Cellular Mechanisms in Acute and Chronic Wounds after PDT Therapy: An Update.

PDT is a two-stage treatment that combines light energy with a photosensitizer designed to destroy cancerous and precancerous cells after light activation. Photosensitizers are activated by a specific wavelength of light energy, usually from a laser. The photosensitizer is nontoxic until it is activated by light. However, after light activation, the photosensitizer becomes toxic to the targeted tissue. Among sensitizers, the topical use of ALA, a natural precursor of protoporphyrin IX, a precursor of the heme group, and a powerful photosensitizing agent, represents a turning point for PDT in the dermatological field, as it easily absorbable by the skin. Wound healing requires a complex interaction and coordination of different cells and molecules. Any alteration in these highly coordinated events can lead to either delayed or excessive healing. The goal of this review is to elucidate the cellular mechanisms involved, upon treatment with ALA-PDT, in chronic wounds, which are often associated with social isolation and high costs in terms of care.