Role of the GRP78-c-Src signaling pathway on osteoblast differentiation of periodontal ligament fibroblasts in-duced by cyclic mechanical stretch
Objective This study aims to investigate the influence of glucose regulated protein(GRP)78 on osteo-blast differentiation in periodontal ligament fibroblasts(PDLFs)under cyclic mechanical stretch and determine the under-lying mechanism.Methods FlexCell 5000 cell mechani-cal device was applied to simulate the stress environment of orthodontic teeth.GRP78High and GRP78Low sub-population were obtained by flow sorting.Gene transfec-tion was performed to knockdown GRP78 and c-Src ex-pression and overexpress c-Src.Western blot analysis was used to detect the protein expression of Runt-related gene 2(RUNX2),Osterix,osteocalcin(OCN),and osteopontin(OPN).Immunoprecipitation assay was used to determine the interaction of GRP78 with c-Src.The formation of cellular mineralized nodules was determined by alizarin red staining.Results GRP78 was heterogeneously expressed in PDLFs,and GRP78High and GRP78Low subpopulations were obtained by flow sorting.The osteogenic differentiation ability and phosphorylation level of c-Src kinase in the GRP78High subpopulation were significantly increased com-pared with those in GRP78Low subpopulation after cyclic mechanical stretch(P<0.05).GRP78 interacted with c-Src in PDLFs.The overexpression c-Src group showed significantly increased osteogenic differentiation ability than the vector group(P<0.05),and the sic-Src group showed significantly decreased osteogenic differentiation ability(P<0.05)after cy-clic mechanical stretch.Conclusion GRP78 upregulates c-Src expression by interacting with c-Src kinase and pro-motes osteogenic differentiation under cyclic mechanical stretch in PDLFs.
cyclic mechanical stretchosteogenic differentiationperiodontal ligament fibroblastsglucose regu-lated protein 78
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