Pig-human embryos have been created in a dramatic bid to solve the organ transplant shortage.
Scientists have successfully combined human stem cells and pig DNA – with the aim of growing a human organ inside a pig.
But critics say the development of such hybrids is ‘offensive to human dignity’.
The ‘chimera’ embryos have been implanted in living sows and allowed to grow for 28 days before being tested and destroyed.
The idea is that if such an embryo matured inside an adult pig, the foetus would have an organ inside made from human cells. This could then be harvested and transplanted into a patient.
Experts are bitterly divided over the ethical implications of the breakthrough and the boundaries of genetic research.
Supporters claim it could spell an end to the shortage of donor organs – which means 1,000 people in the UK die every year while waiting for a transplant.
But others have described it as terrifying
‘Frankenscience’. The technique is being trialled on pig foetuses by US scientists who are experimenting with the genes involved in creating a pancreas.
Strict rules mean that, for now, the embryos cannot be matured past 28 days and no birth of a hybrid animal is allowed.
British universities could soon follow suit, with official UK guidelines published in January paving the way for labs to be granted licences for similar experiments.
The UK Animals in Science Committee, a part of the Home Office, said three-year research licences could be given if there was no viable method for creating organs other than combining human and animal cells.
The Government is keen to keep the UK at the forefront of the rapidly accelerating field of genetic engineering, which is set to revolutionise medicine in the coming years. Britain has already become the first nation to authorise a type of IVF that allows the creation of ‘three-parent babies’, and last week also became the first country to license the genetic editing of human embryos.
The latest breakthrough has been made at the University of California, Davis, where scientists have implanted pig-human hybrids into sows. Doctors have long discussed using pigs for human transplants, as the organs are roughly the same size as a human’s.
But they have repeatedly failed to overcome two hurdles – that the human body would instantly reject the foreign tissue, and that there is a risk of passing animal viruses into people. Those challenges have been surpassed by gene-editing technology called CRISPR, which allows scientists to alter DNA with remarkable precision. They have worked out how to remove from a strand of pig DNA the exact gene responsible for making a pancreas. This creates a void, which they hope will be filled when they inject the embryo with human ‘blank’ stem cells, capable of forming any form of tissue.
The hybrid embryo is then implanted into an adult sow – and as it grows into a foetus it develops a human pancreas. Dr Pablo Ross, leading the research, told BBC Panorama: ‘Our hope is that this pig embryo will develop normally but the pancreas will be made almost exclusively out of human cells and could be compatible with a patient for transplantation.’
But the work is intensely controversial. The main concern is that the human stem cells might migrate to the developing pig’s brain, giving it some human characteristics.
Dr Ross insists: ‘We think there is very low potential for a human brain to grow, but this is something we will be investigating.’
But US regulators remain cautious, insisting the foetus is removed within four weeks, so its cell structure can be examined.
Professor Walter Low of the University of Minnesota, which is researching a similar project, said pigs were an ideal ‘biological incubator’, adding: ‘The organ would be an exact genetic copy of your liver [for example] but a much younger and healthier version and you would not need to take immunosuppressive drugs which carry side-effects.’
Professor Low admitted that human cells spreading to the brain was a concerning prospect, but he added: ‘With every organ we will look at what’s happening in the brain and if we find that it’s too human-like, then we won’t let those foetuses be born.’
But Josephine Quintavalle, of campaign group Comment on Reproductive Ethics, said ‘these experiments is that they are absolutely offensive to human dignity, and no utilitarian justification whatsoever can ever bypass such opposition. We are absolutely horrified at this arrogance.’
Professor Stuart Newman, of New York Medical College, said: ‘You’re getting into unsettling ground that I think is damaging to our sense of humanity.’
Pete UK’s Julia Baines ondemned the research as ‘Frankenscience’, adding: ‘Creating human-animal hybrids is bad for people and worse for animals.’ – Daily Mail