Roles of Vascular Endothelial Cells in The Formation of Neural Pathways

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In the formation of neural pathways during development, a number of adhesion molecules which promote neurite outgrowth have been documented. Peripheral nerves travel long distance in order to reach their appropreate targets, and several adhesion molecules are involved in their pathfinding. We are particularly interested in the roles of the immature vascular endothelial cells before lumen formation for the formation of neural pathways. Several adhesion molecules including fibronectin and vitronectin have been reported to be expressed on the surface of these cells, and we postulated that they are involved in neurite outgrowth over endothelial cells.By the use of in vitro system we have established the method for quantitative evaluation of the neurite elongation of the dorsal root ganglion cells. Adding antibodies, synthetic peptides or carbohydrates, the degree of inhibition of the neurite elongation is measured. The most potent inhibitors of neurite outgrowth are vitronectin antibody, RGD peptides, which is well known to be an adhesion sequence for the binding with integrins, and EC1 monoclonal antibody which was produced in our laboratory.The cahracterization of the EC1 antigen revealed that molecule is heparansulfate proteoglycan with the molecular weigh above 400 kD.As the cleavage of the carbohydrate chain by heparitinase removes the immunoreactivity as well as the neurite promoting function, the heparan sulfate glycan chain has an important role for neurite extension. We are now sequencing the peptide structure of EC1 proteoglycan.