MARY LOUISE KELLY, HOST:
For the first time, scientists have created embryos that are part human, part monkey. They did it for medical research, but the experiment is raising some serious ethical concerns. NPR health correspondent Rob Stein has the story.
ROB STEIN, BYLINE: Thousands of people die every year in the United States waiting for an organ transplant, so researchers have been trying to find new ways to get more hearts, kidneys, livers and other organs for transplantation, including trying to grow human organs inside farm animals, like pigs and sheep, by injecting human stem cells into sheep and pig embryos to see if they can grow into human organs in those animals. Juan Carlos Izpisua Belmonte is at the Salk Institute for Biological Sciences.
JUAN CARLOS IZPISUA BELMONTE: This is one of the major problems in medicine - organ transplantation. The demand for that is much higher than the supply.
STEIN: But it hasn't worked so far, so Belmonte teamed up with scientists in China to try something new - injecting human stem cells into embryos of a species closer to humans, monkeys. They injected 25 human stem cells into 132 monkey embryos and were able to keep the embryos alive for 19 days. They call these part-monkey, part-human embryos chimeras, from the fire-breathing monster of Greek mythology that's part lion, part goat, part snake.
BELMONTE: Our goal is not to generate any new organism, any monster. And we are not doing anything like that. We're trying to understand how cells from different organisms communicate with one another.
STEIN: Belmonte says their chimera embryos have already revealed important new clues about how cells communicate. He thinks this could lead to new insights into early human development, the underlying causes of cancer and other diseases, aging and maybe someday how to grow human organs in farm animals, like sheep and pigs. Other scientists agree. Jeffrey Platt is doing related research at the University of Michigan.
JEFFREY PLATT: This work is an important step that provides very compelling evidence that someday, when we understand fully what the process is, we could make them develop into a heart or kidney or lungs.
STEIN: But this experiment raises some really serious ethical concerns, especially about someone going further and trying to make a baby this way. Or could, for example, some of the human cells accidentally end up in the brain? Kirstin Matthews is a bioethicist at Rice University.
KIRSTIN MATTHEWS: Should it be regulated as a human because it has a significant portion of human cells in it? Or should it be regulated just as an animal? Or should it be something else? And what point are you taking something and using it for organs when it actually is starting to think and have logic?
STEIN: Or emotions. And what happens if the creature makes human eggs or human sperm and they mate? Here's Hank Greely, a bioethicist at Stanford.
HANK GREELY: Nobody really wants monkeys walking around with human eggs and human sperm inside them because, if a monkey with human sperm meets a monkey with human eggs, nobody wants a human embryo inside a monkey's uterus.
STEIN: Now, Belmonte says he doesn't want to do anything like that. He just wants to study these part-human, part-monkey embryos in lab dishes. But bioethicists like Greely say society needs to start thinking about how far scientists should be allowed to go.
GREELY: I don't think we're on the edge of beyond "The Planet Of The Apes." I think rogue scientists are few and far between. But they're not zero. So it is, I think, an appropriate time for us to start thinking about - should we ever let these go beyond a petri dish?
STEIN: The National Institutes of Health has been considering lifting a ban on funding for these kinds of experiments but is waiting for new guidelines from the International Society for STEM Cell Research, which are coming out next month.
Rob Stein, NPR News.
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