Artificial gravity with centrifuge and optimal dose of the intervention to counteract gait alteration in rats exposed to simulated microgravity

Paper number

IAC-19,A1,3,4,x51579

Author

Dr. Junichi Tajino, Japan, Kyoto University

Coauthor

Dr. Akira Ito, Japan, Kyoto University

Coauthor

Dr. Momoko Tanima, United States

Coauthor

Dr. Shoki Yamaguchi, Japan

Coauthor

Dr. Hirotaka Iijima, Japan, Keio University

Coauthor

Dr. Wataru Kiyan, Japan, Kyoto University

Coauthor

Dr. Tomoki Aoyama, Japan, Kyoto University

Coauthor

Dr. Hiroshi Kuroki, Japan, Kyoto University

Year

2019

Abstract

{\bf Introduction/Purpose}
Microgravity could affect many aspects of physiological system such as musculoskeletal features and autonomic regulations. We have previously found that microgravity environment disturbs walking motion in rats and the distortion could be attenuated by hypergravity intervention (twice of usual gravity for one hour a day) using centrifuge. Despite this benefit, the optimal dose of the gravitation is still unclear. The purpose of this study was to explore the range of effectiveness (intensity and duration) and the optimal use of hypergravity intervention.

{\bf Methodology}
Male Wistar rats were distributed into 6 groups according to intensity and duration of the gravitational intervention. They were unloaded by their tail for 2 weeks (unloading period) followed by another 2-week free rearing period (recovery period). During the unloading period, each group was subjected to distinct gravitation as follows: 1) continuously unloaded (UL); 2) reloaded for 1 hour a day (UL+1G); 3) centrifuged at 2G for 1 hour a day (UL+2G); 4) centrifuged at 1.5G for 80 minutes (UL+1.5G80mins); 5) centrifuged at 2.5G for 48 minutes (UL+2.5G48mins); and 6) reared freely throughout the experiment (Ctrl). Muscle weight of hindlimb extensors and kinematics properties of their walking motion were evaluated using 3 dimensional motion capture apparatus.


{\bf Results}
Recoveries of muscle weights were not significantly different across the groups (p > 0.05). The UL group showed significant narrower and forward shifted oscillation of the hindlimb. Also, their knee and ankle joint at stance phase were significantly extended (p < 0.05, respectively). Conversely, those of UL+2G and UL+1.5G were closer to Ctrl whereas those in UL+2.5G were still agitated.


{\bf Discussion/Conclusion}
Despite of little influence on muscle weight recovery, the intermittent gravitation using centrifuge could attenuate the alteration of rats’ walking and this effect had Hertz-like curve shaped range. 2G and 1.5G interventions affected similarly and the most preferable within the parameters we tested this time, whereas 2.5G intervention was less preferable. This findings suggest existence of optimal range of gravitation and might be helpful to figure out the breakeven point to compromise between physiological need and on board regulation of space crafts.

Abstract document

IAC-19,A1,3,4,x51579.brief.pdf

Manuscript document

IAC-19,A1,3,4,x51579.pdf (🔒 authorized access only).

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