Name: minced tissue in compressed collagen: a cell-containing biotransplant for single-staged reconstructive repair
Uploaded: 2016-02-24T13:00:00
Description: Watch this Scientific Journal Video about Minced Tissue in Compressed Collagen: A Cell-containing Biotransplant for Single-staged Reconstructive Repair at JoVE.com

The authors thank the Swedish Society for Medical Research, the Promobilia Foundation, the Crown Princess Lovisa Foundation, the Freemason Foundation for Children&#8217;s Welfare, the Swedish Society of Medicine, the Solstickan Foundation, Karolinska Institutet, and the Stockholm City Council for financial support.

All animal protocols were pre-approved by the Stockholm County Committee on Animals and all procedures conformed to the regulations for animal use, as well as relevant federal statutes.
1. Animal Procedures
<ol>
	<li>Preparing the Animal for Surgery
	<ol>
		<li>Prepare the surgical table with all the materials and instruments needed for the operation under sterile conditions. Perform the surgery exclusively under sterile conditions to reduce the risk of infection and optimize the conditions ...

<ol>
	<li>Rheinwald, J. G., Green, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Serial+cultivation+of+strains+of+human+epidermal+keratinocytes:+the+formation+of+keratinizing+colonies+from+single+cells.">Serial cultivation of strains of human epidermal keratinocytes: the formation of keratinizing colonies from single cells.</a> Cell. 6, 331-343 (1975).</li><li>Fossum, M., Nordenskjold, A., Kratz, 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+of+multilayered+urinary+tissue+in+vitro.">Engineering of multilayered urinary tissue in vitro.</a> Tissue Engineering. 10, 175-180 (2004).</li><li>Salmikangas, 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=Manufacturing,+characterization+and+control+of+cell-based+medicinal+products:+challenging+paradigms+toward+commercial+use.">Manufacturing, characterization and control of cell-based medicinal products: challenging paradigms toward commercial use.</a> Regen Med. 10, 65-78 (2015).</li><li>Fossum, 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=Minced+skin+for+tissue+engineering+of+epithelialized+subcutaneous+tunnels.">Minced skin for tissue engineering of epithelialized subcutaneous tunnels.</a> Tissue Engineering. Part A. 15, 2085-2092 (2009).</li><li>Fossum, 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=Minced+urothelium+to+create+epithelialized+subcutaneous+conduits.">Minced urothelium to create epithelialized subcutaneous conduits.</a> The Journal of Urology. 184, 757-761 (2010).</li><li>Reinfeldt Engberg, G., Lundberg, J., Chamorro, C. L., Nordenskjold, A., Fossum, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transplantation+of+autologous+minced+bladder+mucosa+for+a+one-step+reconstruction+of+a+tissue+engineered+bladder+conduit.">Transplantation of autologous minced bladder mucosa for a one-step reconstruction of a tissue engineered bladder conduit.</a> BioMed Research International. 2013, 212734 (2013).</li><li>Meek, C. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Successful+microdermagrafting+using+the+Meek-Wall+microdermatome.">Successful microdermagrafting using the Meek-Wall microdermatome.</a> Am J Surg. 96, 557-558 (1958).</li><li>Tanner, J. C., Vandeput, J., Olley, J. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Mesh+skin+graft.">The Mesh skin graft.</a> Plastic and Reconstructive Surgery. 34, 287-292 (1964).</li><li>Svensjo, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Autologous+skin+transplantation:+comparison+of+minced+skin+to+other+techniques.">Autologous skin transplantation: comparison of minced skin to other techniques.</a> The Journal of Surgical Research. 103, 19-29 (2002).</li><li>Ajalloueian, F., Zeiai, S., Rojas, R., Fossum, M., Hilborn, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=One-stage+tissue+engineering+of+bladder+wall+patches+for+an+easy-to-use+approach+at+the+surgical+table.">One-stage tissue engineering of bladder wall patches for an easy-to-use approach at the surgical table.</a> Tissue Engineering. Part C, Methods. 19, 688-696 (2013).</li><li>Engelhardt, E. 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=A+collagen-poly(lactic+acid-co-varepsilon-caprolactone)+hybrid+scaffold+for+bladder+tissue+regeneration.">A collagen-poly(lactic acid-co-varepsilon-caprolactone) hybrid scaffold for bladder tissue regeneration.</a> Biomaterials. 32, 3969-3976 (2011).</li><li>Brown, R. A., Wiseman, M., Chuo, C. B., Cheema, U., Nazhat, S. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrarapid+engineering+of+biomimetic+materials+and+tissues:+fabrication+of+nano-+and+microstructures+by+plastic+compression.">Ultrarapid engineering of biomimetic materials and tissues: fabrication of nano- and microstructures by plastic compression.</a> Adv Funct Mater. 15, 1762-1770 (2005).</li><li>Fumagalli Romario, U., Puccetti, F., Elmore, U., Massaron, S., Rosati, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Self-gripping+mesh+versus+staple+fixation+in+laparoscopic+inguinal+hernia+repair:+a+prospective+comparison.">Self-gripping mesh versus staple fixation in laparoscopic inguinal hernia repair: a prospective comparison.</a> Surg Endosc. 27, 1798-1802 (2013).</li><li>Muangman, 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=Complex+Wound+Management+Utilizing+an+Artificial+Dermal+Matrix.">Complex Wound Management Utilizing an Artificial Dermal Matrix.</a> Annals of Plastic Surgery. 57, 199-202 (2006).</li><li>Ajalloueian, F., Zeiai, S., Fossum, M., Hilborn, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Constructs+of+electrospun+PLGA,+compressed+collagen+and+minced+urothelium+for+minimally+manipulated+autologous+bladder+tissue+expansion.">Constructs of electrospun PLGA, compressed collagen and minced urothelium for minimally manipulated autologous bladder tissue expansion.</a> Biomaterials. 35, 5741-5748 (2014).</li><li>Orabi, H., AbouShwareb, T., Zhang, Y., Yoo, J. J., Atala, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell-seeded+tubularized+scaffolds+for+reconstruction+of+long+urethral+defects:+a+preclinical+study.">Cell-seeded tubularized scaffolds for reconstruction of long urethral defects: a preclinical study.</a> Eur Urol. 63, 531-538 (2013).</li><li>Blais, M., Parenteau-Bareil, R., Cadau, S., Berthod, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concise+review:+tissue-engineered+skin+and+nerve+regeneration+in+burn+treatment.">Concise review: tissue-engineered skin and nerve regeneration in burn treatment.</a> Stem Cells Transl Med. 2, 545-551 (2013).</li><li>Serpooshan, V., Muja, N., Marelli, B., Nazhat, S. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fibroblast+contractility+and+growth+in+plastic+compressed+collagen+gel+scaffolds+with+microstructures+correlated+with+hydraulic+permeability.">Fibroblast contractility and growth in plastic compressed collagen gel scaffolds with microstructures correlated with hydraulic permeability.</a> J Biomed Mater Res A. 96, 609-620 (2011).</li></ol>

This study presents an easy-to-use approach to produce bladder wall patches with autologous tissue for transplantation at the surgical table. The patches are formed by the combination of a biodegradable polymer knitting in the middle and collagen with and without minced tissue in the outer surfaces in combination with plastic compression. Plastic compression is a method previously described by other authors and can be defined as a rapid expulsion of fluid from collagen gels12,13. Minced tissue of bladder mucos...

Most tissue engineering studies on transplantation to the skin and urogenital tract include autologous cell harvests from healthy tissue and cell expansion in specially equipped cell-culturing facilities1,2.
After cell expansion, cells are usually stored for later use when the patient is prepared to receive the autograft. Nitrogen freezers allow long-term storage at low temperatures of -150 &#176;C or lower. The process of freezing must be careful and controlled in order not to lose the cells. One risk of cell death is crystallization of intracellular water during the thawing process, which can lead to rupture of the cell membranes. Cell freezing is usually performed by slow and controlled cooling (-1 &#176;C per min), using a high concentration of cells, fetal bovine serum, and dimethyl sulfoxide. After thawing, the cells need to be processed again by removing the freezing medium and culturing on cell culture plastic or a biomaterial before transplantation back to the patient.
All the above-mentioned steps are time-consuming, laborious, and costly3. In addition, all in vitro processing of cells intended for patient transplantation are highly regulated and requires well-trained and accredited personnel and laboratories4. All in all, to procure a safe and reliable manufacturing process, the technique could only be established in a very small number of technically advanced centers and a wider use in common surgical disorders is doubtful.
In order to overcome the limitations of cell culturing in the laboratory environment, the concept of transplanting minced tissue for cell expansion in vivo is introduced by using the body itself as a bioreactor. For these purposes, the autografts would preferentially be transplanted on a 3D mold according to the shape that is needed for the final reconstruction of the organ of interest5-7.
Originally, the idea of transplanting minced epithelium was presented by Meek in 1958&#160;when he described how epithelium grows from the edges of a wound. He demonstrated that a small piece of skin would increase its margins and thereby its potential for cell expansion by 100% by cutting the piece twice in perpendicular directions (Figure 1)8. The theory has been supported by the use of meshed partial thickness skin grafts for skin transplantation9 and in skin wound healing models10.
<img alt="Figure 1" src="/files/ftp_upload/53061/53061fig1.jpg" width="600" /> 
Figure 1: Meek theory. According to Meek&#8217;s theory, epithelium grows from the edges of a wound. By increasing the area exposed by the mincing technology, minced tissue epithelializes wounds from many spots.
The present study is based on the hypothesis that the same principle could be applied to the subcutaneous tissue by placing minced epithelium around a mold. The epithelial cells would mobilize from minced transplants (reorganize), cover the wound areas (migrate) and divide (expand) in order to form a continuous neoepithelium that covers the wound area and separates the foreign body (the mold) from the inner body (Figure 2).
<img alt="Figure 2" src="/files/ftp_upload/53061/53061fig2.jpg" /> 
Figure 2: Cartoon of a 3D mold with minced epithelium for in vivo intracorporal tissue expansion according to the theory of Meek. By using minced tissue placed on a mold and then transplanted to the subcutaneous tissue, the hypothesis is that the epithelial cells migrate from the edges of the minced tissue, reorganize, and expand so as to form a continuous neoepithelium that covers the wound area and separates the foreign body (the mold) from the inner body.
Although previous in vivo studies show promising results, further improvements could be achieved by reinforcing the autografts so that the regenerated epithelium could withstand mechanical trauma better7. For these purposes, important prerequisites for a successful biomaterial were identified, such as: easy diffusion of nutrients and waste products, possibility to mold in a 3D manner and easiness of surgical handling. Conclusions were made that these needs could be met by adding a composite biomaterial to the minced tissue.
The current study aimed at developing a scaffold composed of minced tissue in plastic-compressed collagen containing a reinforcing core of a biodegradable fabric. By these means, viable cells could migrate from the minced tissue particles and proliferate with morphological features characteristic of the original epithelium (skin or urothelium). Using plastic compression, the scaffold was reduced in size from 1 cm to about 420&#8201;&#181;m as the minced particles were encased in the upper layer collagen. The core fabric could be any polymer but needs to be modified with a hydrophilic surface in order to interlink with the covering collagen layers11.
The method provided an enhanced scaffold integrity by incorporating a knitted mesh consisting of poly(&#949;-caprolactone) (PCL) within two plastic compressed collagen gels using it as a scaffold for culturing minced bladder mucosa or minced skin from pigs. The construct was maintained in cell culture conditions for up to 6 weeks in vitro, demonstrating successful formation of a stratified, multilayered urothelium or squamous skin epithelium on the top of a well-consolidated hybrid construct. The construct was easy to handle and could be sutured in place for bladder augmentation purposes or covering of skin defects. All parts of the tissue scaffold are FDA-approved and the technique could be used for single-stage procedures by tissue harvesting, mincing, plastic compression, and transplanting back to the patient as a single-staged intervention. The procedure could be performed for tissue expansion and reconstruction under sterile conditions in any general surgery unit.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Silicone catheter 10-French</td>
			<td></td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>DMEM 10X</td>
			<td>Gibco</td>
			<td>31885-023</td>
			<td>Plastic compression section 4</td>
		</tr>
		<tr>
			<td>24 well plates</td>
			<td>Falcon</td>
			<td>08-772-1</td>
			<td>Plastic compression section 4</td>
		</tr>
		<tr>
			<td>3&#39;3,&#39;5-Triiodothyronine</td>
			<td>Sigma-Aldrich</td>
			<td>IRMM469</td>
			<td>&#160; In vitro culture; Section 5</td>
		</tr>
		<tr>
			<td>4% PFA</td>
			<td>Labmed Solutions</td>
			<td>200-001-8</td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>70% ethanol</td>
			<td>Histolab</td>
			<td></td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>ABC Elite kit: Biotin -Streptavidin detection kit</td>
			<td>Vector</td>
			<td>PK6102</td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>Absolute ethanol</td>
			<td>Histolab</td>
			<td>1399.01</td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>Adenine</td>
			<td>Sigma-Aldrich</td>
			<td>A8626</td>
			<td>&#160; In vitro culture; Section 5</td>
		</tr>
		<tr>
			<td>Atropine 25 &#956;g/kg&#160;</td>
			<td>Temgesic, RB Pharmaceuticals, Great Britain</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Azaperone 2&#8201;mg/kg&#160;</td>
			<td>Stresnil, Janssen-Cilag, Pharma, Austria</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Biosafety Level 2 hood&#160;</td>
			<td></td>
			<td></td>
			<td>Plastic compression; Section 4</td>
		</tr>
		<tr>
			<td>Blocking solution:&#160; Normal serum from the same species as the secondary secondary antibody was generated in.</td>
			<td>Vector</td>
			<td>The blocking solution depends of the&#160; origin of&#160; first antibody</td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>Buprenorphine 45 &#956;g/kg</td>
			<td>Atropin, Mylan Inc, Canonsburg, PA</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Carprofen 3&#8201;mg/kg&#160;&#160;&#160;</td>
			<td>Rimadyl, Orion Pharma, Sweden</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Chlorhexidine gluconate&#160;</td>
			<td>Hibiscrub 40&#8201;mg/mL, Regent Medical, England</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Cholera toxin&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>C8052</td>
			<td>&#160; In vitro culture; Section 5</td>
		</tr>
		<tr>
			<td>Coplin jar: staining jar for boiling</td>
			<td>Histolab</td>
			<td>6150</td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>Stainless mold&#160; (33x22x10 mm) custom made</td>
			<td></td>
			<td></td>
			<td>Plastic compression; Section 4</td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>Gibco</td>
			<td>3188-5023</td>
			<td>Plastic compression section 4. Keep on ice&#160; when using it in plastic compression</td>
		</tr>
		<tr>
			<td>Epidermal growth factor</td>
			<td>Sigma-Aldrich</td>
			<td>E9644</td>
			<td>&#160; In vitro culture; Section 5</td>
		</tr>
		<tr>
			<td>Ethilon (non-absorbable monofilament for skin sutures)</td>
			<td>Ethicon</td>
			<td></td>
			<td>Surgery, Section 1</td>
		</tr>
		<tr>
			<td>Fetal bovine serum (FBS)</td>
			<td>Gibco</td>
			<td>10437-036</td>
			<td>Plastic compression section 4</td>
		</tr>
		<tr>
			<td>Forceps (Adison with tooth)</td>
			<td></td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Gauze (Gazin Mullkompresse)&#160;</td>
			<td></td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Ham&#180;s F12</td>
			<td>Gibco</td>
			<td>31765-027</td>
			<td>Plastic compression section 4</td>
		</tr>
		<tr>
			<td>Hematoxylin</td>
			<td>Histolab</td>
			<td>1820</td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>Humidity chamber</td>
			<td>DALAB</td>
			<td></td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>Hydrocortisone</td>
			<td>Sigma-Aldrich</td>
			<td>H0888</td>
			<td>&#160; In vitro culture; Section 5</td>
		</tr>
		<tr>
			<td>Hydrogen peroxide Solution 30%</td>
			<td>Sigma-Aldrich</td>
			<td>H1009</td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>Insulin</td>
			<td>Sigma-Aldrich</td>
			<td>I3536</td>
			<td>&#160; In vitro culture; Section 5</td>
		</tr>
		<tr>
			<td>Isoflurane&#160;</td>
			<td>Isoflurane, Baxter, Deerfield, IL</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Lidocaine 5 mg/ml</td>
			<td>Xylocaine, AstraZeneca, Sweden</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Lucose 25&#8201;mg/mL&#160;</td>
			<td>Baxter, Deerfield, IL</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Marker pen pap pen</td>
			<td>Sigma-Aldrich</td>
			<td>Z377821-1EA</td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>Medetomidine 25 &#956;g/kg&#160;</td>
			<td>Domitor, Orion Pharma, Sweden</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Mincing device</td>
			<td>Applied Tissue Technologies LLC</td>
			<td></td>
			<td>&#160;Minced tissue preparation, section 2</td>
		</tr>
		<tr>
			<td>Monocryl (absorbable monofilament)</td>
			<td>Ethicon</td>
			<td></td>
			<td>Surgery, Section 1</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma-Aldrich</td>
			<td>S7653</td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>NaOH 1N</td>
			<td>Merck Millipore</td>
			<td>106462</td>
			<td>Plastic compression section 4 and cell culture</td>
		</tr>
		<tr>
			<td>Nylon mesh, 110 uM thick pore size 0.04 sqmm</td>
			<td></td>
			<td></td>
			<td>Plastic compression; Section 4</td>
		</tr>
		<tr>
			<td>Oculentum simplex APL: ointment for eye protection</td>
			<td>APL</td>
			<td>Vnr 336164</td>
			<td>Surgery, Section 1</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>Gibco</td>
			<td>14190-094</td>
			<td>Plastic compression section 4</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>Gibco</td>
			<td>15140-122</td>
			<td>Plastic compression section 4</td>
		</tr>
		<tr>
			<td>Phenobarbiturate 15&#8201;mg/kg&#160;</td>
			<td>Pentobarbital, APL, Sweden</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>PLGA Knitted fabric</td>
			<td></td>
			<td></td>
			<td>Plastic compression; Section 4</td>
		</tr>
		<tr>
			<td>Rat-tail collagen</td>
			<td>First LINK, Ltd, UK</td>
			<td>60-30-810</td>
			<td>Plastic compression section 4, keep on ice</td>
		</tr>
		<tr>
			<td>Scalpel blade - 15</td>
			<td></td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Shaving shears</td>
			<td></td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Stainless stell mesh, 400 uM thick pore size&#160;</td>
			<td></td>
			<td></td>
			<td>Plastic compression; Section 4</td>
		</tr>
		<tr>
			<td>Steril gloves</td>
			<td></td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Sterile gowns</td>
			<td></td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Sterile drapes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sterilium</td>
			<td>Bode Chemie HAMBURG</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Suture Thread Ethilon</td>
			<td></td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>TE-solution (antigen unmasking solution) consist of 10 mM Tris and 1 mM EDTA, pH 9.0</td>
			<td></td>
			<td></td>
			<td>10 mM Tris/1 mM EDTA,&#160; adjust pH to&#160; 9.0</td>
		</tr>
		<tr>
			<td>Tiletamine hypochloride 2,5&#8201;mg/kg</td>
			<td></td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Transferrin&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>T8158</td>
			<td>&#160; In vitro culture; Section 5</td>
		</tr>
		<tr>
			<td>Trizma Base, H2NC&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>T6066</td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>Vector VIP kit: Enzyme&#160; peroxidase substrate&#160; kit</td>
			<td>Vector</td>
			<td>SK4600</td>
			<td>Immunocytochemistry; Section 6</td>
		</tr>
		<tr>
			<td>Vicryl (absorbable braded)</td>
			<td>Ethicon</td>
			<td></td>
			<td>Surgery, Section 1</td>
		</tr>
		<tr>
			<td>Tris buffer pH 7.6 (washing buffer)</td>
			<td></td>
			<td></td>
			<td>TE solution: Make 10X&#160; (0,5M Tris, 1,5M NaCl) by mixing: 60,6 g Tris (Trizma Base, H2NC(CH2OH)3, M=121.14 g/mol), add 800 ml&#160; distilled water adjust the pH till 7.6, add 87,7 g NaCl and fill to 1000 ml with&#160; distilled water. Dilute to 1X with distilled water.</td>
		</tr>
		<tr>
			<td>X-tra solv (solvent)</td>
			<td>DALAB</td>
			<td>41-5213-810</td>
			<td>Immunocytochemistry; Section 6. Use under fume hood</td>
		</tr>
		<tr>
			<td>Zolazepam hypochloride</td>
			<td>Zoletil, Virbac, France</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Depilatory wax strips</td>
			<td>Veet</td>
			<td></td>
			<td>Preparing the animal for surgery , Section 1</td>
		</tr>
		<tr>
			<td>Pentobarbital sodium</td>
			<td>Lundbeck</td>
			<td></td>
			<td>Termination, Section 3</td>
		</tr>
	</tbody>
</table>

minced tissue in compressed collagen: a cell-containing biotransplant for single-staged reconstructive repair

Conventional techniques for cell expansion and transplantation of autologous cells for tissue engineering purposes can take place in specially equipped human cell culture facilities. These methods include isolation of cells in single cell suspension and several laborious and time-consuming events before transplantation back to the patient. Previous studies suggest that the body itself could be used as a bioreactor for cell expansion and regeneration of tissue in order to minimize ex vivo manipulations of tissues and cells before transplanting to the patient. The aim of this study was to demonstrate a method for tissue harvesting, isolation of continuous epithelium, mincing of the epithelium into small pieces and incorporating them into a three-layered biomaterial. The three-layered biomaterial then served as a delivery vehicle, to allow surgical handling, exchange of nutrition across the transplant, and a controlled degradation. The biomaterial consisted of two outer layers of collagen and a core of a mechanically stable and slowly degradable polymer. The minced epithelium was incorporated into one of the collagen layers before transplantation. By mincing the epithelial tissue into small pieces, the pieces could be spread and thereby the propagation of cells was stimulated. After the initial take of the transplants, cell expansion and reorganization would take place and extracellular matrix mature to allow ingrowth of capillaries and nerves and further maturation of the extracellular matrix. The technique minimizes ex vivo manipulations and allow cell harvesting, preparation of autograft, and transplantation to the patient as a simple one-stage intervention. In the future, tissue expansion could be initiated around a 3D mold inside the body itself, according to the specific needs of the patient. Additionally, the technique could be performed in an ordinary surgical setting without the need for sophisticated cell culturing facilities.

This study presents a method that shows how to produce a biomaterial for transplantation using plastic compression of collagen and minced tissue.
Bladder mucosa and skin can be harvested and then mechanically minced into small particles (Figure 3). By plastic compression, the minced particles are incorporated within the composite scaffold composed of a centrally placed biodegradable polymer that is mechanically strong within outer layers of a collagen gel (Figure 4</st...

Watch this Scientific Journal Video about Minced Tissue in Compressed Collagen: A Cell-containing Biotransplant for Single-staged Reconstructive Repair at JoVE.com

Minced Tissue in Compressed Collagen: A Cell-containing Biotransplant for Single-staged Reconstructive Repair

Tissue engineering often includes in vitro expansion in order to create autografts for tissue regeneration. In this study a method for tissue expansion, regeneration, and reconstruction in vivo was developed in order to minimize the processing of cells and biological materials outside the body.

Conventional techniques for cell expansion and transplantation of autologous cells for tissue engineering purposes can take place in specially equipped ...

The overall goal of the following procedure is to transplant autologous tissue for its expansion during reconstructive surgery. This is accomplished by first harvesting a biopsy from the tissue of interest. Next, the biopsy is minced and a plastic compressed polycapro-lactone, or PCL, collagen autograft is constructed.The PCL and otologous minced tissues are then integrated to create the 3D scaffold. We have used a one to six expansion rate. Next, the scaffold is transplanted back into the subject.Ultimately, the regeneration of the autografted tissue can be assessed by immunohistochemical analysis of the proliferation and reorganization of the cells within the scaffolds and minced tissue particles. This method will be demonstrated in an animal model, on skin, and on urothelium. The implication of this technique extends toward the treatment of severely malformed tissues or after trauma in instances where there's severe lack of tissue for the surgical repair.The main advantage of this technique over existing methods, like in vitro culturing, is that this method can be performed as a one-stage surgical procedure. Visual demonstration of this method is critical, as the steps from the tissue harvest to the transplantation need to be performed under sterile conditions. To obtain a porcine bladder biopsy specimen, first, grasp the bladder with the forceps, and use a sterilized measuring tape to determine the dimensions of the tissue.Next, use a sterilized pen to mark an ellipsis shaped biopsy two by one centimeter, aiming for a one to six expansion rate. Then, excise the marked tissue with a scalpel, and place the bladder biopsy specimen in DMEM under sterile conditions. To harvest a skin biopsy specimen, use a dermatome to harvest a 0.3 millimeter partial thickness specimen.Then, place the tissue in DMEM and cover the wound area with a dressing. Next, wash the bladder biopsy twice in DMEM and transfer the tissue onto a sterilized dissecting plate, with the mucosa facing upwards. Using dissection pins, fix one side of the specimen to the plate and use fine scissors and forceps to separate the mucosal tissue from the detrusor muscle.Then, place a mincing device on top of the mucosa and pass it vertically and horizontally from one end of the tissue to the other to obtain 0.8 by 0.8 millimeter pieces of minced tissue. Note that the mincing device needs to be pressed on the tissue while running over it. To prepare a plastic compressed collagen autograft, first add one normal sodium hydroxide drop by drop into 10X DMEM supplemented with collagen type I until the medium turns from intense yellow to pink.After confirming a pH of 7.4 to 8, carefully mix two milliliters of DMEM into the solution. Then, plate approximately two milliliters of collagen into a well of a 20x30x10 millimeter steel rectangular mold and incubate the collagen for ten minutes. When the collagen has set, plate the appropriate volume of PCL biomaterial on top of the gelled collagen and pour the remaining six milliliters of collagen on top of the PCL.Place the mold back into the incubator for another 20 minutes. Next, stack a thick layer of gauze pads onto a sterile surface. Then, place a 400 micron thick stainless steel mesh on top of the gauze, followed by a 110 micron thick sheet of nylon mesh.Gently transfer the collagen gel onto the nylon mesh and carefully remove the rectangular steel mold. Transfer the minced tissue onto the collagen. Here, we aim at a one to six expansion rate.Then, place a new layer of nylon mesh on top of the collagen gel and tissue, then place a second steel mesh on top of the nylon mesh, followed by a loading plate weighing a minimum of 120 grams. After five minutes, remove the weight, steel meshes, and nylon from the autograft. For in vitro culture of the autograft, first cut the thinned construct into pieces small enough to fit into 12 well plates.Then, add one milliliter of keritinocyte medium to each well and incubate the tissues for three to six weeks. To transplant an autograft with minced bladder mucosa to a pig bladder, moisten the graft with DMEM. Then, graft the construct to the healthy tissue with fine running monofilament sutures.Confirm that the graft is water tight by filling the bladder with saline through the indwelling urinary catheter. To transplant an autograft with minced skin epidermis to a full thickness wound, moisten the graft with DMEM. Then, using interrupted sutures in the corners and middle of the autograft, attach the construct to the bottom of the skin full thickness wound.Finally, cover the wound with a plastic dressing to keep it moist. As observed in this image of a minced skin autotransplant, the composite biograft can sustain grasping, suturing, and surgical handling. Immunohistochemistry at different time points during the in vitro culture reveals that the cells proliferate, migrate, and reorganize into a continuous epithelium with a microarchitecture typical for the cell phenotype.For example, at two weeks, the cell layer on the surface of the skin autograft is approximately two layers thick. To the right, bladder epithelium is about eight layers thick after the same culture period. After five to six weeks, the continuous epithelium is approximately eight to ten cell layers thick in both minced skin epithelium and minced bladder mucosa autografts.Compared to tissue expansion in vitro, this method is quick, less labor intensive, and does not require sophisticated laboratory resources. In addition, all parts are FDA approved, allowing their use in standard surgical setting. While attempting this procedure, it's important to remember to prepare the gel, biotransplants, and autologous tissues under sterile conditions.Following this procedure and other methods like in vitro culture of the cells can be performed to answer additional questions about cell proliferation and differentiation. After its development, this technique may pave the way for researchers in the field of regenerative medicine. By these means, we could treat severe malformations in the skin or urinary system with autologous tissue engineered transplants.

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Research

JoVE Journal

Bioengineering

Organotypic Collagen I Assay: A Malleable Platform to Assess Cell Behaviour in a 3-Dimensional Context

Cell migration is fundamental to many aspects of biology, including development, wound healing, the cellular responses of the immune system, and metastasis of tumor cells. Migration has been studied on glass coverslips in order to make cellular dynamics amenable to investigation by light microscopy. However, it has become clear that many aspects of cell migration depend on features of the local environment including its elasticity, protein composition, and pore size, which are not faithfully represented by rigid two dimensional substrates such as glass and plastic 1. Furthermore, interaction with other cell types, including stromal fibroblasts 2 and immune cells 3, has been shown to play a critical role in promoting the invasion of cancer cells. Investigation at the molecular level has increasingly shown that molecular dynamics, including response to drug treatment, of identical cells are significantly different when compared in vitro and in vivo 4. 
Ideally, it would be best to study cell migration in its naturally occurring context in living organisms, however this is not always possible. Intermediate tissue culture systems, such as cell derived matrix, matrigel, organotypic culture (described here) tissue explants, organoids, and xenografts, are therefore important experimental intermediates. These systems approximate certain aspects of an in vivo environment but are more amenable to experimental manipulation such as use of stably transfected cell lines, drug treatment regimes, long term and high-resolution imaging. Such intermediate systems are especially useful as proving grounds to validate probes and establish parameters required to image the dynamic response of cells and fluorescent reporters prior to undertaking imaging in vivo 5. As such, they can serve an important role in reducing the need for experiments on living animals.

A method is described for the preparation of a 3-dimensional matrix consisting of collagen type I and primary human fibroblasts. This organotypic gel serves as a useful substrate to assess invasive cell migration because it mimics basic features of tissue stroma and is amenable to many forms of microscopy.

Cell migration is fundamental to many aspects of biology, including development, wound healing, the cellular responses of the immune system, and ...

Electric Field-controlled Directed Migration of Neural Progenitor Cells in 2D and 3D Environments

Endogenous electric fields (EFs) occur naturally in vivo and play a critical role during tissue/organ development and regeneration, including that of the central nervous system1,2. These endogenous EFs are generated by cellular regulation of ionic transport combined with the electrical resistance of cells and tissues. It has been reported that applied EF treatment can promote functional repair of spinal cord injuries in animals and humans3,4. In particular, EF-directed cell migration has been demonstrated in a wide variety of cell types5,6, including neural progenitor cells (NPCs)7,8. Application of direct current (DC) EFs is not a commonly available technique in most laboratories. We have described detailed protocols for the application of DC EFs to cell and tissue cultures previously5,11. Here we present a video demonstration of standard methods based on a calculated field strength to set up 2D and 3D environments for NPCs, and to investigate cellular responses to EF stimulation in both single cell growth conditions in 2D, and the organotypic spinal cord slice in 3D. The spinal cordslice is an ideal recipient tissue for studying NPC ex vivo behaviours, post-transplantation, because the cytoarchitectonic tissue organization is well preserved within these cultures9,10. Additionally, this ex vivo model also allows procedures that are not technically feasible to track cells in vivo using time-lapse recording at the single cell level. It is critically essential to evaluate cell behaviours in not only a 2D environment, but also in a 3D organotypic condition which mimicks the in vivo environment. This system will allow high-resolution imaging using cover glass-based dishes in tissue or organ culture with 3D tracking of single cell migration in vitro and ex vivo and can be an intermediate step before moving onto in vivo paradigms.

This protocol demonstrates methods used to establish 2D and 3D environments in custom-designed electrotactic chambers, which can track cells in vivo/ex vivo using time-lapse recording at the single cell level, in order to investigate galvanotaxis/electrotaxis and other cellular responses to direct current (DC) electric fields (EFs).

Endogenous electric fields (EFs) occur naturally in vivo and play a critical role during tissue/organ development and regeneration, including that of the ...

Fabrication and Application of Rose Bengal-chitosan Films in Laser Tissue Repair

Photochemical tissue bonding (PTB) is a sutureless technique for tissue repair, which is achieved by applying a solution of rose bengal (RB) between two tissue edges1,2. These are then irradiated by a laser that is selectively absorbed by the RB. The resulting photochemical reactions supposedly crosslink the collagen fibers in the tissue with minimal heat production3. In this report, RB has been incorporated in thin chitosan films to fabricate a novel tissue adhesive that is laser-activated. Adhesive films, based on chitosan and containing ~0.1 wt% RB, are fabricated and bonded to calf intestine and rat tibial nerves by a solid state laser (&lambda;=532 nm, Fluence~110 J/cm2, spot size~0.5 cm). A single-column tensiometer, interfaced with a personal computer, is used to test the bonding strength. The RB-chitosan adhesive bonds firmly to the intestine with a strength of 15 &plusmn; 6 kPa, (n=30). The adhesion strength drops to 2 &plusmn; 2 kPa (n=30) when the laser is not applied to the adhesive. The anastomosis of tibial nerves can be also completed without the use of sutures. A novel chitosan adhesive has been fabricated that bonds photochemically to tissue and does not require sutures.

Sutures are usually needed to repair tissue during surgical procedures. However, their application can be problematic as they are invasive and may damage tissue. The fabrication and application methods of a novel tissue adhesive are here reported. This adhesive film is laser-activated and does not require the use of sutures.

Photochemical tissue bonding (PTB) is a sutureless technique for tissue repair, which is achieved by applying a solution of rose bengal (RB) between two ...

An Improved Method for the Preparation of Type I Collagen From Skin

Soluble type 1 collagen (COL1) is used extensively as an adhesive substrate for cell cultures and as a cellular scaffold for regenerative applications. Clinically, this protein is widely used for cosmetic surgery, dermal injections, bone grafting, and reconstructive surgery. The sources of COL1 for these procedures are commonly nonhuman, which increases the potential for inflammation and rejection as well as xenobiotic disease transmission. In view of this, a method to efficiently and quickly purify COL1 from limited quantities of autologously-derived tissues would circumvent many of these issues; however, standard isolation protocols are lengthy and often require large quantities of collagenous tissues. Here, we demonstrate an efficient COL1 extraction method that reduces the time needed to isolate and purify this protein from about 10 days to less than 3 hr. We chose the dermis as our tissue source because of its availability during many surgical procedures. This method uses traditional extraction buffers combined with forceful agitation and centrifugal filtration to obtain highly-pure, soluble COL1 from small amounts of corium. Briefly, dermal biopsies are washed thoroughly in ice-cold dH2O after removing fat, connective tissue, and hair. The skin samples are stripped of noncollagenous proteins and polysaccharides using 0.5 M sodium acetate and a high speed bench-top homogenizer. Collagen from residual solids is subsequently extracted with a 0.075 M sodium citrate buffer using the homogenizer. These extracts are purified using 100,000 MW cut-off centrifugal filters that yield COL1 preparations of comparable or superior quality to commercial products or those obtained using traditional procedures. We anticipate this method will facilitate the utilization of autologously-derived COL1 for a multitude of research and clinical applications.

Traditional procedures for the isolation of soluble type 1 collagen (COL1) require about 10 days from start to finish because of lengthy buffer incubations and laborious resuspensions of fibrils. Here, we describe a means to purify COL1 from small dermal biopsies in less than 3 hr.

Soluble type 1 collagen (COL1) is used extensively as an adhesive substrate for cell cultures and as a cellular scaffold for regenerative applications. ...

Imaging Denatured Collagen Strands In vivo and Ex vivo via Photo-triggered Hybridization of Caged Collagen Mimetic Peptides

Collagen is a major structural component of the extracellular matrix that supports tissue formation and maintenance. Although collagen remodeling is an integral part of normal tissue renewal, excessive amount of remodeling activity is involved in tumors, arthritis, and many other pathological conditions. During collagen remodeling, the triple helical structure of collagen molecules is disrupted by proteases in the extracellular environment. In addition, collagens present in many histological tissue samples are partially denatured by the fixation and preservation processes. Therefore, these denatured collagen strands can serve as effective targets for biological imaging. We previously developed a caged collagen mimetic peptide (CMP) that can be photo-triggered to hybridize with denatured collagen strands by forming triple helical structure, which is unique to collagens. The overall goals of this procedure are i)&#160;to image denatured collagen strands resulting from normal remodeling activities in vivo, and ii) to visualize collagens in ex vivo tissue sections using the photo-triggered caged CMPs. To achieve effective hybridization and successful in vivo and ex vivo imaging, fluorescently labeled caged CMPs are either photo-activated immediately before intravenous injection, or are directly activated on tissue sections. Normal skeletal collagen remolding in nude mice and collagens in prefixed mouse cornea tissue sections are imaged in this procedure. The imaging method based on the CMP-collagen hybridization technology presented here could lead to deeper understanding of the tissue remodeling process, as well as allow development of new diagnostics for diseases associated with high collagen remodeling activity.

Imaging Denatured Collagen Strands In vivo and Ex vivo via Photo-triggered Hybridization of Caged Collagen Mimetic Peptides

This procedure demonstrates in vivo near IR fluorescence imaging of collagen remodeling activities in mice as well as ex vivo staining of collagens in tissue sections using caged collagen mimetic peptides that can be photo-triggered to hybridize with denatured collagen strands.

Collagen is a major structural component of the extracellular matrix that supports tissue formation and maintenance. Although collagen remodeling is an ...

Analysis of Cell Migration within a Three-dimensional Collagen Matrix

The ability to migrate is a hallmark of various cell types and plays a crucial role in several physiological processes, including&#160;embryonic development, wound healing, and immune responses. However, cell migration is also a key mechanism in cancer enabling these cancer cells to detach from the primary tumor to start metastatic spreading. Within the past years various cell migration assays have been developed to analyze the migratory behavior of different cell types. Because the locomotory behavior of cells markedly differs between a two-dimensional (2D) and three-dimensional (3D) environment it can be assumed that the analysis of the migration of cells that are embedded within a 3D environment would yield in more significant cell migration data. The advantage of the described 3D collagen matrix migration assay is that cells are embedded within a physiological 3D network of collagen fibers representing the major component of the extracellular matrix. Due to time-lapse video microscopy real cell migration is measured allowing the determination of several migration parameters as well as their alterations in response to pro-migratory factors or inhibitors. Various cell types could be analyzed using this technique, including lymphocytes/leukocytes, stem cells, and tumor cells. Likewise, also cell clusters or spheroids could be embedded within the collagen matrix concomitant with analysis of the emigration of single cells from the cell cluster/ spheroid into the collagen lattice. We conclude that the 3D collagen matrix migration assay is a versatile method to analyze the migration of cells within a physiological-like 3D environment.

Cell migration is a biological phenomenon that is involved in a plethora of physiological, such as wound healing and immune responses, and pathophysiological processes, like cancer. The 3D-collagen matrix migration assay is a versatile tool to analyze the migratory properties of different cell types within in a 3D physiological-like environment.

The ability to migrate is a hallmark of various cell types and plays a crucial role in several physiological processes, including&#160;embryonic ...

Generation of a Three-dimensional Full Thickness Skin Equivalent and Automated Wounding

In vitro models are a cost effective and ethical alternative to study cutaneous wound healing processes. Moreover, by using human cells, these models reflect the human wound situation better than animal models. Although two-dimensional models are widely used to investigate processes such as cellular migration and proliferation, models that are more complex are required to gain a deeper knowledge about wound healing. Besides a suitable model system, the generation of precise and reproducible wounds is crucial to ensure comparable results between different test runs. In this study, the generation of a three-dimensional full thickness skin equivalent to study wound healing is shown. The dermal part of the models is comprised of human dermal fibroblast embedded in a rat-tail collagen type I hydrogel. Following the inoculation with human epidermal keratinocytes and consequent culture at the air-liquid interface, a multilayered epidermis is formed on top of the models. To study the wound healing process, we additionally developed an automated wounding device, which generates standardized wounds in a sterile atmosphere.

The goal of this protocol is to build up a three-dimensional full thickness skin equivalent, which resembles natural skin. With a specifically constructed automated wounding device, precise and reproducible wounds can be generated under maintenance of sterility.

In vitro models are a cost effective and ethical alternative to study cutaneous wound healing processes. Moreover, by using human cells, these models ...

Engineering 3D Cellularized Collagen Gels for Vascular Tissue Regeneration

Synthetic materials are known to initiate clinical complications such as inflammation, stenosis, and infections when implanted as vascular substitutes. Collagen has been extensively used for a wide range of biomedical applications and is considered a valid alternative to synthetic materials due to its inherent biocompatibility (i.e., low antigenicity, inflammation, and cytotoxic responses). However, the limited mechanical properties and the related low hand-ability of collagen gels have hampered their use as scaffold materials for vascular tissue engineering. Therefore, the rationale behind this work was first to engineer cellularized collagen gels into a tubular-shaped geometry and second to enhance smooth muscle cells driven reorganization of collagen matrix to obtain tissues stiff enough to be handled.
The strategy described here is based on the direct assembling of collagen and smooth muscle cells (construct) in a 3D cylindrical geometry with the use of a molding technique. This process requires a maturation period, during which the constructs are cultured in a bioreactor under static conditions (without applied external dynamic mechanical constraints) for 1 or 2 weeks. The &#8220;static bioreactor&#8221; provides a monitored and controlled sterile environment (pH, temperature, gas exchange, nutrient supply and waste removal) to the constructs. During culture period, thickness measurements were performed to evaluate the cells-driven remodeling of the collagen matrix, and glucose consumption and lactate production rates were measured to monitor the cells metabolic activity. Finally, mechanical and viscoelastic properties were assessed for the resulting tubular constructs. To this end, specific protocols and a focused know-how (manipulation, gripping, working in hydrated environment, and so on) were developed to characterize the engineered tissues.

In this work, we present a technique for the rapid fabrication of living vascular tissues by direct culturing of collagen, smooth muscle cells and endothelial cells. In addition, a new protocol for the mechanical characterization of engineered vascular tissues is described.

Synthetic materials are known to initiate clinical complications such as inflammation, stenosis, and infections when implanted as vascular substitutes. ...

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

Despite huge efforts to decipher the anatomy, composition and function of the brain, it remains the least understood organ of the human body. To gain a deeper comprehension of the neural system scientists aim to simplistically reconstruct the tissue by assembling it in vitro from basic building blocks using a tissue engineering approach. Our group developed a tissue-engineered silk and collagen-based 3D brain-like model resembling the white and gray matter of the cortex. The model consists of silk porous sponge, which is pre-seeded with rat brain-derived neurons, immersed in soft collagen matrix. Polarized neuronal outgrowth and network formation is observed with separate axonal and cell body localization. This compartmental architecture allows for the unique development of niches mimicking native neural tissue, thus enabling research on neuronal network assembly, axonal guidance, cell-cell and cell-matrix interactions and electrical functions.

Insight into the complex actions of the brain requires advanced research tools. Here we demonstrate a novel silk-collagen-based 3D engineered model of neural tissue resembling brain-like architecture. The model can be used to study neuronal network assembly, axonal guidance, cell-cell interactions and electrical activity.

Despite huge efforts to decipher the anatomy, composition and function of the brain, it remains the least understood organ of the human body. To gain a ...

Layer-by-layer Collagen Deposition in Microfluidic Devices for Microtissue Stabilization

Although microfluidics provides exquisite control of the cellular microenvironment, culturing cells within microfluidic devices can be challenging. 3D culture of cells in collagen type I gels helps to stabilize cell morphology and function, which is necessary for creating microfluidic tissue models in microdevices. Translating traditional 3D culture techniques for tissue culture plates to microfluidic devices is often difficult because of the limited channel dimensions. In this method, we describe a technique for modifying native type I collagen to generate polycationic and polyanionic collagen solutions that can be used with layer-by-layer deposition to create ultrathin collagen assemblies on top of cells cultured in microfluidic devices. These thin collagen layers stabilize cell morphology and function, as shown using primary hepatocytes as an example cell, allowing for the long term culture of microtissues in microfluidic devices.

The creation of functional microtissues within microfluidic devices requires the stabilization of cell phenotypes by adapting traditional cell culture techniques to the limited spatial dimensions in microdevices. Modification of collagen allows the layer-by-layer deposition of ultrathin collagen assemblies that can stabilize primary cells, such as hepatocytes, as microfluidic tissue models.

Although microfluidics provides exquisite control of the cellular microenvironment, culturing cells within microfluidic devices can be challenging. 3D ...