Twenty years ago, Dolly, the first animal derived from adult cells, was born. In 20 years, the technical advances of somatic cell nuclear transfer (SCNT) have not been so impressive as expected and the efficacy of SCNT remains low.

The study of Wilmut and co-workers was really pioneering because it demonstrated the potential to induce pluripotency in terminally differentiated cells and the SCNT is the most efficient way to reprogram somatic cells to a pluripotent state.

Long term health problems in large Cloned animals are a contentious issue from the outset, but few studies have assessed this topic. Dolly prematurely died for osteoarthritis, but other Cloned Sheep did not show any significant healthy problem. Scientist at the University of Nottingham performed musculoskeletal assessments, metabolic tests and blood pressure measurements in 13 aged (7–9 years old) cloned sheep, including four derived from the cell line that gave rise to Dolly. They examined also all main joints, especially the knees, which was joint most affected by osteoarthritis in Dolly. Scientists found that cloned sheep were normotensive, euglycaemic and insulin sensitive; joints resulted as clinically normal for aged sheep.

Although the SCNT continues to show higher embryonic and gestational losses compared to natural mating and assisted reproduction, those clones that survive beyond the perinatal period are healthy and seem to age normally.