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Koreans Say They Cloned Embryos for Stem Cells

Each egg had its own DNA removed and then was fused to a single skin cell taken from one of 11 patients. The patients, ages 2 to 56, had either a spinal cord injury, diabetes or an inborn disease of the immune system.

Of those 185 treated eggs, 31 grew into early embryos in laboratory dishes. The team was able to extract stem cells from 11 of them. Each of the resulting colonies of stem cells is a genetic and immunological match to the patient who supplied the original skin cell.

The overall efficiency was 11 self-perpetuating colonies -- or cell lines -- from 185 eggs, or about one cell line for every 17 eggs. But the procedure was even more efficient with eggs from the youngest donors. For eggs retrieved from women under age 30, one cell line was obtained for every 14 eggs.

In another major advance, the Koreans said they are cultivating the stem cell lines in dishes without any animal cells. Virtually all other human embryonic stem cell lines to date have been grown for at least a while on mouse cells, which secrete a cocktail of hormones that support the growth of finicky stem cells.

By growing the stem cells on a bed of human support cells instead of mouse cells, the team does not have to worry that animal viruses or other contaminants may prevent transplantation of the stem cells, or tissue grown from them, into patients -- the ultimate goal.

"We want to find a way to cure devastating diseases, and one of the big points of our research is patients [now] have immune-matched, cloned, embryonic stem cells," Hwang said in a telephone interview.

The team is now working to transform the cells into various kinds of tissues -- a process at which scientists are becoming increasingly adept -- but has no current plans to put them into patients, Hwang said.

Several experts said they were extremely impressed and predicted that the first therapeutic cloning treatment would come more quickly than they had imagined.

"They have increased the efficiency tenfold over what their paper was a year ago, and this is very important," said John Gearhart, a stem cell researcher at Johns Hopkins University. "It's kind of remarkable. It tells you how quickly things are moving."

Judy Norsigian of the Boston Women's Health Book Collective, who supports stem cell research but has warned against therapeutic cloning's potential to exploit egg donors, said she was relieved that the process would need fewer eggs but still had concerns because the ovarian stimulation used to mass-produce the eggs can lead to complications.

"Young women would still be providing eggs to treat men, children and older women. We need to make sure that those women aren't put at unnecessary risk," she said.

Others voiced greater concerns.

"You're placing the woman at risk to create an embryo that has a 100 percent risk of death, to attempt to treat patients who themselves will face significant risks," said Richard Doerflinger, deputy director of the Secretariat for Pro-Life Activities of the U.S. Conference of Catholic Bishops.

"To say something was initially impossible but is now possible is not enough," Doerflinger said. "We have to make moral decisions about whether we should do this."

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