Long term space exploration comes with many challenges. Not least is how much toilet paper to take but more worryingly is the impact on human physiology. We have not evolved in a weightless environment, we are not used to floating around for months on end nor are we able to cope with increased levels of radiation. It is likely that organs like the kidneys will become damaged but it make take time for signs to appear. Researchers are developing ways to detect organ issues in the early stages and develop ways to protect them during long duration flights.
We have known for some years that space flight causes health problems. Reduced muscle and bone density are the more well known but since the 1970’s we have also seen a weakening of the heart, eyesight issues and kidney stone development. The main cause of the problem is thought to be increased exposure to radiation from space. It’s not just the radiation from the Sun but Galactic Cosmic Radiation from deep space also plays a part. Fortunately for us here on Earth, the magnetic field protects us and those in low Earth orbit to a degree too. Those who travel further afield; to the Moon and other planets will be far more at risk.
To date, no-one has attempted to study what might be happening inside our organs as a result of long duration space flight, until now. A new study, published in Nature Communications, reports upon the analysis of kidney health in space flight. The study was funded by Wellcome, St Peters Trust and Kidney Research UK and was undertaken by a team of researchers from over 40 groups.
The research team collected samples from over 40 low Earth orbit missions from humans and mice chiefly from the International Space Station. Using these samples they conducted biomolecular, physiological and anatomical assessments. Using mice, they were able to simulate Galactic Cosmic Radiation doses equivalent to a 1.5 year to 2.5 year Mars mission.
Indications from the study showed that the kidney from both animal and human experienced changes. Parts of the kidney, known as tubules, are responsible for tweaking the calcium and salt balances and these showed signs of shrinkage after less than a month in space. The researchers believe though that this is more likely the result of weightlessness rather than radiation doses. The team did suggest however that further research is appropriate to see if the combination of increased doses of radiation coupled with microgravity had an increasing effect.
Another finding of the study was the way in which salt is processed by the kidneys. It is now thought that fundamental changes to how this is handled leads to the formation of kidney stones whilst it was originally assumed to be the result solely of microgravity.
Perhaps the most shocking finding of the study though was that anyone venturing beyond the confines fo the Earth’s protective magnetic field for 2.5 years is likely to experience permanent kidney damage and loss of function. This was demonstrated in the mice samples that had experienced a simulated Galactic Cosmic Radiation dose for that period fo time. The impact of this is quite staggering. Currently any astronaut venturing to Mars is likely to need kidney dialysis on the way back! The race is now on to find new ways to protect astronauts, and organs during long duration spaceflights.
Would astronauts’ kidneys survive a roundtrip to Mars?
The structure and function of the kidneys is altered by space flight, with galactic radiation causing permanent damage that would jeopardise any mission to Mars, according to a new study led by researchers from UCL.
The study, published in Nature Communications, is the largest analysis of kidney health in space flight to date and includes the first health dataset for commercial astronauts. It is published as part of a Nature special collection of papers on space and health.
Researchers have known that space flight causes certain health issues since the 1970s, in the years after humans first travelled beyond Earth’s magnetic field, most famously during the first moon landing in 1969. These issues include loss of bone mass, weakening of the heart and eyesight, and development of kidney stones.
It is thought that many of these issues stem from exposure to space radiation, such as solar winds from the Sun and Galactic Cosmic Radiation (GCR) from deep space, that the Earth’s magnetic field protects us from on Earth1. As most manned space flights take place in Low Earth orbit (LEO) and receive partial protection from Earth’s magnetic field, only the 24 people who have travelled to the moon have been exposed to unmitigated GCR and only for a short time (6-12 days).
Nobody has studied what changes might be happening in the kidneys and other organs as a result of conditions that would be experienced during space travel beyond Earth’s magnetic field over longer periods.
In this Wellcome, St Peters Trust and Kidney Research UK (KRUK) funded study, a UCL-led team of researchers from over 40 institutions across five continents conducted a range of experiments and analyses to investigate how the kidneys respond to space flight.
This included biomolecular, physiological and anatomical assessments using data and samples from 20 study cohorts. This included samples from over 40 Low Earth orbit space missions involving humans and mice, most of which were to the International Space Station, as well as 11 space simulations involving mice and rats.
Seven of these simulations involved mice exposed to simulated GCR doses equivalent to 1.5-year and 2.5-year Mars Missions, mimicking space flight beyond Earth’s magnetic field.
The results indicated that both human and animal kidneys are ‘remodelled’ by the conditions in space, with specific kidney tubules responsible for fine tuning calcium and salt balance showing signs of shrinkage after less than a month in space. Researchers say the likely cause of this is microgravity rather than GCR, though further research is required to determine if the interaction of microgravity and GCR can accelerate or worsen these structural changes.
The primary 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. Rather, the UCL team’s findings indicated that the way the kidneys process salts is fundamentally altered by space flight and likely a primary contributor to kidney stone formation.
Perhaps the most alarming finding, at least for any astronaut considering a three-year round trip to Mars, is that the kidneys of mice exposed to radiation simulating GCR for 2.5 years experienced permanent damage and loss of function.
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.”
The authors say that though the results identify serious obstacles to a Mars mission, it is necessary to identify problems before solutions can be developed.
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.”
Though the study only describes what happens to the kidneys up to two and a half years, it is the most comprehensive data available for the time being.
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