Name: procurement and perfusion-decellularization of porcine vascularized flaps in a customized perfusion bioreactor
Uploaded: 2022-08-01T13:00:00
Description: Watch this Scientific Journal Video about Procurement and Perfusion-Decellularization of Porcine Vascularized Flaps in a Customized Perfusion Bioreactor at JoVE.com

All procedures involving animal subjects have been approved by the University Health Network Institutional Animal Care and Use Committee (IACUC) and are performed in accordance with University Health Network Animal Resource Centre protocol and procedures and Canadian Council on Animal Care Guidelines.&#160;Five Yorkshire pigs (35-50 kg; age approximately 12 weeks old) were used for all experiments.
1. Perfusion bioreactor fabrication
<ol>
	<li>See Figure 1 for all t...

<ol>
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Global Open. 6 (2), 1651 (2018).</li><li>Issa, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascularized+composite+allograft-specific+characteristics+of+immune+responses.">Vascularized composite allograft-specific characteristics of immune responses.</a> Transplant International. 29 (6), 672-681 (2016).</li><li>Kueckelhaus, 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=Vascularized+composite+allotransplantation:+Current+standards+and+novel+approaches+to+prevent+acute+rejection+and+chronic+allograft+deterioration.">Vascularized composite allotransplantation: Current standards and novel approaches to prevent acute rejection and chronic allograft deterioration.</a> Transplant International. 29 (6), 655-662 (2016).</li><li>Iske, J., 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=Composite+tissue+allotransplantation:+Opportunities+and+challenges.">Composite tissue allotransplantation: Opportunities and challenges.</a> Cellular and Molecular Immunology. 16 (4), 343-349 (2019).</li><li>Londono, R., Gorantla, V. 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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascularization+in+tissue+engineering.">Vascularization in tissue engineering.</a> Trends in Biotechnology. 26 (8), 434-441 (2008).</li><li>Zhang, Q., 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=Decellularized+skin/adipose+tissue+flap+matrix+for+engineering+vascularized+composite+soft+tissue+flaps.">Decellularized skin/adipose tissue flap matrix for engineering vascularized composite soft tissue flaps.</a> Acta Biomaterialia. 35, 166-184 (2016).</li><li>Jank, B. J., 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=Creation+of+a+bioengineered+skin+flap+scaffold+with+a+perfusable+vascular+pedicle.">Creation of a bioengineered skin flap scaffold with a perfusable vascular pedicle.</a> Tissue Engineering - Part A. 23 (13-14), 696-707 (2017).</li><li>Giatsidis, G., Guyette, J. P., Ott, H. C., Orgill, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+large-volume+human-derived+adipose+acellular+allogenic+flap+by+perfusion+decellularization.">Development of a large-volume human-derived adipose acellular allogenic flap by perfusion decellularization.</a> Wound Repair and Regeneration. 26 (2), 245-250 (2018).</li><li>Zhang, J., 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=Perfusion-decellularized+skeletal+muscle+as+a+three-dimensional+scaffold+with+a+vascular+network+template.">Perfusion-decellularized skeletal muscle as a three-dimensional scaffold with a vascular network template.</a> Biomaterials. 89, 114-126 (2016).</li><li>Duisit, J., 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=Decellularization+of+the+porcine+ear+generates+a+biocompatible,+nonimmunogenic+extracellular+matrix+platform+for+face+subunit+bioengineering.">Decellularization of the porcine ear generates a biocompatible, nonimmunogenic extracellular matrix platform for face subunit bioengineering.</a> Annals of Surgery. 267 (6), 1191-1201 (2018).</li><li>Duisit, J., 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=Perfusion-decellularization+of+human+ear+grafts+enables+ECM-based+scaffolds+for+auricular+vascularized+composite+tissue+engineering.">Perfusion-decellularization of human ear grafts enables ECM-based scaffolds for auricular vascularized composite tissue engineering.</a> Acta Biomaterialia. 73, 339-354 (2018).</li><li>Duisit, J., 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=Bioengineering+a+human+face+graft:+The+matrix+of+identity.">Bioengineering a human face graft: The matrix of identity.</a> Annals of Surgery. 266 (5), 754-764 (2017).</li><li>Haughey, B. 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F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+of+tissue+decellularization+used+for+preparation+of+biologic+scaffolds+and+in+vivo+relevance.">Methods of tissue decellularization used for preparation of biologic scaffolds and in vivo relevance.</a> Methods. 84, 25-34 (2015).</li><li>Mendibil, U., 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-specific+decellularization+methods:+Rationale+and+strategies+to+achieve+regenerative+compounds.">Tissue-specific decellularization methods: Rationale and strategies to achieve regenerative compounds.</a> International Journal of Molecular Sciences. 21 (15), 5447 (2020).</li><li>Lupon, E., 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+composite+allografts+using+natural+scaffolds:+A+systematic+review.">Engineering vascularized composite allografts using natural scaffolds: A systematic review.</a> Tissue Engineering. Part B Reviews. 28 (3), 677-693 (2022).</li><li>Duisit, J., Maistriaux, L., Bertheuil, N., Lellouch, A. G. <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+composite+tissues+by+perfusion+decellularization/recellularization:+Review.">Engineering vascularized composite tissues by perfusion decellularization/recellularization: Review.</a> Current Transplantation Reports. 8, 44-56 (2021).</li><li>Adil, A., Xu, M., Haykal, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recellularization+of+bioengineered+scaffolds+for+vascular+composite+allotransplantation.">Recellularization of bioengineered scaffolds for vascular composite allotransplantation.</a> Frontiers in Surgery. 9, 843677 (2022).</li><li>Phelps, E. A., Garc&#237;a, A. 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The proposed protocol uses the perfusion of low concentration SDS to decellularize a range of porcine-derived flaps. With this procedure, acellular omentum, tensor fascia lata, and radial forearm flaps can be successfully decellularized using a protocol that favors low concentration SDS. Preliminary optimization experiments have determined that SDS at a low concentration (0.05%) between 2 days to 5 days is capable of removing cellular material for the omentum, tensor fascia lata, and radial forearm flap when analyzed wit...

Traumatic injury and tumor removal can lead to large and complex soft tissue defects. These defects can impair patient quality of life, cause loss of function, and result in permanent disability. While techniques such as autologous tissue flap transfer have been commonly practiced, issues with flap availability and donor site morbidity are major limitations1,2,3. Vascularized composite allotransplantation (VCA) is a promising alternative that transfers composite tissues, e.g., muscle, skin, vasculature, as a single unit to recipients. However, VCA requires long-term immunosuppression, which leads to drug toxicity, opportunistic infections, and malignancies4,5,6.
Tissue-engineered acellular scaffolds are a potential solution to these limitations7. Acellular tissue scaffolds can be obtained using decellularization methods, which remove cellular material from native tissues while preserving the underlying extracellular matrix (ECM) microarchitecture. In contrast to the use of synthetic materials in tissue engineering, the use of biologically derived scaffolds offers a biomimetic ECM substrate that allows biocompatibility and the potential for clinical translation8. Following decellularization, the subsequent recellularization of scaffolds with recipient-specific cells can then generate functional, vascularized tissues with little to no immunogenicity9,10,11. By developing an effective protocol to obtain acellular tissues using perfusion decellularization techniques, a broad range of tissue types can be engineered. In turn, building on this technique allows the application to more complex tissues. To date, perfusion decellularization of vascularized soft tissues has been investigated using simple vascularized tissues such as a full thickness fasciocutaneous flap in rodent12, porcine13, and human models14, as well as porcine rectus abdominis skeletal muscle15. Additionally, complex vascularized tissues have also been perfusion decellularized as demonstrated in porcine and human ear16,17 models and human full-face graft models18.
Here, the protocol describes the decellularization of vascularized free flaps using biologically derived ECM scaffolds. We present the decellularization of three clinically relevant flaps: 1) the omentum, 2) the tensor fascia lata, and 3) the radial forearm, all of which are representative of workhorse flaps used routinely in reconstructive surgery and have not been previously examined in animal studies within the context of tissue decellularization. These bioengineered flaps offer a versatile and readily available platform that has the potential for clinical applications for use in the field of large soft tissue defect repair and reconstruction.

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		<tr >
			<td >0.2 &#181;m pore Acrodisk Filter</td>
			<td >VWR</td>
			<td >CA28143-310</td>
			<td ></td>
		</tr>
		<tr >
			<td >0.9 % Sodium Chloride Solution (Normal Saline)</td>
			<td>Baxter</td>
			<td>JF7123</td>
			<td></td>
		</tr>
		<tr >
			<td >20 L Polypropylene Carboy</td>
			<td>Cole-Parmer</td>
			<td>RK-62507-20</td>
			<td></td>
		</tr>
		<tr >
			<td >3-0 Sofsilk Nonabsorbable Surgical Tie</td>
			<td>Covidien</td>
			<td>&#160;LS639</td>
			<td></td>
		</tr>
		<tr >
			<td >3-way Stopcock</td>
			<td>Cole-Parmer</td>
			<td>UZ-30600-04</td>
			<td></td>
		</tr>
		<tr >
			<td >Adson Forceps</td>
			<td>Fine Science Tools</td>
			<td>11027-12</td>
			<td></td>
		</tr>
		<tr >
			<td >Antibiotic-Antimycotic Solution, 100X</td>
			<td>Wisent</td>
			<td>450-115-EL</td>
			<td></td>
		</tr>
		<tr >
			<td >Atropine Sulphate 15 mg/30ml</td>
			<td>Rafter 8 Products</td>
			<td>238481</td>
			<td></td>
		</tr>
		<tr >
			<td >BD Angiocath 20-Gauge</td>
			<td>VWR</td>
			<td>BD381134</td>
			<td></td>
		</tr>
		<tr >
			<td >BD Angiocath 22-Gauge</td>
			<td>VWR</td>
			<td>BD381123</td>
			<td></td>
		</tr>
		<tr >
			<td >BD Angiocath 24-Gauge</td>
			<td>VWR</td>
			<td>BD381112</td>
			<td></td>
		</tr>
		<tr >
			<td >Calcium Chloride</td>
			<td>Sigma-Aldrich</td>
			<td>C4901</td>
			<td>DNAse Co-factor</td>
		</tr>
		<tr >
			<td >DNase I from bovine pancreas</td>
			<td>Sigma-Aldrich</td>
			<td>DN25</td>
			<td></td>
		</tr>
		<tr >
			<td >DNA assay (Quant-iT PicoGreen dsDNA Assay Kit)</td>
			<td>Invitrogen</td>
			<td>P7589</td>
			<td></td>
		</tr>
		<tr >
			<td >DPBS, 10X</td>
			<td>Wisent</td>
			<td>311-415-CL</td>
			<td>&#160;without Ca++/Mg++</td>
		</tr>
		<tr >
			<td >Halsted-Mosquito Hemostat</td>
			<td>Fine Science Tools</td>
			<td>13008-12</td>
			<td></td>
		</tr>
		<tr >
			<td >Heparin, 1000 I.U./mL</td>
			<td>Leo Pharma A/S</td>
			<td>453811</td>
			<td></td>
		</tr>
		<tr >
			<td >Ketamine Hydrochloride&#160; 5000 mg/50 ml</td>
			<td>Bimeda-MTC Animal Health Inc.</td>
			<td>612316</td>
			<td></td>
		</tr>
		<tr >
			<td >Ismatec Pump Tygon 3-Stop Tubing</td>
			<td>Cole-Parmer</td>
			<td>RK-96450-40</td>
			<td>Internal Diameter:&#160; 1.85 mm</td>
		</tr>
		<tr >
			<td >Ismatec REGLO 4-Channel Pump</td>
			<td>Cole-Parmer</td>
			<td>78001-78</td>
			<td></td>
		</tr>
		<tr >
			<td >Ismatec Tubing Cassettes</td>
			<td>Cole-Parmer</td>
			<td>RK-78016-98</td>
			<td></td>
		</tr>
		<tr >
			<td >Isoflurane 99.9%, 250 ml</td>
			<td>Pharmaceutical Partners of Canada Inc.</td>
			<td>2231929</td>
			<td></td>
		</tr>
		<tr >
			<td >LB Agar Lennox</td>
			<td>Bioshop Canada</td>
			<td>LBL406.500</td>
			<td>Sterility testing agar plates</td>
		</tr>
		<tr >
			<td >Magnesium Sulfate</td>
			<td>Sigma-Aldrich</td>
			<td>M7506</td>
			<td>DNAse Co-factor</td>
		</tr>
		<tr >
			<td >Masterflex L/S 16 Tubing</td>
			<td>Cole-Parmer</td>
			<td>RK-96410-16</td>
			<td></td>
		</tr>
		<tr >
			<td >Midazolam 50 mg/10 ml</td>
			<td>Pharmaceutical Partners of Canada Inc.</td>
			<td>2242905</td>
			<td></td>
		</tr>
		<tr >
			<td >Monopolar Cautery Pencil</td>
			<td>Valleylab</td>
			<td>E2100</td>
			<td></td>
		</tr>
		<tr >
			<td >Normal Buffered Formalin, 10%</td>
			<td>Sigma-Aldrich</td>
			<td>HT501128</td>
			<td></td>
		</tr>
		<tr >
			<td >N&#176;11 scalpel blade</td>
			<td>Swann Morton</td>
			<td>303</td>
			<td></td>
		</tr>
		<tr >
			<td >Papain from papaya latex</td>
			<td>Sigma-Aldrich</td>
			<td>P3125</td>
			<td></td>
		</tr>
		<tr >
			<td >Peracetic Acid</td>
			<td>Sigma-Aldrich</td>
			<td>269336</td>
			<td></td>
		</tr>
		<tr >
			<td >Plastic Barbed Connector for 1/4&#34; to 1/8&#34; Tube ID</td>
			<td>McMaster-Carr</td>
			<td>5117K61</td>
			<td></td>
		</tr>
		<tr >
			<td >Plastic Barbed Tube 90&#176; Elbow Connectors</td>
			<td>McMaster-Carr</td>
			<td>5117K76</td>
			<td></td>
		</tr>
		<tr >
			<td >Plastic Quick-Turn Tube Plugs</td>
			<td>McMaster-Carr</td>
			<td>51525K143</td>
			<td>Male Luer</td>
		</tr>
		<tr >
			<td >Plastic Quick-Turn Tube Sockets</td>
			<td>McMaster-Carr</td>
			<td>51525K293</td>
			<td>Female Luer</td>
		</tr>
		<tr >
			<td >Punch Biopsy Tool</td>
			<td>Integra Miltex</td>
			<td>3332</td>
			<td></td>
		</tr>
		<tr >
			<td >Potassium Chloride 40 mEq/20 ml</td>
			<td>Hospira Healthcare Corporation</td>
			<td>37869</td>
			<td></td>
		</tr>
		<tr >
			<td >Povidone-Iodine, 10%</td>
			<td>Rougier</td>
			<td>833133</td>
			<td></td>
		</tr>
		<tr >
			<td >Serological Pipet, 2mL</td>
			<td>Fisher Science</td>
			<td>13-678-27D</td>
			<td></td>
		</tr>
		<tr >
			<td >Snap Lid Airtight Containers</td>
			<td>SnapLock</td>
			<td>142-3941-4</td>
			<td></td>
		</tr>
		<tr >
			<td >Sodium Dodecyl Sulfate Powder</td>
			<td>Sigma-Aldrich</td>
			<td>L4509</td>
			<td></td>
		</tr>
		<tr >
			<td >Surgical Metal Ligation Clips, Small</td>
			<td >Teleflex</td>
			<td >001200</td>
			<td></td>
		</tr>
		<tr >
			<td >Stevens Tenotomy Scissors, 115 mm, straight</td>
			<td >B. Braun</td>
			<td >BC004R</td>
			<td></td>
		</tr>
		<tr >
			<td >TruWave Pressure Monitoring Set</td>
			<td >Edwards Lifesciences</td>
			<td >PX260</td>
			<td></td>
		</tr>
	</tbody>
</table>

procurement and perfusion-decellularization of porcine vascularized flaps in a customized perfusion bioreactor

Large volume soft tissue defects lead to functional deficits and can greatly impact the patient&#39;s quality of life. Although surgical reconstruction can be performed using autologous free flap transfer or vascularized composite allotransplantation (VCA), such methods also have disadvantages. Issues such as donor site morbidity and tissue availability limit autologous free flap transfer, while immunosuppression is a significant limitation of VCA. Engineered tissues in reconstructive surgery using decellularization/recellularization methods represent a possible solution. Decellularized tissues are generated using methods that remove native cellular material while preserving the underlying extracellular matrix (ECM) microarchitecture. These acellular scaffolds can then be subsequently recellularized with recipient-specific cells.
This protocol details the procurement and decellularization methods used to achieve acellular scaffolds in a pig model. In addition, it also provides a description of the perfusion bioreactor design and setup. The flaps include the porcine omentum, tensor fascia lata, and the radial forearm. Decellularization is performed via ex vivo perfusion of low concentration sodium dodecyl sulfate (SDS) detergent followed by DNase enzyme treatment and peracetic acid sterilization in a customized perfusion bioreactor.
Successful tissue decellularization is characterized by a white-opaque appearance of flaps macroscopically. Acellular flaps show the absence of nuclei on histological staining and a significant reduction in DNA content. This protocol can be used efficiently to generate decellularized soft tissue scaffolds with preserved ECM and vascular microarchitecture. Such scaffolds can be used in subsequent recellularization studies and have the potential for clinical translation in reconstructive surgery.

This protocol to decellularize vascularized porcine flaps relies on the perfusion of an ionic-based detergent, SDS, through the flap vasculature in a customized perfusion bioreactor. Prior to decellularization, three vascularized flaps in a porcine model were procured and cannulated according to their main supplying vessels. The flaps were immediately flushed after procurement in order to maintain a patent, perfusable vasculature to allow for successful decellularization. Using airtight snap-lid containers, a customized ...

Watch this Scientific Journal Video about Procurement and Perfusion-Decellularization of Porcine Vascularized Flaps in a Customized Perfusion Bioreactor at JoVE.com

Procurement and Perfusion-Decellularization of Porcine Vascularized Flaps in a Customized Perfusion Bioreactor

The protocol describes the surgical procurement and subsequent decellularization of vascularized porcine flaps by the perfusion of sodium dodecyl sulfate detergent through the flap vasculature in a customized perfusion bioreactor.

Large volume soft tissue defects lead to functional deficits and can greatly impact the patient&#39;s quality of life. Although surgical reconstruction ...

This method describes the surgical procurement of three vascularized porcine flaps and their subsequent perfusion decellularization. This method can aid efforts to regenerate porcine flaps using a tissue decellularization and recellularization approach. The main advantage of this technique is its versatility to achieve profusion decellularization across a variety of vascularized porcine flaps in a simple to assemble bioreactor setup.The technique described here can be broadly applied to other vascularized flaps as a potential tissue engineering solution using porcine flaps in reconstructive surgery. To begin, make an inflow and outflow tubing by measuring approximately 50 centimeters of LS16 platinum-coated silicone tubing. Connect one end to a yellow 3-stop pump tubing and the other to a sterile 2 milliliter serological pipette to carry perfusate from the detergent reservoirs into the bioreactor chamber.Autoclave the chamber and tubings in individually wrapped sterile packaging. For omental flap procurement, place a 12-week old anesthetized Yorkshire pig in the supine position, and then prepare the abdomen in the usual sterile fashion. Perform a xipho-umbilical laparotomy to enter the abdomen and mobilize the stomach cephalad, and place the omentum into the operative field.Starting at the left aspect of the greater curvature, where the left gastroepiploic artery joins the splenic artery, skeletonize the left gastroepiploic artery and vein using straight Stevens tenotomy scissors. Then ligate and divide both separately using surgical ties or clips. Proceed along the greater curvature of the stomach from left to right to ligate and divide the short vascular branches arising from the omentum, supplying the greater curvature of the stomach.Continue the mobilization of the greater omentum until the junction of the right gastroepiploic vessels and gastroduodenal artery is encountered. Then ligate and divide the right gastroepiploic artery and vein to free the omental flap and allow for flap cannulation later. For tensor fascia lata flap procurement, place the pig in the lateral decubitus position.Mark the interior flap boundary from the anterior superior iliac spine, or ASIS, towards the lateral patella, and a posterior boundary approximately 8 to 10 centimeters caudally. Use a scalpel to make a sharp incision at the distal margin at the patella. Deepen the incision through the subcutaneous tissues to reach the fascia overlying the rectus femoris, and continue the incisions towards the ASIS along the marked boundaries.To isolate the fascial flap alone, remove the overlying skin component from the underlying fascia layer. Then ligate or cauterize small perforator vessels to the skin. Return to the distal border of the flap, and incise the deep fascia.Mobilize the fascia off the underlying vastus lateralis muscle towards the ASIS. After tracing the pedicle toward the deep femoral vessels, skeletonize the lateral circumflex femoral artery and vein supplying the fascial flap. Then ligate and divide flap vessels proximally, where they join the deep femoral vessels and allow for later cannulation.For radial forearm flap procurement, mark a 3 by 3 centimeter square on the radial aspect of an extended pig forearm. Draw a line between the midpoint of the proximal flap margin and the antecubital fossa to denote the approximate course of the radial artery pedicle. Confirm the arterial course with palpation.Next, incise the skin using a scalpel at the distal aspect with a depth up to the antebrachial fascia. Blunt dissect with tenotomy scissors until the distal radial artery and its vena comitantes are encountered. Then ligate and divide the artery and veins with surgical ties or clips.Continue the skin incisions on the radial and ulnar margins of the marked skin square. Then mobilize the flap off the underlying radial bone with a surgical blade or cautery, proceeding from an ulnar to radial direction while raising the skin flap proximally toward the antecubital fossa. Using tenotomy scissors, skeletonize the radial artery and vena comitantes proximally at the antecubital fossa, where they join the brachial artery and veins, respectively.Dissect the vessels from the surrounding fibro-fatty tissues to isolate the vascular pedicle. Then ligate and divide the artery and vein separately to free the radial forearm flap. Next, cannulate the pedicle vessels with 20 to 24-gauge angiocatheter secured with 3-0 silk ties.Flush heparinized saline into the flap arterial cannula until a clear venous outflow is observed. While working in a laminar flow Biosafety cabinet, place flaps in the bioreactor tissue chamber. Prime inflow tubing with sterile heparinized saline to remove residual air and arrange flaps to allow connection between the flap arterial cannula and the male luer connector.Then use sterile hemostats to screw the arterial cannula onto the connector. Then flush the heparinized saline through the stopcock to check that the luer connection is without leaks, and that the flops can be perfused with evidence of venous outflow. After closing the tissue chamber lid, connect the inflow tubing with a yellow 3-stop pump tubing to the inflow stopcock of the tissue chamber.Also, attach an inline pressure sensor transducer to the inflow 3-way stopcock for perfusion pressure monitoring. Next, turn on the inflow peristaltic pump and on the initial screen, move to the third tab using the arrow to set the tubing ID to 1.85 millimeters. Then set the perfusion rate from the second tab.The input rate as the mode of delivery is set to 2 milliliters per minute. Ensure the flow direction is correct as displayed on the screen. Load the 3-stop pump tubing to the peristaltic pump with a compatible cassette.Set the outflow pump setting to a rate at 4 milliliters per minute. Connect the outflow tubing with a yellow 3-stop pump tubing to the outflow stopcock of the tissue chamber. Then load the 3-stop pump tubing to the peristaltic pump, and start the flow for both pumps by pressing the power button on each pump.Begin the perfusion decellularization of flaps with heparinized saline in the tissue chamber for 15 minutes to remove any retained blood clots. Upon completion, replace the residual saline with 500 milliliters of sodium dodecyl sulfate, or SDS, decellularization solution to submerge the flap. Next, transfer the inflow tubing to the SDS solution and profuse the tissue.After SDS decellularization, aspirate the remaining SDS before perfusing the flap with PBS for one day. After SDS perfusion decellularization, sequentially perfuse the flaps in DNA solution for two hours, and then in PBS for one day, followed by transferring the inflow tubing into peracetic acid and ethanol in distilled water to sterilize the flaps by perfusing for three hours. Once done, remove the flaps aseptically and immerse them into two washes of PBS containing 1%antibiotics antimycotics for 15 minutes each.Store flaps at 4 degrees Celsius until ready for recellularization. Use a 3 to 10 millimeter punch biopsy tool to obtain tissue samples for evaluation of decellularized flaps. The isolated decellularized flaps flushed under manual control demonstrated evidence of outflow from the freely draining venous cannula of omentum, tensor fascia lata, and radial forearm flap.The gross morphology of the native omentum, tensor fascia lata, and radial forearm flaps appeared pink colored immediately after the procurement. In comparison, decellularized tissues were characteristically white or opaque in appearance. Histological examination of native tissues with hematoxylin and eosin showed the presence of blue nuclei.In decellularized flaps, histological staining revealed loss of cellular material without blue nuclear staining, indicating an acellular tissue scaffold. Additional quantification of DNA content showed a significant decrease in DNA in acellular scaffolds compared to native tissues. The most important consideration is a surgical technique used during procurement, taking care to avoid damage to the flap pedicle in order to permit subsequent perfusion decellularization.Following perfusion decellularization, the resulting flaps may be recellularized with tissue specific cell populations in order to regenerate the native tissue compartments.

procurement-perfusion-decellularization-porcine-vascularized-flaps

Research

JoVE Journal

Bioengineering

Procedure for Decellularization of Porcine Heart by Retrograde Coronary Perfusion

Perfusion-based whole organ decellularization has recently gained interest in the field of tissue engineering as a means to create site-specific extracellular matrix scaffolds, while largely preserving the native architecture of the scaffold. To date, this approach has been utilized in a variety of organ systems, including the heart, lung, and liver 1-5. Previous decellularization methods for tissues without an easily accessible vascular network have relied upon prolonged exposure of tissue to solutions of detergents, acids, or enzymatic treatments as a means to remove the cellular and nuclear components from the surrounding extracellular environment6-8. However, the effectiveness of these methods hinged upon the ability of the solutions to permeate the tissue via diffusion. In contrast, perfusion of organs through the natural vascular system effectively reduced the diffusion distance and facilitated transport of decellularization agents into the tissue and cellular components out of the tissue. Herein, we describe a method to fully decellularize an intact porcine heart through coronary retrograde perfusion. The protocol yielded a fully decellularized cardiac extracellular matrix (c-ECM) scaffold with the three-dimensional structure of the heart intact. Our method used a series of enzymes, detergents, and acids coupled with hypertonic and hypotonic rinses to aid in the lysis and removal of cells. The protocol used a Trypsin solution to detach cells from the matrix followed by Triton X-100 and sodium deoxycholate solutions to aid in removal of cellular material. The described protocol also uses perfusion speeds of greater than 2 L/min for extended periods of time. The high flow rate, coupled with solution changes allowed transport of agents to the tissue without contamination of cellular debris and ensured effective rinsing of the tissue. The described method removed all nuclear material from native porcine cardiac tissue, creating a site-specific cardiac ECM scaffold that can be used for a variety of applications.

A method to rapidly and completely remove cellular components from an intact porcine heart through retrograde perfusion is described. This method yields a site specific cardiac extracellular matrix scaffold which has the potential for use in multiple clinical applications.

Perfusion-based  whole organ decellularization has recently gained interest in the field of  tissue engineering as a means to create site-specific ...

Anatomical Reconstructions of the Human Cardiac Venous System using Contrast-computed Tomography of Perfusion-fixed Specimens

A detailed understanding of the complexity and relative variability within the human cardiac venous system is crucial for the development of cardiac devices that require access to these vessels. For example, cardiac venous anatomy is known to be one of the key limitations for the proper delivery of cardiac resynchronization therapy (CRT)1 Therefore, the development of a database of anatomical parameters for human cardiac venous systems can aid in the design of CRT delivery devices to overcome such a limitation. In this research project, the anatomical parameters were obtained from 3D reconstructions of the venous system using contrast-computed tomography (CT) imaging and modeling software (Materialise, Leuven, Belgium). The following parameters were assessed for each vein: arc length, tortuousity, branching angle, distance to the coronary sinus ostium, and vessel diameter.
	CRT is a potential treatment for patients with electromechanical dyssynchrony. Approximately 10-20% of heart failure patients may benefit from CRT2. Electromechanical dyssynchrony implies that parts of the myocardium activate and contract earlier or later than the normal conduction pathway of the heart. In CRT, dyssynchronous areas of the myocardium are treated with electrical stimulation. CRT pacing typically involves pacing leads that stimulate the right atrium (RA), right ventricle (RV), and left ventricle (LV) to produce more resynchronized rhythms. The LV lead is typically implanted within a cardiac vein, with the aim to overlay it within the site of latest myocardial activation. 
	We believe that the models obtained and the analyses thereof will promote the anatomical education for patients, students, clinicians, and medical device designers. The methodologies employed here can also be utilized to study other anatomical features of our human heart specimens, such as the coronary arteries. To further encourage the educational value of this research, we have shared the venous models on our free access website: <a href="http://www.vhlab.umn.edu/atlas" target="_blank">www.vhlab.umn.edu/atlas</a>.

The objective of this research is to recreate and then access the anatomy of the human cardiac venous system using 3D reconstructions generated from contrast-computed tomography scans.

A detailed  understanding of the complexity and relative variability within the human  cardiac venous system is crucial for the development of cardiac ...

Operation of a Benchtop Bioreactor

Fermentation systems are used to provide an optimal growth environment for many different types of cell cultures. The ability afforded by fermentors to carefully control temperature, pH, and dissolved oxygen concentrations in particular makes them essential to efficient large scale growth and expression of fermentation products. This video will briefly describe the advantages of the fermentor over the shake flask. It will also identify key components of a typical benchtop fermentation system and give basic instruction on setup of the vessel and calibration of its probes. The viewer will be familiarized with the sterilization process and shown how to inoculate the growth medium in the vessel with culture. Basic concepts of operation, sampling, and harvesting will also be demonstrated. Simple data analysis and system cleanup will also be discussed.

Fermentors are used to increase culture yield and productivity of bioengineered cells. After screening multiple microbial or animal cell culture candidates in shake flasks, the next logical step is to increase the selected culture&#x2019;s biomass with the fermentor. This video demonstrates the setup and operation of a typical benchtop bioreactor system.

Fermentation systems are used to provide an optimal growth environment for many different types of cell cultures. The ability afforded by fermentors to ...

Construction and Characterization of a Novel Vocal Fold Bioreactor

In vitro engineering of mechanically active tissues requires the presentation of physiologically relevant mechanical conditions to cultured cells. To emulate the dynamic environment of vocal folds, a novel vocal fold bioreactor capable of producing vibratory stimulations at fundamental phonation frequencies is constructed and characterized. The device is composed of a function generator, a power amplifier, a speaker selector and parallel vibration chambers. Individual vibration chambers are created by sandwiching a custom-made silicone membrane between a pair of acrylic blocks. The silicone membrane not only serves as the bottom of the chamber but also provides a mechanism for securing the cell-laden scaffold. Vibration signals, generated by a speaker mounted underneath the bottom acrylic block, are transmitted to the membrane aerodynamically by the oscillating air. Eight identical vibration modules, fixed on two stationary metal bars, are housed in an anti-humidity chamber for long-term operation in a cell culture incubator. The vibration characteristics of the vocal fold bioreactor are analyzed non-destructively using a Laser Doppler Vibrometer (LDV). The utility of the dynamic culture device is demonstrated by culturing cellular constructs in the presence of 200-Hz sinusoidal vibrations with a mid-membrane displacement of 40 &#181;m. Mesenchymal stem cells cultured in the bioreactor respond to the vibratory signals by altering the synthesis and degradation of vocal fold-relevant, extracellular matrix components. The novel bioreactor system presented herein offers an excellent in vitro platform for studying vibration-induced mechanotransduction and for the engineering of functional vocal fold tissues.

A novel vocal fold bioreactor capable of delivering physiologically relevant, vibratory stimulation to cultured cells is constructed and characterized. This dynamic culture device, when combined with a fibrous poly(&#949;-caprolactone) scaffold, creates a vocal fold-mimetic environment that modulates the behaviors of mesenchymal stem cells.

In vitro engineering of mechanically active tissues requires the presentation of physiologically relevant mechanical conditions to cultured cells. To ...

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.

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 ...

Microfluidic Bioprinting for Engineering Vascularized Tissues and Organoids

Engineering vascularized tissue constructs and organoids has been historically challenging. Here we describe a novel method based on microfluidic bioprinting to generate a scaffold with multilayer interlacing hydrogel microfibers. To achieve smooth bioprinting, a core-sheath microfluidic printhead containing a composite bioink formulation extruded from the core flow and the crosslinking solution carried by the sheath flow, was designed and fitted onto the bioprinter. By blending gelatin methacryloyl (GelMA) with alginate, a polysaccharide that undergoes instantaneous ionic crosslinking in the presence of select divalent ions, followed by a secondary photocrosslinking of the GelMA component to achieve permanent stabilization, a microfibrous scaffold could be obtained using this bioprinting strategy. Importantly, the endothelial cells encapsulated inside the bioprinted microfibers can form the lumen-like structures resembling the vasculature over the course of culture for 16 days. The endothelialized microfibrous scaffold may be further used as a vascular bed to construct a vascularized tissue through subsequent seeding of the secondary cell type into the interstitial space of the microfibers. Microfluidic bioprinting provides a generalized strategy in convenient engineering of vascularized tissues at high fidelity.

We provide a generalized protocol based on a microfluidic bioprinting strategy for engineering a microfibrous vascular bed, where a secondary cell type could be further seeded into the interstitial space of this microfibrous structure to generate vascularized tissues and organoids.

Engineering vascularized tissue constructs and organoids has been historically challenging. Here we describe a novel method based on microfluidic ...

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, ...

A Friction Testing-Bioreactor Device for Study of Synovial Joint Biomechanics, Mechanobiology, and Physical Regulation

In primary osteoarthritis (OA), normal 'wear and tear' associated with aging inhibits the ability of cartilage to sustain its load-bearing and lubrication functions, fostering a deleterious physical environment. The frictional interactions of articular cartilage and synovium may influence joint homeostasis through tissue level wear and cellular mechanotransduction. To study these mechanical and mechanobiological processes, a device capable of replicating the motion of the joint is described. The friction testing device controls the delivery of reciprocal translating motion and normal load to two contacting biological counterfaces. This study adopts a synovium-on-cartilage configuration, and friction coefficient measurements are presented for tests performed in a phosphate-buffered saline (PBS) or synovial fluid (SF) bath. The testing was performed for a range of contact stresses, highlighting the lubricating properties of SF under high loads. This friction testing device can be used as a biomimetic bioreactor for studying the physical regulation of living joint tissues in response to applied physiologic loading associated with diarthrodial joint articulation.

The present protocol describes a friction testing device that applies simultaneous reciprocal sliding and normal load to two contacting biological counterfaces.

In primary osteoarthritis (OA), normal 'wear and tear' associated with aging inhibits the ability of cartilage to sustain its load-bearing and lubrication ...

Fabrication of Engineered Vascular Flaps Using 3D Printing Technologies

Engineering implantable, functional, thick tissues requires designing a hierarchical vascular network. 3D bioprinting is a technology used to create tissues by adding layer upon layer of printable biomaterials, termed bioinks, and cells in an orderly and automatic manner, which allows for creating highly intricate structures that traditional tissue engineering techniques cannot achieve. Thus, 3D bioprinting is an appealing in vitro approach to mimic the native vasculature complex structure, ranging from millimetric vessels to microvascular networks. 
Advances in 3D bioprinting in granular hydrogels enabled the high-resolution extrusion of low-viscosity extracellular matrix-based bioinks. This work presents a combined 3D bioprinting and sacrificial mold-based 3D printing approach for fabricating engineered vascularized tissue flaps. 3D bioprinting of endothelial and support cells using recombinant collagen-methacrylate bioink within a gelatin support bath is utilized for the fabrication of a self-assembled capillary network. This printed microvasculature is assembled around a mesoscale vessel-like porous scaffold, fabricated using a sacrificial 3D printed mold, and is seeded with endothelial cells. 
This assembly induces the endothelium of the mesoscale vessel to anastomose with the surrounding capillary network, establishing a hierarchical vascular network within an engineered tissue flap. The engineered flap is then directly implanted by surgical anastomosis to a rat femoral artery using a cuff technique. The described methods can be expanded for the fabrication of various vascularized tissue flaps for use in reconstruction surgery and vascularization studies.

Engineered flaps require an incorporated functional vascular network. In this protocol, we present a method of fabricating a 3D printed tissue flap containing a hierarchical vascular network and its direct microsurgical anastomoses to rat femoral artery.

Engineering implantable, functional, thick tissues requires designing a hierarchical vascular network. 3D bioprinting is a technology used to create ...

Multi-Stream Perfusion Bioreactor Integrated with Outlet Fractionation for Dynamic Cell Culture

Certain cell and tissue functions operate within the dynamic time scale of minutes to hours that are poorly resolved by conventional culture systems. This work has developed a low-cost perfusion bioreactor system that allows culture medium to be continuously perfused into a cell culture module and fractionated in a downstream module to measure dynamics on this scale. The system is constructed almost entirely from commercially available parts and can be parallelized to conduct independent experiments in conventional multi-well cell culture plates simultaneously. This video article demonstrates how to assemble the base setup, which requires only a single multichannel syringe pump and a modified fraction collector to perfuse up to six cultures in parallel. Useful variants on the modular design are also presented that allow for controlled stimulation dynamics, such as solute pulses or pharmacokinetic-like profiles. Importantly, as solute signals travel through the system, they are distorted due to solute dispersion. Furthermore, a method for measuring the residence time distributions (RTDs) of the components of the perfusion setup with a tracer using MATLAB is described. RTDs are useful to calculate how solute signals are distorted by the flow in the multi-compartment system. This system is highly robust and reproducible, so basic researchers can easily adopt it without the need for specialized fabrication facilities.

This paper presents a method to construct and operate a low-cost, multichannel perfusion cell culture system for measuring the dynamics of secretion and absorption rates of solutes in cellular processes. The system can also expose cells to dynamic stimulus profiles.

Certain cell and tissue functions operate within the dynamic time scale of minutes to hours that are poorly resolved by conventional culture systems. This ...