Ground-Based Facilities for Simulation of Microgravity: Organism-Specific Recommendations for Their Use, and Recommended Terminology

Abstract

Research in microgravity is indispensable to disclose the impact of gravity on biological processes and organisms. However, research in the near-Earth orbit is severely constrained by the limited number of flight opportunities. Ground-based simulators of microgravity are valuable tools for preparing spaceflight experiments, but they also facilitate stand-alone studies and thus provide additional and cost-efficient platforms for gravitational research. The various microgravity simulators that are frequently used by gravitational biologists are based on different physical principles. This comparative study gives an overview of the most frequently used microgravity simulators and demonstrates their individual capacities and limitations. The range of applicability of the various ground-based microgravity simulators for biological specimens was carefully evaluated by using organisms that have been studied extensively under the conditions of real microgravity in space. In addition, current heterogeneous terminology is discussed critically, and recommendations are given for appropriate selection of adequate simulators and consistent use of nomenclature.

A Potential Gravity-Sensing Role of Vascular Smooth Muscle Cell Glycocalyx in Altered Gravitational Stimulation

“…This method has been widely used as an effective ground-based tool to test the effects of microgravity on mammalian cell physiology (Sarkar et al, 2000;Kacena et al, 2002). During rotation, however, other forces, especially shear stress, turbulence, or hydrostatic pressure, may be important factors that affect our results (Herranz et al, 2013). We cannot eliminate the above-mentioned factors completely.…”

Analysis of Statoliths Displacement in Chara Rhizoids for Validating the Microgravity-Simulation Quality of Clinorotation Modes

“…Therefore, different μg simulation facilities like clinostats, Random Positioning Machine (RPM), rotating wall vessels and magnetic levitation are frequently used as attractive alternatives for complementing and preparing real-microgravity experiments in the near-Earth orbit. Furthermore, they enable with some limitations, such as sample diameter, biological studies of the impact of altered gravity conditions on Earth (Herranz et al 2013;Brungs et al 2016).…”

“…The classical 2D clinostat usually rotates constantly and slowly at 1-10 revolutions per minute (rpm), whereas fast rotating clinostats (Briegleb 1992;Herranz et al 2013) run at a selected speed between 60-90 rpm. Due to the physical constraints only small samples placed precisely along the rotation axis will experience acceleration forces which are thought to be below the threshold of the biological system.…”

“…Due to the fact that reports on clinostat and random positioning experimentation frequently do not adequately state the operational modes and precise physical parameters of the treatment (Hammond and Allen 2011), a comparison of experiment results, calculation of forces and determination of threshold values is in many cases very difficult hampering generalization of conclusions (Herranz et al 2013).…”

“…A diversity of model organisms such as Arabidopsis thaliana seedlings and plant cell cultures, characean rhizoids, human immune cells and protists have been investigated by several European science teams on various microgravity simulation facilities and the results were compared with real μg data (Herranz et al 2013;Brungs et al 2016). It became evident that a thoroughly performed assessment of side effects is required to determine the most suitable simulation facility for each biological object chosen.…”