Immortalized mouse brain endothelial cells are ultrastructurally similar to endothelial cells and respond to astrocyte-conditioned medium

Studies of brain microvessel endothelial cell physiology and blood-brain ba rrier properties are often hampered by the requirement of repeatedly produc ing and characterizing primary endothelial cell cultures. The use of viral oncogenes to produce several immortalized brain microvessel cell lines has been reported. The resulting cell lines express many properties of the bloo d-brain barrier phenotype but do not completely mimic primary endothelial c ells in culture. As immortalized brain microvessel endothelial cell lines h ave not yet been produced from mice, we transformed mouse brain endothelial cells with the adenovirus E1A gene using a retroviral vector (DOL). Eight of 11 clones produced exhibited an endothelial-like cobblestone morphology and were characterized as endothelial with a panel of antibodies, lectins, and ultrastructural criteria. These cells are endothelial in origin and sha re ultrastructural features with primary cultures of endothelial cells. Exa mination of freeze fracture and transmission electron micrographs show adhe rens junctions exist between the transformed cells, and culture in astrocyt e-conditioned medium induces the formation of gap junctions. This is one in dication that responses to astrocyte-derived factors are retained by the tr ansformed cell lines.