Dolly the cloned sheep 'aged normally'
When Dolly the sheep was put down before her seventh birthday in 2003, she was said to suffer from age-related osteoarthritis, raising red flags that clones may grow old faster.
But scientists said that the fear of premature, clone-related aging appeared to have been misplaced. Dolly’s joint disease was, in fact, quite normal.
Researchers in Scotland and England based their conclusion on X-rays of Dolly’s skeleton, held by National Museums Scotland, in Edinburgh.
Dolly was lame in one knee. But the extent of osteoarthritis revealed by the scans was “not unusual” for a naturally-conceived sheep aged between 7 and 9.
“The original concerns that cloning had caused early-onset osteoarthritis in Dolly were unfounded,” said the researchers, adding that their research was driven by a desire “to set the record straight.”
The findings were published in the journal Scientific Reports.
Dolly was put down at the age of 6 years and 8 months because of a progressive lung disease. Dolly’s breed of Finn-Dorset sheep normally live between 10 and 12 years.
The researchers said their findings were supported by X-rays of the skeletons of Bonnie, Dolly’s naturally-conceived daughter, and of Megan and Morag — sheep cloned using a different technique.
Their bones are also in the collection of National Museums Scotland.
The only formal record of osteoarthritis in Dolly was a “brief mention” in a submission to a scientific conference, said the team. None of the original diagnostic records or scans were preserved.
The same team published a study last year in which they reported that four genetically-identical copies of Dolly had aged normally with no symptoms of osteoarthritis.
Debbie, Denise, Dianna and Daisy — identical sisters of Dolly born 11 years later — were made from the same mammary gland cell line that yielded the world’s most famous sheep.
None of them were lame, and none had osteoarthritis uncommon for their age.
Osteoarthritis is a condition caused by mechanical wear and tear on joints. It can be genetic in origin, but risk factors include old age, trauma and obesity.
At age 9, none of Dolly’s four sisters were diabetic and all had normal blood pressure — further dousing concerns of premature aging in clones, at least in sheep.