LAUSR

In vitro blood–brain barrier (BBB) models have played an important role in studying processes such as immune cell trafficking and drug delivery, as well as contributing to the understanding of mechanisms of disease progression. Many biological and pathological processes in the cerebrovasculature occur in capillaries and hence the lack of robust hierarchical models at the capillary scale is a major roadblock in BBB research. Here, a double‐templating technique for engineering hierarchical BBB models with physiological barrier function at the capillary scale is reported. First, the formation of hierarchical vascular networks using human umbilical vein endothelial cells is demonstrated. Then, barrier function is characterized in a BBB model using brain microvascular endothelial‐like cells differentiated from induced pluripotent stem cells. Finally, immune cell adhesion and transmigration are characterized in response to perfusion with the inflammatory cytokine tumor necrosis factor‐alpha, and it is shown that capillary‐scale effects, such as leukocyte plugging, observed in mouse models, can be recapitulated. The double‐templated hierarchical model enables the study of a wide range of biological and pathological processes related to the human BBB.