Dolly the sheep, the world’s first cloned mammal, has developed arthritis, one of her creators said today.
Professor Ian Wilmut, who led the team which cloned Dolly in 1996, said her condition could have been caused by the cloning process and called for more research.
The emergence of arthritis in the world’s most famous sheep led to a slump in shares for the company which developed the animal.
Professor Wilmut, of the Roslin Institute, Edinburgh, said: ‘‘Dolly has arthritis in her left hind leg, at the hip and the knee.
‘‘We can’t tell how it will develop but she is responding well to treatment with anti-inflammatory drugs.’’
Asked whether the condition was because Dolly was cloned, he said: ‘‘There is no way of knowing if this is down to cloning or whether it is a coincidence.’’
He also said: ‘‘We know already that there’s an unusual incidence of death of cloned animals around the time of birth.
‘‘What we need to go on studying is whether diseases like arthritis, which tend to be associated with older age, occur in a normal way or whether the incidence is changed.
‘‘The fact that Dolly has arthritis at this comparatively young age suggests that there may be problems. We do not know and it’s very important that we look.’’
He went on: ‘‘We are very disappointed and we will have to keep a careful eye on her. We will be monitoring her condition to see how it develops.
‘‘In every other way she is perfectly healthy and she has given birth to six healthy lambs.’’
Normal sheep of Dolly’s age had been known to develop arthritis, he added.
The development sparked a protest from Dan Lyons, of the animal protection group CAGE, who said: ‘‘Biology is not like Lego, it’s not like Meccano, you can’t just interfere with one aspect of an animal’s system and expect the rest of the system to continue to function perfectly.’’
The research was too commercially motivated, he said.
Dolly made headlines worldwide in 1996 when she became the first mammal to be cloned using DNA taken from an adult cell from a ewe’s udder.
In May 1999, research suggested Dolly might be susceptible to premature ageing.
The possibility that the ground-breaking animal might die early was raised after a study of her genetics.
A team from PPL Therapeutics, which developed Dolly, examined structures in her cells called telomeres.
The team reported in the journal Nature that the structures were slightly shorter than would be expected in a sheep of her age which was born normally.
There was some evidence that telomere length was linked to ageing.
But researchers said it was impossible to predict precisely how long Dolly would live.
News of Dolly’s condition emerged just days after scientists announced they had produced five pig clones which had been genetically modified to help prevent their organs being rejected if they were transplanted into a human.
The pigs - Noel, Angel, Star, Joy and Mary - were said to mark a milestone in the development of animal to human transplants.
The animals, produced by the US subsidiary of Edinburgh-based biotech company PPL Therapeutics, lack the gene which is chiefly responsible for their organs triggering a swift and sudden massive immune reaction in humans.
But a second team of researchers - scientists at the University of Missouri-Columbia and Immerge BioTherapeutics Inc - said yesterday that it had produced a litter of cloned piglets whose organs were also genetically tailored to suit a human.
The American researchers said they were the first to make the xenotransplantation breakthrough, saying their piglets were born about three months before Noel, Angel, Star, Joy and Mary.
Shares in Edinburgh-based PPL Therapeutics slumped 15% in early trading on the London Stock Exchange today, down 11p to 62½p and losing some of the spectacular gains seen on Wednesday, when shares soared 46% to 77½p following the birth of the five piglets.