Stem cells, with ethics
By Nicholas Wade The New York Times
SUNDAY, OCTOBER 16, 2005
NEW YORK In a development that may shift the political debate over
embryonic stem cells, researchers have devised two new techniques designed to
alleviate ethical concerns.
In one, the cells are derived without the need to destroy an embryo, the
principal objection of anti-abortion advocates who have strenuously opposed
federal financing of the research.
The other technique makes a skin cell revert to the embryonic state in a
way that prevents the embryo from implanting in the uterus.
Both techniques, described in the online edition of Nature, have been
developed in mice and have yet to be adapted to people, but the two species are
very similar at this level of embryonic development.
"This gets around all of the ethical arguments except for that small
minority of the pro-life community that doesn't even support in vitro
fertilization," said Representative Roscoe Bartlett, Republican of Maryland, an
abortion opponent, referring to the first technique.
Until now the only way of deriving human embryonic stem cells has been to
break open the embryo before it implants in the uterus, a stage at which it is
called a blastocyst, and take out the inner cell mass, whose cells will form
all the tissues of the future infant.
Although the blastocysts used in the procedure are ones that fertility
clinics have rejected for implantation, anti-abortion advocates say destruction
of any embryo is wrong.
Congress has forbidden the use of federal funds for any such research,
and federally supported scientists can work with only a small number of
existing lines of embryonic stem cells that have been exempted by President
George W. Bush.
Robert Lanza and colleagues at Advanced Cell Technology, a biotechnology
company in Worcester, Massachusetts, have now developed an alternative way of
generating embryonic stem cells that leaves the embryo viable.
At the eight-cell stage, reached by a fertilized mouse egg after its
third division and just before the blastocyst is formed, they removed one cell.
They then coaxed this cell, known as a blastomere, into growing in
glassware and forming cells that have all the same essential properties as
embryonic stem cells derived from the inner cell mass, Lanza's team reports.
The seven-cell embryo was implanted in the mouse uterus and grew
successfully to term. This part of the procedure is known to work with humans
too, because it is the basis of a well-established technique known as
preimplantation genetic diagnosis. In the technique, one cell is removed from
each of a set of embryos and tested for any of 150 genetic defects, giving the
parents the choice of implanting an embryo that is disease-free.
Lanza's technique is likely to be welcomed by many in the middle of the
debate, although it has not won over the United States Conference of Catholic
Bishops.
Richard Doerflinger, its deputy director for pro-life activities,
dismissed the technique, saying that preimplantation genetic diagnosis itself
was unethical. The technique "is done chiefly to select out genetically
imperfect embryos for discarding, and poses unknown risks of future harm even
to the child allowed to be born," he said in an e-mail message.
Only a procedure that generated embryonic stem cells without creating or
destroying embryos "would address the Roman Catholic Church's most fundamental
moral objection to embryonic stem cell research as now pursued," Doerflinger
told the President's Council on Bioethics last December.
Senator Sam Brownback of Kansas, a leader of anti-abortion forces, did
not return a call to his office.
Edmund Pellegrino, the new chairman of the President's Council on
Bioethics, said through a spokeswoman that he would have no comment.
But Markus Grompe, a leading stem cell scientist and a Catholic who
supports the church's teaching on the unacceptability of destroying embryos,
praised the Lanza approach, provided that the extracted blastomere could not
develop into an embryo all by itself. "I find it clearly less objectionable
than the outright destruction of the embryo," said Grompe, who studies liver
stem cells at the Oregon Health and Science University.
In response to Grompe's reservation, Lanza said that individual human
blastomeres had never been shown to create viable embryos. The reason is that
by the eight-cell stage, each blastomere is probably committed to becoming
either the outer shell of the blastocyst, which later forms the placenta, or
the inner cell mass, which forms the fetus. Only the fertilized egg and the
two-cell, and perhaps four-cell, stages retain the ability to form all the
placental and embryonic tissues, Lanza said.
If Lanza's technique works in humans, it could do more than just provide
researchers with a new source of cells. It might allow every child born through
preimplantation genetic testing to have its own line of embryonic cells banked
for the future.
The blastomere removed at the eight-cell stage could be allowed to
divide, with one cell being used for genetic testing and the other for growing
a culture of perfectly matching embryonic stem cells. The cells would be
available throughout the person's lifetime for the kind of tissue and organ
repair that it is hoped stem cells will one day provide.
With the parents' consent, these cells could also be used for research,
providing many new embryonic stem cell lines for laboratories.
The procedure might be even be offered for all embryos generated in
fertility clinics when its theoretical risk has been better assessed.
[Non-text portions of this message have been removed]
------------------------ Yahoo! Groups Sponsor --------------------~-->
Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page
http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/uTGrlB/TM
--------------------------------------------------------------------~->
Post message: [EMAIL PROTECTED]
Subscribe : [EMAIL PROTECTED]
Unsubscribe : [EMAIL PROTECTED]
List owner : [EMAIL PROTECTED]
Homepage : http://proletar.8m.com/
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/proletar/
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
