New evidence that clones are normal has come from detailed investigations of 24 cloned cattle bred in the US.
鈥淚 would challenge anyone to distinguish them from a normal animal,鈥� says Bob Lanza of Advanced Cell Technology, the company that bred the 24 clones in Worcester, Massachusetts.
Lanza鈥檚 findings contradict those of other researchers who鈥檝e found that cloned animals often have fatal congenital abnormalities, or end up larger than normal. 鈥淎ll our data reinforce the view that the animals are physically and phenotypically normal,鈥� he says.
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Detailed clinical investigations of the animals鈥� bodies, blood and urine demonstrated that as well as looking and behaving normally, the cattle have normal immune systems, normal blood and normal organs. The cattle are aged between one to four and two have given birth to calves that appear normal as well.
But Lanza鈥檚 findings have failed to impress other cloning pioneers. They say that simply rubber-stamping the health of animals that survive reveals nothing about the hazards of the cloning process itself, a road strewn with casualties.
Miscarriage and early death
Lanza produced his 24 鈥渘ormal鈥� animals, for example, from almost 500 cloned embryos implanted into 250 cows, only 110 of which became pregnant. Of those, 80 miscarried, leaving the 24 survivors and another six that died at, or soon after, birth.
鈥淕iven that 73 per cent of pregnancies ended in abortion and 20 per cent of the calves died soon after birth, this paper surely confirms that it would be irresponsible to clone a person,鈥� says Ian Wilmut, who created the cloned sheep Dolly at the Roslin Institute in Edinburgh in 1997.
Mark Westhusin of Texas A&M University in College station agrees. 鈥淯nderstanding the early losses of fetuses is much more important,鈥� he says. It might enable individual cloned embryos to be screened to pick out the ones that will survive.
Lanza agrees that despite his encouraging findings, it is too unsafe to attempt cloning humans. 鈥淭he danger of generating a handicapped child is still too high, only if it鈥檚 a few per cent,鈥� he says.
But the results support the safety of 鈥渢herapeutic鈥� cloning, the creation of cloned tissues for transplant. 鈥淭hey suggest we could generate healthy, functioning tissue types by cloning,鈥� says Lanza.
More at: Science (vol 294, p 1893)
