Inflammation down regulates stromal cell-derived factor 1α in the early phase of pulpitis.

The key to prevent pulp necrosis in the early stage of pulpitis is to promote tissue repair, which begins with cell migration. Stromal cell-derived factor 1α (SDF-1α) has been proven to promote cell migration. Related research has so far concentrated on the biological effects of SDF-1α while its expression in pulpitis is still unclear. We investigated the effect of inflammation on SDF-1α in dental pulp and the underlying regulatory mechanisms. First, rat pulpitis models were established by exposing pulp. SDF-1α was decreased on the 3rd day but increased on the 7th day. Next, lipopolysaccharide from Porphyromonas gingivalis (Pg.LPS) was applied to dental pulp cells (DPCs). Within 24 h, SDF-1α decreased, but after 48 h, it steadily increased. Similarly, SDF-1α expression in human chronic pulpitis tissues was also increased. To investigate the effect of altered SDF-1α on DPC migration, cell supernatants collected following Pg.LPS treatment were utilized to stimulate DPCs, and the number of migrated cells was correlated with changes in SDF-1α secretion. Finally, we explored the regulatory mechanisms of SDF-1α down-regulation in the early phase of pulpitis. Within 24 h, JNK/c-Jun pathway was activated in DPC inflammation. When JNK pathway was suppressed, SDF-1α rose. Furthermore, tumor necrosis factor receptor 2 (TNFR2) and apoptosis signal-regulated kinase-interacting protein 1 (AIP1) were up-regulated. Knockdown of them abolished Pg.LPS-induced activation of JNK and c-Jun(Ser63) and significantly enhanced SDF-1α. Our findings indicated that in the early phase of pulpitis, inflammation suppressed SDF-1α by up-regulating TNFR2 and AIP1, which activated JNK/c-Jun(Ser63) pathway.

Identification of Immune-Related lncRNA Regulatory Network in Pulpitis.

Background: Long noncoding RNAs (lncRNAs) are emerging as critical regulators of various biological processes, including immune regulation. Methods: Due to the critical significance of immunological responses in the development and progression of pulpitis, we used an integrated algorithm to identify immune-related lncRNAs and then examined the lncRNA-immunity regulation network in pulpitis. Before identifying immune-related lncRNAs, the data from GEO datasets were precleaned. ConsensusClusterPlus was used to differentiate immune-related pulpitis subgroups. Enrichment analysis using GO and MSigDB databases was employed to determine the differences in molecular function, cellular component, and biological process between the two pulpitis subtypes. Results: An integrated algorithm was designed to filtrate immune-related lncRNAs accurately. 790 immune-related lncRNAs were found in 17 immunological categories, with 38 of them perturbated in pulpitis. The Cytoscape software was used to visualize the relationship between representative immune regulatory pathways and immune-related lncRNAs. Two immune-related pulpitis subtypes were discovered using differentially expressed immune-related lncRNAs. Subtype 2 has a stronger association with immune-related pathways than subtype 1 does. Conclusions: Our study identified many immune-related lncRNAs and investigated potential lncRNA regulation networks; meanwhile, the molecular subtypes of pulpitis were identified, all of which will be relevant for further research into inflammatory and immunological processes in pulpitis.

Comparative Effects of Concentrated Growth Factors on the Biological Characteristics of Periodontal Ligament Cells and Stem Cells from Apical Papilla.

INTRODUCTION: During cell-free regenerative endodontic therapy, both stem cells from apical papilla (SCAPs) and periodontal ligament cells (PDLCs) are possible cell sources because of their proximity. Nonetheless, the regenerative ability of PDLCs and SCAPs under the induction of concentrated growth factors (CGFs) remains unclear. METHODS: PDLCs and SCAPs were treated with various concentrations of CGF-conditioned medium (CCM). The effects of CCM with or without Porphyromonas gingivalis lipopolysaccharide (LPS) on cell migration, odonto/osteogenic differentiation, and the expression of inflammatory cytokines were assessed. Dentin matrix transplants composed of PDLCs or SCAPs cell sheets coupled with CGF were put subcutaneously in immunocompromised mice for 8 weeks to explore their regenerative characteristics in vivo. RESULTS: CCM dose dependently enhanced the migration, proliferation, and odonto/osteogenic differentiation of PDLCs and SCAPs. CCM alleviated LPS-inhibited odonto/osteogenic differentiation of PDLCs and SCAPs as well as the LPS-induced up-regulation of inflammatory cytokines. In vivo, the newly regenerated tissue and microvessels formed by PDLCs and SCAPs were significantly increased under the induction of CGF. SCAPs mainly regenerated pulp/dentinlike tissues and a large number of microvessels, whereas PDLCs mainly formed bone/cementumlike structures. CONCLUSIONS: Overall, PDLCs excelled in cell proliferation, migration, and osteogenic differentiation, whereas SCAPs outperformed PDLCs in terms of angiogenic and odontogenic differentiation. The biological differences between PDLCs and SCAPs provided a possible theoretical basis for the formation of bone/cementum/periodontal ligament-like tissues after cell-free regenerative endodontic therapy.

Wnt4 regulates bone metabolism through IKK-NF-κB and ROCK signaling under occlusal traumatic periodontitis.

BACKGROUND AND OBJECTIVE: Occlusal trauma is one of the most important local contributing factors of periodontitis. It has been reported that Wnt4, a noncanonical Wnt ligand, can inhibit osteoclast formation and inflammation and promote bone formation in vivo. However, the prospects of Wnt4 application in occlusal trauma and periodontitis have not yet been described. This study aimed to investigate the function and the corresponding mechanism of Wnt4 to regulate bone metabolism in occlusal trauma and periodontitis. MATERIAL AND METHODS: Osteogenic-induced MC3T3-E1 cells were treated with or without Porphyromonas gingivalis lipopolysaccharide (Pg. LPS) under cyclic uniaxial compressive stress. After treatment with mouse recombinant protein Wnt4 (rWnt4), the expression of osteogenic markers and activation of the IKK-NF-κB signaling pathway were evaluated in vitro. To investigate whether Wnt4 can promote osteogenesis via the ROCK signaling pathway, the expression of RhoA was evaluated in vitro. Finally, we evaluated the change in bone quantity and the activation of the IKK-NF-κB and ROCK signaling in mice with occlusal trauma and periodontitis to demonstrate the therapeutic efficacy of rWnt4 injection. RESULTS: Stimulation of traumatic force and Pg. LPS stimulation suppressed the expression of osteoblast markers, but their expression was rescued after rWnt4 treatment in vitro. In addition, the inhibition of the ROCK signaling pathway induced by force loading was reversed when rWnt4 was applied in vitro. Micro-CT, H&E, and TRAP staining of the mandibles showed increased bone loss in the occlusal trauma-aggravated periodontitis group, whereas it was rescued after rWnt4 injection. The expression levels of IκBα and p65 were upregulated in occlusal trauma and periodontitis-bearing mice, whereas the expression levels of Runx2 and RhoA were downregulated. After rWnt4 injection, remarkably upregulation of Runx2 and RhoA expression was observed in occlusal trauma and periodontitis- bearing mice. CONCLUSION: Wnt4 not only inhibits IKK-NF-κB signaling but also activates ROCK signaling to inhibit osteoclast formation and promote bone regeneration in occlusal trauma and periodontitis-bearing mice.

EDTA Promotes the Mineralization of Dental Pulp In Vitro and In Vivo.

INTRODUCTION: Dentin regeneration is one of the main goals of vital pulp treatment in which the biological properties of dental pulp cells (DPCs) need to be considered. In our previous study, we showed that EDTA could enhance the stromal cell-derived factor 1 alpha-induced migration of DPCs. The purpose of this study was to explore the effects of EDTA on the mineralization of dental pulp in vitro and in vivo. METHODS: DPCs were obtained from human premolars or third molars. Alkaline phosphatase assays and alizarin red S staining were used to examine the degree of differentiation and mineralized nodule formation of DPCs. Real-time polymerase chain reaction and Western blot analysis were performed to detect the messenger RNA and protein expressions of mineralization-related markers in DPCs. Extracellular-regulated protein kinase and Smad inhibitors were used to study the roles of these 2 signaling pathways in this process. In addition, pulp exposures were created on 18 premolars of 2 beagle dogs (>12 months) using a high-speed dental handpiece. The experimental group (n = 9) was treated with 12% EDTA for 5 minutes, and the control group (n = 9) was treated with sterile saline for the same duration. Mineral trioxide aggregate was used for direct pulp capping followed by glass ionomer cement sealing. Samples were collected 3 months later, and the regenerated dentin was assessed by micro-computed tomographic and histologic analyses. RESULTS: Exposure to 12% EDTA promoted the activity of alkaline phosphatase, the formation of mineralized nodules, and the messenger RNA and protein expressions of mineralization-related markers in DPCs. Furthermore, the process of 12% EDTA enhancing the differentiation of DPCs was mediated by the extracellular-regulated protein kinase 1/2 signaling pathway and inhibited by the Smad2/3 signaling pathway. In vivo, compared with the control group, more regenerated dentin that had fewer tunnel defects was formed in the 12% EDTA-treated group. CONCLUSIONS: Our results showed that 12% EDTA could promote the mineralization of dental pulp in vitro and in vivo.

Modeling of cancer photothermal therapy using near-infrared radiation and functionalized graphene nanosheets.

Photothermal therapy using near-infrared radiation and local heating agents can induce selective tumor ablation with limited harm to the surrounding normal tissue. Graphene sheets are promising local heating agents because of their strong absorbance of near-infrared radiation. Experimental studies have been conducted to study the heating effect of graphene in photothermal therapy, yet few efforts have been devoted to the quantitative understanding of energy conversion and transport in such systems. Herein, a computational study of cancer photothermal therapy using near-infrared radiation and graphene is presented using a Monte Carlo approach. A three-dimensional model was built with a cancer cell inside a cube of healthy tissue. Functionalized graphene nanosheets were randomly distributed on the surface of the cancer cell. The effects of the concentration and morphology of the graphene nanosheets on the thermal behavior of the system were quantitatively investigated. The interfacial thermal resistance around the graphene sheets, which affects the transfer of heat in the nanoscale, was also varied to probe its effect on the temperature increase of the cancer cell and the healthy tissue. The results of this study could guide researchers to optimize photothermal therapy with graphene, while the modeling approach has the potential to be applied for investigating alternative treatment plans.

EDTA Enhances Stromal Cell-derived Factor 1α-induced Migration of Dental Pulp Cells by Up-regulating Chemokine Receptor 4 Expression.

INTRODUCTION: In regenerative endodontics, irrigation is an important step to ensure the success of treatment. EDTA as a common irrigant has been recommended in the American Associations of Endodontists guidelines. It has been suggested that EDTA-treated dentin slices could increase the attachment, differentiation, and migration of dental pulp stem cells. However, no information is available about the effect of EDTA on the migration of dental pulp cells (DPCs). The aim of this study was to explore how EDTA affects the migration of DPCs. METHODS: Cells were obtained from human premolars or third molars, and cell counting kit-8 was used to evaluate the influence of EDTA on cell proliferation at various concentrations and time points. Real-time polymerase chain reaction was used to detect the messenger RNA expression levels of transforming growth factor beta (TGF-ß) and chemokine receptor 4 (CXCR4). Protein expression was tested by the enzyme-linked immunosorbent assay and Western blot, respectively. In addition, the transwell migration assay was performed to investigate the role of EDTA pretreatment in stromal cell-derived factor 1α (SDF-1α)-induced DPC migration. RESULTS: Stimulation with 12% EDTA enhanced SDF-1α-induced migration of DPCs. Both expressions of TGF-ß1 and CXCR4 were increased by 12% EDTA in a time-dependent manner. After silencing CXCR4, EDTA-enhanced migration was decreased. Furthermore, the transcriptional regulation of CXCR4 by EDTA was found to be mediated by TGF-ß1/ERK1/2 and TGF-ß1/Smad2/3 signal pathways. CONCLUSIONS: Our results showed that 12% EDTA could promote SDF-1α-induced migration of DPCs by up-regulating CXCR4 expression in which TGF-ß1 signal pathways were involved.