After a 16-year hiatus, Russia has resumed its program of biomedical research in space, with the successful 30-day flight of the Bion-M 1 biosatellite (April 19–May 19, 2013). The principal species for biomedical research in this project was the mouse. This paper presents an overview of the scientific goals, the experimental design and the mouse training/selection program. The aim of mice experiments in the Bion-M 1 project was to elucidate cellular and molecular mechanisms, underlying the adaptation of key physiological systems to long-term exposure in microgravity. The studies with mice combined in vivo measurements, both in flight and post-flight (including continuous blood pressure measurement), with extensive in vitro studies carried out shortly after return of the mice and in the end of recovery study. Male C57/BL6 mice group housed in space habitats were flown aboard the Bion-M 1 biosatellite, or remained on ground in the control experiment that replicated environmental and housing conditions in the spacecraft. Vivarium control groups were used to account for housing effects and possible seasonal differences. Mice training included the co-adaptation in housing groups and mice adaptation to paste food diet. The measures taken to co-adapt aggressive male mice in housing groups and the peculiarities of “space” paste food are described. The training program for mice designated for in vivo studies was broader and included behavioral/functional test battery and continuous behavioral measurements in the home-cage. The results of the preliminary tests were used for the selection of homogenous groups. After the flight, mice were in good condition for biomedical studies and displayed signs of pronounced disadaptation to Earth's gravity. The outcomes of the training program for the mice welfare are discussed. We conclude that our training program was effective and that male mice can be successfully employed in space biomedical research.

One of the key events that occurs during skeletal muscle inactivation is a change in myosin phenotype, i.e. increased expression of fast isoforms and decreased expression of the slow isoform of myosin heavy chain (MyHC). It is known that calcineurin/nuclear factor of activated T-cells and AMP-activated protein kinase (AMPK) can regulate the expression of genes encoding MyHC slow isoform. Earlier, we found a significant decrease in phosphorylated AMPK in rat soleus after 24 h of hindlimb unloading (HU). We hypothesized that a decrease in AMPK phosphorylation and subsequent histone deacetylase (HDAC) nuclear translocation can be one of the triggering events leading to a reduced expression of slow MyHC. To test this hypothesis, Wistar rats were treated with AMPK activator (AICAR) for 6 days before HU as well as during 24 h of HU. We discovered that AICAR treatment prevented a decrease in pre-mRNA and mRNA expression of MyHC I as well as MyHC IIa mRNA expression. Twenty-four hours of hindlimb suspension resulted in HDAC4 accumulation in the nuclei of rat soleus but AICAR pretreatment prevented this accumulation. The results of the study indicate that AMPK dephosphorylation after 24 h of HU had a significant impact on the MyHC I and MyHC IIa mRNA expression in rat soleus. AMPK dephosphorylation also contributed to HDAC4 translocation to the nuclei of soleus muscle fibres, suggesting an important role of HDAC4 as an epigenetic regulator in the process of myosin phenotype transformation.

The effects of clenbuterol beta(2)-agonist administration were investigated in normal and atrophied [15-day hindlimb-unloaded (HU)] rat soleus muscles. We showed that clenbuterol had a specific effect on muscle tissue, since it reduces soleus atrophy induced by HU. The study of Ca(2+) activation properties of single skinned fibers revealed that clenbuterol partly prevented the decrease in maximal tension after HU, with a preferential effect on fast-twitch fibers. Clenbuterol improved the Ca(2+) sensitivity in slow- and fast-twitch fibers by shifting the tension-pCa relationship toward lower Ca(2+) concentrations, but this effect was more marked after HU than in normal conditions. Whole muscle electrophoresis indicated slow-to-fast transitions of the myosin heavy chain isoforms for unloaded and for clenbuterol-treated soleus. The coupling of the two latter conditions did not, however, increase these phenotypical transformations. Our findings indicated that clenbuterol had an anabolic action and a beta(2)-adrenergic effect on muscle fibers and appeared to counteract some effects of unloading disuse conditions.

Cytoskeletal and contractile proteins degenerate during functional unloading of muscle. The ratio of myosin heavy chain (MHC) expression changes simultaneously. We have supposed that NO can be a signal molecule related to the regulation of protein metabolism upon muscle unloading. To test this hypothesis, Wistar rats underwent functional unloading for 14 days without and with peroral administration of L-arginine (500 mg/kg) as NO precursor. Significant decreases in m. soleus mass, NO, nNOS, dystrophin, Hsp90, p-S6K, and type I MHC mRNA contents were found in the group of animals with unloading without preparation compared to those in control and in the group with unloading and administration of L-arginine; at the same time, increased contents of atrogin-1/MAFbx and MuRF-1 (p < 0.05) were found. No difference in the IGF-1 mRNA content between all three groups was found. Atrophy was significantly less pronounced in the group with unloading and L-arginine administration compared to that without the amino acid, and no destruction of cytoskeletal proteins was observed. We conclude that administration of L-arginine upon functional unloading decreases the extent of m. soleus atrophy, prevents the decrease in it of type I MHC mRNA, and blocks destructive changes in some cytoskeletal proteins. Such effect can be due to the absence of increase in this group of the content of some ubiquitin ligases and decreased intensity of the p70S6 kinase synthesis marker.