Hemangioblastoma Stromal Cells Show Committed Stem Cell Phenotype

Background: Hemangioblastomas are benign vascular tumors of the central nervous system that occur sporadically or in association with von Hippel-Lindau disease. These tumors are characteristically composed of a dense capillary network with intervening stromal/interstitial cells. To date, the histogenesis of hemangioblastoma remains unclear. We hypothesize that hemangioblastomas arise from a defective mesodermal stem cell, which gives rise to the atypical vasculature. Methods: To test our hypothesis, we have characterized the cellular composition of hemangioblastomas by immunophenotyping pluripotent and committed stem cells and vascular endothelial cells. Results: Our findings show that hemangioblastoma endothelial cells are positive for CD133, a stem and progenitor cell marker. Vascular endothelial cells also expressed nuclear Oct4. In addition to the endothelium, both CD 133 and Oct4 were present in stromal and perivascular cells. Interestingly, neither the endothelium nor the stromal cells expressed Sox2 or Nanog suggesting a committed stem cell phenotype. Conclusions: From these findings, we believe that hemangioblastoma stromal cells are committed stem cells producing both vascular cell types. The findings also show an unusual CD133-positive endothelial phenotype in hemangioblastoma.