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

Background: The object of our study is to evaluate the feasibility of photodynamic therapy for complicated hemangiomas. We studied the effect of the photosensitizing agent 5-aminolevulinic acid (5-ALA) in both in vitro and in vivo models. Methods: The in vitro photosensitizing activity of 5-ALA was examined in a microvascular endothelial cell (MEC) culture system. 5-ALA was added in various concentrations and the cells were illuminated at 630 nm. The percentage of MEC killed was measured by either a Live/Dead assay or an lactate dehydrogenase (LDH) assay. The effect of varying the light energy dose develivered at 630 nm after the administration of 5-ALA was studied by determining the amount of necrosis produced in chicken combs. Results: The comination of 5-ALA at a concentration of 35 μ g/ml, and illumination by 100 mW/cm² of laser light at 630 nm wavelength, caused 50% cell kill in the MEC culture system. Chicken combs of animals that received 200 mg/kg of 5-ALA and illumination at a power density of 80 m W/cm² had a depth of injury of 362.5±27.6 μ m upon histological examination. Those combs that received 100 or 120 mW/cm² showed a depth of injury of 732.5±29.1 and 792.5±36.0 μ m respectively. Conclusion: 5-ALA is effective in sensitizing human MEC to laser illumination. However, the degree of absorption and tissue destruction in different anatomical structures should be considered in future clinical studies.