Efforts to create human-animal chimeras have rebooted an ethical debate after reports emerged that scientists have produced monkey embryos containing human cells.
A chimera is an organism whose cells come from two or more “individuals,” with recent work looking at combinations from different species.
The word comes from a beast in Greek mythology which was said to be part lion, part goat and part snake.
The latest report, published in the Spanish newspaper El Pais, claims a team of researchers led by Juan Carlos Izpis Belmonte from the Salk Institute in the US have produced monkey-human chimeras.
The research was conducted in China “to avoid legal issues,” according to the report.
Chimeras are seen as a potential way to address the lack of organs for transplantation, as well as problems of organ rejection.
Scientists believe organs genetically matched to a particular human recipient could one day be grown inside animals.
The approach is based on taking cells from an adult human and reprogramming them to become stem cells, which can give rise to any type of cell in the body. They are then introduced into the embryo of another species.
Izpis Belmonte and other scientists have previously managed to produce both pig embryos and sheep embryos that contain human cells, although the proportions are tiny: In the latter case, researchers estimate that only one cell in 10,000 was human.
Pig-human and sheep-human chimeras are attractive in part because pigs and sheep have organs about the right size for transplantation into humans.
Details of the work reported this week are scarce: Izpis Belmonte and colleagues did not respond to requests for comment.
However, Alejandro De Los Angeles, from the department of psychiatry at Yale University, said it was likely that monkey-human chimeras were being developed to explore how to improve the proportion of human cells in such organisms.
“Making human-monkey chimeras could teach us how to make human-pig chimeras with the hope of making organs for transplantation. It could teach us which types of stem cells we should be using, or other ways of enhancing what’s called ‘human chimerism levels’ inside pigs,” he said.
De Los Angeles pointed out that, as with previous work in pigs and sheep, the human-monkey chimeras have reportedly only been allowed to develop for a few weeks — ie, before organs actually form.
Robin Lovell-Badge, a developmental biologist at London’s Francis Crick Institute, agreed.
“I don’t think it is particularly concerning in terms of the ethics, because you are not taking them far enough to have a nervous system or develop in any way — it’s just really a ball of cells,” he said.
However, he added that if chimeras were allowed to develop further, it could raise concerns.
“How do you restrict the contribution of the human cells just to the organ that you want to make? If that is a pancreas or a heart or something, or kidney, then that is fine if you manage to do that. [But] if you allow these animals to go all the way through and be born, if you have a big contribution to the central nervous system from the human cells, then that obviously becomes a concern,” Lovell-Badge said.
The news of the monkey-human chimeras came shortly after it was reported that Japanese researchers, including Hiromitsu Nakauchi, received government support to create mouse-human chimeras.
In March, Japan lifted a ban on allowing such embryos to develop beyond 14 days and being implanted in a uterus, meaning these chimeras can, if permission for an experiment is granted, be brought to term.
Nakauchi has said he does not plan to bring the human-mouse chimeras to term yet.
Lovell-Badge said it is very unlikely the animals, if brought to term, would take on human-like behavior, but said the animals might not behave like “normal” rodents.
“So there are some animal welfare issues as well as the ‘yuck-factor’ ethical issues from making something more human. Clearly if any animal born had aspects of human appearance, their faces, their hands, their skin, then I suspect, while scientifically very interesting, people might get a little upset with that,” he said.
De Los Angeles and colleagues have suggested monkey-human chimeras could, in theory, provide new ways to study neurological and psychiatric diseases in humans.
“In theory, for diseases where primate models are not good enough, making human-monkey chimeras could provide a better model of brain diseases,” he told the Guardian, adding that in the case of Alzheimer’s, more than 150 trials have failed in 20 years, possibly because of a lack of a good disease model.
One possible approach for brain research is that a monkey embryo could be genetically altered and then injected with human stem cells so that part of the brain, for example the hippocampus, is composed only of human cells.
A similar approach has previously been used by Izpis Belmonte and colleagues to grow a rat pancreas inside a mouse.
“If you just swap the hippocampus, it doesn’t mean you are now going to have a human-functioning brain. It might have perhaps slightly better memories or slightly different memories … but they are not going to have a human cortex, which is what actually makes us human,” Lovell-Badge said.
However, such proposals walk straight into the ethical arena others have been at pains to dodge: The possibility of human cells ending up in monkey brains, a development some fear could result in the creatures being human-like.
Researchers have previously said they are able to prevent human cells from ending up in chimeras’ brains or sex organs.
De Los Angeles said there is still a long way to go before human-monkey chimeras are brought to term.
“The evolutionary distance between humans and monkeys spans 30-40 million years, so it is unclear if this is even possible,” he said.
“This difference is greater than 10 million years between mice and rats, and even the efficiency of making mouse-rat chimeras is already quite low,” De Los Angeles added.
While making monkey brains more human is a red line for some, in some ways it has already been crossed.
In April, scientists in China published a study in which they claimed to have introduced a human brain gene into monkeys, with the animals showing features including better short-term memory and shorter reaction times.
These animals are not chimeras, but it is clear that new boundaries are being pushed.
Lovell-Badge said he thought it possible that the development of human-monkey chimeras to study a part of the central nervous system could gain approval, but that it would take a while.
“In the UK, any proposal to make human-monkey chimeras would have to be very well justified, and it would have to get through a very tough review process. I am sure that any proposal to go straight to live born chimeras would not get approval in the UK and probably not also in Japan,” he said.
Late last month, Beijing introduced changes to school curricula in the Inner Mongolia Autonomous Region, requiring certain subjects to be taught in Mandarin rather than Mongolian. What is Chinese President Xi Jinping (習近平) seeking to gain from sending this message of pernicious intent? It is possible that he is attempting cultural genocide in Inner Mongolia, but does Xi also have the same plan for the democratic, independent nation of Mongolia? The controversy emerged with the announcement by the Inner Mongolia Education Bureau on Aug. 26 that first-grade elementary-school and junior-high students would in certain subjects start learning with Chinese-language textbooks, as
There are worrying signs that China is on the brink of a major food shortage, which might trigger a strategic contest over food security and push Chinese President Xi Jinping (習近平), already under intense pressure, toward drastic measures, potentially spelling trouble for Taiwan and the rest of the world. China has encountered a perfect storm of disasters this year. On top of disruption due to the COVID-19 pandemic, torrential rains have caused catastrophic flooding in the Yangtze River basin, China’s largest agricultural region. Floodwaters are estimated to have already destroyed the crops on 6 million hectares of farmland. The situation has been
In 1955, US general Benjamin Davis Jr, then-commander of the US’ 13th Air Force, drew a maritime demarcation line in the middle of the Taiwan Strait, known as the median line. Under pressure from the US, Taiwan and China entered into a tacit agreement not to cross the line. On July 9, 1999, then-president Lee Teng-hui (李登輝) described cross-strait relations as a “special state-to-state” relationship. In response, Beijing dispatched People’s Liberation Army (PLA) aircraft into the Taiwan Strait, crossing the median line for the first time since 1955. The PLA has begun to regularly traverse the line. On Sept. 18 and 19, it
Midday in Manhattan on Wednesday, September 16, was sunny and mild. Even with the pandemic’s “social distancing” it was a perfect day for “al fresco” dining with linen tablecloths and sidewalk potted palms outside one of New York City’s elegant restaurants. Two members of the press, outfitted with digital SLR cameras and voice recorders, were dispatched by The Associated Press to cover a rare outdoor diplomatic meeting on one of these New York streets. American diplomat Kelly Craft, Chief of the United States Mission to the United Nations, lunched in the open air with Taiwan’s ambassador-ranked representative in New York, James
RSS