Journal of dental research最新文献

Pulpitis is characterized by inflammation within dental pulp tissue, primarily triggered by bacterial infection. Hypoxia-inducible factor-1α (HIF-1α), a key transcriptional regulator, is stabilized under the hypoxic conditions associated with pulpitis. This review examines the roles and molecular mechanisms of HIF-1α in the pathogenesis and progression of pulpitis. Hypoxia in pulpitis prevents the degradation of HIF-1α, leading to its elevated expression. Furthermore, lipopolysaccharide from invading bacteria upregulates HIF-1α transcription through nuclear factor kappa B and mitogen-activated protein kinase pathways. HIF-1α regulates immunity and pulp remodeling in a stage-dependent manner by controlling various cytokines. During the inflammation stage, HIF-1α promotes recruitment of neutrophils and enhances their bactericidal effects by facilitating neutrophil extracellular trap release and M1 macrophage polarization. Concurrently, HIF-1α contributes to programmed cell death by increasing mitophagy. In the proliferation stage, HIF-1α stimulates immune responses involving T cells and dendritic cells. In the remodeling stage, HIF-1α supports angiogenesis and pulp-dentin regeneration. However, excessive pulpitis-induced hypoxia may disrupt vascular dynamics within the pulp chamber. This disruption highlights a critical threshold for HIF-1α, beyond which its effects might accelerate pulp necrosis. Overall, HIF-1α plays a central role in regulating immunity and tissue remodeling during pulpitis. A comprehensive understanding of the physiological and pathological roles of HIF-1α is essential for the advancement of effective strategies to manage irreversible pulpitis.

While Lactiplantibacillus plantarum has shown promise against cariogenic pathogens, its in vivo effects on caries prevention remain unexplored. This study used a rat model to investigate the effect of L. plantarum early-life oral inoculation on oral and gut microbiomes, host immune responses, and serum metabolites. Forty 14-day Sprague-Dawley rat pups were randomly allocated into 5 groups: (1) blank control, (2) L. plantarum colonization alone, (3) Streptococcus mutans and Candida albicans co-colonization, (4) L. plantarum precolonization before S. mutans and C. albicans exposure, and (5) 2-wk treatment of L. plantarum after S. mutans and C. albicans exposure. Dynamic colonization of L. plantarum, S. mutans, and C. albicans in saliva and plaque was assessed using a culture-dependent method. Saliva, plaque, and fecal microbiomes were assessed using 16S ribosomal RNA gene sequencing. Caries scoring was performed using Keyes' scoring system and microcomputed tomography. Serum metabolite and immune markers were assessed through liquid chromatography tandem mass spectrometry untargeted metabolomics and multiplex immune profiling. We found that 3-d L. plantarum inoculation established stable L. plantarum colonization in the oral cavity of young rats. Inoculation timing of L. plantarum was critical for caries prevention. L. plantarum precolonization significantly reduced caries lesions compared with the S. mutans and C. albicans group, whereas 2 wk of postexposure treatment did not demonstrate a protective effect. L. plantarum precolonization led to distinct microbial shifts in saliva, plaque, and gut microbiomes, with an increased abundance of beneficial bacteria, such as Streptococcus azizii, Bifidobacterium animalis, Faecalibaculum rodentium, and Allobaculum stercoricanis, and a decrease in S. mutans. L. plantarum preinoculation also influenced metabolic profiles, with 1 metabolite upregulated and 24 downregulated, although immune marker differences were minimal. In conclusion, L. plantarum oral colonization before host exposure to oral cariogenic pathogens effectively reduced caries and modulated the profile of oral and gut microbiomes and serum metabolic profile.

Amelogenesis, the process of enamel formation, is tightly regulated and essential for producing the tooth enamel that protects teeth from decay and wear. Disruptions in amelogenesis can result in amelogenesis imperfecta, a group of genetic conditions characterized by defective enamel, including enamel hypoplasia, marked by thin or underdeveloped enamel. Mutations in the KMT2D (MLL4) gene, which encodes histone H3 lysine 4 methyltransferase, are associated with Kabuki syndrome, a developmental disorder that can involve dental anomalies such as enamel hypoplasia. However, the specific role of KMT2D in amelogenesis remains poorly understood. To address this gap, we generated a conditional knockout (cKO) mouse model with ectoderm-specific deletion of Kmt2d (Krt14-Cre;Kmt2d^fl/fl, or Kmt2d-cKO) and characterized the resulting enamel defects using gross, radiographic, histologic, cellular, and molecular analyses. Micro-computed tomography and scanning electron microscopy revealed that adult Kmt2d-cKO mice exhibited 100% penetrant amelogenesis imperfecta, characterized by hypoplastic and hypomineralized enamel, partially phenocopying human Kabuki syndrome. Additionally, Kmt2d-cKO neonates developed molar tooth germs with subtle cusp shape alterations and mild delays in ameloblast differentiation at birth. RNA sequencing analysis of the first molar tooth germ at birth revealed that 33.7% of known amelogenesis-related genes were significantly downregulated in the Kmt2d-cKO teeth. Integration with KMT2D CUT&RUN sequencing results identified 8 overlapping genes directly targeted by KMT2D. Reanalysis of a single-cell RNA sequencing data set in the developing mouse incisors revealed distinct roles for these genes in KMT2D-regulated differentiation across various cell subtypes within the dental epithelium. Among these genes, Satb1 and Sp6 are likely direct targets involved in the differentiation of preameloblasts into ameloblasts. Taken together, we propose that KMT2D plays a crucial role in amelogenesis by directly activating key genes involved in ameloblast differentiation, offering insights into the molecular basis of enamel development and related dental pathologies.

Triggering receptor expressed on myeloid cells 2 (TREM2) is an immune receptor that plays a vital role in innate immune responses. This study aims to investigate the effect of TREM2 on synovial barrier homeostasis and synovitis during temporomandibular joint osteoarthritis (TMJOA). The expression level of TREM2 is decreased in the synovium of both patients with TMJOA and a mouse model of TMJOA, accompanied by synovial barrier breakdown. TREM2 overexpression inhibits the macrophage inflammatory response ex vivo and relieves synovial inflammation, cartilage degeneration, and synovial barrier destruction in monosodium iodoacetate-induced TMJOA mice. RNA-seq analysis reveals that Siglec1 serves as a downstream signal that is downregulated after TREM2 activation. Further in vivo and in vitro experiments demonstrate that rhSiglec1 treatment promotes the synthesis and release of inflammatory cytokines, such as interleukin-6 and RANTES, in macrophages and reverses the alleviation effect of TREM2 activation on TMJOA synovial barrier disorders, synovial inflammation, cartilage degradation, and bone destruction. Overall, this study verifies that TREM2 activation alleviates TMJOA pathology by maintaining synovial barrier homeostasis and inhibiting synovial inflammation. These findings provide new insight into the mechanism of TREM2 in the pathogenesis of TMJOA.

Palmitoylation is recognized as a prevalent posttranslational modification of proteins, which is highlighted in recent studies as a key player in regulating protein stability, subcellular localization, membrane transport, and other cellular biological processes. However, its role in peri-implant osteogenesis under type 2 diabetes mellitus (T2DM) remains unclear. During this study, the in vitro high-glucose model based on MC3T3-E1 cells demonstrated that a high-glucose environment in vitro markedly inhibited osteoblasts proliferation and osteogenesis; meanwhile, ZDHHC9 emerged as a significantly upregulated protein. Then, Zdhhc9 knockdown improved the dysfunction of osteoblasts and peri-implant osteogenesis of T2DM mice. In addition, co-immunoprecipitation and fluorescence co-localization analysis revealed an interaction between ZDHHC9 and cyclic guanosine monophosphate (GMP)-dependent protein kinase G 1 (PKG1), and silencing of Prkg1 prevented the improvement in osteoblasts with Zdhhc9 knockdown. Furthermore, we verified that Zdhhc9 knockdown and Prkg1 silencing altered the distance between the endoplasmic reticulum and mitochondria and the expression of mitochondria-associated endoplasmic reticulum membranes (MAMs)-related proteins in osteoblasts. Collectively, our data show that ZDHHC9 could regulate MAMs through palmitoylation of PKG1 to induce osteoblast dysfunction in T2DM. ZDHHC9 might become a novel therapeutic target for peri-implant osteogenesis in diabetes patients.

Orthodontic root resorption (ORR) is a common yet significant complication of orthodontic treatment, largely driven by interactions between periodontal ligament cells (PDLCs) and M1 macrophages. Despite the clinical relevance of ORR, the role of mechanosensitive ion channels in PDLC-mediated ORR and the underlying mechanisms regulating inflammatory cell recruitment remain poorly understood. Here, we identified PIEZO1 as a critical mechanosensitive ion channel that modulates monocyte recruitment and ORR. Using in vivo models treated with the PIEZO1 activator Yoda1 and inhibitor AAV-shPiezo1, we demonstrated that PIEZO1 activation promoted the recruitment of Ly6C^hi inflammatory monocytes and exacerbated ORR. In contrast, PIEZO1 inhibition attenuated ORR and the accumulation of M1 macrophages. Mechanistically, PIEZO1 positively regulated the C-X-C motif chemokine 12 (CXCL12) and its receptor, C-X-C chemokine receptor type 4 (CXCR4). Blocking the CXCL12/CXCR4 axis using the CXCR4 antagonist AMD3100 significantly alleviated ORR, reversed M1 macrophage accumulation, and mitigated the recruitment of CD11b⁺Ly6C^hi monocytes. Transwell migration assays with application of the PIEZO1 activator Yoda1 and PIEZO1 inhibitor GsMTX4 consistently confirmed the PIEZO1/CXCL12/CXCR4 axis as a key driver of PDLC-monocyte interactions. Notably, PIEZO1 overactivation was linked to excessive IL-6 production, and IL-6 deficiency inhibited the activation of PIEZO1 induced by Yoda1, leading to attenuation of ORR, M1 macrophage accumulation, and CXCL12/CXCR4 axis activation. Collectively, these findings reveal PIEZO1 in PDLCs as a pivotal modulator of inflammatory monocyte recruitment via the CXCL12/CXCR4 axis in ORR, with IL-6 playing an essential role in PIEZO1 activation. This study provides new insights into the molecular crosstalk between PDLCs and macrophages, offering potential therapeutic targets for mitigating ORR in orthodontic patients.

It is common to encounter discrepancies between in vitro and in vivo studies, particularly when assessing the antibiofilm efficacy of dental materials. Typically, dental materials are tested in a closed system where fresh nutrients are not replenished, the test conditions are static, and the same planktonic bacteria persist. However, real environments are characterized by the continuous supply of fresh nutrients, dynamic saliva flow, and the periodic removal of planktonic bacteria through swallowing. To address these differences, we used an open system approach using microfluidic chips that simulate the nutrient and fluid flow conditions of the mouth. This setup enables the spatiotemporal development of biofilms, facilitates real-time observation, and provides deeper insights into the biofilm formation and removal processes. Photocatalytic dental materials are particularly suitable for use with microfluidic chips, as these devices allow real-time tracking of biofilm dynamics, both with and without light exposure. Nitrogen-doped titanium dioxide effectively produces reactive oxygen species (ROS) under visible light conditions, even when embedded in a resin matrix. These ROS have been shown to inhibit Enterococcus faecalis biofilms. The evaluation of the photocatalytic effects of dental materials using microfluidic chips showed that both new and established biofilms were disrupted by ROS production. ROS weakens the interface between the biofilm and dental material, allowing the biofilm mass to be removed by fluid flow. Furthermore, the open system provided by microfluidic chips demonstrated higher accuracy in evaluating antibiofilm efficiency than the conventional system did. Thus, the developed microfluidic chip is a novel and promising tool for assessing antibiofilm properties, with potential applications in various fields.

Extracellular DNA (eDNA) is one of the core components of the extracellular matrix (ECM) in biofilms and provides attachment sites for microbes and other ECM components. However, little is known about the functions and underlying mechanisms of eDNA in the cariogenicity of dental plaque biofilms. A recent study demonstrated that conformational diversity of eDNA exists in biofilms, and the transition of eDNA from right-handed (B-DNA) to left-handed (Z-DNA) is associated with the structural stability and pathogenicity of biofilms. Caries-related biofilm is a complex multispecies microenvironment. The presence and biological function of the conformational transition of eDNA within this biofilm have not been previously reported. In this study, we found that extracellular Z-DNA is widely present in carious tissues and cariogenic biofilm, especially Streptococcus mutans, indicating its possible role in the occurrence and activity of dental caries. The content of extracellular Z-DNA showed species heterogeneity. The modulation of Z-DNA formation affected the level of extracellular polysaccharide. Increased formation of Z-DNA substantially strengthened the cariogenicity of the biofilm by increasing DNase resistance, structural density, and acid production. These insights provide a new perspective to understand the underlying function of the conformation transition of eDNA in promoting carious lesions, as well as a possible anti-biofilm strategy targeting extracellular Z-DNA.

Periodontitis has recently been recognized as an inflammatory disease caused by oxidative stress, with mitochondrial dysfunction being a key factor leading to oxidative stress. PTEN-induced kinase 1 (PINK1) is an essential protein for mitochondrial quality control, which protects cells from oxidative stress by inducing mitophagy to degrade damaged mitochondria, but its role in periodontitis has not been elucidated. This study aimed to explore the contribution and underlying mechanisms of Pink1 in regulating the differentiation and function of osteoclasts during periodontitis. Here we observed a significant downregulation of PINK1 expression in periodontitis-affected tissues. Then we constructed a periodontitis model in mice with fluorescently labeled mononuclear/macrophages, and the results showed that as the modeling time extended, the alveolar bone destruction gradually worsened and was accompanied by gradually decreased Pink1 expression in osteoclasts and a significantly increased osteoclast number. In vitro experiments further demonstrated a negative correlation between Pink1 and osteoclast differentiation. In addition, alveolar bone destruction in the Pink1 knockout mice was significantly more advanced than that in the littermate wild type mice after ligature-induced periodontitis and enhanced osteoclastogenesis and bone-resorptive capacity in vitro. RNA-sequencing analysis and in vitro validation revealed that the absence of Pink1 led to a decrease in oxidative phosphorylation levels and an enhancement of calcium-mediated signaling, specifically the calcineurin-NFATc1 pathway, via an intracellular calcium source. Further mechanistic studies found that the deficiency of Pink1 inhibited mitophagy but strengthened mitochondrial-endoplasmic reticulum coupling, which, by promoting the interaction of Mfn2-IP3R-VDAC1 proteins, increased the concentration of mitochondrial calcium ions, thereby triggering more active osteoclast differentiation. The aforementioned process can be reversed by the IP3R channel inhibitor Bcl-XL. These findings unveiled that Pink1 was involved in osteoclast differentiation by regulating mitochondrial calcium transport mediated by mitochondria-associated endoplasmic reticulum membranes, providing a new theoretical basis for the pathogenesis and treatment of periodontitis.

Periodontal and peri-implant diseases are a significant public health problem worldwide, resulting in the destruction of the supporting bone. These bone defects can cause esthetic problems, increased relapse rate, and eventually tooth loss. The etiology of periodontal disease involves an influx of innate immune cells (neutrophils and monocytes) and upregulation of local inflammatory cytokines in the gingiva. Biodegradable polymeric nanoparticles are an inexpensive, safe, and effective means of preventing innate immune activation by bacterial biofilms. We therefore hypothesize that this technology is a potential means of managing periodontal disease. Polylactic acid (PLA) particles were fabricated using an oil-in-water emulsion and used as a therapy in ligature-induced periodontitis and peri-implantitis. Mice were treated daily with nanoparticles or saline control through intravenous injection for 5 or 7 d. Bone loss and quality were characterized using micro-computed tomography and histology, and immune cell infiltrate was characterized by flow cytometry and enzyme-linked immunosorbent assay. PLA particle therapy prevented bone loss in both periodontitis and peri-implantitis. Particle treatment was associated with decreased osteoclast activation. Flow cytometry showed particles were mainly taken up by macrophages and limited inflammatory monocyte recruitment to the ligature site. In vitro evaluation of particle therapy demonstrated the inhibition of toll-like receptor activation during particle treatment. These results extended to monocytes that had been presensitized by titania nanoparticles. Taken together, the results of these experiments demonstrated that cargo-less PLA particle therapy may be a safe, cost-effective therapy to manage inflammatory bone loss in periodontal disease.