It’s one of mankind’s biggest achievements – but travelling to space takes a toll on crucial cells in the human body, according to a new study.
Experts have discovered spaceflight speeds up the ageing of human stem cells, which are critical to the body’s natural repair system.
Astronauts are already known to be at risk from a range of issues caused by microgravity and space radiation, such as muscle loss and an increased risk of cancer.
Now, scientists have been able to measure how spending time in low gravity has an effect at the cellular level.
A team from the University of California sent stem cells to the International Space Station (ISS) on four supply missions that lasted between 32 and 45 days.
Analysis revealed they lost some of their ability to make healthy new cells, became more prone to DNA damage and the protective caps at the ends of chromosomes were shortened – all signs of accelerated ageing.
‘Space is the ultimate stress test for the human body,’ Professor Catriona Jamieson, director of the Sanford Stem Cell Institute (SSCI) at the University of California – San Diego, said. ‘These findings are critically important because they show that the stressors of space – like microgravity and cosmic galactic radiation – can accelerate the molecular aging of blood stem cells.’
The effects of spending time in space became apparent earlier this year when two NASA astronauts returned to Earth after nine months stuck on the ISS – and appeared much older than when they left.
After nine gruelling months in space, Suni Williams (pictured) and Butch Wilmore finally returned to Earth. But shocking before–and–after images show the damage that their unintended stay in space has caused
Even during their time in space, health experts raised concerns that Butch Wilmore (pictured) and Suni Williams were suffering from severe weight loss and muscle atrophy
A graphic abstract of the study’s findings, showing that the stem cells sent to space experienced reduced self–renewal, chronic inflammation, mitochondrial dysfunction and exhaustion
Butch Wilmore and Suni Williams, who were initially scheduled for an eight–day mission, ending up spending 286 days in space due to technical problems with the Boeing Starliner that launched them there.
Shocking before–and–after images showed the terrifying damage that months spent in the harsh conditions of space had on the astronauts.
The pair looked noticeably thin and gaunt, while Williams, 59, sported much greyer hair – although it’s unclear whether it was from ageing or a lack of hair dye.
During time in microgravity, astronauts face a serious risk of muscle atrophy and bone loss which often makes it difficult to walk back on Earth.
After landing, the pair had to be helped out of their capsules onto stretchers to be carried away for medical examination.
Other issues triggered by a stint in space can include ‘chicken legs’ and ‘baby feet’, as well as vision loss.
Previous NASA studies have shown that spaceflight can affect immune function and the length of chromosome ends, known as telomeres.
One landmark, year–long experiment involved astronaut Scott Kelly spending 340 days aboard the ISS while his identical twin, Mark Kelly, remained on Earth.
During their nine months on the ISS, health experts raised concerns over Williams’ ‘gaunt’ appearance. A loss of appetite is common in space due to frequent nausea, sometimes leading to astronauts losing dangerous amounts of weight
The biggest impacts of time in space are caused by exposure to microgravity and intense radiation. Being away from Earth’s pull causes astronauts’ muscles to weaken, leaving them with walking issues upon return
The NASA Twins Study tracked changes across genetics, physiology, cognition and the microbiome and found altered gene expression, shifts in telomere length and changes in the gut microbiome.
But many of those changes reversed or returned to normal after Scott Kelly returned to Earth.
However, the study did identify some persistent changes – such as increased numbers of short telomeres and disruptions in gene expression – which could be relevant for longer space missions.
As part of the new study, published in the journal Cell Stem Cell, the researchers found that stem cells became more active than normal in space.
This meant they burned through their energy reserves and lost the ability to reset and recover – a key trait that allows stem cells to regenerate over time.
The cells also showed signs of inflammation and stress inside their mitochondria – the cell’s energy producers – and began activating hidden sections of the genome that are normally kept quiet to maintain stability.
Such stress responses can impair immune function and increase the risk of diseases, say scientists.
When the space–exposed cells were later placed in a young, healthy environment, some of the damage began to reverse, suggesting it may be possible to rejuvenate ageing cells with the right interventions.
Research has shown that a 30 to 50–year–old astronaut who spends six months in space loses about half their strength
‘This is essential knowledge as we enter a new era of commercial space travel and research in low Earth orbit’, Professor Jamieson said.
Following their return to Earth both Wilmore and Williams made an almost inconceivably rapid recovery.
Both credited it to the rigorous exercise programme all astronauts follow while on the space station and once they return to Earth.
Using specialised exercise equipment, NASA astronauts exercise twice per day to stave off the progress of muscle and bone loss which could cause complications back in Earth’s gravity.
EXPLAINED: THE $100 BILLION INTERNATIONAL SPACE STATION SITS 250 MILES ABOVE THE EARTH
The International Space Station (ISS) is a $100 billion (£80 billion) science and engineering laboratory that orbits 250 miles (400 km) above Earth.
It has been permanently staffed by rotating crews of astronauts and cosmonauts since November 2000.
Crews have come mainly from the US and Russia, but the Japanese space agency JAXA and European space agency ESA have also sent astronauts.
The International Space Station has been continuously occupied for more than 20 years and has been expended with multiple new modules added and upgrades to systems
Research conducted aboard the ISS often requires one or more of the unusual conditions present in low Earth orbit, such as low-gravity or oxygen.
ISS studies have investigated human research, space medicine, life sciences, physical sciences, astronomy and meteorology.
The US space agency, NASA, spends about $3 billion (£2.4 billion) a year on the space station program, with the remaining funding coming from international partners, including Europe, Russia and Japan.
So far 244 individuals from 19 countries have visited the station, and among them eight private citizens who spent up to $50 million for their visit.
There is an ongoing debate about the future of the station beyond 2025, when it is thought some of the original structure will reach ‘end of life’.
Russia, a major partner in the station, plans to launch its own orbital platform around then, with Axiom Space, a private firm, planning to send its own modules for purely commercial use to the station at the same time.
NASA, ESA, JAXA and the Canadian Space Agency (CSA) are working together to build a space station in orbit around the moon, and Russia and China are working on a similar project, that would also include a base on the surface.
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