Could Your Kidneys Handle a Trip to Mars?

Research shows space flight causes significant kidney changes, increasing risks for long-duration missions like Mars trips. Credit: SciTechDaily.com

A new study highlights how space flight alters kidney function, showing structural changes and potential permanent damage due to microgravity and cosmic radiation. This poses risks for long-term space travel, such as missions to Mars.

The structure and function of the kidneys are altered by space flight, with galactic radiation causing permanent damage that would jeopardize any mission to Mars. This is according to a new study led by researchers from UCL.

The study, published today (June 11) 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.

Long-Term Health Effects of Space Travel

Researchers have known that space flight causes certain health issues since the 1970s, in the years after humans first traveled 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 traveled to the moon have been exposed to unmitigated GCR and only for a short time (6-12 days).

The Impact on Kidney Function

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.

The Study’s Methodology and Findings

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.

Implications for Long-Term Space Missions

The results indicated that both human and animal kidneys are ‘remodeled’ 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.

The Mars Mission Conundrum

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.”

Conclusions and Future Directions

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.

Notes

1. A year on the International Space Station (ISS), for example, exposes astronauts to a dose of radiation 50% higher than the five-year dose limit for nuclear energy workers. The Inspiration 4 private space mission, which flew above the ISS by 200km, exposed its crew to as much radiation as a nine-month stint on the ISS in just three days. A year on the surface of Mars would expose you to as much radiation as an eyewitness to the Hiroshima atomic bomb, and a three-year return mission to Mars is estimated to be six times that (or ~10,900 X-rays).

Reference: “Cosmic kidney disease: an integrated pan-omic, physiological and morphological study into spaceflight-induced renal dysfunction” by Keith Siew, Kevin A. Nestler, Charlotte Nelson, Viola D’Ambrosio, Chutong Zhong, Zhongwang Li, Alessandra Grillo, Elizabeth R. Wan, Vaksha Patel, Eliah Overbey, JangKeun Kim, Sanghee Yun, Michael B. Vaughan, Chris Cheshire, Laura Cubitt, Jessica Broni-Tabi, Maneera Yousef Al-Jaber, Valery Boyko, Cem Meydan, Peter Barker, Shehbeel Arif, Fatemeh Afsari, Noah Allen, Mohammed Al-Maadheed, Selin Altinok, Nourdine Bah, Samuel Border, Amanda L. Brown, Keith Burling, Margareth Cheng-Campbell, Lorianna M. Colón, Lovorka Degoricija, Nichola Figg, Rebecca Finch, Jonathan Foox, Pouya Faridi, Alison French, Samrawit Gebre, Peter Gordon, Nadia Houerbi, Hossein Valipour Kahrood, Frederico C. Kiffer, Aleksandra S. Klosinska, Angela Kubik, Han-Chung Lee, Yinghui Li, Nicholas Lucarelli, Anthony L. Marullo, Irina Matei, Colleen M. McCann, Sayat Mimar, Ahmed Naglah, Jérôme Nicod, Kevin M. O’Shaughnessy, Lorraine Christine De Oliveira, Leah Oswalt, Laura Ioana Patras, San-huei Lai Polo, María Rodríguez-Lopez, Candice Roufosse, Omid Sadeghi-Alavijeh, Rebekah Sanchez-Hodge, Anindya S. Paul, Ralf Bernd Schittenhelm, Annalise Schweickart, Ryan T. Scott, Terry Chin Choy Lim Kam Sian, Willian A. da Silveira, Hubert Slawinski, Daniel Snell, Julio Sosa, Amanda M. Saravia-Butler, Marshall Tabetah, Erwin Tanuwidjaya, Simon Walker-Samuel, Xiaoping Yang, Yasmin, Haijian Zhang, Jasminka Godovac-Zimmermann, Pinaki Sarder, Lauren M. Sanders, Sylvain V. Costes, Robert A. A. Campbell, Fathi Karouia, Vidya Mohamed-Alis, Samuel Rodriques, Steven Lynham, Joel Ricky Steele, Sergio Baranzini, Hossein Fazelinia, Zhongquan Dai, Akira Uruno, Dai Shiba, Masayuki Yamamoto, Eduardo A.C.Almeida, Elizabeth Blaber, Jonathan C. Schisler, Amelia J. Eisch, Masafumi Muratani, Sara R. Zwart, Scott M. Smith, Jonathan M. Galazka, Christopher E. Mason, Afshin Beheshti and Stephen B. Walsh, 11 June 2024, Nature Communications.
DOI: 10.1038/s41467-024-49212-1