Title: 1426 - Characterization of Dental Pulp Innervation Using Transgenic Reporter Mice
Kareem Metwalli (Presenter)
UT Health at San Antonio
Obadah Austah, university of texas health science center at san antonio
Anibal Diogenes, University of Texas at San Antonio
Objectives: Trigeminal ganglia neurons are heterogeneous, and have been broadly classified based on their degree of myelination and conduction velocity into C, Aβ and Aδ fibers. Several elegant studies using indirect immunohistochemistry and electrophysiological recordings have demonstrated the dental pulp is mainly innervated with C-fibers followed by Aδ fibers. However, recent studies have established that trigeminal ganglia neurons can be further classified by the following categories: peptidergic (CGRP+) and non-peptidergic C-fibers (MrgprD+), low threshold mechanoreceptor (LTMR) Aδ (TrkB+) and LTMR Aβ (TrkC+) fibers, and high threshold mechanoreceptor (HTMR) Aδ and Aβ fibers (Nav1.8+; CGRP-). We hypothesize that the dental pulp is primarily innervated by Aδ and Aβ fibers, including LTMR subclasses.
Methods: To test this hypothesis, we employed transgenic reporter mice expressing either fluorescence proteins, GFP or TdTomato, under the promoter of either Nav1.8, CGRP, MrgprD, TrkB or TrkC. Mandibular and maxillary en-bloc sections containing molars were harvested from genotyped mice (8-10 week old) for each reporter line (n=6), demineralized and processed for direct detection of immunofluorescence. Images were acquired using laser scanning microscopy with standardized settings from sequential slides for each sample.
Results: The greatest majority of fibers innervating the dental pulp are Aδ and Aβ fibers, including LTMR subclasses, not previously reported. These fibers innervate the most coronal aspects of the pulp and project extensions into the dentinal tubules. C-fibers are more apically positioned than Aβ and Aδ fibers, which have peptidergic subclasses also sending projections into dentinal tubules.
Conclusions: This is the first demonstration of the distribution of LTMR myelinated fibers in the dental pulp. The presence of these fibers, that are typically non-nociceptive, into dentinal tubules sheds light on the uniqueness of dental pulp innervation and neurophysiology.
This abstract is based on research that was funded entirely or partially by an outside source:
American Association of Endodontists Foundation
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: None