NEW YORK — Scientists have grown human cells inside pig embryos, a very early step toward the goal of growing livers and other human organs in animals to transplant into people, they say.
The cells made up just a tiny part of each embryo, and the embryos were grown for only a few weeks in the lab, researchers reported last week Thursday.
As expected however, this human-animal research has raised ethical concerns.
USA Today reports that the U.S. government suspended taxpayer funding of this experiments in 2015. The new work, done in California and Spain, was paid for by private foundations.
“Putting human cells in animals could pay off for studies of how genetic diseases develop and for screening potential drugs.” said Juan Carlos Izpisua Belmonte of the Salk Institute in La Jolla, Calif., an author of the paper in the journal Cell.
It is reported that such mixing has been done before with mice and rats. Larger animals like pigs would be needed to make human-size organs.
“That could help ease the shortage of human donors for transplants.” Scientists say.
The Salk team is working on making humanized pancreases, hearts and livers in pigs. The animals would grow those organs in place of their own, and they’d be euthanized before the organ is removed.
Most of the organ cells would be human. By injecting pig embryos with stem cells from the person who will get the transplant, the problem of rejection should be minimized, said another Salk researcher, Jun Wu.
What they did
Scientists used human stem cells, which are capable of producing a wide variety of specialized cells. They injected pig embryos made in the lab with three to 10 of those cells apiece, and implanted the embryos into sows. At three to four weeks of development, 186 embryos were removed and examined.
Less than 1 in every 100,000 embryonic cells was human, which still comes to about a million human cells, Wu said. That contribution is lower than expected, he said, “but we were very happy to see we actually can see the human cells after four weeks of development.”
Insoo Hyun of Case Western Reserve University in Cleveland told reporters that he understood why some people might object on moral grounds to making animals with human organs.
“It seems kind of creepy,” he said. But “this is a strategy to help save human lives” and so it is justified if properly done, he said.
