Evaluation of rodent spaceflight in the NASA animal enclosure module for an extended operational period (up to 35 days)

The National Aeronautics and Space Administration Animal Enclosure Module (AEM) was developed as a self-contained rodent habitat for shuttle flight missions that provides inhabitants with living space, food, water, ventilation, and lighting, and this study reports whether, after minimal hardware modification, the AEM could support an extended term up to 35 days for Sprague-Dawley rats and C57BL/6 female mice for use on the International Space Station. Success was evaluated based on comparison of AEM housed animals to that of vivarium housed and to normal biological ranges through various measures of animal health and well-being, including animal health evaluations, animal growth and body masses, organ masses, rodent food bar consumption, water consumption, and analysis of blood contents. The results of this study confirmed that the AEMs could support 12 adult female C57BL/6 mice for up to 35 days with self-contained RFB and water, and the AEMs could also support 5 adult male Sprague-Dawley rats for 35 days with external replenishment of diet and water. This study has demonstrated the capability and flexibility of the AEM to operate for up to 35 days with minor hardware modification. Therefore, with modifications, it is possible to utilize this hardware on the International Space Station or other operational platforms to extend the space life science research use of mice and rats. Shuttle-era ‘mousetronaut’ homes tolerate longer space trips than expected, allowing animal experiments on the International Space Station. Eric Moyer at the NASA Ames Research Center in California and colleagues tested whether existing Shuttle-era animal enclosures, which facilitate rat and mouse experiments in space, could accommodate longer stays than their rated 20-day flight window. They found that with minor modifications to feeding hardware, the enclosures handled 35-day rat and mouse experiments, with no ill effects for animal health (e.g, carbon dioxide buildup) or astronauts (e.g, smell confinement). Animals showed slight differences in organ mass compared with controls. This work opens up the possibility of extended animal experiments on International Space Station trips, experiments which examine topics like bone and muscle degradation in astronauts undergoing extended spaceflight.