Histomorphological changes in murine fibrosarcoma after hypericin-based photodynamic therapy.

Histomorphological changes in murine fibrosarcoma after photodynamic therapy (PDT) based on the natural photosensitizer hypericin were evaluated. C3H/DiSn mice were inoculated with fibrosarcoma G5:1:13 cells. When the tumour reached a volume of 40-80 mm(3) the mice were intraperitoneally injected with hypericin, either in a single dose (5 mg/kg; 1 or 6 h before laser irradiation) or two fractionated doses (2.5 mg/kg; 6 and 1 h before irradiation with laser light; 532 nm, 70 mW/cm(2), 168 J/cm(2)). All groups of PDT-treated animals with single and fractionated hypericin dosing presented primary vascular reactions including vascular dilatation, congestion, thrombosis and oedema. Two hours after PDT there were necrotic changes with small, rather focal appearance. One day after therapy the necrotic areas were enhanced, often affecting a complete superficial layer of tumour tissue. Necrotic areas were accompanied with inflammation and haemorrhages.