Cloning may cause long term health defects, a study by French scientists has suggested. A two month old calf, cloned from genes taken from the ear of an adult cow, died after developing blood and heart problems.
The cloning process seemed to have interfered with the normal genetic functioning of the developing calf, according to the researchers whose findings are reported in the Lancet (1999;353:1489-91).
Cloned sheep, cows, and mice have been known to die before or shortly after birth. But the latest case highlights for the first time the long term damage that the cloning process may cause.
It is likely to cast fresh doubts over the safety and efficacy of cloning, which has so far been controversial largely for its ethical dimension. The study could lend weight to warnings that any attempt to clone humans might carry considerable health risks.
“Our observation should be taken into account in debates on reproductive cloning in human beings,” warns Dr Jean-Paul Renard, of the national institute for agricultural research near Paris, who led the study.
The calf that died had been cloned from a skin cell extracted from the ear of a 15 day old calf, itself cloned from a cow embryo. The “offspring” seemed to develop normally for the first month, after being treated with diuretics for an enlarged heart.
But rapid depletion of its red and white blood cells caused its condition to deteriorate. The calf was treated with iron supplements but it died from severe anaemia at the age of 7 weeks. At necropsy researchers found that the calf’s lymphoid tissues—the thymus, spleen, and lymph nodes—had failed to develop normally.
Cloning has regularly hit the headlines since February 1997, when researchers in Scotland successfully cloned a sheep, known as Dolly, using DNA from the mammary cell of an adult ewe. Until then, mammals had been cloned only from genetic material from embryos.
