Healthy clones: Dolly the sheep's heirs reach ripe old age
LONDON (Reuters)-The heirs of Dolly the sheep are enjoying a healthy old age, proving cloned animals can live normal lives and offering reassurance to scientists hoping to use cloned cells in medicine.
Dolly, cloning's poster child, was born in Scotland in 1996. She died prematurely in 2003, aged six, after developing osteoarthritis and a lung infection, raising concerns that cloned animals may age more quickly than normal offspring.
Now researchers have allayed those fears by reporting that 13 cloned sheep, including four genomic copies of Dolly, are still in good shape at between seven and nine years of age, or the equivalent of 60 to 70 in human years.
"Overall, the results are suggesting that these animals are remarkably healthy," said Kevin Sinclair of the University of Nottingham, whose team reported their findings in the journal Nature Communications on Tuesday.
It is the first time experts have made such a detailed age-related health assessment of cloned animals, looking at factors such as blood pressure, diabetes risk and joint damage.
While no animals were lame, there were signs of mild osteoarthritis in some sheep and one had moderate disease, which scientists said was to be expected at their age.
Dolly was the first mammal to be cloned from an adult cell, using a process called somatic cell nuclear transfer (SCNT).
This involved taking a sheep egg, removing its DNA and replacing it with DNA from a frozen udder cell of a sheep that died years before. The egg was then zapped with electricity to make it grow like a fertilized embryo. No sperm were involved.
Dolly's creation triggered fears of human reproductive cloning, or producing genetic copies of living or dead people, but mainstream scientists have ruled this out as far too dangerous.