Lettuce against bone density loss

Genetically-modified lettuce, packed with bone-promoting protein, could keep astronauts healthy in space, NASA scientists announced this week...

Spacefarers experience microgravity, which results in weaker bones as, without the impact loading of daily life, the skeleton thins. This is a condition known as osteopenia, and on extended space missions astronauts can lose up to 1% of their bone mass per month.

Now, as part of NASA's Center for the Utilization of Biological Engineering in Space (CUBES) programme, researchers are genetically modifying lettuce plants to produce drug proteins that can combat bone density loss.

Typically, low bone density can treated with injections of human parathyroid hormone protein (PTH). This is an approved medication. The PTH regulates calcium in the blood and tells your body to absorb more calcium from food, helping to reinforce the skeleton.

Nevertheless, it is challenging to bring this type of medication onto space flight missions. Bringing medication and medical tools such as syringes requires takes up volume and weight on the space flight. Every additional kilogram of mass that we plan to bring into space requires an additional 99 kilograms of support mass for heating, power, cooling and liftoff. Also, cosmic and solar radiation can degrade the medicine.

As an alternative, the CUBES programme is developing methods to grow raw materials in plants or other organisms in space. Under this research programme, Kevin Yates and his collaborators have incorporated into lettuce plants the gene containing the instructions for making the a so-called fusion protein known as PTH-FC.

This comprises two parts: the first is PTH, the same part of the human parathyroid hormone that is already used in existing medication. The second part is FC, which is a bulkier component linked to the PTH and helps to increase the amount of time the protein can spend in the blood, boosting its effects.

Astronauts in space can therefore access medication that treats bone mineral density loss potentially by simply growing lettuce!

Lettuce has already been cultivated successfully on the International Space Station, and seeing and eating leafy green vegetables also seems to have a positive psychological health impact on orbiting astronauts.

Ideally, the astronauts can get a medical dose of the PTH-FC protein simply by eating the lettuce leaves that contains it, although further work will be needed to establish how the protein behaves when ingested, whether it even reaches the bloodstream via this route, and the required dosing regime.

But the applications of this lettuce are not limited to space. "If it works [in the resource limited environment of a space craft], it will work on Earth. There are lots of places on Earth where medication of this type would be hard to produce," says Yates.

Conventionally, these sorts of medications are produced using a bioreactor, which needs fine temperature control and sterilisation. Producing medication by simply planting a plant greatly increases the accessibility of medication in resource limited enviornments.