Transcriptional analysis of kidneys from mice flown on the RR-7 mission

The objective of the Rodent Research-7 mission (RR-7) was to study the impact of the space environment on the gut microbiota of two strains of mice and how any changes in-turn affect the immune system, metabolic system, and circadian or daily rhythms. To this end, ten 11-week-old female C57BL/6J and ten 11-week-old female C3H/HeJ mice were flown to the International Space Station on June 29, 2018 on SpaceX-15 and housed in two Rodent Habitats. Samples of food, swabs from living surfaces, and fecal pellets were collected from each animal before launch and regularly during the mission. The mission also involved extended video collection (48 hr video segments per Habitat) to monitor circadian rhythms, and on-orbit mass measurement. After 25 days on-orbit, half of the mice of each strain were euthanized on the ISS with Ketamine/Xylazine/Acepromazine and cardiac puncture, after which carcasses were segmented in three sections and preserved in RNA later. After 75-76 days the remaining 5 animals from each group were euthanized and processed in the same manner. The 25-day dissected carcasses returned on SpX-15, and the 75-day dissected carcasses returned on SpX-16. In addition to the Flight group, three ground control groups were also part of the study: Basal (representing the pre-launch state), Vivarium (standard vivarium housing for the same duration of time as flight), and Ground (same habitat in the International Space Station Environment Simulator, ISSES). Twenty mice (10 of each strain) were included in each of these control groups, which were euthanized and processed on the same schedule and in the same manner as the flight samples. Dissections for tissues from all experimental groups were completed by the PI groups along with NASA's Biospecimen Sharing Program in February 2019. GeneLab received kidneys from thirty-eight C57BL/6J mice: 9 Basal, 5 Ground (25 days), 4 Ground (75 days), 5 Flight (25 days), 5 Flight (75 days), 5 Vivarium (25 days), 5 Vivarium (75 days). GeneLab received kidneys from thirty-nine C3H/HeJ mice: 9 Basal, 5 Ground (25 days), 5 Ground (75 days), 5 Flight (25 days), 5 Flight (75 days), 5 Vivarium (25 days), 5 Vivarium (75 days). From these kidneys, RNA was extracted, libraries generated (stranded, ribodepleted) and sequenced (target 60 M clusters at PE 98 bp). Since the original RR-7 experiment used different wavelengths of light in the Spaceflight (FLT) and Ground Control (GC) Habitat units (the two GC units had blue-enriched LEDs whereas the two FLT units had the standard white LEDs), the GC was repeated for RR-7 on 07/28/2021 - 07/29/2021 such that mice were exposed to either blue or white light. The GC rerun samples can be compared to the data from the original RR-7 samples to evaluate any biology impact due to exposure to different wavelengths of light.