BEIJING • Scientists in China have created the first monkeys cloned by the same process that produced Dolly the sheep more than 20 years ago, a breakthrough that could boost medical research on human diseases.
The two long-tailed macaques (Macaca fascicularis) named Hua Hua and Zhong Zhong were born at the Chinese Academy of Sciences (CAS) in Shanghai, and are the fruits of years of research into a cloning technique called somatic cell nuclear transfer.
"The barrier has been broken by this work," co-author Muming Poo, director of the Institute of Neuroscience of the CAS Centre for Excellence in Brain Science and Intelligence Technology, said.
Until now, the technique has been used to clone more than 20 different animal species, including dogs, pigs and cats, but primates have proven particularly difficult.
The birth of the now six-and eight-week-old macaque babies also raises ethical questions about how close scientists have come to one day cloning humans.
Humans could be cloned by this technique in principle, said Dr Poo, though this team's focus was on cloning for medical research.
One day, the approach might be used to create large populations of genetically identical monkeys that could be used for medical research - and avoid taking monkeys from the wild.
The process that produced Hua Hua and Zhong Zhong remains "very inefficient and hazardous", because the two babies were the only ones born from a group of 79 cloned embryos, said British scientist Robin Lovell-Badge, who was not involved in the study.
"In the United States alone, they are importing 30,000 to 40,000 monkeys each year (for) drug companies," said Dr Poo.
"Their genetic backgrounds are all variable, they are not identical, so you need a large number of monkeys. For ethical reasons, I think having cloned monkeys will greatly reduce the (number of) monkeys used for drug tests."
Monkeys are commonly used in medical research on brain disorders like Parkinson's, cancer and immune and metabolic disorders.
"The method used for these experiments is similar to that used to clone Dolly" in 1996 but with several "updates", said Dr William Ritchie, an embryologist on the team that cloned Dolly the sheep at the Roslin Institute of the University of Edinburgh.
The process involves removing the nucleus from a healthy egg, and replacing it with another nucleus from another type of body cell.
The clone becomes the same as the creature that donated the replacement nucleus.
Other monkeys have been cloned in the past by a different and simpler technique called embryo splitting, which mimics how twins arise naturally.
The first primate ever cloned this way was Tetra, a rhesus monkey born in 1999. Embryo splitting can produce a maximum of four at a time, while the new technique could in theory clone far more.
Still, the process that produced Hua Hua and Zhong Zhong remains "very inefficient and hazardous", because the two babies were the only ones born from a group of 79 cloned embryos, said British scientist Robin Lovell-Badge.
"While they succeeded in obtaining cloned macaques, the numbers are too low to make many conclusions," said Dr Lovell-Badge, who was not involved in the study.