Homeobox protein MSX‐1 inhibits expression of bone morphogenetic protein 2, bone morphogenetic protein 4, and lymphoid enhancer‐binding factor 1 via Wnt/β‐catenin signaling to prevent differentiation of dental mesenchymal cells during the late bell stage

Homeobox protein MSX‐1 (hereafter referred to as MSX‐1) is essential for early tooth‐germ development. Tooth‐germ development is arrested at bud stage in Msx1 knockout mice, which prompted us to study the functions of MSX‐1 beyond this stage. Here, we investigated the roles of MSX‐1 during late bell stage. Mesenchymal cells of the mandibular first molar were isolated from mice at embryonic day (E)17.5 and cultured in vitro. We determined the expression levels of β‐catenin, bone morphogenetic protein 2 (Bmp2), Bmp4, and lymphoid enhancer‐binding factor 1 (Lef1) after knockdown or overexpression of Msx1. Our findings suggest that knockdown of Msx1 promoted expression of Bmp2, Bmp4, and Lef1, resulting in elevated differentiation of odontoblasts, which was rescued by blocking the expression of these genes. In contrast, overexpression of Msx1 decreased the expression of Bmp2, Bmp4, and Lef1, leading to a reduction in odontoblast differentiation. The regulation of Bmp2, Bmp4, and Lef1 by Msx1 was mediated by the Wnt/β‐catenin signaling pathway. Additionally, knockdown of Msx1 impaired cell proliferation and slowed S‐phase progression, while overexpression of Msx1 also impaired cell proliferation and prolonged G1‐phase progression. We therefore conclude that MSX‐1 maintains cell proliferation by regulating transition of cells from G1‐phase to S‐phase and prevents odontoblast differentiation by inhibiting expression of Bmp2, Bmp4, and Lef1 at the late bell stage via the Wnt/β‐catenin signaling pathway.     

Porphyromonas gingivalis induces autophagy in THP‐1‐derived macrophages

Autophagy provides a mechanism for the turnover of cellular organelles and proteins through a lysosome‐dependent degradation pathway and is a possible mechanism in inflammatory disease. Periodontitis is an inflammatory disease caused by periodontal pathogens. Porphyromonas gingivalis, an important periodontal pathogen, activates cellular autophagy to provide a replicative niche while suppressing apoptosis in endothelial cells. However, the molecular basis for a causal relationship between P. gingivalis and autophagy is unclear. This research examines the involvement of P. gingivalis in autophagy through light chain 3 (LC3) and autophagic proteins, and the role of P. gingivalis‐induced autophagy in the clearance of P. gingivalis and inflammation. To investigate the molecular mechanism of autophagy induced by P. gingivalis, PMA‐differentiated THP‐1‐derived macrophages were infected with live P. gingivalis. The P. gingivalis increased the formation of autophagosomes in a multiplicity of infection‐dependent manner, as well as autophagolysosomes. Porphyromonas gingivalis activated LC3‐I/LC3‐II conversion and increased the conjugation of autophagy‐related 5 (ATG5) –ATG12 and the expression of Beclin1. The expressions of Beclin1, ATG5–ATG12 conjugate, and LC3‐II were significantly inhibited by the presence of 3‐methyladenine, an autophagy inhibitor. Interestingly, 3‐methyladenine increased the survival of P. gingivalis and proinflammatory cytokine interleukin‐1β production. The data indicate that P. gingivalis induces autophagy in PMA‐differentiated THP‐1‐derived macrophages and in turn, macrophages eliminate P. gingivalis through an autophagic response, which can lead to the restriction of an excessive inflammatory response by downregulating interleukin‐1β production. The induction of autophagy by P. gingivalis may play an important role in the periodontal inflammatory process and serve as a target for the development of new therapies.     

Efficacy of stabilisation splint treatment on facial pain – 1‐year follow‐up

The aim of this randomised controlled trial was to assess the efficacy of stabilisation splint treatment on TMD‐related facial pain during a 1‐year follow‐up. Eighty patients were randomly assigned to two groups: splint group (n = 39) and control group (n = 41). The patients in the splint group were treated with a stabilisation splint and received counselling and instructions for masticatory muscle exercises. The controls received only counselling and instructions for masticatory muscles exercises. The outcome variables were the change in the intensity of facial pain (as measured with visual analogue scale, VAS) as well as the patients' subjective estimate of treatment outcome. The differences in VAS changes between the groups were analysed using variance analysis and linear regression models. The VAS decreased in both groups, the difference between the groups being not statistically significant. The group status did not significantly associate with the decrease in VAS after adjustment for baseline VAS, gender, age, length of treatment and general health status. The only statistically significant predicting factor was the baseline VAS, which was also confirmed by the mixed‐effect linear model. After 1‐year follow‐up, 27·6% of the patients in the splint group and 37·5% of the patients in the control group reported ‘very good' treatment effects. The findings of this study did not show stabilisation splint treatment to be more effective in decreasing facial pain than masticatory muscle exercises and counselling alone in the treatment of TMD‐related facial pain over a 1‐year follow‐up.