Study on Effect of Low-Level Laser on Osteogenic Differentiation of Periodon-tal Ligament Fibroblasts under Mechanical Stress
Objective To investigate the effect of low-level laser(LLL)on the osteogenic differentiation of human periodontal ligament fibroblasts(hPDLFs)under mechanical stress.Methods The hPDLFs cultured in vitro were used as the object in this research.The hPDLFs were cultured in vitro and divided into a blank group,a model group and an intervention group.The cells in the blank group were given neither mechanical stress nor LLL intervention,the cells in the model group were given 2 g/cm2 mechanical static stress intervention,and the cells in the intervention group were given both mechanical stress and LLL intervention.The parameters of the LLL laser used were set as below:wavelength:810 nm,fiber diameter:400 nm,frequency:2.46 Hz,power:100 mW,spot area:9.6 cm2,power density:10 mW/cm2 and energy density:3.75 J/cm2.After 24 hours'intervention,the mRNA levels of osteogenic genes Runt-related transcription factor 2(Runx2),osteocalcin(OCN)and bone morphogenetic protein 2(BMP2)were detected with qPCR.The osteogenic differentiation of cells was detected with alkaline phosphatase(ALP)and alizarin red staining(ARS).The phosphorylation levels of BMP2 protein and Smad1/5/9 protein were detected with Western blotting.Results The isolated and cultured hPDLFs expressed vimentin and cytokeratin,which were consistent with the characteristics of hPDLFs.The mRNA levels of RUNX2,OCN and BMP2,ALP and ARS staining area and BMP2 protein and Smad1/5/9 protein phosphorylation levels in the model group and the intervention group were significantly higher than those in the blank group(P＜0.05).In addition,the levels of above indexes in the intervention group were significantly higher than those in the model group(P＜0.05).It was found that,when the cells in the intervention group were further treated with BMP/Smad pathway inhibitor LDN-193189,LDN-193189 intervention significantly reduced the ALP and ARS staining areas(P＜0.05).Conclusions LLL will promote the osteogenic differentiation of hPDLFs under mechanical stress through BMP2/Smad1/5/9 pathway.
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