Animal-Human 'Chimera' Embryo Experiments To Be Given 'OK' By Japan's Regulatory Panel

iPS cell mice
This file photo, released from Kyoto University on October 5, 2012, shows two mice which were born from egg cells, made from induced pluripotent stem (iPS) cells of a mouse. Japanese experts were on Tuesday set to discuss rules for experiments with animal-human embryos, as scientists seek permission for tests that could see human organs produced inside the growing body of an animal.

A series for experiments in animal-human bio-engineering proposed by a team of Japanese researchers has cleared its first regulatory hurdles, news sources inside Japan reported Tuesday. The purpose of the proposed experiments is to grow human organs inside the body of a non-human animal.

While many in the US, Canada and Europe might have some foreboding about this ‘Island of Dr. Moreau’ – esque scenario, there is little aversion or opposition to such chimeric tinkering in Japan. In Japan, levels of scientific literacy are quite high by global standards and the culture takes enormous pride in its innovative talent — especially in the sciences; full approval for the experiments is expected in the next 30 days.

Once approval happens, the recommendation will be sent to a special committee charged with drafting guidelines regulating Japan’s state-of-the-Science bio-engineering programs.

The Japanese regulatory board currently permits the growing of chimeric (i.e., a combination of human and animal genomes) embryos in vitro for up to two weeks but prohibits transplanting of these into the uterus of an animal.

The team, led by by Hiromitsu Nakauchi of Tokyo University, wants to implant an embryo made from a fertilized pig egg and a special type of human stem cell called an “induced Pluripotent Stem cell” (iPS) into the uterus of a pig.

In 2012, Japanese biologist Shinya Yamanaka received a Nobel prize for his 2005-6 pioneering work in cell reprogramming that induced skin cells to revert to a younger cell state called ‘pluripotency’ called iPS cells) from which any cell type can be created. The technique does not require the destruction of an actual human embryo. This was welcome news for a new science that was being held back by various Bio-ethics concerns (beyond even destruction of the embryo).

This technique is at the heart of Nakauchi’s experiments.* [see note below] The team hopes that the iPS cell contained within the embryo will develop into a fully-functional and human compatible human organ (e.g., a kidney, liver or spleen) as part of the chimeric piglet fetus (whose native genes for the specific organ have been deleted; the human stem cell’s genes replace these), as it also develops “normally.”

Speaking to the AFP, Nakauchi commented:

“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.”

Earlier this year, Nakauchi’s team successfully grew a white pig (that was engineered to not produce its own pancreas) to produce the pancreas of a black pig whose DNA was different from the white pig’s DNA

While some might find this manipulation of genomes disturbing or dangerous, Nakauchi does not see why it should viewed much differently from what we are already doing.

“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 commented, “We have long used pigs in medicine, too. So they are thought to be acceptable to human bodies.”

Indeed, Nakauchi noted several examples: pig-grown insulin for diabetics and pig-grown pancreases and cardiac-valves have been successfully transplanted into humans.

However, there would be some strong religious objections to accepting organ transplants with organs grown in pigs.

But, these experiments — if successful — will represent a double advance: the creation of a viable animal embryo with a human iPS cell in it, and, the first time such organs will be grown in utero.

It is not clear if the new born piglet in the recently proposed experiments is intended to survive once the human organ has been “harvested”. Stay tuned to Planet save for more on this fascinating and controversial research.

* NOTE: This technique, though a breakthrough and marvel of science, is imperfect; the procedure of implanting genes (long sequences of the nucleotide bases: A, T, C or G) creates “insertional defects” (like copy number variations) which can cause serious metabolic problems and diseases. However, as reported here on PS, a major advance in this discipline occurred in 2010 (Warren et al) with the invention of RNA-induced Pluripotent Stem cells (RiPS cells) which use RNA (instead of actual DNA) to induce the pluripotent (multi-potent) state (the RNA molecules are then rapidly degraded by the cell, leaving no trace).

It is not clear at this stage if the Japanese research team will be using the newest technique, or the older version, with the risks that entails.

Source material for this post came from June 18 article: ‘Japan experts to OK animal-human embryos test: reports (Update) by Kyoko Hasegawa


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