This work was supported by grants from the SNF [31003A-138528], the Octav and the Marcella Botnar Foundation, the Novartis Foundation and the Emma Muschamp Foundation. We thank Martine Lambelet, and&#160;Jean-Christophe Stehle for their excellent technical assistance.

The Ethical Committee of the University of Lausanne approved the experiments, which are in accordance with the principles outlined in the Declaration of Helsinki of 1975, as revised in 1983 for the use of human tissues.
1. Human Great Saphenous Vein Harvest
<ol>
	<li>Obtain surplus segments of non-varicose human saphenous veins from patients undergoing lower limb bypass surgery for ischemia. In the operating room, disinfect the entire leg with an iodine solution and drape the patient to expose the leg from the groin to the foot.</li>
	<li>Make a median incision from the groin to the knee (leaving the interrupted skin portion).</li>
	<li>Harvest the great saphenous vein with a pedicle of surrounding tissue (no-touch technique). Secure side branches of the veins with 4-0 silk ties. Immediately store a minimum of 9 cm long surplus segment of the greater saphenous vein, with an external diameter of 2.5-4 mm at 4 &#176;C in a RPMI-1640 Glutamax medium, supplemented with 12.5% fetal calf serum and bring it to the laboratory.</li>
</ol>
2. EVPS Design
<ol>
	<li>Assemble the general equipment shown in Figure 1. Autoclave all equipment and keep all components under sterile conditions. In addition, ensure that the system is waterproof and does not leak chemicals into the medium. Use polymethacrylate methyl (PMMA-GS) for the cover. Steel (X5 Cr Ni 18 10) and polyoxymethylene plastic (POM) as the vein support.</li>
	<li>Design the perfusion chamber to the desired geometry to allow the placement of the vein and its connection. Make sure the depth (or radius if using cylindrical construction) is at least 2.5 cm so it allows minimal flexion and dilatation of the vessel along with constant coverage by the culture media (Figure 1). Sealing is a major issue and is the reason rectangular PMMA-GS construction is used.</li>
	<li>Design the vein support to the desired geometry. To avoid vein kinking or over distension, allow length adjustment by pushing or pulling (screw cannot be used to that purpose, as the vein would be twisted along with the screw). 
	NOTE: A full steel rod connected by 2 sliding L-shaped pieces that support the 2 vein cylinders (5 mm diameter to fit the vessel) and the vein (Figure 1B and Figure 2) is used here.</li>
	<li>Design the pressure column, such that the &#8220;resting pressure&#8221; applied to the system is: p = 0-10 = h x &#961; x g, where p = pressure (N/m2, Pa) h = height of fluid column (m) &#961; = density of liquid (kg/m3) and g = the gravitational constant (9.81 m/sec2). Design four connection ducts, from top to bottom: to apply pressure, for the outflow (from the vein), the inflow (to the vein) and to allow medium change.</li>
	<li>Prepare the medium. Based on previous studies5,11-14, choose RPMI-1640, supplemented with Glutamax, 12.5% fetal calf serum, and 1% antibiotic-antimycotic solution (10,000 U/ml penicillin G, plus 10 mg/ml streptomycin sulfate, plus 25 mg/ml amphotericin B, plus 0.5 &#956;g/ml: gentamycin). Shear stress (SS) is given by SS= 4 &#956;Q/&#960;*r3Q is the flow rate (ml/sec), r the radius (cm) of the vein segment, and &#956; is the viscosity of the perfusion medium.
	<ol>
		<li>Modulate SS by adjusting the viscosity through addition of 70 kDa dextran. Measure the viscosity with a viscometer. Here, add 8% 70 kDa dextran to set SS to 9-15 dyn/cm2.</li>
	</ol>
	</li>
	<li>Set the gearing pump to induce a pulsatile cardioid signal of 60 pulses/min and constant amplitude generating a unidirectional flow of 150 &#177; 15 ml/min, independent from the pressure applied in the system and controlled by a computer. Ensure that the driving software integrates constant acquisition and monitoring of pressures, flow velocity, pulse rate, and signal. If desired, use a second pump (non synchronized) to produce a non-laminar, turbulent flow.</li>
</ol>
3. EVPS Assembly (Figure 1)
<ol>
	<li>Before starting, make sure all the equipment is sterile. Perform all the following steps under asepsis in a laminar flow hood.</li>
	<li>Place the vein in a Petri dish filled with medium. Use a surgical blade and divide the vein into 3 equal segments.</li>
	<li>Immediately rinse one segment in PBS. Divide the segment in 3 parts, fix one in formalin for morphometry. Freeze the other two for quantitative transcript (RT-PCR) and protein (western blot) analysis. Consider these segments as a control, non-perfused vein.</li>
	<li>Use the 2 remaining segments for perfusion.
	<ol>
		<li>Very gently inject medium into the vein and determine the normal flow direction; in presence of valves the vein is reversed.</li>
		<li>Sealing the veins is of utmost importance to experimental success. Check for leaks through collaterals. Secure any leaks with 6-0 silk sutures.</li>
	</ol>
	</li>
	<li>Connect the vein segment between the two metallic cylinders, one end at a time (2.3, Figure 1). Secure the cylinders with Ethibon 3-0 around the indentations (Figure 1A and B).
	<ol>
		<li>Place the entire venous segment into the perfusion chamber previously filled with medium. Repeat the same procedure for the second segment. 
		NOTE: Failure to properly seal the vein to the cylinder will be a source of leak, require reintervention, and significantly increase the risk of infection and experimental failure.</li>
	</ol>
	</li>
	<li>To reinforce (mesh) the second segment, release the two cylinders (with the vein attached) from the L-shaped pieces (2.3 and Figure 1).
	<ol>
		<li>Be gentle and do not touch the vein with any instruments. Slide the mesh first on the cylinder then onto the vein. A push/pull jostling will get the mesh on the vein.</li>
		<li>Once the mesh covers the entire surface of the vein secure the jacketed vein to the cylinders with Ethibon 3-0.</li>
		<li>Reassemble the vein/cylinder compound to the L-shaped support and transfer it to the perfusion chamber, previously filled with medium.</li>
	</ol>
	</li>
	<li>Connect each metallic cylinder (in-and outflow) to a Y-splitter using peroxide-treated silicone tubing with an internal diameter of 3.2 mm.</li>
	<li>Connect the outflow splitter to a second Y-splitter using the same type of tubing. From this Y-splitter, use one tube to measure the perfusion pressure through both vessels. Connect the other one back to the column to form a closed loop system (Figure 2).</li>
	<li>Inside the incubator, use a long (one-meter length) tube to connect the pressure column to the pump head.</li>
	<li>Complete the set up by connecting the pump head to the inflow Y-splitter with another long length tube (Figure 1).</li>
</ol>
4. Veins Perfusion
<ol>
	<li>After the EVPS assembly has been completed, fill the column with medium (stay below the vein outflow duct to allow refilling). Add more medium into the column until the system is full. Move all the system into the incubator maintained at 37 &#177; 0.1 &#176;C with a pH kept constant at 7.40 &#177; 0.01 (using a CO2/pH algorithm based on the Henderson-Hasselbach equation).</li>
	<li>Bring the gear pump head outside the incubator and connect it to the gear pump drive. Screw the rods to secure the assembly.</li>
	<li>Switch on the pump power, make sure it is activated on the driving software and allow 5 min for the medium to be equally distributed in every compartment.</li>
	<li>To monitor the pressure, use an arterial line monitoring. Connect the EVPS pressure output (it corresponds to the arterial catheter) to the pressure transducer linked to the computer.
	<ol>
		<li>Make sure the tube is entirely filled with medium and does not contain any bubbles. De-bubble the culture system through the &#8220;arterial line&#8221; tube (Figure 2). Pay attention to the display and look for a pulsatile cardioid signal of 60 pulses/min of constant amplitude. At this point, the average pressure is between 0-10 mm Hg. If the pressure is &#60; 0 and the column progressively empties look for a leak (vein collateral or inadequate seal between the vein and the tube).</li>
	</ol>
	</li>
	<li>Set the minimal pressure to 6 mm Hg for a venous test or at 90 mm Hg for an arterial test. Under these conditions, an air injector applies the required pressure to the column and system.</li>
	<li>Change the medium every 2 days by using the tube connected to the pressure column. To prevent pressure change damage, open the column plug first.</li>
</ol>
5. Completion of the Perfusion
<ol>
	<li>After 3 or 7 days of perfusion: take the EVPS out of the incubator and dismount the veins. Discard the 5 mm proximal and distal vein ends attached to the equipment. Cut a central, 5 mm thick rings from the remaining segment and fix in formalin (morphometry). Freeze the remaining fragments and reduce into powder for further molecular analyses.</li>
</ol>

<ol><li>Sal Go, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Executive+summary%3A+heart+disease+and+stroke+statistics--2014+update%3A+a+report+from+the+american+heart+association%5BTitle%5D)+AND+%22Circulation%22%5BJournal%5D)">Executive summary: heart disease and stroke statistics--2014 update: a report from the american heart association.</a> Circulation. 129, 399-410 (2014).</li>
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<li>Yu, P., Nguyen, B. T., Tao, M., Bai, Y., Ozaki, C. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mouse+vein+graft+hemodynamic+manipulations+to+enhance+experimental+utility%5BTitle%5D)+AND+%22The+American+Journal+of+Pathology%22%5BJournal%5D)">Mouse vein graft hemodynamic manipulations to enhance experimental utility.</a> The American Journal of Pathology. 178, 2910-2919 (2011).</li>
<li>Davies, M. G., Hagen, P. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Reprinted+article+%26%2334%3BPathophysiology+of+vein+graft+failure%3A+a+review%26%2334%3B%5BTitle%5D)+AND+%22European+journal+of+vascular+and+endovascular+surgery+%3A+the+official+journal+of+the+European+Society+for+Vascular+Surgery%22%5BJournal%5D)">Reprinted article &#34;Pathophysiology of vein graft failure: a review&#34;.</a> European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery. 42, Suppl 1. S19-S29 (2011).</li>
<li>Berard, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Role+of+hemodynamic+forces+in+the+ex+vivo+arterialization+of+human+saphenous+veins%5BTitle%5D)+AND+%22Journal+of+Vascular+Surgery%22%5BJournal%5D)">Role of hemodynamic forces in the ex vivo arterialization of human saphenous veins.</a> Journal of Vascular Surgery. 57, 1371-1382 (2013).</li>
<li>Vijayan, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Long-term+reduction+of+medial+and+intimal+thickening+in+porcine+saphenous+vein+grafts+with+a+polyglactin+biodegradable+external+sheath%5BTitle%5D)+AND+%22Journal+of+Vascular+Surgery%22%5BJournal%5D)">Long-term reduction of medial and intimal thickening in porcine saphenous vein grafts with a polyglactin biodegradable external sheath.</a> Journal of Vascular Surgery. 40, 1011-1019 (2004).</li>
<li>Jeremy, J. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((On+the+biology+of+saphenous+vein+grafts+fitted+with+external+synthetic+sheaths+and+stents%5BTitle%5D)+AND+%22Biomaterials%22%5BJournal%5D)">On the biology of saphenous vein grafts fitted with external synthetic sheaths and stents.</a> Biomaterials. 28, 895-908 (2007).</li>
<li>Zilla, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Constrictive+external+nitinol+meshes+inhibit+vein+graft+intimal+hyperplasia+in+nonhuman+primates%5BTitle%5D)+AND+%22The+Journal+of+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">Constrictive external nitinol meshes inhibit vein graft intimal hyperplasia in nonhuman primates.</a> The Journal of Thoracic and Cardiovascular Surgery. 136, 717-725 (2008).</li>
<li>Zilla, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Utilization+of+shape+memory+in+external+vein-graft+meshes+allows+extreme+diameter+constriction+for+suppressing+intimal+hyperplasia%3A+a+non-human+primate+study%5BTitle%5D)+AND+%22Journal+of+Vascular+Surgery%22%5BJournal%5D)">Utilization of shape memory in external vein-graft meshes allows extreme diameter constriction for suppressing intimal hyperplasia: a non-human primate study.</a> Journal of Vascular Surgery. 49, 1532-1542 (2009).</li>
<li>Yeoman, M. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+constitutive+model+for+the+warp-weft+coupled+non-linear+behavior+of+knitted+biomedical+textiles%5BTitle%5D)+AND+%22Biomaterials%22%5BJournal%5D)">A constitutive model for the warp-weft coupled non-linear behavior of knitted biomedical textiles.</a> Biomaterials. 31, 8484-8493 (2010).</li>
<li>Longchamp, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+use+of+external+mesh+reinforcement+to+reduce+intimal+hyperplasia+and+preserve+the+structure+of+human+saphenous+veins%5BTitle%5D)+AND+%22Biomaterials%22%5BJournal%5D)">The use of external mesh reinforcement to reduce intimal hyperplasia and preserve the structure of human saphenous veins.</a> Biomaterials. 35, 2588-2599 (2014).</li>
<li>Saucy, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Ex+vivo+pulsatile+perfusion+of+human+saphenous+veins+induces+intimal+hyperplasia+and+increased+levels+of+the+plasminogen+activator+inhibitor+1%5BTitle%5D)+AND+%22European+Surgical+Research.+Europaische+Chirurgische+Forschung.+Recherches+Chirurgicales+Europeennes%22%5BJournal%5D)">Ex vivo pulsatile perfusion of human saphenous veins induces intimal hyperplasia and increased levels of the plasminogen activator inhibitor 1.</a> European Surgical Research. Europaische Chirurgische Forschung. Recherches Chirurgicales Europeennes. 45, 50-59 (2010).</li>
<li>Dubuis, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Atorvastatin-loaded+hydrogel+affects+the+smooth+muscle+cells+of+human+veins%5BTitle%5D)+AND+%22The+Journal+of+pharmacology+and+experimental%22%5BJournal%5D)">Atorvastatin-loaded hydrogel affects the smooth muscle cells of human veins.</a> The Journal of pharmacology and experimental. 347, 574-581 (2013).</li>
<li>Deglise, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Increased+connexin43+expression+in+human+saphenous+veins+in+culture+is+associated+with+intimal+hyperplasia%5BTitle%5D)+AND+%22Journal+of+Vascular+Surgery%22%5BJournal%5D)">Increased connexin43 expression in human saphenous veins in culture is associated with intimal hyperplasia.</a> Journal of Vascular Surgery. 41, 1043-1052 (2005).</li>
<li>Muto, A., Model, L., Ziegler, K., Eghbalieh, S. D., Dardik, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Mechanisms+of+vein+graft+adaptation+to+the+arterial+circulation%3A+insights+into+the+neointimal+algorithm+and+management+strategies%5BTitle%5D)+AND+%22Circulation+Journal+%3A+Official+Journal+of+the+Japanese+Circulation+Society%22%5BJournal%5D)">Mechanisms of vein graft adaptation to the arterial circulation: insights into the neointimal algorithm and management strategies.</a> Circulation Journal : Official Journal of the Japanese Circulation Society. 74, 1501-1512 (2010).</li>
<li>Tao, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+simplified+murine+intimal+hyperplasia+model+founded+on+a+focal+carotid+stenosis%5BTitle%5D)+AND+%22The+American+Journal+of+Pathology%22%5BJournal%5D)">A simplified murine intimal hyperplasia model founded on a focal carotid stenosis.</a> The American Journal of Pathology. 182, 277-287 (2013).</li>
<li>Berard, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Salvage+treatment+for+venous+aneurysm+complicating+vascular+access+arteriovenous+fistula%3A+use+of+an+exoprosthesis+to+reinforce+the+vein+after+aneurysmorrhaphy%5BTitle%5D)+AND+%22European+Journal+of+Vascular+and+Endovascular+Surgery+%3A+the+Official+Journal+of+the+European+Society+for+Vascular+Surgery%22%5BJournal%5D)">Salvage treatment for venous aneurysm complicating vascular access arteriovenous fistula: use of an exoprosthesis to reinforce the vein after aneurysmorrhaphy.</a> European Journal of Vascular and Endovascular Surgery : the Official Journal of the European Society for Vascular Surgery. 40, 100-106 (2010).</li>
</ol>

The authors have nothing to disclose.

This study uncovers an ex&#160;vivo vein perfusion system (EVPS) to perform extensive hemodynamic studies in human veins. This system allows saphenous veins perfusion under defined hemodynamic parameters in the absence of aggravating inflammatory and growth factors released by circulating cells in vivo. Thus, it provides a better understanding of the underlying pathways involved in the control of IH in human veins grafts5,11,12,15.
Reproducible and quantifiable hem...

Cardiovascular diseases are the leading cause of morbidity and mortality in Western countries1. Despite advances made in endovascular treatments, bypass surgery remains the mainstay of contemporary therapies, thus over half a million vein grafts are performed annually in the United States. However, despite decades of research, 30-60% of lower extremity vein grafts fail within the first years due to intimal hyperplasia (IH)2. Mechanical forces, particularly low shear stress (SS) and high wall tension, are pivotal in the initiation and development of this hyperplastic response3,4. To address this issue, an ex&#160;vivo veins perfusion system (EVPS) was generated to study, under strictly controlled hemodynamic conditions (pressure and shear stress), the behavior of human saphenous veins. In this study, following insertion into the arterial-like circulation, high pressure (mean = 100 mm Hg) was sufficient to stimulate proliferation and migration of smooth muscle cells into the intimal layer (IH)5.
Mammalian studies have suggested the use of external reinforcement as an efficient method to support the &#8220;arterialized vein&#8221; and counteract the acute hemodynamic changes the vein faces once implanted into an arterial milieu. The mesh prevented over-distension, increased shear stress, and reduced wall tension and consequently IH6-10. However, the underlying mechanisms and its applicability to human veins in improving bypass patency have not been fully characterized. Our EVPS was used to compare, in condition mimicking the alterations a vein faces once inserted into an arterial regimen (high shear stress and pressure), the behavior of human saphenous veins in the absence and presence of an external macroporous polyester tubular mesh. By preventing pathological remodeling and IH, the mesh provided evidence of its potential clinical efficiency11.
This study 1) introduces a model of ex&#160;vivo human saphenous veins perfusion under controlled pressure and shear stress 2) demonstrates that external macro-porous polyester mesh reduces IH and provides crucial information for its potential clinical application.

<table><tbody><tr><td>RPMI 1640 - Glutamax</td><td>Life Technologies</td><td>61870-010</td><td></td></tr><tr><td>Penicilline/Streptomycine/Fungizone</td><td>Bioconcept</td><td>4-02F00-H</td><td></td></tr><tr><td>Dextran from Leuconostoc spp. 500 g</td><td>Sigma-Aldrich</td><td>31390</td><td></td></tr><tr><td>Tampon PBS CHUV pH 7.1-7.3 1 L</td><td>Laboratorium und Grosse Apotheke Dr. G. Bichsel AG</td><td>100 0 324 00</td><td></td></tr><tr><td>Cryosectionning embedding medium - Tissue-Tek OCT Compound</td><td>Fisher Scientific</td><td>14-373-65</td><td></td></tr><tr><td>Silicon Tubing (Peroxide) L/S 16 (96400-16 ) - 7.5 m</td><td>Idex Health &amp;amp; Science GMBH</td><td>MF0037ST</td><td></td></tr><tr><td>Y-splitter&amp;nbsp;</td><td>Idex Health &amp;amp; Science GMBH</td><td>Y-connector</td><td></td></tr><tr><td>35 mm Culture dish</td><td>Sigma-Aldrich</td><td>CLS430165-100EA</td><td></td></tr><tr><td>15 ml Falcon tube</td><td>BD Bioscence</td><td>352096</td><td></td></tr><tr><td>50 ml Falcon tube</td><td>BD Bioscence</td><td>352098</td><td></td></tr><tr><td>Gearing pump - Reglo-Z</td><td>Idex Health &amp;amp; Science GMBH</td><td>SM 895&amp;nbsp;</td><td>&amp;nbsp;App-Nr 03736-00194</td></tr><tr><td>Pump Head</td><td>Idex Health &amp;amp; Science GMBH</td><td>MI0008&amp;nbsp;</td><td></td></tr><tr><td>Monitoring Kit TRANSPAC IV</td><td>icumedical</td><td>011-0J736-01</td><td></td></tr><tr><td>20 ml Syringes</td><td>B. Braun Medical SA</td><td>4612041-02</td><td></td></tr><tr><td>Etibon 3-0 FS-2</td><td>Ethicon- Johnson&amp;amp;Johnson</td><td>EH7346H</td><td></td></tr><tr><td>Mesh ProVena 6-8mm</td><td>B. Braun Medical SA</td><td>1105012-14</td><td></td></tr><tr><td>NaCl: Sodium chloride solution perfusion 0.9% (100 ml)</td><td>B. Braun Medical SA</td><td>534534</td><td></td></tr><tr><td>Masterflex L/S Standard Drive</td><td>Cole-Parmer Instrument Co</td><td>7521-10</td><td></td></tr><tr><td>Acquisition card</td><td>National Instruments</td><td>PCI-6024 E</td><td></td></tr><tr><td>Flowmeter module</td><td>Transonic Systems Inc.</td><td>TS410 and T402</td><td></td></tr><tr><td>Stopcock with 3-ways</td><td>BD Connexta Luerlock</td><td>394600</td><td></td></tr><tr><td>Millex Filter</td><td>Milian</td><td>SE2M229I04</td><td></td></tr></tbody></table>

procedure for human saphenous veins ex vivo perfusion and external reinforcement

The mainstay of contemporary therapies for extensive occlusive arterial disease is venous bypass graft. However, its durability is threatened by intimal hyperplasia (IH) that eventually leads to vessel occlusion and graft failure. Mechanical forces, particularly low shear stress and high wall tension, are thought to initiate and to sustain these cellular and molecular changes, but their exact contribution remains to be unraveled. To selectively evaluate the role of pressure and shear stress on the biology of IH, an ex&#160;vivo perfusion system (EVPS) was created to perfuse segments of human saphenous veins under arterial regimen (high shear stress and high pressure). Further technical innovations allowed the simultaneous perfusion of two segments from the same vein, one reinforced with an external mesh. Veins were harvested using a no-touch technique and immediately transferred to the laboratory for assembly in the EVPS. One segment of the freshly isolated vein was not perfused (control, day 0). The two others segments were perfused for up to 7 days, one being completely sheltered with a 4 mm (diameter) external mesh. The pressure, flow velocity, and pulse rate were continuously monitored and adjusted to mimic the hemodynamic conditions prevailing in the femoral artery. Upon completion of the perfusion, veins were dismounted and used for histological and molecular analysis. Under ex&#160;vivo conditions, high pressure perfusion (arterial, mean = 100 mm Hg) is sufficient to generate IH and remodeling of human veins. These alterations are reduced in the presence of an external polyester mesh.

The EVPS provides a valuable tool to independently assess the hemodynamic forces on human saphenous vein grafts remodeling and IH.
Figure 1 shows the perfusion chamber and the vein support. In Figures 1A and B, the vein support before (Figure 1A) and after (Figure 1B) assembly, respectively, is pictured. It is composed (from the top to the bottom) of 1 plain stainless steel tube measuring 9 cm, which serves as...

Watch this Scientific Journal Video about Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement at JoVE.com

Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement

The mechanisms leading to the development of intimal hyperplasia (IH) and vein graft failure are still poorly understood. This study describes an ex&#160;vivo system to perfuse human veins under controlled flow and pressure. Furthermore the efficiency of external mesh reinforcement to limit the development of IH was evaluated.

Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement

The mainstay of contemporary therapies for extensive occlusive arterial disease is venous bypass graft. However, its durability is threatened by intimal ...

procedure-for-human-saphenous-veins-ex-vivo-perfusion-external

Research

JoVE Journal

Medicine

11.3K Views.  Brigham and Women's Hospital/Harvard Medical School.  De mechanismen die leiden tot de ontwikkeling van intimale hyperplasie (IH) en bypass falen nog steeds slecht begrepen. Deze studie beschrijft een ex vivo-systeem voor de menselijke aderen onder gecontroleerde flow en druk perfuseren. Verder is de efficiëntie van het extern wapeningsnet beperken de ontwikkeling van IH werd geëvalueerd. 

Video: Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement

Tissue Engineering by Intrinsic Vascularization in an In Vivo Tissue Engineering Chamber

In reconstructive surgery, there is a clinical need for an alternative to the current methods of autologous reconstruction which are complex, costly and trade one defect for another. Tissue engineering holds the promise to address this increasing demand. However, most tissue engineering strategies fail to generate stable and functional tissue substitutes because of poor vascularization. This paper focuses on an in vivo tissue engineering chamber model of intrinsic vascularization where a perfused artery and a vein either as an arteriovenous loop or a flow-through pedicle configuration is directed inside a protected hollow chamber. In this chamber-based system angiogenic sprouting occurs from the arteriovenous vessels and this system attracts ischemic and inflammatory driven endogenous cell migration which gradually fills the chamber space with fibro-vascular tissue. Exogenous cell/matrix implantation at the time of chamber construction enhances cell survival and determines specificity of the engineered tissues which develop. Our studies have shown that this chamber model can successfully generate different tissues such as fat, cardiac muscle, liver and others. However, modifications and refinements are required to ensure target tissue formation is consistent and reproducible. This article describes a standardized protocol for the fabrication of two different vascularized tissue engineering chamber models in vivo.

Tissue Engineering by Intrinsic Vascularization in an In Vivo Tissue Engineering Chamber

This is a guideline for constructing in vivo vascularized tissue using a microsurgical arteriovenous loop or a flow-through pedicle configuration inside a tissue engineering chamber. The vascularized tissues generated can be employed for organ regeneration and replacement of tissue defects, as well as for drug testing and disease modeling.

In reconstructive surgery, there is a clinical need for an alternative to the current methods of autologous reconstruction which are complex, costly and ...

Bioengineering

The Arteriovenous (AV) Loop in a Small Animal Model to Study Angiogenesis and Vascularized Tissue Engineering

A functional blood vessel network is a prerequisite for the survival and growth of almost all tissues and organs in the human body. Moreover, in pathological situations such as cancer, vascularization plays a leading role in disease progression. Consequently, there is a strong need for a standardized and well-characterized in vivo model in order to elucidate the mechanisms of neovascularization and develop different vascularization approaches for tissue engineering and regenerative medicine.
We describe a microsurgical approach for a small animal model for induction of a vascular axis consisting of a vein and artery that are anastomosed to an arteriovenous (AV) loop. The AV loop is transferred to an enclosed implantation chamber to create an isolated microenvironment in vivo, which is connected to the living organism only by means of the vascular axis. Using 3D imaging (MRI, micro-CT) and immunohistology, the growing vasculature can be visualized over time. By implanting different cells, growth factors and matrices, their function in blood vessel network formation can be analyzed without any disturbing influences from the surroundings in a well controllable environment. 
In addition to angiogenesis and antiangiogenesis studies, the AV loop model is also perfectly suited for engineering vascularized tissues. After a certain prevascularization time, the generated tissues can be transplanted into the defect site and microsurgically connected to the local vessels, thereby ensuring immediate blood supply and integration of the engineered tissue. By varying the matrices, cells, growth factors and chamber architecture, it is possible to generate various tissues, which can then be tailored to the individual patient's needs.

The Arteriovenous AV Loop in a Small Animal Model to Study Angiogenesis and Vascularized Tissue Engineering

We describe a microsurgical approach for the generation of an arteriovenous (AV) loop as a model for analyzing vascularization in vivo in an isolated and well-characterized environment. This model is not only useful for the investigation of angiogenesis, but is also optimally suited for engineering axially vascularized and transplantable tissues.

A functional blood vessel network is a prerequisite for the survival and growth of almost all tissues and organs in the human body. Moreover, in ...

Decellularization and Recellularization Methodology for Human Saphenous Veins

Vascular conduits used during most vascular surgeries are allogeneic or synthetic grafts that often lead to complications caused by immunosuppression and poor patency. Tissue engineering offers a novel solution to generate personalized grafts with a natural extracellular matrix containing the recipient&#39;s cells using the method of decellularization and recellularization. We show a detailed method for performing decellularization of the human saphenous vein and recellularization by perfusion of peripheral blood. The vein was decellularized by perfusing 1% Triton X-100, 1% tri-n-butyl-phosphate (TnBP) and 2,000 Kunitz units of deoxyribonuclease (DNase). Triton X-100 and TnBP were perfused at 35 mL/min for 4 h while DNase was perfused at 10 mL/min at 37 &#176;C for 4 h. The vein was washed in ultrapure water and PBS and then sterilized in 0.1% peracetic acid. It was washed again in PBS and preconditioned in endothelial medium. The vein was connected to a bioreactor and perfused with endothelial medium containing 50 IU/mL heparin for 1 h. Recellularization was performed by filling the bioreactor with fresh blood, diluted 1:1 in Steen solution, and adding endocrine gland-derived vascular endothelial growth factors (80 ng/mL), basic fibroblast growth factors (4 &#181;L/mL), and acetyl salicylic acid (5 &#181;g/mL). The bioreactor was then moved into an incubator and perfused for 48 h at 2 mL/min while maintaining glucose between 3 - 9 mmol/L. Later, the vein was washed with PBS, filled with endothelial medium and perfused for 96 h in the incubator. Treatment with Triton X-100, TnBP and DNase decellularized the saphenous vein in 5 cycles. The decellularized vein looked white in contrast to normal and recellularized veins (light red). The hematoxylin &#38; eosin (H&#38;E) staining showed the presence of nuclei only in normal but not in decellularized veins. In the recellularized vein, H&#38;E-staining showed the presence of cells on the luminal surface of the vein.

Here, we describe a protocol for the saphenous vein decellularization using detergents and recellularization by perfusion of the peripheral blood and the endothelial medium.

Vascular conduits used during most vascular surgeries are allogeneic or synthetic grafts that often lead to complications caused by immunosuppression and ...

Vein Interposition Model: A Suitable Model to Study Bypass Graft Patency

Bypass grafting is an established treatment method for coronary artery disease. Graft patency continues to be the Achilles heel of saphenous vein grafts. Research models for bypass graft failure are essential for a better understanding of pathobiological and pathophysiological processes during graft patency loss. Large animal models, such as pigs or sheep, resemble human anatomical structures but require special facilities and equipment. This video describes a rat vein interposition model to investigate vein graft patency loss. Rats are inexpensive and easy to handle. Compared to mouse models, the convenient size of rats permits better operability and enables a sufficient amount of material to be obtained for further diverse analysis. In brief, the inferior epigastric vein of a donor rat is harvested and used to replace a segment of the femoral artery. Anastomosis is conducted via single stitches and sealed with fibrin glue. Graft patency can be monitored non-invasively using duplex sonography. Myointimal hyperplasia, which is the main cause for graft patency loss, develops progressively over time and can be calculated from histological cross sections.

This video demonstrates a model to study the development of myointimal hyperplasia after venous interposition surgery in rats.

Bypass grafting is an established treatment method for coronary artery disease. Graft patency continues to be the Achilles heel of saphenous vein grafts. ...

A Reliable Porcine Fascio-Cutaneous Flap Model for Vascularized Composite Allografts Bioengineering Studies

Vascularized Composite Allografts (VCA) such as hand, face, or penile transplant represents the cutting-edge treatment for devastating skin defects, failed by the first steps of the reconstructive ladder. Despite promising aesthetic and functional outcomes, the main limiting factor remains the need for a drastically applied lifelong immunosuppression and its well-known medical risks, preventing broader indications. Therefore, lifting the immune barrier in VCA is essential to tip the ethical scale and improve patients&#39; quality of life using the most advanced surgical techniques. De novo creation of a patient-specific graft is the upcoming breakthrough in reconstructive transplantation. Using tissue engineering techniques, VCAs can be freed of donor cells and customized for the recipient through perfusion-decellularization-recellularization. To develop these new technologies, a large-scale animal VCA model is necessary. Hence, swine fascio-cutaneous flaps, composed of skin, fat, fascia, and vessels, represent an ideal model for preliminary studies in VCA. Nevertheless, most VCA models described in the literature include muscle and bone. This work reports&#160;a reliable and reproducible technique for saphenous fascio-cutaneous flap harvest in swine, a practical tool for various research fields, especially vascularized composite tissue engineering.

The present protocol describes the porcine fascio-cutaneous flap model and its potential use in vascularized composite tissue research.

Vascularized Composite Allografts (VCA) such as hand, face, or penile transplant represents the cutting-edge treatment for devastating skin defects, ...

Synergizing Antegrade Endoscopic with Bridging Vein Harvesting for Improvement of Great Saphenous Vein Graft Quality from the Lower Leg

Antegrade endoscopic harvesting of autografts for bypass grafting may be an optimal strategy addressing excellent graft quality and reduced post-operative wound complications. This standardized protocol for antegrade endoscopic vein harvesting (EVH) from the lower leg has the potential to be introduced to routine coronary artery bypass grafting (CABG). Patients undergoing CABG surgery are positioned on a surgical table with two additional foam rollers below the extended legs, enabling antegrade EVH from the lower leg. Following minimally invasive surgical access through a bridging vein harvest technique, an endoscopic optical dissector is inserted antegrade into the wound. The main vessel and side branches are dissected under continuous optical control of vein quality status and the working channel. After, an endoscopic optical retractor is inserted with an internal bipolar electrocoagulation device for precise, safe, and tissue-protective interruption of side branches. After release of the vein, the vessel is cut off at the proximal and distal ends under optical control, retrieved from the wound, then cannulated and flushed with heparinized saline. Finally, all side branches of the vein graft are double-clipped. Vascular histology is analyzed in a randomized selection of vein samples. After applying this standardized EVH protocol, the learning curve was shown to be steep, and graft quality was sufficient for coronary artery bypass grafting in every case. There was no conversion to surgical harvesting and low risks for tissue damage and bleeding. Leg positioning and synergizing EVH with bridging vein harvesting improved procedural success and vein graft quality. In our hands, antegrade EVH from the lower leg was feasible, demonstrating straightforward graft dissection as well as adequate macroscopic and microscopic graft quality with preserved endothelial integrity. In conclusion, the introduced technique is safe, shows excellent vein autograft quality, and illustrates feasibility for elective and urgent isolated CABG and combined CABG scenarios.

Presented here is a protocol for antegrade endoscopic vein harvesting from the lower leg, which can safely be introduced in routine coronary artery bypass grafting. Vein grafts present excellent graft quality following this standardized protocol with positioning of the legs, minimally invasive access to the vein, and antegrade endoscopic vein harvesting.

Antegrade endoscopic harvesting of autografts for bypass grafting may be an optimal strategy addressing excellent graft quality and reduced post-operative ...

A Training and Testing System for Performing Vascular Reconstruction In Vitro

Manual vascular reconstruction training is essential for a beginner surgeon. However, an optimal training system for vascular reconstruction in vitro has yet to be developed. In this study, we introduce an in vitro training and testing system using a magnetic anchoring technique with which a trainee can practice manual vascular reconstruction individually. Additionally, this system can also be used to test the quality of the reconstruction. The described system includes a vascular reconstruction training machine, magnetic tractors, and a magnetic suture puller. In this manuscript, we detail an end-to-end vein anastomosis using porcine right and left iliac veins. To identify the potential damage caused by a magnetic suture puller on the suture, we created three groups with six segments of 4-0 polypropylene sutures each: a control group with no intervention on the polypropylene suture, a group in which the polypropylene suture is manually pulled with sterile gloves 20x, and a magnetic puller group in which the magnetic puller pulled the polypropylene suture 20x. These groups were tested by light microscopy and breaking strength tests, and the effect of reconstruction was assessed. In the light microscopy test, the control group was less likely to be damaged (p &#60; 0.05) and the number of damaged points of the manual group and magnetic puller group were similar (p &#62; 0.05). The results of the breaking strength test were compared across groups and no significant difference was observed (p &#62; 0.05). The end-to-end anastomosis of the porcine iliac veins was successfully performed using this training system, and the reconstructed veins could undergo 2.0 kPa perfusion pressure. Using this training and testing system the trainee can practice manual vascular reconstruction in vitro individually with the aid of magnetic tractors and a magnetic suture puller, and the quality of the reconstruction can be tested.

Here we present a training and testing system where a trainee can complete manual vascular reconstruction in vitro individually using a magnetic anchoring technique. The system can also be used to test the quality of reconstruction.

Manual vascular reconstruction training is essential for a beginner surgeon. However, an optimal training system for vascular reconstruction in vitro has ...

A Rabbit Venous Interposition Model Mimicking Revascularization Surgery using Vein Grafts to Assess Intimal Hyperplasia under Arterial Blood Pressure

Although vein grafts have been commonly used as autologous grafts in revascularization surgeries for ischemic diseases, the long-term patency remains poor because of the acceleration of intimal hyperplasia due to the exposure to arterial blood pressure. The present protocol is designed for the establishment of experimental venous intimal hyperplasia by interposing rabbit jugular veins to the ipsilateral carotid arteries. The protocol does not require surgical procedures deep in the body trunk and the extent of the incision is limited, which is less invasive for the animals, allowing long-term observation after implantation. This simple procedure enables researchers to investigate strategies to attenuate the progression of intimal hyperplasia of the implanted vein grafts. Using this protocol, we reported the effects transduction of microRNA-145 (miR-145), which is known to control the phenotype of vascular smooth muscle cells (VSMCs) from the proliferative to the contractile state, into harvested vein grafts. We confirmed the attenuation of intimal hyperplasia of vein grafts by transducing miR-145 before implantation surgery through the phenotype change of the VSMCs. Here we report a less invasive experimental platform to investigate the strategies that can be used to attenuate intimal hyperplasia of vein grafts in revascularization surgeries.

The present protocol aims to experimentally create venous intimal hyperplasia by subjecting veins to arterial blood pressure for developing strategies to attenuate venous intimal hyperplasia following revascularization surgery using vein grafts.

Although vein grafts have been commonly used as autologous grafts in revascularization surgeries for ischemic diseases, the long-term patency remains poor ...

Occlusion of the Great and Small Saphenous Vein Using Copolymeric Glue Based on N-Butyl Cyanoacrylate and Methacryloxy Sulfolane

We present the preliminary results of a longitudinal observational study aimed at evaluating the effectiveness and safety at different short- and long-term follow-ups of vascular occlusion of the great saphenous vein (GSV) and small saphenous vein (SSV) affected by severe pathological reflux, using an innovative modified cyanoacrylate surgical glue composed of N-butyl cyanoacrylate and methacryloxy sulfolane (NBCA+MS). Ninety patients, prospectively recruited for 1 year, underwent the study with EcoColor-Doppler (ECD) to evaluate the maximum diameters of the GSV and SSV in the orthostatic position and the reflux time (RT). An RT greater than 0.5 s was considered pathologic. Clinical, etiology, anatomy, and pathophysiology (CEAP) assessment was used for the complete evaluation of each patient in the study. All the patients were treated by NBCA+MS glue to obtain vein occlusion and observed before treatment (baseline; T0), within 6 h after treatment (T1), 1 month after treatment (T2), 3 months after treatment (T3), 6 months after treatment (T4), and 1 year after treatment (T5). Chi-square (&#967;) analysis was performed to evaluate the effectiveness and safety of the treatment. All the patients participated in the entire duration of the study. Complete occlusion was maintained in 100% of patients at T1, 98.9% at T2 and T3, and 97.8% at T4 and T5 (p &lt; 0.001). None of the patients suffered from post-surgical thrombosis. No blue hyperpigmentation, or paresthesia was observed during the entire observation period. Immediately after treatment, 7.7% of patients needed painkillers; 1 week after treatment, 100% of patients returned to normal life. Vascular occlusion of the great or small saphenous vein using NBCA+MS glue is a safe procedure with persistent benefits after a 1 year follow-up. This procedure can be performed with local anesthesia, allowing a quick return to normal life. Thanks to its low invasiveness, the treatment is not painful.

Here, we present a protocol to treat the great saphenous vein (GSV) and the small saphenous vein (SSV) affected by severe pathological reflux, using an original sclerosing and embolizing cyanoacrylate-based glue composed of N-butyl cyanoacrylate and methacryloxy sulfolane (NBCA+MS).

We present the preliminary results of a longitudinal observational study aimed at evaluating the effectiveness and safety at different short- and ...

Human Saphenous Vein Endothelial Cell Isolation and Exposure to Controlled Levels of Shear Stress and Stretch

Coronary artery bypass graft (CABG) surgery is a procedure to revascularize ischemic myocardium. Saphenous vein remains used as a CABG conduit despite the reduced long-term patency compared to arterial conduits. The abrupt increase of hemodynamic stress associated with the graft arterialization results in vascular damage, especially the endothelium, that may influence the low patency of the saphenous vein graft (SVG). Here, we describe the isolation, characterization, and expansion of human saphenous vein endothelial cells (hSVECs). Cells isolated by collagenase digestion display the typical cobblestone morphology and express endothelial cell markers CD31 and VE-cadherin. To assess the mechanical stress influence, protocols were used in this study to investigate the two main physical stimuli, shear stress and stretch, on arterialized SVGs. hSVECs are cultured in a parallel plate flow chamber to produce shear stress, showing alignment in the direction of the flow and increased expression of KLF2, KLF4, and NOS3. hSVECs can also be cultured in a silicon membrane that allows controlled cellular stretch mimicking venous (low) and arterial (high) stretch. Endothelial cells' F-actin pattern and nitric oxide (NO) secretion are modulated accordingly by the arterial stretch. In summary, we present a detailed method to isolate hSVECs to study the influence of hemodynamic mechanical stress on an endothelial phenotype.

We describe a protocol to isolate and culture human saphenous vein endothelial cells (hSVECs). We also provide detailed methods to produce shear stress and stretch to study mechanical stress in hSVECs.

Coronary artery bypass graft (CABG) surgery is a procedure to revascularize ischemic myocardium. Saphenous vein remains used as a CABG conduit despite the ...

Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement

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