By Edie Lau
Bee Staff Writer
(Published Nov. 6, 1998)
Using donated surplus human embryos fertilized
in laboratories, scientists have grown
a versatile cell type that potentially can become
any part of the body.
The development of human embryonic stem cells, as
they are called, is a stride toward
custom-making tissues and organ parts to repair
damage by injury or disease, the
scientists say.
"We see it as a whole new biotechnology industry,"
said Dr. Thomas Okarma, vice
president of research and development at Geron
Corp., a Menlo Park company that
partly funded the project. The work was done at
the University of Wisconsin with Israeli
collaborators and is published in today's issue of
the journal Science.
Characteristic of the swiftly advancing field of
developmental biology, the experiment
raises ethical and legal questions.
The stem cell research was supported with private
money because U.S. law prohibits
the use of federal funds for research that
creates, injures or destroys human embryos.
Now scientists need to know whether working with
the cells themselves is also
prohibited. Legal advisers at the National
Institutes of Health are looking into it.
The research also treads on the sensitive issue of
what happens to surplus embryos from
in vitro fertilization, the procedure by which
eggs are united with sperm outside the body
in petri dishes.
The procedure often results in more embryos than
are needed to produce a pregnancy.
The rest typically are frozen, available for
another pregnancy later.
Even then, there may be extras. "It's a big
problem," said James Thomson, a
developmental biologist at the University of
Wisconsin and lead researcher on the stem
cell study. "There are a lot of embryos that are
frozen that couples don't know what to
do with. They have the families they want, and
there could be 20 more embryos sitting
there."
Thomson's team obtained embryos from clinics at
the university's school of medicine and
Rambam Medical Center in Haifa, Israel. The embryo
donors were informed of the
research and gave their written consent.
Before supporting the research, Geron Corp.
consulted a panel of ethicists. "We look
upon it as utilizing tissue that would otherwise
be discarded or frozen indefinitely -- i.e.,
denied life -- and we're using it to save and
prolong life," Okarma said.
The 5-year-old company is trying to develop drugs
to counter aging and degenerative
diseases associated with aging.
Geron is funding similar research at Johns Hopkins
University, where scientists have
derived embryonic stem cells from aborted fetuses.
Their study will be published next
week.
Researchers envision using stem cells to, for
example, grow heart cells to replace those
killed in cardiac arrest. The cells also could be
useful for testing the effects of new drugs.
Stem cells previously made in animals also have
proven to be relatively easy to
manipulate genetically.
However, scientists do not know how to make stem
cells specialize into specific organ
or tissue cells. The specialized cells that have
grown to date did so spontaneously,
Okarma said.
The quest to make embryonic stem cells dates to
the 1960s when scientists found that
certain tumor cells in mice could form a variety
of tissue types. Moreover, the cells are
seemingly immortal, capable of dividing
indefinitely.
The search for non-cancerous versions of these
cells led researchers to embryos. Since
1981, scientists have made stem cells from mice,
sheep, hamsters, pigs, rabbits and
rhesus macaques.
In the human experiment, researchers used embryos
about 6 days old. At that stage, the
embryos are an undefined ball of cells.
The scientists extracted cells that, under the
right conditions, would develop into an
entire person. Their goal was to culture the cells
in a state of suspended potential --
countering their natural tendency to differentiate
into organs and other body parts.
Of 36 embryos, 14 developed suitably for the
experiment. From those, five separate
lines of embryonic stem cells grew.
To test the cells' potency, researchers analyzed
them in a variety of ways. In the most
telling test, the cells were injected into mice
with suppressed immune systems. Tumors
grew, and in the tumors were cells similar to
those in guts, neurons, bones, cartilage,
muscles and kidneys.
The scientists stopped short of running the
definitive test used with laboratory animals:
seeing whether the cells could form an entire
organism.
Researchers using experimental animals test stem
cells by injecting them into a viable
embryo and growing the embryo to term in a
surrogate mother. If the stem cells work,
the offspring, called a chimera, has four genetic
parents -- the parents of the embryo
from which the stem cells were derived, and the
parents of the embryo in which the cells
were injected.
Scientifically, omitting this experiment is a
flaw, said Gary Anderson, an animal scientist
at the University of California, Davis, who has
made embryonic stem cells from pigs.
"They did not hold these cell types up to the same
scrutiny as what we are expected to
do with other animal species," said Anderson. But
their decision was right to not make a
human chimeric baby, "which would be so horrific,"
he said.
Ethical dilemmas posed by human embryo research
led the American Society for
Reproductive Medicine last year to set guidelines
for embryo donations. The society
supports research for purposes such as
understanding and treating disease.
"It certainly has promise," said Dr. Benjamin
Younger, executive director of the society.
Citing diabetes, Younger said, "Gee, wouldn't it
be nice to have cells back that made
insulin, and you wouldn't have diabetes any more?
Or you have a spinal cord injury and
you get cells that . . . make your spinal cord
function again?
"What's important in all this," he said, "is that
none of this is aimed at making people.
This is not a way to reproduce."
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