Activation of Mechanosensitive Transient Receptor Potential/Piezo Channels in Odontoblasts Generates Action Potentials in Cocultured Isolectin B4–negative Medium-sized Trigeminal Ganglion Neurons

Introduction

Various stimuli to the dentin surface elicit dentinal pain by inducing dentinal fluid movement causing cellular deformation in odontoblasts. Although odontoblasts detect deformation by the activation of mechanosensitive ionic channels, it is still unclear whether odontoblasts are capable of establishing neurotransmission with myelinated A delta (Aδ) neurons. Additionally, it is still unclear whether these neurons evoke action potentials by neurotransmitters from odontoblasts to mediate sensory transduction in dentin. Thus, we investigated evoked inward currents and evoked action potentials form trigeminal ganglion (TG) neurons after odontoblast mechanical stimulation.

Poly(Adenosine Phosphate Ribose) Polymerase 1 Inhibition Enhances Brain-derived Neurotrophic Factor Secretion in Dental Pulp Stem Cell–derived Odontoblastlike Cells

Introduction

The nuclear enzyme poly(adenosine phosphate ribose) polymerase 1 (PARP-1) has been implicated in the maintenance and differentiation of several stem cells. The role of PARP-1 in dental pulp stem cell (DPSC) differentiation, especially in the context of its ability to modulate nerve regeneration factors, has not been investigated. Regeneration of neuronal components in pulp tissue is important for the assessment of tooth vitality. Brain-derived neurotrophic factor (BDNF) is known to play an integral signaling factor during nerve regeneration. In this study, we identified the role of PARP-1 in the modulation of BDNF in DPSC differentiation into odontoblastlike cells.

Immunocytochemical detection of apoptosis in human odontoblasts

Pulpal chamber size decreases on ageing due to primary and secondary dentin deposition. This work was designed to find out the consequences of this pulp chamber reduction on odontoblast number and distribution. Twenty-one healthy human premolars were equally divided into three groups from 11-, 12.5- and 14-yr-old adolescents, respectively). The external and the internal perimeters of dentin were recorded on vestibulo-lingual sections, from buccal to lingual cemento-enamel junction using an image analysis system. Nuclei of the odontoblasts were recorded on 12 automatically selected fields. On nine erupted premolars (3 teeth from each 11-, 12.5- and 14-yr-old patients), apoptosis was detected by confocal microscopy using a modification of the original TUNEL method. Apoptotic cells were labeled in central pulp fibroblasts, perivascular endothelial cells, and in odontoblasts. When the pulp volume decreases due to primary dentin production, the decrease of the surface available for odontoblasts is compensated for by a multilayer distribution of cells. Secondary dentin deposition, associated with odontoblasts reorganization in a single layer, results in a hyperbolic decrease of the odontoblasts number. This decrease seems to result from a programmed cell death, which eliminates half of the odontoblasts over a 4-yr period.     

热休克蛋白70在两个年龄组前磨牙成牙本质细胞表达的比较研究

目的观察热休克蛋白(HSP)70在前磨牙成牙本质细胞表达的增龄变化特点。方法采用免疫组化法结合图像分析系统,对HSP70在年老组(71~80岁)和年轻组(13~20岁)前磨牙成牙本质细胞和成牙本质细胞胞质中的表达强度进行比较。结果年老组成牙本质细胞内总的HSP70免疫组化染色的平均吸光度值比年轻组降低,而胞质内HSP70免疫组化染色的平均吸光度值平均值比年轻组略高,但无显著性差异。结论年老患者成牙本质细胞抵御急性刺激的能力下降可能与胞核内HSP70表达强度下降有关。     

SD大鼠牙髓增龄变化对Nd：YAG激光照射的应激反应观察

目的：观察增龄牙髓对Nd：YAG激光照射的应激反应变化。方法：观察幼年组（6周龄）、成年组（12周龄）、老年组（72周龄）雄性SD大鼠切牙经不同能量密度脉冲式Nd：YAG激光照射后6h牙髓的组织形态学变化,利用图像分析系统对不同年龄大鼠成牙本质细胞中诱导型热休克蛋白（HSP70）表达的平均光密度值进行分析比较。结果：激光能量密度为1433mJ／mm^2和1910mJ／mm^2时,老年组成牙本质细胞中诱导型HSP70的表达强度显著高于幼年和成年组（P〈0．05）;能量密度为2388mJ／mm^2时,老年组成牙本质细胞中诱导型HSP70的表达强度显著低于幼年和成年组（P〈0．05）,且老年组部分成牙本质细胞变性坏死。结论：老年大鼠牙髓对激光刺激的耐受性下降。     

KLF4 promotes the odontoblastic differentiation of human dental pulp cells

Introduction

Krüppel-like factor 4 (KLF4) plays an important role in cytodifferentiation and proliferation. Our previous study showed that KLF4 was specifically expressed in polarizing and elongating odontoblasts. However, the role of KLF4 in odontoblast differentiation was still unknown. The purpose of this study was to investigate the role of KLF4 in odontoblastic differentiation of human dental pulp cells (hDPCs).

Methods

hDPCs were treated with odontoblastic induction medium. Odontoblastic differentiation was determined by the detection of alkaline phosphatase (ALPase) activity and the expression of mineralization-related genes including ALP, dentin sialophosphoprotein (DSPP), and dentin matrix protein-1 (DMP-1). Also, cell proliferation ability was examined by the 5-ethynyl-2’-deoxyuridine (EdU) incorporation assay. Simultaneously, messenger RNA and protein levels of KLF4 were detected. pKLF4-IRES2-EGFP plasmid encoding full-length KLF4 was constructed to overexpress KLF4, and biologic effects of KLF4 on hDPCs were investigated by the evaluation of ALPase activity and the detection of ALP, DSPP, and DMP-1 expression and analysis of cell proliferation ability.

Results

ALPase activity and the expression of odontoblastic differentiation markers progressively increased in hDPCs cultured with odontoblastic induction medium. Meanwhile, the proliferation ability decreased in this procedure; messenger RNA and protein levels of KLF4 increased significantly on day 5 after the odontoblastic induction of hDPCs and kept increasing until day 14. hDPCs showed up-regulated activity of ALPase and the expression of mineralization-related genes, including ALP, DMP-1, and dentin sialoprotein (DSP), after KLF4 overexpression. Besides, the proliferation ability of hDPCs decreased significantly in the KLF4 overexpression group by EdU incorporation assay.

Conclusions

Our findings suggest that KLF4 is able to promote odontoblastic differentiation of hDPCs and inhibit proliferation of hDPCs.