This colored image of a chimeric blastoid shows the hollow cell ball of two types that is very similar to a blastocyst, an embryo in the stage of development when it is usually implanted in the uterus. Weizhi Ji / Kunming University of Science and Technology Hide caption
Weizhi Ji / Kunming University of Science and Technology
Weizhi Ji / Kunming University of Science and Technology
For the first time, scientists have created embryos that are a mixture of human and monkey cells.
The embryos described on Thursday in the journal Cell, were created, in part, to find new ways to make organs for people in need of transplants, says the international team of scientists who collaborated on the work. However, research raises a number of concerns.
“My first question is why?” says Kirstin Matthews, Science and Technology Scholar at Rice University’s Baker Institute. “I think the public will be concerned, and I agree that we are just kind of advancing science without having proper conversation about what we should and shouldn’t do.”
Still, the scientists who conducted the research and several other bioethicists defended the experiment.
“This is one of the main problems in medicine – organ transplants,” says Juan Carlos Izpisua Belmonte, Professor in the Gene Expression Lab at the Salk Institute for Life Sciences in La Jolla, California, and co-author of the Cell study. “The demand for it is much higher than the supply.”
“I don’t see this type of research as ethically problematic,” he says Insoo Hyun, Bioethicist at Case Western Reserve University and Harvard University. “It aims at high humanitarian goals.”
Thousands of people die every year in the United States Waiting for an organ transplantHyun notes. So in recent years there have been quite a few researchers in the US and beyond Injection of human stem cells into sheep and pig embryos to see if they might grow human organs for transplant in such animals.
So far, however, this approach has not worked. That’s why Belmonte has teamed up with scientists in China and elsewhere to try something different. The researchers injected 25 cells known as induced pluripotent stem cells from humans – commonly referred to as iPS cells – in macaque monkey embryos, which are genetically much more closely related to humans than sheep and pigs.
After one day, the researchers report, they were able to detect human cells growing in 132 of the embryos and examine the embryos for up to 19 days. This enabled scientists to learn more about how animal and human cells communicate. This is an important step in eventually helping researchers find new ways to grow organs for transplantation in other animals, Belmonte says.
“This knowledge will allow us to now go back and try to re-engineer those pathways that are successful in allowing human cells to properly develop in these other animals,” Belmonte told NPR. “We’re very, very excited.”
Such mixed-species embryos are known as Chimeras, named after the fire-breathing creature from Greek mythology that is part lion, part goat, part snake.
“Our goal is not to create a new organism or monster,” says Belmonte. “And we don’t do that. We try to understand how cells from different organisms communicate with one another.”
In addition, Belmonte hopes that this type of work could lead to new insights into early human development, aging, and the underlying causes of cancer and other diseases.
Some other scientists NPR spoke to agreed that the research could be very useful.
“This work is an important step that provides very compelling evidence that one day, when we fully understand the process, we can develop it into a heart, kidney, or lung,” he says Dr. Jeffrey Platt, Professor of Microbiology and Immunology at the University of Michigan who does related experiments but was not involved in the new research.
However, this type of scientific work and the opportunities it offers raise serious questions for some ethicists. The biggest concern, they say, is that someone might try to continue this work and turn an embryo made in this way into a baby. In particular, critics fear that human cells could become part of the developing brain of such an embryo – and the brain of the resulting animal.
“Should it be regulated as a human because it contains a significant proportion of human cells? Or should it only be regulated as an animal? Or something else?” says Matthews. “When do you start taking something and using it for organs when it actually starts to think and has logic?”
Another problem is that using human cells in this way could result in animals having human sperm or eggs.
“Nobody really wants monkeys walking around with human eggs and human sperm,” he says Hank Greely, a Stanford University bioethicist who co-wrote one Article in the same issue of the magazine This criticizes the research direction and states that this particular study was conducted in an ethically correct manner. “Because when a monkey with human sperm meets a monkey with human eggs, nobody wants a human embryo in a monkey’s uterus.”
Belmonte recognizes the ethical concerns. However, he emphasizes that his team has no intention of creating animals with partially human, partially monkey embryos, or even attempting to grow human organs in such a closely related species. He says his team consulted closely with bioethicists, including Greely.
Greely hopes the work will spark a more general debate about how far scientists can go with this type of research.
“I don’t think we’re on the verge of the afterlife planet of monkeys. I think there are few rogue scientists out there. But they’re not zero, “says Greely.” I think it is an appropriate time for us to think about, “Should we ever let this go over a petri dish?” “”
For several years the National Institutes of Health has weighed the idea of lifting a ban on funding this type of researchbut has been waiting for new guidelines expected to come out next month International Society for Stem Cell Research.
The idea of using organs from animals for transplants has also long raised concerns about the spread of viruses from animals to humans. If current research comes to fruition, scientists say steps will need to be taken to reduce this risk of infection, such as carefully sequestering animals used for this purpose and screening all organs used for transplantation.