Cellular mechanisms and photon propagation in low level laser therapy

Underlying mechanisms of low power laser irradiation beneficial effects in treatment of chronic inflammatory conditions are yet far from being explained, as there are many aspects of photon propagation in anisotropic media. Aims of present studies were to disclose characteristics of laser light penetration in live tissues and to reveal processes involved in cellular effects of soft laser irradiation at power densities comparable to those achievable in in vivo irradiated living tissues. We measured the diffuse reflectance in the area of inflammation of laser treated patients and used Monte Carlo simulations in order to obtain characteristic parameters of absorption and scattering phenomena and to compute the absorbed radiation dose at cellular level. Undertaking cell suspension studies we followed up low level long wavelength laser irradiation effects on survival/proliferation/death options of human mononuclear cells in normal and in energy/nutrient restriction caused stress conditions. Selecting appropriate nuclear stains and cell surface markers, we revealed cell kind and state, cell microenvironment, laser wavelength, total dose and irradiation regime dependent changes in cell cycle progression, apoptosis induction / survival of cells exposed to power densities similar to those calculated for target tissue following Monte Carlo simulations.