- NEW HAVEN, Conn. (AP) - At a top-secret farm hidden in the Northeast, scientists
are growing pigs whose DNA has been altered with human genes.
-
- It sounds like the stuff of science fiction,
yet officials at Alexion Pharmaceuticals Inc. say they are close to figuring
out how these pigs can figure in the treatment of human organ failures,
spinal cord injuries and illnesses such as Parkinson's disease.
-
- The idea of transplanting animal parts
to humans, called xenotransplantation, isn't new. But, until recently,
nobody knew how to keep the human body from rejecting the organs.
-
- About 18,000 organ transplants are performed
in the United States each year and more than 40,000 patients are waiting
for donor organs, according to the http://www.unos.org/frame_Default.asp
United Network for Organ Sharing. About 10 Americans die each day waiting
for transplants, network officials say.
-
- Alexion's first altered pigs, created
with the help of researchers at Virginia Tech in the early 1990s, contained
a human gene called CD-59. Scientists hoped the grafted gene would trick
the human body's immune system into believing that the pig parts were human.
-
- While transplanted organs from those
pigs were able to survive for a couple of days in their new host, the body
eventually rejected the parts.
-
- A major breakthrough came last year when
the small biotechnology firm, working with scientists in Australia, figured
out a way to alter a sugar-like molecule in pig cells so that human antibodies
would not recognize it as foreign.
-
- The molecule had been acting as a magnet
for human antibodies, betraying the fact that the transplanted tissue was
not human. Alexion quickly patented the process.
-
- ``If you now take cells from those animals
and challenge them with human serum, they are almost indestructible in
the lab,'' said Stephen P. Squinto, the chief technology officer at Alexion.
-
- Scientists at Alexion have already transplanted
brain cells from their transgenic pigs into rodents with a syndrome similar
to Parkinson's, a degenerative nerve condition that affects motor function.
-
- The transplanted cells not only survived,
they became neurotransmitters in the animals' brains and helped correct
the tremors, Squinto said.
-
- The same experiments are now being conducted
in baboons. If those experiments work, Alexion hopes to begin human trials
by the end of the year. Researchers hope that within 15 years humans will
be able to receive permanent organ transplants from swine.
-
- The company also has seen remarkable
results by transplanting cells from a pig's snout into the damaged spinal
columns of rodents, Squinto said. The cells replace the damaged protective
sheath around the spine and allow nerve cells to regenerate.
-
- ``Would we expect that we will be able
to take a person who is a paraplegic and have them walking or running in
the Olympics?'' Squinto said. ``No, I don't think that's the case. But
restoring some function to that person is certainly a goal.''
-
- Xenotransplantation faces stiff opposition
from some in the medical community and from animal-rights activists. Alexion
was unwilling to allow a reporter or photographer to visit their facilities,
in part because they could be targeted by animal rights protesters.
-
- Among the medical concerns: the fear
that transplanted organs could bring with them new diseases caused by viruses
now living only in pigs. A virus originally transmitted from chimpanzees
to humans is believed to have caused AIDS.
-
- Because a transplant patient's immune
system is suppressed with drugs, xenotransplantation provides an ideal
environment for pig viruses to mutate, said Dr. Thomas Murray, director
of the http://www.cwru.edu/med/bioethics/bioethics.html Center for Biomedical
Ethics at Case Western Reserve University.
-
- ``There are risks to third parties here,''
he said. ``If you get an organ from a cadaver, you decide whether to accept
that risk for yourself. But if you get an organ from a pig, many more people
are put at an unknown risk.''
-
- The FDA had temporarily banned animal-to-human
transplant experiments because of pig viruses, but dropped the ban late
in 1997. Scientists now believe they have identified all the so-called
retroviruses that are unique to pigs and can screen for them, Squinto said.
-
- Dr. David Hull, director of the clinical
transplant program at Hartford Hospital, is excited by the idea of farms
filled with transplantable organs.
-
- The technology could dramatically improve
the lives of thousands of people, many of whom can no longer even get out
of bed because their own hearts or livers are failing, he said.
-
- ``You'd be able to meet the needs of
everybody,'' he said. ``You would save a tremendous amount of money and
lives.''
-
- But animal rights activists say they
whole process is unnecessary. Rather than killing animals for organs, they
suggest everyone be considered an organ donor unless they specifically
request an exemption, the opposite of the current policy.
-
- ``That is the way to save a lot of money,
and it would save a lot of suffering,'' said Sandra Larson, with the http://www.neavs.org/
New England Anti-Vivisection Society.
|
