Capsaicin-sensitive Innervation Modulates the Development of Apical Periodontitis

Area of Science:

• Neuroscience
• Immunology
• Dentistry

Background:

• Nociceptive neurons detect injury and mediate neurogenic inflammation via neuropeptide release (e.g., CGRP).
• Capsaicin-sensitive neurons, known CGRP releasers, innervate dental pulp and periradicular tissues.
• The role of these neurons in apical periodontitis is not well understood.

Purpose of the Study:

• To investigate the contribution of peptidergic (capsaicin-sensitive) neurons to apical periodontitis development.

Main Methods:

• Peptidergic neurons were ablated in neonatal rats using capsaicin.
• Neuron ablation was confirmed via microscopy, behavioral tests, and CGRP measurement.
• Apical periodontitis was induced by pulp exposure, and lesion volume was quantified using micro-CT over 28 days.

Main Results:

• Capsaicin treatment successfully ablated capsaicin-sensitive neurons and depleted CGRP in dental pulp.
• Rats lacking these neurons exhibited significantly larger periradicular lesions at 7 and 14 days post-pulp exposure.
• Control rats showed robust nocifensive responses to capsaicin, which were absent in the ablated group.

Conclusions:

• Capsaicin-sensitive neurons play a protective role during the initial stages of apical periodontitis.
• Alterations in capsaicin-sensitive fiber activity may influence the progression of apical periodontitis.