Calcium-sensing receptor-ERK signaling promotes odontoblastic differentiation of human dental pulp cells

Strontium-Containing Piezoelectric Biofilm Promotes Dentin Tissue Regeneration

It remains an obstacle to induce the regeneration of hard dentin tissue in clinical settings. To overcome this, a P(VDF-TrFE) piezoelectric film with 2 wt% SrCl2 addition is designed. The biofilm shows a high flexibility, a harmonious biocompatibility, and a large piezoelectric d33 coefficient of 14 pC N-1, all contributing to building an electric microenvironment that favor the recruitment of dental pulp stem cells (DPSCs) and their differentiation into odontoblasts during normal chewing, speaking, etc. On the other hand, the strontium ions can be gradually released from the film, thus promoting DPSC odonto-differentiation. In vivo experiments also demonstrate that the film induces the release of dentin minerals and regeneration of dentin tissue. In the large animal dentin defect models, this piezoelectric film induces in situ dentin tissue formation effectively over a period of three months. This study illustrates a therapeutic potential of the piezoelectric film to improve dentin tissue repair in clinical settings.

Assessment of the biointeractivity of a novel vital pulp therapy agent derived from eggshell biowaste: An in vitro study

This study aimed to assess the calcium (Ca2+) and hydroxyl (OH-) ion-releasing ability, namely the biointeractivity of eggshell-derived hydroxyapatite (ESDHA) in comparison with mineral trioxide aggregate (MTA) and calcium hydroxide (CH). ESDHA, MTA and CH samples (n = 10; 8 × 1.6 mm) were immersed in 10 mL of deionised water (37°C, pH 6.8). Ca2+ and OH- ion releases were detected in 1, 7 and 21 days. Scanning electron microscopy and Fourier transform infrared spectroscopy analyses were also conducted. IBM SPSS 20.0 was used for statistical analyses. The cumulative Ca2+ ions (56.22 ± 11.28 ppm) were detected as most significant in ESDHA (day 21; p < 0.05). The OH- ion values of the ESDHA group were statistically higher than MTA and CH (days 1 and 7; p < 0.05). ESDHA and CH showed a similar pattern with sharp peaks in Ca2+, oxygen and carbon elements. ESDHA being a sustainable material with a high ion-releasing ability may be a preferable alternative to the commercial vital pulp therapy agents.

Detection of orthodontically induced inflammatory root resorption-associated biomarkers from the gingival crevicular fluid by proteomics analysis: a randomized-controlled clinical trial

Orthodontically induced inflammatory root resorption (OIIRR) is an undesirable complication of orthodontic treatment (OT) with an ambiguous aetiologic mechanism. This study aimed to identify OIIRR-associated biomarkers in the gingival crevicular fluid (GCF) using proteomic analysis. In this randomized clinical trial, the upper first premolars (UFP) were exposed either to light or heavy force. The GCF was collected at 1 h, 1 day, 7 days, 14 days, 21 days, and 28 days following force application. After extraction of UFP, roots were imaged and resorption premolar, was used to deliver either light forcecraters were measured. Proteomic analysis of GCF was performed using 2D gel electrophoresis with MALDI-TOF/TOF MS/MS. Results were further analyzed by bioinformatics analyses showing the biological functions and predicted pathways. The predicted canonical pathways showed that the expression of immunoglobulin kappa (IGKC), neutrophil gelatinase-associated lipocalin (NGAL), neurolysin mitochondrial (NEUL), keratin, type II cytoskeletal 1 (K2C1), S100-A9, and the extracellular calcium-sensing receptor (CASR) were significantly associated with a range of biological and inflammatory processes. In conclusion, up-regulation of S100A9, CASR, and K2C1 suggested a response to force-related inflammation, chemotactic activities, osteoclastogenesis, and epithelial cell breakdown. Meanwhile, the up-regulation of IGKC, NGAL, and K2C1 indicated a response to the inflammatory process, innate immunity activation, and epithelial cell breakdown.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03572-5.

Dopamine is involved in reparative dentin formation through odontoblastic differentiation of dental pulp stem cells

Conventional direct pulp-capping materials induce pulp cells to secrete various biomolecules in pulp tissues that promote reparative dentin formation through induction of odontoblastic differentiation of dental pulp stem cells (DPSCs). However, these biomolecules sometimes induce bone-like dentin with poor sealing properties. Therefore, exploration of biomolecules that allow tight sealing by tubular reparative dentin is required. We recently reported that dopamine (DA) is involved in dentinogenesis. Hence, we investigated the effect of DA on odontoblastic differentiation of DPSCs and reparative dentin formation. Both tyrosine hydroxylase (TH), a DA synthetase, and DA were expressed in odontoblast-like cells in vivo. In vitro, their expression was increased during odontoblastic differentiation of DPSCs. Furthermore, TH-overexpressing DPSCs had promoted odontoblastic differentiation and DA production. Moreover, DA stimulation promoted their differentiation and induced tubular reparative dentin. These results suggest that DA produced by TH is involved in odontoblastic differentiation of DPSCs and has an inductive capacity for reparative dentin formation similar to primary dentin. This study may lead to the development of therapy to preserve vital pulp tissues.

Alkaline earth metals for osteogenic scaffolds: From mechanisms to applications

Regeneration of bone defects is a significant challenge today. As alternative approaches to the autologous bone, scaffold materials have remarkable features in treating bone defects; however, the various properties of current scaffold materials still fall short of expectations. Due to the osteogenic capability of alkaline earth metals, their application in scaffold materials has become an effective approach to improving their properties. Furthermore, numerous studies have shown that combining alkaline earth metals leads to better osteogenic properties than applying them alone. In this review, the physicochemical and physiological characteristics of alkaline earth metals are introduced, mainly focusing on their mechanisms and applications in osteogenesis, especially magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). Furthermore, this review highlights the possible cross-talk between pathways when alkaline earth metals are combined. Finally, some of the current drawbacks of scaffold materials are enumerated, such as the high corrosion rate of Mg scaffolds and defects in the mechanical properties of Ca scaffolds. Moreover, a brief perspective is also provided regarding future directions in this field. It is worth exploring that whether the levels of alkaline earth metals in newly regenerated bone differs from those in normal bone. The ideal ratio of each element in the bone tissue engineering scaffolds or the optimal concentration of each elemental ion in the created osteogenic environment still needs further exploration. The review not only summarizes the research developments in osteogenesis but also offers a direction for developing new scaffold materials.

Effects of a co-stimulation with S-PRG filler eluate and muramyl dipeptide (MDP) on matrix metalloproteinase-1 production by human dental pulp fibroblast-like cells

The present study investigated the effects of a co-stimulation with surface reaction-type pre-reacted glass-ionomer (S-PRG) filler eluate and muramyl dipeptide (MDP) on matrix metalloproteinase (MMP)-1 production by human dental pulp fibroblast-like cells (hDPFs). S-PRG filler eluate contains 6 ions (F, Na, Al, B, Sr, and Si) released from S-PRG filler. Each S-PRG filler eluate and MDP stimulation enhanced MMP-1 production by hDPFs. The co-stimulation with S-PRG filler eluate and MDP enhanced MMP-1 production more than the MDP stimulation alone. A similar stimulation induced the phosphorylation of ERK 1/2. The increased secretion of MMP-1 and enhanced phosphorylation of ERK 1/2 by the co-stimulation with S-PRG filler eluate and MDP were suppressed by the selective and potent CaSR antagonist NPS 2143. Since strontium binds to CaSR, these results suggest that the enhanced production of MMP-1 by the co-stimulation with S-PRG filler eluate and MDP was due to the effects of strontium.

Involvement of M1/M2 Macrophage Polarization in Reparative Dentin Formation

In cases in which dental pulp tissue is accidentally exposed, direct pulp capping is often performed to induce reparative dentin formation. Although macrophages are essential for the inflammatory response and tissue repair, the emergence pattern and the role of macrophages in dental pulp tissue have not been clarified. Here, we investigated the emergence of M1/M2 macrophages in dental pulp tissue after a direct pulp capping and the effects of M2 macrophages on odontoblastic differentiation of the dental pulp stem cell (DPSC) clones. The emergence of macrophages in dental pulp tissue was investigated using a rat direct pulp capping model. Alizarin Red S staining and quantitative RT-PCR was performed to examine the effect of M2 macrophages on the mineralization and odontoblastic differentiation of DPSC clones. Immunohistochemical staining revealed that M1 macrophages were detected in dental pulp tissue after treatment and increased in number at three days after treatment. However, M2 macrophages gradually increased in number in dental pulp tissue after treatment, with the highest level recorded at seven days post-operation. Additionally, conditioned medium from M2 macrophages induced odontoblast-like differentiation of DPSC clones. These results suggest that macrophages play a role in the inflammatory response and reparative dentin formation after dental pulp exposure.

Sensitivity of Ca2+-sensing receptor-transient receptor potential-mediated Ca2+ influx to extracellular acidity in bEND.3 endothelial cells

Ca²⁺-sensing receptors (CaSRs) are G protein-coupled receptors activated by elevated concentrations of extracellular Ca²⁺. In our previous works, we showed protein and functional expression of CaSR in mouse cerebral endothelial cell (EC) (bEND.3); the CaSR response (high Ca²⁺-elicited cytosolic [Ca²⁺] elevation) was unaffected by suppression of phospholipase C but in part involved Ca²⁺ influx through transient receptor potential V1 (TRPV1) channels. In this work, we investigated if extracellular acidity affected CaSR-mediated Ca²⁺ influx triggered by high (3 mM) Ca²⁺ (CaSR agonist), 3 mM spermine (CaSR agonist), and 10 mM cinacalcet (positive allosteric modulator of CaSR). Extracellular acidosis (pH 6.8 and pH 6.0) strongly suppressed cytosolic [Ca²⁺] elevation triggered by high Ca²⁺, spermine, and cinacalcet; acidosis also inhibited Mn²⁺ influx stimulated by high Ca²⁺ and cinacalcet. Purinoceptor-triggered Ca²⁺ response, however, was not suppressed by acidosis. Extracellular acidity also did not affect membrane potential, suggesting suppressed CaSR-mediated Ca²⁺ influx in acidity did not result from the reduced electrical driving force for Ca²⁺. Our results suggest Ca²⁺ influx through a putative CaSR-TRP complex in bEND.3 EC was sensitive to extracellular pH.

Bu-Gu-Sheng-Sui decoction promotes osteogenesis via activating the ERK/Smad signaling pathways

Osteoporosis is a systemic metabolic skeletal disease, which becomes a common public health problem that seriously endangers people’s health. Bu-Gu-Sheng-Sui decoction (BGSSD) is a safe and effective Chinese medicine formulation for the treatment of osteoporosis. Numerous studies have indicated that it played a significant role in bone anabolism. However, the underlying mechanism remains unclear. Herein, we selected senescence-accelerated mice prone 6 (SAMP6) and MC3T3-E1 cells to study the effects of BGSSD on osteogenesis and then investigated the potential mechanism of BGSSD. Our research found that BGSSD protected the bone mass in SAMP6, increased the expression of osteogenic specific factor Runx2, and improved bone trabecular structure. In vitro, BGSSD accelerated the proliferation and differentiation of MC3T3-E1 cells, which was characterized by stimulating the activity of Alkaline phosphatase (ALP) and raising the expression of Runx2. Moreover, BGSSD could effectively boost the expression levels of ERK and Smad in SAMP6 and MC3T3-E1. Therefore, we speculate that BGSSD may promote bone formation through ERK/Smad pathways. Collectively, our results highlight the importance of BGSSD as a compound in promoting osteogenic differentiation and osteogenesis, demonstrating that BGSSD may become a latent drug to prevent and treat osteoporosis.

A role for the calcium-sensing receptor in the expression of inflammatory mediators in LPS-treated human dental pulp cells

The aim of this study is to investigate the role of calcium-sensing receptor (CaSR) in the expression of inflammatory mediators of lipopolysaccharide (LPS)-treated human dental pulp cells (hDPCs). The expression profile of CaSR in LPS-simulated hDPCs was detected using immunofluorescence, real time quantitative PCR (RT-qPCR), and Western blot analyses. Then, its regulatory effects on the expression of specific inflammatory mediators such as interleukin (IL)-1β, IL-6, cyclooxygenase 2 (COX2)-derived prostaglandin E2 (PGE₂), tumor necrosis factor (TNF)-α, and IL-10 were determined by RT-qPCR and enzyme-linked immunosorbent assay (ELISA). LPS significantly downregulated the gene expression of CaSR, but upregulated its protein expression level in hDPCs. Treatments by CaSR agonist R568 or its antagonist Calhex231, and their combinations with protein kinase B (AKT) inhibitor LY294002 showed obvious effects on the expression of selected inflammatory mediators in a time-dependent manner. Meanwhile, an opposite direction was found between the action of R568 and Calhex231, as well as the expression of the pro- (IL-1β, IL-6, COX2-derived PGE₂, and TNF-α) and anti-inflammatory (IL-10) mediators. The results provide the first evidence that CaSR-phosphatidylinositol-3 kinase (PI3K)-AKT-signaling pathway is involved in the release of inflammatory mediators in LPS-treated hDPCs, suggesting that the activation or blockade of CaSR may provide a novel therapeutic strategy for the treatment of pulp inflammatory diseases.

Pathophysiology of Demineralization, Part I: Attrition, Erosion, Abfraction, and Noncarious Cervical Lesions

PURPOSE OF THE REVIEW

Compare pathophysiology for infectious and noninfectious demineralization disease relative to mineral maintenance, physiologic fluoride levels, and mechanical degradation.

RECENT FINDINGS

Environmental acidity, biomechanics, and intercrystalline percolation of endemic fluoride regulate resistance to demineralization relative to osteopenia, noncarious cervical lesions, and dental caries. Demineralization is the most prevalent chronic disease in the world: osteoporosis (OP) >10%, dental caries ~100%. OP is severely debilitating while caries is potentially fatal. Mineralized tissues have a common physiology: cell-mediated apposition, protein matrix, fluid logistics (blood, saliva), intercrystalline ion percolation, cyclic demineralization/remineralization, and acid-based degradation (microbes, clastic cells). Etiology of demineralization involves fluid percolation, metabolism, homeostasis, biomechanics, mechanical wear (attrition or abrasion), and biofilm-related infections. Bone mineral density measurement assesses skeletal mass. Attrition, abrasion, erosion, and abfraction are diagnosed visually, but invisible subsurface caries <400μm cannot be detected. Controlling demineralization at all levels is an important horizon for cost-effective wellness worldwide.

Development of a novel direct dental pulp-capping material using 4-META/MMA-TBB resin with nano hydroxyapatite

In the case of dental pulp exposure, direct pulp capping is often performed to preserve vital dental pulp tissue. Numerous studies regarding the development of direct pulp-capping materials have been conducted, but materials with an appropriate sealing ability, which induce dense reparative dentin formation, have not been developed. Although nano hydroxyapatite (naHAp) is a bone-filling material with bioactivity and biocompatibility, the inductive effects of naHAp on reparative dentin formation remain unclear. In the present study, the effects of dental adhesive material 4-methacryloxyethyl trimellitate anhydride/methyl methacrylate tri-n-butylborane [4-META/MMA-TBB or Super-bond (SB)], which included 10%, 30%, and 50% naHAp (naHAp/SB) on odontoblastic differentiation of dental pulp stem cells (DPSCs) and reparative dentin formation were investigated. Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer analysis were performed to verify the existence of naHAp particles on the surface of naHAp/SB discs. The tensile adhesive strength of naHAp/SB was measured using a universal testing machine. As a result, 10% naHAp/SB and 30% naHAp/SB showed almost the same tensile adhesive strength as SB but 50% naHAp/SB showed significantly lower than the other experimental group. WST-1 proliferation assay and SEM analysis revealed that naHAp/SB did not affect the proliferation of DPSCs. Calcium release assay, quantitative RT-PCR, and western blotting analysis demonstrated that naHAp/SB did not release calcium ion but 30% naHAp/SB increased the expression of calcium-sensing receptor (CaSR) in DPSCs. Additionally, quantitative RT-PCR, western blotting analysis, Alizarin Red S- and von Kossa staining revealed that 30% naHAp/SB induced odontoblastic differentiation of DPSCs, which was inhibited by a MEK/ERK inhibitor and CaSR antagonist. Furthermore, 30% naHAp/SB promoted dense reparative dentin formation in an experimentally-formed rat dental pulp exposure model. These findings suggest that 30% naHAp/SB can be used as an ideal direct pulp capping material.

Secreted Frizzled-Related Protein 1 Promotes Odontoblastic Differentiation and Reparative Dentin Formation in Dental Pulp Cells

Direct pulp capping is an effective treatment for preserving dental pulp against carious or traumatic pulp exposure via the formation of protective reparative dentin by odontoblast-like cells. Reparative dentin formation can be stimulated by several signaling molecules; therefore, we investigated the effects of secreted frizzled-related protein (SFRP) 1 that was reported to be strongly expressed in odontoblasts of newborn molar tooth germs on odontoblastic differentiation and reparative dentin formation. In developing rat incisors, cells in the dental pulp, cervical loop, and inner enamel epithelium, as well as ameloblasts and preodontoblasts, weakly expressed Sfrp1; however, Sfrp1 was strongly expressed in mature odontoblasts. Human dental pulp cells (hDPCs) showed stronger expression of SFRP1 compared with periodontal ligament cells and gingival cells. SFRP1 knockdown in hDPCs abolished calcium chloride-induced mineralized nodule formation and odontoblast-related gene expression and decreased BMP-2 gene expression. Conversely, SFRP1 stimulation enhanced nodule formation and expression of BMP-2. Direct pulp capping treatment with SFRP1 induced the formation of a considerable amount of reparative dentin that has a structure similar to primary dentin. Our results indicate that SFRP1 is crucial for dentinogenesis and is important in promoting reparative dentin formation in response to injury.

Inductive Materials for Regenerative Engineering

Regenerative engineering has pioneered several novel biomaterials to treat critical-sized bone injuries. However, despite significant improvement in synthetic materials research, some limitations still exist. The constraints correlated with the current grafting methods signify a treatment paradigm shift to osteoinductive regenerative engineering approaches. Because of their intrinsic potential, inductive biomaterials may represent alternative approaches to treating critical bone injuries. Osteoinductive scaffolds stimulate stem cell differentiation into the osteoblastic lineage, enhancing bone regeneration. Inductive biomaterials comprise polymers, calcium phosphate ceramics, metals, and graphene family materials. This review will assess the cellular behavior toward properties of inductive materials.

Activation of Transient Receptor Potential Ankyrin 1 and Vanilloid 1 Channels Promotes Odontogenic Differentiation of Human Dental Pulp Cells

INTRODUCTION

Transient receptor potential ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) are thermosensitive channels that play an important role in thermal sensation or tooth pain by regulating intracellular Ca²⁺ concentration that is essential for pulp tissue repair. The aim of this study was to evaluate the role of TRPA1 and TRPV1 channels in the odontogenic differentiation of human dental pulp cells (HDPCs).

METHODS

HDPCs were isolated from healthy human intact third molars and cultured in odontogenic differentiation medium. Gene and protein expression levels of TRPA1 and TRPV1 channels during the odontogenic differentiation of HDPCs were evaluated by real-time quantitative polymerase chain reaction and Western blot analysis. HDPCs were then treated with channel agonists or antagonists, and the expression levels of odontogenic markers dentin sialophosphoprotein (DSPP) and osteopontin (OPN) were examined. Alkaline phosphatase activity and alizarin red staining were also conducted to detect mineralization levels.

RESULTS

Consistent with the mineralization degree and DSPP and OPN expression, messenger RNA and protein expression of TRPA1 and TRPV1 channels was up-regulated during the odontogenic differentiation of HDPCs. The application of TRPA1 or TRPV1 agonists increased the mineralized nodules of alizarin red staining and alkaline phosphatase activity and up-regulated the messenger RNA and protein expression of DSPP and OPN, respectively, with the highest values reached on the seventh day (P < .05). On the contrary, the mineralization level and DSPP and OPN expression could be suppressed by using the antagonists of these 2 channels.

CONCLUSIONS

TRPA1 and TRPV1 channels not only showed up-regulated expression along with the odontogenic differentiation of HDPCs but also could affect the odontogenic differentiation by regulating intracellular Ca²⁺ concentration.

Characterization of Ca2+-Sensing Receptor-Mediated Ca2+ Influx in Microvascular bEND.3 Endothelial Cells

Ca²⁺-sensing receptors (CaSR), activated by elevated concentrations of extracellular Ca²⁺, have been known to regulate functions of thyroid cells, neurons, and endothelial cells (EC). In this report, we studied CaSR-mediated Ca²⁺ influx in mouse cerebral microvascular EC (bEND.3 cells). Cytosolic free Ca²⁺ concentration and Mn²⁺ influx were measured by fura-2 microfluorometry. High (3 mM) Ca²⁺ (CaSR agonist), 3 mM spermine (CaSR agonist), and 10 μM cinacalcet (positive allosteric modulator of CaSR) all triggered Ca²⁺ influx; however, spermine, unlike high Ca²⁺ and cinacalcet, did not promote Mn²⁺ influx and its response was poorly sensitive to SKF 96365, a TRP channel blocker. Consistently, 2-aminoethoxydiphenyl borate and ruthenium red (two other general TRP channel blockers) suppressed Ca²⁺ influx triggered by cinacalcet and high Ca²⁺ but not by spermine. Ca²⁺ influx triggered by high Ca²⁺, spermine, and cinacalcet was similarly suppressed by A784168, a potent and selective TRPV1 antagonist. Our results suggest that CaSR activation triggered Ca²⁺ influx via TRPV1 channels; intriguingly, pharmacological, and permeability properties of such Ca²⁺ influx depended on the stimulating ligands.

PFK activation is essential for the odontogenic differentiation of human dental pulp stem cells

Dental pulp stem cells (DPSCs) can differentiate into diverse cell lineages, including odontogenic cells that are responsible for dentin formation, which is important in pulp repair and tooth regeneration. While glycolysis plays a central role in various cellular activities in both physiological and pathological conditions, its role and regulation in odontogenic differentiation are unknown. Here, we show that aerobic glycolysis is induced during odontoblastic differentiation from human DPSCs. Importantly, we demonstrate that during odontoblastic differentiation, protein expression levels of phosphofructokinase 1 muscle isoform (PFKM) and PFK2, but not other glycolytic enzymes, are mainly upregulated by AKT activation, resulting in increased total PFK enzyme activity. Increased PFK activity is essential to enhance aerobic glycolysis, which plays an important role in the odontoblastic differentiation of human DPSCs. These findings underscore that PFK activation-induced aerobic glycolysis accompanies, and participates in, human DPSCs differentiation into odontogenic lineage, and could play a role in the regulation of dental pulp repair.

Aberrant upregulation of CaSR promotes pathological new bone formation in ankylosing spondylitis

Pathological new bone formation is a typical pathological feature in ankylosing spondylitis (AS), and the underlying molecular mechanism remains elusive. Previous studies have shown that the calcium‐sensing receptor (CaSR) is critical for osteogenic differentiation while also being highly involved in many inflammatory diseases. However, whether it plays a role in pathological new bone formation of AS has not been reported. Here, we report the first piece of evidence that expression of CaSR is aberrantly upregulated in entheseal tissues collected from AS patients and animal models with different hypothetical types of pathogenesis. Systemic inhibition of CaSR reduced the incidence of pathological new bone formation and the severity of the ankylosing phenotype in animal models. Activation of PLCγ signalling by CaSR promoted bone formation both in vitro and in vivo. In addition, various inflammatory cytokines induced upregulation of CaSR through NF‐κB/p65 and JAK/Stat3 pathways in osteoblasts. These novel findings suggest that inflammation‐induced aberrant upregulation of CaSR and activation of CaSR‐PLCγ signalling in osteoblasts act as mediators of inflammation, affecting pathological new bone formation in AS.

Transient Receptor Potential Ankyrin 1 Is Up-Regulated in Response to Lipopolysaccharide via P38/Mitogen-Activated Protein Kinase in Dental Pulp Cells and Promotes Mineralization

Increased expression of the transient receptor potential ankyrin 1 (TRPA1) channel has been detected in carious tooth pulp, suggesting involvement of TRPA1 in defense or repair of this tissue after exogenous noxious stimuli. This study aimed to elucidate the induction mechanism in response to lipopolysaccharide (LPS) stimulation and the function of TRPA1 in dental pulp cells. Stimulation of human dental pulp cells with LPS up-regulated TRPA1 expression, as demonstrated by quantitative RT-PCR and Western blotting. LPS stimulation also promoted nitric oxide (NO) synthesis and p38/mitogen-activated protein kinase (MAPK) phosphorylation. NOR5, an NO donor, up-regulated TRPA1 expression, whereas 1400W, an inhibitor of inducible nitric oxide synthase, and SB202190, a p38/MAPK inhibitor, down-regulated LPS-induced TRPA1 expression. Moreover, JT010, a TRPA1 agonist, increased the intracellular calcium concentration and extracellular signal-regulated kinase 1/2 phosphorylation, and up-regulated alkaline phosphatase mRNA in human dental pulp cells. Icilin-a TRPA1 agonist-up-regulated secreted phosphoprotein 1 mRNA expression and promoted mineralized nodule formation in mouse dental papilla cells. In vivo expression of TRPA1 was detected in odontoblasts along the tertiary dentin of carious teeth. In conclusion, this study demonstrated that LPS stimulation induced TRPA1 via the NO-p38 MAPK signaling pathway and TRPA1 agonists promoted differentiation or mineralization of dental pulp cells.

TRPM8-regulated calcium mobilization plays a critical role in synergistic chemosensitization of Borneol on Doxorubicin

Background: Lung cancer has a high mortality rate and is resistant to multiple chemotherapeutics. Natural Borneol (NB) is a monoterpenoid compound that facilitates the bioavailability of drugs. In this study, we investigated the effects of NB on chemosensitivity in the A549 human lung adenocarcinoma cell line and to elucidate therapeutic molecular target of NB. Methods: The chemosensitivity effects of NB in A549 cells were examined by MTT assay. The mechanism of NB action was evaluated using flow cytometry and Western blotting assays. Surface plasmon resonance (SPR) and LC-MS combined analysis (MS-SPRi) was performed to elucidate the candidate molecular target of NB. The chemosensitizing capacity of NB in vivo was assessed in nude mice bearing A549 tumors. Results: NB pretreatment sensitized A549 cells to low doxorubicin (DOX) dosage, leading to a 15.7% to 41.5% increase in apoptosis. This increase was correlated with ERK and AKT inactivation and activation of phospho-p38 MAPK, phospho-JNK, and phosphor-p53. Furthermore, this synergism depends on reactive oxygen species (ROS) generation. MS-SPRi analysis revealed that transient receptor potential melastatin-8 (TRPM8) is the candidate target of NB in potentiating DOX killing potency. Genetically, TRPM8 knock-down significantly suppresses the chemosensitizing effects of NB and inhibits ROS generation through restraining calcium mobilization. Moreover, pretreatment with NB synergistically enhances the anticancer effects of DOX to delay tumor progression in vivo. Conclusions: These results suggest that TRPM8 may be a valid therapeutic target in the potential application of NB, and show that NB is a chemosensitizer for lung cancer treatment.

Sensing Extracellular Calcium - An Insight into the Structure and Function of the Calcium-Sensing Receptor (CaSR)

The calcium-sensing receptor (CaSR) is a G protein-coupled receptor that plays a key role in calcium homeostasis, by sensing free calcium levels in blood and regulating parathyroid hormone secretion in response. The CaSR is highly expressed in parathyroid gland and kidney where its role is well characterised, but also in other tissues where its function remains to be determined. The CaSR can be activated by a variety of endogenous ligands, as well as by synthetic modulators such as Cinacalcet, used in the clinic to treat secondary hyperparathyroidism in patients with chronic kidney disease. The CaSR couples to multiple G proteins, in a tissue-specific manner, activating several signalling pathways and thus regulating diverse intracellular events. The multifaceted nature of this receptor makes it a valuable therapeutic target for calciotropic and non-calciotropic diseases. It is therefore essential to understand the complexity behind the pharmacology, trafficking, and signalling characteristics of this receptor. This review provides an overview of the latest knowledge about the CaSR and discusses future hot topics in this field.

Expression and function of dopamine in odontoblasts

Dopamine (DA) is produced from tyrosine by tyrosine hydroxylase (TH). A recent study has reported that DA promotes the mineralization of murine preosteoblasts. However, the role of DA in odontoblasts has not been examined. Therefore, in this investigation, we researched the expression of TH and DA in odontoblasts and the effects of DA on the differentiation of preodontoblasts (KN-3 cells). Immunostaining showed that TH and DA were intensely expressed in odontoblasts and preodontoblasts of rat incisors and molars. KN-3 cells expressed D1-like and D2-like receptors for DA. Furthermore, DA promoted odontoblastic differentiation of KN-3 cells, whereas an antagonist of D1-like receptors and a PKA signaling blocker, inhibited such differentiation. However, antagonists of D2-like receptors promoted differentiation. These results suggested that DA in preodontoblasts and odontoblasts might promote odontoblastic differentiation through D1-like receptors, but not D2-like receptors, and PKA signaling in an autocrine or paracrine manner and plays roles in dentinogenesis.

Astragaloside IV attenuates inflammatory injury and promotes odontoblastic differentiation in lipopolysaccharide-stimulated MDPC-23 cells and rat pulpitis

BACKGROUND

Astragaloside IV (AS-IV), a natural herbal compound from Astragalus membranaceus, has inhibitory effects on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis, and RANKL signal helps to regulate odontoblast differentiation. However, whether and how AS-IV affects odontoblastic differentiation remains unclear.

METHODS

Lipopolysaccharide (LPS)-stimulated MDPC-23 cells and rat pulpitis were treated with AS-IV, cell viability, and LDH leakage was analyzed by CCK-8 assay and LDH Leakage assay. The production of TNF-α and IL-6 was determined by ELISA and qRT-PCR assay. The expression of alkaline phosphatase (ALP) was detected using an ALP assay kit, and the expression of dentin sialophos-phoprotein (DSPP), dentin matrix protein-1 (DMP1), basic fibroblast growth factor (FGF2), and phosphorylated extracellular signal-regulated kinase (p-ERK) was determined by western blot.

RESULTS

AS-IV dose dependently increased in cell viability and decreased the overproduction of TNF-α and IL-6 in LPS-stimulated MDPC-23 cells. AS-IV also counteracted LPS-induced downregulation of ALP, DSPP, and DMP1 in MDPC-23 cells. Furthermore, AS-IV significantly decreased the expression of FGF2 and p-ERK in LPS-stimulated MDPC-23 cells. More important, the addition of FGF2 partly neutralized AS-IV-mediated inhibition of FGF2/ERK signaling, abolished AS-IV-induced reduction of TNF-α and IL-6, and counteracted AS-IV-induced upregulation of DSPP and DMP-1 in these cells. Meanwhile, AS-IV inhibited the excessive production of TNF-α and IL-6, suppressed the downregulation of DSPP and DMP1, and disturbed the up-regulation of FGF2 and p-ERK in the pulp tissues of rat pulpitis model.

CONCLUSIONS

AS-IV exerted anti-inflammatory and pro-differentiation effects in LPS-stimulated MDPC-23 cells and rat pulpitis via inhibiting the FGF2/ERK signaling pathway.

Sensory Axon Growth Requires Spatiotemporal Integration of CaSR and TrkB Signaling

Neural circuit development involves the coordinated growth and guidance of axons. During this process, axons encounter many different cues, but how these cues are integrated and translated into growth is poorly understood. In this study, we report that receptor signaling does not follow a linear path but changes dependent on developmental stage and coreceptors involved. Using developing chicken embryos of both sexes, our data show that calcium-sensing receptor (CaSR), a G-protein-coupled receptor important for regulating calcium homeostasis, regulates neurite growth in two distinct ways. First, when signaling in isolation, CaSR promotes growth through the PI3-kinase-Akt pathway. At later developmental stages, CaSR enhances tropomyosin receptor kinase B (TrkB)/BDNF-mediated neurite growth. This enhancement is facilitated through a switch in the signaling cascade downstream of CaSR (i.e., from the PI3-kinase-Akt pathway to activation of GSK3α Tyr279). TrkB and CaSR colocalize within late endosomes, cotraffic and coactivate GSK3, which serves as a shared signaling node for both receptors. Our study provides evidence that two unrelated receptors can integrate their individual signaling cascades toward a nonadditive effect and thus control neurite growth during development.SIGNIFICANCE STATEMENT This work highlights the effect of receptor coactivation and signal integration in a developmental setting. During embryonic development, neurites grow toward their targets guided by cues in the extracellular environment. These cues are sensed by receptors at the surface that trigger intracellular signaling events modulating the cytoskeleton. Emerging evidence suggests that the effects of guidance cues are diversified, therefore expanding the number of responses. Here, we show that two unrelated receptors can change the downstream signaling cascade and regulate neuronal growth through a shared signaling node. In addition to unraveling a novel signaling pathway in neurite growth, this research stresses the importance of receptor coactivation and signal integration during development of the nervous system.

L-type voltage-gated calcium channels in stem cells and tissue engineering

L‐type voltage‐gated calcium ion channels (L‐VGCCs) have been demonstrated to be the mediator of several significant intracellular activities in excitable cells, such as neurons, chromaffin cells and myocytes. Recently, an increasing number of studies have investigated the function of L‐VGCCs in non‐excitable cells, particularly stem cells. However, there appear to be no systematic reviews of the relationship between L‐VGCCs and stem cells, and filling this gap is prescient considering the contribution of L‐VGCCs to the proliferation and differentiation of several types of stem cells. This review will discuss the possible involvement of L‐VGCCs in stem cells, mainly focusing on osteogenesis mediated by mesenchymal stem cells (MSCs) from different tissues and neurogenesis mediated by neural stem/progenitor cells (NSCs). Additionally, advanced applications that use these channels as the target for tissue engineering, which may offer the hope of tissue regeneration in the future, will also be explored.

Craniofacial, orofacial and dental disorders: the role of the RAS/ERK pathway

Deviations from the precisely coordinated programme of human head development can lead to craniofacial and orofacial malformations often including a variety of dental abnormalities too. Although the aetiology is still unknown in many cases, during the last decades different intracellular signalling pathways have been genetically linked to specific disorders. Among these pathways, the RAS/extracellular signal-regulated kinase (ERK) signalling cascade is the focus of this review since it encompasses a large group of genes that when mutated cause some of the most common and severe developmental anomalies in humans. We present the components of the RAS/ERK pathway implicated in craniofacial and orodental disorders through a series of human and animal studies. We attempt to unravel the specific molecular targets downstream of ERK that act on particular cell types and regulate key steps in the associated developmental processes. Finally we point to ambiguities in our current knowledge that need to be clarified before RAS/ERK-targeting therapeutic approaches can be implemented.

Antagonism of Ca2+-sensing receptors by NPS 2143 is transiently masked by p38 activation in mouse brain bEND.3 endothelial cells

Ca²⁺-sensing receptors (CaSR) are G protein-coupled receptors which are activated by a rise in extracellular Ca²⁺. CaSR activation has been known to inhibit parathyroid hormone release and stimulate calcitonin release from parathyroid glands and thyroid parafollicular C cells, respectively. The roles of CaSR in other cell types including endothelial cells (EC) are much less understood. In this work, we demonstrated protein and functional expression of CaSR in mouse cerebral EC (bEND.3). Unexpectedly, CaSR response (high Ca²⁺-elicited cytosolic [Ca²⁺] elevation) was unaffected by edelfosine or U73122 but strongly suppressed by SK&F 96365, ruthenium red, and 2-aminoethoxydiphenyl borate (2-APB), suggesting involvement of TRPV and TRPC channels but not Gq-phospholipase C. Acute application of NPS2143, a negative allosteric modulator of CaSR, suppressed CaSR response. However, a 40-min NPS2143 pre-treatment surprisingly enhanced CaSR response. After 4-24 h of application, this enhancement faded away and suppression of CaSR response was observed again. Similar results were obtained when La³⁺ and Sr²⁺ were used as CaSR agonists. The transient NPS 2143 enhancement effect was abolished by SB203580, a p38 inhibitor. Consistently, NPS 2143 triggered a transient p38 activation. Taken together, results suggest that in bEND.3 cells, NPS 2143 caused acute suppression of CaSR response, but then elicited a transient enhancement of CaSR response in a p38-dependent manner. NPS 2143 effects on CaSR in bEND.3 cells therefore depended on drug exposure time. These findings warrant cautious use of this agent as a CaSR modulator and potential cardiovascular drug.

Abrogation of Fam20c altered cell behaviors and BMP signaling of immortalized dental mesenchymal cells

FAM20C mutations compromise the mineralization of skeleton and tooth in both human and mouse. Putatively, the mineralization disorder is attributed to the elevated fibroblast growth factor 23 (FGF23), which reduced the serum phosphorus by suppressing the reabsorption of phosphorus in kidney. Besides the regulation on systemic phosphorus homeostasis, FAM20C was also implicated to regulate cell behaviors and gene expression through a cell-autonomous manner. To identify the primary effects of Fam20c on dental mesenchymal cells, mouse Fam20c-deficient dental mesenchymal cells were generated by removing the floxed alleles from the immortalized mouse Fam20c^f/f dental mesenchymal cells with Cre-expressing lentivirus. The removal of Fam20c exerted no impact on cell morphology, but suppressed the proliferation and mobility of the dental mesenchymal cells. Fam20c deficiency also significantly reduced the expression of Osterix, Runx2, type I Collagen a 1 (Col1a1), Alkaline phosphatase (Alpl) and the members of the small integrin-binding ligand, N-linked glycoprotein (SIBLING) family, but increased Fgf23 expression. Consistently, the in vitro mineralization of Fam20c-deficient dental mesenchymal cells was severely disabled. However, supplements of the non-collagenous proteins from wild type rat dentin failed to rescue the compromised mineralization, suggesting that the roles of FAM20C in tooth mineralization are more than phosphorylating local matrices and regulating systemic phosphorus metabolism. Moreover, the down-regulated BMP signaling pathways in the Fam20c deficient dental mesenchymal cells revealed that the kinase activity of FAM20C might be required to maintain BMP signaling. In summary, our study discloses that Fam20c indeed regulates cell behaviors and cell signaling pathway in a cell-autonomous manner.