This work was supported, in part, by a grant from the NIH (RO1 HL098228) to CKB.

NOTE: All animal procedures were approved by the Nationwide Children&#39;s Hospital Institutional Animal Care and Use Committee.
1.&#160;Graft Manufacturing
<ol>
	<li>Make the &#949;-caprolactone and L-lactide copolymer P(LA/CL) solution by adding 100mg P(LA/CL) in 2 ml dioxane under a fume hood. Place the solution on a vortex and mix continuously for 1-1.5 hr to dissolve completely.&#160;</li>
	<li>In the meantime, remove a sheet of polyglycolic acid (PGA) felt from the freezer and cut out several 5 x 8 mm sections. Also cut off the tip of a 0.1-10 &#181;l pipette just above the filter.</li>
	<li>Insert a 19 G needle (1.5 length) into the distal end of a pipet tip and wrap the PGA felt around the needle using micro forceps.</li>
	<li>Carefully push the felt to the distal end of the pipet tip, where the lumen is straighter than the proximal part, using a blunt 18 G needle, while the 19 G needle is inserted into it.</li>
	<li>Pipette 40 &#181;l P(CL/LA) solution into the pipette tip from the top. Saturate the PGA felt with the solution. Then push air bubbles out using a pipette dispenser. Repeat this process if needed.</li>
	<li>Place grafts in a 50 ml tube and place it in a -80 &#176;C freezer for 20 min. Make sure the head of the needles face downward.</li>
	<li>Transfer the tube into a lyophilizer and vacuum for 24 hr. Make sure to open the lid of the tube to have airflow.</li>
	<li>Take out the grafts and remove them from the needles. Cut both ends of the graft leaving a ~5 mm section and put them back onto the needles to maintain their shape. Keep the grafts in a desiccator.</li>
	<li>Place the scaffold under UV light in a biosafety hood O/N before cell seeding.</li>
</ol>
2. Bone Marrow Mononuclear Cell Harvesting and Isolation
<ol>
	<li>Euthanize the mice with ketamine/xylazine overdose (ketamine, 200 mg/kg and xylazine, 20 mg/kg).</li>
	<li>Remove bones (femurs and tibias) from 3 mice for 10 graft implantations and place in a Petri dish with 10 cc RPMI. Cut both ends of the bones and flush bone marrow using a syringe with a 25 G needle into a new Petri dish with 3 cc RPMI. Collect bone marrow and RPMI solution in a 15 cc tube and wash the petri dish with additional 2 cc RPMI to collect the remainder of BM.</li>
	<li>Take sample (5-10 &#181;l) and count cell using an automated cell counter or hemocytometer. Record the result.</li>
	<li>Put 5 cc Ficoll in a 15 cc centrifuge tube and add bone marrow and RPMI solution. Add the solution very gently to prevent it from mixing with Ficoll.</li>
	<li>Centrifuge at 528 x g for 30 min with &#34;NO BRAKE&#34; at 24 &#176;C.</li>
	<li>Remove the upper pink layer. Collect the middle clear layer Figure 1, which is the MNC layer, and dilute it with PBS 1:1.</li>
	<li>Centrifuge the dilute MNC solution at 528 x g for 10 min at 24 &#176;C.</li>
	<li>Remove the supernatant and dilute the pellet with 5 ml PBS.</li>
	<li>Centrifuge the pellet solution at 528 x g for 10 min at 24 &#176;C.</li>
	<li>Remove the supernatant. Dilute the pellet with the appropriate volume of RPMI (~200 &#181;l).</li>
	<li>Take a 5-10 &#181;l sample and count cells using an automated cell counter or hemocytometer. Record the result. Repeat the cell counting one more time and calculate the average cell number.</li>
	<li>Dilute cell concentration to 1,000,000 cells/10 &#181;l using RPMI.</li>
</ol>
3.&#160;Cell Seeding
<ol>
	<li>Prewet scaffold by adding 5 &#181;l RPMI luminally for 5 min, then remove RPMI.</li>
	<li>Add 10 &#181;l bone marrow derived mono nuclear cells in RPMI from Step 2.12&#160;to scaffold lumen and wait for 10 min&#160;to allow cells to attach onto the scaffold.</li>
	<li>Cut a 19 G needle to 1 cm length and put the needle into the lumen of the scaffold to keep the shape of the scaffold. Place the sample in a 24-well plate.</li>
	<li>Add 1,000 &#181;l RPMI to each well and incubate O/N in an incubator.</li>
</ol>
4.&#160;Graft Implantation
<ol>
	<li>Autoclave all the surgical tools before the surgery: 1x fine scissors, 3x micro forceps, 2x micro vascular clamps, 1x clamp applying forceps, 1x micro needle holder, 1x spring scissors, 1x retractor.</li>
	<li>6-8 weeks old female C57BL/6 are used as tissue engineered vascular graft recipients. Remove the mouse from its cage and weigh it, then anesthetize through an intraperitoneal injection into the lower right quadrant of the abdomen with a ketamine/xylazine cocktail (ketamine, 100 mg/kg and xylazine, 10 mg/kg). Ketoprofen (5&#160;mg/kg, IP) is used as a pre-anesthesia analgesic.</li>
	<li>Check the level of sedation by tale pinching, then clip the abdominal hair. Lubricate the eyes with sterile ophthalmic ointment, and place the mouse in a dorsal recumbence position on a pad. Disinfect the abdomen with betadine and alcohol pads. Cover the mouse with a sterile drape and expose the incision area only.</li>
	<li>Make a midline laparotomy incision from below the xyphoid to the suprapubic region, and insert a self-retaining retractor. Wrap the intestines in saline moistened gauze. Bluntly define the infrarenal aorta and vena cava.</li>
	<li>Place two micro vascular clamps on both proximal and distal sides of the aorta and vena cava then bluntly separate the aorta from the vena cava Transect the vena cava. If necessary, ligate the abdominal aortic branches with a 10-0 monofilament sutures on tapered needles.</li>
	<li>Implant an inferior vena cava interposition graft with proximal and distal end to end anastomoses using a sterile 10-0 suture. Trim the graft, usually 1-2 mm, dependent on the anatomy of the mouse. Secure the graft with one stitch on both proximal and distal ends and start to suture continuously with 4-5 stiches from the other side of the graft. After finishing the front side, flip the clamps and grafts to the other side and suture the back side of the graft. During implantation, flush the graft with heparin solution frequently to prevent acute thrombosis.</li>
	<li>Remove the proximal clamp and control the hemorrhage by applying a topical absorbable sterile hemostat agent. When the hemorrhage stops completely, remove the distal clamp and control the hemorrhage the same way. Make sure blood flows through the graft.</li>
	<li>Close the abdominal musculature and skin in two layers using a 6-0 black polyamide monofilament suture with included threaded needle.</li>
	<li>Inject 0.5 ml saline subcutaneously and place the mouse in a recovery cage on a warming pad until the mouse is fully mobile. Upon recovery, return the mouse to a new cage with paper bedding. Give pain medication (Ibuprofen, 30 mg/kg, drinking water) for 48 hr.</li>
</ol>

<ol><li>Heart Association, A. merican <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Heart+Disease+and+Stroke+Statistics%E2%80%942012+Update%5BTitle%5D)+AND+%22Circulation%22%5BJournal%5D)">Heart Disease and Stroke Statistics—2012 Update.</a> Circulation. 125, (2012).</li>
<li>Shinoka, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Creation+Of+Viable+Pulmonary+Artery+Autografts+Through+Tissue+Engineering%5BTitle%5D)+AND+%22The+Journal+of+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">Creation Of Viable Pulmonary Artery Autografts Through Tissue Engineering.</a> The Journal of Thoracic and Cardiovascular Surgery. 115, 536-546 (1998).</li>
<li>Hibino, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Late-term+results+of+tissue-engineered+vascular+grafts+in+humans%5BTitle%5D)+AND+%22The+Journal+of+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">Late-term results of tissue-engineered vascular grafts in humans.</a> The Journal of Thoracic and Cardiovascular Surgery. 139, 431-436 (2010).</li>
<li>Shin'oka, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Midterm+clinical+result+of+tissue-engineered+vascular+autografts+seeded+with+autologous+bone+marrow+cells%5BTitle%5D)+AND+%22The+Journal+of+Thoracic+and+Cardiovascular+Surgery%22%5BJournal%5D)">Midterm clinical result of tissue-engineered vascular autografts seeded with autologous bone marrow cells.</a> The Journal of Thoracic and Cardiovascular Surgery. 129, 1330-1338 (2005).</li>
<li>Brennan, M. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tissue-engineered+vascular+grafts+demonstrate+evidence+of+growth+and+development+when+implanted+in+a+juvenile+animal+model%5BTitle%5D)+AND+%22Ann+Surg%22%5BJournal%5D)">Tissue-engineered vascular grafts demonstrate evidence of growth and development when implanted in a juvenile animal model.</a> Ann Surg. 248, 370-377 (2008).</li>
<li>Roh, J. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Construction+of+an+autologous+tissue-engineered+venous+conduit+from+bone+marrow-derived+vascular+cells%3A+optimization+of+cell+harvest+and+seeding+techniques%5BTitle%5D)+AND+%22Journal+of+Pediatric+Surgery%22%5BJournal%5D)">Construction of an autologous tissue-engineered venous conduit from bone marrow-derived vascular cells: optimization of cell harvest and seeding techniques.</a> Journal of Pediatric Surgery. 42, 198-202 (2007).</li>
<li>Hibino, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tissue-engineered+vascular+grafts+form+neovessels+that+arise+from+regeneration+of+the+adjacent+blood+vessel%5BTitle%5D)+AND+%22The+FASEB+Journal%22%5BJournal%5D)">Tissue-engineered vascular grafts form neovessels that arise from regeneration of the adjacent blood vessel.</a> The FASEB Journal. 25, 2731-2739 (2011).</li>
<li>Hibino, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+critical+role+for+macrophages+in+neovessel+formation+and+the+development+of+stenosis+in+tissue-engineered+vascular+grafts%5BTitle%5D)+AND+%22The+FASEB+Journal%22%5BJournal%5D)">A critical role for macrophages in neovessel formation and the development of stenosis in tissue-engineered vascular grafts.</a> The FASEB Journal. 25, 4253-4263 (2011).</li>
<li>Naito, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Characterization+of+the+Natural+History+of+Extracellular+Matrix+Production+in+Tissue-Engineered+Vascular+Grafts+during+Neovessel+Formation%5BTitle%5D)+AND+%22Cells+Tissues+Organs%22%5BJournal%5D)">Characterization of the Natural History of Extracellular Matrix Production in Tissue-Engineered Vascular Grafts during Neovessel Formation.</a> Cells Tissues Organs. 195, 60-72 (2012).</li>
<li>Naito, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Beyond+Burst+Pressure%3A+Initial+Evaluation+of+the+Natural+History+of+the+Biaxial+Mechanical+Properties+of+Tissue+Engineered+Vascular+Grafts+in+the+Venous+Circulation+Using+a+Murine+Model%5BTitle%5D)+AND+%22Tissue+Eng.+Part+A%22%5BJournal%5D)">Beyond Burst Pressure: Initial Evaluation of the Natural History of the Biaxial Mechanical Properties of Tissue Engineered Vascular Grafts in the Venous Circulation Using a Murine Model.</a> Tissue Eng. Part A. 20, (2013).</li>
<li>Mirensky, T. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tissue-engineered+vascular+grafts%3A+does+cell+seeding+matter%5BTitle%5D)+AND+%22Journal+of+Pediatric+Surgery%22%5BJournal%5D)">Tissue-engineered vascular grafts: does cell seeding matter.</a> Journal of Pediatric Surgery. 45, 1299-1305 (2010).</li>
<li>Roh, J. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tissue-engineered+vascular+grafts+transform+into+mature+blood+vessels+via+an+inflammation-mediated+process+of+vascular+remodeling%5BTitle%5D)+AND+%22Proceedings+of+the+National+Academy+of+Sciences%22%5BJournal%5D)">Tissue-engineered vascular grafts transform into mature blood vessels via an inflammation-mediated process of vascular remodeling.</a> Proceedings of the National Academy of Sciences. 107, 4669-4674 (2010).</li>
<li>Mirensky, T. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Tissue-engineered+arterial+grafts%3A+long-term+results+after+implantation+in+a+small+animal+model%5BTitle%5D)+AND+%22Journal+of+Pediatric+Surgery%22%5BJournal%5D)">Tissue-engineered arterial grafts: long-term results after implantation in a small animal model.</a> Journal of Pediatric Surgery. 44, 1127-1133 (2009).</li>
<li>Lee, Y. U., Naito, Y., Kurobe, H., Breuer, C. K., Humphrey, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Biaxial+mechanical+properties+of+the+inferior+vena+cava+in+C57BL%2F6+and+CB-17+SCID%2Fbg+mice%5BTitle%5D)+AND+%22Journal+of+Biomechanics%22%5BJournal%5D)">Biaxial mechanical properties of the inferior vena cava in C57BL/6 and CB-17 SCID/bg mice.</a> Journal of Biomechanics. 46, 2277-2282 (2013).</li>
</ol>

&#160;The authors&#160;have nothing to disclose.

The mouse model of TEVG is a valuable tool to study cellular and molecular mechanisms of neotissue formation and the development of stenosis. The seeded BM-MNC was shown in both histological and SEM images of the seeded cells on the graft11. Cell seeding efficiency was also shown using a DNA assay7. Using this model system we showed that cell seeding reduces the incidence of the development of TEVG stenosis, which was the primary mode of failure in our human clinical trial3. The seeded ce...

Congenital heart defects are serious conditions that affect nearly 8% of live births in the United States. Approximately 25% of those infants with congenital heart defects or 2.4 per 1,000 live birth, require invasive treatment in the first year of their life1. The most effective treatment for congenital heart disease is reconstructive surgery. Unfortunately, complications arising from the use of currently available vascular conduits are the most significant cause of postoperative morbidity and mortality.
To address this problem, we developed the first tissue engineered vascular grafts (TEVGs) for clinical use2. TEVGs were constructed from biodegradable polyester tubes seeded with autologous bone marrow derived-mononuclear cells (BM-MNCs) and implanted as venous conduits for congenital heart surgery. The results showed excellent patency rates at 1-3 years of follow-up, but with significant incidence of stenosis3,4. It was clear that a better understanding of vascular neotissue formation and the mechanism underlying the development of TEVG stenosis was needed. In order to better understand the development of TEVGs and the mechanism of stenosis development, an ovine model was created5,6. In this model, the TEVGs successfully transformed into living vessels and were similar in both morphology and function of native veins. This use of a large animal model was a good first step in providing important pre-clinical information that aided clinical usage of TEVGs. However, full understanding of the cellular and molecular mechanisms of vascular neotissue formation in TEVGs using large animal models is limited due to limitations in molecular characterization of vascular cell phenotypes due to lack of species specific molecular tools. To overcome these shortcomings, a murine model of TEVGs was developed by reason of the rapid advancement in mouse genetics and their extensive molecular characterization with the added advantage of a shortened time scale.
The murine IVC interposition model faithfully recapitulated the process of neovessel formation that occurs in large animals and humans, but over a much shorter time course6-9. Here, a detailed protocol for small-scale graft manufacturing using biodegradable scaffolds, BM-MNC harvesting and isolation, BM-MNC seeding on scaffold, and graft implantation in a murine model were described.

<table><tbody><tr><td>Polyglycolic acid (PGA) felt</td><td>Biomedical Structures</td><td></td><td>Custome ordered</td></tr><tr><td>Pipet tip, 0.1-10 &amp;mu;l&amp;nbsp;</td><td>Fisher Sientific</td><td>02-707-456</td><td></td></tr><tr><td>Lyophilizer&amp;nbsp;</td><td>Labconco</td><td>7070020</td><td></td></tr><tr><td>RPMI medium 1604</td><td>Gibco</td><td>11875-093</td><td></td></tr><tr><td>Petri dish</td><td>BD</td><td>353003</td><td></td></tr><tr><td>24-well plate</td><td>Corning</td><td>3526</td><td></td></tr><tr><td>15 cc tube&amp;nbsp;</td><td>BD</td><td>352096</td><td></td></tr><tr><td>Ficoll</td><td>Sigma</td><td>10831-100ml</td><td>Also called &#039;Histopaque&#039;</td></tr><tr><td>DPBS</td><td>Gibco</td><td>14190-144</td><td></td></tr><tr><td>Littauer bone cutter 4.5&quot; Straight</td><td>Roboz</td><td>RS-8480</td><td>For BM harvesting</td></tr><tr><td>Forceps 4.5&quot;</td><td>Roboz</td><td>RS-8120</td><td>For BM harvesting</td></tr><tr><td>Scissors 4.5&quot;</td><td>Roboz</td><td>RS-5912</td><td>For BM harvesting</td></tr><tr><td>Microscope</td><td>Leica</td><td>M80</td><td></td></tr><tr><td>C57BL/6J (H-2b), Female</td><td>Jackson Laboratories</td><td>664</td><td>8-12 weeks</td></tr><tr><td>Ketamine hydrochloride injection</td><td>Hospira Inc.</td><td>NDC 0409-2053</td><td></td></tr><tr><td>Xylazine sterile solution</td><td>Akorn Inc.</td><td>NADA# 139-236</td><td></td></tr><tr><td>Ketoprofen</td><td>Fort Dodge Animal Health</td><td>NDC 0856-4396-01</td><td></td></tr><tr><td>Ibuprofen</td><td>PrecisionDose</td><td>NDC 68094-494-59</td><td></td></tr><tr><td>Heparin sodium</td><td>Sagent Pharmaceticals</td><td>NDC 25021-400</td><td></td></tr><tr><td>Saline solution (sterile 0.9% sodium chloride)</td><td>Hospira Inc.</td><td>NDC 0409-0138-22</td><td></td></tr><tr><td>0.9% Sodium chloride injection</td><td>Hospira Inc.</td><td>NDC 0409-4888-10</td><td></td></tr><tr><td>Petrolatum ophthalmic ointment</td><td>Dechra Veterinary Products</td><td>NDC 17033-211-38</td><td></td></tr><tr><td>Iodine prep pads</td><td>Triad Disposables, Inc.</td><td>NDC 50730-3201-1</td><td></td></tr><tr><td>Alcohol prep pads</td><td>McKesson Corp.</td><td>NDC 68599-5805-1</td><td></td></tr><tr><td>Cotton tipped applicators</td><td>Fisher Scientific</td><td>23-400-118</td><td></td></tr><tr><td>Fine scissor</td><td>FST</td><td>14028-10</td><td></td></tr><tr><td>Micro-adson forcep</td><td>FST</td><td>11018-12</td><td></td></tr><tr><td>Clamp applying forcep</td><td>FST</td><td>00072-14</td><td></td></tr><tr><td>S&amp;amp;T Vascular clamp</td><td>FST</td><td>00396-01</td><td></td></tr><tr><td>Spring scissors</td><td>FST</td><td>15008-08</td><td></td></tr><tr><td>Colibri retractors</td><td>FST</td><td>17000-04</td><td></td></tr><tr><td>Dumont #5 forcep</td><td>FST</td><td>11251-20</td><td></td></tr><tr><td>Dumont #7 - fine forceps</td><td>FST</td><td>11274-20</td><td></td></tr><tr><td>Dumont #5/45 forceps</td><td>FST</td><td>11251-35</td><td></td></tr><tr><td>Tish needle holder/forceps</td><td>Micrins</td><td>MI1540</td><td></td></tr><tr><td>Black polyamide monofilament suture, 10-0</td><td>AROSurgical Instruments Corporation</td><td>TI638402</td><td>For suturing the graft</td></tr><tr><td>Black polyamide monofilament suture, 6-0</td><td>AROSurgical Instruments</td><td>SN-1956</td><td>For musculature and skin closure</td></tr><tr><td>Non-woven sponges</td><td>McKesson Corp.</td><td>94442000</td><td></td></tr><tr><td>Absorbable hemostat</td><td>Ethicon</td><td>1961</td><td></td></tr><tr><td>1 ml Syringe</td><td>BD</td><td>309659</td><td></td></tr><tr><td>3 ml Syringe</td><td>BD</td><td>309657</td><td></td></tr><tr><td>10 ml Syringe</td><td>BD</td><td>309604</td><td></td></tr><tr><td>18 G 1.5 in, Needle</td><td>BD</td><td>305190</td><td></td></tr><tr><td>25 G 1 in, Needle</td><td>BD</td><td>305125</td><td></td></tr><tr><td>30 G 1 in, Needle</td><td>BD</td><td>305106</td><td></td></tr><tr><td>Warm water recirculator</td><td>Gaymar</td><td>TP-700</td><td></td></tr><tr><td>Warming pad</td><td>Gaymar</td><td>TP-22G</td><td></td></tr><tr><td>Trimmer</td><td>Wahl</td><td>9854-500</td><td></td></tr></tbody></table>

implantation of inferior vena cava interposition graft in mouse model

Biodegradable scaffolds seeded with bone marrow mononuclear cells (BMCs) are often used for reconstructive surgery to treat congenital cardiac anomalies. The long-term clinical results showed excellent patency rates, however, with significant incidence of stenosis. To investigate the cellular and molecular mechanisms of vascular neotissue formation and prevent stenosis development in tissue engineered vascular grafts (TEVGs), we developed a mouse model of the graft with approximately 1 mm internal diameter. First, the TEVGs were assembled from biodegradable tubular scaffolds fabricated from a polyglycolic acid nonwoven felt mesh coated with &#949;-caprolactone and L-lactide copolymer. The scaffolds were then placed in a lyophilizer, vacuumed for 24 hr, and stored in a desiccator until cell seeding. Second, bone marrow was collected from donor mice and mononuclear cells were isolated by density gradient centrifugation. Third, approximately one million cells were seeded on a scaffold and incubated O/N. Finally, the seeded scaffolds were then implanted as infrarenal vena cava interposition grafts in C57BL/6 mice. The implanted grafts demonstrated excellent patency (&#62;90%) without evidence of thromboembolic complications or aneurysmal formation. This murine model will aid us in understanding and quantifying the cellular and molecular mechanisms of neotissue formation in the TEVG.

A schematic of TEVG implantation is shown in Figure 1. Bone marrow was harvested from a donor mouse and mono nuclear cells were isolated using density centrifugation and then seeded onto a biodegradable scaffold. The seeded scaffolds were incubated O/N and implanted to a recipient mouse as an inferior vena cava interposition graft.
Figure 2 illustrates the scanning electron microscopy of the PGA-P(CL/LA) scaffold. The internal diameter was approximately 1 mm a...

Watch this Scientific Journal Video about Implantation of Inferior Vena Cava Interposition Graft in Mouse Model at JoVE.com

Implantation of Inferior Vena Cava Interposition Graft in Mouse Model

To improve our knowledge of cellular and molecular neotissue formation, a murine model of the TEVG was recently developed. The grafts were implanted as infrarenal vena cava interposition grafts in C57BL/6 mice. This model achieves similar results to those achieved in our clinical investigation, but over a far shortened time-course.

Biodegradable scaffolds seeded with bone marrow mononuclear cells (BMCs) are often used for reconstructive surgery to treat congenital cardiac anomalies. ...

implantation-of-inferior-vena-cava-interposition-graft-in-mouse-model

Research

JoVE Journal

Medicine

11.8K Views.  Nationwide Children's Hospital. To improve our knowledge of cellular and molecular neotissue formation, a murine model of the TEVG was recently developed. The grafts were implanted as infrarenal vena cava interposition grafts in C57BL/6 mice. This model achieves similar results to those achieved in our clinical investigation, but over a far shortened time-course.

Video: Implantation of Inferior Vena Cava Interposition Graft in Mouse Model

Heterotopic Heart Transplantation in Mice

The mouse heterotopic heart transplantation has been used widely since it was introduced by Drs. Corry and Russell in 1973. It is particularly valuable for studying rejection and immune response now that newer transgenic and gene knockout mice are available, and a large number of immunologic reagents have been developed. The heart transplant model is less stringent than the skin transplant models, although technically more challenging. We have developed a modified technique and have completed over 1000 successful cases of heterotopic heart transplantation in mice. When making anastomosis of the ascending aorta and abdominal aorta, two stay sutures are placed at the proximal and distal apexes of recipient abdominal aorta with the donor s ascending aorta, then using 11-0 suture for anastomosis on both side of aorta with continuing sutures. The stay sutures make the anastomosis easier and 11-0 is an ideal suture size to avoid bleeding and thrombosis.
When making anastomosis of pulmonary artery and inferior vena cava, two stay sutures are made at the proximal apex and distal apex of the recipient s inferior vena cava with the donor s pulmonary artery. The left wall of the inferior vena cava and donor s pulmonary artery is closed with continuing sutures in the inside of the inferior vena cava after, one knot with the proximal apex stay suture the right wall of the inferior vena cava and the donor s pulmonary artery are closed with continuing sutures outside the inferior vena cave with 10-0 sutures. This method is easier to perform because anastomosis is made just on the one side of the inferior vena cava and 10-0 sutures is the right size to avoid bleeding and thrombosis. In this article, we provide details of the technique to supplement the video.

The mouse heterotopic heart transplantation model has been proven by many investigators to be an important method for studying mechanisms of rejection and immune response. However, the techniques involved are still challenging. By modifying standard techniques we have had success with more than 1000 transplants.

The mouse heterotopic heart transplantation has been used widely since it was introduced by Drs. Corry and Russell in 1973. It is particularly valuable ...

Biology

Transplantation of Pulmonary Valve Using a Mouse Model of Heterotopic Heart Transplantation

Tissue engineered heart valves, especially decellularized valves, are starting to gain momentum in clinical use of reconstructive surgery with mixed results. However, the cellular and molecular mechanisms of the neotissue development, valve thickening, and stenosis development are not researched extensively. To answer the above questions, we developed a murine heterotopic heart valve transplantation model. A heart valve was harvested from a valve donor mouse and transplanted to a heart donor mouse. The heart with a new valve was transplanted heterotopically to a recipient mouse. The transplanted heart showed its own heartbeat, independent of the recipient&#8217;s heartbeat. The blood flow was quantified using a high frequency ultrasound system with a pulsed wave Doppler. The flow through the implanted pulmonary valve showed forward flow with minimal regurgitation and the peak flow was close to 100 mm/sec. This murine model of heart valve transplantation is highly versatile, so it can be modified and adapted to provide different hemodynamic environments and/or can be used with various transgenic mice to study neotissue development in a tissue engineered heart valve.

In order to understand the cellular and molecular mechanisms underlying neotissue formation and stenosis development in tissue engineered heart valves, a murine model of heterotopic heart valve transplantation was developed. A pulmonary heart valve was transplanted to recipient using the heterotopic heart transplantation technique.

Tissue engineered heart valves, especially decellularized valves, are starting to gain momentum in clinical use of reconstructive surgery with mixed ...

Heterotopic Cervical Heart Transplantation in Mice

The heterotopic cervical heart transplantation in mice is a valuable tool in transplant and cardiovascular research. The cuff technique greatly simplifies this model by avoiding challenging suture anastomoses of small vessels thereby reducing warm ischemia time. In comparison to abdominal graft implantation the cervical model is less invasive and the implanted graft is easily accessible for further follow-up examinations. Anastomoses are performed by pulling the ascending aorta of the graft over the cuff with the recipient&#8217;s common carotid artery and by pulling the main pulmonary artery over the cuff with the external jugular vein. Selection of appropriate cuff size and complete mobilization of the vessels are important for successful revascularization. Ischemia-reperfusion (I/R) injury can be minimized by perfusing the graft with a cardioplegic solution and by hypothermia. In this article, we provide technical details for a simplified and improved cuff technique, which should allow surgeons with basic microsurgical skills to perform the procedure with a high success rate.

The cuff technique shortens and facilitates the model of heterotopic cervical heart transplantation in mice by avoiding technically challenging suture anastomoses of small vessels. The technical details shown in this video paper should allow researches to establish this model in their laboratories.

The heterotopic cervical heart transplantation in mice is a valuable tool in transplant and cardiovascular research. The cuff technique greatly simplifies ...

Stenosis of the Inferior Vena Cava: A Murine Model of Deep Vein Thrombosis

Deep vein thrombosis (DVT) and its devastating complication, pulmonary embolism, are a severe health problem with high mortality. Mechanisms of thrombus formation in veins remain obscure. Lack of mobility (e.g., after surgery or long-haul flights) is one of the main factors leading to DVT. The pathophysiological consequence of the lack of mobility is blood flow stagnation in venous valves. Here, a model is described that mimics such flow disturbance as a thrombosis-driving factor. In this model, partial flow restriction (stenosis) in the inferior vena cava (IVC) is created. Closure of about 90% of the IVC lumen for 48 h results in development of thrombi structurally similar to those in humans. The similarities are: i) most of the thrombus volume is red, i.e., consists of red blood cells and fibrin, ii) presence of a white part (lines of Zahn), iii) non-denuded endothelial monolayer, iv) elevated plasma D-Dimer levels, and v) possibility to prevent thrombosis by low molecular weight heparin. Limitations include variable size of thrombi and the fact that a certain percentage of wild-type mice (0 - 35%) may not produce a thrombus. In addition to visual observation and measurement, thrombi may be visualized by non-invasive technologies, such as ultrasonography, which allows for monitoring the dynamics of thrombus development. At shorter time points (1 - 6 h), intravital microscopy may be applied to directly observe events (e.g., recruitment of cells to the vessel wall) preceding thrombus formation. Use of this method by several teams around the world has made it possible to uncover basic mechanisms of DVT initiation and identify potential targets that might be beneficial for its prevention.

We describe here stenosis in the inferior vena cava as a murine model of deep vein thrombosis. This model recapitulates blood flow restriction, one of the major triggers of venous thrombosis in humans.

Deep vein thrombosis (DVT) and its devastating complication, pulmonary embolism, are a severe health problem with high mortality. Mechanisms of thrombus ...

Immunology and Infection

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. ...

Mouse Heterotopic Cervical Cardiac Transplantation Utilizing Vascular Cuffs

Murine models of cardiac transplantation are frequently utilized to study ischemia-reperfusion injury, innate and adaptive immune responses after transplantation, and the impact of immunomodulatory therapies on graft rejection. Heterotopic cervical heart transplantation in mice was first described in 1991 using sutured anastomoses and subsequently modified to include cuff techniques. This modification allowed for improved success rates, and since then, there have been multiple reports that have proposed further technical improvements. However, translation into more widespread utilization remains limited due to the technical difficulty associated with graft anastomoses, which requires precision to achieve adequate length and caliber of the cuffs to avoid vascular anastomotic twisting or excessive tension, which can result in damage to the graft. The present protocol describes a modified technique for performing heterotopic cervical cardiac transplantation in mice which involves cuff placement on the recipient's common carotid artery and the donor's pulmonary artery in alignment with the direction of the blood flow.

Mouse cardiac transplantation models represent valuable research tools for studying transplantation immunology. The present protocol details mouse heterotopic cervical cardiac transplantation that involves the placement of cuffs on the recipient's common carotid artery and the donor's pulmonary artery trunk to allow for laminar blood flow.

Murine models of cardiac transplantation are frequently utilized to study ischemia-reperfusion injury, innate and adaptive immune responses after ...

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 ...

Implantation of Tissue-Engineered Vascular Graft in Mouse Carotid Artery via Cuff Technique

The development of small-diameter vascular grafts has been a global endeavor, with numerous research groups contributing to this field. Animal experimentation plays a pivotal role in assessing the efficacy and safety of vascular grafts, particularly in the absence of clinical applications. Compared to alternative animal models, the mouse implantation model offers several advantages, including a well-defined genetic background, a mature method for disease model construction, and a straightforward surgical procedure. Based on these advantages, the present study devised a simple cuff technique for the implantation of tissue-engineered vascular grafts in the mouse carotid artery. This technique began with the fabrication of polycaprolactone (PCL) small-diameter vascular grafts via electrostatic spinning, followed by the seeding of macrophages onto the grafts through perfusion adsorption. Subsequently,&#160;the cellularized tissue-engineered vascular grafts were transplanted into the mouse carotid artery using the cuff technique to evaluate patency and regenerative capability. After 30 days of in vivo implantation, vascular patency was found to be satisfactory, with evidence of neo-tissue regeneration and the formation of an endothelial layer within the lumen of the grafts. All data were analyzed using statistical and graphing software. This study successfully established a mouse carotid artery implantation model that can be used to explore the cellular sources of vascular regeneration and the mechanisms of action of active substances. Furthermore, it provides theoretical support for the development of novel small-diameter vascular grafts.

Here, a protocol is presented for the implantation of a tissue-engineered vascular graft into the mouse carotid artery using the cuff technique, providing a suitable animal model for investigating vascular tissue regeneration mechanisms.

The development of small-diameter vascular grafts has been a global endeavor, with numerous research groups contributing to this field. Animal ...

Bioengineering

Blood Circuit Reconstruction in an Abdominal Mouse Heart Transplantation Model

The surgical technique of heterotopic abdominal heart transplantation in mice is a standard model for research in transplantation immunology. Here, the established technique for a modified blood circuit reconstruction in a heterotopic abdominal heart transplantation model is presented. This method uses the intrathoracic inferior vena cava (IIVC) instead of the pulmonary artery of the donor heart for the anastomosis to the inferior vena cava of the recipient. It is facilitating and improving success rates for abdominal heart transplantation in mice.

A novel technique for blood circuit reconstruction in a heterotopic abdominal mouse heart transplantation model is demonstrated.

The surgical technique of heterotopic abdominal heart transplantation in mice is a standard model for research in transplantation immunology. Here, the ...

A Modified Cuff Technique for Mouse Cervical Heterotopic Heart Transplantation Model

Cardiac allograft rejection limits the long-term survival of patients after heart transplantation. A mouse heart transplantation model is ideal for investigating the mechanism of cardiac allograft rejection in preclinical studies because of their high homology with human genes. This understanding would help develop unique approaches to improving patients&#39; long-term survival treated with cardiac allografts. In a mouse model, abdominal donor heart implantation is commonly performed with an end-to-end&#160;anastomosis to the recipient&#39;s aorta and inferior vena cava using stitches. In this model, the donor&#39;s heart is implanted by end-to-end anastomosis to the recipient&#39;s carotid artery and jugular vein by the modified-Cuff technique. The transplantation surgery is performed without stitching and thus may increase the survival of the recipient since there is no interference with the blood supply and venous reflux of the lower body. This mouse model would help investigate the mechanisms underlying the immunological and pathological (acute/chronic) rejection of cardiac allografts.

In the present protocol, a mouse heart transplantation model is used for investigating the mechanism of cardiac allograft rejection. In this heterotopic heart transplantation model, operation efficiency is improved, and the survival of cardiac grafts is ensured by a cervical end-to-end anastomosis of heart implantation using a modified Cuff technique.

Cardiac allograft rejection limits the long-term survival of patients after heart transplantation. A mouse heart transplantation model is ideal for ...