P066 miR-342-3p promotes cell survival and motility of osteoclast precursors

Career situation of first and presenting author Young investigator. Introduction Chronic inflammatory joint disorders are associated with bone destruction by osteoclasts (OC), which derive from myeloid precursors. Recent findings reveal that OC are not only professional bone-resorbing cells but also directly involved in controlling inflammatory responses. Depending on the pathophysiological context, OC can polarize the immune response towards tolerance or inflammation. Aiming at identifying key regulators of inflammatory OC functions, we have defined a miRNA-based signature, which includes miR-342-3p. MiRNAs are key regulators of gene expression that control cellular processes, including osteoclastogenesis, and few miRNAs have been described in the differentiation of myeloid precursors into mature OC. Objectives To study the role of miR-342-3p in inflammatory OC. Methods OC were derived from the murine monocyte RAW264.7 cells. The expression levels of miR-342-3p and OC-specific genes were monitored by qRT-PCR. RAW264.7 cells were transfected with either miR-342-3p mimics, neutralizing molecules or control miRNAs. Cell survival and proliferation were assessed at 48 hour after RANKL incubation using quantification of the caspase3-7 activity, ATP production and BrDU incorporation. Motility of OC precursors was monitored using time-laps during the course of OC differentiation. The K/BxN serum-transfer arthritis (STA) model was performed in 8 weeks old C57BL/6 males and bone marrow was flushed. Primary OC were generated from either total bone marrow or sorted CD11b+ and CD11c+ cell subsets of healthy and arthritic mice. Results The expression of miR-342-3p was transiently up-regulated in the early phase of OC generation and was down-regulated after 24–48 hour in OC precursors. While pre-miR-342-3p promoted the motility of RAW264.7 cells, anti-miR-342-3p inhibited all motility parameters recorded (p Conclusions Our data suggest that miR-342-3p promotes the early phase of osteoclastogenesis by enhancing the cell survival and motility of OC precursors. The up-regulation of miR-342-3p in OC isolated from arthritic mice may reflect the increased osteoclastogenic potential of inflammatory precursors in arthritis. Disclosure of Interest None declared.