Dr. Cruz-Orengo was supported by the University of California, Davis, School of Veterinary Medicine Start Up Funds.

All procedures of the present study are in accordance with the guidelines set by the University of California (UC), Davis Institutional Animal Care and Use Committee (IACUC). Animal care at UC Davis is regulated by several independent resources and has been fully accredited by the Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC) since 1966. Porcine CNS tissues were obtained from UCD Department of Animal Sciences, Meat Sciences Laboratory. CNS tissues from rhesus macaques were obtained from the California National Primate Research Center Pathology Department (NIH P51OD011107). No anesthesia, euthanasia, or necropsy was performed by laboratory staff on pigs and macaques. Therefore, there are no particular recommendations regarding these matters.
NOTE: This method was validated for multiple species, but the provided protocol corresponds more directly to mouse and porcine tissues. Details pertaining to the optic lobe do not apply when using mammalian specimens. All biohazardous materials must be handled in an appropriate biosafety level (BSL) facility. All acutely toxic materials must be handled underneath a fume hood. All biohazardous medical waste and acutely toxic waste must be disposed of properly.
1. Preparation
<ol>
	<li>Prepare solutions (Table 1) at least one day ahead. 
	NOTE: It is very difficult to dissolve 70 kDa molecular weight (MW) dextran. It is more efficient to let the solution stir overnight covered with either paraffin film or foil. The protocol requires the use two different MV-2 solutions depending on the specimen under investigation. The 18% dextran efficiently separates the myelin from the microvessel pellet when performing the protocol on small lissencephalic specimens. However, it develops a smear of myelin within the interface of CNS tissues from large gyrencephalic specimens, as well as the hypothalamus and the pituitary from small specimens. This smear is prevented by using 20% dextran.</li>
	<li>Prepare well-slides by loading 50 &#181;L per well of poly-D-lysine and let dry for 2 h at room temperature (RT), preferably in a biological safety cabinet-class 2 (BSC-2). Do not overdry. Rinse twice with phosphate-buffered saline (PBS) and keep in the fridge until ready to use.</li>
</ol>
2. CNS Tissue Dissection from Small Lissencephalic Vertebrate Specimen
NOTE: The article demonstrates the application of the protocol on a C57BL6/J, 10 week-old, ~25 g, male mouse.
<ol>
	<li>Prepare two 15 mL conical tubes and a 1.7 mL microcentrifuge tube with 5 mL and 1 mL, respectively, of MV-1 solution per specimen. Keep tubes on ice.</li>
	<li>Anesthetization
	<ol>
		<li>Anesthetize mice by intraperitoneal injection of a ketamine, xylazine, and acepromazine anesthetic cocktail at 100/10/3 mg per kg body weight and spray with 70% ethanol. Confirm anesthesia by assessing the absence of palpebral and pedal reflexes by touching an eye and pinching a foot, respectively.</li>
		<li>Anesthetize pigeons by inhalation of 5% isoflurane using an induction anesthesia box.</li>
		<li>Anesthetize fish and frogs in 1% Tricaine in either a fish holding water tank or amphibian Ringer&#39;s solution (Table of Materials), respectively.</li>
		<li>Anesthetize lizards by cooling at 4 &#176;C prior to euthanasia.</li>
	</ol>
	</li>
	<li>Decapitate the animal with surgical scissors, peel away the skin with forceps to expose the skull, and cut with LaGrange scissors through the foramen magnum (Figure 1A).</li>
	<li>Dissect the brain out with a spatula and transfer to a 15 mL conical tube with MV-1 solution. Keep tube on ice.</li>
	<li>Retrieve the pituitary from the skull&#39;s sella turcica with forceps and transfer to a 1.7 mL microcentrifuge tube with MV-1 solution. Keep tube on ice.</li>
	<li>Remove the skin and muscle to expose the vertebral column. Cut out the limbs, rib cage, and internal organs (Figure 1B).</li>
	<li>Dissect the spinal cord by one of the two methods described below. Then, transfer to a 5 mL conical tube with MV-1 solution. Keep tube on ice.
	<ol>
		<li>Perform laminectomy by cutting in a rostral to caudal direction with LaGrange scissors, starting through the cervical vertebral foramen, until reaching the lumbar cord.</li>
		<li>Perform flushing in a caudal to rostral direction throughout the lumbar vertebral foramen with an 18 G needle and 10 mL syringe loaded with MV-1 solution (Figure 1C,D). 
		NOTE: This method only works with very small specimens, mostly rodents (&#60;100 g).</li>
	</ol>
	</li>
	<li>Using a dissecting scope, cut the dural sac from the spinal cord with spring scissors and remove the remaining meninges with a double-pronged pick (Figure 2).</li>
	<li>Transfer the brain to a Petri dish and, using a dissecting scope, remove the meninges with a double-pronged pick (Figure 2A&#8211;C).</li>
	<li>Excise the olfactory bulbs and thalamus with forceps, iris scissors, and spring scissors. Using the double-pronged pick, remove the choroid plexus from all the brain ventricles. Make sure to remove all the choroid plexus. 
	NOTE: The choroid plexus and olfactory bulbs are a massive source of contamination. In contrast to the BBB, these capillaries are highly fenestrated and the results of the subsequent experiments will be compromised if they are not removed.</li>
	<li>Using forceps, separate the distinct CNS regions: cortex, cerebellum, brainstem, optic lobe (not on mammalian specimens), and hypothalamus.</li>
</ol>
3. CNS Tissue Dissection from a Large Gyrencephalic Vertebrate Specimen
NOTE: This protocol uses porcine CNS tissues obtained from an abattoir. Therefore, no anesthesia, euthanasia, or necropsy is described or shown here.
<ol>
	<li>Transport porcine CNS tissues in a 0.946 L (32 oz) histology container loaded with MV-1 solution inside an ice chest/bucket.</li>
	<li>Using a dissecting scope, remove the meninges with a double-pronged pick, forceps, iris scissors, and spring scissors from each CNS tissue. Make sure to remove any pieces of choroid plexus from the brain ventricles.</li>
</ol>
4. CNS Tissue Homogenization
NOTE: It is more efficient when two investigators engage in the homogenization process: one dissecting the meninges under the stereoscope and the other homogenizing the minced tissues. This way, the tissues are quickly returned to the ice bucket and kept cold.
<ol>
	<li>Place each CNS region on a Petri dish with ~1 mL of MV-1 solution. Using a single-edge blade, mince the tissue to obtain 1&#8211;2 mm pieces.
	<ol>
		<li>For a small vertebrate specimen, use a 100 mm x 20 mm Petri dish.</li>
		<li>For a large vertebrate specimen, use a 150 mm x 15 mm Petri dish.</li>
	</ol>
	</li>
	<li>Homogenization of a small vertebrate specimen (Table 2 and Table 3)
	<ol>
		<li>Transfer the cortex, cerebellum, brainstem, optic lobe, and spinal cord to ~1 mL of MV-1 solution in an individual 10 mL Potter-Elvehjem glass tissue grinder with a PTFE pestle using a transfer pipette. Add 5 mL of MV-1 solution and homogenize each tissue (~10 strokes). Transfer to individual 15 mL conical tubes. Keep tubes on ice. 
		NOTE: For a small vertebrate, 5 or 4, with or without optic lobe, respectively, 10 mL Potter-Elvehjem grinders and 15 mL conical tubes are needed.</li>
		<li>Transfer the hypothalamus and pituitary with forceps to ~100 &#181;L of MV-1 solution in an individual 1.7 mL tube and carefully homogenize with a glass micropestle. Rinse each micropestle with ~1 mL of MV-1 solution. Keep tube on ice. 
		NOTE: For a small vertebrate, 2 glass micropestles and 1.7 mL tubes are needed.</li>
	</ol>
	</li>
	<li>Homogenization of a large vertebrate specimen (Table 4 and Table 5)
	<ol>
		<li>Using a transfer pipette, transfer the minced tissue to a 55 mL Potter-Elvehjem glass tissue grinder with a PTFE pestle and attach to overhead stirrer. Add half of the recommended volume of MV-1 solution, according to the specific CNS portion being homogenized (Table 5).</li>
		<li>Turn on the overhead stirrer at very low speed (~150 rpm) and carefully move the glass tube up and down for about 30 s.</li>
		<li>Turn off overhead stirrer, add more MV-1 solution, and repeat step 4.3.2 until obtaining a homogenous slurry.</li>
		<li>Transfer to a 50 mL conical tube. Keep tube on ice.</li>
		<li>Wash the grinder with deionized water between each CNS tissue homogenization. 
		NOTE: For a large vertebrate 5 or 4, with or without white matter, respectively, 50 mL conical tubes are needed. Likewise, two (2) 15 mL conical tubes are needed for the hypothalamus and pituitary.</li>
	</ol>
	</li>
</ol>
5. Microvessel Purification
<ol>
	<li>Centrifuge tissue homogenates resulting from step 4.2.1, 4.2.2, or 4.3.4 at 2,000 x g for 10 min at 4 &#176;C. A large white interface of myelin will form on the top of the reddish microvessels&#39; pellets. Discard the supernatants.
	<ol>
		<li>Small vertebrate specimen (Table 2 and Table 3)
		<ol>
			<li>Resuspend the cortex, cerebellum, brainstem, optic lobe, and spinal cord pellets in 5 mL of ice-cold MV-2 solution with a 5 mL serological pipette (~10 flushes). Add 5 mL of ice-cold MV-2 solution to each suspension and carefully mix by flipping the tubes.</li>
			<li>Resuspend the hypothalamus and pituitary pellets with 1 mL of MV-2 solution.</li>
		</ol>
		</li>
		<li>Large vertebrate specimen (Table 4 and Table 5)
		<ol>
			<li>Add 20 mL of ice-cold MV-2 solution to the cortex, cerebellum, brainstem, and spinal cord microvessel pellets. Resuspend the pellets by mixing on a tube revolver shaker, stirring at 40 rpm for ~5 min. Balance the conical tubes&#39; volumes of the cortex, cerebellum, brainstem, and spinal cord suspensions by adding more MV-2 solution.</li>
			<li>Resuspend the hypothalamus and pituitary microvessel pellets in 5 mL of MV-2 solution with a 5 mL serological pipette (~10 flushes). Add 5 mL of ice-cold MV-2 solution to the suspensions and carefully mix by flipping the tube.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Centrifuge at 4,400 x g for 15 min at 4 &#176;C.</li>
	<li>Carefully detach the thick and dense myelin layer on the liquid interface from each tube&#39;s walls by slowly rotating the tubes and allowing the supernatant to pass along the walls.</li>
	<li>Discard the myelin and liquid interface and blot the inside wall of each tube with a spatula wrapped with a low-lint paper wipe. For small vertebrate specimens, remove myelin layer from each hypothalamus and pituitary tube by suctioning carefully with a transfer pipette.</li>
	<li>Wipe out excess liquid with a twisted low-lint paper wipe. Resuspend each pellet with 1 mL of MV-3 solution using low-binding tips. Keep tubes on ice.</li>
</ol>
6. Microvessel Elution and Filtration
<ol>
	<li>Pour ice-cold MV-3 solution in individual beakers for each CNS region. Keep at 4 &#176;C.
	<ol>
		<li>For small vertebrate specimens, use 10 mL of MV-3 solution per 50 mL beaker. A total of 6&#8211;7 beakers is necessary depending on whether or not the optic lobe is included.</li>
		<li>For large vertebrate specimens, use 30 mL of MV-3 solution per 100 mL beaker. A total of 6&#8211;7 beakers is necessary depending on whether or not white matter is included.</li>
	</ol>
	</li>
	<li>Place a cell strainer on top of a 50 mL conical tube. Use one per CNS region. Use a 100 &#181;m strainer for the cortex, brainstem, optic lobe, spinal cord, and pituitary. Use a 70 &#181;m cell strainer for the cerebellum and hypothalamus.</li>
	<li>Wet each strainer with 1 mL of ice-cold MV-3 solution.</li>
	<li>Add more MV-3 solution to the suspensions prepared in step 5.5 with a serological pipette while mixing to avoid aggregates. Carefully load microvessels on top of the strainer. Rinse with ice-cold MV-3 solution.
	<ol>
		<li>For small vertebrate specimens (Table 2 and Table 3), add 10&#8211;15 mL of MV-3 solution with a serological pipette and rinse with 5 mL of MV-3 solution.</li>
		<li>For large vertebrate specimens, add 20 mL of MV-3 solution with a serological pipette and rinse with 10 mL of MV-3 solution.</li>
	</ol>
	</li>
	<li>Assemble the filtration unit by placing a 20 &#181;m nylon net filter on a modified filter holder (Figure 2D), one per CNS region.
	<ol>
		<li>For small vertebrate specimens (Table 2 and Table 3), use 25 mm modified filter holders for the cortex, cerebellum, brainstem, optic lobe, and spinal cord. Use 13 mm modified filter holders for the hypothalamus and pituitary.</li>
		<li>For large vertebrate specimens (Table 4 and Table 5), use 47 mm modified filter holders for the cortex, cerebellum, brainstem, and spinal cord. Use 25 mm for the hypothalamus and pituitary.</li>
	</ol>
	</li>
	<li>Place filter on top of a 50 mL conical tube and wet filter with 5 mL of ice-cold MV-3 solution making sure buffer pours down the filter holder to the conical tube.</li>
	<li>Transfer the eluted microvessels (from step 6.4) on top of the 20 &#181;m nylon net filter and rinse the microvessels with 5&#8211;10 mL of ice-cold MV-3 solution.</li>
	<li>Recover the filter using clean forceps and immerse it in the beaker containing the ice-cold MV-3 solution prepared in step 6.1.</li>
	<li>Detach the microvessels from the filter by shaking it gently for about 30 s. For small vertebrate specimens, pour the beaker content in a 15 mL conical tube. For large vertebrate specimens, pour the beaker content in a 50 mL conical tube.</li>
	<li>Centrifuge at 2,000 x g for 5 min at 4 &#176;C and resuspend the pellet in 1 mL of ice-cold MV-3 solution using a low-binding pipette tip.
	<ol>
		<li>For small vertebrate specimens, transfer the suspension (from step 6.10) into a 1.7 mL microcentrifuge tube and centrifuge at 20,000 x g for 5 min at 4 &#176;C. 
		NOTE: This spin is performed on a benchtop centrifuge at maximum speed (~20,000 x g) to ensure a robust yield.</li>
		<li>For large vertebrate specimens, transfer the suspension from step 6.10 into a 5.0 mL microcentrifuge tube, add 4 mL of MV-3 solution, and centrifuge at 2,000 x g for 5 min at 4 &#176;C.</li>
	</ol>
	</li>
</ol>
7. Immunostaining
NOTE: Hematoxylin and eosin (H&#38;E) staining was performed on reptile, amphibian, and fish specimens as a proof-of-concept of the protocol feasibility. Therefore, there is no recommendation for immunolabeling for these specimens.
<ol>
	<li>Remove the supernatant from the microcentrifuge tubes.</li>
	<li>Resuspend the pellet in 1x sterile PBS using a low-binding pipette tip (Table of Materials). Keep the microvessels from forming aggregates by pipetting multiple times. For small vertebrate specimens (Table 3), use ~100 &#181;L&#8211;2,000 &#181;L according to the pellet size. For large vertebrate specimens (Table 5), use ~1,000 &#181;L&#8211;4,000 &#181;L according to the pellet size.</li>
	<li>Using a low-binding pipette tip, transfer the microvessels to well slides, being careful to add them to the center of each well, avoiding the sidewalls.</li>
	<li>Set the well slides, uncovered, inside a BSC-2, and let dry for 20 to 30 min at RT. 
	NOTE: A relatively high volume of 1x PBS is used to avoid aggregate formation. Because of this, it is necessary to let the slides dry prior to fixation to make sure the microvessels are being held by the poly-D-lysine coating.</li>
	<li>Remove residual 1x PBS by pipetting out with a transfer pipette, add 200 &#181;L of 4% paraformaldehyde (PFA) and incubate for 30 min at RT.</li>
	<li>Pipette out the fixative solution and wash 3x with 200 &#181;L of 1x PBS for 5 min at RT. 
	NOTE: H&#38;E staining on fish, amphibian, and reptile CNS microvessels was performed at this point.</li>
	<li>Add 200 &#181;L of blocking buffer to the well slide and incubate for 60 min at 37 &#176;C.</li>
	<li>Remove the blocking buffer with a transfer pipette and add 200 &#181;L of the primary antibody cocktail in antibody diluent (Table of Materials). Incubate at 4 &#176;C overnight.</li>
	<li>Pipette out the primary antibody cocktail and wash 3x with 200 &#181;L of 1x PBS for 5 min at RT.</li>
	<li>Load the secondary antibody cocktail (Table of Materials) diluted in 1x PBS and incubate for 2 h at RT, protected from light.</li>
	<li>Pipette out the secondary antibody cocktail and wash 3x with 200 &#181;L of 1x PBS for 5 min at RT, protected from light. After the last wash detach the well-slide&#39;s frame and blot-dry any excess 1x PBS with a low lint paper wipe.</li>
	<li>Add a coverslip, liquid antifade mountant medium, and 4&#8242;,6-diamidino-2-phenylindole (DAPI) for nuclear staining. Let dry overnight at RT protected from light.</li>
	<li>Once dry, keep protected from light on a slide box at 4 &#176;C until ready for confocal microscopy and data acquisition.</li>
</ol>

<ol>
	<li>Bundgaard, M., Abbott, N. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=All+vertebrates+started+out+with+a+glial+blood-brain+barrier+4-500+million+years+ago.">All vertebrates started out with a glial blood-brain barrier 4-500 million years ago.</a> Glia. 56, 699-708 (2008).</li><li>Daneman, R., Prat, A. <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> Cold Spring Harbor Perspectives in Biology. 7, a020412 (2015).</li><li>Obermeier, B., Verma, A., Ransohoff, R. M. <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> Handbook of Clinical Neurology. 133, 39-59 (2016).</li><li>Kealy, J., Greene, C., Campbell, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blood-brain+barrier+regulation+in+psychiatric+disorders.">Blood-brain barrier regulation in psychiatric disorders.</a> Neuroscience Letters. , (2018).</li><li>Sweeney, M. D., Kisler, K., Montagne, A., Toga, A. W., Zlokovic, B. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+brain+vasculature+in+neurodegenerative+disorders.">The role of brain vasculature in neurodegenerative disorders.</a> Nature Neuroscience. 21, 1318-1331 (2018).</li><li>Sweeney, M. D., Zhao, Z., Montagne, A., Nelson, A. R., Zlokovic, B. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blood-Brain+Barrier:+From+Physiology+to+Disease+and+Back.">Blood-Brain Barrier: From Physiology to Disease and Back.</a> Physiological Reviews. 99, 21-78 (2019).</li><li>Wilhelm, I., Nyul-Toth, A., Suciu, M., Hermenean, A., Krizbai, I. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heterogeneity+of+the+blood-brain+barrier.">Heterogeneity of the blood-brain barrier.</a> Tissue Barriers. 4, e1143544 (2016).</li><li>O'Brown, N. M., Pfau, S. J., Gu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bridging+barriers:+a+comparative+look+at+the+blood-brain+barrier+across+organisms.">Bridging barriers: a comparative look at the blood-brain barrier across organisms.</a> Genes &amp; Development. 32, 466-478 (2018).</li><li>Cruz-Orengo, L., 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=CXCR7+influences+leukocyte+entry+into+the+CNS+parenchyma+by+controlling+abluminal+CXCL12+abundance+during+autoimmunity.">CXCR7 influences leukocyte entry into the CNS parenchyma by controlling abluminal CXCL12 abundance during autoimmunity.</a> Journal of Experimental Medicine. 208, 327-339 (2011).</li><li>Serres, S., 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=VCAM-1-targeted+magnetic+resonance+imaging+reveals+subclinical+disease+in+a+mouse+model+of+multiple+sclerosis.">VCAM-1-targeted magnetic resonance imaging reveals subclinical disease in a mouse model of multiple sclerosis.</a> FASEB Journal. 25, 4415-4422 (2011).</li><li>Tietz, S., Engelhardt, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Brain+barriers:+Crosstalk+between+complex+tight+junctions+and+adherens+junctions.">Brain barriers: Crosstalk between complex tight junctions and adherens junctions.</a> Journal of Cell Biology. 209, 493-506 (2015).</li><li>Sohet, F., 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=LSR/angulin-1+is+a+tricellular+tight+junction+protein+involved+in+blood-brain+barrier+formation.">LSR/angulin-1 is a tricellular tight junction protein involved in blood-brain barrier formation.</a> Journal of Cell Biology. 208, 703-711 (2015).</li><li>Cruz-Orengo, L., 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+sphingosine-1-phosphate+receptor+2+expression+underlies+female+CNS+autoimmunity+susceptibility.">Enhanced sphingosine-1-phosphate receptor 2 expression underlies female CNS autoimmunity susceptibility.</a> Journal of Clinical Investigation. 124, 2571-2584 (2014).</li><li>Dayton, J. R., Franke, M. C., Yuan, Y., Cruz-Orengo, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Straightforward+method+for+singularized+and+region-specific+CNS+microvessels+isolation.">Straightforward method for singularized and region-specific CNS microvessels isolation.</a> Journal of Neuroscience Methods. 318, 17-33 (2019).</li><li>Smyth, L. C. 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=Markers+for+human+brain+pericytes+and+smooth+muscle+cells.">Markers for human brain pericytes and smooth muscle cells.</a> Journal of Chemical Neuroanatomy. 92, 48-60 (2018).</li><li>Granberg, T., 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=In+vivo+characterization+of+cortical+and+white+matter+neuroaxonal+pathology+in+early+multiple+sclerosis.">In vivo characterization of cortical and white matter neuroaxonal pathology in early multiple sclerosis.</a> Brain. 140, 2912-2926 (2017).</li><li>Datta, 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=Neuroinflammation+and+its+relationship+to+changes+in+brain+volume+and+white+matter+lesions+in+multiple+sclerosis.">Neuroinflammation and its relationship to changes in brain volume and white matter lesions in multiple sclerosis.</a> Brain. 140, 2927-2938 (2017).</li><li>Tommasin, S., Gianni, C., De Giglio, L., Pantano, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuroimaging+Techniques+to+Assess+Inflammation+in+Multiple+Sclerosis.">Neuroimaging Techniques to Assess Inflammation in Multiple Sclerosis.</a> Neuroscience. 403, 4-16 (2019).</li><li>Liebner, S., 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=Functional+morphology+of+the+blood-brain+barrier+in+health+and+disease.">Functional morphology of the blood-brain barrier in health and disease.</a> Acta Neuropathologica. 135, 311-336 (2018).</li><li>Cornford, E., Hyman, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Localization+of+brain+endothelial+luminal+and+abluminal+transporters+with+immunogold+electron+microscopy.">Localization of brain endothelial luminal and abluminal transporters with immunogold electron microscopy.</a> NeuroRx. 2, 27-43 (2005).</li><li>Boulay, A. C., Saubamea, B., Decleves, X., Cohen-Salmon, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Purification+of+Mouse+Brain+Vessels.">Purification of Mouse Brain Vessels.</a> Journal of Visualized Experiments. , 53208 (2015).</li><li>Paul, D., Cowan, A. E., Ge, S., Pachter, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Novel+3D+analysis+of+Claudin-5+reveals+significant+endothelial+heterogeneity+among+CNS+microvessels.">Novel 3D analysis of Claudin-5 reveals significant endothelial heterogeneity among CNS microvessels.</a> Microvascular Research. , (2012).</li><li>Munikoti, V. V., Hoang-Minh, L. B., Ormerod, B. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enzymatic+digestion+improves+the+purity+of+harvested+cerebral+microvessels.">Enzymatic digestion improves the purity of harvested cerebral microvessels.</a> Journal of Neuroscience Methods. 207, 80-85 (2012).</li><li>Yousif, S., Marie-Claire, C., Roux, F., Scherrmann, J. M., Decleves, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+of+drug+transporters+at+the+blood-brain+barrier+using+an+optimized+isolated+rat+brain+microvessel+strategy.">Expression of drug transporters at the blood-brain barrier using an optimized isolated rat brain microvessel strategy.</a> Brain Research. 1134, 1-11 (2007).</li><li>Bourassa, P., Tremblay, C., Schneider, J. A., Bennett, D. A., Calon, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Beta-amyloid+pathology+in+human+brain+microvessel+extracts+from+the+parietal+cortex:+relation+with+cerebral+amyloid+angiopathy+and+Alzheimer's+disease.">Beta-amyloid pathology in human brain microvessel extracts from the parietal cortex: relation with cerebral amyloid angiopathy and Alzheimer's disease.</a> Acta Neuropathologica. 137, 801-823 (2019).</li><li>Porte, B., 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=Proteomic+and+transcriptomic+study+of+brain+microvessels+in+neonatal+and+adult+mice.">Proteomic and transcriptomic study of brain microvessels in neonatal and adult mice.</a> PLoS One. 12, e0171048 (2017).</li></ol>

The authors have nothing to disclose.

The BBB includes the unique properties of the brain microvasculature endothelial cells coupled by a sophisticated architecture of tight-, adherens-, &#34;peg-socket&#34;- junctions, and adhesion plaques critical for CNS homeostasis2,3,19. Endothelial cells properties are induced and maintained by pericytes and the surrounding astroglia end-foot processes2,3,<s...

Our brain is the most important organ in our body. For this reason, keeping brain homeostasis despite external factors that may trigger a deviation from normalcy is a priority. According to some scholars, about 400&#8211;500 million years ago1, vertebrate animals developed what we now know as the blood-brain barrier (BBB)2,3. This protective &#34;fence&#34; exerts the greatest influence over central nervous system (CNS) homeostasis and functions by tightly regulating the transport of ions, molecules, and cells between blood and CNS parenchyma. When the BBB is disrupted, the brain becomes susceptible to toxic exposure, infection, and inflammation. Therefore, BBB dysfunction is associated with many, if not all, neurological and neurodevelopmental disorders4,5,6.
The sophisticated function of the BBB is attributed to the unique CNS microvasculature conformed by the neurovascular unit (NVU)2,3. Highly specialized endothelial cells, pericytes, and astrocytic end-feet are the cellular components of the NVU2,3. The extracellular matrix generated by these cells is also essential to the NVU and BBB physiology2,3. Although essential cellular and molecular components of the NVU are conserved among vertebrates, heterogeneity is reported among orders and species7,8. However, technical limitations impede our ability to fully consider these differences in neurobiology, biomedical, or translational research.
Because of this, we expanded a CNS region-specific microvessel-isolation method to make it applicable to numerous species from all five vertebrate groups: fish, amphibians, reptiles, birds, and mammals. The protocol is described for use on small-lissencephalic and large-gyrencephalic vertebrates, including species with translational relevance9. Additionally, we include other regions of the CNS not investigated before within this context, but relevant to neurophysiology and with tremendous clinical implications: the hypothalamus, pituitary, and white matter. Lastly, we tested the capacity of this isolation method as a reliable tool to identify changes in protein expression along the NVU and/or BBB9,10,11. As a proof-of-concept, we showed how to determine changes in VCAM-1 and JAM-B expression during EAE using the isolation method followed by immunofluorescence.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>10X PBS</td>
			<td>ThermoFisher</td>
			<td>BP39920</td>
			<td>Used for blocking and antibody diluent.</td>
		</tr>
		<tr>
			<td>20% PFA</td>
			<td>Electron Microscopy Sciences</td>
			<td>15713-S</td>
			<td>Used as fixative (4% PFA)</td>
		</tr>
		<tr>
			<td>70,000 MW Dextran</td>
			<td>Millipore Sigma</td>
			<td>9004-54-0</td>
			<td>Used for MV-2 solution</td>
		</tr>
		<tr>
			<td>Adson Forceps</td>
			<td>Fine Science Tools (FST)</td>
			<td>11006-12</td>
			<td>Used for removal of muscle and skin</td>
		</tr>
		<tr>
			<td>Adson Forceps, student quality</td>
			<td>FST</td>
			<td>91106-12</td>
			<td>Same as above but cheaper</td>
		</tr>
		<tr>
			<td>Bovine serum albumin (BSA)</td>
			<td>Millipore Sigma</td>
			<td>A7906-100G</td>
			<td>Used for MV-3 solution, blocking and antibody diluent</td>
		</tr>
		<tr>
			<td>Corning 100 &#956;m Cell strainer</td>
			<td>Millipore Sigma</td>
			<td>CLS431752-50EA</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning 70 &#956;m Cell strainer</td>
			<td>Millipore Sigma</td>
			<td>CLS431751-50EA</td>
			<td></td>
		</tr>
		<tr>
			<td>Corning Deskwork low-binding tips</td>
			<td>Millipore Sigma</td>
			<td>CLS4151</td>
			<td>Same as below but cheaper.</td>
		</tr>
		<tr>
			<td>Cultrex Poly-D-Lysine</td>
			<td>R&#38;D</td>
			<td>3439-100-01</td>
			<td>Used for slide coating</td>
		</tr>
		<tr>
			<td>Donkey anti-Goat IgG-ALEXA 555</td>
			<td>Thermo</td>
			<td>A21432</td>
			<td>Used as secondary antibody. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Donkey anti-Mouse IgG-ALEXA 488</td>
			<td>Thermo</td>
			<td>A21202</td>
			<td>Used as secondary antibody. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Donkey anti-Rabbit IgG-ALEXA 488</td>
			<td>Thermo</td>
			<td>A21206</td>
			<td>Used as secondary antibody. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Donkey anti-Rabbit IgG-ALEXA 647</td>
			<td>Thermo</td>
			<td>A31573</td>
			<td>Used as secondary antibody. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Donkey anti-Rat IgG-DyLight 650</td>
			<td>Thermo</td>
			<td>SA5-10029</td>
			<td>Used as secondary antibody. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Double-Pronged Tissue Pick</td>
			<td>FST</td>
			<td>18067-11</td>
			<td>Used for removal of meninges and choroid plexus</td>
		</tr>
		<tr>
			<td>Dumont #3c Forceps</td>
			<td>FST</td>
			<td>11231-20</td>
			<td>Used for more delicate and/or small CNS tissue handling (like pituitary)</td>
		</tr>
		<tr>
			<td>Dumont #7 Forceps</td>
			<td>FST</td>
			<td>11274-20</td>
			<td>Used for CNS tisssue dissection and handling</td>
		</tr>
		<tr>
			<td>Dumont #7 Forceps, student</td>
			<td>FST</td>
			<td>91197-00</td>
			<td>Same as above but cheaper</td>
		</tr>
		<tr>
			<td>ep Dualfilter T.I.P.S. LoRetention Tips</td>
			<td>Eppendorf</td>
			<td>22493008</td>
			<td>Better quality than the tips above (more expensive).</td>
		</tr>
		<tr>
			<td>Extra Fine Graefe Forceps, serrated</td>
			<td>FST</td>
			<td>11151-10</td>
			<td>Used for bone removal</td>
		</tr>
		<tr>
			<td>Fine Scissors, sharp</td>
			<td>FST</td>
			<td>14060-09</td>
			<td>Used for removal of pig and macaque dural sac</td>
		</tr>
		<tr>
			<td>Glass Pestle 1.5 mL Microcentrifuge Tube Tissue Grinder Homogenizer, Pack of 10</td>
			<td>Chang Bioscience Inc. (eBay)</td>
			<td>GP1.5_10</td>
			<td>Used for small vetebrate hypothalus and pituitary.</td>
		</tr>
		<tr>
			<td>Goat anti-CXCL12, biotinylated</td>
			<td>PeproTech</td>
			<td>500-P87BGBT</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended dilution: 1:20.</td>
		</tr>
		<tr>
			<td>Goat anti-JAM-B</td>
			<td>R&#38;D</td>
			<td>AF1074</td>
			<td>Used as primary antibody to assess neuroinflammation. Recommended concentration: 5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Goat anti-Mouse IgG-ALEXA 488</td>
			<td>Thermo</td>
			<td>A11001</td>
			<td>Used as secondary antibody. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Goat anti-Mouse IgG-ALEXA 555</td>
			<td>Thermo</td>
			<td>A21424</td>
			<td>Used as secondary antibody. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Goat anti-PDGFR&#946;</td>
			<td>R&#38;D</td>
			<td>AF1042</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended concentration: 5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Goat anti-Rabbit IgG-ALEXA 555</td>
			<td>Thermo</td>
			<td>A21249</td>
			<td>Used as secondary antibody. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Goat anti-Rabbit IgG-DyLight 488</td>
			<td>Thermo</td>
			<td>35552</td>
			<td>Used as secondary antibody. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Goat anti-Rat IgG-DyLight 650</td>
			<td>Thermo</td>
			<td>SA5-10021</td>
			<td>Used as secondary antibody. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Graefe Forceps, curved tip, 1X2 teeth</td>
			<td>FST</td>
			<td>11054-10</td>
			<td>Use for nylon filter net holding and shaking</td>
		</tr>
		<tr>
			<td>HBSS, 1X buffer with calcium and magnesium</td>
			<td>Corning</td>
			<td>21-022-CM</td>
			<td>Used for MV-1 solution</td>
		</tr>
		<tr>
			<td>HEPES, 1M liquid buffer</td>
			<td>Corning</td>
			<td>25-060-CI</td>
			<td>Used for MV-1 solution</td>
		</tr>
		<tr>
			<td>Isolectin GS-IB4-Biotin-XX</td>
			<td>ThermoFisher Scientific (Thermo)</td>
			<td>I21414</td>
			<td>Glycoprotein isolated from legume Griffonia simplicifolia that binds D-galactosyl residues of endothelial cell glycocalysx. Used for avian and porcine CNS microvessels. Recommended concentration: 5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>LaGrange Scissors, serrated</td>
			<td>FST</td>
			<td>14173-12</td>
			<td>Used for skull dissection and laminectomy (except pig and macaque)</td>
		</tr>
		<tr>
			<td>Millicell EZ slide 8-well unit</td>
			<td>Millipore Sigma</td>
			<td>PEZGS0816</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse anti-CLDN5</td>
			<td>Thermo</td>
			<td>35-2500</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended concentration: 5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Mouse anti-GGT1</td>
			<td>Abcam</td>
			<td>ab55138</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended concentration: 5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Mouse anti-Human CD31</td>
			<td>R&#38;D</td>
			<td>BBA7</td>
			<td>Used as primary antibody on primate CNS microvessels. Recommended concentration: 16.5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Mouse anti-NFM</td>
			<td>Thermo</td>
			<td>RMO-270</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended concentration: 5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Mouse anti-&#945;SMA</td>
			<td>Thermo</td>
			<td>MA5-11547</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Nylon Filter Net, roll</td>
			<td>Millipore Sigma</td>
			<td>NY6000010</td>
			<td>Laser-cut to 13 mm diameter filter net discs. Used for small vetebrate hypothalus and pituitary.</td>
		</tr>
		<tr>
			<td>Nylon Filter Nets, 25 mm</td>
			<td>Millipore Sigma</td>
			<td>NY2002500</td>
			<td>Used on most small vertebrates CNS tissues, except hypothalamus and pituitary. Used for macaque and pig hypothalamus and pituitary.</td>
		</tr>
		<tr>
			<td>Nylon Filter Nets, 47 mm</td>
			<td>Millipore Sigma</td>
			<td>NY2004700</td>
			<td>Used for macaque and pig CNS tissues, except hypothalamus and pituitary.</td>
		</tr>
		<tr>
			<td>ProLong Gold antifade reagent with DAPI</td>
			<td>ThermoFisher</td>
			<td>P36935</td>
			<td>Used to coverslip slides.</td>
		</tr>
		<tr>
			<td>Rabbit anti-AQP4</td>
			<td>Millipore Sigma</td>
			<td>A5971</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Rabbit anti-LSR</td>
			<td>Millipore Sigma</td>
			<td>SAB2107967</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended concentration: 5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Rabbit anti-NG2</td>
			<td>Millipore Sigma</td>
			<td>AB5320</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Rabbit anti-OSP</td>
			<td>Abcam</td>
			<td>ab53041</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended concentration: 1 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Rabbit anti-VE-Cadherin</td>
			<td>Abcam</td>
			<td>ab33168</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended concentration: 5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Rabbit anti-ZO-1</td>
			<td>Thermo</td>
			<td>61-7300</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended concentration: 5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Rat anti-CD31</td>
			<td>Becton Dickinson</td>
			<td>BD 550274</td>
			<td>Used as primary antibody for murine CNS microvessels. Recommended concentration: 5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Rat anti-GFAP</td>
			<td>Thermo</td>
			<td>13-0300</td>
			<td>Used as primary antibody on CNS microvessels from all specimens. Recommended dilution of 1:200.</td>
		</tr>
		<tr>
			<td>Rat anti-VCAM-1</td>
			<td>Becton Dickinson</td>
			<td>BD 553329</td>
			<td>Used as primary antibody to assess neuroinflammation. Recommended concentration: 5 &#956;g/mL.</td>
		</tr>
		<tr>
			<td>Sterile Ringer&#39;s Solution, Frog</td>
			<td>Aldon Corporation</td>
			<td>IS5066</td>
			<td>Used for amfibian anesthesia</td>
		</tr>
		<tr>
			<td>Streptavidin-ALEXA 555</td>
			<td>Thermo</td>
			<td>S32355</td>
			<td>Used as secondary antibody to label biotinylated primary antibodies. Recommended dilution of 1:500.</td>
		</tr>
		<tr>
			<td>Streptavidin-ALEXA 647</td>
			<td>Thermo</td>
			<td>S32357</td>
			<td>Used as secondary antibody to label biotinylated primary antibodies. Recommended dilution of 1:500.</td>
		</tr>
		<tr>
			<td>Surgical Scissors, sharp</td>
			<td>FST</td>
			<td>14002-12</td>
			<td>Used for removal of muscle and skin</td>
		</tr>
		<tr>
			<td>Surgical Scissors, sharp-blunt</td>
			<td>FST</td>
			<td>14001-16</td>
			<td>Used for decapitation (except pig and macaque)</td>
		</tr>
		<tr>
			<td>Swinnex Filter Holder, 13 mm</td>
			<td>Millipore Sigma</td>
			<td>SX0001300</td>
			<td>Modified by laser-cut. Used for small vetebrate hypothalus and pituitary.</td>
		</tr>
		<tr>
			<td>Swinnex Filter Holder, 25 mm</td>
			<td>Millipore Sigma</td>
			<td>SX0002500</td>
			<td>Modified by laser-cut. Used on most small vertebrates CNS tissues, except hypothalamus and pituitary. Used for macaque and pig hypothalamus and pituitary.</td>
		</tr>
		<tr>
			<td>Swinnex Filter Holder, 47 mm</td>
			<td>Millipore Sigma</td>
			<td>SX0004700</td>
			<td>Modified by laser-cut. Used for macaque and pig CNS tissues, except hypothalamus and pituitary.</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>ThermoFisher</td>
			<td>50-165-7277</td>
			<td>Used for blocking and antibody diluent.</td>
		</tr>
		<tr>
			<td>Wheaton 120 Vac Overhead Stirrer</td>
			<td>VWR (Supplier DWK Life Sciences)</td>
			<td>62400-904 (DWK #903475)</td>
			<td>Used for macaque and pig CNS tissues with 55 mL tissue grinder, except hypothalamus and pituitary.</td>
		</tr>
		<tr>
			<td>Wheaton Potter-Elvehjem tissue grinder with PTFE pestle, 10 mL</td>
			<td>VWR (Supplier DWK Life Sciences)</td>
			<td>14231-384 (DWK #357979)</td>
			<td>Used on most small vertebrates CNS tissues, except hypothalamus and pituitary. Used for macaque and pig hypothalamus and pituitary.</td>
		</tr>
		<tr>
			<td>Wheaton Potter-Elvehjem tissue grinder with PTFE pestle, 55 mL</td>
			<td>VWR (Supplier DWK Life Sciences)</td>
			<td>14231-372 (DWK #357994)</td>
			<td>Used for macaque and pig CNS tissues, except hypothalamus and pituitary.</td>
		</tr>
	</tbody>
</table>

reliable isolation of central nervous system microvessels across five vertebrate groups

Isolation of microvessels from the central nervous system (CNS) is commonly performed by combining cortical tissue from multiple animals, most often rodents. This approach limits the interrogation of blood-brain barrier (BBB) properties to the cortex and does not allow for individual comparison. This project focuses on the development of an isolation method that allows for the comparison of the neurovascular unit (NVU) from multiple CNS regions: cortex, cerebellum, optic lobe, hypothalamus, pituitary, brainstem, and spinal cord. Moreover, this protocol, originally developed for murine samples, was successfully adapted for use on CNS tissues from small and large vertebrate species from which we are also able to isolate microvessels from brain hemisphere white matter. This method, when paired with immunolabeling, allows for quantitation of protein expression and statistical comparison between individuals, tissue type, or treatment. We proved this applicability by evaluating changes in protein expression during experimental autoimmune encephalomyelitis (EAE), a murine model of a neuroinflammatory disease, multiple sclerosis. Additionally, microvessels isolated by this method could be used for downstream applications like qPCR, RNA-seq, and Western blot, among others. Even though this is not the first attempt to isolate CNS microvessels without the use of ultracentrifugation or enzymatic dissociation, it is unique in its adeptness for the comparison of single individuals and multiple CNS regions. Therefore, it allows for investigation of a range of differences that may otherwise remain obscure: CNS portions (cortex, cerebellum, optic lobe, brainstem, hypothalamus, pituitary, and spinal cord), CNS tissue type (gray or white matter), individuals, experimental treatment groups, and species.

Microvessels isolated from murine CNS showed all intrinsic cellular components of the neurovascular unit2,3. Using either platelet endothelial cell adhesion molecule-1 (PECAM, also known as CD31) or isolectin IB4 (a glycoprotein that binds the endothelial cell glycocalyx) for endothelial cells, platelet derived growth factor-&#946; (PDGFR&#946;) or neuron-glial antigen 2 (NG2) for pericytes and aquaporin-4 (AQP4) for astrocytic en...

Watch this Scientific Journal Video about Reliable Isolation of Central Nervous System Microvessels Across Five Vertebrate Groups at JoVE.com

Reliable Isolation of Central Nervous System Microvessels Across Five Vertebrate Groups

The goal of this protocol is to isolate microvessels from multiple regions of the central nervous system of lissencephalic and gyrencephalic vertebrates.

Isolation of microvessels from the central nervous system (CNS) is commonly performed by combining cortical tissue from multiple animals, most often ...

reliable-isolation-central-nervous-system-microvessels-across-five

Research

JoVE Journal

Neuroscience

8.4K Views.  University of California Davis. The goal of this protocol is to isolate microvessels from multiple regions of the central nervous system of lissencephalic and gyrencephalic vertebrates.

Video: Reliable Isolation of Central Nervous System Microvessels Across Five Vertebrate Groups

Optic Nerve Transection: A Model of Adult Neuron Apoptosis in the Central Nervous System

Retinal ganglion cells (RGCs) are CNS neurons that output visual information from the retina to the brain, via the optic nerve. 
The optic nerve can be accessed within the orbit of the eye and completely transected (axotomized), cutting the axons of the entire RGC population. Optic nerve 
transection is a reproducible model of apoptotic neuronal cell death in the adult CNS 1-4. This model is particularly attractive because the vitreous
 chamber of the eye acts as a capsule for drug delivery to the retina, permitting experimental manipulations via intraocular injections. The diffusion of chemicals 
through the vitreous fluid ensures that they act upon the entire RGC population. Moreover, RGCs can be selectively transfected by applying short interfering RNAs 
(siRNAs), plasmids, or viral vectors to the cut end of the optic nerve 5-7 or injecting vectors into their target, the superior colliculus 8. 
This allows researchers to study apoptotic mechanisms in the desired neuronal population without confounding effects on other bystander neurons or surrounding glia. 
An additional benefit is the ease and accuracy with which cell survival can be quantified after injury. The retina is a flat, layered tissue and RGCs are localized in 
the innermost layer, the ganglion cell layer. The survival of RGCs can be tracked over time by applying a fluorescent tracer (3% Fluorogold) to the cut end of the 
optic nerve at the time of axotomy, or by injecting the tracer into the superior colliculus (RGC target) one week prior to axotomy. The tracer is retrogradely transported, labeling 
the entire RGC population. Because the ganglion cell layer is a monolayer (one cell thick), RGC densities can be quantified in flat-mounted tissue, without the need 
for stereology. Optic nerve transection leads to the apoptotic death of 90% of injured RGCs within 14 days postaxotomy 9-11. RGC apoptosis has a 
characteristic time-course whereby cell death is delayed 3-4 days postaxotomy, after which the cells rapidly degenerate. This provides a time window for 
experimental manipulations directed against pathways involved in apoptosis.

Optic Nerve transection is a widely used model of adult CNS injury. Ninety percent of retinal ganglion cells (RGCs) whose axons are completely transected (axotomy) die within 14 days after axotomy. This model is easily amenable to experimental manipulations and highly reproducible.

Retinal ganglion cells (RGCs) are CNS neurons that output visual information from the retina to the brain, via the optic nerve. 
The optic nerve can be ...

Multimodal Imaging of Stem Cell Implantation in the Central Nervous System of Mice

During the past decade, stem cell transplantation has gained increasing interest as primary or secondary therapeutic modality for a variety of diseases, both in preclinical and clinical studies. However, to date results regarding functional outcome and/or tissue regeneration following stem cell transplantation are quite diverse. Generally, a clinical benefit is observed without profound understanding of the underlying mechanism(s)1. Therefore, multiple efforts have led to the development of different molecular imaging modalities to monitor stem cell grafting with the ultimate aim to accurately evaluate survival, fate and physiology of grafted stem cells and/or their micro-environment. Changes observed in one or more parameters determined by molecular imaging might be related to the observed clinical effect. In this context, our studies focus on the combined use of bioluminescence imaging (BLI), magnetic resonance imaging (MRI) and histological analysis to evaluate stem cell grafting.
BLI is commonly used to non-invasively perform cell tracking and monitor cell survival in time following transplantation2-7, based on a biochemical reaction where cells expressing the Luciferase-reporter gene are able to emit light following interaction with its substrate (e.g. D-luciferin)8, 9. MRI on the other hand is a non-invasive technique which is clinically applicable10 and can be used to precisely locate cellular grafts with very high resolution11-15, although its sensitivity highly depends on the contrast generated after cell labeling with an MRI contrast agent. Finally, post-mortem histological analysis is the method of choice to validate research results obtained with non-invasive techniques with highest resolution and sensitivity. Moreover end-point histological analysis allows us to perform detailed phenotypic analysis of grafted cells and/or the surrounding tissue, based on the use of fluorescent reporter proteins and/or direct cell labeling with specific antibodies.
In summary, we here visually demonstrate the complementarities of BLI, MRI and histology to unravel different stem cell- and/or environment-associated characteristics following stem cell grafting in the CNS of mice. As an example, bone marrow-derived stromal cells, genetically engineered to express the enhanced Green Fluorescent Protein (eGFP) and firefly Luciferase (fLuc), and labeled with blue fluorescent micron-sized iron oxide particles (MPIOs), will be grafted in the CNS of immune-competent mice and outcome will be monitored by BLI, MRI and histology (Figure 1).

This article describes an optimized sequence of events for multimodal imaging of cellular grafts in rodent brain using: (i) in vivo bioluminescence and magnetic resonance imaging, and (ii) post mortem histological analysis. Combining these imaging modalities on a single animal allows cellular graft evaluation with high resolution, sensitivity and specificity.

During the past decade, stem cell transplantation has gained increasing interest as primary or secondary therapeutic modality for a variety of diseases, ...

Production of Lentiviral Vectors for Transducing Cells from the Central Nervous System

Efficient gene delivery in the central nervous system (CNS) is important in studying gene functions, modeling neurological diseases and developing therapeutic approaches. Lentiviral vectors are attractive tools in transduction of neurons and other cell types in CNS as they transduce both dividing and non-dividing cells, support sustained expression of transgenes, and have relatively large packaging capacity and low toxicity 1-3. Lentiviral vectors have been successfully used in transducing many neural cell types in vitro 4-6 and in animals 7-10.
Great efforts have been made to develop lentiviral vectors with improved biosafety and efficiency for gene delivery. The current third generation replication-defective and self-inactivating (SIN) lentiviral vectors are depicted in Figure 1. The required elements for vector packaging are split into four plasmids. In the lentiviral transfer plasmid, the U3 region in the 5' long terminal repeat (LTR) is replaced with a strong promoter from another virus. This modification allows the transcription of the vector sequence independent of HIV-1 Tat protein that is normally required for HIV gene expression 11. The packaging signal (&Psi;) is essential for encapsidation and the Rev-responsive element (RRE) is required for producing high titer vectors. The central polypurine tract (cPPT) is important for nuclear import of the vector DNA, a feature required for transducing non-dividing cells 12. In the 3' LTR, the cis-regulatory sequences are completely removed from the U3 region. This deletion is copied to 5' LTR after reverse transcription, resulting in transcriptional inactivation of both LTRs. Plasmid pMDLg/pRRE contains HIV-1 gag/pol genes, which provide structural proteins and reverse transcriptase. pRSV-Rev encodes Rev which binds to the RRE for efficient RNA export from the nucleus. pCMV-G encodes the vesicular stomatitis virus glycoprotein (VSV-G) that replaces HIV-1 Env. VSV-G expands the tropism of the vectors and allows concentration via ultracentrifugation 13. All the genes encoding the accessory proteins, including Vif, Vpr, Vpu, and Nef are excluded in the packaging system. The production and manipulation of lentiviral vectors should be carried out according to NIH guidelines for research involving recombinant DNA (<a href="http://oba.od.nih.gov/oba/rac/Guidelines/NIH_Guidelines.pdf" target="_blank">http://oba.od.nih.gov/oba/rac/Guidelines/NIH_Guidelines.pdf</a>). An approval from individual Institutional Biological and Chemical Safety Committee may be required before using lentiviral vectors. Lentiviral vectors are commonly produced by cotransfection of 293T cells with lentiviral transfer plasmid and the helper plasmids encoding the proteins required for vector packaging. Many lentiviral transfer plasmids and helper plasmids can be obtained from Addgene, a non-profit plasmid repository (<a href="http://www.addgene.org/" target="_blank">http://www.addgene.org/</a>). Some stable packaging cell lines have been developed, but these systems provide less flexibility and their packaging efficiency generally declines over time 14, 15. Commercially available transfection kits may support high efficiency of transfection 16, but they can be very expensive for large scale vector preparations. Calcium phosphate precipitation methods provide highly efficient transfection of 293T cells and thus provide a reliable and cost effective approach for lentiviral vector production.
In this protocol, we produce lentiviral vectors by cotransfection of 293T cells with four plasmids based on the calcium phosphate precipitation principle, followed by purification and concentration with ultracentrifugation through a 20% sucrose cushion. The vector titers are determined by fluorescence- activated cell sorting (FACS) analysis or by real time qPCR. The production and titration of lentiviral vectors in this protocol can be finished with 9 days. We provide an example of transducing these vectors into murine neocortical cultures containing both neurons and astrocytes. We demonstrate that lentiviral vectors support high efficiency of transduction and cell type-specific gene expression in primary cultured cells from CNS.

In this protocol we describe production, purification and titration of lentiviral vectors. We provide an example of lentiviral vector-mediated gene delivery in primary cultured neurons and astrocytes. Our methods may also apply to other cell types in vitro and in vivo.

Efficient gene delivery in the central nervous system (CNS) is important in studying gene functions, modeling neurological diseases and developing ...

Labeling of Single Cells in the Central Nervous System of Drosophila melanogaster

In this article we describe how to individually label neurons in the embryonic CNS of Drosophila melanogaster by juxtacellular injection of the lipophilic fluorescent membrane marker DiI. This method allows the visualization of neuronal cell morphology in great detail. It is possible to label any cell in the CNS: cell bodies of target neurons are visualized under DIC optics or by expression of a fluorescent genetic marker such as GFP. After labeling, the DiI can be transformed into a permanent brown stain by photoconversion to allow visualization of cell morphology with transmitted light and DIC optics. Alternatively, the DiI-labeled cells can be observed directly with confocal microscopy, enabling genetically introduced fluorescent reporter proteins to be colocalised. The technique can be used in any animal, irrespective of genotype, making it possible to analyze mutant phenotypes at single cell resolution.

Labeling of Single Cells in the Central Nervous System of Drosophila melanogaster

We present a technique for labeling single neurons in the central nervous system (CNS) of Drosophila embryos, which allows the analysis of neuronal morphology by either transmitted light or confocal microscopy.

In this  article we describe how to individually label neurons in the embryonic CNS of Drosophila melanogaster by juxtacellular injection of the ...

An Injury Paradigm to Investigate Central Nervous System Repair in Drosophila

An experimental method has been developed to investigate the cellular responses to central nervous system (CNS) injury using the fruit-fly Drosophila. Understanding repair and regeneration in animals is a key question in biology. The damaged human CNS does not regenerate, and understanding how to promote the regeneration is one of main goals of medical neuroscience. The powerful genetic toolkit of Drosophila can be used to tackle the problem of CNS regeneration.
A lesion to the CNS ventral nerve cord (VNC, equivalent to the vertebrate spinal cord) is applied manually with a tungsten needle. The VNC can subsequently be filmed in time-lapse using laser scanning confocal microscopy for up to 24 hr to follow the development of the lesion over time. Alternatively, it can be cultured, then fixed and stained using immunofluorescence to visualize neuron and glial cells with confocal microscopy. Using appropriate markers, changes in cell morphology and cell state as a result of injury can be visualized. With ImageJ and purposely developed plug-ins, quantitative and statistical analyses can be carried out to measure changes in wound size over time and the effects of injury in cell proliferation and cell death. These methods allow the analysis of large sample sizes. They can be combined with the powerful genetics of Drosophila to investigate the molecular mechanisms underlying CNS regeneration and repair.

An Injury Paradigm to Investigate Central Nervous System Repair in Drosophila

An injury paradigm using the Drosophila larval ventral nerve cord to investigate central nervous system regeneration and repair is described. Stabbing followed by laser scanning confocal microscopy in time-lapse and fixed specimens, combined with quantitative analysis with purposefully developed software and genetics, are used to investigate the molecular mechanisms of CNS regeneration and repair.

An experimental method has been developed to investigate the cellular responses to central nervous system (CNS) injury using the fruit-fly Drosophila. ...

Direct Intraventricular Delivery of Drugs to the Rodent Central Nervous System

Due to an inability to cross the blood brain barrier, certain drugs need to be directly delivered into the central nervous system (CNS). Our lab focuses specifically on antisense oligonucleotides (ASOs), though the techniques shown in the video here can also be used to deliver a plethora of other drugs to the CNS. Antisense oligonucleotides (ASOs) have the capability to knockdown sequence-specific targets 1 as well as shift isoform ratios of specific genes 2. To achieve widespread gene knockdown or splicing in the CNS of mice, the ASOs can be delivered into the brain using two separate routes of administration, both of which we demonstrate in the video.
The first uses Alzet osmotic pumps, connected to a catheter that is surgically implanted into the lateral ventricle. This allows the ASOs to be continuously infused into the CNS for a designated period of time. The second involves a single bolus injection of a high concentration of ASO into the right lateral ventricle. Both methods use the mouse cerebral ventricular system to deliver the ASO to the entire brain and spinal cord, though depending on the needs of the study, one method may be preferred over the other.

We describe a method to target drugs to the central nervous system by either implanting a catheter or performing a bolus injection into the right lateral ventricle in mice. We focus specifically on the delivery of antisense oligonucleotides. This technique is readily adaptable to other drugs and to rats.

Due to an inability to cross the blood brain barrier, certain drugs need to be directly delivered into the central nervous system (CNS). Our lab focuses ...

In vivo Interrogation of Central Nervous System Translatome by Polyribosome Fractionation

Multiple processes are involved in gene expression including transcription, translation and stability of mRNAs and proteins. Each of these steps are tightly regulated, affecting the final dynamics of protein abundance. Various regulatory mechanisms exist at the translation step, rendering mRNA levels alone an unreliable indicator of gene expression. In addition, local regulation of mRNA translation has been particularly implicated in neuronal functions, shifting &#39;translatomics&#39; to the focus of attention in neurobiology. The presented method can be used to bridge transcriptomics and proteomics.
Here we describe essential modifications to the technique of polyribosome fractionation, which interrogates the translatome based on the association of actively translated mRNAs to multiple ribosomes and their differential sedimentation in sucrose gradients. Traditionally, working with in vivo samples, particularly of the central nervous system (CNS), has proven challenging due to the restricted amounts of material and the presence of fatty tissue components. In order to address this, the described protocol is specifically optimized for use with minimal amount of CNS material, as demonstrated by the use of single mouse spinal cord and brain. Briefly, CNS tissues are extracted and translating ribosomes are immobilized on mRNAs with cycloheximide. Myelin flotation is then performed to remove lipid rich components. Fractionation is performed on a sucrose gradient where mRNAs are separated according to their ribosomal loading. Isolated fractions are suitable for a range of downstream assays, including new genome wide assay technologies.

In vivo Interrogation of Central Nervous System Translatome by Polyribosome Fractionation

This protocol illustrates essential modifications of polyribosome fractionation in order to study the translatome of in vivo CNS samples. It allows global assessment of translation and transcription regulation through the isolation and comparison of total RNA to ribosome bound RNA fractions.

Multiple processes are involved in gene expression including transcription, translation and stability of mRNAs and proteins. Each of these steps are ...

In vivo Optogenetic Stimulation of the Rodent Central Nervous System

The ability to probe defined neural circuits in awake, freely-moving animals with cell-type specificity, spatial precision, and high temporal resolution has been a long sought tool for neuroscientists in the systems-level search for the neural circuitry governing complex behavioral states. Optogenetics is a cutting-edge tool that is revolutionizing the field of neuroscience and represents one of the first systematic approaches to enable causal testing regarding the relation between neural signaling events and behavior. By combining optical and genetic approaches, neural signaling can be bi-directionally controlled through expression of light-sensitive ion channels (opsins) in mammalian cells. The current protocol describes delivery of specific wavelengths of light to opsin-expressing cells in deep brain structures of awake, freely-moving rodents for neural circuit modulation. Theoretical principles of light transmission as an experimental consideration are discussed in the context of performing in vivo optogenetic stimulation. The protocol details the design and construction of both simple and complex laser configurations and describes tethering strategies to permit simultaneous stimulation of multiple animals for high-throughput behavioral testing.

In vivo Optogenetic Stimulation of the Rodent Central Nervous System

Optogenetics has become a powerful tool for use in behavioral neuroscience experiments. This protocol offers a step-by-step guide to the design and set-up of laser systems, and provides a full protocol for carrying out multiple and simultaneous in vivo optogenetic stimulations compatible with most rodent behavioral testing paradigms.

The ability to probe defined neural circuits in awake, freely-moving animals with cell-type specificity, spatial precision, and high temporal resolution ...

Functional Evaluation of Biological Neurotoxins in Networked Cultures of Stem Cell-derived Central Nervous System Neurons

Therapeutic and mechanistic studies of the presynaptically targeted clostridial neurotoxins (CNTs) have been limited by the need for a scalable, cell-based model that produces functioning synapses and undergoes physiological responses to intoxication. Here we describe a simple and robust method to efficiently differentiate murine embryonic stem cells (ESCs) into defined lineages of synaptically active, networked neurons. Following an 8 day differentiation protocol, mouse embryonic stem cell-derived neurons (ESNs) rapidly express and compartmentalize neurotypic proteins, form neuronal morphologies and develop intrinsic electrical responses. By 18 days after differentiation (DIV 18), ESNs exhibit active glutamatergic and &#947;-aminobutyric acid (GABA)ergic synapses and emergent network behaviors characterized by an excitatory:inhibitory balance. To determine whether intoxication with CNTs functionally antagonizes synaptic neurotransmission, thereby replicating the in vivo pathophysiology that is responsible for clinical manifestations of botulism or tetanus, whole-cell patch clamp electrophysiology was used to quantify spontaneous miniature excitatory post-synaptic currents (mEPSCs) in ESNs exposed to tetanus neurotoxin (TeNT) or botulinum neurotoxin (BoNT) serotypes /A-/G. In all cases, ESNs exhibited near-complete loss of synaptic activity within 20 hr. Intoxicated neurons remained viable, as demonstrated by unchanged resting membrane potentials and intrinsic electrical responses. To further characterize the sensitivity of this approach, dose-dependent effects of intoxication on synaptic activity were measured 20 hr after addition of BoNT/A. Intoxication with 0.005 pM BoNT/A resulted in a significant decrement in mEPSCs, with a median inhibitory concentration (IC50) of 0.013 pM. Comparisons of median doses indicate that functional measurements of synaptic inhibition are faster, more specific and more sensitive than SNARE cleavage assays or the mouse lethality assay. These data validate the use of synaptically coupled, stem cell-derived neurons for the highly specific and sensitive detection of CNTs.

A custom protocol is described to differentiate mouse ES cells into defined populations of highly pure neurons exhibiting functioning synapses and emergent network behavior. Electrophysiological analysis demonstrates the loss of synaptic transmission following exposure to botulinum neurotoxin serotypes /A-/G and tetanus neurotoxin.

Therapeutic and mechanistic studies of the presynaptically targeted clostridial neurotoxins (CNTs) have been limited by the need for a scalable, ...

Optical Clearing of the Mouse Central Nervous System Using Passive CLARITY

Traditionally, tissue visualization has required that the tissue of interest be serially sectioned and imaged, subjecting each tissue section to unique non-linear deformations, dramatically hampering one's ability to evaluate cellular morphology, distribution and connectivity in the central nervous system (CNS). However, optical clearing techniques are changing the way tissues are visualized. These approaches permit one to probe deeply into intact organ preparations, providing tremendous insight into the structural organization of tissues in health and disease. Techniques such as Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging-compatible Tissue-hYdrogel (CLARITY) achieve this goal by providing a matrix that binds important biomolecules while permitting light-scattering lipids to freely diffuse out. Lipid removal, followed by refractive index matching, renders the tissue transparent and readily imaged in 3 dimensions (3D). Nevertheless, the electrophoretic tissue clearing (ETC) used in the original CLARITY protocol can be challenging to implement successfully and the use of a proprietary refraction index matching solution makes it expensive to use the technique routinely. This report demonstrates the implementation of a simple and inexpensive optical clearing protocol that combines passive CLARITY for improved tissue integrity and 2,2&#8242;-thiodiethanol (TDE), a previously described refractive index matching solution.

Optical clearing techniques are revolutionizing the way tissues are visualized. In this report we describe modifications of the original Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging-compatible Tissue-hYdrogel (CLARITY) protocol that yields more consistent and less expensive results.

Traditionally, tissue visualization has required that the tissue of interest be serially sectioned and imaged, subjecting each tissue section to unique ...