Leon Tai is funded by University of Illinois Chicago start-up funds.

All experiments follow the University of Illinois, Chicago Institutional Animal Care and Use Committee protocols.
1. General Preparation
NOTE: The brain microvascular endothelial cell line (hCMEC/D3) is an extensively characterized immortalized human BEC line14,15,16,18,19. Culture the hCMEC/D3 cells on tissue culture flasks coated with collagen Type I (calf skin, 1:20 dilution of 0.1% solution in Hank&#39;s Balanced Salt Solution (HBSS) containing Ca2+ and Mg2+) in basal Endothelial Growth Basal Medium (EBM-2) containing 2-5% Fetal Bovine Serum (FBS), 10% ascorbic acid, 10% gentamicin sulphate, 25% hydrocortisone and 1/4 of the total volume of the supplied growth factor supplements per 500 mL of media [vascular endothelium growth factor (VEGF), epidermal growth factor (EGF), insulin-like growth factor 1 (IGF-1) and human basic fibroblastic growth factor (bFGF), see Table of Materials]. 
NOTE: EBM-2 medium with FBS and growth factors is referred to as &#34;EBM-2 complete&#34;. EBM-2 without FBS and supplements is referred to as &#34;EBM-2 basal&#34;. At full confluence, the hCMEC/D3 cells are ~1 x 105 cells/cm2.
<ol>
	<li>Passage the hCMEC/D3 cells at a ratio of 1:5 by first incubating with HBSS for 3 min without Ca2+ and Mg2+ followed by detachment with 5 mL trypsin/EDTA (0.25%) for 5 min. Neutralize the trypsin using EBM-2 complete (1:1 neutralization), and centrifuge at 290 x g for 5 min at 4 &#176;C; discard the supernatant. Resuspend the pellet in EBM-2 complete and re-plate at 1:5 ratio.</li>
	<li>Culture the primary human pericytes and astrocytes according to the supplier&#39;s protocol [Table of Materials]. Culture the pericytes in pericyte basal medium with FBS and pericyte growth supplement.</li>
	<li>Culture the human astrocytes in astrocyte medium containing astrocyte growth factors. Culture both the pericytes and the astrocytes in tissue culture flasks coated with 3 mL of poly-L-lysine (PLL) for cell adherence and utilize the cells between passages 2 and 5.</li>
	<li>Euthanize 7 mice and remove the brain stems and cerebella with forceps; detach the meninges by carefully rolling the brains on gauze. Mince the remaining brain tissue in a Petri dish in Minimal Essential Medium (MEM) with HEPES (5 mL per brain) with a sterile razor blade. Isolate the primary mouse BECs from 2-month-old C57BL/6J mice according to the referenced protocol20.</li>
	<li>Transfer the minced brain tissue to a 15 mL conical tube. Centrifuge at 290 x g for 5 min at 4 &#176;C. Remove the supernatant and incubate the tissue in a papain (833.33 &#181;L per brain) and DNase (41.7 &#181;L per brain) solution, in a 37 &#176;C water bath for 1 h, to digest the tissue.</li>
	<li>Triturate the homogenate sequentially through 19 and 21 gauge needles, mix at a 1:1 ratio with a 22% Bovine Serum Albumin (BSA) solution, and centrifuge at 1360 x g for 10 min at 4 &#176;C.</li>
	<li>Resuspend the resulting pellet in 1 mL EBM-2 complete and centrifuge at 290 x g for 5 min at 4 &#176;C. Resuspend again in 1 mL EBM-2 complete and plate the cells (1 mL/well) on 6-well plates coated with collagen (~1 brain per well).</li>
	<li>Replace the media 24 h later with EBM-2 complete containing 4 &#181;g/mL puromycin hydrochloride; replace with EBM-2 complete after 2 days. The primary BECs are cultured as for the hCMEC/D3 cells and are at full confluence at 1 x 105 cells/cm2.</li>
	<li>Prepare a 100 &#181;M of oA&#946;, 24 h before the assay. 
	NOTE: oA&#946; is considered the disease relevant form of A . For oA&#946;, use the well-characterized preparations described by Dahlgren et al.21.</li>
	<li>Thaw the basement membrane stock solution overnight at 4 &#176;C and aliquot into sterile PCR tube strips (8 tubes) at 140 &#181;L basement membrane per tube. Refreeze each strip and store at -20 &#176;C. Thaw one strip per 96-well plate at 4 &#176;C, 24 h prior to the assay. Pre-cool the pipette tips to avoid solidification. 
	NOTE: All handling of the basement membrane matrix must be carried out on ice to avoid rapid solidification. As 10 &#181;L per well of basement membrane is used on the day of the assay, each strip is sufficient for one 96-well plate.</li>
	<li>Incubate fully confluent BECs in EBM-2 basal, 24 h prior to the assay. 
	NOTE: The rationale is: EBM-2 complete contains supplemented factors and FBS with the purpose of promoting optimal cell growth; however, the same molecular pathways that promote cell growth are also important for brain endothelial cell coverage and dynamics, both in the presence and absence of a stressor. We therefore serum and supplement starve the BECs to reduce the confounding effect of residual activation of cellular signaling pathways. Of note, the cells are briefly (5 min) exposed to FBS during the neutralization of trypsinized cells prior to the assay. In contrast to BECs, the pericytes and astrocytes are not serum starved, due to the requirement of different factors for growth and the relative instability of these cell types in response to serum starvation (Tai laboratory, unpublished observations). 
	NOTE: EBM-2 basal is utilized during the assay for the single and triple culture meshwork formation and disruption assays. This is critical to prevent confounding stressor or treatment dependent signaling.</li>
</ol>
2. Meshwork-like Formation and Disruption Assays
<ol>
	<li>Single BEC culture assays: 
	NOTE: Three different paradigms for the single cultures of BECs are shown in Figure 1A. Each paradigm is designed to assess the response of BECs in different models of vessel coverage. Paradigm 1 is meshwork formation. This paradigm is designed to examine the effects of stressors and/or treatments on angiogenesis and meshwork formation. BECs, oA&#946;, and treatments are all added to the plate at the 0 h time point. Paradigm 2 is prevention of meshwork disruption. Cells are plated in the presence of a growth factor or drug and incubated for 4 h to form meshwork-like structures. A stressor, oA&#946; in this case, is added after 4 h. This paradigm assesses the ability of a treatment to prevent stressor-induced damage to preformed meshwork-like structures. Paradigm 3 is simultaneous treatment of meshwork disruption. Cells are plated and allowed to form meshwork-like structures for 4 h. Treatments and oA&#946; are then added simultaneously at the 4 h time point, assessing the ability of the preformed cell network to respond to various treatments. All the paradigms follow similar common steps, except with differences in the timing of treatment addition.
	<ol>
		<li>On the day of the assay, pipette the basement membrane matrix at 10 &#181;L/well into the bottom of 96-well plates and allow to set for 1 h at 37 &#176;C.</li>
		<li>Suspend the lyophilized green cell tracking dye (see Table of Materials) in 10 &#181;L DMSO to generate a 10-mM stock solution, and dilute to 10 &#181;M (1:1000) in EBM-2 basal. Remove the media from the fully confluent flask and replace with EBM-2 basal containing the green cell tracking dye (5 mL for a 75 cm2 flask). Preload BECs with the green cell tracking dye, 20 min prior to the start of the assay.</li>
		<li>Incubate the cells for 20-30 min at 37 &#176;C, remove the medium with cell tracking dye, and detach the cells as described in Step 1.1. Neutralize the media with EBM-2 containing 10% FBS and centrifuge at 240 x g for 5 min at 4 &#176;C. Resuspend the pellet in 1 mL of EBM-2 basal.</li>
		<li>Plate the BECs in the 96-well plate at 10,000 cells/well in EBM-2 basal (0 h time point in all paradigms). 
		NOTE: Depending on the paradigm being utilized, treatments, stressors, or vehicle controls are added at the specified time points. In all paradigms, the medium is harvested for subsequent analysis (e.g. ELISA analysis) and cells are fixed at 24 h with freshly prepared 4% paraformaldehyde in Phosphate Buffered Serum (PBS). As an alternative approach to determine the term effects of oA&#946; on mesh formation, the protocol could be modified to pre-incubate confluent cell culture flasks with oA&#946;, and then perform the meshwork formation paradigms (+/-oA&#946;). 
		NOTE: The final volume in each well for all paradigms is 70 &#181;L. All treatments (oA&#946;, EGF, etc.) are added to their respective wells at a 1:20 dilution i.e. 3.5 &#181;L per treatment. For Paradigm 1, the cells are added in a cell suspension solution at 63 &#181;L/well. Immediately oA&#946;, desired treatments, and controls are added at 3.5 &#181;L/well each, giving a total of 70 &#181;L. For Paradigm 2, 63 &#181;L of cell suspension and 3.5 &#181;L of treatment (e.g. 100 ng/mL EGF) are added at the 0 h time point. After 4 h incubation, 3.5 &#181;L of an oA&#946; stock is added (e.g. for 100 nM final oA&#946; concentration, 3.5 &#181;L of 2 &#181;M oA&#946; stock). For Paradigm 3, 63 &#181;L of cell suspension is added at the 0 h time point and at 4 h, oA&#946; and desired treatments are added at 3.5 &#181;L/well each, giving a total of 70 &#181;L. These volumes can be adjusted according to treatments. For example, if only one treatment is required, the cell suspension volume can be adjusted to 66.5 &#181;L (maintaining 10,000 cells/well) and the treatment volume can remain at 3.5 &#181;L.</li>
	</ol>
	</li>
	<li>Triple culture assay: 
	NOTE: In addition to the single culture assays of BECs, we have developed a triple culture assay paradigm (Figure 1B) to determine the response of BECs, pericytes, and astrocytes within preformed networks to relevant stressors (e.g.oA&#946;). BECs are plated in the presence of desired treatments at 0 h. At 4 h, pericytes are gently added to the plate. At 7 h, astrocytes are added to the plate, followed by the addition of a stressor at 11 h. Cells are then incubated until the 24 h time point. 
	NOTE: For the triple culture assays, it is important to consider timing to ensure all cells are confluent at the same time. Human astrocytes and pericytes should be cultured 1 week before the assay, whereas the hCMEC/D3 cells need to be plated or passaged 4-5 days before the assay date. Further, it is important to use low passage (2-5) primary cells to avoid phenotypic drift.
	<ol>
		<li>Add the green cell tracking dye working solution to the hCMEC/D3 cells 20 min prior to starting the assay. Plate the hCMEC/D3 cells at 10,000 cells/well in EBM-2 basal (0 h time point). The volumes used are 45 &#181;L of cell suspension and 3.5 &#181;L of treatment (i.e. final EGF concentrations of 50 ng/mL, 100 ng/mL, or 1,000 ng/mL from stocks that are 20 times more concentrated).</li>
		<li>Following the 3.5 h incubation at 37 &#176;C, add the blue cell tracking dye working solution (10 &#181;M cell tracker blue in EBM-2 basal) to the human primary pericytes. At the 4 h time point (~30 min incubation with cell tracking dye), gently add 2,000 pericytes/well to the plate containing the hCMEC/D3 in a volume of 6 &#181;L/well.</li>
		<li>Following an additional 2.5 h incubation (total 6.5 h from 0 h time point), add the orange cell tracking dye working solution (10 &#181;M cell tracker orange in EBM-2 basal) to the human primary astrocytes. At the 7 h time point, gently add 10,000 astrocytes/well to the plate in 12 &#181;L volume. Therefore, the overall cellular ratio for endothelial cells:pericytes:astrocytes is 5:1:5. Further, the volume achieved to this point is 66.5 &#181;L.</li>
		<li>Add oA&#946; (3.5 &#181;L of 100 &#181;M stock) 4 h later (total 11 h from 0 h time point).</li>
		<li>Fix the cells 13 h later in freshly prepared 4% paraformaldehyde in PBS. 
		Caution: Wear protective clothing, gloves and eyeglasses while handling paraformaldehyde.</li>
	</ol>
	</li>
</ol>
3. Quantification
<ol>
	<li>Capture fluorescence images of the whole well of the 96-well plate at 1.6X magnification with a 2 s exposure time at 50% maximum power using a dissecting microscope. 
	NOTE: Equivalent microscopes can be utilized; however, it is critical to capture the entire well for comprehensive analysis.</li>
	<li>For quantitative analysis, process the images using the ImageJ angiogenesis analyzer plugin22 to quantify the number of branches, number of meshes, and total cell length (these readouts are automatically tabulated by the software) as described below. A detailed visual protocol of this step is provided in Figure 2.
	<ol>
		<li>Open fiji ImageJ by clicking on the software icon.</li>
		<li>Click on the double red forward arrows located at the end of the toolbar, then click &#34;Angiogenesis Analyzer&#34;.</li>
		<li>Select the folder with image files, click &#34;Open&#34;.</li>
		<li>When the &#34;settings for analysis&#34; box appears, click &#34;OK&#34;.</li>
		<li>When the &#34;processing images&#34; box appears, which indicates the number of images to be processed, click &#34;OK&#34;.</li>
		<li>When the &#34;batch progress window&#34; box appears, which indicates the estimated processing time. During this time the program quantifies the outputs including the number of branches, number of meshes, and total cell length. 
		NOTE: Once all the images are quantified, the results file will appear in the original image folder as a spreadsheet document.</li>
		<li>Select the spreadsheet file containing results and compare the number of branches, meshes and total cell length between groups. 
		NOTE: In the triple culture assay ImageJ is further utilized to analyze pericyte/astrocyte coverage and number. Images are thresholded by a blinded experimenter and the &#34;analyze particles&#34; function utilized to generate readouts. Fixed cells and tube-like structures can also be immunostained for A&#946;17 or other markers.</li>
	</ol>
	</li>
</ol>

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The authors have nothing to disclose.

The methods described can be utilized to address several fundamental biological questions surrounding cerebrovascular coverage24. Specifically, they can identify which receptors and signaling pathways play a role in angiogenesis, vessel coverage in cancer tissue, and peripheral endothelial cells relevant to the brain. Examples include angiogenic growth factor receptors, nitric oxide, mitogen activated protein kinase signaling and calcium signaling25,<sup class="x...

The blood-brain barrier (BBB) of cerebral capillaries is the largest interface of blood-to-brain contact and plays a central role in the homeostasis of the central nervous system (CNS)1,2. Dynamic processes at the BBB prevent the uptake of unwanted molecules from the blood, remove waste products from the CNS, supply essential nutrients and signaling molecules to the CNS, and modulate neuroinflammation1,2,3,4,5. BBB damage is prevalent during aging and several neurodegenerative disorders including Alzheimer&#39;s disease (AD), multiple sclerosis and stroke1,2,3,4,5,6. Therefore, BBB dysfunction may play a key role in neurodegenerative disorders, including as a therapeutic target.
Maintaining vessel coverage is important for the homeostatic functions of the BBB. However, in vivo and in vitro data conflict on whether the processes involved in neurodegenerative disorders cause higher or lower BBB coverage6,7,8,9,10,11,12,13, particularly in AD. Therefore, there is a strong rationale for the development of in vitro models using relevant cell types to assess and more comprehensively understand the dynamics of BBB coverage. Cerebral capillaries are composed of astrocytes, pericytes and brain endothelial cells (BECs)3. All cell types contribute to the function of the BBB through structural support and via the secretion of effector molecules such as angiogenic growth factors, cytokines and chemokines that act in paracrine- and autocrine-like fashion. However, the major effector cells of the BBB are BECs3. In general, the cell culture techniques for assessing BBB function are permeability assays performed on cells grown on filter inserts, or assessing levels of key BEC proteins, both after the addition of stressors14,15,16. Although important, these assays do not focus on the cerebrovascular coverage.
Here, our previous methods17 are detailed to assess BEC coverage and meshwork-like structures using single cultures of immortalized human BECs, single cultures of primary mouse BECs, and a humanized triple culture model (BECs, astrocytes and pericytes) of the BBB. The goal was to demonstrate the detrimental effect of oA&#946;, which is considered an important contributor to AD progression, on BEC coverage. The protective effect of the epidermal growth factor (EGF) highlights the potential of the technique as a therapeutic screening tool. The technique has several broad applications for basic and applied research including: 1) delineating the role of specific pathways on angiogenesis and vessel coverage, 2) evaluating the effects of disease and aging-relevant factors on angiogenesis and vessel coverage, and 3) identifying pharmacological targets.

<table><tbody><tr><td>hCMEC/D3 cells</td><td>Milipore</td><td>SCC066</td><td></td></tr><tr><td>EBM-2 basal media</td><td>Lonza</td><td>CC-3156</td><td></td></tr><tr><td>Collagen Type 1</td><td>ThermoFisher</td><td>A1064401</td><td></td></tr><tr><td>HBSS, calcium, magnesium, no phenol red</td><td>ThermoFisher</td><td>14025092</td><td></td></tr><tr><td>HBSS, no calcium, no magnesium, no phenol red</td><td>ThermoFisher</td><td>14175095</td><td></td></tr><tr><td>Trypsin-EDTA (0.25%)</td><td>ThermoFisher</td><td>25200056</td><td></td></tr><tr><td>Final concentrations of the SingleQuot growth factor supplements for EBM2 media</td><td>Lonza</td><td>CC-4147</td><td></td></tr><tr><td>5% FBS</td><td>Lonza</td><td>CC-4147</td><td></td></tr><tr><td>10% Ascorbic acid</td><td>Lonza</td><td>CC-4147</td><td></td></tr><tr><td>10% Gentamycin sulphate</td><td>Lonza</td><td>CC-4147</td><td></td></tr><tr><td>25% Hydrocortisone</td><td>Lonza</td><td>CC-4147</td><td></td></tr><tr><td>1/4 volume of the supplied growth factors: fibroblast growth factor, epidermal growth factor, insulin-like growth factor, vascular endothelial growth factor</td><td>Lonza</td><td>CC-4147</td><td></td></tr><tr><td>Puromycin hydrochloride</td><td>VWR</td><td>80503-312</td><td></td></tr><tr><td>MEM-HEPES</td><td>Thermo Scientific</td><td>12360-038</td><td></td></tr><tr><td>Papain cell dissociation system (papain and DNase1)</td><td>Worthington Biochemical</td><td>LK003150</td><td></td></tr><tr><td>Human pericytes</td><td>Sciencell</td><td>1200</td><td></td></tr><tr><td>Pericyte basal media</td><td>Sciencell</td><td>1201</td><td></td></tr><tr><td>Pericyte growth supplement</td><td>Sciencell</td><td>1252</td><td></td></tr><tr><td>Human Astrocytes</td><td>Sciencell</td><td>1800</td><td></td></tr><tr><td>Astrocyte media</td><td>Sciencell</td><td>1801</td><td></td></tr><tr><td>Astrocyte growth supplement</td><td>Sciencell</td><td>1852</td><td></td></tr><tr><td>Basement membrane (Matrigel Growth Factor Reduced)</td><td>Corning</td><td>356231</td><td></td></tr><tr><td>Angiogenesis m-plates (96-well)</td><td>ibidi</td><td>89646</td><td></td></tr><tr><td>Human Epidermal growth factor</td><td>Shenendoah Biotechnology</td><td>100-26</td><td></td></tr><tr><td>CellTracker green</td><td>ThermoFisher</td><td>C7025</td><td></td></tr><tr><td>CellTracker orange</td><td>ThermoFisher</td><td>C34551</td><td></td></tr><tr><td>CellTracker blue</td><td>ThermoFisher</td><td>C2110</td><td></td></tr><tr><td>Poly-l-lysine</td><td>Sciencell</td><td>0403</td><td></td></tr><tr><td>10% Neutral Buffered Formalin</td><td>Sigma-Aldrich</td><td>HT5012-60ML</td><td></td></tr><tr><td>C57BL mice</td><td>Jackson Laboratory</td><td>na</td><td></td></tr><tr><td>PCR tube strips</td><td>GeneMate</td><td>T-3014-2</td><td></td></tr><tr><td>Zeiss stereo discover v.8 dissecting microscope</td><td>Zeiss</td><td>na</td><td></td></tr></tbody></table>

in vitro assays to assess blood-brain barrier mesh-like vessel formation and disruption

Blood-brain barrier (BBB) coverage plays a central role in the homeostasis of the central nervous system (CNS). The BBB is dynamically maintained by astrocytes, pericytes and brain endothelial cells (BECs). Here, we detail methods to assess BBB coverage using single cultures of immortalized human BECs, single cultures of primary mouse BECs, and a humanized triple culture model (BECs, astrocytes and pericytes) of the BBB. To highlight the applicability of the assays to disease states, we describe the effect of oligomeric amyloid-&#946; (oA&#946;), which is an important contributor to Alzheimer&#39;s disease (AD) progression, on BBB coverage. Further, we utilize the epidermal growth factor (EGF) to illuminate the drug screening potential of the techniques. Our results show that single and triple cultured BECs form meshwork-like structures under basal conditions, and that oA&#946; disrupts this cell meshwork formation and degenerates the preformed mesh structures, but EGF blocks this disruption. Thus, the techniques described are important for dissecting fundamental and disease-relevant processes that modulate BBB coverage.

In single cultures, both the hCMEC/D3 cells (Figure 3A) and the primary mouse BECs (Figure 3B) form meshwork-like structures throughout the well. The structures are characterized by a meshwork of interlinked nodes (Figure 3). In all the paradigms described (Figure 1), the meshwork-like structures are similar after 24 h in the control groups, forming ~20 meshwork-like str...

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In Vitro Assays to Assess Blood-brain Barrier Mesh-like Vessel Formation and Disruption

Maintaining blood-brain barrier coverage is key for the homeostasis of the central nervous system. This protocol describes in vitro techniques to delineate the fundamental and pathological processes that modulate blood-brain barrier coverage.

In Vitro Assays to Assess Blood-brain Barrier Mesh-like Vessel Formation and Disruption

Blood-brain barrier (BBB) coverage plays a central role in the homeostasis of the central nervous system (CNS). The BBB is dynamically maintained by ...

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Research

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Medicine

8.4K Views.  University of Illinois at Chicago. Maintaining blood-brain barrier coverage is key for the homeostasis of the central nervous system. This protocol describes in vitro techniques to delineate the fundamental and pathological processes that modulate blood-brain barrier coverage.

Video: In Vitro Assays to Assess Blood-brain Barrier Mesh-like Vessel Formation and Disruption

Predicting In Vivo Payloads Delivery using a Blood-brain Tumor-barrier in a Dish

Highly selective by nature, the blood-brain barrier (BBB) is essential for the brain homeostasis in physiological conditions. However, in the context of brain tumors, the molecular selectivity of BBB also shields the neoplastic cells by blocking the delivery of peripherally administered chemotherapies. The development of novel drugs (including nanoparticles) targeting malignant brain tumors ideally requires the use of preclinical animal models to study the drug&#8217;s transcytosis and antitumor efficacy. In order to comply with the 3R principle (refine, reduce, and replace) to reduce the number of laboratory animals in experimental setup and perform the high-throughput screening of a large library of antitumor agents, we developed a reproducible in vitro human and murine mimic of the blood-brain tumor-barrier (BBTB) using three-layered cultures of endothelial cells, astrocytes, and patient-derived glioblastoma spheres. For higher scalability and reproducibility, commercial cell lines or immortalized cells have been used in tailored conditions to allow the formation of a barrier resembling the actual BBB. Here we describe a protocol to obtain a BBTB mimic by culturing endothelial cells in contact with astrocytes at specific cell densities on inserts. This BBTB mimic can be used, for instance, for the quantification and confocal imaging of the nanoparticle passage through the endothelial and astrocytic barriers, in addition to the evaluation of the tumor cell targeting within the same assay. Moreover, we show that the obtained data can be used to predict the behavior of nanoparticles in preclinical animal models. In a broader perspective, this in vitro model could be adapted to other neurodegenerative diseases for the determination of the passage of new therapeutic molecules through the BBB and/or be supplemented with brain organoids to directly evaluate the efficacy of drugs.

Drug targeting to central nervous system tumors is a major challenge. Here we describe a protocol to produce an in vitro mimic of the blood-brain tumor-barrier using murine and/or human cells and discuss their relevance for the predictability of central nervous system tumor targeting in vivo.

Highly selective by nature, the blood-brain barrier (BBB) is essential for the brain homeostasis in physiological conditions. However, in the context of ...

Cancer Research

Improved Method for the Preparation of a Human Cell-based, Contact Model of the Blood-Brain Barrier

The blood-brain barrier (BBB) comprises impermeable but adaptable brain capillaries which tightly control the brain environment. Failure of the BBB has been implied in the etiology of many brain pathologies, creating a need for development of human in vitro BBB models to assist in clinically-relevant research. Among the numerous BBB models thus far described, a static (without flow), contact BBB model, where astrocytes and brain endothelial cells (BECs) are cocultured on the opposite sides of a porous membrane, emerged as a simplified yet authentic system to simulate the BBB with high throughput screening capacity. Nevertheless the generation of such model presents few technical challenges. Here, we describe a protocol for preparation of a contact human BBB model utilizing a novel combination of primary human BECs and immortalized human astrocytes. Specifically, we detail an innovative method for cell-seeding on inverted inserts as well as specify insert staining techniques and exemplify how we use our model for BBB-related research.

Establishment of human models of the blood-brain barrier (BBB) can benefit research into brain conditions associated with BBB failure. We describe here an improved technique for preparation of a contact BBB model, which permits coculturing of human astrocytes and brain endothelial cells on the opposite sides of a porous membrane.

The blood-brain barrier (BBB) comprises impermeable but adaptable brain capillaries which tightly control the brain environment. Failure of the BBB has ...

Bioengineering

Setting-up an In Vitro Model of Rat Blood-brain Barrier (BBB): A Focus on BBB Impermeability and Receptor-mediated Transport

The blood brain barrier (BBB) specifically regulates molecular and cellular flux between the blood and the nervous tissue. Our aim was to develop and characterize a highly reproducible rat syngeneic in vitro model of the BBB using co-cultures of primary rat brain endothelial cells (RBEC) and astrocytes to study receptors involved in transcytosis across the endothelial cell monolayer. Astrocytes were isolated by mechanical dissection following trypsin digestion and were frozen for later co-culture. RBEC were isolated from 5-week-old rat cortices. The brains were cleaned of meninges and white matter, and mechanically dissociated following enzymatic digestion. Thereafter, the tissue homogenate was centrifuged in bovine serum albumin to separate vessel fragments from nervous tissue. The vessel fragments underwent a second enzymatic digestion to free endothelial cells from their extracellular matrix. The remaining contaminating cells such as pericytes were further eliminated by plating the microvessel fragments in puromycin-containing medium. They were then passaged onto filters for co-culture with astrocytes grown on the bottom of the wells. RBEC expressed high levels of tight junction (TJ) proteins such as occludin, claudin-5 and ZO-1 with a typical localization at the cell borders. The transendothelial electrical resistance (TEER) of brain endothelial monolayers, indicating the tightness of TJs reached 300 ohm&#183;cm2 on average. The endothelial permeability coefficients (Pe) for lucifer yellow (LY) was highly reproducible with an average of 0.26 &#177;&#160;0.11 x 10-3 cm/min. Brain endothelial cells organized in monolayers expressed the efflux transporter P-glycoprotein (P-gp), showed a polarized transport of rhodamine 123, a ligand for P-gp, and showed specific transport of transferrin-Cy3 and DiILDL across the endothelial cell monolayer. In conclusion, we provide a protocol for setting up an in vitro BBB model that is highly reproducible due to the quality assurance methods, and that is suitable for research on BBB transporters and receptors.

Setting-up an In Vitro Model of Rat Blood-brain Barrier BBB: A Focus on BBB Impermeability and Receptor-mediated Transport

The aim of the present study was to validate the reproducibility of an in vitro BBB model involving a rat syngeneic co-culture of endothelial cells and astrocytes. The endothelial cell monolayer presented high TEER and low LY permeability. Expression of specific TJ proteins, functional responses to inflammation and functionality of transporters and receptors were assessed.

The blood brain barrier (BBB) specifically regulates molecular and cellular flux between the blood and the nervous tissue. Our aim was to develop and ...

An In Vitro Model of the Blood-brain Barrier Using Impedance Spectroscopy: A Focus on T Cell-endothelial Cell Interaction

Breakdown of the blood-brain barrier (BBB) is a critical step in the development of autoimmune diseases such as multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). This process is characterized by the transmigration of activated T cells across brain endothelial cells (ECs), the main constituents of the BBB. However, the consequences on brain EC function upon interaction with such T cells are largely unknown. Here we describe an assay that allows for the evaluation of primary mouse brain microvascular EC (MBMEC) function and barrier integrity during the interaction with T cells over time. The assay makes use of impedance cell spectroscopy, a powerful tool for studying EC monolayer integrity and permeability, by measuring changes in transendothelial electrical resistance (TEER) and cell layer capacitance (Ccl). In direct contact with ECs, stimulated but not na&#239;ve T cells are capable of inducing EC monolayer dysfunction, as visualized by a decrease in TEER and an increase in Ccl. The assay records changes in EC monolayer integrity in a continuous and automated fashion. It is sensitive enough to distinguish between different strengths of stimuli and levels of T cell activation and it enables the investigation of the consequences of a targeted modulation of T cell-EC interaction using a wide range of substances such as antibodies, pharmacological reagents and cytokines. The technique can also be used as a quality control for EC integrity in in vitro T-cell transmigration assays. These applications make it a versatile tool for studying BBB properties under physiological and pathophysiological conditions.

An In Vitro Model of the Blood-brain Barrier Using Impedance Spectroscopy: A Focus on T Cell-endothelial Cell Interaction

Here, we describe an in vitro murine model of the blood-brain barrier that makes use of impedance cell spectroscopy, with a focus on the consequences on endothelial cell integrity and permeability upon interaction with activated T cells.

Breakdown of the blood-brain barrier (BBB) is a critical step in the development of autoimmune diseases such as multiple sclerosis (MS) and its animal ...

Immunology and Infection

Analysis of Lymphocyte Extravasation Using an In Vitro Model of the Human Blood-brain Barrier

Lymphocyte extravasation into the central nervous system (CNS) is critical for immune surveillance. Disease-related alterations of lymphocyte extravasation might result in pathophysiological changes in the CNS. Thus, investigation of lymphocyte migration into the CNS is important to understand inflammatory CNS diseases and to develop new therapy approaches. Here we present an in vitro model of the human blood-brain barrier to study lymphocyte extravasation. Human brain microvascular endothelial cells (HBMEC) are confluently grown on a porous polyethylene terephthalate transwell insert to mimic the endothelium of the blood-brain barrier. Barrier function is validated by zonula occludens immunohistochemistry, transendothelial electrical resistance (TEER) measurements as well as analysis of evans blue permeation. This model allows investigation of the diapedesis of rare lymphocyte subsets such as CD56brightCD16dim/- NK cells. Furthermore, the effects of other cells, cytokines and chemokines, disease-related alterations, and distinct treatment regimens on the migratory capacity of lymphocytes can be studied. Finally, the impact of inflammatory stimuli as well as different treatment regimens on the endothelial barrier can be analyzed.

Analysis of Lymphocyte Extravasation Using an In Vitro Model of the Human Blood-brain Barrier

Here, we describe a human blood-brain barrier model enabling to investigate lymphocyte transmigration into the central nervous system in vitro.

Lymphocyte extravasation into the central nervous system (CNS) is critical for immune surveillance. Disease-related alterations of lymphocyte ...

An In Vivo Blood-brain Barrier Permeability Assay in Mice Using Fluorescently Labeled Tracers

Blood-brain barrier (BBB) is a specialized barrier that protects the brain microenvironment from toxins and pathogens in the circulation and maintains brain homeostasis. The principal sites of the barrier are endothelial cells of the brain capillaries whose barrier function results from tight intercellular junctions and efflux transporters expressed on the plasma membrane. This function is regulated by pericytes and astrocytes that together form the neurovascular unit (NVU). Several neurological diseases such as stroke, Alzheimer&#39;s disease (AD), brain tumors are associated with an impaired BBB function. Assessment of the BBB permeability is therefore crucial in evaluating the severity of the neurological disease and the success of the treatment strategies employed.
We present here a simple yet robust permeability assay that have been successfully applied to several mouse models both, genetic and experimental. The method is highly quantitative and objective in comparison to the tracer fluorescence analysis by microscopy that is commonly applied. In this method, mice are injected intraperitoneally with a mix of aqueous inert fluorescent tracers followed by anesthetizing the mice. Cardiac perfusion of the animals is performed prior to harvesting brain, kidneys or other organs. Organs are homogenized and centrifuged followed by fluorescence measurement from the supernatant. Blood drawn from the cardiac puncture just before perfusion serves for normalization purpose to the vascular compartment. The tissue fluorescence is normalized to the wet weight and serum fluorescence to obtain a quantitative tracer permeability index. For additional confirmation, the contralateral hemi-brain preserved for immunohistochemistry can be utilized for tracer fluorescence visualization purposes.

An In Vivo Blood-brain Barrier Permeability Assay in Mice Using Fluorescently Labeled Tracers

Here we present a mouse brain vascular permeability assay using intraperitoneal injection of fluorescent tracers followed by perfusion that is applicable to animal models of blood-brain barrier dysfunction. One hemi-brain is used for assessing permeability quantitatively and the other for tracer visualization/immunostaining. The procedure takes 5 - 6 h for 10 mice.

Blood-brain barrier (BBB) is a specialized barrier that protects the brain microenvironment from toxins and pathogens in the circulation and maintains ...

Neuroscience

An In Vivo Assessment of Blood-Brain Barrier Disruption in a Rat Model of Ischemic Stroke

Ischemic stroke leads to vasogenic cerebral edema and subsequent primary brain injury, which is mediated through destruction of the blood-brain barrier (BBB). Rats with induced ischemic stroke were established and used as in vivo models to investigate the functional integrity of the BBB. Spectrophotometric detection of Evans blue (EB) in the brain samples with ischemic injury could provide reliable justification for the research and development of novel therapeutic modalities. This method generates reproducible results, and is applicable in any laboratory without a need for special equipment. Here, we present a visualized and technical guideline on the detection of the extravasation of EB following induction of ischemic stroke in rats.

An In Vivo Assessment of Blood-Brain Barrier Disruption in a Rat Model of Ischemic Stroke

The overall goal of this procedure is to provide a highly reproducible technique for in vivo assessment of the blood-brain barrier disruption in rat models of ischemic stroke.

Ischemic stroke leads to vasogenic cerebral edema and subsequent primary brain injury, which is mediated through destruction of the blood-brain barrier ...

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

The aim of this protocol presents an optimized procedure for the purification and cultivation of pBECs and to establish in vitro blood-brain barrier (BBB) models based on pBECs in mono-culture (MC), MC with astrocyte-conditioned medium (ACM), and non-contact co-culture (NCC) with astrocytes of porcine or rat origin. pBECs were isolated and cultured from fragments of capillaries from the brain cortices of domestic pigs 5-6 months old. These fragments were purified by careful removal of meninges, isolation and homogenization of grey matter, filtration, enzymatic digestion, and centrifugation. To further eliminate contaminating cells, the capillary fragments were cultured with puromycin-containing medium. When 60-95% confluent, pBECs growing from the capillary fragments were passaged to permeable membrane filter inserts and established in the models. To increase barrier tightness and BBB characteristic phenotype of pBECs, the cells were treated with the following differentiation factors: membrane permeant 8-CPT-cAMP (here abbreviated cAMP), hydrocortisone, and a phosphodiesterase inhibitor, RO-20-1724 (RO). The procedure was carried out over a period of 9-11 days, and when establishing the NCC model, the astrocytes were cultured 2-8 weeks in advance. Adherence to the described procedures in the protocol has allowed the establishment of endothelial layers with highly restricted paracellular permeability, with the NCC model showing an average transendothelial electrical resistance (TEER) of 1249 &#177; 80 &#937; cm2, and paracellular permeability (Papp) for Lucifer Yellow of 0.90 10-6 &#177; 0.13 10-6 cm sec-1 (mean &#177; SEM, n=55). Further evaluation of this pBEC phenotype showed good expression of the tight junctional proteins claudin 5, ZO-1, occludin and adherens junction protein p120 catenin. The model presented can be used for a range of studies of the BBB in health and disease and, with the highly restrictive paracellular permeability, this model is suitable for studies of transport and intracellular trafficking.

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

The aim of the protocol is to present an optimized procedure for the establishment of an in vitro blood-brain barrier (BBB) model based on primary porcine brain endothelial cells (pBECs). The model shows high reproducibility, high tightness, and is suitable for studies of transport and intracellular trafficking in drug discovery.

The aim of this protocol presents an optimized procedure for the purification and cultivation of pBECs and to establish in vitro blood-brain barrier (BBB) ...

Blood-Brain Barrier Mimic Permeability Assay: An In Vitro Assay to Assess the Permeability of BBB Mimic to Tracer Molecules

Source: Le Joncour, V. et al. <a href="https://www.jove.com/v/59384/predicting-vivo-payloads-delivery-using-blood-brain-tumor-barrier">Predicting In Vivo Payloads Delivery using a Blood-Brain Tumor-Barrier in a Dish.</a> J. Vis. Exp. (2019)
This video describes a permeability assay to evaluate the permeability of in vitro blood-brain barrier using sodium fluorescein molecules.

Test przepuszczalności naśladującej barierę krew-mózg: Test in vitro do oceny przepuszczalności naśladownictwa BBB dla cząsteczek znacznikowych

Source: Le Joncour, V. et al. Predicting In Vivo Payloads Delivery using a Blood-Brain Tumor-Barrier in a Dish. J. Vis. Exp. (2019)
This video describes a ...

JoVE Encyclopedia of Experiments

Cancers of the Nervous System

In vitro studies

Assessing Transendothelial Electrical Resistance in an In Vitro Blood-Brain Barrier Model

Source: Kuzmanov, I., et al. <a href="https://app.jove.com/v/54592">An In Vitro Model of the Blood-brain Barrier Using Impedance Spectroscopy: A Focus on T Cell-endothelial Cell Interaction.</a> J. Vis. Exp. (2016)
This video demonstrates a method for assessing transendothelial electrical resistance (TEER) in mouse brain microvascular endothelial cells in vitro. A high TEER value indicates intact endothelial cell junctions, while the addition of activated T cells lowers the TEER value, reflecting disruption of the junctional barrier.

Source: Kuzmanov, I., et al. An In Vitro Model of the Blood-brain Barrier Using Impedance Spectroscopy: A Focus on T Cell-endothelial Cell Interaction. J. ...

In Vitro Assays to Assess Blood-brain Barrier Mesh-like Vessel Formation and Disruption

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Predicting In Vivo Payloads Delivery using a Blood-brain Tumor-barrier in a Dish

Improved Method for the Preparation of a Human Cell-based, Contact Model of the Blood-Brain Barrier

Setting-up an In Vitro Model of Rat Blood-brain Barrier (BBB): A Focus on BBB Impermeability and Receptor-mediated Transport

An In Vitro Model of the Blood-brain Barrier Using Impedance Spectroscopy: A Focus on T Cell-endothelial Cell Interaction

Analysis of Lymphocyte Extravasation Using an In Vitro Model of the Human Blood-brain Barrier

An In Vivo Blood-brain Barrier Permeability Assay in Mice Using Fluorescently Labeled Tracers

An In Vivo Assessment of Blood-Brain Barrier Disruption in a Rat Model of Ischemic Stroke

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

Test przepuszczalności naśladującej barierę krew-mózg: Test in vitro do oceny przepuszczalności naśladownictwa BBB dla cząsteczek znacznikowych

Assessing Transendothelial Electrical Resistance in an In Vitro Blood-Brain Barrier Model