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.

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.

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.