Vascular effects of photodynamic and pulsed dye laser therapy protocols

Abstract

Background and objective: Pulsed dye laser (PDL) treatment of cutaneous vascular lesions is associated with variable and unpredictable efficacy. Thus, alternative treatment modalities are needed. Previous in vitro and in vivo studies have demonstrated enhanced selective vascular destruction with benzoporphyrin derivative (BPD) monoacid ring A photodynamic therapy (PDT) followed immediately by PDL irradiation (PDT+PDL). Here, we evaluate PDT alone, PDL alone, and PDT+PDL protocols using an optimized in vivo rodent dorsal window chamber model.

Study design/materials and methods: A dorsal window chamber was surgically installed on male Golden Syrian hamsters. BPD solution was administered intravenously via a jugular venous catheter. Evaluated interventions included: (1) Control (no BPD, no light); (2) Control (BPD, no light); (3) PDT alone (lambda = 576 nm; 25, 50, 75, or 96 J/cm2 radiant exposure; 15 minutes post-BPD injection); (4) PDL alone at 7 J/cm2 (585 nm, 1.5 milliseconds pulse duration, 7 mm spot); and (5) PDT (25 or 75 J/cm2)+PDL (7 J/cm2). Laser speckle imaging was used to monitor blood flow dynamics before, immediately after, and 1, 3, and 5 days post-intervention.

Results: Perfusion reduction on day 1 post-intervention was achieved with PDT>50 J/cm2, PDL alone, and PDT+PDL. However, by day 5 post-intervention, recovery of flow was observed with PDT alone at 50 J/cm2 (-15.1%) and PDL alone (+215%). PDT (75 J/cm2)+PDL resulted in the greatest prolonged reduction in vascular perfusion (-99.8%).

Conclusions: Our in vivo data suggest that the PDT+PDL therapeutic protocol can result in enhanced and persistent vascular shutdown compared to PDT or PDL alone. The PDT+PDL approach has potential for considerable superficial vascular destruction and should be considered as a treatment modality for cutaneous vascular lesions. Monitoring of blood flow changes for as long as possible is crucial for accurate assessment of light-based vascular interventions.

Fig. 1

Mean blood flow change for eight experimental groups. Chronic LSI of the hamster dorsal window chamber micro-vascular network demonstrates two hemodynamic trends: (A) absence of persistent vascular shutdown and (B) presence of persistent vascular shutdown. Day 0 data points represent the percent change in SFI after intervention. A value of — 100% represents complete vascular shutdown. Based on application of repeated measures ANOVA to the experimental data, combination of PDT at 75 J/cm² with PDL therapy at 7 J/cm² [shown in (B)] resulted in a significant reduction in blood flow as compared to PDL therapy alone [shown in (A)] (P = 0.003).

Fig. 2

Representative SFI images [5×4mm² (640×480 pixels)] of the microvasculature following interventions: (A) Saline control, (B) PDT at 25 J/cm²,(C) PDT at 75 J/cm²,(D) PDL at 7 J/cm², (E) PDT (25 J/cm²)+PDL, and (F) PDT (75 J/cm²) PDL from pre-intervention to day 5 post-intervention. Mean percent changes in SFI from immediately post-intervention, and 1, 3, and 5 days post-intervention were calculated relative to pre-intervention. Perfusion reduction on day 1 post-intervention was achieved with PDT at 75 J/cm², PDL alone, and PDT+PDL. However, by day 5 post-intervention, recovery of flow was observed with PDT alone and PDL alone. Combined PDT (at 25 or 75 J/cm²)+ PDL resulted in greater flow reduction than PDT (at 25 or 75+J/cm²) or PDL alone. PDT (75 J/cm²)+PDL resulted in the greatest prolonged reduction in vascular perfusion (P = 0.003).