The Synergistic Effect of Oscillatory Fluid Shear and <i>Porphyromonas gingivalis</i> Lipopolysaccharide Promotes the Inflammatory Response of Periodontal Ligament Cells

This study aimed to investigate how oscillatory fluid shear (OFS), induced by occlusal loading, influences periodontal ligament cells (PDLCs) in both healthy and inflammatory environments and to clarify its potential role in periodontitis progression. PDLCs were cultured under healthy or Porphyromonas gingivalis lipopolysaccharide (Pg.LPS)-induced inflammatory conditions and subjected to OFS. Cell proliferation was assessed via CCK-8 and EdU staining, while migration was evaluated using wound healing assays. Inflammatory mediator expression (IL-1β, IL-6, IL-8, CCL2, GM-CSF) was measured by RT-qPCR and ELISA. Reactive oxygen species (ROS) levels were detected using DCFH-DA probes. THP-1 cell adhesion assays and macrophage polarization experiments were conducted to evaluate immune cell interactions. OFS significantly suppressed PDLC proliferation in both healthy and inflammatory conditions. Combined OFS and Pg.LPS treatment further inhibited cell migration and synergistically upregulated proinflammatory cytokines and ROS levels. Additionally, OFS and Pg.LPS synergistically enhanced monocyte adhesion and promoted macrophage polarization toward the proinflammatory M1 phenotype. OFS exacerbates inflammatory responses in PDLCs under Pg.LPS stimulation, promoting monocyte adhesion and M1 macrophage polarization. These findings highlight the critical role of oscillatory fluid shear in periodontitis progression and provide insights into potential therapeutic targets for periodontitis management.