Interleukin-1 Induces Receptor Activator Of Nuclear Factor-κB Ligand-independent Osteoclast Differentiation In RAW264.7 Cells

Background:The elderly patients with osteoporosis has increased significantly during the last twenty years,which brings a heavy burden to their family and society.The pathophysilogical changes of osteoporosis mainly lie in the loss of bone mass,caused by abnormal inhibition of osteoblasts or excessive activation of osteoclasts.The differentiation pathways of osteoclasts and their possible inhibitory targets have been the focus of researches.Interleukin-1(IL-1)is a pro-inflammatory cytokine which induces bone destruction in various diseases,such as osteoporosis and rheumatoid arthritis.RAW264.7 cells are frequently used in studies as osteoclast precursors,however it ramains unclear whether IL-1 can induce osteoclast differentiation from RAW264.7 cells without the stimulation of receptor activator of nuclear factor-κB ligand(RANKL).Objective:Hence,the present study aimed to investigate the effects of IL-1 on the formation of osteoclasts from RAW264.7 cells and to detemine whether IL-1 could upregulate the number and resorptive ability of osteoclasts formed under RANKL induction.Materials and Methods:The cell viability was determined via the Cell Counting Kit-8(CCK-8)assay.Protein and gene expression were measured by western blotting and revose transcription-quantitative PCR,respectively.Tartrate-resistant acid phosphatase(TRAP)staining and the resorption pit assay were performed to determine the formation and activity of osteoclasts.Results:There was no statistical difference in cell viability in three experiment groups compared with the blank control grorp.A significantly increased quantity of osteoclasts were found in the IL-1 group compared with the control group,and also in the IL+1+RANKL group compared to the RANKL group.In addition IL-1 significantly increased both the protein and mRNA expression of specific genes associated with osteoclastogenesis,including nuclear factor of activated T cells cytoplasmic 1,matrix metalloprotein-9,cathepsin K and TRAP.Conclusions:In vitro,the findings of the present study suggested that IL-1 can induce osteoclast differentiation and up-regulate the quantity of osteoclasts differatiated RAW264.7 cells The possible reason that IL-1 can induce osteoclast differentiation in RAW264.7 cells lies in the considerable amounts of IL-1RI expressed by itself These results may lay a foundation for further study of diseases involving inflammation-associated bone loss.The combined blockade of IL-1 and RANKL may be effective for the prevention of inflammatory bone loss.