Angiogenesis in extracranial human glioma implanted in nude mice: an immunohistochemical, corrosion casting – scanning electron microscopy study

Introduction: We applied corrosion casting–scanning electron micro- scopic analysis (CC-SEM) and immunohistochemistry (IHC) to study the three-dimensional microvascular architecture of a malignant human extra- cranial glioma implanted in the epicranic tissues of nude mice. Materials and methods: A total of 50,000 U87–MG glioma human modified cells were implanted intracranially in 40 nude mice to obtain malignant gliomas. After 30 days of growth, the tumor infiltrated the dural sheet and the bone, exiting the cranium through the site of injection and diffusing into the subcutaneous connective and muscular tissues. The CC technique and IHC were performed to better understand the two- and three-dimensional microvasculature architecture of both the tumor and the host epicranic tissues, along with its modifications. Results: CC-SEM analysis and IHC document a gradual change both in orientation and shape of epicranic muscular vessels. In comparison to the control, the longitudinally oriented vascular trabeculae turn into enlarged disorganized vessels oriented toward the tumor. The intervascular dis- tances, branching angles, and interbranching distances gradually decrease next to the tumor. On the vascular casts, it is possible to observe both dome sprouts and intussusceptive holes, clear signs of remodeling neoangiogenic effects. Entering the tumors, these vessels end into vascular lacunae, some- times delimited by the tumor cells themselves. The intratumoral vessels have a great variability in diameter, becoming tortuous, and losing any architectural organization. The endothelial cell lining is impaired, with a visible enlargement of intercellular junctions, and the consequent leakage of the resin in the interstitial spaces is documented. Conclusions: CC-SEM and IHC analysis revealed a sharp method for focusing on the remodeling effects that infiltrating gliomas have on the microvascular structure of epicranic tissues and a good model for studying