(PR58) Therapeutic Bystander Effects of Photobiomodulation on LPS Stressed Osteoblasts Following Antimicrobial Photodynamic Therapy

Abstract:

Objectives: To assess photobiomodulation (PBM) bystander effects on osteoblasts following antimicrobial Photodynamic Therapy (aPDT) against Enterococcus fecalis for endodontic disinfection.

Methods: Indocyanine Green (ICG) of various serial concentrations were activated with 810 nm diode laser and ROS generation was quantified using Luminol assay. Effects of aPDT on E. fecalis was assessed using CFUs assay. The osteoblast cell line MC3T3-E1 was assessed for aPDT cytotoxicity assay in healthy and infection-simulation (lipopolysaccharide) conditions using AlamarBlue assay. Finally, gene expression with qRT-PCR and mineralization was assessed using Alizarin red staining at 7 and 14 days. Statistical significance was assessed with ANOVA and adjusted for multiple comparisons.

Results: We noted 0.1 μM ICG and at 10 J/cm2 at 810 nm generated ROS (~ 40%) levels following aPDT. These parameters demonstrated clear reduction in E. fecalis CFUs, but this was not statistically significant. However, no significant toxicity was noted with MC3T3 cells in both healthy and LPS-treated cells. LPS treatments significantly reduced normalized gene expression of ALP, Runx-2, BSP and OCN that was significantly improved with aPDT treatments at 14 days. Further, Alizarin red staining assay for mineralization also demonstrated significant improvement at both 7 and 14 days in the aPDT group.

Conclusions: These results demonstrate that optimized ICG and laser parameters for aPDT is effective at disinfection and concurrent improvement in inflamed osteoblast cell functions, attributed to a bystander PBM response on osteoblast differentiation and mineralization.