Therapy salad developed for astronauts

This lettuce produces a substance that can combat bone loss in space. © Kevin Yates

Tasty greens instead of injections – to protect themselves from bone loss, travelers to Mars could eat special raw vegetables they have grown themselves: scientists have produced lettuce plants that produce a substance that stimulates bone formation. They could allow for a sufficient supply of the therapeutic substance through the diet, making daily injections unnecessary. In addition, the salad could enrich the astronauts’ diet with a fresh component, say the scientists.

NASA has ambitious plans again: After the moon, Mars is now the target of manned space travel – sometime in the 2030s, people are supposed to set foot on our neighboring planet. Compared to the moon missions, however, this project involves significantly more effort. One of the biggest challenges is keeping the astronauts healthy on the three-year journey. One problem is the bone loss caused by weightlessness: Studies have shown that astronauts lose more than one percent of their bone mass every month in space. So far, the damage has been limited with the usual stay times in space, but it will probably become critical on a long journey to Mars.

Brittle bones threaten

“Astronauts are typically no longer than six months on the International Space Station. In contrast, it will take about ten months to get to Mars. After the astronauts have studied the planet for about a year, they will then make the long journey back to Earth again,” explains Kevin Yates of the University of California at Davis. As a result of the mission, the astronauts could eventually develop osteoporosis, which makes their bones susceptible to fractures. As Yates and his colleagues explain, there is a way to counteract bone loss with medication, but it is problematic.

The astronauts would have to inject themselves daily with syringes a peptide fragment of the human parathyroid hormone (PTH), which stimulates bone formation. Transporting and administering large quantities of the drug and syringes would be impractical on space missions. That’s why Yates and his colleagues have dedicated themselves to developing a better care option. Their result is an anti-bone-loss lettuce that, by transferring genes, forms the PTH peptide in its leaves. They are now presenting their results at the spring conference of the American Chemical Society in San Diego.

The scientists chose garden lettuce (Lactuca sativa) because the fast-growing plants have already been successfully cultivated under the resource-constrained conditions on the International Space Station. As they explain, the challenge was getting the lettuce to make the PTH peptide in a form that can be ingested through food rather than injected. In order to increase the stability and availability of the substance, the researchers used a genetic code that leads to the formation of a special protein appendage to the PTH peptide. Previous studies have shown that this so-called Fc fragment can ensure better bioavailability and thus effectiveness.

Bone-strengthening fresh food on the horizon

The researchers used the microbe Agrobacterium tumefaciens, which is common in genetic laboratories and can also naturally transfer DNA to plants, to transmit the genetic information for the PTH-Fc. As they report, the transfer was successful: Plants emerged that produce the modified peptide hormone. “We’ve only analyzed a few of them so far and found that the average is 10 to 12 milligrams of the modified peptide hormone per kilogram of fresh lettuce,” says co-author Karen McDonald of the University of California at Davis. This means that the astronauts would have to eat around 380 grams a day – a fairly large portion of lettuce – to get a sufficient dose. “But we think that we can further increase the values ​​so that less has to be consumed. To do this, we now have to test all transgenic lettuce lines to find the one with the highest PTH-Fc expression,” says McDonald.

Further research must follow before the anti-bone-loss salad can enrich the diet in space. Animal experiments are first necessary to confirm the tolerability of the transgenic lettuce, then experiments will follow to test the extent to which it can actually prevent bone loss. In addition, investigations on the International Space Station should show whether the lettuce also produces the PTH-Fc in weightlessness. But the researchers are confident. Yates concludes, “I would be very surprised if by the time we send astronauts to Mars, plants are not being used to make medicines and other useful substances.”

Source: American Chemical SocietyPresentation at the American Chemical Society Spring Meeting in San Diego

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