>>LONDON (AP) - The world's first cloned sheep has developed arthritis at the relatively early age of 5 1/2 years, scientists said Friday, stirring debate that the current cloning procedures might be flawed.
The announcement of Dolly's problem could raise new doubts about cloning animals for use in human transplantation and about cloning humans themselves.
``Dolly has arthritis in her left hind leg at the hip and the knee,'' said the scientist, Ian Wilmut, of the Edinburgh-based Roslin Institute. ``We will never know in the case of Dolly whether her condition is because she was cloned or whether this was an unfortunate accident.''
He said normal sheep of Dolly's age have been known to develop arthritis, but most don't until they are older.
``But this provides one more piece of evidence that unfortunately the present cloning procedures are rather inefficient.''
Dolly was born in a Scottish research compound in 1996, the world's first sheep to be successfully cloned from an adult cell. Roslin scientists announced her birth on Feb. 23, 1997, creating front-page news headlines around the world.
Wilmut said that apart from the arthritis, Dolly remained a healthy animal who has given birth to six lambs.
He also said Dolly was responding well to a treatment with anti-inflammatory drugs and that her condition will be closely monitored.
There are now hundreds of animal clones, including cows, pigs, mice and goats, many of them appearing robust and healthy.
But since Dolly is the oldest one, no one knows what could happen to the rest of them in the future.
Sheep can live to between 15 and 17 years. Arthritis typically does not develop until age 10 to 11.
In some ways, Dolly remains a rarity.
Many attempts to clone animals have ended in failure. Deformed fetuses have died in the womb with oversized organs, while others were born dead. Still others died days after being born, some twice as large as they should have been.
In 1999, scientists noticed that the cells in Dolly's body - cloned from a 6-year-old sheep - had started to show signs of wear more typical of an older animal. Some geneticists said the finding provided evidence that researchers could not manufacture copies of animals without the original genetic blueprint eventually wearing out.
``We know already that there's an unusual incidence of death of cloned animals around the time of birth,'' Wilmut said.
``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.
Animal rights groups said Dolly's problem showed that developments in cloning have outstripped scientific knowledge of its consequences.
Two research teams, one of which was Wilmut's group, announced this week that they have cloned piglets that were genetically modified to help prevent their organs being rejected if they were transplanted into a human.
``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,'' said Dan Lyons of the animal protection group CAGE.<<
Cheers, Tuck |
