Hypomineralized Enamel Alters Trigeminal Sensory Afferent Architecture, Transcriptome, and Dental Injury Responses
At barrier tissues such as the skin and gut, sensory neurons interface with environmental stimuli and coordinate with neighboring epithelial and immune cells to detect tissue perturbations. In teeth, however, the sensory dentin-pulp complex is insulated from the oral environment by highly mineralized enamel. Although dentin-pulp responses to severe injury have been studied in models with direct pulp exposure, it remains unclear whether enamel barrier dysfunction alone alters pulpal and neuronal homeostasis. Using a kallikrein-related peptidase 4 knockout (KLK4 KO) mouse model of enamel hypomineralization, we demonstrated that defective enamel induced structural, molecular, and transcriptional responses in the dental pulp and in the trigeminal system innervating teeth, despite the absence of direct pulp exposure to the oral cavity. Hypomineralized molars exhibited increased reactionary dentin formation accompanied by retraction of sensory afferents from the dentin-pulp junction. Consistent with these structural findings, trigeminal ganglia of KLK4 KO mice displayed upregulation of genes associated with cytoskeletal remodeling and stimulus response pathways. Despite increased bacterial burden and biofilm accumulation on the enamel surface, enamel hypomineralization did not induce substantial innate immune responses in the pulp. In addition, following severe dental pulp injury, teeth with hypomineralized enamel exhibited reduced sensory afferent loss and tissue damage. Together, these findings reveal that enamel integrity functions as a critical regulator of dentin-pulp homeostasis and that barrier dysfunction alone can precondition tissue responses to subsequent injury.