ABSTRACT
Objective:To investigate the protective effect and mechanism of low-intensity pulsed ultrasound on human periodontal ligament stem cells (hPDLSCs) injured by high glucose.Methods:hPDLSCs were cultured in vitro and randomly divided into normal control group, high glucose model group and three low intensity pulsed ultrasound groups (30, 60, 90 mW/cm 2). Cells in the high glucose model group and three low intensity pulsed ultrasound groups were treated with high glucose medium (glucose 40 mmol/L) for 48 h to establish high glucose model. Cells in the normal control group were treated with normal medium (glucose 11 mmol/L). After modeling, three low intensity pulsed ultrasound groups were treated with low-frequency pulse for 20 min each day for 7 days at a dose of 30, 60 and 90 mW/cm 2 respectively. After 7 days, the proliferation ability of each group was determined by MTT assay. The changes of cell cycle and apoptosis were detected by flow cytometry. The level of Caspase-3, Caspase-6, and Caspase-9 was detected by colorimetry. The levels of Wnt1, Wnt10b and β-catenin genes and proteins were detected by reverse transcription PCR and Western Blot respectively. Results:Compared with the hPDLSCs in the normal control group, the hPDLSCs in the high glucose model group have the following changes except for the cell cycles (all P>0.05), i.e. the activity of the cells was decreased and the apoptosis was increased (all P<0.05), the activities of Caspase-3, Caspase-6, and Caspase-9 were increased (all P<0.05), and the expressions of Wnt1, Wnt10b and β-catenin genes and proteins were decreased (all P<0.05). Compared with the hPDLSCs in the high glucose model group, the hPDLSCs in low-intensity pulsed ultrasound groups have the following changes expect for the cell cycles (all P>0.05), i.e. cell viabilities were increased (all P<0.05), proliferation abilities were increased (all P<0.05), apoptosis rates were decreased (all P<0.05), the activities of Caspase-3, Caspase-6, Caspase-9 were decreased (all P<0.05), and the expressions of Wnt1, Wnt10b and β-catenin genes and proteins were up-regulated ( P<0.05). Among the three low-intensity pulsed ultrasound groups, when the ultrasonic intensity is 90 mW/cm 2, the above-mentioned index changes most obviously (all P<0.05). Conclusions:Low-intensity pulsed ultrasound can significantly alleviate the hPDLSCs damage induced by high glucose, which may be achieved by reducing the activities of Caspase-3, Caspase-6 and Caspase-9, and up-regulating the expression of Wnt1, Wnt10b and β-catenin.
ABSTRACT
BACKGROUND:The biomechanical effect of the implant-bone interface is one of the most important factors for bone resorption. The new structure of the periodontal-ligament-like implants may improve the distribution of the interfacial stress. OBJECTIVE:To discuss the effect of the internal structure changes of traditional implants on the cortical bone stress distribution and peak at the implant-bone interface under different occlusal load conditions, so as to provide a theoretical basis for the optimization design and clinical application of new structure implants. METHODS:Two kinds of digital models, new structure implant (model A) and non-threaded cylindrical implant (model B), were established by Pro/ENGINEER software. Variations of the stress peak and stress distribution of implant-bone interface cortical bone area under the same bone and force environment were analyzed using Ansys software. RESULTS AND CONCLUSION: Under a vertical loading, the stress peak under different forces was reduced by 17.54% in model A compared with model B; under a 45° loading, the stress peak of model A was reduced by 2.59% compared with model B, and it showed an evident tendency of high stress area focusing to the buccal side of model B. Under the chew-simulation loading, the stress peak of model A was lower than that of model B. The biggest difference (0.353 2 MPa) appeared atβ=12°(β is the angle of force direction and the implant axis), and it gradualy reduced atβ > 12°. At the same time, model A had a wider range of application degree compared with model B in two quantitative indicators, including optimal peak stress of promoting bone tissue growth and stress peak of maintaining healthy bone tissue. These results suggest that the optimized structure of implants contributes to improve the cortical bone stress distribution at the implant-bone interface, decrease the peak stress, and reduce the risk of cortical bone absorption in a wider range.