To create this particular chimera, the researchers injected human stem cells into embryos from monkeys. They then cultured the cells for 20 days. The details of their study were published in the journal Cell.
The chimeras didn’t survive longer than 19 days. But according to study co-author Juan Belmonte, director of the Gene Expression Laboratory at SIBS, they do not intend to create a living chimera.
Instead, he and his colleagues are paving the way for scientists to one day be able to grow human organs for transplants or to test new drugs. But their work is bound to raise serious ethical questions.
Preempting such questions, lead author Tan Tao, an assistant professor at the Institute of Primate Translational Medicine, said that their work is not one of "bad taste" but is one of "highly practical value."
Thousands of people die every year because the organs they need are not donated in time, prompting researchers to conduct experiments with chimeras. The idea is that injecting human stem cells, which can develop into any kind of tissue, into animal embryos may allow scientists to grow human organs for transplantation. So far, that approach hasn’t worked.
For their experiment, Tao and his colleagues injected human stem cells into 132 embryos of macaque monkeys. Each embryo received 25 human stem cells. The stem cells were labeled with a fluorescent red protein for visualization.
The researchers put the embryos in a petri dish to be observed. The next day, they found that the embryos glowed, suggesting that the human stem cells had become successfully integrated into the embryos.
The experiment was far more successful than previous experiments using embryos from other animals like pigs. And though none of the embryos survived longer than 19 days, the experiment was still a huge success. In fact, their study could allow scientists to go back and try to re-engineer those pathways that were successful in allowing the development of human cells in animals.
According to Belmonte, organ transplantation is one of the major problems in medicine because the demand is always higher than the supply. "Our goal is not to generate any new organism, any monster," added Belmonte. Instead, they only want to understand how cells from different organisms communicate with each other. He also hopes that their work could lead to new insights into early human development, aging and the underlying causes of diseases.
The chimera embryos were destroyed after the experiment, according to the paper.
Other experts who weren’t involved in the work were also hopeful about the experiment’s implications. Jeffrey Platt, a professor of microbiology at the University of Michigan, said the work could help scientists better understand the process of developing stem cells into human organs, such as a heart, a kidney or lungs.
Nita Farahany, a professor of law and philosophy at Duke University in North Carolina, said there were lots of breakthroughs in the experiment. However, she said the work still raises urgent issues of public concern, adding that experts need to figure out what the right path forward is for responsible progress.
Others were more cautious about the experiment and its implications. Julian Savulescu, Uehiro Chair in Practical Ethics at the University of Oxford in England, said the research opens Pandora’s box. "What looks like a non-human animal may mentally be close to a human," said Savulescu.
He pointed out that such studies could become dangerous. Although the embryos were destroyed, it could only be a matter of time before human-non-human chimeras are successfully developed, he said. (Related: FDA now harvesting “fresh” aborted baby tissue to create “humanized mice.”)
"The key ethical question is: What is the moral status of these novel creatures?"
WeirdScienceNews.com has more articles about chimeras and other bizarre animal experiments.