Screening and identification of novel mechanoresponsive microRNAs in rat femur under simulated microgravity

Space bone loss is the most serious medical problem experienced by astronauts during mid- and long-term flights. Previous reports had shown that miRNAs were associated in bone remodeling and space bone loss. The present study is addressed screening and identify novel miRNAs associated with the skeletal response to gravity changes which play important roles in the regulation of bone formation. Tail-suspension and cell clinorotation were used to simulate microgravity. sRNA deep sequencing, bioinformatics analysis and clone technique were performed to find potential novel gravity-response miRNAs in the bone femur after 28 days’ rat tail-suspension. Six candidate novel miRNAs were selected and analyzed their expression in simulated microgravity and fluid shear stress conditions by quantitative real-time polymerase chain reaction (RT-qPCR). The expression of five novel miRNAs (RN4, RN21, RN43, RN48 and RN50) were changed in tail-suspended rat femurs and clinorotated UMR-106 cells, and up-regulated in UMR-106 after fluid force stress stimulation. Furthermore, The prediction and their enrichment analysis of miRNA targets showed the potential pathways by which RN4, RN43 and RN50 affected osteoblast differentiation and proliferation. Subsequently, we performed and identified the effects of RN4, RN43 and RN50 on the differentiation and proliferation of UMR-106. Taken together, we identified 3 novel miRNAs in bone which may respond to gravity change and regulate osteoblast differentiation or proliferation.