Modified lettuce boosting astronaut bones
Up into space now, and astronauts experiencing microgravity during prolonged stays in space can develop osteopenia, or weakening of their bones. This can be significant, with a loss of up to 1% of their bone mass per month. But Kevin Yates, part of NASA’s Center for the Utilization of Biological Engineering in Space (CUBES) programme, explains to Evelyna Wang, how he’s grown a genetically modified lettuce that could help prevent bone mineral density loss...
Kevin - We modified this lettuce to include a gene which instructs the plant to produce a fusion protein, which we call PTHFC.
Evelyna - This fusion protein is composed of two parts. The first is PTH.
Kevin - The PTH part regulates calcium in the blood and therefore regulates the amount of bone mineral density that you have.
Evelyna - The second part of the protein is called FC, a bulky component that they attach to the active PTH.
Kevin - And by adding that we increase the amount of time the fusion protein can stay in the blood, thereby increasing its expected efficiency.
Evelyna - So, your hope is to have this lettuce that produces and contains the protein that treats bone mineral density loss?
Kevin - That's right. So, either it may be possible that you can simply eat the lettuce, and get the dose that way, otherwise the protein can be extracted from the plant leaves.
Evelyna - Is this protein an existing medication? And how is it typically administered?
Kevin - As a drug, a portion of the naturally occurring human parathyroid hormone is an FDA approved drug called Teriparatide, and that is given in a daily injection.
Evelyna - So, why can't you just bring the medicine with you into space?
Kevin - So, for one thing, a primary concern is the amount of mass you'd have to carry to do that. As a rule of thumb, for every one kilogram of mass that you want to bring with you, you need 99 kilograms of support, power, heating and cooling, this sort of thing. The other issue is that cosmic and solar radiation can cause pharmaceuticals to degrade over time. But, if you just bring seeds to grow plants which will produce the medicine that you need, seeds are of course of a much smaller volume when you consider what you'll get out. And, of course, you can take these plants to the seeding stage and make more plants from the seeds that are produced.
Evelyna - Right. Why did you pick lettuce?
Kevin - We know that lettuce can be grown in microgravity. It's been done on the International Space Station. One interesting fact about lettuce is that it's seen as having benefits for psychological health, and that, for a long time spent in space, having a green leafy plant growing, and also as food, offers a lot of mental health benefits to astronauts.
Evelyna - Oh wow. So there are both psychological and medicinal benefits to this lettuce. Are there other applications you can use this lettuce for?
Kevin - Yes. I think that the fact that this works in the resource limited environment of a spacecraft, if it works there, it will work on earth. And there are a lot of places on earth where medicine of this type would be hard to produce because you need something like a bio reactor, which has to be temperature controlled, powered, etc., and sterile as well. But if you can simply plant a plant in the soil, or there's a greenhouse, or in a field, to get medicine, I think there are a lot of places that could benefit from that.
Julia - I am surprised he went for lettuce and not rocket, but there we are. Evelyna Wang speaking to Kevin Yates. He presented that work at the American Chemical Society spring meeting this week.