Effect of photobiomodulation on the viability of osteoblasts and fibroblasts submitted to alendronate sodium or zoledronic acid

The goal of this study is to evaluate the effect of photobiomodulation therapy (PBMT) on the viability of osteoblasts and cultured fibroblasts in different concentrations of alendronate or zoledronic acid. Two cell lines: osteoblast-like mouse cells (OSTEO 1) and human buccal mucosa fibroblast (FMM1) were used. Cells were submitted to different concentrations of bisphosphonates (1 μM, 10 μM, and 100 μM sodium alendronate and 3 μM, 5 μM and 10 μM zoledronic acid) for 24 hours. Next, the cultures received PBMT. The irradiations were applied with a diode laser (InGaAIP, 660 nm, 30 mW, spot 0.028 cm2) in continuous, punctual and contact mode at two energy densities: 5 J/cm2 (4.5 s) or 10 Jcm2 (9s) with 6 hours-intervals. Cell viability was determined by mitochondrial activity assay (MTT) 24 h after the last irradiation. The data were compared by the one way- ANOVA, complemented by the Tukey’s test (p < 0.05). Sodium alendronate at concentrations of 100 μM and 10 μM and zoledronic acid at 10 μM concentration showed higher long-term toxicity. The cellular viability of the PBMT treated group was significantly higher than that of the negative control group. The same occurred with the osteoblasts treated with the highest concentrations of the drug (5 and 10 μM), despite not reaching the cell viability of the positive control group, it presented greater viability than the negative control where the cells were not irradiated. In the groups submitted to zoledronic acid, positive controls presented greater cell viability. We concluded that under the parameters applied in this study, PBMT at an energy density of 5 J/cm2 was able to revert the toxicity of sodium alendronate applied at the higher concentrations in both cell types, whereas zoledronic acid toxicity, regardless of its concentrations, was not influenced by PBMT.