Table 1 Recommendations in short (3 years), middle (6 years), and long term (>10 years)
Open fundamental scientific question | Proposed research activities including ground & space experiments | Suitable testbed environment (Ground, LEO, BLEO, Moon, Mars,) | Space relevance (importance of altered gravity and/or relevance for space exploration) | Timeline (short, medium, long) |
|---|---|---|---|---|
1. Identifying changes in the mechanical properties of single cells, tissue models and organisms in response to gravity alterations | Clarify the mechano-biological coupling mechanisms through which gravity regulates biological responses at biopolymers, sub-cellular, cellular, tissue and organism levels with the aim to reproduce fundamental cell–cell contacts, intra- and inter-cellular signaling. | Ground-based (micro- and partial gravity simulation and hyper-gravity) in vitro and in vivo models in/beyond LEO Humans in LEO Humans beyond LEO | Use of spaceflight environment for basic research: Understanding the role of gravity in biological systems Extended microgravity to permit the effect of sub 1×g accelerations to be explored Ground-based studies can explore response in microgravity analog or hypergravity | Short - Medium |
2. Assessing gravity-induced mechanical and functional alterations in complex 3D cell/tissue models. | Implementing 3D model systems for biological studies in altered gravity conditions: 3D cell cultures (spheroids, organoids, 3D bioprinter, organ-on-a-chip, organotypic cultures) and ex vivo tissue cultures (e.g. skin, cornea, eye lens, retina, blood vessel, muscle tissues, brain slices, spinal cord slices, etc.) with the aim to reproduce fundamental cell-cell contacts, inter-cellular signaling, and mechanical properties of organs (e.g. liver, pancreas, gut, brain). The full physiological complexity of an organ cannot be recapitulated, yet specific organ compartments and functions become experimentally accessible with 3D models, which allow studying the tissue-like response to altered gravity at levels of morphology and structure, gene and protein expression, cell function, and physiological processes. 3D cell cultures and ex vivo tissue cultures can be used also as models of injuries and diseases and to evaluate or develop new therapeutic treatments. Understanding the effects of changes in the transport coefficient of culture fluids on the growth and development of tissues and 3D constructs. Understanding the role of functional changes in mitochondrial and energy metabolism in the overall response to spaceflight. (*)Studying how gravity determines intercellular communication and exchange (proteins, lipids, genetic material, role of extracellular vesicles (EVs)), the regulation of cell cycle and death (in particular cell senescence and apoptosis), and consequent protective and deleterious effects in 2D and 3D in vitro models. (*)Identify the cellular and sub-cellular processes that underlie the effects of altered gravity (micro-, partial, one, and hypergravity) seen in 2D and 3D in vitro models, ex-vivo explants, and higher tissue and organism organizations. (*)Studying nanomaterial interaction with biological systems in altered gravity conditions at any level (molecular, transcriptional, translational, phenotypic, etc.). The deriving knowledge may offer opportunities for developing effective countermeasures (including medications carrying physicochemical cues) against deleterious effects of the space environment. (*)Note: These statements are very true both for 2D and 3D systems and the comparison between 2D and 3D systems is very interesting. Therefore, these activities should take place for questions 1 and 2. | Ground-based (micro- and partial gravity simulation and hyper-gravity) in vitro and ex vivo models in/beyond LEO | Use of spaceflight environment for basic and applied research: Extended microgravity to permit the effect of sub 1×g accelerations to be explored Ground based studies can explore response in micro- and partial gravity analog and hypergravity Microgravity conditions may facilitate assembly of 3D cell constructions and bioprinting due to lack of sedimentation Space Exploration relevance: Understanding effect of spaceflight on human tissues and organ systems & development of countermeasures. 3D cell cultures provide in-vitro models to understand how tissue/organ function is altered by spaceflight & potentially explore therapeutic / countermeasures | Medium |
3. Evaluating the effects of altered gravity on epigenetics, genetic protection, and repair mechanisms. | Analyzing the activation of the DNA Damage Response (DDR) which encompasses e.g. DNA repair, cell cycle arrest, possibly cell death, and gene expression changes after 2D/3D cell cultures exposure to real and simulated microgravity, also in association with “in vitro” exposure to high energy particle radiation and countermeasures. | Ground-based (micro- and partial gravity simulation and hyper-gravity) in combination with radiation (e.g. clinostat at heavy ion accelerator and other altered gravity simulation systems coupled with radiation sources) in vitro and in vivo models in/beyond LEO Humans in LEO Humans beyond LEO | Use of spaceflight environment for basic and applied research: Extended microgravity to permit the effect of sub 1×g accelerations to be explored on processes Interaction between microgravity and cosmic radiation effects | Short Medium |
4. Investigating the stress response induced by altered gravity conditions and possible countermeasures. | In-flight studies should be accompanied by a well-designed ground-based research program exploring the impact of gravity to better understand the in-flight results. Studies should explore the gravity continuum (from microgravity to hypergravity) of their in vitro and/or in vivo systems | Ground-based (micro- and partial gravity simulation and hyper-gravity) in vitro and in vivo models in/beyond LEO Humans in LEO Humans beyond LEO | Use of spaceflight environment for basic and applied research: Extended microgravity to permit the effect of sub 1×g accelerations to be explored Ground-based studies can explore response in microgravity analog or hypergravity. | Short Medium |
5. Understanding how gravitational alterations affect other space-related physiological responses. | In-flight studies should be designed to link mechanisms identified in question 1 to space-related physiological changes at the tissue and/or whole organism level. | Ground-based (micro- and partial gravity simulation and hyper-gravity) in vitro and in vivo models in/beyond LEO Humans in LEO Humans beyond LEO | Use of spaceflight environment for basic and applied research: Linking basic gravity sensing mechanisms to physiological alterations. Applying knowledge of basic gravity sensing mechanisms regulating physiological alterations to applied countermeasures. Space Exploration relevance: Understanding the effect of spaceflight on human tissues and organ systems & development of countermeasures. | Medium Long |
