Back in April, the Salk Institute for Biological Studies in La Jolla, California, said that it participated in an experiment with Chinese researchers and managed to grow embryos that combined both monkey cells and human stem cells. Although none of the chimeras lasted longer than 19 days, the researchers still considered the experiment a success, noting that previous experiments with other animal embryos failed to produce viable chimeras.
The researchers said that their goal is to use these human-animal hybrids as models for testing new drugs, as well as for growing human organs for transplants. But lawmakers are beginning to fear that such experiments will cross ethical boundaries and contravene the dignity and sanctity of human life.
"I mean, any of us could speculate on kind of the Frankenstein concept, let’s put it that way, which that was being referred to as in terms of what this leads to," said Republican Sen. Mike Braun of Indiana.
"I don’t know. I think that I do believe that there’s a genuine interest in taking so much that we’ve learned through DNA analysis, understanding the genome of not only human beings but other animals, that there’s going to be that [temptation] contagion to go beyond maybe, just the altruistic effort of finding cures for very, very vexing ailments like ALS, like Alzheimer’s, like any of the diseases that are out there that are significant, that we're not even to the point where we know exactly what causes it, let alone cures."
Although federal officials have placed a moratorium on U.S. funding of chimera research, they are also reviewing restrictions and scientific developments. Meanwhile, Congress is debating a bill to spend nearly $200 million on research and development endeavors to counter China.
For Braun and his fellow Republicans, experiments involving the blending of human embryos with animal wombs and vice versa should be outlawed. In late May, Braun, along with Sens. James Lankford of Oklahoma and Steve Daines of Montana, sought to amend the Senate's massive research and development spending bill. They moved to block funding for experiments on certain human-animal chimeras, but the amendment failed by a 48-49 vote. Three senators, including two Republicans, did not vote.
According to Braun, the two absent Republicans – Sens. Marsha Blackburn of Tennessee and Thom Tillis of North Carolina – could not have changed the vote's outcome. He said that Senate Majority Leader Chuck Schumer, a Democrat from New York, would have blocked a vote on the amendment or ensured that the one absent Democrat, Sen. Joe Manchin III of West Virginia, would have joined the Democratic Caucus.
Braun, Lankford, five other senators and 25 House members led by Republican Rep. Chris Smith of New Jersey recently wrote to the National Institutes of Health (NIH) to voice their concerns about chimera research. In the letter, the lawmakers also requested details about any ethical analysis that the NIH is funding. The NIH did not respond to their request.
International guidelines are beginning to catch up to the advances in chimera research. This June, the International Society for Stem Cell Research (ISSCR) is expected to publish revised research guidelines. These guidelines are meant to address non-human-primate and human chimera research, according to Insoo Hyun, a bioethicist at Case Western Reserve University, who is leading an ISSCR committee discussing chimeras.
The ISSCR's current guidelines already prohibit researchers from letting human-animal chimeras mate. The group is also recommending additional oversight in cases where human cells could integrate with an animal host's developing central nervous system. Hyun pointed out that combining human cells with closely related primate embryos prompts questions about the status and identity of the resulting chimeras.
"Some people may see that you’re creating morally ambiguous entities there," he said.
Besides the U.S., other countries like the United Kingdom and Japan have, at points, limited research on chimeras involving human cells. But Japan lifted its ban on experiments with animal embryos containing human cells in 2019.
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