Credit:image by NASA

On September 23, 2024, at 7:59 AM Eastern Time, astronauts Tracy C. Dyson, Nikolai Chub, and Oleg Kononenko successfully returned to Earth aboard the Russian Soyuz MS-25 spacecraft, landing safely in Kazakhstan. All three astronauts are reported to be in stable condition. Meanwhile, NASA astronauts Sunita Williams and Butch Wilmore, who were aboard Boeing's "Starliner" spacecraft, remain stranded on the International Space Station (ISS) due to unresolved technical issues with the spacecraft. Their stay on the ISS has been extended, with current plans for them to return to Earth in February next year via SpaceX's "Dragon" spacecraft. However, given the unpredictability of space travel, much could change in the coming four months.

The prolonged stay of Sunita Williams and Butch Wilmore in space raises concerns about potential health impacts. Recent research may provide some answers.

A study titled "Spaceflight-induced contractile and mitochondrial dysfunction in an automated heart-on-a-chip platform," published in the Proceedings of the National Academy of Sciences (PNAS), revealed some concerning findings. Researchers discovered that after just one month in space, human-engineered heart tissues began to deteriorate. The heart’s rhythm became irregular, and molecular and genetic changes resembling those seen in aging were observed.

Stanford University cardiologist Joseph Wu noted that the study offers an effective method for identifying the molecular pathways behind the harmful effects of spaceflight on the human heart. The research points to the dangers posed by microgravity, which can harm the human body. Monitoring astronauts upon their return to Earth revealed cardiovascular issues such as arrhythmia, following prolonged exposure to microgravity.

Co-author of the study, Deok Ho Kim, a biomedical engineer at Johns Hopkins University, emphasized that understanding the molecular changes behind the effects of long-duration spaceflights (lasting several months) on the heart remains a distant challenge. This study was made possible by sending samples aboard a spacecraft to the ISS, where 30 days of research led to these findings.

The researchers observed that after only 12 days on the ISS, the contractile strength of the heart tissues was nearly halved, and this reduction persisted even nine days after returning to Earth. In contrast, the ground samples maintained stable contractile strength throughout. As the tissues spent more time in space, their contraction patterns became more erratic, with the interval between beats increasing more than fivefold by day 19. However, this irregularity disappeared once the tissues returned to Earth. Upon return, Kim and his team used transmission electron microscopy to examine the sarcomeres—structures responsible for muscle contraction—and found them to be shorter and more disorganized than those in ground-based samples. Additionally, the mitochondria in tissues that had spent 30 days in space were swollen or even fragmented. Sequencing the RNA from these samples revealed increased expression of genes and pathways related to inflammation and heart disease. Simultaneously, there was a reduction in the expression of genes necessary for normal heart contractions and mitochondrial function.

In conclusion, astronauts venturing into space face significant health risks. Only with medications or treatments that can counteract the effects of long-term exposure to microgravity will humanity be able to further explore space.

As for Sunita Williams and Butch Wilmore, who are currently stranded on the ISS due to technical issues, we hope they can overcome this challenge and wish them a safe return!

Reference:

https://www.pnas.org/doi/10.1073/pnas.2404644121