Resolvin E1 modulates RAW 2647 cell-derived osteoclast differentiation and function
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Background and Purpose: Bone is an active tissue that is remodeled by osteoblasts and osteoclasts (OC) throughout life. Osteoclastogenesis, the formation of osteoclasts, is a complex process involving several specific molecules modulating different stages of differentiation. The relationship between bone and the immune system has been explored for years. Resolvin E1 (RvE1) is a lipid mediator that accelerates resolution of inflammation and return to homeostasis in inflamed tissues. RvE1 has been found to prevent periodontal inflammation and to reduce bone loss in vivo. RvE1 inhibits the formation of mature multinucleated OC in primary bone marrow cultures. However, it is not known whether RvE1 acts directly on OC or the contribution of another cell type is required. RAW 264.7 cells are a cell line that can differentiate into functional OC. This study explored whether RvE1 can inhibit osteoclast-like cell (OCL) differentiation from RAW 264.7 cells. Furthermore, the molecular action of RvE1 on osteoclastogenesis was also explored. The hypothesis was that RvE1 inhibits OC infusion; therefore, the cell fusion molecule DC-STAMP was tested in this study. Materials and Methods: RÅW 264.7 cells were differentiated into OCL with Receptor Activator of Nuclear kB Ligand (RANKL) and simultaneously treated with RvE1, and the formation of mature multinucleated OCL was analyzed after Tartrate-Resistant Acid Phosphatase (TRAP) staining. The function of RAW 264.7 cell-derived OCL was tested by analyzing resorption pits on calcium phosphate films of Osteologic slides. DC-STAMP messenger RNA expression levels of genes were examined by RT-PCR, including both end-point and real-time PCR. Results: OCL-covered area lowered by RvE1(30nM)treatment compared to control group treated with vehicle by 8.3% but this change was not statistically significant (P=0.07). Resorption pit area on Osteologic slides was significantly reduced by RvE1 (10 nm, P=0.02). RvE1 lowered average DC-STAMP gene expression by 16% as determined with end-point PCR. In real-time PCR, RVE1 lowered average DC-STAMP gene expression 4.6%. Both PCR methods showed that RvE1 lowered average DC-STAMP gene expression; however the differences were not statistically significant (p=0.28). Conclusion and implication: These results indicate that RvE1 inhibits mature OCL resorptive function, but does not affect OCL formation. This is in contrast with RvE1 ability to inhibit OC differentiation in primary bone marrow cultures. These observations favor the theory that RvE1 modulates OC differentiation indirectly. The identity of the intermediate cell type deserves further exploration.
PLEASE NOTE: This work is protected by copyright. Downloading is restricted to the BU community: please click Download and log in with a valid BU account to access. If you are the author of this work and would like to make it publicly available, please contact email@example.com.Thesis (MSD) --Boston University, Henry M. Goldman School of Dental Medicine, 2012 (Department of Oral Biology and Periodontology).Includes bibliographic references: leaves 73-85.
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