A team of scientists in the USA and Spain claims to have produced human-monkey hybrid embryos in China.
According to a report in El País, researchers led by Professor Juan Carlos Izpisúa Belmonte at the Salk Institute in La Jolla, California, genetically modified monkey embryos to deactivate genes essential for organ formation. Human stem cells - which can grow into any type of tissue - were then injected into these embryos. Although none of the embryos were reportedly allowed to develop beyond a few weeks, it could open doors for future use of animals in human organ transplants. The team plans to publish their findings in a scientific journal.
Dr Estrella Núñez, project collaborator and vice chancellor of research at Murcia Catholic University in Guadalupe, Spain, said: 'The results are very promising.'
Professor Izpisúa Belmonte added: 'We are now trying not only to move forward and continue experimenting with human cells and rodent and pig cells, but also with non-human primates.'
This type of research had previously raised technical and ethical concerns and is currently heavily restricted in Spain and the USA. Dr Núñez told El País: 'We are doing the experiments with monkeys in China because, in principle, they cannot be done here [Spain] because of lack of infrastructure.'
Professor Robin Lovell-Badge at the Francis Crick Institute in London, told the Guardian: 'I don't think it is particularly concerning in terms of the ethics, because you are not taking them far enough to have a nervous system or develop in any way - it's just really a ball of cells.'
However, he added that if the hybrid embryos were developed further, it could raise concerns: 'How do you restrict the contribution of the human cells just to the organ that you want to make. If that is a pancreas or a heart or something, or kidney, then that is fine if you manage to do that. [But] if you allow these animals to go all the way through and be born, if you have a big contribution to the central nervous system from the human cells, then that obviously becomes a concern.'
Dr Alejandro De Los Angeles at Yale University in New Haven, Connecticut, believes that there is still a long way to go before human-monkey chimeras are brought to term. 'The evolutionary distance between humans and monkeys spans 30-40 million years, so it is unclear if this is even possible,' he told the Guardian.
In a final comment, Dr Núñez said: 'The ultimate goal would be to create a human organ that could be transplanted, but the path itself is almost more interesting for today's scientists. I am essentially aware that I will not see it happen [the development of human organs in animals] but to arrive at that point, it's necessary to pass through this one.'
The report follows a recent announcement that a Japanese researcher received government approval to create human-animal embryos and bring them to term (see BioNews 1009).