Abstract: Abstract: Objective To investigate the effects of different concentrations of crocin on receptor activator of nuclear factor kappa B ligand (RANKL) - induced osteoclastogenesis using the monocyte-macrophage cell line RAW264.7. Methods The monocyte-macrophage cell line RAW264.7 was cultured routinely. After treatment with 0, 6.25, 12.5, 25, 50, 100, 200 and 400 μmol/L crocin, cell counting kit-8 (CCK-8) assay was used to analyze the viability of RAW264.7 cells to screen out the appropriate experimental concentration. RAW264.7 cells were induced by RANKL (100 ng / L) to form osteoclasts. After treated with 0, 12.5, 50 and 100 μmol / L crocin respectively, the number of osteolasts was counted by tatrate resistant acid phosphatasec (TRAP) staining. Real-time PCR was used to detect the mRNA expression levels of calcitonin receptor (CTR), nuclear factor of active T cells 1 (NFATC1), C-fos and TRAP. Results No significant effects of crocin (within 0-100 μmol / L) were found on the viability of RAW264.7 cells (P＞0.05). However, When crocin concentration was over 100 μmol/L, the cell proliferation was decreased, and which showed a significant inhibitory effect on proliferation (P＜0.05). Thus, 0-100 μmol / L crocin was selected as the experiment concentration. The amount of differentiated osteolasts and the expression levels of CTR, NFATC1, C-fos and TRAP mRNA were decreased significantly with the increased concentrations of crocin (P＜0.05). Conclusion At a certain concentration (0-100 μmol/L), the higher levels of crocin could inhibit RANKL-induced osteoclastogenesis.

Key words: Key words：CROCUS SATIVUS, macrophages, cell differentiation, osteoclasts, periodontitis, cell proliferation, crocin, receptor activator of nuclear factor kappa B ligand