from JapanTimes.co.jp: 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
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
“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.
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
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,
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
“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.