We would like to acknowledge Robert Strouse and the Research Information Solutions &#38; Innovations division at Nationwide Children&#39;s Hospital for their support in graphic design. This work was supported by a grant from the NIH (NHLBI K08HL138460).

All methods described here have been approved by the Institutional Animal Care and Use Committee (IACUC) at Nationwide Children&#39;s Hospital.
1. Scaffold Manufacturing
<ol>
	<li>Prepare a polymer nanofiber precursor solution by: 1) dissolving 8 wt% PET in 1,1,1,3,3,3-hexafluoroisopropanol and heating the solution to 60 &#176;C and by 2) dissolving 3 wt% PU in 1,1,1,3,3,3-hexafluoroisopropanol at room temperature.</li>
	<li>Once cooled, combine the solutions to create a final polymer mixture of PET and PU (20:80).</li>
	<li>Electrospin the PET+ PU solution onto a stainless steel rod (1 mm diameter) utilizing a 20G blunt tip needle on a 60 mL syringe filled with the PET:PU solution using a high-voltage DC power supply set to +14 kV on the needle, another high-voltage DC power supply set to -3 kV, a 5 mL/h flow rate, and a 20 cm tip-to-substrate distance. Rotate the rod at 350 rpm during fiber deposition.</li>
	<li>Continue electrospinning until the desired scaffold wall thickness of 300 &#181;m is achieved. Slide the scaffold off the rod, then hold it under vacuum overnight to remove any residual solvent.</li>
	<li>Sterilize the scaffold using an ultraviolet light dosage of 350 mJ/cm2 prior to implantation.</li>
</ol>
2. Bone Marrow-Derived Mononuclear Cell (BM-MNC) Harvesting
<ol>
	<li>Euthanize a 6-8 weeks old, female, C57BL/6 mouse with a cocktail of ketamine (200 mg/kg), xylazine (20 mg/kg) and ketoprofen (10 mg/kg). Check for complete euthanasia by tail-pinch method. Be sure to follow local guidelines for euthanasia.&#160;</li>
	<li>Under sterile conditions, remove the skin over the femurs and tibias to expose bone using fine scissors and micro-Adson forceps. Use Dumont #5 forceps and Dumont #5/45 forceps to remove the fascia and the tendons. Separate the bones and cut each of them on both the ends. Using a 5 mL syringe and a 25G needle, flush the bone marrow in a Petri dish containing 30 mL of Rosewell Park Memorial Institute (RPMI) media. Filter this RPMI with bone marrow through a 70 &#181;m nylon cell strainer into a 50 mL tube.</li>
	<li>In a Biosafety Cabinet, place 5 mL of polysurcrose and sodium diatrizoate in a 15 mL tube. Gently add the RPMI containing bone marrow mononuclear cells down the side of the tube to avoid mixing of the two layers. Centrifuge at 461 x g for 30 min with &#34;Brake 1&#34; at 24 &#176;C. 
	NOTE: On our centrifuge, brake 1 stands for the longest run out time during deceleration.</li>
	<li>Out of the three layers formed, discard the top (pink) layer of plasma and collect the middle (clear) layer consisting of the bone marrow mononuclear cells. Discard the precipitate of red blood cells.</li>
	<li>Dilute the bone marrow mononuclear cells (BM-MNC) in phosphate buffered saline (PBS) in a 1:1 ratio and centrifuge at 461 x g for 10 min with &#34;Brake 9&#34; at 24 &#176;C.</li>
	<li>Remove the supernatant and dilute the pellet with 5 mL of PBS. Centrifuge at 461 x g for 10 min with &#34;Brake 9&#34; at 24 &#176;C.</li>
	<li>Remove the supernatant and dilute the pellet with ~10 mL of RPMI.</li>
	<li>Dilute 10 &#181;L of the BM-MNC solution with an equal volume of 0.4% trypan blue in a 1 mL tube. Place 10 &#181;L of the solution in a cell counting chamber slide. Count the cells using an automated cell counter. Repeat the step and calculate the average number of cells. 
	NOTE: An average cell count of 1 X 108 cells was obtained from the use of two donor mice. This would be equivalent to two femurs, and two tibias that bone marrow is isolated from.</li>
	<li>Centrifuge the BM-MNC solution at 461 x g for 10 min with &#34;Brake 9&#34; at 24 &#176;C. Remove the supernatant and dilute the cell concentration to 107 cells/graft. 
	NOTE: We have studied seeding efficiency between 1, 10 and 100 million cells and found that 10 million cells per graft yields the highest seeding efficiency.</li>
</ol>
3. Cell Seeding on the Grafts
<ol>
	<li>Measure the lengths of the scaffolds and if needed, cut them to a length of 5 mm.</li>
	<li>Pre-wet the scaffold with 5 &#181;L of RPMI for 5 min. Remove the RPMI.</li>
	<li>Add 5 &#181;L of the BM-MNC solution to the lumen of the scaffold for 10 min.</li>
	<li>Pass a 21G needle through the lumen of the graft and incubate the graft in 1000 &#181;L of RPMI overnight at 37 &#176;C in an incubator.</li>
</ol>
4. Graft Implantation
NOTE: Care should be taken to maintain aseptic technique during the graft implantation procedure.
<ol>
	<li>Use 6-8-week-old female C57BL/6 mice as recipients for the cell seeded grafts. Inject enrofloxacin (10mg/kg) subcutaneously 24 h before surgery and just before incision.</li>
	<li>Weigh the mouse and administer a 0.1 mL/10 g dose of the anesthetic cocktail of ketamine (100 mg/kg), xylazine (10 mg/kg) and ketoprofen (5 mg/kg) as analgesia intraperitoneally.</li>
	<li>Check if the plane of anesthesia has been achieved by tail-pinch method. On confirming the level of sedation, apply a sterile ophthalmic ointment to the eyes and clip the hair on the surgical site from chin to clavicles. Place the animal on a pad in a dorsal recumbent position. Disinfect the surgical site using first a povidone-iodine prep pad, followed by an alcohol prep pad (70% alcohol), and once more a povidone-iodine prep pad.</li>
	<li>Place the animal under the dissecting microscope with its head away from the surgeon. Make a midline incision ranging from the clavicles to the hyoid bone with the help of fine scissors and micro-Adson forceps. Clean the fascia with Dumont #5 and Dumont #7 fine forceps, along with a sterile cotton swab if needed, and insert a self-retaining Colibri retractor.</li>
	<li>Open the strap muscles (Figure 3A) with Dumont #5 and Dumont #7 fine forceps to expose the thyroid cartilage, cricoid cartilage and the trachea. Bluntly separate the trachea from the recurrent laryngeal nerves running parallel on either side, followed by circumferential separation of the trachea from the esophagus (Figure 3B).</li>
	<li>Using a 20G needle and surgical marker, stain the anterior portion of the trachea.</li>
	<li>Identify the trachea and make an incision below the third tracheal cartilage ring and transect the trachea using a pair of Vannas-Tubingen spring scissors and a pair of Dumont #7 fine forceps. Holding it with the fine curved forceps, secure&#160;the distal trachea to the sternum using sterile 9-0 nylon suture to create a temporary tracheostomy (Figure 3C). NOTE: An alternative suture material that can be used is the 9-0 PDS for tracheal implantation and muscle reapproximation.&#160;</li>
	<li>With a 20G needle and a surgical marker, stain the graft to represent the anterior portion.</li>
	<li>Implant the graft inserting the proximal-posterior, proximal-lateral and proximal-anterior sutures, in that order using 9-0 sterile nylon suture (Figure 3D), Dumont #7 fine forceps and a needle holder.</li>
	<li>Turn the animal 180&#176; to place its tail away from the surgeon. Release the temporary tracheostomy. The distal trachea is incompletely transected to permit the use of the resected segment as a stump for retraction. When no longer needed, the 5 MM trachea segment is removed completely.</li>
	<li>Complete the distal anastomosis by placing the sutures in the similar fashion as the proximal anastomosis.</li>
	<li>Re-approximate the graft position and the strap muscles. Close the incision using 9-0 sterile nylon sutures in a running pattern.</li>
	<li>Inject 0.1 mL of buprenorphine (0.1 mg/kg) subcutaneously and place the animal in a recovery cage placed on a heating pad without other animals in the cage.</li>
	<li>Observe the mouse until it is conscious and able to ambulate, then transfer the mouse to a new cage with soft bedding, moist chow and medicated water (ibuprofen, 30 mg/kg) for 48 h. After this time period, return the mouse to a normal cage with other mice. 
	NOTE: Mice that maintain respiratory distress or decreased activity after implantation are observed by laboratory and/or animal staff in a 32 &#176;C incubator. If this continues for more than 48 h, then the mice should be euthanized.</li>
</ol>
5. Histology and Immunohistochemistry
NOTE: Hematoxylin and eosin stains were performed using standard technique by Nationwide Children&#39;s Hospital Morphology Core. Immunohistochemistry was performed according to the below steps.
<ol>
	<li>Deparaffinize the slides using 1) xylene for 5 min, 2) xylene for 5 min, 3) 100% ethanol for 5 min, 4) 90% ethanol for 5 min, 5) 70% ethanol for 5 min, 6) distilled H2O (dH2O) for 5 min.</li>
	<li>Submerge the slides in citrate buffer and place in water-filled pressure cooker. Heat for 10 min then allow to cool to room temperature. Wash with 0.1% bovine serum albumin in PBS (BSA-PBS) for 5 min. Rinse with dH2O. 
	NOTE: Heating can also be done with a hot water bath or microwave for 15 min.</li>
	<li>Incubate the slides with 3% normal goat serum in PBS for 1 h at room temperature. Wash with 0.1% BSA-PBS for 5 min. Incubate in primary antibody with concentrations for keratin 5 (1:1000)6, keratin 14 (1:250)6 and F4/80 (1:100)7 for 18 h overnight at 4 &#176;C.</li>
	<li>Wash with 0.1% BSA-PBS twice for 10 min each wash. Incubate with appropriate secondary antibody at concentration of 1:500 for K5/K14 and 1:300 F4/80 for 1 h at room temperature. Wash with 0.1% BSA-PBS twice for 10 min each wash.</li>
	<li>Mount using 4&#39;, 6-diamidino-2-phenolindole (DAPI) containing mounting media and glass cover slips. Allow to sit for 30 min before imaging.</li>
</ol>

<ol>
	<li>Macchiarini, P., 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=Clinical+transplantation+of+a+tissue-engineered+airway.">Clinical transplantation of a tissue-engineered airway.</a> The Lancet. 372 (9655), 2023-2030 (2008).</li><li>Jungebluth, P., 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=Tracheobronchial+transplantation+with+a+stem-cell-seeded+bioartificial+nanocomposite:+A+proof-of-concept+study.">Tracheobronchial transplantation with a stem-cell-seeded bioartificial nanocomposite: A proof-of-concept study.</a> The Lancet. 378 (9808), 1997-2004 (2011).</li><li>Elliott, M. 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=Stem-cell-based,+tissue+engineered+tracheal+replacement+in+a+child:+A+2-year+follow-up+study.">Stem-cell-based, tissue engineered tracheal replacement in a child: A 2-year follow-up study.</a> The Lancet. 380 (9846), 994-1000 (2012).</li><li>Chiang, T., Pepper, V., Best, C., Onwuka, E., Breuer, C. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+Translation+of+Tissue+Engineered+Trachea+Grafts.">Clinical Translation of Tissue Engineered Trachea Grafts.</a> Annals of Otology, Rhinology and Laryngology. 125 (11), 873-885 (2016).</li><li>Clark, E. 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=Effect+of+cell+seeding+on+neotissue+formation+in+a+tissue+engineered+trachea.">Effect of cell seeding on neotissue formation in a tissue engineered trachea.</a> Journal of Pediatric Surgery. 51 (1), 49-55 (2016).</li><li>Cole, B. B., Smith, R. W., Jenkins, K. M., Graham, B. B., Reynolds, P. R., Reynolds, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracheal+basal+cells:+A+facultative+progenitor+cell+pool.">Tracheal basal cells: A facultative progenitor cell pool.</a> American Journal of Pathology. 177 (1), 362-376 (2010).</li><li>Onwuka, 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=The+role+of+myeloid+cell-derived+PDGF-B+in+neotissue+formation+in+a+tissue-engineered+vascular+graft.">The role of myeloid cell-derived PDGF-B in neotissue formation in a tissue-engineered vascular graft.</a> Regenerative Medicine. 12 (3), 249-261 (2017).</li><li>Grimmer, J. F., 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=Tracheal+reconstruction+using+tissue-engineered+cartilage.">Tracheal reconstruction using tissue-engineered cartilage.</a> Archives of Otolaryngology - Head and Neck Surgery. 130 (10), 1191-1196 (2004).</li><li>Wood, M. W., Murphy, S. V., Feng, X., Wright, S. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tracheal+reconstruction+in+a+canine+model.">Tracheal reconstruction in a canine model.</a> Otolaryngology - Head and Neck Surgery (United States). 150 (3), 428-433 (2014).</li><li>Haag, 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=Biomechanical+and+angiogenic+properties+of+tissue-engineered+rat+trachea+using+genipin+cross-linked+decellularized+tissue.">Biomechanical and angiogenic properties of tissue-engineered rat trachea using genipin cross-linked decellularized tissue.</a> Biomaterials. 33 (3), 780-789 (2012).</li><li>Best, C. 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=Designing+a+tissue-engineered+tracheal+scaffold+for+preclinical+evaluation.">Designing a tissue-engineered tracheal scaffold for preclinical evaluation.</a> International Journal of Pediatric Otorhinolaryngology. 104, 155-160 (2018).</li></ol>

The authors declare no competing financial interests.

Development of a mouse model for tissue engineered tracheas is essential in understanding the factors that have limited clinical translation of the TETGs; namely graft collapse, stenosis and delayed epithelialization4. A few factors that contribute to these limitations include selection of graft material, the manufacturing process, scaffold design and cell seeding protocols. This model allows for faster evaluation of these factors in order to understand the cellular and molecular mechanisms affect...

Long-segment tracheal defects can present as rare congenital conditions such as complete tracheal rings and tracheal agenesis, as well as trauma, malignancy, and infection. When exceeding 6 cm in adults or 30% of the tracheal length in children, these defects cannot be treated by surgical reconstruction. Attempts to replace the airway with autologous tissue, cadaveric transplants, and artificial constructs have been plagued by chronic infection, granulation, mechanical failure, and stenosis.
Tissue engineered tracheal grafts (TETGs) can potentially address these problems while avoiding the need for life-long immunosuppression. In the last decade, TETGs have been tested in animal models and utilized clinically in rare instances of compassionate use1,2,3. In both clinical and large animal studies, post-operative recovery from tissue engineered airway replacement required numerous interventions to combat stenosis (defined as &#62;50% luminal narrowing) and maintain airway patency. Additional TETG work has sought to reduce this stenosis through evaluating the role of cell seeding choice, vascularization and scaffold design. Cell seeding choices and scaffold design aimed at restoring native trachea structure/function have mainly been focused on respiratory epithelial cells and chondrocytes seeded on various resorbable, non-resorbable and decellularized scaffolds. As vascularization likely plays an major role in the development of stenosis, other groups have focused on optimizing in vitro or heterotopic models to expedite revascularization or neoangiogenesis4. Nonetheless, achieving successful vascularization while also maintaining a mechanically competent and functional TETG remains a challenge. Despite recent advances, minimizing stenosis remains a critical obstacle to clinical translation.
To investigate this histopathological response to TETG implantation in vivo, we developed an ovine model of tissue engineered tracheal replacement. The graft was composed of a mixed polyethylene terephthalate (PET) and polyurethane (PU) electrospun scaffold seeded with bone marrow-derived mononuclear cells (BM-MNCs). In this small cohort, we demonstrated that seeded autologous BM-MNCs accelerated re-epithelialization and delayed stenosis5. Although seeding with autologous BM-MNCs improved survival, the cellular mechanism by which BM-MNCs modulate the formation of functional neotissue remains unclear.
Investigation on the cellular level required development of a murine model of tissue engineered tracheal replacement. Similar to the ovine study, we utilized a PET:PU electrospun scaffold seeded with BM-MNCs. Consistent with the ovine model, TETG stenosis developed over the course of the first two weeks following implantation1,2,3,5. This suggested that the murine model recapitulated the pathology observed previously, enabling us to further interrogate the cellular mechanisms underlying airway stenosis.
In this report, we detail our protocol for tissue engineered tracheal replacement in the mouse model including scaffold manufacturing, BM-MNC isolation, graft seeding, and implantation (Figure 1, Figure 2).

<table border="0" cellpadding="0" cellspacing="0" style="width:827px;" width="827">
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		<col />
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		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:423px;">0.9% Sodium chloride injection</td>
			<td style="width:119px;">APP Pharmaceuticals</td>
			<td style="width:119px;">NDC 63323-186-10</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">10cc serological pipet</td>
			<td style="width:119px;">Falcon</td>
			<td style="width:119px;">357551</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">18G 1.5in. Needle</td>
			<td style="width:119px;">BD</td>
			<td style="width:119px;">305190</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">1mL Syringe</td>
			<td style="width:119px;">BD</td>
			<td style="width:119px;">309659</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">24-well plate</td>
			<td style="width:119px;">Corning</td>
			<td style="width:119px;">3526</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">25cc serological pipet</td>
			<td style="width:119px;">Falcon</td>
			<td style="width:119px;">356535</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">25G 1in. Needle</td>
			<td style="width:119px;">BD</td>
			<td style="width:119px;">305125</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">50cc tube</td>
			<td style="width:119px;">BD</td>
			<td style="width:119px;">352070</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:423px;">Alcohol prep pads</td>
			<td style="width:119px;">Fisher Healthcare</td>
			<td style="width:119px;">NDC 69250-661-02</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:423px;">Baytril (enrofloxacin) solution</td>
			<td style="width:119px;">Bayer Healthcare, LLC</td>
			<td style="width:119px;">NDC 0859-2267-01</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:423px;">Black polyamide monofilament suture, 9-0</td>
			<td style="width:119px;">AROSurgical Instruments Corporation</td>
			<td style="width:119px;">T05A09N10-13</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:423px;">C57BL/6, female</td>
			<td style="width:119px;">Jackson laboratories</td>
			<td style="width:119px;">664</td>
			<td style="width:167px;">6-8 weeks old</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Citrate Buffer pH 6.0 20x concentrate</td>
			<td style="width:119px;">ThermoFisher</td>
			<td style="width:119px;">5000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Colibri retractors</td>
			<td style="width:119px;">F.S.T</td>
			<td style="width:119px;">17000-04</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Cotton tipped applicators</td>
			<td style="width:119px;">Fisher scientific</td>
			<td style="width:119px;">23-400-118</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Cytokeratin 14 Monoclonal Antibody</td>
			<td style="width:119px;">ThermoFisher</td>
			<td style="width:119px;">MA5-11599</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Dumont #5 Forceps</td>
			<td style="width:119px;">F.S.T</td>
			<td style="width:119px;">11251-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Dumont #5/45 forceps</td>
			<td style="width:119px;">F.S.T</td>
			<td style="width:119px;">11251-35</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Dumont #7 - Fine Forceps</td>
			<td style="width:119px;">F.S.T</td>
			<td style="width:119px;">11274-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">F4/80 Rat anti-mouse antibody</td>
			<td style="width:119px;">Bio-Rad</td>
			<td style="width:119px;">MCA497R</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Ficoll</td>
			<td style="width:119px;">Sigma</td>
			<td style="width:119px;">10831-100mL</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Fine scissors- Sharp-blunt</td>
			<td style="width:119px;">F.S.T</td>
			<td style="width:119px;">14028-10</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Fisherbrand Premium Cover Glasses</td>
			<td style="width:119px;">ThermoFisher</td>
			<td style="width:119px;">12-548-5M</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Fluoroshield Mounting Media with DAPI</td>
			<td style="width:119px;">Abcam</td>
			<td style="width:119px;">ab104139</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Goat-anti mouse IgG Secondary Antibody Alexa Fluor 594</td>
			<td style="width:119px;">ThermoFisher</td>
			<td style="width:119px;">A-11001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Goat-anti Rabbit IgG Secondary Antibody Alexa Fluor 594</td>
			<td style="width:119px;">ThermoFisher</td>
			<td style="width:119px;">A-11012</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Goat-anti Rat IgG Secondary Antibody Alexa Fluor 647</td>
			<td style="width:119px;">ThermoFisher</td>
			<td style="width:119px;">A-21247</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:423px;">Ibuprofen</td>
			<td style="width:119px;">Precision Dose, Inc</td>
			<td style="width:119px;">NDC 68094-494-59</td>
			<td></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:423px;">Iodine prep pads</td>
			<td style="width:119px;">Professional disposables international, Inc.</td>
			<td style="width:119px;">NDC 10819-3883-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Keratin 5 Polyclonal Antibody, Purified</td>
			<td style="width:119px;">BioLegend</td>
			<td style="width:119px;">905501</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Ketamine hydrochloride injection</td>
			<td style="width:119px;">Hospira Inc.</td>
			<td style="width:119px;">NDC 0409-2053</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Micro-Adson forceps</td>
			<td style="width:119px;">F.S.T</td>
			<td style="width:119px;">11018-12</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Microscope</td>
			<td style="width:119px;">Leica</td>
			<td style="width:119px;">M80</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Non-woven sponges</td>
			<td style="width:119px;">Covidien</td>
			<td style="width:119px;">441401</td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:423px;">Opthalmic ointment</td>
			<td style="width:119px;">Dechra Veterinary products</td>
			<td style="width:119px;">NDC 17033-211-38</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">PBS</td>
			<td style="width:119px;">Gibco</td>
			<td style="width:119px;">10010-023</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:423px;">PET/PU (Polyethylene terephthalate &#38; Polyurethane) scaffolds</td>
			<td style="width:119px;">Nanofiber solutions</td>
			<td style="width:119px;"></td>
			<td>Custom ordered</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Petri dish</td>
			<td style="width:119px;">BD</td>
			<td style="width:119px;">353003</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">RPMI 1640 Medium</td>
			<td style="width:119px;">Gibco</td>
			<td style="width:119px;">11875-093</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">TISH Needle Holder/Forceps</td>
			<td style="width:119px;">Micrins</td>
			<td style="width:119px;">MI1540</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Trimmer</td>
			<td style="width:119px;">Wahl</td>
			<td style="width:119px;">9854-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vannas-T&#252;bingen Spring Scissors</td>
			<td>F.S.T</td>
			<td>15008-08</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:423px;">Warm water recirculator</td>
			<td style="width:119px;">Gaymar</td>
			<td style="width:119px;">TP-700</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:423px;">Xylazine sterile solution</td>
			<td style="width:119px;">Akorn animal health</td>
			<td style="width:119px;">NDC 59399-110-20</td>
			<td></td>
		</tr>
	</tbody>
</table>

seeding and implantation of a biosynthetic tissue-engineered tracheal graft in a mouse model

Treatment options for congenital or secondary long segment tracheal defects have historically been limited due to an inability to replace functional tissue. Tissue engineering holds great promise as a potential solution with its ability to integrate cells and signaling molecules into a 3-dimensional scaffold. Recent work with tissue engineered tracheal grafts (TETGs) has seen some success but their translation has been limited by graft stenosis, graft collapse, and delayed epithelialization. In order to investigate the mechanisms driving these issues, we have developed a mouse model for tissue engineered tracheal graft implantation. TETGs were constructed using electrospun polymers polyethylene terephthalate (PET) and polyurethane (PU) in a mixture of PET and PU (20:80 percent weight). Scaffolds were then seeded using bone marrow mononuclear cells isolated from 6-8 week-old C57BL/6 mice by gradient centrifugation. Ten million cells per graft were seeded onto the lumen of the scaffold and allowed to incubate overnight before implantation between the third and seventh tracheal rings. These grafts were able to recapitulate the findings of stenosis and delayed epithelialization as demonstrated by histological analysis and lack of Keratin 5 and Keratin 14 basal epithelial cells on immunofluorescence. This model will serve as a tool for investigating cellular and molecular mechanisms involved in host remodeling.

Figure 1 illustrates a schematic of TETG seeding and implantation. Bone marrow was harvested from C57BL/6 mice and cultured in vitro. BM-MNCs were isolated by density centrifugation and seeded onto the TETG. Seeded TETGs were implanted into a syngeneic C57BL/6 recipient mouse.
Figure 2 is an overview of the PET:PU TETG scaffold manufacturing process. PET:PU sol...

Watch this Scientific Journal Video about Seeding and Implantation of a Biosynthetic Tissue-engineered Tracheal Graft in a Mouse Model at JoVE.com

Seeding and Implantation of a Biosynthetic Tissue-engineered Tracheal Graft in a Mouse Model

Graft stenosis poses a critical obstacle in tissue engineered airway replacement. To investigate cellular mechanisms underlying stenosis, we utilize a murine model of tissue engineered tracheal replacement with seeded bone marrow mononuclear cells (BM-MNC). Here, we detail our protocol, including scaffold manufacturing, BM-MNC isolation, graft seeding, and implantation.

Treatment options for congenital or secondary long segment tracheal defects have historically been limited due to an inability to replace functional ...

seeding-implantation-biosynthetic-tissue-engineered-tracheal-graft

Research

JoVE Journal

Bioengineering

7.2K Views.  Nationwide Children's Hospital. Graft stenosis poses a critical obstacle in tissue engineered airway replacement. To investigate cellular mechanisms underlying stenosis, we utilize a murine model of tissue engineered tracheal replacement with seeded bone marrow mononuclear cells (BM-MNC). Here, we detail our protocol, including scaffold manufacturing, BM-MNC isolation, graft seeding, and implantation.

Video: Seeding and Implantation of a Biosynthetic Tissue-engineered Tracheal Graft in a Mouse Model

Autologous Endothelial Progenitor Cell-Seeding Technology and Biocompatibility Testing For Cardiovascular Devices in Large Animal Model

Implantable cardiovascular devices are manufactured from artificial materials (e.g. titanium (Ti), expanded polytetrafluoroethylene), which pose the risk of thromboemboli formation1,2,3. We have developed a method to line the inside surface of Ti tubes with autologous blood-derived human or porcine endothelial progenitor cells (EPCs)4. By implanting Ti tubes containing a confluent layer of porcine EPCs in the inferior vena cava (IVC) of pigs, we tested the improved biocompatibility of the cell-seeded surface in the prothrombotic environment of a large animal model and compared it to unmodified bare metal surfaces5,6,7 (Figure 1). This method can be used to endothelialize devices within minutes of implantation and test their antithrombotic function in vivo. 
Peripheral blood was obtained from 50 kg Yorkshire swine and its mononuclear cell fraction cultured to isolate EPCs4,8. Ti tubes (9.4 mm ID) were pre-cut into three 4.5 cm longitudinal sections and reassembled with heat-shrink tubing. A seeding device was built, which allows for slow rotation of the Ti tubes. 
We performed a laparotomy on the pigs and externalized the intestine and urinary bladder. Sharp and blunt dissection was used to skeletonize the IVC from its bifurcation distal to the right renal artery proximal. The Ti tubes were then filled with fluorescently-labeled autologous EPC suspension and rotated at 10 RPH x 30 min to achieve uniform cell-coating9. After administration of 100 USP/ kg heparin, both ends of the IVC and a lumbar vein were clamped. A 4 cm veinotomy was performed and the device inserted and filled with phosphate-buffered saline. As the veinotomy was closed with a 4-0 Prolene running suture, one clamp was removed to de-air the IVC. At the end of the procedure, the fascia was approximated with 0-PDS (polydioxanone suture), the subcutaneous space closed with 2-0 Vicryl and the skin stapled closed. 
After 3 - 21 days, pigs were euthanized, the device explanted en-block and fixed. The Ti tubes were disassembled and the inner surfaces imaged with a fluorescent microscope.
We found that the bare metal Ti tubes fully occluded whereas the EPC-seeded tubes remained patent. Further, we were able to demonstrate a confluent layer of EPCs on the inside blood-contacting surface.
Concluding, our technology can be used to endothelialize Ti tubes within minutes of implantation with autologous EPCs to prevent thrombosis of the device. Our surgical method allows for testing the improved biocompatibility of such modified devices with minimal blood loss and EPC-seeded surface disruption.

A method for seeding titanium blood-contacting biomaterials with autologous cells and testing biocompatibility is described. This method uses endothelial progenitor cells and titanium tubes, seeded within minutes of surgical implantation into porcine venae cavae. This technique is adaptable to many other implantable biomedical devices.

Implantable cardiovascular devices are manufactured from artificial materials (e.g. titanium (Ti), expanded polytetrafluoroethylene), which pose the risk ...

Surgical Technique for the Implantation of Tissue Engineered Vascular Grafts and Subsequent In Vivo Monitoring

The development of Tissue Engineered Vessels (TEVs) is advanced by the ability to routinely and effectively implant TEVs (4-5 mm in diameter) into a large animal model. A step by-step protocol for inter-positional placement of the TEV and real-time digital assessment of the TEV and native carotid arteries is described here. In vivo monitoring is made possible by the implantation of flow probes, catheters and ultrasonic crystals (capable of recording dynamic diameter changes of implanted TEVs and native carotid arteries) at the time of surgery. Once implanted, researchers can calculate arterial blood flow patterns, invasive blood pressure and artery diameter yielding parameters such as pulse wave velocity, augmentation index, pulse pressures and compliance. Data acquisition is accomplished using a single computer program for analysis throughout the duration of the experiment. Such invaluable data provides insight into TEV matrix remodeling, its resemblance to native/sham controls and overall TEV performance in vivo.

Surgical Technique for the Implantation of Tissue Engineered Vascular Grafts and Subsequent In Vivo Monitoring

A step-by-step protocol for the inter-positional placement of Tissue Engineered Vessels (TEVs) into the carotid artery of a sheep using end-to-end anastomosis and real-time digital assessment in vivo until animal sacrifice.

The development of Tissue Engineered Vessels (TEVs) is advanced by the ability to routinely and effectively implant TEVs (4-5 mm in diameter) into a large ...

Generation and Grafting of Tissue-engineered Vessels in a Mouse Model

The construction of vascular conduits is a fundamental strategy for surgical repair of damaged and injured vessels resulting from cardiovascular diseases. The current protocol presents an efficient and reproducible strategy in which functional tissue engineered vessel grafts can be generated using partially induced pluripotent stem cell (PiPSC) from human fibroblasts. We designed a decellularized vessel scaffold bioreactor, which closely mimics the matrix protein structure and blood flow that exists within a native vessel, for seeding of PiPSC-endothelial cells or smooth muscle cells prior to grafting into mice. This approach was demonstrated to be advantageous because immune-deficient mice engrafted with the PiPSC-derived grafts presented with markedly increased survival rate 3 weeks after surgery. This protocol represents a valuable tool for regenerative medicine, tissue engineering and potentially patient-specific cell-therapy in the near future.

Here, we present a protocol to generate tissue engineered vessel grafts that are functional for grafting into mice by double seeding partially induced pluripotent stem cell (PiPSC) - derived smooth muscle cells and PiPSC - derived endothelial cells on a decellularized vessel scaffold bioreactor.

The construction of vascular conduits is a fundamental strategy for surgical repair of damaged and injured vessels resulting from cardiovascular diseases. ...

Production, Characterization and Potential Uses of a 3D Tissue-engineered Human Esophageal Mucosal Model

The incidence of both esophageal adenocarcinoma and its precursor, Barrett&#8217;s Metaplasia, are rising rapidly in the western world. Furthermore esophageal adenocarcinoma generally has a poor prognosis, with little improvement in survival rates in recent years. These are difficult conditions to study and there has been a lack of suitable experimental platforms to investigate disorders of the esophageal mucosa.
A model of the human esophageal mucosa has been developed in the MacNeil laboratory which, unlike conventional 2D cell culture systems, recapitulates the cell-cell and cell-matrix interactions present in vivo and produces a mature, stratified epithelium similar to that of the normal human esophagus. Briefly, the model utilizes non-transformed normal primary human esophageal fibroblasts and epithelial cells grown within a porcine-derived acellular esophageal scaffold. Immunohistochemical characterization of this model by CK4, CK14, Ki67 and involucrin staining demonstrates appropriate recapitulation of the histology of the normal human esophageal mucosa.
This model provides a robust, biologically relevant experimental model of the human esophageal mucosa. It can easily be manipulated to investigate a number of research questions including the effectiveness of pharmacological agents and the impact of exposure to environmental factors such as alcohol, toxins, high temperature or gastro-esophageal refluxate components. The model also facilitates extended culture periods not achievable with conventional 2D cell culture, enabling, inter alia, the study of the impact of repeated exposure of a mature epithelium to the agent of interest for up to 20 days. Furthermore, a variety of cell lines, such as those derived from esophageal tumors or Barrett&#8217;s Metaplasia, can be incorporated into the model to investigate processes such as tumor invasion and drug responsiveness in a more biologically relevant environment.

This manuscript describes the production, characterization and potential uses of a tissue engineered 3D esophageal construct prepared from normal primary human esophageal fibroblast and squamous epithelial cells seeded within a de-cellularized porcine scaffold. The results demonstrate the formation of a mature stratified epithelium similar to the normal human esophagus.

The incidence of both esophageal adenocarcinoma and its precursor, Barrett&#8217;s Metaplasia, are rising rapidly in the western world. Furthermore ...

A Combined 3D Tissue Engineered In Vitro/In Silico Lung Tumor Model for Predicting Drug Effectiveness in Specific Mutational Backgrounds

In the present study, we combined an in vitro 3D lung tumor model with an in silico model to optimize predictions of drug response based on a specific mutational background. The model is generated on a decellularized porcine scaffold that reproduces tissue-specific characteristics regarding extracellular matrix composition and architecture including the basement membrane. We standardized a protocol that allows artificial tumor tissue generation within 14 days including three days of drug treatment. Our article provides several detailed descriptions of 3D read-out screening techniques like the determination of the proliferation index Ki67 staining&#39;s, apoptosis from supernatants by M30-ELISA and assessment of epithelial to mesenchymal transition (EMT), which are helpful tools for evaluating the effectiveness of therapeutic compounds. We could show compared to 2D culture a reduction of proliferation in our 3D tumor model that is related to the clinical situation. Despite of this lower proliferation, the model predicted EGFR-targeted drug responses correctly according to the biomarker status as shown by comparison of the lung carcinoma cell lines HCC827 (EGFR -mutated, KRAS wild-type) and A549 (EGFR wild-type, KRAS-mutated) treated with the tyrosine-kinase inhibitor (TKI) gefitinib. To investigate drug responses of more advanced tumor cells, we induced EMT by long-term treatment with TGF-beta-1 as assessed by vimentin/pan-cytokeratin immunofluorescence staining. A flow-bioreactor was employed to adjust culture to physiological conditions, which improved tissue generation. Furthermore, we show the integration of drug responses upon gefitinib treatment or TGF-beta-1 stimulation - apoptosis, proliferation index and EMT - into a Boolean in silico model. Additionally, we explain how drug responses of tumor cells with a specific mutational background and counterstrategies against resistance can be predicted. We are confident that our 3D in vitro approach especially with its in silico expansion provides an additional value for preclinical drug testing in more realistic conditions than in 2D cell culture.

A Combined 3D Tissue Engineered In Vitro/In Silico Lung Tumor Model for Predicting Drug Effectiveness in Specific Mutational Backgrounds

We present a three-dimensional (3D) lung cancer model based on a biological collagen scaffold to study sensitivity towards non-small-cell-lung-cancer-(NSCLC)-targeted therapies. We demonstrate different read-out techniques to determine the proliferation index, apoptosis and epithelial-mesenchymal transition (EMT) status. Collected data are integrated into an in silico model for prediction of drug sensitivity.

In the present study, we combined an in vitro 3D lung tumor model with an in silico model to optimize predictions of drug response based on a specific ...

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

Despite the regenerative capacity of skeletal muscle, permanent functional and/or cosmetic deficits (e.g., volumetric muscle loss (VML) resulting from traumatic injury, disease and various congenital, genetic and acquired conditions are quite common. Tissue engineering and regenerative medicine technologies have enormous potential to provide a therapeutic solution. However, utilization of biologically relevant animal models in combination with longitudinal assessments of pertinent functional measures are critical to the development of improved regenerative therapeutics for treatment of VML-like injuries. In that regard, a commercial muscle lever system can be used to measure length, tension, force and velocity parameters in skeletal muscle. We used this system, in conjunction with a high power, bi-phase stimulator, to measure in vivo force production in response to activation of the anterior crural compartment of the rat hindlimb. We have previously used this equipment to assess the functional impact of VML injury on the tibialis anterior (TA) muscle, as well as the extent of functional recovery following treatment of the injured TA muscle with our tissue engineered muscle repair (TEMR) technology. For such studies, the left foot of an anaesthetized rat is securely anchored to a footplate linked to a servomotor, and the common peroneal nerve is stimulated by two percutaneous needle electrodes to elicit muscle contraction and dorsiflexion of the foot. The peroneal nerve stimulation-induced muscle contraction is measured over a range of stimulation frequencies (1-200 Hz), to ensure an eventual plateau in force production that allows for an accurate determination of peak tetanic force. In addition to evaluation of the extent of VML injury as well as the degree of functional recovery following treatment, this methodology can be easily applied to study diverse aspects of muscle physiology and pathophysiology. Such an approach should assist with the more rational development of improved therapeutics for muscle repair and regeneration.

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

We describe an in vivo protocol to measure dorsiflexion of the foot following stimulation of the peroneal nerve and contraction of the anterior crural compartment of the rat hindlimb. Such measurements are an indispensable translational tool for evaluating skeletal muscle pathology and tissue engineering approaches to muscle repair and regeneration.

Despite the regenerative capacity of skeletal muscle, permanent functional and/or cosmetic deficits (e.g., volumetric muscle loss (VML) resulting from ...

Three-dimensional Tissue Engineered Aligned Astrocyte Networks to Recapitulate Developmental Mechanisms and Facilitate Nervous System Regeneration

Neurotrauma and neurodegenerative disease often result in lasting neurological deficits due to the limited capacity of the central nervous system (CNS) to replace lost neurons and regenerate axonal pathways. However, during nervous system development, neuronal migration and axonal extension often occur along pathways formed by other cells, referred to as &#34;living scaffolds&#34;. Seeking to emulate these mechanisms and to design a strategy that circumvents the inhibitory environment of the CNS, this manuscript presents a protocol to fabricate tissue engineered astrocyte-based &#34;living scaffolds&#34;. To create these constructs, we employed a novel biomaterial encasement scheme to induce astrocytes to self-assemble into dense three-dimensional bundles of bipolar longitudinally-aligned somata and processes. First, hollow hydrogel micro-columns were assembled, and the inner lumen was coated with collagen extracellular-matrix. Dissociated cerebral cortical astrocytes were then delivered into the lumen of the cylindrical micro-column and, at a critical inner diameter of &#60;350 &#181;m, spontaneously self-aligned and contracted to produce long fiber-like cables consisting of dense bundles of astrocyte processes and collagen fibrils measuring &#60;150 &#181;m in diameter yet extending several cm in length. These engineered living scaffolds exhibited &#62;97% cell viability and were virtually exclusively comprised of astrocytes expressing a combination of the intermediate filament proteins glial-fibrillary acidic protein (GFAP), vimentin, and nestin. These aligned astrocyte networks were found to provide a permissive substrate for neuronal attachment and aligned neurite extension. Moreover, these constructs maintain integrity and alignment when extracted from the hydrogel encasement, making them suitable for CNS implantation. These preformed constructs structurally emulate key cytoarchitectural elements of naturally occurring glial-based &#34;living scaffolds&#34; in vivo. As such, these engineered living scaffolds may serve as test-beds to study neurodevelopmental mechanisms in vitro or facilitate neuroregeneration by directing neuronal migration and/or axonal pathfinding following CNS degeneration in vivo.

We showcase the development of self-assembled, three-dimensional bundles of longitudinally aligned astrocytic somata and processes within a novel biomaterial encasement. These engineered &#34;living scaffolds&#34;, exhibiting micron-scale diameter yet extending centimeters in length, may serve as test-beds to study neurodevelopmental mechanisms or facilitate neuroregeneration by directing neuronal migration and/or axonal pathfinding.

Neurotrauma and neurodegenerative disease often result in lasting neurological deficits due to the limited capacity of the central nervous system (CNS) to ...

Fabrication of Custom Agarose Wells for Cell Seeding and Tissue Ring Self-assembly Using 3D-Printed Molds

Engineered tissues are being used clinically for tissue repair and replacement, and are being developed as tools for drug screening and human disease modeling. Self-assembled tissues offer advantages over scaffold-based tissue engineering, such as enhanced matrix deposition, strength, and function. However, there are few available methods for fabricating 3D tissues without seeding cells on or within a supporting scaffold. Previously, we developed a system for fabricating self-assembled tissue rings by seeding cells into non-adhesive agarose wells. A polydimethylsiloxane (PDMS) negative was first cast in a machined polycarbonate mold, and then agarose was gelled in the PDMS negative to create ring-shaped cell seeding wells. However, the versatility of this approach was limited by the resolution of the tools available for machining the polycarbonate mold. Here, we demonstrate that 3D-printed plastic can be used as an alternative to machined polycarbonate for fabricating PDMS negatives. The 3D-printed mold and revised mold design is simpler to use, inexpensive to produce, and requires significantly less agarose and PDMS per cell seeding well. We have demonstrated that the resulting agarose wells can be used to create self-assembled tissue rings with customized diameters from a variety of different cell types. Rings can then be used for mechanical, functional, and histological analysis, or for fabricating larger and more complex tubular tissues.

This protocol describes a platform for fabricating self-assembled tissue rings in variable sizes using a customized 3D-printed plastic mold. PDMS negatives are cured in the 3D-printed mold; then agarose is cast in the cured PDMS negatives. Cells are seeded into the resulting agarose wells where they aggregate into tissue rings.

Engineered tissues are being used clinically for tissue repair and replacement, and are being developed as tools for drug screening and human disease ...

A Novel Tenorrhaphy Suture Technique with Tissue Engineered Collagen Graft to Repair Large Tendon Defects

Surgical management of large tendon defects with tendon grafts is challenging, as there are a finite number of sites where donors can be readily identified and used. Currently, this gap is filled with tendon auto-, allo-, xeno-, or artificial grafts, but clinical methods to secure them are not necessarily translatable to animals because of the scale. In order to evaluate new biomaterials or study a tendon graft made up of collagen type 1, we have developed a modified suture technique to help maintain the engineered tendon in alignment with the tendon ends. Mechanical properties of these grafts are inferior to the native tendon. To incorporate engineered tendon into clinically relevant models of loaded repair, a strategy was adopted to offload the tissue engineered tendon graft and allow for the maturation and integration of the engineered tendon in vivo until a mechanically sound neo-tendon was formed. We describe this technique using incorporation of the collagen type 1 tissue engineered tendon construct.

In this paper, we present an in vitro and in situ protocol to repair a tendon gap of up to 1.5 cm by filling it with engineered collagen graft. This was performed by developing a modified suture technique to take the mechanical load until the graft matures into the host tissue.

Surgical management of large tendon defects with tendon grafts is challenging, as there are a finite number of sites where donors can be readily ...

Tissue-Engineered Graft for Circumferential Esophageal Reconstruction in Rats

The use of biocompatible materials for circumferential esophageal reconstruction is a technically challenging task in rats and requires an optimal implant technique with nutritional support. Recently, there have been many attempts at esophageal tissue engineering, but the success rate has been limited due to difficulty in early epithelization in the special environment of peristalsis. Here, we developed an artificial esophagus that can improve the regeneration of the esophageal mucosa and muscle layers through a two-layered tubular scaffold, a mesenchymal stem cell-based bioreactor system, and a bypass feeding technique with modified gastrostomy. The scaffold is made of polyurethane (PU) nanofibers in a cylindrical shape with a three-dimensional (3D) printed polycaprolactone strand wrapped around the outer wall. Prior to transplantation, human-derived mesenchymal stem cells were seeded into the lumen of the scaffold, and bioreactor cultivation was performed to enhance cellular reactivity. We improved the graft survival rate by applying surgical anastomosis and covering the implanted prosthesis with a thyroid gland flap, followed by temporary nonoral gastrostomy feeding. These grafts were able to recapitulate the findings of initial epithelialization and muscle regeneration around the implanted sites, as demonstrated by histological analysis. In addition, increased elastin fibers and neovascularization were observed in the periphery of the graft. Therefore, this model presents a potential new technique for circumferential esophageal reconstruction.

Esophageal reconstruction is a challenging procedure, and development of a tissue-engineered esophagus that enables regeneration of esophageal mucosa and muscle and that can be implanted as an artificial graft is necessary. Here, we present our protocol to generate an artificial esophagus, including scaffold manufacturing, bioreactor cultivation, and various surgical techniques.

The use of biocompatible materials for circumferential esophageal reconstruction is a technically challenging task in rats and requires an optimal implant ...