The Effect Of Resolvin D1 On Reconstruction Of Rat Calvarial Defects

Objective: Tumors,trauma,and congenital disorders can cause substantial facial bone defects.Autologous bone grafting is the gold standard in regeneration,however,there are still some disadvantages that limit its application.Bone tissue engineering has emerged as an alternative approach for autologous bone grafting.Inflammation prevents tissue repair,and tissue regeneration requires the resolution of inflammation.Resolvin D1（Rv D1）is an endogenous lipid mediator synthesized from ω-3docosahexaenoic acid,which plays an important role in anti-inflammatory effect and promoting tissue repair.This study aimed to investigate the effects of Rv D1 on bone regeneration in a rat calvarial defect model.Methods: In vitro,to examine the effects of RvD1 on cell viability,MG63 cells were treated with Rv D1（10,100 ng/ml）for 24 h and 48 h.To study the effects of RvD1 on lipopolysaccharides（LPS）influenced cell viability and alkaline phosphatase（ALP）expression,cells were incubated for 48 h with LPS alone,LPS + Rv D1（10,100 ng/ml）.Then cell viability was determined by CCK-8,and the expression of ALP was detected by ALP ELISA kits.In vivo,symmetrical calvarial defects,5 mm in diameter,were established on the calvaria of Sprague Dawley（SD）rats.Symmetrical defects of 10 rats were filled with 3D collagen scaffold（COL）and Pluronic F127hydrogel（F127）incorporated with Rv D1（Rv D1-COL-F127 group）;symmetrical defects of 10 rats were filled with COL and F127（COL-F127 group）;symmetrical defects of 6 rats were not treated（Empty group）.After implantation,Rv D1 was injected subcutaneously every 7 days for 4 weeks in the Rv D1-COL-F127 group,while the same volume of phosphate buffer saline was injected subcutaneously in the other groups.The animals were sacrificed at weeks 1 and 8 after implantation.Tissue samples were analyzed by quantitative real-time PCR and histology at week 1.Radiological and histological analyses were performed at week 8.Results: The in vitro data revealed that RvD1 and LPS did not alter the cell viability of MG63 cells compared with the control group.Moreover,RvD1 could increase the ALP expression of MG63 cells treated with LPS.At week 1,calvarial defects treated with Rv D1 exhibited decreased numbers of inflammatory cells and tartrate-resistant acid phosphatase positive cells,greater numbers of newly formed blood vessels,upregulated gene expression of vascular endothelial growth factor and ALP,and downregulated gene expression of receptor activator of nuclear factor-κB ligand,interleukin 1β,and tumor necrosis factor-α.At week 8,the radiographical results showed that osteoid area fraction was higher in the Rv D1-COL-F127 group than that in the COL-F127 group,and histological examination exhibited enhanced osteoid formation and newly formed blood vessels in the Rv D1-COL-F127 group.Conclusion: This study showed that RvD1 had no toxic effect on MG63 cells,and increased ALP expression of MG63 cells.In rat calvarial defects,RvD1 enhanced bone formation and vascularization.