Adapting to Outer Space

Samantha Christoforetti prepares the Biolab aboard the ISS Columbus module for the cell adaptation experiments.

NASA

Around 550 people have traveled to space, including four who have spent more than a year there and another twelve who have spent at least seven months. None have shown any outward ill effects from living in near-weightless conditions. At the same time, experiments outside the human body have indicated severe effects of low gravity conditions at the cellular and molecular levels. But such studies have focused mostly on identifying initial changes, not the adaptation thought to come later, and many have occurred on the ground. Now, researchers have completed an experiment on the International Space Station (ISS) to vary the pull of gravity and examine its effects on a biochemical reaction crucial to immune response.

A team of 22 scientists, led by anatomists Cora S. Thiel and Oliver Ullrich, both affiliated with the University of Zurich, Switzerland; Otto von Guericke University Magdeburg, Germany; and Kennedy Space Center, USA, designed an experiment to examine the oxidative burst reaction in macrophage cells from rat lungs. The oxidative burst reaction, an important component of immune response in all multicellular life, is “part of the cellular anti-microbial defense program,” explains Thiel.

After five years of careful pre-mission testing, the cells under investigation were frozen in the lab in Zürich, then sent to the Biolab on the ISS Columbus module, where European Space Agency astronaut Samantha Christoforetti thawed them for experimentation. Thereafter, ground control at the German Aerospace Center in Cologne automated, controlled, and guided the experiment.

First, a yeast cell wall fragment was introduced into the rat macrophages as a microbial stimulus to induce the oxidative burst reaction. Then the gravitational force placed on cells was altered using a centrifuge. The experiment tested the effects of a stepwise increase or decrease in gravitational force in comparison with cells held constant at normal and low gravity as controls. The rate of the oxidative burst reaction, as indicated by the production of reactive oxygen species, was measured using a chemical assay that detects biochemical changes via the production of light.

As found in previous experiments using parabolic flight, the oxidative burst reaction was inhibited when macrophages first encountered near-zero gravity. However, the researchers were surprised to find that adaptation to the microgravity environment began after only 14 seconds. By 42 seconds, the immune response was fully restored. The mechanisms behind this ultra-rapid adaptation to microgravity conditions are not yet known, and provide the group’s next study question. (Scientific Reports)

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