‘Descendants’ outliving Dolly the cloned sheep
that would spell disaster, with any tissues or organs created from the cells of healthy adults running on a shortened biological clock.
But according to research published this week in Nature Communications, Dolly’s premature aging isn’t likely to extend to all clones or tissues formed using adult cells. Four sheep clones formed from the same cell line as Dolly seem to be in perfect health, and are now pushing nine years of age.
“When we did the study, these clones were already two and a half years older than Dolly was when she died,” lead study author Kevin Sinclair of the University of Nottingham told The Post. “And they appeared to be perfectly healthy, but we wanted to see if they might be harboring subtle defects.”
Sinclair and his colleagues failed to measure the telomere lengths of these Dollies and another nine cloned sheep from other cell lines that they studied with them. They will investigate molecular aging in about a year, when the sheep — who will then have reached the truly impressive sheep age of 10, a milestone rarely seen in farm animals — are humanely put down.
But the research team did undertake the most comprehensive study of physical aging ever in cloned animals — other than mice, according to Sinclair — by looking for signs of non-communicable diseases including obesity, hypertension and osteoarthritis.
They found some signs of very early osteoarthritis in the sheep, but none was showing symptoms over three years after their genetic identical had. Now, a year later, one sheep is starting to exhibit signs of stiffness — but given their age, Sinclair said, it wouldn’t be unusual for one sheep out of four to have arthritis. The four were completely cleared of all other health issues.