Dicer-independent miR-451a is upregulated in periodontitis and potentiates inflammation by impairing macrophage polarization and SOCS activity.

Abstract

Background: Periodontitis (PD) is characterized by localized inflammatory tissue destruction, yet the lesion-associated microRNA (miRNA)networks that regulate host immune responses remain incompletely defined. In this study, we aimed to identify and characterize dysregulated gingivalmiRNAs in PD that modulate inflammatory responses.

Methods: Using a split-mouth design, miRNA expression was profiled in gingival biopsies fromperiodontal lesions and clinically healthy sites. Differentially expressed miRNAs were identified by microarray analysis, and selected candidates werevalidated by RT-qPCR. The responses of candidate miRNAs to periodontal bacterial challenge were evaluated, followed by functional studies ofmacrophage polarization, phagocytosis, inflammatory cytokine production, and target-gene regulation.

Results: Microarray analysis identified 48differentially expressed miRNAs, including several upregulated non-canonical miRNAs. Among these, the Dicer-independent miRNAs miR-451a andmiR-1228 showed dose- and time-dependent induction following periodontal bacterial challenge. miR-451a, but not miR-1228, promoted a pro-inflammatory M1-like macrophage phenotype, characterized by increased HLA-DR and CD32 and reduced CD206 and CD163 expression. miR-451adirectly targeted multiple genes associated with M2 macrophage polarization, and its expression in inflamed gingival tissues inversely correlated with M2markers. miR-451a overexpression also reduced macrophage phagocytosis of E. coli and P. gingivalis while increasing pro-inflammatory cytokineproduction. Mechanistically, miR-451a directly suppressed SOCS3 and SOCS5, key negative regulators of JAK/STAT signaling, in TLR4-stimulated cells.The antagonistic expression patterns of miR-451a, SOCS3, and SOCS5 in PD further supported the functional relevance of this regulatory axis.

Conclusion: miR-451a is a pathogen-responsive, PD-associated miRNA that promotes pro-inflammatory macrophage polarization, impairs bacterialphagocytosis, and amplifies inflammation through suppression of SOCS-mediated immune regulation. These findings identify the miR-451a-SOCS3/SOCS5 axis as a potential mechanism linking bacterial challenge to dysregulated macrophage responses in PD.