French scientists raised fresh fears today about the dangers of cloning humans, saying it may cause serious long-term health problems.
Researchers at France’s Institut National de la Recherche Agronomique said a cow they cloned with DNA from an adult somatic cell appeared healthy but died from anaemia at seven weeks.
They believe the animal, whose immune system did not develop properly after birth, died because of errors in its DNA genetic reprogramming during the cloning process.
“This is the first report of a long-lasting defect associated with somatic cloning,” Dr Jean-Paul Renard and his colleagues said in a report in The Lancet medical journal.
“Our observation should be taken into account in debates on reproductive cloning in human beings.”
Cloning animals from adult somatic cells, which make up most of the body, is difficult because the DNA from the adult cells need to be reprogrammed, or set back to their embryonic state. The French cow was cloned from a cell taken from the ear of an adult cow that was an embryonic clone.
Renard and his team suspect something went wrong in the cloning process that interfered with the clone’s genetic reprogramming which stopped its immune system from developing.
When the cow died there was no evidence of infection or malformation but a post-mortem examination showed the spleen and lymph nodes had not formed properly.
Scientists at Edinburgh’s Roslin Institute, where Dolly the sheep was cloned, described the French study as probably the most detailed investigation of cloned animals.
Scientist Says It’s a Bad Sign
“It should be viewed as an important contribution to the evidence that nobody should be contemplating cloning human beings,” Dr Harry Griffin, Roslin’s assistant director, said in a telephone interview.
“All those that are working in this field know that the technology is unsafe. We have been working hard to get this point over to people speculating about the possibility of using it in cloning of human beings.”
The ethical issues of cloning humans have been hotly debated in the media hype that followed the birth of Dolly and other cloned mammals, but the discussions have paid less attention to the medical risks.
All the cloning groups around the world have produced cloned animals that died before or shortly after birth. Griffin said reprogramming could account for the very low success rate of the technique and the immature development of tissues, in this case the immune system.
“The reality is we know very little about the reprogramming process and we are going to have to work hard on that in order to ensure acceptable developments of this technology come to fruition,” he said.
The reprogramming of the somatic cells may not be 100 percent complete even if the animal is born at full term. Griffin thinks developmental abnormality is going to be a common phenomenon in cloning.
“It may well be that there are different tissues or aspects of physiology that are incompletely developed in different animals,” he said.