Vascular microenvironment in gliomas

Structural and functional abnormalities of the vascular microenvironment determine pathophysiological characteristics of gliomas, such as loss of blood-brain barrier function, tumor cell invasiveness, or permselectivity for large molecules. Moreover, the effectiveness of various therapeutic strategies critically depends upon the successful transvascular delivery of molecules. In order to shed more light on the vascular microenvironment in gliomas, a variety of experimental and clinical techniques have been applied to study the glioma microvasculature, including histology, vascular corrosion casts, microangiography by injection of dyes, blood flow measurements by autoradiography, tracer washout techniques, magnetic resonance imaging, as well as intravital fluorescence microscopy. This review summarizes the characteristic features of vascular morphology, angio-architecture, tumor perfusion, microvascular permeability, as well as microvessel-related immunological competence in gliomas. An improved understanding of the vascular microenvironment in gliomas will help in the future to optimize glioma imaging and delivery of vectors for gene therapy or encapsulated drug carriers in patients.