Low-level laser irradiation (InGaAlP-660 nm) increases fibroblast cell proliferation and reduces cell death in a dose-dependent manner.

BACKGROUND AND OBJECTIVE: Impaired cell metabolism and increased cell death in fibroblast cells are physiological features of chronic tendinopathy. Although several studies have shown that low-level laser therapy (LLLT) at certain parameters has a biostimulatory effect on fibroblast cells, it remains uncertain if LLLT effects depend on the physiological state. STUDY DESIGN/MATERIAL AND METHODS: High-metabolic immortal cell culture and primary human keloid fibroblast cell culture were used in this study. Trypan blue exclusion and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test were used to determine cell viability and proliferation. Propidium iodide stain was used for cell-cycle analysis by flow cytometry. Laser irradiation was performed daily on three consecutive days with a GaAlAs 660-nm laser (mean output: 50 mW, spot size 2 mm(2), power density =2.5 W/cm(2)) and a typical LLLT dose and a high LLLT dose (irradiation times: 60 or 420 s; fluences:150 or 1050 J/cm(2); energy delivered: 3 or 21 J). RESULTS: Primary fibroblast cell culture from human keloids irradiated with 3 J showed significant proliferation by the trypan blue exclusion test (p < 0.05), whereas the 3T3 cell culture showed no difference using this method. Propidium iodide staining flow cytometry data showed a significant decrease in the percentage of cells being in proliferative phases of the cell cycle (S/g(2)/M) when irradiated with 21 J in both cell types (hypodiploid cells increased). CONCLUSIONS: Our data support the hypothesis that the physiological state of the cells affects the LLLT results, and that high-metabolic rate and short- cell-cycle 3T3 cells are not responsive to LLLT. In conclusion, LLLT with a dose of 3 J reduced cell death significantly, but did not stimulate cell cycle. A LLLT dose of 21 J had negative effects on the cells, as it increased cell death and inhibited cell proliferation.

Low-Level Laser Irradiation (InGaAlP-660 nm) Increases Fibroblast Cell Proliferation and Reduces Cell Death in a Dose-Dependent Manner

Background and Objective: Impaired cell metabolism and increased cell death in fibroblast cells are physiologicalfeatures of chronic tendinopathy. Although several studies have shown that low-level laser therapy (LLLT) atcertain parameters has a biostimulatory effect on fibroblast cells, it remains uncertain if LLLT effects depend on thephysiological state. Study Design/Material and Methods: High-metabolic immortal cell culture and primaryhuman keloid fibroblast cell culture were used in this study. Trypan blue exclusion and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test were used to determine cell viability and proliferation. Propidiumiodide stain was used for cell-cycle analysis by flow cytometry. Laser irradiation was performed daily onthree consecutive days with a GaAlAs 660-nm laser (mean output: 50mW, spot size 2mm2, power density»2.5W=cm2) and a typical LLLT dose and a high LLLT dose (irradiation times: 60 or 420 s; fluences:150 or1050 J=cm2; energy delivered: 3 or 21 J). Results: Primary fibroblast cell culture from human keloids irradiated with3 J showed significant proliferation by the trypan blue exclusion test ( p<0.05), whereas the 3T3 cell cultureshowed no difference using this method. Propidium iodide staining flow cytometry data showed a significantdecrease in the percentage of cells being in proliferative phases of the cell cycle (S=g2=M) when irradiated with 21 Jin both cell types (hypodiploid cells increased). Conclusions: Our data support the hypothesis that the physiologicalstate of the cells affects the LLLT results, and that high-metabolic rate and short- cell-cycle 3T3 cells are notresponsive to LLLT. In conclusion, LLLT with a dose of 3 J reduced cell death significantly, but did not stimulatecell cycle. A LLLT dose of 21 J had negative effects on the cells, as it increased cell death and inhibited cellproliferation.