There are four ongoing projects in our laboratory that investigate the mechanisms of close neuro-vascular interactions and generate genomic tools to study vascular branching networks.? 1) Nerve-derived vascular branching patterning signals? Our in vitro and in vivo experiments suggest that vascular endothelial growth factor (VEGF)-A is necessary for arterial differentiation but not for the nerve-blood vessel alignment. This highlights the unresolved nature of the nerve-derived signal(s) that control vascular branching patterns and nerve-blood vessel alignment. Our principal accomplishment is the discovery of nerve-derived C-X-C motif chemokine ligand (CXCL) 12 that controls the nerve-blood vessel alignment. In collaboration with the laboratory of Takashi Nagasawa (KYOTO UNIVERSITY, JAPAN), we are analyzing the expression of its receptor CXCR4 for this alignment signal and the mechanisms to recruit a subset of arterial vessels for the nerves.? 2) Lymphatic vessel development in the central nervous system (CNS)? The second line of research is to understand how the spinal cord in the central nervous system (CNS) inhibits lymphatic vessel branching, which is a feature of immune privilege within the CNS. We have developed a method to isolate lymphatic endothelial progenitors from mouse embryos and examine inhibitory signals for lymphatic endothelial cell differentiation in culture. Among tested soluble factors, we have found that basic fibroblast growth factor (bFGF) and VEGF-A blocks formation of lymphatic endothelial clusters, while enhancing growth of blood endothelial capillaries. To further address the role of neuronal bFGF and VEGF-A in the spinal cord, we are analyzing chick embryos carrying out RNAi-mediated knockdown of bFGF and VEGF-A in the CNS. These experiments suggest that genetic programs are fundamental for organ-specific vascular branching patterns. ? 3) Genetic tools to analyze peripheral vascular development? The third is to develop in vivo loss-of-function tools to better understand the biological function of genes in vascular development. Previous studies demonstrate that heart function and normal blood flow are necessary for vascular development. However, current genetic tools for mice fail to uncouple vascular and heart abnormalities. To circumvent this problem, we are searching for promoters and enhancers that are active in endothelial cells but not active in heart endocardial cells. Now we have identified the fragment of GATA2 enhancer that selectively regulates activity in peripheral endothelial cells but not heart endocardial cells. Additionally, we are developing a local gene knockdown system in chick embryos using in ovo electroporation delivery of RNAi and see the role of these genes in the peripheral vascular development.? 4) Vascular niche for adult neurogenesis? Given the importance of the vascular niche for a variety of stem cells, understanding the paracrine signals for stem cell maintenance has become more important. Our challenge is to search vascular signals that support neurogenesis in the subventricular zone (SVZ) and dentate gyrus (DG) of the hippocampus in the adult brain. We have analyzed the expression profiles of genes in the SVZ and DG vasculature using Affymetrix mouse cDNA microarrays. To unravel the signals of the vascular niche, we are developing in vivo gain- and loss-of-function experiments using a tissue-specific viral delivery system. This system utilizes the avian RCAS retrovirus as a vehicle to deliver genes of interest into the transgenic mice in which endothelial cells express the gene encoding the avian receptor TVA.? ? Publications generated by this research:? Jones, C.A., et al., Robo4 stabilizes the vascular network by inhibiting pathologic angiogenesis? and endothelial hyperpermeability. Nat Med, 2008. 14: p. 448-453.
