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.

BACKGROUND:There are some problems such as bone fusion failure or peri-implant infection after implantation of pure titanium implants.Therefore,surface improvement of titanium implants has become a hot topic in research.Macrophages are an immune defense line of the body in response to external stimuli,and the relevant immune response of any biomaterials implanted in the body is related to macrophages. OBJECTIVE:The graphene oxide/hydroxyapatite composite coating on titanium alloy surface was prepared by electrochemical deposition method.The surface characteristics of the coating and the growth and polarization of macrophage RAW264.7 on the surface were analyzed. METHODS:The graphene oxide coating and graphene oxide/hydroxyapatite composite coating on titanium alloy surface was prepared by electrochemical deposition method.The physical properties of the coating were characterized.Pure titanium sheets(blank group),titanium sheets deposited with pure GO coating(control group)and titanium sheets deposited with graphene oxide/hydroxyapatite composite coating(experimental group)were co-cultured with macrophages RAW264.7,respectively.Cell proliferation was detected by CCK-8 assay and DAPI staining.Cell adhesion on the surface of titanium was observed by scanning electron microscopy,and cell polarization phenotype was detected by flow cytometry. RESULTS AND CONCLUSION:(1)Under scanning electron microscope,the pure titanium sheet showed directional scratches and a few punctate pits.After the pure graphene oxide coating was deposited,the surface of titanium sheet showed more cracks,gullies and particles of uneven size,and the wrinkle-like structure characterized by graphene oxide.After the composite coating was deposited,the surface of the titanium sheet was smooth,and the pellet size was more uniform.The water contact angle of composite coated titanium sheet was lower than that of pure titanium sheet and pure graphene oxide coated titanium sheet(P<0.05).(2)CCK-8 assay and DAPI staining showed that compared with the blank group and the control group,the cell proliferation in the experimental group was faster.Scanning electron microscopy showed that RAW264.7 cells all adhered to the surface of the three groups of titanium sheets.With the extension of culture time,cell morphology changed from round to spindle shape.After 7 days of culture,cells in the blank group extended short and few pseudopods;cells in the control group extended long and more pseudopods,and cells in the experimental group extended short and more pseudopods,and the overall cell fullness in the experimental group was the best.Flow cytometry results showed that the cells in the experimental group showed a higher proportion of M2 polarization in the anti-inflammatory direction.(3)These findings conclude that graphene oxide/hydroxyapatite composite coating has good physical,chemical,and biological properties.