Microvascular blood flow dynamics associated with photodynamic therapy, pulsed dye laser irradiation and combined regimens

Background and Objectives: Previous in vitro studies demonstrated the potential utility of benzoporphyrin derivative monoacid ring A (BPD) photodynamic therapy (PDT) for vascular destruction. Moreover, the effects of PDT were enhanced when this intervention was followed immediately by pulsed dye laser (PDL) irradiation (PDT/PDL). We further evaluate vascular effects of PDT alone, PDL alone and PDT/PDL in an in vivo rodent dorsal skinfold model. Study Design/Materials and Methods: A dorsal skinfold window chamber was installed surgically on female Sprague-Dawley rats. One milligram per kilogram of BPD solution was administered intravenously via a jugular venous catheter. Evaluated interventions were: control (no BPD, no light), PDT alone (576 nm, 16 minutes exposure time, 15 minutes post-BPD injection, 10 mm spot), PDL alone at 7 J/cm(2) (585 nm, 1.5 ms pulse duration, 7 mm spot), PDL alone at 10 J/cm(2), PDT/PDL (PDL at 7 J/cm(2)), and PDT/PDL (PDL at 10 J/cm(2)). To assess changes in microvascular blood flow, laser speckle imaging was performed before, immediately after, and 18 hours post-intervention. Results: Epidermal irradiation was accomplished without blistering, scabbing or ulceration. A reduction in perfusion was achieved in all intervention groups. PDT/PDL at 7 J/cm 2 resulted in the greatest reduction in vascular perfusion (56%). Conclusions: BPD PDT can achieve safe and selective vascular flow reduction. PDT/PDL can enhance diminution of microvascular blood flow. Our results suggest that PDT and PDT/PDL should be evaluated as alternative therapeutic options for treatment of hypervascular skin lesions including port wine stain birthmarks.