Artificial gravity provides partial protection for the biology in space

Space travel to the moon, Mars and beyond can expose astronauts to extreme conditions, causing potential health problems. To prepare for future long-duration missions, NASA is studying how the effects of space—changes in gravity, radiation and more—affect “model organisms,” or other forms of life that are biologically similar to humans. New results from a study with fruit flies on the International Space Station suggest that space travel has an impact on the central nervous system, but that artificial gravity provides partial protection against these changes.

“Microgravity poses risks to the central nervous system, suggesting that countermeasures may be necessary for long-duration space travel,” said Dr. Janani Iyer, a Universities Space Research Association (USRA) project scientist at NASA’s Ames Research Center in California’s Silicon Valley and an author on the paper published today in Cell reports. “As we head back to the moon and on to Mars, reducing the harmful effects of microgravity will be key to keeping future explorers safe. This study is a step in the right direction to explore the protective effects of artificial gravity in space and to understand the adaptation to Earth conditions after returning from space.”

Fruit flies are the ideal organism for this type of research because of their similarities to humans. There is a considerable amount of overlap between the cellular and molecular processes in flies and humans. Almost 75% of the genes that cause disease in humans are shared by fruit flies, which means that the more we learn about fruit flies, the more information scientists have to study how the space environment can affect human health. Flies also have much shorter lifespans – about two months and reproduce in two weeks. The three weeks the flies spend in space is equivalent to about three decades of a human’s life, giving scientists more biological information in less time.

Understand the gravity of the situation

In this study, researchers sent flies to the space station on a month-long mission in a newly developed piece of hardware called the Multi-use Variable-gravity Platform (MVP), which is capable of housing flies at different levels of gravity. The flies in this hardware had access to fresh food while they lived and reproduced. Using different compartments allowed the MVP to separate different generations of flies. On the space station, a group of fruit flies experienced microgravity similar to their human counterparts. Another group was exposed to artificial gravity by simulating Earth’s gravity on the space station using a centrifuge – an instrument that spins to simulate gravity. While on the space station, cameras in the hardware recorded the behavior of these “flyonauters”. At various times, some of the flies were frozen and returned to Earth to study their gene expression.

After the flies returned to Earth, aboard a SpaceX Dragon capsule that splashed into the Pacific Ocean, the flies were brought back to Ames for further analysis. Upon arrival, researchers in Ames worked around the clock for two days to sort the flies and conduct behavioral and biochemical tests. The same analyzes were run on a set of flies kept on Earth as a control experiment, to provide a baseline against which to compare the data from the “flynauts”.

This study was one of the first of its kind to take an integrated approach to how the space environment affects the nervous system. Researchers looked at fly behavior by observing the movements of flies as they moved around their habitat, changes at the cellular level in the fly brain, how gene expression modifications affect the nervous system, and more. Observed changes came in many forms, some easy to see just by looking at the cameras included in the MVP’s compartment, others that required further investigation on return to Earth. The behaviors studied included flight activity and climbing ability on return to Earth. Flies have a natural response to climb into their container when knocked down, and this was used as a test of their post-flight abilities. Flies in microgravity were more active than those in artificial Earth gravity, but also showed difficulty during this climbing test after returning to Earth.

More in-depth analysis on the ground immediately after flight revealed neurological changes in flies exposed to microgravity. As the flies got used to being back on Earth after their journey, the flies that experienced artificial gravity in space aged differently. They faced similar but less severe challenges to the flies that were in microgravity.

Paving the way for future studies

The results from this study suggest that spaceflight causes stress in the fly’s cells, leading to negative behavioral and neurological effects, as well as changes in gene expression in the fly brain. However, using artificial gravity can provide temporary relief from the difficulties microgravity in space causes on the nervous system of a fruit fly, although there are still long-term health complications.

Because fruit flies and humans are very different organisms, despite their genetic overlap, these results may not speak directly to what humans will experience during a lifetime in space—but it paves the way for scientists to follow up when they designing ways to protect astronauts as they travel to destinations with different gravity levels in the future.

“With upcoming long-duration deep space missions where astronauts will be exposed to varying levels of gravity, it is imperative that we understand the effects of altered gravity on neurological function,” said Dr. Siddhita Mhatre, a KBR Wyle senior research fellow at Ames and an author of the published paper. “If we can use artificial gravity to delay space-related deficits, we might be able to extend future mission timelines. And flying in space, along with the astronauts, will help advance our efforts to keep astronauts healthy.”

More information:
Siddhita D. Mhatre et al., Artificial gravity partially protects space-induced neurological deficits in Drosophila melanogaster, Cell reports (2022). DOI: 10.1016/j.celrep.2022.111279