Optimisation of low-level light therapy (lllt) parameters and evaluation of its immunomodulatory effect on fibroblasts

Low-level laser therapy (LLLT) is being increasingly applied in regenerative medicine due to its ability to modulate cellular metabolism and support repair processes. However, the effect of various exposure parameters on fibroblast activity still does not remain fully understood. The study aim was to evaluate the effect of selected LLLT parameters (808 nm, 100 and 200 mW, 2 and 10 J/cm², pulsed beam) on the biological activity of fibroblasts in vitro. Fibroblasts were exposed to the established exposure parameters, and then the number of adherent and metabolically active cells, their migration, adenylate kinase (AK) as well as nitric oxide (NO) levels, cytokine secretion, metalloproteinase (MMP-2, MMP-9) activity, and oxidative-antioxidant potential were assessed. The most favourable effects were achieved with 200 mW; 2 J/cm² and 100 m; 10 J/cm² exposure parameters. In these conditions, increased number of adherent and metabolically active cells, and elevated migration were observed. Moreover, in this condition decreased AK release and NO secretion were found. Furthermore, LLLT reduced in fibroblasts interleukin 6 (IL-6) and interleukin 8 (IL-8) secretion as well as affected the activity of metalloproteinases, what corresponded with subsequent wound healing process. Additionally, a beneficial effect on maintaining the oxidative-antioxidant balance in fibroblasts was noted. In summary, the effects of LLLT on fibroblasts depend on the applied irradiation parameters, and appropriately selected LLLT treatment (200 mW; 2 J/cm² and 100 mW; 10 J/cm²,) stabilise fibroblast metabolism, limits their proinflammatory response and promotes extracellular matrix remodelling (ECM). These results confirm the potential of LLLT as an effective method supporting regenerative processes in the treatment of tissue damage.