Orbital Insights: Heart Cells in Microgravity

February 1, 2024 • By Amy Thompson, Staff Writer

NASANational Aeronautics and Space Administration astronaut Kate Rubins conducted hundreds of experiments during her time on the International Space Station (ISSInternational Space Station), but as a biologist, one has stood out above others. In 2016, two researchers designed an investigation that used human induced pluripotent stem cells (iPSCs) to grow heart muscle cells, called cardiomyocytes, in space. The ISS National Lab-sponsored research, developed by Arun Sharma and Joseph Wu and carried out by Rubins, was designed to study the effects of microgravityThe condition of perceived weightlessness created when an object is in free fall, for example when an object is in orbital motion. Microgravity alters many observable phenomena within the physical and life sciences, allowing scientists to study things in ways not possible on Earth. The International Space Station provides access to a persistent microgravity environment. on heart muscle cells.

Previous research on the space station focused on the heart as a whole, but this investigation was the first to concentrate on heart functionality on the cellular level. Results from this project laid the foundation for other space-based stem cell research and helped to prove that iPSC-derived heart muscle cells can be used as an accurate model to study cardiac function in microgravity.

Below, Rubins discusses her experience conducting this pioneering research on the orbiting laboratory. Learn more about this innovative experiment in the article, “Stem Cells and Space,” featured in Upward, official magazine of the ISS National Lab.

Taking stem cells to space to study the human heart and help patients on Earth sounds really exciting. Can you explain a bit about the purpose of this investigation and what it was aiming to do?

The experiment focused on reprogramming blood cells into cardiac cells. For this experiment, iSPCs were used to derive heart cells in order to understand how microgravity affects their function. iPSCs, which are made from blood and skin cells, are on the forefront of regenerative medicine and are a powerful new tool to help us study how the heart functions on a cellular level.

This experiment was pioneering in a way. Can you talk about what makes it unique?

This was the first time long-duration cell culture was performed on the ISS. Previously, astronauts performed cell culture experiments on space shuttle missions but were always limited by how long the shuttle was in space, as missions typically lasted approximately 14 to 17 days. The ISS could support longer experiments but, prior to being equipped for this experiment, lacked some of the necessary hardware. One of the key things this experiment did was to change the way we do cell culture in space.

So, why space? What is the value of doing long-duration cell culture on the ISS?

There are benefits to long-duration cell culture. Regenerative medicine is a promising field that could benefit from long-duration space cell culture practices established by this experiment—in particular if you’re trying to build something up with bioprinting or study heritability through multiple generations. For example, one day, we are going to go beyond low Earth orbit(Abbreviation: LEO) The orbit around the Earth that extends up to an altitude of 2,000 km (1,200 miles) from Earth’s surface. The International Space Station’s orbit is in LEO, at an altitude of approximately 250 miles., and we need to be able to understand how the human body is affected by radiation exposure. The way to do that is by studying a cell culture experiment over longer periods of time. We could perform that experiment by sending cells up on a cargo spacecraft and then returning them months later.

The space station is totally unlike any lab on the ground. What were some challenges of working with lab equipment in space?

There were some equipment challenges in microgravity. In space, liquid can escape from a container. So, we had to think of inventive ways to feed the cells and wash the waste products away without creating a mess. We designed a special plate for the cells to grow on that was outfitted with a gas-permeable membrane on the top. From there, we could change the media through a little syringe port without fear that the liquid would float about the station.

It sounds like there’s a lot to consider when doing microgravity research. What are some key differences between doing lab work in space versus on the ground?

We take for granted how we manage stuff in our labs on Earth. If you’re sitting at a desk, all your stuff tends to stay put, but that’s not the case in space. You can’t put anything down without making sure it’s attached to something else, so it doesn’t float away. That made pipetting very interesting. I came up with an idea to use a sharps box (like for needles and other sharp objects), and we basically taped up the whole thing except for a small hole that we could inject the tips into. This way they could float around the box and not the space station.

As a scientist yourself, what was it like to work on this project? Was it exciting?

Very! What scientist doesn’t love lab equipment? I geeked out over the microscope we used to image the cells as they grew. My crewmates were probably tired of hearing about how psyched I was for the new microscope we installed on station to perform this experiment. We captured photos and videos of the cells using a technique called microscopy, and I would babble on at dinner about how excited I was, and they’d be like, “Kate, we know you’re excited.”

What was the best part of working on this research?

Seeing beating heart cells on the space station for the first time was incredible. I think NASA has me on video making all kinds of scientific proclamations and squeaky noises when I saw the cells beat for the first time—it was so incredible! But it wasn’t just me. When I was doing the experiment, all my crewmates would come down and watch because you could see the cells beating on the video screen. They all thought it was so cool.

Cool factor aside, why is it important to be able to capture photos and videos of an experiment like this?

There’s valuable data in the images we collected. Pictures and videos tell a story and can teach us a lot about how the cardiomyocytes were affected by microgravity. We can learn about how the cells’ size and morphology (structure, shape, function) change over time. Additionally, we can measure the contractile function of the cardiomyocytes and see if they beat more (or less) efficiently in microgravity.

What does this research mean for the future?

This experiment laid the foundation for future stem cell experiments in space. Not only did it add more equipment to the lab, but it also increased our knowledge, opening up what we can do for future experiments. So now if a researcher comes in and they want to do cell culture for 30 days, we really know how to do it. We’ve gotten a lot of the details worked out so they’re not spending their valuable research time and their valuable research budget figuring out how to even do these experiments in space because we’ve got all that under our belt now.