We thank and acknowledge Dr. Peter Nelson and Sonya Anderson at the UK-ADC Brain Tissue Bank for providing all human brain tissue samples (NIH grant number: P30 AG028383 from the National Institute on Aging). We thank Matt Hazzard and Tom Dolan, Information Technology Services, Academic Technology and Faculty Engagement, University of Kentucky for graphical assistance. This project was supported by grant number 1R01NS079507 from the National Institute of Neurological Disorders and Stroke (to B.B.) and by grant number 1R01AG039621 from the National Institute on Aging (to A.M.S.H.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Neurological Disorders and Stroke or the National Institute on Aging. The authors declare no competing financial interests.

The information below is based on current safety and regulatory standards at the University of Kentucky, Lexington, KY, USA. As a safety precaution, refer to the institution&#39;s biological safety program and the most current regulations and recommendations before working with human tissue.
CAUTION: Human tissue can be a source of blood-borne pathogens, including human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), and others. Working with human tissue poses t...

The authors have nothing to disclose.

The present protocol describes the isolation of intact and viable human brain capillaries from fresh tissue. In this section, we discuss in detail the following: 1) modifications to the protocol, 2) troubleshooting of common errors, 3) limitations of the technique, 4) the significance of the model with respect to existing and alternative blood-brain barrier models, and 5) potential applications for isolated human brain capillaries.
The protocol described here is optimized for 10 g of fresh hum...

The blood-brain barrier is a tightly controlled interface between the blood and brain that determines what goes into and comes out of the brain. Anatomically, endothelial cells compose the blood-brain barrier and forms a complex, continuous capillary network. Physiologically, this capillary network supplies the brain with oxygen and nutrients while simultaneously disposing of carbon dioxide and metabolic waste products. Importantly, evidence supports that the changes to the barrier contribute to numerous pathologies, including Alzheimer&#39;s disease, epilepsy, and stroke1,2,3,4,5,6,7. Brain endothelial cells also serve as a barrier to treatment by blocking drug uptake into the brain, e.g., chemotherapy of glioblastoma multiforme following tumor resection8,9,10. In this regard, isolated human brain capillaries represent a unique ex vivo blood-brain barrier model that closely resembles barrier properties in vivo, which allows for the study of barrier function and dysfunction in health and disease. In this article, we provide a protocol to isolate brain capillaries from human brain at a consistently high capillary quality and yield to study the blood-brain barrier.
In 1969, Siakotos et al.11 were the first to report the isolation of brain capillaries from bovine and human brain tissue using density gradient centrifugation and glass bead column separation. Later, Goldstein et al.12 improved this method by adding multiple filtration steps to decrease the amount of tissue needed to study brain capillaries isolated from rats, while maintaining the metabolic activity of glucose transport. Since then, researchers optimized the capillary isolation procedure numerous times, improving the method and brain capillary model with each iteration13,14,15. For example, Pardridge et al.16 isolated bovine capillaries using enzymatic digestion rather than mechanical homogenization, and then subsequently passed a capillary suspension through a 210 &#181;m mesh filter and a glass bead column. These modifications improved the trypan blue exclusion stain of isolated brain capillaries, and thus, increased endothelial cell viability. In the early 1990s, Dallaire et al.17 isolated bovine and rat capillaries that were clear of neuronal contamination and maintained metabolic activity of &#947;-glutamyl transpeptidase (&#947;-GTase) and alkaline phosphatase. In 2000, Miller et al.18, used isolated rat and porcine brain capillaries in combination with confocal microscopy to show the accumulation of transport substrates into the lumen of capillaries. Subsequently, our laboratory has continued to optimize the brain capillary isolation procedure and we have established transport assays to determine P-glycoprotein (P-gp)19,20,21, breast cancer resistance protein (BCRP)22,23, and multi-drug resistance protein 2 (Mrp2)24 transport activity. In 2004, we published two reports where we used isolated rat brain capillaries to investigate various signaling pathways. In Hartz et al.21, we found that the peptide endothelin-1 rapidly and reversibly reduced P-gp transport function in brain capillaries by acting through the endothelin receptor B (ETB) receptor, nitric oxide synthase (NOS), and protein kinase C (PKC). In Bauer et al.19, we demonstrated expression of the nuclear receptor pregnane X receptor (PXR) and showed PXR-modulation of P-gp expression and transport function in brain capillaries. In experiments with transgenic humanized PXR mice, we expanded this line of research and showed in vivo tightening of the barrier by upregulating P-gp through hPXR activation25. In 2010, Hartz et al.26 used this approach to restore P-gp protein expression and transport activity in transgenic human amyloid precursor protein (hAPP) mice that overexpress hAPP. Moreover, restoring P-gp in hAPP mice significantly reduced amyloid beta (A&#946;)40and A&#946;42brain levels.
In addition to studying signaling pathways, isolated brain capillaries can be used to determine changes in capillary permeability which we refer to as capillary leakage. In particular, the Texas Red leakage assay is used to assess leakage of the fluorescent dye Texas Red from the capillary lumen over time and these data are then used to analyze leakage rates. Increased capillary leakage rates compared to those from control capillaries indicate changes in the physical integrity of the blood-brain barrier2. This is valuable because there are numerous disease states associated with barrier disruption, e.g., epilepsy, multiple sclerosis, Alzheimer&#39;s disease, and traumatic brain injury27,28,29,30. Other groups have also utilized isolated capillaries to discern signaling pathways that regulate protein expression and transport activity of proteins31,32,33,34,35,36,37. Finally, we have continued to optimize this method for the isolation of human brain capillaries and, recently, we showed increased P-gp expression at the human blood-brain barrier in patients with epilepsy compared to seizure-free control individuals38. Taken together, these developments demonstrate that isolated brain capillaries can serve as a versatile model to study barrier function.
Various in vivo, ex vivo, and in vitro blood-brain barrier models have been used in basic research and industrial drug screening, mainly with the goal of testing drug delivery to the brain39,40,41,42,43,44. In addition to isolated ex vivo brain capillaries, current blood-brain barrier models include in silico models, in vitro cell culture of isolated brain capillary endothelial cells or immortalized cell lines from various species, in vitro culture of human pluripotent stem cells (hPSC) that differentiate into brain capillary endothelial cells, and microfluidic models on a chip.
In silico models are most commonly used in drug development for selecting drug candidates based on predicted absorption, distribution, metabolism, and excretion (ADME) properties. Methods such as quantitative structure-property relationship (QSPR) models and quantitative structure-activity relationship (QSAR) models are popular methods used in high-throughput screening of libraries to predict brain penetration of drug candidates45,46. These models are useful to screen molecules for barrier penetration properties.
Betz et al.47 established monolayers of cultured brain capillary endothelial cells as an in vitro blood-brain barrier model system. In vitro cell culture models using fresh tissue or immortalized endothelial cell lines such as human cerebral microvessel endothelial cells (hCMECs) can be another high-throughput screening tool for brain penetration or mechanistic studies. However, brain capillary endothelial cell culture models lack the physiologic shear stress of blood flow inside the capillary lumen, are limited in overall biologic complexity, and undergo changes in expression and localization of important barrier components such as tight junction proteins, surface receptors, transporters, enzymes, and ion channels48,49,50. Conversely, endothelial monolayers derived from hPSCs, have low sucrose permeability compared to hCMEC/D3 cultures and contain polarized expression of some blood-brain barrier transporters, adhesion molecules, and tight junctions51,52. However, these cells are also subject to changing properties in the culture, and the system must be validated for its recapitulation of in vivo barrier properties52.
Newer trends in blood-brain barrier research include utilizing 3D tissue culture systems to create artificial capillaries, using the organ-on-chip technology to generate microfluidic devices, or utilizing the hollow fiber technology53,54,55. Artificial capillaries, however, have significantly larger diameters (100&#8211;200 &#181;m) than brain capillaries (3&#8211;7 &#181;m). Hence, the shear forces in vitro do not fully resemble the in vivo situation. This is addressed in &#34;blood-brain-barrier-on-a-chip&#34; microfluidic devices, where artificial membranes form &#34;blood&#34; and &#34;brain&#34; compartments and fluids are pumped through these devices generating microfluidic shear forces. Similarly, co-cultures of endothelial cells in various combinations with astrocytes and vascular smooth muscle cells have also been used with the hollow fiber technology to recreate rheological parameters present under in vivo conditions56,57,58. However, it is unclear how well this model reflects other properties of the blood-brain barrier such as transport, metabolism, signaling, and others. These artificial capillary and chip models are suitable for high-throughput screening of drugs, but the cells used to generate these models are also subject to change during culture.
Frozen and fixed brain slices or primary brain capillary endothelial cell cultures are additional models that can be used tostudy the human microvasculature5,59,60,61. For example, immunohistochemistry of fixed brain tissue is used to determine protein localization and expression in healthy compared to diseased tissue.
In addition to tissue slices and the in vitro models described above, freshly isolated brain capillaries can be utilized to study blood-brain barrier function. Limitations of this isolated capillary model include the difficulty to obtain fresh human brain tissue, absence of astrocytes and neurons, and a relatively time-consuming isolation process. An advantage of the isolated brain capillary model is that this model closely resembles the in vivo situation and, therefore, can be used to characterize barrier function and dysfunction. Importantly, it can also be used to discern signaling mechanisms using a multitude of assays and molecular techniques3,19,62,63.
Our laboratory has access to both fresh and frozen human brain tissue through the Sanders-Brown Center on Aging (IRB #B15-2602-M)64. In this context, autopsies follow a standard protocol, brains are obtained in &#60;4 h, and all procedures conform to NIH Biospecimen Best Practice Guidelines65. Given this unique access to human brain tissue, we established and optimized a protocol to isolate brain capillaries from human brain tissue that results in a high yield of intact, viable human brain capillaries. Two common endpoints of interest are to determine the protein expression and activity. In this regard, we and others have established various assays that can be used with isolated brain capillaries to study protein expression and activity levels. These assays include Western blotting, Simple Western assay, enzyme-linked immunosorbent assay (ELISA), reverse transcription polymerase chain reaction (RT-PCR), quantitative polymerase chain reaction (qPCR), zymography, transport activity assays, and capillary leakage assays. These assays allow researchers to study changes in barrier function in human pathologic conditions, determine pathways that govern protein expression and activity, and identify pharmacologic targets for the treatment of blood-brain barrier associated diseases.
Taken together, freshly isolated brain capillaries can serve as a robust and reproducible model of the blood-brain barrier. Especially, this model can be combined with many different assays to determine a wide array of endpoints to study barrier function.

<table>
	<tbody>
		<tr>
			<td>Personal Protective Equipment (PPE)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Diamond Grip Plus Latex Gloves, Microflex Medium</td>
			<td>VWR, Radnor, PA, USA</td>
			<td>32916-636</td>
			<td>PPE</td>
		</tr>
		<tr>
			<td>Disposable Protective Labcoats</td>
			<td>VWR, Radnor, PA, USA</td>
			<td>470146-214</td>
			<td>PPE; due to the nature of the human source material, the use of a disposable lab coat is recommended</td>
		</tr>
		<tr>
			<td>Face Shield, disposable</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>19460102</td>
			<td>PPE; due to the nature of the human source material, the use of a disposable face shield is recommended</td>
		</tr>
		<tr>
			<td>Safety Materials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Clavies High-Temperature Autoclave Bags 8X12</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>01-815-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Versi Dry Bench Paper 18&#34; x 20&#34;</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>14-206-32</td>
			<td>to cover working areas</td>
		</tr>
		<tr>
			<td>VWR Sharps Container Systems</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>75800-272</td>
			<td>for used scalpels</td>
		</tr>
		<tr>
			<td>Bleach 8.2% Clorox Germicidal 64 oz</td>
			<td>UK Supply Center, Lexington, KY, USA</td>
			<td>323775</td>
			<td></td>
		</tr>
		<tr>
			<td>Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>4&#176;C Refrigerator</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>13-986-148</td>
			<td></td>
		</tr>
		<tr>
			<td>Accume BASIC AB15 pH Meter</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>AB15</td>
			<td></td>
		</tr>
		<tr>
			<td>Heidolph RZR 2102 Control</td>
			<td>Heidolph, Elk Grove Village, IL, USA</td>
			<td>501-21024-01-3</td>
			<td></td>
		</tr>
		<tr>
			<td>Sorvall LEGEND XTR Centrifuge</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>75004521</td>
			<td></td>
		</tr>
		<tr>
			<td>Leica L2 Dissecting Microscope</td>
			<td>Leica Microsystems Inc, Buffalo Grove IL, USA</td>
			<td></td>
			<td>used to remove meninges</td>
		</tr>
		<tr>
			<td>POLYTRON PT2500 Homogenizer</td>
			<td>Kinematica AG, Luzern, Switzerland</td>
			<td>9158168</td>
			<td></td>
		</tr>
		<tr>
			<td>Scale P-403</td>
			<td>Denver Instrument, Bohemia, NY, USA</td>
			<td>0191392</td>
			<td></td>
		</tr>
		<tr>
			<td>Standard mini Stir</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>1151050</td>
			<td></td>
		</tr>
		<tr>
			<td>Thermo-Flasks Liquid Nitrogen Dewar</td>
			<td>Thermal Scientific, Mansfiled, TX, USA</td>
			<td>11-670-4C</td>
			<td>used to freeze the tissue?</td>
		</tr>
		<tr>
			<td>Voyager Pro Analytical Balance</td>
			<td>OHAUS, Parsippany, NJ, USA</td>
			<td>VP214CN</td>
			<td></td>
		</tr>
		<tr>
			<td>ZEISS Axiovert Microcope</td>
			<td>Carl Zeiss, Inc Thornwood, NY, USA</td>
			<td></td>
			<td>used to check isolated capillaries</td>
		</tr>
		<tr>
			<td>Tools and Glassware</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Finnpipette II Pipette 1-5mL</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>21377823T1</td>
			<td>wash capillaries off filter</td>
		</tr>
		<tr>
			<td>Finnpipette II Pipette 100-1000 &#181;L</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>21377821T1</td>
			<td>resuspend pellet in BSA</td>
		</tr>
		<tr>
			<td>Pipet Boy</td>
			<td>Integra, Hudson, NH, USA</td>
			<td>739658</td>
			<td></td>
		</tr>
		<tr>
			<td>50mL Falcon tubes 25/rack - 500/cs</td>
			<td>VWR, Radnor, PA, USA</td>
			<td>21008-951</td>
			<td></td>
		</tr>
		<tr>
			<td>EISCO Scalpel Blades</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>S95938C</td>
			<td>to mince brain tissue</td>
		</tr>
		<tr>
			<td>PARAFILM</td>
			<td>VWR, Radnor, PA, USA</td>
			<td>52858-000</td>
			<td>to cover beaker and volumetric flask</td>
		</tr>
		<tr>
			<td>Thermo Scientific Finntip Pipet Tips 5 ml</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>21-377-304</td>
			<td>to wash capillaries off filter</td>
		</tr>
		<tr>
			<td>60 ml syringe with Luer-Lok</td>
			<td>Thermo Fisher Scientific, Pittsburgh, PA, USA</td>
			<td>BD309653</td>
			<td>used with connector ring to filter capillaries</td>
		</tr>
		<tr>
			<td>Scalpel Handle #4</td>
			<td>Fine Science Tools, Foster City, CA, USA</td>
			<td>10060-13</td>
			<td>used for mincing</td>
		</tr>
		<tr>
			<td>Dumont Forceps #5</td>
			<td>Fine Science Tools, Foster City, CA, USA</td>
			<td>11251-10</td>
			<td>used to remove meninges</td>
		</tr>
		<tr>
			<td>Potter-Elvehjem Tissue Grinder</td>
			<td>Thomas Scientific, Swedesboro, NJ, USA</td>
			<td>3431E25</td>
			<td>50 ml volume, clearance: 150-230 &#956;m</td>
		</tr>
		<tr>
			<td>Dounce Homogenizer</td>
			<td>VWR, Radnor PA USA</td>
			<td>62400-642</td>
			<td>15 ml volume, clearance: 80-130 &#956;m</td>
		</tr>
		<tr>
			<td>Spectra/Mesh Woven Filters (300 &#181;m)</td>
			<td>Spectrum Laboratories, Rancho Dominguez, CA, USA</td>
			<td>146424</td>
			<td>Used to filter capillary suspension to remove any meninges that may be left</td>
		</tr>
		<tr>
			<td>pluriStrainers (pore size: 30 &#181;m)</td>
			<td>pluriSelect Life Science, Leipzig, Germany</td>
			<td>43-50030-03</td>
			<td></td>
		</tr>
		<tr>
			<td>Connector Ring</td>
			<td>pluriSelect Life Science, Leipzig, Germany</td>
			<td>41-50000-03</td>
			<td>reuse multiple time</td>
		</tr>
		<tr>
			<td>1 l Volumetric Flask</td>
			<td></td>
			<td></td>
			<td>for preparation of Isolation Buffer</td>
		</tr>
		<tr>
			<td>1 l Beaker</td>
			<td></td>
			<td></td>
			<td>for preparation of 1% BSA</td>
		</tr>
		<tr>
			<td>Stir Bar</td>
			<td></td>
			<td></td>
			<td>for preparation of 1% BSA and Ficoll&#174;</td>
		</tr>
		<tr>
			<td>Schott Bottle (60 ml)</td>
			<td></td>
			<td></td>
			<td>for preparation of Ficoll&#174;</td>
		</tr>
		<tr>
			<td>Ice Bucket</td>
			<td></td>
			<td></td>
			<td>to keep everything cold</td>
		</tr>
		<tr>
			<td>100 mm Petri Dish</td>
			<td></td>
			<td></td>
			<td>for mincing of brain tissue</td>
		</tr>
		<tr>
			<td>Tissue Culture Cell Scraper</td>
			<td>VWR, Radnor, PA, USA</td>
			<td>89260-222</td>
			<td>to remove supernatant after centrifugation</td>
		</tr>
		<tr>
			<td>Chemicals</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>BSA Fraction V, A-9647</td>
			<td>Sigma-Aldrich, St. Louis, MO, USA</td>
			<td>A9647-500g</td>
			<td>prepare in DPBS with Ca2+ &#38; Mg2+ the day before. Avoid bubbles during preparation. Store in the refrigerator. Slowly stir for 10 min before use.</td>
		</tr>
		<tr>
			<td>DPBS with Ca2+ &#38; Mg2+</td>
			<td>Hyclone</td>
			<td>SH30264.FS</td>
			<td>DPBS - part of the Isolation Buffer</td>
		</tr>
		<tr>
			<td>Ficoll PM400</td>
			<td>Sigma-Aldrich, St. Louis, MO, USA</td>
			<td>F4375</td>
			<td>Exact measurement is important here. Weigh out in bottle with stir bar. Shake vigurously after adding DPBS. Keep in the fridge O/N. It will be clear in the morning. Stir gently for 10-15 min before use. Keep on ice until use.</td>
		</tr>
		<tr>
			<td>Glucose (D-(+) Dextrose)</td>
			<td>Sigma-Aldrich, St. Louis, MO, USA</td>
			<td>G7528</td>
			<td>Glucose (D-(+) Dextrose) Concentration: 5 mM</td>
		</tr>
		<tr>
			<td>Sodium Hydroxide Standard Solution</td>
			<td>Sigma-Aldrich, St. Louis, MO, USA</td>
			<td>71474</td>
			<td>to adjust pH of the DPBS</td>
		</tr>
		<tr>
			<td>Sodium Pyruvate</td>
			<td>Sigma-Aldrich, St. Louis, MO, USA</td>
			<td>P2256</td>
			<td>Concentration: 1 mM</td>
		</tr>
	</tbody>
</table>

isolation of cerebral capillaries from fresh human brain tissue

Understanding blood-brain barrier function under physiological and pathophysiological conditions is critical for the development of new therapeutic strategies that hold the promise to enhance brain drug delivery, improve brain protection, and treat brain disorders. However, studying the human blood-brain barrier function is challenging. Thus, there is a critical need for appropriate models. In this regard, brain capillaries isolated from human brain tissue represent a unique tool to study barrier function as close to the human in vivo situation as possible. Here, we describe an optimized protocol to isolate capillaries from human brain tissue at a high yield and with consistent quality and purity. Capillaries are isolated from fresh human brain tissue using mechanical homogenization, density-gradient centrifugation, and filtration. After the isolation, the human brain capillaries can be used for various applications including leakage assays, live cell imaging, and immune-based assays to study protein expression and function, enzyme activity, or intracellular signaling. Isolated human brain capillaries are a unique model to elucidate the regulation of the human blood-brain barrier function. This model can provide insights into central nervous system (CNS) pathogenesis, which will help the development of therapeutic strategies for treating CNS disorders.

The isolations from human brain tissue yield a suspension enriched in human brain capillaries (Figure 1B) with small amounts of larger vessels, red blood cells, other single cells, and some cell debris. Some capillaries are branched, and, in some, red blood cells are entrapped in the capillary lumens. The typical capillary has a 3&#8211;7 &#181;m diameter and is approximately 100-200 &#181;m long with open lumens; most capillary ends are collapsed. Using conf...

Watch this Scientific Journal Video about Isolation of Cerebral Capillaries from Fresh Human Brain Tissue at JoVE.com

Isolation of Cerebral Capillaries from Fresh Human Brain Tissue

Isolated brain capillaries from human brain tissue can be used as a preclinical model to study barrier function under physiological and pathophysiological conditions. Here, we present an optimized protocol to isolate brain capillaries from fresh human brain tissue.

Understanding blood-brain barrier function under physiological and pathophysiological conditions is critical for the development of new therapeutic ...

This method can help answer key questions in the field of blood-brain barrier research, such as blood-brain barrier dysfunction, barrier leakage and signaling pathways that are specific for the human blood-brain barrier. The main advantage of this technique is that it allows the study of intact, physiologically active human brain capillaries that have been isolated from fresh human brain tissue. To begin this procedure, document the weight of the human brain tissue, which should be about 10 grams.Under the microscope, carefully remove all the meninges with forceps and use a scalpel to cut off the white matter. Then carefully cut up the brain tissue and mince it with a scalpel for about five minutes. Transfer the brain tissue to the tissue grinder and add 30 milliliters of isolation buffer.Subsequently, homogenize each sample with 100 strokes at 50 rpm. Do no stir in air to prevent bubbles. Document the time every 25 strokes and the total time needed for 100 strokes.Afterward, transfer the homogenate to a Dounce homogenizer on ice. Homogenize the suspension for about 20 strokes and avoid bubbles. Then distribute the brain homogenate equally into four 50 milliliter centrifugation tubes.And document the total volume of the homogenate. Ensure to add the correct volume of Ficoll. Too little or too much Ficoll will result in an incorrect density to separate capillaries from cellular debris and thus will reduce the capillary palette and limit the yield.Use 10 milliliters of isolation buffer to rinse the pestle and homogenizer and distribute it into the four centrifugation tubes. Next, distribute 50 milliliters of density gradient buffer into the centrifugation tubes. Tightly close the centrifuge tubes with caps.Afterward mix the homogenate, density gradient medium and buffer by vigorously shaking the tubes. Centrifuge at 5, 800 times gravity for 15 minutes at four degrees Celsius. Subsequently, discard the supernatant and resuspend each pellet in two milliliters of 1%BSA.After resuspending the pellet, filter the suspension through the 300 micrometer mesh. Capillaries are filtered through the mesh, whereas larger vessels and larger brain debris remain on the mesh. Carefully wash the mesh with up to 50 milliliters of 1%BSA.Then discard the mesh. To separate the capillaries from red blood cells and other brain debris, distribute the capillary filtrate over five 30 micrometer cell strain filters. Capillaries are held back by this filter, whereas red blood cells, other single cells and small brain debris pass through the filter and are collected in the filtrate.Next wash each filter with 25 milliliters of 1%BSA. Pour all filtrates over the sixth filter to increase the yield. Wash each filter with 50 milliliters of 1%BSA.Keep the cell strain filters containing the capillaries and discard the filtrate. Then turn the filters upside down and wash the capillaries with 50 milliliters of 1%BSA into 50 milliliter tubes. Gently apply pressure with the pipette tip and move it across the filter to wash off the brain capillaries.Make sure to wash off all brain capillaries especially from the rim of the filter. Avoid bubbles, since this makes the filtration process more difficult and increases the chance of capillary loss. After collecting the capillaries, centrifuge all the samples at 1, 500 times gravity for three minutes at four degrees Celsius.Remove the supernatant and resuspend the pellet in approximately three milliliters of isolation buffer. Then combine all resuspended pellets from one sample in a 15 milliliter conical tube and fill it with isolation buffer. Centrifuge again at 1, 500 times gravity for three minutes at four degrees Celsius and wash two more times.Document the capillary purity with a microscope at 100 times magnification and camera. The isolated brain capillaries can now be used for experiments, processed or be flash-frozen and stored at minus 80 degrees Celsius in cryotubes for a minimum of six to 12 months. This figure shows a representative transmitted light image of a human brain capillary with an attached pericyte and a red blood cell in the lumen.The isolated human brain capillary was immunostained for PGP using C219 as the primary antibody and the nuclei were counterstained with DAPI. While attempting this procedure, it's important to remember to avoid loss of capillaries during pipetting and filtration steps to ensure a good capillary yield. Following this procedure, isolated human brain capillaries can be utilized for a wide range of studies such as pharmacological and physiological studies, as well as genomic, proteomic and cellomic studies.This technique paved the way for researchers in the blood-brain barrier field to study barrier function in human brain capillaries as close to the human in vivo situation as possible. Don't forget that working with human brain tissue poses the risk of infection from blood-borne pathogens. Safety precautions should be taken, such as wearing a lab coat, face shield and gloves, as well as handling tissue samples in a BSL-2 setting while performing this procedure.

isolation-of-cerebral-capillaries-from-fresh-human-brain-tissue

Research

JoVE Journal

Neuroscience

12.4K vistas.  University of Kentucky. This method can help answer key questions in the field of blood-brain barrier research, such as blood-brain barrier dysfunction, barrier leakage and signaling pathways that are specific for the human blood-brain barrier. The main advantage of this technique is that it allows the study of intact, physiologically active human brain capillaries that have been isolated from fresh human brain tissue. To begin this procedure, document the weight of the human brain tissue, which should be about 10 g...