By Dan Vergano, USA TODAY
An international research team has achieved a scientific first
by producing embryonic stem cells from cloned embryos, advancing the
effort to generate replacement tissues for sick patients.
stems cells are the starter cells to all others in the body, which
means potentially they can grow into any type of tissue, from blood to
bone to brain. For a decade-and-a-half, they have been seen as a
potential source of rejection-free transplant tissues for ailments
ranging from diabetes to paralysis. They were also the subject of a
fierce political fight over the medical ethics of using human embryos in
research during the Bush administration because the embryos had to be
destroyed in the process of retrieving the embryonic cells.
have now refined the steps to come up with a process for generating
these cells that is pretty efficient," says Shoukhrat Mitalipov of
Oregon Health & Science University in Beaverton, who headed the cell
cloning study released by the journal Cell. "There
is no one trick to making this work. It is like winning the lottery, all
the numbers have to line up the right way to win."
The study team reports a number of steps perfected in monkeys
allowed them to take eggs donated by women volunteers and successfully
implant the chromosomes taken from skin cells of other people into the
eggs. They successfully start the fused egg growing and dividing to
become a human embryo. The cells of these embryos were as a result,
genetic copies, or clones, of the cells of three different people who
donated the skin cells, one of them a patient afflicted with a genetic
disorder called Leigh syndrome.
In a first, Mitalipov and
his privately funded team report that these cloned embryos were grown
past an eight-cell size (where earlier attempts had stopped) into a
full-blown early embryo, containing hundreds of embryonic stem cells.
Embryonic cells taken from these cloned embryos were grown into six
colonies of cells, the first successfully grown cloned human embryonic
stem cells. The embryos were destroyed in the cell collection process.
of the cells were successfully prompted to become more specialized
skin and heart cells. That is the next step in someday using the cells
in "regenerative" medicine, where cells cloned from a patient would be
used to grow into transplant organs to treat diseases and injuries such
"For stem cell biology, there will be history before
this result and then history after it with the study as the dividing
line," says stem cell researcher Paul Knoepfler of the University of
California, Davis. "No doubt This is a real milestone."
1998, when a University of Wisconsin team first isolated embryonic stem
cells grown from a human embryo, researchers have sought to use cloning
techniques to create such cells that would be genetic copies of ones
belonging to sick patients. The same cloning techniques, which
essentially place a new set of genes into a hollowed-out egg, and then
kick-start the combination to start dividing and become an embryo, have
been used since the cloning of "Dolly the Sheep" in 1996. That helped to
create genetic copies, twins, of animals ranging from prize bulls to an
extinct kind of wild goat. In those cases, the embryos were implanted
into a surrogate mother instead of being destroyed to harvest stem
Knoepfler warned that fertility clinic operators outside
the USA might try to replicate the team's method to try to clone a human
baby. However, Mitalipov says that his team's technique would not
likely create a cloned embryo that could be implanted into a surrogate
mother's womb and lead to a pregnancy. "The embryos we produce this way
did not lead to pregnancy in monkeys," he says. "We think there is
something in the manipulations to make them that make a successful
Attention has drifted away from these once
hotly contested embryonic stem cells since 2007, with the rise of
"induced" stem cells. Those are grown using gene alterations to regular
cells to become near-copies of embryonic stem cells, without the need
for embryos. There have also been repeated failures (in one famous case,
outright academic fraud by a South Korean researcher) to grow cell
lines from cloned human embryos, until now.
With the announcement, a race of sorts starts between those who
produce induced stem cells and cloned cells to see which type can most
safely be grown into transplant tissues, Knoepfler suggests. Hundreds of
researchers are working with induced stem cells, seeking ways to grow
them into viable transplant tissues. Two clinical trials are underway
sponsored by Advanced Cell Technology of Marlborough, Mass., that use
retinal cells grown from embryonic stem cells to treat eye disease. The
cells in those pilot trials are not cloned copies of the patient's
The real significance of the advance may be to re-ignite
debate over human cloning, says bioethicist Insoo Hyun of Case Western
Reserve University in Cleveland.
"Basically, FDA has jurisdiction
over clinical research using cloning technology to create a human
being," says the Food and Drug Administration's Curtis Allen. "To date, FDA has not licensed such a therapy."
legitimate scientists would want to use this technology for
reproductive purposes," says stem cell expert George Daley of Children's
Hospital Boston. "They would see it not only as unethical, but unsafe
and probably illegal."
Still, "This study shows that
human cloning can be done," said Richard Doerflinger of the U.S.
Conference of Catholic Bishops, which opposes research that destroys
embryos."The more important debate is whether it should be done."
points to advances in induced stem cells, created without controversy,
as a reason for leaving cloned stem cells on the shelf. "If these cells
are the answer, then what was the question," he asks.
however, points to genetic abnormalities seen in induced stem cells
that are absent from embryonic ones. He also cites the clinical trials
already approved for embryonic-derived cells that set an easier
regulatory path for them to be tested on patients, as reasons why cloned
cells might prove more useful to patients than induced stem cells in
some cases. "We would like to see other labs confirm our work as well,"
he says, noting that outside labs have already requested copies of the
cloned cells. Because of federal regulations, the cells are not eligible
for research funding from the National Institutes of Health, which now
lists 209 embryonic stem cell cell "lines" on its research funding