Endothelium-Independent Primitive Myxoid Vascularization Creates Invertebrate-Like Channels to Maintain Blood Supply in Optic Gliomas.

Optic gliomas are brain tumors characterized by slow growth, progressive loss of vision, and limited therapeutic options. Optic gliomas contain various amounts of myxoid matrix, which can represent most of the tumor mass. We sought to investigate biological function and protein structure of the myxoid matrix in optic gliomas to identify novel therapeutic targets. We reviewed histological features and clinical imaging properties, analyzed vasculature by immunohistochemistry and electron microscopy, and performed liquid chromatography-mass spectrometry on optic gliomas, which varied in the amount of myxoid matrix. We found that although subtypes of optic gliomas are indistinguishable on imaging, the microvascular network of pilomyxoid astrocytoma, a subtype of optic glioma with abundant myxoid matrix, is characterized by the presence of endothelium-free channels in the myxoid matrix. These tumors show normal perfusion by clinical imaging and lack histological evidence of hemorrhage organization or thrombosis. The myxoid matrix is composed predominantly of the proteoglycan versican and its linking protein, a vertebrate hyaluronan and proteoglycan link protein 1. We propose that pediatric optic gliomas can maintain blood supply without endothelial cells by using invertebrate-like channels, which we termed primitive myxoid vascularization. Enzymatic targeting of the proteoglycan versican/hyaluronan and proteoglycan link protein 1 rich myxoid matrix, which is in direct contact with circulating blood, can provide novel therapeutic avenues for optic gliomas of childhood.

Vascularity and angiogenesis as predictors of growth in optic pathway/hypothalamic gliomas.

OBJECT: The authors' aim in conducting this study was to investigate retrospectively the prognostic significance of angiogenic features in optic pathway/hypothalamic gliomas (OPHGs) in children. METHODS: Patients were identified in whom a diagnosis of OPHG was made using pathological analysis at the Toronto Hospital for Sick Children between 1985 and 2002. Tumor specimens were reviewed for diagnostic accuracy and adequacy of the specimen. Sections were immunostained with factor VIII to assess microvessel density (MVD). A ratio of alpha-smooth muscle actin to factor VIII immunostaining was calculated to arrive at a vascular maturity index (VMI). Vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR) immunostaining were performed to evaluate angiogenic factors. In addition, the MIB-1 labeling index (LI) was used to assess proliferation. These factors were evaluated with respect to progression-free survival (PFS). Forty-one of 60 patients originally identified had adequate samples and follow up for inclusion in the study. Of these, eight patients had coexisting neurofibromatosis Type 1. Twenty-eight patients experienced tumor progression after the initial treatment (surgery with or without adjuvant treatment). Thirty-eight patients are still alive. A high MVD (> 21 vessels/1.2 mm2) was associated with a significantly higher rate of progression compared with a low MVD (< 21 vessels/1.2 mm2; p = 0.017). Microvessel density was also predictive of reduced PFS on multivariate analysis stratified for extent of resection (p = 0.04), and VMI as well as intensity and distribution of VEGF and VEGFR staining and the MIB-1 LI were not significantly associated with PFS. CONCLUSIONS: These findings suggest that MVD is the best current predictor of PFS in incompletely resected OPHGs. This information highlights the importance of angiogenesis in regard to low-grade gliomas.

Orbital color Doppler imaging of optic nerve tumors.

OBJECTIVE: To report changes in retinal arterial and venous blood flow pattern in two patients with tumors involving the entire optic nerve. METHODS: Retrospective review of one patient with clinical and neuroimaging characteristics typical of bilateral optic nerve gliomas and one patient with a probable meningioma of the left optic nerve sheath. RESULTS: The optic nerve glioma patient had reduced peak systolic velocity of central retinal arteries bilaterally, while the patient with an optic nerve sheath meningioma had relatively low central retinal artery flow velocity and intermittent blood flow in the central retinal vein on the affected side. CONCLUSIONS: Reduced retinal arterial flow velocities in the setting of optic nerve gliomas may correlate with the presence of optic nerve disease. Phasic blood flow in the central retinal vein with optic nerve sheath meningioma may be the reason that some patients with this tumor develop retinal choroidal venous anastomoses.