Background Human periodontal ligament fibroblasts (HPDLFs) represent the first line of defense against pathogens in the periodontal tissue. Porphyromonas gingivialis (P. gingivalis) has been known to be most strongly associated with periodontitis. MicroRNA (miR)‐146a is involved in the inflammatory regulation of periodontitis. However, the regulatory mechanism of miR‐146a on in P. gingivalis‐induced inflammation response in HPDLFs was still unclear. The aim of this study was to investigate whether miR‐146a plays a key role in P. gingvalis‐induced inflammation responses through regulation of TRAF6 in HPDLFs. Methods MiR‐146a expression was measured by real‐time polymerase chain reaction (PCR) in HPDLFs stimulated with P. gingivalis and its lipopolysaccharide (LPS). IL‐1ß, IL‐6, and IL‐8 were determined by enzyme‐linked immunosorbent assay (ELISA) in the culture supernatants of HPDLFs after transfected with miR‐146a mimic or inhibitor. Meanwhile, the expression of TRAF6 was measured by real‐time PCR and Western blot. Then, we used luciferase reporter assay to detect whether miR‐146a binds to the 3′‐UTR of TRAF6. By using small interfering RNA (siRNA) of TRAF6, the phosphorylation of p38 mitogen‐activated protein kinase (MAPK) was measured by Western blot. Finally, after inhibition of TRAF6 and p38 in HPDLFs, we analyzed the expression of miR‐146a upon P. gingivalis challenge. Results P. gingivalis and its LPS significantly induced miR‐146a expression in HPDLFs. Overexpression of miR‐146a significantly suppressed the IL‐1ß, IL‐6 and IL‐8 secretion, TRAF6 expression, and p38 phosphorylation. In contrast, the levels of these indexes significantly increased by inhibition of miR‐146a. Furthermore, MiR‐146a directly binds to the 3′‐UTR of TRAF6 in P. gingivalis‐induced HPDLFs, but not in P. gingivalis LPS stimulation. Suppression of TRAF6 could inhibit the phosphorylation of p38. Finally, inhibition of TRAF6 and p38 significantly abolished P. gingivalis‐induced miR‐146a upregulation in HPDLFs. Conclusions MiR‐146a contribute to negative regulation of P. gingivalis‐induced proinflammatory cytokines secretion in HPDLFs though TRAF6/p38 MAPK pathway. Maintaining miR‐146a homeostasis plays a key role in controlling inflammatory response in periodontal tissues.
Background and Objectives Photon‐induced photoacoustic streaming (PIPS) and shockwave‐enhanced emission photoacoustic streaming (SWEEPS) are two promising laser‐activated irrigation (LAI) methods for root canal irrigation. Their performance in driving irrigant flush in a complex root canal system will be evaluated by microscale particle image velocimetry (μPIV) measurement and will be compared with that of ultrasonic‐activated irrigation (UAI). Study Design/Materials and Methods A μPIV system with 7 μm fluorescent tracer particles was adopted to measure two‐dimensional (2D) velocity fields around the junction region, with a size of 1.8 mm × 1.5 mm, between one main canal and one lateral canal in an endodontic training block, which was driven by SWEEPS (Er:YAG laser) operating at 15 Hz and 20 mJ. The flow field driven by PIPS (Er:YAG laser) at the same frequency and energy, as well as by UAI (with non‐cutting insert) operating at 40% unit power, was also measured for a direct comparison. Results It was found that both SWEEPS and PIPS can activate a so‐called “breath mode” during the irrigation. Namely, the induced irrigant flush presented a back‐and‐forth oscillation along both the main canal and the lateral one. The maximum flow speed in the lateral canal was observed to be up to 10 m/s in the SWEEPS modality, while reduced to around 7 m/s in the PIPS modality. The penetration length in the lateral canal in both modalities was estimated to be larger than 1 mm. In comparison, the flow field induced by UAI was characterized as irregular vortical structures, the maximum flow speed in the lateral canal was 0.15 m/s and significantly lower than LAI (P < 0.01), and the penetration length was less than 300 μm and lower than LAI (P < 0.05). Conclusion Compared to UAI, PIPS, and SWEEPS are more capable of delivering the irrigant deeper into the lateral canal. Furthermore, the back‐and‐forth flush in the breath mode is ideal for removing debris during irrigation. Lasers Surg. Med. © 2020 Wiley Periodicals LLC
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