Capsaicin-sensitive Innervation Modulates the Development of Apical Periodontitis

Obadah N. Austah, Nikita B Ruparel, Michael A. Henry, Roberto J. Fajardo, James E. Schmitz, Anibal R Diogenes

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

Introduction Nociceptive neurons play a critical role in the detection of stimuli evoking actual or potential tissue injury. In addition, they are involved in neurogenic inflammation by the peripheral release of neuropeptides such as calcitonin gene-related peptide (CGRP). The dental pulp and periradicular tissues are innervated by capsaicin-sensitive neurons known to release CGRP. However, the role of these capsaicin-sensitive neurons in the development of apical periodontitis is largely unknown. The aim of this study was to evaluate the contribution of peptidergic neurons to the development of apical periodontitis. Methods Neonatal Sprague-Dawley rats were injected with vehicle (control group) or a single subcutaneous capsaicin dose to cause the selective ablation of peptidergic neurons (neonatal capsaicin group). Ablation of capsaicin-sensitive neurons was verified with confocal microscopy, capsaicin-induced eye-wipe nocifensive behavior test, and by measurement of immunoreactive CGRP levels in the dental pulp. Five weeks after ablation, standardized pulp exposures were made in the mandibular left first molars. Mandibles were harvested at 7, 14, 21, and 28 days after pulp exposure and imaged with micro–computed tomography (μCT) to quantify apical lesion volume. Data were analyzed by using 2-way ANOVA analysis with Bonferroni post hoc test. Results Rats in the control group displayed a robust capsaicin-induced nocifensive behavior, which was nearly abolished in the neonatal capsaicin group. In addition, the neonatal capsaicin group showed a significant depletion of susceptible neurons and CGRP in the dental pulp compared with control. Importantly, micro–computed tomography analysis showed larger periradicular lesions at 7 and 14 days after pulp exposure in the neonatal capsaicin group when compared with control. Conclusions Results identify a protective role for capsaicin-sensitive neurons in the initial phase of apical periodontitis. Thus, interventions or disorders that alter activity of capsaicin-sensitive fibers are likely to alter the development of apical periodontitis.

Original languageEnglish (US)
Pages (from-to)1496-1502
Number of pages7
JournalJournal of Endodontics
Volume42
Issue number10
DOIs
StatePublished - Oct 1 2016

Keywords

  • Apical periodontitis
  • CGRP
  • endodontic infection
  • microCT
  • neurogenic inflammation
  • peptidergic nociceptors
  • TRPV1

ASJC Scopus subject areas

  • Dentistry(all)

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