Methods to assess pericyte-endothelial cell interactions in a coculture model.

The blood-brain barrier (BBB) comprises the microvascular endothelial cells, pericytes, and astrocytes, which are connected by the extracellular matrix (ECM). Current BBB models focus solely on the microvascular endothelial cells which constitute a physical barrier by formation of tight junctions (TJs), while the impact of pericytes on barrier regulation is poorly understood. We established a coculture model from primary porcine brain capillary endothelial cells (PBCECs) and pericytes (PBCPs) to approach the in vivo situation. This model allows the examination of pericyte impact on pharmacological, transport, migration, and metabolic activity of the BBB. In vivo the interaction between pericytes and endothelial cells is partly controlled by the ECM which is remodeled by matrix metalloproteinases (MMPs). Both endothelial cells and pericytes secrete MMPs which are important not only for ECM remodeling but also for TJ cleavage. In this chapter, current methods to study the interactions of these cell types by ECM signaling as well as MMP secretion are described.