A collaborative research group led by Professor Nobuo Suzuki of the Institute of Nature and Environmental Technology, Kanazawa University; Associate Professor Mika Ikegame of Okayama University; Specially Appointed Professor Atsuhiko Hattori and Assistant Professor Yusuke Maruyama of Rikkyo University; and Professor Jun Hirayama of Bunkyo University has demonstrated that the activities of osteoblasts and osteoclasts present in goldfish (Carassius auratus) scales (Figure 1) are maintained, and that these cells remain responsive to gravity even after the scales are sterilized with 0.1% hypochlorous acid and stored at a low temperature (4°C) for more than one week without changing the culture medium.
Preliminary experiments have also confirmed that this technique can maintain the cellular activity of goldfish scales for more than three weeks without changing the culture medium. This achievement eliminates the need to raise goldfish at the launch site and prepare the scales there, enabling scales prepared and packed in Japan to be transported at low temperature to NASA and other launch sites. In addition, this method allows researchers to accommodate unexpected delays in rocket launches. This research is expected to make a significant contribution to the technical aspects of space experiments (*1).
This research has been supported by the JAXA ISAS Space Environment Utilization Special Committee (*2) since FY2024 (FY2024 front-loading research). Furthermore, it was also selected as a FY2025 front-loading research project, and space experiments using this technology are planned for the International Space Station (ISS) in the future.
The results of this study were published in the online edition of the American international journal "Life Sciences in Space Research" on April 7, 2025.
Figure 1. Schematic diagram of fish scales. Fish scales contain osteoblasts, osteoclasts, and osteocytes on a calcified matrix and exhibit bone metabolism comparable to that of human bone.
Figure 2. Osteoblast activity (alkaline phosphatase: ALP) staining of goldfish scales before and after storage at low temperature (4°C) for 1 week. A and C: before storage. B and D: after storage. C and D show magnified views of A and B, respectively.
【Glossary】
*1 Space experiment (Fish Scales)
Fish scales contain both bone-forming cells (osteoblasts) and bone-resorbing cells (osteoclasts). Unlike mammals, fish regulate calcium levels mainly through their scales rather than their vertebrae. For example, when female salmon migrate upstream from the ocean to rivers for spawning, they mobilize calcium from their scales to supply their eggs. During this process, osteoclasts in the scales become activated, causing the scales to partially dissolve and decrease in size.
Because of these unique properties, fish scales can serve as a useful experimental model for space research and allow space experiments to be prepared within a relatively short period. In fact, fish scales were selected in 2008 for a space experiment conducted in the Japanese Experiment Module “Kibo” on the International Space Station (ISS), and the experiment was implemented after only two years of preparation.
While many space experiments require more than ten years of preparation after selection, the short preparation time in this case was possible because fish scales provide an excellent experimental material.
Using this model, the authors’ research group previously conducted a space experiment (Fish Scales). In that study, they reported that osteoclasts were activated after only three days in space, leading to bone resorption in the scales, and that melatonin inhibited this bone resorption. In the future, the researchers plan to investigate the additive and synergistic effects of melatonin in combination with other hormones and to conduct further space experiments.
?
*2 Open call program of the Space Environment Utilization Committee, Institute of Space and Astronautical Science (ISAS), JAXA
This program is an open call for front-loading research projects organized by the Space Environment Utilization Committee of the Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA). It aims to promote research that will lead to concrete proposals for space experiments, including “Small-Scale Projects” and “Kibo” utilization flagship missions, in the fields of microgravity science and space life sciences. The program supports preparations for space experiments, such as the development of experimental hardware prior to spaceflight.
Click here to see the press release【Japanese only】
Journal : Life Sciences in Space Research
Researcher's Information: Nobuo Suzuki
Related Information
School of Biological Science and Technology, College of Science and Engineering, Kanazawa University : https: //www.se.kanazawa-u.ac.jp/lifescience
Graduate School of Natural Science and Technology, Kanazawa University : https://www.nst.kanazawa-u.ac.jp/
PAGE TOP