Wnt/β-catenin signaling regulates Dental Pulp Stem Cells' responses to pulp injury by resinous monomers.
OBJECTIVE
Aim 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.


METHODS
DPSCs cultures were established from third molars of healthy donors and characterized for stem cell markers with flow cytometry. Cells were exposed to TEGDMA (T: 0.5-2mM) with or without presence of the Wnt-1 ligand (W:25-100ng/ml) or the GSK3β inhibitor Lithium (L:1-10mM), 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.


RESULTS
DPSC 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.


CONCLUSIONS
These findings highlight the important role of Wnt canonical signaling in pulp repair responses to common injuries.
Department of Fixed Prosthesis & Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece; Department of Conservative Dentistry, Periodontology & Preventive Dentistry, School of Dentistry, Hannover Medical School, Hannover D-30625, Germany.
Athina
A
Bakopoulou
Department of Conservative Dentistry, Periodontology & Preventive Dentistry, School of Dentistry, Hannover Medical School, Hannover D-30625, Germany.
Gabriele
G
Leyhausen
Department of Conservative Dentistry, Periodontology & Preventive Dentistry, School of Dentistry, Hannover Medical School, Hannover D-30625, Germany.
Joachim
J
Volk
Department of Fixed Prosthesis & Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece.
Eleni
E
Papachristou
Department of Fixed Prosthesis & Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece.
Petros
P
Koidis
Department of Conservative Dentistry, Periodontology & Preventive Dentistry, School of Dentistry, Hannover Medical School, Hannover D-30625, Germany. Electronic address: Geurtsen.Werner@mh-hannover.de.
Werner
W
Geurtsen
D000293:Adolescent; D015153:Blotting, Western; D002470:Cell Survival; D002478:Cells, Cultured; D003782:Dental Pulp / Q000166:cytology*; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping; D066298:In Vitro Techniques; D008094:Lithium / Q000494:pharmacology; D008964:Molar, Third; D009942:Organometallic Compounds / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000494:pharmacology; D011109:Polymethacrylic Acids / Q000494:pharmacology; D060888:Real-Time Polymerase Chain Reaction; D060449:Wnt Signaling Pathway / Q000187:drug effects* / Q000502:physiology*; D055815:Young Adult
C000609764:GSK3iXV; D009942:Organometallic Compounds; D011109:Polymethacrylic Acids; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D008094:Lithium
Dental Pulp Stem Cells-DPSCs; Pulp repair; Resinous monomers; Wnt/β-catenin signaling