A new study has dismissed concerns that cloning caused early-onset osteoarthritis (OA) in Dolly the sheep.
Scientists from the University of Nottingham and the University of Glasgow have published a radiographic assessment of the skeletons of Dolly, Bonnie (Dolly’s naturally conceived daughter) and Megan and Morag (the first two animals to be cloned from differentiated cells) that shows no abnormal OA.
The study follows the team’s research last year into the Nottingham ‘Dollies’, a quartet of sheep cloned in 2007 from the same line as Dolly, that showed the cloned sheep to age the same as naturally born sheep.
According to their assessment of the skeletons, the OA observed within the skeletons is similar to that naturally conceived sheep and Nottingham’s healthy aged clones.
Professor Sandra Corr, Professor of Small Animal Orthopaedic Surgery who has since moved to Glasgow University, said: “We found that the prevalence and distribution of radiographic-OA was similar to that observed in naturally conceived sheep, and our healthy aged cloned sheep.
As a result we conclude that the original concerns that cloning had caused early-onset OA in Dolly were unfounded.”
The new study arose after the findings regarding the Nottingham ‘Dollies’.
Derived from the same cell line that produced Dolly, the four sheep originated from Professor Keith Campbell’s attempts to improve the efficiency of the cloning method somatic-cell nuclear transfer (SCNT) and were left as his legacy to the University of Nottingham.
Studying the ‘Dollies’, Kevin Sinclair, Professor of Developmental Biology, in the School of Biosciences, along with Corr and David Gardner, Professor of Physiology at Nottingham’s School of Veterinary Medicine and Science, found radiographic evidence of only mild or, in one case, moderate OA.
Given that the ‘Dollies’ had aged so apparently normal, the team felt that their findings stood in too stark a contrast to reports that cloning had caused Dolly to suffer from early-onset OA. First emerging in 2003, reports stated that at the age of 5½ Dolly was suffering from OA.
However, the only formal record of any OA in Dolly was a brief mention in a conference abstract, stating that Dolly had OA of the left knee.
In the absence of the original records however, the team were compelled to travel to Edinburgh, where the skeletons are stored in the collections of National Museums Scotland.
With special permission from Dr Andrew Kitchener, Principal Curator of Vertebrates at National Museums Scotland, the team then performed the X-rays on Dolly and her contemporary clones to reassess that 2003 diagnosis.
Sinclair said: “Our findings of last year appeared to be at odds with original concerns surrounding the nature and extent of osteoarthritis in Dolly – who was perceived to have aged prematurely. Yet no formal, comprehensive assessment of osteoarthritis in Dolly was ever undertaken. We therefore felt it necessary to set the record straight.”