GoKawiilThe mitochondrion (green in this false-colour transmission electron micrograph) could have a role in the physiological effects of microgravity.Credit: Jose Calvo/Science Photo Library
Exposure to microgravity aboard the International Space Station causes mitochondria in human cells and in worms to produce fewer proteins, researchers have found.
The work also identified a previously unknown molecular pathway that translates the effects of gravity on mitochondria through the mechanical action of cell adhesion — and which could explain why protein activity drops when those effects are removed. The study was published in Nature Communications on 30 June1.
The findings “might have implications for space travellers”, says Thomas Corydon, a space biologist at Aarhus University in Denmark. “This could be used to understand how we should better prepare astronauts going into space.”
Previous studies2 of cells and mice flown in space and of samples from astronauts have suggested that space flight leads to damage in mitochondria. “We saw the general overview of how mitochondrial dysregulation was happening,” says Afshin Beheshti, a space biomedicine researcher at the University of Pittsburgh in Pennsylvania who took part in the earlier work. But the molecular mechanisms through which gravity affects mitochondrial biology are poorly understood, he adds. Earlier research3 also found that reduced gravity had an impact on the transcription of DNA into messenger RNA.
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But for the most recent study, Shintaro Iwasaki, a molecular biologist at Japan’s national scientific research institute RIKEN in Wako, and his colleagues wanted instead to look at the effects on translation, whereby molecular machines called ribosomes use mRNAs to synthesize proteins.
With the help of International Space Station astronauts, the team cultured human cells in a laboratory module aboard the station for either 24 or 48 hours, and then froze them. Control cell samples were kept in a centrifuge that simulated standard Earth gravity while being cultured.
After all the samples were returned to Earth, their analysis revealed that cells that had been exposed to microgravity for 24 hours had reduced mitochondrial mRNAs compared with the controls, and that their mitochondrial ribosomes made fewer proteins.
The researchers found similar, although less marked, results in larvae of Caenorhabditis elegans worms that were cultured in microgravity on the space station for four days, compared with worms that were kept in a centrifuge.
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