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The human body undergoes various transformations in space. However, a direct examination of organs and tissues is challenging. This study successfully identified these changes inside the body by analyzing tiny quantities of DNA and RNA molecules released from various tissues into the bloodstream while the astronauts were on the International Space Station (ISS).

Tsukuba, Japan—The acceleration of space exploration, promoted by astronaut recruitment and private space travel, heralds an imminent future where space travel becomes increasingly common. However, numerous questions persist regarding the physical changes that humans undergo in space. Known effects of weightlessness include muscle atrophy, reduced bone density, and fluctuations in body fluid distribution. However, recent research on mice and other organisms has uncovered a range of other changes. In this study, blood samples were collected from six astronauts during and after their 120-day mission on the ISS to characterize these changes. Extracellular DNA and RNA in the blood samples were analyzed in a process called "liquid biopsies."

Previous studies have shown that mitochondria are released from cells into the bloodstream during space missions. This study confirmed that mitochondria are involved in responses to the space environment and can be isolated using CD36 as a marker. This technique allows the condition of extracellular mitochondria to be estimated and the cell type they originate from to be identified. This process has successfully elucidated previously unknown systemic responses to the space environment, including brain, eyes, heart, vascular system, lungs, and skin changes. A similar analysis of mouse samples revealed that mice experience changes similar to those observed in humans and that mitochondrial changes are induced in response to gravity changes.

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This study was supported by JAXA, NASA, and JSPS KAKENHI JP20H03234, JP23H02458. The MHU-1 experiment, which provided mouse plasma samples, was supported by JAXA and 14YPTK-005512.

Original Paper

Title of original paper:

Release of CD36-associated cell-free mitochondrial DNA and RNA as a hallmark of space environment response.

Journal:

Nature Communications

DOI:

10.1038/s41467-023-41995-z

Correspondence

Professor MURATANI Masafumi
Institute of Medicine, University of Tsukuba

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