Glioblastoma stem cell differentiation into endothelial cells evidenced through live-cell imaging

AbstractBACKGROUND: Glioblastoma cell initiated vascularization is an alternative angiogenesis called vasculogenic mimicry (VM). However, current knowledge on the mechanism of de novo vessel formation from glioblastoma stem cells (GSCs) is limited. METHODS: Sixty-four glioblastoma samples from patients and 10 fluorescent glioma xenograft samples were examined by immunofluorescence staining for endothelial marker (CD34) and glial cell marker glial fibrillary acidic protein (GFAP) expression. Then, we isolated GSCs from human glioblastoma tissue and established CD133+/SOX-2+ RFP-GSC-1 cells. The ability of these cells to form vascular structures was examined by live cell imaging of three-dimensional cultures. Results: CD34/CD31 and GFAP co-expressing glioblastoma-derived endothelial cells (GDEC) glioma cells were found in 30 of 64(46.9%) the clinical glioblastoma samples. These CD34/CD31 and GFAP co-expressing glioblastoma-derived endothelial cells (GDEC) were found to form vessel structures in 21 out of 30 (70%) clinical samples. In those (with GDEC vessels) samples, the CD34+ GDEC vessels were counted around 14.16% of total vessels and CD31+ GDEC vessels were counted around 18.08% of total vessels. In the xenograft tumor tissue, CD34+ GDECs were found in 7 out of 10 mice and 4 out of 10 mice had CD34+ GDEC vessels. CD31+ GDECs were also found in 7 mice and 4 mice had CD31+ GDEC vessels (10 mice in total). Through live cell imaging, we observed gradually CD34 expression when cultural with VEGF in some glioma cells, and a dynamic increase in endothelial marker expression in RFP-GSC-1 in vitro was recorded. Up to 6 hours of cultural, CD34-positive cell reach to 9.46%. (Video S1 and S2). Conclusions: The results demonstrated that GSCs may differentiate into endothelial cells and promote angiogenesis in glioblastomas.