Human-Sheep Hybrids May Supply New Pancreas Source For Type 1 Diabetics

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There are so many amazing people with diabetes out there. So many people who keep a good attitude, advocate for other people with diabetes, and patiently raise awareness every time someone asks them, “Should you be eating that?”

But it’s tiring. It’s exhausting. Even the most dedicated blood-sugar managers deal with unexplained highs and lows, and as years pass the risk of serious complications increases. A brand new pancreas, one that doesn’t make your life so incessantly complicated, would be a dream come true. For a few very lucky folks, a pancreas transplant may be possible. But it’s not for everyone.

Bob Ethier had to wait 2 1/2 years before he could get his pancreas, and that was only after he had been approved. Just being on the waiting list for a pancreas is currently only available to those with severe complications of diabetes. And a person with a new pancreas must take immunosuppressant drugs to keep their immune system from destroying their new pancreas as it did the old one.

But pancreases aren’t available at every corner drugstore, and there are other desperately needed organs that are in short supply. According to the UNOS national registry for organ donation, about 20 people die each day waiting for a transplant. But researchers at Stanford hope to change all that. They hope, within the next 5 to 10 years, to be able to grow organs in human-sheep hybrids and transplant them into humans.

The hybrids are created when scientists remove part of a sheep embryo’s DNA, making a hole or vacuum into which they insert human stem cells. Then the hybrid embryos are inserted into a surrogate sheep’s womb. The hope is that the hybrid’s resulting human organs would be fit for human use.

Current regulations prohibit labs from allowing hybrid animals to develop longer than 21 days, so sadly the surrogate animals carrying the hybrids have to be put down before the hybrids are born. Researchers are applying for permission to extend their experiment longer so that they can better test the viability of the developing organs.

Dr. Hiro Nakauchi, the Stanford geneticist leading the research, said the team has successfully created a mouse pancreas in a rat that was then successfully transplanted into a diabetic mouse. The mouse accepted the pancreas, was cured of diabetes, and did not require any immunosuppressant drugs.

Scientists have already succeeded in creating human-pig hybrids, but have not yet been successful in creating a human organ. The human-pig hybrids had 1 human cell for every 100,000 pig cells. The new experiment with sheep creates hybrids with 1 human cell for every 10,000 sheep cells. Sheep have hearts and lungs similar to those of humans, and the embryo to fetus process is more efficient in sheep than in pigs.

Now, ethical questions aside (for the moment), there is still a real chance that a human pancreas grown successfully in a sheep’s body would be rejected when transplanted to a human. Robin Lovell-Badge, of the Francis Crick Institute in London, noted that even if science were able to ensure that all the pancreas cells were human, there would still be sheep blood vessels in the pancreas, and that may very well cause rejection.

Still, being able to grow human organs inside animals would be a huge scientific breakthrough, and if all the hurdles were crossed and organs could be transplanted, people on the organ donor list would have much more hope—they’d no longer have to wait for someone else’s death to mean their second chance at life. And a viable supply of healthy pancreases would mean that type 1 diabetes could become a temporary rather than lifelong disease. Scientific breakthroughs promise us so many possibilities.

But they also offer us ethical questions. Animal rights groups object to animal experimentation, some without exception, but at what point is a hybrid animal no longer an animal? At what percentage of human cells does it gain human status? That’s not an easy question to answer.

An associate professor of animal science at the University of California (Davis), Pablo Ross, has some concerns about these experiments and notes that if human cells spread further than anticipated, this research would cross ethical boundaries.

How successful the research will be, and how human and sheep cells will interact in the experiment’s final iteration, are yet to be seen. It would be a first if a human organ could be grown inside an animal. And for those waiting for a donor organ, a lifesaving development.

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Katie Taylor started writing in 5th grade and hasn't stopped since. Her favorite place to pen a phrase is in front of her fireplace with a cup of tea, but she's been known to write in parking lots on the backs of old receipts if necessary. She and her husband live cozily in the Pacific Northwest enjoying rainy days and Netflix.
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