Biological Effect of Helium-Neon (He-Ne) Laser Irradiation on Mouse Myeloma (Sp2-Ag14) Cell Line In Vitro

We examined the effect of helium-neon (He-Ne) laser irradiation with a wavelength of 632.8 nm on cell cycle synchronisation of monolayer growing mouse myeloma (Sp2-Ag14) cell line. The monolayer cultures were exposed to repeated doses of different energy densities (4–64 J/cm²). The nuclear DNA content has been studied by flow cytometry to obtain the cell percentage in each cell cycle phase. Results showed that the He-Ne laser irradiation at energy densities of 8–64 J/cm² produced a significative and different effect on the G0–G1 and S phases of cell cycle over control. In contrast, no significant effect in G2–M phase was produced by He-Ne laser irradiation at any energy density compared with non-treated control. These results support previous observations suggesting that He-Ne laser irradiation of low energy density interferes with cell cycling and may inhibit cell proliferation when irradiation is performed at doses of 8 J/cm² or more.