Rats Exposed to Mars-Like Radiation Developed Twice as Much Heart Scarring

Radiation like that astronauts would face on a trip to Mars may raise the risk of a dangerous heart condition, a new study in rats suggests, according to Live Science. The effect appeared long after exposure, which leads the authors to argue that astronauts need health monitoring for years after they come home.

The research was published Sept. 30 in the journal PLOS One. Because it was done in rats, it cannot show whether the same thing would happen in people.

What the researchers found

Rats exposed to radiation resembling what an astronaut might encounter on a long deep-space trip developed more scar tissue around the small blood vessels of the heart than unexposed rats. After 360 days, the exposed animals had twice as much scar tissue. That kind of scarring is a sign of cardiac fibrosis, a condition known to raise the risk of heart failure.

Study co-author John Baker, a professor of surgery in the Radiation Bioscience Laboratory at the Medical College of Wisconsin, told Live Science that the scarring means the heart cannot relax as much as it needs to.

How the experiment worked

The team used NASA's Simulated Galactic Cosmic Ray Simulation, a newer tool that more closely matches the radiation an astronaut might meet during more than a year in deep space. Baker said that no astronaut has ever been exposed to galactic cosmic radiation for long periods, which makes the heart effects hard to pin down. His team had earlier found cardiac problems in irradiated rats.

The researchers exposed the animals to several minutes of radiation scaled to their size, meant to resemble a Mars round trip, which Live Science described as roughly 18 months with current technology. Some rats also had their hind legs suspended to mimic weightlessness.

The scarring did not appear in rats that experienced only simulated weightlessness, which Baker said confirms that radiation alone caused the harm to the heart. Those rats did, however, have lower levels of key immune cells in long-term testing, a hint that microgravity may also affect long-term health.

Limits of the findings

Live Science noted that humans live longer than rats, 80 years versus 2 to 4 years, so effects seen in rats might take around 30 years to show up in people. Rupak Pathak, an associate professor of pharmaceutical science at the University of Arkansas for Medical Sciences who was not involved in the work, called the study a valuable contribution to space biology. He said rats and humans share more than 90% of their genetic information and have very similar cardiac systems.

Pathak also pointed out that the authors could expose the rats to radiation only once. He would like to see experiments testing whether chronic exposure affects the heart and other vital organs.

Why it matters: the health of astronauts after the mission

The practical message, Baker said, is that follow-up time is important. Astronauts who return from long missions expect to live for a long time, he said, and doctors should be wary that some may develop heart disease.

The authors hope the work will help NASA prepare safeguards for long missions, such as giving astronauts heart medications or improving spacecraft shielding. The more scientists know before such missions begin, Baker said, the better NASA can work out which countermeasures to develop.

Around Prague, based on reporting by Live Science