London: Three weeks after scientists marked the 20th birth anniversary of Dolly the sheep, a new study has shown that four genomic copies of the world's first animal cloned from an adult cell have reached their 9th birthdays in good health.
Nottingham's Dollies - Debbie, Denise, Dianna and Daisy - along with nine other clones are part of a unique flock of cloned sheep under the care of Professor Kevin Sinclair, an expert at University of Nottingham in the UK. The study is the first comprehensive assessment of age-related non-communicable disease in cloned offspring.
It shows that at between seven to nine years of age (60 to 70 in human years) these cloned sheep were showing no long-term detrimental health effects. Dolly made history as the first animal to be cloned from an adult cell using a technique known as somatic-cell nuclear transfer (SCNT). "This could lead to the realistic prospect of using SCNT to generate stem cells for therapeutic purposes in humans as well as generating transgenic animals that are healthy, fertile and productive," said Sinclair.
Nottingham's oldest clone was born in July 2006. The four Finn-Dorset clones - 'the Dollies' - were born in July 2007. A female Lleyn clone was born in August 2007 along with a second clone. In June 2008 six more Lleyn ewes were born.
Longevity and healthy ageing among SCNT clones have long been contentious issues and much was made of Dolly having to undergo treatment for osteoarthritis before her death in 2003.
Last year Nottingham's cloned sheep underwent a series of comprehensive assessments for non-communicable diseases including obesity, hypertension and osteoarthritis - three major comorbidities in aged human populations. The examinations included the use of anaesthesia to carry out X-rays and MRI scans.
The flock was tested for glucose tolerance and insulin sensitivity. They underwent radio-telemetric assessments to check their heart rate and blood pressure.
They had a full musculoskeletal examination carried out by Dr Sandra Corr, a veterinary orthopaedic specialist from the university's School of Veterinary Medicine and Science. Radiological examinations of all main joints were followed by MRI scans of their knees, the joint most affected by osteoarthritis in Dolly.
Their health was compared with a group of naturally bred six-year-old sheep living under similar conditions at the University.
Despite their advanced age the cloned sheep - including the four Dollies - were showing no signs of diabetes, high blood pressure, or clinical degenerative-joint disease. Although some of the animals were showing radiographic evidence of mild, and in Debbie's case, moderate osteoarthritis none of the animals were lame and none required treatment for osteoarthritis.
There is still a long way to go before SCNT is perfected. However, this research has shown that cloned animals can live long and healthy lives, researchers said.
