(CNN)Though growing old, Dolly's sheep siblings are no worse for wear. Debbie, Denise, Dianna and Daisy, clones all derived from the same cell line as the first cloned mammal, show no signs of long-term health issues, according to research published Tuesday in the journal Nature Communications. The clones are, in fact, in vigorous good condition despite the fact that they range in age from 7 to 9, or about 60 to 70 in human years.
This happy news arrived just weeks after embryologists around the globe raised a glass for Dolly's 20th anniversary. Born July 5, 1996, Dolly resulted from an experiment performed at the Roslin Institute
in Scotland led by Dr. Ian Wilmut.
Surprisingly, Wilmut and his team's primary intention wasn't to become the first scientists to clone a mammal. The group simply wanted to genetically modify the genes of sheep. Creating Dolly was a first experimental step toward learning to make a genetic "tweak."
Still, Dolly herself died prematurely of lung disease in 2003. Though the illness that did her in had nothing to do with her origins, healthy aging among clones is a contentious issue, Sinclair and his co-authors wrote. Much was made of the fact that she'd been suffering from osteoarthritis, a sign of premature aging.
Mindful of Campbell's legacy, Sinclair decided to assess the long-term health of the four most elderly members of his flock. And so the foster father measured the sheep's blood pressure, metabolism, heart function, blood glucose levels and insulin levels and x-rayed their muscles and joints, looking for signs of premature aging.
What did Sinclair discover? Mild osteoarthritis, nothing else. The four sheep are "remarkably healthy," Sinclair said in a university video
, adding that he has no conflicts of interest and no agenda.
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These days, science has moved on, according to Sinclair. The focus is now on stem cell science and reprogramming cells in efficient ways to achieve the benefits of regenerative medicine.
Cibelli believes that "we are on the verge of a breakthrough" with stem cell research and cloning research working synergistically.
Though somatic cell nuclear transfer has been used in humans, it has been performed only to generate stem cells, Sinclair said, adding that "there's nobody out there interested in generating clones of humans."
Read more: http://www.cnn.com/2016/07/27/health/cloned-sheep-age/index.html