What is JAXA’s approach toward solving musculoskeletal challenges in space?
“What happens to our bodies in zero gravity?” Examples are skeletal muscle atrophy and bone loss due to zero gravity, a dull headache by body fluid shifts, biological rhythm dysfunction because of the enclosed environment, space radiation exposure, microbial risks, etc. These challenges need to be resolved to keep humans healthy in space. Among them, we focus on muscle and bone risks here. The Japan Aerospace Exploration Agency (JAXA) has conducted several spaceflight experiments for musculoskeletal research using the Space Shuttle, Soyuz, SpaceX, and the ISS. To develop unique scientific research environment in space and provide it to researchers, JAXA has explored and transported various experimental facilities to the ISS, for example, an aquatic habitat (AQH) for aquatic animals and a multiple artificial-gravity research system (MARS) for rodents. JAXA hopes that researches utilizing these facilities would further reveal the mechanisms of muscle atrophy and bone loss in zero gravity, leading to the countermeasures.
What was a trigger to conduct a “Living in Space” project?
As an astronaut and doctor, Satoshi Furukawa, the first author of the review article, experienced zero gravity during a five-and-a-half month stay on the International Space Station (ISS) in 2011. Furukawa suffered from the challenges described above, sensed the synergistic interactions among these factors, and thought that comprehensive and collaborative research, not only on the ISS, but also on Earth, on living in space should be conducted. Therefore, Furukawa formed a scientific research team “Living in Space” of the Japanese Ministry of Education, Culture, Sports, Science and Technology to focus on the biological risks and stresses encountered in Space in order to mitigate them. Experts that use various species from wide variety of fields made a team, joined forces, and carried out a project on what it takes to live in space.
What is the feature of this review article?
This review focuses on the musculoskeletal findings of recent terrestrial experiments conducted as part of the “Living in Space” project, and of spaceflight experiments conducted in the “Kibo” Japanese Experiment Module of the ISS. We present the results and current status of space experiments using various model organisms such as in vitro cultured cells, nematodes, medaka, goldfish scales, zebrafish, and mice. The current exercise program for ISS astronauts is fairly effective, but it cannot completely prevent muscle atrophy and bone loss under zero gravity. Therefore, as possible future countermeasures for further mitigating these risks, we introduce the effect of exercise on epigenetics and the development of exercise pills (exercise mimetic).
How will it lead to the future?
We hope that this review will be enjoyed by many readers and will serve as a milestone for space life sciences focused on musculoskeletal atrophy in space and on Earth. We are very glad if this review article leads to new research ideas that progress towards the resolution of the risks. Furthermore, we are sure that these findings contribute to the aging and high-stress society on Earth. With these thoughts in mind, Astronaut Furukawa will take on his next spaceflight around 2023.