Evaluation of Blood–Brain Barrier Permeability and Integrity in Juvenile Rodents: Dynamic Contrast-Enhanced (DCE), Magnetic Resonance Imaging (MRI), and Evans Blue Extravasation

Abstract

Focal ischemic stroke is the result of a blockage in an artery that leads to decreased blood flow to the neuronal cells in the brain. The middle cerebral artery (MCA) is the most common artery that is occluded in adult and pediatric stroke patients. The pathophysiology is challenging to study in either of these populations because of the highly variable clinical state in humans. Many of these variables can be eliminated when using in vivo models of stroke in rodents. Here, we describe a technique called the transient MCA occlusion (tMCAo) model in a juvenile rat model of stroke. This technique utilizes a filament that is advanced to block the origin of the MCA to induce focal ischemia. The filament is then retracted 60–90 min later allowing for secondary reperfusion. By incorporating reperfusion, this model mimics embolic strokes in humans and provides the opportunity to uncover injury associated with reflow through ischemic tissue. We are particularly interested in the reperfusion-induced injury to the blood–brain barrier (BBB) that follows after blood flow to the ischemic brain is restored. Our goal is to provide the reader with guidelines on how to execute the tMCAo surgical procedure, with notes highlighting the advantages and limitations of the method. We also include directions on how to conduct the techniques used to evaluate the permeability of the blood–brain barrier including Evans blue extravasation, a histological procedure, and dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI), a technique used to evaluate blood–brain barrier permeability that can be applied to study stroke in a rodent model.