A Replacement Heart, From A Pig

12:16 minutes

a cute pig staring at the camera
Credit: Shutterstock

This week, doctors reported that they had successfully transplanted a heart taken from a pig into a human being, a type of procedure known as xenotransplantation. The pig had been genetically modified to lack a certain protein thought to be responsible for organ rejection in previous transplant attempts. 

The patient, a 57 year-old man, will be monitored for any sign of rejection or infection with a porcine virus—but doctors are hopeful that the work will lead to further transplants and a new source of replacement organs for people. 

Science journalist Roxxane Kamsi joins Ira to talk about that and other stories from the week in science, including research into how antivirals work in people infected with HIV,  the role of clothes dryers on microplastics pollution, a push to make the U.S. electric grid greener, and more.

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Segment Guests

Roxanne Khamsi

Roxanne Khamsi is a science writer based in Montreal, Quebec.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. Coming up later this hour, a look at what we know about the Omicron variant and children. But first, in this week’s top stories, Harvard Med School reports that multiple sclerosis is likely caused by infection by Epstein-Barr virus.

It suggests, says Alberto Ascherio, senior author of research published in Science, that most MS cases could be prevented by stopping EBV infection, and that targeting EBV could lead to the discovery of a cure for MS. We’ll be following up this story in weeks to come.

Here with other science and medical news, including news of transplanting a gene-modified pig heart into a human for the first time is Roxanne Khamsi, science journalist based in Montreal, Quebec. Welcome back, Roxanne.

ROXANNE KHAMSI: Thank you, Ira. It’s great to be here.

IRA FLATOW: A few weeks ago, we reported about another team that tested a pig kidney in a person for a few days. But this is something different. Tell us about this field of getting organs from animals– what, xenotransplantation, right?

ROXANNE KHAMSI: Yes, xeno– meaning, from other. This is something that happened in Baltimore where a patient who was 57 years old, who had a failing heart, was given an entire organ inside his body from a pig. And as you alluded to, the heart was from a pig that had been genetically engineered in a certain way to make the organ more acceptable for the human body.

IRA FLATOW: So what do you mean genetically engineered to be more acceptable?

ROXANNE KHAMSI: So what they did is they changed 10 genes in the pig. They took away four of the genes that make these molecules in pigs that would make the organ more likely to be rejected by somebody. And then they added six human genes to the pig so that it would kind of be almost disguised as something that a human body could accept.

IRA FLATOW: Sort of MacGyvered the pig heart just a bit.

ROXANNE KHAMSI: Exactly, exactly.

IRA FLATOW: And what are they looking for in this case to tell if they have been successful?

ROXANNE KHAMSI: Well, I think that the main thing with organ transplantation, especially when it’s from a whole other species, is you want to make sure that the immune system from the person who is receiving the organ doesn’t start attacking that organ, what we say is rejecting that organ. So they’ll be watching and monitoring this person who received the heart last Friday to see if his body is OK to accept this organ. And likely, he’s on immunosuppressant drugs that will tame the immune system to prevent that from happening.

IRA FLATOW: And of course, pigs have other kinds of viruses that they carry with them. We want to make sure that they don’t affect the human.

ROXANNE KHAMSI: Yes, so this includes porcine retrovirus, which is a pig virus. But the chances of this, scientists say, are low. That being said, they’re still monitoring it to make sure that it doesn’t happen.

IRA FLATOW: Now, there’s really interesting history about xenotransplantation, isn’t there?

ROXANNE KHAMSI: Yeah, so this is not, as we were talking about, the first time that an organ has been transplanted into a human being from an animal. In the 1960s, scientists tried– or I should say, doctors tried– transplanting chimpanzee kidneys into some human patients. There was a little bit of success for some months in at least one recipient, but in general it didn’t work out.

And maybe more known to people is that in 1984, there was a baby named Baby Fay, to the literature. She received a baboon heart from an infant baboon. And she lived 20 days. But unfortunately, her body started to reject the organ.

So this is something that’s been tried before. And of course, there’s all sorts of questions with ethics, as well about whether the animals consent to this or– I mean, clearly they don’t. So it’s a complicated field.

But it gives a lot of hope because so many people are on organ transplant waiting lists. I think it’s 100,000 in the US, mostly, for kidney transplants. So it’s a much needed scientific advance.

IRA FLATOW: Let’s talk about other health news that you have been looking at. You have a story about HIV that could be very promising. Tell us.

ROXANNE KHAMSI: I love this story. And I should make it clear. I didn’t write it. It was John Cohen writing about a paper in the Journal Cell. He wrote it for a science magazine.

And it’s a fantastic story because I think it’s so hopeful. Scientists, they looked at what happened when people had been on antivirals against HIV for years and years and years, like decades. And what seems to be happening is that that long treatment of antiviral drug therapy almost pushes HIV into parts of our genome that are less active. And what it suggests is that maybe this is a way that HIV is being kept in check.

Also, I think another thing that’s fascinating about this is that same pattern of sequestration of HIV is seen in people who are known as elite controllers, who are kind of naturally good at keeping HIV at Bay.

I should also mention that HIV is one of rare viruses that actually integrates into our genomes. So HIV doesn’t just hang around in our body. It becomes part of our DNA when we’re infected. And that’s why they were able to do this study to see where it goes in the genome.

IRA FLATOW: That’s an interesting point you make because I don’t know if many people think about the virus incorporating itself right into the human genome.

ROXANNE KHAMSI: Yes. And not a lot of viruses do this. Viruses that are with us for life are more likely to do it.

IRA FLATOW: Do we know why the virus gets shoved into these corners of the DNA, and not just omit it?

ROXANNE KHAMSI: So, this is something that I was also curious about. And I went back and I read the paper. And what the scientists suggest is that the cells where HIV goes into more active regions are kind of more easily detected by the immune system. So they’re killed or swept away. And the cells in which the virus goes into these less active regions are less likely for antivirals and the immune system to go after. So the idea is it’s almost like a selective pressure, if you will, of the cells where it happened to integrate into the quieter regions of the genome.

IRA FLATOW: Very interesting. In other news, you have a story about plastic pollution and my dryer.


IRA FLATOW: My spin dryer.

ROXANNE KHAMSI: It hits home because I was just drying laundry last night. So it’s definitely a story I think that anyone who does laundry with a dryer– and I lived in England for a while and there weren’t as many dryers. Over here in North America, a lot of people have dryers.

And what happens is if you have fabric that contains something like plastic, like polyester, as that fabric is rubbing up against itself and other things are washing and drying, it’s releasing tiny, tiny, tiny, tiny, tiny bits of plastic that aren’t captured by your dryer filter.

What happens is these small little microplastics end up in things we don’t want to see them in, like the placenta of unborn babies, or as far away as the Arctic and in the Earth’s troposphere. They’re so small that they can go to these many places. And it doesn’t seem great to me.

IRA FLATOW: Well, how much could my tumble dryer be affecting the release of these particles? Is it a big source?

ROXANNE KHAMSI: So the scientists in Hong Kong found that, based on their calculations and their simulations, each dryer would be releasing about 120 million microplastic fibers each year into the air. So it’s kind of a lot if you ask me.

IRA FLATOW: And the lint filter is not going to catch this stuff, right?

ROXANNE KHAMSI: It’s not. And what the scientists did is they started designing a 3D version of a filter that they hope would be more effective at capturing the microfibers, which I think is great because a lot of us do wear microfibers. I’m sitting here in fleece in Canada. So I mean, I hope that this is going to be something that we can really make progress on.

IRA FLATOW: Yeah, yeah, absolutely. I will think twice about when I look into my lint filter, what it’s missing.


IRA FLATOW: Especially those microfibers. Let’s talk about other emissions news– a movement to a cleaner electric grid. That’s something we’d like to have.

ROXANNE KHAMSI: Definitely. This is progress happening. As you might know, there was recently a big infrastructure bill that was passed in the US. And that allocated $65 billion for improvement of the electric grid and. That’s been earmarked for all these really important things.

Like, $2.5 billion is earmarked for making better transmission lines. And then there’s also a portion of money that’s going to go towards making the electrical grid smarter, like a smart grid that can allocate energy better so that people don’t have as many blackouts, which are happening more often. This is a piece of good news. And hopefully, some of these changes will have a real effect.

IRA FLATOW: I’m hoping that they find a way to bury a lot of these transmission lines– and I was hoping– so we don’t have these giant towers.

ROXANNE KHAMSI: Spoken by someone who might have had one knocked out in a snowstorm, perhaps, right?

IRA FLATOW: Well, you just see them. They need big right of ways. And going to have to carve out big areas to put these giant structures in there.


IRA FLATOW: So, and then if you’re in an urban area or actually if you’re in a rural area. When the snows come and wind comes and knocks down the power lines, your power lines go down.

ROXANNE KHAMSI: Don’t I know it.


IRA FLATOW: We’ve been thinking a lot about health testing lately, of course. But I understand that you have news about an approval for a new cancer risk test. Tell us about that.

ROXANNE KHAMSI: Yeah, so this comes from the company 23andMe, which is one of the biggest genetic testing companies, direct to consumer. So you spit in a tube, you send it off, and they look at your DNA, and they tell you all sorts of things about even the kinds of foods that you might like or not like.

So 23andMe have has been gradually adding some health tests over the years. A few years ago they got approval from the FDA to include a breast cancer risk test. It looks only for a few variants, but tells people if they have an elevated risk of breast cancer.

So they added to that something for colorectal cancer in the years since. And now there’s one for prostate cancer that they hope will tell people you might have an elevated risk. It only looks for a few variations.

And the statistic I saw was it was maybe one in 70 people of European ancestry would have this in their potential list of variations that they have. But importantly, the company doesn’t just tell you this. You have to opt in to find out. So you could do the genetic testing without knowing about your disease risk, which not everyone wants to know necessarily.

IRA FLATOW: Yeah, and you would hope that these are accurate predictions and not something that just makes you worry or not worry.

ROXANNE KHAMSI: Yeah, and also, since they’re only looking at some variants, it won’t tell you for sure if you don’t have the risk.


ROXANNE KHAMSI: It’s complicated.

IRA FLATOW: Finally, word about an onion that doesn’t make you cry. Is that true?

ROXANNE KHAMSI: It’s true. And I was thinking about this story and I was like, after the last two years, something that doesn’t make me cry is a really good thing.


And these onions have been gradually bred over decades. So it wasn’t genetically engineered. This is really a product of breeding. And in the US, it’s kind of known as the Sunion.

IRA FLATOW: The Sunion.

ROXANNE KHAMSI: Yeah, supposedly a little sweeter. Although I think the Washington Post, when it reviewed it a few years ago, said it was tasteless or maybe lacking in flavor. But this has been available for a couple of years in the US and then in Spain. And now people in the UK, now they have the chance to buy it because it’s now gone on sale there.

IRA FLATOW: One would think that the very chemical combinations– and you have to cut the onion to make that stuff get together to make you cry– would be the same things that give it its good taste that you like.

ROXANNE KHAMSI: I think you might not be too far off.

IRA FLATOW: Who knows?

ROXANNE KHAMSI: But there’s many layers to this story, just like there are an onion.

IRA FLATOW: Oh, oh, ooh, ending with a dad joke. Thank you very much, Roxanne.

[LAUGHING] Always.

Roxanne Khamsi. Science journalist based in Montreal, Quebec.

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