The subventricular zone (SVZ) has been shown to be the largest germinal region in the adult rodent brain. Recent studies have also demonstrated not only that a similar neurogenic region exists in the SVZ of the adult human brain, but also that the cytoarchitecture is different in the human SVZ: a hypocellular gap and a ribbon of astrocytes is present under the ependyma. It remains unknown whether neural stem cells in the human brain are precisely localized in this ribbon of astrocytes lining the adult human SVZ and whether these adult neural stem cells have the ability to migrate. What exactly regulates the migratory capacity of stem cells or the transformation of brain tumors is not known, but epidermal growth factor (EOF) has been implicated in this process. Within this context we will pursue the following Specific Aims:
Aim 1 : To precisely localize the adult human neural stem cells with respect to the ependyma and to compare the adult human SVZ to the fetal human SVZ and to the SVZ of patients with gliomas. The hypothesis is that stem cells are concentrated in the band of astrocytes parallel to the ependyma and that this ribbon of astrocytes is 1) more prominent when patients have gliomas that are adjacent and/or part of the subventricular zone;2) there is a larger population of CD 133+cells within this ribbon of astrocytes in patients with brain tumors 3) this ribbon of astrocytes does not exist in the fetal human SVZ.
Aim 2 : To establish the role of EGF in the migratory ability of adult, fetal, and human brain cancer stem cells using both in vitro migration assays and an in vivo rodent model. The hypothesis is that human adult stem cells have the ability to migrate and that their manipulation with EGF can change them to a more aggressive migratory behavior that resembles that of the fetal human brain and/or high grade tumors. This project has direct relevance to public health. If adult neural stem cells have the ability to migrate we will further elucidate the human brain's capacity for self-repair and may be able to figure out ways to make these cells migrate to replace those lost following extensive neuronal damage or disease. In addition, neural stem cells and cancer stem cells may share similar mechanisms of migration and invasion and understanding this mechanism may lead to better treatments of brain tumors.
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