[Analysis of tumor vascular density using the window chamber technique].

ABSTRACT

Vascular structure is indispensable for a tumor to maintain its growth. The structure also affects drug delivery over chemotherapy, and oxygen tension in the tissue during irradiation. Therefore, measuring the vascular density in the tumor will help to reach an expected level or to evaluate the effect of those therapies. Through previous observation, changes in vascular structure, like the vascular density, have been reported. However, the tissue was usually removed from the deceased animal and examined in the microscope. Not many studies have shown changes in one and the same animal's tissue. In this study, we used the dorsal flap window chamber technique, and observed changes in the development of vascular structure and vascular density in a tumor. Window chambers were attached to the backs of 3 rats, and they anesthetized every 24 hours for microscopic observation. Vascular growth in the tumor started 8 to 9 days after implantation. Their average vascular density was about 25%, and this ratio continued till necrosis started in the tumor. "Necrosis occurs in a tumor because its growth is so rapid that the vascular development can not maintain the same speed." This has been a kind of established theory. During observation, we recognized blood stagnation in vessels as the tumor grew, and the relationship between tumor size and its vascular density was significant (r = 0.926). Our data lead us to another conclusion that "Vascular growth is as fast as tumor growth, keeping a ratio of about 25%, but necrosis is caused by deficiency of blood flow circulation."