Mythological Human-Animal Chimeras Are Here And Are Grown On U.S. Research Farms
Mixing Human DNA with Animal DNA
US labs growing human-animal hybrids for organs amid controversy
Labs in the US are growing human-animal hybrids that could one day be used to grow organs for transplants. The idea of human-animal chimeras is not new – in 2003, scientists in China announcing they had successfully fused human cells with rabbit eggs. Ethical questions have surrounded the issue ever since, and America’s National Institutes of Health put a ban on funding into such research until scientific and social implications had been fully assessed.
However, MIT Technology Review has reported some research centres in the US are pushing ahead with experiments, finding there have been 20 pregnancies of pig-human or sheep-human chimeras in the last 12 months. As of yet, there have been no scientific papers describing the work, and no animal has been brought to full term.
Chimeras (which in Greek mythology are fire-breathing hybrid creatures) are created by adding human cells to animal embryos, which are then implanted into a host for gestation. To grow human organs, for example, scientists could engineer an embryo so it is missing a specific organ. Human stem cells can be injected into it so when it grows in the womb, a human organ replaces that which has been removed. This organ could then be harvested from the animal for use in transplants.
While promising, the technology is highly controversial. Animal welfare groups say it is cruel, while others cite concerns over regulation. Animals could turn out to be too human (say brain cells were introduced, for example), as David Resnik from the NIH explains: “The spectre of an intelligent mouse stuck in a laboratory somewhere screaming: ‘I want to get out’ would be very troubling to people.”
Another issue is the moral and legal status of these animals. Would any human-animal chimera have human rights? If a chimera was created that was mostly human, would it still be owned by the laboratory? These are among the issues that prevent research moving forward.
Instead, scientists working on such projects are currently collecting foetuses to gather preliminary information on how much human cells contribute to the animals’ bodies. University of Minnesota scientists developed a 62-day-old pig foetus that appeared to have a reversed a congenital eye defect thanks to the addition of human cells. “We can make an animal without a heart. We have engineered pigs that lack skeletal muscles and blood vessels,” Daniel Garry, a cardiologist who leads a chimera project at the University of Minnesota, is quoted as saying.
Pablo Ross, a veterinarian and developmental biologist at the University of California, Davis, said at present they do not want the animals to fully develop as they need to ascertain if human cells are contributing to the organs: “We don’t want to grow them to stages we don’t need to, since that would be more controversial.
“My view is that the contribution of human cells is going to be minimal, maybe 3%, maybe 5%. But what if they contributed to 100% of the brain? 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.”
According to The Times, the UK Home Office will publish its own guidelines on human-animal chimeras this week, possibly paving the way for researchers here to carry out their own experiments. It is expected the guidelines will be in line with rules regarding other animal research.
U.S. Research Farms growing human organs inside pigs and sheep
United States Research Farms have decided to continue their efforts to grow live human organs inside animals like pigs and sheep. The process has been under fire regarding the issue’s ethics and concerns stemming from crossing animal DNA with human organs. The human-animal Chimeras are stirring ethical and health debates in many venues regarding the studies. The term Chimera was coined after years of experiments have taken place, as explained in the 2013 article on the Slate website by Daniel Engber.
The recent MIT Technology Review article details efforts to grow organs like hearts, livers, and lungs. According to the article at least 20 pig pregnancies containing human DNA have been confirmed. Although the pregnancies took place, no experimental publications have been published and none of the pregnancies have made it to full term.
Last September, in a reversal of earlier policy, the National Institutes of Health announced it would not support studies involving such “human-animal chimeras” until it had reviewed the scientific and social implications more closely. At that point the NIH stopped all funding to the project.
In a statement recently released the NIH also explained the ethical issues of blurring the lines between species and expressed concerns about the chance that animals’ “cognitive state” could be altered if they ended up with human brain cells.
The human cells are being added to the animal embryos in the very beginning stages of growth. Without published reports and the ongoing experiments taking place, the only information on the controversial tests is the presentation made to NIH’s Maryland campus at the request of the agency. The findings were presented by Daniel Garry, who leads the chimera project at the University of Maryland:
We can make an animal without a heart. We have engineered pigs that lack skeletal muscles and blood vessels. While such pigs aren’t viable, they can develop properly if a few cells are added from a normal pig embryo. With already melded two pigs in this way and recently won a $1.4 million grant from the U.S. Army, which funds some biomedical research, to try to grow human hearts in swine.
While some believe that the Chimeras could help the harvesting of human organs for transplants and the possibility of producing stem cells for research could save countless lives, others have begun the process of dismantling the experiments. NIH ethicist David Resnik made statements regarding the issue during the agency’s meeting last November:
The worry is that the animals might turn out to be a little too human for comfort, say ending up with human reproductive cells, patches of people hair, or just higher intelligence. We are not near the island of Dr. Moreau, but science moves fast. The specter of an intelligent mouse stuck in a laboratory somewhere screaming ‘I want to get out’ would be very troubling to people.
None of the experiments have been brought to full term at this point and researchers are only using the fetuses involved in the experiment for further testing no one knows what will happen next. The issue is clearly one that will bring ethical and moral debates and the ongoing experiments will need continued monitoring but at this point no clear laws regarding Chimeras have been implemented.