2016 Volume 59 Issue 4 Pages 317-332
Purpose: This study investigated the effect of low-level Nd: YAG laser irradiation on human gingival fibroblasts (Gin-1). We assayed cell proliferation, cell migration, LDH activity, FGF-2, TGF-β1, and HSP47 expression.
Methods: Gin-1 was irradiated for 30 s at a distance of 20 mm at three laser outputs: 0.5 W (90 μs/pulse, 100 mJ/s, 5 pps), 1.0 W (90 μs/pulse, 200 mJ/s, 5 pps), and 2.0 W (90 μs/pulse, 400 mJ/s, 5 pps). Cell proliferation was also measured 1, 3, and 5 d after irradiation using an improved MTT method. Next, an ELISA was performed on the culture supernatants at the same time points to measure FGF-2 and TGF-β1 expression at 1, 2, and 3 d. Cell migration was assayed at 5 and 24 h and LDH was employed to determine cell cytotoxicity at 3 h, 1 d, and 3 d, post irradiation. For each time point, we compared the results of a scratch assay between the control and irradiation group for analysis of cell migration. After 3 h of irradiation, we performed an immunofluorescence assay for HSP47.
Results: Compared with that in the non-irradiated control, cell proliferation was significantly higher in the groups exposed to 100, 200, and 400 mJ/s of radiation after 3 d, and to 200 and 400 mJ/s after 5 d. There was an increase in FGF-2 expression in every experimental group at 1 and 2 d. However, at 3 d, only the 100 mJ/s group continued to show an increase in FGF-2 expression. TGF-β1 expression increased significantly in the 200 mJ/s group compared to the control at 1 and 2 d. At 3 d, both the 100 mJ/s and 200 mJ/s groups showed a significant increase in TGF-β1 expression compared with the control. With regard to the scratch assay, cells in the 200 mJ/s group showed significantly higher migration than the control at 5 h. At 24 h, both the 200 mJ/s and 400 mJ/s groups also showed significantly higher migration than the control. No significant changes were observed in LDH levels in any of the irradiated groups. Furthermore, HSP47 expression was observed between the control and all laser irradiation groups.
Conclusion: The Nd: YAG irradiation conditions reported here harmlessly promote Gin-1 activity.
