The long term objectives of this research program are to understand, using a well-established in vivo system specific cellular and molecular influences of reactive astroglia on angiogenesis in the CNS. The primary purpose of this proposal is to determine the extent to which reactive astroglia have the capacity to produce growth factors that may support vascular growth following directed brain injury. Two hypotheses will be tested: 1) Reactive astrocytes are an endogenous source of endothelial growth factors, including vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), and thus can influence the rate of wound vascularization which subsequently influences the level of neuronal injury; and 2) Exogenous VEGF is a potent mitogen for both brain endothelium and astroglia in the injured and intact CNS. The experiments herein will determine whether activated astroglia associated with brain wounds in both developing and mature brain produce VEGF and bFGF. Preliminary studies have shown that reactive astrocytes in injured adult brain express vascular endothelial growth factor (VEGF) mRNA and VEGF receptors. There is no data, so far as can be determined, regarding the role of either VEGF or bFGF in traumatically injured developing brain. VEGF and bFGF protein expression by reactive astrocytes will be correlated with vascular growth and endothelial VEGF and bFGF receptor expression in cerebral stab wounds of neonatal and adult animals using immunohistochemistry and in vivo astoradiography. Further, these data will be quantified using an innovative microdissection technique combined with immunochemical analyses. Neutralizing antibodies to VEGF and bFGF will be administered to intracerebral wounds to determine if inhibition of the angiogenic factors impedes revascularization and causes increased neuronal injury subsequent to injury-induced hypoxia. Preliminary evidence is also presented which suggests that directly administered (exogenous) VEGF induces both angiogenesis and gliosis in the developing and adult brain in both intact and injured brain paradigms. The proposed experiments will compare the angiogenic response to exogenous VEGF and bFGF applied to injured brain with data from the studies of endogenous astroglial VEGF and bFGF to determine if delivery of these growth factors enhances neovascularization and potentially ameliorates neuronal damage. These experiments will also provide data about the astroglial response to exogenous VEGF including its potential role as an astroglial mitogen and autrocrine factor. The proposed studies could offer important basic insights about growth factor mediated interactions between astroglia and blood vessels following direct brain injury in the mature and developing CNS. Since increased vascularization and decreased astroglial """"""""scar"""""""" formation are important goals for healing damaged CNS tissue, the characterization of astroglial """"""""scar"""""""" formation are important goals for healing damaged CNS tissue, the characterization of astroglial interactions with angiogenic cytokines may be useful as a fundamental cellular basis for growth factor-based therapy following brain trauma.
