In 2002, when Dolly the sheep, the first truly cloned mammal, died at age 6, scientists studied her telomeres — the structure at the end of DNA strands that shorten with age — and found that Dolly’s were much shorter than they should be. Initially, scientists thought this meant clones would age prematurely, following the biological clock of the original cells. If so, it would be a terrible prospect for cloned human organs.
But new research in the journal Nature Communications undercuts that conclusion because animals cloned from the same cell line as Dolly didn’t suffer the same fate, writes The Washington Post. They are currently age nine and in perfect health.
“It was quite obvious that the concerns of Dolly just didn’t relate,” says lead study author Kevin Sinclair of the University of Nottingham.”So you can’t extend beyond the Dolly experience and say this premature aging applies to all clones.”
Sinclair’s team tested the sheep for Type 2 diabetes, cardiovascular disease and osteoarthritis, a disease that afflicted Dolly, and found that only one sheep exhibited signs of stiffness, normal for a nine-year-old sheep.
Scientists aren’t sure why the original Dolly died so early and with such short telomeres, while her clones surpass her in health and age, says the Post, but “it may come down to the very methods with which the cloned embryos are cultured and implanted.”
Sinclair says that they’ll know for sure in another year, when they humanely kill the sheep and study their telomeres to better understand stem cell research and cloning human organs.