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Ronan EA, Nagel M, Emrick JJ. The anatomy, neurophysiology, and cellular mechanisms of intradental sensation. FRONTIERS IN PAIN RESEARCH 2024; 5:1376564. [PMID: 38590718 PMCID: PMC11000636 DOI: 10.3389/fpain.2024.1376564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 03/11/2024] [Indexed: 04/10/2024] Open
Abstract
Somatosensory innervation of the oral cavity enables the detection of a range of environmental stimuli including minute and noxious mechanical forces. The trigeminal sensory neurons underlie sensation originating from the tooth. Prior work has provided important physiological and molecular characterization of dental pulp sensory innervation. Clinical dental experiences have informed our conception of the consequence of activating these neurons. However, the biological role of sensory innervation within the tooth is yet to be defined. Recent transcriptomic data, combined with mouse genetic tools, have the capacity to provide important cell-type resolution for the physiological and behavioral function of pulp-innervating sensory neurons. Importantly, these tools can be applied to determine the neuronal origin of acute dental pain that coincides with tooth damage as well as pain stemming from tissue inflammation (i.e., pulpitis) toward developing treatment strategies aimed at relieving these distinct forms of pain.
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Affiliation(s)
- Elizabeth A. Ronan
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI, United States
| | - Maximilian Nagel
- Sensory Cells and Circuits Section, National Center for Complementary and Integrative Health, Bethesda, MD, United States
| | - Joshua J. Emrick
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI, United States
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Devor M. Pain in osteoarthritis: Driven by intrinsic rather than extrinsic joint afferents and why this should impact treatment. INTERVENTIONAL PAIN MEDICINE 2024; 3:100381. [PMID: 39239488 PMCID: PMC11372874 DOI: 10.1016/j.inpm.2023.100381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2023] [Revised: 12/07/2023] [Accepted: 12/11/2023] [Indexed: 09/07/2024]
Abstract
Pain in osteoarthritis (OA) results from erosion of joint cartilage, resulting in bone contacting bone without an intervening cushion. The periosteum, including its nociceptive innervation, ends at the border of the cartilage. No other innervated tissue is present between the denuded articular bone ends that could serve as a neuronal pathway to carry a bone-on-bone pain signal to the brain. The pain signaling pathway must therefore originate in afferent axons with electrogenic nociceptive sensory endings that reside within the bone itself, specifically in the opposing surfaces of epiphyseal subchondral bone. Selective ablation of this intrinsic nerve pathway, using any of a variety of approaches, is expected to permanently eliminate OA pain.
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Affiliation(s)
- Marshall Devor
- Institute of Life Sciences and Center for Research on Pain, The Hebrew University of Jerusalem, Jerusalem, Israel
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3
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Thai J, Fuller‐Jackson J, Ivanusic JJ. Using tissue clearing and light sheet fluorescence microscopy for the three-dimensional analysis of sensory and sympathetic nerve endings that innervate bone and dental tissue of mice. J Comp Neurol 2024; 532:e25582. [PMID: 38289188 PMCID: PMC10952626 DOI: 10.1002/cne.25582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Revised: 12/05/2023] [Accepted: 12/30/2023] [Indexed: 02/01/2024]
Abstract
Bone and dental tissues are richly innervated by sensory and sympathetic neurons. However, the characterization of the morphology, molecular phenotype, and distribution of nerves that innervate hard tissue has so far mostly been limited to thin histological sections. This approach does not adequately capture dispersed neuronal projections due to the loss of important structural information during three-dimensional (3D) reconstruction. In this study, we modified the immunolabeling-enabled imaging of solvent-cleared organs (iDISCO/iDISCO+) clearing protocol to image high-resolution neuronal structures in whole femurs and mandibles collected from perfused C57Bl/6 mice. Axons and their nerve terminal endings were immunolabeled with antibodies directed against protein gene product 9.5 (pan-neuronal marker), calcitonin gene-related peptide (peptidergic nociceptor marker), or tyrosine hydroxylase (sympathetic neuron marker). Volume imaging was performed using light sheet fluorescence microscopy. We report high-quality immunolabeling of the axons and nerve terminal endings for both sensory and sympathetic neurons that innervate the mouse femur and mandible. Importantly, we are able to follow their projections through full 3D volumes, highlight how extensive their distribution is, and show regional differences in innervation patterns for different parts of each bone (and surrounding tissues). Mapping the distribution of sensory and sympathetic axons, and their nerve terminal endings, in different bony compartments may be important in further elucidating their roles in health and disease.
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Affiliation(s)
- Jenny Thai
- Department of Anatomy and PhysiologyUniversity of MelbourneParkvilleVictoriaAustralia
| | | | - Jason J. Ivanusic
- Department of Anatomy and PhysiologyUniversity of MelbourneParkvilleVictoriaAustralia
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4
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Lee PR, Kim J, Rossi HL, Chung S, Han SY, Kim J, Oh SB. Transcriptional profiling of dental sensory and proprioceptive trigeminal neurons using single-cell RNA sequencing. Int J Oral Sci 2023; 15:45. [PMID: 37749100 PMCID: PMC10519964 DOI: 10.1038/s41368-023-00246-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2023] [Revised: 08/30/2023] [Accepted: 08/31/2023] [Indexed: 09/27/2023] Open
Abstract
Dental primary afferent (DPA) neurons and proprioceptive mesencephalic trigeminal nucleus (MTN) neurons, located in the trigeminal ganglion and the brainstem, respectively, are essential for controlling masticatory functions. Despite extensive transcriptomic studies on various somatosensory neurons, there is still a lack of knowledge about the molecular identities of these populations due to technical challenges in their circuit-validated isolation. Here, we employed high-depth single-cell RNA sequencing (scRNA-seq) in combination with retrograde tracing in mice to identify intrinsic transcriptional features of DPA and MTN neurons. Our transcriptome analysis revealed five major types of DPA neurons with cell type-specific gene enrichment, some of which exhibit unique mechano-nociceptive properties capable of transmitting nociception in response to innocuous mechanical stimuli in the teeth. Furthermore, we discovered cellular heterogeneity within MTN neurons that potentially contribute to their responsiveness to mechanical stretch in the masseter muscle spindles. Additionally, DPA and MTN neurons represented sensory compartments with distinct molecular profiles characterized by various ion channels, receptors, neuropeptides, and mechanoreceptors. Together, our study provides new biological insights regarding the highly specialized mechanosensory functions of DPA and MTN neurons in pain and proprioception.
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Affiliation(s)
- Pa Reum Lee
- Department of Neurobiology and Physiology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Republic of Korea
- Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea
| | - Jihoon Kim
- Genomics and Computational Biology Graduate Group, University of Pennsylvania, Philadelphia, PA, USA
| | - Heather Lynn Rossi
- Department of Pathobiology, University of Pennsylvania, Philadelphia, PA, USA
| | - Sena Chung
- Department of Neurobiology and Physiology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Republic of Korea
| | - Seung Yub Han
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Junhyong Kim
- Genomics and Computational Biology Graduate Group, University of Pennsylvania, Philadelphia, PA, USA.
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA.
| | - Seog Bae Oh
- Department of Neurobiology and Physiology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul, Republic of Korea.
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Ibrahim T, Wu P, Wang LJ, Fang-Mei C, Murillo J, Merlo J, Shein SS, Tumanov AV, Lai Z, Weldon K, Chen Y, Ruparel S. Sex-dependent differences in the genomic profile of lingual sensory neurons in naïve and tongue-tumor bearing mice. Sci Rep 2023; 13:13117. [PMID: 37573456 PMCID: PMC10423281 DOI: 10.1038/s41598-023-40380-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2023] [Accepted: 08/09/2023] [Indexed: 08/14/2023] Open
Abstract
Mechanisms of sex-dependent orofacial pain are widely understudied. A significant gap in knowledge exists about comprehensive regulation of tissue-specific trigeminal sensory neurons in diseased state of both sexes. Using RNA sequencing of FACS sorted retro-labeled sensory neurons innervating tongue tissue, we determined changes in transcriptomic profiles in males and female mice under naïve as well as tongue-tumor bearing conditions Our data revealed the following interesting findings: (1) FACS sorting obtained higher number of neurons from female trigeminal ganglia (TG) compared to males; (2) Naïve female neurons innervating the tongue expressed immune cell markers such as Csf1R, C1qa and others, that weren't expressed in males. This was validated by Immunohistochemistry. (3) Accordingly, immune cell markers such as Csf1 exclusively sensitized TRPV1 responses in female TG neurons. (4) Male neurons were more tightly regulated than female neurons upon tumor growth and very few differentially expressed genes (DEGs) overlapped between the sexes, (5) Male DEGs contained higher number of transcription factors whereas female DEGs contained higher number of enzymes, cytokines and chemokines. Collectively, this is the first study to characterize the effect of sex as well as of tongue-tumor on global gene expression, pathways and molecular function of tongue-innervating sensory neurons.
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Affiliation(s)
- Tarek Ibrahim
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Ping Wu
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Li-Ju Wang
- Greehey Children's Cancer Institute, University of Texas Health San Antonio, San Antonio, USA
- Department of Population Health Sciences, University of Texas Health at San Antonio, San Antonio, USA
| | - Chang Fang-Mei
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Josue Murillo
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Jaclyn Merlo
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA
| | - Sergey S Shein
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas Health San Antonio, San Antonio, USA
| | - Alexei V Tumanov
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas Health San Antonio, San Antonio, USA
| | - Zhao Lai
- Greehey Children's Cancer Institute, University of Texas Health San Antonio, San Antonio, USA
- Department of Molecular Medicine, University of Texas Health at San Antonio, San Antonio, TX, USA
| | - Korri Weldon
- Greehey Children's Cancer Institute, University of Texas Health San Antonio, San Antonio, USA
- Department of Molecular Medicine, University of Texas Health at San Antonio, San Antonio, TX, USA
| | - Yidong Chen
- Greehey Children's Cancer Institute, University of Texas Health San Antonio, San Antonio, USA
- Department of Population Health Sciences, University of Texas Health at San Antonio, San Antonio, USA
| | - Shivani Ruparel
- Department of Endodontics, School of Dentistry, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX, 78229, USA.
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6
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Ibrahim T, Wu P, Wang LJ, Fang-Mei C, Murillo J, Merlo J, Tumanov A, Lai Z, Weldon K, Chen Y, Ruparel S. Sex-dependent Differences in the Genomic Profile of Lingual Sensory Neurons in Naïve and Tongue-Tumor Bearing Mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.14.524011. [PMID: 36711730 PMCID: PMC9882171 DOI: 10.1101/2023.01.14.524011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Mechanisms of sex-dependent orofacial pain are widely understudied. A significant gap in knowledge exists about comprehensive regulation of tissue-specific trigeminal sensory neurons in diseased state of both sexes. Using RNA sequencing of FACS sorted retro-labeled sensory neurons innervating tongue tissue, we determined changes in transcriptomic profiles in males and female mice under naïve as well as tongue-tumor bearing conditions Our data revealed the following interesting findings: 1) Tongue tissue of female mice was innervated with higher number of trigeminal neurons compared to males; 2) Naïve female neurons innervating the tongue exclusively expressed immune cell markers such as Csf1R, C1qa and others, that weren't expressed in males. This was validated by Immunohistochemistry. 4) Accordingly, immune cell markers such as Csf1 exclusively sensitized TRPV1 responses in female TG neurons. 3) Male neurons were more tightly regulated than female neurons upon tumor growth and very few differentially expressed genes (DEGs) overlapped between the sexes, 5) Male DEGs contained higher number of transcription factors whereas female DEGs contained higher number of enzymes, cytokines and chemokines. Collectively, this is the first study to characterize the effect of sex as well as of tongue-tumor on global gene expression, pathways and molecular function of tongue-innervating sensory neurons.
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Affiliation(s)
- Tarek Ibrahim
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Ping Wu
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Li-Ju Wang
- Greehey Children’s Cancer Institute, University of Texas Health San Antonio, USA
- Department of Population Health Sciences, University of Texas Health at San Antonio, USA
| | - Chang Fang-Mei
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Josue Murillo
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Jaclyn Merlo
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
| | - Alexei Tumanov
- Department of Microbiology, Immunology and Molecular Genetics, University of Texas Health San Antonio, USA
| | - Zhao Lai
- Greehey Children’s Cancer Institute, University of Texas Health San Antonio, USA
- Department of Molecular Medicine, University of Texas Health at San Antonio, San Antonio, TX, USA
| | - Korri Weldon
- Greehey Children’s Cancer Institute, University of Texas Health San Antonio, USA
- Department of Molecular Medicine, University of Texas Health at San Antonio, San Antonio, TX, USA
| | - Yidong Chen
- Greehey Children’s Cancer Institute, University of Texas Health San Antonio, USA
- Department of Population Health Sciences, University of Texas Health at San Antonio, USA
| | - Shivani Ruparel
- Department of Endodontics, School of Dentistry, University of Texas Health San Antonio, USA
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Ohyama S, Ouchi T, Kimura M, Kurashima R, Yasumatsu K, Nishida D, Hitomi S, Ubaidus S, Kuroda H, Ito S, Takano M, Ono K, Mizoguchi T, Katakura A, Shibukawa Y. Piezo1-pannexin-1-P2X 3 axis in odontoblasts and neurons mediates sensory transduction in dentinal sensitivity. Front Physiol 2022; 13:891759. [PMID: 36589456 PMCID: PMC9795215 DOI: 10.3389/fphys.2022.891759] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 11/22/2022] [Indexed: 12/15/2022] Open
Abstract
According to the "hydrodynamic theory," dentinal pain or sensitivity is caused by dentinal fluid movement following the application of various stimuli to the dentin surface. Recent convergent evidence in Vitro has shown that plasma membrane deformation, mimicking dentinal fluid movement, activates mechanosensitive transient receptor potential (TRP)/Piezo channels in odontoblasts, with the Ca2+ signal eliciting the release of ATP from pannexin-1 (PANX-1). The released ATP activates the P2X3 receptor, which generates and propagates action potentials in the intradental Aδ afferent neurons. Thus, odontoblasts act as sensory receptor cells, and odontoblast-neuron signal communication established by the TRP/Piezo channel-PANX-1-P2X3 receptor complex may describe the mechanism of the sensory transduction sequence for dentinal sensitivity. To determine whether odontoblast-neuron communication and odontoblasts acting as sensory receptors are essential for generating dentinal pain, we evaluated nociceptive scores by analyzing behaviors evoked by dentinal sensitivity in conscious Wistar rats and Cre-mediated transgenic mouse models. In the dentin-exposed group, treatment with a bonding agent on the dentin surface, as well as systemic administration of A-317491 (P2X3 receptor antagonist), mefloquine and 10PANX (non-selective and selective PANX-1 antagonists), GsMTx-4 (selective Piezo1 channel antagonist), and HC-030031 (selective TRPA1 channel antagonist), but not HC-070 (selective TRPC5 channel antagonist), significantly reduced nociceptive scores following cold water (0.1 ml) stimulation of the exposed dentin surface of the incisors compared to the scores of rats without local or systemic treatment. When we applied cold water stimulation to the exposed dentin surface of the lower first molar, nociceptive scores in the rats with systemic administration of A-317491, 10PANX, and GsMTx-4 were significantly reduced compared to those in the rats without systemic treatment. Dentin-exposed mice, with somatic odontoblast-specific depletion, also showed significant reduction in the nociceptive scores compared to those of Cre-mediated transgenic mice, which did not show any type of cell deletion, including odontoblasts. In the odontoblast-eliminated mice, P2X3 receptor-positive A-neurons were morphologically intact. These results indicate that neurotransmission between odontoblasts and neurons mediated by the Piezo1/TRPA1-pannexin-1-P2X3 receptor axis is necessary for the development of dentinal pain. In addition, odontoblasts are necessary for sensory transduction to generate dentinal sensitivity as mechanosensory receptor cells.
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Affiliation(s)
- Sadao Ohyama
- Department of Physiology, Tokyo Dental College, Tokyo, Japan,Oral Surgery, Tokyo Metropolitan Cancer and Infectious Diseases Center, Komagome Hospital, Tokyo, Japan
| | - Takehito Ouchi
- Department of Physiology, Tokyo Dental College, Tokyo, Japan
| | - Maki Kimura
- Department of Physiology, Tokyo Dental College, Tokyo, Japan
| | - Ryuya Kurashima
- Department of Physiology, Tokyo Dental College, Tokyo, Japan
| | | | - Daisuke Nishida
- Oral Health Science Center, Tokyo Dental College, Tokyo, Japan
| | - Suzuro Hitomi
- Department of Physiology, Nihon University School of Dentistry, Tokyo, Japan,Division of Physiology, Kyushu Dental University, Fukuoka, Japan
| | - Sobhan Ubaidus
- Department of Physiology, Tokyo Dental College, Tokyo, Japan
| | - Hidetaka Kuroda
- Department of Physiology, Tokyo Dental College, Tokyo, Japan,Department of Dental Anesthesiology, Kanagawa Dental University, Yokosuka, Japan
| | - Shinichirou Ito
- Department of Oral and Maxillofacial Surgery, Tokyo Dental College, Tokyo, Japan
| | - Masayuki Takano
- Department of Oral and Maxillofacial Surgery, Tokyo Dental College, Tokyo, Japan
| | - Kentaro Ono
- Division of Physiology, Kyushu Dental University, Fukuoka, Japan
| | | | - Akira Katakura
- Department of Oral Pathological Science and Surgery, Tokyo Dental College, Tokyo, Japan
| | - Yoshiyuki Shibukawa
- Department of Physiology, Tokyo Dental College, Tokyo, Japan,*Correspondence: Yoshiyuki Shibukawa,
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Kakuta W, Matsunaga S, Otsu Y, Kitamura K, Abe S, Yajima Y, Sekine H. Regeneration of sensory nerve branches in extraction socket and surrounding alveolar bone in rat: immunohistochemical observation of the axon and myelin sheath changes. Odontology 2022:10.1007/s10266-022-00772-y. [DOI: 10.1007/s10266-022-00772-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Accepted: 11/15/2022] [Indexed: 12/04/2022]
Abstract
AbstractThe purpose of this study was to investigate the process and derivation of the distribution of the sensory nerves that appear in the extraction socket and surrounding alveolar bone following tooth extraction. The right mandibular first molar of rats and periodontal ligament were extracted as a single mass, and the mandible was harvested after days 1, 3, 5, and 7 after extraction. Serial sections of 7 µm thickness were prepared for the proximal root (Section A), buccolingual root (Section B), and centrifugal root (Section C) of the first molar. H–E staining and immunohistochemical staining with anti-S100 antibody and anti-NF-L antibody were carried out. The presence of nerve fiber bundles in the blood clot was already evident on post-extraction day 3, and on post-extraction day 7. On day 3, the number of axons in Sections B and C had greatly decreased, indicating that, after extraction, the connection between peripheral nerve tissue and the trigeminal ganglion was temporarily markedly reduced in the region of the alveolar branch. Although the myelin sheaths were regenerating on day 5, the majority of the axons of the alveolar branches extending from the inferior alveolar nerve were seen to be extremely thin and scattered, despite their further regeneration. The above results suggest that the newly myelinated nerves are actually derived from the bone marrow to the extraction socket, so few nerves, rather than being derived from the alveolar branches that had innervated the extracted tooth.
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Han HM, Jeong SY, Cho YS, Choi SY, Bae YC. Expression of Piezo2 in the dental pulp, sensory root and trigeminal ganglion and it's coexpression with vesicular glutamate transporters. J Endod 2022; 48:1407-1413. [PMID: 35952898 DOI: 10.1016/j.joen.2022.07.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 07/14/2022] [Accepted: 07/21/2022] [Indexed: 01/10/2023]
Abstract
INTRODUCTION Information on the type of vesicular glutamate transporter (VGLUT) that is expressed in the Piezo2-positive (+) neurons in the trigeminal ganglion (TG), and on the type of Piezo2+ axons and their distribution in the dental pulp is important for understanding dental pain elicited by mechanical stimuli and developing new therapeutic strategies. METHODS We examined expression of Piezo2 and its coexpression with VGLUT1 and VGLUT2 in rat TG, sensory root and in human dental pulp by light and electron microscopic immunohistochemistry and quantitative analysis. RESULTS VGLUT1 and VGLUT2 were expressed in the TG neurons. Piezo2 was expressed in axons of all types but primarily in small myelinated (Aδ) axons in the sensory root. In the dental pulp, Piezo2 was expressed densely in the numerous axons that form plexus in the peripheral pulp. Piezo2+ axons in the peripheral pulp were mostly unmyelinated and the Piezo2-immunoreactivity was often concentrated near the axolemma, suggesting that it may represent functional receptors. CONCLUSIONS These findings suggest that 1) VGLUT1 and VGLUT2 are involved in the glutamate signaling in Piezo2+ neurons, 2) Piezo2 may be primarily activated by noxious mechanical stimuli and 3) Piezo2-mediated dental mechanotransduction may be primarily elicited in the peripheral pulp.
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Affiliation(s)
- Hye Min Han
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - Soon Youn Jeong
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - Yi Sul Cho
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - So Young Choi
- Department of Oral & Maxillofacial Surgery, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - Yong Chul Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea.
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Immunohistochemistry as a detection tool for ion channels involved in dental pain signaling. Saudi Dent J 2022; 34:155-166. [PMID: 35935722 PMCID: PMC9346947 DOI: 10.1016/j.sdentj.2022.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Revised: 02/21/2022] [Accepted: 02/23/2022] [Indexed: 11/21/2022] Open
Abstract
Background Despite advances in pain detection, diagnosis, and management, the prevalence of dental pain is still on the rise. Although dental pain is not directly related to fatal outcomes, the two most common types of dental pain—dental caries and dentin hypersensitivity—have a significant impact on an individual’s quality of life. Understanding the mechanism of the pain pathway is one of the crucial steps in providing better treatment for these patients. Ion channels are critical biomolecules that have been the subject of dental study owing to their roles in the transmission and transduction of external stimuli, as well as in the control and perception of pain. Numerous immunohistochemical (IHC) staining approaches have also been used to identify the many ion channels implicated in peripheral pain signaling in dental pulp. Highlight This review highlights the critical steps in IHC and its role in the detection of ion channels involved in the dental pain signaling pathway. Conclusion The key ion channels identified using IHC and whose functions have been widely researched in dental tissues are addressed in this review article.
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11
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Lee PR, Lee JH, Park JM, Oh SB. Upregulation of Toll-like Receptor 2 in Dental Primary Afferents Following Pulp Injury. Exp Neurobiol 2021; 30:329-340. [PMID: 34737238 PMCID: PMC8572661 DOI: 10.5607/en21018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2021] [Revised: 10/23/2021] [Accepted: 10/24/2021] [Indexed: 11/19/2022] Open
Abstract
Pulpitis (toothache) is a painful inflammation of the dental pulp and is a prevalent problem throughout the world. This pulpal inflammation occurs in the cells inside the dental pulp, which have host defense mechanisms to combat oral microorganisms invading the pulp space of exposed teeth. This innate immunity has been well studied, with a focus on Toll-like receptors (TLRs). The function of TLR4, activated by Gram-negative bacteria, has been demonstrated in trigeminal ganglion (TG) neurons for dental pain. Although Gram-positive bacteria predominate in the teeth of patients with caries and pulpitis, the role of TLR2, which is activated by Gram-positive bacteria, is poorly understood in dental primary afferent (DPA) neurons that densely innervate the dental pulp. Using Fura-2 based Ca2+ imaging, we observed reproducible intracellular Ca2+ responses induced by Pam3CSK4 and Pam2CSK4 (TLR2-specific agonists) in TG neurons of adult wild-type (WT) mice. The response was completely abolished in TLR2 knock-out (KO) mice. Single-cell RT-PCR detected Tlr2 mRNA in DPA neurons labeled with fluorescent retrograde tracers from the upper molars. Using the mouse pulpitis model, real-time RT-PCR revealed that Tlr2 and inflammatory-related molecules were upregulated in injured TG, compared to non-injured TG, from WT mice, but not from TLR2 KO mice. TLR2 protein expression was also upregulated in injured DPA neurons, and the change was corresponded with a significant increase in calcitonin gene-related peptide (CGRP) expression. Our results provide a better molecular understanding of pulpitis by revealing the potential contribution of TLR2 to pulpal inflammatory pain.
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Affiliation(s)
- Pa Reum Lee
- Department of Neurobiology and Physiology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 03080, Korea
| | - Jin-Hee Lee
- Department of Neurobiology and Physiology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 03080, Korea
| | - Ji Min Park
- Department of Neurobiology and Physiology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 03080, Korea
| | - Seog Bae Oh
- Department of Neurobiology and Physiology, School of Dentistry and Dental Research Institute, Seoul National University, Seoul 03080, Korea
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12
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Current Concepts of Dentinal Hypersensitivity. J Endod 2021; 47:1696-1702. [PMID: 34302871 DOI: 10.1016/j.joen.2021.07.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 07/13/2021] [Accepted: 07/13/2021] [Indexed: 11/21/2022]
Abstract
INTRODUCTION Although many clinical studies have reported on the prevalence of dental pain, far fewer studies have focused on the mechanisms of dental pain. This is an important gap because increased understanding of dental pain mechanisms may lead to improved diagnostic tests or therapeutic interventions. The aim of this study was to comprehensively review the literature on the mechanisms of dentinal sensitivity. METHODS PubMed and Ovid were searched for articles that addressed dentinal pain and or pulpal sensitivity. Because of the breadth of research ranging from cellular/molecular studies to clinical trials, a narrative review on the mechanisms of dentinal sensitivity was constructed based on the literature. RESULTS Five various mechanisms for dentinal sensitivity have been proposed: (1) the classic hydrodynamic theory, (2) direct innervation of dentinal tubules, (3) neuroplasticity and sensitization of nociceptors, (4) odontoblasts serving as sensory receptors, and (5) algoneurons. CONCLUSIONS These theories are not mutually exclusive, and it is possible that several of them contribute to dentinal sensitivity. Moreover, pulpal responses to tissue injury may alter the relative contribution of these mechanisms. For example, pulpal inflammation may lead to neuronal sprouting and peripheral sensitization. Knowledge of these mechanisms may prompt the development of therapeutic drugs that aim to disrupt these mechanisms, leading to more effective treatments for pulpal pain.
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Erdogan O, Malek M, Gibbs JL. Associations between Pain Severity, Clinical Findings, and Endodontic Disease: A Cross-Sectional Study. J Endod 2021; 47:1376-1382. [PMID: 34256059 DOI: 10.1016/j.joen.2021.07.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 06/25/2021] [Accepted: 07/01/2021] [Indexed: 10/20/2022]
Abstract
INTRODUCTION Thorough pain assessment and thermal and mechanical testing are the primary diagnostic tools used to assess the status of pulp and periapical tissues in teeth with potential endodontic pathology. This study evaluated predictors of acute odontogenic pain to better understand the relationship between endodontic pain, clinical testing, endodontic disease, and diagnoses. METHODS Participants (N = 228) presenting with acute odontogenic pain underwent standardized clinical testing and reported their pain intensity. Univariate and multiple regression analyses were performed to evaluate the predictors of acute endodontic pain. Chi-square tests with Bonferroni adjustments were conducted to measure the frequency of endodontic diagnostic test findings and clinical observations in patients with different pulpal diagnoses. RESULTS A negative response to cold stimulation on the causative tooth and percussion hypersensitivity on the healthy adjacent tooth were the strongest predictors of higher levels of acute endodontic pain. Percussion hypersensitivity on the healthy adjacent tooth was present in a quarter of the cohort and was reported with equal frequency in teeth diagnosed with irreversible pulpitis, necrotic pulp, and previously initiated/treated teeth. Although painful percussion on the causative tooth was more frequently reported in teeth diagnosed with necrotic pulp, painful palpation was more frequently reported on teeth diagnosed with previously initiated/treated teeth. CONCLUSIONS Percussion hypersensitivity on the healthy adjacent tooth may reveal a lowered pain threshold and heightened pain sensitization. It is also possible that the 2 commonly performed mechanical sensory tests, percussion and palpation hypersensitivity, may detect different aspects of endodontic pathophysiology and pain processing.
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Affiliation(s)
- Ozge Erdogan
- Division of Endodontics in Restorative Dentistry and Biomaterials Sciences, Harvard School of Dental Medicine, Boston, Massachusetts; Department of Endodontics, New York University, College of Dentistry, New York, New York.
| | - Matthew Malek
- Department of Endodontics, New York University, College of Dentistry, New York, New York
| | - Jennifer L Gibbs
- Division of Endodontics in Restorative Dentistry and Biomaterials Sciences, Harvard School of Dental Medicine, Boston, Massachusetts; Department of Endodontics, New York University, College of Dentistry, New York, New York
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Byers MR, Calkins DF. Trigeminal sensory nerve patterns in dentine and their responses to attrition in rat molars. Arch Oral Biol 2021; 129:105197. [PMID: 34146928 DOI: 10.1016/j.archoralbio.2021.105197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 06/03/2021] [Accepted: 06/08/2021] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Our goal was to define trigeminal nerve ending quantities and patterns in rat molar dentine, their responses to attrition (tooth wear), and their associated odontoblasts and connections with pulpal plexuses. DESIGN Trigeminal ganglia were labeled for axonal transport of 3H-proteins to dentinal nerve endings in male rats (3-13 months old). Autoradiography detected radio-labeled dentinal tubules as indicators of nerve ending locations. Quantitative morphometry was done (ANOVA, t-tests), and littermates were compared for attrition and innervation. RESULTS There were six dentinal patterns, only two of which had an associated neural plexus of Raschkow and cell-free zone (Den-1, Den-2). Other nerves entered dentin from bush-like endings near elongated odontoblasts (Den-B), as single fibers (Den-X), as networks in predentine (PdN), or as single fibers in tertiary dentine at cusp tips (Den-S). There were at least 186,600 innervated dentinal tubules within the set of three right maxillary molars of the best-labeled rat, and similar densities were found in other rats. Attrition levels differed among cusps and in littermates (t-test p < 0.02-0.0001), but the matched right/left cusps per rat were similar. Innervations of tertiary and enamel-free dentine (Den-S, Den-X) were preserved in all rats. Den-B and Den-2 coronal patterns were unchanged unless displaced by dentinogenesis. Den-1 losses occurred in older cusps, while Den-2 patterns increased near cervical and intercuspal odontoblasts. CONCLUSIONS The extensive molar dentinal innervation had unique distributions per rat per cusp that depended on region (buccal, middle, palatal) and attrition, but only two of six patterns connected to a plexus of Raschkow.
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Affiliation(s)
- Margaret R Byers
- Department of Anesthesiology and Pain Medicine, Univ. Washington, Seattle, WA, 98195-6540, USA.
| | - Dianne F Calkins
- Department of Anesthesiology and Pain Medicine, Univ. Washington, Seattle, WA, 98195-6540, USA
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15
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Glia and Orofacial Pain: Progress and Future Directions. Int J Mol Sci 2021; 22:ijms22105345. [PMID: 34069553 PMCID: PMC8160907 DOI: 10.3390/ijms22105345] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 05/12/2021] [Accepted: 05/14/2021] [Indexed: 12/14/2022] Open
Abstract
Orofacial pain is a universal predicament, afflicting millions of individuals worldwide. Research on the molecular mechanisms of orofacial pain has predominately focused on the role of neurons underlying nociception. However, aside from neural mechanisms, non-neuronal cells, such as Schwann cells and satellite ganglion cells in the peripheral nervous system, and microglia and astrocytes in the central nervous system, are important players in both peripheral and central processing of pain in the orofacial region. This review highlights recent molecular and cellular findings of the glia involvement and glia–neuron interactions in four common orofacial pain conditions such as headache, dental pulp injury, temporomandibular joint dysfunction/inflammation, and head and neck cancer. We will discuss the remaining questions and future directions on glial involvement in these four orofacial pain conditions.
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"Shooting pain" in lumbar radiculopathy and trigeminal neuralgia, and ideas concerning its neural substrates. Pain 2021; 161:308-318. [PMID: 31651576 DOI: 10.1097/j.pain.0000000000001729] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Patients with radicular low back pain (radicular LBP, sciatica) frequently describe their pain as "shooting" or "radiating." The dictionary meaning of these words implies rapid movement, and indeed, many sufferers report feeling pain moving rapidly from the lower back or buttock into the leg. But, others do not. Moreover, the sensation of movement is paradoxical; it is neither predicted nor accounted for by current ideas about the pathophysiology of radicular LBP. We have used a structured questionnaire to evaluate the sensory qualities associated with "shooting" and "radiating" in 155 patients, 98 with radicular LBP and 57 with trigeminal neuralgia, a second chronic pain condition in which shooting/radiating are experienced. Results indicated a spectrum of different sensations in different people. Although many sciatica patients reported rapid downward movement of their pain, even more reported downward expansion of the area of pain, some reported upward movement, and for some, there was no spatial dynamic at all. The velocity of movement or expansion was also variable. By cross-referencing sensations experienced in the sciatica and trigeminal neuralgia cohorts with known signal processing modes in the somatosensory system, we propose testable hypotheses concerning the pathophysiology of the various vectorial sensations reported, their direction and velocity, and the structures in which they are generated. Systematic evaluation of qualitative features of "shooting" and "radiating" pain at the time of diagnosis can shed light on the pain mechanism in the individual patient and perhaps contribute to a better therapeutic outcomes.
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Cho YS, Ko HG, Han HM, Park SK, Moozhayil SJ, Choi SY, Bae YC. Vesicular glutamate transporter-immunopositive axons that coexpress neuropeptides in the rat and human dental pulp. Int Endod J 2020; 54:377-387. [PMID: 33090483 DOI: 10.1111/iej.13427] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 10/05/2020] [Accepted: 10/05/2020] [Indexed: 12/17/2022]
Abstract
AIM To examine the type of vesicular glutamate transporter (VGLUT)-immunopositive (+) axons that coexpress neuropeptides in the rat and human dental pulp, which may help understand peripheral mechanism of pulpal inflammatory pain in rats and humans. METHODOLOGY The trigeminal ganglia (TG) and the dental pulp of the maxillary molar teeth from three male Sprague-Dawley rats weighing 300-330 g and dental pulps of three healthy human (male) maxillary premolar teeth from three 16 to 28-year-old patients extracted for orthodontic treatment were used. The type of VGLUT + axons that coexpress substance P (SP)- and/or calcitonin gene-related peptide (CGRP) and parvalbumin in the rat TG and in the axons of the rat and the human dental pulp was examined by double fluorescence immunohistochemistry and quantitative analysis. Results were analyzed using one-way anova and the Kruskal-Wallis test. RESULTS SP and CGRP were expressed in many human VGLUT1 + pulpal axons but not in the rat VGLUT1 + TG neurons and pulpal axons (P < 0.05). SP and CGRP were expressed in a considerable number of human VGLUT2 + pulpal axons and also in many rat TG neurons and pulpal axons. The fraction of VGLUT1 + axons expressing parvalbumin was about three times higher in the rat than in the human dental pulp (P < 0.05). CONCLUSIONS These findings suggest that the types of VGLUT + axons, which release neuropeptides, may be different between the rat and the human dental pulp, raising a possibility that peripheral mechanism of pulpal inflammatory pain may be different between rats and humans.
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Affiliation(s)
- Y S Cho
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - H G Ko
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - H M Han
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - S K Park
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - S J Moozhayil
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - S Y Choi
- Department of Oral & Maxillofacial Surgery, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - Y C Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea
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18
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Allison JR, Stone SJ, Pigg M. The painful tooth: mechanisms, presentation and differential diagnosis of odontogenic pain. ACTA ACUST UNITED AC 2020. [DOI: 10.1111/ors.12481] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- J. R. Allison
- School of Dental Sciences Faculty of Medical Sciences Newcastle University Newcastle upon Tyne UK
| | - S. J. Stone
- School of Dental Sciences Faculty of Medical Sciences Newcastle University Newcastle upon Tyne UK
| | - M. Pigg
- Department of Endodontics Faculty of Odontology Scandinavian Centre for Orofacial Neurosciences (SCON) Malmö University Malmö Sweden
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19
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Affiliation(s)
- Yong-Chul Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University
| | - Atsushi Yoshida
- Department of Oral Anatomy and Neurobiology, Graduate School of Dentistry, Osaka University
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20
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Lee PR, Lee JY, Kim HB, Lee JH, Oh SB. TRPM8 Mediates Hyperosmotic Stimuli-Induced Nociception in Dental Afferents. J Dent Res 2019; 99:107-114. [PMID: 31718465 DOI: 10.1177/0022034519886847] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Hyperosmolar sweet foods onto exposed tooth dentin evoke sudden and intense dental pain, called dentin hypersensitivity. However, it remains unclear how hyperosmolar stimuli excite dental primary afferent (DPA) neurons and thereby lead to dentin hypersensitivity. This study elucidated whether TRPM8, which is well known as a cold temperature- or menthol-activated receptor, additionally mediates nociception in response to hyperosmolar stimuli in adult mouse DPA neurons, which are identified by a fluorescent retrograde tracer: DiI. Single-cell reverse transcription polymerase chain reaction revealed that TRPM8 was expressed in subsets of DPA neurons and that TRPM8 was highly colocalized with TRPV1 and Piezo2. Immunohistochemical analysis also confirmed TRPM8 expression in DPA neurons. By using Fura-2-based calcium imaging, application of hyperosmolar sucrose solutions elicited calcium transients in subsets of the trigeminal ganglion neurons, which was significantly abolished by a selective TRPM8 antagonist: N-(3-Aminopropyl)-2-[(3-methylphenyl)methoxy]-N-(2-thienylmethyl)benzamide (AMTB) hydrochloride. When we further examined changes of c-fos expression (a neuronal activation marker) in the spinal trigeminal nucleus after hyperosmolar stimulation onto exposed tooth dentin, c-fos mRNA and protein expression were increased and were also significantly reduced by AMTB, especially in the spinal trigeminal interpolaris-caudalis transition zone (Vi/Vc). Taken together, our results provide strong evidence that TRPM8 expressed in DPA neurons might mediate dental pain as a hyperosmosensor in adult mice.
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Affiliation(s)
- P R Lee
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - J Y Lee
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - H B Kim
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - J H Lee
- Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea
| | - S B Oh
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea.,Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea
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21
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Byers MR. Chewing causes rapid changes in immunoreactive nerve patterns in rat molar teeth: Implications for dental proprioception and pain. Arch Oral Biol 2019; 107:104511. [PMID: 31445382 DOI: 10.1016/j.archoralbio.2019.104511] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 07/19/2019] [Accepted: 07/28/2019] [Indexed: 01/06/2023]
Abstract
OBJECTIVE This study tests the hypothesis that normal use of teeth (chewing) causes changes in immunoreactive-(IR) patterns for endings of large Aβ and CGRP axons in rat molar cusps. DESIGN First, a new paradigm to test chewing in adult male rats was developed. Then IR patterns for large dental axons were analysed for a calcium-binding protein, parvalbumin (PV), heavy neurofilament protein-200 (NFP), and vesicle-release molecule synaptophysin (SYN) that all typify large dental axons and proprioceptors for comparison with endings of CGRP-IR neuropeptide axons. The behavior groups were: (1) daytime sleeping/fasting (Group:SF); (2) brief feeding after 8-11 h of daytime sleeping/fasting (Group:SF-C); (3) normal nocturnal feeding (Group:N); (4) nocturnal fasting (Group:NF); (5) brief feeding/chewing after nocturnal fasting (Group:NF-C). RESULTS Nerve endings with NFP-, PV-, or SYN-IR were lost or altered in pulp and dentin in all chewing groups. Other endings with CGRP-IR were near those with PV-, NFP- and SYN-IR at the pulp-dentin border and in dentin, and they also lost immunoreactivity in all chewing groups. The special beaded regions along the crown pulp/dentin borders lost neural labeling in all chewing groups. Nerves of molar roots and periodontal ligament were not changed. CONCLUSIONS Rapid neural reactions to chewing show extensive, reversible, non-nociceptive depletions of crown innervation. Those changes were rapid enough to occur during normal feeding followed by recovery during rest. The new dental paradigm related to chewing and fasting allows dissection of intradental proprioceptive-like mechanisms during normal tooth functions for comparison with nociceptive and mechanosensitive reactions after injury or inflammation.
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Affiliation(s)
- Margaret R Byers
- Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA, 98195-6540 USA.
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22
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Erdogan O, Malek M, Janal MN, Gibbs JL. Sensory testing associates with pain quality descriptors during acute dental pain. Eur J Pain 2019; 23:1701-1711. [DOI: 10.1002/ejp.1447] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 06/22/2019] [Accepted: 06/23/2019] [Indexed: 11/10/2022]
Affiliation(s)
- Ozge Erdogan
- Department of Endodontics New York University College of Dentistry New York New York
- Department of Endodontics Faculty of Dentistry, Hacettepe University Ankara Turkey
| | - Matthew Malek
- Department of Endodontics New York University College of Dentistry New York New York
| | - Malvin N. Janal
- Department of Epidemiology and Health Promotion New York University College of Dentistry New York New York
| | - Jennifer L. Gibbs
- Department of Endodontics New York University College of Dentistry New York New York
- Department of Restorative Dentistry and Biomaterials Sciences Harvard School of Dental Medicine Boston Massachusetts
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23
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Lee K, Lee BM, Park CK, Kim YH, Chung G. Ion Channels Involved in Tooth Pain. Int J Mol Sci 2019; 20:ijms20092266. [PMID: 31071917 PMCID: PMC6539952 DOI: 10.3390/ijms20092266] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 05/03/2019] [Accepted: 05/03/2019] [Indexed: 01/05/2023] Open
Abstract
The tooth has an unusual sensory system that converts external stimuli predominantly into pain, yet its sensory afferents in teeth demonstrate cytochemical properties of non-nociceptive neurons. This review summarizes the recent knowledge underlying this paradoxical nociception, with a focus on the ion channels involved in tooth pain. The expression of temperature-sensitive ion channels has been extensively investigated because thermal stimulation often evokes tooth pain. However, temperature-sensitive ion channels cannot explain the sudden intense tooth pain evoked by innocuous temperatures or light air puffs, leading to the hydrodynamic theory emphasizing the microfluidic movement within the dentinal tubules for detection by mechanosensitive ion channels. Several mechanosensitive ion channels expressed in dental sensory systems have been suggested as key players in the hydrodynamic theory, and TRPM7, which is abundant in the odontoblasts, and recently discovered PIEZO receptors are promising candidates. Several ligand-gated ion channels and voltage-gated ion channels expressed in dental primary afferent neurons have been discussed in relation to their potential contribution to tooth pain. In addition, in recent years, there has been growing interest in the potential sensory role of odontoblasts; thus, the expression of ion channels in odontoblasts and their potential relation to tooth pain is also reviewed.
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Affiliation(s)
- Kihwan Lee
- Gachon Pain Center and Department of Physiology, College of Medicine, Gachon University, Incheon 406-799, Korea.
| | - Byeong-Min Lee
- Department of Oral Physiology and Program in Neurobiology, School of Dentistry, Seoul National University, Seoul 08826, Korea.
| | - Chul-Kyu Park
- Gachon Pain Center and Department of Physiology, College of Medicine, Gachon University, Incheon 406-799, Korea.
| | - Yong Ho Kim
- Gachon Pain Center and Department of Physiology, College of Medicine, Gachon University, Incheon 406-799, Korea.
| | - Gehoon Chung
- Department of Oral Physiology and Program in Neurobiology, School of Dentistry, Seoul National University, Seoul 08826, Korea.
- Dental Research Institute, Seoul National University, Seoul 03080, Korea.
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Hossain MZ, Bakri MM, Yahya F, Ando H, Unno S, Kitagawa J. The Role of Transient Receptor Potential (TRP) Channels in the Transduction of Dental Pain. Int J Mol Sci 2019; 20:ijms20030526. [PMID: 30691193 PMCID: PMC6387147 DOI: 10.3390/ijms20030526] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2018] [Revised: 01/18/2019] [Accepted: 01/24/2019] [Indexed: 12/18/2022] Open
Abstract
Dental pain is a common health problem that negatively impacts the activities of daily living. Dentine hypersensitivity and pulpitis-associated pain are among the most common types of dental pain. Patients with these conditions feel pain upon exposure of the affected tooth to various external stimuli. However, the molecular mechanisms underlying dental pain, especially the transduction of external stimuli to electrical signals in the nerve, remain unclear. Numerous ion channels and receptors localized in the dental primary afferent neurons (DPAs) and odontoblasts have been implicated in the transduction of dental pain, and functional expression of various polymodal transient receptor potential (TRP) channels has been detected in DPAs and odontoblasts. External stimuli-induced dentinal tubular fluid movement can activate TRP channels on DPAs and odontoblasts. The odontoblasts can in turn activate the DPAs by paracrine signaling through ATP and glutamate release. In pulpitis, inflammatory mediators may sensitize the DPAs. They could also induce post-translational modifications of TRP channels, increase trafficking of these channels to nerve terminals, and increase the sensitivity of these channels to stimuli. Additionally, in caries-induced pulpitis, bacterial products can directly activate TRP channels on DPAs. In this review, we provide an overview of the TRP channels expressed in the various tooth structures, and we discuss their involvement in the development of dental pain.
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Affiliation(s)
- Mohammad Zakir Hossain
- Department of Oral Physiology, School of Dentistry, Matsumoto Dental University, 1780 Gobara Hirooka, Shiojiri, Nagano 399-0781, Japan.
| | - Marina Mohd Bakri
- Department of Oral and Craniofacial Sciences, Faculty of Dentistry, University of Malaya, Kuala Lumpur 50603, Malaysia.
| | - Farhana Yahya
- Department of Oral and Craniofacial Sciences, Faculty of Dentistry, University of Malaya, Kuala Lumpur 50603, Malaysia.
| | - Hiroshi Ando
- Department of Biology, School of Dentistry, Matsumoto Dental University, 1780 Gobara, Hirooka, Shiojiri, Nagano 399-0781, Japan.
| | - Shumpei Unno
- Department of Oral Physiology, School of Dentistry, Matsumoto Dental University, 1780 Gobara Hirooka, Shiojiri, Nagano 399-0781, Japan.
| | - Junichi Kitagawa
- Department of Oral Physiology, School of Dentistry, Matsumoto Dental University, 1780 Gobara Hirooka, Shiojiri, Nagano 399-0781, Japan.
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Michot B, Lee CS, Gibbs JL. TRPM8 and TRPA1 do not contribute to dental pulp sensitivity to cold. Sci Rep 2018; 8:13198. [PMID: 30181551 PMCID: PMC6123413 DOI: 10.1038/s41598-018-31487-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 08/15/2018] [Indexed: 01/17/2023] Open
Abstract
Sensory neurons innervating the dental pulp have unique morphological and functional characteristics compared to neurons innervating other tissues. Stimulation of dental pulp afferents whatever the modality or intensity of the stimulus, even light mechanical stimulation that would not activate nociceptors in other tissues, produces an intense pain. These specific sensory characteristics could involve receptors of the Transient Receptor Potential channels (TRP) family. In this study, we compared the expression of the cold sensitive receptors TRPM8 and TRPA1 in trigeminal ganglion neurons innervating the dental pulp, the skin of the cheek or the buccal mucosa and we evaluated the involvement of these receptors in dental pulp sensitivity to cold. We showed a similar expression of TRPM8, TRPA1 and CGRP in sensory neurons innervating the dental pulp, the skin or the mucosa. Moreover, we demonstrated that noxious cold stimulation of the tooth induced an overexpression of cFos in the trigeminal nucleus that was not prevented by the genetic deletion of TRPM8 or the administration of the TRPA1 antagonist HC030031. These data suggest that the unique sensory characteristics of the dental pulp are independent to TRPM8 and TRPA1 receptors expression and functionality.
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Affiliation(s)
- Benoit Michot
- Department of Endodontics, New York University College of Dentistry, New York, USA.
| | - Caroline S Lee
- Department of Endodontics, New York University College of Dentistry, New York, USA
| | - Jennifer L Gibbs
- Department of Endodontics, New York University College of Dentistry, New York, USA
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Bae JY, Mun CJ, Kim YS, Ahn DK, Bae YC. Quantitative ultrastructural analysis of fibers expressing parvalbumin, calretinin, calbindin D-28k, stage specific embryonic antigen-4, and phosphorylated neurofilament 200 in the peripheral sensory root of the rat trigeminal ganglion. J Comp Neurol 2018; 526:2204-2214. [DOI: 10.1002/cne.24476] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 04/02/2018] [Accepted: 05/14/2018] [Indexed: 11/07/2022]
Affiliation(s)
- Jin Young Bae
- Department of Anatomy and Neurobiology, School of Dentistry; Kyungpook National University; Daegu South Korea
| | - Cheol Ju Mun
- Department of Anatomy and Neurobiology, School of Dentistry; Kyungpook National University; Daegu South Korea
| | - Yun Sook Kim
- Department of Anatomy and Neurobiology, School of Dentistry; Kyungpook National University; Daegu South Korea
| | - Dong Kuk Ahn
- Department of Physiology, School of Dentistry; Kyungpook National University; Daegu South Korea
| | - Yong Chul Bae
- Department of Anatomy and Neurobiology, School of Dentistry; Kyungpook National University; Daegu South Korea
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Bakri MM, Yahya F, Munawar KMM, Kitagawa J, Hossain MZ. Transient receptor potential vanilloid 4 (TRPV4) expression on the nerve fibers of human dental pulp is upregulated under inflammatory condition. Arch Oral Biol 2018; 89:94-98. [PMID: 29499561 DOI: 10.1016/j.archoralbio.2018.02.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 12/27/2017] [Accepted: 02/15/2018] [Indexed: 10/18/2022]
Abstract
OBJECTIVE Transient receptor potential vanilloid 4 (TRPV4) has been considered as a mechano-, thermo- and osmo-receptor. Under inflammatory conditions in dental pulp, teeth can become sensitive upon exposure to a variety of innocuous stimuli. The objective of the present study was to investigate the expression of the TRPV4 channel on nerve fibers in human dental pulp of non-symptomatic and symptomatic teeth associated with inflammatory conditions. DESIGN Dental pulp from extracted human permanent teeth was processed for fluorescence immunohistochemistry. Ten asymptomatic (normal) and 10 symptomatic (symptoms associated with pulpitis) teeth were used in this study. Nerve fibers were identified by immunostaining for a marker, protein gene product 9.5, and the cells were counterstained with 4',6-diamidino-2-phenylindole. An anti-TRPV4 antibody was used to trace TRPV4 expression. RESULTS TRPV4 expression was co-localized with the nerve fiber marker. Immunoreactivity for TRPV4 was more intense (p < 0.05) in the nerves of symptomatic teeth than those of normal teeth. The number of co-localization spots was increased significantly (p < 0.05) in the dental pulp of symptomatic teeth compared with that of asymptomatic (normal) teeth. CONCLUSIONS There is expression of TRPV4 channels on the nerve fibers of human dental pulp. Our findings suggest upregulation of TRPV4 expression under inflammatory conditions in the pulp. The upregulation of TRPV4 channels may be associated with the exaggerated response of dental pulp to innocuous mechanical, thermal and osmotic stimuli under inflammatory conditions.
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Affiliation(s)
- Marina M Bakri
- Department of Oral and Craniofacial Sciences, Faculty of Dentistry, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | - Farhana Yahya
- Department of Oral and Craniofacial Sciences, Faculty of Dentistry, University of Malaya, 50603 Kuala Lumpur, Malaysia
| | | | - Junichi Kitagawa
- Department of Oral Physiology, School of Dentistry, Matsumoto Dental University, 1780 Gobara Hirooka, Shiojiri, Nagano 399-0781, Japan
| | - Mohammad Zakir Hossain
- Department of Oral Physiology, School of Dentistry, Matsumoto Dental University, 1780 Gobara Hirooka, Shiojiri, Nagano 399-0781, Japan.
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Heft MW, Litaker MS, Kopycka-Kedzierawski DT, Meyerowitz C, Chonowski S, Yardic RL, Gordan VV, Mungia R, Gilbert GH. Patient-Centered Dentinal Hypersensitivity Treatment Outcomes: Results from the National Dental PBRN. JDR Clin Trans Res 2017; 3:76-82. [PMID: 29276777 DOI: 10.1177/2380084417742099] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Dentinal hypersensitivity (DH) can have a significant impact on oral health and functioning, and it is a clinical symptom commonly managed by dentists during routine clinical practice. DH symptoms are typically elicited by otherwise innocuous, nonpainful stimuli applied to exposed dentin (e.g., tactile stimuli, warming or cooling temperatures or air puffs). Treatment approaches have sought to directly target the dentinal pulp tissues or close dentinal tubules via dental office care and treatment services (fluoride varnishes, glutaraldehydes, bonding agents, sealants, oxalates, or lasers) or home care services (toothpastes or dentifrices containing fluoride or potassium nitrate compounds). The purpose of this prospective multicenter cohort study was to assess how community-based dentists from the National Dental Practice-Based Research Network (National Dental PBRN) manage DH and whether the effectiveness of DH treatments can be assessed in those settings. A total of 171 dentists recruited 1862 subjects with DH from their existing patients. Dentists then recommended and provided DH treatment as appropriate. Treatment choice was at the discretion of the dentists. Patients rated their DH pain at baseline and 1, 4, and 8 wk during the course of their treatments. They used pain intensity and unpleasantness visual analog scales and 4 labeled magnitude scales and rated their satisfaction with treatment after 8 wk. Patients were provided reminders postbaseline via email, texting, or voice mail. These patient-centered outcomes served as the principal measures for the assessment of treatment because treatments sought to alleviate DH symptoms. The patients with DH who reported pain reduction from dentist-provided treatments (glutaraldehyde/HEMA [hydroxyethyl methacrylate] compounds, oxalates, and bonding agents), dentists' advice and counseling regarding oral habits and diet, and patient-applied fluoride toothpaste reported a concomitant positive rating of satisfaction with DH treatments. The results from this study support the feasibility of engaging network practices to assess the effectiveness of clinical DH treatments. Knowledge Transfer Statement: National Dental PBRN dentists provide a range of procedures to treat dentinal hypersensitivity. In this large nonrandomized study designed to assess clinical care and to capture patient-reported outcomes, about 60% of patients reported improvement in pain. This study demonstrated the feasibility of engaging network dentists and their patients to assess treatment effectiveness. Future studies will explore the feasibility of imposing randomization and measuring patient compliance with treatment in the manner that this treatment is provided.
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Affiliation(s)
- M W Heft
- Department of Oral and Maxillofacial Surgery, College of Dentistry, University of Florida, Gainesville, FL, USA
| | - M S Litaker
- Department of Clinical and Community Sciences, School of Dentistry, University of Alabama at Birmingham, Birmingham, AL, USA
| | | | - C Meyerowitz
- Eastman Institute for Oral Health, University of Rochester, Rochester, NY, USA
| | - S Chonowski
- Private practice, general dentistry, Morristown, NJ, USA
| | - R L Yardic
- HealthPartners Apple Valley Dental Clinic, Apple Valley, MN, USA
| | - V V Gordan
- College of Dentistry, University of Florida, Gainesville, FL, USA
| | - R Mungia
- Department of Periodontology, The University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - G H Gilbert
- School of Dentistry, University of Alabama at Birmingham, Birmingham, AL, USA
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Byers MR, Cornel LM. Multiple complex somatosensory systems in mature rat molars defined by immunohistochemistry. Arch Oral Biol 2017; 85:84-97. [PMID: 29035722 DOI: 10.1016/j.archoralbio.2017.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 08/24/2017] [Accepted: 09/13/2017] [Indexed: 12/25/2022]
Abstract
OBJECTIVE Intradental sensory receptors trigger painful sensations and unperceived mechanosensitivity, but the receptor bases for those functions are only partly defined. We present new evidence here concerning complex endings of myelinated axons in rat molars. DESIGN We sectioned mature rat jaws in sagittal and transverse planes to analyze neural immunoreactivity (IR) for parvalbumin, peripherin, neurofilament protein, neurotrophin receptors, synaptophysin, calcitonin gene-related peptide (CGRP), or mas-related g-protein-receptor-d (Mrgprd). RESULTS We found two complex sensory systems in mature rat molar dentin that labeled with neurofilament protein-IR, plus either parvalbumin-IR or peripherin-IR. The parvalbumin-IR system made extensively branched, beaded endings focused into dentin throughout each pulp horn. The peripherin-IR system primarily made unbeaded, fork-shaped dentinal endings scattered throughout crown including cervical regions. Both of these systems differed from neuropeptide CGRP-IR. In molar pulp we found peripherin- and parvalbumin-IR layered endings, either near special horizontal plexus arrays or in small coiled endings near tangled plexus, each with specific foci for specific pulp horns. Parvalbumin-IR nerve fibers had Aβ axons (5-7μm diameter), while peripherin-IR axons were thinner Aδ size (2-5μm). Mechano-nociceptive Mrgprd-IR was only found in peripherin-IR axons. CONCLUSIONS Complex somatosensory receptors in rat molars include two types of dentinal endings that both differ from CGRP-IR endings, and at least two newly defined types of pulpal endings. The PV-IR neurons with their widely branched, synaptophysin-rich, intradentinal beaded endings are good candidates for endodontic non-nociceptive, low threshold, unperceived mechanoreceptors. The complex molar dentinal and pulpal sensory systems were not found in rat incisors.
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Affiliation(s)
- Margaret R Byers
- Department of Anesthesiology & Pain Medicine, Box 356540, University of Washington, Seattle, WA 98195-6540, USA.
| | - Leanne M Cornel
- Department of Anesthesiology & Pain Medicine, Box 356540, University of Washington, Seattle, WA 98195-6540, USA
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Krivanek J, Adameyko I, Fried K. Heterogeneity and Developmental Connections between Cell Types Inhabiting Teeth. Front Physiol 2017. [PMID: 28638345 PMCID: PMC5461273 DOI: 10.3389/fphys.2017.00376] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Every tissue is composed of multiple cell types that are developmentally, evolutionary and functionally integrated into the unit we call an organ. Teeth, our organs for biting and mastication, are complex and made of many different cell types connected or disconnected in terms of their ontogeny. In general, epithelial and mesenchymal compartments represent the major framework of tooth formation. Thus, they give rise to the two most important matrix–producing populations: ameloblasts generating enamel and odontoblasts producing dentin. However, the real picture is far from this quite simplified view. Diverse pulp cells, the immune system, the vascular system, the innervation and cells organizing the dental follicle all interact, and jointly participate in transforming lifeless matrix into a functional organ that can sense and protect itself. Here we outline the heterogeneity of cell types that inhabit the tooth, and also provide a life history of the major populations. The mouse model system has been indispensable not only for the studies of cell lineages and heterogeneity, but also for the investigation of dental stem cells and tooth patterning during development. Finally, we briefly discuss the evolutionary aspects of cell type diversity and dental tissue integration.
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Affiliation(s)
- Jan Krivanek
- Department of Molecular Neurosciences, Center for Brain Research, Medical University ViennaVienna, Austria
| | - Igor Adameyko
- Department of Molecular Neurosciences, Center for Brain Research, Medical University ViennaVienna, Austria.,Department of Physiology and Pharmacology, Karolinska InstitutetStockholm, Sweden
| | - Kaj Fried
- Department of Neuroscience, Karolinska InstitutetStockholm, Sweden
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Won J, Vang H, Lee P, Kim Y, Kim H, Kang Y, Oh S. Piezo2 Expression in Mechanosensitive Dental Primary Afferent Neurons. J Dent Res 2017; 96:931-937. [DOI: 10.1177/0022034517702342] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Mechanosensitive ion channels have been suggested to be expressed in dental primary afferent (DPA) neurons to transduce the movement of dentinal fluid since the proposal of hydrodynamic theory. Piezo2, a mechanosensitive, rapidly inactivating (RI) ion channel, has been recently identified in dorsal root ganglion (DRG) neurons to mediate tactile transduction. Here, we examined the expression of Piezo2 in DPA neurons by in situ hybridization, single-cell reverse transcriptase polymerase chain reaction, and whole-cell patch-clamp recordings. DPA neurons with Piezo2 messenger RNA (mRNA) or Piezo2-like currents were further characterized based on their neurochemical and electrophysiological properties. Piezo2 mRNA was found mostly in medium- to large-sized DPA neurons, with the majority of these neurons also positive for Nav1.8, CGRP, and NF200, whereas only a minor population was positive for IB4 and peripherin. Whole-cell patch-clamp recordings revealed Piezo2-like, RI currents evoked by mechanical stimulation in a subpopulation of DPA neurons. RI currents were pharmacologically blocked by ruthenium red, a compound known to block Piezo2, and were also reduced by small interfering RNA-mediated Piezo2 knockdown. Piezo2-like currents were observed almost exclusively in IB4-negative DPA neurons, with the current amplitude larger in capsaicin-insensitive DPA neurons than the capsaicin-sensitive population. Our findings show that subpopulation of DPA neurons is indeed mechanically sensitive. Within this subpopulation of mechanosensitive DPA neurons, we have identified the Piezo2 ion channel as a potential transducer for mechanical stimuli, contributing to RI inward currents. Piezo2-positive DPA neurons were characterized as medium- to large-sized neurons with myelinated A-fibers, containing nociceptive peptidergic neurotransmitters.
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Affiliation(s)
- J. Won
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - H. Vang
- Dental Research Institute and Department of Neurobiology & Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea
| | - P.R. Lee
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - Y.H. Kim
- Dental Research Institute and Department of Neurobiology & Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea
- Department of Physiology, College of Medicine, Gachon University, Incheon, Republic of Korea (present address)
| | - H.W. Kim
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
| | - Y. Kang
- Dental Research Institute and Department of Neurobiology & Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea
- Department of Neuroscience and Oral Physiology, Osaka University Graduate School of Dentistry, Osaka, Japan
| | - S.B. Oh
- Department of Brain and Cognitive Sciences, College of Natural Sciences, Seoul National University, Seoul, Republic of Korea
- Dental Research Institute and Department of Neurobiology & Physiology, School of Dentistry, Seoul National University, Seoul, Republic of Korea
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Kim TH, Park SK, Choi SY, Lee JS, Bae YC. Morphologic Change of Parvalbumin-positive Myelinated Axons in the Human Dental Pulp. J Endod 2017; 43:977-981. [PMID: 28389070 DOI: 10.1016/j.joen.2017.01.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 12/22/2016] [Accepted: 01/09/2017] [Indexed: 12/13/2022]
Abstract
INTRODUCTION Information on the nerve fibers innervating the dental pulp is crucial for understanding dental pain and hypersensitivity. This study investigated the morphologic differences of parvalbumin (PV)-positive (+) myelinated fibers in 3 different regions of the human dental pulp. METHODS Light and electron microscopic immunohistochemistry for parvalbumin, a marker for myelinated fibers, and quantitative analysis were performed in the apical root, core of coronal pulp, and peripheral pulp of human premolar teeth. RESULTS About 40% of the myelinated fibers in the apical root pulp became unmyelinated in the core of the coronal pulp, and virtually all the remaining fibers became unmyelinated at the peripheral pulp. The size of myelinated axons decreased from root to peripheral pulp. PV+ axons showed extensive axonal varicosities in the peripheral pulp. CONCLUSIONS These findings suggest that the myelinated fibers innervating the human dental pulp undergo extensive morphologic change in the extrapulpal region and in the coronal and peripheral pulp, and that PV-mediated regulation of calcium concentration and its downstream events may occur primarily in axonal varicosities in the peripheral pulp.
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Affiliation(s)
- Tae Heon Kim
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - Sook Kyung Park
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - So Young Choi
- Department of Oral & Maxillofacial Surgery, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - Jae Sik Lee
- Department of Pediatric Dentistry, School of Dentistry, Kyungpook National University, Daegu, South Korea
| | - Yong Chul Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, South Korea.
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Rezende M, De Geus JL, Loguercio AD, Reis A, Kossatz D. Clinical Evaluation of Genotoxicity of In-office Bleaching. Oper Dent 2016; 41:578-586. [DOI: 10.2341/15-207-c] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
SUMMARY
Objective: The aim of this study was to evaluate the genotoxicity of in-office bleaching with 35% hydrogen peroxide in epithelial cells from the gingival and lip tissues.
Methods and Materials: Thirty volunteers with central incisors shade A1 or darker were selected for this study. The gingival tissue of the teeth to be bleached was isolated with a light-polymerized resin dam, and the 35% hydrogen peroxide gel was administered during three 15-minute applications over the course of the 45-minute application period. Two bleaching sessions with a one-week interval in between were performed. Exfoliated oral mucosa gingival epithelial cells and upper lip lining were collected at baseline and one month after the in-office dental bleaching. The scraped cells were placed on clean glass slides and smears were prepared. After staining with Giemsa solution, two blinded examiners performed cell and micronuclei counts under a 100× optical microscope. Tooth sensitivity was evaluated using the Visual Analogue Scale (VAS). Shade evaluation was recorded before and one month after the bleaching treatment with the value-oriented shade guide Vita Bleachedguide 3D-MASTER and the spectrophotometer Vita Easyshade. Data from the shade guide units and the micronuclei (MN) frequency were subjected to a Mann-Whitney test (α=0.05). The overall difference between before and one month after the bleaching treatment (ΔE and ΔSGU), absolute risk, and intensity of tooth sensitivity (TS) were calculated, as was the 95% confidence interval (CI).
Results: The frequency of MN was not increased after bleaching with 35% hydrogen peroxide in both study groups (p>0.05). The absolute risk of TS of the participants was 93% (95% CI, 79%-98%), with a mean VAS intensity of 5.7 ± 2.9 (95% CI, 4.6-6.8). Meaningful whitening was observed after bleaching. The change in shade guide units in the Bleachedguide 3D-MASTER was 2.3 ± 1.4. In terms of ΔE, the change in color was 7.7 ± 3.5.
Conclusions: The in-office bleaching did not induce DNA damage to the gingival and lip tissue during the bleaching period. Although effective whitening was observed, most of the participants experienced TS.
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Affiliation(s)
- M Rezende
- Márcia Rezende, DDS, MS, postdoctoral student, Department of Restorative Dentistry, University Estadual de Ponta Grossa, Ponta Grossa, Brazil
| | - JL De Geus
- Juliana Larocca De Geus, DDS, MS, doctoral student, Department of Restorative Dentistry, University Estadual de Ponta Grossa, Ponta Grossa, Brazil
| | - AD Loguercio
- Alessandro Dourado Loguercio, DDS, MS, PhD, professor, School of Dentistry, State University of Ponta Grossa, Ponta Grossa, Brazil
| | - A Reis
- Alessandra Reis, DDS, PhD, professor, School of Dentistry, Department of Restorative Dentistry, University Estadual de Ponta Grossa, Ponta Grossa, Brazil
| | - D Kossatz
- Stella Kossatz, DDS, MS, PhD, professor, School of Dentistry, Department of Restorative Dentistry, University Estadual de Ponta Grossa, Ponta Grossa, Brazil
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Hargreaves KM, Ruparel S. Role of Oxidized Lipids and TRP Channels in Orofacial Pain and Inflammation. J Dent Res 2016; 95:1117-23. [PMID: 27307050 DOI: 10.1177/0022034516653751] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Acute or chronic inflammation comprises a highly prevalent type of orofacial pain and is mediated by the generation of endogenous agonists that activate numerous receptors expressed on terminals of trigeminal (TG) nociceptive afferent neurons. One such studied receptor is transient receptor potential vanilloid subtype 1 (TRPV1). TRPV1 is a ligand-gated cation channel that is expressed on a major subclass of nociceptors and is found in many orofacial tissues, including dental pulp. Antagonists to TRPV1 reveal an important role for this channel in mediating hypersensitivity in preclinical models of inflammatory or neuropathic pain. Recent studies have demonstrated that endogenous TRPV1 agonists are generated by oxidation of omega-6 polyunsaturated fatty acids, including both linoleic acid and arachidonic acid. A major mechanism triggering the release of oxidative linoleic acid metabolites (OLAMs) and oxidative arachidonic acid metabolites (OAAMs) is the action of oxidative enzymes. Oxidative enzymes such as cytochrome P450 isozymes are rapidly upregulated in TG neurons after orofacial inflammation and increase the capacity of TG neurons to generate OLAMs. Cytochrome P450 isozymes are also increased in immune cells in irreversibly inflamed human dental pulp, and extracts of this tissue have significantly increased capacity to generate OLAMs. Together, these studies point to a novel pain mechanism involving the enzymatic generation of endogenous OLAM and OAAM agonists of TRPV1. This finding provides a rationale for an entirely new class of analgesics by inhibition of oxidative enzyme activity.
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Affiliation(s)
- K M Hargreaves
- Department of Endodontics, University of Texas Health Science Center at San Antonio, TX, USA
| | - S Ruparel
- Department of Endodontics, University of Texas Health Science Center at San Antonio, TX, USA
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Variability in Capsaicin-stimulated Calcitonin Gene-related Peptide Release from Human Dental Pulp. J Endod 2016; 42:542-6. [PMID: 26898566 DOI: 10.1016/j.joen.2015.12.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 12/14/2015] [Accepted: 12/15/2015] [Indexed: 12/16/2022]
Abstract
INTRODUCTION The unique innervation and anatomic features of dental pulp contribute to the remarkable finding that any physical stimulation of pulpal tissue is painful. Furthermore, when pathological processes such as caries affect teeth and produce inflammation of the pulp, the pain experienced can be quite intense and debilitating. To better understand these underlying neurobiological mechanisms and identify novel analgesic targets for pulpally derived pain, we have developed a powerful ex vivo model using human tooth slices. METHODS Noncarious, freshly extracted teeth were collected and sectioned longitudinally into 1-mm-thick slices containing both dental pulp and the surrounding mineralized tissues. Tooth slices from 36 patients were exposed to 60 μmol/L capsaicin to stimulate the release of calcitonin gene-related peptide (CGRP) from nerve terminals in the pulp. Patient factors were analyzed for their effects on capsaicin-stimulated CGRP release using a mixed model analysis of variance. RESULTS Approximately one third of the variability observed in capsaicin-evoked CGRP release was attributable to differences between individuals. In terms of individual factors, there was no effect of anesthesia type, sex, or age on capsaicin-stimulated CGRP release. Using a within-subject study design, a significant effect of capsaicin on CGRP release was observed. CONCLUSIONS Capsaicin-stimulated CGRP release from dental pulp is highly variable between individuals. A within-subject study design improves the variability and maximizes the potential of this powerful translational model to test the efficacy of novel pharmacotherapeutic agents on human peripheral nociceptors.
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Ettlin DA, Lukic N, Abazi J, Widmayer S, Meier ML. Tracking local anesthetic effects using a novel perceptual reference approach. J Neurophysiol 2016; 115:1730-4. [PMID: 26792885 DOI: 10.1152/jn.00917.2015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 01/15/2016] [Indexed: 11/22/2022] Open
Abstract
Drug effects of loco-regional anesthetics are commonly measured by unidimensional pain rating scales. These scales require subjects to transform their perceptual correlates of stimulus intensities onto a visual, verbal, or numerical construct that uses a unitless cognitive reference frame. The conceptual understanding and execution of this magnitude estimation task may vary among individuals and populations. To circumvent inherent shortcomings of conventional experimental pain scales, this study used a novel perceptual reference approach to track subjective sensory perceptions during onset of an analgesic nerve block. In 34 male subjects, nociceptive electric stimuli of 1-ms duration were repetitively applied to left (target) and right (reference) mandibular canines every 5 s for 600 s, with a side latency of 1 ms. Stimulus strength to the target canine was programmed to evoke a tolerable pain intensity perception and remained constant at this level throughout the experiment. A dose of 0.6 ml of articaine 4% was submucosally injected at the left mental foramen. Subjects then reported drug effects by adjusting the stimulus strength (in milliamperes) to the reference tooth, so that the perceived intensity in the reference tooth was equi-intense to the target tooth. Pain and stimulus perception offsets were indicated by subjects. Thus, the current approach for matching the sensory experience in one anatomic location after regional anesthesia allows detailed tracking of evolving perceptual changes in another location. This novel perceptual reference approach facilitates direct and accurate quantification of analgesic effects with high temporal resolution. We propose using this method for future experimental investigations of analgesic/anesthetic drug efficacy.
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Affiliation(s)
- Dominik A Ettlin
- Center of Dental Medicine, University of Zurich, Zurich, Switzerland
| | - Nenad Lukic
- Center of Dental Medicine, University of Zurich, Zurich, Switzerland
| | - Jetmir Abazi
- Center of Dental Medicine, University of Zurich, Zurich, Switzerland
| | - Sonja Widmayer
- Department of Psychiatry, Universitäre Psychiatrische Kliniken, University of Basel, Basel, Switzerland
| | - Michael L Meier
- Center of Dental Medicine, University of Zurich, Zurich, Switzerland; Balgrist University Hospital, Zurich, Switzerland; and
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Rezende M, Bonafé E, Vochikovski L, Farago PV, Loguercio AD, Reis A, Kossatz S. Pre- and postoperative dexamethasone does not reduce bleaching-induced tooth sensitivity: A randomized, triple-masked clinical trial. J Am Dent Assoc 2015; 147:41-9. [PMID: 26562735 DOI: 10.1016/j.adaj.2015.07.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Revised: 06/29/2015] [Accepted: 07/01/2015] [Indexed: 10/22/2022]
Abstract
BACKGROUND Tooth sensitivity (TS) is the most common side effect of dental bleaching therapies. Dexamethasone has been used with tooth bleaching to reduce TS. The efficacy of dexamethasone for this purpose has not been well studied. METHODS The authors conducted a triple-masked, randomized, clinical trial with a parallel design involving 63 healthy participants who received either a placebo or dexamethasone. The placebo or dexamethasone (8 milligrams) was administered 1 hour before the in-office bleaching (35% hydrogen peroxide) and extra doses of 4 mg were administered every 6 hours for a total of 48 hours. TS was recorded on 2 scales: visual analog scale (0-10) and numeric rating scale (0-4) in different periods. The color evaluations were performed before and 1 month after dental bleaching with visual shade guides VITA Classical (VITA Zahnfabrik) and VITA Bleachedguide 3D-MASTER (VITA Zahnfabrik), and for a shade guide evaluation, the authors used a digital spectrophotometer, VITA Easyshade (VITA Zahnfabrik). The absolute risk of TS was evaluated by a Fisher exact test. Data of TS intensity using the NRS scale for the 2 groups were compared with Mann-Whitney and Friedman tests, whereas data from the visual analog scale were evaluated by 2-way repeated measures analysis of variance. The color changes between groups were compared using a t test (α = .05). RESULTS In both groups, the authors detected a high risk of TS, which was approximately 90%. No significant difference was observed in terms of TS intensity. A whitening of approximately 3 shade guide units of the VITA Classical was detected in both groups, which were statistically similar. CONCLUSIONS The use of dexamethasone before bleaching did not reduce the risk and intensity of bleaching-induced TS. PRACTICAL IMPLICATIONS The use of the steroidal anti-inflammatory agent dexamethasone was not capable of preventing TS arising from in-office dental bleaching.
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Cho Y, Kim Y, Moozhayil S, Yang E, Bae Y. The expression of hyperpolarization-activated cyclic nucleotide-gated channel 1 (HCN1) and HCN2 in the rat trigeminal ganglion, sensory root, and dental pulp. Neuroscience 2015; 291:15-25. [DOI: 10.1016/j.neuroscience.2015.01.066] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Revised: 01/27/2015] [Accepted: 01/28/2015] [Indexed: 10/24/2022]
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40
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Oral somatosensory awareness. Neurosci Biobehav Rev 2014; 47:469-84. [DOI: 10.1016/j.neubiorev.2014.09.015] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 09/03/2014] [Accepted: 09/10/2014] [Indexed: 12/19/2022]
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Expression of vesicular glutamate transporters VGLUT1 and VGLUT2 in the rat dental pulp and trigeminal ganglion following inflammation. PLoS One 2014; 9:e109723. [PMID: 25290694 PMCID: PMC4188624 DOI: 10.1371/journal.pone.0109723] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 09/04/2014] [Indexed: 01/07/2023] Open
Abstract
Background There is increasing evidence that peripheral glutamate signaling mechanism is involved in the nociceptive transmission during pathological conditions. However, little is known about the glutamate signaling mechanism and related specific type of vesicular glutamate transporter (VGLUT) in the dental pulp following inflammation. To address this issue, we investigated expression and protein levels of VGLUT1 and VGLUT2 in the dental pulp and trigeminal ganglion (TG) following complete Freund’s adjuvant (CFA) application to the rat dental pulp by light microscopic immunohistochemistry and Western blot analysis. Results The density of VGLUT2− immunopositive (+) axons in the dental pulp and the number of VGLUT2+ soma in the TG increased significantly in the CFA-treated group, compared to control group. The protein levels of VGLUT2 in the dental pulp and TG were also significantly higher in the CFA-treated group than control group by Western blot analysis. The density of VGLUT1+ axons in the dental pulp and soma in the TG remained unchanged in the CFA-treated group. Conclusions These findings suggest that glutamate signaling that is mediated by VGLUT2 in the pulpal axons may be enhanced in the inflamed dental pulp, which may contribute to pulpal axon sensitization leading to hyperalgesia following inflammation.
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Stimulation-induced ectopicity and propagation windows in model damaged axons. J Comput Neurosci 2014; 37:523-31. [PMID: 25110188 PMCID: PMC4224747 DOI: 10.1007/s10827-014-0521-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 07/21/2014] [Accepted: 07/23/2014] [Indexed: 12/04/2022]
Abstract
Neural tissue injuries render voltage-gated Na+ channels (Nav) leaky, thereby altering excitability, disrupting propagation and causing neuropathic pain related ectopic activity. In both recombinant systems and native excitable membranes, membrane damage causes the kinetically-coupled activation and inactivation processes of Nav channels to undergo hyperpolarizing shifts. This damage-intensity dependent change, called coupled left-shift (CLS), yields a persistent or “subthreshold” Nav window conductance. Nodes of Ranvier simulations involving various degrees of mild CLS showed that, as the system’s channel/pump fluxes attempt to re-establish ion homeostasis, the CLS elicits hyperexcitability, subthreshold oscillations and neuropathic type action potential (AP) bursts. CLS-induced intermittent propagation failure was studied in simulations of stimulated axons, but pump contributions were ignored, leaving open an important question: does mild-injury (small CLS values, pumps functioning well) render propagation-competent but still quiescent axons vulnerable to further impairments as the system attempts to cope with its normal excitatory inputs? We probe this incipient diffuse axonal injury scenario using a 10-node myelinated axon model. Fully restabilized nodes with mild damage can, we show, become ectopic signal generators (“ectopic nodes”) because incoming APs stress Na+/K+ gradients, thereby altering spike thresholds. Comparable changes could contribute to acquired sodium channelopathies as diverse as epileptic phenomena and to the neuropathic amplification of normally benign sensory inputs. Input spike patterns, we found, propagate with good fidelity through an ectopically firing site only when their frequencies exceed the ectopic frequency. This “propagation window” is a robust phenomenon, occurring despite Gaussian noise, large jitter and the presence of several consecutive ectopic nodes.
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Egbuniwe O, Grover S, Duggal AK, Mavroudis A, Yazdi M, Renton T, Di Silvio L, Grant AD. TRPA1 and TRPV4 activation in human odontoblasts stimulates ATP release. J Dent Res 2014; 93:911-7. [PMID: 25062738 DOI: 10.1177/0022034514544507] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The mechanism of pain in dentine hypersensitivity is poorly understood but proposed to result from the activation of dental sensory neurons in response to dentinal fluid movements. Odontoblasts have been suggested to contribute to thermal and mechanosensation in the tooth via expression of transient receptor potential (TRP) channels. However, a mechanism by which odontoblasts could modulate neuronal activity has not been demonstrated. In this study, we investigated functional TRP channel expression in human odontoblast-like cells and measured ATP release in response to TRP channel activation. Human immortalized dental pulp cells were driven toward an odontoblast phenotype by culture in conditioned media. Functional expression of TRP channels was determined with reverse transcription polymerase chain reaction and ratiometric calcium imaging with Fura-2. ATP release was measured using a luciferin-luciferase assay. Expression of mRNA for TRPA1, TRPV1, and TRPV4 but not TRPM8 was detected in odontoblasts by reverse transcription polymerase chain reaction. Expression of TRPV4 protein was detected by Western blotting and immunocytochemistry. The TRPA1 agonists allyl isothiocyanate and cinnamaldehyde and the TRPV4 agonist GSK1016790A caused a concentration-dependent increase in intracellular Ca(2+) concentration that was inhibited by the selective antagonists HC030031, AP18, and HC067047, respectively. In contrast, exposure to the TRPV1 agonist capsaicin or the TRPM8 agonist icilin had no effect on intracellular Ca(2+) concentration. Treatment with allyl isothiocyanate, cinnamaldehyde, or GSK1016790A caused an increase in ATP concentration in culture medium that was abolished by preincubation with TRP channel antagonists. These data demonstrate that activation of TRPA1 and TRPV4 channels in human odontoblast-like cells can stimulate ATP release. We were unable to confirm the presence of thermosensitive TRPV1 and TRPM8 that has previously been reported in odontoblasts.
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Affiliation(s)
- O Egbuniwe
- Biomaterials, Tissue Engineering, and Imaging, King's College London, London, UK Department of Oral Surgery, Dental Institute, King's College London, London, UK
| | - S Grover
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
| | - A K Duggal
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
| | - A Mavroudis
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
| | - M Yazdi
- Department of Oral Surgery, Dental Institute, King's College London, London, UK
| | - T Renton
- Department of Oral Surgery, Dental Institute, King's College London, London, UK
| | - L Di Silvio
- Biomaterials, Tissue Engineering, and Imaging, King's College London, London, UK
| | - A D Grant
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
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Kramer PR, Bellinger LL. Meal duration as a measure of orofacial nociceptive responses in rodents. J Vis Exp 2014:e50745. [PMID: 24457843 DOI: 10.3791/50745] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
A lengthening in meal duration can be used to measure an increase in orofacial mechanical hyperalgesia having similarities to the guarding behavior of humans with orofacial pain. To measure meal duration unrestrained rats are continuously kept in sound attenuated, computerized feeding modules for days to weeks to record feeding behavior. These sound-attenuated chambers are equipped with chow pellet dispensers. The dispenser has a pellet trough with a photobeam placed at the bottom of the trough and when a rodent removes a pellet from the feeder trough this beam is no longer blocked, signaling the computer to drop another pellet. The computer records the date and time when the pellets were taken from the trough and from this data the experimenter can calculate the meal parameters. When calculating meal parameters a meal was defined based on previous work and was set at 10 min (in other words when the animal does not eat for 10 min that would be the end of the animal's meal) also the minimum meal size was set at 3 pellets. The meal duration, meal number, food intake, meal size and inter-meal interval can then be calculated by the software for any time period that the operator desires. Of the feeding parameters that can be calculated meal duration has been shown to be a continuous noninvasive biological marker of orofacial nociception in male rats and mice and female rats. Meal duration measurements are quantitative, require no training or animal manipulation, require cortical participation, and do not compete with other experimentally induced behaviors. These factors distinguish this assay from other operant or reflex methods for recording orofacial nociception.
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Affiliation(s)
- Phillip R Kramer
- Department of Biomedical Sciences, Texas A&M University Baylor College of Dentistry
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Abstract
Due, in part, to the unique structure of the tooth, dental pain is initiated via distinct mechanisms. Here we review recent advances in our understanding of inflammatory tooth pain and discuss 3 hypotheses proposed to explain dentinal hypersensitivity: The first hypothesis, supported by functional expression of temperature-sensitive transient receptor potential channels, emphasizes the direct transduction of noxious temperatures by dental primary afferent neurons. The second hypothesis, known as hydrodynamic theory, attributes dental pain to fluid movement within dentinal tubules, and we discuss several candidate cellular mechanical transducers for the detection of fluid movement. The third hypothesis focuses on the potential sensory function of odontoblasts in the detection of thermal or mechanical stimuli, and we discuss the accumulating evidence that supports their excitability. We also briefly update on a novel strategy for local nociceptive anesthesia via nociceptive transducer molecules in dental primary afferents with the potential to specifically silence pain fibers during dental treatment. Further understanding of the molecular mechanisms of dental pain would greatly enhance the development of therapeutics that target dental pain.
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Affiliation(s)
- G Chung
- Pain Cognitive Function Research Center, Dental Research Institute and Department of Neurobiology and Physiology, School of Dentistry, Seoul National University, Seoul 110-749, Republic of Korea
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Logan SM, Romero MI, Nguyen DH, Benson MD. Ephrin-B2 expression in the proprioceptive sensory system. Neurosci Lett 2013; 545:69-74. [PMID: 23623938 PMCID: PMC3867235 DOI: 10.1016/j.neulet.2013.04.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 04/04/2013] [Accepted: 04/10/2013] [Indexed: 11/17/2022]
Abstract
Recent studies have shown that ephrin-B2 on sensory afferent fibers from the dorsal root ganglia (DRG) controls transmission of pain sensation to the spinal cord. We examined ephrin-B2 expression in mouse DRG and spinal cord using an ephrin-B2/ß-galactosidase chimeric allele. We found that ephrin-B2 is expressed exclusively in proprioceptive neurons and fibers in neonates, while expression in lamina III and IV of the adult spinal cord was observed in addition to that in the deeper laminae. We confirmed that ephrin-B2 protein causes co-clustering of EphB2 and glutamate receptors in spinal cord neurons. Our data are consistent with a role for ephrin-B2 in transmission of positional information to the CNS, and thus suggest a role in synaptic plasticity of spinal cord locomotor circuits that are known to be sensitive to proprioceptive sensory input after spinal cord injury.
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Affiliation(s)
- Shaun M. Logan
- Department of Biomedical Sciences, Texas A&M Health Science Center Baylor College of Dentistry, 3302 Gaston Ave., Dallas, TX, 75246
| | - Mario I. Romero
- Department of Bioengineering, The University of Texas Arlington, 500 UTA Blvd., Arlington, TX, 76019
| | - Dianna H. Nguyen
- Department of Bioengineering, The University of Texas Arlington, 500 UTA Blvd., Arlington, TX, 76019
| | - M. Douglas Benson
- Department of Biomedical Sciences, Texas A&M Health Science Center Baylor College of Dentistry, 3302 Gaston Ave., Dallas, TX, 75246
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Gibbs JL, Urban R, Basbaum AI. Paradoxical surrogate markers of dental injury-induced pain in the mouse. Pain 2013; 154:1358-67. [PMID: 23719574 DOI: 10.1016/j.pain.2013.04.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 04/01/2013] [Accepted: 04/09/2013] [Indexed: 12/29/2022]
Abstract
Dental pain, including toothache, is one of the most prevalent types of orofacial pain, causing severe, persistent pain that has a significant negative effect on quality of life, including eating disturbances, mood changes, and sleep disruption. As the primary cause of toothache pain is injury to the uniquely innervated dental pulp, rodent models of this injury provide the opportunity to study neurobiological mechanisms of tissue injury-induced persistent pain. Here we evaluated behavioral changes in mice with a dental pulp injury (DPI) produced by mechanically exposing the pulp to the oral environment. We monitored the daily life behaviors of mice with DPI, including measures of eating, drinking, and movement. During the first 48 hours, the only parameter affected by DPI was locomotion, which was reduced. There was also a significant short-term decrease in the amount of weight gained by DPI animals that was not related to food consumption. As cold allodynia is frequently observed in individuals experiencing toothache pain, we tested whether mice with DPI demonstrate an aversion to drinking cold liquids using a cold-sucrose consumption test. Surprisingly, mice with DPI increased their consumption of sucrose solution, to over 150% of baseline, regardless of temperature. Both the weight loss and increased sucrose intake in the first 2 days of injury were reversed by administration of indomethacin. These findings indicate that enhanced sucrose consumption may be a reliable measure of orofacial pain in rodents, and suggest that alterations in energy expenditure and motivational behaviors are under-recognized outcomes of tooth injury.
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Affiliation(s)
- Jennifer L Gibbs
- Department of Preventive and Restorative Dental Sciences, Division of Endodontics, UCSF School of Dentistry, San Francisco, CA, USA.
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Kovačič U, Tesovnik B, Molnar N, Cör A, Skalerič U, Gašperšič R. Dental pulp and gingivomucosa in rats are innervated by two morphologically and neurochemically different populations of nociceptors. Arch Oral Biol 2013; 58:788-95. [PMID: 23411402 DOI: 10.1016/j.archoralbio.2013.01.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Revised: 01/14/2013] [Accepted: 01/17/2013] [Indexed: 12/25/2022]
Abstract
OBJECTIVES Difference in phenotypes of sensory neurons innervating dental pulp or gingivomucosa may be responsible for intense pain sensations in pulpitis in contrast to relatively painless chronic periodontitis. Therefore, we classified these neurons according to their size and two neurochemical characteristics of nociceptors, their TrkA expression and isolectin IB4 binding. DESIGN In rats (n=6) fluorescent tracers Fluorogold and TrueBlue were simultaneously applied into the standard-sized tooth cavity and nearby gingival sulcus, respectively. After the fluorescence on paraffin trigeminal ganglia (TG) sections was identified and photographed, immunohistochemistry for TrkA expression and IB4 binding was performed on the same sections. RESULTS The average sizes of TG neurons projecting to the gingivomucosa and dental pulp were 894±441μm(2) and 1012±381μm(2), respectively. The proportions of small-sized gingival and pulpal neurons were 14% and 5%, respectively (p<0.05). The proportions of TrkA-positive neurons among all gingival or pulpal neurons were 76% and 86%, respectively (p<0.05). Among all gingival or pulpal neurons the proportions of IB4-positive neurons were 46% and 3% (p<0.001), respectively, and the majority of them were small-medium sized. CONCLUSIONS Dental pulp and gingivomucosa are richly innervated by nociceptive TrkA-expressing neurons. However, while great majority of pulpal neurons are larger NGF-dependent A-fibre nociceptors without affinity to bind IB4, almost half of the gingival neurons are smaller IB4 binding C-fibre nociceptors. The difference in phenotype of sensory neurons might partially explain the different sensitivity of both tissues during normal and pathological conditions.
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Affiliation(s)
- Uroš Kovačič
- Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Zaloška 2, 1000 Ljubljana, Slovenia
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Petho G, Reeh PW. Sensory and signaling mechanisms of bradykinin, eicosanoids, platelet-activating factor, and nitric oxide in peripheral nociceptors. Physiol Rev 2013; 92:1699-775. [PMID: 23073630 DOI: 10.1152/physrev.00048.2010] [Citation(s) in RCA: 191] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Peripheral mediators can contribute to the development and maintenance of inflammatory and neuropathic pain and its concomitants (hyperalgesia and allodynia) via two mechanisms. Activation or excitation by these substances of nociceptive nerve endings or fibers implicates generation of action potentials which then travel to the central nervous system and may induce pain sensation. Sensitization of nociceptors refers to their increased responsiveness to either thermal, mechanical, or chemical stimuli that may be translated to corresponding hyperalgesias. This review aims to give an account of the excitatory and sensitizing actions of inflammatory mediators including bradykinin, prostaglandins, thromboxanes, leukotrienes, platelet-activating factor, and nitric oxide on nociceptive primary afferent neurons. Manifestations, receptor molecules, and intracellular signaling mechanisms of the effects of these mediators are discussed in detail. With regard to signaling, most data reported have been obtained from transfected nonneuronal cells and somata of cultured sensory neurons as these structures are more accessible to direct study of sensory and signal transduction. The peripheral processes of sensory neurons, where painful stimuli actually affect the nociceptors in vivo, show marked differences with respect to biophysics, ultrastructure, and equipment with receptors and ion channels compared with cellular models. Therefore, an effort was made to highlight signaling mechanisms for which supporting data from molecular, cellular, and behavioral models are consistent with findings that reflect properties of peripheral nociceptive nerve endings. Identified molecular elements of these signaling pathways may serve as validated targets for development of novel types of analgesic drugs.
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Affiliation(s)
- Gábor Petho
- Pharmacodynamics Unit, Department of Pharmacology and Pharmacotherapy, Faculty of Medicine, University of Pécs, Pécs, Hungary
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Boada MD. Relationship between electrophysiological signature and defined sensory modality of trigeminal ganglion neurons in vivo. J Neurophysiol 2012; 109:749-57. [PMID: 23155179 DOI: 10.1152/jn.00693.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The trigeminal ganglia (TG) innervate a heterogeneous set of highly sensitive and exposed tissues. Weak, innocuous stimuli can evoke pain as a normal response in some areas such as the cornea. This observation implies, however, the capability of low-threshold mechanoreceptors, inducing pain in the normal condition. To clarify this matter, the present study correlates the electrical signature (both fiber conduction velocity and somatic electrical properties) with receptor field, mechanical threshold, and temperature responsiveness of sensory afferents innervating tissues with dissimilar sensitivity (skin vs. cornea) in the trigeminal domain. Intracellular recordings were obtained in vivo from 148 neurons of the left TG of 62 mice. In 111 of these neurons, the peripheral receptor field was successfully localized: 96 of them innervated the hairy skin, while the remaining 15 innervated the cornea. The electrical signature was defined and peripheral responses correlated with tissue target. No high threshold neurons were found in the cornea. Moreover, the electrical signature of corneal afferents resembles nociceptive neurons in the skin. TG skin afferents showed similar membrane electrical signature and sensory modality as skin afferents from dorsal root ganglion, although TG afferents exhibited a shorter duration of afterhyperpolarization then those previously described in dorsal root ganglion. These data suggest than new or different ways to classify and study TG sensory neurons may be required.
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Affiliation(s)
- M Danilo Boada
- Dept. of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, NC 27157-1009, USA.
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