Inhibitory effect of saliva on osteoclastogenesis in vitro requires toll-like receptor 4 signaling

Atorvastatin Upregulates microRNA-186 and Inhibits the TLR4-Mediated MAPKs/NF-κB Pathway to Relieve Steroid-Induced Avascular Necrosis of the Femoral Head

Steroid-induced avascular necrosis of the femoral head (SANFH) is caused by the death of active components of the femoral head owing to hormone overdoses. The use of lipid-lowering drugs to prevent SANFH in animals inspired us to identify the mechanisms involving Atorvastatin (Ato) in SANFH. However, it is still not well understood how and to what extent Ato affects SANFH. This study aimed to figure out the efficacy of Ato in SANFH and the underlying molecular mechanisms. After establishment of the SANFH model, histological evaluation, lipid metabolism, inflammatory cytokines, oxidative stress, apoptosis, and autophagy of the femoral head were evaluated. The differentially expressed microRNAs (miRs) after Ato treatment were screened out using microarray analysis. The downstream gene and pathway of miR-186 were predicted and their involvement in SANFH rats was analyzed. OB-6 cells were selected to simulate SANFH in vitro. Cell viability, cell damage, inflammation responses, apoptosis, and autophagy were assessed. Ato alleviated SANFH, inhibited apoptosis, and promoted autophagy. miR-186 was significantly upregulated after Ato treatment. miR-186 targeted TLR4 and inactivated the MAPKs/NF-κB pathway. Inhibition of miR-186 reversed the protection of Ato on SANFH rats, while inhibition of TLR4 restored the protective effect of Ato. Ato reduced apoptosis and promoted autophagy of OB-6 cells by upregulating miR-186 and inhibiting the TLR4/MAPKs/NF-κB pathway. In conclusion, Ato reduced apoptosis and promoted autophagy, thus alleviating SANFH via miR-186 and the TLR4-mediated MAPKs/NF-κB pathway.

Liquid PRF Reduces the Inflammatory Response and Osteoclastogenesis in Murine Macrophages

Macrophage activation and osteoclastogenesis are hallmarks of inflammatory osteolysis and may be targeted by the local application of liquid platelet-rich fibrin (PRF). Liquid PRF is produced by a hard spin of blood in the absence of clot activators and anticoagulants, thereby generating an upper platelet-poor plasma (PPP) layer, a cell-rich buffy coat layer (BC; termed concentrated-PRF or C-PRF), and the remaining red clot (RC) layer. Heating PPP has been shown to generate an albumin gel (Alb-gel) that when mixed back with C-PRF generates Alb-PRF having extended working properties when implanted in vivo. Evidence has demonstrated that traditional solid PRF holds a potent anti-inflammatory capacity and reduces osteoclastogenesis. Whether liquid PRF is capable of also suppressing an inflammatory response and the formation of osteoclasts remains open. In the present study, RAW 264.7 and primary macrophages were exposed to lipopolysaccharides (LPS), lactoferrin, and agonists of Toll-like receptors (TLR3 and TLR7) in the presence or absence of lysates prepared by freeze-thawing of liquid PPP, BC, Alb-gel, and RC. For osteoclastogenesis, primary macrophages were exposed to receptor activator of nuclear factor kappa B ligand (RANKL), macrophage colony-stimulating factor (M-CSF), and human transforming growth factor-β1 (TGF-β1) in the presence or absence of PPP, BC, Alb-gel, RC lysates and hemoglobin. We show here that it is mainly the lysates prepared from PPP and BC that consistently reduced the agonist-induced expression of interleukin 6 (IL6) and cyclooxygenase-2 (COX2) in macrophages, as determined by RT-PCR and immunoassay. With respect to osteoclastogenesis, lysates from PPP and BC but also from RC, similar to hemoglobin, reduced the expression of osteoclast marker genes tartrate-resistant acid phosphatase (TRAP) and cathepsin K, as well as TRAP histochemical staining. These findings suggest that liquid PRF holds a potent in vitro heat-sensitive anti-inflammatory activity in macrophages that goes along with an inhibition of osteoclastogenesis.

Analysis of osseous tissue temperature during preparation of recipient bed for cylindrical implants

In the early 21st century, robot-assisted dental implant surgery became a popular alternative to classic implant placement protocols. Postoperative complications are often provoked by poor compliance with surgical guidelines for implant placement, resulting in the overheating of the osteotomy site. The aim of this study was to measure the temperature of osseous tissue at the dental implant site during classic and robot-assisted dental implant placement performed at different cooling modes. Avital skeletonized mandibles of Vietnamese pot-bellied pigs were used as an experimental model. The recipient bed was prepared following the classic surgical protocol. Three cooling modes were tested: no irrigation, irrigation with sterile saline at 25–30 ml/min and standard 75 ml/min irrigation recommended by the standard surgical protocol. The temperature of the isotonic solution was 25 °С. The study showed that both classic and robot-assisted dental implant placement techniques are safe if there is sufficient irrigation and good compliance with the surgical protocol.

Saliva enhances infection of gingival fibroblasts by herpes simplex virus 1

Oral herpes is a highly prevalent infection caused by herpes simplex virus 1 (HSV-1). After an initial infection of the oral cavity, HSV-1 remains latent in sensory neurons of the trigeminal ganglia. Episodic reactivation of the virus leads to the formation of mucocutaneous lesions (cold sores), but asymptomatic reactivation accompanied by viral shedding is more frequent and allows virus spread to new hosts. HSV-1 DNA has been detected in many oral tissues. In particular, HSV-1 can be found in periodontal lesions and several studies associated its presence with more severe periodontitis pathologies. Since gingival fibroblasts may become exposed to salivary components in periodontitis lesions, we analyzed the effect of saliva on HSV-1 and -2 infection of these cells. We observed that human gingival fibroblasts can be infected by HSV-1. However, pre-treatment of these cells with saliva extracts from some but not all individuals led to an increased susceptibility to infection. Furthermore, the active saliva could expand HSV-1 tropism to cells that are normally resistant to infection due to the absence of HSV entry receptors. The active factor in saliva was partially purified and comprised high molecular weight complexes of glycoproteins that included secretory Immunoglobulin A. Interestingly, we observed a broad variation in the activity of saliva between donors suggesting that this activity is selectively present in the population. The active saliva factor, has not been isolated, but may lead to the identification of a relevant biomarker for susceptibility to oral herpes. The presence of a salivary factor that enhances HSV-1 infection may influence the risk of oral herpes and/or the severity of associated oral pathologies.

[The level of bone metabolism in patients with dental implants]

The aim of the study was to determine the activity of alkaline phosphatase (AP), tartrate-resistant acid phosphatase (TRAP) and osteocalcin in oral fluid (OF) in patients with dental implants. Dental intraosseous implantation was performed in 164 patients, aged 45 to 60 years (mean age 54.6±4.17 years), 78 (47.6%) males and 86 (52.4%) females. In 75.6% of patients more than 3 teeth were absent. A total of 641 screw intraosseous implants of the MIS system were installed. Studies were performed prior to implant placement, at 7, 14, 21 days and 3 and 6 months. The control group consisted of 20 volunteers of comparable age, 9 (45.0%) males and 11 (55.0%) females. An increased activity of AP and TPAP was revealed, but the activity change of AP in comparison with the control group was not statistically significant. Activity of TRAP in patients before implantation was higher than in controls by 40.5% (p<0.05) in group without complications and by 61.9% (p<0.05) in patients with mucositis. After implantation, the activity of TPAP remained elevated for 6 months, the maximum activity was observed after 14 days and was 3 times higher than at baseline (p<0.01). The amount of osteocalcin increased, especially in the complicated course after the implantation. The highest values of osteocalcin were observed 14 days after implantation. Determination of the activity of TPAP in the OF after implantation can be used as an indicator of the state of bone metabolism.