Knockdown of microRNA-584 promotes dental pulp stem cells proliferation by targeting TAZ.

Proliferation of dental pulp stem cells (DPSCs) is crucial in tooth development and damage repairing, also includes its therapy application for tissue engineering. MicroRNAs (miRNAs) are key players in biological processes of DPSCs, and transcriptional co-activator with PDZ-binding motif (TAZ) also plays important roles in cell proliferation and differentiation, however, the roles of miR-584 and TAZ in DPSCs are not known. We found up-regulated miR-584 expression and down-regulated TAZ expression levels in aging dental pulp tissue compare to those in young dental pulp tissue. In proliferating DPSCs we demonstrated the decreased miR-584 expression and increased TAZ expression. miR-584 mimics suppressed DPSCs proliferation and migration, and significantly reduced TAZ production, whereas miR-584 inhibition exerted the converse effects. Knocking down of the TAZ in DPSCs had a similar effect as overexpression of miR-584. Furthermore, luciferase reporter assay demonstrated that miR-584 could directly bind to the TAZ mRNA 3'UTR to repress its translation. Overexpression of TAZ can partly rescue miR-584 mimic-mediated the inhibition of proliferation. Additionally, miR-584 inhibited cell proliferation and downregulated expression of cell cycle proteins by AKT signaling pathway. Together, we identified that miR-584 may be a key regulator in the proliferation of DPSCs by regulating TAZ expression via AKT signaling pathway. It would be a promising biomarker and therapeutic target for pulp disease.

Association of S100 calcium-binding protein A12, receptor for advanced glycation endproducts, and nuclear factor-κB expression with inflammation in pulp tissues from tooth caries.

AIM: S100 calcium-binding protein A1 (S100A12) is a pro-inflammatory molecule which is secreted during inflammation and induces chemotaxis and the production of pro-inflammatory cytokines via interaction with receptor for advanced glycation endproducts (RAGE) and subsequent, activation of nuclear factor-κB (NF-κB). The present study was designed to determine the expression levels of S100A12, RAGE, and NF-κB in the inflamed pulp of carried teeth. METHODS: In the present study, mRNA from 50 inflamed pulp and 50 healthy pulp were used for expression studies using real-time polymerase chain reaction. The expression levels of S100A12, RAGE, and NF-κB were compared between inflamed and healthy tissues. RESULTS: The results revealed that the expression of S100A12, but not of RAGE or NF-κB, was significantly decreased in inflamed pulp when compared to healthy pulp. mRNA levels of RAGE were also increased in the inflamed pulp taken from men when compared with women. CONCLUSION: The results suggest that S100A12 does not participate in the induction of inflammation in dental pulp. However, RAGE can participate in the inflammation in the pulp of males.

Axin2-expressing cells differentiate into reparative odontoblasts via autocrine Wnt/ß-catenin signaling in response to tooth damage.

In non-growing teeth, such as mouse and human molars, primary odontoblasts are long-lived post-mitotic cells that secrete dentine throughout the life of the tooth. New odontoblast-like cells are only produced in response to a damage or trauma. Little is known about the molecular events that initiate mesenchymal stem cells to proliferate and differentiate into odontoblast-like cells in response to dentine damage. The reparative and regenerative capacity of multiple mammalian tissues depends on the activation of Wnt/ß-catenin signaling pathway. In this study, we investigated the molecular role of Wnt/ß-catenin signaling pathway in reparative dentinogenesis using an in vivo mouse tooth damage model. We found that Axin2 is rapidly upregulated in response to tooth damage and that these Axin2-expressing cells differentiate into new odontoblast-like cells that secrete reparative dentine. In addition, the Axin2-expressing cells produce a source of Wnt that acts in an autocrine manner to modulate reparative dentinogenesis.

Regenerative endodontics--Creating new horizons.

Trauma to the dental pulp, physical or microbiologic, can lead to inflammation of the pulp followed by necrosis. The current treatment modality for such cases is non-surgical root canal treatment. The damaged tissue is extirpated and the root canal system prepared. It is then obturated with an inert material such a gutta percha. In spite of advances in techniques and materials, 10%-15% of the cases may end in failure of treatment. Regenerative endodontics combines principles of endodontics, cell biology, and tissue engineering to provide an ideal treatment for inflamed and necrotic pulp. It utilizes mesenchymal stem cells, growth factors, and organ tissue culture to provide treatment. Potential treatment modalities include induction of blood clot for pulp revascularization, scaffold aided regeneration, and pulp implantation. Although in its infancy, successful treatment of damaged pulp tissue has been performed using principles of regenerative endodontics. This field is dynamic and exciting with the ability to shape the future of endodontics. This article highlights the fundamental concepts, protocol for treatment, and possible avenues for research in regenerative endodontics.

The expression of hyperpolarization-activated cyclic nucleotide-gated channel 1 (HCN1) and HCN2 in the rat trigeminal ganglion, sensory root, and dental pulp.

Hyperpolarization-activated cyclic nucleotide-gated channel 1 (HCN1) and 2 (HCN2) are abundantly expressed in primary sensory neurons and contribute to neuronal excitability and pathological pain. We studied the expression of HCN1 and HCN2 in the rat trigeminal ganglion (TG) neurons and axons in the dental pulp, and the changes in their expression following inflammation, using light- and electron-microscopic immunocytochemistry and quantitative analysis. HCN1 and HCN2 were expressed predominantly in large-sized, neurofilament 200-immunopositive (+) or parvalbumin+ soma in the TG whereas they were expressed mostly in unmyelinated and small myelinated axons in the sensory root. The expression was particularly strong along the plasma membrane in the soma. In the dental pulp, majority of HCN1+ and HCN2+ axons coexpressed calcitonin gene-related peptide. They were expressed mainly in the peripheral pulp and pulp horn where the axons branch extensively in the dental pulp. The expression of HCN1 and HCN2 in TG neurons increased significantly in rats with experimentally induced inflammation of the dental pulp. Our findings support the notion that HCN1 and HCN2 are expressed mainly by both the soma of mechanosensitive neurons in the TG and peripheral axons of nociceptive neurons in the sensory root, and may play a role in the mechanisms of inflammatory pain from the dental pulp.

Sodium channel Na v 1.7 immunoreactivity in painful human dental pulp and burning mouth syndrome.

BACKGROUND: Voltage gated sodium channels Na v 1.7 are involved in nociceptor nerve action potentials and are known to affect pain sensitivity in clinical genetic disorders. AIMS AND OBJECTIVES: To study Na v 1.7 levels in dental pulpitis pain, an inflammatory condition, and burning mouth syndrome (BMS), considered a neuropathic orofacial pain disorder. METHODS: Two groups of patients were recruited for this study. One group consisted of patients with dental pulpitis pain (n = 5) and controls (n = 12), and the other patients with BMS (n = 7) and controls (n = 10). BMS patients were diagnosed according to the International Association for the Study of Pain criteria; a pain history was collected, including the visual analogue scale (VAS). Immunohistochemistry with visual intensity and computer image analysis were used to evaluate levels of Na v 1.7 in dental pulp tissue samples from the dental pulpitis group, and tongue biopsies from the BMS group. RESULTS: There was a significantly increased visual intensity score for Na v 1.7 in nerve fibres in the painful dental pulp specimens, compared to controls. Image analysis showed a trend for an increase of the Na v 1.7 immunoreactive % area in the painful pulp group, but this was not statistically significant. When expressed as a ratio of the neurofilament % area, there was a strong trend for an increase of Na v 1.7 in the painful pulp group. Na v 1.7 immunoreactive fibres were seen in abundance in the sub-mucosal layer of tongue biopsies, with no significant difference between BMS and controls. CONCLUSION: Na v 1.7 sodium channel may play a significant role in inflammatory dental pain. Clinical trials with selective Na v 1.7 channel blockers should prioritize dental pulp pain rather than BMS.

Expression changes of K+-Cl- co-transporter 2 and Na+-K+-Cl- co-transporter1 in mouse trigeminal subnucleus caudalis following pulpal inflammation.

Cation chloride co-transporters, including K(+)-Cl(-) co-transporter 2 (KCC2) and Na(+)-K(+)-Cl(-) co-transporter 1 (NKCC1), are of particular importance to GABAergic transmission and thus involved in the development of hyperalgesia at the spinal level. However, it is largely unknown whether these co-transporters in the trigeminal system contribute to dental pain. In this study, we investigated the expression of KCC2 and NKCC1 mRNAs in mouse trigeminal subnucleus caudalis (Vc) after lipopolysaccharide (LPS) application to the tooth pulp by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) method. KCC2 mRNA was found to be down-regulated at 1d after pulpal inflammation, while NKCC1 was up-regulated. Blockade of endogenous brain-derived neurotrophic factor-tyrosine receptor kinase B pathway with K252a produced pronounced antinociception as evidenced by decreased tongue protrusion behavior in LPS-treated mice. These data suggest that KCC2 and NKCC1 in Vc may play a critical role in the nociception and transmission of dental pain during pulpal inflammation.

Pulpal status of hypomineralized permanent molars.

PURPOSE: Young patients with hypomineralized teeth frequently complain of symptoms suggestive of dentin hypersensitivity. It has been proposed that these symptoms may be exacerbated by an underlying pulpal inflammation. The purpose of the study was to determine the pulpal status of hypomineralized teeth. METHODS: The experimental material comprised 25 sound and 19 hypomineralized permanent first molars obtained from children requiring dental extractions under general anesthesia. Pulp sections were processed for indirect immunofluorescence using combinations of: (1) protein gene product 9.5; (2) leukocyte common antigen; and (3) Ulex europaeus I lectin. Image analysis was then used to determine the percentage area of staining of each label. RESULTS: Innervation density was significantly greater in the pulp horn and subodontoblastic region of hypomineralized teeth than in sound teeth. Immune cells were most abundant within pulps of hypomineralized teeth exhibiting enamel loss. Vascularity was found to be similar for both hypomineralized and sound teeth, but was significantly greater in hypersensitive hypomineralized samples. CONCLUSION: This study provides biological evidence that inflammatory changes may be present within the pulpal tissue of these teeth.

Ameloblastin fusion protein enhances pulpal healing and dentin formation in porcine teeth.

Ameloblastin (Ambn, also named "amelin" or "sheathlin") is a protein participating in enamel formation and mesenchymal-ectodermal interaction during early dentin formation in developing teeth. Experiments have demonstrated an association between Ambn expression and healing of acute pulp wounds. The purpose of this study was to investigate if local application of recombinant fusion Ambn (rAmbn) could influence reparative dentin formation in pulpotomized teeth. In this randomized, double-blinded study, pulpotomy was performed in 28 lower central incisors in 17 adult miniature pigs. Following the surgical procedure, the exposed pulp tissue was covered either with rAmbn or with calcium hydroxide. After 2, 4, or 8 weeks, the teeth were extracted and examined by histomorphometry and immunohistochemistry using antibodies against porcine ameloblastin, collagen type I, and dentin sialoprotein (DSP). In rAmbn-treated teeth, a substantial amount of newly formed reparative dentin was observed at the application site, completely bridging the pulpal wound. Dentin formation was also observed in calcium hydroxide-treated teeth; however, the amount of reparative dentin was significantly smaller (P < 0.001) than after rAmbn treatment. Immunohistochemistry confirmed that the new hard tissue formed was similar to dentin. This is the first time a direct link between ameloblastin and dentin formation has been made in vivo. The results suggest potential for rAmbn as a biologically active pulp-dressing agent for enhanced pulpal wound healing and reparative dentin formation after pulpotomy procedures.

Sex hormone receptor status of the dental pulp and lesions of pulpal origin.

OBJECTIVE: The purpose of this study was to determine whether the dental pulp and lesions of pulpal origin (eg, pulp polyps, periapical granulomas, and periapical cysts) exhibit receptors for the sex steroid hormones estrogen, progesterone, and androgen. STUDY DESIGN: Staining for the receptors of the hormones estrogen, progesterone, and androgen was accomplished through use of available immunohistochemical detection techniques. Pulpal tissues were obtained from freshly extracted human third molars; the other tissues were obtained from the Oral and Maxillofacial Pathology Laboratory archives. Ten samples of each tissue were processed and immunostained for these specific receptors. RESULTS: Staining for estrogen and androgen receptors was essentially negative for all cell populations examined. However, positive progesterone receptor staining of varying degrees was noted in 8 of 10 pulpal specimens. Primarily, pulpal fibroblasts and odontoblasts exhibited positive immunoreactivity. CONCLUSIONS: The results of this study suggest that although the dental pulp may be a potential target tissue for progesterone, evidence is lacking with respect to the other sex steroid hormones.

Characterization of induced pulpal hypoxia using 3H-misonidazole.

Tritiated misonidazole (3H-MISO) is a bioreductively activated marker which preferentially binds to cells with decreased oxygen tension (hypoxia). Detection of hypoxia may be an important indicator of metabolic imbalance. For 3H-MISO to be functional as a marker, normal oxygen (normoxic) levels must be distinguishable from increased hypoxic retention. This investigation characterized retention of 3H-MISO in: (a) normoxic pulp, (b) induced hypoxic pulp, and (c) reoxygenated hypoxic pulp. Rats were injected intraperitoneally with either 3H-MISO, unlabeled MISO, or saline, then divided into normoxic and hypoxic groups with appropriate controls. Normoxic animals were maintained at ambient pressure. Hypoxia was induced by placing animals in a hypobaric chamber at 0.5 atm. Pulps were then removed and prepared for liquid scintillation counting. Hypoxic pulps retained significantly more 3H-MISO than normoxic pulps (analysis of variance, p = 0.001). Hypoxic 3H-MISO retention was unaffected by subsequent, transient tissue reoxygenation. 3H-MISO detects changes in pulpal oxygen status that deviate from normal.

Fluoride distribution in dentine and cementum in human permanent teeth with vital and non-vital pulps.

Twenty-two selected permanent teeth [11 with vital pulps and 11 with non-vital (necrotic) pulps] were obtained from patients aged from 20 to 73 yr in Nagoya, Japan. Fluoride (F) profiles in tooth samples were examined by using an abrasive micro-sampling technique. F levels in the pulpal dentine were significantly higher in vital than non-vital teeth for each age group, although there were observed increases of F with age. In the cementum the F levels were strongly related to age and there were few differences in profiles and levels of F between vital and non-vital teeth. It was concluded that vital pulp is an important factor for the pulpal dentine to absorb fluoride.

[The correlation between the derivatives of the arachidonic acid cascade and oral pathology. A review of the literature]. / Correlazione tra i derivati della cascata dell'acido arachidonico e la patologia orale. Revisione della letteratura.

The effects of several metabolites deriving from the arachidonic acid cascade on oral tissues are reviewed. These include the effects on the pulp, tissues and gingiva, and on the development of radicular cysts and epithelial tumours of the oral cavity.

Leukotrienes: inflammatory mediators--a review.

This article reviews a group of inflammatory mediators called leukotrienes. It includes their historical background, chemical pathway of formation, presence in cells and fluids, and biologic activity. These potent substances may be involved in pulpal and periradicular disease, but such involvement has not yet been reported.