(PO94) Understanding Painful vs Non-Painful Apical Periodontitis

Abstract: Apical periodontitis (AP) is characterized by significant clinical variability. While 60% of individuals experience mechanical allodynia, approximately 40% remain asymptomatic. Given that a substantial proportion of AP patients (7-19%) experience post-treatment pain resistant to commonly used analgesics, it's crucial to differentiate between the painful and non-painful phenotypes within AP. This differentiation offers insights into distinct molecular signatures associated with AP-induced pain pathophysiology. The primary objective of this study was to identify pain-associated genes and cellular regulators using single-cell RNA sequencing (scRNA-seq) of painful and non-painful AP lesions. Surgical biospecimens obtained from patients undergoing endodontic microsurgeries were stratified into symptomatic apical periodontitis and asymptomatic apical periodontitis. Samples underwent single-cell suspension procedures, after which cells were sorted and subjected to scRNA-seq using 10X Genomics at the Genome Sequencing Facility (GSF). Analysis of asymptomatic periapical lesions indicated 97% cell viability post-sorting, revealing 16 distinct cell clusters including both immune and non-immune cell networks. Multiple immune cell clusters displayed distinctive subtypes based on single-cell gene expression profiles, with the dominant cell type identified as CD8+ T cells, followed by CD4+ T cells and CD4+ regulatory T cells. Several nociceptor/pain regulators were identified within specific cell clusters. Future investigations will include pseudotime analysis, lineage trajectories, and gene ontology assessments. Moreover, a larger sample size of asymptomatic samples will be compared with symptomatic biospecimens. The collective findings from this study aim to unveil unique cellular signatures characterizing symptomatic and asymptomatic patients, laying the foundation for future therapeutic developments in pain management.