(PR53) Dual-RNA Sequencing Technology Reveals Host-Pathogen Relationships in Apical Periodontitis

Abstract: Apical periodontitis (AP) results from the progression of microorganisms within a necrotic root canal to the periapical area, triggering the host immune-response leading to local inflammation and bone resorption. The aim of this study was to understand the mechanisms of AP microbial pathogenesis and its relationship to host response. Root canal fluid and/or infected root samples from nine patients presenting with symptomatic irreversible pulpitis with and without AP were collected for analysis of microbial and associated host transcriptomes. Total RNA was extracted followed by rRNA depletion and submitted for dual RNA-sequencing. After quality control procedures, parallel-reads of host and bacterial genomes were aligned and normalized to standardized parameters. Differential expression analysis of genes and pathways, functional annotation and integration of microbial and transcriptome parameters were performed using various tools (e.g., DESeq, Gene Ontology, KOBAS, KRONA). False Discovery Rate and Benjamini-Hochberg methods were applied and a fold-changes >5 and p<0.0001 were used as significant threshold levels. Results showed over 1,000 differentially expressed genes between groups. Upregulated genes belonged to pathways involved in B cell activation, immune response, immunoglobulin receptor binding; whereas down-regulated genes were involved in extracellular matrix and extracellular structure organization, ossification, focal adhesion, among others. Along with differentially expressed genes, higher abundance and consistent presence of Porphyromonas, Treponema, Fusobacterium were observed. Our findings suggest the presence of specific microbial species influencing host gene expression and vice versa. Additional studies are warranted to confirm these findings and identify novel host-pathogen relationships to improve understanding of pulpal and periapical disease.