Astrocyte Reactivity under Space Conditions: Protocol Testing and Optimization of an ISS (International Space Station) Experiment

Abstract

Long-term space missions pose significant challenges for astronauts health, including physiological changes in the brain that can lead to cognitive impairment. Astrocytes, the primary glial cells of the Central Nervous System (CNS), are essential for the maintenance of neuronal function and the homeostasis of brain tissue. They create a stable environment and regulate neuronal activity, while neurons are responsible for direct signal transmission and processing. Additional tasks of astrocytes include the supply of nutrients to neurons and the removal of excess neurotransmitters and waste products from the extracellular space. Following a CNS injury, astrocytes change, proliferate and migrate to the sites of injury, leading to the formation of glial scars through a process called astrogliosis. These scars, characterized by the production of extracellular matrix and the release of cytokines or growth inhibitory factors, hinder the regeneration of neural tissue. The Live Assessment of Astrocytic Reactivity under Space Conditions (LAARA) project investigates how astrocytes adapt to microgravity aboard the International Space Station (ISS) using the FLUorescence MIcroscopic Analysis in Space (FLUMIAS) platform. FLUMIAS is an advanced fluorescence microscope that combines automated imaging with life-support functions in a centrifuge, allowing real-time monitoring of astrocytic processes under varying gravitational loads up to 1g. A Scientific Reference Model (SRM) at DLR generates consistent data for standardizing conditions in biological studies. The project focuses on the dynamics of the cytoskeleton and mitochondrial activity, which are crucial for astrogliosis. Primary murine astrocytes will be isolated and transported to the ISS in a specialized FLUMIAS Experiment Block (EB). Onboard, researchers will analyze cell morphology and migration patterns in microgravity, comparing the results with ground-based controls at the Deutsches Zentrum für Luft- und Raumfahrt (German Aerospace Center, DLR), Institute of Aerospace Medicine to confirm that the observed changes are specific to the space environment. Ground-based studies in this thesis using the FLUMIAS SRM and simulated microgravity platforms will further refine the experimental protocols and validate the results. The LAARA experiment will allow us to identify potential effects on astronaut cognition and motor performance, as well as broader implications for neurodegenerative diseases and cognitive decline. Astrocytic dysfunction, often linked to astrogliosis, is associated with conditions such as brain trauma, Alzheimer, Parkinson disease, and spinal cord injuries. Insights from the present research could enhance our understanding of these diseases in the context of spaceflight, with important applications for both astronaut health and neuroscience.