Space Travel Weakens the Heart: Challenges for Astronauts on Space Exploration Missions!

Prolonged space travel has been shown to cause serious damage to the human body.

Long-term space travel is becoming an important goal for humanity, especially as missions to the Moon, Mars and beyond are being planned by space agencies around the world. However, along with the scientific and technical benefits that space exploration brings, scientists also face a number of physiological challenges. One of the biggest concerns is the negative impact of microgravity on the human body, including cardiovascular health.

Previous studies have shown that when humans spend extended periods in zero gravity, their organs can undergo a variety of changes. From muscle atrophy, loss of bone density, vision changes, to psychological problems, all have been reported in astronauts returning from the International Space Station (ISS). Now, a new study led by scientists at Johns Hopkins University has made a disturbing finding: The human heart also weakens when living in space .

 In a prolonged zero gravity environment, the human body will undergo many changes.

Special experiments on the ISS

The study was conducted on bioengineered human heart tissue samples. In the experiment, 48 tissue samples were sent to the International Space Station for 30 days to test how microgravity affects heart muscle cells. This could help scientists better understand how the heart functions in a weightless environment and what changes might occur at the cellular and molecular level.

The results showed that when exposed to microgravity, heart muscle cells not only became weaker, but also had difficulty maintaining a regular rhythm . The heart cells developed arrhythmias – a common symptom seen in people with age-related cardiovascular problems. Notably, these changes occurred after only a short period of exposure to space , suggesting that microgravity may have a more profound impact on cardiovascular health than previously thought.

"Heart on a Chip" and Technology Platform

"Heart on a chip" for experimentation. (Illustration photo).

The research team, led by Deok-Ho Kim, a professor in the Department of Biomedical Engineering at Johns Hopkins University, and his colleagues, developed a 'heart-on-a-chip' platform for the experiment. The platform uses human induced pluripotent stem cells, which can turn into many different cell types, including heart muscle cells. These cells are placed on a miniature bioengineered chip that mimics the way an adult heart functions.

The heart tissue chips were then transported to the ISS on a SpaceX flight in March 2020. There, astronaut Jessica Meir took care of the experiment on behalf of the research team, maintaining the living conditions of the heart tissue by changing the nutrients around it on a weekly basis. The tissue samples were also preserved for genetic analysis and imaging upon their return to Earth, allowing the research team to collect comprehensive data on how microgravity affects the heart's contractions and rhythmic activity.

This experiment is a major step forward in the study of cardiovascular health in space. Unlike previous experiments that focused on the physiological effects of microgravity on astronauts, this time the team focused on the cellular and molecular levels, helping us better understand how the space environment affects heart muscle function.

In microgravity, heart muscle cells lose their ability to contract strongly.

Unexpected results

Data from the 'heart-on-a-chip' experiment showed that in microgravity, heart muscle cells lost their ability to contract as strongly as they do on Earth . The tissue samples developed an irregular heartbeat , with the time between beats being nearly five times longer than the normal beat of a healthy heart. This is particularly worrying because it suggests that not only is the heart muscle's strength reduced, but the heart's rhythmic function is also severely affected.

Another key finding was that bundles of proteins in heart muscle cells called sarcomeres – which are responsible for the contraction of the heart muscle – were shorter and less organized than in control cells, a sign of heart damage similar to what is often seen in patients with age-related heart disease.

Additionally, the mitochondria – the energy-producing organs in cells – in the heart tissue samples became larger, rounder, and lost their characteristic folds, disrupting energy production. This reduced energy-producing capacity may explain why heart muscle cells are significantly weakened in microgravity.

Not only did the heart tissue samples show increased markers of inflammation and oxidative stress, but they also showed an imbalance between free radicals and antioxidants. These markers not only suggest the effects of microgravity, but they also fit with what we know about aging and cardiovascular disease on Earth.

Mitochondria become larger, rounder, and lose their characteristic folds. (Illustration).

Applications and future

The findings from this experiment have important implications for both astronaut health and medical research on Earth. First, they help expand our understanding of how microgravity affects the human body, especially cardiovascular health. This will help space agencies like NASA develop health protections for astronauts on future long-duration missions.

In 2023, Kim's lab will send another batch of heart tissue samples to the ISS to test drugs that could protect the heart muscle from the negative effects of microgravity. This is a major step forward that could not only help astronauts maintain cardiovascular health, but could also pave the way for new therapies to treat cardiovascular disease in people on Earth.

Kim's team is also working with NASA to study the effects of space radiation on cardiovascular health. Cosmic and solar radiation are among the major risks astronauts face when they travel beyond Earth's orbit, where the planet's magnetic field shields them from much of the cosmic radiation. Understanding the effects of this radiation will help scientists develop preventive measures and protect astronauts' cardiovascular health during space missions.

Radiation from cosmic rays and the Sun is also one of the major risks for astronauts.

New research on the effects of microgravity on cardiovascular health suggests that long-term space travel affects the body not only superficially, but also profoundly at the cellular level . Changes in the function and structure of the heart muscle in the space environment pose major challenges for extraterrestrial missions, but also open up new opportunities for research and development of novel therapies for cardiovascular disease on Earth.

Advances in biotechnology, tissue engineering, and space medicine not only help protect the health of astronauts, but can also bring major advances in medicine for all of humanity. With these important discoveries, the future of space travel will become increasingly safe and efficient, bringing humans closer to conquering distant planets.