This episode is brought to you by  the Music for Scientists album, now available on all streaming services. [♪ INTRO] 200 years from now, it's entirely possible that  we will have people living off-Earth full time, either on another planet like Mars,  or in some kinda space station.

By then, we'll probably be pros at  living in low-gravity environments. We'll have figured out how to  solve the problems we have today, like how spaceflight can take a  toll on the heart and immune system.

And when we get to that next  big chapter of humanity, we'll have a tiny test  subject to thank: fruit flies. While they may not seem like  useful stand-ins for humans, fruit flies have more in common  with us than you might think. Many fruit fly genes mirror  the functions of human ones, making them useful in  understanding what those genes do.

And they also have some characteristics that make them especially great  for studies performed in space. For one, they don’t take up a lot of room, which is super important in an  environment where space is limited. Thousands of flies can be housed in a  container the size of a deck of cards.

Also, their lifespan is only about two weeks, so scientists can study several  generations of them in a month. So, fruit flies have been sent  to space over and over again to test different effects of spaceflight,  especially how microgravity affects living bodies. And while we still have plenty of questions,  they are already teaching us a lot.

For instance, in space, the  heart acts a little differently. Like, among other things, its muscles get  weaker since they’re not fighting gravity. We know this is true of other muscles as well,  but considering how important the heart is, figuring out exactly how  it changes in microgravity   will be huge for our long-term future in space.

And these are, of course,  things we’re studying in humans, but we can only send so many people  to the Space Station at a time. Which means we can only learn so much about exactly what’s happening to  the heart and how to combat it. So one study, published in November  2020, used more than 200 fruit flies as a model for how spaceflight  affects cardiac disease and function.

The scientists found that flies living  in microgravity had smaller hearts that weren’t as effective at pumping blood, which  is similar to what can happen to astronauts. But the researchers also  found the flies had problems creating the proteins needed to  keep the heart working properly. So now, that’s something else for  cardiac researchers to keep an eye on.

And eventually, studying these proteins could accelerate the development of new  treatments, especially for longer missions. But as important as our hearts are, one area of fly research that’s been especially  fruitful is studying the immune system. Astronauts experience a  suppression of their immune system during and right after spaceflight that  makes them more susceptible to infection.

And flies offer a very specific advantage  for helping us understand how and why. See, the human immune system has  two branches: innate and adaptive. The innate immune system is  something you are born with.

It’s essentially a system of barriers that protect against foreign particles  like viruses, bacteria, and parasites. These include physical barriers like your skin, and general immune responses like inflammation. Meanwhile, the adaptive  immune system is the part that learns to respond to threats as it’s exposed to  them, using specialized cells and antibodies.

Untangling what each branch  does and how it changes in space is somehow even harder than it sounds. And that’s where fruit flies come in. They do not have adaptive immune systems;  that’s limited to us vertebrates.

So they can allow us to really dial into  just how the innate immune system works without the whole other part getting  in the way and confusing things. The key with the innate immune  system is that, for it to work, your body has to recognize  pathogens as foreign objects. Then, it can work on fighting them.

To do that, the innate immune system  uses molecules called receptors to bind and recognize other molecules  on the surface of infectious agents, like bacteria and viruses. And when it comes to spaceflight,  studies have found that the immune system can become impaired when communication  to these receptors is disrupted. Like, a 2014 study showed that fruit flies born  and raised aboard the space shuttle Discovery were a lot more susceptible to certain  infections compared to flies on Earth.

But in that study, only one of the two receptor  systems the researchers looked at was impaired, the one that responds to fungal infections. The other, which responds to certain types  of bacterial infection, was unaffected. They haven’t quite figured out why, and propose that it could have something to do with how  the specific proteins act in each system.

But it could mean that the fungal receptor is  more sensitive to disruption in microgravity. Which would suggest that the  effects on the innate immune system aren’t the same across the board. Meanwhile, the study also found that fruit  flies that experienced increased gravity, which happens during launch and reentry,  had a boosted immune response to fungus.

Again, it’s not clear why. Maybe it’s that something about the  proteins is more stable in hypergravity. But maybe, somehow intentionally  subjecting astronauts to increased gravity could have therapeutic uses  on long-duration missions.

Or maybe it just means we need to put more time and research into  developing anti-fungal coatings. To extend space fly research even further,. NASA established the Fruit Fly  Lab onboard the ISS in 2015.

This small, long-term housing for the flies allows   more in-depth study than  those on the Space Shuttle, such as studying the effects of spaceflight on  the interactions between a microbe and host. And results from this lab are still coming in, teaching us even more about how  our immune systems work in space. So, it seems weird that we’d  use those buzzing nuisances always drowning in your tea  to learn about ourselves.

And even weirder that we  would launch them into space, taking them to the one place where we  can finally be free of them, to do it! But researchers are carrying out even  more experiments using the Fruit Fly Lab to learn more about immunity  and life in microgravity. Meaning fruit flies still have more to teach  us about what living in space is really like.

So someday, when our first people  do move off-Earth permanently, they’ll not only know what to expect,  but how to stay as healthy as possible. And whether you’re a fruit fly, a human  astronaut or a regular ole earthling like me, all our lives are better when  we have good music to listen to. Patrick Olson created the Music for Scientists  album as a celebration of the beauty of science, and an homage to the people who make  science happen, on Earth, and in space!

It’s a gift from Patrick Olson  to scientists to thank them for making the world known to us,  but it’s something we all can enjoy. So give it a listen! We’ve got a link  in the description all ready for you!

And thank you for your support. [♪ OUTRO].