Neutrophils cross the BBB primarily on transcellular pathways: an in vitro study

Area of Science:

• Neuroscience
• Immunology
• Cell Biology

Background:

• The blood-brain barrier (BBB) is crucial for CNS homeostasis, regulating molecule and cell passage.
• Leukocyte extravasation occurs via paracellular or transcellular routes in CNS diseases.
• Understanding neutrophil transmigration is vital for neuroinflammatory disease research.

Purpose of the Study:

• To investigate neutrophil transmigration pathways across an inflamed BBB in vitro.
• To assess the impact of neutrophil migration on endothelial barrier integrity.

Main Methods:

• Primary porcine brain capillary endothelial cells cultured to model an inflamed BBB.
• Electron microscopy, scanning force microscopy, and immunofluorescence imaging.
• Electric cell-substrate impedance sensing and transendothelial electrical resistance measurements.

Main Results:

• Neutrophils predominantly utilized the transcellular pathway for migration across the BBB model.
• Neutrophil-endothelial interactions did not compromise the endothelial barrier function.
• Paracellular migration was observed but played a minor role.

Conclusions:

• Neutrophils preferentially migrate transcellularly across the inflamed BBB.
• Endothelial barrier integrity is maintained during neutrophil transmigration via the transcellular route.
• The developed in vitro model effectively simulates inflammatory BBB conditions for studying leukocyte trafficking.