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Squeezing Out Monkey Clones  
By Kristen Philipkoski 

09:00 AM Dec. 06, 2004 PT

University of Pittsburgh researchers have cloned the first monkey embryos 
from which stem
cells could be removed, a feat that the very same researchers once suggested 
might be
impossible. 

While scientists have cloned sheep, pigs, cows, cats and other animals, 
cloned primates
remained elusive until South Korean researchers cloned human embryos earlier 
this year
using a new technique. 

Gerald Schatten, the lead researcher on the latest study, to be published in 
the Dec. 11
issue of Developmental Biology, wrote in April 2003 in Science that perhaps 
primates pose
a unique challenge because of a fundamental molecular obstacle. But now, 
Schatten is
delighted to have proven himself wrong. He and his colleagues did it by 
adopting the
cloning method pioneered by the South Korean scientists. 

"Having come out with a discouraging prediction," Schatten said, "we wanted 
to be among
the first, if (the Korean) methods really were a great breakthrough, to stand 
up and say,
my gosh, this really is quite impressive." 

While Schatten's group did not achieve a live clone birth, they did manage to 
grow
macaque monkey embryos to about 200 cells, the stage at which the embryo is 
called a
blastocyst and stem cells could be removed. It's the most developed monkey 
embryo anyone
has grown to date. In previous efforts, the clones died at the 16-cell stage. 


Video

Watch the video of the new technique for human DNA extraction. Embryonic stem 
cells from
monkeys could be a handy model for studying human cells, considering the 
federal
restraints on human embryonic stem-cell research funding. The researchers 
hope that by
studying monkey clones and stem cells, they'll be able to answer questions 
about how
embryonic stem cells work, and whether they can safely treat disease or 
injury. They also
believe the nonhuman primate clones could act as research models, in place of 
grown
animals. 

Researchers perform cloning, also known as somatic cell nuclear transfer, by 
starting
with an egg. They remove the nucleus of the egg, then replace the nucleus 
with a cell
from the person or animal to be cloned. They then use a cocktail of 
electricity and
chemicals to trick the clone into dividing. 

The old method involved sucking the nucleus out of the egg using a tiny 
needle. The new
and improved South Korean "squish" method forgoes the needle. Instead, the 
egg is gently
squeezed until its nucleus pops out. 

No one is certain what makes the squish method better. Schatten theorizes 
it's superior
because the squeezing is performed using more immature eggs, combined with 
the fact that
unlike the needle method, gentle squeezing doesn't strip the egg of critical 
proteins
that are necessary for later development. 

If using a younger egg is critical, that could be problematic because most 
embryonic
stem-cell researchers use older embryos that have been left behind at in vitro
fertilization clinics. 

The Pitt researchers also managed to improve upon the Korean method, which 
resulted in
one stem cell line out of 242 donor eggs and 30 blastocysts. Some scientists 
were
concerned that the technique might be limited to ovulating women, because 
when the Korean
researchers removed the nucleus of the donor egg, they replaced it with cells 
taken from
the cell surface of that same egg. 

But Schatten's group was able to use skin cells from an unrelated monkey to 
create
clones, which is good news for men and menopausal women who might one day 
need stem-cell
therapy. They did not, however, derive stem cells from any of the clones. 

Researchers believe that embryonic stem cells could provide replacement cells 
for
patients with Parkinson's disease, spinal cord injury and other ailments. And 
if the stem
cells were taken from a clone of that person, they would potentially be an 
exact
biological match, preventing immune rejection. 

But a more near-term benefit of cloning could be to create a clone of a 
person with, for
example, multiple sclerosis, extract stem cells from the clone, coax them to 
become
neurons and observe their development as they begin to exhibit signs of the 
disease. By
observing the earliest stages of the disease, researchers could find ways to 
stop it. 

Schatten's group also transferred 135 embryos into 25 surrogate monkeys, but 
achieved no
pregnancies. While cloning animals could be useful for research, most 
scientists agree
that cloning humans for reproduction should not be done. 

"Using this to derive stem cells for therapies I think is perfectly fine," 
Schatten said.
"But everything we know about cloned animals is they are all abnormal. That 
is why I'm so
unalterably opposed to any attempt at human (reproductive) cloning. It ought 
to be
illegal everywhere." 

Bills to outlaw cloning in the United State have languished for several years 
because
they also seek to ban therapeutic cloning, a prospect that legislators can't 
agree on. 

Calvin Simerly, first author on the Pitt study and associate professor of 
obstetrics,
gynecology and reproductive sciences at the University of Pittsburgh School 
of Medicine,
will present the findings on Monday at the annual American Society for Cell 
Biology
meeting in Washington, D.C.