Scientists Are Trying To Study Human Neurons… In Rat Brains?

12:11 minutes

simple solid black colored pattern of rats on a blue background
Credit: Shutterstock

Scientists have a tricky time studying neurons, partially because they are remarkably difficult to grow in a lab. They need other cells around them, and they don’t replicate or reproduce like other cells do. In a new study in Nature, researchers figured out that they can take a ball of human brain tissue and frankenstein it into a rat’s brain, and the rat can respond to it. This exciting discovery could offer scientists a new way to study the human brain. 

This week’s co-host Kathleen Davis talks with Umair Irfan, staff writer at Vox, about this story and other science news of the week. They chat about neurons that can play ping pong, COVID updates, a disturbing uptick in STI cases, how deep sea mining could destroy an underappreciated ecosystem, and how a mummified dinosaur named Dakota is challenging what paleontologists knew about dino preservation.

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Segment Guests

Umair Irfan

Umair Irfan is a senior correspondent at Vox, based in Washington, D.C.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow.

KATHLEEN DAVIS: And I’m SciFri producer Kathleen Davis.

IRA FLATOW: Kathleen is co-hosting the show with me this week. A bit later in the hour, we’ll talk about how gamification– playing games– is infiltrating corporate America and our day-to-day lives. And we’ll talk about the history behind a drink you’ve probably never heard of, the gruit.

KATHLEEN DAVIS: But first, a new study from this week’s show, that human nerve cells can be coaxed to grow– not in a Petri dish, not in a test tube, but in a rat brain. And these little Frankenstein rat brains may offer researchers a more accessible way to study our brains.

Here to fill us in on this story and other science news of the week is my guest Umair Irfan, staff writer for Vox, based in Washington, DC.

Umair, welcome back to Science Friday.

UMAIR IRFAN: Hello, Kathleen.

KATHLEEN DAVIS: So before we get into the rat brains, why is it so hard to grow nerve cells in the first place?

UMAIR IRFAN: Nerve cells, as you may know, don’t reproduce very much in the human body or in an animal after they’ve been born. Basically, the nerve cells that you have as a baby are most of the ones that you’re going to be having throughout the rest of your life. And because of that, it’s really hard to regenerate them and grow them in an artificial environment. And most often, when people do try to do that, they use stem cells. And when they do that in a Petri dish, they often don’t get good results that can actually mimic the human brain or an actual organism in a realistic way.

KATHLEEN DAVIS: So in this experiment, how did researchers actually go about growing the cells?

UMAIR IRFAN: What they did was they developed these three-dimensional clusters– they call them organoids– of human neurons. And rather than putting them in a Petri dish, what they did was they implanted these stem cells of neurons in rat brains. And they found that the rat brains actually provided a very nurturing environment for human cells. There was plenty of nutrients and flow, but also that the rat brains provided signals that encouraged these neurons to grow and develop. Human neurons were actually interacting with the rat neurons in the brain and actually sending signals back and forth.

So it shows that not only that can you grow these cells, but you can actually get them to function in a limited way.

KATHLEEN DAVIS: I mean, this sounds fascinating. It sounds like something right out of a science fiction novel. But how big of a deal is this actually?

UMAIR IRFAN: It could be a pretty big deal. Because it’s really hard to do brain research in situ, right? You don’t want to be doing experiments in a real human subject. But if you can start from the individual cells and scale up, you can learn a lot more about the fundamentals. And that gives you a lot more room to experiment and maybe potentially find out new treatments for illnesses or just uncover better understanding of how our brains actually work.

KATHLEEN DAVIS: Neurons are really the stars of the week. Because our next story, another study, showed that neuron cells can play ping pong. Umair, how did this even happen?

UMAIR IRFAN: Yeah. So imagine sort of a Petri dish. And at the bottom of the Petri dish is a network of sensors– basically, these little dots that can both send and receive signals– electronic signals. And on top of those sensors in this Petri dish are a network of neurons of human brain cells, basically, grown on top of these.

And what they found was, by using an appropriate level of stimuli and interfacing it with this computer program, they could actually coax these cells to play the game Pong. You may know this game as the game where you have this giant sliding paddle and a small ball that bounces off the wall and off of different angles. By interpreting signals, they were able to essentially respond to the stimuli of positive and negative reinforcement to move this paddle.

KATHLEEN DAVIS: So not to brag, but I am pretty good at Pong. How good are these neurons at this game? Could I take on a cell in a game of Pong?

UMAIR IRFAN: You probably could. Because these cells were only playing against themselves. But the researchers found that these cells actually learned to play the game faster than they could have done that with an AI. So it was actually learning in real time, in about five minutes, to actually move the slider around and bounce the ball around.

So it shows that these biological and electronic networks have this capacity to learn, and could potentially have an advantage over just computer programs alone.

KATHLEEN DAVIS: So let’s move on to some health news. This is sadly not the most positive news of the week, and it’s about COVID. So Umair, where do COVID cases stand right now?

UMAIR IRFAN: We’re seeing about 300 deaths per day from COVID-19, and that’s been holding at that level for a few weeks now. But health officials from the White House this week warned that, as people head back indoors during the winter and as holiday travel picks up, we’re going to likely see another wave of COVID-19 infections, but also another rise with other respiratory viruses, like RSV and influenza. And the combination of these things may become another public health threat this winter.

KATHLEEN DAVIS: There is a new booster out, one that targets both the original COVID strain and Omicron. How big of a difference could this booster make in the grand scheme of the pandemic?

UMAIR IRFAN: It all depends on how many people actually get the booster. There was a study by this group called the Commonwealth Fund. And they studied what would happen if people actually got boosters at the current rates compared to what would happen if people were boosted at the same rate as people get the flu vaccine. So roughly about 50%.

If 50% of US adults got the COVID-19 boosters, these bivalent boosters that target both the original and the latest variants of the COVID-19 virus, they found that, by next spring, we could avoid 75,000 deaths. If we got the booster uptake rate to about 80%, you could get up to 90% avoided deaths. However, the current booster rate is less than 4% of eligible Americans. And these boosters have been out for more than a month right now.

KATHLEEN DAVIS: 4% is very low. Do we know why more people haven’t gotten their boosters yet?

UMAIR IRFAN: Part of it is that people have largely checked out from COVID. We’ve seen, basically, a rollback of every other kind of public health measure, like mask wearing and social distancing. Testing rates have dropped as well. But a big thing is that people just don’t know about them. There was another poll that looked at awareness of these bivalent COVID-19 boosters.

And the Kaiser Family Foundation, they found that half of Americans have either heard very little or nothing about these new bivalent vaccines. So there seems to be this big information gap as far as who is aware of these boosters and what they can actually do for them.

KATHLEEN DAVIS: So our next health story is about STIs, or sexually transmitted infections, which are also on the rise. Umair, what is going on here?

UMAIR IRFAN: Right. Health officials have been raising the alarm recently that there’s the big rise in sexually transmitted infections and diseases. And these include diseases like chlamydia and gonorrhea. But one of the largest spikes is in syphilis. And that increased almost three-fold, particularly among women, between 2017 and 2021. And as a consequence of that, the number of infants that have been born with syphilis, prenatally infected with syphilis, has increased. And that is also a major public health threat.

It can be very dangerous and lethal to a baby or an infant. And about 40% of pregnancies in people with syphilis end up with the death of the fetus or the newborn.


UMAIR IRFAN: That’s why health officials are really concerned about screening and testing this. Because syphilis is treatable if you detect it early on. But you have to actually administer treatment in time. And that’s difficult if people aren’t being screened.

So my colleague Karen Landman just wrote about this this week. And she highlighted the fact that this is partially due to a decline in maternal health care. That, basically, mothers are having a harder time getting prenatal treatment, but also things like screening and other kinds of health access that would potentially catch these illnesses early on, and have the resources potentially to prevent them in the future as well.

Unfortunately, many of the same patterns we see with health care in the US are playing out here. The people that are most at risk are going to be people with less means. So people who are poor, but also people of color, who have less access to health care to begin with across the board.

KATHLEEN DAVIS: So let’s shift gears a little bit and head to our next story, which takes us all the way to the sea floor, where deep sea mining is happening. Umair, has deep sea mining increased in recent years, and why?

UMAIR IRFAN: It hasn’t really taken off just yet, but there’s a lot of interest that’s been increasing in recent years because we’ve seen this rise in a lot of electronic devices. And also, particularly with electric vehicles, you need minerals like manganese, nickel, lithium. And increasingly, we’re finding it harder to extract them on land, and we find that we can see a lot of the environmental consequences of mining on land.

But at the bottom of the sea, it turns out that these minerals can actually form in these aggregates, called nodules, and they just sit on the bottom of the sea floor. And the thinking is that, if you could go down there and just scoop them up, you could actually have access to a vast reservoir of minerals that you could potentially use to build electric cars and phones and all sorts of other devices.

KATHLEEN DAVIS: So have there been advancements in trying to access those nodules?

UMAIR IRFAN: Just this week, a company began testing a crawler, a device that’s going to scrape across the bottom of the ocean and scoop up these nodules. The issue, though, is that we don’t know very much about the bottom of the ocean. It’s a very unfamiliar territory to us, because light doesn’t even penetrate down there. And researchers have found that there’s actually a fair amount of biodiversity on the seafloor. And that area, this abyssal zone, has all sorts of creatures, like sea cucumbers and sea stars and other things that maybe we haven’t even found yet.

And so the concern is we might be interfering with a delicate ecosystem in ways that we don’t fully understand. And that could potentially have consequences that ripple throughout the whole ocean. So a lot of folks are saying now that we should probably put a pause on this until we can figure out just exactly what would happen if this mining actually did take off.

KATHLEEN DAVIS: Well, we have time for one more story. And this one is about one of my favorite topics, which is dinosaurs. But this story in particular is about a mummified dinosaur. I mean, when I think about dinosaur remains, I think about bones in a museum. This is the first time that I’m actually hearing of a dino-mummy. I mean, what do they look like, and how common are they?

UMAIR IRFAN: Right. You’re right that our conception of dinosaurs often comes from their hard tissue, their bones and nails and things like that. And very rarely do we see things like intact skin and muscle. Well, recently scientists were reporting their findings of this dinosaur that they found in North Dakota that they called Dakota. It’s a duck-billed herbivore. And they found that a big chunk of its skin was actually left intact on its tail, on its forelimb, and on its foot.

And these things are actually fairly rare, because soft tissue tends to decay very quickly. But by examining these dinosaur remains, they found that, in some circumstances, you can actually get the soft tissue to be preserved. And it turns out that these conditions might actually be more common than they realized, and there might actually be many more dinosaur mummies out there that we may have yet to discover.

KATHLEEN DAVIS: So does Dakota shed some light on what might be the key to dino-mummification?

UMAIR IRFAN: Yeah. When we talk about fossils, we typically have dinosaurs that are preserved in a dry, arid environment, and mummification tends to take place in those environments as well. What they found with Dakota was that it actually died in a very wet and humid environment, and its remains were actually right next to the water. And some teeth marks on the corpse show that it was probably scavenged.

And it turns out that might have actually been the key. Basically, when these scavengers started taking bites out of its corpse, it created opportunities for fluids and gases to escape. That allowed its skin to desiccate and dry out. And by drying out, that actually ended up serving as sort of a way to preserve it, essentially, kind of turning its skin into beef jerky, and letting it withstand these millions of years of erosion and sediment accumulation, and for us to eventually look at it.

KATHLEEN DAVIS: Well, that was quite an end for Dakota. That’s all the time we have for now. I’d like to thank my guest, Umair Irfan, staff writer for Vox, based in Washington, DC. Thanks so much for joining me.

UMAIR IRFAN: My pleasure. Thanks for having me.

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