Xenotransplantation

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By Kary Vannice

In Mexico, 21,000+ people are currently waiting for an organ transplant. Eighty percent will die waiting. In the United States, 20 people a day die awaiting a transplant. Canadians in need of organs face a similar fate, made worse due to a very low donor rate in that country.  

Some patients are so desperate they turn to disreputable doctors in third-world countries to receive black market body parts. The New England Journal of Medicine reported that in countries like India and the Philippines a human kidney can be purchased for the sum of $1,000 – $2,000 USD. The article also noted that in Latin America a kidney could potentially cost more than $10,000 USD.

The harsh reality is, demand is outstripping supply in every corner of the globe. Viable donors just aren’t dying fast enough to replace all the needed organs, either by natural causes or underground doctors of death. 

Scientists and medical professionals have long known that a better alternative was needed.

Enter Sus scrofa domesticus – the common pig. 

Cross-species transplantation, known as xenotransplantation, dates back to the 19th century, when doctors began using frogs for skin grafting on human tissue. After centuries of experimentation, doctors have settled on the common pig for our best hope of animal-to-human organ transplant. 

Of course, it’s not as easy as taking the heart out of a live pig and sewing it into a dying human. There is a lot more bio-engineering involved, almost all of it taking place in high-tech labs where pig tissues are changed and manipulated. In 2017, scientists made a significant breakthrough by successfully “editing” out retroviruses found in pigs that could be fatal to humans. 

While other species may be more closely related to humans, genetically speaking, organs from a fully-grown pig are remarkably similar in size and function to human organs. Pigs mature quickly, breed young, and produce a lot of offspring, making them one of the most natural animals to work with in the field of organ transplantation.  

Using “pig parts” in humans isn’t new news, as Ian McConnell, emeritus professor of veterinary science at the University of Cambridge pointed out in an interview:  “There are several medical procedures using pig tissues such as heart valves in cardiac surgery, insulin-producing pancreatic cells to correct diabetes in man and corneal transplants which have been used safely in man for many years.”

But, he explains, going from heart valves to a whole heart is a bit of a quantum leap in the medical community. He finished the interview with these words of warning, “The use of animal organs such as pig kidneys and hearts is not without serious ethical and biosecurity concerns.”

And the medical community is not ready to take that quantum leap just yet. Labs all over the world are hard at work proving and perfecting their theories. One lab recently succeeded in harvesting lungs from one pig, “scrubbing” them clean of the donor’s blood and cells, then introducing them into a bath of nutrients and cells from the recipient. The lungs “grew” in this bath for 30 days, allowing the tissue to take on the “identity” of the recipient to reduce the chances of rejection. They were then able to successfully transplant that tissue into the recipient pig, which remained healthy for two months. 

Another lab is testing human-pig compatibility by introducing human stem cells into pig embryos to see what happens to the tissues when they grow in baby piglets. 

As scientists better understand xenotransplantation, the viability of pig-to-human organ transplants now offers real hope to those on organ donor waiting lists.

In February 2018, Time profiled George Church, a professor of genetics at Harvard Medical School. According to the article, Church “anticipates that pig-to-human organ transplant clinical trials could happen in as little as two years.”   He also “believes genetic editing could lead to organs that are such a good biological match that people would not need to take the anti-rejection drugs that can cause so many side effects.”

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