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For the first time, scientists
have derived embryonic stem cells from a primate without fertilizing the
female egg -- raising the possibility that human stem cells could be created
without destroying viable human embryos.
This is because the monkey
embryos in this case were created through a process called parthenogenesis,
in which an unfertilized egg is coaxed into becoming an early embryo.
Unlike the human embryos that have been used for stem cell research, embryos
created in this manner cannot become a viable fetus.
The technique has been used
before in primates, but until now scientists have not been able to derive
stem cells lines from the resulting embryo.
Because stem cells can potentially
differentiate into any type of body tissue, scientists believe they
can be used to replace the diseased cells that mark conditions such as
Alzheimer's disease, Parkinson's, heart disease and diabetes.
But as the stem cells used
in research are usually derived from embryos, which are destroyed in the
process, controversy has surrounded stem cell research. In the US, federal
funds can only go toward research on existing human stem cell lines, and
not work in which an embryo will be destroyed.
For those who are concerned
about the ethics of destroying potentially viable embryos, parthenogenesis
could be an attractive approach to obtaining stem cells.
It is possible that, in the future, advances in parthenogenesis and in
getting stem cells from adult tissue could "wipe out" the debate
over embryonic stem cell research.
The principle that parthenogenesis
could also work in humans has already been demonstrated. Collaborators
on this work from the Massachusetts-based biotech firm Advanced Cell Technology
(ACT) reported last November that they had induced human eggs to develop
into early embryos. No stem cells were produced.
But that part of their work
was overshadowed by news that they had also cloned the first human embryo.
This was achieved through a process called somatic cell nuclear transfer,
in which the nucleus of an egg is replaced with that of a cell from a
donor's body. When an early embryo results, it is a genetic match to the
donor.
When the aim of such cloning
is to produce stem cells that match the donor -- and not a cloned human
being -- it is called therapeutic cloning. If stem cells are to be useful
in treating disease, many experts believe that they will have to be generated
through therapeutic cloning to avoid rejection. But therapeutic cloning
also creates a potentially viable early embryo that must be destroyed
to get the stem cells.
Parthenogenesis might offer
another option in harvesting genetically matched stem cells for patients,
according to the current report.
Science February 1, 2002;295:819
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