Cloned cows show signs of reversed ageing

A head of cloned cows has baffled scientists by showing signs of reversed ageing - suggesting that the cloned cells' internal clocks have been reset.

A head of cloned cows has baffled scientists by showing signs of reversed ageing - suggesting that the cloned cells' internal clocks have been reset.

The US team that discovered the effect suggests it could lead to cures for age-related diseases such as Parkinson's and Alzheimer's.

But the finding contradicts earlier research on Dolly the sheep, the first cloned mammal, whose cells are older than her physical years - because she was cloned from a six-year-old sheep. Professor Ian Wilmut at the Roslin Institute, where Dolly was born, was cautious about any early application of this latest finding to medicine.

The latest discovery, reported today in Science magazine, was made by scientists at Advanced Cell Technologies (ACT) in Worcester, Massachusetts. Their holstein cows were cloned from connective tissue called fibroblasts, rather than mammary cells as were used for Dolly.

They also used cells near the end of their lifespan,as measured by telomeres, strings of DNA on the ends of chromosomes that shorten each time the cell divides. Once the telomere reaches a critical length, the cell dies instead of dividing again.

The ACT researchers found that the cloning process restored the cells' telomeres so that they were longer than normal animals of the same age: instead of being between zero and four division cycles away from cell death, those taken from the clones now had more than 90 division cycles left.

Robert Lanza, one of the cloning team at ACT, said: "Telomeres from all of the cows, including one who is celebrating her first birthday this week, look like those of newborns.

"The extra population doublings of these cells means that we could get a billion-fold increase in the number of replacement cells that can be used for tissue engineering and transplant therapies."