Follicle‐stimulating hormone impairs dental pulp stem cells odontogenic differentiation

In addition to bone, the dentin‐pulp complex is also influenced by menopause, showing a decreased regenerative capacity. High levels of follicle‐stimulating hormone (FSH) during menopause could directly regulate bone metabolism. Here, the role of FSH in the odontogenic differentiation of the dentin‐pulp complex was investigated. Dental pulp stem cells (DPSCs) were isolated. CCK‐8 assays, cell apoptosis assays, Western blotting (WB), real‐time RT‐PCR, alkaline phosphatase activity assays, and Alizarin Red S staining were used to clarify the effects of FSH on the proliferation, apoptosis and odontogenic differentiation of the DPSCs. MAPK pathway‐related factors were explored by WB assays. FSH and its inhibitor were used in OVX rats combined with a direct pulp‐capping model. HE and immunohistochemistry were used to detect reparative dentin formation and related features. The results indicated that FSH significantly decreased the odontogenic differentiation of the DPSCs without affecting cell proliferation and apoptosis. Moreover, FSH significantly activated the JNK signalling pathway, and JNK inhibitor partly rescued the inhibitory effect of FSH on DPSC differentiation. In vivo, FSH treatment attenuated the dentin bridge formation and mineralization‐related protein expression in the OVX rats. Our findings indicated that FSH reduced the odontogenic capacity of the DPSCs and was involved in reparative dentinogenesis during menopause.     

Stem cells of dental pulp

Any clinician dreams to obtain the regeneration of the destroyed organ for his patient. In the human being, the regeneration of complex structures is not possible, except the liver and the bone marrow, which can be regenerated because of the presence of adult stem cells in these tissues. The stem cells have two principal properties: they ensure their self-renewal and they have the ability to differentiate into several cellular types. Using specific markers allowing the identification of the stem cells in bone marrow, stem cells were observed in dental pulp tissues. Although the origin, the identification, and the localization of these stem cells of dental pulp remain under consideration, the optimism in research on stem cells permits to believe that the knowledge on dental stem cells will lead to their use in therapeutics.     

Optical assessment of dental pulp vitality

The assessment of dental pulp vitality is an important part of oral diagnosis. Conventional tests stimulate the nerves in the pulp and rely on a subjective response from the patient. The use of an optical method for assessment of pulp vitality has been investigated. Fibre optic light guides were used to transmit light to and from the tooth and signal processing was employed to enhance the resulting signal. Valid pulse signals were differentiated from artefactual signals by analysis of signal parameters. Artefactual signals were found to have coefficients of variability that are greater than 40% for amplitude and greater than 25% for phase. With this technique it has been possible to recognize a pulse signal from over 70% of healthy teeth. Further work is in progress to develop the technique to a state where it can be used as a routine clinical tool.     

Peptidergic nerves in human dental pulp

Summary The peptidergic innervation of human dental pulp was studied with indirect immunofluorescence and immunoperoxidase techniques. Pulpal nerve fibres displaying immunoreactivity for cholecystokinin, calcitonin gene-related peptide, C-terminal flanking peptide of neuropeptide tyrosine, leucine-enkephalin, methionine-enkephalin, neuropeptide K, neuropeptide tyrosine, peptide with N-terminal histidine and C-terminal isoleucine, somatostatin-28, substance P and vasoactive intestinal polypeptide were observed. Immunoreactive axon varicosities were detectable within radicular and coronal nerve trunks and within the nerve plexus of Raschkow in the para-odontoblastic region. Many peptidergic nerve fibres were observed in association with blood vessels of various sizes. Substance P- and calcitonin-gene-related peptide-immunoreactive axons were visible in the odontoblastic layer. The occurrence of VIP- and PHI-immunoreactive fibres lends support to the hypothesis that human tooth may be supplied by parasympathetic nerves. The immunocytochemical results here shown provide a morphological basis to previous experimental studies concerning the possible roles of neuropeptides in nociception mechanisms, control of the blood flow and modulation of the inflammatory response in dental tissues.     

Pannexin3 inhibits TNF‐α‐induced inflammatory response by suppressing NF‐κB signalling pathway in human dental pulp cells

Human dental pulp cells (HDPCs) play a crucial role in dental pulp inflammation. Pannexin 3 (Panx3), a member of Panxs (Pannexins), has been recently found to be involved in inflammation. However, the mechanism of Panx3 in human dental pulp inflammation remains unclear. In this study, the role of Panx3 in inflammatory response was firstly explored, and its potential mechanism was proposed. Immunohistochemical staining showed that Panx3 levels were diminished in inflamed human and rat dental pulp tissues. In vitro, Panx3 expression was significantly down‐regulated in HDPCs following a TNF‐α challenge in a concentration‐dependent way, which reached the lowest level at 10 ng/ml of TNF‐α. Such decrease could be reversed by MG132, a proteasome inhibitor. Unlike MG132, BAY 11‐7082, a NF‐κB inhibitor, even reinforced the inhibitory effect of TNF‐α. Quantitative real‐time PCR (qRT‐PCR) and enzyme‐linked immunosorbent assay (ELISA) were used to investigate the role of Panx3 in inflammatory response of HDPCs. TNF‐α‐induced pro‐inflammatory cytokines, interleukin (IL)‐1β and IL‐6, were significantly lessened when Panx3 was overexpressed in HDPCs. Conversely, Panx3 knockdown exacerbated the expression of pro‐inflammatory cytokines. Moreover, Western blot, dual‐luciferase reporter assay, immunofluorescence staining, qRT‐PCR and ELISA results showed that Panx3 participated in dental pulp inflammation in a NF‐κB‐dependent manner. These findings suggested that Panx3 has a defensive role in dental pulp inflammation, serving as a potential target to be exploited for the intervention of human dental pulp inflammation.     

Recruitment of dental pulp cells by dentine and pulp extracellular matrix components

The present study aimed to determine whether dentine tissue and preparations of extracellular matrix (ECM) from pulp (pECM) and dentine (dECM), and breakdown products, influenced pulp cell migration. Chemotaxis transwell and agarose spot assays demonstrated that both dentine and pulp ECM molecules acted as chemoattractants for primary pulp cells. Chemoattractant activities of dECM and pECM were enhanced when subjected to acid and enzymatic breakdown, respectively. This enhanced activity following physiologically relevant breakdown may be pertinent to the disease environment. Pulp cell migration in response to dental ECMs was dependent on an active rho pathway. Recruited cells exhibited increased stem cell marker expression indicating that dental ECMs and their breakdown products selectively attract progenitor cells that contribute to repair processes. In conclusion, combined these results indicate that ECM molecules contribute to cell recruitment necessary for regeneration of the dentine-pulp complex after injury.     

Semicarbazide-sensitive amine oxidases in pig dental pulp

The behaviour of semicarbazide-sensitive amine oxidase (SSAO; E.C. 1.4.3.6) in dental pulp has been studied, with particular reference to the metabolism of 5-hydroxytryptamine (5-HT; serotonin). Kinetic studies using radioactively labelled substrates have confirmed benzylamine, 2-phenylethylamine (PEA) and 5-HT to be substrates for microsomal SSAO from porcine dental pulp. Kinetic substrate-competition studies indicated the presence of two forms of SSAO in dental pulp; one that oxidises benzylamine and PEA but not 5-HT and a second that oxidises 5-HT and PEA but not benzylamine. These two forms also differ in their thermostabilities at 60 and 70 degrees C, although this thermal inactivation is partly reversible.     

牙髓干细胞的研究进展

牙髓干细胞是来源于牙髓组织中的一种成体干细胞,该种细胞具有高度增殖、自我更新的能力和多向分化潜能。牙髓干细胞的研究对牙髓再生、牙体修复等牙组织工程将产生重要的意义。该文就牙髓干细胞的研究现状作一综述,并对其应用前景进行探讨。     

Distal C‐terminus of Cav1.2 is indispensable for the chondrogenic differentiation of rat dental pulp stem cells

The α1 subunit (Cav1.2) of the L‐type calcium channel (LTCC), which is presently existing in both excitatory cells and non‐excitatory cells, is involved in the differentiation and proliferation of mesenchymal stem cells (MSCs). Dental pulp stem cells (DPSCs), MSCs derived from dental pulp, exhibit multipotent characteristics similar to those of MSCs. The aim of the present study was to examine the contribution of Cav1.2 and its distal C‐terminus (DCT) to the commitment of rat DPSCs (rDPSCs) toward chondrocytes and adipocytes in vitro. The expression of Cav1.2 was obviously elevated in chondrogenic differentiation but did not differ significantly in adipogenic differentiation. The chondrogenic differentiation but not adipogenic of rDPSCs was inhibited by either blocking LTCC using nimodipine or knockdown of Cav1.2 via short hairpin RNA (shRNA). Overexpression of DCT rescued the inhibition by Cav1.2‐shRNA during chondrogenic differentiation, indicating that DCT is essential for the chondrogenic differentiation of rDPSCs. However, the protein level of DCT decreased after chondrogenic differentiation in wild‐type cells, and overexpression of DCT in rDPSCs inhibited the phenotype. These data suggest that DCT is indispensable for chondrogenic differentiation of rDPSCs but that superfluous DCT inhibits this process. Through the analysis of differentially expressed genes using RNA‐seq data, we speculated that the regulation of DCT might be mediated by the mitogen‐activated protein kinase/extracellular‐regulated kinase and c‐Jun N‐terminal kinase signaling pathways, or Chondromodulin‐1.