This work was funded by the National Heart, Lung, and Blood Institute (R01 HL073965, IL) and (T32 HL007829-24, ISF). The authors would also like to acknowledge the Scientific Machine Shop at the University of Illinois at Chicago for generating our latest MPP flow chambers.

The use of animals in our studies is approved by the University of Illinois at Chicago Animal Care Committee (#16-183).
1. Assembly of the Modified Parallel Plate Flow Chamber
NOTE: Please refer to Table 1 and Figure 1 for MPP flow chamber piece IDs. Please refer to Figure 1 for a schematic detailing the orientation of chamber pieces for assembly.
<ol>
	<li>To adhere the ...

<ol>
	<li>Green, D. J., Hopman, M. T., Padilla, J., Laughlin, M. H., Thijssen, D. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascular+Adaptation+to+Exercise+in+Humans:+Role+of+Hemodynamic+Stimuli.">Vascular Adaptation to Exercise in Humans: Role of Hemodynamic Stimuli.</a> Physiological Reviews. 97 (2), 495-528 (2017).</li><li>Gimbrone, M. A., Topper, J. N., Nagel, T., Anderson, K. R., Garcia-Cardena, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+dysfunction,+hemodynamic+forces,+and+atherogenesis.">Endothelial dysfunction, hemodynamic forces, and atherogenesis.</a> Annals of the New York Academy of Sciences. 902, 230-239 (2000).</li><li>Olesen, S. P., Clapham, D. E., Davies, P. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Haemodynamic+shear+stress+activates+a+K++current+in+vascular+endothelial+cells.">Haemodynamic shear stress activates a K+ current in vascular endothelial cells.</a> Nature. 331 (6152), 168-170 (1988).</li><li>Barakat, A. I., Lieu, D. K., Gojova, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Secrets+of+the+code:+do+vascular+endothelial+cells+use+ion+channels+to+decipher+complex+flow+signals?.">Secrets of the code: do vascular endothelial cells use ion channels to decipher complex flow signals?.</a> Biomaterials. 27 (5), 671-678 (2006).</li><li>Beech, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+Piezo1+channels+as+sensors+of+exercise.">Endothelial Piezo1 channels as sensors of exercise.</a> Journal of Physiology. 596 (6), 979-984 (2018).</li><li>Ahn, S. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inwardly+rectifying+K(+)+channels+are+major+contributors+to+flow-induced+vasodilatation+in+resistance+arteries.">Inwardly rectifying K(+) channels are major contributors to flow-induced vasodilatation in resistance arteries.</a> Journal of Physiology. 595 (7), 2339-2364 (2017).</li><li>Fancher, I. 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=Hypercholesterolemia-Induced+Loss+of+Flow-Induced+Vasodilation+and+Lesion+Formation+in+Apolipoprotein+E-Deficient+Mice+Critically+Depend+on+Inwardly+Rectifying+K(+)+Channels.">Hypercholesterolemia-Induced Loss of Flow-Induced Vasodilation and Lesion Formation in Apolipoprotein E-Deficient Mice Critically Depend on Inwardly Rectifying K(+) Channels.</a> Journal of the American Heart Association. 7 (5), (2018).</li><li>Rode, 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=Piezo1+channels+sense+whole+body+physical+activity+to+reset+cardiovascular+homeostasis+and+enhance+performance.">Piezo1 channels sense whole body physical activity to reset cardiovascular homeostasis and enhance performance.</a> Nature Communications. 8 (1), 350 (2017).</li><li>Li, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Piezo1+integration+of+vascular+architecture+with+physiological+force.">Piezo1 integration of vascular architecture with physiological force.</a> Nature. 515 (7526), 279-282 (2014).</li><li>Levitan, I., Helmke, B. P., Davies, P. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+chamber+to+permit+invasive+manipulation+of+adherent+cells+in+laminar+flow+with+minimal+disturbance+of+the+flow+field.">A chamber to permit invasive manipulation of adherent cells in laminar flow with minimal disturbance of the flow field.</a> Annals of Biomed Engineering. 28 (10), 1184-1193 (2000).</li><li>Fang, Y., 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=Hypercholesterolemia+suppresses+inwardly+rectifying+K++channels+in+aortic+endothelium+in+vitro+and+in+vivo.">Hypercholesterolemia suppresses inwardly rectifying K+ channels in aortic endothelium in vitro and in vivo.</a> Circulation Research. 98 (8), 1064-1071 (2006).</li><li>Shetty, S., Weston, C. J., Adams, D. H., Lalor, P. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+flow+adhesion+assay+to+study+leucocyte+recruitment+to+human+hepatic+sinusoidal+endothelium+under+conditions+of+shear+stress.">A flow adhesion assay to study leucocyte recruitment to human hepatic sinusoidal endothelium under conditions of shear stress.</a> Journal of Visualized Experiments. (85), e51330 (2014).</li><li>Man, H. S. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gene+Expression+Analysis+of+Endothelial+Cells+Exposed+to+Shear+Stress+Using+Multiple+Parallel-plate+Flow+Chambers.">Gene Expression Analysis of Endothelial Cells Exposed to Shear Stress Using Multiple Parallel-plate Flow Chambers.</a> Journal of Visualized Experiments. (140), e58478 (2018).</li><li>White, L. 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=The+Assembly+and+Application+of+'Shear+Rings':+A+Novel+Endothelial+Model+for+Orbital,+Unidirectional+and+Periodic+Fluid+Flow+and+Shear+Stress.">The Assembly and Application of 'Shear Rings': A Novel Endothelial Model for Orbital, Unidirectional and Periodic Fluid Flow and Shear Stress.</a> Journal of Visualized Experiments. (116), e54632 (2016).</li><li>Franzoni, M., 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=Design+of+a+cone-and-plate+device+for+controlled+realistic+shear+stress+stimulation+on+endothelial+cell+monolayers.">Design of a cone-and-plate device for controlled realistic shear stress stimulation on endothelial cell monolayers.</a> Cytotechnology. 68 (5), 1885-1896 (2016).</li><li>Dewey, C. F., Bussolari, S. R., Gimbrone, M. A., Davies, P. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+dynamic+response+of+vascular+endothelial+cells+to+fluid+shear+stress.">The dynamic response of vascular endothelial cells to fluid shear stress.</a> Journal of Biomechanical Engineering. 103 (3), 177-185 (1981).</li><li>Hoger, J. H., Ilyin, V. I., Forsyth, S., Hoger, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Shear+stress+regulates+the+endothelial+Kir2.1+ion+channel.">Shear stress regulates the endothelial Kir2.1 ion channel.</a> Proceedings of the National Academy of Sciences of the United States of America. 99 (11), 7780-7785 (2002).</li><li>Moccia, F., Villa, A., Tanzi, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow-activated+Na(+)and+K(+)Current+in+cardiac+microvascular+endothelial+cells.">Flow-activated Na(+)and K(+)Current in cardiac microvascular endothelial cells.</a> Journal of Molecular and Cellular Cardiology. 32 (8), 1589-1593 (2000).</li><li>Crane, G. J., Walker, S. D., Dora, K. A., Garland, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence+for+a+differential+cellular+distribution+of+inward+rectifier+K+channels+in+the+rat+isolated+mesenteric+artery.">Evidence for a differential cellular distribution of inward rectifier K channels in the rat isolated mesenteric artery.</a> Journal of Vascular Research. 40 (2), 159-168 (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+SK(Ca)+and+IK(Ca)+channels+regulate+brain+parenchymal+arteriolar+diameter+and+cortical+cerebral+blood+flow.">Endothelial SK(Ca) and IK(Ca) channels regulate brain parenchymal arteriolar diameter and cortical cerebral blood flow.</a> Journal of Cereberal Blood Flow and Metabolism. 31 (5), 1175-1186 (2011).</li><li>Lane, W. O., 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=Parallel-plate+flow+chamber+and+continuous+flow+circuit+to+evaluate+endothelial+progenitor+cells+under+laminar+flow+shear+stress.">Parallel-plate flow chamber and continuous flow circuit to evaluate endothelial progenitor cells under laminar flow shear stress.</a> Journal of Visualized Experiments. (59), e3349 (2012).</li><li>Lieu, D. K., Pappone, P. A., Barakat, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+membrane+potential+and+ion+current+responses+to+different+types+of+shear+stress+in+vascular+endothelial+cells.">Differential membrane potential and ion current responses to different types of shear stress in vascular endothelial cells.</a> American Journal of Physiology-Cell Physiology. 286 (6), C1367-C1375 (2004).</li><li>Le Master, E., 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=Proatherogenic+Flow+Increases+Endothelial+Stiffness+via+Enhanced+CD36-Mediated+Uptake+of+Oxidized+Low-Density+Lipoproteins.">Proatherogenic Flow Increases Endothelial Stiffness via Enhanced CD36-Mediated Uptake of Oxidized Low-Density Lipoproteins.</a> Arteriosclerosis, Thrombosis, and Vascular Biology. 38 (1), 64-75 (2018).</li><li>Kim, J. 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=Measurement+of+Ion+Concentration+in+the+Unstirred+Boundary+Layer+with+Open+Patch-Clamp+Pipette:+Implications+in+Control+of+Ion+Channels+by+Fluid+Flow.">Measurement of Ion Concentration in the Unstirred Boundary Layer with Open Patch-Clamp Pipette: Implications in Control of Ion Channels by Fluid Flow.</a> Journal of Visualized Experiments. (143), e58228 (2019).</li><li>Kim, J. 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=Fluid+flow+facilitates+inward+rectifier+K(+)+current+by+convectively+restoring+[K(+)]+at+the+cell+membrane+surface.">Fluid flow facilitates inward rectifier K(+) current by convectively restoring [K(+)] at the cell membrane surface.</a> Scientific Reports. 6, 39585 (2016).</li><li>Malek, A. M., Alper, S. L., Izumo, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hemodynamic+shear+stress+and+its+role+in+atherosclerosis.">Hemodynamic shear stress and its role in atherosclerosis.</a> Journal of the American Medical Association. 282 (21), 2035-2042 (1999).</li><li>Jacobs, E. R., 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=Shear+activated+channels+in+cell-attached+patches+of+cultured+bovine+aortic+endothelial+cells.+Pflugers+Archiv.">Shear activated channels in cell-attached patches of cultured bovine aortic endothelial cells. Pflugers Archiv.</a> European Journal of Physiology. 431 (1), 129-131 (1995).</li><li>Barakat, A. I., Leaver, E. V., Pappone, P. A., Davies, P. 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The vascular system is constantly exposed to active hemodynamic forces, which activate mechanosensitive ion channels3,22 but the physiological roles of these channels in shear stress-induced mechanotransduction is only starting to emerge4,6,8. The mechanisms responsible for the mechanosensitivity of shear stress-activated channels remain unknown. The protocol detailed he...

Hemodynamic forces generated by the blood flow are well known to play major roles in endothelial and vascular function1,2. It is also well known that several types of ion channels acutely respond to changes in shear stress3,4,5 leading to the hypothesis that ion channels can be primary shear stress sensors. More recently, we and others showed that mechanosensitive ion channels play critical roles in several shear-stress sensitive vascular functions, including the vasoactive response to shear stress6,7,8, and developmental angiogenesis9. The mechanisms of the shear-stress sensitivity of ion channels, however, are almost totally unknown. This gap of knowledge is likely to be due to the technical difficulty of performing electrophysiological recordings under well-defined shear stress. In this article, therefore, we provide a step by step detailed protocol routinely performed in our lab to achieve this goal6,7,10,11.
The overall goal of this method is to allow the real-time investigation of ion channel mechanoactivation under well-defined shear stress in the physiological range. This is achieved by modifying a standard parallel plate flow chamber to allow an electrophysiological pipette to be lowered into the chamber and access cells grown on the bottom plate during the real time exposure to flow, providing a unique approach to achieve this goal6,7,11. In contrast, standard parallel plate flow chambers, described in prior publications can be used for the real time imaging analysis of cells exposed to shear forces12 or other non-invasive approaches13,14 but not for electrophysiology. Similarly, the cone and plate apparatus, another powerful approach to expose cells to shear stress15,16 is also not suitable for electrophysiological recordings. Thus, these flow devices do not allow the investigation of shear stress sensitivity of ion channels. The difficulty in performing electrophysiological recordings under flow is the main reason for the paucity of information about the mechanisms responsible for these crucial effects.
In terms of the alternative approaches to achieve the same goal, there are none that are as accurate or controlled. Some earlier studies attempted to record ion channel activity under flow by exposing cells to a stream of liquid coming from another pipette brought to the vicinity of a cell from above17,18. This is highly non-physiological, as the mechanical forces generated under these conditions have little in common with the physiological profiles of shear stress in the blood vessels. Similar concerns apply to the attempts to simulate physiological shear stress by perfusion of open chambers. As discussed in detail in our earlier study10, an open liquid-air interface creates multiple disturbances and recirculation, which are non-physiological. To address all these concerns, we have designed a modified parallel plate (MPP) flow chamber, also referred to as the &#8220;minimally invasive flow device&#8221; in our earlier studies6,7,10,11, made from acrylic and extensively used in our lab. However, in spite of the fact that the original description of the design has been published almost 20 years ago and is the only flow device that allows performing electrophysiological recordings under well-defined shear stress, this methodology has not been adopted by other labs and there are only very few studies that attempt to record currents under flow. We believe, therefore, that providing a detailed description for using the MPP flow chamber will be of great help to researches who are interested in mechanosensitive ion channels and vascular biology.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.2 &#181;m sterile syringe filters</td>
			<td>VWR</td>
			<td>28145-501</td>
			<td>Used for filtering electrophysiolgoical pipette solution</td>
		</tr>
		<tr>
			<td>5 grade forceps</td>
			<td>Fine Scientific Tools</td>
			<td>1252-30</td>
			<td>Used for transferring digested arteries to fresh solution</td>
		</tr>
		<tr>
			<td>9&#34; Pasteur Pipet</td>
			<td>Fisher Scientifc</td>
			<td>13-678-20D</td>
			<td>Used for mechanically disrupting digested arteries and transferring freshly isolated endohtelial cells&#160;</td>
		</tr>
		<tr>
			<td>12 mm diameter Cover glass circles</td>
			<td>Fisher Scientifc</td>
			<td>12-545-80</td>
			<td>For use with studies involving cultured cells and multiple treatments. Cells adhered to the cover glass are used for patch clamp analyses</td>
		</tr>
		<tr>
			<td>24 x 40 mm Rectangluar Cover glass</td>
			<td>Sigma-Aldrich</td>
			<td>CLS2975224</td>
			<td>Cover glass to be added to MPP flow chamber pieces C (Figure 1)</td>
		</tr>
		<tr>
			<td>24 x 50 mm Rectangluar Cover glass</td>
			<td>Sigma-Aldrich</td>
			<td>CLS2975245</td>
			<td>Cover glass to be added to MPP flow chamber E (Figure 1)</td>
		</tr>
		<tr>
			<td>20 gauge syringe needles</td>
			<td>Becton Dickinson and Co</td>
			<td>305175</td>
			<td>For use in mechanical disruption of digested mesenteric arteries</td>
		</tr>
		<tr>
			<td>35 mm Petri dish</td>
			<td>Genesee Scientific</td>
			<td>32-103</td>
			<td>For use in mechanical disruption of digested mesenteric arteries</td>
		</tr>
		<tr>
			<td>Amphotericin B solubilized</td>
			<td>Sigma-Aldrich</td>
			<td>A9528-50MG</td>
			<td>Used for generating the perforated whole-cell patch configuration.</td>
		</tr>
		<tr>
			<td>collagenase, type I</td>
			<td>Worthington Biochemical</td>
			<td>100 mg - LS004194</td>
			<td>Enzyme used in our laboratory as a brief digestion following the initial cocktail of neutral protease and elastase</td>
		</tr>
		<tr>
			<td>Dimethyl Sulfoxide (DMSO)</td>
			<td>Fisher Scientifc</td>
			<td>67-68-5</td>
			<td>Solvent for Amphotericin B used in perforated whole-cell patch clamp</td>
		</tr>
		<tr>
			<td>elastase, lyophilized</td>
			<td>Worthington Biochemical</td>
			<td>25 mg - LS002290&#160;</td>
			<td>Enzyme used in our laboratory in a cocktail with neutral protease/dispase to begin digestion of arteries for endothelial cell isolation.</td>
		</tr>
		<tr>
			<td>Falcon Tissue culture Plate, 6-well, Flat Bottom with Low Evaporation Lid&#160;</td>
			<td>Corning</td>
			<td>353046</td>
			<td>For use with studies involving cultured cells and multiple treatments</td>
		</tr>
		<tr>
			<td>neutral protease/dispase</td>
			<td>Worthington Biochemical</td>
			<td>10 mg- LS02100 50 mg - LS02104</td>
			<td>Enzyme used in our laboratory in a cocktail with elastase to begin digestion of arteries for endothelial cell isolation</td>
		</tr>
		<tr>
			<td>SylGard&#160;</td>
			<td>World Precision Instruments</td>
			<td>SYLG184</td>
			<td>Silicone elastomer for adhering the rectangular cover slip to the MPP flow chamber pieces C and E (Figure 1)</td>
		</tr>
		<tr>
			<td>Tygon ND 10-80 tubing</td>
			<td>Microbore Tubing</td>
			<td>AAQ04133</td>
			<td>ID: 0.05 in, OD: 0.09 in, inlet perfusion tubing for adminsitering flow to the chamber</td>
		</tr>
	</tbody>
</table>

electrophysiological recordings of single-cell ion currents under well-defined shear stress

Fluid shear stress is well known to play a major role in endothelial function. In most vascular beds, elevated shear stress from acute increases in blood flow triggers a signaling cascade resulting in vasodilation thereby alleviating mechanical stress on the vascular wall. The pattern of shear stress is also well known to be a critical factor in the development of atherosclerosis with laminar shear stress being atheroprotective and disturbed shear stress being pro-atherogenic. While we have a detailed understanding of the various intermediate cell signaling pathways, the receptors that first translate the mechanical stimulus into chemical mediators are not completely understood. Mechanosensitive ion channels are critical to the response to shear and regulate shear-induced cell signaling thereby controlling the production of vasoactive mediators. These channels are among the earliest activated signaling components to shear and have been linked to shear-induced vasodilation through promoting nitric oxide production (e.g., inwardly rectifying K+ [Kir] and transient receptor potential [TRP] channels) and endothelium hyperpolarizing factor (e.g., Kir and calcium-activated K+ [KCa] channels) and shear-induced vasoconstriction through an undetermined mechanism that involves piezo channels. Understanding the biophysical mechanism by which these channels are activated by shear forces (i.e., directly or through a primary mechano-receptor) could provide potential new targets to resolve the pathophysiology associated with endothelial dysfunction and atherogenesis. It is still a major challenge to record flow-induced activation of ion channels in real time using electrophysiology. The standard methods to expose cells to well-defined shear stress, such as the cone and plate rheometer and closed parallel plate flow chamber do not allow real time study of ion channel activation. The goal of this protocol is to describe a modified parallel plate flow chamber that allows real time electrophysiological recording of mechanosensitive ion channels under well-defined shear stress.

Multiple photographs showing different views of the MPP flow chamber on the microscope stage (upper panel) and a schematic representation of the MPP flow chamber (bottom panel) are shown in Figure 1. The schematic details the dimensions of the entire device and flow chamber. Figure 2 shows a photograph of the gravity perfusion system to the MPP flow chamber in our laboratory (upper panel). Also shown is a schematic representation...

Watch this Scientific Journal Video about Electrophysiological Recordings of Single-cell Ion Currents Under Well-defined Shear Stress at JoVE.com

Electrophysiological Recordings of Single-cell Ion Currents Under Well-defined Shear Stress

The goal of this protocol is to describe a modified parallel plate flow chamber for use in investigating real time activation of mechanosensitive ion channels by shear stress.

Fluid shear stress is well known to play a major role in endothelial function. In most vascular beds, elevated shear stress from acute increases in blood ...

Use of the modified parallel plate flow chamber can help researchers answer key questions pertaining to the functional response of mechanosensitive ion channels to shear stress. The main advantage of this technique is that it allows real-time investigation to flow activated ion channels in an easily assembled, reusable parallel plate flow chamber. To begin the procedure, apply a thin layer of silicone elastomer solution around the edges of the rectangular space of piece C, and gently place the rectangular cover glass, piece D, directly on the elastomer solution to completely cover the open rectangular space of piece C.Carefully wipe away excess silicone elastomer solution.Then, repeat the procedure for adhering the rectangular cover glass, piece F, to the bottom of piece E and allow the silicone elastomer solution to cure overnight at room temperature. Now, assemble the MPP flow chamber by sequentially placing each piece on top of the previous, beginning with the bottom chamber, piece E, then piece C, piece B, followed by piece A on the top. Next, align the screw holes of each piece at the corners and tightly screw the pieces together to prevent leaks from occurring while administering flow to the MPP flow chamber.In a six-well plate, place four to five, 12 millimeter cover glass circles in each well. Save the cells between 10%and 30%confluency, such that single cells can be accessed for electrophysiological recordings. Subsequently, incubate the cells under standard culture conditions for no less than two hours to allow cells to adhere, and no more than 24 hours, as endothelial cells will become flat and difficult to patch when seeded at subconfluency for more than 24 hours.Next, remove a cover glass containing the adhered cells from a well of the six-well plate and quickly rinse in PBS. Then, transfer the cover glass with cells to a 35 millimeter Petri dish containing two milliliters of electrophysiological BAF solution. Immediately transfer the cover glass with cells to the MPP flow chamber.Transfer the cover glass circle to the rectangular cover glass, piece D, which is adhered to piece C of the MPP flow chamber. Add the BAF solution to completely submerge the cover glass circle and the cells. Subsequently, position the cover glass circle on piece D such that the cells will be in line with the slit openings of piece B.Ensure that the cover glass circle adheres to piece D through solution glass adhesion to avoid disruption of the cover glass circle's position by the flow application.Then, assemble the MPP flow chamber by screwing the pieces together in the appropriate order. Transfer the chamber to the microscope stage and immediately perfuse the chamber with BAF solution. Next, identify a healthy cell with a dark border and obvious nucleus for the experiment.Avoid cells that appear to be blubbing or cells that are in contact with other cells. To control shear stress, set up a gravity perfusion system by connecting a 30 milliliter graduated syringe cylinder to a three-way Luer lock fitted with microbore tubing. Next, attach the graduated cylinder to the Faraday cage surrounding the electrophysiology rig using double-sided tape.Prior to inserting the tubing in the MPP chamber, pre-fill the syringe and tubing with BAF solution. Then, insert the tubing into the MPP flow chamber inlet hole of piece A.Pre-fill the MPP flow chamber with solution, such that it is being removed in the vacuum reservoir. Stop the flow to the chamber and refill the graduated cylinder to the top mark.Calculate the flow rate manually using a stopwatch by allowing the solution to flow through the chamber at a given syringe cylinder height. Raise or lower the syringe to alter the flow and calculate the shear stress in a parallel chamber using this equation. Repeat this process until a desired level of shear stress is found.Subsequently, transfer an assembled chamber containing adhered cells to the microscope stage of the electrophysiology rig. And insert the tubing, pre-filled with BAF solution, into the hole of piece A.Then, fill the chamber and wash the cells with 10 milliliters of BAF solution, simultaneously. Once the desired patch configuration is successfully obtained, allow channel currents to stabilize in a static bath at room temperature.As soon as the currents have stabilized, apply shear in a step-wise fashion, allowing the increased current to stabilize prior to the next step of shear stress increase. Remove shear exposure to the cells by stopping the flow to the chamber, allowing mechanosensitive channel currents to return to baseline currents observed in the static bath. Shown here is a representative raw recording of Kir current from a primary mouse mesenteric endothelial cell with notable linear outward leak current.A ramp of negative 140 to positive 40 millivolts was applied to the patch over 400 milliseconds. Leak current prevents the analysis of real Kir channel activity. To subtract leak current, first calculate the linear slope conductance of leak current.Multiple G slope by corresponding voltages of the entire raw trace to plot leak current on the raw data. The line should overlay the outward linear leak exactly. Then, subtract the plotted leak current from the entire trace so that the linear outward current is about zero picoamperes per picofarad, and the real Kir current can be analyzed.The most important thing to remember when attempting this procedure is to properly position the cover glass in the chamber so that cells are accessible for experiments. In addition, be sure that the cover slip is adequately adhered to piece D, such that fluid flow does not disrupt the cover glass containing cells.

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Research

JoVE Journal

Immunology and Infection

6.1K visualizações.  University of Illinois at Chicago. O uso da câmara de fluxo de placas paralelas modificadas pode ajudar os pesquisadores a responder a perguntas-chave relativas à resposta funcional dos canais de íons mecanosensíveis ao estresse de cisalhamento. A principal vantagem desta técnica é que ela permite que a investigação em tempo real flua canais de íons ativados em uma câmara de fluxo de placa paralela facilmente montada e reutilizável. Para iniciar o procedimento, aplique uma fina camada de solução de elastômero de ...