Date of Award
Doctor of Philosophy
Human malignant glial tumors are highly vascular compared to normal brain. Increased tumor vessel permeability contributes to patient morbidity and mortality. An in vitro model of neoplastic and non-neoplastic brain microvasculature was established to address questions related to human glial tumor-associated angiogenesis. Investigation of tumor and non-tumor microvessel endothelial growth characteristics and ultrastructural properties related to permeability revealed detectable alterations as a result of tumor modulation. Endothelium derived from malignant glial tumor microvessels displayed decreased longevity and intercellular contact, and increased vesicle density in vitro compared to non-tumor microvessel endothelium. Human cerebral microvascular endothelium maintains properties noted in vivo, validating this in vitro model for subsequent studies.;The initiation phase of glial tumor-associated angiogenesis involves dissolution of microvessel basement membrane. The proteolytic contribution of human cerebral endothelium and glial cells to basement membrane degradation was investigated in vitro. Type IV collagen is the major fibrous protein of basement membrane and is degraded by specific proteases. Type IV collagen degrading enzymes were investigated at the levels of mRNA, protein and activity production in human brain tumors, cerebral microvascular endothelium and glial cells. Using Northern hybridization, gelatinase A mRNA was detected at higher levels in malignant glioma than non-neoplastic tissue. Gelatinase A mRNA was detected in cerebral endothelium, C6 and HTB14 glioma cells in vitro. Gelatinase A mRNA production was detected only in migrating and dividing endothelium using in situ hybridization. Endothelial proteolytic activity release was increased by conditioning with malignant glial tumor media and decreased by non-neoplastic glial conditioning. Endothelial type IV collagenase activity was identified as gelatinase A using Western blot analysis. Type IV collagenase activity was released by C6 glioma, U251 gliablastoma and HT1080 fibrosarcoma cell lines. Gelatinase A was detected using Western blot analysis of these cell lines. Gelatinase A was localized to glial tumor cells and microvasculature of surgical specimens using immunohistochemistry. Cerebral endothelium and malignant glioma cells contribute gelatinase A to collagen IV degradation in vitro and in vivo. Inhibition of type IV collagenase activity may be effective in reducing angiogenesis in malignant gliomas and consequently, reducing tumor growth.
Costello, Penelope Catherine, "Human Cerebral Microvascular Endothelial Involvement In Neovascularization Of Malignant Glial Tumors" (1993). Digitized Theses. 2302.