In vitro and in vivo photosensitizing capabilities of 5-ALA versus Photofrin® in vascular endothelial cells

Background and Objective: The objective of the present study was to evaluate the feasibility of photodynamic therapy (PDT) for complicated hemangiomas. The photosensitizing activities of 5-aminolevulinic acid (5- ALA) and Photofrin® were evaluated in vitro with human dermal microvascular endothelial cells (MEC) and in vivo with the chicken cox comb. Study Design/Materials and Methods: The in vitro absorption and photosensitizing activities of 5-ALA and Photofrin® were examined in a MEC culture system. The percentages of MEC killed by different drug concentrations at a wavelength of 630 nm were measured by either live/dead or lactate dehydrogenase-released assays. Similarly, the in vivo biological activities of 5-ALA and Photofrin® exposed to different total light dosages at 630 nm were studied by determining the amount of necrosis produced in chicken combs. Results: MEC incubated with 5-ALA at a concentration of 35 μg/ml and exposed to laser light at 630 nm at a power density of 100 mW/cm² showed a 50% cell kill. MEC incubated with Photofrin® at a concentration of 3.5 μg/ml and exposed to laser light at 630 nm at a power density of 100 mW/cm² showed a 50% cell kill. Chicken combs that received 200 mg/kg of 5-ALA exposed to laser light at 630 nm at a power density of 100 mW/cm² had an injury depth of 362.5 ± 27.6 μm at histologic examination. Combs exposed to a power density of 100 or 120 mW/cm² showed injury depths of 732.5 ± 29.1 and 792.5 ± 36.0 μm, respectively. Chicken combs that received 2.5 mg/kg of Photofrin® exposed to laser light at 630 nm at a power density of 80 mW/cm² had an injury depth of 535.6 ± 22.3 μm at histologic examination. Combs exposed to a power density of 100 or 120 mW/cm² showed injury depths of 795.8 ± 32.5 and 805.2 ± 49.1 μm, respectively. Conclusion: Both 5-ALA and Photofrin® have the capability to destroy MEC in vitro and vasculature in vivo. However, Photo 5-ALA and Photofrin® in Vascular Endothelial Cells frin® achieved a higher degree of cell kill and tissue destruction at lower drug concentrations and at lower power densities.