Scientists clone human embryos from eggs matured in laboratory

COPENHAGEN, Denmark – Scientists have cloned human embryos for the first time using eggs matured in a laboratory – 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 are a genetic match for injured or sick patients.

The goal of such therapeutic cloning is not to create babies but to extract stem cells, which are created in the earliest days after conception and give rise to the human body. Scientists hope to use the cells as replacement parts for diseased and injured organs. Cells taken from cloned embryos would be a genetic match and theoretically avoid transplant rejection problems.

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.

Until now, scientists have only used mature eggs to create cloned embryos, but if immature eggs work too, the egg supply problem may be significantly eased, said Josiane Van der Elst, who conducted the research at Ghent University in Belgium.

About 10 percent of eggs retrieved from women during infertility treatment are immature. Scientists have matured eggs in a lab before and have reported pregnancies from such eggs, but that is rare, and immature eggs are usually discarded.

“As a concept, the idea is great, but unfortunately I think the real capability is limited,” said Dr. Gianpiero Palermo, an embryology expert who was not connected with the research.