ALA-PDT exerts beneficial effects on chronic venous ulcers by inducing changes in inflammatory microenvironment, especially through increased TGF-beta release: a pilot clinical and translational study

A cohort of 19 patients affected by chronic venous ulcers was recruited from our centre. A 4-mm punch biopsy from wound bed was taken before application of ALA 20% gel and repeated one hour after the first PDT irradiation. We observed a significant and progressive reduction of wounds mean volumes right after three ALA-PDT sessions (once per week; 4479.9 +/- 345.5 mm3 vs 3459 +/- 190.3 mm3, p<0.01). On immunofluorescence staining from biopsy specimens, we observed a change in all tested stains of post treatment specimens compared to pre-treatment ones. An increase of plasmacytoid dendritic cells (from 69 +/- 22 cells/0.018 mm2 to 136 +/- 27 cells/0.018 mm2, p<0.0001); MHC-II expression (260.3 +/- 99.7 Red, Green, Blue [RGB 0-255] to 370.2 +/- 162.6 RGB (0-255), p<0.01), TNF-alpha positive mast cells expression (4 +/- 0.3 cells/0.018 mm2 to 6 +/- 0.4 cells/0.018 mm2, p<0.001), TGF-beta expression (59.8 +/- 23.2 RGB (0-255)/cell vs 137.3 +/- 56.6 RGB (0-255)/cell, p<0,01) and CD4+/CD25+ Treg cells (3 +/- 1 cells/0.018 mm2 vs 20 +/- 10 cells/0.018 mm2, p<0.001) was observed. An increase of TGF-beta was correlated in a statistical significant manner with a reduction of wounds’ mean volumes.