Single ALA-PDT irradiation induces increase in mast cells degranulation and neuropeptide acute response in chronic venous ulcers: a pilot study

Background: The behavior of mast cells, their interaction with neuronal cells or nerve fibers, the expression of neuropeptides and the distribution of skin neuronal cells or nerve fibers after ALA-PDT treated vs untreated chronic wounds were investigated. Methods: Nineteen patients suffering from chronic venous ulcers (CVU) were enrolled in this study. Skin samples from wound bed before and after irradiation with ALA-PDT were taken. All specimens were anonymized and analyzed by immunohistochemistry. Results: After completion of ALA-PDT, mast cells, showed an increase of degranulation index and expression of NGF and VIP. Amongst all the neuronal mediators tested, all except for SP showed an increase of cellular expression after ALA-PDT therapy. Conclusion: Our study shows preliminary evidences that ALA-PDT induces rapid recruitment of mast cells around dermal fibers in chronic venous ulcers. This finding is also associated with increase in expression of multiple peripheral neuropeptides except SP by skin neuronal cells. ALA-PDT may promote healing of chronic venous ulcers via stimulation of quiescent peripheral nerves, possibly after release of inflammatory molecules by degranulating mast cells.