BACKGROUND:The osteogenic differentiation ability of exosomes derived from osteogenic mesenchymal stem cells is well established.However,their impact on the osteogenic differentiation of human periodontal ligament stem cells in an inflammatory microenvironment remains unclear. OBJECTIVE:To examine the impact of exosomes derived from osteogenesis-induced human periodontal ligament stem cells on the osteogenic differentiation of human periodontal ligament stem cells within an inflammatory microenvironment. METHODS:Human periodontal ligament stem cells were isolated and cultured.After 3 days of osteogenic induction,exosomes were extracted.Human periodontal ligament stem cells were divided into four groups.Control group was treated with osteogenesis-induced medium.The exosome group was treated with osteogenesis-induced medium containing 5 μg/mL exosomes.Inflammatory model and inflammatory model+exosome groups were treated with 1 μg/mL lipopolysaccharide for 24 hours to construct a cellular inflammatory microenvironment.The inflammatory model group was treated with osteogenesis-induced medium after lipopolysaccharide intervention.The inflammatory model+exosome group was treated with osteogenesis-induced medium containing 5 μg/mL exosome.The osteogenic differentiation ability of human periodontal ligament stem cells was assessed using alkaline phosphatase staining and alizarin red staining.The expressions of Runt-related transcription factor 2,osteopontin,osteoblast-specific transcription factor Osterix(OSX)and wnt pathway-related protein β-catenin were detected by real-time fluorescence quantitative PCR and western blot assay. RESULTS AND CONCLUSION:(1)Compared with the control group,the relative area stained by alkaline phosphatase,the relative area stained by mineralized nodules and the expression levels of Runx2,osteopontin,and OSX were significantly decreased in the inflammatory model group(P<0.05).(2)Compared with the inflammatory model group,the expression of Runx2,osteopontin,and OSX in the inflammatory model+exosome group was significantly increased in the relative area of alkaline phosphatase staining,the relative area of mineralized nodules staining(P<0.05).(3)Compared with the control group,the expression of wnt pathway-related protein β-catenin was significantly increased in the inflammatory model group(P<0.05).Compared with the inflammatory model group,the expression of β-catenin in the inflammatory model+exosome group was significantly decreased(P<0.05).These findings indicate that exosomes derived from human periodontal ligament stem cells induced by bone formation can enhance the osteogenic differentiation of human periodontal ligament stem cells within an inflammatory microenvironment,and the mechanism may be related to wnt/β-catenin signaling pathway.