Hibernating zebrafish offer lessons for healthy human spaceflight

Getting humans safely to a place like Mars is going to pose all kinds of scientific challenges, and a particularly pressing one centers on the rather important issue of human health. Astronauts enduring long-periods in space may be in danger of changes to the gut microbiome, reactivation of dormant viruses, leukemia and malfunctioning mitochondria, just to name a few examples, but new research in zebrafish has demonstrated how induced hibernation may help limit the risk.

If the idea of falling asleep on a long-haul flight sounds like good way to pass the time, consider a six-month journey to Mars. But astronauts heading to the Red Planet will have much more than boredom to contend with. The high-radiation environment of space can have a range of adverse effects on human health, including muscle atrophy, bone loss and blurred vision.

In approaching this problem, scientists at Queen’s University Belfast sought inspiration from the way some species use hibernation to protect against inhospitable conditions, and turned to zebrafish to explore their ideas further. Zebrafish often serve as models for scientific study as they feature a remarkably similar genome to humans, and these efforts have previously demonstrated how we might better tackle blindness, understand sleep and repair damaged hearts. This time around, the scientists triggered a form of hibernation in the animals called torpor, which reduces their metabolic activity.

The scientists induced torpor in one group of zebrafish, while another group served as a control, with both groups subjected to levels of radiation humans would be expected to experience on a six-month journey to Mars. They then used genomic analysis to investigate the gene expression in both groups.

In the regular zebrafish, the scientists observed signs of oxidative stress, DNA damage, stress hormone signaling and changes to the cell-division cycle. In the hibernating zebrafish, however, the scientists found that the lower metabolic activity provided protective effects against the radiation by reducing oxidative stress and increasing the detection and removal of misfolded proteins.

“Our results reveal that whilst in induced torpor, the zebrafish showed that a reduction in metabolism and oxygen concentration in cells promotes less oxidative stress and greater resistance to radiation,” says Thomas Cahill, co-first author of the research. “These insights into how a reduction in metabolic rate can offer protection from radiation exposure and could help humans achieve a similar kind of hibernation, counter measuring the damage they currently face during spaceflight.”

While there is a lot of work to do before this is proven to be an effective technique for space-faring humans, the scientists describe it as compelling initial evidence. And the idea isn’t as niche as it might seem, with the ESA conducting its own research into the impacts of hibernating astronauts not just for health reasons, but because it could reduce the amount of consumables required for a space journey and allow the mass of a spacecraft to be reduced by a third.

The research was published in the journal MDPI Cells.

Source: Queen’s University Belfast

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