Photobiomodulation and purinergic signaling: in vivo and in vitro approaches for new and innovative treatments in skin fibrosis and remyelination

Keloids are an exuberant response to wound healing, characterized by an exaggerated synthesis of collagen, probably due to the increase of fibroblasts activity and to the reduction of their apoptosis rate: currently no standard treatments or pharmacological therapies are able to prevent keloid recurrence. To reach this goal, in recent years some physical treatments have been proposed, and among them the PhotoBioModulation therapy (PBM). This work analyses the eects of a blue LED light irradiation (410-430 nm, 0.69 W/cm2 power density) on human fibroblasts, isolated from both keloids and perilesional tissues. Dierent light doses (3.43-6.87-13.7-20.6-30.9 and 41.2 J/cm2) were tested. Biochemical assays and specific staining were used to assess cell metabolism, proliferation and viability. Micro-Raman spectroscopy was used to explore direct eects of the blue LED light on the Cytochrome C (Cyt C) oxidase. We also investigated the eects of the irradiation on ionic membrane currents by patch-clamp recordings. Our results showed that the blue LED light can modulate cell metabolism and proliferation, with a dose-dependent behavior and that these eects persist at least till 48 h after treatment. Furthermore, we demonstrated that the highest fluence value can reduce cell viability 24 h after irradiation in keloid-derived fibroblasts, while the same eect is observed 48 h after treatment in perilesional fibroblasts. Electrophysiological recordings showed that the medium dose (20.6 J/cm2) of blue LED light induces an enhancement of voltage-dependent outward currents elicited by a depolarizing ramp protocol. Overall, these data demonstrate the potentials that PBM shows as an innovative and minimally-invasive approach in the management of hypertrophic scars and keloids, in association with current treatments.