Elucidation of the cause of bone loss is an important issue in the prevention of senile osteoporosis on the ground and in long-term manned space exploration.Observation and analysis are important for investigating the functions of cultured cells and individual organisms.In presbycusis osteoporosis, bone mass decreases sharply immediately after bedridden.In addition, astronauts' bone mass decreases sharply within a month immediately after being exposed to weightlessness.There was an urgent need to elucidate the initial response of the organism to weightlessness.

　In collaboration with the Japan Aerospace Exploration Agency (JAXA) and others, the research group contained medaka fish modified with four types of bone-related genes in a gel in a newborn state, and at the "Kibo" Japanese Experiment Module. We shot continuously for 4 days.When the region (promoter) involved in transcription of the modified bone-related gene works, it emits fluorescence.As a result, the fluorescence signal specifically expressed in osteoblasts, which are bone-forming cells, and osteoclasts, which are bone-breaking cells, increased significantly from 8 day after exposure to zero gravity, and its expression was increased for 1 days. The rise was maintained.

　In addition, when the gene expression after 2 days of exposure to zero gravity was examined, it was revealed that the expression of 5 genes in addition to the bone-related gene was significantly increased.It is said to be the first achievement in the world to show a part of the initial response of an individual organism to weightlessness using an organism (medaka) that can be analyzed at the individual level.

　In the future, we will elucidate the molecular mechanisms of the newly discovered five genes that are thought to be involved in the weightless response, and clarify their involvement in presbycusis osteoporosis.