Laser photodynamic therapy of cancer: the chorioallantoic membrane model for measuring damage to blood vessels in-vivo

摘要

The mechanism of photodynamic therapy (PDT) involves, as a primary step, damage either directly to the tumor cells or to the surrounding vasculature which, in turn, causes disruption of tumor blood flow and, ultimately, tissue necrosis by anoxia. We report here a novel in-vivo model for investigating vascular events during PDT. The chick chorioallantoic membrane (CAM) model was chosen since it is an established model for studying biological processes such as implantation and angiogenesis. The photosensitizers meso-tetraphenylporphine tetrasulfonate (TPPS$-4$/) and chloro-aluminum phthalocyanine tetrasulfonate (CAPcS$-4$/) were topically applied onto the CAM. In all cases where sensitizer plus radiation was administered, changes in the CAM microcirculation occurred, as viewed through a stereoscopic microscope. With increasing light/drug dose we observed capillary leakage, stasis, occlusion, hemorrhage, and engorgement. The course of damage formation was documented in real time by video photography. All controls (sensitizer alone or light alone) remained unchanged compared to treated CAM . This work also describes preliminary experiments on tumor cells transplanted onto the CAM.