The Sciences

What are Fruit Flies and Human Cells Doing in a Rotating Laboratory in Space?

Scientists are using microgravity conditions onboard the International Space Station to perform experiments that would be too tricky on Earth.

On a sunny Tuesday afternoon at the southernmost end of the United States stood a 230-ft-tall rocket. It was a Falcon 9, a full-thrust reusable rocket developed by SpaceX. Its uppermost stage had been affixed with a capsule called Dragon, also reusable.

The launch was part of a series of contracts awarded by NASA to SpaceX, called the commercial resupply services. To fulfill each contract, SpaceX would have to hoick cargo to the International Space Station (ISS), a large laboratory and station orbiting Earth at about 35,800 km.

The Falcon 9 took off on April 2, 2018. The Dragon capsule onboard carried about 2,500 kg of supplies, research equipment and experiments.

One of the experiments was called ‘Comparative real-time metabolic activity tracing for improved therapeutic assessment screening panels’. Complicated though it sounds, it described sometime quite simple.

Luciferase, also called firefly luciferase, is an enzyme that causes organisms containing it to produce light inside their bodies, in their cells, much like a firefly. Researchers have been trying to use this internal glow to track the health of the cells.

A major drawback of this technology is that the glow doesn’t last for long, going from a few hours to several days. As a result, experiments that use it will have to be wrapped up in time.

In light of this, 490 Biotech, a small life-sciences company from Tennessee, has been able to engineer so called ‘auto-bioluminescent’ cells. These cells are equipped to be able to produce a continuous glow without human intervention for as long as experiments need it.

“This is basically a big step forward in bioluminescent imaging where instead of intermittent snapshots of data acquisition, we can continuously monitor any living cell, whether that’s a bacterium, a yeast, a human cell culture, or a small animal model, and we can track their metabolic activity in real life,” Dan Close, of 490 Biotech, told NASA Spaceflight.

Auto-bioluminescence is currently being used to check the effect of several anticancer drugs. Scientists are running an experiment whereby the effect of each drug can be interpreted using the intensity of light a cell emits: healthy cells glow brightly and dead cells, not at all.

Although these drugs are already being screened on Earth, the microgravity environment onboard the ISS is better-suited to study human cells. This is because the cells in a petri-dish on Earth tend to grow in a two-dimensional manner, whereas those in low-Earth orbit grow in a three-dimensional pattern similar to cells growing in the human body.

Several companies have developed machines to simulate microgravity environments on Earth. However, these devices tend to bring their own uncertainties to the table. For example, rotating parts could provide an unwanted source of mechanical stimulus to cells attached to some surfaces during testing. So auto-bioluminescent cells are sent to space to improve our knowledge of the effects of drugs, to test their efficacy and safety, and to accelerate essential drug screening.

Next, the ‘Fruit Fly Lab’ (FFL) onboard the ISS studies the innate immune system, which is responsible for quick and non-specific responses to infections. Did you know that the first lifeform (deliberately) sent to space in a human’s company was a fruit fly (Drosophila melanogaster) in 1947?

It has been known that space does strange things to an astronaut’s immune system. It’s important we understand ‘what exactly’ so we can protect humans during long space journeys.

A fruit fly has a natural parasite wasp called Leptopilina. The FFL-03 mission on the ISS tests how the host and its parasites interact in microgravity. The fruit flies are housed in small cylindrical vials, placed inside the vented fly box (VFB). The VFB is special hardware used to control and monitor temperature and humidity.

Six VFBs were sent to the ISS by the April 2 Dragon launch. Each VFB contained 15 vials each. Sixty vials of the 90 contained flies co-cultured with wasps and the other 30 hosted just the flies.

A Vented Fly Box is used in experiments aboard the ISS to test the innate immunity of flies. Credit: NASA

A month after the flies have arrived, the 30 fly-only cultures will be infected with wasps from Earth to find out whether spaceflight has altered the flies’ immunity. In turn, the space-grown wasps will be used to infect Earth-grown and space-grown flies.

This may be an elementary study to understand how our immune systems might change in space but it’s a necessary first step. Although a fruit fly’s immune system is not the same as that of a mammal, such studies provide important insights in a short period of time, since a fruit fly’s life cycle lasts 40-50 days.

Once the mission is complete, the flies will be sent back to Earth in a Dragon capsule.

A third bit of science onboard the ISS is the Genes in Space programme, which helps students of grades 7 to 12 (in the US) send their DNA amplification experiments to space. Studies have shown that spaceflight can cause epigenetic changes in the DNA, i.e. modify the DNA without changing its actual nucleotide sequence.

Thus, students can design experiments to detect these changes, which can be pivotal in studying how DNA can be affected in longer space journeys.

These three initiatives are a small snapshot of all the science in the 2,500 kilograms being sent to the ISS. At the time of writing this article, the Dragon capsule had been successfully captured by the ISS and berthed to its Harmony module.

Pratik Pawar is content developer at Monk Prayogshala and is based in Mumbai.