Human-pig chimeras created, sparks hope and debate

 Human stem cells can, in fact, survive in pig embryos. | PC: National Geographic

Human stem cells can, in fact, survive in pig embryos. | PC: National Geographic

On Jan. 26, 2017 Jun Wu, professor in biological chemistry at University of Michigan, and his researchers published a paper entitled “Interspecies Chimerism with Mammalian Pluripotent Stem Cells” about a new creature he created. Wu planted human stem cells into a pig embryo. Those human cells survived. Hence, a chimera.

However, the human stem cells were quite dispersed throughout the tissue. About 1 in every 100,000, reported Wu. Now, jump a day before to Jan. 25 and we find Tomoyuki Yamaguchi and his researchers published their own paper. Yamaguchi’s research was groundbreaking in that he was able to grow mice organs in rats. It doesn’t end there, though. First, they had the rats grow pancreases using stem cells from the mice. Then, they induced diabetes in the mice (poor mice). Finally, they transplanted the rat’s pancreas, which was actually made of mouse cells, into the mouse and the mouse was effectively cured of its diabetes.

They cured diabetes! (at least in mice)

Why do these articles have the scientific community buzzing? Yamaguchi established that it’s possible to grow and transplant organs between different species. Wu discovered human stem cells can, in fact, survive in pig embryos. Put the two together and suddenly ordering organs, from a pig, on Craigslist is plausible. Potentially, no more waiting lists for organs.

At this point you may be wondering, “Sean, I understand scientists would use rats and mice because they’re genetically similar. But why on earth are scientists trying to fuse pigs with humans?” I hear you. Dr. Corraine McNeill, a biology professor, explained, “Scientists have already done experiments using pigs. A lot is understood about the physiology and how everything works in pigs. It isn’t uncommon to use pig parts in humans. Pig heart valves are being used to replace human heart valves. Also, pig organs are similar in size to humans.”

How exactly does one accomplish growing organs anyway? Dr. McNeill continued, “What they do is use a machine called Crispr. Basically, what it does is delete certain genes in the DNA so the physical structures they code for can no longer be read. For example, in the rat and mouse experiment they used Crispr to delete the genes that coded for a pancreas which would cause the rat embryo to develop without a pancreas. This would prove a problem if the embryo were left to continue developing. Which is why the stem cells of the mouse were inserted to play that role of creating a pancreas for the rat.” Dr. McNeill informed me the process would be similar to further experiments with pigs and humans where, for example, a pig embryo wouldn’t naturally develop a heart, but as soon as human stem cells are introduced, heart development begins.

The benefits of investing in such a project are inherent. However, do they outweigh the costs? Are they ethical? Religion and ethics professor Dr. Ben Holdsworth explained both sides of the spectrum. Dr. Holdsworth said, “There are a number of folks who argue in favor of such type of experiments. Their primary support for pursuing this line of research is that it may be possible to take stem cells of a human in need of an organ and introduce these stem cells into a pig embryo to develop an organ. Then they would harvest the organ and transplant it to the human.

“This will minimize organ rejection by the human body and possibly reduce healing time after surgery. It will lower the overall cost of organ transplants over time and increase the availability of organs to those who might need it.” He continued to explain the reason some people are against the pursuit of this line of research is because animals have rights. Certain animals have personhood, and using them for these experiments violates those rights. Dr. Holdsworth also offered a Biblical perspective. “God created human and animals separately, and because they were created separately to co-mingle the different kinds would be seen as a violation of divine order.”

Whatever stance one may take, wonder remains. What does the future hold for medical advancements? What I do know now is that as knowledge increases so will our responsibility to use it justly.

Disclaimer: Dr. Holdsworth does not necessarily claim any of the above views as his own, and provided them for perspective only.


Sean Hendrix is a senior studying biomedical science.