Human space biology at SCK-CEN: from in vitro cell experiments to the follow-up of astronauts

Prolonged exposure to space radiation and extended microgravity has revealed profound physiological and clinical changes in astronauts. The health problems thought to be related to the effects of microgravity include a decrease in the heart and the respiratory rates, a loss of body weight, changes in bone calcium, a redistribution of body fluids with a greater amount in the upper body, a decrease in muscle tissue, a weakening of the veins and arteries in the legs, as well as an underproduction of red blood cells leading to anaemia. At the cellular and molecular levels, microgravity is known to induce both a loss of T-cell activation and changes in gene expression patterns, as well as a three-dimensional growth of normal cells and tumour cells, an alteration of the mitochondrial organization, a modification of the production of extracellular matrix proteins and apoptosis in some types of cells. The Earth's magnetic field protects us from harmful radiation. On Earth, we are still exposed to small amounts of radiation when we go for medical x-rays, when we travel on transcontinental flights or just from radon in the air. However, astronauts are exposed to 50 to 100 times as much radiation - and that is just in a low Earth orbit. In deep space, astronauts can be exposed to even higher doses. It is well known that large amounts of radiation can cause severe health effects by altering DNA in our cells. The health effects from space radiation are therefore a critical safety concern for long-term space travel. Possible health risks include cancer, cataracts, acute radiation sickness, hereditary effects, and damage to the central nervous system. The aims of this research are 1) to ensure the immunological monitoring of a cohort of astronauts (having spent around 6 months aboard the International Space Station ISS) and 2) to investigate the effects of an in vitro exposure of endothelial cells and other types of cells to radiation and/or microgravity conditions