Blood brain barrier | Mimetas

Blood brain barrier

Blood brain barrier

The blood–brain barrier (BBB) ensures a homeostatic environment for the central nervous system (CNS) and is essential for healthy brain functioning. However, the BBB’s barrier properties also complicate the treatment of CNS disorders, as many small- and large-molecule pharmaceuticals are restricted from entering the brain in quantities that are large enough to elicit a therapeutic response. Receptor-mediated transcytosis is one of the major routes for drug delivery of large molecules into the brain. Here we describe a human model of the blood-brain barrier in the MIMETAS OrganoPlate® comprising a vessel of brain endothelial cells, supported by astrocytes and pericytes. The model shows expression of adherens- and tight junction proteins, barrier formation, and antibody transcytosis.

Method

Figure 1

A MIMETAS OrganoPlate® 3-lane was employed to establish the blood-brain barrier model. The OrganoPlate® 3-lane comprises 40 tissue culture chips, which each consist of three channels. An ECM gel was seeded in the middle channel of each chip and is patterned by PhaseGuides. Endothelial cells are grown in the top channel of each chip and form an endothelial vessel under perfusion by placing the OrganoPlate® on the OrganoFlow platform. Astrocytes and pericytes are added to the bottom channel and complete the BBB co-culture. Immunostaining shows presence of adherens and tight junctions, indicative of barrier formation (figure 1). 

 

Barrier integrity

Figure 2

To confirm barrier function of the BBB on-a-chip, a fluorescent dye (FITC-dextran) was perfused through the lumen of the model and distribution of the dye through the chip was monitored over time. Monocultures of brain endothelial cells as well as BBB co-cultures (endothelium, astrocytes, pericytes) retain the dye within the endothelial vessel, while cell-free controls show leakage of the dye into the adjacent ECM gel channel. Culture of endothelial cells under perfusion strongly improves barrier function compared to static culture conditions (figure 2). 

Antibody transcytosis

Figure 3b
Figure 3a

Figure 3

To study antibody transcytosis, antibodies were perfused through the lumen of the BBB on-a-chip model. Samples were taken from the basal compartment and analyzed using an MSD system, after which their apparent permeability was determined. Results show that the apparent permeability of both antibodies is greatly reduced in the BBB model compared to cell-free controls, which indicates the model has sufficient barrier function to strongly limit paracellular antibody flux. Furthermore, we find that antibodies that target the BBB’s transferrin receptor show an approximately 2-fold higher passage across the model compared to antibodies that don’t bind a target on human cells (figure 3).

 

This work was partly supported by the European Union under grant agreement No 667375 (CoStream) and No 115975 (Adapted).