LONDON — Dolly, the world's first cloned sheep, has developed arthritis, raising fears that the cloning process may have given her a genetic defect.
Professor Ian Wilmut of the Roslin Institute in Scotland said today that Dolly, the first mammal cloned from a cell taken from an adult animal, had arthritis in her left hind leg.
Arthritis is not unknown in sheep, but Dolly, born in 1996, has developed it at an unusually young age, suggesting it may be the result of a genetic defect, possibly caused by cloning.
"The fact that Dolly has arthritis at this comparatively young age suggests that there may be problems," Wilmut told BBC radio.
Cloning is a hot area of medical research. Rival teams this week announced the birth of cloned, genetically engineered pigs that may be suitable for animal-to-human transplants.
Wilmut said it was too early to draw conclusions from Dolly's case, and he urged biotech companies and research labs to share information about the health of their cloned animals to see if there was a common thread.
"We know already there is an unusual incidence of death in 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," he said.
Researchers at PPL Therapeutics Plc, which helped to produce Dolly, and a U.S. joint venture company set up by Novartis AG and BioTransplant Inc. have both recently cloned pigs whose organs may be compatible with humans.
Pig kidneys, hearts and other organs could help solve a dire shortage of donated human tissue—and create a multi-billion dollar market for successful companies.
Some scientists think it is inevitable that human cloning will also become a reality one day, whether it is reproductive cloning to enable the infertile to become parents or therapeutic cloning to create embryos that can be used as a source of stem cells.