Quantification and distribution of neovascularization following microinjection of C6 glioma cells in rat brain

Background: It has been suggested that the switch to an angiogenic phenotyp e can sepal-ate the development of a tumor into two Stages: the prevascular phase and the vascular phase. The purpose of the present work is to demons trate the existence of an angiogenic switch in a longitudinal study of a br ain tumor model during tumor growth by means of microvessel density measure ments. Materials and Methods: The study was performed on 32 rats bearing C6 glioma. At different stages of tumor growth, the histological aspects were described and sections were immunostained for factor VIII-related antigen in order to highlight microvessel endothelial cells. Microvessels were coun ted at 400 magnification for different areas (central non necrotic area, pe ripheral area, contralateral grey and white matter area), using image analy sis software. Results: Vessel density was signtficantly higher at the tumor -brain interface than in the center of the tumor or, in the contralateral c ol tex. The vessel density remains stable in the tumor during the first 3 w eeks after cell implantation after which a clear increase of vessel density can be observed. Conclusion: The present study demonstrates the presence o f an angiogenic switch which is concomitant with the development of necrosi s and pseudo palisading pattern.