Despite a National Institutes of Health moratorium on the funding of such research, scientists at the University of California, Davis have injected pig embryos with human stem cells as an effort to produce hybrids known as chimeras, BBC News revealed over the weekend.
The UK media organization, which was granted access to the work for their program Medicine’s Big Breakthrough: Editing Your Genes, explained that these human-pig embryos known as “chimeras” are being allowed to develop in sows for 28 days before the pregnancies are terminated and the tissues removed and analyzed by the laboratory team.
Pablo Ross, a reproductive biologist at UC Davis, and his colleagues told BBC News that these creatures should look and behave like normal pigs, except that one organ will be made up totally of human cells. The goal is to develop new organs to transplant into human patients.
The researchers are using CRISPR gene editing is used to extract DNA from a newly fertilized pig to prevent it from developing a pancreas, with the hopes that the human cells injected into it will cause the fetus to develop a human version of the organ instead. “Our hope,” Ross said, “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.”
Revelation again leads to debate over ethics of controversial research
Last September, the NIH said that it would not support the funding of such research until it had a better notion of the possible implications, according to The Guardian. Specifically, they said that they had concerns that the presence of human cells could travel to an animal’s brain, thus making it more human. Ross told BBC News that such an occurrence is unlikely.
“We think there is very low potential for a human brain to grow, but this is something we will be investigating,” he said. Previously, he and his colleagues have injected human stem cells into pig embryos without first removing an organ (like the pancreas) to create what is known as a genetic niche – a biological void that the inserted stem cells could potentially help to fill. Other scientists in the US have conducted similar work, but no other have allowed the fetuses to be born.
Walter Low, a professor in the University of Minnesota department of neurosurgery, told BBC News that while pigs were essentially an ideal “biological incubator” for growing human organs, and that they could ultimately be used to create hearts, livers, kidneys, lungs or other body parts, that such research was still in its preliminary stages and a long way off from clinical use.
Others, such as Peter Stevenson, chief policy advisor with Compassion in World Farming, have qualms with such research. Stevenson told the BBC that he was “nervous about opening up a new source of animal suffering” that that the first step should be to encourage more people to be organ donors. “If there is still a shortage after that, we can consider using pigs,” he added, “but on the basis that we eat less meat so that there is no overall increase in the number of pigs being used for human purposes.”