Keeping a patient alive with a gene-edited pig kidney

HostIt's a bit strange to think about how many people are waiting for an organ right now. There are tens of thousands of names on a list, and most of them are waiting for a kidney. We have known for a long time that pigs are a close match for us in size and how their parts work, but the human body usually just sees a pig organ as a foreign invader and kills it instantly. Recently though, a man lived for weeks with a pig kidney working inside him. How did we finally get the human body to stop fighting and let that kidney do its job?

GuestIt really comes down to a massive rewrite of the pig’s own code. If you just took a regular kidney from a pig and put it in a person, the body would attack it in minutes. The blood would clot and the organ would turn black almost before the surgeons could finish the last stitch. The reason is that pigs have certain sugars on the surface of their cells that humans don't have. Our bodies see those sugars and basically scream that there's a massive infection. So, the first big move was to go into the pig’s DNA and cut out the bits that make those sugars. By removing them, the kidney becomes much more stealthy. It's like taking off a bright red coat and putting on a grey one so the immune system just walks right past it.

HostBut we have known about those sugars for a while now. I mean, scientists have been talking about this for decades. If that was the only wall in the way, why did it take until this year to actually keep someone alive for months?

GuestWell, the sugars were just the first wall. Once you get past that immediate attack, the body starts to notice other things that are wrong. The second big move was adding human DNA into the pig. In the most recent case, they added seven human genes that help control how blood flows and how the body handles swelling. Pig organs don't always play nice with human blood. It can cause tiny clots that eventually choke the organ to death. These human genes act like a peace treaty. They tell the human blood and the pig cells how to talk to each other so the kidney can keep filtering waste without the pipes getting clogged up. It's not just about hiding the pig parts anymore, it's about making those parts look and act like they belong to a person.

HostWait, you said they had to do a massive rewrite. How many changes are we talking about here? It sounds like you're basically building a whole new creature from scratch.

GuestIn this case, there were sixty-nine separate changes made to the DNA. That's a huge jump from what we were doing even five years ago. And a big chunk of those changes had nothing to do with the body attacking the kidney. They were actually about safety. Pigs have these tiny, old viruses hidden deep inside their DNA. They have been there for thousands of years, just sleeping. They don't hurt the pig at all, but there's a fear that if you put those cells into a human, those viruses could wake up. They could jump from the kidney into the rest of the person and maybe even start a new kind of sickness that we can't treat. So, the team had to go in and find every single one of those viral spots and snip them out.

HostThat sounds like a lot of cutting and pasting. Does it actually work? I mean, sixty-nine changes is a lot, but we're still talking about an organ that only lasted for about two months in a living patient. Is that really a success?

GuestIt's a massive success because of how well the kidney worked while it was there. The man who received it, Richard Slayman, had his own kidneys fail completely. Within days of getting the pig kidney, it was making urine and cleaning his blood just like a human one would. He was even able to go home and spend time with his family. The fact that he passed away two months later was a tragedy, but the surgeons found no signs that his body had actually rejected the pig kidney. That's the key part. The organ stayed healthy and did its work. We're learning that the hurdle might not be the pig itself anymore, but just how sick these patients are by the time they get to this point.

HostSo if the kidney was working, why did he die? It feels like we're still missing something if we can only get a few weeks of life out of this.

GuestThat's the big question everyone is looking at now. When someone is in total kidney failure, their whole body is under a huge amount of stress. They often have heart issues or problems with their blood pressure. While the pig kidney was doing its job of cleaning the blood, the rest of the body was already very worn down. We're also using very strong drugs to keep the immune system quiet. Those drugs are new and they're very powerful. They're not like the ones we use for regular human transplants. They're designed to block very specific paths that the body uses to sense animal tissue. It's a delicate balance. If you turn the guard dogs off too much, the patient gets an infection. If you don't turn them off enough, they eat the kidney.

HostIt still feels a bit like we're playing with fire. We're changing the code of an animal, cutting out viruses we don't fully understand, and using drugs that might be too strong for a sick person to handle. Are we moving too fast?

GuestThere's always that tension. But you have to look at the people on the waitlist. Most of them will never get a human kidney. They spend hours every week hooked up to machines just to stay alive, and many of them die while waiting. This technology is a way to stop that clock. Even if we can only get a few months right now, that's a few months where someone isn't stuck in a hospital bed. The goal is to get to a place where a pig kidney is just a bridge. It keeps you healthy and strong for a year or two until a human organ becomes available. Or, if we get good enough at these DNA edits, the pig kidney might just be the last transplant you ever need.

HostThe idea that we can edit a pig to the point where its kidney can sit inside a person and filter their blood for weeks is a huge shift in what we thought was possible.

GuestThe work done on those sixty-nine tiny changes in the DNA showed that the wall between us and other animals isn't as thick as we used to think.

HostThat list of thousands of people waiting for a phone call feels a little different now that we know we can build a bridge to keep them alive.

GuestThe pig kidney is no longer a dream for the far future, it's a tool we're learning to use right now.

HostThose thousands of names might finally have a reason to hope for a second chance.