Scientists have moved a step closer to the goal of creating stem cells perfectly matched to a patient's DNA in order to treat diseases, they announced on Thursday, creating patient-specific cell lines out of the skin cells of two adult men.

The advance, described online in the journal Cell Stem Cell, is the first time researchers have achieved "therapeutic cloning" of adults. Technically called somatic-cell nuclear transfer, therapeutic cloning means producing embryonic cells genetically identical to a donor, usually for the purpose of using those cells to treat disease.

But nuclear transfer is also the first step in reproductive cloning, or producing a genetic duplicate of someone - a technique that has sparked controversy since the 1997 announcement that it was used to create Dolly, the clone of a ewe. In 2005, the United Nations called on countries to ban it, and the United States prohibits the use of federal funds for either reproductive or therapeutic cloning.

The new study was funded by a foundation and the South Korean government.

If confirmed by other labs, it could prove significant because many illnesses that might one day be treated with stem cells, such as heart failure and vision loss, primarily affect adults. Patient-specific stem cells would have to be created from older cells, not infant or fetal ones. That now looks possible, though far from easy: Out of 39 tries, the scientists created stem cells only once for each donor.

Outside experts had different views of the study, which was led by Young Gie Chung of the Research Institute for Stem Cell Research at CHA Health Systems in Los Angeles.

Stem cell biologist George Daley of the Harvard Stem Cell Institute called it "an incremental advance" and "not earth-shattering."

Reproductive biologist Shoukhrat Mitalipov of Oregon Health and Science University, who developed the technique the CHA team adapted, was more positive. "The advance here is showing that (nuclear transfer) looks like it will work with people of all ages," he said in an interview.

A year ago, Mitalipov led the team that used nuclear transfer of fetal and infant DNA to produce stem cells, the first time that had been accomplished in humans of any age.

ELECTRIC JOLT

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In a cloning first, scientists create stem cells from ...