Tasty greens instead of injections – to protect themselves from bone loss, travelers to Mars could eat special raw vegetables that they grew themselves: scientists bred lettuce plants that produce a substance that stimulates bone formation. They could ensure sufficient intake of the therapeutic substance through the diet, making daily injections unnecessary. In addition, the salad could enrich the cosmonauts’ diet with a fresh component, scientists say.
NASA has ambitious plans again: after the Moon, Mars became the object of manned space flights – sometime in the 2030s, people should set foot on our neighboring planet. However, compared to missions to the moon, this project requires much more effort. One of the biggest challenges is keeping the astronauts healthy during the three-year journey. One problem is bone loss caused by weightlessness: studies have shown that astronauts lose more than one percent of their bone mass each month in space. So far the damage has been limited to normal time in space, but it is likely to become critical during the long journey to Mars.
Fragile bones threaten
“Astronauts are usually on the International Space Station for no more than six months. In contrast, it will take about ten months to reach Mars. After the astronauts have studied the planet for about a year, they will make the long journey back to Earth,” explains Kevin Yates of the University of California, Davis. As a result of the mission, astronauts may later develop osteoporosis, leaving their bones vulnerable to fractures. As Yates and his colleagues explain, there is a way to counteract bone loss with medication, but it’s problematic.
Astronauts would have to inject themselves daily with syringes a peptide fragment of human parathyroid hormone (PTH), which stimulates bone formation. Transporting and administering large quantities of drug and syringes would be impractical in space missions. That’s why Yates and his colleagues dedicated themselves to developing a better care option. Their result is a bone-loss-preventing lettuce that, by gene transfer, produces the PTH peptide in its leaves. They are now presenting their results at the American Chemical Society Spring Conference in San Diego.
The scientists chose lettuce (Lactuca sativa) because fast-growing plants have already been successfully grown in the limited resources of the International Space Station. The challenge, they explain, was to get the lettuce to produce the PTH peptide in a form that could be consumed with food, rather than injected. 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 provide better bioavailability and therefore effect.
Fresh, bone-strengthening foods are on the horizon
As a carrier of genetic information for PTH-Fc, the researchers used the microbe Agrobacterium tumefaciens, which is common in genetic laboratories and can naturally transfer DNA to plants. As they report, the transfer was successful: plants appeared that produce a modified peptide hormone. “So far we’ve only analyzed a few of them and found that, on average, there are 10 to 12 milligrams of the modified peptide hormone per kilogram of fresh lettuce,” says co-author Karen MacDonald of the University of California, Davis. This means that the astronauts would have to eat about 380 grams a day – a fairly large portion of salad – to get a sufficient dose. “But we think we can increase the value even more to consume less. To do this, we now have to screen all transgenic lines of lettuce to find the one with the highest expression of PTH-Fc,” says McDonald.
Further research is needed before anti-bone loss salad can enrich the diet in space. First, animal experiments must be conducted to confirm the tolerability of the transgenic lettuce, and then there will be experiments to test to what extent it can actually prevent bone loss. In addition, studies on the International Space Station should show whether lettuce also produces PTH-Fc in zero gravity. But the researchers are sure. Yates concludes, “I’d be very surprised if by the time we send astronauts to Mars, plants aren’t being used to make medicine and other useful substances.”
Source: American Chemical Society, presentation at the American Chemical Society Spring Meeting, San Diego