It's no secret that spending extended periods in space takes its toll on the human body. For years, NASA and other space agencies have been researching the effects of microgravity on humans, animals and plants on board spacecraft. International Space Station (ISS). Research has so far shown that being in space for extended periods causes muscle atrophy, loss of bone density, changes in vision, genetic expression, and psychological problems. Understanding these effects and how to mitigate them is essential for our future space exploration goals, which include long-duration missions to the Moon, Mars, and beyond.
However, according to a Recent experiment Led by researchers at Johns Hopkins University and supported by NASA's Johnson Space Center, it appears that heart tissue “really doesn't behave well in space.” The experiment involved sending 48 samples of bioengineered human heart tissue to the ISS for 30 days. As they indicate in His roleThe experiment demonstrates that exposure to microgravity weakens cardiac tissue and its ability to maintain heart rhythm. These results indicate that additional measures must be taken to ensure that humans can maintain their cardiovascular health in space.
The study was led by Deok-Ho Kim and colleagues at the Department of Biomedical Engineering at Johns Hopkins University (BME-JHU) and the JHU Center for Microphysiological SystemsThey were joined by researchers from the University of California, Boulder. Ann and H.J. Smead Department of Aerospace Engineering Scienceshe Institute of Stem Cells and Regenerative Medicine (ISCRM) and the Center for Cardiovascular Biology At the University of Washington, the Stanford Institute for Stem Cell and Regenerative Medicine, BioServe Space Technologiesand NASA's Johnson Space Center. The paper detailing their findings was published yesterday (September 23) in the journal Proceedings of the National Academy of Sciences.
Previous research has shown that astronauts returning to Earth from the ISS suffer a host of health effects that are typical of certain age-related conditions, such as reduced heart muscle function and irregular heartbeats (arrhythmias), most of which will dissipate over time. However, none of this research has addressed what happens at the cellular and molecular level. To learn more about these effects and how to mitigate them, Kim and his colleagues sent an automated “heart-on-a-chip” platform to the ISS for study.
To create this payload, the team relied on human induced pluripotent stem cells (iPSCs), which can develop into many cell types, to produce cardiomyocytes (heart muscle cells). These resulting tissues were placed on a miniaturized bioengineered tissue chip designed to mimic the environment of an adult human heart. The chips would then collect data on how the tissues would rhythmically contract, mimicking the heartbeat. One set of biochips launched aboard the SpaceX CRS-20 mission to the ISS in March 2020, while another remained on Earth as a control group.
Once on the ISS, the astronaut Jessica Meir The experiment was carried out by changing the liquid nutrients surrounding the tissues once a week and preserving the tissue samples at specific intervals so that genetic readings and image analysis could be performed upon return to Earth. Meanwhile, the experiment sent real-time data back to Earth every 30 minutes (for 10 seconds at a time) on the tissue samples' contractions and any irregular heartbeat patterns (arrhythmias).
“An incredible amount of cutting-edge technology in the areas of tissue and stem cell engineering, biosensors and bioelectronics, and microfabrication was used to ensure the viability of these tissues in space,” Kim said in a recent Hub article. press release.
When the tissue chambers returned to Earth, he and his colleagues continued to maintain and collect data on the samples to see if there were any changes in their contractile abilities. In addition to losing strength, the muscle tissues developed arrhythmias, consistent with age-related heart disease. In a healthy human heart, the time between heartbeats is about one second, while the tissue samples lasted nearly five times longer, though they returned to near normal once they returned to Earth.
The team also found that the protein bundles in tissue cells that help them contract (sarcomeres) were shorter and more disordered than those in the control group, another symptom of heart disease. In addition, mitochondria in the tissue samples grew larger and rounder and lost the characteristic folds that help them produce and use energy. Finally, gene readings in the tissues showed increased production of genes related to inflammation and an imbalance of free radicals and antioxidants (oxidative stress).
Not only is this consistent with age-related heart disease, but it is also consistently demonstrated in astronauts’ post-flight checks. The team says these findings expand our scientific knowledge about the potential effects of microgravity on human health in space and could also advance the study of heart muscle aging and therapy on Earth. In 2023, Kim’s lab followed up on this experiment by sending a second batch of tissue samples to the ISS to test drugs that could help protect heart muscles from the effects of microgravity and help people maintain heart function as they age.
Meanwhile, the team continues to improve its tissue-on-a-chip system and has partnered with NASA's Massachusetts Institute of Technology (MIT). Space Radiation Laboratory to study the effects of space radiation on heart muscles. These tests will assess the threat posed by solar and cosmic rays to cardiovascular health beyond low Earth orbit (LEO), where Earth's magnetic field shields against most space radiation.
Further reading: Johns Hopkins University, PNAS
