A new study finds that the rigors of space travel alter astronauts’ genes, leading to compromised immune systems that could leave them vulnerable to infections, especially when they first return to Earth.
Space is an extreme environment, and astronauts may face various hazards, including health hazards. There is evidence that short- and long-duration spaceflight negatively affects many physiological functions, primarily due to fluid shifts in and out of microgravity.
Previous research has looked at the effects of spaceflight on the human immune system. Even during the Apollo missions in the 1960s and 1970s, slightly more than half of the astronauts were observed to have a cold or other infection within a week of returning to Earth. Evidence suggests space travel can weaken the immune system, and researchers at the University of Ottawa in Canada are trying to understand why.
The researchers studied gene expression in the white blood cells (white blood cells) of 14 astronauts who lived on the International Space Station (ISS) between 2015 and 2019 for four and a half months to six and a half months. Blood samples were taken from each astronaut at 10 time points: once before the flight, four times during the flight, and five times upon return to Earth.
They identified 15,410 genes that were differentially expressed in white blood cells, and among these genes, identified two clusters that changed their expression along the time axis. These two gene clusters are mainly composed of protein-coding genes, but there are differences between the two. The function of the first gene cluster is mainly related to immunity, while the second gene cluster is related to cell structure and function.
The researchers observed that the first cluster of genes declined when astronauts went to space and returned when they were on Earth; the opposite was true for the second cluster.
“We show here that the expression of many genes related to immune function declines rapidly when astronauts arrive in space, and the opposite is true when they return to Earth after six months on the International Space Station,” said one of the study’s authors. 1Odette Laneuville said.
These results suggest that space travel can cause a rapid decline in the strength of the immune system, the researchers said.
“Weaker immunity increases the risk of contracting disease and limits astronauts’ ability to perform difficult missions in space,” said another co-author, Guy Trudel. “Astronauts’ access to care, medication, or evacuation in space would be limited if the infection or immune-related disease progressed to a serious condition requiring medical attention.”
However, the study also brought some good news. The researchers found that most genes in both clusters returned to their pre-flight expression levels within a year of returning to Earth. Usually, this happens within a few weeks. Still, the researchers say that means returning astronauts are at higher risk of infection for about a month after returning home.
Researchers aren’t sure how long it takes an astronaut’s immune system to recover to maximum strength, but they think it may depend on age, sex, genetic differences and childhood exposure to pathogens.
The next step for the researchers is to develop measures to prevent space-induced immune suppression.
“The next question is how to apply our findings to guide the design of countermeasures to prevent immune suppression in space, especially during long-duration flights,” Laneuville said.
The study was published in the journal Frontiers of Immunology.