It was 20 years ago when Dolly the Sheep was born as the first mammal created through real cloning. The famous sheep of the University of Edinburgh did not come to exist through sexual intercourse or stem cells of another sheep.
She was the first to be made of mature cells taken from the mammary tissue of a donor. When middle age hit Dolly – at five years old – the sheep living the good life in the University’s research facility started developing osteoarthritis.
A year later, Dolly died due to lung and joint problems that are usually signs of old age. When researchers performed post-mortem DNA tests, they discovered that Dolly’s biological age had surpassed her chronological age.
Seeing that her cells looked older than the time Dolly had actually been alive, some experts expressed their concerns about the possibility that clones age prematurely, continuing the biological clock of the adult cells used to create them.
Will Dolly’s cloned sheep have the same fate?
From a biomedical perspective, if that is true, it would spell disaster for all the healthy adults who have organs and tissues created from the cloned cells; they run on shortened biological clocks.
However, new research featured in Nature Communications has some good news; a team from the University of Nottingham suggests that Dolly’s premature aging and death is not something universally true for all clones or organs formed using adult cells.
As a matter of fact, four sheep clones that were created from the same cell batch as Dolly are all in perfect health, and they’re all around nine years old.
Kevin Sinclair, the leading author of the study, said that even though they surpassed Dolly’s age by two years already, they all appear in perfect health. The team performed some tests nevertheless to see if subtle defects are hiding in their DNA.
These evaluations will be repeated in about a year to measure molecular aging in the cloned sheep. By that time, they will be 10 years of age – a truly impressive milestone rarely reached by farm animals – and they will be humanely put down.
The results of the evaluations showed that there were little to no signs of non-communicable diseases, such as osteoarthritis, obesity, and hypertension. One sheep of four has started to exhibit symptoms of arthritis, but it’s not surprising, given their old age.