Fish in Space — “Traveling Aboard the ISS Suffered Immediate Microgravitational Stress” (VIDEO)




Life in so-called 'microgravity' environments—where the force of gravity is considerably less than on Earth—can cause significant problems for the human body. Astronauts who spend a number of months in space have been shown to suffer from reduced bone mineral density, leading to skeletal problems as well as fluid shift, increase in blood pressure, and dizziness. Surprisingly, the loss of calcium starts at least 10 days after launch in astronauts in Skylab Flights, but the precise molecular mechanisms responsible for such changes in bone structure are unclear.

To further study the effects of microgravity, fish were launched in 2014 to travel aboard the International Space Station where they suffered a near-immediate reduction in bone density upon encountering the microgravity environment of orbit, according to research published recently in Scientific Reports by a team of biologists at Tokyo Institute of Technology led by Akira Kudo who conducted remote imaging experiments on the newly-hatched medaka fish, also known Japanese rice fish native to east and mainland southeast Asia is a common denizen of rice paddies, marshes, ponds, slow-moving streams and tide pools. The mekaka is used in many areas of biological research, most notably in toxicology. They can withstand cold and can be easily or launched intospace. Most importantly, the medaka's process of skeletogenesis is similar to that of humans.




The Tokyo Tech team, performed remote, real-time, live imaging for fluorescent signals derived from osteoblasts and osteoclasts of medaka fish after only one day of exposure to microgravity aboard the International Space Station (ISS). They found increases in both osteoblast- and osteoclast-specific, promoter-driven GFP and DsRed signals one day after launch, which continued for up to eight days.

In their experiments, the team used four different double medaka transgenic lines focusing on up-regulation of fluorescent signals of osteoblasts and osteoclasts to clarify the effect of gravity on the interaction of osteoblast-osteoclast. They also studied changes in the gene expression in the transgenic fish by so-called transcriptome analysis.

These findings suggest that exposure to microgravity induced an immediate "dynamic alteration of gene expressions in osteoblasts and osteoclasts." Namely, these experiments based on real-time imaging of medaka from Earth and transcriptome analysis could be the prelude to the establishment of a new scientific research field of "gravitational biology."

The fish spent the first six weeks of their strange lives at the launch site before being embedded in a special gel for their voyage aboard Soyuz flight TMA-10M. They then spent the next two months being reared aboard the ISS. The first eight days of that stay were spent underneath a fluorescence microscope as researchers at the from a remote lab at the Tsukuba Space Center observed the fish's bone cells degenerating in real-time and compared to an Earth-bound control group of medaka fish.

The negative effects of microgravity on bone density has been observed in human astronauts aboard the ISS, where bone deterioration begins after about 20 days in orbit in a process resembling the sort of osteoporosis more often associated with old age. The process behind this, however, are still being explored, both for the sake of long-term space travel and for treating osteoporosis here on Earth's surface.



To better understand these biological effects of “microgravitational stress,” there are two varieties of cell that need to be observed: osteoclasts, responsible for breaking down bone tissue, a key role in repairing and maintaining bones, and osteoblasts that secrete the matrix used in bone formation.

The gravitational biology image shown below: (a-d) Whole-body imaging of the osterix-DsRed transgenic line. The left-side images show the same ground control at day 1; and the right-side images, the same flight medaka at day 1. Arrows point to the head and fin region.



Montage images were made from 6 captured optical images, divided by dotted lines (a,b). The white region shows an osterix-DsRed fluorescent signal. Embedded views show the enlarged head region (c,d). (e) The fluorescent intensity from day 1 to 7 of observation day constantly increased in the flight group. (f-h) The representative visualizing data for osterix-DsRed/TRAP-GFP in the flight group.

All images show ventral views in the head region. (i-l) The merged images were captured by 3D views for osterix-DsRed and TRAP-GFP in the pharyngeal bone region of the double transgenic line. The pharyngeal bone region in the ground control (i) or the flight (k) group at day 4. The image for TRAP-GFP in the pharyngeal bone region of "i" (j) or "k" (l). lp, lower pharyngeal bone; c, cleithrum. GFP signals identify osteoclasts (OC). (Tokyo Institute of Technology)

Aborad the ISS, the increase in osteoclasts and osteoblasts appeared simultaneously, offering a new clue into the fundamental mechanism behind spaceflight-related bone loss, and, hopefully, widespread but poorly treated osteoporosis in elderly humans.

Of course, we're still just talking about lab-bred fish on a space station, so obviously more research is needed if we're to ever apply this knowledge to humans. But tucked into the paper, Kudo and his team tease at the possibility of their research opening up a whole new scientific field: "gravitational biology."

The Daily Galaxy via Tokyo Institute of Technology and and

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