Morphological and Physiological Changes in Mature In Vitro Neuronal Networks towards Exposure to Short-, Middle- or Long-Term Simulated Microgravity

Giuseppe Pani,Roel Quintens,Nada Samari,Louis De Saint-Georges,Mariantonia Meloni,Patrick Van Oostveldt,Mohammed Abderrafi Benotmane,Sarah Baatout,Friedemann Paul

doi:10.1371/journal.pone.0073857

Giuseppe Pani, Roel Quintens + Show 7 more

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https://doi.org/10.1371/journal.pone.0073857

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Abstract

One of the objectives of the current international space programmes is to investigate the possible effects of the space environment on the crew health. The aim of this work was to assess the particular effects of simulated microgravity on mature primary neuronal networks and specially their plasticity and connectivity. For this purpose, primary mouse neurons were first grown for 10 days as a dense network before being placed in the Random Positioning Machine (RPM), simulating microgravity. These cultures were then used to investigate the impact of short- (1 h), middle- (24 h) and long-term (10 days) exposure to microgravity at the level of neurite network density, cell morphology and motility as well as cytoskeleton properties in established two-dimensional mature neuronal networks. Image processing analysis of dense neuronal networks exposed to simulated microgravity and their subsequent recovery under ground conditions revealed different neuronal responses depending on the duration period of exposure. After short- and middle-term exposures to simulated microgravity, changes in neurite network, neuron morphology and viability were observed with significant alterations followed by fast recovery processes. Long exposure to simulated microgravity revealed a high adaptation of single neurons to the new gravity conditions as well as a partial adaptation of neuronal networks. This latter was concomitant to an increase of apoptosis. However, neurons and neuronal networks exposed for long-term to simulated microgravity required longer recovery time to re-adapt to the ground gravity. In conclusion, a clear modulation in neuronal plasticity was evidenced through morphological and physiological changes in primary neuronal cultures during and after simulated microgravity exposure. These changes were dependent on the duration of exposure to microgravity.

Highlights

In an orbital spaceflight, astronauts are exposed to the orbital gravity (1022–10266g), called microgravity, which is a continuous free-fall condition, resulting from the Earth’s gravitational pull and the centrifugal forces from the spacecraft’s propulsion
In this study we investigated the effects of simulated microgravity using the Random Positioning Machine (RPM) on in vitro dense mature neuronal networks obtained from primary mouse neurons with a particular emphasis on neuronal network morphology and cell death during short, middle and long-term exposure to simulated microgravity
Microgravity To investigate the effects of simulated microgravity on dense neuronal networks, 10-day cultures were exposed for short, middle- and long-terms to the RPM

Summary

Introduction

Astronauts are exposed to the orbital gravity (1022–10266g), called microgravity, which is a continuous free-fall condition, resulting from the Earth’s gravitational pull and the centrifugal forces from the spacecraft’s propulsion. When astronauts and/or animals are exposed to microgravity, a particular number of neurological disorders, such as space adaptation syndrome (SAS), space motion sickness (SMS), postural illusion, visual disturbances, nausea and headaches, neuromuscular fatigue and weakness as well as postural imbalance and ataxia may appear and persist until return to Earth [11]. These pathological changes affect both motor and sensory functions, and the effects can be long lasting. The nature of the functional and structural mechanisms involved in these changes is currently not well understood

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