Abstract
Angiogenesis is essential for tumor growth, progression and metastasis. To gain a more complete understanding of angiogenic mechanisms, it is important to have an animal model for examining time-lapse imaging series and real-time functional analysis of tumor vasculature. In this study, we used the window chamber and intravital microscopy systems to serially monitor the initial process of tumor vascular formation in primary and recurrence tumors on the same observational area for 12-days. Pre-irradiation is frequently used to simulate the clinical environment for the tumor relapse after the radiotherapy. To explore the relationship of tumor cells and surrounding host vasculature, murine prostate TRAMP-C1-GFP tumors expressing green fluorescence protein were implanted into non-irradiated (non-IR) or pre-irradiated (pre-IR) tissue. The vascular distribution and morphological variation of tumor neovasculature in these two groups were compared under bright-field image, fluorescence image and confocal image using fluorescence microscopy and confocal laser scanning microscopy. Tumor cells grown in non-IR tissue (control group) begin the initial tumor angiogenesis obviously at 6-7 days after implantation with the evidence of the appearance of red hemorrhage spot in the bright-field images and irregular sprouting neovessles in the confocal images. The microvessel density (MVD) is around 25.43%. By day 10~11, the tread-like blood vessels distribute among whole tumor densely, and the MVD is increased to 49.82%. In pre-IR group, the onset of tumor angiogenesis also occurs 6-7 days, which is similar to what have been seen in control tumors. However, by day 10~11, the vessels are larger and more dilated, but the MVD (35.55%) is less than that in control tumor. In conclusion, we have established a suitable monitor system to not only qualitatively, but also quantitatively analyze the tumor growth and vascular change in vivo serially. It can certainly be an useful system for understanding the working mechanism when radiation therapy is combined with other forms of anti-angionesis or anti-vascular therapy.