Optimization of an in vitro human blood–brain barrier model: Application to blood monocyte transmigration assays

The blood–brain barrier (BBB) is a selectively permeable barrier that separates the circulating blood from the extracellular fluid of the brain and is an essential component in brain homeostasis. In vitro BBB models are valuable supporting tools that can precede and complement animal and human studies of the development and progression of the central nervous system diseases. At present, mono-, co-, and tri-culture models that use porcine, murine, or human cells have been developed. We have optimized a two-dimensional model of the human BBB using primary human brain microvascular endothelial cells and normal human astrocytes. We have validated the effectiveness of our model with transmigration assays of human blood monocytes toward CCL19, a natural ligand of the chemokine receptor CCR7. This model offers the following advantages: • It is simple, convenient, and requires small quantities of material, reagents, and primary cells. • It can be used to monitor cell migration through the BBB. • It can be used to assess brain capillary permeability in the presence of xenobiotic, pro-inflammatory, or other substances.