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A fascinating array of new research papers is highlighting the various health risks associated with long-duration space missions, including troublesome observations related to the aging process and radiation-induced DNA damage.
Space, as we are learning, really sucks for us little humans.
Without gravity continually pulling us down and without a protective atmosphere to protect us from the sun’s deadly rays, we are exposed to a myriad of health risks – things like loss of bone density and muscle mass, cardiovascular and neurological problems. and even eye ailments. And it seems that the longer we stay in space, the more severe the impacts. This could throw a serious keystone in our plans to conquer deep space, whether it be building bases on the Moon and Mars or traveling to the outer solar system and beyond.
Unfortunately, the risks don’t stop there. A gigantic package of 30 research papers was published today in five Cell Press journals, all related to the health problems posed by long-duration space missions. Collectively, these documents represent “the largest set of data on space biology and astronaut health effects ever produced,” according to a Colorado State University press release.
These new studies of astronauts and model organisms have revealed six potentially damaging aspects of long-term spaceflight: oxidative stress (an imbalance of free radicals and antioxidants that leads to tissue damage); DNA damage; mitochondrial dysfunction (mitochondria are the power supplies of our cells); alterations in telomere length; changes to the genome and epigenome (i.e. gene expression influenced by the environment); and changes to the microbiome (the totality of microorganisms that live outside and inside our body).
Of these, two in particular caught my attention: the alternating telomere length and DNA damage. All six health characteristics listed in the new studies play a profound role when it comes to our health, but telomeres and DNA damage in particular can be linked to the aging process.
Telomeres are the protective caps located at the ends of chromosomes (threaded structures in the nucleus of the cells that carry our genes). Telomeres progressively shorten as a person ages, and significant changes in the length of these plugs can be interpreted as a sign of accelerated aging and / or increased risk of developing age-related diseases such as cancer, cardiovascular disease, and dementia.
That exposure to space alters telomere length is no surprise. Previous research involving identical twin astronauts Scott and Mark Kelly (Scott spent nearly a year in space while his brother stayed on the ground) showed that, for Scott, the telomeres in his white blood cells lengthened while they were in space. , but they basically returned to normal once I returned to normal gravity conditions.
Susan Bailey, a biologist at Colorado State University and a veteran of the pioneering twin study, is now co-author of a new article, published in Cell, in which her team studied 10 other astronauts, all of whom flew long-duration missions aboard. the ISS. And for long-duration missions, we usually talk about periods that last around six months or more.
Blood samples were taken by the astronauts before and after their time on the ISS. Just like in the twin study, long-term exposure to space resulted in elongation of the telomeres. In this case, however, the researchers also found that astronauts, in general, had shorter telomeres after their missions. Biologists refer to this as ALT, or alternating telomere lengthening – and it was not something they expected, as is typically seen in cancer cases or in developing embryos. Surprisingly, ALT was observed in all 10 astronauts studied.
Now, telomere lengthening may sound promising as far as extended longevity is concerned, but as Bailey explained in an email, this shouldn’t be interpreted as good news.
“Both short and long telomeres are associated with an increased risk of disease,” Bailey said. “Short telomeres are associated with accelerated aging and associated degenerative diseases such as cardiovascular disease and some cancers.”
Long telomeres may be associated with longevity, he said, “but they are also associated with cancer,” because mutated cells live longer, which increases the risk. The 10 astronauts showed dramatic changes in telomere length over time, but the researchers still don’t know the associated health effects.
“Longer telomeres during space flight, rapid shortening on return to Earth,” he summed up. “And overall, they ended up with shorter telomeres than they started with,” adding that “individual differences in response were also observed.”
As for the cause of the wobbly lengths seen in telomeres, Bailey pointed the finger at chronic oxidative stress.
“Acute exposure to ionizing radiation has been shown to cause oxidative stress,” Bailey explained. “In the space radiation environment, chronic exposure would be associated with chronic oxidative stress” and telomeres “are very susceptible to oxidative damage.”
As the new research also shows, exposure to space causes DNA damage. Specifically, the scientists documented chromosomal reversals, which are signs of radiation exposure. Chromosomal reversals occur when “two breaks occur within the same chromosome and the genetic material between the breaks is reversed,” according to ScienceDirect.
“Consistent with chronic environmental exposure to space radiation, inversions were high during space flight for all crew members,” Bailey said. “And the increased frequencies of reversals persisted after spaceflight – potentially indicative of genomic instability and / or clonal hematopoiesis,” which is an increased risk of cancer.
The long-term health effects of space missions will continue to be Bailey’s main focus, including ongoing investigations into the dynamics of telomere length (how it changes over time) and persistent DNA damage, which in this case involved chromosomal inversions – biomarkers associated with cancer and cardiovascular disease.
To that end, this team will participate in NASA’s One Year Mission Project, which Bailey says will be called CIPHER. For that project, the team will conduct similar studies, in which they will monitor telomere length dynamics and DNA damage among astronauts involved in long-duration missions.
This work is very important, because it could eventually lead to medical interventions that will allow for safer long-term missions. The humble tardigrade, for example, can tolerate large doses of radiation. Eventually we may find a way to adapt this ability to ourselves. In fact, in order to live and work in space, we will have to become a little less human.
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