Animal-human embryo test clears first hurdle


Proposed experiments with animal-human embryos cleared the first regulatory hurdle Tuesday as Japanese scientists seek permission for tests that could see human organs produced inside the growing body of an animal.

Researchers want to introduce a human stem cell into an animal embryo, to create a so-called chimeric embryo, which they can implant into an animal’s womb.

The hope is that this stem cell will grow into a fully-functioning human organ — a kidney or a liver, for example — as the animal matures.

This would mean when the creature is fully grown, the organ could be harvested from the animal and used for transplanting into a person in need.

“Experts will study what possibilities this kind of research will generate,” especially with regard to ethics and human dignity, a government official said of the panel, which is comprised of scientists, law professors and journalists.

During the meeting the government-appointed panel on bioethics under the Cabinet Office agreed on the framework of its recommendation and is expected to announce its final conclusion as early as this summer.

That recommendation will be sent to an education ministry committee tasked with drafting guidelines shaping the boundaries for cutting-edge embryonic research.

Unlike in the United States, there is little public opposition to research of this kind, with domestic media coverage overwhelmingly positive, reflecting relatively high levels of scientific literacy in the country.

Japan currently allows scientists to grow chimeric embryos in test-tubes for up to two weeks, but prohibits them from putting those embryos into an animal’s womb, the official said.

In the proposed experiment, researchers, led by Hiromitsu Nakauchi of the University of Tokyo, want to implant a chimeric embryo made from a fertilized pig egg and a human induced pluripotent stem (iPS) cell into a pig’s womb, he said.

Stem cells are infant cells that can develop into any part of the body.

Until the discovery of iPS cells several years ago, the only way to obtain stem cells was to harvest them from human embryos.

This is controversial because it results in the destruction of the embryo, a process that has seen objections from religious conservatives, among others.

Pioneering work done in 2006 by Kyoto University’s Shinya Yamanaka — a Nobel Laureate in medicine last year — succeeded in generating stem cells from skin tissue.

Like embryonic stem cells, iPS cells are also capable of developing into any cell in the body, but crucially their source material is readily available.

“We’ll see if the experiment goes well, but if we succeed in producing a human organ, the rest of the work toward practical use would be done within five years,” Nakauchi said.

Nakauchi’s team earlier this year succeeded in getting a white pig, which had been genetically altered so that it did not develop its own pancreas, to produce the pancreas of a black pig. The gland was genetically different to its host.

“Pigs have organs that are similar to human’s, in terms of both size and shape. In addition, we eat them on a daily basis,” he said.

“We have long used pigs in medicine, too. So they are thought to be acceptable to human bodies,” he said, noting that pig insulin has been used to treat diabetics and that pigs’ cardiac valves and pancreases have been successfully transplanted into humans.