Building on the human-pig hybrid engineered in the lab last year, scientists have now gone all Dolly on us, and have made a controversial human-sheep chimera that is 0.01% human.
Presenting their findings at the American Association for the Advancement of Science in Austin, Texas over the weekend, the team from the University of California announced that they managed to make a breakthrough in human-animal cell count. Boosting human cell counts from 1 in 100,000 in their original study in pigs, to a human cell count of 1 in 10,000 in sheep, the team were able to further improve the procedure.
The scientists introduced human stem cells into an early-stage sheep embryo cell. Then, by returning the hybridised sheep-human cell into the sheep embryo, the scientists were able to make a sheep with a little bit of human in it.
But why?
As the rewired embryo’s DNA is unable to grow a certain organ, the 0.01% of human is there to fill in the gap. This means that the sheep will be able to grow a working human pancreas, for example.
The hope is that chimeras, like the human-sheep hybrid, will be able to pave the way for the quicker, more successful production of donor organs. At the moment, there is a shortfall of organ availability and, according to NHS Blood and Transplant, almost 460 people died waiting for organs in the UK in 2016 – not including those who died after the transplant, because their bodies rejected the organ.
“Even today the best-matched organs, except if they come from identical twins, don’t last very long because with time, the immune system continuously is attacking them,” Pablo Ross, reproductive biologist and one of the researchers, said during the press briefing.
Last year, the same team produced human-pig chimeras. According to the scientists, sheep are better candidates for growing organs. For one, they can be produced using IVF, and they have organs that are similar in size to ours. And secondly, fewer embryos are needed to be transplanted into an adult for it to be successful.
Though, it’s still early days. The researchers think that at least 1% of the embryo needs to be human before they can start successfully growing organs inside sheep or pigs.
That’s also not to mention the obvious ethical concerns about raising a sheep just to grow a human’s vital organs inside it.
Ethical concerns
“All of these approaches are controversial, and none of them are perfect, but they offer hope to people who are dying on a daily basis,” Ross added. “We need to explore all possible alternatives to provide organs to ailing people.”
“The contribution of human cells so far is very small,” stem cell biologist, Hiro Nakauchi from Stanford University, said at the press briefing. “It’s nothing like a pig with a human face or human brain.”
Still, the concerns are there. Could a chimera end up growing a human brain and then having the ability to think like a human?
“I have the same concerns,” Ross said. “Let’s say if our results indicate that the human cells all go to the brain of the animal, then we may never carry this forward.”
While the small percentage of human in the sheep was destroyed after 28 days, the slippery slope arguments still remain. With the team first creating pig-human hybrids and now sheep-human hybrids, the ethical questions will need to be answered before we see scientists incubating human organs in the bodies of animals.
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