This little piggy could save your life

There is a fair share of non-trivial differences between humans and pigs, yet, things are a bit more ambiguous at the cellular level. Finding the differences at this resolution could potentially save the lives of millions of people in line for organ transplants.

On average, 18 people die a day because they did not receive an organ transplant. This problem is only worsening due to a shortage in human organ donors.

In light of this, many healthcare professionals and researchers are considering inter-species organ transplantation as a viable alternative (i.e. transplanting animal organs into humans). This is technically known as xenotransplantation; and for several reasons, scientists are finding that pigs seem to be the best donor candidate.

To begin with, pig tissue is very similar to humans. At 98% similar DNA to pigs, we share the exact same cellular machinery (e.g. ER, Lysozymes, Golgi, etc). Another benefit is that pig organs, on average, are about the same size and weight as human organs, meaning they are capable of processing similar levels of metabolites and fluids. Equally important is that pigs have coexisted with humans for thousands of years, making it unlikely that they are carrying any unknown infectious agents. Finally, pigs are a central food source, and questions of availability are moot.

Beyond these benefits, it turns out that humans bodies do not tolerate pig cells very well. Often the immune system will quickly recognize and destroy the foreign entity. Luckily, researchers are figuring out ways to elude this ‘rejection’ response, without using hazardous immunosuppressive drugs.

How is this being done?

One of the most remarkable differences between pig and human cells is presence of a molecule called Galactose-alpha-1,3–galactose  (alpha Gal). Alpha gal coats the surface of most mammalian cells, but is not present in humans or other apes (e.g. chimpanzee, gorilla).

As it turns out, the human immune system will not recognize and attack a pig cells if alpha gal is removed from its surface.

This knowledge has led scientists to create genetically engineered pigs which lack a gene required for alpha gal processing. Xenotranplantations from these animals into non-human apes has shown extreme promise, and prolonged the lives of non-human test subjects who experienced organ failure – for years in some cases.

The hunt for more cellular differences and their genetic manifestation continues, in hopes that an  ‘100% human friendly’ pig breed will one day be available and ready to extend the lives of millions of suffering individuals.

Photo credit: Image of piglet from cute-n-tiny.com

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