Chimeras May Not Be a Fantasy Anymore

A group of U.S. scientists are attempting to do something that many people find troubling--creating embryos that are both human and animal. These scientists are trying to create these embryos, termed chimeras, in hopes that they can eventually help save numerous lives that have been affected by a wide range of diseases. One way these embryos could help is through their possible use as a model for how human diseases occur and progress. A more daring hope is one day being able to create domestic animals containing human organs that could be transplanted into patients.

But as with most genetic technology, these advances worry some scientists and biochemists. They fret that it would cross the ethical line on which bioengineering balances. "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. In fact, the situation is so delicate that the National Institutes of Health have ceased funding for the experiments until all ethical issues have been resolved. Yet, some researchers still march on with alternative sources of funding in hopes of finding something new. They claim that the product of this research, a chimera, is not just going to be for show. Rather, it would be used for biomedical purposes--saving lives.

Pablo Ross, a reproductive biologist at the University of California, Davis is one of these scientists. Recently, he has been trying to produce a pancreas that could be transplanted into diabetics. The first step, he says, involves gene-editing techniques that remove genes used in making pig embryos. This would involve making a small hole in the embryo’s outer membrane with a laser and then injecting a molecule that could eradicate the pancreas gene. After the deletion process, another hole is created in the pig embryo in order to inject human-induced pluripotent stem cells (iPS).

Similar to embryonic stem cells, iPS cells can transform into different cells or tissues that are in the body. The hope is that using iPS cells from human patients who need transplants can aid the process of transplanting organs. This is because using the specific patient’s iPS cells lowers the chance of the organ being rejected during the transplant.

Unfortunately, this is where the ethical line begins to blur. After the step mentioned above, the chimera embryos have to be put into the womb of an adult pig through a surgical process. In order to make sure results are statistically significant, more than twenty-five embryos would be injected into the pig’s uterus. This way, there is a higher chance that some iPS cells create the desired organs. The first checkpoint for these pigs is after four weeks, when organ-like structures begin to form. Scientists would examine the pig’s uterus in order to find out if and what organs are being made. At this point, it is important that all of the embryos be retrieved. In fact, Ross hasn’t allowed any of his experiments to go past twenty-eight days -- for a very important reason.

Recall that iPS cells can turn into anything they want. This quality of iPS cells is what makes the topic so controversial. Researchers can’t go on with the project without knowing exactly what the stem cells will do. They might form a pancreas, but there is also a chance they might yield a heart or a brain instead.

"If you have pigs with partly human brains you would have animals that might actually have consciousness like a human," Newman says. "It might have human-type needs. We don't really know."

An additional concern is that the stem cells could create human sperm and eggs. If a female and male chimera were to get together, there is a possibility that the uterus of the female could end up with a human fetus or even one that’s a pig-human combo. Many people believe that there is something sacred about DNA, something that defines us humans. If we were to insert this into other animals, we would be playing the role of god.

The researchers don’t see it that way. Although they acknowledge the issues, they insist the experiments are for the biomedical advancements. The researchers have vowed to never let the situation get out of hand. "We're very aware and sensitive to the ethical concerns," Ross says. "One of the reasons we're doing this research the way we're doing it is because we want to provide scientific information to inform those concerns."

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