May 14, 2024PRESS RELEASE
Research proposal adopted for an open-call project by Japan Aerospace Exploration Agency (JAXA)’s Special Committee of Space Environment Utilization
Keyword:RESEARCH
OBJECTIVE.
A research proposal by a joint research group to develop therapeutic agents designed to prevent and treat space environment-induced symptoms such as bone density loss, radiation damage, and circadian rhythm disruptions has been accepted for an open-call project(*1) by a Japan Aerospace Exploration Agency (JAXA) committee. This project, offered by the Special Committee of Space Environment Utilization, involves experimenting with fish scales(*2) on an artificial satellite. The joint team includes Professor Nobuo Suzuki from the Institute of Nature and Environmental Technology and Associate Professor Isao Kobayashi from the Institute of Science and Engineering, both at Kanazawa University; Professor Jun Hirayama from Bunkyo University; Specially Appointed Professor Atsuhiko Hattori and Assistant Professor Yusuke Maruyama, both from Rikkyo University; and IDDK Co., Ltd.
Astronauts can currently stay on the International Space Station (ISS) for up to one year. Additionally, manned exploration of the Moon and Mars, as well as civilian space travel, is becoming increasingly feasible. However, the longer a person is in space, the greater the impact of the space environment on the human body, potentially causing damage to various parts of the body (Figure 1). There is thus a growing need to assess the impacts of the space environment on the human body and to develop therapeutic agents to prevent and treat space environment-induced symptoms and disorders.
The group plans to conduct experiments in space using a commercial satellite in collaboration with IDDK Co., Ltd. within the next three years. This plan is based on the results of sample preparations and research conducted on the ISS using fish scales in 2010. The team will focus on the following aspects of the space environment: 1) microgravity, 2) space radiation, and 3) extremely short light-dark cycles compared to those on Earth.
The group plans to conduct experiments in space using a commercial satellite in collaboration with IDDK Co., Ltd. within the next three years. This plan is based on the results of sample preparations and research conducted on the ISS using fish scales in 2010. The team will focus on the following aspects of the space environment: 1) microgravity, 2) space radiation, and 3) extremely short light-dark cycles compared to those on Earth.
In the 2010 project, nicknamed Fish Scales, led by Kanazawa University’s Professor Suzuki, experiments were conducted using fish scales aboard Space Shuttle Atlantis. During the experiment, the group assessed the impacts of microgravity and space radiation on the fish scales, discovering that both microgravity and space radiation decreased melatonin production, a factor impacting the human body in space. This finding suggested that melatonin could play a key role in preventing and treating symptoms resulting from the effects of microgravity and space radiation. In addition to its protective role against these space-related effects, melatonin serves as a hormone that regulates circadian rhythms, a homeostatic mechanism. The group considered the potential of melatonin as a therapeutic agent to address the disrupted light-dependent regulation of circadian rhythms (light-dark cycles) in the space environment. To validate this hypothesis, the group plans to conduct an experiment using scales from zebrafish*3, in which the light-dependent regulation of the circadian rhythm is disrupted.
The mission of the ISS is set to be completed in 2030. Artificial satellites are promising candidates to replace the ISS as experimental facilities in the space environment. To assess and overcome the risks associated with human exploration of the Moon and Mars, as well as space habitation, the group is scheduled to conduct space experiments using an artificial satellite. The aim is to develop drugs to prevent and treat diseases triggered by the space environment.
The mission of the ISS is set to be completed in 2030. Artificial satellites are promising candidates to replace the ISS as experimental facilities in the space environment. To assess and overcome the risks associated with human exploration of the Moon and Mars, as well as space habitation, the group is scheduled to conduct space experiments using an artificial satellite. The aim is to develop drugs to prevent and treat diseases triggered by the space environment.
Figure 1: Examples of diseases triggered in space
Melatonin has the potential of preventing and treating diseases A, C and D.
Melatonin has the potential of preventing and treating diseases A, C and D.
Research background
The space environment significantly impacts the human body, causing disorders in various parts (Figure 1). Therefore, it is essential to assess these impacts and develop preventive and therapeutic medicines. Conducting risk assessments is an urgent task to pave the way for human exploration of the Moon and Mars after the completion of the ISS mission in 2030, as well as to enable humans to live in space. Additionally, it is crucial to develop drugs to prevent and treat diseases associated with the space environment.
The team focuses on the following aspects of the space environment: 1) microgravity, 2) space radiation, and 3) extremely short light-dark cycles compared to those on Earth. Microgravity, which is a completely different condition from that on Earth, affects the human body in many ways. For example, it changes body fluid circulation, causing about 2 liters of fluid to move to the head and chest, resulting in a "moon-face" appearance (Figure 1B) and bone and muscle atrophy (Figure 1D). Bones can lose about 1% of their volume per month, leading to calcium being excreted through urine. This condition increases the risk of developing kidney stones (Figure 1C). In space, people are exposed to significant levels of space radiation from solar flares as well as high-energy, heavy particle beams generated by supernova explosions, which can penetrate the walls of spaceships. Additionally, the ISS orbits the Earth every 90 minutes, creating 45-minute light-dark cycles (Figure 1A). In summary, the unique environment in space greatly affects the human body, triggering various diseases.
The team focuses on the following aspects of the space environment: 1) microgravity, 2) space radiation, and 3) extremely short light-dark cycles compared to those on Earth. Microgravity, which is a completely different condition from that on Earth, affects the human body in many ways. For example, it changes body fluid circulation, causing about 2 liters of fluid to move to the head and chest, resulting in a "moon-face" appearance (Figure 1B) and bone and muscle atrophy (Figure 1D). Bones can lose about 1% of their volume per month, leading to calcium being excreted through urine. This condition increases the risk of developing kidney stones (Figure 1C). In space, people are exposed to significant levels of space radiation from solar flares as well as high-energy, heavy particle beams generated by supernova explosions, which can penetrate the walls of spaceships. Additionally, the ISS orbits the Earth every 90 minutes, creating 45-minute light-dark cycles (Figure 1A). In summary, the unique environment in space greatly affects the human body, triggering various diseases.
Figure 2: Analysis of aanat mRNA expressed in fish scales
Ground: Experiment on ground, F-1g: Fish scales cultivated in equipment that can create a 1g condition (equivalent to the condition on ground, which is 1g) by using a centrifugal machine in space (space control group), F-μg: Fish scales cultivated in space (microgravity group), **: P < 0.01，n = 4（From Ikegame et al., J. Pineal Res., 2019）
Ground: Experiment on ground, F-1g: Fish scales cultivated in equipment that can create a 1g condition (equivalent to the condition on ground, which is 1g) by using a centrifugal machine in space (space control group), F-μg: Fish scales cultivated in space (microgravity group), **: P < 0.01，n = 4（From Ikegame et al., J. Pineal Res., 2019）
The factors mentioned above led the group to focus on bones and conduct space experiments in 2010, using fish scales as a bone model. In these experiments, the group assessed 1) bone density loss due to microgravity and 2) the effects of space radiation. Based on these assessments, the group suggested the potential of melatonin, an indole compound, as a therapeutic agent to prevent and treat these symptoms (Microgravity: Ikegame et al., J. Pineal Res., 2019; Hirayama et al., J. Pineal Res., 2023. Space radiation: Furusawa et al., Mol. Med. Rep., 2020; Hirayama et al., J. Pineal Res., 2023). The group also found that melatonin is produced in the osteoblasts of goldfish scales, a discovery that led them to investigate the expression of a rate-limiting enzyme (aanat: arylalkylamine N‐acetyltransferase).
The results showed that the expression of aanat mRNA in fish scales cultured under microgravity (F-μg) was lower than in those cultured under 1g gravity on orbit (F-1g) and on the ground. A significant difference was found in expression levels between scales cultivated on the ground and those under microgravity (Figure 2). These results indicated that a decline in melatonin production is one of the factors affecting the human body in the space environment. The group also confirmed that melatonin can rescue cells from space radiation-induced damage (Furusawa et al., Mol. Med. Rep., 2020; Hirayama et al., J. Pineal Res., 2023). Additionally, melatonin functions as a hormone that regulates circadian rhythms, which maintain homeostasis using light. The team considered the possibility that disrupted light-dependent regulation in circadian rhythms in space could be treated with melatonin. Based on these findings, the group believes that melatonin has strong potential to be an effective drug for preventing and treating diseases developed in space.
The results showed that the expression of aanat mRNA in fish scales cultured under microgravity (F-μg) was lower than in those cultured under 1g gravity on orbit (F-1g) and on the ground. A significant difference was found in expression levels between scales cultivated on the ground and those under microgravity (Figure 2). These results indicated that a decline in melatonin production is one of the factors affecting the human body in the space environment. The group also confirmed that melatonin can rescue cells from space radiation-induced damage (Furusawa et al., Mol. Med. Rep., 2020; Hirayama et al., J. Pineal Res., 2023). Additionally, melatonin functions as a hormone that regulates circadian rhythms, which maintain homeostasis using light. The team considered the possibility that disrupted light-dependent regulation in circadian rhythms in space could be treated with melatonin. Based on these findings, the group believes that melatonin has strong potential to be an effective drug for preventing and treating diseases developed in space.
Outlines of planned space experiment
With the fiscal 2023 applications now closed for flagship missions using the Japanese Experimental Module, nicknamed Kibo, on the ISS, which will complete its mission in 2030, Japan is transferring space launching resources to the private sector. Against this backdrop, the group, together with IDDK Co., Ltd., a private company, is planning a space experiment utilizing an artificial satellite.
The outlines of IDDK Co., Ltd.’s space bio-experiment platform, are shown in Figure 3. IDDK has successfully developed a groundbreaking microimaging device (MID) based on microscope observation technology. This technology merges optical and semiconductor technologies and operates on fundamentally different principles from those of conventional microscopes. The company is now developing an automated space bio-experimental device based on the MID technology.
In pursuit of post-ISS platforms, many companies have been established in Japan and other countries with the aim of offering microsatellite payload services capable of returning samples from space. IDDK has already forged partnerships with several of these companies with the goal of establishing Japan’s first private-led space bio-experiment platform in low Earth orbit using microsatellites. The company is scheduled to conduct demonstration experiments in 2023, preceding the launch of the service in 2025.
The outlines of IDDK Co., Ltd.’s space bio-experiment platform, are shown in Figure 3. IDDK has successfully developed a groundbreaking microimaging device (MID) based on microscope observation technology. This technology merges optical and semiconductor technologies and operates on fundamentally different principles from those of conventional microscopes. The company is now developing an automated space bio-experimental device based on the MID technology.
In pursuit of post-ISS platforms, many companies have been established in Japan and other countries with the aim of offering microsatellite payload services capable of returning samples from space. IDDK has already forged partnerships with several of these companies with the goal of establishing Japan’s first private-led space bio-experiment platform in low Earth orbit using microsatellites. The company is scheduled to conduct demonstration experiments in 2023, preceding the launch of the service in 2025.
Figure 3: Outline of IDDK Co., Ltd.’s space bio-experiment platform service
Possesses superiority and originality for planning and conducting space experiments for the present study
Materials
1. Fish scales as a bone model
Fish scales serve as a compact bone model, featuring osteoblasts and osteoclasts coexisting in a calcified bone matrix and containing osteocyte-like cells. Fish scales can be easily cultivated in a medium, allowing the cultivation apparatus to be lightweight. The osteoblasts and osteoclasts of zebrafish scales are labeled with fluorescent markers, making it possible to analyze osteoblasts and osteoclasts in orbit thanks to IDDK’s microscopic observation technology.
2. Cultivation of fish scales at low temperatures and for long periods
Immediately after the Space Shuttle lifted off, osteoblasts were seen becoming active due to the hypergravity response at the time of launch. This activity later declined in response to the microgravity applied to the fish scales. Therefore, if fish scales can be cultured for at least 86 hours or longer, it will be unnecessary to create a 1g condition in orbit. This would allow the equipment sent to space to be lighter, facilitating space experiments on an artificial satellite. Additionally, long-term cultivation can accommodate delays in rocket launches.
Fish scales serve as a compact bone model, featuring osteoblasts and osteoclasts coexisting in a calcified bone matrix and containing osteocyte-like cells. Fish scales can be easily cultivated in a medium, allowing the cultivation apparatus to be lightweight. The osteoblasts and osteoclasts of zebrafish scales are labeled with fluorescent markers, making it possible to analyze osteoblasts and osteoclasts in orbit thanks to IDDK’s microscopic observation technology.
2. Cultivation of fish scales at low temperatures and for long periods
Immediately after the Space Shuttle lifted off, osteoblasts were seen becoming active due to the hypergravity response at the time of launch. This activity later declined in response to the microgravity applied to the fish scales. Therefore, if fish scales can be cultured for at least 86 hours or longer, it will be unnecessary to create a 1g condition in orbit. This would allow the equipment sent to space to be lighter, facilitating space experiments on an artificial satellite. Additionally, long-term cultivation can accommodate delays in rocket launches.
Therapeutics
3. Effectiveness of melatonin as a drug to prevent and treat space-related diseases
Melatonin has diverse effects, making it an excellent drug to enable people to live in space. In Japan, Nobelpharma Co., Ltd. markets a sleep-inducing pill for children called Melatobel. In the 2010 space experiment on fish scales exposed to space radiation for 86 hours, melatonin's ability to curb bone resorption and provide radiation protection was verified. In the present study, involving low-temperature, long-term cultivation of fish scales, the group will verify the combined effects of melatonin on osteoblasts and bone matrix and the radioprotective effects of melatonin. Additionally, using scales from genetically modified zebrafish, the group will verify melatonin's ability to restore disrupted light-dependent regulation of circadian rhythms.
Melatonin has diverse effects, making it an excellent drug to enable people to live in space. In Japan, Nobelpharma Co., Ltd. markets a sleep-inducing pill for children called Melatobel. In the 2010 space experiment on fish scales exposed to space radiation for 86 hours, melatonin's ability to curb bone resorption and provide radiation protection was verified. In the present study, involving low-temperature, long-term cultivation of fish scales, the group will verify the combined effects of melatonin on osteoblasts and bone matrix and the radioprotective effects of melatonin. Additionally, using scales from genetically modified zebrafish, the group will verify melatonin's ability to restore disrupted light-dependent regulation of circadian rhythms.
IDDK Co., Ltd.’s space bio-experiment platform
4. Microscopic observation of osteoblasts and osteoclasts of fish scales
Microscopic observation will be carried out using MID technology, which has been successfully commercialized. A fluorescence observation method is currently under development for the space mission, which will allow results to be obtained from the space experiment in orbit upon its completion. The development of a method tailored to the requirements of this study will be feasible by considering conditions suitable for fish scales. This is because the equipment is based on a bio-experimental device for space, the development of which is underway.
5. Sample return
As shown in Figure 3, IDDK has established partnerships with multiple artificial satellite companies involved in the development of sample-return technology for the space bio-experimental platform. By the time space verification of this study's results is conducted, the sample-return feasibility is expected to be extremely high due to the selection of partners who have already verified their sample-return technologies. By securely storing samples in formalin in orbit and automating operations similar to those currently conducted by astronauts on the ISS, the group will be able to analyze the effects of melatonin on preventing and treating diseases triggered in the space environment.
Microscopic observation will be carried out using MID technology, which has been successfully commercialized. A fluorescence observation method is currently under development for the space mission, which will allow results to be obtained from the space experiment in orbit upon its completion. The development of a method tailored to the requirements of this study will be feasible by considering conditions suitable for fish scales. This is because the equipment is based on a bio-experimental device for space, the development of which is underway.
5. Sample return
As shown in Figure 3, IDDK has established partnerships with multiple artificial satellite companies involved in the development of sample-return technology for the space bio-experimental platform. By the time space verification of this study's results is conducted, the sample-return feasibility is expected to be extremely high due to the selection of partners who have already verified their sample-return technologies. By securely storing samples in formalin in orbit and automating operations similar to those currently conducted by astronauts on the ISS, the group will be able to analyze the effects of melatonin on preventing and treating diseases triggered in the space environment.
Future prospects
The group will analyze the pseudo-microgravity response of goldfish scales, focusing particularly on Type 1 collagen and hydroxyapatite of the bone matrix. Zebrafish species have been generated by crossing two types: one created by Kobayashi, in which osteoblasts and osteoclasts were labeled with a fluorescent protein (Kobayashi et al., Com. Biol., 2020), and the other developed by Hirayama, genetically modified to exhibit a disruption in the light-dependent regulation in circadian rhythms (Hirayama et al., Sci. Rep., 2019). This crossbred zebrafish is designed to study how bone cells behave when the light-dependent regulation of the circadian rhythm is disrupted. Additionally, as with a sterilization method used for goldfish scales, zebrafish scales will be sterilized. The group will then assess their pseudo-microgravity response post-sterilization. The group aims to develop equipment, including a container capable of maintaining a constant temperature and a device capable of automatically treating fish scales with formalin and other solvents.
Glossary
- *1: Open-call project by JAXA’s Special Committee of Space Environment Utilization
The project is sponsored by the Special Committee of Space Environment Utilization at the Institute of Space and Astronautical Science (ISAS) within the Japan Aerospace Exploration Agency (JAXA). The committee is seeking proposals for frontloading research that could progress into specific space experiment projects. This frontloading research encompasses "small-scale plans" within the realm of microgravity science and space life science, as well as flagship missions utilizing the "Kibo" module. The project offers assistance in preparing space experiments, including the development of space experiment equipment prior to the experiments being conducted.
- *2: Fish scales
Fish scales contain both osteoblasts (bone-making cells) and osteoclasts (bone-destroying cells). Fish absorb and release calcium through their scales rather than their vertebrae. For instance, female salmon extract calcium from their scales when migrating from the sea to rivers to provide calcium for their eggs. During this process, it has been observed that osteoclasts are activated, leading to scale reduction due to calcium dissolution. Conducting previous space experiments on fish scales using the "Kibo" experimental module aboard the International Space Station, the research group led by Suzuki found that osteoclasts were activated after just three days of cultivation, initiating bone resorption. Additionally, the group identified the production of melatonin, an indole compound, in the osteoblasts of fish scales. Melatonin was found to inhibit bone resorption by stimulating the secretion of calcitonin, a hormone composed of 32 amino acids that suppresses osteoclast activity.
Figure 4: Diagram of fish scales
Fish scales consist of osteoblasts, osteoclasts, and osteocyte-like cells on calcified bone matrix, engaging in bone metabolism similar to that of the human body.
Fish scales consist of osteoblasts, osteoclasts, and osteocyte-like cells on calcified bone matrix, engaging in bone metabolism similar to that of the human body.
- *3: Zebrafish of disrupted light-dependent regulation model
Bunkyo University’s Hirayama has documented the presence of light-controlling molecules in circadian rhythms, which are found in mammals, by utilizing zebrafish, which have a circadian clock formation mechanism equivalent to that of humans (Hirayama et al., PNAS, 2005; Hirayama et al., PNAS, 2007; Hirayama et al., Cell Cycle, 2009). Hirayama also reports that genetically modified zebrafish, in which these molecules were destroyed, display light-controlling disorders in circadian rhythms (Hirayama et al., Sci. Rep., 2019). This zebrafish model is distinctive in that only the light-dependent regulation in circadian rhythm is impaired, while the formation of the circadian rhythm itself remains intact.