Photoradiation of perfused placental tissue--a suitable in vitro model for photodynamic therapy?

Abstract

Our aim was to evaluate the isolated placental lobule as a model to study the cytotoxic effects of photodynamic therapy (PDT) in vitro. Ten human placental lobules were dually perfused with a modified medium 199 for a 4-hour period. Photosan III was added to the fetal perfusate at a dose of 5 mg/kg tissue, and laser light (630 nm wavelength) provided by an argon-pumped dye laser was applied at 50 J/cm2 in the experimental group (n=5). Potassium and lactate dehydrogenase (LDH) release into the perfusate as well as the transplacental creatinine passage from PDT-treated placentas and control placentas (n=5) were compared, and light microscopic examinations of the placental tissue were performed after the experiments. Potassium release into the fetal perfusate was higher in the PDT-treated placental lobules (p<0.05), and weight gain during the artificial perfusion suggests the development of edema only in the photoradiated lobules (p<0.01). The release of the bigger molecules of the LDH however was comparable in the two experimental groups, and transplacental creatinine passage was not affected by photoradiation. Light microscopic examinations demonstrated lesions at the cytotrophoblast, the syncytiotrophoblast and the endothelium of the fetal vessels of the photoradiated placentas, although they were not specific and could also be found in the control tissue. We conclude that the isolated placenta may be used to study cytotoxic effects of photoradiation in vitro, but better specifity and sensitivity might be achieved if a. The perfusion time is prolonged to make the difference between the experimental and the control group clearer and b. Electron microscopic investigations are made to demonstrate intracellular lesions of the mitochondria and the endoplasmic reticulum.