When astronauts travel into space they can expect some extraordinary new experiences. But they may also face a more mundane and potentially mission-ending one: kidney stones.
According to Nasa, kidney stones have been reported more than 30 times by astronauts upon returning to earth. Now researchers are beginning to unpick why space travel is linked to the painful condition.
“The pain you get when you’re passing a kidney stone is the worst pain you can experience,” said Dr Stephen Walsh, clinical senior lecturer in experimental medicine and honorary consultant in nephrology at University College London, who is involved in the research.
“There is one cosmonaut who got renal colic [where a stone gets blocked in the urinary tract] in orbit and they almost had to de-orbit him because of his kidney stone.”
It is already known that spending time in microgravity is linked to a drop in bone density: this loss of calcium into the blood offers one possible explanation for the buildup of mineral-rich kidney stones in astronauts, with dehydration another potential cause.
However, the project aims to dig deeper into these mechanisms.
The team are analysing the kidneys of 10 mice that were on the International Space Station (ISS) in late 2020 before being put down onboard, and the kidneys of 20 mice that were exposed to galactic cosmic radiation in laboratories on Earth. They compared these kidneys with those of control mice.
While the research has not yet been published, the team say they have early indications that galactic cosmic radiation – which includes gamma radiation as well as high energy particles – may cause damage to DNA in the kidneys as well as affecting the transport and metabolism of fats. The researchers said there were even some signs of changes in proteins around the cells of the kidney, potentially indicating either adaptation or damage of the organs.
In addition, mice exposed to the galactic cosmic radiation had lower levels of proteins involved in transporting ions such as those of sodium, calcium and phosphate. The findings also hint at damage to the powerhouses of cells – the mitochondria. That is problematic as a key component of the kidney, the proximal tubular cells, rely entirely on the energy they produce.
“When the proximal tubular cells go down, it gives you kidney failure,” said Walsh. “You might make it to Mars, but we recommend dialysis on the way back,” he added.
A similar collection of results were found for the mice that had spent time onboard the ISS.
“For me, that’s surprising,” said Dr Keith Siew, a research fellow and renal specialist at UCL, as he said mice exposed to radiation in the laboratory were given a dose equivalent to a year and a half trip to Mars; those that travelled to space were only onboard the ISS for a month.
Siew said the team believe it is possible the microgravity environment could be amplifying the impact of the radiation, although further work is needed to explore this.
Siew added that the study might prove useful not only for astronauts.
“We’re seeing increases year on year of kidney stones occurring on Earth,” he said, adding that improving ways to identify how and why they form, countering their formation or treating them could bring benefits. In addition, insights into the effects of radiation on astronauts could open up new avenues for preserving healthy tissue in patients on Earth who are undergoing radiotherapy.
Prof Ben Turney, a consultant urological surgeon at the Oxford University hospitals NHS trust, who is not involved in the work, welcomed the project.
“Currently, considering the prevalence of kidney stone disease, the understanding of how the majority of stones form is surprisingly poor. This [project] will hopefully contribute to the understanding of the processes involved in kidney stone formation,” he said.
