CLONING: Return to the Future

Applied Genetics News, May, 2000

Cells from six healthy cow clones show no signs of the premature aging reported for Dolly the cloned sheep, according to researchers from Advanced Cell Technologies, Inc. (One Innovation Dr., Worcester, MA 01650; Tel: 508/756-1212, Fax: 508/756-0931; Website: www.advancedcell.com). To the contrary, the cloning process seems to have sent the cow cells' aging backward, making them appear even younger than cells from normal cows of the same age.

To create the cow clones, the researchers used cells that were near the end of their life span in terms of division cycles, with only a few rounds of cell division left. Surprisingly, they discovered that the cloning process seemed to restore the division potential of these cells in the six cows. Instead of being 0-4 division cycles away from the end of their lives, cells taken from the cows were more than 90 cycles away from their end.

Shorter telomeres are often found in older cells. Scientists spotted this telltale sign of maturity in Dolly, the original cloned sheep. Telomeres from the cloned cows, however, are actually longer than those from normal cows of the same age, and in most cases even longer than those from newborn calves.

"It's really remarkable," says Lanza. "Telomeres from all of the cows, including one who is celebrating her first birthday this week, look like those of a newborn."

Robert P. Lanza and his co-authors don't know exactly how cloning helps these cells shrug off the signs of aging, or whether this translates into a longer life span for the animals themselves. They are continuing their work to discover exactly how the cloning process reprograms the youth back into cells.

Despite these unsolved mysteries, the finding erases a lingering doubt about the utility of cloned animals by demonstrating that the process doesn't automatically rob cells of a normal life span. In fact, say Lanza and colleagues, cloning could supply a crop of youthful cells for a variety of uses, from medical applications like designing and transplanting replacement tissues for the human body to increasing the breeding years of farm animals.