Cloning Advance, With Question Marks
Pastor Dale Morgan
Cloning Advance, With Question Marks*
By WILLIAM HATHAWAY
Courant Staff Writer
November 20, 2007
The disclosure that scientists in Oregon have cloned embryos from
monkeys a close genetic relative of mankind and harvested precious stem
cells comes at a time when scientists themselves are debating the future
of cloning.
Results of the work, released Wednesday by the journal Nature, mark the
first time a primate embryo has been cloned. The research is an
important step in the efforts of scientists to create potentially
lifesaving human embryonic cells, which can generate any tissue in the
body, from simple skin cells.
"This is one big step toward cloning a human embryo," said Xiangzhong
"Jerry" Yang, a cloning pioneer and professor at the University of
Connecticut.
However, as scientists at labs in several countries pursue controversial
human cloning projects, other researchers are making advances in
alternate and less controversial ways to create embryonic-like cells.
In the somatic cell nuclear transfer experiment announced Wednesday, the
DNA of skin cells was taken from a 9-year-old adult rhesus monkey and
fused into a monkey egg that had its own basic genetic material removed.
Two of the resulting embryos produced stem cells valued because they can
become every sort of tissue.
Such "patient-specific stem cells" are critical because they are an
exact genetic match of the DNA donor. In theory, cells from cloned human
embryos could be used without fear of rejection in transplant procedures
for a host of diseases and injuries, such as Parkinson's disease and
spinal cord injuries.
Scientists also value them because they could be used for research in a
variety of hard-to-study diseases, such as dementia and mental illness.
The method has promise, but it also has critics. Opponents of cloning
say such work is unethical because early-stage embryos must be destroyed
to obtain the stem cells.
And some scientists are also now arguing that it may not be necessary to
destroy embryos to obtain such valuable cells. Several labs in the past
two years have reported creating embryonic-like cells, in laboratory
dishes, that are exact genetic matches of animal donors.
Under a technique called nuclear reprogramming, scientists take skin
cells from mice and activate a few dormant genes that are crucial to
development of the fetus. The resulting cells appear to be able to do
many of the things embryonic cells do without destroying an embryo.
Yang acknowledges that the technique is very promising, but he also said
that many obstacles need to be overcome before reprogramming can create
human cells that can be used in therapy.
"The bottom line is that for treatment of human disease, [cloning] is
really the closest to creating cures for disease," Yang said.
Although many animal species have been cloned Yang made headlines in
1999 when he cloned a cow primates posed so many problems that a few
biologists suggested that it might be impossible to clone any primate,
including humans.
That view gained support when assertions by a South Korean researcher in
2004 that he had cloned a human embryo proved to be fraudulent.
But the researchers at the Oregon Primate Research Center in Portland,
led by Shoukhrat Mitalipov, overcame some of the technical problems in
cloning primates by using imaging technology that enabled them to
inflict less damage on the monkey egg while removing its nucleus.
Previously, only cloned mice had been used to produce stem cells.
As a result of the South Korean controversy, a second group of
scientists reviewed the results of the Oregon group and confirmed that
two new lines of stem cells were, indeed, created from skin cells taken
from the 9-year-old monkey.
Still, it took more than 300 eggs from 14 monkeys to create the two cell
lines. In human terms, that means at least 20 women would have to donate
eggs to ensure the creation of a line of embryonic cells, Yang estimated.
Until primate cloning efficiency improves, it will be hard to find women
who are willing to donate eggs for research, and human embryo cloning
will remain impractical, Yang said. However, he also noted that
efficiency in creating embryos has improved dramatically in all animals
cloned so far.
Yang, who is on indefinite leave while battling cancer, has suspended
his own efforts to clone a human embryo and is helping students to
develop animal models of cloning for stem cells. However, other
laboratories around the world, including labs in his native China, are
continuing the effort.