Why do muscles and bones weaken in space?
How animals and plants sense gravity in space
As manned Mars exploration and commercial space travel are becoming a reality, living in good health in space is becoming more and more important. On the other hand, it is known that if you stay in space for a long time, your muscles and bones will weaken. It is believed that this is due to the effects of the weightless environment on the human body, but the mechanism is not yet well understood.
A review article summarizing the latest findings on how animals and plants sense gravity has been published in NPJ Microgravity, a sister journal of the leading international scientific journal Nature.
Takahashi K, Takahashi H, Furuichi T, Toyota M, Furutani-Seiki M, Kobayashi T, Watanabe-Takano H, Shinohara M, Numaga-Tomita T, Sakaue-Sawano A, Miyawaki A, Naruse K. Gravity sensing in plant and animal cells. NPJ Microgravity. 2021 Feb 8. doi: 10.1038/s41526-020-00130-8.
Plants can grow their roots downwards and stems upwards on the Earth without the cue of light. It has become clear that this “gravitropism” is carried out by the plant cells sensing gravity and transmitting information within and between cells. In addition, following the preceding research on gravity sensing in plants, the research in animal cells has become active. Space biology research has discovered that, seemingly different organisms such as plants and animals share a common mechanism by which cells sense the physical stimulus of gravity. They use a protein called actin that forms the cytoskeleton of cells as a mechanotransducer. In addition, it has become elucidated that the cause of muscle atrophy and bones loss in long-term space life lies in the unique gravity sensing and response mechanism of each tissue.
This article is a compilation of the results of the research project “Living in Space,” which brings together Japanese space medicine research experts, represented by astronaut Satoshi Furukawa. This project was carried out from 2015 to 2020 as a Grant-in-Aid for Scientific Research on Innovative Areas funded by the Ministry of Education, Culture, Sports, Science and Technology. Takahashi is the first author of this article.
* * *
Takahashi Lab at Okayama University uses principles of physiology, cellular and molecular biology, and biophysics. The purpose of the lab is to develop science and medicine by unveiling the mechanisms of diseases through collaborations with scientists, epidemiologists, and corporate alliances. The alliance includes Harvard University, Boston University, Tokyo University of Science, and PD Aerospace, Ltd.