Wnt/β-catenin signaling regulates Dental Pulp Stem Cells’ responses to pulp injury by resinous monomers

• Wnt canonical signaling is activated in DPSCs via GSK3β inhibition or Wnt-1 induction.
• Wnt canonical signaling is also activated as a response to resinous monomers, like TEGDMA.
• TEGDMA exerts an additive effect on canonical Wnt activation by other agents.
• TEGDMA caused a G1 or G2/M cell cycle arrest depending on concentration.
• These data highlight the important role of Wnt/β-catenin signaling in pulp repair.

ObjectivesAim of this study was to investigate whether Dental Pulp Stem Cells-DPSCs responses to pulp injury caused by resinous monomers is be mediated through activation of Wnt/β-catenin signaling.MethodsDPSCs cultures were established from third molars of healthy donors and characterized for stem cell markers with flow cytometry. Cells were exposed to TEGDMA (T: 0.5–2 mM) with or without presence of the Wnt-1 ligand (W:25–100 ng/ml) or the GSK3β inhibitor Lithium (L:1–10 mM), used both as activators of Wnt/β-catenin signaling. Cell viability was evaluated by MTT assay, cell cycle profiles by flow cytometry and expression of key molecules of Wnt/β-catenin signaling by Real-time PCR and Western Blot.ResultsDPSC exposure to TEGDMA caused a concentration-dependent cytotoxicity, accompanied by G1 arrest at lower and G2/M arrest at higher concentrations or after prolonged exposure. Lithium caused a dual effect, by stimulating/inhibiting cell proliferation at lower/higher concentrations respectively and causing a G2/M arrest in a concentration-dependent manner. Wnt signaling could be activated in DPSCs after Lithium or Wnt-1 treatment, as shown by accumulation of β-catenin, its translocation into the nucleus and enhanced expression of key pathway players, like LEF1 and Cyclin D1. Importantly, exposure to TEGDMA caused a more pronounced activation of the pathway, whereas cumulative effects were observed after T/L or T/W co-treatment, indicating a very strong activation of Wnt signaling after treatment of already “activated” (by Lithium or Wnt-1) cells with TEGDMA.SignificanceThese findings highlight the important role of Wnt canonical signaling in pulp repair responses to common injuries.