Some U.S. scientists are trying to make embryos that are part human, part animal.
These embryos, known as chimeras, could eventually help save lives of people with diseases.
The chimera embryos would be used to create animal models to study how human diseases happen.
"You're getting into unsettling ground that I think is damaging to our sense of humanity," says Stuart Newman, a professor of cell biology and anatomy at the New York Medical College.
The National Institutes of Health has since imposed a moratorium on funding the experiments while officials explore the ethical issues involved.
"We're not trying to make a chimera just because we want to see some kind of monstrous creature," says Pablo Ross, a reproductive biologist at the University of California, Davis. "We're doing this for a biomedical purpose."
In one case, Ross attempted to create a pancreas that could theoretically be transplanted into a patient with diabetes.
For the embryo to develop and produce an organ, Ross has to put the chimera embryos into the wombs of adult pigs.
First, he uses the gene-editing technique to remove the gene from pig embryos to make a pancreas. He then makes a small hole in the embryo’s outer membrane to inject a molecule synthesized in the laboratory to delete the pancreas gene inside.
He then creates another hole to inject human induced pluripotent stem cells into the pig embryos. These cells can turn into any kind of cell or tissue in the body.
"One of the concerns that a lot of people have is that there's something sacrosanct about what it means to be human expressed in our DNA," says Jason Robert, a bioethicist at Arizona State University. "And that by inserting that into other animals and giving those other animals potentially some of the capacities of humans that this could be a kind of violation — a kind of, maybe, even a playing God."
Photo courtesy: Thinkstockphotos.com
Publication date: May 20, 2016