MANCHESTER, July 26 (Xinhua) -- The analysis of 13 cloned sheep, including four created from the same genetic material as the first cloned animal, Dolly the sheep, has proved that they can live long and healthy lives, according to a study published Tuesday in the journal Nature Communications.
Three weeks after the scientific world marked the 20th anniversary of the birth of Dolly the sheep, a group of researchers from The University of Nottingham, who led the study, revealed their latest findings about age-related non-communicable disease in cloned offspring. They also discussed the topic during the EuroScience Open Forum 2016 (ESOF16) held in Manchester this week.
Dolly made history as the first animal to be cloned from an adult cell using a technique known as somatic-cell nuclear transfer (SCNT). However, the longevity and healthy aging among SCNT clones have long been contentious issues and much was made of Dolly having to undergo treatment for osteoarthritis some time prior to her death in 2003 at the relatively young age of 6.5 years.
The new study shows that at between seven to nine years of age (roughly 60 to 70 in human years) these cloned sheep were showing no long-term detrimental health effects.
During 2015, these cloned sheep underwent a series of comprehensive assessments for non-communicable diseases including obesity, hypertension and osteoarthritis - three major diseases usually found in aged human populations, according to the researchers.
Radiological examinations of all main joints were followed by MRI (magnetic resonance imaging) 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 The University of Nottingham.
"(Naturally-bred) sheep can live beyond 10 years of age for sure...But it's kind of like humans. Humans can live to their 80s or their 90s or even some beyond their 100s, but very few do," said Professor Kevin Sinclair from the University of Nottingham at a press conference during the ESOF16. He is one of the authors of the study.
One of the concerns in the early days was that cloned offspring were aging prematurely and Dolly was diagnosed with osteoarthritis at the age of around five, so clearly this was a relevant area to investigate, said Sinclair.
Despite their advanced age the cloned sheep, including the four "sisters" of Dolly, were showing no signs of diabetes, high blood pressure, or clinical degenerative-joint disease.
Although some of the animals did show mild - and in one case moderate - signs of osteoarthritis, none of the animals were lame and none required treatment for osteoarthritis, according to the study.
But there is still a long way to go before SCNT is perfected.
"It is well established that prior to conception and in the early stages of pregnancy during natural or assisted reproduction subtle chemical changes can affect the human genome leading to development and late-onset chronic diseases. Given that SCNT requires the use of assisted reproductive procedures it is important to establish if similar diseases or disorders exist in apparently healthy aged cloned offspring," said Sinclair.
