This work was funded by a National Health and Medical Research Council (NHMRC) Project Grant 568721 (SRT) and, in part, by a UNSW Faculty of Medicine Faculty Research Grant (MDR).

1. General Endothelial Cell Culture
<ol>
	<li>Culture bovine aortic endothelial cells (passages 4&#8211;9) on gelatin-coated tissue culture flasks (coat tissue culture surface with 0.1% w/v gelatin in PBS at RT for 15 min) in EGM-2 media (with the EGM-2 bullet kit containing 5% fetal bovine serum, growth factors and all supplements provided by the manufacturer, except for hydrocortisone).</li>
	<li>When cells are near-confluent (ca. 3 days post seeding after a 1:4 split), harvest cells by treatment with 0.05% w/v tryps...

<ol>
	<li>Wu, M. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endothelial+focal+adhesions+and+barrier+function.">Endothelial focal adhesions and barrier function.</a> J Physiol. 569, 359-366 (2005).</li><li>Geiger, B., Yamada, K. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+architecture+and+function+of+matrix+adhesions.">Molecular architecture and function of matrix adhesions.</a> Cold Spring Harb Perspect Biol. 3, (2011).</li><li>Rees, M. D., Kennett, E. C., Whitelock, J. M., Davies, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Oxidative+damage+to+extracellular+matrix+and+its+role+in+human+pathologies.">Oxidative damage to extracellular matrix and its role in human pathologies.</a> Free Radic Biol Med. 44, 1973-2001 (2008).</li><li>Cox, T. R., Erler, J. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Remodeling+and+homeostasis+of+the+extracellular+matrix:+implications+for+fibrotic+diseases+and+cancer.">Remodeling and homeostasis of the extracellular matrix: implications for fibrotic diseases and cancer.</a> Dis Model Mech. 4, 165-178 (2011).</li><li>Baldus, 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=Endothelial+transcytosis+of+myeloperoxidase+confers+specificity+to+vascular+ECM+proteins+as+targets+of+tyrosine+nitration.">Endothelial transcytosis of myeloperoxidase confers specificity to vascular ECM proteins as targets of tyrosine nitration.</a> J Clin Invest. 108, 1759-1770 (2001).</li><li>Baldus, 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=Spatial+mapping+of+pulmonary+and+vascular+nitrotyrosine+reveals+the+pivotal+role+of+myeloperoxidase+as+a+catalyst+for+tyrosine+nitration+in+inflammatory+diseases.">Spatial mapping of pulmonary and vascular nitrotyrosine reveals the pivotal role of myeloperoxidase as a catalyst for tyrosine nitration in inflammatory diseases.</a> Free Radic Biol Med. 33, 1010-1019 (2002).</li><li>Thomas, S. R., Witting, P. K., Drummond, G. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Redox+control+of+endothelial+function+and+dysfunction:+molecular+mechanisms+and+therapeutic+opportunities.">Redox control of endothelial function and dysfunction: molecular mechanisms and therapeutic opportunities.</a> Antioxid Redox Signal. 10, 1713-1765 (2008).</li><li>Rees, M. 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=Myeloperoxidase-derived+oxidants+selectively+disrupt+the+protein+core+of+the+heparan+sulfate+proteoglycan+perlecan.">Myeloperoxidase-derived oxidants selectively disrupt the protein core of the heparan sulfate proteoglycan perlecan.</a> Matrix Biol. 29, 63-73 (2010).</li><li>Rees, M. 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=Targeted+subendothelial+matrix+oxidation+by+myeloperoxidase+triggers+myosin+II-dependent+de-adhesion+and+alters+signaling+in+endothelial+cells.">Targeted subendothelial matrix oxidation by myeloperoxidase triggers myosin II-dependent de-adhesion and alters signaling in endothelial cells.</a> Free Radic Biol Med. 53, 2344-2356 (2012).</li><li>Solly, K., Wang, X., Xu, X., Strulovici, B., Zheng, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Application+of+real-time+cell+electronic+sensing+(RT-CES)+technology+to+cell-based+assays.">Application of real-time cell electronic sensing (RT-CES) technology to cell-based assays.</a> Assay Drug Dev Technol. 2, 363-372 (2004).</li><li>Giaever, I., Keese, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micromotion+of+mammalian+cells+measured+electrically.">Micromotion of mammalian cells measured electrically.</a> Proc Natl Acad Sci U S A. 88, 7896-7900 (1991).</li><li>Vissers, M. C., Thomas, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hypochlorous+acid+disrupts+the+adhesive+properties+of+subendothelial+matrix.">Hypochlorous acid disrupts the adhesive properties of subendothelial matrix.</a> Free Radic Biol Med. 23, 401-411 (1997).</li><li>Ziv, N. E., Schiller, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+Interference+Contrast+(DIC)+Imaging+of+Living+Cells.">Differential Interference Contrast (DIC) Imaging of Living Cells.</a> CSH Protoc. 2007, (2007).</li><li>Kennett, E. 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=Peroxynitrite+modifies+the+structure+and+function+of+the+extracellular+matrix+proteoglycan+perlecan+by+reaction+with+both+the+protein+core+and+the+heparan+sulfate+chains.">Peroxynitrite modifies the structure and function of the extracellular matrix proteoglycan perlecan by reaction with both the protein core and the heparan sulfate chains.</a> Free Radic Biol Med. 49, 282-293 (2010).</li><li>Sen, S., Ng, W. P., Kumar, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Contractility+dominates+adhesive+ligand+density+in+regulating+cellular+de-adhesion+and+retraction+kinetics.">Contractility dominates adhesive ligand density in regulating cellular de-adhesion and retraction kinetics.</a> Ann Biomed Eng. 39, 1163-1173 (2011).</li><li>Wildt, B., Wirtz, D., Searson, P. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Programmed+subcellular+release+for+studying+the+dynamics+of+cell+detachment.">Programmed subcellular release for studying the dynamics of cell detachment.</a> Nat Methods. 6, 211-213 (2009).</li></ol>

Cell-matrix adhesion and de-adhesion processes can be quantified accurately in real time with high temporal resolution using cell-substrate impedance and live cell imaging analyses. These real-time approaches provide a major advantage over end-point analyses of cell adhesion, which provide poor temporal resolution. By accurately quantifying rapid de-adhesion responses with high temporal resolution, these analyses can provide critical insights into how morphological responses to matrix modifications are regulated and how ...

Stable adhesive contacts between cells and their surrounding extracellular matrix are required for maintenance of tissue homeostasis. For example, endothelial cell adhesion to the subendothelial matrix in blood vessels plays a critical role in maintaining the integrity of the endothelial layer and its homeostatic function as a regulatory, semi-permeable vascular barrier1. The actin cytoskeleton is mechanically coupled to adhesive matrix molecules at sites of cell-matrix adhesion and adhesive contacts at the cell-matrix interface play an important role in determining the position of the cell membrane by resisting centrally-directed actomyosin tensile forces. Extracellular stimuli that alter cell-matrix adhesion necessarily alter the balance of forces at the cell-matrix interface, an event that is rapidly &#8216;sensed&#8217; by mechano-sensitive signaling proteins, resulting in the transduction of &#8220;outside-in signaling&#8221;. This cross-talk between cells and their surrounding extracellular matrix plays a key role in controlling cell shape, motility, function, proliferation and survival2.
Diverse patho-physiological processes (embryonic development, inflammation, wound repair and cancer metastasis) are characterized by dynamic remodeling of adhesive matrix substrates by matrix-degrading oxidants and/or enzymes3,4. For example, adhesive subendothelial matrix proteins in blood vessels (e.g., fibronectin) are implicated as major targets for modification or degradation in human inflammatory diseases due to the localized production of reactive oxidants (e.g., hypochlorous acid, HOCl) by the leukocyte-derived enzyme myeloperoxidase (MPO), which accumulates within the subendothelium during inflammatory vascular disease (Figure 1)5-9. Changes in cell-matrix adhesion induced by MPO-derived oxidants and other matrix-modifying stimuli are likely to play important roles in altering vascular homeostasis during a variety of pathological processes; e.g., by altering endothelial cell signaling, morphology and viability, which in turn perturbs endothelial function and barrier integrity. However, the morphological and cell signaling responses of adherent cells to extracellular matrix modifications are only beginning to be understood.
To understand how matrix modifications drive changes in cell adhesion dynamics and adhesion-dependent cell signaling pathways, techniques are required that accurately quantify changes in cell-matrix adhesion in real time, with high temporal resolution. Here, we describe complementary cell-substrate impedance and live cell imaging techniques that fulfill these criteria and provide a platform to quantify cell adhesion and de-adhesion processes in a non-invasive manner.
We show how these cell-substrate impedance and live cell imaging approaches can be readily employed to (i) monitor the dynamics of cell attachment and spreading (i.e., de novo cell adhesion) onto native and modified matrix substrates and (ii) to measure the dynamics of cell-matrix detachment (i.e., de-adhesion) by adherent cells exposed to matrix-modifying stimuli. The xCELLigence cell-substrate impedance biosensor system provides a continuous measurement of the area of cell-matrix contact by quantifying electrical impedance at the surface of 96-well gold microelectrode arrays and expresses these electrical impedance measurements as &#8216;cell index&#8217;, a dimensionless value that is largely proportional to the area of cell-substrate contact10 (Figure 2), whilst also being sensitive to changes in the average distance between the (insulating) cell membrane and the electrode surface11. A further increase in cell index values is also achieved upon formation of tight cell-cell contacts that restrict paracellular current flows,11 conditions that do not prevail within the experiments described in this study. Measurement of the projected area of individual cells over time by image analysis of time-lapse differential interference contrast (DIC) movies provides a complementary measure of changes in the area of cell-substrate contact and provides additional information regarding the precise nature and dynamics of the morphological changes quantified by the cell-substrate impedance approach.
Specifically, we describe the application of these approaches to monitor how MPO-mediated oxidation of adhesive subendothelial matrix proteins (e.g., fibronectin) (i) reduces the de novo adhesion of suspended endothelial cells onto purified fibronectin and (ii) triggers cell-matrix de-adhesion in endothelial cells with established adhesion on fibronectin. By performing parallel cell signaling analyses over time using relevant biochemical assays (e.g., Western blotting), the temporal and causal relationships between adhesion/de-adhesion processes and associated changes in adhesion-dependent cell signaling events can be determined.
These approaches were recently used to demonstrate that extracellular matrix oxidation catalyzed by subendothelial deposits of MPO triggers a rapid loss in cell-matrix adhesion of endothelial cells that is driven by pre-existing actomyosin contractile forces9. Importantly, by enabling the temporal relationship between changes in both cell adhesion and adhesion-dependent cell signaling to be determined, these approaches identified that MPO-induced matrix modification and cellular de-adhesion triggers changes in important adhesion-dependent cell signaling pathways including Src kinase-dependent paxillin phosphorylation and myosin light chain II phosphorylation (Figure 1)9. This mode of redox-dependent signaling, involving the activation of intracellular signaling events by extracellular oxidative reactions that disrupt cell-matrix adhesion, represents a novel mode of cell signaling termed &#8220;outside-in redox signaling&#8221; (Figure 1)9.
In general, these complementary cell-substrate impedance biosensor and live cell imaging approaches should be valuable in revealing how different matrix-modifying stimuli or agents drive changes in cell adhesion dynamics, morphology and signaling within different adherent cell-types subject to a wide variety of experimental settings.
The following protocol describes how to quantify the impact of MPO-mediated matrix oxidation on de novo endothelial cell adhesion (Experiment 1) and endothelial cell de-adhesion (Experiment 2) processes. MPO binds avidly to fibronectin and other adhesive subendothelial extracellular matrix proteins and uses hydrogen peroxide (H2O2) to convert chloride ions (Cl&#8211;) to the highly reactive chlorinating oxidant hypochlorous acid (HOCl), which reacts locally with these matrix proteins and disrupts their cell adhesive properties (Figure 1)8,9,12.

<table border="0" cellpadding="0" cellspacing="0" width="1328">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Name of Material/ Equipment</td>
			<td style="width:223px;">Company</td>
			<td style="width:151px;">Catalog Number</td>
			<td style="width:551px;">Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">96 well gold cell-substrate impedance microelectrode array</td>
			<td style="width:223px;">ACEA Biosciences / Roche</td>
			<td style="width:151px;">E-Plate 96</td>
			<td>single-use plate used for performing cell-based assays on the xCELLigence system</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">blebbistatin</td>
			<td style="width:223px;">Sigma</td>
			<td style="width:151px;">B0560</td>
			<td>selective inhibitor of non-muscle myosin-II</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Bovine Aortic Endothelial Cells, cryopreserved&#160;</td>
			<td style="width:223px;">Lonza</td>
			<td style="width:151px;">BW-6001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Bovine serum albumin</td>
			<td style="width:223px;">Sigma</td>
			<td style="width:151px;">05470</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">EGM-2 BulletKit</td>
			<td style="width:223px;">Lonza</td>
			<td style="width:151px;">CC-3162</td>
			<td>endothelial cell growth media kit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Fibronectin, lyophilized powder</td>
			<td style="width:223px;">Sigma</td>
			<td style="width:151px;">F-4759</td>
			<td>from bovine plasma</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Fluorodish 35 mm glass-bottomed cell culture dish</td>
			<td style="width:223px;">World Precision Instruments</td>
			<td style="width:151px;">FD35-100</td>
			<td>Cell cuture dish with optical quality glass bottom for imaging</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Gelatin from bovine skin</td>
			<td style="width:223px;">Sigma</td>
			<td style="width:151px;">G9391</td>
			<td>cell culture substratum</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Hank&#39;s Balanced Salt Solution</td>
			<td style="width:223px;">Life Technologies</td>
			<td style="width:151px;">14025076</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Hydrogen peroxide</td>
			<td style="width:223px;">Merck</td>
			<td style="width:151px;">107298</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Medium-199</td>
			<td style="width:223px;">Life Technologies</td>
			<td style="width:151px;">11150-059</td>
			<td>serum-free cell media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Methionine</td>
			<td style="width:223px;">Sigma</td>
			<td style="width:151px;">M9500</td>
			<td>quenches chlorinating oxidants generated by myeloperoxidase</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Myeloperoxidase, Human Polymorphonuclear Leukocytes</td>
			<td style="width:223px;">Millipore</td>
			<td style="width:151px;">475911</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:405px;">RTCA MP Instrument / xCELLigence cell substrate impedance system</td>
			<td style="width:223px;">ACEA Biosciences / Roche</td>
			<td style="width:151px;">-</td>
			<td>Consists of RTCA Analyzer, RTCA (Multiple Plate) MP Station and RTCA Control Unit</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:405px;">Trypsin-EDTA (0.5%)</td>
			<td>Gibco</td>
			<td>15400-054&#160;</td>
			<td></td>
		</tr>
	</tbody>
</table>

using cell-substrate impedance and live cell imaging to measure real-time changes in cellular adhesion and de-adhesion induced by matrix modification

Cell-matrix adhesion plays a key role in controlling cell morphology and signaling. Stimuli that disrupt cell-matrix adhesion (e.g., myeloperoxidase and other matrix-modifying oxidants/enzymes released during inflammation) are implicated in triggering pathological changes in cellular function, phenotype and viability in a number of diseases. Here, we describe how cell-substrate impedance and live cell imaging approaches can be readily employed to accurately quantify real-time changes in cell adhesion and de-adhesion induced by matrix modification (using endothelial cells and myeloperoxidase as a pathophysiological matrix-modifying stimulus) with high temporal resolution and in a non-invasive manner. The xCELLigence cell-substrate impedance system continuously quantifies the area of cell-matrix adhesion by measuring the electrical impedance at the cell-substrate interface in cells grown on gold microelectrode arrays. Image analysis of time-lapse differential interference contrast movies quantifies changes in the projected area of individual cells over time, representing changes in the area of cell-matrix contact. Both techniques accurately quantify rapid changes to cellular adhesion and de-adhesion processes. Cell-substrate impedance on microelectrode biosensor arrays provides a platform for robust, high-throughput measurements. Live cell imaging analyses provide additional detail regarding the nature and dynamics of the morphological changes quantified by cell-substrate impedance measurements. These complementary approaches provide valuable new insights into how myeloperoxidase-catalyzed oxidative modification of subcellular extracellular matrix components triggers rapid changes in cell adhesion, morphology and signaling in endothelial cells. These approaches are also applicable for studying cellular adhesion dynamics in response to other matrix-modifying stimuli and in related adherent cells (e.g., epithelial cells).

Real-time quantification of endothelial cell de-adhesion from fibronectin in response to MPO-mediated fibronectin oxidation (Experiment 2). The seeding of endothelial cell suspensions onto native (MPO free) fibronectin or MPO-bearing fibronectin results in maximal cell attachment and spreading within 2 hr, as judged by a plateauing of cell index values in the cell substrate impedance measurements (Figure 3A). This initial phase of cell attachment and spreading is markedly reduced when MP...

Watch this Scientific Journal Video about Using Cell-substrate Impedance and Live Cell Imaging to Measure Real-time Changes in Cellular Adhesion and De-adhesion Induced by Matrix Modification at JoVE.

Using Cell-substrate Impedance and Live Cell Imaging to Measure Real-time Changes in Cellular Adhesion and De-adhesion Induced by Matrix Modification

Here, we present a protocol to continuously quantify cell adhesion and de-adhesion processes with high temporal resolution in a non-invasive manner by cell-substrate impedance and live cell imaging analyses. These approaches reveal the dynamics of cell adhesion/de-adhesion processes triggered by matrix modification and their temporal relationship to adhesion-dependent signaling events.

Cell-matrix adhesion plays a key role in controlling cell morphology and signaling. Stimuli that disrupt cell-matrix adhesion (e.g., myeloperoxidase and ...

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JoVE Journal

Bioengineering

10.8K Views.  University of New South Wales.  Qui, vi presentiamo un protocollo per quantificare continuamente i processi di adesione cellulare e de-adesione con alta risoluzione temporale in modo non invasivo per impedenza cellule-substrato e imaging cellulare dal vivo analisi. Questi approcci rivelano le dinamiche dei processi di adesione cellulare / de-adesione innescato da modifica della matrice e la loro relazione temporale con gli eventi di segnalazione adesione-dipendente. 

Video: Using Cell-substrate Impedance and Live Cell Imaging to Measure Real-time Changes in Cellular Adhesion and De-adhesion Induced by Matrix Modification