Photo‐stimulatory effect of LLLT on the proliferation rate of human monocytic leukaemia cells

Abstract

Low-level laser therapy (LLLT) is a form of phototherapy used to promote cell proliferation. This study investigates the potential role of LLLT in cellular proliferation of human monocytic leukaemia cells Tamm-Horsfall Protein 1 (THP-1) under in vitro conditions. Cells were irradiated with an 850 nm diode laser and exposed to doses ranging from 0 to 26.8 J/cm 2 . After irradiation, cells were incubated for 12 and 24 h to allow time for proliferation. Comet assay was conducted to evaluate genotoxicity of the irradiated cells. Trypan blue was used to estimate cytotoxicity, which peaked at the highest dose as expected. Preliminary results suggest that cell counts increase at low doses, whereas a decrease in cell number at high doses was noted compared with controls. Comet assay showed no significant difference between irradiated and non-irradiated cells at low doses. In contrast, DNA damage increased at doses ≥8.9 J/cm 2 and was comparable with the 100 μM hydrogen peroxide positive control at the highest fluence. It could be concluded that LLLT has the ability to stimulate the THP-1 cell line to proliferate if supplied with the correct energy and dose.