This new laboratory is tackling a fundamental problem in the nervous and vascular system: how these two systems with distinct functions but similar anatomical architecture are established during development? To study this question, we have now focused on developing interaction between these two systems, particularly neuronal influences on vascular identity such as artery, vein and lymphatic vessels and branching pattern, and vascular influences on the maintenance of stem cell capacity in neural stem cells (NSCs) in the developing brain and spinal cord. ? 1) Nerve-derived vascular branching patterning signals? Our previous studies demonstrated that in the developing limb skin, peripheral nerves provide to pattern the branching of arterial blood vessels and peripheral nerve-derived vascular endothelial growth factor (VEGF) controls arterial differentiation. Analysis of conditional inactivation of Vefg-A in the peripheral nerve suggests that nerve-derived VEGF controls arterial differentiation but not the nerve-blood vessel alignment. This raised a question about what nerve-derived signals control vascular branching pattern and nerve-vessel alignment. In collaboration with the laboratory of Takashi Nagasawa (KYOTO UNIVERSITY, JAPAN), we are currently analyzing the role of chemokine signals in the nerve-vessel alignment.? 2) Coronary vessel development? Coronary blood vessels are highly branched structure. We are interested in what control the branching pattern of the coronary vessels. Interestingly, peripheral nerves (cardiac nerves) are also highly branched and aligned with remodeled (large-diameter) coronary vessels. Whether cardiac nerves control the branching of the coronary vessels as we see in the embryonic limb skin or vice versa have been examined.? 3) Lymphatic vessel development in the central nervous system (CNS)? Lymphatic endothelial progenitors arise from venous endothelial cells and migrate away from the cardinal vein to form lymphatic vessel networks, including collecting lymphatic vessels and lymphatic capillaries. The CNS (especially spinal cord), however, maintains an immuno-privileged microenvironment in which lymphatic vessels do not develop. We are interested in discerning the reason for how the CNS inhibits the lymphatic vessel development. We have developed procedures to isolate lymphatic endothelial progenitors directly from mouse embryos using fluorescence-activated cell sorting (FACS). We can then examine the inhibitory signals by co-culturing freshly isolated lymphatic endothelial progenitors with spinal cord in vitro.? 4) Genetic tools to analyze peripheral vascular development? Most mutants with embryonic angiogenesis defects show severe defects in the heart as well. This raised a fundamental issue in the field of cardiovascular development, that how the angiogenesis defects is uncoupled from the heart defects. The genes are mostly expressed in both peripheral endothelial and heart endocardial cells. Efforts to identify promoters and enhancers, which are active in peripheral endothelial cells but not endocardial cells, are underway. These promoters and enhancers should be useful for making peripheral endothelial cell-sepcific Cre deleter lines.? In parallel with this study, we have been developing spatial and temporal gene knockdown system in chick embryos. Our goal is to inactivate the angiogenic genes using shRNAi by in ovo electroporation and see the role of these genes in the peripheral vascular development.? 5) Vascular niche for adult neurogenesis? Several evidences suggest that adult neurogenesis occurs around blood vessels in the brain. We are interested in what endothelial signals control adult neurogenesis and maintenance of neural stem cells/progenitors. We have analyzed the expression profiles of genes in the SVZ endothelial cells using Affymetrix mouse cDNA microarrays and have confirmed the expression of candidate genes by immunohistochemical and/or in situ hybridization analysis. We can then perform in vivo gain- or loss-of-function experiments to analyze the role of candidate genes for vascular niche using an endothelial cell-specific gene transfer system being developed by the Silvio Gutkind laboratory (NIDCR).
