Because an early embryo is almost invisible to the human eye, the room houses special microscopes equipped with micro-needles used to inject the human cells into them.Ī pig at the swine unit of the University of California, Davis. He opened the door to a small room containing incubators where the chimeric embryos are stored. “I want to show you some chimeras,” Nakauchi said when I visited his laboratory at Stanford last month. While the NIH funding ban doesn’t affect Nakauchi, it has put researchers under pressure to explain the purpose of their work. Stanford was able to recruit him with the help of a $6 million grant from the California Institute of Regenerative Medicine, a state agency set up a decade ago to bypass political interference from Washington.
“What if the embryo that develops is mostly human? It’s something that we don’t expect, but no one has done this experiment, so we can’t rule it out.”Īlthough Nakauchi was a star scientist, Japanese regulators were slow to approve his idea for chimeras-a “pig man” as critics put it-and by 2013 Nakauchi decided to move to the U.S., where no federal law restricts the creation of chimeras. “If it works as it does in rodents,” he says, “we should be able have a pig with a human organ.” In 2010, while working in Japan, Nakauchi used the embryo complementation method to show he could generate mice with a pancreas made entirely of rat cells. This process, called “embryo complementation,” is significant because the human cells can multiply, specialize, and potentially contribute to any part of the animal’s body as it develops. The new line of research goes further because it involves placing human cells into an animal embryo at the very earliest stage, when it is a sphere of just a dozen cells in a laboratory dish. In November, he was one of 11 authors who published a letter criticizing the agency for creating “a threat to progress” that “casts a shadow of negativity” on their work. “The specter of an intelligent mouse stuck in a laboratory somewhere screaming ‘I want to get out’ would be very troubling to people.”īecause chimeras could provide a new supply of organs for needy patients and also lead to basic discoveries, researchers including Garry say they intend to press forward despite the NIH position. Army, which funds some biomedical research, to try to grow human hearts in swine. Garry says he’s already melded two pigs in this way and recently won a $1.4 million grant from the U.S. While such pigs aren’t viable, they can develop properly if a few cells are added from a normal pig embryo. We have engineered pigs that lack skeletal muscles and blood vessels,” says Daniel Garry, a cardiologist who leads a chimera project at the University of Minnesota. Then, by adding stem cells from a person, they hope the human cells will take over the job of forming the missing organ, which could then be harvested from the animal for use in a transplant operation. By modifying genes, scientists can now easily change the DNA in pig or sheep embryos so that they are genetically incapable of forming a specific tissue. The experiments rely on a cutting-edge fusion of technologies, including recent breakthroughs in stem-cell biology and gene-editing techniques. Another, from the University of Minnesota, provided photographs of a 62-day-old pig fetus in which the addition of human cells appeared to have reversed a congenital eye defect. One researcher, Juan Carlos Izpisua Belmonte of the Salk Institute, showed unpublished data on more than a dozen pig embryo containing human cells. The extent of the research was disclosed in part during presentations made at the NIH’s Maryland campus in November at the agency’s request.
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