[Nematode Muscles]
Alterations of C. elegans muscle fibers by microgravity

RESEARCH OVERVIEW

• Spaceflight appears to induce metabolic changes and muscle atrophy in crew members, many of which are suggested to have detrimental consequences for crew heath and performance. To overcome this obstacle, it is important to understand the molecular mechanisms regulating spaceflight-induced alterations.
• This investigation seeks to clarify whether C. elegans muscle fibers and cytoskeleton networks are altered in response to microgravity. The investigation also studies whether insulin/IGF-1 (Insulin-like growth factor -1) signaling is sufficient to account for the alterations using Green Fluorescence Protein (GFP) imaging. Wild-type and certain mutants are cultured in both microgravity and 1G centrifuge conditions on board for 4 days starting from each L1 larva. All samples are fixed on board, and recovered for analysis on earth.
• The results are utilized for combating deleterious spaceflight-induced adaptations, for maintained crew health and mission performance in future.

DESCRIPTION

This research team successfully confirmed the effectiveness of RNAi technology under microgravity in the C. elegans RNA interference space experiment (CERISE) (PLoS One 2011, 6, e204591). The research team also found that the expression levels of muscle and cytoskeleton proteins were repressed in the spaceflown C. elegans. Moreover, certain gene expressions involved in energy metabolism were repressed and oppositely sirtuin gene induced by caloric restriction was upregulated under microgravity. These findings indicate that spaceflown C. elegans 1) have reduced muscle and cytoskeletal protein concentration, and 2) demonstrate altered mitochondrial energy metabolism towards a saving energy mode. This investigation clarifies whether C. elegans muscle fibers and cytoskeleton networks in each cell and individual were altered in response to microgravity. This investigation also studies whether insulin/IGF-1 signaling is sufficient to account for the muscular, cytoskeletal and metabolic changes using a GFP imaging system. As summary of space flight experiment, wild-type and certain mutants are cultured in both microgravity and 1G centrifuge conditions on board for 4 days starting from each L1 larva. All samples are fixed on board and recovered, and analyzed on the earth. The results can help to provide clues as to the effects of microgravity on muscle atrophy in humans during long-duration space flight.

SPACE APPLICATIONS

By studying muscle and metabolism changes in a small worm, scientists may be able to understand similar physical changes that take place in the human body during spaceflight. Worms are grown from larvae samples, and returned to Earth for later study. Examining muscle fibers and cellular scaffolding in the worms can help researchers better understand muscle atrophy, and bone density loss, in astronauts.

EARTH APPLICATIONS

Patients on prolonged bed rest experience muscle atrophy, bone density loss and changes in metabolism, similar to the effects of spaceflight. Understanding the molecular changes that take place in microgravity could help researchers develop treatments or therapies to counteract the physical changes associated with aging and bed rest.

OPERATIONAL REQUIREMENTS AND PROTOCOLS

A specific launch orientation is not required. Incubation is started within 14 days after sample turnover, because the survival rate of the nematode sample decreases notably after that day. Sample fixation should be achieved at 4 (-0/+1) days after starting incubation. Nematodes and E.coli should be kept cooled at +4°C (+3-+8°C) before starting incubation. Chemical Fixation Apparatus should be kept cooled at +2°C (+0.5-+6°) before and after fixation. Chemical Fixation Apparatus should be recovered in six months. Nematode Muscles is to be implemented together with Space Aging, another JAXA experiment. Nematodes are injected into Culture Bag by syringe. Two sample bags are placed into the CBEF, and incubation at 20°C.