New research shows that space travel has a major impact on the human body.
A paper published May 28 in Nature Communications examined the effects of space travel on the immune system.
Researchers collected data from the two men and two women who orbited Earth in 2021 during the SpaceX Inspiration4 mission.
They found that the immune system became dysregulated, causing inflammatory responses and chaos at the cellular level.
Muscles
The team found evidence that a three-day spaceflight at high altitude induces the production of known cytokine signatures and previously undocumented cytokines.
Cytokines are substances secreted by the immune system. They play a crucial role in the immune response and the regulation of muscles.
The scientists noted that these complaints are not normally associated with systemic inflammation, an immune response that affects the entire body.
Some cytokines have been considered exerkines, a specific type of protein produced by muscles and other tissues during exercise.
The scientists wanted to investigate whether muscle tissue could be the source of these immune markers.
They discovered a significant increase in certain myokines, proteins produced by skeletal muscle cells.
The article notes that this increase is a “physiological response to microgravity” and not merely an immune response.
In non-muscle tissue, no changes were observed in interleukin 6, a protein that signals inflammation, or in interleukin 10, an anti-inflammatory molecule.
However, a muscle in the back of the leg, called the soleus, showed a significant increase in a molecule linked to muscle effort.
In addition, an increase in interleukins was observed in the tibialis anterior muscle, at the front of the leg. These interleukins play an important role in the activation of immune cells.
The greatest increase upon landing was noted for the pro-inflammatory cytokine Interleukin 5, suggesting muscle is a possible source for the cytokines found in the I4 crew.
Blood
The researchers collected blood from the Inspiration4 crew before and after the journey into space.
Analysis revealed cell-specific and sex-specific responses to spaceflight.
The increases in interleukin 6, interleukin 10 and MCP-1, a pro-inflammatory molecule, were consistent with changes seen in other astronauts after long-duration missions.
A number of other pro-inflammatory proteins were also significantly upregulated.
However, proteins such as fibrinogen, which is involved in the formation of blood clots, and hemoglobin, which carries oxygen through the bloodstream, did not change significantly.
Mutations
To better understand the impact of space travel on different cell types, the scientists dug even deeper and examined changes that occur at the cellular level.
One observation stood out. While other cell types remained stable in terms of mutations, the total number of B cell receptor mutations increased compared to pre-flight data.
These mutations are usually caused by inflammatory responses or exposure to antigens, which are substances that trigger an immune response.
The scientists also found evidence for possible upregulation of BCR signaling pathway genes immediately after flight.
Although no full conclusions could be drawn, the data indicate that B cells are more active after space travel.
These cells produce antibodies to neutralize harmful substances and contribute to the body’s immune response.
Cell differentiation
Cell differentiation is the process by which young cells acquire specialized properties and achieve their mature functions.
Scientists found that this is less common in CD4 T and CD8 T cells.
T cells are a type of white blood cell called lymphophytes. They develop from stem cells in the bone marrow and play an important role in protecting the body from infection.
These findings mirrored the T cell suppression previously observed with simulated radiation and microgravity.
Upon returning to SoilThe astronauts’ serum showed higher concentrations of cytokines associated with inflammation.
At the same time, the scientists noted an increase in cytokines with an anti-inflammatory effect, “which probably balances the inflammation coming back to Earth.”
The researchers observed significant changes in secreted proteins associated with the migration of monocytes and neutrophils, which travel to the site of injury.
Gender differences
Previous studies have shown that women are better able to withstand the stress of space travel than men, and may recover more quickly after returning to Earth.
The scientists set out to test this theory. They looked at differentially expressed genes, or DEGs, which show different levels of activity under different conditions.
The team compared the ratio of up- and down-regulated DEGs between males and females, showing that DEG numbers were higher in males for almost all cell types.
The scientists also observed a higher number of altered gene expression pathways in males.
The scientists also observed a significant difference between men and women in the levels of interleukin 8 and fibrinogen.
Interleukin 8, or IL-8, plays an important role in the body’s inflammatory response by activating the movement of a certain type of white blood cell to the site of injury.
Ultimately, the scientists concluded that gene activity was more disrupted in men than in women, possibly indicating that women are better able to withstand the stressors of space travel.
Implications for space travel
The researchers concluded that they had found evidence in the Inspiration4 data for an immune response to space travel.
“We found that 18 cytokines/chemokines related to inflammation, aging, and muscle homeostasis were altered after spaceflight,” they wrote.
And while the findings may seem like they have implications for future As for crew selection, the scientists noted that they still have a long way to go.
They noted that their sample size of four astronauts was small, even though they used data from previous missions and studies to support their findings.
The I4 mission was “not intended to determine the safety of spaceflight for all citizens,” the team concluded.
However, the consistent cellular and molecular responses can help ‘narrow the targets for countermeasures and monitoring’ future “study.”
What was the NASA Twins Study?
The Twins Study provided much-needed insight into the effects of space travel on the human body.
The NASA Twins Study examined identical twin astronauts, Scott Kelly and Mark Kelly, who spent about a year in different environments. While Scott spent 340 days in space, Mark was on Earth.
Because identical twins have the same genetic makeup, they are physically very similar. This takes into account other variables that could affect the study results and gives scientists a way to study how the environment affects health.
Samples taken before, during and after Scott’s space flight showed changes in gene expression. This involves the process by which our DNA instructs cells to make components such as proteins, which are used to build and repair tissue.
Mark experienced changes in gene expression on Earth, but not to the same extent as Scott in space.
One of the most striking discoveries was the evidence of telomere shortening. Telomeres are the ends of each DNA strand, which protects them from “fraying.” Without telomeres, our chromosomes would become damaged and our cells would no longer function properly.
Scott appeared to have experienced a change in telomere length dynamics during his flight. These findings could help evaluate the overall health and potential long-term risks of astronauts in space.