Human keloid cultured fibroblasts irradiated with blue LED light: evidence from an in vitro study

Keloids are an exuberant response to cutaneous wound healing, characterized by an exaggerated synthesis of collagen probably due to the increase of fibroblasts activity and their proliferation rate. Currently, there are not definitive treatments or pharmacological therapies able to prevent keloid formation and its recurrence. In the last years, physical treatments have been proposed and among them the photobiomodulation therapy. In this work, the effects of Blue LED light (410-430 nm wavelength, 0.69 W/cm2 power density, 5÷60s treatment time) were evaluated on seven boundary keloid tissues by using two different colorimetric assays. Micro-Raman spectroscopy was used to explore direct effects of the Blue LED light on the endogenous cellular redox system and in particular to probe any variation in the oxidation state of the photosensitive heme-protein Cytochrome C (Cyt C) upon irradiation. We also investigated the effects of Blue LED light on membrane currents correlated to cell cycle modulation by patch-clamp recordings. Twenty-four hours after irradiation, a significant reduction of cell metabolism and proliferation was observed. The decrease in cell metabolism was maintained up to 48 hours when we found also an increased reduction in cell proliferation. Electrophysiological recordings showed an enhancement of voltage-dependent outward currents elicited by a depolarizing ramp protocol after a 30s irradiation. Data indicates that Blue LED light irradiation directly affects human keloid fibroblasts: it possesses a long lasting inhibitory effect on cell metabolism and proliferation whereas acutely increases membrane currents. Similar responses were obtained in our recent works conducted on human keloid tissues. The proposed photomodulation treatment by using Blue LED light represents a non-invasive approach in the management of hypertrophic scars and keloids.