South Koreans Streamline Cloning of Human Embryos

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South Koreans Streamline Cloning of Human Embryos

 

 

 

 

By GINA KOLATA

 

Published: May 19, 2005

 

In what scientists say is a stunning leap forward, a team of South

Korean researchers has developed a highly efficient recipe for producing

human embryos by cloning and then extracting their stem cells.

 

Writing today in the journal Science, they report that they used their

method to produce 11 human stem cells lines that are genetic matches of

11 patients aged 2 to 56.

 

Previously, the same group, led by Dr. Woo Suk Hwang and Dr. Shin Yong

Moon of Seoul National University, produced a single stem cell line from

a cloned embryo, but the process was so onerous that scientists said it

was not worth trying to repeat it, and some doubted the South Koreans'

report was even correct.

 

Now things have changed.

 

" It is a tremendous advance, " said Dr. Leonard Zon, a stem cell

researcher at Harvard Medical School and president of the International

Society for Stem Cell Research, who was not involved in the research.

 

The method, called therapeutic cloning, is one of the great hopes of the

stem cell field. It produces stem cells, universal cells that are

extracted from embryos, killing the embryos in the process, and, in

theory, can be directed to grow into any of the body's cell types. And

since the stem cells come from embryos that are clones of individuals,

they should be exact genetic matches. Scientists want to obtain such

stem cells from patients to study the origin of diseases and to develop

replacement cells that would be identical to ones a patient has lost.

 

Dr. Zon cautioned that " it will take a lot of work " before stem cells

fulfill those promises, but said the new finding would bring scientists

significantly closer to the goals.

 

" It will spearhead the effort, for sure, " Dr. Zon said.

 

Until now, scientists have been studying human embryonic stem cells they

extracted from embryos that were created for that purpose or from

embryos created at fertility clinics and donated by couples who no

longer needed them. They also are studying mouse stem cells, working on

the extraordinarily difficult task of directing them to develop into

specific tissue types.

 

But researchers wanted embryos that were genetic matches of patients.

The only way to do that is to use embryos that were clones of patients.

And human cloning had seemed all but impossible.

 

To produce a clone, scientists slip the genetic material from a

patient's cell into an unfertilized egg from another person whose

genetic material has been removed. The genes from the patient's cell

take over, directing the egg to divide and develop into an embryo that

is genetically identical to the patient, rather than the egg donor.

About five days later, when the cloned embryo contains about 100 cells,

stem cells appear, looking like a ball of cells encased in a sphere.

 

The process, however, fails more often than it succeeds and in humans it

seemed to fail almost all the time. In their previous report, published

in February, Dr. Hwang and Dr. Moon used 248 human eggs to produce a

single stem cell line.

 

But this time, with a handful of technical improvements that mostly

involved such things as methods for growing cells and breaking open

embryos, they used an average of 17 eggs per stem cell line and could

almost guarantee success with a single woman's eggs obtained in a single

month. And it did not matter if the patient whose cells were being

cloned was young or middle aged, male or female, sick or well - the

process worked.

 

" You almost have no reason not to do it, " said Dr. Davor Solter, the

director of the Max Planck Institute for Immunobiology in Freiberg,

Germany.

 

In fact, Dr. Solter added, it now looks like it is much more efficient

to clone and obtain human stem cells than it is to do the same

experiment in animals.

 

Seven states ban cloning for any reason and 11 have laws that prevent

embryonic stem cell research, said Lori B. Andrews, a law professor at

Chicago-Kent College of Law. And the federal government will not pay for

the creation of new stem cell lines. But where such work is legal,

increasing numbers of scientists, including Dr. Zon, say they have

private financing and plan to go forward using cloning to produce stem

cells.

 

The new paper, said Dr. John Gearhart, a stem cell researcher at Johns

Hopkins University, will provide an impetus. " I think you will see more

people in the game, " he said.

 

But not everyone is excited.

 

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