Space travel has long been seen as the final frontier of human exploration. However, it comes with hidden dangers, even for the human heart.
A recent study has revealed that just one month in space can weaken engineered human heart tissue, cause irregular heartbeats, and trigger molecular and genetic changes similar to aging.
These findings, published in the Proceedings of the National Academy of Sciences, shed light on how space travel affects the cardiovascular system.
Microgravity, the condition in which objects appear to be weightless, takes a toll on the human body, especially the heart.
Astronauts exposed to microgravity have experienced cardiovascular changes, including irregular heartbeats.
However, understanding the molecular effects of long-duration space travel on the heart has been challenging.
Biomedical engineer Deok-Ho Kim from Johns Hopkins University explains, “It’s not possible to do the different molecular and functional studies in human astronauts.”
To tackle this challenge, Kim and his research team engineered human heart tissue and sent it to the International Space Station (ISS) for 30 days.
They used human induced pluripotent stem cells, which can transform into any cell type, to develop heart muscle cells arranged in a ‘heart-on-a-chip’ system — a tiny structure that mimics the beating function of a heart.
Once the heart-on-a-chip system was onboard the ISS, sensors monitored the tissue’s strength and beating patterns in real-time.
The results were striking: after just 12 days, the heart tissue’s contraction strength had nearly halved, while samples that remained on Earth stayed stable.
By day 19, the time between beats had stretched over five times longer, though these irregularities resolved after the tissue returned to Earth.
This suggests that astronauts like Sunita Williams and Butch Wilmore, currently on the ISS, may experience similar cardiovascular stress that could subside upon returning to Earth.
Further analysis revealed that space travel caused significant structural changes in heart tissue.
Protein bundles responsible for muscle contractions, called sarcomeres, became shorter and more disordered.
Mitochondria, the cells’ energy producers, appeared swollen and fragmented.
Additionally, genes linked to inflammation and heart disorders became more active, while those crucial for heart contraction and energy production had reduced expression.
While the heart-on-a-chip model doesn’t capture all cardiovascular changes, it offers a valuable tool for studying the effects of microgravity on the human body.
Cardiologist Joseph Wu of Stanford University believes this approach could help explore how other organs fare in space.
Kim and his team now plan to send other tissues into space for longer periods to deepen their understanding of microgravity’s effects and to test potential drugs to counteract these changes.
These findings offer new insights into how extended space missions might affect astronaut health at a molecular level, paving the way for more informed preparations for future long-distance space travel.