Space Life Science
Gravity has constantly influenced both physical and biological phenomena throughout Earth’s history. The gravitational field has played a major role in shaping evolution when life moved from water to land. However, gravity may influence in a more deep and subtle fashion the way the cells behave and build themselves. Cells may indeed ‘sense’ changes in the microgravitational field through (1) an indirect mechanism (mainly based on the modification of physical properties of their microenvironment); (b) the development of specialized structures for the mechanical perception and transduction of gravitational forces (like the cytoskeleton); (c) changes in the dynamics of enzymes kinetics or protein network self-assembly. It is worth noting that the latter two processes are dramatically affected by non-equilibrium dynamics. Non-linear dynamical processes far from equilibrium, involve an appropriate combination of reaction and diffusion, and the pattern arising from those interactions are tightly influenced by even minimal changes in reactant concentrations or modification in the strength of the morphogenetic field. Processes of this kind are called dissipative structures, given that a consumption of energy is required to drive and maintain the system far from equilibrium. That prerequisite is needed in order to allow the system to promptly change its configuration, according to the system’s needs. In turn, the dissipative energy provides the thermodynamic driving force for the self-organization processes. Accordingly to some preliminary results, gravity seems to influence non-equilibrium processes (like the cytoskeleton reorganization), acting as an ‘inescapable’ constraint that obliges living beings to adopt only a few configurations among many others. By ‘removing’ the gravitational field, living structures are free to recover more degrees of freedom, thus acquiring new phenotypes and new functions/properties.
These data raise several crucial questions. Some of these entail fundamentals of theoretical biology, as they question the gene-centric paradigm, according to which biological behavior can be explained by solely genetic mechanisms. Indeed, influence of physical cues in biology (and, in particular, on gene expression) is still now largely overlooked. This is why it has been argued that the ultimate reason for human space exploration is precisely to enable us to discover ourselves. Undoubtedly, the microgravitational space-field presents an unlimited horizon for investigation and discovery. Controlled studies conducted in microgravity can advance our knowledge, providing amazing insights into the biological mechanism underlying physiology as well as many relevant diseases, like cancer. Thereby, space-based investigations may serve as a novel paradigm for innovation in basic and applied science.