Name: engineered vascularized muscle flap
Uploaded: 2016-01-11T09:30:00
Description: Watch this Scientific Journal Video about Engineered Vascularized Muscle Flap at JoVE.com

This research was supported by the FP7 European Research Council Grant 281501, ENGVASC.

All animal studies were approved by the Committee of the Ethics of Animal Experiments of the Technion. For this procedure, athymic nude mice were used to avoid immunological rejection. If using another type of mouse, the mice should be shaved prior to the surgical procedure and administration of cyclosporine (or another anti-rejection substitute) is recommended.
1. Scaffold Preparation and Cell Embedding
<ol>
	<li>Prepare scaffolds composed of 1:1 mixture of poly-L-lactic-acid (PLLA) and pol...

<ol>
	<li>Engelsman, A. F., van der Mei, H. C., Ploeg, R. J., Busscher, H. 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S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Abdominal+wall+reconstruction+using+biological+tissue+grafts:+present+status+and+future+opportunities.">Abdominal wall reconstruction using biological tissue grafts: present status and future opportunities.</a> Exp rev of med dev. 3 (5), 657-675 (2006).</li><li>Caspi, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue+engineering+of+vascularized+cardiac+muscle+from+human+embryonic+stem+cells.">Tissue engineering of vascularized cardiac muscle from human embryonic stem cells.</a> Circ Res. 100 (2), 263-272 (2007).</li><li>Kaufman-Francis, K., Koffler, J., Weinberg, N., Dor, Y., Levenberg, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineered+vascular+beds+provide+key+signals+to+pancreatic+hormone-producing+cells.">Engineered vascular beds provide key signals to pancreatic hormone-producing cells.</a> PloS one. 7 (7), e40741 (2012).</li><li>Kaully, T., Kaufman-Francis, K., Lesman, A., Levenberg, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascularization--the+conduit+to+viable+engineered+tissues.">Vascularization--the conduit to viable engineered tissues.</a> Tiss eng. 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Part A. 16 (1), 115-125 (2010).</li><li>Levenberg, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+vascularized+skeletal+muscle+tissue.">Engineering vascularized skeletal muscle tissue.</a> Nat Biotechnol. 23 (7), 879-884 (2005).</li><li>Bearzi, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PlGF-MMP9-engineered+iPS+cells+supported+on+a+PEG-fibrinogen+hydrogel+scaffold+possess+an+enhanced+capacity+to+repair+damaged+myocardium.">PlGF-MMP9-engineered iPS cells supported on a PEG-fibrinogen hydrogel scaffold possess an enhanced capacity to repair damaged myocardium.</a> Cell death &amp; disease. 5, e1053 (2014).</li><li>Zhang, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SDF-1+expression+by+mesenchymal+stem+cells+results+in+trophic+support+of+cardiac+myocytes+after+myocardial+infarction.">SDF-1 expression by mesenchymal stem cells results in trophic support of cardiac myocytes after myocardial infarction.</a> FASEB J : official publication of the .Fed Am Soc Exp Biol. 21 (12), 3197-3207 (2007).</li><li>Dvir, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prevascularization+of+cardiac+patch+on+the+omentum+improves+its+therapeutic+outcome.">Prevascularization of cardiac patch on the omentum improves its therapeutic outcome.</a> PNAS. 106 (35), 14990-14995 (2009).</li><li>Marsano, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+controlled+expression+of+VEGF+by+transduced+myoblasts+in+a+cardiac+patch+on+vascularization+in+a+mouse+model+of+myocardial+infarction.">The effect of controlled expression of VEGF by transduced myoblasts in a cardiac patch on vascularization in a mouse model of myocardial infarction.</a> Biomaterials. 34 (2), 393-401 (2013).</li><li>Rufaihah, A. 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The advances in tissue engineering have been met with a growing demand for substitute tissues for reconstruction of various tissue types. A variety of synthetic 1,17,18 and biological 14-16 materials as well as fabrication methods have been assessed for their capacity to address these demands. However, despite the progress in clinical care and in tissue engineering, the restoration of full-thickness abdominal wall defects remains a challenge. A tissue adequate for reconstruction of such massive defe...

Abdominal wall defects often arise following severe trauma, cancer treatment, burns and removal of infected mesh. These defects often involve significant tissue loss, requiring complicated surgical procedures and presenting a major challenge for plastic reconstruction surgeons 1-4. Tissue engineering researchers seeking new sources for artificial tissues have explored different materials, cell sources and growth factors. Successful restorations of various tissues, such as trachea 5,6, bladder 7, cornea 8, bone 9and skin 10, by implantation of engineered tissues were previously reported. However, fabrication of a thick vascularized engineered tissue, particularly for reconstruction of large defects, remains a significant challenge in tissue engineering.
One of the main factors limiting the thickness of a viable tissue construct is the control of oxygen supply to its constituent cells. When relying on diffusion, construct thickness is limited to that of a very thin layer. The maximum distance between oxygen- and nutrient-supplying capillaries in vivo is approximately 200&#160;&#181;m, which correlates with the diffusion limit of oxygen11,12. Insufficient vascularization can result in tissue ischemia and escalate to tissue resorption or necrosis 13.
In addition, the ideal material used for tissue reconstruction must be biocompatible and non-immunogenic. It must also be capable of promoting further integration of host cells with the biomaterial, and maintaining structural integrity. Various biological 14-16 and synthetic 1,17,18 matrices have been previously explored for tissue reconstruction, however their use remain limited due to lack of effective blood supply, infections or insufficient tissue strength.
In this study, a biocompatible, cell-embedded scaffold comprised of Food and Drug Administration (FDA)-approved poly L-lactic acid (PLLA)/poly lactic-co-glycolic acid (PLGA), was implanted around the femoral artery and vein (AV) vessels of a nude mouse and separated from the surrounding tissue, ensuring vascularization from the AV vessels only. One week post-implantation, the graft was viable, thick and well vascularized. This thick vascularized tissue with the AV vessels, was then transferred as a pedicled flap to an abdominal full-thickness defect in the same mouse. One week post-transfer, the flap was viable, vascularized and well integrated with the surrounding tissue, bearing sufficient strength to support abdominal viscera. Thus, the engineered thick, vascularized tissue flap, bearing an autologous pedicle, presents a novel method for repairing full-thickness abdominal wall defects.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>small fine straight scissors</td>
			<td>Fine Science Tools (FST)</td>
			<td>14090-09</td>
			<td></td>
		</tr>
		<tr>
			<td>spring scissors</td>
			<td>Fine Science Tools (FST)</td>
			<td>15003-08</td>
			<td></td>
		</tr>
		<tr>
			<td>straight forceps with fine tip</td>
			<td>Fine Science Tools (FST)</td>
			<td>11251-20</td>
			<td></td>
		</tr>
		<tr>
			<td>serrated forceps&#160;</td>
			<td>Fine Science Tools (FST)</td>
			<td>11050-10</td>
			<td></td>
		</tr>
		<tr>
			<td>needle holder</td>
			<td>Fine Science Tools (FST)</td>
			<td>12500-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Small vessel cauterizer&#160;</td>
			<td>Fine Science Tools (FST)</td>
			<td>18000-00</td>
			<td></td>
		</tr>
		<tr>
			<td>Duratears</td>
			<td>Alcon</td>
			<td align="right">5686</td>
			<td></td>
		</tr>
		<tr>
			<td>Sedaxylan</td>
			<td>Euravet</td>
			<td>DJ03</td>
			<td></td>
		</tr>
		<tr>
			<td>Clorketam 1000</td>
			<td>Vetoquinol</td>
			<td>4A0726B</td>
			<td></td>
		</tr>
		<tr>
			<td>Buprenorphine</td>
			<td>vetmarket</td>
			<td>B15100</td>
			<td></td>
		</tr>
		<tr>
			<td>4-0 silk sutures</td>
			<td>Assut sutures</td>
			<td align="right">647</td>
			<td></td>
		</tr>
		<tr>
			<td>6-0 polypropylene sutures</td>
			<td>Assut sutures</td>
			<td>9351F</td>
			<td></td>
		</tr>
		<tr>
			<td>8-0 silk sutures</td>
			<td>Assut sutures</td>
			<td align="right">684568</td>
			<td></td>
		</tr>
		<tr>
			<td>Insulin syringe (6mm needle)</td>
			<td>BD</td>
			<td align="right">324911</td>
			<td></td>
		</tr>
		<tr>
			<td>Vevo 2100 high-resolution ultrasound system</td>
			<td>VisualSonics inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MS250 non-linear transducer</td>
			<td>VisualSonics inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Micromarker non-targeted contrast agent</td>
			<td>VisualSonics inc.</td>
			<td>VS-11694</td>
			<td></td>
		</tr>
		<tr>
			<td>tail vein catheter</td>
			<td>VisualSonics inc.</td>
			<td>VS-11912</td>
			<td></td>
		</tr>
		<tr>
			<td>Vevo 2100 software</td>
			<td>VisualSonics inc.</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>fluorescein isothiocyanate-conjugated dextran</td>
			<td>Sigma</td>
			<td>FD500S</td>
			<td></td>
		</tr>
		<tr>
			<td>Matlab</td>
			<td>Mathworks, MA, USA</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Kimwipes</td>
			<td>Kimtech</td>
			<td align="right">34120</td>
			<td></td>
		</tr>
		<tr>
			<td>antigen unmasking solution</td>
			<td>Vector laboratories</td>
			<td>H-3300</td>
			<td></td>
		</tr>
		<tr>
			<td>anti-CD31 antibody</td>
			<td>Abcam&#160;</td>
			<td>ab28364</td>
			<td></td>
		</tr>
		<tr>
			<td>biotinylated goat anti-rabbit (secondary) antibody</td>
			<td>Vector laboratories</td>
			<td>BA-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>streptavidin-peroxidase</td>
			<td>Jackson&#160;</td>
			<td>016-030-084</td>
			<td></td>
		</tr>
		<tr>
			<td>Mayer&#39;s hamatoxylin solution</td>
			<td>Sigma-Aldrich</td>
			<td>MHS-16</td>
			<td></td>
		</tr>
		<tr>
			<td>aminoethylcarbazole (AEC) substrate kit</td>
			<td>Life technologies, Invitrogen&#160;</td>
			<td>00-2007</td>
			<td></td>
		</tr>
		<tr>
			<td>Vectamount</td>
			<td>Vector laboratories</td>
			<td>H-5501</td>
			<td></td>
		</tr>
	</tbody>
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engineered vascularized muscle flap

One of the main factors limiting the thickness of a tissue construct and its consequential viability and applicability in vivo, is the control of oxygen supply to the cell microenvironment, as passive diffusion is limited to a very thin layer. Although various materials have been described to restore the integrity of full-thickness defects of the abdominal wall, no material has yet proved to be optimal, due to low graft vascularization, tissue rejection, infection, or inadequate mechanical properties. This protocol describes a means of engineering a fully vascularized flap, with a thickness relevant for muscle tissue reconstruction. Cell-embedded poly L-lactic acid/poly lactic-co-glycolic acid constructs are implanted around the mouse femoral artery and vein and maintained in vivo for a period of one or two weeks. The vascularized graft is then transferred as a flap towards a full thickness defect made in the abdomen. This technique replaces the need for autologous tissue sacrifications and may enable the use of in vitro engineered vascularized flaps in many surgical applications.

Graft vascularization and perfusion in vivo
The grafts were implanted one or two weeks prior to their transfer as axial flaps. At one and two weeks post-implantation, gross observation of the graft area revealed viable and vascularized tissue grafts. These grafts proved to be highly vascularized, as determined by positive CD31 immunostaining (Figure 1A), and highly perfused, as evidenced by FITC-dextran tail vein injection and ultrasound measurements. Many vessels wer...

Watch this Scientific Journal Video about Engineered Vascularized Muscle Flap at JoVE.com

Engineered Vascularized Muscle Flap

To date, thick tissue defects are typically reconstructed by applying autologous tissue flaps or engineered tissues. In this protocol, we present a new method for engineering vascularized tissue flap bearing an autologous pedicle, to serve as a substitute to autologous flaps.

One of the main factors limiting the thickness of a tissue construct and its consequential viability and applicability in vivo, is the control of oxygen ...

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Bioengineering

Engineered 3D Silk-collagen-based Model of Polarized Neural Tissue

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Applications of In Vivo Functional Testing of the Rat Tibialis Anterior for Evaluating Tissue Engineered Skeletal Muscle Repair

Applications of In Vivo Functional Testing of the Rat Tibialis Anterior for Evaluating Tissue Engineered Skeletal Muscle Repair

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Fabrication of Zero Mode Waveguides for High Concentration Single Molecule Microscopy

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Generation of Self-assembled Vascularized Human Skin Equivalents

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Assessing Functional Metrics of Skeletal Muscle Health in Human Skeletal Muscle Microtissues

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Engineered Lung Tissues Prepared from Decellularized Lung Slices

There is a need for improved 3-dimensional (3D) lung models that recapitulate the architectural and cellular complexity of the native lung alveolus ex ...

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