Ccloned Human Embryo Provides Stem Cells

Article excerpt

Scientists have for the first time used cloning to create human embryos that live long enough in a laboratory dish to have their stem cells harvested. The feat could set the stage for physicians to produce cells and tissues, tailored to a patient's genetic identity, that can treat a wide variety of human illnesses. The accomplishment also pro vides a road map for how to clone a person, an even more divisive undertaking.

The new work, performed in South Korea, represents "a major advance in stem cell research.... It could help spur a medical revolution as important as antibiotics and vaccines," says Robert Lanza of Advanced Cell Technology (ACT), a company in Worcester, Mass., that's also investigating the promising stem cell strategy dubbed therapeutic cloning.

"However, now that the methodology is publicly available," Lanza adds, "I think it is absolutely imperative that we pass laws worldwide to prevent the technology from being abused for reproductive-cloning purposes."

While some fertility doctors and a religious cult have claimed success at creating a pregnancy via cloning, they've offered no convincing proof. In contrast, the South Korean research is being reported at the meeting of the American Association for the Advancement of Science in Seattle and will appear in an upcoming Science. "This is reality," says stem cell researcher John Gearhart of Johns Hopkins University. "Here is a bona fide, refereed journal saying that a human embryo has been cloned and a cell line derived from it."

The South Korean team, led by Woo Suk Hwang of Seoul Nation University, initially collected 242 eggs from 16 volunteers. The investigators removed each egg's chromosomes and, to replace that DNA, fused the egg with another cell from the same woman. They used cumulus cells, which normally surround eggs in the ovary.

Next, the biologists treated the eggs with two chemicals to trick them into dividing as if fertilized by sperm. The eggs then grew in the lab dish until they became blastocysts, which are balls of about 100 cells.

No human-cloning experiment previously reported in a scientific journal had generated embryos that survived this long. Once Hwang and his colleagues optimized experimental conditions, about 25 percent of the eggs reached the blastocyst stage.

For example, they settled on a 2-hour delay between fusing a cumulus cell with an egg and chemically activating the product. This window may give the egg time to reprogram the incoming DNA to act more like the DNA of a fertilized egg than like that of a cumulus cell. …