An exploratory comparative analysis of MicroRNA networks in external cervical resorption, periodontal ligament, and periapical lesions: an ex vivo laboratory investigation.

To determine whether external cervical resorption (ECR)a demonstrates a unique microRNA (miRNA) expression profile compared with healthy periodontal ligament (PDL) and periapical lesion (PA). Tissue samples from ECR, PDL, and PA were obtained from systemically healthy donors aged 18-70 years. Total RNA, including small RNAs, was isolated using a silica-membrane-based purification system with on-column DNase digestion. RNA quality was assessed by spectrophotometry (NanoDrop) and microfluidics electrophoresis (Agilent 2100 Bioanalyzer). Samples were hybridized to Affymetrix GeneChip miRNA 4.0 arrays, and data processed with RMA normalization and DABG filtering. Principal component analysis (PCA) was used for clustering. Differential expressions were analyzed by moderated ANOVA with FDR adjustment, and enrichment analysis identified tissue-specific miRNA networks. PCA analysis explained approximately 22% of the total variance, demonstrating that PA clustered separately from PDL and ECR, while ECR samples occupied an intermediate position between the two groups. Differential expression analysis identified 63 miRNAs between ECR and PA and 322 miRNAs between PA and PDL (p< 0.05). Among the ECR and PA comparison, 60 miRNAs were downregulated and three (miR-200c-3p, miR-205-5p, and miR-579-3p) were upregulated in ECR. No significant differences were detected in the ECR- PDL comparison (p> 0.05). Functional enrichment of PA-related miRNAs indicated pathways linked to proliferation, cytoskeletal remodeling, and inflammation, with MTX3, RSBN1L, and STMN3 as predicted targets. This study presents the first comparative analysis of miRNA expressions among ECR, PDL, and PA. PA exhibited distinct differences, whereas ECR and PDL showed similar molecular profiles.