Cultured adult muscle fibers in the microgravity environment. The MYO experiment in the Foton-M3 space flight mission

Loss of skeletal muscle mass and force occurs in situations of altered use such as\ndenervation, immobilization, aging and microgravity. The atrophy program induced under\nthese conditions leads to an enhanced muscle protein degradation mainly via the ubiquitinproteasome\nand the autophagy-lysosome systems. The aim of our work is the definition of\nsignaling pathways involved in muscle atrophy during space flights, that were never\nexplored so far. As cellular model, we used cultured single skeletal muscle fibers isolated\nfrom adult mice. On September 2007, we had the unique opportunity to expose skeletal\nmuscle fibers to microgravity condition during the unmanned Russian Foton-M3 mission,\nsponsored by Italian Space Agency (ASI) LIFE program. We utilized six pre-existing\nSTROMA bioreactors (produced by Kayser Italia), four of which were for molecular\nanalyses and two for morphology. Here we report the results of this space flight experience\nwhose specific objective was to determine the effects of launch mechanical solicitations\nand four days space flight on single muscle fibers. Electron microscopy and gene\nexpression analyses showed that space flight caused only minor modifications to cultured\nmuscle fibers. Importantly, Foton-M3 mission provided useful indications on the\nrequirements necessary to develop a novel bioreactor to be used in microgravity\nenvironment as well as in on ground experiments.