Dysregulation of MicroRNA-455-5p Contributes to Pulpitis Pathogenesis Through Modulating MYD88.

Objective: The study was designed to investigate the molecular mechanism of microRNA-455-5p (miR-455-5p) in the initiation and progression of pulpitis.

Methods: MiR-455-5p expression was examined using quantitative real-time polymerase chain reaction assay (qRT-PCR). Its diagnostic capacity was evaluated using receiver operating characteristic (ROC) analysis. Impacts of miR-455-5p on cellular activity was investigated in human dental pulp cells (hDPCs). ELISA assay was used for the inflammatory indicators. Oxidative stress reaction was also examined. Bioinformatic analysis was used for miR-455-5p target prediction. Luciferase reporter detection and Pearson's correlation coefficient were carried out to confirm target association.

Results: A significant reduction of miR-455-5p was observed in pulpitis patients, and ROC analysis displayed a high diagnostic capacity of this miRNA for pulpitis. Moreover, an obvious reduction in levels of miR-455-5p was discovered in LPS-induced hDPCs. Enforced miR-455-5p expression could increase cell viability and decrease cell apoptosis in pulpitis cell model. A heightened expression in levels of miR-455-5p could restrain the inflammatory response and alleviate the oxidative stress reaction. Notably, the LDH release reduced significantly when transfected with miR-455-5p mimic in pulpitis cell model. MYD88 (myeloid differentiation primary response gene 88) was predicted as a possible biomarker of miR-455-5p via bioinformatic tools. The target association between miR-455-5p and MYD88 was confirmed, and a negative correlation was found. The influences of miR-455-5p on cell behaviours were reversed after MYD88 transfection.

Conclusion: Abnormal miR-455-5p participated in cellular behaviours and inflammatory and oxidative stress in the development and progression of pulpitis, providing a novel strategic and a therapeutic perspective.