[Porphyromonas gingivalis outer membrane vesicles activate Toll-like receptor 2 to promote osteoclast differentiation by carrying lipopolysaccharide].

Objective: To investigate the effects of Porphyromonas gingivalis derived outer membrane vesicles (Pg OMV) on osteoclast differentiation of macrophages and its underlying mechanisms. Methods: The morphology and the size distribution of Pg OMV were analyzed by transmission electron microscopy and nanoparticle tracing analysis, respectively. The osteoclast precursors were treated with 1, 3 and 10 mg/L Pg OMV (1, 3 and 10 mg/L OMV treatment group) or phosphate buffer solution (PBS)(control group). The formation of osteoclasts was analyzed by tartrate-resistant acid phosphase (TRAP) staining and F-actin staining and real-time quantitative PCR (RT-qPCR) were used to detect the expression of Fos and matrix metallopeptidase 9 (MMP9). Polymyxin B (PMB) was used to block lipopolysaccharide (LPS) and then Pg OMV was used to treat osteoclast precursor (PMB-OMV treatment group), and OMV treatment group was used as control. TRAP and F-actin staining were used to observe the formation of osteoclasts and actin rings. The effect of Pg OMV on the expression of Toll-like receptor (TLR) 2 and TLR4 in preosteoclasts was detected by Western blotting. The osteoclast precursors were pretreated with 10, 50, 100 and 200 µmol/L C29, an inhibitor of TLR2, and then treated with Pg OMV(OMV+10, 50, 100 and 200 µmol/L C29 treatment group) and OMV treatment group without C29 pretreatment was control. TRAP and F-actin staining were used to observe the formation of osteoclasts and actin rings. The osteoclast precursor cells were treated with OMV (OMV treatment group) and OMV incubated with PMB (PMB-OMV treatment group) and the expression of TLR2 in osteoclast precursor was detected by Western blotting. Results: Pg OMV showed classical vesicular structures, and the average particle size of Pg OMV were 179.2 nm. A large number of actin rings were observed in the 3 and 10 mg/L OMV treatment groups. The percentages of TRAP-positive osteoclast area in 3 mg/L OMV treatment group [(22.6±2.1)%] and 10 mg/L OMV treatment group [(32.0±2.3)%] were significantly increased compared with control group [(4.9±0.5)%] (P<0.001). Compared with the control group (1.000±0.029), the mRNA relative expression of Fos in 3 mg/L OMV treatment group (1.491±0.114) and 10 mg/L OMV treatment group (1.726±0.254) was significantly increased (P=0.013, P=0.001). Compared with the control group (1.007±0.148), the mRNA relative expression of MMP9 in the group of 10 mg/L OMV (2.232±0.097) was significantly increased (P<0.001). Actin ring formation was less in PMB-OMV treatment groups than in OMV treatment groups. The proportion of TRAP-positive osteoclasts area [(14.8±3.8)%] in PMB-OMV treatment group was significantly lower than OMV treatment group [(31.5±6.7) %] (P=0.004). The relative expression of TLR2 in OMV treatment group (1.359±0.134) was significantly higher than that in the control group (1.000±0.000) (t=4.62, P=0.044). Compared with the OMV treatment group [(29.4±1.7)%], 50, 100 and 200 µmol/L C29 significantly decreased the formation of osteoclasts [(24.0±1.7)%, (18.5±2.1)%, (9.1±1.3) %] (P=0.026, P<0.001, P<0.001). TLR2 protein expression in PMB-OMV group (0.780±0.046) was significantly lower than that in OMV group (1.000±0.000)(t=8.32, P=0.001). Conclusions: Pg OMV can promote osteoclast differentiation by carrying LPS, TLR2 plays an important role in Pg OMV mediated osteoclast differentiation.

[Removal or retention of nonimpacted third molars].

Nonimpacted third molars (N-M3s) refer to the third molars (M3s) that completely erupt and reach the occlusal plane without rotation. Although the removal of unerupted M3s in young adults is generally approved by most dentists, the decision on removal or retention of N-M3s remains challenging as a result of unawareness of the potential harm of N-M3s. Recent studies suggested that N-M3s were associated with deteriorated effects to the health of adjacent teeth, including higher risks of caries and alveolar bone resorption. Therefore, regular monitoring and early clinical decision on N-M3s are essential to reduce the risks of adverse effects on adjacent teeth. This review is structure to give a comprehensive overview of the negative impact of N-M3s to the adjacent teeth, in order to provide rational guidelines for clinical decision-making of N-M3s.

[Long non-coding RNA LINC01133 regulates cementogenic differentiation of human periodontal ligament stem cells by modulating mitochondrial functions].

Objective: To investigate the effects of long non-coding RNA (lncRNA) LINC01133 on the cementogenic differentiation of human periodontal ligament stem cells (hPDLSC) and the underlying mechanism. Methods: A total of 12 teeth were harvested from 10 patients aged 17-30 years in the Department of Oral and Maxillofacial Surgery, School of Stomatology, The Fourth Military Medical University for impacted or orthodontic reasons from September 2021 to January 2022. The hPDLSCs were isolated from the teeth and transfected with small interfering RNA-LINC01133 (si-LINC01133) or small interfering RNA-negative control (si-NC). The si-LINC01133 was regarded as the experimental group, and the si-NC was regarded as the control one. The silencing efficiency of LINC01133 in the hPDLSCs was evaluated by real-time quantitative PCR (RT-qPCR). Western blotting was used to detect the protein expression levels of cementogenic differentiation-related factors including bone sialoprotein (BSP), cementum attachment protein (CAP), and cementum protein-1 (CEMP-1). Mitochondrial reactive oxygen species (mtROS) production was assessed using the MitoSox by flow cytometry. Mitochondrial membrane potential (MMP) was detected by JC-1 fluorescence staining. Mitochondrial respiratory chain complexes proteins including NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 8 (NDUFB8), succinate dehydrogenase complex flavoprotein subunit A (SDHA), ubiquinol-cytochrome c reductase core protein 1 (UQCR1), cytochrome c oxidase subunit 4 isoform 1 (COXⅣ), and ATP synthase F1 subunit alpha (ATP5A) were evaluated by Western blotting. Results: The expression levels of LINC01133 could be suppressed by more than 60% with si-LINC01133 (control group: 1.000±0.000, experimental group: 0.385±0.128) (t=10.72, P<0.01). Suppression of LINC01133 in hPDLSCs decreased the levels of cementogenic differentiation-related proteins including BSP (control group: 1.000±0.000, experimental group: 0.664±0.179) (t=4.62, P<0.01) and CAP (control group: 1.000±0.000, experimental group: 0.736±0.229) (t=2.83, P<0.05). Suppression of LINC01133 in hPDLSCs increased the production of mtROS (control group: 1.000±0.000, experimental group: 1.458±0.185) (t=4.96, P<0.05) and the expression of NDUFB8 (control group: 1.000±0.000, experimental group: 1.683±0.397) (t=3.45, P<0.05), as well as decreased MMP levels (control group: 1.000±0.000, experimental group: 0.209±0.029) (t=53.99, P<0.01) and the expression of SDHA (control group: 1.000±0.000, experimental group: 0.428±0.228) (t=5.02, P<0.05). No significant changes in the UQCR1, COXⅣ, and ATP5A expression levels were found between the control group and exprimental group (P>0.05). Conclusions: LINC01133 regulates the cementogenic differentiation of hPDLSCs possibly via modulating the mitochondrial functions.