Moove Over, Dolly New Cloning Technology Yields Cows That Appear To Have Youthful Cells

Cloned cows have youthful cells and should live at least as long as ordinary animals, say researchers at Advanced Cell Technology, a company interested in using cloning to treat human disease and extend life.

The finding, reported in Friday’s issue of Science, is significant because tests of Dolly, the cloned sheep, had shown that the tips of her chromosomes, known as telomeres, were short, suggesting a severe drawback in the cloning process. Telomeres get shorter each time a cell divides, so are shorter in the body cells of older animals.

Cells with longer telomeres can divide more often and live longer than normal. No one yet knows if longer telomeres will increase lifespan in whole organisms. If they do, the cloned cows “could be the longest-lived cows on the planet,” said Dr. Robert P. Lanza, lead author of the report.

Michael D. West, the chief executive of Advanced Cell Technology, hopes to develop methods of creating replacement tissues by cloning a patient’s cells. The fear that such tissues would have short telomeres and abbreviated lifetime now seems dispelled by the news from the cloned cows, and makes Dolly’s case appear to be an unexplained anomaly.

The essence of the cloning process is that the nucleus of an adult cell is reprogrammed to its embryonic state by the cytoplasm, or inner fluids, of an egg cell. The process is ethically fraught because cloning a patient’s cell would create an entity with the same potential as a fertilized human egg. The patient’s reprogrammed cell would be merely cultured in glassware, however, and used to produce replacement cells for failing organs.

In the new experiment, the cow cells being cloned were old and had short telomeres. Yet the calves seem more youthful than normal as judged by measures of cellular aging, and their telomeres are longer than the usual. Cows live for more than 20 years. But Dr. Peter Mombaerts, a biologist at Rockefeller University, noted that only one calf had been cloned for every 271 attempts, and that the cloning process might have selected some specially youthful class of cell. The inefficiency of the process is one of the obstacles facing Advanced Cell Technology’s cloning plans.