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.

The authors report no conflict of interest.

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 microvessels, digestion with collagenase, DNase and trypsin, with an initial culture of microvessel fragments. In general, one of the major challenges during purification and cultivation of primary cells is the elimination of contaminating cells. Experience with purification of primary brain endothelial cells has indicated that thorough removal of both meninges and white matter results in improved purity and yield of capillaries, as well as increased endothelial cell growth and expression of BBB characteristics. For this reason, careful removal of meninges (including inside sulci) in the presented protocol was designed to ensure removal of leptomeningeal cells (which have fibroblast-like properties), as well as of arterial and arteriolar smooth muscle cells, which grow more rapidly than endothelial cells in culture. Likewise, minimization of the white matter material resulted in purer endothelial cell cultures, with fewer contaminating cells growing from the isolated capillary fragments. However, this simplified and quick method applied for isolation lowers the yield of isolated capillaries, and optimization of grey matter isolation could improve the yield of each brain significantly. A density gradient, which is included in an alternative purification protocol69, can be used for isolating free endothelial cells and improving endothelial cell purity, but it is time consuming and can likewise lower the yield. Both of these purification methods have been extensively used and characterized, and share the characteristics of generating high TEER pBEC models in both MC and astrocyte co-culture (normally 500-1500 &#937; cm2)7,16,21,22,49,57,70,71.
In order to establish monolayers with high paracellular restrictiveness, experience has shown that pericytes must be eliminated from the endothelial cultures16. Porcine brain pericytes generally grow below the pBEC layers and do not cause holes in the endothelial layers, as observed for cultures of rat brain endothelial cells72,73. Pericytes in pBEC cultures do, however, tend to affect the morphology of the endothelial cells, which appear broader and with irregular cell boarders16. Because brain endothelial cells express higher levels of efflux transporters (e.g. P-glycoprotein) than other cell types in the microvessels, the number of contaminating cells can be reduced by puromycin treatment74. Additionally, use of plasma-derived serum (PDS) rather than fetal or neonatal calf derived serum favors the growth of endothelial cells, as the PDS has a lower concentration of growth factors such as platelet-derived growth factor and vascular endothelial growth factor, which are shown to increase BBB permeability and stimulate angiogenesis14,75,76,77. By introducing an initial culture of isolated capillary fragments and combining this with puromycin treatment (4 &#181;g/mL) and use of PDS, we succeeded in greatly reducing the number of contaminating cells remaining after the purification, so that thereafter we could establish tight endothelial monolayers on permeable membrane inserts. In order to ensure the best attachment of endothelial cells on both culture dishes and permeable membrane insert surfaces, it has been observed that a coating mixture of collagen type IV (from human placenta) and fibronectin greatly increases the proliferation yields, and the combined mixture was therefore favored over the traditional method using only collagen type I78.
Differentiation of Cells and the Establishment of a High TEER In Vitro BBB Model
The pBECs in MC generally retain many BBB key features following isolation, so that co-culture with astrocytes is not essential for inducing functional tight junctions and achieving high TEER values16,57. Efforts to optimize the conditions for differentiation of the endothelial cells into BBB phenotype include use of serum-containing medium supplemented with 8-CPT-cAMP, hydrocortisone7 (increasing the intracellular cAMP level13) and RO 20-1724 (maintaining the intracellular cAMP level), which in accordance with previous findings74,79 together successfully improved the barrier tightness and increased TEER, and may also have helped to restore a more in vivo like gene expression profile80. However, the use of hydrocortisone for the tightening of the endothelial layer may modify the response of the endothelial cells to certain stimuli, and for the purpose of using the model for investigation of responses to chemo- and cytokines during inflammation, the use of hydrocortisone may need to be avoided.
From comparative studies with MC, MC with ACM and astrocyte co-cultures in both the participating laboratories and elsewhere, it has been shown that astrocytic contribution is capable of improving endothelial BBB features and increasing the barrier tightness21,40,42,49,79,81,82,83. In order to achieve such high expression of BBB phenotype in pBECs, we established a NCC with astrocytes and found that both porcine and rat primary astrocytes were beneficial, as also observed in other laboratories22. During the establishment of the astrocyte NCCs, experience has shown that the purity and age of the astrocyte cultures influence the resulting endothelial barrier tightness, with the optimum age of the astrocytes being 2-8 weeks, which correlates with an observed change in the astrocyte morphology over time. On the day before establishing the NCC, a medium change for the astrocytes is intended to remove harmful metabolites and allow enough time for the astrocytes to release stimulation and signaling factors influencing the barrier development. When co-culturing the endothelial cells and astrocytes in the permeable membrane insert system, it is important to pay special attention to the handling of the barrier model. During medium change, both aspiration and addition of the medium and the movements of the inserts must be done carefully in order to minimize disruption of the endothelial barrier.
Reproducibility and Reliability
A great challenge when using primary cells for establishing in vitro models is to achieve high reproducibility between cultures. Such standardization may be met by the choice of method, use of high quality tools and reagents, and experience in microdissection. The high reproducibility with low batch-to-batch variation for the presented method is therefore highly dependent on strict adherence to the described procedures.
To achieve a good reproducibility between batches and vials during TEER measurements, a tissue resistance measurement chamber or epithelial voltmeters with rigid miniature electrodes, rather than flexible chopstick electrodes can be used, reducing the variability of observed TEER values. In addition to achieving high TEER values (Figure 4), the reliability of the presented model is confirmed by the corresponding low small solute permeability (Figure 4), and by the immunocytochemical characterization of the pBECs (Figure 5).
Limitations of the Applied Method and Model
The use of transgenic and miniature pigs has increased during the last decades, but the amount of in vivo data is still limited compared to data available for rodent models, and therefore may pose a challenge for comparing the in vitro porcine data with in vivo results. However, as the biology of the pig reflects human biology more closely than many established laboratory animals, and transgenic pig models for studying neurological diseases such as Alzheimer&#39;s disease have now been established84, the availability of in vivo data is expected to become less problematic with time.
A limitation of the current permeable membrane insert system models of the BBB is the inability to mimic the blood flow in microvessels. In vivo, shear stress has been shown to affect many aspects of endothelial cell physiology such as division, differentiation, migration and apoptosis85,86, and to influence important BBB characteristics such as the expression of junctional proteins, and the induction and polarization of transporters61,85,87. To introduce such conditions, newly developed microfluidic systems can be considered88,89,90.
A useful method to correct for the effect of the unstirred water layer (aqueous boundary layer) from in vitro permeability data is to derive the predicted &#39;intrinsic permeability&#39; in vivo, using the software based approach21. This software can also be used for detailed permeability data analysis21.
Future Applications and Directions for the Method
As the components of neurovascular unit have been shown to play important roles in inducing and maintaining BBB features, and no current in vitro model has yet been able to fully mimic the in vivo conditions, important constituents and interactions may still be missing. Current efforts in developing the presented model include establishing triple-culture models with both astrocytes and pericytes, and experiments combining cells of different species. Incorporation of pericytes has so far has not been observed to significantly increase the TEER levels of the barrier. However, syngeneic porcine models have been observed to be comparable to triple cultures using porcine brain endothelial cells, rat astrocytes, and rat pericytes with respect to barrier tightness and expression of hallmark proteins characteristic of the brain endothelium22. In order to develop a model based on human cells, future developments of in vitro BBB models for drug discovery and delivery may rely on the derivation of human pluripotent stem cells and adult stem and/or progenitor cells21.

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 combined with puromycin treatment for a maximum of 5 days, which eliminated most contaminating cells and promoted the growth of spindle-shaped endothelial cells from the capillary fragments (Figure 3A-C). At day 4-6, pBECs had proliferated to a confluency of 60-95%, growing as non-overlapping, contact-inhibited, longitudinally aligned cells. When the cells had reached the desired confluency, pBECs were plated on collagen IV and fibronectin coated permeable membrane insert filter membranes (1.12 cm2 surface area, 0.4 &#181;m pores) at a density of 1.1 x 105 cells/insert, at which they normally formed confluent monolayers after 4 days (day 8-10 post isolation). When co-culturing pBECs, astrocytes of rat or porcine origin were plated on poly-L-lysine coated bottom wells for a minimum of 2 weeks before starting the NCC (Figure 3D). When establishing the NCC, experience has shown that astrocytes cultured for 2-8 weeks provide the best support for promoting the BBB phenotype in pBECs; within this time, the astrocytes formed confluent cultures with cells arranged in a honeycomb-like structure (Figure 3E-F). On day 4 in the permeable membrane insert system model (day 8-10 post isolation), cells were stimulated with cAMP, hydrocortisone and RO to increase the barrier tightness and BBB characteristic expression pattern of tight junctional proteins, transporters, and receptors.
Characterization of pBEC Phenotype and Paracellular Permeability
Visual cell inspection combined with TEER measurement are routinely the most reliable ways to assess the confluency and tightness of the endothelial cell layer growing on the permeable membrane inserts prior to experiments. Figure 4 shows results from two series of experiments to assess small molecule drug permeability through the BBB, the control parameters of TEER (reflecting ionic permeability) combined with apparent permeability21 (Papp, cm s-1) of either radiolabeled sucrose or the dye tracer Lucifer yellow (LY), reflecting paracellular permeability of typical small drug molecules (~200-600 Da). A compound of interest with a Papp greater than the Papp of sucrose or LY (depending on the molecular weight of the drug) could suggest transcellular permeability and/or transport across the cells. Figure 4 shows that in permeable membrane inserts with pBECs cultured above rat astrocytes, good batches of pBEC (e.g. here the LY set) will generate TEERs in the range ~500-2000 &#937; cm2, with a few higher or lower. Some batches, especially during early stages of learning the protocol, may have lower TEERs around 100-900 &#937; cm2 (e.g. here the sucrose set). TEER measurement allows selection of filters, for example with starting TEER &#62;500 &#937; cm2, and over the range of TEER shown, Papp is relatively independent of TEER, indicative of a sufficiently tight barrier layer for these experiments. The protocol for measuring permeability depends on the type of solute/construct. For a description of the procedure for measuring permeability of small molecules in NCC, a protocol is described in Yusof, SR, et. al21. Evaluation of expression of the tight junction proteins in pBECs in NCC with rat astrocytes showed localization of claudin 5, occludin, and ZO-1 along the cell-cell junctions, as shown by immunofluorescence (Figure 5A-C). Also, the adherens junction protein p120 catenin showed well-defined distribution along the cell-cell junctions (Figure 5D).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56277/56277fig1.jpg" /> 
Figure 1: Schematic representation of the applied in vitro BBB models. Schematic representation of the permeable membrane insert system models of pBECs in MC (A), MC with ACM (B), and NCC with astrocytes (C). In the MC, either pBEC growth medium or ACM were applied in the bottom wells, whereas in the NCC, inserts with pBECs were placed in wells with 2-8-week-old astrocytes. <a href="https://cloudflare.jove.com/files/ftp_upload/56277/56277fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56277/56277fig2.jpg" /> 
Figure 2: Flow chart of the main steps during pBEC cultivation and the establishment of the presented models. For an overview and timeline for the method, this schematic presentation summarizes the main steps in the culturing procedure of pBECs and establishment of the presented models, i.e. MC with or without ACM, and NCC with astrocytes. <a href="https://cloudflare.jove.com/files/ftp_upload/56277/56277fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/56277/56277fig3.jpg" /> 
Figure 3: Representative time course of initial cultures of pBECs and rat astrocytes. Phase contrast microscopy images of cultures of pBECs (A-C) and astrocytes (D-F) viewed over 5 days. Purified capillary fragments on the first day of the initial culture showed presence of both capillaries and contaminating cells (A, day 1), which after medium change on day 2 and an additional day of growth, showed selection for pBECs, starting their growth from the capillary fragments (B, day 3). Confluent monolayers of pBECs were usually achieved on day 4-6, at which time pBECs showed spindle-shaped morphology and were longitudinally aligned (C). Rat astrocytes seeded in bottom wells normally proliferated to confluent layers within 5 days (D-F), and were used for NCC models after 2 weeks of growth. Scale bar for all pictures: 200 &#181;m. <a href="https://cloudflare.jove.com/files/ftp_upload/56277/56277fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/56277/56277fig4.jpg" /> 
Figure 4: Tight junction integrity of pBECs. Apparent permeability (Papp) of pBECs to paracellular markers Sucrose (MW 342.5 14C-labelled, 14.8-25.9 GBq/mmol) and Lucifer Yellow (MW 521.57, 10 &#181;g mL-1), plotted against TEER. pBECs were grown on 1.12 cm2 permeable membrane insert filters above rat astrocytes in the base of the well and markers added to the apical chamber. After 1 hour at 37 &#730;C, appearance of marker in the basal chamber was measured and apical-to-basal Papp (x 10-6 cm sec-1) calculated. TEER was measured &#62;3 h before Papp, using STX100C EVOM electrodes, corrected for the blank permeable membrane insert filter with resistance 150 &#937;. Average TEER for the Lucifer Yellow data set was 1249 &#177; 80 &#937; cm2 (mean &#177; SEM, n=55). <a href="https://cloudflare.jove.com/files/ftp_upload/56277/56277fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/56277/56277fig5.jpg" /> 
Figure 5: Immunocytochemical characterization of pBECs. For pBECs grown on 1.12 cm2 permeable membrane insert filter inserts above rat astrocytes in the base well, immunofluorescence microscopy analysis of the tight junction components (A) Claudin 5 (B) Occludin (C) ZO-1, and adherens junction protein (D) p120 catenin showed well-defined localization at cell-cell junctions and revealed confluent brain endothelial cell layers with spindle-shaped, non-overlapping cells. Scale bar for all pictures: 10 &#181;m. <a href="https://cloudflare.jove.com/files/ftp_upload/56277/56277fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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) ...

improved-method-for-establishment-an-vitro-blood-brain-barrier-model

Nanyang Technological University

Research

JoVE Journal

Medicine

14.7K Views.  Aarhus University. 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. 

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

MRI-guided Disruption of the Blood-brain Barrier using Transcranial Focused Ultrasound in a Rat Model

Focused ultrasound (FUS) disruption of the blood-brain barrier (BBB) is an increasingly investigated technique for circumventing the BBB1-5. The BBB is a significant obstacle to pharmaceutical treatments of brain disorders as it limits the passage of molecules from the vasculature into the brain tissue to molecules less than approximately 500 Da in size6. FUS induced BBB disruption (BBBD) is temporary and reversible4 and has an advantage over chemical means of inducing BBBD by being highly localized. FUS induced BBBD provides a means for investigating the effects of a wide range of therapeutic agents on the brain, which would not otherwise be deliverable to the tissue in sufficient concentration. While a wide range of ultrasound parameters have proven successful at disrupting the BBB2,5,7, there are several critical steps in the experimental procedure to ensure successful disruption with accurate targeting. This protocol outlines how to achieve MRI-guided FUS induced BBBD in a rat model, with a focus on the critical animal preparation and microbubble handling steps of the experiment.

Microbubble-mediated focused ultrasound disruption of the blood-brain barrier (BBB) is a promising technique for non-invasive targeted drug delivery in the brain1-3. This protocol outlines the experimental procedure for MRI-guided transcranial BBB disruption in a rat model.

Focused ultrasound (FUS) disruption of the blood-brain barrier (BBB) is an increasingly investigated technique for circumventing the BBB1-5. The BBB is a ...

Rat Model of Blood-brain Barrier Disruption to Allow Targeted Neurovascular Therapeutics

Endothelial cells with tight junctions along with the basement membrane and astrocyte end feet surround cerebral blood vessels to form the blood-brain barrier1. The barrier selectively excludes molecules from crossing between the blood and the brain based upon their size and charge. This function can impede the delivery of therapeutics for neurological disorders. A number of chemotherapeutic drugs, for example, will not effectively cross the blood-brain barrier to reach tumor cells2. Thus, improving the delivery of drugs across the blood-brain barrier is an area of interest.
The most prevalent methods for enhancing the delivery of drugs to the brain are direct cerebral infusion and blood-brain barrier disruption3. Direct intracerebral infusion guarantees that therapies reach the brain; however, this method has a limited ability to disperse the drug4. Blood-brain barrier disruption (BBBD) allows drugs to flow directly from the circulatory system into the brain and thus more effectively reach dispersed tumor cells. Three methods of barrier disruption include osmotic barrier disruption, pharmacological barrier disruption, and focused ultrasound with microbubbles. Osmotic disruption, pioneered by Neuwelt, uses a hypertonic solution of 25% mannitol that dehydrates the cells of the blood-brain barrier causing them to shrink and disrupt their tight junctions. Barrier disruption can also be accomplished pharmacologically with vasoactive compounds such as histamine5 and bradykinin6. This method, however, is selective primarily for the brain-tumor barrier7. Additionally, RMP-7, an analog of the peptide bradykinin, was found to be inferior when compared head-to-head with osmotic BBBD with 25% mannitol8. Another method, focused ultrasound (FUS) in conjunction with microbubble ultrasound contrast agents, has also been shown to reversibly open the blood-brain barrier9. In comparison to FUS, though, 25% mannitol has a longer history of safety in human patients that makes it a proven tool for translational research10-12.
In order to accomplish BBBD, mannitol must be delivered at a high rate directly into the brain's arterial circulation. In humans, an endovascular catheter is guided to the brain where rapid, direct flow can be accomplished. This protocol models human BBBD as closely as possible. Following a cut-down to the bifurcation of the common carotid artery, a catheter is inserted retrograde into the ECA and used to deliver mannitol directly into the internal carotid artery (ICA) circulation. Propofol and N2O anesthesia are used for their ability to maximize the effectiveness of barrier disruption13. If executed properly, this procedure has the ability to safely, effectively, and reversibly open the blood-brain barrier and improve the delivery of drugs that do not ordinarily reach the brain 8,13,14.

Blood-brain barrier disruption aids the delivery of certain drugs to the brain. Mannitol delivered intra-arterially shrinks cells surrounding blood vessels in order to physically disrupt the barrier.

Endothelial cells with tight junctions along with the basement membrane and astrocyte end feet surround cerebral blood vessels to form the blood-brain ...

Stretch in Brain Microvascular Endothelial Cells (cEND) as an In Vitro Traumatic Brain Injury Model of the Blood Brain Barrier

Due to the high mortality incident brought about by traumatic brain injury (TBI), methods that would enable one to better understand the underlying mechanisms involved in it are useful for treatment. There are both in vivo and in vitro methods available for this purpose. In vivo models can mimic actual head injury as it occurs during TBI. However, in vivo techniques may not be exploited for studies at the cell physiology level. Hence, in vitro methods are more advantageous for this purpose since they provide easier access to the cells and the extracellular environment for manipulation.
Our protocol presents an in vitro model of TBI using stretch injury in brain microvascular endothelial cells. It utilizes pressure applied to the cells cultured in flexible-bottomed wells. The pressure applied may easily be controlled and can produce injury that ranges from low to severe. The murine brain microvascular endothelial cells (cEND) generated in our laboratory is a well-suited model for the blood brain barrier (BBB) thus providing an advantage to other systems that employ a similar technique. In addition, due to the simplicity of the method, experimental set-ups are easily duplicated. Thus, this model can be used in studying the cellular and molecular mechanisms involved in TBI at the BBB.

Stretch in Brain Microvascular Endothelial Cells cEND as an In Vitro Traumatic Brain Injury Model of the Blood Brain Barrier

In vitro traumatic brain injury models are being developed to reproduce in vivo brain deformation. Stretch-induced injury has been employed for astrocytes, neurons, glial cells, aortic, and brain endothelial cells. However, our system uses a blood brain barrier (BBB) model that possesses properties constituting a legitimate model of the BBB to establish an in vitro&#160;TBI model.

Due to the high mortality incident brought about by traumatic brain injury (TBI), methods that would enable one to better understand the underlying ...

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 ...

Excitotoxic Stimulation of Brain Microslices as an In vitro Model of Stroke

Examining molecular mechanisms involved in neuropathological conditions, such as ischemic stroke, can be difficult when using whole animal systems. As such, primary or &#39;neuronal-like&#39; cell culture systems are commonly utilized. While&#160;these systems are relatively easy to work with, and are useful model systems in which various functional outcomes (such as cell death) can be readily quantified, the examined outcomes and pathways in cultured immature neurons (such as excitotoxicity-mediated cell death pathways) are not necessarily the same as those observed in mature brain, or in intact tissue. Therefore, there is the need to develop models in which cellular mechanisms in mature neural tissue can be examined. We have developed an in vitro technique that can be used to investigate a variety of molecular pathways in intact nervous tissue. The technique described herein utilizes rat cortical tissue, but this technique can be adapted to use tissue from a variety of species (such as mouse, rabbit, guinea pig, and chicken) or brain regions (for example, hippocampus, striatum, etc.). Additionally, a variety of stimulations/treatments can be used (for example, excitotoxic, administration of inhibitors, etc.). In conclusion, the brain slice model described herein can be used to examine a variety of molecular mechanisms involved in excitotoxicity-mediated brain injury.

Excitotoxic Stimulation of Brain Microslices as an In vitro Model of Stroke

We have developed a brain slice model which can be used to examine molecular mechanisms involved in excitotoxicity-mediated brain injury.&#160;This technique generates viable mature brain tissue and reduces animal numbers required for experimentation, whilst keeping the neuronal circuitry, cellular interactions, and postsynaptic compartments partly intact.

Examining molecular mechanisms involved in neuropathological conditions, such as ischemic stroke, can be difficult when using whole animal systems. As ...

Oxygen-Glucose Deprivation and Reoxygenation as an In Vitro Ischemia-Reperfusion Injury Model for Studying Blood-Brain Barrier Dysfunction

Ischemia-Reperfusion (IR) injury is known to contribute significantly to the morbidity and mortality associated with ischemic strokes. Ischemic cerebrovascular accidents account for 80% of all strokes. A common cause of IR injury is the rapid inflow of fluids following an acute/chronic occlusion of blood, nutrients, oxygen to the tissue triggering the formation of free radicals.
Ischemic stroke is followed by blood-brain barrier (BBB) dysfunction and vasogenic brain edema. Structurally, tight junctions (TJs) between the endothelial cells play an important role in maintaining the integrity of the blood-brain barrier (BBB). IR injury is an early secondary injury leading to a non-specific, inflammatory response. Oxidative and metabolic stress following inflammation triggers secondary brain damage including BBB permeability and disruption of tight junction (TJ) integrity.
Our protocol presents an in vitro example of oxygen-glucose deprivation and reoxygenation (OGD-R) on rat brain endothelial cell TJ integrity and stress fiber formation. Currently, several experimental in vivo models are used to study the effects of IR injury; however they have several limitations, such as the technical challenges in performing surgeries, gene dependent molecular influences and difficulty in studying mechanistic relationships. However, in vitro models may aid in overcoming many of those limitations. The presented protocol can be used to study the various molecular mechanisms and mechanistic relationships to provide potential therapeutic strategies. However, the results of in vitro studies may differ from standard in vivo studies and should be interpreted with caution.

Oxygen-Glucose Deprivation and Reoxygenation as an In Vitro Ischemia-Reperfusion Injury Model for Studying Blood-Brain Barrier Dysfunction

Ischemia-Reperfusion (IR) injury is associated with a high rate of morbidity and mortality. The goal of the in vitro model of oxygen-glucose deprivation and reoxygenation (OGD-R) described here is to assess the effects of ischemia reperfusion injury on a variety of cells, particularly in blood-brain barrier (BBB) endothelial cells.

Ischemia-Reperfusion (IR) injury is known to contribute significantly to the morbidity and mortality associated with ischemic strokes. Ischemic ...

An Improved Method for Rapid Intubation of the Trachea in Mice

Despite some anatomical and physiological differences, mouse models continue to be an essential tool for studying human lung disease. Bleomycin toxicity is a commonly used model to study both acute lung injury and fibrosis, and multiple methods have been developed for administering bleomycin (and other toxic agents) into the lungs. However, many of these approaches, such as transtracheal instillation, have inherent drawbacks, including the need for strong anesthetics and survival surgery. This paper reports a quick, reproducible method of intratracheal intubation that involves mild inhaled anesthesia, visualization of the trachea, and the use of a surrogate spirometer to confirm exposure. As a proof of concept, 8-12 week old C57BL/6 mice were administered either 2.0 U/kg of bleomycin or an equivalent volume of PBS, and both damage and fibrotic endpoints were measured post-exposure. This procedure allows researchers to treat a large cohort of mice in a relatively short period with little expense and minimal post-procedure care.

This article presents a rapid and simple method for administering bleomycin directly into the mouse trachea via intubation. Key advantages of this method are that it is highly reproducible, easy to master, and does not require specialized equipment or lengthy recovery times.

Despite some anatomical and physiological differences, mouse models continue to be an essential tool for studying human lung disease. Bleomycin toxicity ...

An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model

Pedicle screw fixation is the gold standard for the treatment of spinal diseases. However, many studies have reported the issue of loosening pedicle screws after spinal surgery, which is a serious concern. To address this problem, diverse types of pedicle screws have been examined to identify those with good fixation strength and osseointegration in spine bone. The porcine spine is a good alternative for the human spine in the evaluation of pedicle screws due to the anatomical size, mechanical characteristics, and cost. Although several studies have reported that pedicle screws are efficient in the porcine model, no study has described detailed protocols for the evaluation of a pedicle screw using the porcine model. Here, we describe a detailed method for evaluating transpedicular screws using an in vivo porcine lumbar spine model. The technical details for anesthesia, spine surgery, and harvest provided here will facilitate with the evaluation of the transpedicular screw fixation model.

An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model

Here, we introduce a method to evaluate transpedicular screws by using an in vivo porcine lumbar spine model.

Pedicle screw fixation is the gold standard for the treatment of spinal diseases. However, many studies have reported the issue of loosening pedicle ...

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 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.

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

Establishment and Evaluation of a Porcine Vein Graft Disease Model

Venous graft disease (VGD) is the leading cause of coronary artery bypass graft (CABG) failure. Large animal models of CABG-VGD are needed for the investigation of disease mechanisms and the development of therapeutic strategies. 
To perform the surgery, we enter the cardiac chamber through the third intercostal space and carefully dissect the internal mammary vein and immerse it in normal saline. The right main coronary artery is then treated for ischemia. The target vessel is incised, a shunt plug is placed, and the distal end of the graft vein is anastomosed. The ascending aorta is partially blocked, and the proximal end of the graft vein is anastomosed after perforation. The graft vein is checked for patency, and the proximal right coronary artery is ligated. 
CABG surgery is performed in minipigs to harvest the left internal mammary vein for its use as a vascular graft. Serum biochemical tests are used to evaluate the physiological status of the animals after surgery. Ultrasound examination shows that the proximal, middle, and distal end of the graft vessel are unobstructed. In the surgical model, turbulent blood flow in the graft is observed upon histological examination after the CABG surgery, and venous graft stenosis associated with intimal hyperplasia is observed in the graft. The study here provides detailed surgical procedures for the establishment of a repeatable CABG-induced VGD model.

In this protocol, novel pig vein bypass grafting was performed through a small incision in the left chest wall without cardiopulmonary bypass. A postoperative pathology study was done, which showed intimal thickening.