The aim of this project is to develop a blood-brain barrier (BBB) on chip, valuable for the screening of newly developed drug compounds, studying pathological conditions and nanotoxicity research.
The BBB is the unique transport regulator of nutrients, inflammation cytokines, disease pathogens and peripheral cell types into and out of the brain tissue, thereby preserving brain homeostasis. In Figure 1 the BBB in rat cortex is shown: a blood vessel (endothelial cells) lined by astrocytic endfeet. Additionally, the breakdown of the BBB is involved in several neurodegenerative diseases such as Parkinson’s disease, Alzheimer’s disease and Multiple Sclerosis. The key characteristic of the BBB is the formation of tight junctions between adjacent endothelial cells, which prevent paracellular transport of e.g. drug compounds. Hence, to study disease characteristics and perform drug screening experiments, it is essential to have a realistic model of the BBB. The transendothelial electrical resistance (TEER) and the permeability of the monolayer are widely used to assess the integrity of the BBB.
Figure 1. Rat cerebral cortex with astrocytic (yellow) endfeet wrapping around blood vessels (red). Cell nuclei are cyan. [Madelyn May / Rensselaer Polytechnic Institute/Troy, New York, USA].
Conventional in vitro methods such as the Transwell® system are static, laborious, lack reproducibility and need a relative high cell number. Therefore, new in vitro models have been developed. An emerging topic in the field of tissue engineering is the use of microfluidics for the development of so called “organs-on-chips”. These promising micro-environment models include physiologically relevant shear stress and smaller working volumes, and these models are able to integrate both TEER and permeability analysis in a single device.
At the BIOS group, we are developing a BBB on chip, using human (primary) cells, which enables both TEER and permeability measurements and facilitates mechanical and biochemical modulation of the barrier in a physiologically relevant setting. The BBB chip consists of two channels separated by a permeable membrane. Brain endothelial cells are cultured on top of the membrane in the top channel (blood compartment). In the bottom channel (brain compartment) cells closely associated with the brain capillaries can be cultured, such as astrocytes. In Figure 2 a cross section of the device is shown and in Figure 3 an assembled BBB device is shown. A schematic representation of the chip design is shown in Figure 4.
Figure 2. Cross section of the BBB on chip including: electrodes (E), endothelial monolayer (EM), membrane (M) and astrocytes (A).
Figure 3. Assembled BBB device. Electrodes are sticking out of the chip. Tubes can be connected to the four inlets to supply the cells inside the chip with medium and apply shear stress.
Figure 4. Schematic representations of the chip design. TC = top channel (blood compartment in which brain endothelial cells are cultured). BC = bottom channel (brain compartment). M = porous membrane. 1,2,3,4 = platinum electrodes, used to measure TEER.
Once this BBB on chip has been validated, it will be used as a platform to test drug delivery methods. Nanocarriers designed for delivering Alzheimer drugs into the brain are being developed, and their efficiency will be assessed using this BBB model. In addition, to gain more insight into BBB pathology, studies of disease mechanisms will be carried out. For example, the influence of amyloid beta fibrils on the BBB physiology and permeability will be studied to gain more insight into plaque formation in Alzheimer’s disease. This is in close collaboration with the Nanobiophysics and the Biomaterials Science and Technology groups at the UT.
Furthermore, brain endothelial cells derived from induced pluripotent stem cells will be used in this device. Using these cells a patient-specific model of the BBB can be made and studied to gaoin more insight in (genetic) disorders of the BBB. This is in collaboration with the Department of Anatomy and Embryology of Leiden University Medical Center.
If you have questions or are interested in doing a bachelor or master assignment in this project, feel free to contact us: