16/09/2025
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Muscle weakening, bone density loss and an impaired immune system: the systemic health impacts of spaceflight bear many similarities to ageing. Sharon van Rijthoven, a student from Delft University of Technology and Vrije Universiteit Amsterdam, compared the effects of ageing and altered gravity from a cellular perspective during her internship at the European Space Agency (ESA).
When astronauts visit the International Space Station (ISS), they experience a weightless environment. Although it might sound like fun to float about in space, the lack of gravity means that the bones and muscles that support and move the body do not need to work as hard. To ensure they can safety return to Earth’s gravity, astronauts visiting the ISS must exercise for two and a half hours per day, six days per week to keep their muscles and bones strong.
“At a body systems level, we see many similarities between the effects of ageing and the effects of microgravity,” says Sharon. “However, few studies look at the changes on a cellular level. For our study, we focused on the similarities and differences between ageing and altered gravity from a cellular perspective.”
To investigate this topic, Sharon considered three types of gravity that differ from what we experience on Earth, collectively called altered gravity.
Sharon explains: “First there’s microgravity, which is what astronauts experience in space. Then there’s simulated microgravity, which we can create on Earth using, for example, a random position machine or clinostat that rotates to simulate microgravity conditions for biological samples. We can also use head down tilt bedrest for human studies. Finally, there’s hypergravity, which we can create using facilities like ESA’s Large Diameter Centrifuge.”
The study, recently published in the FASEB Journal, compares 165 signs of ageing at the cellular level with research on the cellular effects of altered gravity. Because microgravity causes similar systemic symptoms as ageing, Sharon expected to find that the cellular signs of ageing were similar to those of real or simulated microgravity but opposite to those of hypergravity.
As often happens in research, the outcome was not clear-cut. Of the 165 signs investigated, less than one third had a similar effect between ageing and real or simulated microgravity, and another third have not yet been investigated in altered gravity. Meanwhile, fifteen percent had opposite effects between ageing and real or simulated microgravity. This leaves plenty of room for further research but does not answer the question of why the systemic effects of ageing and microgravity are similar.
In the paper, Sharon proposes a theory. Although both ageing and altered gravity impact the way cells ‘talk’ to one another, she suggests that the mechanisms are different. In microgravity, she predicts that mechanotransduction – the way cells translate physical forces into electrical or chemical signals – is impacted. “It’s like a game of telephone, where you try to pass a sentence down a line of people,” Sharon explains. “By the end, the sentence is completely wrong.”
The paper suggests that this garbled communication causes cells in microgravity to behave as if they are ageing, but unlike in biological ageing, the effects are (mostly) reversible. This is good news for astronauts visiting the ISS. On a larger scale, this research indicates there are still unknowns when it comes to the cellular effects of altered gravity.
Jack van Loon of ESA’s centrifuge team, Sharon’s internship supervisor at the agency’s Life Support and Physical Sciences Laboratory, points out: “This study demonstrates the benefits of giving students the opportunity to conduct research at ESA. Sharon’s internship resulted in an impressive publication and identified many areas for future research.”