GroEL triggers NLRP3 inflammasome activation through the TLR/NF-κB p-p65 axis in human periodontal ligament stem cells.

The interaction between bacteria and the host plays a vital role in the initiation and progression of systemic diseases, including gastrointestinal and oral diseases, due to the secretion of various virulence factors from these pathogens. GroEL, a potent virulence factor secreted by multiple oral pathogenic bacteria, is implicated in the damage of gingival epithelium, periodontal ligament, alveolar bone and other peripheral tissues. However, the underlying biomechanism is still largely unknown. In the present study, we verify that GroEL can trigger the activation of NLRP3 inflammasome and its downstream effector molecules, IL-1ß and IL-18, in human periodontal ligament stem cells (hPDLSCs) and resultantly induce high activation of gelatinases (MMP-2 and MMP-9) to promote the degradation of extracellular matrix (ECM). GroEL-mediated activation of the NLRP3 inflammasome requires the participation of Toll-like receptors (TLR2 and TLR4). High upregulation of TLR2 and TLR4 induces the enhancement of NF-κB (p-p65) signaling and promotes its nuclear accumulation, thus activating the NLRP3 inflammasome. These results are verified in a rat model with direct injection of GroEL. Collectively, this study provides insight into the role of virulence factors in bacteria-induced host immune response and may also provide a new clue for the prevention of periodontitis.

PDGF-AA guides cell crosstalk between human dental pulp stem cells in vitro via the PDGFR-α/PI3K/Akt axis.

AIM: To explore the influence of PDGF-AA on cell communication between human dental pulp stem cells (DPSCs) by characterizing gap junction intercellular communication (GJIC) and its potential biomechanical mechanism. METHODOLOGY: Quantitative real-time PCR was used to measure connexin family member expression in DPSCs. Cell migration and CCK-8 assays were utilized to examine the influence of PDGF-AA on DPSC migration and proliferation. A scrape loading/dye transfer assay was applied to evaluate GJIC triggered by PDGF-AA, a PI3K/Akt signalling pathway blocker (LY294002) and a PDGFR-α blocker (AG1296). Western blotting and immunofluorescence were used to test the expression and distribution of the Cx43 and p-Akt proteins in DPSCs. Scanning electron microscopy (SEM) and immunofluorescence were used to observe the morphology of GJIC in DPSCs. RESULTS: PDGF-AA promoted gap junction formation and intercellular communication between human dental pulp stem cells. PDGF-AA upregulates the expression of Cx43 to enhance gap junction formation and intercellular communication. PDGF-AA binds to PDGFR-α and activates PI3K/Akt signalling to regulate cell communication. CONCLUSIONS: This research demonstrated that PDGF-AA can enhance Cx43-mediated GJIC in DPSCs via the PDGFR-α/PI3K/Akt axis, which provides new cues for dental pulp regeneration from the perspective of intercellular communication.