"We found significantly impaired development in the cloned embryos compared with those derived from more conventional ART techniques", said Dr. Takeuchi, "and this has made us more convinced that reproductive cloning is unsafe and should not be applied to humans."
Drs. Takeuchi and Palermo were prompted to undertake the research by concerns about the increased incidence of imprinting abnormalities in children born after ARTs. The most prominent of these is Beckwith-Wiedemann syndrome, where children are born larger than normal.
Scientists also knew that cloned animals had been born with a similar condition, called 'large offspring syndrome'. Dr.Takeuchi's team set out to study whether the disorders arising in the ART system and those in cloned animals were comparable. The team took mouse oocytes and divided them into three groups. 68 were inseminated by ICSI, 37 activated parthenogenetically (without involving male gametes), and 77 were cloned by injected a cell nucleus into an egg where the nucleus had been removed. Of this latter group, 43 underwent first embryonic cleavage (the first few divisions of an embryonic egg) and 15 became full blastocysts.
"The embryos created by parthenogenesis and those from ICSI reached the blastocyst stage at the same rate, unlike the clones, where only 30% got that far", said Dr. Takeuchi. "Thi
Contact: Mary Rice
European Society for Human Reproduction and Embryology