Low-power laser irradiation promotes the proliferation and osteogenic differentiation of human periodontal ligament cells via cyclic adenosine monophosphate

Retaining or improving periodontal ligament （PDL） function is crucial for restoring periodontal defects. The aim of this study was to evaluate the physiological effects of low-power laser irradiation （LPLI） on the proliferation and osteogenic differentiation of human PDL （hPDL） cells. Cultured hPDL cel Is were irradiated （660 nm） daily with doses of O, 1, 2 or 4 J .cm-2. Cell proliferation was evaluated by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide （MTT） assay, and the effect of LPLI on osteogenic differentiation was assessed by Alizarin Red S staining and alkaline phosphatase （ALP） activity. Additionally, osteogenic marker gene expression was confirmed by real-time reverse transcription-polymerase chain reaction （RT-PCR）. Our data showed that LPLI at a dose of 2 J.cm-2 significantly promoted hPDL cell proliferation at days 3 and 5. In addition, LPLI at energy doses of 2 and 4 J.cm-2 showed potential osteogenic capacity, as it stimulated ALP activity, calcium deposition, and osteogenic gene expression. We also showed that cyclic adenosine monophosphate （cAMP） is a critical regulator of the LPLI-mediated effects on hPDL cells. This study shows that LPLI can promote the proliferation and osteogenic differentiation of hPDL cells. These results suggest the potential use of LPLI in clinical applications for periodontal tissue regeneration.

Influence of baicalin on the expression of receptor activator of nuclear factor-κB ligand and osteoprotegerin in human periodontal ligament cells

Objective To study the effect of baicalin on the expression of receptor activator of nuclear factor-κB ligand(RANKL)and osteoprotegerin(OPG)in cultured human periodontal ligament(HPDL)cells.Methods Small interfering RNA(siRNA)eukaryotic expression vector targeted transforming growth factor βⅡ receptor(TGF-β RⅡ)was constructed and transfected into T cells.HPDL cells with T cells transfected with siRNA or not were placed in the culture medium that had been added with lipopolysaccharide(LPS)and baicalin.The obtained solution was divided into six groups according to the components(group Ⅰ:HPDL cells+LPS+T cells transfected with siRNA1+baicalin;group Ⅱ:HPDL cells+LPS+T cells transfected with siRNA1;group Ⅲ:HPDL cells+LPS+T cells+baicalin;group Ⅳ:HPDL cells+LPS+T cells;group Ⅴ:HPDL cells+baicalin;group Ⅵ:HPDL cells)and was cultured for 48 hours.RT-PCR was used to observe the effect of baicalin on the expression of OPG-RANKL in HPDL cells.Results The ratio of RANKL/OPG in group Ⅰ was lower than that in group Ⅱ(P<0.01)and higher than that in group Ⅲ(P<0.01);The ratio of RANKL/OPG in group Ⅲ was lower than that in group Ⅳ(P<0.01);the ratio of RANKL/OPG in group Ⅳ was higher than that in group Ⅵ(P<0.01);the ratio of RANKL/OPG in group Ⅴ was lower than that in group Ⅵ(P<0.05).Conclusion ① Baicalin could decrease the ratio of RANKL/OPG in HPDL cells.② The TGF-β signaling transduction plays an important role in the effect of baicalin on the RANKL/OPG ratio in HPDL cells.③ Baicalin acts not only through TGF-β to regulate RANKL/OPG in HPDL cells,but also through other pathways.

Effects of Ginsenoside Rg-1 on the Proliferation and Osteogenic Differentiation of Human Periodontal Ligament Stem Cells

Objective： TO evaluate the effects of ginsenoside Rg-1 on the proliferation and osteogenic differentiation of human periodontal ligament stem cells （hPDLSCs） and to explore the possible application on the alveolar bone regeneration. Methods： To determine the optimum concentration, the effects of ginsenoside Rg-1 ranging from 10 to 100 μmol/L were evaluated by 3-（4,5）-dimethylthiahiazo（-z-yl）-3,5-di-phenytetrazoliumromide, alkaline phosphatase activity and calcium deposition. Expressions of runt-related transcription factor 2, collagen alpha-2（I） chain, osteopontin, osteocalcin protein were examined using real-time polymerase chain reaction. Results： Compared with the control group, a certain concentration （10 μmol/L） of the Rg-1 solution significantly enhanced the proliferation and osteogenic differentiation of hPDLSCs （P〈0.05）. However, concentrations that exceeds 100 μmol/L led to cytotoxicity whereas concentrations below 10 nmol/L showed no significant effect as compared with the control. Conclusion： Ginsenoside Rg-1 can enhance the proliferation and osteogenic differentiation of hPDLSCs at an optimal concentration of 10 μmol/L.

AMP-activated protein kinase acts as a negative regulator of high glucose-induced RANKL expression in human periodontal ligament cells

Methods We examined the expression of osteoprotegerin in hPDL cells cultured at different concentrations of glucose using real-time polymerase chain reaction （PCR）, and Western blotting analysis. AMPK phosphorylation in hPDL cells was studied using immunoprecipitate kinase assay and Western blotting. The effect of AMPK activation on RANKL expression in hPDL cells was investigated by real-time PCR and Western blotting. Results High glucose levels caused an increase in RANKL mRNA and protein expression in hPDL cells. Moreover, the amount of p-AMPK and AMPK activity was lower in hPDL cells exposed to high glucose levels than in cells exposed to normal glucose levels. Suppression of AMPK by Compound C augmented RANKL expression, and AMPK activation by metformin significantly decreased RANKL expression in hPDL cells. Additionally, metformin down-regulated RANKL expression in hPDL cells exposed to high glucose via AMPK activation. Conclusion High glucose-induced up-regulation of RANKL could be due to decreased AMPK activity, and AMPK activation may be involved in regulating of RANKL expression in hPDL cells.