After a successful harvest of chili peppers, the astronauts on the Space Station (ISS) are now trying to grow lettuce. These vegetables can help the astronauts nutritional intake and maintain their bone health.
Research shows that astronauts can lose about 1% of bone mass per month they spend in space. In addition to the impact of microgravity on bones, being in space can affect genes that affect bone health.
That's why astronauts perform special exercises to help mitigate this effect. In a new study, researchers from the University of California, Davis (UC Davis) created an experimental strain of lettuce that produces a drug containing a human parathyroid hormone (PTH) peptide fragment. PTH is naturally produced by the parathyroid glands and helps stimulate bone growth, among other functions.
Researchers think that this new type of 'space lettuce' could help astronauts maintain their bone density while in space. The new study was presented at a meeting of the American Chemical Society. According to the researchers, giving PTH to treat bone loss may not work as well for longer trips, such as missions to Mars.
Drugs containing PTH, which are usually used by people with low hormone levels in their bodies to increase calcium in the blood, are usually given by injection. However, these injections would not be an ideal long-term solution for long-range missions to destinations as distant as Mars.
Quoted from Space.com, Friday (25/2/2022) astronauts can get PTH by planting and eating this lettuce. Astronauts on the ISS have grown two types of lettuce and other types of vegetables such as mustard greens, turnips and chili peppers through the Veggie and Advanced Plant Habitat experiment.
"Astronauts can carry very small GMO seeds, up to a few thousand seeds in a thumb-sized bottle. These seeds can then be grown like regular lettuce," said study author Somen Nandi, a chemical engineer at UC Davis.
Lettuce is transgenic because it contains a gene from another organism, the gene that codes for human PTH. To develop a lettuce strain containing PTH, the research team injected lettuce plants with a bacterium known as Agrobacterium tumefaciens, which transfers the gene the plant needs to produce PTH.
They also transfer genes to plants that allow them to produce human antibody 'tails', disease-fighting proteins in the immune system. This part of the antibody, called the crystallized fragment domain (Fc), was used because the researchers thought it would make the hormone more stable and easier for the body to process.
The researchers found that the lettuce they produced contained 10-12 milligrams of PTH-Fc per kilogram of fresh lettuce. To get enough PTH from lettuce to maintain their bone density, astronauts would have to eat about eight cups of a large salad per day.
"There may be a way to increase the amount of hormone in plants so that astronauts don't have to eat as much lettuce," the researchers said.
They are currently exploring which strain of lettuce they produce has the highest PTH-Fc levels. The team is also thought to need to do a lot of additional testing on the lettuce before astronauts can grow it and eat it in space.
For example, by conducting tests on animal models and running clinical trials on humans to test how effectively lettuce can treat bone loss.
As part of the study, the researchers did not sample the lettuce because it had not been tested for safety. Additionally, the team needed to have astronauts grow them on the ISS to see if lettuce plants contained the same amount of PTH-Fc when grown in space as on Earth.
This lettuce could have a valuable impact in space, the researchers said. They predict that lettuce could eventually be used by people on Earth who are not getting enough nutrition and are at risk of developing osteoporosis, which puts people at increased risk of fractures.
Additionally, the team says that the same method could be used with other drugs, to provide astronauts with an effective and efficient way to maintain their health in environments like those on the ISS.