Transcriptional analysis of femoral skin from mice flown on the RR-5 mission

The objective of the Rodent Research-5 (RR-5) study was to evaluate bone loss in mice during spaceflight and to determine if treatment with a modified version of NEL-like molecule-1 (NELL-1) can reduce or prevent bone loss that would otherwise occur during spaceflight. To this end, a cohort of forty 30-weeks-old female BALB/cAnNTac mice were flown to the ISS and housed in the Rodent Habitat. Six days after launch half of the mice were treated with NELL-1 (10 mg/kg in 0.3 ml PBS), while the other half were treated with vehicle control (0.3 ml PBS). Fourteen days after launch animals were again treated with NELL-1 or vehicle control as before, except that all animals were also injected with the bone marker, calcein green (20 mg/kg in 0.1 ml). Injections of vehicle, NELL-1, and bone markers were intraperitoneal. After all forty mice on orbit received two treatments; ten control mice and ten experimental mice were randomly selected for live animal return (LAR). At approximately 30 days after launch the twenty LAR mice were transported live back to Earth. Animals were allowed to recover for 30 days in standard habitats before euthanasia via intraperitoneal injection with ketamine/xylazine. During the recovery, the animals received another two treatments. GeneLab received RNA later preserved femoral skin from nine live animal return and ten matching ground control mice. These were from the vehicle control animals only. RNA was extracted, libraries generated (stranded, ribodepleted) and sequenced (target 60 M clusters at PE 150 bp).