A pump‐free tricellular blood–brain barrier on‐a‐chip model to understand barrier property and evaluate drug response

Abstract

Disruption of the blood–brain barrier (BBB) leads to various neurovascular diseases. Development of therapeutics required to cross the BBB is difficult due to a lack of relevant in vitro models. We have developed a three‐dimensional (3D) microfluidic BBB chip (BBBC) to study cell interactions in the brain microvasculature and to test drug candidates of neurovascular diseases. We isolated primary brain microvascular endothelial cells (ECs), pericytes, and astrocytes from neonatal rats and cocultured them in the BBBC. To mimic the 3D in vivo BBB structure, we used type I collagen hydrogel to pattern the microchannel via viscous finger patterning technique to create a matrix. ECs, astrocytes, and pericytes were cocultured in the collagen matrix. The fluid flow in the BBBC was controlled by a pump‐free strategy utilizing gravity as driving force and resistance in a paper‐based flow resistor. The primary cells cultured in the BBBC expressed high levels of junction proteins and formed a tight endothelial barrier layer. Addition of tumor necrosis factor alpha to recapitulate neuroinflammatory conditions compromised the BBB functionality. To mitigate the neuroinflammatory stimulus, we treated the BBB model with the glucocorticoid drug dexamethasone, and observed protection of the BBB. This BBBC represents a new simple, cost‐effective, and scalable in vitro platform for validating therapeutic drugs targeting neuroinflammatory conditions.

Emerging Approaches to Understanding Microvascular Endothelial Heterogeneity: A Roadmap for Developing Anti-Inflammatory Therapeutics

“…This microphysiological system was used to screen combinations of pro-and anti-angiogenic compounds to identify key mechanisms involved in the complex multicellular process of angiogenesis. Mimetic 3D models of the BBB have also been used to examine neuroinflammation and the impact on brain endothelial barrier permeability [159]. When brain microvascular endothelial cells were cocultured with astrocytes and pericytes to model the BBB, the addition of TNF compromised barrier function and increased permeability, as demonstrated by decreased TEER and a reduction in the expression of tight junction proteins.…”

Three-Dimensional in vitro Models of Healthy and Tumor Brain Microvasculature for Drug and Toxicity Screening

“…The blood flow is simulated using a pulsatile pump which injects the medium inside the blood vessel and reproduces the rheological features like those observed in vivo . The flow can also be driven by gravity and by capillary effect to eliminate the need for pumps for a more robust and scalable model (Sugihara et al, 2020 ; Yu et al, 2020 ). ECM channels can display an array of blood vessels embedded in a hydrogel, usually type I collagen (Kim et al, 2015 ; Partyka et al, 2017 ; Yu et al, 2020 ).…”

“…The flow can also be driven by gravity and by capillary effect to eliminate the need for pumps for a more robust and scalable model (Sugihara et al, 2020 ; Yu et al, 2020 ). ECM channels can display an array of blood vessels embedded in a hydrogel, usually type I collagen (Kim et al, 2015 ; Partyka et al, 2017 ; Yu et al, 2020 ). The preparation of the microchannels often involves the use of microneedles to create holes in the matrix, resulting in vessels with a diameter of around 300 to 400 μm (Kim et al, 2015 ; Yu et al, 2020 ).…”

“…ECM channels can display an array of blood vessels embedded in a hydrogel, usually type I collagen (Kim et al, 2015 ; Partyka et al, 2017 ; Yu et al, 2020 ). The preparation of the microchannels often involves the use of microneedles to create holes in the matrix, resulting in vessels with a diameter of around 300 to 400 μm (Kim et al, 2015 ; Yu et al, 2020 ). Frequent collapses of those microchannels follow the withdrawal of these microneedles.…”

“…The formation of the TJ and the selective permeation are important criteria for the successful engineering of the brain microvasculature. Permeation studies with templated fluorescent tracers, such as dextran with different molecular weights and TEER measurement are the common methods for evaluating the BBB permeability (Yu et al, 2020 ) before testing for xenobiotic transport potency through the BBB. Xenobiotics are compounds, either from natural or synthetic sources which are foreign to the body, thus are not expected to be naturally found in the organism.…”