Method: Cultured human periodontal ligament fibroblasts (PDLFs) were exposed to 0 or 45 J/cm2 (90 sec) doses of blue light delivered from a quartz-tungsten-halogen dental curing light (VIP, Bisco, 600 mW/cm2), then left to incubate for an additional 2 h before Substance P (10-6M) was added to all cultures. Parallel cultures were harvested 48 h later for either RNA or protein analysis. RNA samples underwent quantitative RT-PCR analysis using primers specific for the cytoprotective protein HO-1, and the bone metabolism regulators RANKL and OPG. Proteins from whole cell lysates were separated by SDS-PAGE, transferred to PVDF membranes, and analyzed using immunoblot detection and Odyssey® quantification of RANKL, OPG, and HO-1.
Result: Light pre-treatment of PDLFs resulted in a 1.8-fold increase in HO-1-specific RNA transcripts, suggesting a sustained cytoprotective response to the light exposure. Moreover, light-treated cells exhibited a ~9.7-fold increase in OPG-specific RNA transcripts with a concurrent 2.6-fold decrease in RANKL. Immunblot analysis resulted in similar changes that were less prominent, but remained significant (p<0.05).
Conclusion: These data suggest that blue light initiates a cytoprotective response that ultimately shifts the RANKL:OPG ratio away from bone resorption. This effect may eventually prove useful in the clinical treatment of periodontitis.
Keywords: Bone, Curing lights, Fibroblasts, Inflammation and Inflammatory mediators
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