Living in Space
Integral Understanding of life-regulation mechanism from "SPACE"

Vestibular Plasticity – Programmed Research

1. A01-1
2. A01-2
3. A01-3
4. A02-1
5. A02-2
6. A02-3
7. A02-4
8. A02-5
9. A03-1
10. A03-2
11. A03-3

Research Subject	A02-2 Comprehensive Understanding of the Adaptive Response of Vestibular Plasticity and Strategies against Adaptation Disorders
Research Group Leader	Hironobu Morita Professor, Graduate School of Medicine, Gifu University Website http://www1.gifu-u.ac.jp/~physiol/ (*Japanese)
Research Group Members	Yoichi Ueta Professor, School of Medicine, University of Occupational and Environmental Health, Japan Hiroshi Kaji Professor, Faculty of Medicine, Kindai University Masafumi Muratani Associate Professor, Faculty of Medicine, University of Tsukuba Shinichi Iwasaki Associate Professor, The University of Tokyo Hospital
Research Collaborator(s)	Chikara Abe Associate Professor, Graduate School of Medicine, Gifu University

During the fifty-odd years of human spaceflights, many cases of adaptation disorders due to microgravity have been reported. Among the most typical and serious are space sickness, balance disorder, atrophy of anti-gravity muscles, decrease in bone mass, and cardiovascular dysfunction. These must be resolved in order for humans to be able to stay longer and reach farther in Space. We focus on the plasticity of the vestibular system as a precursor of adaptation disorders. The objective of this research is to elucidate the plastic alteration mechanism of the vestibular system associated with the changes in gravity using a physiological and molecular-genetic approach and to propose strategies against adaptation disorders.

In this research, we will focus on the autonomic nervous, cardiovascular, endocrine, stress response (including gravity sickness), motor regulatory, muscle and bone coordination systems, and examine how various non-1 G gravity environments (microgravity or hypergravity) induce changes in the adaptive functions of these systems, which are mediated by the vestibular system. We will then elucidate genetic and epigenetic changes occurring in each pathway cyclopaedically. Furthermore, varying the time when subjects are exposed to various magnitudes of gravity (at the phases of formation, development, and maturity of the vestibular system) and the duration of exposure (several days, several weeks, and several months), we will investigate the plasticity (adaptation, restoration, and robustness) of the vestibular system and its failure (irreversible damage) comprehensively. With these findings, we intend to propose preventive measures against the functional deterioration of the vestibular system attributed to its plasticity. Furthermore, we will construct a new theory of excellent plasticity of organisms against the mechanical stress of gravity, encompassing adaptability, repair capability, and robustness of organisms, as well as the process leading to failure and irreversible damage due to stress exceeding a certain threshold.

Using mice raised in a hypergravity environment artificially created by a centrifuge as well as in a microgravity environment on the International Space Station, we will elucidate the plastic alteration of the vestibular-mediated adaptive functions with a physiological and molecular-genetic approach. We will propose new preventive strategies against the decline in the adaptive functions based on these findings.