Concerns that the cloning process had caused the early-onset of osteoarthritis in Dolly the sheep - the first animal cloned from adult cells - may have been unfounded, according to a study in Scientific Reports.
In a conference abstract, it was mentioned briefly that Dolly had osteoarthritis of the left knee at 5 - years of age. This in turn led to concerns being raised over the possibility of early-onset age-related diseases in cloned animals. However, a 2016 study of four, eight-year-old cloned ewes derived from the same cell line that gave rise to Dolly found radiographic evidence of only mild or, in one case, moderate osteoarthritis.
As none of the original clinical or radiographic records were preserved, Kevin Sinclair and colleagues undertook a radiographic examination of the skeletons of Dolly, along with Bonnie (her naturally conceived daughter), and Megan and Morag (the first two animals to be cloned from differentiated cells). The authors found that radiographic osteoarthritis (rOA) was more severe and affected a greater number of joints in the two older sheep (Bonnie and Megan) when compared to Dolly. They found that Dolly had no rOA in her shoulder, carpal or hock joints at the age of six years and eight months and the overall distribution of rOA was similar to that described in seven- to nine-year-old cloned sheep.
The authors conclude that the prevalence and distribution of rOA in Dolly and her contemporary clones is no different to that observed in naturally conceived sheep and in healthy, aged cloned sheep.