For the first time, a country officially authorized scientists to promote the creation of half human and half animal beings from stem cells. Scientific journal Nature announced that Japan gave the green light to Hiromitsu Nakauchi, who leads research groups at universities in Tokyo (Japan) and Stanford (USA), to advance his researches in this field.

This type of scientific research purports to generate hybrid animals with certain human cells, tissues and organs – beings called chimeras, a reference to the creatures from Greek mythology. The idea is that these human organs developed inside chimeras are compatible with patients having disease requiring transplant.

Since 2010, when he presented his first work on chimeras, including rats and mice, Nakauchi has been a reference in this research field. With permission from the Ministry of Science of Japan to advance with a chimera gestation for more than 14 days, he can go a step further and try to create a human pancreas inside the body of a rodent. However, the challenge isn’t easy at all.

“To date, human cells have not survived in animal embryos. However, the goal of our research is to make human cells survive and contribute to the formation of chimeras,” he explained in a statement to Nature.

His first experiments tried to cross sheep and human cells, but the result did not meet expectation and no organ was even formed.

“It doesn’t make sense to bring human–animal hybrid embryos to term using evolutionarily distant species such as pigs and sheep because the human cells will be eliminated from host embryos early on,” criticized Jun Wu, scientist at University of Texas, to Nature.

Ethical Conflict

The 14-day limit for chimera gestations is not random: this is the limit outlined by the scientific community for the emergence of a human central nervous system. So, any embryo whose gestation is stopped up to 14 days will not have developed human brain cells yet.

The concern of many bioethicists is that chimeras grow not only human-like organs (for example, pancreas), but also that human cells spread over the body, especially in the brain. The ethical concern, they reiterate, is even greater: would an animal with human-like brain have conscience? Would this being, at some level, be human? 

For a while, Nakauchi has said that he does not intend to advance the gestation of human-rat hybrids for more than 15.5 days. However, he says that he soon plans to request approval from the government to grow human-pig embryos for up to 70 days.

Human-monkey is here, says scientist

In a lab in China (a country that does not approve nor forbid this type of research), scientist Juan Carlos Izpisúa and his team successfully grew a human-monkey for the first time, said the Spanish newspaper El País.

The process was similar to that of the Japanese researchers. Izpisúa genetically modified monkey embryos and inserted human stem cells able to generate any type of tissue in the ape body. In his work, the Spanish stopped gestation before the birth of the monkey.

The Spanish team says they went a step further in this type of technology: a biological mechanism that self-destroys human cells has been enabled, should they migrate outside the target-organ.

Content published in September 18, 2019