This work was supported by the J.B. Marshall Foundation.

1. Prepare Animal and Equipment for Procedure
<ol>
	<li>Before beginning surgery, prepare the surgical area and the animal. Make the carotid catheter by inserting a 23-gauge blunt needle into one end of 12" of PE50 tubing. Cut an approximately 45&deg; bevel in the opposite end of the catheter. Sterilize equipment prior to the procedure. Wear a hair bonnet, surgical mask, and sterile gloves.</li>
	<li>Place a heating pad on the surface where the surgery will be performed. Activate it and allow it to warm. Cover the area with an absorbent bench pad.</li>
	<li>Verify that you have 25% mannitol in solution without crystals. If crystals are present, dissolve them by placing the vial in a hot water bath at 80 &deg;C and agitating periodically.</li>
	<li>Record the mass of the animal.</li>
	<li>Make a propofol dilution for delivery at 0.8 mg/kg/min at a rate of 0.1 ml/min.</li>
	<li>Place the rat in the induction box for 3 min. Settings: 5% isoflurane, 2 L/min flow rate on ventilator.</li>
	<li>On top of a disposable towel, shave the neck and both inner thighs.</li>
</ol>
2. Intubate the Rat
<ol>
	<li>Place the animal back in the induction box for 3 min.</li>
	<li>Prepare your endotracheal tube with an IV catheter. For this size and strain of rat, we use an 18 ga catheter. The tube must be large enough to allow adequate airflow, but small enough to fit into the trachea without causing damage. Pull the needle out of the plastic catheter and carefully break the needle approx. 1 cm from its sharp tip. The bunted needle will be your stylus. Put the needle back into the catheter.</li>
	<li>Hang the rat by its teeth on an angled surface.</li>
	<li>Shine a light directly against the animal's neck and lined up between its ears.</li>
	<li>Insert a small spatula approx. 3 cm into the oropharynx. Lift upward while gently pulling the tongue out of the mouth.</li>
	<li>Visualize the opening of the trachea. You will see a small hole open and close with each breath.</li>
	<li>Gently insert catheter into the hole. You can sometimes feel the plastic enter the cartilage of the trachea. The trachea is sensitive. Do not force the catheter.</li>
	<li>Set the ventilator to 1 L/min and 60 bpm and the isoflurane to 2%.</li>
	<li>Connect the catheter to the ventilator and tape the tube to the operating surface.</li>
	<li>Verify the animal is anesthetized by performing a toe pinch.</li>
</ol>
3. Establish Propofol IV Anesthesia
<ol>
	<li>Secure the rat by taping all four limbs and the tail to the operating surface.</li>
	<li>Scrub the shaved neck and groin sites with chlorhexidine soap three times. Then scrub with chlorhexidine rinse three times.</li>
	<li>Attach a syringe of propofol to an IV extension set. Mount the syringe on an infusion pump.</li>
	<li>Using a scalpel, cut through the skin of the shaved thigh. Avoid cutting muscle.</li>
	<li>Open the incision with forceps to visualize the femoral vein.</li>
	<li>Pull away tissue over the artery to expose the vessel.</li>
	<li>Insert a 26 ga monoject veterinary IV catheter into vein. When the needle punctures the wall of the vein you will feel it become easier to push. Retract the needle and push the catheter into the vessel.</li>
	<li>Start the propofol infusion at 0.1 ml/min.</li>
	<li>3-5 min after beginning the propofol infusion, switch the anesthesia gas to a mixture of 50% O2 and 50% N2O and shut off the isoflurane.</li>
</ol>
4. Expose the Bifurcation of the Common Carotid Artery
<ol>
	<li>Make a midline incision at the neck with scalpel blade.</li>
	<li>Cut between the two large salivary glands with scissors or scalpel.</li>
	<li>Dissect away tissue lateral to the midline to expose the carotid artery. Use forceps to open layers of tissue. You can use scissors to remove pieces that you expose with the forceps and determine to be minimally vascular. Control bleeding with gauze, cotton swabs, and cautery if necessary.</li>
	<li>Inject 3 ml saline IP if there has been moderate to heavy bleeding.</li>
	<li>Use retractors to pull tissue away from the carotid. Find the bifurcation.</li>
	<li>Expose the occipital artery just distal to the bifurcation. Cauterize it between forceps and separate it with an electrocautery.</li>
	<li>Use forceps to fully expose the carotid bifurcation and as much of the ECA as possible.</li>
	<li>Expose the superior thyroid artery branching off the ECA distal to the occipital artery. Cauterize it between forceps and separate it with an electrocautery.</li>
</ol>
5. Catheterize the External Carotid Artery
<ol>
	<li>Place 2 lengths of 4/0 silk under the ECA.</li>
	<li>Grab 1 length of suture with your hemostat and retract the ECA back caudally (toward the rat's feet).</li>
	<li>Take the other suture and tie as far cranially (toward the rat's mouth) as possible with a surgeon's knot. This forms a permanent ligature to sacrifice the ECA.</li>
	<li>Remove the first hemostat (the one that was applying caudal tension) and grab the other suture (the one that is knotted around the ECA) and apply gentle tension cranially with the hemostat.</li>
	<li>Tie another surgeon's knot loosely (do not secure - leave barely tied) distal to the bifurcation and proximal to the permanent ligature.</li>
	<li>Irrigate with 1% lidocaine to relax the artery.</li>
	<li>Fill your catheter with heparinized saline.</li>
	<li>Place a temporary vessel clip as close as possible to the bifurcation. Place vessel clip at an angle to maximize space for catheterization. Slide the loose knot toward the clip.</li>
	<li>Make a small arteriotomy (cut) in ECA just proximal to the ligature using microscissors. There should be no bleeding if the clip and ligature are secure.</li>
	<li>Using forceps to control the ECA walls, feed the beveled end of the catheter into the vessel.</li>
	<li>Secure the catheter with the loose suture knot. Tie the artery around the catheter.</li>
	<li>Remove the clip and clean the area with a cotton swab.</li>
	<li>Advance the catheter to about 1 mm distal to bifurcation. Hold the artery with forceps proximal to the knot to ensure the vessel is immobilized.</li>
</ol>
6. Administer Mannitol
<ol>
	<li>Fill an 8" IV extension set and a 6 ml syringe with mannitol without creating any air bubbles. Store this in the incubator at 37 &deg;C. Note: work quickly with mannitol - it will readily precipitate out of solution at room temperature.</li>
	<li>In order to visualize BBBD, you may administer Evans blue dye and watch it enter the areas of the brain where the barrier has been disrupted. To do this, give the animal 2 ml/kg of 2% Evans Blue through a new IV site on leg contralateral to the propofol infusion.</li>
	<li>Attach the extension set to a 5 &mu;m filter and fill it with mannitol to remove air bubbles. Then, attach this to the stopcock without creating bubbles.</li>
	<li>Administer mannitol at 0.09 ml/sec for 25 sec. Watch for the mannitol to reach equilibrium with the flow in common carotid at a point just proximal to the ICA. It should appear to pulse with the rat's heart rate. If the mannitol simply flows down toward the heart you have overcome the rat's blood pressure. This can cause life-threatening complications and poor BBBD.</li>
</ol>

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	<li>Abbott, N. J., Patabendige, A. A. K., Dolman, D. E. M., Yusof, S. R., Begley, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+and+function+of+the+blood-brain+barrier.">Structure and function of the blood-brain barrier.</a> Neurobiology of disease. 37, 13-25 (2010).</li><li>Smith, Q. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Blood-Brain+Barrier.">The Blood-Brain Barrier.</a> 89, 193-208 (2003).</li><li>Kroll, R. A., Neuwelt, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Outwitting+the+blood-brain+barrier+for+therapeutic+purposes:+osmotic+opening+and+other+means.">Outwitting the blood-brain barrier for therapeutic purposes: osmotic opening and other means.</a> Neurosurgery. 42, 1083 (1998).</li><li>Kroll, R. A., Pagel, M. A., Muldoon, L. L., Roman-Goldstein, S., Neuwelt, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increasing+volume+of+distribution+to+the+brain+with+interstitial+infusion:+dose,+rather+than+convection,+might+be+the+most+important+factor.">Increasing volume of distribution to the brain with interstitial infusion: dose, rather than convection, might be the most important factor.</a> Neurosurgery. 38, 746-754 (1996).</li><li>Butt, A. M., Jones, H. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+histamine+and+antagonists+on+electrical+resistance+across+the+blood-brain+barrier+in+rat+brain-surface+microvessels.">Effect of histamine and antagonists on electrical resistance across the blood-brain barrier in rat brain-surface microvessels.</a> Brain research. 569, 100-105 (1992).</li><li>Inamura, T., Black, K. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bradykinin+selectively+opens+blood-tumor+barrier+in+experimental+brain+tumors.">Bradykinin selectively opens blood-tumor barrier in experimental brain tumors.</a> Journal of Cerebral Blood Flow &amp; Metabolism. 14, 862-870 (1994).</li><li>Matsukado, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+tumor+uptake+of+carboplatin+and+survival+in+glioma-bearing+rats+by+intracarotid+infusion+of+bradykinin+analog,+RMP-7.">Enhanced tumor uptake of carboplatin and survival in glioma-bearing rats by intracarotid infusion of bradykinin analog, RMP-7.</a> Neurosurgery. 39, 125 (1996).</li><li>Kroll, R. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improving+drug+delivery+to+intracerebral+tumor+and+surrounding+brain+in+a+rodent+model:+a+comparison+of+osmotic+versus+bradykinin+modification+of+the+blood-brain+and/or+blood-tumor+barriers.">Improving drug delivery to intracerebral tumor and surrounding brain in a rodent model: a comparison of osmotic versus bradykinin modification of the blood-brain and/or blood-tumor barriers.</a> Neurosurgery. 43, 879 (1998).</li><li>Kinoshita, M., McDannold, N., Jolesz, F. A., Hynynen, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Noninvasive+localized+delivery+of+Herceptin+to+the+mouse+brain+by+MRI-guided+focused+ultrasound-induced+blood-brain+barrier+disruption.">Noninvasive localized delivery of Herceptin to the mouse brain by MRI-guided focused ultrasound-induced blood-brain barrier disruption.</a> Proceedings of the National Academy of Sciences. 103, 11719-11723 (2006).</li><li>Neuwelt, E. A., Dahlborg, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemotherapy+administered+in+conjunction+with+osmotic+blood-brain+barrier+modification+in+patients+with+brain+metastases.">Chemotherapy administered in conjunction with osmotic blood-brain barrier modification in patients with brain metastases.</a> Journal of neuro-oncology. 4, 195-207 (1987).</li><li>Doolittle, N. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safety+and+efficacy+of+a+multicenter+study+using+intraarterial+chemotherapy+in+conjunction+with+osmotic+opening+of+the+blood-brain+barrier+for+the+treatment+of+patients+with+malignant+brain+tumors.">Safety and efficacy of a multicenter study using intraarterial chemotherapy in conjunction with osmotic opening of the blood-brain barrier for the treatment of patients with malignant brain tumors.</a> Cancer. 88, 637-647 (2000).</li><li>Guillaume, D. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intra-arterial+chemotherapy+with+osmotic+blood-brain+barrier+disruption+for+aggressive+oligodendroglial+tumors:+results+of+a+phase+I+study.">Intra-arterial chemotherapy with osmotic blood-brain barrier disruption for aggressive oligodendroglial tumors: results of a phase I study.</a> Neurosurgery. 66, 48 (2010).</li><li>Remsen, L. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+anesthetic+choice,+PaCO2,+and+other+factors+on+osmotic+blood-brain+barrier+disruption+in+rats+with+brain+tumor+xenografts.">The influence of anesthetic choice, PaCO2, and other factors on osmotic blood-brain barrier disruption in rats with brain tumor xenografts.</a> Anesthesia &amp; Analgesia. 88, 559-559 (1999).</li><li>Nilaver, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Delivery+of+herpesvirus+and+adenovirus+to+nude+rat+intracerebral+tumors+after+osmotic+blood-brain+barrier+disruption.">Delivery of herpesvirus and adenovirus to nude rat intracerebral tumors after osmotic blood-brain barrier disruption.</a> Proceedings of the National Academy of Sciences. 92, 9829 (1995).</li><li>Fortin, D., McCormick, C. I., Remsen, L. G., Nixon, R., Neuwelt, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unexpected+neurotoxicity+of+etoposide+phosphate+administered+in+combination+with+other+chemotherapeutic+agents+after+blood-brain+barrier+modification+to+enhance+delivery,+using+propofol+for+general+anesthesia,+in+a+rat+model.">Unexpected neurotoxicity of etoposide phosphate administered in combination with other chemotherapeutic agents after blood-brain barrier modification to enhance delivery, using propofol for general anesthesia, in a rat model.</a> Neurosurgery. 47, 199 (2000).</li><li>Neuwelt, E. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Primary+CNS+lymphoma+treated+with+osmotic+blood-brain+barrier+disruption:+prolonged+survival+and+preservation+of+cognitive+function.">Primary CNS lymphoma treated with osmotic blood-brain barrier disruption: prolonged survival and preservation of cognitive function.</a> Journal of clinical oncology. 9, 1580 (1991).</li><li>Remsen, L. G., Trail, P. A., Hellstr&#246;m, I., Hellstr&#246;m, K. E., Neuwelt, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+delivery+improves+the+efficacy+of+a+tumor-specific+doxorubicin+immunoconjugate+in+a+human+brain+tumor+xenograft+model.">Enhanced delivery improves the efficacy of a tumor-specific doxorubicin immunoconjugate in a human brain tumor xenograft model.</a> Neurosurgery. 46, 704 (2000).</li><li>Neuwelt, E. A., Pagel, M. A., Kraemer, D. F., Peterson, D. R., Muldoon, L. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+marrow+chemoprotection+without+compromise+of+chemotherapy+efficacy+in+a+rat+brain+tumor+model.">Bone marrow chemoprotection without compromise of chemotherapy efficacy in a rat brain tumor model.</a> Journal of Pharmacology and Experimental Therapeutics. 309, 594-599 (2004).</li></ol>

No conflicts of interest declared.

There are a few means of maximizing the efficacy of BBBD. It is important to minimize bleeding during the cut-down phase. Blood pressure and heart rate can be affected by substantial bleeding and these factors are known to affect the degree of BBBD13. Bleeding can be reduced by using sutures to ligate major vessels, such as the superior thyroid and occipital arteries, which must be divided. Additionally, electrocautery can be used to divide vessels and dissect areas that have a rich blood supply. It is also im...

<table><tbody><tr><td>Long Evans rat</td><td>Harlan Laboratories</td><td></td><td>210-250 g, male</td></tr><tr><td>PE 50 Tubing</td><td>Beckton-Dickinson</td><td></td><td></td></tr><tr><td>18 gauge x 2.5&quot; IV catheter</td><td>Terumo</td><td></td><td>For ET tube</td></tr><tr><td>30&quot; IV extension sets</td><td>Abbott</td><td></td><td></td></tr><tr><td>26 gauge veterinary IV catheter</td><td>Monoject</td><td></td><td></td></tr><tr><td>Evans blue dye</td><td>Sigma</td><td>E2129</td><td></td></tr><tr><td>Bipolar</td><td>Codman</td><td></td><td></td></tr><tr><td>Filter, 5 &amp;mu;m</td><td>Braun</td><td></td><td></td></tr></tbody></table>

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.

<img alt="Figure 1" src="/files/ftp_upload/50019/50019fig1.jpg" /> 
Figure 1. Visualizing blood-brain barrier disruption via Evans blue dye extravasation. Evans blue dye is a pigment that binds to albumin and is not extravasated into the brain under physiological conditions. Disruption of the blood-brain barrier on one side of the brain allows Evans blue to enter and stain the disrupted hemisphere blue while the non-disrupted hemisphere remains unchanged. Thus...

Watch this Scientific Journal Video about Rat Model of Blood-brain Barrier Disruption to Allow Targeted Neurovascular Therapeutics at JoVE.com

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

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 ...

rat-model-blood-brain-barrier-disruption-to-allow-targeted

Research

JoVE Journal

Medicine

19.3K Views.  Vanderbilt University School of Medicine. 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.

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

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

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

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

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

Cancer Research

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

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

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

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

Bioengineering

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

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

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

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

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

Generation of a Human iPSC-Based Blood-Brain Barrier Chip

The blood brain barrier (BBB) is formed by neurovascular units (NVUs) that shield the central nervous system (CNS) from a range of factors found in the blood that can disrupt delicate brain function. As such, the BBB is a major obstacle to the delivery of therapeutics to the CNS. Accumulating evidence suggests that the BBB plays a key role in the onset and progression of neurological diseases. Thus, there is a tremendous need for a BBB model that can predict penetration of CNS-targeted drugs as well as elucidate the BBB&#39;s role in health and disease.
We have recently combined organ-on-chip and induced pluripotent stem cell (iPSC) technologies to generate a BBB chip fully personalized to humans. This novel platform displays cellular, molecular, and physiological properties that are suitable for the prediction of drug and molecule transport across the human BBB. Furthermore, using patient-specific BBB chips, we have generated models of neurological disease and demonstrated the potential for personalized predictive medicine applications. Provided here is a detailed protocol demonstrating how to generate iPSC-derived BBB chips, beginning with differentiation of iPSC-derived brain microvascular endothelial cells (iBMECs) and resulting in mixed neural cultures containing neural progenitors, differentiated neurons, and astrocytes. Also described is a procedure for seeding cells into the organ chip and culturing of the BBB chips under controlled laminar flow. Lastly, detailed descriptions of BBB chip analyses are provided, including paracellular permeability assays for assessing drug and molecule permeability as well as immunocytochemical methods for determining the composition of cell types within the chip.

The blood-brain barrier (BBB) is a multicellular neurovascular unit tightly regulating brain homeostasis. By combining human iPSCs and organ-on-chip technologies, we have generated a personalized BBB chip, suitable for disease modeling and CNS drug penetrability predictions. A detailed protocol is described for the generation and operation of the BBB chip.

The blood brain barrier (BBB) is formed by neurovascular units (NVUs) that shield the central nervous system (CNS) from a range of factors found in the ...

Developmental Biology

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

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

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

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

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

Neuroscience

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

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

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

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

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

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

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

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

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

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

A Human Blood-Brain Interface Model to Study Barrier Crossings by Pathogens or Medicines and Their Interactions with the Brain

The early screening of nervous system medicines on a pertinent and reliable in cellulo BBB model for their penetration and their interaction with the barrier and the brain parenchyma is still an unmet need. To fill this gap, we designed a 2D in cellulo model, the BBB-Minibrain, by combining a polyester porous membrane culture insert human BBB model with a Minibrain formed by a tri-culture of human brain cells (neurons, astrocytes and microglial cells). The BBB-Minibrain allowed us to test the transport of a neuroprotective drug candidate (e.g., Neurovita), through the BBB, to determine the specific targeting of this molecule to neurons and to show that the neuroprotective property of the drug was preserved after the drug had crossed the BBB. We have also demonstrated that BBB-Minibrain constitutes an interesting model to detect the passage of virus particles across the endothelial cells barrier and to monitor the infection of the Minibrain by neuroinvasive virus particles. The BBB-Minibrain is a reliable system, easy to handle for researcher trained in cell culture technology and predictive of the brain cells phenotypes after treatment or insult. The interest of such in cellulo testing would be twofold: introducing derisking steps early in the drug development on the one hand and reducing the use of animal testing on the other hand.

Here we present a protocol describing the setting of an in cellulo BBB (Blood brain barrier)-Minibrain polyester porous membrane culture insert system in order to evaluate the transport of biomolecules or infectious agents across a human BBB and their physiological impact on the neighboring brain cells.

The early screening of nervous system medicines on a pertinent and reliable in cellulo BBB model for their penetration and their interaction with the ...

A 3D Blood-Brain Barrier Model Derived from Human Pluripotent Stem-Cells

Reconstruction of the Blood-Brain Barrier In Vitro to Model and Therapeutically Target Neurological Disease

The blood-brain barrier (BBB) is a key physiological component of the central nervous system (CNS), maintaining nutrients, clearing waste, and protecting the brain from pathogens. The inherent barrier properties of the BBB pose a challenge for therapeutic drug delivery into the CNS to treat neurological diseases. Impaired BBB function has been related to neurological disease. Cerebral amyloid angiopathy (CAA), the deposition of amyloid in the cerebral vasculature leading to a compromised BBB, is a co-morbidity in most cases of Alzheimer&#39;s disease (AD), suggesting that BBB dysfunction or breakdown may be involved in neurodegeneration. Due to limited access to human BBB tissue, the mechanisms that contribute to proper BBB function and BBB degeneration remain unknown. To address these limitations, we have developed a human pluripotent stem cell-derived BBB (iBBB) by incorporating endothelial cells, pericytes, and astrocytes in a 3D matrix. The iBBB self-assembles to recapitulate the anatomy and cellular interactions present in the BBB. Seeding iBBBs with amyloid captures key aspects of CAA. Additionally, the iBBB offers a flexible platform to modulate genetic and environmental factors implicated in cerebrovascular disease and neurodegeneration, to investigate how genetics and lifestyle affect disease risk. Finally, the iBBB can be used for drug screening and medicinal chemistry studies to optimize therapeutic&#160;delivery to the CNS. In this protocol, we describe the differentiation of the three types of cells (endothelial cells, pericytes, and astrocytes) arising from human pluripotent stem cells, how to assemble the differentiated cells into the iBBB, and how to model CAA in vitro using exogenous amyloid. This model overcomes the challenge of studying live human brain tissue with a system that has both biological fidelity and experimental flexibility, and enables the interrogation of the human BBB and its role in neurodegeneration.

Author Spotlight: A Personalized Approach Towards Investigating Alzheimer's Disease Using an In Vitro Blood-Brain Barrier Model 

The blood-brain barrier (BBB) has a crucial role in sustaining a stable and healthy brain environment. BBB dysfunction is associated with many neurological diseases. We have developed a 3D, stem-cell-derived model of the BBB to investigate cerebrovascular pathology, BBB integrity, and how the BBB is altered by genetics and disease.

The blood-brain barrier (BBB) is a key physiological component of the central nervous system (CNS), maintaining nutrients, clearing waste, and protecting ...

A Triple Culture Cell System Modeling the Human Blood-Brain Barrier

The delivery of drugs to the brain remains a challenge due to the blood-brain barrier's (BBB) highly specific and restrictive properties, which controls and restrict access to the brain parenchyma. However, with the development of nanotechnologies, large panels of new nanomaterials were developed to improve drug delivery, highlighting the need for reliable in vitro microsystems to predict brain penetration in the frame of preclinical assays. Here is a straightforward method to set up a microphysiological system to model the BBB using solely human cells. In its configuration, the model consists of a triple culture including brain-like endothelial cells (BLECs), pericytes, and astrocytes, the three main BBB cellular actors necessary to induce and regulate the BBB properties in a more physiological manner without the requirement of tightening compounds. The model developed in a 12-well plate format, ready after 6 days of triple culture, is characterized in physical properties, gene, and protein expressions and used for polymeric nanogel transport measurement. The model can be used for an extensive range of experiments in healthy and pathological conditions and represents a valuable tool for preclinical assessments of molecule and particle transport, as well as inter-and intracellular trafficking.

This protocol describes a method to establish a human blood-brain barrier (BBB) in vitro model. The endothelial cells and pericytes are seeded on each side of an insert filter (blood compartment), and astrocytes are seeded in the bottom well (brain compartment). The model characterized was used for nanoparticles transport experiments.

The delivery of drugs to the brain remains a challenge due to the blood-brain barrier's (BBB) highly specific and restrictive properties, which controls ...

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

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Chapters in this video

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

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

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

Generation of a Human iPSC-Based Blood-Brain Barrier Chip

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

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

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

A Human Blood-Brain Interface Model to Study Barrier Crossings by Pathogens or Medicines and Their Interactions with the Brain

Reconstruction of the Blood-Brain Barrier In Vitro to Model and Therapeutically Target Neurological Disease

A Triple Culture Cell System Modeling the Human Blood-Brain Barrier