
Drawing ethical boundaries that no research appears to have crossed
yet, the Academies recommend a prohibition on mixing human stem
cells with embryos from monkeys and other primates.
But even that policy recommendation
isn’t tough enough for some researchers.
“The boundary is going to push
further into larger animals,” New York Medical College professor
Stuart Newman said. “That’s just asking for trouble.”
Newman and anti-biotechnology activist
Jeremy Rifkin have been tracking this issue for the last
decade and were behind a rather creative assault on both
interspecies mixing and the government’s policy of patenting
individual human genes and other living matter.
Years ago, the two applied for a patent for what they called a “humanzee,”
a hypothetical - but very possible - creation that was half human
The U.S. Patent and Trademark Office finally denied their
application this year, ruling that the proposed invention was too
Constitutional prohibitions against slavery prevents the
patenting of people.
Newman and Rifkin were delighted, since they never intended to
create the creature and instead wanted to use their application to
protest what they see as science and commerce turning people into
And that’s a point, Newman warns, that stem scientists are edging
closer to every day:
“Once you are on the slope, you tend
to move down it.”