The joint research group, whose core members are Professor Nobuo Suzuki of Institute of Nature and Environmental Technology Kanazawa University, Associated Professor Isao Kobayashi of Institute of Science and Engineering Kanazawa University, Professor Jun Hirayama of Bunkyo University, Specially Appointed Professor Atsuhiko Hattori of Rikkyo University, Assistant Professor Yusuke Maruyama of Rikkyo University, and IDDK Corporation ("IDDK"), has been selected by JAXA's Special Committee of Space Environment Utilization for the publicly solicited project (*1). In this project, the group aims to develop therapeutic agents to prevent space environment-induced bone density loss, radiation damage, and circadian rhythm disorders by using fish scales (*2) on a man-made satellite.
Currently, humans are able to stay on the International Space Station (ISS) for as long as a year. In addition, manned exploration of the moon and Mars and space travel by civilians are becoming feasible. The longer the stay in space, the greater the impact of the space environment on the human body, and the more likely it is that various parts of the body will be affected (Figure 1). Against this background, along with the evaluation of the effects of the space environment on the human body, there is a need for drugs to prevent and treat these effects. The research group plans to conduct a space experiment using a commercial satellite in cooperation with IDDK in three years, based on the results of the sample preparation and research conducted on the ISS with fish scales in 2010. In particular, the group focuses on the following three space environments: (1) microgravity, (2) cosmic radiation, and (3) extremely short light/dark cycles compared to those on Earth. The research group led by Professor Suzuki studied the effects of (1) microgravity and (2) cosmic radiation in the space experiment (project name; Fish scales) conducted on the Space Shuttle Atlantis in 2010. The study provided evidence that the effects of microgravity and cosmic radiation on humans are mediated by "a decrease in melatonin production". Thus, melatonin may be able to prevent or treat the effects of microgravity and cosmic radiation on humans. In addition, since melatonin is a hormone that regulates circadian rhythms, the homeostatic mechanism of living organisms, we considered the possibility that disrupted light-dependent regulation of the circadian rhythm induced in space environment could also be treated by melatonin. Therefore, we are planning to conduct experiments using the scales obtained from the zebrafish model, in which light-response of circadian rhythm is disrupted (*3).
It has already been decided that ISS operations will end in 2030. Satellites are a promising alternative to the ISS as an experimental facility in the space environment. To assess and overcome the risks associated with human expansion to the Moon and Mars and human habitation in space, we plan to conduct space experiments using artificial satellites and develop drugs to prevent and treat diseases caused in space.
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Figure 1: Examples of diseases caused by space
Melatonin has the potential to prevent and treat diseases A, C and D.
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【Glossary】
*1：The publicly solicited project of JAXA's Special Committee of Space Environment
An open call for front-loading research leading to specific space experiment proposals sponsored by the Expert Committee on Space Environment Utilization of the Institute of Space and Astronautical Science (ISAS) of the Japan Aerospace Exploration Agency (JAXA).
*2：Fish Scales
Fish scales contain both bone-forming cells (osteoblasts) and bone-destroying cells (osteoclasts). For example, when female salmon migrate upstream from the sea to rivers, they extract calcium from the scales to supply it to their eggs. It has been proven that osteoclasts in the scales are activated at that time, causing the scales to dissolve and become smaller. Professor Suzuki and his research group have conducted space experiments using scales on the Japanese Experiment Module "Kibo," which is a component of the International Space Station. In their previous study, they reported that osteoclasts were activated after only three days of culture in space, causing bone resorption in the scales. They also found that melatonin, a type of indole compound, is produced by osteoblasts in scales, and that melatonin inhibits bone resorption by stimulating the secretion of a calcitonin hormone, an inhibitor of osteoclast activity.
Reference: Kanazawa University Press Release "Bone Resorption Induced in Space is Suppressed by melatonin!"
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*3：?Zebrafish model, in which light-response of circadian rhythm is disrupted
Previous studies have reported the zebrafish molecules involved in light-dependent regulation of circadian rhythms, which are conserved in mammals (Hirayama et al., PNAS, 2005; Hirayama et al., Cell Cycle, 2009). In addition, it was reported that genetically engineered zebrafish, in which these molecules are disrupted, show impaired light regulation of circadian rhythms (Hirayama et al., Sci. Rep., 2019). This zebrafish model is unique in that only the light response of the circadian rhythm is impaired, while the rhythm formation itself is normal.
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Click here to see the press release【Japanese only】
Researcher's Information: Nobuo Suzuki
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