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Dolly the sheep was as healthy as a normal ewe, scientists conclude after studying bones

Dolly the sheep did not develop arthritis or age prematurely, scientists have found, in research which suggests cloning is far safer than previously thought.

The world’s first animal cloned from an adult cell, was born in Edinburgh in 1996 and died in 2003 aged six.

At the time scientists believed that genetic problems caused by the cloning process had led Dolly to age more quickly, leading her to develop painful osteoarthritis.

But a new radiographic assessment of her skeleton by experts the universities of Nottingham and Glasgow found that she had no more signs of ageing than any other sheep of a similar age.

The team also looked at her offspring Bonnie, as well as two other cloned sheep, Megan and Morag, and found none of them showed any signs of unusual arthritis.

Sandra Corr, professor of small animal orthopaedic surgery at Glasgow University, said: “We found that the prevalence and distribution of radiographic osteoarthritis was similar to that observed in naturally conceived sheep, and our healthy aged cloned sheep.

“As a result we conclude that the original concerns that cloning had caused early-onset osteoarthritis in Dolly were unfounded.”

Dolly the Sheep and Prof Ian Wilmut - Credit:  chris watt
Dolly the Sheep and Prof Ian Wilmut Credit: chris watt

Dolly was created using a technique called somatic cell nuclear transfer, whereby the nucleus from the cell of an adult sheep was transferred to an unfertilised egg then implanted into a surrogate ewe for birth. It meant that Dolly had exactly the same DNA as the donor sheep.  

Initially she seemed healthy and was successfully mated to produce six lambs naturally. However in late 2001 she began to walk stiffly.

The following year,  Prof Ian Wilmut, who led the team which cloned Dolly at the Roslin Institute at Edinburgh University, announced that she had gone lame and was suffering from arthritis in her left hind leg, hip and knee. She was euthanised in February 2003.

At the time, Prof Wilmut said there was no way of knowing if the problems were down to cloning or were just a coincidence, but the scientific community became concerned, and shares in the PPL Therapeutics who largely funded the project, immediately slumped.

The 'Nottingham' Dollies who were created from the same cell line as Dolly  - Credit:  University of Nottingham
The 'Nottingham' Dollies who were created from the same cell line as Dolly Credit: University of Nottingham

However the Nottingham team decided to look at the skeleton to find out for themselves whether Dolly really was suffering from premature arthritis. The travelled to the National Museum of Scotland in Edinburgh, where Dolly is kept, to scan her bones.

The team found no evidence of any abnormal bone conditions that would not normally be expected of a sheep of the same age.

Prof David Gardner setting up radiographs - Credit: University of Nottingham 
Prof David Gardner setting up radiographs Credit: University of Nottingham

Last year the same team proved that clones produced from Dolly’s cell-line, dubbed the Nottingham Dollies, also had not aged prematurely.

“Our findings of last year appeared to be at odds with original concerns surrounding the nature and extent of osteoarthritis in Dolly – who was perceived to have aged prematurely,” added Professor Kevin Sinclair of Nottingham University.

“Yet no formal, comprehensive assessment of osteoarthritis in Dolly was ever undertaken. We therefore felt it necessary to set the record straight.

“She did become lame at around 5½ years and an x-ray of her left knee at the time revealed evidence of osteoarthritis and that was about as far as it went.”

Prof Sinclair concluded that there were no signs that Dolly had aged prematurely.

 The research was published in the journal Scientific Reports.