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"Fishonauts" to enter space again

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November 12, 2013

On November 7, a long-term space mission including astronaut Koichi Wakata departed for the International Space Station on board a Russian Soyuz spacecraft. During their roughly six months aboard the space station, Wakata and others will conduct various scientific experiments, one of which is a bone regeneration experiment, the Medaka Osteoclast II, using Medaka Ricefish and run by a team including Professor Akira Kudo from the School of Bioscience and Biotechnology at Tokyo Institute of Technology (Tokyo Tech).

When astronauts live for a long time in an environment with extremely little gravity, they experience a decrease in bone density, which poses a problem for future long-term space exploration. It is believed to be due to an imbalance in the activities of osteoblasts, which create bone, and those of osteoclasts, which break down bone. Professor Kudo and his team are attempting to clarify this mechanism. The current experiment follows in the footsteps of the bone regeneration experiment, Medaka Osteoclast, carried out on board the International Space Station in 2012.

In the previous experiment, transgenic Medaka Ricefish were also used. Fluorescent proteins in the fish enabled the identification of osteoblasts and osteoclasts and samples of Medaka Ricefish bred under long-term microgravity were obtained. In the current experiment, the plan is to observe live transgenic Medaka Ricefish in real time over a period of one week in order to get closer insights into the workings of bone cells. If this can become clear, it may lead not only to lengthier stays for astronauts in space, but also to uncovering the causes of osteoporosis.

The Medaka "fishonauts" are set to head into space in February 2014, one step behind Wakata and his team. For more information about the experiment, visit the links below.

Visible fluorescent bone cells glow in a Medaka Ricefish. The cells that create bone are red, while those that break it down are green.


  • Breeding the Medaka Ricefish on board the space station.
    Image credit: Japan Aerospace Exploration Agency (JAXA)


  • Professor Akira Kudo watches over the experiment
    from the experiment control room.
    Image credit: Japan Aerospace Exploration Agency (JAXA)

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