Summary: A 30-day experiment on the International Space Station shows that low gravity conditions weaken human heart tissue and disrupt normal beating rhythms, raising concerns for long-term space missions.
Estimated reading time: 6 minutes
In a groundbreaking study, scientists from Johns Hopkins Medicine have uncovered alarming effects of low gravity on human heart tissue. The research, conducted over 30 days aboard the International Space Station (ISS), reveals that space conditions significantly weaken heart muscle cells and disrupt their normal rhythmic beats.
The findings, published in the Proceedings of the National Academy of Sciences, shed light on the potential health risks faced by astronauts during extended space missions. This study marks a crucial step in understanding the physiological challenges of long-term space travel and may have implications for heart health research on Earth.
The Space Experiment
To investigate the effects of microgravity on heart tissue, the research team, led by Dr. Deok-Ho Kim, a professor of biomedical engineering and medicine at Johns Hopkins University School of Medicine, sent 48 bioengineered heart tissue samples to the ISS. These samples were housed in specially designed tissue chips, each about half the size of a cell phone.
The tissues were created using human induced pluripotent stem cells (iPSCs), which were coaxed into developing into heart muscle cells (cardiomyocytes). This innovative approach allowed the scientists to study the effects of space conditions on human heart tissue without putting actual astronauts at risk.
Dr. Jonathan Tsui, a key researcher on the project, explained the meticulous process of preparing the tissues for their journey to space: “I had to hand carry the tissue chambers on a plane to Florida, and continue caring for the tissues for a month at the Kennedy Space Center.”
Once aboard the ISS, the tissues were monitored continuously, with data on contraction strength and beating patterns transmitted back to Earth every 30 minutes. Astronaut Jessica Meir, Ph.D., M.S., played a crucial role in maintaining the experiment, changing the tissues’ nutrient solution weekly and preserving samples at specific intervals for later analysis.
Alarming Results
The results of the experiment were stark. Dr. Kim’s team reported that the heart tissues “really don’t fare well in space.” Over the course of the 30-day study, the tissues aboard the ISS beat at only half the strength of identical samples kept on Earth.
Key findings include:
- Weakened contraction strength: The space-bound tissues showed a significant decrease in their ability to contract forcefully.
- Irregular beating patterns: The time between beats in the space tissues increased to nearly five times that of Earth-bound samples, indicating severe arrhythmias.
- Structural changes: Sarcomeres, the protein bundles responsible for muscle contraction, became shorter and more disorganized in the space tissues.
- Mitochondrial alterations: The energy-producing mitochondria in the space-bound cells grew larger and rounder, losing their characteristic folds crucial for energy production and utilization.
- Genetic changes: The tissues exposed to microgravity showed increased production of genes associated with inflammation and oxidative damage, both hallmarks of heart disease.
Implications for Space Travel and Beyond
These findings have significant implications for long-term space missions, such as potential trips to Mars. The weakening of heart tissue and development of arrhythmias could pose serious health risks for astronauts spending extended periods in space.
Dr. Devin Mair, a postdoctoral fellow at Johns Hopkins who analyzed the tissues’ contraction ability, noted, “Many of these markers of oxidative damage and inflammation are consistently demonstrated in post flight checks of astronauts.”
The study also provides valuable insights into heart muscle aging and disease progression on Earth. The researchers are now exploring potential drug therapies that could protect heart cells from the effects of microgravity. These same drugs may help maintain heart function in aging populations on Earth.
Future Research
Building on this study, Dr. Kim’s lab has already sent a second batch of 3D engineered heart tissues to the ISS in 2023. This ongoing research aims to screen for drugs that may protect cells from the effects of low gravity.
The team is also investigating the effects of space radiation on heart tissues at the NASA Space Radiation Laboratory, as the ISS’s low Earth orbit is largely shielded from these effects by the planet’s magnetic field.
As we continue to push the boundaries of space exploration, studies like this one are crucial in ensuring the health and safety of astronauts on long-duration missions. Moreover, the insights gained from this research may lead to breakthroughs in treating heart disease and age-related cardiac issues here on Earth.
Quiz
- What was the duration of the heart tissue experiment on the International Space Station? a) 15 days b) 30 days c) 60 days d) 90 days
- How did the beating strength of the space-bound heart tissues compare to those on Earth? a) They beat twice as strong b) They beat at the same strength c) They beat at half the strength d) They stopped beating entirely
- Which structural change was observed in the mitochondria of space-bound heart cells? a) They became smaller and more compact b) They disappeared completely c) They grew larger and rounder d) They multiplied in number
Answers:
- b) 30 days
- c) They beat at half the strength
- c) They grew larger and rounder
Further Reading:
- NASA’s Human Research Program: https://www.nasa.gov/hrp
- Effects of Spaceflight on the Human Body: https://www.nasa.gov/hrp/bodyinspace
- Stem Cells in Space Research: https://stemcell.nasa.gov/
Glossary of Terms:
- Microgravity: A state of near weightlessness experienced in space.
- Cardiomyocytes: Heart muscle cells responsible for generating contractile force.
- Arrhythmia: Irregular heartbeat or abnormal heart rhythm.
- Sarcomeres: The basic functional units of muscle fibers that enable contraction.
- Mitochondria: Organelles within cells responsible for energy production.
- Induced Pluripotent Stem Cells (iPSCs): Adult cells that have been genetically reprogrammed to an embryonic stem cell-like state.
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