Thu. Nov 26th, 2020

Scientists inject mice with human stem cells creating 'chimera' embryo

3 min read

Scientists create the most advanced human-mouse ‘hybrid’ embryo ever, with as much as 4% of its blood, brain tissue, and heart cells coming from human stem cells

  • Researchers created a hybrid embryo of mice cells and human stem cells
  • The embyros are the most advanced human-mice hybrids, with some made of up to 4% human stem cells found in the heart, eyes, brain, liver, and blood
  • The team hopes the technique could be used to future organ transplants

Scientists have successfully mixed human and mice cells in a hybrid ‘chimera’ embryo, the most advanced example of its kind.

The project was organized by researchers at State University of New York at Buffalo, and could point to a major advance in hybrid embryo creation that could be used in the future to harvest organs for human transplants.

The team successfully combined human stem cells with embryonic mice cells by temporarily deactivating a protein called mTOR in the human cells.

Researchers at State University of New York at Buffalo devised a new technique to mix human stem cells with embryonic mice cells, creating hybrid embryos made with up to four percent human cells

This protein regulates cell growth, and after several hours without the protein active, the human stem cells reverted to a ‘naïve’ state, their earliest form where they can grow into the widest range of possible organs or tissues.

These ‘naïve’ human stem cells raised the chances of successful integration with the mice embryo cells, according to a report in Science News.

The team injected between 10 and 12 batches of these naïve human stem cells into mice embryos and left them to develop for 17 days.

The resulting embryos had between 0.1 and four percent of their total cells from the human stem cells.

‘You put the same human cells in a mouse embryo, [and] they go fast,’ SUNY Buffalo’s Jian Feng told Science News.

‘In 17 days, you get all these mature cells that would otherwise take months to get in a normal human embryo.’

The researchers deactivated a protein that governs cellular growth to force the human stem cells to revert to a ‘naïve’ state where they could grow into the widest range of organs and tissues and thus had the highest chance of mixing with the mice cells

The human stem cells were most abundant in the red blood cells circulating through the embryo, and they were also present in liver tissue, heart, eye cells, and even the brain.

One area where the human stem cells weren’t found were in the reproductive organs, meaning the team won’t have to worry about the prospect of the chimera creatures potentially reproducing.

Many scientists are still concerned about the ethics of producing such mixed-species chimera embryos.

In 2019, Chinese researchers attempted to create hybrid human-pig embryos. They implanted 4,000 pig embryos with human stem cells, from which two survived gestation and birth, but both died less than a week later

In 2019, Chinese researchers created more than 4,000 pig pig embryos injected with human stem cells, of which two piglets survived gestation and were actually born, though both died within a week.

Douglas Munoz of Queen’s University in Kingston, Canada feared these attempts posed ethical risks that were beyond most scientists’ abilities to predict.

‘For us to start to manipulate life functions in this kind of way without fully knowing how to turn it off, or stop it if something goes awry really scares me,’ Munoz said in 2019.

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