The Trouble With Cloned Mice

Despite the hype, cloning is still a hit and miss science. In a new report published in the latest edition of the journal Nature Genetics, scientists have shown there to be a link between cloning and early death.

Researchers of Tokyo's National Institute of Infectious Diseases said ten out of their 12 mice died young. Pneumonia and liver failure had brought the lives of the clones to an early end.

The researchers found that the mice clones had a degraded immune system compared with normal mice of their age, which could have caused the pneumonia.

The team reported that the cloned mice looked normal at birth, although certain liver enzymes, used to monitor liver activity, were abnormal.

"The cloned mice started to die 311 days after birth, and 10 of the 12 cloned mice died before 800 days," they wrote.

The findings give new cause for concern about attempts to produce a human baby clone, says the team in Japan responsible for the latest study.

"Much controversy has been generated over the ethics of human cloning," the researchers wrote. "The possible negative long-term effects of cloning, as well as the high incidence of spontaneous abortion and abnormal birth of cloned animals, give cause for concern about attempts to clone humans for reproductive purposes."

Hit and miss science

Cloning science remains in its infancy, with researchers still unsure exactly how the process works or how it affects the long-term health of cloned animals.

Researchers have cloned mice, pigs, cattle, and sheep, with mixed and confusing results: In many cases, clones have developed chronic health problems, while in a few other cases they appear healthy.

The first cloned animal, Dolly the sheep, is 5 years old and developed early-onset arthritis late last year - the first warning that even apparently healthy clones might have subtle abnormalities that emerge over time.

Some scientists said this was ample proof that human cloning, regardless of future advances in technology, should never be attempted.