Name: isolation and functional analysis of arteriolar endothelium of mouse brain parenchyma
Uploaded: 2022-03-11T14:00:00
Description: Watch this Scientific Journal Video about Isolation and Functional Analysis of Arteriolar Endothelium of Mouse Brain Parenchyma at JoVE.com

This research has been supported by grants from the National Institutes of Health (R00AG047198 &#38; R56AG062169 to EJB; R00HL140106 to PWP) and the Alzheimer&#39;s Association (AZRGD-21-805835 to PWP). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health or the Alzheimer&#39;s Association.

Experimenters should ensure that designated use of animals and associated protocols are approved by their Institutional Animal Care and Use Committee (IACUC) and performed in accordance with the National Research Council&#39;s &#34;Guide for the Care and Use of Laboratory Animals&#34; (8th Edition, 2011) and the ARRIVE guidelines. The IACUC of Loma Linda University and the University of Arizona has approved all protocols used for this manuscript for C57BL/6N and 3xTg-AD mice (males and females; age ra...

<ol>
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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=Capillary+K+-sensing+initiates+retrograde+hyperpolarization+to+increase+local+cerebral+blood+flow.">Capillary K+-sensing initiates retrograde hyperpolarization to increase local cerebral blood flow.</a> Nature Neuroscience. 20 (5), 717-726 (2017).</li><li>Kelleher, R. J., Soiza, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+of+endothelial+dysfunction+in+the+development+of+Alzheimer's+disease:+Is+Alzheimer's+a+vascular+disorder.">Evidence of endothelial dysfunction in the development of Alzheimer's disease: Is Alzheimer's a vascular disorder.</a> American Journal of Cardiovascular Disease. 3 (4), 197-226 (2013).</li><li>Hakim, M. A., Behringer, E. 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C., 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=Amyloid-beta+disrupts+unitary+calcium+entry+through+endothelial+NMDA+receptors+in+mouse+cerebral+arteries.">Amyloid-beta disrupts unitary calcium entry through endothelial NMDA receptors in mouse cerebral arteries.</a> Journal of Cerebral Blood Flow and Metabolism. , (2021).</li><li>De Silva, T. M., Modrick, M. L., Dabertrand, F., Faraci, F. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+cerebral+arteries+and+parenchymal+arterioles+with+aging:+Role+of+rho+kinase+2+and+impact+of+genetic+background.">Changes in cerebral arteries and parenchymal arterioles with aging: Role of rho kinase 2 and impact of genetic background.</a> Hypertension. 71 (5), 921-927 (2018).</li><li>Fontaine, J. T., Rosehart, A. C., Joutel, A., Dabertrand, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HB-EGF+depolarizes+hippocampal+arterioles+to+restore+myogenic+tone+in+a+genetic+model+of+small+vessel+disease.">HB-EGF depolarizes hippocampal arterioles to restore myogenic tone in a genetic model of small vessel disease.</a> Mechanisms of Ageing and Development. 192, 111389 (2020).</li><li>Pires, P. W., Dabertrand, F., Earley, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+cannulation+of+cerebral+parenchymal+arterioles.">Isolation and cannulation of cerebral parenchymal arterioles.</a> Journal of Visualized Experiments: JoVE. (111), e53835 (2016).</li><li>Rosehart, A. C., Johnson, A. C., Dabertrand, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+pressurized+hippocampal+capillary-parenchymal+arteriole+preparation+for+functional+study.">Ex vivo pressurized hippocampal capillary-parenchymal arteriole preparation for functional study.</a> Journal of Visualized Experiments: JoVE. (154), e60676 (2019).</li><li>Hakim, M. A., Behringer, E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simultaneous+measurements+of+intracellular+calcium+and+membrane+potential+in+freshly+isolated+and+intact+mouse+cerebral+endothelium.">Simultaneous measurements of intracellular calcium and membrane potential in freshly isolated and intact mouse cerebral endothelium.</a> Journal of Visualized Experiments: JoVE. (143), e58832 (2019).</li><li>Hakim, M. A., Chum, P. P., Buchholz, J. N., Behringer, E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aging+alters+cerebrovascular+endothelial+GPCR+and+K++channel+function:+Divergent+role+of+biological+sex.">Aging alters cerebrovascular endothelial GPCR and K+ channel function: Divergent role of biological sex.</a> Journals of Gerontology, Series A: Biological Sciences and Medical Sciences. 75 (11), 2064-2073 (2020).</li><li>Behringer, E. J., Hakim, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Functional+interaction+among+KCa+and+TRP+channels+for+cardiovascular+physiology:+Modern+perspectives+on+aging+and+chronic+disease.">Functional interaction among KCa and TRP channels for cardiovascular physiology: Modern perspectives on aging and chronic disease.</a> International Journal of Molecular Sciences. 20 (6), 1380 (2019).</li><li>Marrelli, S. P., Eckmann, M. S., Hunte, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+endothelial+intermediate+conductance+KCa+channels+in+cerebral+EDHF-mediated+dilations.">Role of endothelial intermediate conductance KCa channels in cerebral EDHF-mediated dilations.</a> American Journal of Physiology-Heart and Circulatory Physiology. 285 (4), 1590-1599 (2003).</li><li>Hannah, R. M., Dunn, K. M., Bonev, A. D., Nelson, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+SKCa+and+IKCa+channels+regulate+brain+parenchymal+arteriolar+diameter+and+cortical+cerebral+blood+flow.">Endothelial SKCa and IKCa channels regulate brain parenchymal arteriolar diameter and cortical cerebral blood flow.</a> Journal of Cerebral Blood Flow and Metabolism. 31 (5), 1175-1186 (2011).</li><li>Hakim, M. A., Buchholz, J. N., Behringer, E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+dynamics+of+isolated+cerebral+and+skeletal+muscle+endothelial+tubes:+Differential+roles+of+G-protein-coupled+receptors+and+K++channels.">Electrical dynamics of isolated cerebral and skeletal muscle endothelial tubes: Differential roles of G-protein-coupled receptors and K+ channels.</a> Pharmacological Research and Perspectives. 6 (2), 00391 (2018).</li><li>Hakim, M. A., Behringer, E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methyl-beta-cyclodextrin+restores+KIR+channel+function+in+brain+endothelium+of+female+Alzheimer's+disease+Mice.">Methyl-beta-cyclodextrin restores KIR channel function in brain endothelium of female Alzheimer's disease Mice.</a> Journal of Alzheimers Disease Reports. 5 (1), 693-703 (2021).</li><li>Behringer, E. J., Shaw, R. L., Westcott, E. B., Socha, M. J., Segal, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aging+impairs+electrical+conduction+along+endothelium+of+resistance+arteries+through+enhanced+Ca2+-activated+K++channel+activation.">Aging impairs electrical conduction along endothelium of resistance arteries through enhanced Ca2+-activated K+ channel activation.</a> Arteriosclerosis Thrombosis and Vascular Biology. 33 (8), 1892-1901 (2013).</li><li>Attems, J., Jellinger, K. 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+overlap+between+vascular+disease+and+Alzheimer's+disease--lessons+from+pathology.">The overlap between vascular disease and Alzheimer's disease--lessons from pathology.</a> BMC Medicine. 12, 206 (2014).</li><li>Fisher, C. 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+arterial+lesions+underlying+lacunes.">The arterial lesions underlying lacunes.</a> Acta Neuropathologica. 12 (1), 1-15 (1968).</li><li>Behringer, E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium+and+electrical+signaling+in+arterial+endothelial+tubes:+New+insights+into+cellular+physiology+and+cardiovascular+function.">Calcium and electrical signaling in arterial endothelial tubes: New insights into cellular physiology and cardiovascular function.</a> Microcirculation. 24 (3), (2017).</li><li>Dunn, K. M., Nelson, M. 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Growing evidence suggests that cerebrovascular disease (CVD), aging, and Alzheimer&#39;s disease are strongly correlated and are a current topic of dementia research4,8,14,21. Thus, it is obvious that studies of the cerebrovascular network would have a broad impact on health while requiring continued extensive investigation during conditions of&#160;disease. As a significant point of vascular r...

Parenchymal arterioles directly deliver essential oxygen and nutrients throughout the brain1. While interfacing with capillaries, highly vasoactive arterioles respond to retrograde signaling initiated by capillary ion channels that sense metabolic signals from specific neuronal regions2. With brain parenchyma having historically received the bulk of investigation, a role for endothelial dysfunction has now emerged for clarifying pathological mechanisms associated with various cerebrovascular disorders that underlie dementia (e.g., ischemic stroke, Alzheimer&#39;s disease)3,4,5,6. The endothelium is integral to perfusion of the brain in accord with the heterogeneity of genetics, structure, and function throughout vascular segments7. Pial arteries have been extensively studied due to their relatively large size, high segmental vascular resistance, and role in blood flow distribution to the underlying cerebrum8,9. Thus, a better understanding of arteriolar endothelial mechanisms will likely enhance the understanding of brain blood flow regulation in health and disease towards the development of novel therapeutic regimens.
Emerging evidence highlights the importance of studying parenchymal arterioles in relation to different signaling pathways and diseases8,10. However, this approach has been limited to using intact pressurized arteriole11 and/or capillary-parenchymal arteriole (CaPA) preparations12. Freshly isolated, native cerebral arteriolar endothelial cells devoid of other cell types and confounding factors have not been examined, likely due to technical difficulties in their isolation. This paper advances a previous technique highlighting the isolation of pial arterial endothelium13 to now reliably and reproducibly isolate the endothelium of brain parenchymal arterioles (width: ~25 &#181;m, length: ~250 &#181;m). This technique helps achieve optimal resolution of electrically and chemically coupled cells in their individual orientation and cellular networks.
Key pathways of interest have included the interaction of intracellular Ca2+ ([Ca2+]i) signaling and hyperpolarization of membrane potential (Vm)14,15&#8212;integral to vasodilation16&#8212;to allow blood to enter the capillaries and deliver oxygen and nutrients to active parenchyma17. These preparations allow for real-time electrophysiological recordings of ion channels, including Ca2+-permeant, transient receptor potential (TRP) and K+ channels and/or fluorescent imaging of intracellular organelles within endothelial cell tubes in near-physiological conditions. This is a suitable technique for researchers interested in physiological cellular mechanisms that govern endothelial cell control of cerebral blood flow delivery to the brain parenchyma. Altogether, this technique will help researchers better understand fundamental endothelial signaling pathways and network communication of arterioles embedded in brain parenchyma while&#160;addressing questions related to cerebrovascular physiology and pathology.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Amplifiers</td>
			<td>Molecular Devices, Sunnyvale, CA, USA</td>
			<td>Axoclamp 2B &#38; Axoclamp 900A</td>
			<td></td>
		</tr>
		<tr>
			<td>Audible baseline monitors</td>
			<td>Ampol US LLC, Sarasota, FL, USA</td>
			<td>&#160;BM-A-TM</td>
			<td></td>
		</tr>
		<tr>
			<td>Bath Chiller (Isotemp 500LCU)</td>
			<td>ThermoFisher Scientific</td>
			<td>13874647</td>
			<td></td>
		</tr>
		<tr>
			<td>Borosilicate glass capillaries (Pinning)</td>
			<td>Warner Instruments</td>
			<td>G150T-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Borosilicate glass capillaries (Sharp Electrodes)</td>
			<td>Warner Instruments</td>
			<td>GC100F-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Borosilicate glass capillaries (Trituration)</td>
			<td>World Precision Instruments (WPI), Sarasota, FL, USA</td>
			<td>1B100-4</td>
			<td></td>
		</tr>
		<tr>
			<td>BSA: Bovine Serum Albumin</td>
			<td>Sigma</td>
			<td>A7906</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2: Calcium Chloride</td>
			<td>Sigma</td>
			<td>223506</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase (Type H Blend)</td>
			<td>Sigma</td>
			<td>C8051</td>
			<td></td>
		</tr>
		<tr>
			<td>Cover Glass (2.4&#160;&#215;&#160;5.0&#160;cm)</td>
			<td>ThermoFisher Scientific</td>
			<td>12-548-5M</td>
			<td></td>
		</tr>
		<tr>
			<td>Data Acquision Digitizer</td>
			<td>Molecular Devices, Sunnyvale, CA, USA</td>
			<td>Digidata 1550A</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissection Dish (Glass Petri with Charcoal Sylgard bottom)</td>
			<td>Living Systems Instrumentation, St. Albans City, VT, USA</td>
			<td>DD-90-S-BLK</td>
			<td></td>
		</tr>
		<tr>
			<td>Dithioerythritol</td>
			<td>Sigma</td>
			<td>D8255</td>
			<td></td>
		</tr>
		<tr>
			<td>DMSO: Dimethyl Sulfoxide</td>
			<td>Sigma</td>
			<td>D8418</td>
			<td></td>
		</tr>
		<tr>
			<td>Elastase (porcine pancreas)</td>
			<td>Sigma</td>
			<td>E7885</td>
			<td></td>
		</tr>
		<tr>
			<td>Endoplasmic Reticulum Tracker (ER-Tracker Red, BODIPY TR Glibenclamide)</td>
			<td>ThermoFisher Scientific</td>
			<td>E34250</td>
			<td></td>
		</tr>
		<tr>
			<td>Fiber optic light sources</td>
			<td>&#160;Schott, Mainz, Germany &#38; KL200, Zeiss</td>
			<td>Fostec 8375</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow Control Valve</td>
			<td>Warner Instruments</td>
			<td>&#160;FR-50</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescence system interface, ARC lamp &#38; power supply, hyperswitch and PMT</td>
			<td>Molecular Devices, Sunnyvale, CA, USA</td>
			<td>IonOptix Systems</td>
			<td></td>
		</tr>
		<tr>
			<td>Forceps (Fine-tipped, sharpened)</td>
			<td>FST</td>
			<td>Dumont #5 &#38; Dumont #55</td>
			<td></td>
		</tr>
		<tr>
			<td>Function Generator</td>
			<td>EZ Digital, Seoul, South Korea</td>
			<td>FG-8002</td>
			<td></td>
		</tr>
		<tr>
			<td>Fura-2 AM dye</td>
			<td>Invitrogen, Carlsbad, CA, USA</td>
			<td>F14185</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma-Aldrich (St. Louis, MO, USA)</td>
			<td>G7021</td>
			<td></td>
		</tr>
		<tr>
			<td>HCl: Hydrochloric Acid</td>
			<td>ThermoFisher Scientific (Pittsburgh, PA, USA)</td>
			<td>A466250</td>
			<td></td>
		</tr>
		<tr>
			<td>Headstages</td>
			<td>Molecular Devices</td>
			<td>HS-2A &#38; HS-9A</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES: (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid)</td>
			<td>Sigma</td>
			<td>H4034</td>
			<td></td>
		</tr>
		<tr>
			<td>Inline Solution Heater</td>
			<td>Warner Instruments</td>
			<td>SH-27B</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl: Potassium Chloride</td>
			<td>Sigma</td>
			<td>P9541</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2: Magnesium Chloride</td>
			<td>Sigma</td>
			<td>M2670</td>
			<td></td>
		</tr>
		<tr>
			<td>Microforge</td>
			<td>Narishige, East Meadow, NY, USA</td>
			<td>&#160;MF-900</td>
			<td></td>
		</tr>
		<tr>
			<td>Micromanipulator</td>
			<td>Siskiyou</td>
			<td>&#160;MX10</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropipette puller (digital)</td>
			<td>Sutter Instruments, Novato, CA, USA</td>
			<td>P-97 or P-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope (Nikon-inverted)</td>
			<td>Nikon Instruments Inc, Melville, NY, USA</td>
			<td>Ts2</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope (Nikon-inverted)</td>
			<td>Nikon Instruments Inc</td>
			<td>Eclipse TS100</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope objectives</td>
			<td>Nikon Instruments Inc</td>
			<td>20X (S-Fluor) and 40X (Plan Fluor)</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope platform (anodized aluminum; diameter, 7.8&#160;cm)</td>
			<td>Warner Instruments</td>
			<td>PM6 or PH6</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope Stage (Aluminum)</td>
			<td>Siskiyou, Grants Pass, OR, USA</td>
			<td>8090P</td>
			<td></td>
		</tr>
		<tr>
			<td>Microsyringe Pump Controller</td>
			<td>World Precision Instruments (WPI), Sarasota, FL, USA</td>
			<td>SYS-MICRO4</td>
			<td></td>
		</tr>
		<tr>
			<td>MTA: 2-Methylthioadenosine diphosphate trisodium salt</td>
			<td>Tocris</td>
			<td>1624</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl: Sodium Chloride</td>
			<td>Sigma</td>
			<td>S7653</td>
			<td></td>
		</tr>
		<tr>
			<td>NaOH: Sodium Hydroxide</td>
			<td>Sigma</td>
			<td>S8045</td>
			<td></td>
		</tr>
		<tr>
			<td>Nuclear Stain (NucBlue Live ReadyProbes Reagent; Hoechst 33342)</td>
			<td>ThermoFisher Scientific</td>
			<td>R37605</td>
			<td></td>
		</tr>
		<tr>
			<td>Oscilloscope</td>
			<td>Tektronix, Beaverton, Oregon, USA</td>
			<td>&#160;TDS 2024B</td>
			<td></td>
		</tr>
		<tr>
			<td>Papain</td>
			<td>Sigma</td>
			<td>P4762</td>
			<td></td>
		</tr>
		<tr>
			<td>Phase contrast objectives</td>
			<td>Nikon Instruments Inc</td>
			<td>&#160;(Ph1 DL; 10X &#38; 20X)</td>
			<td></td>
		</tr>
		<tr>
			<td>Plasma Membrane Stain (CellMask Deep Red)</td>
			<td>ThermoFisher Scientific</td>
			<td>C10046</td>
			<td></td>
		</tr>
		<tr>
			<td>Plexiglas superfusion chamber</td>
			<td>Warner Instruments, Camden, CT, USA</td>
			<td>RC-27</td>
			<td></td>
		</tr>
		<tr>
			<td>Scissors (3 mm &#38; 7 mm blades)</td>
			<td>Fine Science Tools (or FST), Foster City, CA, USA</td>
			<td>Moria MC52 &#38; 15000-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Scissors (Vannas style; 9.5&#160;mm &#38; 3&#160;mm blades)</td>
			<td>World Precision Instruments</td>
			<td>555640S, 14364</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereomicroscopes</td>
			<td>Zeiss, NY, USA</td>
			<td>Stemi 2000 &#38; 2000-C</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe filter (0.22 &#181;m)</td>
			<td>ThermoFisher Scientific</td>
			<td>722-2520</td>
			<td></td>
		</tr>
		<tr>
			<td>Temperature Controller (Dual Channel)</td>
			<td>Warner Instruments</td>
			<td>TC-344B or C</td>
			<td></td>
		</tr>
		<tr>
			<td>Valve Control System</td>
			<td>Warner Instruments</td>
			<td>VC-6</td>
			<td></td>
		</tr>
		<tr>
			<td>Vibration Isolation Table</td>
			<td>Technical Manufacturing, Peabody, MA, USA</td>
			<td>&#160;Micro-g</td>
			<td></td>
		</tr>
	</tbody>
</table>

isolation and functional analysis of arteriolar endothelium of mouse brain parenchyma

Cerebral blood flow is conveyed by vascular resistance arteries and downstream parenchymal arterioles. Steady-state vascular resistance to blood flow increases with decreasing diameter from arteries to arterioles that ultimately feed into capillaries. Due to their smaller size and location in the parenchyma, arterioles have been relatively understudied and with less reproducibility in findings than surface pial arteries. Regardless, arteriolar endothelial cell structure and function&#8212;integral to the physiology and etiology of chronic degenerative diseases&#8212;requires extensive investigation. In particular, emerging evidence demonstrates that compromised endothelial function precedes and exacerbates cognitive impairment and dementia.
In the parenchymal microcirculation, endothelial K+ channel function is the most robust stimulus to finely control the spread of vasodilation to promote increases in blood flow to areas of neuronal activity. This paper illustrates a refined method for freshly isolating intact and electrically coupled endothelial &#34;tubes&#34; (diameter, ~25 &#181;m) from mouse brain parenchymal arterioles. Arteriolar endothelial tubes are secured during physiological conditions (37 &#176;C, pH 7.4) to resolve experimental variables that encompass K+ channel function and their regulation, including intracellular Ca2+ dynamics, changes in membrane potential, and membrane lipid regulation. A distinct technical advantage versus arterial endothelium is the enhanced morphological resolution of cell and organelle (e.g., mitochondria) dimensions, which expands the usefulness of this technique. Healthy cerebral perfusion throughout life entails robust endothelial function in parenchymal arterioles, directly linking blood flow to the fueling of neuronal and glial activity throughout precise anatomical regions of the brain. Thus, it is expected that this method will significantly advance the general knowledge of vascular physiology and neuroscience concerning the healthy and diseased brain.

A demonstration of the protocol is shown in Figure 1 with arteriolar dissection and endothelial tube isolation steps as Figure 2 and Figure 3, respectively. Here, endothelial function was assessed by measuring [Ca2+]i and Vm using Fura-2 photometry and sharp electrode electrophysiology (Figure 4A) in response to a pharmacological agent [2-methylthioadenosine diphosphate ...

Watch this Scientific Journal Video about Isolation and Functional Analysis of Arteriolar Endothelium of Mouse Brain Parenchyma at JoVE.com

Isolation and Functional Analysis of Arteriolar Endothelium of Mouse Brain Parenchyma

Intensive preparation of intact mouse cerebral endothelial &#34;tubes&#34; from cerebral parenchymal arterioles is illustrated for studying cerebral blood flow regulation. Further, we demonstrate the experimental strengths of this endothelial study model for fluorescence imaging and electrophysiology measurement of key cellular signaling pathways, including changes in intracellular [Ca2+] and membrane potential.

Cerebral blood flow is conveyed by vascular resistance arteries and downstream parenchymal arterioles. Steady-state vascular resistance to blood flow ...

This method will provide better insight into the function of parenchymal arteriolar endothelium which directly links intracerebral blood flow to the fueling of neuronal and glial activity throughout the brain. A distinct technical advantage over arteriole endothelium is the enhanced resolution of morphological dimensions and calcium and electrical signaling among individual intracerebral endothelial cells and their respective organelles. Initially, isolation and examination of intracerebral endothelium will be very challenging.However, it is possible to master this technique with plenty of practice accompanied by patience and dedication. Wash the isolated brain with a cold dissection solution in a beaker or Petri dish to remove remaining blood from the surface of the brain. Place the ventral brain side facing up in a chamber containing cold dissection solution to isolate parenchymal arterioles.To isolate parenchymal arterioles, secure the isolated brain with steel pins in cold dissection solution in a Petri dish containing more than 50 centimeter deep charcoal-infused silicon polymer coating. Cut a rectangle of brain tissue from both hemispheres with sharp and aligned dissection scissors around the MCA while ensuring that the upper part of the tissue segment is past the branching point from the circle of Willis. Secure the brain tissue into the dish with the MCA facing upwards with steel pins.Carefully make a shallow incision near the pins and remove the pia with small forceps, gently peeling from one end towards the other. Carefully secure the isolated pia with parenchymal arterioles branched from MCA in the dish with the pins and carefully dissect the parenchymal arterioles. Cut off any remaining distal branches and ensure the arteriole is clean with no tissue attached.Use this clean intact arteriole for enzymatic digestion. Alternatively, cut each arteriole into two pieces for enzymatic digestion to prepare endothelial tubes if desired. For partial digestion of arteriolar segments, place intact arteriolar segments into one milliliter of dissociation solution in a 10 milliliter glass tube containing papain, dithioerythritol, collagenase, and elastase.Incubate arteriolar segments at 34 degrees Celsius for 10 to 12 minutes. To isolate the arteriolar endothelial tube, place the trituration pipette attached with the micro syringe injector in the dissociation solution in the chamber and position it close to one end of the digested vessel segment. Set a rate within the range of one to three nanoliters per second on the pump controller for gentle trituration.While maintaining 100X to 200X magnification, withdraw the arteriolar segment into the pipette and then inject to dissociate the adventitia and smooth muscle cells. Triturate the vessel segment until all smooth muscle cells are dissociated and only endothelial cells remain as an intact tube. With micro manipulators, secure each end of the endothelial tube on the glass coverslip in the chamber with borosilicate glass pinning pipettes To measure endothelial membrane potential, while viewing through the 4X objective, carefully position the sharp electrode tip just over a cell of the arteriolar endothelial tube into the flowing physiological salt solution with a micro manipulator.Gradually increase magnification to 400X and reposition the electrode tip as needed. Using the micro manipulator, gently insert the tip of a sharp electrode into one of the cells of the endothelial tube and start recording VM using an electrometer. Once the endothelial resting VM is stable from minus 30 to minus 40 millivolts, apply the desired pharmacological agents per experimental objective.Load the endothelial tube with the fluorescence tracker for the plasma membrane or desired organelle at 37 degrees Celsius for 15 to 30 minutes. Wash the cells with fresh superfusion physiological salt solution and image live cells under the microscope at the excitation wavelength of the respective dyes. Endothelial function was assessed by measuring intracellular calcium and membrane potential in response to a pharmacological agent MTA, a potent purinergic receptor agonist at 37 degrees Celsius.Upon application of one micromolar MTA, intracellular calcium concentration rapidly increases with a concomitant hyperpolarization. Furthermore, the intact endothelium was incubated at 37 degrees Celsius with fluorescent trackers for visualization to examine cellular morphology. Live endothelial cell imaging showed co-staining for plasma membrane and nuclei.The plasma membrane was stained together with an endoplasmic reticulum fluorescent stain whereby areas of apparent overlap of ER within proximity of the plasma membrane appear orange. The experimenter should be careful during dissection and isolation to avoid damage to the arterioles because a damaged arteriole will definitely not yield an intact endothelial tube. Following the procedure, the cells may be used for fixed immunohistochemistry with fluorescent antibodies or live cell staining of organelles and membrane lipids.This technique will generate new information for understanding mechanisms underlying cerebral blood flow at the fundamental level for physiology and select transitions towards pathology for therapy.

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