Travelling into space changes the structure of kidneys, with galactic radiation causing damage that could potentially put human missions to Mars at risk, new research suggests.
Spaceflight is known to cause a number of changes in astronauts’ bodies, and as more people venture into space, understanding the health risks associated with space exploration is key for the preparation of long-duration, lunar, and potentially Martian missions, experts say.
Despite the findings in relation to kidneys, researchers suggest that short-duration space flights pose no significant health risks to private astronauts.
It's really mostly good news in the sense that there are many, many changes across all those layers of biology and modalities of biochemistry, but the vast majority of them return to baseline quickly— Christopher Mason, Weill Cornell Medicine
Other findings indicated that women may be better able to physiologically tolerate space flight than men, but further research is needed.
The new research analysed samples collected from the first all-civilian crew from the SpaceX Inspiration4 mission which launched on September 15 2021 and returned three days later.
As well as the harm caused to kidneys, the research suggests that the effects of short term spaceflight mirror those of longer missions.
This includes elevated levels of a protein (cytokines) that could lead to excess inflammation, and lengthening of sections of DNA found at the ends of each of our chromosomes (telomeres) – which could result in mutations.
The research found that although more than 95% of changes returned to normal in the months after the mission, some proteins, genes, and cytokines appeared to be still activated in the recovery period after spaceflight and persisted after flight for at least three months.
Christopher Mason, of Weill Cornell Medicine, New York, USA, one of the authors of the papers published in the Space Omics and Medical Atlas (SOMA) package, said: “It’s really mostly good news in the sense that there are many, many changes across all those layers of biology and modalities of biochemistry, but the vast majority of them return to baseline quickly.
“So I think it bodes well for people who think: ‘Maybe I’ll go to space in six months’ because anyone can really quickly get ready to go, and not only go and safely go and return, but also get trained and get just skills and tools to do experiments in space very quickly.”
Researchers at UCL looked at the effect of space flight on the kidneys.
They found that both human and animal kidneys are remodelled by the conditions in space, with specific parts of the organs showing signs of shrinkage after less than a month in space.
Researchers suggest the likely cause of this is microgravity rather than galactic cosmic radiation (GCR), though further research is required to determine if the interaction of microgravity and GCR can accelerate or worsen these structural changes.
The main reason that kidney stones develop during space missions had previously been assumed to be solely due to microgravity-induced bone loss that leads to a build-up of calcium in the urine.
However, the new findings, published in Nature Communications, indicated that the way the kidneys process salts is fundamentally altered by space flight and likely a primary contributor to kidney stone formation.
The scientists suggest the most alarming finding is that the kidneys of mice exposed to radiation simulating GCR for 2.5 years experienced permanent damage and loss of function.
They say it will be necessary to develop measures to protect the kidneys from harm if missions to Mars are to be successful.
Dr Keith Siew, first author of the study from the London Tubular Centre, based at the UCL Department of Renal Medicine, said: “We know what has happened to astronauts on the relatively short space missions conducted so far, in terms of an increase in health issues such as kidney stones.
“What we don’t know is why these issues occur, nor what is going to happen to astronauts on longer flights such as the proposed mission to Mars.
“If we don’t develop new ways to protect the kidneys, I’d say that while an astronaut could make it to Mars they might need dialysis on the way back.
“We know that the kidneys are late to show signs of radiation damage; by the time this becomes apparent it’s probably too late to prevent failure, which would be catastrophic for the mission’s chances of success.”
Professor Stephen B Walsh, senior author of the study from the London Tubular Centre, UCL Department of Renal Medicine, said: “Our study highlights the fact that if you’re planning a space mission, kidneys really matter.
“You can’t protect them from galactic radiation using shielding, but as we learn more about renal biology it may be possible to develop technological or pharmaceutical measures to facilitate extended space travel.
“Any drugs developed for astronauts may also be beneficial here on Earth, for example by enabling cancer patients’ kidneys to tolerate higher doses of radiotherapy, the kidneys being one of the limiting factors in this regard.”
In the Wellcome, St Peters Trust and Kidney Research UK (KRUK) funded study, the UCL-led team of researchers from more 40 institutions across the world looked at data and samples from more than 40 Low Earth orbit space missions involving humans and mice, as well as 11 space simulations involving mice and rats.
The SOMA package, published in Nature, includes data from a range of missions, including the SpaceX Inspiration4, Polaris Dawn, Axiom, Nasa Twins and Jaxa missions, and researchers across the world.
In a flagship paper Eliah Overbey, Cem Meydan, Susan Bailey, Afshin Beheshti, Christopher Mason and colleagues offer a detailed guide to the data.
Speaking about the findings into the differences between men and women, Prof Mason said: “There are a couple of things we know that women seem to be less affected by.
“One is spaceflight associated neuro-ocular syndrome – or the damage that can happen to their eyes – I think that’s been established already, and I think in this case, the genetic and epigenetic resilience is something we observed here seems to be a new finding.
“It may be just by the fact that women have to give childbirth, so maybe being able to tolerate large changes in physiology and fluid dynamics may be great for being able to manage pregnancy but also manage the stress of spaceflight at a physiological level.
“We don’t have the full answer yet as to why women seem to be, so far, a little bit more tolerant of the stressors of spaceflight, but we’re looking into it.”
