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  • A natural factor has intervened
  • Kidneys receive special attention from scientists
  • The only way out when thinking about flight is to reconstruct the kidneys
Traveling to other planets might not be suitable for many. NASA

A natural factor has intervened

Scientists have identified a factor that will prevent the first manned flight to Mars from happening with the current state of medicine. Experiments on mice and astronauts have shown that human kidneys cannot withstand a long-duration flight to Mars and back without special measures, according to a study published in the journal Nature Communications.

Mankind is already planning manned flights to deep space this decade, starting with the American Artemis program for lunar exploration, which will then work out the details of possible flights to Mars. Scientists have long been studying the various medical aspects of long-duration spaceflight, which could make expeditions to even the closest planet to us difficult or impossible. These include issues of radiation safety, nutrition, psychological compatibility, the effects of long-term weightlessness and other factors.

Experiments of all kinds, revealing the effects of space factors on the human body, were carried out just after the beginning of the space age. However, near-Earth crewed flights are carried out in low orbits, shielding the crew from solar and galactic cosmic radiation in the Earth's magnetosphere. The first studies outside the magnetosphere, therefore, only became possible in 1969, when observations of American lunar astronauts revealed a loss of bone mass, a weakening of the heart muscle and visual acuity, and the formation of kidney stones[1].

Kidneys receive special attention from scientists

For the first time, scientists at University College London have studied the full impact of space conditions on the kidney, a human organ particularly vulnerable to cosmic radiation and weightlessness.

To understand how space affects kidney function during long-duration flight, the researchers analyzed the results of 20 separate cohort studies, most of which were carried out on space stations. They were carried out in astronauts, mice and rats on long-term expeditions.

It is known that a year spent on the space station gives the crew a radiation dose that is 50% above the safe dose for nuclear workers. In addition, in seven separate experiments, rodents were exposed to artificial radiation that simulated cosmic radiation outside the Earth's magnetosphere during a 1.5 and 2.5-year expedition to Mars. Data from the Inspiration 4 expedition, organized by SpaxeX on its Dragon spacecraft, were analyzed. The latter flew 200 km above the space station, giving the astronauts a dose of the space station's 9-month population over three days.

The results show that prolonged exposure to space causes structural and functional changes (remodeling) in the kidneys of both humans and animals. The special tubules responsible for maintaining calcium and salt balance shrink after less than a month of exposure to space. According to the researchers, this is most likely due to microgravity.

"We analyzed urine and plasma parameters for nephrolithiasis (stone formation) in 66 astronauts who spent up to 180 days on the Space Station. Our data showed increased urinary excretion of metabolites and electrolytes, which are considered to be risk factors for nephrothylase," the study said.

Previously, it was assumed that kidney stones formed during spaceflight due to the loss of bone mass, which leads to calcium in the urine. Now, scientists have found that it is due to a restructuring of salt recycling processes in the kidneys.

The only way out when thinking about flight is to reconstruct the kidneys

But the most worrying result, which is directly related to a possible future three-year flight to Mars, came from experiments on mice: their kidneys irreversibly deteriorated or stopped functioning within 2.5 years under artificial radiation.

"Unless we develop new ways to protect the kidneys, even if astronauts can get to Mars, they may need a hemodialysis machine on their return. We know that the kidneys have a delayed response to radiation damage. And by the time this becomes apparent, it may be too late to prevent their loss, which would prevent a successful mission," said study author Keith Siew.

Scientists believe kidney damage could be a serious obstacle to future Mars missions if a solution is not found.

"You can't shield the kidneys from galactic radiation with a shield, but by better studying the biology of the kidneys, you can develop technological or pharmacological ways to make spaceflight easier," said co-author of the paper, Stephen Walsh, "Any drugs developed for astronauts could be used on Earth, for example, to allow the kidneys of cancer patients to cope with high doses of radiotherapy."
Agnė Belanauskaitė
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, Stephen B. Walsh. Cosmic kidney disease: an integrated pan-omic, physiological and morphological study into spaceflight-induced renal dysfunction Nature