Naked Mole-Rats Are Eternally Fertile
There may be no stranger—or more impressive—critter than the naked mole-rat. They may look unassuming, but they can defy aging, have an astonishingly high pain tolerance, and are resistant to cancer. And their list of superpowers doesn’t stop there.
Scientists recently discovered yet another way these rodents reject the mammalian status quo: by producing egg cells, and staying fertile, until the day they die. This makes them unlike humans, whose ovaries eventually stop producing eggs. So what can we learn about fertility from these strange critters?
Ira talks with the lead researcher of this study, Dr. Miguel Brieño-Enriquez, assistant professor at the Magee-Womens Research Institute and the University of Pittsburgh School of Medicine’s Department of Obstetrics, Gynecology and Reproductive Sciences.
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Dr. Miguel Brieño-Enriquez is an assistant professor in the Department of Obstetrics, Gynecology and Reproductive Sciences at the University of Pittsburgh Magee-Womens Research Institute in Pittsburgh, Pennsylvania.
IRA FLATOW: Believe me when I say that there may be no stranger-looking or more impressive critter than the naked mole rat. They may look unassuming, but they can defy aging, have an astonishingly high pain tolerance, and can be resistant to cancer. It is truly incredible. And it doesn’t stop there.
Scientists recently discovered yet another way these rodents reject the mammalian status quo by producing egg cells and staying fertile until the day they die. Yes, unlike humans, whose ovaries eventually stop producing eggs.
Here to tell us what we can learn about fertility from naked mole rats is Dr. Miguel Brieno-Enriquez, assistant professor at the Magee-Womens Research Institute at the University of Pittsburgh. Welcome to Science Friday.
MIGUEL BRIENO-ENRIQUEZ: Hello. How are you?
IRA FLATOW: Fine, thanks. Thanks for joining us. This is truly an amazing animal. Miguel, you study reproduction of all the critters in the world. Why do you look to the naked mole rat for answers?
MIGUEL BRIENO-ENRIQUEZ: Well, sometimes science is weird and it comes to you. I used to work with human and mouse. And it was more like an accident that these little creatures came into my life. We found these magic cells in the ovary, and everything started there. So I think that they found me.
IRA FLATOW: Let’s go into this. Because you knew that naked mole rats could breed at older ages, but you didn’t know how they did it, right?
MIGUEL BRIENO-ENRIQUEZ: Yeah, correct. So the last paper that was published before our work was from 1978. And they said, OK, it seems like they have a lot of germ cells, but we don’t know anything about that. So we decided to dig into how they do it. And for that, we started these experiments and this research. And it has been an incredible journey to learn how they do it.
IRA FLATOW: So you looked into the germ cells in these eggs. Tell us about the theories you were looking at.
MIGUEL BRIENO-ENRIQUEZ: Yeah. So if you think in other mammals, including the human, basically, you create a lot of germ cells, but you kill them a lot. At birth, they have a certain number, and everything starts to go down. So if you have a lot in the naked mole rat, that should be because either they have millions and millions and millions, or B, they don’t have this kind of apoptosis, or third, because they are creating more.
And in fact, we tried to look for all of them. And now we know that the real answer is a cocktail of the three options.
IRA FLATOW: Well, explain that to me. What do you mean by that?
MIGUEL BRIENO-ENRIQUEZ: That means that when we analyze the ovarian reserve of the naked mole rat and we count the germ cells, we see that postnatal they ate about 1.5 million. That is 95 times more than the mouse. But also we saw that those cells, they have the capacity to divide. And the division is not just during that small period postnatally, it’s also layered in stages in life.
And the third thing is, as I mentioned, a lot of cells go to apoptosis, or cell death, in human. And we found that, in the case of the naked mole rat, even when they have a little bit of this kind of cell death, it’s really limited, and there’s still being a lot of germ cells.
IRA FLATOW: Wow. So naked mole rats had 95 times more egg cells than a mouse of the same age, and those cells kept dividing throughout their lives. Wow. So these eggs aren’t running out?
MIGUEL BRIENO-ENRIQUEZ: Yeah, correct.
IRA FLATOW: So they’re producing eggs right until their death.
MIGUEL BRIENO-ENRIQUEZ: Well, so far, we analyzed them up to 12 years old. So they live for 37 years. And in all the cases, we see cells that are positive for the markers of germ cells and division. So it seems like we can say that it’s for the entire life. My lab is working to look in these, in 37-year-old ovaries. So hopefully, soon, I will be able to confirm you this. But, I mean, we know that they have babies forever. So a big chance that this is real.
IRA FLATOW: Wow. And you don’t know how that happens.
MIGUEL BRIENO-ENRIQUEZ: Well, it seems like what we see in these ages is that they have the population of cells that, once they turn into a queen, they start dividing a little bit faster than in the other ones. So it’s a mix of putting more germ cells into the pool at the same time that they have a big pool of cells.
IRA FLATOW: Right. Now, you’re a professor of reproductive sciences, right? There’s got to be something you want to learn about how these reproduce, how the naked mole rat is so great at making all these eggs and reproducing.
MIGUEL BRIENO-ENRIQUEZ: I mean, we want to learn everything about them. They’re so weird. But if we think in the human, there are a lot of things that are similar. First, if you think for how many years a female will be able to have babies, it’s kind of the same age. But also, how the processes in the ovary are happening are quite similar, up to a certain point.
That is great. For us, what is really important is how we can understand how they do it to bring to the human population the capacity, or in the future, develop strategies to improve the quality of the germ cells or extending the lifespan of the germ cells. But at the same time, we want to learn how they operate, per se, keep the animal healthy. Because in the case of the human, what we know is that, as soon as a female hits menopause, there is an increased risk of cancer, mental disease, et cetera, et cetera.
So in one side, it’s how we can help for reproduction, but at the same time how we can use what are we learning from them to improve aging in the female.
IRA FLATOW: Great point. Great point. And we wish you great luck in your research. And when you learn that stuff, will you come back and tell us?
MIGUEL BRIENO-ENRIQUEZ: For sure. I would love to talk to you and tell you more stories about our lovely creatures.
IRA FLATOW: We love them. We love them. Thank you very much for joining us today.
MIGUEL BRIENO-ENRIQUEZ: Thank you. Muchas gracias.
IRA FLATOW: Dr. Miguel Brieno-Enriquez, assistant professor at the Magee-Womens Research Institute at the University of Pittsburgh.
Rasha Aridi is a producer for Science Friday. She loves stories about weird critters, science adventures, and the intersection of science and history.
Ira Flatow is the host and executive producer of Science Friday. His green thumb has revived many an office plant at death’s door.