A Novel piRNA-Mediated Epigenetic Axis: piR-36241 Exacerbates Pulpitis by Silencing the Protective Receptor ADGRG2 in Human Dental Pulp Stem Cells.
BACKGROUND: Pulpitis, a prevalent inflammatory dental disease, primarily results from bacterial infection, yet its epigenetic regulatory mechanisms remain poorly understood. PIWI-interacting RNAs (piRNAs), a class of small non-coding RNAs known to maintain genomic stability, have not been investigated in the context of pulpitis. OBJECTIVE: This study aimed to profile piRNA expression patterns in pulpitis and to elucidate the functional role and underlying mechanism of a specific piRNA, piR-36241 and its target gene ADGRG2 in disease progression. METHODS: piRNA and mRNA sequencing were performed on pulp tissues from patients with irreversible pulpitis and healthy controls. Potential piRNA targets were predicted bioinformatically. The interaction between piR-36241 and the 3'UTR of ADGRG2, an orphan adhesion G protein-coupled receptor (GPCR), was validated using dual-luciferase reporter assay, quantitative Real-Time PCR (qRT-PCR), fluorescence in situ hybridization (FISH), Western blot (WB), hematoxylin-eosin staining (HE), immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA). Functional analyses were conducted in LPS-stimulated human dental pulp cells (HDPCs) through gain-of-function and rescue experiments. RESULTS: We identified a distinct piRNA expression profile in pulpitis, with 21 piRNAs differentially expressed. piR-36241 was notably upregulated. It directly targeted the 3'UTR of ADGRG2 and suppressed its expression. ADGRG2, hypothesised to exert protective and homeostatic functions, was downregulated in pulpitis tissues and LPS-induced HDPCs. Overexpression of piR-36241 inhibited ADGRG2 expression and promoted the secretion of pro-inflammatory cytokines (IL-6, IL-8). Conversely, knockdown of ADGRG2 similarly enhanced inflammatory responses. Rescue experiments demonstrated that piR-36241 primarily regulates inflammation through ADGRG2 silencing. CONCLUSION: Our study reveals a novel pathogenic axis in pulpitis whereby upregulation of piR-36241 exacerbates inflammatory progression by repressing the protective receptor ADGRG2. These findings provide the first evidence of piRNA-mediated epigenetic regulation in pulpitis and highlight the piR-36241/ADGRG2 pathway as a potential therapeutic target for preserving pulp vitality.