Effect of hematoporphyrin monomethyl ether-mediated photodynamic therapy on hypertrophic scar fibroblasts

Background Clinical studies have demonstrated that photodynamic therapy (PDT) for hyperplastic dermatosis results in a beneficial outcome. Hypertrophic scar (HS) is a pathological process characterized by fibroblastic hyperproliferation. However, it is unclear whether photochemical interactions between PDT and fibroblasts contribute to a beneficial outcome. To investigate the primary photochemical effects of PDT, we studied the efficacy of 630 nm PDT on human fibroblasts from HS using hematoporphyrin monomethyl ether (HMME) as a photosensitizer. Methods Fibroblasts were cultured from nontreated HSs, and cells at passage 4-6 were used for the experiments. Morphological and biochemical changes in fibroblasts were assessed by Hoechst 33258 staining and annexin V-FITC/PI flow cytometry (FCM). Caspase-3 activity assay and immunofluorescence staining were performed to investigate caspase-3 expression in fibroblasts. Results The morphological features of cell apoptosis were viewed under a fluorescent microscope by Hoechst 33258 staining. FCM indicated that the apoptotic rate was significantly increased after HMME-PDT, and caspase-3 activity was observed. Conclusions Low-level exposure to 630 nm PDT mediated by HMME appears to induce fibroblast apoptosis and stimulate caspase-3 activation. However, the effect of HMME-PDT on fibroblasts needs further investigation to determine its therapeutic potential for HS.