Bone density loss is the most common problem facing astronauts. In fact, it’s estimated that astronauts could lose up to 2% of their bone density each month in space. To address this issue, researchers have grown a genetically modified lettuce that could produce a key drug to help prevent the loss of bone density in astronauts.
Because of gravitational differences in space, bones are under different kinds of pressure. Or rather, less of it. Research suggests that many of the key functions of bones are negatively affected due to the gravitational differences in space, including bones ability to store nutrients and act in a load bearing way. Non-pharmaceutical interventions tend to have only a minimal effect (such as exercise), ultimately leaving astronauts with few options to keep their bones healthy.
One type of pharmaceutical intervention, parathyroid hormone (PTH), has been shown to treat bone density loss in space and maintain adequate bone function. However, that drug would currently need to be injected on a regular basis and available on demand for astronauts.
The genetically-modified lettuce is designed to produce PTH. Specifically, it produces a sort of combination protein, combining PTH with a human protein antibody. The hope is that this combination protein would remain stable and work effectively in the bloodstream. Researchers also hope astronauts could extract the protein from the plant, purify it, and use it as a treatment.