Notch is activated in RANKL-induced osteoclast differentiation and resorption.

The process of osteoclast differentiation and resorption is fine-tuned by signal pathways, which need to be further elucidated. The aim of this study was to explore the possible connections between NF-kappaB and Notch in RANKL-induced osteoclast activity. To this end, RANKL was used to stimulate mouse osteoclast precursor cell line RAW264.7. The number of multinucleated TRAP+ osteoclasts was counted and the resorption area was measured. NF-kappaB transcriptional factor activity was determined by EMSA. Quantitative RT-PCR and Western blotting analysis were used to determine Hes1 (one of Notch signaling primary targets) mRNA and protein expressions respectively. Mature osteoclasts and bone resorption areas were detected in the present study. NF-kappaB activity was increased in RANKL-induced osteoclast differentiation and resorption. mRNA and protein expressions of Hes1 in RAW264.7 cells were up-regulated after RANKL stimulation. In conclusion, NF-kappaB signaling mediated RANKL-induced osteoclast differentiation and resorption, during which, Notch signaling was activated. Therefore, Notch could be a novel therapeutic target for bone resorption related diseases.