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BACKGROUND:Pulp regeneration has been a hot and difficult research topic in recent years,and the construction of composite bio-scaffolding materials provides new ideas and methods for pulp regeneration. OBJECTIVE:To observe the effect of freeze-dried gelatin modified by methacrylic anhydride/treated dentin matrix bioactive scaffolds on proliferation,migration,and osteogenic differentiation of human dental pulp stem cells. METHODS:The mass ratios of gelatin modified by methacrylic anhydride and treated dentin matrix at 2:1,1:1 and 1:2 were obtained by dispersing different masses of treated dentin matrix into gelatin modified by methacrylic anhydride solution.The gelatin modified by methacrylic anhydride/treated dentin matrix bioactive scaffolds were prepared by vacuum freeze-drying.The microstructure,water absorption,and mechanical properties of the scaffolds were measured.Human dental pulp stem cells were cultured with different mass ratios of scaffold extract and DMEM(control group)to detect cell proliferation and migration.Human dental pulp stem cells were cultured with different mass ratios of scaffold extract + osteogenic induction solution and DMEM + osteogenic induction solution(control group),and their osteogenic ability was analyzed by alkaline phosphatase staining. RESULTS AND CONCLUSION:(1)Under scanning electron microscopy,the scaffolds of the three groups all had porous structures.The porosity of the scaffolds increased with the increase of treated dentin matrix quality,and there was significant difference between the two groups(P＜0.05).The water absorption of scaffolds increased with the increase of treated dentin matrix mass,and there was significant difference between groups(P＜0.05).The compressive strength and shear strength of the scaffold increased with the increase of the mass of treated dentin matrix.(2)CCK-8 assay showed that after 3,5,and 7 days of culture,the cell proliferation absorbance values in the 2:1,1:1,and 1:2 scaffold groups were higher than those in the control group(P＜0.05).The cell proliferation absorbance values increased with the increase of treated dentin matrix mass in the scaffold(P＜0.05).The cell scratch test showed that the cell migration rate in the 2:1,1:1,and 1:2 scaffold groups was higher than that in the control group(P＜0.05),and the cell migration rate increased with the increase of treated dentin matrix mass in the scaffold(P＜0.05).(3)Alkaline phosphatase staining showed that the osteogenic differentiation ability of cells in the 2:1,1:1,and 1:2 scaffold groups was stronger than that in the control group,and the osteogenic ability of cells was enhanced with the increase of treated dentin matrix mass in the scaffold.(4)The results showed that the scaffold with a mass ratio of 1:2 between gelatin modified by methacrylic anhydride and treated dentin matrix was the most suitable for the proliferation and differentiation of dental pulp stem cells.
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ABSTRACT:In recent years ,there has been high prevalence of murine typhus in Yunnan Province ,People's Republic of China .A large outbreak of murine typhus occurred in Xishuangbanna Prefecture ,Yunnan Province in 2010 .However ,not all cases were confirmed by laboratory assays ;therefore ,field epidemiologic and laboratory investigations of murine typhus in Xishuangbanna Prefecture were conducted in 2011 .Blood samples were collected from clinical diagnostic cases at the acute and convalescence stages of murine typhus in Xishuangbanna Prefecture ,Yunnan Province ,from June to September of 2011 ,and blood and spleen samples were collected from mice sharing the same habitats as the patients .Immunofluorescence assays were used to test for the presence of IgM and IgG antibodies against Rickettsia typhi in sera from patients and mice .Real‐time PCR was used to detect the groEL gene of R .typhi in blood clots from patients at the acute stage and in spleen tissue from mice .A total of 1 157 clinically diagnosed murine typhus cases occurred in Xishuangbanna Prefecture ,Yunnan Province in 2011 ,with an incidence of 102 .10/100 000 .Of these cases ,80 were investigated by laboratory assays and 74 of 80 patients were confirmed to have murine typhus .The coincidence rate between the clinical diagnosis and laboratory detection was 92 .50% .The positivi‐ty rate for IgG antibodies against R .typhi was 14 .0% (14/100) for Rattus f lavipectus ,while the rate by PCR was 9 .0%(9/100) .That laboratory diagnoses confirmed that the severity of the murine typhus outbreak in Xishuangbanna cannot be ig‐nored .The distribution of host animals transmitting R .typhi underscores this conclusion .