By Maxwell Allison
Space, the final frontier, the last place humanity has yet to explore. In the past fifty years, space exploration has expanded to levels never seen before. We’ve sent people to the moon, probes out of our solar system and we are now planning to send people to an entirely different planet. Despite all this progress, space still remains completely inhospitable for the human body. This remains a barrier for the future of human space flight and exploration. The hazards in space are countless, from the vacuum of space being deadly to all humans, to the increase in ionizing radiation all astronauts face. However, a much more subtle, but just as dangerous, problem exists in the form of epigenetic changes.
Epigenetics is the study of the changes in gene expression, specifically DNA methylation and histone acetylation. Changes to someone’s epigenetic makeup, or pattern of gene expression, can be induced by environmental changes, such as increase in stress or in certain chemicals. This is unique because these are long term changes, and can be passed onto offspring. The environmental changes people go through when they travel to space are considerable, and can induce epigenetic changes. This is where the problems begin. The delicate molecular machinery that controls all of the functions in the body can be disrupted quite easily, and the microgravity in space can easily do this. The Twins study is the best example of how space can change the human body.
The Twins study surrounds identical twins Scott Kelly and Mark Kelly. Scott was sent to space for 340 days in the ISS, International Space Station, and Mark stayed safely on Earth. Despite only having preliminary data at this time, researchers were still able to see significant results. After Scott returned to Earth, researchers analyzed the levels of metabolites, cytokines, proteins, and other indicators of gene expression for changes. They found that 93% of Scott Kelly’s genes’ expression returned to normal one year after returning from space. However, 7% of his genes’ expression did not return to normal, hinting at long term changes in gene expression. The researchers also studied changes in Scott’s DNA and DNA methylation. They found changes in levels of methylation in genes involved in telomere repair and in a gene encoding collagen (which makes sense as his telomeres temporarily extended during space flight), however the levels returned to normal after returning to Earth. The researchers also discovered multiple new mutations in Scott, mainly in cell-free DNA in the bloodstream, most likely from the stresses of spaceflight. The researchers also studied everything from Scott’s biochemical profile to changes in his gut microbiome, but couldn’t find any major changes that could not be explained or did not return to normal after returning to Earth. Changes in Scott’s methylation and gene expression points to long term effects space has on the human body that must be addressed before we can shoot for the stars.