This work was supported by the Sonderforschungsbereich Transregio 19 (SFB/TR19, C2) of the Deutsche Forschungsgemeinschaft (DFG), the Federal Ministry of Economics and Technology project ZIM-KF 2727801MD0 and the Centre for Innovation Competence - Humoral Immune Responses in Cardiovascular Diseases (ZIK-HIKE, BMBF FKZ 03Z2CN12) of the Federal Ministry of Education and Research, Germany. Housing and experiments with animals were performed in accordance with the recommendations of the Society for Laboratory Animal Science (Gesellschaft f&uuml;r Versuchstierkunde, GV-SOLAS) and the Federation of European Laboratory Animal Science Association (FELASA).

1. IgG Isolation from Patient Samples
<ol>
	<li>Prepare mini-immunoadsorption columns by filling 3 ml anti-IgG sepharose per 2 ml patient EDTA plasma into an empty Econo Pac column. IgG isolation requires at least 2 ml of patient plasma.</li>
	<li>Place a filter on top of the anti-IgG sepharose, cut open the lower tip of the column and press the filter to reach a flow rate of approximately 1 drop/sec. Let the preservation solution run out of the column.</li>
	<li>Wash the column with 3 volumes 0.9% NaCl per volume of plasma.</li>
	<li>Pipette the plasma on the column. When the plasma has completely immersed in the anti-IgG sepharose, wash with the same volume 0.9% NaCl.</li>
	<li>Pipette one plasma volume of 0.2 M glycine HCl, pH 2.8 on the column and let immerse into the sepharose. Add another volume of glycine HCl onto the column. Collect the flow through in a 15 ml tube and adjust the pH to 7.3 with 0.5 M Tris-HCl, pH 8.0.</li>
	<li>To regenerate the column, wash with 3 plasma volumes glycine HCl. After a final wash with 2 volumes 0.9% NaCl, the column may be used for the next plasma sample. Alternatively, the column can be filled with preservation solution and stored at 4 - 8 &deg;C for up to 4 weeks.</li>
	<li>For use on cardiomyocytes, the collected IgG fraction has to be dialyzed against experimental buffer (EB). For preparation of EB, add 117 mM NaCl, 2.8 mM KCl, 0.6 mM MgCl2, 1.2 mM KH2PO4, 1.2 mM CaCl2,10 mM HEPES and 20 mM glucose to 1 L distilled water on a magnetic stirrer and adjust pH to 7.3.</li>
	<li>Fill the IgG fraction to a cellulose ester dialysis membrane tube with a molecular weight cut off of 100 kDa. Put the tube in 1 L EB and stir slowly with a magnetic stirrer at 4 &deg;C. After 8 hr, transfer the dialysis tube into 3 L of fresh EB and dialyze for another 20 hr at 4 &deg;C.</li>
	<li>Following dialysis, heat the sample for 30 min at 57 &deg;C in a water bath to inactivate complement factors. Determine total IgG concentration and prepare aliquots containing 330 &mu;g IgG each. When adding the sample to cardiomyocytes for measurement (step 4.3), fill up the aliquots to 1 ml with EB. Undiluted aliquots can be stored at -20 &deg;C until further use.</li>
</ol>
2. Isolation of Rat Cardiomyocytes
<ol>
	<li>For preparation of Ca2+-free isolation buffer (IB), add 110 mM NaCl, 2.6 mM KCl, 1.2 mM MgSO4, 1.2 mM KH2PO4, 20 mM HEPES and 11 mM glucose to 1 L distilled water using a magnetic stirrer. Adjust pH to 7.4 at room temperature and filter through a 0.2 &mu;m bottle top filter for sterilization.</li>
	<li>Fill 80 ml of IB in the upper reservoir of a thermostated Langendorff perfusion system. Adjust thermostat settings to maintain a buffer temperature of 37 &deg;C and aerate buffer with 95% O2/5% CO2 for 30 min.</li>
	<li>Weigh approximately 10,000 - 12,000 U of collagenase type II, 175 mg fatty acid free BSA and dissolve in 20 ml IB containing 22.5 &mu;l of a 100 mM CaCl2 stock solution. Control the pH of the isolation buffer in the upper reservoir and adjust if required.</li>
	<li>Anaesthetize a Wistar rat of 175 - 200 g with 375 &mu;g/kg body weight thiopental. Add 2500 IU Heparin to thiopental solution. After thoracotomy, excise the heart carefully with an intact aortic arch and transfer it into ice-cold 0.9% NaCl. Clean the heart from blood and surrounding tissue and transfer to fresh 0.9% NaCl. Expose the aorta, open the flow reducer of the Langendorff system to obtain a dropping speed of 2-3/sec and attach the heart to the cannula.</li>
	<li>Perfuse the heart for up to 3 min with a flow rate of 1 drop/sec to wash out remaining blood. Start to circulate the IB in the Langendorff system. Remove 20 ml buffer from the upper reservoir, fill in the collagenase solution and refill as much buffer as required to reach 80 ml. Circulate the collagenase solution for another 27 min. Flow rate should be controlled periodically and maintained at 1 drop/sec using the flow reducer.</li>
	<li>Detach the heart from the cannula, clean from atria and aorta and chop into small pieces. Allow the collagenase solution to run into the lower reservoir, reduce the volume to a maximum of 40 ml and further digest the chopped ventricles for 10 - 15 min under continuous aeration with 95% O2/5% CO2. Afterwards, filter the cell suspension through a 200 &mu;m mesh size gauze into a 50 ml tube.</li>
	<li>Restore the Ca2+ content of the cells in 3 steps: centrifuge the cell suspension at 43 x g for 2 min at room temperature and resuspend cells in 10 ml IB containing 200 &mu;M CaCl2. Centrifuge again and resuspend cells in 10 ml IB with 500 &mu;M CaCl2. After a final centrifugation resuspend cardiomyocytes in sterile filtered EB (see 1.8) to a density of 50,000 cells/ml.</li>
</ol>
3. Fura-2 Staining of Cardiomyocytes
<ol>
	<li>Coat a 4 well chambered coverglass with 10 &mu;g laminin per well and wait until it is fully dried.</li>
	<li>Fill 1 ml of the cardiomyocyte suspension into each well using a micropipette with a cut tip. Allow the cells to adhere for 1 hr at room temperature.</li>
	<li>Dilute 10 &mu;l of the 1 mg/ml Fura-2 AM stock solution in 5 ml EB. Keep the staining solution in the dark.</li>
	<li>Take off buffer and unattached cells from the coverglass and pipette 0.5 ml of the staining solution into each well. Incubate the cells for 10 min under moderate shaking. Subsequently, take off the staining solution, wash cells once with 1 ml EB and finally fill 0.5 ml EB into each well. Avoid direct light during the staining process and always keep the stained cells in the dark.</li>
</ol>
4. Recording of Cell Shortening and Ca2+ Transients
<ol>
	<li>Place the chambered coverglass on an inverse fluorescence microscope connected to a myocyte calcium and contractility recording system. Position a custom made electrode with an influx and efflux tube in the first well. Superfuse cardiomyocytes with 1 ml/min EB and start the electric stimulation (20 V, 1 Hz, 5 msec duration). Allow the cells to adapt to the stimulation for about 2 min.</li>
	<li>Choose an intact rod shaped cardiomyocyte with clear striation and constant contraction. Position the cell in the center of the visual field and open the camera channel. Orientate the cell horizontally within the video area by rotating the cell framing adapter and moving the microscope stage.</li>
	<li>Adjust the edge detecting control elements of the video area (Figure 2), open the fluorescent channel and record 10 - 15 contractions to obtain the initial cell shortening and Ca2+ transient.</li>
	<li>Close the microscope light channel to avoid bleaching of the fluorescence stain. Switch the flow through from EB to the sample bypass with a 3-way valve and superfuse cardiomyocytes with 1 ml of patient IgG. Stop the pump just before air reaches the well.</li>
	<li>Open the light channel and record another 10 - 15 contractions to obtain the acute cell response. Pause the recording and close the light channel again. Repeat recording after 2 and 5 min.</li>
	<li>Take out the electrode of the well. Clean the tubes thoroughly with EB and continue with the next well of the chambered coverglass.</li>
	<li>Analyze the cell shortening and Ca2+ transient with the IonWizard software using the "Edge-Length/Length" and the "fura 2-Numeric subtracted/Ratio" window, respectively. Calculate the percent change from the initial cell shortening and Ca2+ transient of the peak height referred to the baseline (bl%peak h) for the acute, the 2 min and the 5 min response.</li>
</ol>

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	<li>Roger, V. 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=Heart+disease+and+stroke+statistics--2011+update:+a+report+from+the+American+Heart+Association.">Heart disease and stroke statistics--2011 update: a report from the American Heart Association.</a> Circulation. 123 (4), e18 (2011).</li><li>Caforio, A. L., Vinci, A., Iliceto, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anti-heart+autoantibodies+in+familial+dilated+cardiomyopathy.">Anti-heart autoantibodies in familial dilated cardiomyopathy.</a> Autoimmunity. 41 (6), 462 (2008).</li><li>Yoshikawa, T., Baba, A., Nagatomo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Autoimmune+mechanisms+underlying+dilated+cardiomyopathy.">Autoimmune mechanisms underlying dilated cardiomyopathy.</a> Circ. J. 73 (4), 602 (2009).</li><li>Felix, S. 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=Hemodynamic+effects+of+immunoadsorption+and+subsequent+immunoglobulin+substitution+in+dilated+cardiomyopathy:+Three-month+results+from+a+randomized+study.">Hemodynamic effects of immunoadsorption and subsequent immunoglobulin substitution in dilated cardiomyopathy: Three-month results from a randomized study.</a> Journal of the American College of Cardiology. 35 (6), 1590 (2000).</li><li>Staudt, 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=Role+of+immunoglobulin+G3+subclass+in+dilated+cardiomyopathy:+results+from+protein+A+immunoadsorption.">Role of immunoglobulin G3 subclass in dilated cardiomyopathy: results from protein A immunoadsorption.</a> Am. Heart J. 150 (4), 729 (2005).</li><li>Nikolaev, V. 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=A+novel+fluorescence+method+for+the+rapid+detection+of+functional+beta1-adrenergic+receptor+autoantibodies+in+heart+failure.">A novel fluorescence method for the rapid detection of functional beta1-adrenergic receptor autoantibodies in heart failure.</a> J. Am. Coll. Cardiol. 50 (5), 423 (2007).</li><li>Jahns, 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=Autoantibodies+activating+human+beta1-adrenergic+receptors+are+associated+with+reduced+cardiac+function+in+chronic+heart+failure.">Autoantibodies activating human beta1-adrenergic receptors are associated with reduced cardiac function in chronic heart failure.</a> Circulation. 99 (5), 649 (1999).</li><li>Gocayne, 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=Primary+structure+of+rat+cardiac+beta-adrenergic+and+muscarinic+cholinergic+receptors+obtained+by+automated+DNA+sequence+analysis:+further+evidence+for+a+multigene+family.">Primary structure of rat cardiac beta-adrenergic and muscarinic cholinergic receptors obtained by automated DNA sequence analysis: further evidence for a multigene family.</a> Proceedings of the National Academy of Sciences. 84 (23), 8296 (1987).</li><li>Jaenicke, 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=The+complete+sequence+of+the+human+beta-myosin+heavy+chain+gene+and+a+comparative+analysis+of+its+product.">The complete sequence of the human beta-myosin heavy chain gene and a comparative analysis of its product.</a> Genomics. 8 (2), 194 (1990).</li><li>Piper, H. M., Volz, A., Schwartz, P., Piper, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Cell Culture Techniques in Heart and Vessel Research. , (1990).</li><li>Kubin, 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=Microvascular+endothelial+cells+remodel+cultured+adult+cardiomyocytes+and+increase+their+survival.">Microvascular endothelial cells remodel cultured adult cardiomyocytes and increase their survival.</a> Am. J. Physiol. 276 (6 Pt. 2), H2179 (1999).</li><li>Grynkiewicz, G., Poenie, M., Tsien, R. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+generation+of+Ca2++indicators+with+greatly+improved+fluorescence+properties.">A new generation of Ca2+ indicators with greatly improved fluorescence properties.</a> J. Biol. Chem. 260 (6), 3440 (1985).</li><li>Magnusson, 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=Autoimmunity+in+idiopathic+dilated+cardiomyopathy.+Characterization+of+antibodies+against+the+beta+1-adrenoceptor+with+positive+chronotropic+effect.">Autoimmunity in idiopathic dilated cardiomyopathy. Characterization of antibodies against the beta 1-adrenoceptor with positive chronotropic effect.</a> Circulation. 89 (6), 2760 (1994).</li><li>Wakefield, I. 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=The+application+of+in+vitro+methods+to+safety+pharmacology.">The application of in vitro methods to safety pharmacology.</a> Fundam. Clin. Pharmacol. 16 (3), 209 (2002).</li><li>Kajzar, 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=Toward+physiological+conditions+for+cell+analyses:+forces+of+heart+muscle+cells+suspended+between+elastic+micropillars.">Toward physiological conditions for cell analyses: forces of heart muscle cells suspended between elastic micropillars.</a> Biophys. J. 94 (5), 1854 (2008).</li></ol>

No conflicts of interest declared.

The presented method offers a suitable way to detect functionally effective cardiac autoantibodies in patients with DCM of unclear origin. In comparison to other methods, e.g. the detection of functional active antibodies against the &beta;1-adrenoceptor by their impact on cAMP levels6, our method is independent of a specific epitope. Of course there are other epitope independent assays described in the literature, i.e. counting the beating rate of neonatal cardiomyocytes13, ...

<table><tbody><tr><td>Immunosorba preservation solution</td><td>Fresenius Medical Care</td><td>903609211</td><td></td></tr><tr><td>Collagenase type 2</td><td>Cell System</td><td>LS004176</td><td></td></tr><tr><td>BSA, fatty acid free</td><td>Sigma-Aldrich</td><td>A6003</td><td></td></tr><tr><td>Laminin</td><td>Sigma-Aldrich</td><td>L2020</td><td></td></tr><tr><td>Fura-2 AM</td><td>Sigma-Aldrich</td><td>F0888</td><td>1 mg/ml in DMSO</td></tr><tr><td>Econo Pac Chromatography Columns</td><td>BioRad</td><td>732-1010</td><td></td></tr><tr><td>Spectra/Por Biotech Cellulose Ester Dialysis Membrane</td><td>Spectrumlabs</td><td>131417</td><td></td></tr><tr><td>4 well Chambered Coverglass</td><td>Nunc</td><td>155383</td><td></td></tr><tr><td>Myocyte Calcium and Contractility Recording System</td><td>IonOptix</td><td></td><td></td></tr><tr><td>IonWizard 6.0 analysis software</td><td>IonOptix</td><td></td><td></td></tr></tbody></table>

measurement of antibody effects on cellular function of isolated cardiomyocytes

Dilated cardiomyopathy (DCM) is one of the main causes for heart failure in younger adults1. Although genetic disposition and exposition to toxic substances are known causes for this disease in about one third of the patients, the origin of DCM remains largely unclear. In a substantial number of these patients, autoantibodies against cardiac epitopes have been detected and are suspected to play a pivotal role in the onset and progression of the disease2,3. The importance of cardiac autoantibodies is underlined by a hemodynamic improvement observed in DCM patients after elimination of autoantibodies by immunoadsorption3-5. A variety of specific antigens have already been identified2,3 and antibodies against these targets may be detected by immunoassays. However, these assays cannot discriminate between stimulating (and therefore functionally effective) and blocking autoantibodies. There is increasing evidence that this distinction is crucial6,7. It can also be assumed that the targets for a number of cardiotropic antibodies are still unidentified and therefore cannot be detected by immunoassays. Therefore, we established a method for the detection of functionally active cardiotropic antibodies, independent of their respective antigen. The background for the method is the high homology usually observed for functional regions of cardiac proteins in between mammals8,9. This suggests that cardiac antibodies directed against human antigens will cross-react with non-human target cells, which allows testing of IgG from DCM patients on adult rat cardiomyocytes. Our method consists of 3 steps: first, IgG is isolated from patient plasma using sepharose coupled anti-IgG antibodies obtained from immunoadsorption columns (PlasmaSelect, Teterow, Germany). Second, adult cardiomyocytes are isolated by collagenase perfusion in a Langendorff perfusion apparatus using a protocol modified from previous works10,11. The obtained cardiomyocytes are attached to laminin-coated chambered coverglasses and stained with Fura-2, a calcium-selective fluorescent dye which can be easily brought into the cell to observe intracellular calcium (Ca2+) contents12. In the last step, the effect of patient IgG on the cell shortening and Ca2+ transients of field stimulated cardiomyocytes is monitored online using a commercial myocyte calcium and contractility monitoring system (IonOptix, Milton, MA, USA) connected to a standard inverse fluorescent microscope.

Two examples for the measurement of cellular inotropy in field stimulated adult cardiomyocytes (Figure 2) using a myocyte Ca2+ and contractility recording system are given below. Figure 3 gives an impression of a control measurement, while in Figure 4 the effect of cardiodepressive antibodies of a patient with DCM is shown.
In both examples, initial cell shortening and Ca2+ transient during superfusion with EB exhibi...

Watch this Scientific Journal Video about Measurement of Antibody Effects on Cellular Function of Isolated Cardiomyocytes at JoVE.com

Measurement of Antibody Effects on Cellular Function of Isolated Cardiomyocytes

The presented method offers a way to detect functional effective cardiotropic autoantibodies in the plasma of patients with dilated cardiomyopathy, irrespective of the specific antigen, by analysing the impact of isolated patient immunoglobulin on cellular shortening and intracellular calcium transients in isolated rat cardiomyocytes.

Dilated cardiomyopathy  (DCM) is one of the main causes for heart failure in younger adults1.  Although genetic disposition and exposition to toxic ...

measurement-antibody-effects-on-cellular-function-isolated

Universidad de Cartagena UDEC

Research

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Immunology and Infection

11.8K Views.  University Medicine Greifswald. The presented method offers a way to detect functional effective cardiotropic autoantibodies in the plasma of patients with dilated cardiomyopathy, irrespective of the specific antigen, by analysing the impact of isolated patient immunoglobulin on cellular shortening and intracellular calcium transients in isolated rat cardiomyocytes.

Video: Measurement of Antibody Effects on Cellular Function of Isolated Cardiomyocytes

Isolation of Functional Cardiac Immune Cells

Cardiac immune cells are gaining interest for the roles they play in the pathological remodeling in many cardiac diseases.1-5 These immune cells, which include mast cells, T-cells and macrophages; store and release a variety of biologically active mediators including cytokines and proteases such as tryptase.6-8 These mediators have been shown to be key players in extracellular matrix metabolism by activating matrix metalloproteinases or causing collagen accumulation by modulating the cardiac fibroblasts' function.9-11 However, available techniques for isolating cardiac immune cells have been problematic because they use bacterial collagenase to digest the myocardial tissue. This technique causes activation of the immune cells and thus a loss of function. For example, cardiac mast cells become significantly less responsive to compounds that cause degranulation.12 Therefore, we developed a technique that allows for the isolation of functional cardiac immune cells which would lead to a better understanding of the role of these cells in cardiac disease.13, 14
This method requires a familiarity with the anatomical location of the rat's xiphoid process, axilla and falciform ligament, and pericardium of the heart. These landmarks are important to increase success of the procedure and to ensure a higher yield of cardiac immune cells. These isolated cardiac immune cells can then be used for characterization of functionality, phenotype, maturity, and co-culture experiments with other cardiac cells to gain a better understanding of their interactions.

This method for isolating functional immune cells from the heart provides an alternative to the conventional methods of collagenase digestion, which causes unwanted immune cell activation, resulting in a decreased responsiveness of these cells. Our method of isolation yields functional cardiac immune cells by avoiding problems associated with enzymatic digestion.

Cardiac immune cells are gaining interest for the roles they play in the pathological remodeling in many cardiac diseases.1-5  These immune cells, which ...

Single-Cell Optical Action Potential Measurement in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Conventional intracellular microelectrode techniques to quantify cardiomyocyte electrophysiology are extremely complex, labor intensive, and typically carried out in low throughput. Rapid and ongoing expansion of induced pluripotent stem cell (iPSC) technology presents a new standard in cardiovascular research and alternate methods are now necessary to increase throughput of electrophysiological data at a single cell level. VF2.1Cl is a recently derived voltage sensitive dye which provides a rapid single channel, high magnitude response to fluctuations in membrane potential. It possesses kinetics superior to those of other existing voltage indicators and makes available functional data equivalent to that of traditional microelectrode techniques. Here, we demonstrate simplified, non-invasive action potential characterization in externally paced human iPSC derived cardiomyocytes using a modular and highly affordable photometry system.

Here we describe optical acquisition and characterization of action potentials from induced pluripotent stem cell derived cardiomyocytes using a high-speed modular photometry system.

Conventional intracellular microelectrode techniques to quantify cardiomyocyte electrophysiology are extremely complex, labor intensive, and typically ...

Bioengineering

Hybrid Cell Analysis System to Assess Structural and Contractile Changes of Human iPSC-Derived Cardiomyocytes for Preclinical Cardiac Risk Evaluation

Cardiac contractility assessment is of immense importance for the development of new therapeutics and their safe transition into clinical stages. While human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) hold promise to serve as a human-relevant model in preclinical phases of drug discovery and safety pharmacology, their maturity is still controversial in the scientific community and under constant development. We present a hybrid contractility and impedance/extracellular field potential (EFP) technology, adding significant pro-maturation features to an industry-standard 96-well platform.
The impedance/EFP system monitors cellular functionality in real-time. Besides the beat rate of contractile cells, the electrical impedance spectroscopy readouts detect compound-induced morphological changes like cell density and integrity of the cellular monolayer. In the other component of the hybrid cell analysis system, the cells are cultured on bio-compliant membranes that mimic the mechanical environment of real heart tissue. This physiological environment supports the maturation of hiPSC-CMs in vitro, leading to more adult-like contractile responses including positive inotropic effects after treatment with isoproterenol, S-Bay K8644, or omecamtiv mecarbil. Parameters such as the amplitude of contraction force (mN/mm2) and beat duration also reveal downstream effects of compounds with influence on electrophysiological properties and calcium handling.
The hybrid system provides the ideal tool for holistic cell analysis, allowing preclinical cardiac risk assessment beyond the current perspectives of human-relevant cell-based assays.

The analysis of changes in contractile function and cellular integrity of human iPSC-derived cardiomyocytes is of immense importance for nonclinical drug development. A hybrid 96-well cell analysis system addresses both parameters in a real-time and physiological manner for reliable, human-relevant results, necessary for a safe transition into clinical stages.

Cardiac contractility assessment is of immense importance for the development of new therapeutics and their safe transition into clinical stages. While ...

Isolation of Atrial Cardiomyocytes from a Rat Model of Metabolic Syndrome-related Heart Failure with Preserved Ejection Fraction

In this article, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes (ACMs) from a rat model of metabolic syndrome (MetS)-related heart failure with preserved ejection fraction (HFpEF). The prevalence of MetS-related HFpEF is rising, and atrial cardiomyopathies associated with atrial remodeling and atrial fibrillation are clinically highly relevant as atrial remodeling is an independent predictor of mortality. Studies with isolated single-cell cardiomyocytes are frequently used to corroborate and complement in vivo findings. Circulatory vessel rarefication and interstitial tissue fibrosis pose a potentially limiting factor for the successful single-cell isolation of ACMs from animal models of this disease.
We have addressed this issue by employing a device capable of manually regulating the intraluminal pressure of cardiac cavities during the isolation procedure, substantially increasing the yield of morphologically and functionally intact ACMs. The acquired cells can be used in a variety of different experiments, such as cell culture and functional Calcium imaging (i.e., excitation-contraction-coupling).
We provide the researcher with a step-by-step protocol, a list of optimized solutions, thorough instructions to prepare the necessary equipment, and a comprehensive troubleshooting guide. While the initial implementation of the procedure might be rather difficult, a successful adaptation will allow the reader to perform state-of-the-art ACM isolations in a rat model of MetS-related HFpEF for a broad spectrum of experiments.

Here, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes from a rat model of metabolic syndrome-related heart failure with preserved ejection fraction. A manual regulation of intraluminal pressure of cardiac cavities is implemented to yield functionally intact myocytes suitable for excitation-contraction-coupling studies.

In this article, we describe an optimized, Langendorff-based procedure for the isolation of single-cell atrial cardiomyocytes (ACMs) from a rat model of ...

Medicine

High-Throughput Cardiotoxicity Screening Using Mature Human Induced Pluripotent Stem Cell-Derived Cardiomyocyte Monolayers

Human induced stem cell-derived cardiomyocytes (hiPSC-CMs) are used to replace and reduce the dependence on animals and animal cells for preclinical cardiotoxicity testing. In two-dimensional monolayer formats, hiPSC-CMs recapitulate the structure and function of the adult human heart muscle cells when cultured on an optimal extracellular matrix (ECM). A human perinatal stem cell-derived ECM (maturation-inducing extracellular matrix-MECM) matures the hiPSC-CM structure, function, and metabolic state in 7 days after plating. 
Mature hiPSC-CM monolayers also respond as expected to clinically relevant medications, with a known risk of causing arrhythmias and cardiotoxicity. The maturation of hiPSC-CM monolayers was an obstacle to the widespread adoption of these valuable cells for regulatory science and safety screening, until now. This article presents validated methods for the plating, maturation, and high-throughput, functional phenotyping of hiPSC-CM electrophysiological and contractile function. These methods apply to commercially available purified cardiomyocytes, as well as stem cell-derived cardiomyocytes generated in-house using highly efficient, chamber-specific differentiation protocols. 
High-throughput electrophysiological function is measured using either voltage-sensitive dyes (VSDs; emission: 488 nm), calcium-sensitive fluorophores (CSFs), or genetically encoded calcium sensors (GCaMP6). A high-throughput optical mapping device is used for optical recordings of each functional parameter, and custom dedicated software is used for electrophysiological data analysis. MECM protocols are applied for medication screening using a positive inotrope (isoprenaline) and human Ether-a-go-go-related gene (hERG) channel-specific blockers. These resources will enable other investigators to successfully utilize mature hiPSC-CMs for high-throughput, preclinical cardiotoxicity screening, cardiac medication efficacy testing, and cardiovascular research.

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) offer an alternative to using animals for preclinical cardiotoxicity screening. A limitation to the widespread adoption of hiPSC-CMs in preclinical toxicity screening is the immature, fetal-like phenotype of the cells. Presented here are protocols for robust and rapid maturation of hiPSC-CMs.

Human induced stem cell-derived cardiomyocytes (hiPSC-CMs) are used to replace and reduce the dependence on animals and animal cells for preclinical ...

Isolation and Physiological Analysis of Mouse Cardiomyocytes

Cardiomyocytes, the workhorse cell of the heart, contain exquisitely organized cytoskeletal and contractile elements that generate the contractile force used to pump blood. Individual cardiomyocytes were first isolated over 40 years ago in order to better study the physiology and structure of heart muscle. Techniques have rapidly improved to include enzymatic digestion via coronary perfusion. More recently, analyzing the contractility and calcium flux of isolated myocytes has provided a vital tool in the cellular and sub-cellular analysis of heart failure. Echocardiography and EKGs provide information about the heart at an organ level only. Cardiomyocyte cell culture systems exist, but cells lack physiologically essential structures such as organized sarcomeres and t-tubules required for myocyte function within the heart. In the protocol presented here, cardiomyocytes are isolated via Langendorff perfusion. The heart is removed from the mouse, mounted via the aorta to a cannula, perfused with digestion enzymes, and cells are introduced to increasing calcium concentrations. Edge and sarcomere detection software is used to analyze contractility, and a calcium binding fluorescent dye is used to visualize calcium transients of electrically paced cardiomyocytes; increasing understanding of the role cellular changes play in heart dysfunction. Traditionally used to test drug effects on cardiomyocytes, we employ this system to compare myocytes from WT mice and mice with a mutation that causes dilated cardiomyopathy. This protocol is unique in its comparison of live cells from mice with known heart function and known genetics. Many experimental conditions are reliably compared, including genetic or environmental manipulation, infection, drug treatment, and more. Beyond physiologic data, isolated cardiomyocytes are easily fixed and stained for cytoskeletal elements. Isolating cardiomyocytes via perfusion is an extremely versatile method, useful in studying cellular changes that accompany or lead to heart failure in a variety of experimental conditions.

Individual cardiomyocytes from wild type and mutant mice can be isolated from the heart in order to study their contractility and calcium transients. This allows characterization of the contribution of cellular dysfunction to heart dysfunction from any cause.

Cardiomyocytes, the workhorse cell of the heart, contain exquisitely organized cytoskeletal and contractile elements that generate the contractile force ...

Biology

Flow Cytometry-Based Quantification and Analysis of Myocardial B-Cells

A growing body of evidence shows that B-lymphocytes play an important role in the context of myocardial physiology and myocardial adaptation to injury. However, the literature reports contrasting data on the prevalence of myocardial B-cells. B-cells have been reported to be both among the most prevalent immune cells in the rodent heart or to be present, but at a markedly lower prevalence than myeloid cells, or to be quite rare. Similarly, several groups have described that the number of myocardial B-cells increases after acute ischemic myocardial injury, but one group reported no changes in the number of B-cells of the injured myocardium. Implementation of a shared, reproducible method to assess the prevalence of myocardial B-cells is critical to harmonize observations from different research groups and thus promote the advancement of the study of B-cell myocardial interactions. Based on our experience, the seemingly contrasting observations reported in the literature likely stem from the fact that murine myocardial B-cells are mostly intravascular and connected to the microvascular endothelium. Therefore, the number of B-cells recovered from a murine heart is exquisitely sensitive to the perfusion conditions used to clean the organ and to the method of digestion used. Here we report an optimized protocol that accounts for these two critical variables in a specific way. This protocol empowers reproducible, flow cytometry-based analysis of the number of murine myocardial B-cells and allows researchers to distinguish extravascular vs. intravascular myocardial B-cells.

Here we report a protocol for the quantification and differentiation of myocardial B-lymphocytes based on their location in the intravascular or endothelial space using flow cytometry.

A growing body of evidence shows that B-lymphocytes play an important role in the context of myocardial physiology and myocardial adaptation to injury. ...

In Vitro Assessment of Cardiac Function Using Skinned Cardiomyocytes

In this article, we describe the steps required to isolate a single permeabilized (&#34;skinned&#34;) cardiomyocyte and attach it to a force-measuring apparatus and a motor to perform functional studies. These studies will allow measurement of cardiomyocyte stiffness (passive force) and its activation with different calcium (Ca2+)-containing solutions to determine, amongst others: maximum force development, myofilament Ca2+-sensitivity (pCa50), cooperativity (nHill) and the rate of force redevelopment (ktr). This method also enables determination of the effects of drugs acting directly on myofilaments and of the expression of exogenous recombinant proteins on both active and passive properties of cardiomyocytes. Clinically, skinned cardiomyocyte studies highlight the pathophysiology of many myocardial diseases and allow in vitro assessment of the impact of therapeutic interventions targeting the myofilaments. Altogether, this technique enables the clarification of cardiac pathophysiology by investigating correlations between in vitro and in vivo parameters in animal models and human tissue obtained during open heart or transplant surgery.

This protocol aims to describe step-by-step the technique of extraction and assessment of cardiac function using skinned cardiomyocytes. This methodology allows measurement and acutemodulation of myofilament function using small frozen biopsies that can be collected from different cardiac locations, from mice to men.

In this article, we describe the steps required to isolate a single permeabilized (&#34;skinned&#34;) cardiomyocyte and attach it to a force-measuring ...

Measurement of Heart Contractility in Isolated Adult Human Primary Cardiomyocytes

The evaluation of changes in heart contractility is essential during preclinical development for new cardiac- and non-cardiac-targeted compounds. This paper describes a protocol for assessing changes in contractility in adult human primary ventricular cardiomyocytes utilizing the MyoBLAZER, a non-invasive optical method that preserves the normal physiology and pharmacology of the cells. This optical recording method continuously measures contractility transients from multiple cells in parallel, providing both medium-throughput and valuable information for each individual cell in the field of view, enabling the real-time tracking of drug effects. The cardiomyocyte contractions are induced by paced electrical field stimulation, and the acquired bright field images are fed to an image-processing software that measures the sarcomere shortening across multiple cardiomyocytes. This method rapidly generates different endpoints related to the kinetics of contraction and relaxation phases, and the resulting data can then be interpreted in relation to different concentrations of a test article. This method is also employed in the late stages of preclinical development to perform follow-up mechanistic studies to support ongoing clinical studies. Thus, the adult human primary cardiomyocyte-based model combined with the optical system for continuous contractility monitoring has the potential to contribute to a new era of in vitro cardiac data translatability in preclinical medical therapy development.

This protocol describes how to measure contractility in adult human primary cardiomyocytes from donor hearts with the MyoBLAZER system, a reliable platform for assessing drug-induced changes in contractility during preclinical development.

The evaluation of changes in heart contractility is essential during preclinical development for new cardiac- and non-cardiac-targeted compounds. This ...

An Antegrade Perfusion Method for Cardiomyocyte Isolation from Mice

In basic research using mouse heart, isolating viable individual cardiomyocytes is a crucial technical step to overcome. Traditionally, isolating cardiomyocytes from rabbits, guinea pigs or rats has been performed via retrograde perfusion of the heart with enzymes using a Langendorff apparatus. However, a high degree of skill is required when this method is used with a small mouse heart. An antegrade perfusion method that does not use a Langendorff apparatus was recently reported for the isolation of mouse cardiomyocytes. We herein report a complete protocol for the improved antegrade perfusion of the excised heart to isolate individual heart cells from adult mice (8 - 108 weeks old). Antegrade perfusion is performed by injecting perfusate near the apex of the left ventricle of the excised heart, the aorta of which was clamped, using an infusion pump. All procedures are carried out on a pre-warmed heater mat under a microscope, which allows for the injection and perfusion processes to be monitored. The results suggest that ventricular and atrial myocytes, and fibroblasts can be well isolated from a single adult mouse simultaneously.

We developed a simple method for isolating high quality individual mouse heart cells by the antegrade perfusion technique. This method is Langendorff-free and useful for isolating ventricular and atrial myocytes or interstitial cells, such as cardiac fibroblasts or progenitors.