Human Embryo Cloned From Immature Eggs

This undated microscopic photo shows eight cloned embryos that are currently in the eight-cell stage each, released by Seoul National University in Seoul Thursday, Feb. 12, 2004. Researchers in South Korea for the first time have cloned a human embryo and then culled stem cells from it, marking an important step toward one day growing patients' own replacement tissue to treat diseases. The reports appears in Friday's edition of Science magazine. (AP Photo/Seoul National University)

COPENHAGEN, Denmark (AP) _ Scientists have cloned human embryos for the first time using unripe eggs matured in a dish _ a technique that may help cloning become a viable option for growing patients' own replacement tissue to treat diseases.

The experiment, outlined Monday at the annual conference of the European Society of Human Reproduction and Embryology, brings the Belgians to the forefront of human cloning aimed at producing stem cells that would be a genetic match for injured or sick patients.

South Korean scientists last year were the first to clone a human embryo. Last month, the same group achieved another major advance, creating cloned embryos from nine patients and extracting stem cells from them.

Until now, scientists investigating human cloning for medical purposes have been limited to using mature eggs. Some experts have said cloning may not become a practical approach for creating tailor-made stem cells because it requires huge numbers of eggs. There aren't enough mature eggs left over from infertility treatments to meet that need, which means scores of women would have to be willing to donate them.

However, up to 15 percent of eggs retrieved from women for infertility treatment are unripe and not used. If those can be used for cloning, the egg supply problem may be significantly eased, said Josiane Van der Elst, who conducted the research at Ghent University in Belgium.