Palmitic acid induces GSDMD-mediated pyroptosis in periodontal ligament cells via the NF-κB pathway.

OBJECTIVE: Obesity can affect periodontal tissues and exacerbate periodontitis. Pyroptosis, a newly identified type of inflammatory cell death, is involved in the development of periodontal inflammation. The saturated fatty acid palmitic acid (PA) is elevated in obese patients. The effect of PA on pyroptosis in periodontal ligament cells (PDLCs) and its underlying mechanisms remain unknown. MATERIALS AND METHODS: Human PDLCs were isolated from healthy individuals and cultured for experiments. The effects of PA on PDLC pyroptosis and the underlying mechanisms were examined by transmission electron microscopy, quantitative real-time PCR and western blotting. RESULTS: The morphology of PDLCs in the PA group indicated pyroptotic characteristics, including swollen cells, plasma membrane rupture and changes in subcellular organelles. PA induced inflammatory responses in PDLCs, as indicated by an increase in IL-1ß in the cell culture supernatant. Furthermore, we found that the pyroptosis-related proteins caspase-1, caspase-4 and GSDMD were involved in PA-induced cell death. GSDMD and caspase-4 inhibitors alleviated pyroptotic death of PDLCs. Moreover, PA promoted NF-κB P65 phosphorylation. A NF-κB inhibitor decreased IL-1ß expression and partly rescued cell death induced by PA. CONCLUSION: PA activated the NF-κB pathway and induced the inflammatory response in PDLCs. Caspase-4/GSDMD mediated PDLC pyroptosis induced by PA.

[Isolation and biological characteristics of exosomes derived from periodontal ligament stem cells].

PURPOSE: To isolate and identify exosomes derived from periodontal ligament stem cells (PDLSCs) collected by ultracentrifugation. METHODS: Using the limiting dilution technique, human PDLSCs were isolated and expanded. The cell culture supernatant of PDLSCs was collected. Exosomes were collected and purified with a ultracentrifugation method. Biological characteristics of exosomes derived from PDLSCs were measured by transmission electron microscopy (TEM), Western blot and nanosight tracing analysis (NTA). RESULTS: Exosomes could be successfully isolated from the supernatant of PDLSCs by a ultracentrifugation method. Under TEM, the PDLSC-derived exosomes exhibited elliptic or saucer-like shape and the central area had lower electron density than the circum area. The PDLSC-derived exosomes could express the common surface adhesion molecules CD9, CD63, CD81 and TSG101. NTA results showed that the collected exosomes had a size around (119±12.1) nm and an approximate concentration of (3.80±0.39)×108 particles/mL. CONCLUSIONS: Exosomes derived from PDLSCs can be collected by a ultracentrifugation method, which expresses common membrane proteins and morphological characteristics of exosomes.

[Drug release from electrospun simvastatin/polycaprolactone fibrous membranes].

PURPOSE: To prepare electrospun simvastatin/polycaprolactone(SMV/PCL) membrane scaffolds and to evaluate the release properties of this formulation. METHODS: Electrospun SMV/PCL membrane scaffolds were prepared as the experimental group, and electrospun PCL membrane as the control group. The morphology and characteristics of membrane surface were determined by scanning electron microscopic(SEM) and X-ray diffraction(XRD). The release profile of SMV was determined using an ultraviolet-visible spectrometer. The data were analyzed statistically with SPSS 17.0 software package. RESULTS: SEM and XRD indicated that SMV/PCL nanofibers were successfully electrospun and SMV was encapsulated into the fibers. In vitro drug release studies showed that simultaneous SMV release, being nearly linear with time, was achieved and sustained SMV release was prolonged to 28 days. CONCLUSIONS: Electrospun SMV/PCL nanofiber membranes demonstrate sustained drug release properties, suggesting their potential applicability as prospective scaffolds in periodontal regeneration.

Simvastatin induces the osteogenic differentiation of human periodontal ligament stem cells.

Periodontal ligament stem cells (PDLSCs) are considered as potential mesenchymal stem cell sources for future clinical applications in periodontal regeneration therapy. Simvastation, widely used for lowering serum cholesterol, is known to have a bone stimulatory effect. However, it is not clear whether simvastation affects the differentiation of PDLSCs. This study examined the effects of simvastatin on human PDLSCs in vitro and in vivo. Using the limiting dilution technique, human PDLSCs were isolated and expanded. PDLSCs were cultured with simvastatin (0.01-10 µM), and the proliferation was measured. The osteogenic differentiation was characterized by alkaline phosphatase (ALP) activity and Alizarin Red-S staining for calcium deposition. The gene expression levels of osteogenic markers were evaluated by RT-PCR. In addition, PDLSCs were transplanted into nude mice with ceramic bovine bone powders as carriers to observe the capacity of mineralized tissue formation in vivo. Simvastatin at concentrations <1 µM did not suppress the proliferation of PDLSCs. After the administration of 0.1 µM simvastatin, the expression of ALP, bone sialoprotein, and bone morphogenetic protein-2 genes were significantly upregulated, and the ALP activity and mineralized nodule formation were significantly higher in the simvastatin-treated cells than the control cells. In addition, the in vivo transplantation results showed that simvastatin treatment promoted the degree of mineralized tissue formation. Collectively, simvastatin has positive effects on osteogenic differentiation of human PDLSCs in vitro and in vivo. This suggests that simvastatin might be a useful osteogenic induction agent for periodontal bone regeneration.

[Enamel surface roughness after interproximal enamel reduction with different methods in vitro].

PURPOSE: To assess the surface roughness after application of interproximal enamel reduction(IER) with different methods under a pH cycling experiment in vitro. METHODS: Thirty healthy premolars were used after removal for orthodontic reasons and divided into three groups. One proximal surface underwent IER as the experimental surface while the other was untreated as control. Each group underwent IER according to one of the following techniques: tungsten carbide bur and Sof-Lex disks (group 1); tungsten carbide bur and 10% maleic acid on Sof-Lex disk (group 2); tungsten carbide bur, Sof-Lex disks and fluor protector (group 3). All samples were treated using the pH cycling experiment everyday for 60 days. Enamel surface roughness value (Ra) was measured with profilemetry and morphology was observed under scanning electron microscopy (SEM). Statistical analysis was performed using SPSS 13.0 software package by means of paired t test or one way ANOVA. RESULTS: Ra of the experimental surface increased significantly than that of control in each group (P < 0.01). There was no significant difference among the experimental surfaces among the three groups (P > 0.05). SEM images demonstrated that enamel surfaces were smoother in the group 2 and group 3 compared with the experimental surfaces in group 1. CONCLUSIONS: IER significantly increases surface roughness of the proximal enamel. The application of topical fluride on the enamel surface seems to be advantageous.

[Comparison of different means for tooth surface polishing after bracket debonding].

PURPOSE: To observe the tooth surface after acid etching and removing of bonding adhesive by two means for polishing. METHODS: Thirty extracted premolars for orthodontic purpose were used in this experiment. The brackets were adhered and debonded. Then the premolars were randomly divided into two groups. They were treated by traditional method and silicone particles, and observed by roughness instrument and scanning electronic microscope. The polishing-time and surface roughness value(Ra) were recorded. SPSS13.0 software package was used for paired t test. RESULTS: There was no significant difference in Ra and polishing-time between the two groups (P>0.05). Under SEM, the scratches on tooth surface polished by silicone particles were shallower and thinner. CONCLUSION: The silicone particles could provide good requirement for tooth polishing after bracket debonding clinically.

[The effect of different polishing methods on enamel after interproximal enamel reduction].

PURPOSE: The aim of this study is to compare the effect of the enamel demineralization degree after interproximal enamel reduction (IER) on extracted teeth with different polishing methods. METHODS: 20 extracted premolars were chosen as samples. In one premolar, a randomized approximal surface was selected as control surface while the other as experimental surface. After IER, the control surface was physically polished and the experimental surface was chemically polished. All samples were treated under the pH cycling experiment for 60 days. Then the enamel demineralization degree was measured with laser fluorescence diagnostic equipment. The data was analyzed by paired t test using SPSS10.0 software package. Some samples were selected to observe the enamel surface morphology through scanning electron microscope (SEM). RESULTS: The enamel demineralization degree of the control group increased significantly than that of the experimental group(P<0.01). SEM images demonstrated that the enamel surface was smoother in the experimental group than the control group. CONCLUSION: Compared with physical polishing,chemical polishing can increase the smooth degree of enamel surface and reduce the risk of enamel demineralization after IER.

[Dentoalveolar characteristics in skeletal class I patients with excessive overjet].

OBJECTIVE: To investigate the dentoalveolar characteristics in skeletal class I patients with excessive overjet. METHODS: Ten cephalometric measurements of 60 skeletal class I patients with excessive overjet were analyzed. RESULTS: Compared with patients with normal overjet, 1-SN, 1-NA and MxAAH were significantly increased in excessive overjet group I (overjet: 3 - 5 mm) and 1-SN, 1-NA and MxAAH were significantly increased in excessive overjet group II (overjet: 5 - 7 mm). CONCLUSIONS: The protrusion and tipping of maxillary incisor, and absence of compensatory proclination of mandibular incisor may be the factors, caused skeletal class I excessive overjet. Increased height of anterior maxillary anterior alveolar process was the compensatory change in skeletal class I patients with excessive overjet.