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. Last Updated: 07/27/2016

Cloned Organisms May Live Longer




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 unusually short, suggesting a severe and possibly life-shortening 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. But 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 Lanza, lead author of the report.


Michael 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 an abbreviated lifetime seems dispelled by the news from the cloned cows, which 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.


Because of problems with using human egg cells, Advanced Cell Technology has been working with cow eggs. The new experiment is encouraging with respect to the telomere problem because the cow cells being cloned were old and had short telomeres. Yet the calves seem more youthful than normal as judged by various measures of cellular aging, and their telomeres are longer than the usual.


Cows live for more than 20 years, however, so the only quick way to an answer about telomeres and lifespan will be with mice. Lanza said that in serially cloned mice generated by other researchers the telomeres were getting longer at each generation.