Scientists create first human-pig 'chimera'

Scientists have created the first human-pig hybrid in the search for ways to grow human organs for transplantation.

The so-called "chimera" - named after the hybrid creature in Greek mythology - was created through the injection of human stem cells into a pig embryo and was less than 0.001 per cent human.

It was only allowed to grow for 28 days, the BBC reports. Scientists said they imposed the limit so they could see whether the cells were assimilating together without allowing the development of a creature that would raise significant ethical concerns.

Subscribe to The Week

Escape your echo chamber. Get the facts behind the news, plus analysis from multiple perspectives.

SUBSCRIBE & SAVE

Sign up for The Week's Free Newsletters

From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.

From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.

Sign up

"We are restricting development to one month in the pig," said Professor Juan Carlos Izpisua Belmonte, who led the work at the Salk Institute for Biological Studies in La Jolla, California. "The reason is this is enough for us now to understand how cells mix, differentiate and integrate.

"Not everything that science can do we should do. We are not living in a niche in lab; we live with other people and society needs to decide what can be done."

The report, published in the journal Cell, "inevitably raises the spectre of intelligent animals with humanised brains", The Guardian says, as well as the risk that a chimera could escape into the wild. The US National Institutes of Health put a moratorium on funding for such experiments last year while these risks were considered.

Izpisua Belmonte said there was a "long distance" to go before it would be possible to grow animals with human organs that could be transplanted.

Added to that, the process is also inefficient. Of 2,075 embryos implanted, only 186 developed up to the 28-day stage, partly because of the major differences between human and pig make-up but also because pigs only have a pregnancy of four months, compared with around nine months in humans.

Researchers say chimeras could also be used to screen drugs ahead of human trials, studying the onset of human diseases and understanding how our embryos develop.

Salk scientist Jun Wu, the paper's lead author, said: "When the public hears the word 'chimera', it is always associated with Greek mythology; there is always this associated fear.

"But angels are chimeras. It can be a positive image and hopefully help with a worldwide shortage of organs, not create a monster."