Space travel alters gene expression, making astronauts susceptible to infections

A new study shows how space travel may modify the gene expression in white blood cells (WBCs), which fight infections.
Mrigakshi Dixit
Representational image of astronauts in an microgravity environment.
Representational image of astronauts in an microgravity environment.


Beyond Earth, a less gravity environment poses a significant risk to the health of astronauts, particularly during longer-duration missions. 

Understanding how the human body reacts to the space environment is crucial for the long term and designing countermeasures to protect astronauts' health. 

Several scientific observations have previously revealed the effects of microgravity on the human body, ranging from changes in brain structure to decreased bone density. 

Another new study shows how space travel may modify the expression of some genes in white blood cells (WBCs), which fight infections. This, in turn, may weaken the astronauts' immune systems. 

Infections in space

Studies have already documented evidence that an astronaut’s body may be more susceptible to contracting infections while in space.

For example, astronauts on the International Space Station (ISS) have commonly complained about suffering from skin rashes, respiratory and non-respiratory disorders. 

While in microgravity, astronauts are also known to shed more live virus particles, including Epstein-Barr, varicella-zoster, and herpes-simplex-1 virus. 

These infections hint at a weaker immune system due to space travel. However, what exactly causes such an immunological deficiency in space is still being researched. 

Researchers from the University of Ottawa noted that gene expression changes might be one of the causes of such infections in space. 

“We show that the expression of many genes related to immune functions rapidly decreases when astronauts reach space, while the opposite happens when they return to Earth after six months aboard the ISS,” said Odette Laneuville, an associate professor at the Department of Biology of the University of Ottawa, leading author of this new study, in an official release

Gene analysis of astronauts 

But what changes the gene expression? Of course, microgravity. Under low gravity, leukocytes undergo a fluid shift, moving blood plasma from the lower to the upper body. Just within the first several days in space, this shift could lower plasma volume by 10 percent to 15 percent. 

The team hypothesized this could be the reason behind the change in gene expressions. 

For this study, the researchers analyzed the gene expression of leukocytes (WBCs) in 14 astronauts. Those included three women and eleven male astronauts, who served aboard the space station for 4.5 to 6.5 months between 2015 and 2019. 

Four milliliters of blood were taken from each astronaut at ten different points: once before the flight, four times during the flight, and five times after landing. From each sample, the leukocytes were isolated to investigate any changes. 

The findings showed that up to 15,410 genes were identified differently as expressed in leukocytes. Two detected gene clusters — 247 and 29 genes — mainly altered their expression in tandem across the study period.

Genes in the 247 cluster decreased when the astronaut reached the ISS and increased again when the astronaut landed back on Earth. In the 29 clusters, the reverse pattern of this up and down was seen. 

The study's findings also include some encouraging news. The sample analysis found that most genes (in both clusters) reverted to pre-flight levels within a year of landing on Earth. In several situations, gene expression returned to normal within a few weeks. 

Despite that, the team asserts that returning astronauts could still be at an increased risk of contracting infections for at least one month after arrival on Earth.

The team's results will now be used to identify viable countermeasures to tackle this health issue for future astronauts.

The results have been published in the journal Frontiers in Immunology.

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