In 1996, Dolly the Sheep made headlines around the world for being the first successfully cloned animal.
After starting her life in a test tube, Dolly was plagued with health problems, from osteoarthritis to tumors in her lungs from an incurable infectious disease. At six years old, scientists decided to put Dolly down to end her suffering.
Many believed that Dolly had aged so prematurely due to the fact that she was a cloned animal. But a new study from the University of Nottingham published Tuesday in Nature Communications has found results quite the contrary. They found these results by studying none other than Dolly’s “relatives,” so to speak.
Dolly was made with a single cell from a sheep’s udder and an egg cell that had been stripped of its original DNA, creating a sheep almost genetically identical to its owner. Daisy, Diana, Debbie, and Denise were created from the same cell line as Dolly. They were originally part of a separate study looking into artificial reproduction among cloned sheep embryos. When the scientist in charge of Dolly’s relatives passed away in 2012, developmental biologist Keith Sinclair was asked if anything valuable could be learned from studying the older sheep. So they began studying the aging process in the animals, as well as nine other cloned sheep.
Previously, signs of early aging were blamed on the cloning process. But this new study contradicts that.
The cloned sheep are all “old ladies” now, Sinclair told The New York Times. Their ages range between seven and nine, which is roughly 60 in human years, and they’ve led relatively normal lives. They spend most of the summer outside, and most of the winter in the barn. They were normal reproductively, though they never bred.
The scientists put them through a battery of tests to determine just how well they’ve aged over the years.
Here’s Joanna Klein, reporting for The New York Times:
“All we wanted to establish was: Are they normal?” Dr. Sinclair said.
And for the most part, they were. Glucose tolerance and insulin resistance tests revealed nothing abnormal. Blood pressure was fine, whether measured remotely while the sheep did what normal sheep do or under stressful conditions induced with a drug that constricts the blood vessels. The sheep were flexible and reactive in musculoskeletal tests, but some did show early signs of osteoarthritis. Debbie’s X-ray indicated her arthritis was slightly more advanced, but Dr. Sinclair said it was nothing out of the ordinary.
The study confirms that if cloned animals survive through the fetal development and the first few years of life, they won’t age any faster than other animals.
But the question of the safety still remains. Based on these results, it appears that cloning in safe, but only if the animals survive the embryonic stage and infancy. The high attrition rate makes cloning a risky proposition.
Still, Dolly’s relatives are proof that cloned animals can live happy, healthy lives amongst their genetically-unique peers.