Expression of Blood-Brain Barrier Antigens in Non-Brain Derived Endothelial Cells Despite Lack of Astrocyte Interactions

Endothelial cells of different vascular beds display diverse functional and morphological characteristics. Specifically, brain-derived endothelial cells exhibit specialized properties that form the blood-brain barrier, an important structure that ensures homeostasis within the neural environment. Classic proteins associated with the blood-brain barrier include neurothelin (also known as CD147), neuroblast differentiation-associated protein, glucose transporter-1 and gamma-glutamyltranspeptidase. Astrocytes are believed to be responsible for inducing the expression of blood-brain barrier proteins in brain endothelial cells. We evaluated the induction property of astrocytes in this study. Human umbilical vein endothelial cells and human dermal microvascular endothelial cells, both non-brain derived, were grown as co-cultures with human astrocytes or as monocultures for various periods. Blood-brain barrier marker mRNA levels were quantified using real-time reverse transcriptase polymerase chain reaction and protein localization was determined through immunofluorescence staining. Our results demonstrate expression of neurothelin, glucose transporter-1, and gamma-glutamyltranspeptidase mRNA in endothelial cells even in the absence of astrocytes. Co-culturing endothelial cells with astrocytes induced the expression of glucose transporter-1 and gamma-glutamyltranspeptidase but not neurothelin. Immunofluorescence staining revealed expression and localization of neuroblast differentiation-associated protein at cell membranes of non-brain derived endothelial cells. Non-brain endothelial cells also showed glucose transporter-1, gamma-glutamyltranspeptidase and neurothelinimmunoreactivity in expected subcellular compartments. These findings indicate that endothelial cells in culture express markers of blood-brain barrier and that astrocytes have differential inductive capacity depending of the endothelial cell type.