Scientists Create Part-Human, Part-Pig Embryo

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THURSDAY, Jan. 26, 2017 (HealthDay News) — It might sound like science fiction, but researchers have successfully used human stem cells to create embryos that are part-human, part-pig.

Scientists said the long-range goal is to better understand and treat an array of human diseases.

The researchers hope to ultimately cultivate human tissue that can be given to patients awaiting transplants.

But that’s a long way off, said Jun Wu, who worked on the research.

“This study is reporting an important first step,” said Wu, a staff scientist at the Salk Institute, in La Jolla, Calif.

That step, specifically, was to insert human stem cells into pig embryos. Weeks later, some of the embryos showed signs that the human cells were beginning to mature and turn into “tissue precursors.”

Such embryos are known as chimeras, and they are controversial.

In 2015, the U.S. National Institutes of Health declared a moratorium on funding chimera research while officials assessed the ethical issues that the work raises. Last year, the agency proposed changes to that policy — though, it said, certain restrictions would still apply.

What are the ethical concerns?

For one, aspects of the technology make some people uneasy, said Jason Robert, a bioethicist at Arizona State University.

Before human stem cells are inserted, the animal embryos undergo “gene editing.” That capability — altering the genes of an embryo — raises red flags for some, Robert said.

And then there are the chimeras themselves. Some critics, Robert said, object on the basis of “human dignity” — arguing that transferring human characteristics to animals could denigrate what it means to be human.

Other concerns are less philosophical. Human stem cells can, in theory, grow into any mature tissue. So, some ask, what if the cells formed human sperm or eggs in the pig, or another animal?

Robert mentioned another issue some have raised. Could the stem cells get into the brain of a developing animal and endow it with human-like mental abilities or consciousness?

To Robert, that worry is a “peculiar” one. But he said the bigger point — that human stem cells are powerful, and research needs to proceed cautiously — is well taken.

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