Expression of Blood-Brain Barrier Antigens in Non-Brain Derived Endothelial Cells Despite Lack of Astrocyte Interactions
Andrew J. MacDonald
Department of Pathology, University of Western Ontario, London, ON, Canada.
Zia A. Khan
Department of Pathology, University of Western Ontario, London, ON, Canada and Metabolism and Diabetes Research Program, Lawson Health Research Institute, London, ON, Canada.
*Author to whom correspondence should be addressed.
Abstract
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.
Keywords: Blood-brain barrier, endothelial cell, astrocytes, co-culture, induction, CD147, AHNAK, glut