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N.I.H. May Resume Funding Experiments With Human Stem Cells in Animal Embryos N.I.H. May Resume Funds for Human-Animal Stem Cell Research
(about 2 hours later)
The National Institutes of Health announced on Thursday it is considering lifting its ban on funding some research that injects human stem cells into animal embryos. The National Institutes of Health announced on Thursday it is planning to lift its ban on funding some research that injects human stem cells into animal embryos.
The N.I.H. announced its proposal in a blog post by Carrie Wolinetz, the associate director for science policy, and in the Federal Register.The N.I.H. announced its proposal in a blog post by Carrie Wolinetz, the associate director for science policy, and in the Federal Register.
The purpose of trying to grow human tissues or organs in animals is to better understand human diseases and further progress in developing therapies to treat them. No one is proposing making, for example, a mouse with a human brain — if that were even possible with today’s technology. Rather, the work is an extension of something researchers have long been doing — putting pieces of human tumors in a mouse, for example, to test drugs that might destroy the tumor. The purpose of trying to grow human tissues or organs in animals is to better understand human diseases and further progress in developing therapies to treat them. While no one is proposing making, for example, a mouse with a human brain, the work is an extension of something researchers have long been doing — like putting pieces of human tumors in a mouse to test drugs that might destroy the tumor.
But the idea of human cells developing inside an animal embryo and forming, in effect, a human-animal chimera, has alarmed some people. Last September, the N.I.H. put a moratorium on funding such experiments. But the very idea can be chilling: human cells getting into animal brains or human organs grown in pigs that would then be used for transplant, killing the animals, for example. Scientists have already grown a rat pancreas in a mouse.
Two months later, the N.I.H. convened a workshop to hear from researchers and experts in animal welfare. Some animal welfare experts are concerned that human stem cells added to early animal embryos might injure animals in unexpected ways. That, Dr. Wolinetz wrote in the blog post announcing the proposal, “raises ethical and animal welfare concerns.” The end goals of the science are to improve human health, to develop new therapies and to understand diseases like schizophrenia. The means to those goals, however, by making human-animal chimeras, will never meet with universal acceptance.
Two types of experiments are now being reconsidered for funding. The first is adding human stem cells to the embryos of animals that are not nonhuman primates before the embryos have developed to a stage when organs are starting to develop. With nonhuman primates like monkeys and chimpanzees, according to the proposal, researchers would have to wait until an embryo was further developed before adding human stem cells. The path ahead can be fraught, noted Paul Knoepfler, a stem cell researcher at the University of California, Davis. When human cells injected into an animal embryo develop into part of that animal’s brain, he said, difficult questions arise. “There’s no clear dividing line because we lack an understanding of at what point humanization of an animal brain could lead to more humanlike thought or consciousness,” he cautioned.
The N.I.H.’s plan will likely go into effect this fall — perhaps with some modifications — after a 30-day comment period that is now open for members of the public and researchers to express their opinions.
The N.I.H had put a moratorium on funding some stem cell work last September to consider some concerns that were being raised. For scientists, who had exciting plans to move forward with this type of research, the moratorium was “a little jarring,” said Dr. George Q. Daley, a Harvard professor and director of the stem cell transplantation program at Boston Children’s Hospital.
Two months later, the N.I.H. convened a workshop to hear from researchers and experts in animal welfare.
Two types of experiments that are now being considered for funding would still have to undergo a review by an N.I.H advisory committee. The first is adding human stem cells to the embryos of animals except nonhuman primates like monkeys or chimpanzees, before the embryos reach a stage when organs are starting to develop. With nonhuman primates, , according to the proposal, researchers would have to wait until an embryo was further developed before adding human stem cells.
The second type of study that would get extra scrutiny involves introducing stem cells into embryos of animals other than rodents where the cells could get into and modify the animals’ brains.
The N.I.H. would continue its ban on funding any research that could result in an animal with human sperm or eggs that would then be bred.The N.I.H. would continue its ban on funding any research that could result in an animal with human sperm or eggs that would then be bred.
Dr. Daley described some of the work researchers have been doing in this area.
First, they wanted to know if they had isolated new types of stem cells even more primitive than classical embryonic stem cells — ones that could turn into any type of tissue of organ. Accomplishing that involves putting the new cells into an embryo and seeing if they turn into the placenta, as well as every cell type in the adult animal..
In other experiments, they wanted to look at human stem cells that developed into very specific tissues. For example, one research team found that if they put rat stem cells into the embryo of a mouse that was missing genes needed to make a pancreas, they ended up with a mouse that had a rat pancreas.
Now, Dr. Daley said, the hope is to do the same sort of experiments with pigs missing genes for organs like a kidney or a liver and see if human stem cells can be used to grow human organs in the animals for transplants.
“It’s science fiction today but there has been enough progress in rat to mouse and even in pigs that it is at least theoretically possible,” Dr. Daley said.
Another team studied mice with mutations that do not allow glial cells of the brain to develop. Glial cells support and protect neurons in the brain. The scientists added human stem cells to the mouse embryos and ended up with mice whose brains harbored human glial cells. One goal is to do the same experiment with stem cells from people with psychiatric disorders to create new animal models to understand disease.
Dr. Wolinetz of the N.I.H. said during a teleconference that said she expected “some on the job learning.” As other types of brain research advance and as the stem cell research leads to new insights, the effects of putting human cells in animal brains will become clearer, she said.
“There is a lot we don’t understand about the brain,” she said, “ which is one reason the possibility of these animal models is really exciting.”