- U.S. NEWS
- Updated May 15, 2013, 9:40 p.m. ET
Experiment Brings Human Cloning One Step Closer
By GAUTAM NAIK
Scientists have used cloning technology to transform human skin cells
into embryonic stem cells, an experiment that may revive the controversy over
human cloning. WSJ�s Gautam Naik reports. Photo: OHSU
Scientists have used cloning
technology to transform human skin cells into embryonic stem cells, an
experiment that may revive the controversy over human cloning.
The researchers stopped well
short of creating a human clone. But they showed, for the first time, that it is
possible to create cloned embryonic stem cells that are genetically identical to
the person from whom they are derived.
These stem cells could go on to
differentiate into heart, nerve, muscle, bone and all the other tissue types
that make up a human body.
Since the birth of Dolly the
sheep in 1996, researchers have cloned about 20 species, including rabbits,
goats, cows and cats. Yet they have been unable to create biologically identical
copies of any monkey or primate, including humans, possibly because their
reproductive biology is more complicated.
But the refinements described
Wednesday in the latest experiment suggest that "it's a matter of time before
they produce a cloned monkey," said Jose Cibelli, a cloning expert at Michigan
State University, who wasn't involved in the study. It also means, he added,
"that they are one step closer to where the efficiency is high enough that
someone is willing to try" to clone a person, though that remains a distant�and
to some, disturbing�prospect.
The experiment was published
online in the journal Cell. It was funded by Oregon Health and Science
University and a grant from Leducq Foundation of France.
Oregon
Health & Science University
Stem
cell colony developed through cloning.
The researchers weren't simply
trying to reach a cloning milestone. Instead, they were looking for a better way
to make fresh human tissue for the treatment of severe injuries or disease.
Lab-grown tissue has the potential to transform medicine, though it is still a
long way from routine clinical use. For example, fresh nerve cells could
alleviate spinal-cord injuries, or newly made heart cells could repair a site
scarred by a heart attack.
One way to harvest fresh tissue
is from human embryos. That is controversial because the embryos get destroyed
in the process. Another way is to reprogram mature cells into an embryonic-like
state, which can then be turned into other tissues of the body. But this method
is relatively new and has yet to yield consistent results.
A third approach is to use
cloning, as described in the Cell paper. This technique can yield fresh tissue
that is an exact genetic match for the patient for whom it is
intended.
The scientists first removed the
DNA from an unfertilized human egg, and then inserted a patient's mature skin
cell�containing the patient's DNA�into that egg. Next, they prompted a chemical
reaction, causing the cells to fuse and begin development.
That led to a blastocyst, a
hollow ball of 50 to 100 cells. For a fetus to form, the blastocyst must be
implanted in a womb. An inner clump of cells in the blastocyst goes on to form
the embryo, while an outer layer goes on to make the placenta.
For the tissue-growing
experiment, the researchers focused on the clump of cells containing embryonic
stem cells.
With the help of certain "growth"
chemicals, they were able to transform the stem cells into "various cell lines
and tissues, including beating human heart cells," said Shoukhrat Mitalipov, a
developmental biologist at Oregon Health and Science University in Portland,
Ore., and a lead author of the study.
The achievement is a long way
from creating a cloned human embryo. Even if the entire blastocyst had been
implanted into a womb, it wouldn't have yielded a human clone. The blastocyst
was "missing a few cell types that it would need to implant" and was suffering
other deficiencies, said Dr. Mitalipov.
Never mind the prospect of cloned
humans; despite years of experiments, scientists have failed to clone
monkeys.
Dr. Mitalipov said his lab had
tried transplanting entire blastocysts into a monkey's womb, but those
experiments hadn't yielded a single successful pregnancy.
"We don't know why this is," said
Dr. Mitalipov. "You can make embryonic stem cells, but it doesn't mean the
embryo will implant."
He speculates that one reason why
it may be more difficult to clone monkeys and humans is because the egg cells
are more fragile than those of other species.
Dr. Mitalipov's main goal is to
use cloning to treat illnesses. He next plans to use lab-made tissue and see if
he can successfully treat a degenerative, blindness-causing eye disease in
monkeys.
Write to Gautam Naik at gautam.naik@wsj.com
A version of this article appeared May 15, 2013, on page A2 in
the U.S. edition of The Wall Street Journal, with the headline: Experiment
Brings Human Cloning One Step Closer.
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