Transcriptomic Changes in Spaceflight Mice

Female C57BL/6J mice aged 8–9 weeks old were obtained from The Jackson Laboratory (Bar Harbor, ME). Mice were shipped to the Kennedy Space Center (KSC) Space Life Sciences Laboratory (SLSL). Although there were several groups in this study, this report focuses on the transcriptomic changes in the heart when mice are housed in the spaceflight environment for 30 days. Mice were acclimatized for 1–2 weeks prior to the initiation of the study. Their living conditions were controlled for temperature and humidity and included a 12:12 h light–dark cycle. Food and water were provided ad libitum. During this adaptation period, the mice were adapted to the flight hardware (Rodent Research Hardware System). Mice flown on the International Space Station (ISS) and comparable ground control mice were maintained under identical conditions, including a single injection of saline. At 30 days, flight mice were transferred into the ISS Microgravity Sciences Glovebox (MSG), were euthanized via intraperitoneal (IP) injection of Ketamine/Xylazine (150/45 mg/kg) anesthesia followed by closed-cardiac puncture exsanguination and cervical dislocation. After removal of the spleen, mice were wrapped in foil, frozen and stored in the Minus Eighty Laboratory Freezer for ISS (MELFI) at −96 °C until sample return. NASA GLACIER and Cold Bag lockers were used to transport samples back to the ground following mission completion.