Scientists Claim an Advance in Therapeutic Cloning
Mass. Firm Uses Embryonic Cow Cells to Create Kidney-Like Organs; Transplant Success
Reported
By Rick Weiss
Washington Post Staff Writer
Wednesday, January 30, 2002; Page A04
Scientists in Massachusetts said they have used cells derived from cloned cow embryos to grow
kidney-like organs that function and are not rejected when implanted into adult cows, marking
the first use of cloning technology to grow personalized, genetically matched organs for
transplantation.
The research, described in an interview yesterday by the scientist who led the work, has not
been published in a scientific journal or confirmed by others. And although the organs can
apparently remove toxins from the body and produce urine, it's not known whether they can
perform all of the many jobs for which kidneys are responsible.
But if the approach can be used to make human kidneys from cloned human embryos, as the
Massachusetts team expects, it could dramatically reduce the need for donor kidneys and
transplants in the future, experts said.
More immediately, the findings could influence the bioethics debate in Washington as the Senate
considers legislation that would ban the kind of cloning research that led the scientists to create
the new organs.
Some people consider research on human embryo clones inherently unethical and have been
calling for a federal ban on such work. But others believe that such objections might be
outweighed if the research were shown to be the most promising means of growing compatible
replacement tissues.
While the work remains preliminary -- and some scientists suspect that less ethically contentious
cells from adults may have the same potential as embryo cells -- the cow study is the first to
indicate that cells taken from a newly created clone can be made to grow and work together as
an apparently functioning organ and coexist with the body's immune system as scientists have
predicted.
"We can say clearly that these kidneys produced urine and survived for several months inside
the cows," said Robert P. Lanza, chief scientist on the project at Advanced Cell Technology in
Worcester, Mass.
The work is "proof of principle that 'therapeutic cloning' can work," said Lanza, referring to an
experimental and still largely theoretical approach to treating degenerative diseases in which
replacement tissues would be grown for patients from embryos that were genetic clones of those
patients. Since the replacement tissues would be genetically identical to the patient, they would
not be rejected by the patient's immune system. But the approach is controversial because it
requires the production and preordained destruction of cloned human embryos.
Last year the House passed a bill that would ban both the production of cloned human babies
("reproductive cloning") and cloned human embryos for medical research ("therapeutic" or
"research" cloning). The Senate is considering whether to pass an identical bill or a more
narrowly worded one that would outlaw only reproductive cloning.
Advanced Cell Technology has been criticized in the past for publicizing its results before
submitting them for professional peer review -- something Lanza said had not been the
company's intention in this case. He answered questions about the work yesterday, he said,
because he wanted to correct errors in news reports that appeared in The Times and the Daily
Mail of London, which were first to write about the work yesterday.
At the same time, Lanza said he was reluctant to reveal many details of the work because the
team hopes to publish the new results and science journals tend not to publish results that have
already been publicly released.
Lanza said the team started by taking a single skin cell from an adult cow's ear and fusing it with
a cow's egg whose own genetic material had been removed -- a standard method for making a
cow embryo that is a clone of, and thus virtually genetically identical to, the starter cow.
Embryos contain so-called embryonic stem cells, which have the potential to turn into all kinds of
cells and tissues. In recent years, scientists working with mouse, human and monkey embryos
have cultivated these cells in laboratory dishes and learned how to get them to morph into
whatever kind of specialized cell they want -- heart cells that may be used to repair hearts, for
example.
Scientists have not gained that kind of power over cow stem cells yet. So in the latest
experiments the team grew the cloned embryos to an early fetal stage, at which point they were
able to identify immature cells starting to turn into kidney cells.
Working with Anthony Atala at Children's Hospital in Boston, they seeded some of those
immature renal cells onto a sponge-like, two-inch-long biocompatible scaffolding. As the cells
matured and colonized that structure, the mass came to resemble -- and function like -- a
miniature kidney.
The team implanted several of the mini-organs under the skin of the cow that donated the ear
cell. (Lanza would not reveal how many kidneys were made or cows used). The organs obtained
nutrients from surrounding blood vessels. And the kidneys produced urine, which drained into
small synthetic bags, or bladders, the scientists had attached to the kidneys under the skin.
By contrast, a second experiment -- in which similar kidneys were made from fetal cells not
derived from clones -- failed, perhaps because those organs were rejected by the recipient cow's
body.
That finding, Lanza said, supports the idea that an organ made from a person's own cloned
embryo would work better than one from someone else. And since scientists are getting good at
making renal cells from stem cells retrieved from early embryos, he said, there should be no
need to grow the human embryo clones to the fetal stage, as was done with the cow work.
John Gearhart, a stem cell expert at Johns Hopkins University, said the results sounded
promising. But he said the work's relevance to the human cloning and stem cell debate would
depend on the maturity of the fetal kidney cells used in the cow study. It will be important to
prove that kidneys can be made from human embryo cells, not just from older fetal cells,
Gearhart said, because even proponents of human embryo cell research do not favor growing
human fetuses for research.
Leaders of two groups leading the opposition to human embryonic cell research could not be
reached yesterday evening for comment.
© 2002 The Washington Post Company
|
|
