'Welcome to Paging Dr. Gupta. This is one of my favorite parts of the week, because I get a chance to connect with you, to answer your questions, and to hear what's on your mind. I also often get to talk about some of the big medical developments that are shaping our lives. If you caught last week's episode, for example, you know that we've been diving into something that sounds very much like science fiction, but at the same time has become very real, quickly, xeno-transplantation, X-E-N-O, transplantation. That is the medical term for transplanting organs from one species into another. In this case, specifically from animals into humans. Even more specifically, from pigs into people. Now, I'm so fascinated by this. I spent two years working on a documentary and we covered everything from the special pig farms to operating rooms. Scientists, surgeons, and patients who are making this happen. I spent a lot of time with all of them. Today, I'm really excited to keep the conversation going by answering the many questions you guys sent in. So let's get into it. Kyra's back with us. What do we have, Kyra? What's up first?

Yeah, so Paul wrote in wondering something pretty fascinating about personalized organs, and I'm gonna read it to you. So he wrote: over the past two decades, work was happening in the area of using one's cell makeup to create an organ in the lab. Is this still an approach being considered?

Okay, Paul, this is a great question. And the answer is yes. There is work that is being done in this particular space of creating basically individualized organs. One of the efforts of a company known as United Therapeutics, they work in the xenotransplant area, one of their efforts is also in creating what can best be called ghost organs. And we got a chance to see this. So imagine this, okay, so you have a pig organ, maybe a pig heart in this case, and it essentially is cleansed using these detergents of all of its biology, of all its cells. The only thing left is the scaffolding of the organ, okay? And then that scaffolding is essentially repopulated, reseeded with human cells, a specific human cells. Now, if you think about that, that essentially now is a personalized organ for somebody. This approach, this idea of creating ghost organs, is still further off than where we are currently with xenotransplantation. But I think to your question, this is the future. These ghost organs that are repopulated with an individual's human cells to create a personalized organ, that may be what we can expect in the future, so for example, let's say you have cardiac disease or you have some sort of disease where you know you're gonna need a transplant in the feature. You could potentially create a personalized organ that would be ready to go when you need it. Before your condition gets too far along, scientists could take some of your cells, simply from your blood or your skin, grow those cells, and then use them to populate the ghost organ scaffolding. Not only do you have an organ designed for you, but because they are your cells immunosuppression, rejection, acceptance, that shouldn't be an issue. It is essentially your organ. Now stick around, after the break we're going to get into just how many of these pig kidneys have actually made it into humans, and the bigger question, could this really solve the organ shortage crisis?

Okay, we're gonna try and get to as many pages as possible. Kyra, what do we have next?

'Next is Ann from Kansas, and she wants to know, you know, how many pig kidney transplants have been done? Whether anyone's lived long-term with them? And if they use different anti-rejection meds than the typical transplant.

'All right, first of all, how many kidney xenotransplants? Four in two living patients. And the reason I say living patients is because the first couple of transplants were actually done into patients who were brain dead. These were patients who had signed up to be organ donors, but instead in a way they became organ recipients when they were brain-dead. It was an opportunity for scientists to try and study, could these pig organs actually survive in the human body and they found that it worked. So in March of 2024, the first patient, a guy named Rick Slayman at Massachusetts General Hospital got a transplant, a xenotransplant, and he lived for two additional months. In April 2024, a month later, Lisa Pisano got a transplant, lived for a two additional month. A few months later, November of 2024 the third patient, Towana Looney at NYU got a pig kidney. She is still alive, but had to have the pig kidney removed after 130 days because of an unrelated infection. And then in January of 2025, this year, Tim Andrews, the fourth patient, he still has his xenotransplant and soon is gonna surpass 130 days, becoming the longest survivor in the world with a xenotransplant. Now, in addition to the four xeno kidney transplants, there have been two pig heart transplants as well, both at the University of Maryland School of Medicine. January of 2022, David Bennett lived for two additional months. September of 2023, Larry Faucette lived for an additional six weeks. Now, I just wanted to name everybody there because all the folks I just mentioned are pioneers. They volunteered, they put their hands up to do something that had never been done before. And they really sort of ventured out into the unknown. Very, very brave. And as a result of their efforts, they have really advanced science. That's why I wanted to give you all their names. Now, with regard to the second part of your question, the immunosuppression or the anti-rejection medications are very similar to what a human-to-human transplant would take, but typically at higher doses. So similar meds, but higher doses of the meds. And typically a few other drugs that have been added into the regimen, which have been shown to be effective so far in these early studies. The key to the success though, make no mistake, is the engineering of the pig's DNA to make it more similar to a human's. In some cases, there were some genes that were removed. In other cases, certain trans genes were added. So human genes actually added into pig's genome. All right, Kyra, what's our last question?

All right, Sanjay, we're wrapping up with one from Alia in Kuwait. She's asking a pretty big picture question: how far are we from this being a solution to the organ crisis?

Well, Alia, first of all, thanks for calling us from Kuwait. Five years. Five years is the number that I was given over and over again. Kidneys, in part, are going to be the first organs to really get to scale, but it sounds like they're also going to get to hearts, livers, and possibly lungs. We're about to enter clinical trials this summer with United Therapeutics, and we had a chance to visit the farm where they're raising the pigs for the trials. These are biosecure farms, look nothing like a typical farm. They have these filters and clean water and air. In some ways the food and the water and the air that the pigs are getting is even cleaner than what the humans are getting that work there. They have a high level of security. They have their operating rooms right there on campus. So they take the organs there and then send the organs directly to recipients around the country. I don't know, Alia, that I would necessarily say that this is going to solve the organ shortage crisis, but I think it's going to be a very important stopgap. Keep in mind, some of these farms can raise thousands of pigs, and there's a few of these farms around the country, but there's 100,000 people on the waiting list for organs in the United States alone. 17 people who die waiting for an organ. So we're going to need hundreds of thousands of organs potentially to try and solve the organ shortage crisis. And then there are a lot of people who don't currently qualify for transplant, even though they probably should, they're just not sick enough. Then the question becomes, could these pig organs start to supply organs to those folks as well? It's a fascinating field. It combines so many different scientific developments. IVF, cloning, CRISPR gene editing, transplant immunology, transplant surgery. All these scientific developments, some of them Nobel Prize winning developments, came together to create this field of xenotransplantation and potentially save and extend a lot of lives in the process.

'Thanks for being so fascinated by this like I am and thank you for writing in your questions, sending in your question. I always love hearing what you're curious about. And if there's something else health related you've been wondering about, don't be shy, record a voice memo, email it to AskSanjay@cnn.com, or give us a call, 470-396-0832, leave a message, and be sure to check out part two of our Chasing Life special on xenotransplantation. I'm gonna dive even deeper into what this breakthrough could mean for the future of medicine overall. The documentary is called Animal Pharm, P-H-A-R-M, and part two will be on the feed Friday. Thanks for listening, and I'll be back next Tuesday. Chasing Life is a production of CNN Audio. Our podcast is produced by Eryn Mathewson, Jennifer Lai, Grace Walker, Lori Galaretta, Jesse Remedios, Sofia Sanchez, Kyra Dahring, and Madeleine Thompson. Andrea Kane is our medical writer, our senior producer is Dan Bloom, Amanda Sealy is our showrunner, Dan Dzula is our technical director, and the executive producer of CNN Audio is Steve Lickteig. With support from Jamus Andrest, Jon Dianora, Haley Thomas, Alex Manasseri, Robert Mathers, Leni Steinhardt, Nichole Pesaru, and Lisa Namerow. Special thanks to Ben Tinker and Nadia Kounang of CNN Health and Wendy Brundige.