The authors would like to acknowledge Elisabeth Helena Bruun, Sarah Christine Christensen, and Niels M. Kristiansen for technical assistance, and the Lundbeck Foundation grant number R155-2013-14113.

Porcine brains were obtained as byproducts of the Danish food industry. Danish Slaughterhouses are under strict supervision and observation by the Danish Ministry of Environment and Food.
Rats used for isolation of astrocytes were bred and group-housed in the local animal facility at an ambient temperature of 22 &#176;C-23 &#176;C and on a 12/12 h dark/light cycle under inspection of the veterinarian and according to Danish regulations for lab animals. The rats were euthanized before they were...

Purification and Proliferation of pBEC
During the purification procedure, critical steps include rapid and effective removal of meninges and separation of white and grey matter, which is important for the purification yield and purity and for the proper establishment of the model. For the presented in vitro BBB model using pBECs, we have improved and simplified a purification procedure based on mechanical homogenization of isolated grey matter, size-selective filtering for isolation of m...

Cellular Structure and Function of the Blood-Brain Barrier
At the interface of the circulatory and central nervous system (CNS), the BBB acts as a key regulatory site for homoeostatic control of the CNS microenvironment, which is essential for proper function and protection of the nervous system. The site of the BBB is the endothelial cells lining the blood vessel lumen. In brain capillaries, endothelial cells form complex intercellular tight junctions and strongly polarized expression patterns of particular influx and efflux transporters ensure highly specific molecular transport between the blood and the brain 1. The structural components of the tight junction complexes include proteins from the occludin and claudin family, zonula occludens (ZO) proteins, cingulin, and associated junctional adhesion molecules (JAMs). Claudin 5 is particularly important in the paracellular junctional restriction. Induction and maintenance of this characteristic BBB endothelial phenotype involve dynamic interactions with surrounding cells, including pericytes, astrocytes, neurons and the basement membranes, which together with brain endothelial cells form the neurovascular unit (NVU)2,3. The mechanisms involved in these interactions are not yet fully understood, but include exchange of chemical signals between cells, which allows modulation of BBB permeability in the short term and induces long-term BBB features4. Astrocytes especially are known to contribute to the brain endothelial cell phenotype and are a source of regulatory factors such as glial-derived neurotrophic factor (affecting intracellular cAMP)5, basic fibroblast growth factor6, hydrocortisone7, and transforming growth factor &#946; (TGF-&#946;)8. The effect of TGF-&#946;, however, has been debated9.
From In Vivo to In Vitro BBB
In vivo studies continue to provide valuable information on BBB biology. However, cell culture models can provide additional insights and constitute useful tools for understanding detailed molecular and functional aspects of the BBB in both health and disease. Although the complex interactions between the cell types and constituents of the BBB are difficult to fully achieve in in vitro models, there has been, since the first purification of brain endothelial cells and application of these in mono-cultures10,11,12, extensive development of the purification procedures and growth conditions of the BBB cell culture models, resulting in greater resemblance to the in vivo barrier. The commonly used in vitro BBB models are based on primary cells of rodent, porcine, and bovine origin, and on immortalized cell lines. Each model has different advantages and drawbacks. For comparison and model choice, validation markers such as expression of BBB enzymes, transporters, receptors, and structural proteins are used to create overviews of the current established models1.
Aim of the Protocol
One important feature of the BBB is barrier tightness and high TEER, yet a large number of the available models do not reflect well the in vivo levels. Incorporating development and optimization contributions from several laboratories, the aim of this protocol is to present a method for establishing a high TEER in vitro BBB model based on primary pBECs in MC with or without ACM, or in NCC with primary astrocytes of rat or porcine origin. The applied procedures and establishment of the model include efforts to eliminate contaminating cells and to improve differentiation of pBECs into a BBB phenotype. This work has resulted in the establishment of reliable, high TEER models with low paracellular permeability and good functional expression of key tight junctional proteins, transporters, and receptors. However, as the astrocytes are a contributing factor to the brain endothelial cell phenotype, the three different conditions of culture represent three different phenotypes of brain endothelial cells. The NCC model is specifically useful for studies of certain specialized mechanisms involved in drug discovery, transport studies and intracellular trafficking, as well as for investigation of cell-cell interactions where maximal expression of BBB features is advantageous.
Origin and History of the Protocol
The pBEC model described here is largely based on the porcine model developed at Eisai Laboratories (London) by Dr. Louise Morgan and colleagues, whichis based on a successful earlier bovine brain endothelial cell model13. The original method of cell preparation was a two-stage filtration using nylon meshes to catch the microvessels, followed by a subculturing step to improve purity. In the earlier development of the method, optimal BBB phenotype and barrier tightness were achieved by growth in supplemented medium, including ACM. Further modifications to the method were made by R. Skinner in Prof N. Rothwell&#39;s lab in Manchester UK14,15. The method was adopted by the Abbott laboratory, KCL London, where Patabendige made it significantly simpler to prepare by avoiding the use of astrocytes or ACM and by eliminating contaminating cells such as pericytes with puromycin. The first papers confirmed that the MC model preserved several important features of the in vivo BBB, including effective tight junctions, membrane transport systems and receptor-mediated transcytosis16,17,18,19,20. Later S. Yusof again tested astrocyte co-culture and found it significantly improved TEER, so this is the preferred variant currently used in the Abbott lab21. The model has now been successfully transferred to the M. Nielsen lab in Aarhus, where further modifications have been introduced (this protocol), including simplifying grey matter extraction, using only one mesh filtration step, and a single filter coating step combining collagen and fibronectin. The applied procedure for isolation of porcine astrocytes (this protocol) was based on protocols developed by the T. Moos laboratory in Aalborg, described by Thomsen et al22. The TEER and other properties of the model generated in London and Aarhus are similar, which lends confidence to the notion that the model is readily transferred between labs and responds well to careful observation and rationalization of method steps. Indeed, S. Yusof has now established the MC model in a tropical country (Malaysia)23, which involved further adjustment for local conditions and tissue sources.
Advantages over Alternative Methods and Currently Established Models
Compared to brain endothelial cells of bovine and rodent origin, pBECs provide the advantage of having a lower rate of loss of the in vivo BBB phenotype following isolation24. Furthermore, pBECs are capable of forming relatively tight endothelial barriers, even when grown in MC (800 &#937; cm2)16 as compared to the commonly reported levels for monolayers of cell lines such as bEND.5 and bEND.3 (50 &#937; cm2)25,26,27, cEND (300-800 &#937; cm2)28,29,30, and cerebEND (500 &#937; cm2)29,31,32, and primary brain endothelial cells of mouse (100-300 &#937; cm2)33,34,35,36 and rat (100-300 &#937; cm2)37,38. However, the TEER has shown dependency on the purification and culture procedures. In most cases, the addition of ACM or co-culture with astrocytes shows differentiating effects on the endothelial cells and an increase in tightness of the endothelial layers1. Nevertheless, with efforts to optimize the culturing conditions, only the bovine-based models have shown TEER values comparable to the porcine-based models (averages of 800 &#937; cm2 in MC, up to 2500 &#937; cm2 in astrocyte co-culture)13,39,40,41,42,43,44,45. As the models based on primary bovine brain endothelial cells have shown large variations, both between and within laboratories14,45,46,47,48, reproducibility could be an issue. In the pBEC model reported here, the contributing laboratories have achieved very similar TEER and paracellular permeability values with low variability, both in and between laboratories. Hence, it should be possible for other laboratories to establish a robust model with low variability using the method presented here. In addition to forming tight endothelial layers, models with pBECs have previously been validated by expression of tight junction proteins, functional BBB transporters, receptors and enzymes, and demonstrated suitability for a range of studies15,16,17,19,20,22,49,50,51,52,53,54,55,56,57,58,59. Furthermore, unpublished transcriptome data on the co-cultures of pBECs shows an expected profile of BBB transporters and receptors (unpublished results, Nielsen et al.).
The porcine-based BBB model has a further advantage as the genome, anatomy, physiology, and disease progression of the pig reflect the human biology to a higher degree than other established models60, which are favorable features for the pharmaceutical industry. As porcine brains are a common by-product of the meat industry, they constitute an easily accessible source of brain endothelial cells, minimizing the number of animals needed for the experiments, and providing a high purification yield from one porcine brain. Although purification and cultivation of primary cells is somewhat time-consuming and requires expertise for standardization in setting up the model, primary cells generate the most reliable BBB models. Immortalized cell lines cannot be a substitute, as important properties such as barrier tightness, transporter expression profiles, and microenvironment regulation do not reflect the experimental findings in vivo61,62. In vitro models provide the advantage of live-cell imaging with higher resolution, making visualization of intracellular processes possible by allowing a close proximity approach to the sampled or observed cells, using objectives with higher magnification and better optical quality63. This is not the case for the use of two-photon microscopy in living animals. Furthermore, in vitro models provide the ability to transfect cells, allowing visualization of tagged proteins and investigation of their trafficking.
Applications of the Model
The function of the BBB is not fixed and can be dynamically modulated in both physiology and pathology. In many neurological diseases, including neurodegenerative, inflammatory and infectious diseases, disruption and increased permeability of the BBB is observed64,65,66,67. In order to reduce and prevent disease progression and subsequent damage, identification and characterization of the molecular mechanisms underlying the modulation of the BBB are of major importance. In this context, reliable in vitro models are in high demand by the pharmaceutical industry, and furthermore play important roles in predicting BBB permeability of drugs to the CNS. Any in vitro model serving as a permeability screen should display a restrictive paracellular pathway, a physiologically realistic cell architecture and functional expression of transporter mechanisms68. Demonstrated in previous studies16,17,57, and by paracellular permeability and expression of TJ and AJ proteins here, the presented model meets all these criteria and is suitable for a range of BBB studies in both normal physiology and in pathology. The strengths of the presented purification and cultivation method include a combination of simplicity and reproducibility and the ability to include astrocytic influence with a resulting robust and reliable high TEER in vitro BBB model. For this purpose, astrocytes of porcine and rat origin have been shown to augment the BBB phenotype of pBECs in a similar way22.

<table>
	<tbody>
		<tr>
			<td>Fibronectin</td>
			<td>Sigma-Aldrich</td>
			<td>F1141</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagen IV</td>
			<td>Sigma-Aldrich</td>
			<td>C5533</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly-L-lysine</td>
			<td>Sigma-Aldrich</td>
			<td>P1524</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM/F-12</td>
			<td>Lonza</td>
			<td>BE12-719F</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM/Low Glucose</td>
			<td>Sigma-Aldrich</td>
			<td>D6046</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin</td>
			<td>Gibco Invitrogen</td>
			<td>15140</td>
			<td></td>
		</tr>
		<tr>
			<td>Plasma derived serum (PDS)</td>
			<td>First Link UK Ltd.</td>
			<td>60-00-89</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum (FBS)</td>
			<td>Gibco Invitrogen</td>
			<td>10-270-106</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin/EDTA</td>
			<td>Gibco Invitrogen</td>
			<td>15090-046</td>
			<td></td>
		</tr>
		<tr>
			<td>Heparin</td>
			<td>Sigma-Aldrich</td>
			<td>H3393</td>
			<td></td>
		</tr>
		<tr>
			<td>Puromycin</td>
			<td>Sigma-Aldrich</td>
			<td>P8833</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrocortisone</td>
			<td>Sigma-Aldrich</td>
			<td>H4001</td>
			<td></td>
		</tr>
		<tr>
			<td>8-CPT-cAMP</td>
			<td>Biolog</td>
			<td>C010</td>
			<td></td>
		</tr>
		<tr>
			<td>RO 20-1724</td>
			<td>Sigma-Aldrich</td>
			<td>B8279</td>
			<td></td>
		</tr>
		<tr>
			<td>Gentamicin Sulfate</td>
			<td>Lonza</td>
			<td>17-518Z</td>
			<td></td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>Sigma-Aldrich</td>
			<td>34896</td>
			<td></td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Sigma-Aldrich</td>
			<td>D8537</td>
			<td></td>
		</tr>
		<tr>
			<td>EtOH</td>
			<td>VWR</td>
			<td>20,824,296</td>
			<td>Mix the 70 % solution from the 96 % EtOH</td>
		</tr>
		<tr>
			<td>DNAse 1</td>
			<td>Sigma-Aldrich</td>
			<td>D4513</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase CLS2</td>
			<td>Sigma-Aldrich</td>
			<td>C6885</td>
			<td></td>
		</tr>
		<tr>
			<td>ddH2O</td>
			<td></td>
			<td></td>
			<td>Made with Elga System</td>
		</tr>
		<tr>
			<td>T75 flasks</td>
			<td>Thermo Scientific</td>
			<td>156499</td>
			<td></td>
		</tr>
		<tr>
			<td>Costar Transwell inserts (Cell permeable membrane inserts)</td>
			<td>Costar</td>
			<td>CLS3401</td>
			<td>12-well plate, 12 mm diameter, 0.4 &#956;m polycarbonate membrane</td>
		</tr>
		<tr>
			<td>15 ml centrifuge tubes</td>
			<td>Cellstar</td>
			<td>188271</td>
			<td></td>
		</tr>
		<tr>
			<td>50 ml centrifuge tubes</td>
			<td>Cellstar</td>
			<td>227261</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dishes</td>
			<td>Thermo Scientific</td>
			<td>150350</td>
			<td></td>
		</tr>
		<tr>
			<td>Cryo vials</td>
			<td>Thermo Scientific</td>
			<td>377224</td>
			<td></td>
		</tr>
		<tr>
			<td>500 ml bottle</td>
			<td>Thermo Scientific</td>
			<td>159910/159920</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpels</td>
			<td>Swann-Morten</td>
			<td>REF0211</td>
			<td>Type 24</td>
		</tr>
		<tr>
			<td>Tissue homogenizer</td>
			<td>Sigma</td>
			<td>D9188</td>
			<td></td>
		</tr>
		<tr>
			<td>140 &#956;m filters</td>
			<td>MERCK</td>
			<td>NY4H04700</td>
			<td></td>
		</tr>
		<tr>
			<td>40 &#956;m filters</td>
			<td>Corning</td>
			<td>431750</td>
			<td></td>
		</tr>
		<tr>
			<td>EndOhm chamber system</td>
			<td>World Precision Instruments</td>
			<td>ENDOHM-12</td>
			<td>EndOhm chamber for 12mm Culture Cups</td>
		</tr>
		<tr>
			<td>EVOM2 electrode system</td>
			<td>World Precision Instruments</td>
			<td>300523+STX100C</td>
			<td>TEER measurement system with rigid STX-100C electrode pair</td>
		</tr>
		<tr>
			<td>Long needle</td>
			<td>Sigma</td>
			<td></td>
			<td>Attach to a syringe</td>
		</tr>
		<tr>
			<td>Fine-tip curved forceps</td>
			<td>KLS Martin</td>
			<td>12-409-12-07</td>
			<td></td>
		</tr>
		<tr>
			<td>Broad tip forceps</td>
			<td>VWR</td>
			<td>82027-390</td>
			<td></td>
		</tr>
		<tr>
			<td>Filter holder</td>
			<td>MERCK Milipore</td>
			<td>Swinnex-47</td>
			<td></td>
		</tr>
		<tr>
			<td>50 ml syringe</td>
			<td>Braun</td>
			<td>4617509F</td>
			<td></td>
		</tr>
		<tr>
			<td>10 ml syringe</td>
			<td>Terumo</td>
			<td>SSt20ESI</td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-Occludin antibody</td>
			<td>Abcam</td>
			<td>ab31721</td>
			<td>1:100</td>
		</tr>
		<tr>
			<td>Anti-p120 Catenin antibody</td>
			<td>BD Transduction laboratories</td>
			<td>610133</td>
			<td>1:200</td>
		</tr>
		<tr>
			<td>Anti-ZO-1 antibody</td>
			<td>Invitrogen</td>
			<td>61-7300</td>
			<td>1:200</td>
		</tr>
		<tr>
			<td>Anti-Claudin 5 antibody</td>
			<td>Sigma-Aldrich</td>
			<td>SAB4502981</td>
			<td>1:100</td>
		</tr>
		<tr>
			<td>Donkey anti rabbit IgG conjugated with Alexa Flour 568</td>
			<td>Thermo Scientific</td>
			<td>A10042</td>
			<td>1:500</td>
		</tr>
		<tr>
			<td>Donkey anti mouse IgG conjugated with Alexa Flour 488</td>
			<td>Thermo Scientific</td>
			<td>A21202</td>
			<td>1:500</td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Perkin Elmer</td>
			<td>NEC100X250UC</td>
			<td>0.15&#181;l/ml final working conc</td>
		</tr>
		<tr>
			<td>Lucifer Yellow</td>
			<td>Sigma</td>
			<td>L0144</td>
			<td>10 &#181;g/ml final working conc</td>
		</tr>
	</tbody>
</table>

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.

Establishment of the BBB In Vitro Models
In the presented, optimized method, cultivation of pBECs and the establishment of the permeable membrane insert system with MC or without ACM or NCC with astrocytes (Figure 1) was carried out for a period of 9-11 days (Figure 2). For selection of endothelial cells, an initial culture of purified capillary fragments was comb...

Watch this Scientific Journal Video about Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells at JoVE.com

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.

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) ...

The overall goal of this protocol is to purify and isolate primary porcine brain endothelial cells in order to set up a tight in vitro blood-brain barrier model. This method can help answer key questions in the blood-brain barrier field, such as drug delivery, permeability, receptor trafficking, as well as the tightness and polarity of the BB.The main advantage of this model is the high yield of primary brain endothelial cells that can be used to create an in vitro blood-brain barrier model which has high TEER and low permeability. To begin this procedure, place the brains in a sterile flow bench and gently wash them with one liter of PBS in a beaker placed on ice.Next, carefully remove the meninges from each brain using fine-tip forceps. Using a scalpel, scrape off gray matter from the brains one at at time and transfer the isolated material to Petri dishes containing 20 milliliters of DMEM/F-12 placed on ice. For initial fragmentation, run the gray matter material through a 50-milliliter syringe without the needle.Repeat the procedure for all brains and pool the collected gray matter material together. Transfer the isolated gray matter material with DMEM/F-12 medium to the grinder tube of a handheld tissue homogenizer. Homogenize the material by making eight up-and-down strokes with a loose pestle, followed by eight up-and-down strokes with a tight pestle.Next, isolate the capillaries by filtering the homogenate using a 500-milliliter blue cap bottle with filter holder and 140-micron filter mesh. Place the capillary-containing filters in Petri dishes with a digestion solution. Subsequently, incubate the Petri dishes at 37 degrees Celsius for one hour on an orbital shaker at 180 RPM, or stir them gently every 10 minutes.After one hour, wash off the capillaries from the filters with suspension from the Petri dish. Then, split the suspension from the three dishes into two 50-milliliter tubes and stop the digestion by adding 10 milliliters of DMEM/F-12 to each 50-milliliter tube. Centrifuge the cell suspensions at 250 times g, four degrees Celsius for five minutes.Afterward, aspirate the supernatants and resuspend each pellet in 10 milliliters of DMEM/F-12. Then, add a further 20 milliliters of DMEM/F-12 to each tube. To optimize the conditions for the attachment of PBECs, add coating solution to the T-75 flask, resulting in the final concentrations of collagen four at 150 micrograms per milliliter and fibronectin at 50 micrograms per milliliter and by distilled water, making sure that the solution covers the whole surface.Next, thaw the capillaries in a 37-degree Celsius water bath. To remove freezing medium, spin the capillaries down at 250 times g, four degrees Celsius, for seven minutes. After that, carefully aspirate the supernatant and resuspend the pellet in one to two milliliters of the 10-milliliter aliquot.Following that, transfer the capillary suspension to the coated T-75 flask, and gently tilt the flask to ensure equal distribution over the surface. Place the T-75 flask at 37 degrees Celsius and 5%carbon dioxide. After overnight incubation, prepare 10 milliliters of PBEC growth medium, supplemented with puromycin at four micrograms per milliliter for one T-75 flask and perform a medium change.Then, prepare the permeable membrane inserts for PBEC seeding by coating them with collagen IV at 500 micrograms per milliliter, and fibronectin at 100 micrograms per milliliter, and by distilled water. Trypsin-ize the cells by adding two milliliters of trypsin-EDTA solution to the T-75 flask, and place it at 37 degrees Celsius, 5%carbon dioxide, for five to seven minutes. To detach the brain endothelial cells, gently tap the side of the T-75 flask with fingertips.Subsequently, transfer the cell solution to a 15-milliliter tube, and spin down the brain endothelial cells by centrifugation at 250 times g, four degrees Celsius, for seven minutes. Afterward, carefully remove the supernatant, and resuspend the pellet in one milliliter of medium. Then, add a further two milliliters of medium to bring the total volume to three milliliters.Count the number of cells manually using a cell-counting chamber or an automatic cell-counting system. For non-contact coculture, transfer inserts to the wells that have astrocytes, which were refreshed with astrocyte growth medium the day before. The next day, replace the medium on the permeable membrane inserts containing PBECs.Then, carefully aspirate the medium from the wells and add 750 microliters of differentiation medium to each well. Following that, carefully aspirate medium from the inserts and add 500 microliters of differentiation medium per insert. Then, add the remaining 750 microliters of differentiation medium to each astrocyte well.After that, incubate the cells with differentiation medium at 37 degrees Celsius, 5%carbon dioxide, until the next day. On the day after stimulating the cells with differentiation medium, prepare the tissue-resistance measurement chamber system for TEER measurements by rinsing the chamber two times with bi-distilled water, one time with 70%ethanol for five minutes and two more times with bi-distilled water. Next, connect the chamber to the system, add four milliliters of DMEM/F-12 to the tissue-resistance measurement chamber, and let it stay at room temperature for approximately 30 minutes.After that, perform TEER measurements by carefully placing the inserts in the tissue-resistance measurement chamber. Here are the phase phase-contrast microscopy images of PBECs, cultures, and astrocytes viewed over five days. Purified capillary fragments on the first day of the initial culture showed presence of both capillaries and contaminating cells, which after medium change on day two and an additional day of growth, showed selection for PBECs, starting their growth from the capillary fragments.Confluent monolayers of PBECs were usually achieved on day four through six, at which time PBECs showed spindle-shaped morphology and were longitudinally-aligned. Rat astrocytes seeded in the bottom wells normally proliferated to confluent layers within five days, and were used for non-contact coculture models after two weeks of growth. Once mastered, this technique can be done in seven hours.After its development, this technique paved the way for researchers to explore drug delivery and receptor trafficking in tight and polarized brain endothelial cells. After watching this video, you should have a good understanding how to create an in vitro blood-brain barrier model that can be used for new studies that cannot carry out in vivo.

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14.6K visualizações.  Aarhus University. The overall goal of this protocol is to purify and isolate primary porcine brain endothelial cells in order to set up a tight in vitro blood-brain barrier model. This method can help answer key questions in the blood-brain barrier field, such as drug delivery, permeability, receptor trafficking, as well as the tightness and polarity of the BB.The main advantage of this model is the high yield of primary brain endothelial cells that can be used to create an in vitro blood-brain barrier model w...