The authors are grateful to Shad Schipke and Daniel Chesser for their assistance with the design and fabrication of the system and Valtresa Myles for assistance with preparing the manuscript.

1.	Tissue Harvest and Preparation
<ol>
<li>Aortic valves should be collected from adult pigs weighing no more than 120 lbs immediately after death.</li>
<li>Wash the valves twice with sterile phosphate buffered saline (PBS) and transport to the laboratory on ice.</li>
<li>All subsequent steps should be performed under sterile conditions.</li>
<li>Ensure that leaflets do not show any sign of degeneration, tearing or calcification. Remove leaflets from the aortic root by cutting 1/3 of the distance from the annulus.</li>...

<ol>
	<li>Freeman, R. V., Otto, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spectrum+of+calcific+aortic+valve+disease:+pathogenesis,+disease+progression,+and+treatment+strategies.">Spectrum of calcific aortic valve disease: pathogenesis, disease progression, and treatment strategies.</a> Circulation. 111, 3316-3326 (2005).</li><li>Robicsek, F., Thubrikar, M. J., Fokin, A. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cause+of+degenerative+disease+of+the+trileaflet+aortic+valve:+review+of+subject+and+presentation+of+a+new+theory.">Cause of degenerative disease of the trileaflet aortic valve: review of subject and presentation of a new theory.</a> Ann Thorac Surg. 73, 1346-1354 (2002).</li><li>Thubrikar, M. J., Aouad, J., Nolan, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patterns+of+calcific+deposits+in+operatively+excised+stenotic+or+purely+regurgitant+aortic+valves+and+their+relation+to+mechanical+stress.">Patterns of calcific deposits in operatively excised stenotic or purely regurgitant aortic valves and their relation to mechanical stress.</a> Am J Cardiol. 58, 304-308 (1986).</li><li>Agno, F. S., Chinali, M., Bella, J. N., Liu, J. E., Arnett, D. K., Kitzman, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aortic+valve+sclerosis+is+associated+with+preclinical+cardiovascular+disease+in+hypertensive+adults:+the+Hypertension+Genetic+Epidemiology+Network+study.">Aortic valve sclerosis is associated with preclinical cardiovascular disease in hypertensive adults: the Hypertension Genetic Epidemiology Network study.</a> J Hypertens. 23, 867-8673 (2005).</li><li>Cawley, P. J., Otto, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prevention+of+calcific+aortic+valve+stenosis+-+fact+or+fiction.">Prevention of calcific aortic valve stenosis - fact or fiction.</a> Annals of Medicine. 41, 100-108 (2009).</li><li>Durst, C. A., Grande-Allen, J. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+and+physical+characterization+of+a+synchronous+multivalve+aortic+valve+culture+system.">Design and physical characterization of a synchronous multivalve aortic valve culture system.</a> Ann Biomed Eng. 38, 319-3125 (2010).</li><li>Engelmayr, G. C., Soletti, L., Vigmostad, S. C., Budilarto, S. G., Federspiel, W. J., Chandran, K. B. <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+flex-stretch-flow+bioreactor+for+the+study+of+engineered+heart+valve+tissue+mechanobiology.">A novel flex-stretch-flow bioreactor for the study of engineered heart valve tissue mechanobiology.</a> Ann Biomed Eng. 36, 700-712 (2008).</li><li>Sucosky, P., Padala, M., Elhammali, A., Balachandran, K., Jo, H., Yoganathan, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+of+an+ex+vivo+culture+system+to+investigate+the+effects+of+shear+stress+on+cardiovascular+tissue.">Design of an ex vivo culture system to investigate the effects of shear stress on cardiovascular tissue.</a> J Biomech Eng. 130, 035001-03 (2008).</li><li>Syedain, Z. H., Tranquillo, R. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+cyclic+stretch+bioreactor+for+tissue-engineered+heart+valves.">Controlled cyclic stretch bioreactor for tissue-engineered heart valves.</a> Biomaterials. 30, 4078-4084 (2009).</li><li>Lagana, K., Moretti, M., Dubini, G., Raimondi, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+bioreactor+for+the+controlled+application+of+complex+mechanical+stimuli+for+cartilage+tissue+engineering.">A new bioreactor for the controlled application of complex mechanical stimuli for cartilage tissue engineering.</a> Proc Inst Mech Eng H. 222, 705-715 (2008).</li><li>Wartella, K. A., Wayne, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioreactor+for+biaxial+mechanical+stimulation+to+tissue+engineered+constructs.">Bioreactor for biaxial mechanical stimulation to tissue engineered constructs.</a> J Biomech Eng. 131, 044501-044501 (2009).</li><li>Wallis, M. C., Yeger, H., Cartwright, L., Shou, Z., Radisic, M., Haig, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Feasibility+study+of+a+novel+urinary+bladder+bioreactor.">Feasibility study of a novel urinary bladder bioreactor.</a> Tissue Eng Part A. 14, 339-348 (2008).</li><li>Butcher, J. T., Nerem, R. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Valvular+endothelial+cells+regulate+the+phenotype+of+interstitial+cells+in+co-culture:+effects+of+steady+shear+stress.">Valvular endothelial cells regulate the phenotype of interstitial cells in co-culture: effects of steady shear stress.</a> Tissue Eng. 12, 905-915 (2006).</li><li>Metzler, S. A., Pregonero, C. A., Butcher, J. T., Burgess, S. C., Warnock, J. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cyclic+Strain+Regulates+Pro-Inflammatory+Protein+Expression+in+Porcine+Aortic+Valve+Endothelial+Cells.">Cyclic Strain Regulates Pro-Inflammatory Protein Expression in Porcine Aortic Valve Endothelial Cells.</a> J Heart Valve Dis. 17, 571-578 (2008).</li><li>Schipke, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Design of a cyclic pressure bioreactor for the ex vivo study of aortic heart valve mechanobiology. , (2008).</li><li>Smith, K. E., Metzler, S. A., Warnock, J. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cyclic+strain+inhibits+acute+pro-inflammatory+gene+expression+in+aortic+valve+interstitial+cells.">Cyclic strain inhibits acute pro-inflammatory gene expression in aortic valve interstitial cells.</a> Biomechanics and Modeling in Mechanobiology. , (2009).</li><li>Warnock, J. N., Burgess, S. C., Shack, A., Yoganathan, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+immediate-early+gene+responses+to+elevated+pressure+in+porcine+aortic+valve+interstitial+cells.">Differential immediate-early gene responses to elevated pressure in porcine aortic valve interstitial cells.</a> J Heart Valve Dis. 15, 34-41 (2006).</li><li>Brathwaite, D., Weissman, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+new+onset+of+atrial+arrhythmias+following+major+noncardiothoracic+surgery+is+associated+with+increased+mortality.">The new onset of atrial arrhythmias following major noncardiothoracic surgery is associated with increased mortality.</a> Chest. 114, 462-468 (1998).</li><li>Walsh, S. R., Oates, J. E., Anderson, J. A., Blair, S. D., Makin, C. A., Walsh, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Postoperative+arrhythmias+in+colorectal+surgical+patients:+incidence+and+clinical+correlates.">Postoperative arrhythmias in colorectal surgical patients: incidence and clinical correlates.</a> Colorectal Dis. 8, 212-216 (2006).</li><li>Walsh, S. R., Tang, T., Gaunt, M. E., Schneider, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+arrhythmias+after+non-cardiothoracic+surgery.">New arrhythmias after non-cardiothoracic surgery.</a> BMJ. 7, 333-333 (2006).</li><li>Walsh, S. R., Tang, T., Wijewardena, C., Yarham, S. I., Boyle, J. R., Gaunt, M. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Postoperative+arrhythmias+in+general+surgical+patients.">Postoperative arrhythmias in general surgical patients.</a> Ann R Coll Surg Engl. 89, 91-95 (2007).</li></ol>

No conflicts of interest declared.

The pressure system successfully exposed aortic valve leaflets to cyclic pressures that were representative of diastolic transvalvular pressure. However, it was not able to mimic systolic transvalvular pressure, as the pressure only dropped to 40 mmHg. Transvalvular pressure is the difference between pressure in the ascending aorta and the left ventricle. During diastole, when the valve is closed, the pressure difference is 80mmHg under normotensive conditions and 90 mmHg and 100mmHg in stage I and stage II hypertension,...

<table border="1">
	<tbody>
		<tr>
			<th>Name of the reagent</th>
			<th>Company</th>
			<th>Catalogue number</th>
			<th>Comments (optional)</th>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Sigma</td>
			<td>D5671</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Dulbecco's PBS</td>
			<td>Sigma</td>
			<td>D5652</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Anti-mycotic/antibiotic solution</td>
			<td>Sigma</td>
			<td>A5955</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum</td>
			<td>ThermoScientific</td>
			<td>SH30070</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Viton diaphragm solenoid valves</td>
			<td>McMaster Carr</td>
			<td>4868K11</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Pressure Transducer		</td>
			<td>Omega Engineering, Inc.</td>
			<td>PX302-200GV</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Load cell conditioner		</td>
			<td>Encore Electronics, Inc.</td>
			<td>4025-101</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Data Acquisition (DAQ) Module		</td>
			<td>Measurement Computing</td>
			<td>PMD1608</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

design of a cyclic pressure bioreactor for the ex vivo study of aortic heart valves

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic valve leaflets are composed of interstitial cells suspended within an extracellular matrix (ECM) and are lined with an endothelial cell monolayer. The valve withstands a harsh, dynamic environment and is constantly exposed to shear, flexion, tension, and compression. Research has shown calcific lesions in diseased valves occur in areas of high mechanical stress as a result of endothelial disruption or interstitial matrix damage1-3. Hence, it is not surprising that epidemiological studies have shown high blood pressure to be a leading risk factor in the onset of aortic valve disease4. 
The only treatment option currently available for valve disease is surgical replacement of the diseased valve with a bioprosthetic or mechanical valve5. Improved understanding of valve biology in response to physical stresses would help elucidate the mechanisms of valve pathogenesis. In turn, this could help in the development of non-invasive therapies such as pharmaceutical intervention or prevention. Several bioreactors have been previously developed to study the mechanobiology of native or engineered heart valves6-9. Pulsatile bioreactors have also been developed to study a range of tissues including cartilage10, bone11 and bladder12. The aim of this work was to develop a cyclic pressure system that could be used to elucidate the biological response of aortic valve leaflets to increased pressure loads. 
The system consisted of an acrylic chamber in which to place samples and produce cyclic pressure, viton diaphragm solenoid valves to control the timing of the pressure cycle, and a computer to control electrical devices. The pressure was monitored using a pressure transducer, and the signal was conditioned using a load cell conditioner. A LabVIEW program regulated the pressure using an analog device to pump compressed air into the system at the appropriate rate. The system mimicked the dynamic transvalvular pressure levels associated with the aortic valve; a saw tooth wave produced a gradual increase in pressure, typical of the transvalvular pressure gradient that is present across the valve during diastole, followed by a sharp pressure drop depicting valve opening in systole. The LabVIEW program allowed users to control the magnitude and frequency of cyclic pressure. The system was able to subject tissue samples to physiological and pathological pressure conditions. This device can be used to increase our understanding of how heart valves respond to changes in the local mechanical environment.

Watch this Scientific Journal Video about Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves at JoVE.com

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

A cyclic pressure bioreactor capable of subjecting heart valve tissue to physiological and pathological pressure conditions has been designed. A LabVIEW program allows users to control pressure magnitude, amplitude and frequency. This device can be used to study the mechanobiology of heart valve tissue or isolated cells.

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic ...

design-cyclic-pressure-bioreactor-for-ex-vivo-study-aortic-heart

Research

Education

JoVE Core

JoVE Journal

Physics

Bioengineering

Unit 1

Sources of Magnetic Fields

SCIENTISTS IN ACTION

15.6K Görüntüleme.  Mississippi State University. Basınç koşulları fizyolojik ve patolojik kalp kapakçığı dokusu tabi yapabilen bir siklik basınç biyoreaktör dizayn edilmiştir. LabVIEW programı, kullanıcıların basınç büyüklüğü, genlik ve frekans kontrol etmenizi sağlar. Bu cihaz, kalp kapakçığı dokusu veya izole hücrelerin mechanobiology incelemek için kullanılabilir.