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Background Micro-RNAs (miRNAs) have been reported to play an important role during orthodontic tooth movement (OTM) through the regulation of periodontal soft and hard tissue homeostasis and functions. The aim of the present study was to assess the effects of miRNAs on OTM and to evaluate possible predictors that influenced the overall OTM amount at a 3-month follow-up. Methods Through a split-mouth design, 21 healthy patients (mean age 13.2 ± 1.8 years) were enrolled in the present study. Clinical parameters and gingival crevicular fluid (GCF) sampling were performed on both compression and tension sides of a random canine to be distalized (test groups) at baseline and at 1 h, 1 day, 1 month and at 3-month after OTM, while the contralateral canine served as a control group. miRNAs − 7a-3p, -7a-2-3p, -7a-5p, -21-3p, -21-5p, -100-3p, -100-5p, -125b-2-3p, -125b-5p, -200b-3p, and − 200b-5p expression was analyzed using a real-time quantitative polymerase chain reaction (RT-PCR). Data were analyzed to assess miRNAs change following OTM. Spearman test, two-way ANOVA and a multivariate regression model were established to evaluate the correlation among miRNAs and clinical parameters and to explore possible predictors of OTM amount at 3-month follow-up. Results At 3-month follow-up, there was an increase of miRNA-7a-2-3p, -21-5p, -100-5p, a decrease of miRNA-125b-5p, 200b-3p and − 200b-5p in the compression side and an increase of miRNA-7a-3p, 100-5p in the tension side ( p  < 0.05). The two-way ANOVA revealed that OTM determined, on the compression side, a significant upregulation on miRNA-7a-3p ( p  = 0.017), -7a-2-3p ( p  = 0.023), -21-5p ( p  = 0.007), -100-5p ( p  = 0.025) and a significant downregulation of miRNA-125b-2-3p ( p  = 0.019) and − 200b-5p ( p  = 0.017). The multivariate model highlighted that high baseline miRNA-7a2-3p ( p  = 0.025), -21-5p ( p  = 0.014), -200b-3p ( p  = 0.041), young age ( p  = 0.042), lower bleeding on probing (BOP) ( p  = 0.021) and miRNA-125b-2-3p ( p  = 0.021) levels were significant predictors of OTM at 3-month follow-up. Conclusions In the present study, OTM significantly impacted the expression of the miRNAs analyzed, in both the tension and compression side of traction tooth at 3-month follow-up. High baseline miRNA-7a2-3p, -21-5p, -200b-3p, and lower miRNA-125b-2-3p, together with younger age and lower BOP, were significant predictors of OTM amount at 3-month follow-up. Trial registration ClinicalTrials.gov NCT06023433 (retrospectively registered).

Periodontitis affects billions of people worldwide. To address relationships of periodontal niche cell types and microbes in periodontitis, we generated an integrated single-cell RNA sequencing (scRNAseq) atlas of human periodontium (34-sample, 105918-cell), including sulcular and junctional keratinocytes (SK/JKs). SK/JKs displayed altered differentiation states and were enriched for effector cytokines in periodontitis. Single-cell metagenomics revealed 37 bacterial species with cell-specific tropism. Fluorescence in situ hybridization detected intracellular 16   S and mRNA signals of multiple species and correlated with SK/JK proinflammatory phenotypes in situ. Cell-cell communication analysis predicted keratinocyte-specific innate and adaptive immune interactions. Highly multiplexed immunofluorescence (33-antibody) revealed peri-epithelial immune foci, with innate cells often spatially constrained around JKs. Spatial phenotyping revealed immunosuppressed JK-microniches and SK-localized tertiary lymphoid structures in periodontitis. Here, we demonstrate impacts on and predicted interactomics of SK and JK cells in health and periodontitis, which requires further investigation to support precision periodontal interventions in states of chronic inflammation. Here, Easter et al. generate a single-cell atlas of human periodontium including sulcular and junctional keratinocytes. Cell-cell communication analysis is used to predict keratinocyte-specific immune cell interactions.

Periodontal tissue is a distinctive tissue structure composed three-dimensionally of cementum, periodontal ligament (PDL) and alveolar bone. Severe periodontal diseases cause fundamental problems for oral function and general health, and conventional dental treatments are insufficient for healing to healthy periodontal tissue. Cell sheet technology has been used in many tissue regenerations, including periodontal tissue, to transplant appropriate stem/progenitor cells for tissue regeneration of a target site as a uniform tissue. However, it is still difficult to construct a three-dimensional structure of complex tissue composed of multiple types of cells, and the transplantation of a single cell sheet cannot sufficiently regenerate a large-scale tissue injury. Here, we fabricated a three-dimensional complex cell sheet composed of a bone-ligament structure by layering PDL cells and osteoblast-like cells on a temperature responsive culture dish. Following ectopic and orthotopic transplantation, only the complex cell sheet group was demonstrated to anatomically regenerate the bone-ligament structure along with the functional connection of PDL-like fibers to the tooth root and alveolar bone. This study represents successful three-dimensional tissue regeneration of a large-scale tissue injury using a bioengineered tissue designed to simulate the anatomical structure.

This 12-week prospective, randomized, double-blind, two-center trial evaluated the impact of a microcrystalline zinc hydroxyapatite (mHA) dentifrice on plaque formation rate (PFR) in chronic periodontitis patients. We hypothesized that mHA precipitates cause delayed plaque development when compared to a fluoridated control (AmF/SnF2), and therefore would improve periodontal health. At baseline and after 4 and 12 weeks, PFR and other clinical and microbiological parameters were recorded. Seventy periodontitis patients received a mHA or AmF/SnF2 dentifrice as daily oral care without hygiene instructions. Four weeks after baseline, participants received full mouth debridement and continued using the dentifrices for another 8 weeks. Primary outcome PFR did not change statistically significantly from baseline to weeks 4 and 12, neither in mHA (n = 33; 51.7±17.2% vs. 48.5±16.65% vs. 48.4±19.9%) nor in AmF/SnF2-group (n = 34; 52.3±17.5% vs. 52.5±21.3% vs. 46.1±21.8%). Secondary clinical parameters such as plaque control record, gingival index, bleeding on probing, and pocket probing depth improved, but between-group differences were not statistically significant. Microbiological analyses showed similar slight decreases in colony-forming units in both groups. In patients with mild-to-moderate periodontitis, periodontal therapy and use of a mHA-or AmF/SnF2 dentifrice without instructions induced comparable improvements in periodontal health but did not significantly reduce the PFR. ClincalTrials.gov NCT02697539.

Key Points Periodontitis is intimately associated with a characterized polymicrobial dental-plaque community. However, the species and mechanisms that result in disease remain unclear. The main protective mechanism of the periodontium is the orchestrated expression of select innate host defence mediators. These mediators reduce the microbial load on the epithelial-cell surface by both neutralization and bacterial killing. The main mechanism of bone loss in periodontitis seems to be mediated by the host response to a unique microbial consortium. However, most of the bacteria found in the dental-plaque biofilm are capable of initiating inflammatory cytokine responses, rendering identification of key indicators of disease difficult. Examination of gingival crevicular fluid from clinically healthy sites revealed that this fluid contains cytokines that may induce inflammation. However, the levels of these cytokines in healthy sites are lower than levels in diseased sites, indicating that a disruption of host homeostasis contributes to disease. Extensive analysis of dental-plaque bacteria associated with disease has revealed three bacterial species that display strong associations both with each other and diseased sites. Evidence indicates that these bacteria, designated the 'red-complex' species, may interfere with the protective barrier of the host innate defence response. Red-complex bacteria maybe key species in the pathogenic dental-plaque biofilm. By modulating the innate host defence barrier, they facilitate the growth of other members of the dental-plaque biofilm. The increase in the number and types of bacterial species that occupy the gingival crevice present multiple opportunities to disrupt host homeostasis programmes. Physical removal of the dental-plaque biofilm remains the most effective treatment. However, vaccine strategies targeting red-complex bacteria have also shown efficacy in animal models of disease. The ability to attenuate bone loss by the inhibition of a single bacterial species is consistent with the key species concept. A novel pro-resolving mediator shows promise as an effective periodontitis treatment in pre-clinical studies. A compound that restores host homeostasis is consistent with the theory that an important component of the disease is disruption of host homeostasis programmes. The health of the periodontium, the tissue surrounding the teeth, is a delicate balance between host factors and bacterial stimulation. Richard Darveau discusses the factors that are involved in maintaining a healthy periodontium and how pathogens shift the balance to induce disease. Periodontitis, or gum disease, affects millions of people each year. Although it is associated with a defined microbial composition found on the surface of the tooth and tooth root, the contribution of bacteria to disease progression is poorly understood. Commensal bacteria probably induce a protective response that prevents the host from developing disease. However, several bacterial species found in plaque (the 'red-complex' bacteria: Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola ) use various mechanisms to interfere with host defence mechanisms. Furthermore, disease may result from 'community-based' attack on the host. Here, I describe the interaction of the host immune system with the oral bacteria in healthy states and in diseased states.

The enamel matrix derivative (EMD) contains hundreds of peptides in different levels of proteolytic processing that may provide a range of biological effects of importance in wound healing. The aim of the present study was to compare the effect of EMD and its fractions on the cytokine profiles from human gingival fibroblasts in vitro and in gingival crevicular fluid (GCF) in a randomized controlled split-mouth clinical study (n = 12). Levels of cytokines in cell culture medium and in GCF were measured by Luminex over a 2-week period. In the clinical study, levels of pro-inflammatory cytokines and chemokines were increased, whereas the levels of transforming growth factor-α (TGF-α) and platelet-derived growth factor-BB (PDGF-BB) were reduced. The in vitro study showed that EMD and its high and low molecular weight fractions reduced the secretion of pro-inflammatory cytokines and chemokines compared to untreated cells. EMD had an effect on levels of cytokines related to fibroplasia, angiogenesis, inflammation and chemotaxis both in vitro and in vivo , however, the anti-inflammatory effect induced by EMD observed in the in vitro study could not be confirmed clinically.

The aim of the study was to clarify whether orthodontic forces and periodontitis interact with respect to the anti-apoptotic molecules superoxide dismutase 2 (SOD2) and baculoviral IAP repeat-containing protein 3 (BIRC3). SOD2, BIRC3, and the apoptotic markers caspases 3 (CASP3) and 9 (CASP9) were analyzed in gingiva from periodontally healthy and periodontitis subjects by real-time PCR and immunohistochemistry. SOD2 and BIRC3 were also studied in gingiva from rats with experimental periodontitis and/or orthodontic tooth movement. Additionally, SOD2 and BIRC3 levels were examined in human periodontal fibroblasts incubated with Fusobacterium nucleatum and/or subjected to mechanical forces. Gingiva from periodontitis patients showed significantly higher SOD2, BIRC3, CASP3, and CASP9 levels than periodontally healthy gingiva. SOD2 and BIRC3 expressions were also significantly increased in the gingiva from rats with experimental periodontitis, but the upregulation of both molecules was significantly diminished in the concomitant presence of orthodontic tooth movement. In vitro, SOD2 and BIRC3 levels were significantly increased by F. nucleatum, but this stimulatory effect was also significantly inhibited by mechanical forces. Our study suggests that SOD2 and BIRC3 are produced in periodontal infection as a protective mechanism against exaggerated apoptosis. In the concomitant presence of orthodontic forces, this protective anti-apoptotic mechanism may get lost.

The periodontium hosts diverse populations of mesenchymal stem and progenitor cells that are essential for maintaining homeostasis and driving regeneration. These include cells derived from the periodontal ligament, gingiva, and apical papilla. In health and disease, the fate and function of these stem cell populations are shaped by their microenvironment, particularly by inflammatory signals and their resolution. Chronic inflammation, such as that observed in periodontitis, disrupts the regenerative capabilities, impairing stem cell function and biasing differentiation pathways. Inflammation resolution is an active, instructive process that can restore stem cell plasticity and re-establish regenerative potential. Specialized pro-resolving lipid mediators and immune-regulatory cell types play a central role in this reprogramming. We explore how inflammation and its resolution actively shape the behavior of multiple stem cell compartments in the periodontium, highlight the emerging role of spatially organized immunoregulation, and discuss how these insights may be leveraged to develop regenerative therapies for oral and mucosal tissues. We focused on how inflammatory and resolution signals modulate osteogenic programs in periodontal MSCs and contrast these responses with those in bone marrow–derived MSCs, highlighting source-dependent differences in inflammatory susceptibility and regenerative potential.

Periodontal disease is one of the most common infectious diseases in adults and is characterized by the destruction of tooth-supporting tissues. Mesenchymal stem cells (MSCs) comprise the mesoderm-originating stem cell population, which has been studied and used for cell therapy. However, because of the lower rate of cell survival after MSC transplantation in various disease models, paracrine functions of MSCs have been receiving increased attention as a regenerative mechanism. The aim of this study was to investigate the regenerative potential of transplanted conditioned medium (CM) obtained from cultured periodontal ligament stem cells (PDLSCs), the adult stem cell population in tooth-supporting tissues, using a rat periodontal defect model. Cell-free CM was collected from PDLSCs and fibroblasts, using ultrafiltration and transplanted into surgically created periodontal defects. Protein content of CM was examined by antibody arrays. Formation of new periodontal tissues was analyzed using microcomputed tomography and histological sections. PDLSC-CM transplantation enhanced periodontal tissue regeneration in a concentration-dependent manner, whereas fibroblast-CM did not show any regenerative function. Proteomic analysis revealed that extracellular matrix proteins, enzymes, angiogenic factors, growth factors and cytokines were contained in PDLSC-CM. Furthermore, PDLSC-CM transplantation resulted in the decreased mRNA level of tumor necrosis factor-α (TNF-α) in healing periodontal tissues. In addition, we found that PDLSC-CM suppressed the mRNA level of TNF-α in the monocyte/macrophage cell line, RAW cells, stimulated with IFN-γ. Our findings suggested that PDLSC-CM enhanced periodontal regeneration by suppressing the inflammatory response through TNF-α production, and transplantation of PDLSC-CM could be a novel approach for periodontal regenerative therapy.

Dental follicle stem cells (DFSCs) have been verified to promote periodontal regeneration in an inflammatory microenvironment. When coping with inflammatory stimulation, DFSCs highly express periostin, a bioactive molecule closely related to periodontal homeostasis. It is worth exploring whether and how periostin plays a role in the promotion of periodontal regeneration by DFSCs. By tracking the fate of DFSCs, it was found that DFSCs significantly contributed to periodontal regeneration in rat periodontal defects while they had a low survival rate. They highly expressed periostin and improved the immune microenvironment in the defect area, especially via the recruitment and reprogramming of macrophages. Silencing periostin attenuated the effects of DFSCs in promoting periodontal regeneration and regulating macrophages. Recombinant human periostin (rhPeriostin) could not only directly promote macrophage reprogramming through the integrin αM/phosphorylated extracellular signal-regulated kinase (p-Erk)/Erk signaling pathway, but it also exhibited the potential to promote periodontal regeneration in rats when loaded in a collagen matrix. These results indicated that periostin is actively involved in the process by which DFSCs promote periodontal regeneration through the regulation of macrophages and is a promising molecular agent to promote periodontal regeneration. This study provides new insight into the mechanism by which DFSCs promote periodontal regeneration and suggests a new approach for periodontal regeneration therapy.