While many nations around the world have prohibited these ethically fraught procedures completely, human-animal hybrid got approval in Japan recently.
Hiromitsu Nakauchi, the stem cell scientist, has been waiting for this time for over a decade. After years of planning, the persistent researcher was finally approved by a government ready to undertake one of the most controversial science research: experiments on human-animal embryos.
While many nations around the world have limited, defunded, or prohibited these ethically fraught procedures completely, Japan has now formally lifted the lid of this proverbial Pandora’s box. The nation made it legal earlier this year not only to transplant hybrid embryos into surrogate animals but also to take them to completion.
Nakauchi a leading stem cell researcher at Tokyo University and Stanford University has moved from nation to nation, pursuing his dream of one day growing customized human organs in animals such as sheep or pigs. Alone in the United States, more than 116,000 patients are on the waiting list for transplants. He hopes his idea can transform lives.
That ultimate objective is still a long way off, but ministry officials in Japan have finally given the green light to the next step in their research. As the first scientist to obtain government permission since the 2014 ban, Nakauchi is planning to take stuff slowly to catch up with public understanding and trust.
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“We don’t expect to immediately produce human organs, but this enables us to progress our research based on the know-how we have acquired up to this stage,” said Nakauchi.
The tests will begin by injecting human-induced pluripotent stem cells into embryos of rats and mice, all of which have been genetically manipulated to prevent pancreases from being produced.
The goal is for the rodent embryo to use the human cells to build itself a pancreas, and the team plans to watch these rodents develop and grow for two years, monitoring their organs and brains carefully throughout the process. Only then will the researchers request permission for pigs to do the same.
Although human-animal embryos, such as pig-human embryos and sheep-human embryos, have been produced in the past, they have never been permitted to develop to term before.
With this form of the research, one of the greatest fears is precisely where these human stem cells go in an animal and what sort of cells they might grow into when they are injected.
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While Nakauchi and his team are attempting to target this therapy to the pancreas alone, they will stop the test if they detect more than 30% of the rodent brains are human. These are part of the conditions of the government to avoid the ever coming into existence of a “humanized” animal.
However, Nakauchi doesn’t believe this will happen. He and his colleagues at Stanford made the first human-sheep embryo successfully last year, and although it was destroyed after 28 days, the hybrid did not contain any organs and very few human cells-only about one out of 10,000 or less.
“We are attempting to make sure that the human cells only contribute to the generation of certain organs,” Nakauchi explained the winter edition of Stanford Medicine’s Out There.
“We don’t need to worry about integrating human cells where we don’t want them with our new, targeted organ generation, so there should be many fewer ethical concerns.”