This research is supported by the CounterACT Program, National Institutes of Health (NIH), Office of the Director, and the National Institute of Environmental Health Sciences (NIEHS) Grant Number U54 ES015678 (CWW). SA is also supported by Children&#39;s hospital Colorado/Colorado School of Mines Collaboration Pilot Award #G0100394 and Children&#39;s Hospital Colorado Research Institue Pilot Award #G0100471.

1. Rat Cardiomyocyte Cultures
<ol>
	<li>All experiments were performed under protocols approved by the institutional animal care and use committee, IACUC.</li>
	<li>Obtain rat cardiomyocytes from the hearts (ventricles) of male rats (240-260 g) using methods described previously4. Briefly, anesthetize animals using an intraperitoneal injection of pentobarbital (100 mg/kg; confirm anesthesia by toe pinch method) and then remove hearts into 10.0 ml, 1 mM Ca2+ containing Krebs Ringer buffer, pH 7.4.</li>
	<li>Rinse the hearts 5-6x&#160;to remove blood and then switch to a Ca2+ free Krebs Ringer buffer containing 0.02% protease and 0.06% collagenase A (5.0 ml/heart). Incubate the hearts in this solution for 10-15 min&#160;at 37 &#176;C with occasional shaking.</li>
	<li>After 10-15 min, wash out the enzymatic solution with Ca2+ free Krebs Ringer buffer for an additional 5 min. Release the cells from the flaccid tissue using a 25 ml pipette by pipetting the suspension up and down several times.</li>
	<li>Separate the cells from tissue by filtering through a 70 &#956;m nylon mesh and allow them to settle in Krebs Ringer buffer containing 0.1 mM Ca2+. Suspend the cell pellet in 1.0 ml Krebs Ringer buffer containing 0.2 mM Ca2+.</li>
	<li>Carefully layer over 5.0 ml 60 &#956;g/ml bovine serum albumin, BSA, in 15 ml centrifuge tubes, to separate cardiomyocytes from nonmyocytes and allow them to settle for 30 min. The cardiomyocytes are heavier and move to the bottom of the tube. Remove carefully the supernatant cells and media. Repeat this step once to further purify the cells.</li>
	<li>Gradually transition by washing (in steps using 0.25 mM, 0.5 mM, 0.75 mM, and 1.0 mM Ca2+ containing buffer) the ventricular myocytes/cardiomyocytes to 1.0 mM Ca2+ containing buffer and resuspended in ACCT medium consisting of Dulbecco&#8217;s Modified Eagle Medium, DMEM containing 2 mg/ml BSA, 2 mM L-carnitine, 5 mM creatine, 5 mM taurine, 100 IU/ml penicillin, and 100 &#956;g/ml&#160;streptomycin.</li>
	<li>Plate the cardiomyocytes in ACCT medium at a density of 100 to 150 cells/mm2 on 100 mm or 35 mm laminin coated plastic culture dishes or 40 x 22 mm glass coverslips precoated with laminin (1 &#956;g/cm2). After 1 hr, wash the dishes with 2.0 ml ACCT to remove cells that are not attached. Add 10.0 ml of fresh media and incubate the cells.</li>
</ol>
2. Differentiated Air-liquid Interface (ALI) Culture of Human Airway Epithelial Basal Cells
<ol>
	<li>Procure human tracheobronchial tissues from National Disease Research Interchange under Institutional Review Board approved protocols. Cell harvest and perform culture using a published procedure5,6. This procedure uses cell cultures as they are a precise model for human inhalation exposures to TICs, however, if needed one can isolate and grow at ALI mouse and/or rat airway epithelial cells7,8.</li>
	<li>Briefly, make small pieces (~&#188; inch) of the tissue after removing all connective tissue and lymph nodes. Wash tissue several times in Lactated Ringer solution. Add tissues to a 50 ml conical tube and add protease solution (1% Protease/0.01% DNase in minimal essential media, MEM, tissue to fluid ratio (1:10)).</li>
	<li>Rock the tissue at 4 &#176;C for overnight. End the dissociation of the tissue by adding 10% fetal bovine serum. Scrape the epithelial surface with a surgical scalpel and collect the cells by centrifugation (2,000 rpm for 10 min).</li>
	<li>Plate cells at passage one on collagen-coated snapwells in special ALI medium prepared as described in detail by Fulcher et al9. Culture for 5 days before changing to air-liquid&#160;interface (ALI) by removing apical media.</li>
	<li>Feed the cells using ALI media every alternate day and allow the cells to differentiate for additional 2-3 weeks (observe numerous beating cilia and mucus secretion) before performing exposures. Wash the apical surface with warm PBS along with media changes.</li>
</ol>
3. Chlorine Exposure
<ol>
	<li>Contain the chlorine exposure system (CES) inside a qualified chemical hood with an operational face velocity of 100 fpm that provides the necessary secondary containment to prevent exposure of personnel in the event of accidental chlorine leaks.</li>
	<li>Operate the system under slight positive pressure (0.5 inches of water). Dry air is fed at 15 L/min and an appropriate level of chlorine is fed to attain the desired final chlorine concentration. The chambers have a locking lid with 4 mini BCU locks and a low durometer silicone gasket to provide the pressure seal.</li>
	<li>Deliver the Cl2 mixture through a Mass Flow Controller. The CES uses a compressed gas cylinder containing 1.0% Cl2 in dry nitrogen.</li>
	<li>Regulate the dilution airflow using the custom designed control panel and similarly regulate the Cl2 concentration delivered to the exposure chambers. A low volume sampling pump pulls the exhaust from the chambers into a chlorine analyzer to monitor concentrations that are then recorded on a data logger connected to the analyzer.</li>
	<li>Measure the flow rates within the chambers prior to exposure using a flow meter to assure equal delivery and exhaust rates.</li>
	<li>Prepare the cell cultures for exposure by removing the supernatant media and adding fresh media (basolateral media in ALI cultures). Any pretreatments with agents could be performed at this time.</li>
	<li>Expose the ALI cultures of airway epithelial cells to Cl2 gas (50, 100, or 300 ppm for 30 min) in the two sealed polysulfone biocontainment chambers. The cardiomyocytes (submerged or confluent cultures on membranes) are exposed to 50 or 100 ppm Cl2 for 15 min.</li>
	<li>After exposure flush the chambers with air until the Cl2 level falls below 1 ppm and can be safely opened to remove cells (within 5 min).</li>
</ol>
4. Transepithelial Electrical Resistance (TER) Measurement
<ol>
	<li>Measure the TER of air-liquid-interface, ALI, cultures using an epithelial voltohmmeter with a pair of silver chloride &#8220;chopstick&#8221; electrodes.</li>
	<li>Equilibrate the chopstick electrode in the ALI media 15 min&#160;before use.</li>
	<li>Add warm media to the apical (1.0 ml) and basolateral (2.0 ml) surface and measure the TER using the chopstick electrodes of the voltohmmeter.</li>
	<li>Dip the shorter arm of the electrode in apical media and the longer arm in the basolateral media. Click the &#8216;measure&#8217; button on the voltohmmeter to evaluate the electrical resistance.</li>
	<li>The voltohmmeter has the option to measure ohms or k ohms. Subtract the resistance across a cell-free culture support from the resistance measured across each cell layer to yield the transepithelial resistance (TER).</li>
</ol>
5. Caspase Measurement
<ol>
	<li>Add fresh ALI media (2.0 ml) to the basolateral surface post exposure and incubate the cell at room temperature. Collect supernatant media at 4 and 24 hr.</li>
	<li>Measure caspase 3/7 activity in the media supernatants by using a commercial caspase 3/7 assay kit.</li>
</ol>
6. Western Blot and Immunocytochemistry
<ol>
	<li>Perform western blots using cell lysates as previously described10. Suspend the protein lysate (20 &#956;g) in 5x reduced sample buffer and boil for 5 min. Subject the protein lysate to SDS-PAGE (4-15%) and transfer the separated proteins to a nitrocellulose membrane by electrophoretic blotting.</li>
	<li>Block non-specific binding by incubating the membrane with 5% milk in wash buffer (PBS + 0.1% detergent) and probe the membranes with primary antibodies against SERCA2 or sarcomeric actin at 1:1,000 dilution, overnight at 4 &#176;C. Next, wash and incubate membranes with the respective peroxidase-conjugated secondary antibodies and develop for detection as described before10 using commercial peroxidase detection kit.</li>
	<li>For immunocytochemistry treat live cells grown on inserts or glass coverslips in 6-well plates with 0.4% Triton-X-100 in 10 mM sodium citrate buffer for 20 min&#160;after rinsing with PBS.</li>
	<li>Block nonspecific binding by treating the cells with 5% donkey serum for 20 min, and then incubate the cells with non-specific IgG or individual primary antibodies specific to sarcomeric actin or Ki-67.</li>
	<li>Wash the cells with PBS and incubate with fluorescent-conjugated secondary antibodies to detect the primary antibody and a nuclear stain (1 &#956;g/ml DAPI).</li>
	<li>Wash with PBS and mount coverslips using commercial mounting media.</li>
	<li>Visualize the staining using a fluorescent microscope.</li>
</ol>

<ol>
	<li>Mohan, 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=Acute+accidental+exposure+to+chlorine+gas:+clinical+presentation,+pulmonary+functions+and+outcomes.">Acute accidental exposure to chlorine gas: clinical presentation, pulmonary functions and outcomes.</a> Indian J Chest Dis Allied Sci. 52, 149-152 (2010).</li><li>Kose, 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=Myocardial+infarction,+acute+ischemic+stroke,+and+hyperglycemia+triggered+by+acute+chlorine+gas+inhalation.">Myocardial infarction, acute ischemic stroke, and hyperglycemia triggered by acute chlorine gas inhalation.</a> Am J Emerg Med. 27, 1021-1024 (2009).</li><li>Das, R., Blanc, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chlorine+gas+exposure+and+the+lung:+a+review.">Chlorine gas exposure and the lung: a review.</a> Toxicol Ind Health. 9, 439-455 (1993).</li><li>Claycomb, W. C., Palazzo, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Culture+of+the+terminally+differentiated+adult+cardiac+muscle+cell:+a+light+and+scanning+electron+microscope+study.">Culture of the terminally differentiated adult cardiac muscle cell: a light and scanning electron microscope study.</a> Dev Biol. 80, 466-482 (1980).</li><li>Ahmad, 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=Bcl-2+suppresses+sarcoplasmic/endoplasmic+reticulum+Ca2+-ATPase+expression+in+cystic+fibrosis+airways:+role+in+oxidant-mediated+cell+death.">Bcl-2 suppresses sarcoplasmic/endoplasmic reticulum Ca2+-ATPase expression in cystic fibrosis airways: role in oxidant-mediated cell death.</a> Am J Respir Crit Care Med. 179, 816-826 (2009).</li><li>Ahmad, 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=Tissue+factor+signals+airway+epithelial+basal+cell+survival+via+coagulation+and+protease-activated+receptor+isoforms+1+and+2.">Tissue factor signals airway epithelial basal cell survival via coagulation and protease-activated receptor isoforms 1 and 2.</a> Am J Respir Cell Mol Biol. 48, 94-104 (2013).</li><li>Lam, H. 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=Isolation+of+mouse+respiratory+epithelial+cells+and+exposure+to+experimental+cigarette+smoke+at+air+liquid+interface.">Isolation of mouse respiratory epithelial cells and exposure to experimental cigarette smoke at air liquid interface.</a> J Vis Exp. (48), (2011).</li><li>Hosokawa, 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=Differentiation+of+tracheal+basal+cells+to+ciliated+cells+and+tissue+reconstruction+on+the+synthesized+basement+membrane+substratum+in+vitro.">Differentiation of tracheal basal cells to ciliated cells and tissue reconstruction on the synthesized basement membrane substratum in vitro.</a> Connect Tissue Res. 48, 9-18 (2007).</li><li>Fulcher, M. 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The authors declare that they have no competing financial interests.

The most common type of acute toxic exposures occurs when one breathes a poisonous chemical into the lungs. These chemicals may also be quickly taken up in the bloodstream and may impact other organs such as brain and heart. Inhalation toxicity of various agents using animal models are studied and reported widely, however the mechanisms are less well understood. This is a major hurdle in developing effective therapies. Absence of in vitro exposure systems is a primary reason behind the lack of mechanistic insigh...

Exposure to toxic inhaled chemicals (TICs)/gases such as chlorine (Cl2) remains an ongoing health concern in accidental exposures as well as in their potential use as a chemical threat agent. Although the lungs are the primary target, organs such as heart and brain are also affected1-3. In vivo models are generally used for testing toxicity from TICs, but in vitro assays for toxicity assessment are simpler, faster and more cost effective. In vitro models also allow for extensive investigation of agent-cell interactions that may be difficult to evaluate in vivo. Such in vitro exposure systems are rare and moreover, in some conventional models where toxic agents are added to the culture medium in which cells are submerged, the properties of the agents can change due to interactions and binding to components in the medium. In such scenarios cell culture systems such as air-liquid&#160;interface (ALI) cultures of primary human airway epithelial cells, proposed here, that can be directly exposed to gaseous agents could be promising.
Epithelial cells lining the airway are the first lines of defense against inhaled toxic chemicals. The human airway epithelium forms a physical barrier between the lumen and the underlying cells in the lung and participates in the response of the lung. It produces a number of cytokines and other pro- and anti-inflammatory agents as well as secretes mucus/airway surface liquid (ASL) covering the epithelium. One of the limitations in conventional submerged in vitro culture systems is also that the ASL and mucus that cover the epithelial surface is removed or diluted. This does not reflect the physiological condition of lung epithelial cells that are exposed to air. Thus, an ideal in vitro system for TIC toxicity testing should replicate this architecture. There is great interest in developing rapid screening methods that predict in vivo toxicity. Epithelial cells grown at the ALI differentiate and have well-differentiated structures and functions compared to cells grown submerged and serve a superior model of the airways.
In this study, we describe the use of air-liquid-interface culture of human airway (tracheobronchial) epithelial cells for testing poisonous inhaled gas toxicity and compare it with a submerged cell culture of cardiomyocyte, hence studying another important target of toxicity.

<table border="0" cellpadding="0" cellspacing="0" width="1128">
	<tbody>
		<tr height="22">
			<td height="22" style="height:22px;width:487px;">Name</td>
			<td style="width:329px;">Company</td>
			<td style="width:147px;">Catalog Number</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:487px;">Rats</td>
			<td style="width:329px;">Harlan Laboratories</td>
			<td>Sprague-Dawley&#160;</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:487px;">Pentobarbital</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">P3761</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:487px;">Chlorine</td>
			<td style="width:329px;">AirGas, Inc</td>
			<td style="width:147px;">X02NI99CP163LS1</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:487px;">Caspase 3/7 kit&#160;</td>
			<td style="width:329px;">Promega</td>
			<td style="width:147px;">G8091</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:487px;">Epithelial voltohmmeter and chopstick electrode</td>
			<td style="width:329px;">World Precision Instruments</td>
			<td style="width:147px;">EVOM and STX2</td>
			<td></td>
		</tr>
		<tr height="22">
			<td height="22" style="height:22px;width:487px;">Snapwell inserts</td>
			<td style="width:329px;">Corning</td>
			<td style="width:147px;">07-200-708</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">70 micron nylon cell strainer</td>
			<td style="width:329px;">Corning</td>
			<td style="width:147px;">#352360</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Polysulfone biocontainment chambers&#160;</td>
			<td style="width:329px;">BCU, Allentown Cage Equipment</td>
			<td style="width:147px;">BCU</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DMEM</td>
			<td style="width:329px;">Life technologies</td>
			<td style="width:147px;">12491-015</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Sarcomeric actin antibody</td>
			<td style="width:329px;">Abcam Cambridge, MA</td>
			<td style="width:147px;">ab28052</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SERCA2 antibody</td>
			<td style="width:329px;">&#160;Affinity Bioreagents, Golden, CO</td>
			<td style="width:147px;">MA3-9191</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ki-67 antibody</td>
			<td style="width:329px;">&#160;Dako, Carpinteria, CA</td>
			<td style="width:147px;">M7248</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Alexa-488-conjugated secondary antibody</td>
			<td style="width:329px;">&#160;Invitrogen, Grand Island, NY</td>
			<td style="width:147px;">A11029</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">BSA</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">A9418</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Carnitine</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">C0283</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Taurine</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">T8691</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Creatinine</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">C6257</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Krebs Ringer Buffer</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">K4002</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Protease</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">P5147</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Collagenase</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">C6885</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160; DNAase</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">DN-25</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Lactated Ringer solution</td>
			<td style="width:329px;">Abott Laboratories</td>
			<td style="width:147px;">7953</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Donkey serum</td>
			<td style="width:329px;">Fisher Scientific</td>
			<td style="width:147px;">017-000-001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">PBS, phosphate buffered saline</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">D1408</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">4-15% SDS-PAGE gels</td>
			<td style="width:329px;">Bio-Rad</td>
			<td style="width:147px;">456-1083</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Nitrocellulose membrane</td>
			<td style="width:329px;">Bio-Rad</td>
			<td style="width:147px;">162-0115</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Dergent, Tween&#160;</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">P1379</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Peroxidase detection kit</td>
			<td style="width:329px;">Pierce</td>
			<td align="right" style="width:147px;">3402</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">DAPI</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">D9542</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Mounting media, Fluormount G</td>
			<td style="width:329px;">eBiosciences</td>
			<td style="width:147px;">00-4958-02</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Sodium citrate</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">71497</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Collagen</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">C7521</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">MEM</td>
			<td style="width:329px;">Sigma-Aldrich</td>
			<td style="width:147px;">M8028</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Laminin</td>
			<td style="width:329px;">BD biosciences</td>
			<td style="width:147px;">354259</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">Penicillin/Streptomycin</td>
			<td style="width:329px;">Life Technologies</td>
			<td style="width:147px;">15070063</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:487px;">FBS</td>
			<td style="width:329px;">Gibco</td>
			<td style="width:147px;">200-6140AJ</td>
			<td></td>
		</tr>
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in vitro cell culture model for toxic inhaled chemical testing

Cell cultures are indispensable to develop and study efficacy of therapeutic agents, prior to their use in animal models. We have the unique ability to model well differentiated human airway epithelium and heart muscle cells. This could be an invaluable tool to study the deleterious effects of toxic inhaled chemicals, such as chlorine, that can normally interact with the cell surfaces, and form various byproducts upon reacting with water, and limiting their effects in submerged cultures. Our model using well differentiated human airway epithelial cell cultures at air-liqiuid interface circumvents this limitation as well as provides an opportunity to evaluate critical mechanisms of toxicity of potential poisonous inhaled chemicals. We describe enhanced loss of membrane integrity, caspase release and death upon toxic inhaled chemical such as chlorine exposure. In this article, we propose methods to model chlorine exposure in mammalian heart and airway epithelial cells in culture and simple tests to evaluate its effect on these cell types.

Primary rod shaped cardiomyocytes attach on laminin matrices and spread and differentiate into confluent cultures (Figure 1A and its inset). These cells were further characterized on the basis of sarcomeric actin and SERCA2 expression (Figures 1B and 1C). Rat cardiomyocytes are highly susceptible to chlorine toxicity as 15 min exposure to 100 ppm chlorine caused extensive cell rounding and death in submerged cultures and disruption of confluent layers on cells grown on l...

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In vitro Cell Culture Model for Toxic Inhaled Chemical Testing

This protocol is designed to demonstrate exposure method of cell cultures to inhaled toxic chemicals. Exposure of differentiated air-liquid&#160;interface (ALI) cultures of airway epithelial cells provides a unique model of airway exposure to toxic gases such as chlorine. In this manuscript we describe effect of chlorine exposure on air-liquid&#160;interface cultures of epithelial cells and submerged culture of cardiomyocytes. In vitro exposure systems allow important mechanistic studies to evaluate pathways that could then be utilized to develop novel therapeutic agents.

In vitro Cell Culture Model for Toxic Inhaled Chemical Testing

Cell cultures are indispensable to develop and study efficacy of therapeutic agents, prior to their use in animal models. We have the unique ability to ...

in-vitro-cell-culture-model-for-toxic-inhaled-chemical-testing

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JoVE Journal

Bioengineering

10.6K Views.  University of Colorado. This protocol is designed to demonstrate exposure method of cell cultures to inhaled toxic chemicals. Exposure of differentiated air-liquid interface (ALI) cultures of airway epithelial cells provides a unique model of airway exposure to toxic gases such as chlorine. In this manuscript we describe effect of chlorine exposure on air-liquid interface cultures of epithelial cells and submerged culture of cardiomyocytes. In vitro exposure systems allow impo...

Video: In vitro Cell Culture Model for Toxic Inhaled Chemical Testing

Microfluidic Device for Recreating a Tumor Microenvironment in Vitro

We have developed a microfluidic device that mimics the delivery and systemic clearance of drugs to heterogeneous three-dimensional tumor tissues in vitro. Nutrients delivered by vasculature fail to reach all parts of tumors, giving rise to heterogeneous microenvironments consisting of viable, quiescent and necrotic cell types. Many cancer drugs fail to effectively penetrate and treat all types of cells because of this heterogeneity. Monolayers of cancer cells do not mimic this heterogeneity, making it difficult to test cancer drugs with a suitable in vitro model. Our microfluidic devices were fabricated out of PDMS using soft lithography. Multicellular tumor spheroids, formed by the hanging drop method, were inserted and constrained into rectangular chambers on the device and maintained with continuous medium perfusion on one side. The rectangular shape of chambers on the device created linear gradients within tissue. Fluorescent stains were used to quantify the variability in apoptosis within tissue. Tumors on the device were treated with the fluorescent chemotherapeutic drug doxorubicin, time-lapse microscopy was used to monitor its diffusion into tissue, and the effective diffusion coefficient was estimated. The hanging drop method allowed quick formation of uniform spheroids from several cancer cell lines. The device enabled growth of spheroids for up to 3 days. Cells in proximity of flowing medium were minimally apoptotic and those far from the channel were more apoptotic, thereby accurately mimicking regions in tumors adjacent to blood vessels. The estimated value of the doxorubicin diffusion coefficient agreed with a previously reported value in human breast cancer. Because the penetration and retention of drugs in solid tumors affects their efficacy, we believe that this device is an important tool in understanding the behavior of drugs, and developing new cancer therapeutics.

Microfluidic Device for Recreating a Tumor Microenvironment in Vitro

We present the procedure for fabrication and operation of a microfluidic device that recreates heterogeneous tumor microenvironments in vitro. The variability in apoptosis within tumor tissue was quantified using fluorescent stains and the effective diffusion coefficient of the chemotherapeutic drug doxorubicin into tumor tissue was evaluated.

We have developed a microfluidic device that mimics the delivery and systemic clearance of drugs to heterogeneous three-dimensional tumor tissues in ...

Shape Memory Polymers for Active Cell Culture

Shape memory polymers (SMPs) are a class of "smart" materials that have the ability to change from a fixed, temporary shape to a pre-determined permanent shape upon the application of a stimulus such as heat1-5. In a typical shape memory cycle, the SMP is first deformed at an elevated temperature that is higher than its transition temperature, Ttrans [either the melting temperature (Tm) or the glass transition temperature (Tg)]. The deformation is elastic in nature and mainly leads to a reduction in conformational entropy of the constituent network chains (following the rubber elasticity theory). The deformed SMP is then cooled to a temperature below its Ttrans while maintaining the external strain or stress constant. During cooling, the material transitions to a more rigid state (semi-crystalline or glassy), which kinetically traps or "freezes" the material in this low-entropy state leading to macroscopic shape fixing. Shape recovery is triggered by continuously heating the material through Ttrans under a stress-free (unconstrained) condition. By allowing the network chains (with regained mobility) to relax to their thermodynamically favored, maximal-entropy state, the material changes from the temporary shape to the permanent shape.
Cells are capable of surveying the mechanical properties of their surrounding environment6. The mechanisms through which mechanical interactions between cells and their physical environment control cell behavior are areas of active research. Substrates of defined topography have emerged as powerful tools in the investigation of these mechanisms. Mesoscale, microscale, and nanoscale patterns of substrate topography have been shown to direct cell alignment, cell adhesion, and cell traction forces7-14. These findings have underscored the potential for substrate topography to control and assay the mechanical interactions between cells and their physical environment during cell culture, but the substrates used to date have generally been passive and could not be programmed to change significantly during culture. This physical stasis has limited the potential of topographic substrates to control cells in culture.
Here, active cell culture (ACC) SMP substrates are introduced that employ surface shape memory to provide programmed control of substrate topography and deformation. These substrates demonstrate the ability to transition from a temporary grooved topography to a second, nearly flat memorized topography. This change in topography can be used to control cell behavior under standard cell culture conditions.

A method for developing cell culture substrates with the ability to change topography during culture is described. The method makes use of smart materials known as shape memory polymers that have the ability to memorize a permanent shape. This concept is adaptable to a wide range of materials and applications.

Shape memory polymers (SMPs) are a class of "smart" materials that have the ability to change from a fixed, temporary shape to a pre-determined permanent ...

Autologous Endothelial Progenitor Cell-Seeding Technology and Biocompatibility Testing For Cardiovascular Devices in Large Animal Model

Implantable cardiovascular devices are manufactured from artificial materials (e.g. titanium (Ti), expanded polytetrafluoroethylene), which pose the risk of thromboemboli formation1,2,3. We have developed a method to line the inside surface of Ti tubes with autologous blood-derived human or porcine endothelial progenitor cells (EPCs)4. By implanting Ti tubes containing a confluent layer of porcine EPCs in the inferior vena cava (IVC) of pigs, we tested the improved biocompatibility of the cell-seeded surface in the prothrombotic environment of a large animal model and compared it to unmodified bare metal surfaces5,6,7 (Figure 1). This method can be used to endothelialize devices within minutes of implantation and test their antithrombotic function in vivo. 
Peripheral blood was obtained from 50 kg Yorkshire swine and its mononuclear cell fraction cultured to isolate EPCs4,8. Ti tubes (9.4 mm ID) were pre-cut into three 4.5 cm longitudinal sections and reassembled with heat-shrink tubing. A seeding device was built, which allows for slow rotation of the Ti tubes. 
We performed a laparotomy on the pigs and externalized the intestine and urinary bladder. Sharp and blunt dissection was used to skeletonize the IVC from its bifurcation distal to the right renal artery proximal. The Ti tubes were then filled with fluorescently-labeled autologous EPC suspension and rotated at 10 RPH x 30 min to achieve uniform cell-coating9. After administration of 100 USP/ kg heparin, both ends of the IVC and a lumbar vein were clamped. A 4 cm veinotomy was performed and the device inserted and filled with phosphate-buffered saline. As the veinotomy was closed with a 4-0 Prolene running suture, one clamp was removed to de-air the IVC. At the end of the procedure, the fascia was approximated with 0-PDS (polydioxanone suture), the subcutaneous space closed with 2-0 Vicryl and the skin stapled closed. 
After 3 - 21 days, pigs were euthanized, the device explanted en-block and fixed. The Ti tubes were disassembled and the inner surfaces imaged with a fluorescent microscope.
We found that the bare metal Ti tubes fully occluded whereas the EPC-seeded tubes remained patent. Further, we were able to demonstrate a confluent layer of EPCs on the inside blood-contacting surface.
Concluding, our technology can be used to endothelialize Ti tubes within minutes of implantation with autologous EPCs to prevent thrombosis of the device. Our surgical method allows for testing the improved biocompatibility of such modified devices with minimal blood loss and EPC-seeded surface disruption.

A method for seeding titanium blood-contacting biomaterials with autologous cells and testing biocompatibility is described. This method uses endothelial progenitor cells and titanium tubes, seeded within minutes of surgical implantation into porcine venae cavae. This technique is adaptable to many other implantable biomedical devices.

Implantable cardiovascular devices are manufactured from artificial materials (e.g. titanium (Ti), expanded polytetrafluoroethylene), which pose the risk ...

Rotating Cell Culture Systems for Human Cell Culture: Human Trophoblast Cells as a Model

The field of human trophoblast research aids in understanding the complex environment established during placentation. Due to the nature of these studies, human in vivo experimentation is impossible. A combination of primary cultures, explant cultures and trophoblast cell lines1 support our understanding of invasion of the uterine wall2 and remodeling of uterine spiral arteries3,4 by extravillous trophoblast cells (EVTs), which is required for successful establishment of pregnancy. Despite the wealth of knowledge gleaned from such models, it is accepted that in vitro cell culture models using EVT-like cell lines display altered cellular properties when compared to their in vivo counterparts5,6. Cells cultured in the rotating cell culture system (RCCS) display morphological, phenotypic, and functional properties of EVT-like cell lines that more closely mimic differentiating in utero EVTs, with increased expression of genes mediating invasion (e.g. matrix metalloproteinases (MMPs)) and trophoblast differentiation7,8,9. The Saint Georges Hospital Placental cell Line-4 (SGHPL-4) (kindly donated by Dr. Guy Whitley and Dr. Judith Cartwright) is an EVT-like cell line that was used for testing in the RCCS.
The design of the RCCS culture vessel is based on the principle that organs and tissues function in a three-dimensional (3-D) environment. Due to the dynamic culture conditions in the vessel, including conditions of physiologically relevant shear, cells grown in three dimensions form aggregates based on natural cellular affinities and differentiate into organotypic tissue-like assemblies10,11,12 . The maintenance of a fluid orbit provides a low-shear, low-turbulence environment similar to conditions found in vivo. Sedimentation of the cultured cells is countered by adjusting the rotation speed of the RCCS to ensure a constant free-fall of cells. Gas exchange occurs through a permeable hydrophobic membrane located on the back of the bioreactor. Like their parental tissue in vivo, RCCS-grown cells are able to respond to chemical and molecular gradients in three dimensions (i.e. at their apical, basal, and lateral surfaces) because they are cultured on the surface of porous microcarrier beads. When grown as two-dimensional monolayers on impermeable surfaces like plastic, cells are deprived of this important communication at their basal surface. Consequently, the spatial constraints imposed by the environment profoundly affect how cells sense and decode signals from the surrounding microenvironment, thus implying an important role for the 3-D milieu13.
We have used the RCCS to engineer biologically meaningful 3-D models of various human epithelial tissues7,14,15,16. Indeed, many previous reports have demonstrated that cells cultured in the RCCS can assume physiologically relevant phenotypes that have not been possible with other models10,17-21. In summary, culture in the RCCS represents an easy, reproducible, high-throughput platform that provides large numbers of differentiated cells that are amenable to a variety of experimental manipulations. 
In the following protocol, using EVTs as an example, we clearly describe the steps required to three-dimensionally culture adherent cells in the RCCS.

Traditional, two dimensional cell culture techniques often result in altered characteristics with respect to differentiation markers, cytokines and growth factors. Three-dimensional cell culture in the rotating cell culture system (RCCS) reestablishes expression of many of these factors as shown here with an extravillous trophoblast cell line.

The field of human trophoblast research aids in  understanding the complex environment established during placentation. Due to the  nature of these ...

Eye Irritation Test (EIT) for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial (RhCE) Tissue Model

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and accurate assessment of ocular toxicity in man are needed. To address this need, we have developed an eye irritation test (EIT) which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model that is based on normal human cells. The EIT is able to separate ocular&#160;irritants and corrosives (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category). The test utilizes two separate protocols, one designed for liquid chemicals and a second, similar protocol for solid test articles. The EIT prediction model uses a single exposure period (30 min for liquids, 6 hr for solids) and a single tissue viability cut-off (60.0% as determined by the MTT assay). Based on the results for 83 chemicals (44 liquids and 39 solids) EIT achieved 95.5/68.2/ and 81.8% sensitivity/specificity and accuracy (SS&#38;A) for liquids, 100.0/68.4/ and 84.6% SS&#38;A for solids, and 97.6/68.3/ and 83.1% for overall SS&#38;A. The EIT will contribute significantly to classifying the ocular irritation potential of a wide range of liquid and solid chemicals without the use of animals to meet regulatory testing requirements. The EpiOcular EIT method was implemented in 2015 into the OECD Test Guidelines as TG 492.

Eye Irritation Test EIT for Hazard Identification of Eye Irritating Chemicals using Reconstructed Human Cornea-like Epithelial RhCE Tissue Model

We have developed an eye irritation test which utilizes a three dimensional reconstructed human cornea-like epithelial (RhCE) tissue model. The test is able to discriminate between ocular irritant and corrosive materials (GHS Categories 1 and 2 combined) and those that do not require labeling (GHS No Category).

To comply with the Seventh Amendment to the EU Cosmetics Directive and EU REACH legislation, validated non-animal alternative methods for reliable and ...

Light-mediated Formation and Patterning of Hydrogels for Cell Culture Applications

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In particular, light-mediated click reactions, such as photoinitiated thiol&#8722;ene and thiol&#8722;yne reactions, afford spatiotemporal control over material properties and allow the design of systems with a high degree of user-directed property control. Fabrication and modification of hydrogel-based biomaterials using the precision afforded by light and the versatility offered by these thiol&#8722;X photoclick chemistries are of growing interest, particularly for the culture of cells within well-defined, biomimetic microenvironments. Here, we describe methods for the photoencapsulation of cells and subsequent photopatterning of biochemical cues within hydrogel matrices using versatile and modular building blocks polymerized by a thiol&#8722;ene photoclick reaction. Specifically, an approach is presented for constructing hydrogels from allyloxycarbonyl (Alloc)-functionalized peptide crosslinks and pendant peptide moieties and thiol-functionalized poly(ethylene glycol) (PEG) that rapidly polymerize in the presence of lithium acylphosphinate photoinitiator and cytocompatible doses of long wavelength ultraviolet (UV) light. Facile techniques to visualize photopatterning and quantify the concentration of peptides added are described. Additionally, methods are established for encapsulating cells, specifically human mesenchymal stem cells, and determining their viability and activity. While the formation and initial patterning of thiol-alloc hydrogels are shown here, these techniques broadly may be applied to a number of other light and radical-initiated material systems (e.g., thiol-norbornene, thiol-acrylate) to generate patterned substrates.

We describe a sequential process for light-mediated formation and subsequent biochemical patterning of synthetic hydrogel matrices for three-dimensional cell culture applications. The construction and modification of hydrogels with cytocompatible photoclick chemistry is demonstrated. Additionally, facile techniques to quantify and observe patterns and determine cell viability within these hydrogels are presented.

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In ...

An In Vitro Organ Culture Model of the Murine Intervertebral Disc

Intervertebral disc (IVD) degeneration is a significant contributor to low back pain. The IVD is a fibrocartilaginous joint that serves to transmit and dampen loads in the spine. The IVD consists of a proteoglycan-rich nucleus pulposus (NP) and a collagen-rich annulus fibrosis (AF) sandwiched by cartilaginous end-plates. Together with the adjacent vertebrae, the vertebrae-IVD structure forms a functional spine unit (FSU). These microstructures contain unique cell types as well as unique extracellular matrices. Whole organ culture of the FSU preserves the native extracellular matrix, cell differentiation phenotypes, and cellular-matrix interactions. Thus, organ culture techniques are particularly useful for investigating the complex biological mechanisms of the IVD. Here, we describe a high-throughput approach for culturing whole lumbar mouse FSUs that provides an ideal platform for studying disease mechanisms and therapies for the IVD. Furthermore, we describe several applications that utilize this organ culture method to conduct further studies including contrast-enhanced microCT imaging and three-dimensional high-resolution finite element modeling of the IVD.

An In Vitro Organ Culture Model of the Murine Intervertebral Disc

Whole organ culture of the intervertebral disc (IVD) preserves the native extracellular matrix, cell phenotypes, and cellular-matrix interactions. Here we describe an IVD culture system using mouse lumbar and caudal IVDs in their functional spinal units and several applications utilizing this system.

Intervertebral disc (IVD) degeneration is a significant contributor to low back pain. The IVD is a fibrocartilaginous joint that serves to transmit and ...

Methodology for Biomimetic Chemical Neuromodulation of Rat Retinas with the Neurotransmitter Glutamate In Vitro

Photoreceptor degenerative diseases cause irreparable blindness through the progressive loss of photoreceptor cells in the retina. Retinal prostheses are an emerging treatment for photoreceptor degenerative diseases that seek to restore vision by artificially stimulating the surviving retinal neurons in the hope of eliciting comprehensible visual perception in patients. Current retinal prostheses have demonstrated success in restoring limited vision to patients using an array of electrodes to electrically stimulate the retina but face substantial physical barriers in restoring high acuity, natural vision to patients. Chemical neurostimulation using native neurotransmitters is a biomimetic alternative to electrical stimulation and could bypass the fundamental limitations associated with retinal prostheses using electrical neurostimulation. Specifically, chemical neurostimulation has the potential to restore more natural vision with comparable or better visual acuities to patients by injecting very small quantities of neurotransmitters, the same natural agents of communication used by retinal chemical synapses, at much finer resolution than current electrical prostheses. However, as a relatively unexplored stimulation paradigm, there is no established protocol for achieving chemical stimulation of the retina in vitro. The purpose of this work is to provide a detailed framework for accomplishing chemical stimulation of the retina for investigators who wish to study the potential of chemical neuromodulation of the retina or similar neural tissues in vitro. In this work, we describe the experimental setup and methodology for eliciting retinal ganglion cell (RGC) spike responses similar to visual light responses in wild-type and photoreceptor-degenerated wholemount rat retinas by injecting controlled volumes of the neurotransmitter glutamate into the subretinal space using glass micropipettes and a custom multiport microfluidic device. This methodology and protocol are general enough to be adapted for neuromodulation using other neurotransmitters or even other neural tissues.

Methodology for Biomimetic Chemical Neuromodulation of Rat Retinas with the Neurotransmitter Glutamate In Vitro

This protocol describes a novel method for investigating a form of chemical neurostimulation of wholemount rat retinas in vitro with the neurotransmitter glutamate. Chemical neurostimulation is a promising alternative to the conventional electrical neurostimulation of retinal neurons for treating irreversible blindness caused by photoreceptor degenerative diseases.

Photoreceptor degenerative diseases cause irreparable blindness through the progressive loss of photoreceptor cells in the retina. Retinal prostheses are ...

A Human 3D Extracellular Matrix-Adipocyte Culture Model for Studying Matrix-Cell Metabolic Crosstalk

The extracellular matrix (ECM) plays a central role in regulating tissue homeostasis, engaging in crosstalk with cells and regulating multiple aspects of cellular function. The ECM plays a particularly important role in adipose tissue function in obesity, and alterations in adipose tissue ECM deposition and composition are associated with metabolic disease in mice and humans. Tractable in vitro models that permit dissection of the roles of the ECM and cells in contributing to global tissue phenotype are sparse. We describe a novel 3D in vitro model of human ECM-adipocyte culture that permits study of the specific roles of the ECM and adipocytes in regulating adipose tissue metabolic phenotype. Human adipose tissue is decellularized to isolate ECM, which is subsequently repopulated with preadipocytes that are then differentiated within the ECM into mature adipocytes. This method creates ECM-adipocyte constructs that are metabolically active and retain characteristics of the tissues and patients from which they are derived. We have used this system to demonstrate disease-specific ECM-adipocyte crosstalk in human adipose tissue. This culture model provides a tool for dissecting the roles of the ECM and adipocytes in contributing to global adipose tissue metabolic phenotype and permits study of the role of the ECM in regulating adipose tissue homeostasis.

We describe a 3D human extracellular matrix-adipocyte in vitro culture system that permits dissection of the roles of the matrix and adipocytes in contributing to adipose tissue metabolic phenotype.

The extracellular matrix (ECM) plays a central role in regulating tissue homeostasis, engaging in crosstalk with cells and regulating multiple aspects of ...

In Vitro Model of Human Cutaneous Hypertrophic Scarring using Macromolecular Crowding

It has been shown that in vivo tissues are highly crowded by proteins, nucleic acids, ribonucleoproteins, polysaccharides, etc. The following protocol applies a macromolecular crowding (MMC) technique to mimic this physiological crowding through the addition of neutral polymers (crowders) to cell cultures in vitro. Previous studies using Ficoll or dextran as crowders demonstrate that the expression of collagen I and fibronectin in WI38 and WS-1 cell lines are significantly enhanced using the MMC technique. However, this technique has not been validated in primary hypertrophic scar-derived human skin fibroblasts (hHSFs). As hypertrophic scarring arises from the excessive deposition of collagen, this protocol aims to construct a collagen-rich in vitro hypertrophic scar model by applying the MMC technique with hHSFs. This optimized MMC model has been shown to possess more similarities with in vivo scar tissue compared to traditional 2-dimensional (2-D) cell culture systems. In addition, it is cost-effective, time-efficient, and ethically desirable compared to animal models. Therefore, the optimized model reported here offers an advanced &#8220;in vivo-like&#8221; model for hypertrophic scar-related studies.

This protocol describes the use of macromolecular crowding to create an in vitro human hypertrophic scar tissue model that resembles in vivo conditions. When cultivated in a crowded macromolecular environment, human skin fibroblasts exhibit phenotypes, biochemistry, physiology, and functional characteristics resembling scar tissue.

It has been shown that in vivo tissues are highly crowded by proteins, nucleic acids, ribonucleoproteins, polysaccharides, etc. The following protocol ...