Transplanting a pig heart

The Problem

Heart failure is unfortunately common and difficult to treat. In the worst cases, the only treatment is to transplant another working heart to replace the damaged one.

However, there’s a serious shortage of organs to transplant. The grim reality is that not every patient that needs a transplant gets one.

That’s why scientists and physicians have been working on making some animal organs compatible for transplant. Specifically, pigs hearts are similar in size and structure to human hearts, making them promising candidates for transplantation.

And frankly, patients who need a heart transplant don’t have many other options. In many cases, it’s transplant or nothing.

The Solution

So, pig hearts. No one had ever tried transplanting one until last year.

In early 2022, a US patient facing near-certain death from heart failure made the decision to have the first-ever transplantation of an animal heart into a human. He was far down on the organ transplant list and elected to try the highly experimental pig heart transplant.

You might be thinking, how did they ever get permission to try this? Did the FDA actually approve it?

It turns out the FDA permits experimental therapies (read: “untested in humans”) in situations where the patient has no other options, knows the risks the experimental treatments pose, and chooses to try them anyway. The situations are called “compassionate use” cases.

The surgery itself was a success and the patient able to survive for several months before passing away. While not a long term success, it gave the patient a few more months and provided the doctors with valuable insight into how the transplanted heart functioned.

They used these insights to alter their treatment plan to hopefully improve how long the transplant lasts. Earlier this month, a 2nd patient in a similar circumstance to the first received the newly modified transplant.

The physician scientists involved had been working on genetically modifying pig hearts for years before the surgery happened. You can’t use a non-modified non-human organ for transplantation; the patient immune system would attack and destroy it almost immediately.

To prevent this, the scientists genetically alter the pig hearts to make them compatible with human cells. This, combined with carefully purifying the pig hearts (for viruses and such) and an undisclosed combination of other drugs will hopefully keep patient #2 going for much longer than they would have had otherwise.

If you’re interested in more of the biology behind the process, here’s an article written by one of the physician scientists about the biology of animal transplants.

See you next week for more science,

Neil

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