Mice in Bion-M 1 space mission: training and selection

Abstract

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.

Figure 1. Schematic diagram of the experiments.

Mice of SF, SFV and backup SF groups were co-adapted in housing groups of 3 mice each, SF mice were adapted to paste food diet, and mice of in vivo subgroups passed through preliminary tests. After transportation to and adaptation at Baikonur, SF mice were flown aboard the Bion-M 1 satellite for 30 days. After landing mice were examined and transported to Moscow, where animals of the in vitro subgroup were dissected, while recovery dynamics was followed in the in-vivo subgroup before dissection 7 days after landing. Ground control experiment replicated the principal stages of the spaceflight experiment.

Figure 2. Habitat interior.

Figure 3. Metabolic parameters in mice fed pelleted food and paste diet.

Body weight (A), food (B) and water (C) consumption, feces (D) and urine (E) production. Differences significant at p<0.05 are marked with an asterisk. When the paste food diet with high water content was introduced mice displayed an increase in bodyweight, stopped drinking, while diuresis and feces weight were increased indicating excretion of excess water consumed with the paste diet.

Figure 4. Bodyweight (A) and relative BW change (B) after telemetry probe implantation.

Differences significant at p<0.05 are marked with an asterisk. As can be considered from bodyweight data, acute recovery was over by day 5 after surgery.

Figure 5. Mice bodyweight dynamics after transportation to the launch site.

Differences significant at p<0.05 are marked with an asterisk. Transportation did not seriously affect the mice, as can be concluded from a slight drop of bodyweight and its rapid recovery.

Figure 6. A representative photograph of mice in the flight habitats.

Note that mice occupy the floor grid before launch (upper row) and cling to the feeder (lower row) in microgravity. The same cages are shown.

Figure 7. Mice body weight during training (A) and bodyweight before and after the experiments (B).

The pairs of bars on the (B) panel represent body weight before (left box) and after (right box) the corresponding experiment. Points represent individual mice data, boxes – lower to upper quartile, whiskers – minimum and maximum. Differences significant at p<0.05 are marked with an asterisk.

Figure 8. Post-flight open field behavior parameters expressed as percent of pre-flight background values.

Total (A), center (B) and periphery (C) distance moved, rearing frequency (D), center entries frequency (E), time in center (F), latency to the first center zone entry (G) and grooming duration (H). SF mice displayed reduced activity compared to any of the control groups (GC, SFV or GCV). Mice housed in habitats (SF and GC) were reluctant to explore the center of the arena. Statistical analysis was performed using Mann-Whitney test (*−p<0.05, **−p<0.01, ***− p<0.005 and ****−p<0.0001, ns – not significant or the p value is indicated).