Name: a novel surgical technique as a foundation for in vivo partial liver engineering in rat
Uploaded: 2018-10-06T14:00:00
Description: Watch this Scientific Journal Video about A Novel Surgical Technique As a Foundation for In Vivo Partial Liver Engineering in Rat at JoVE.com

The authors would like to thank Jens Geiling from the Institute of Anatomy I, Jena University Hospital, for producing the schematic drawings of rat liver anatomy.

The housing and all procedures carried out were in accordance with German animal welfare legislation. All gauze, covering clothes, and surgical instruments are autoclaved and prepared before the operation. All procedures are carried out under sterile conditions.
1. Preparation of the Rat for the Surgical Procedure
<ol>
	<li>Place the rat in an induction chamber and anesthetize the rat with 4% vaporized isoflurane and 100% oxygen at 0.5 L/min for about 3 min, until the rat is completely anest...

<ol>
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K., 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=Bioengineered+transplantable+porcine+livers+with+re-endothelialized+vasculature.">Bioengineered transplantable porcine livers with re-endothelialized vasculature.</a> Biomaterials. 40, 72-79 (2015).</li><li>Bao, 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=Construction+of+a+portal+implantable+functional+tissue-engineered+liver+using+perfusion-decellularized+matrix+and+hepatocytes+in+rats.">Construction of a portal implantable functional tissue-engineered liver using perfusion-decellularized matrix and hepatocytes in rats.</a> Cell Transplantation. 20, 753-766 (2011).</li><li>Pan, 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=In-vivo+organ+engineering:+Perfusion+of+hepatocytes+in+a+single+liver+lobe+scaffold+of+living+rats.">In-vivo organ engineering: Perfusion of hepatocytes in a single liver lobe scaffold of living rats.</a> The International Journal of Biochemistry &amp; Cell Biology. 80, 124-131 (2016).</li><li>Madrahimov, N., 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=Marginal+hepatectomy+in+the+rat:+from+anatomy+to+surgery.">Marginal hepatectomy in the rat: from anatomy to surgery.</a> Annals of Surgery. 244, 89-98 (2006).</li><li>Mussbach, F., Settmacher, U., Dirsch, O., Dahmen, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bioengineered+Livers:+A+New+Tool+for+Drug+Testing+and+a+Promising+Solution+to+Meet+the+Growing+Demand+for+Donor+Organs.">Bioengineered Livers: A New Tool for Drug Testing and a Promising Solution to Meet the Growing Demand for Donor Organs.</a> European Surgical Research. 57, 224-239 (2016).</li><li>Mussbach, F., Settmacher, U., Dirsch, O., Dahmen, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Liver+engineering+as+a+new+source+of+donor+organs:+A+systematic+review.">Liver engineering as a new source of donor organs: A systematic review.</a> Der Chirurg. 87, 504-513 (2016).</li><li>Xie, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+of+systemic+and+hepatic+hemodynamic+parameters+in+mice.">Monitoring of systemic and hepatic hemodynamic parameters in mice.</a> Journal of Visualized Experiments. 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By blocking and cannulating the left portal vein with a catheter as a fluid inlet and the left lateral hepatic vein with another catheter as a fluid outlet, we successfully generated an in vivo fluid bypass within the left lateral lobe, indicating that although the technique is highly challenging due to the small size of the vessels for cannulation and a high risk of causing bleeding, it is feasible. Even the rats undergoing a long perfusion period of 4 hours survived at least 1 week, showing that the rats could...

The indications for organ transplantation are constantly expanding. In contrast, organ donation rates and overall quality of organs are declining, leading to an increasing demand for grafts. The number of candidates added to the liver transplant waiting list continued to increase (e.g., in the United States, 11,340 patients were added in 2016, compared with 10,636 in 2015)1. Despite substantial efforts, the number of available organs does not meet clinical needs. Due to the increased incidence of liver disease, many patients with end-stage liver diseases die on the transplant waiting list before a donor organ becomes available. To meet the huge demand for donor liver grafts, alternative approaches using liver tissue engineering principles are being actively pursued2. Nowadays, a newly developed biological technique of liver engineering could potentially overcome this shortage.
Liver engineering consists of two steps: the generation of an acellular scaffold, followed by a repopulation of the scaffold. To obtain a biological acellular liver scaffold, the explanted liver is perfused via the vascular system with ionic or nonionic detergents, which can remove the cellular material from the liver. In most previous studies, a biological acellular liver scaffold was achieved by perfusion of the liver with a combination of sodium dodecyl sulfate and TritonX100. As a result, all cells were removed, whereas the structure of the extracellular matrix was maintained. The organ scaffolds were reseeded with mature cells, hepatocellular, as well as endothelial cell lines, and primary hepatocytes with or without the simultaneous application of endothelial cells or mesenchymal stem cells (MSC). Most researchers focus on ex vivo liver engineering3,4,5,6,7,8,9,10,11,12,13,14. However, in most previous studies, only small pieces of repopulated scaffold cubes were transplanted into different heterotopic implantation sites. In a few studies, partial repopulated scaffolds were transplanted as an auxiliary graft. However, the maximal reported survival time was only 72 h8,14. As far as we know, orthotopic transplantation of a repopulated full liver graft has not yet been performed or published about. The long-term function and transplantation of engineered organs are still in their infancy. Therefore, an alternative approach to ex vivo liver engineering is needed.
In vivo liver engineering may represent an alternative to study hepatic repopulation under physiological conditions. The advantages of in vivo liver engineering compared to ex vivo liver engineering are manifold. The in vivo repopulated partial liver scaffold is subjected to physiological blood perfusion with proper temperature, sufficient oxygen, nutrients, and growth factors in contrast to ex vivo perfusion with artificial culture medium. Furthermore, the remaining partial normal liver maintains the hepatic function, principally allowing long-term survival. Since an implanted ex vivo engineered liver graft is still incapable of sustaining the long-term survival of experimental animals by its liver function8,&#160;we envision that in vivo partial liver engineeringwould ultimately become a promising model to further study the evolution of engineered livers with longer survival observations than ex vivo.
Recently, one research group (Pan and colleagues) presented, for the first time, a technique of in vivo liver engineering15. They achieved the isolated perfusion of the right inferior liver lobe in living rats despite anatomic and technical challenges. They reported the first intraoperative results of in vivo repopulation using a rat primary hepatocyte cell line. However, the in vivo surgical perfusion model of Pan et al. has disadvantages. They achieved single liver lobe perfusion in rats at the expense of completely blocking the portal vein and inferior vena cava, which may cause severe harm to the animal. The experimental rats were sacrificed after only 6 hours of intraoperative observation time. Therefore, the in vivo liver lobe perfusion technique needs further improvement to achieve postoperative survival.
We developed a novel survival model for in vivo liver lobe perfusion, based on previous studies of the hepatic anatomy of rat16, the portal vein cannulation technique for hemodynamic monitoring in mice17, and liver bioengineering18,19. The key steps for the procedure are illustrated in Figure&#160;1A - 1E.
This technique is suitable for those who want to use this experimental in vivo perfusion model for basic research on partial organ treatment by infusion with drugs, in vivo decellularization as a chemical resection for organ diseases (e.g., liver cancer), in vivo cell culture in a decellularized matrix comparing ex vivo two-dimensional and three-dimensional cell culture systems20,21,22,23,24,25,26, and in vivo liver engineering by decellularization and repopulation.

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			<td height="21" style="height:21px;width:216px;">Perfusion Pump</td>
			<td style="width:104px;"></td>
			<td style="width:119px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Perfusor VI</td>
			<td colspan="2">B. Braun, Melsungen</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Catheter</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Versatus-W&#160; Catheter</td>
			<td>Terumo</td>
			<td>SR+DU2419PX</td>
			<td>24G, 0.74&#215;19mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Versatus-W&#160; Catheter</td>
			<td>Terumo</td>
			<td>SR+DU2225PX</td>
			<td>22G, 0.9&#215;25mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">micro surgical instrument</td>
			<td></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">micro scissors</td>
			<td>F&#183;S&#183;L</td>
			<td>No. 14058-09</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">micro serrefine</td>
			<td>F&#183;S&#183;L</td>
			<td>No.18055-05</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Micro clamps applicator</td>
			<td>F&#183;S&#183;L</td>
			<td>No. 18057-14</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Straight micro forceps</td>
			<td>F&#183;S&#183;L</td>
			<td>No. 00632-11</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Curved micro forceps</td>
			<td>F&#183;S&#183;L</td>
			<td>No. 00649-11</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">micro needle-holder</td>
			<td>F&#183;S&#183;L</td>
			<td style="width:119px;">No. 12061-01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">general surgical instruments</td>
			<td></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">standard sissors</td>
			<td>F&#183;S&#183;L</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">mosquito clamp</td>
			<td>F&#183;S&#183;L</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">serrated forcep</td>
			<td>F&#183;S&#183;L</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">teethed forcep</td>
			<td>F&#183;S&#183;L</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">needle-holder</td>
			<td>F&#183;S&#183;L</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">suture</td>
			<td style="width:104px;"></td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">4-0 prolene</td>
			<td style="width:104px;">ethicon</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">4-0 ETHICON*II</td>
			<td style="width:104px;">ethicon</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">6-0 silk</td>
			<td style="width:104px;">ethicon</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">11-0 polyamide</td>
			<td style="width:104px;">ethicon</td>
			<td style="width:119px;"></td>
			<td></td>
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a novel surgical technique as a foundation for in vivo partial liver engineering in rat

Organ engineering is a novel strategy to generate liver organ substitutes that can potentially be used in transplantation. Recently, in vivo liver engineering, including in vivo organ decellularization followed by repopulation, has emerged as a promising approach over ex vivo liver engineering. However, postoperative survival was not achieved. The aim of this study is to develop a novel surgical technique of in vivo selective liver lobe perfusion in rats as a prerequisite for in vivo liver engineering. We generate a circuit bypass only through the left lateral lobe. Then, the left lateral lobe is perfused with heparinized saline. The experiment is performed with 4 groups (n = 3 rats per group) based on different perfusion times of 20 min, 2 h, 3 h, and 4 h. Survival, as well as the macroscopically visible change of color and the histologically determined absence of blood cells in the portal triad and the sinusoids, is taken as an indicator for a successful model establishment. After selective perfusion of the left lateral lobe, we observe that the left lateral lobe, indeed, turned from red to faint yellow. In a histological assessment, no blood cells are visible in the branch of the portal vein, the central vein, and the sinusoids. The left lateral lobe turns red after reopening the blocked vessels. 12/12 rats survived the procedure for more than one week. We are the first to report a surgical model for in vivo single liver lobe perfusion with a long survival period of more than one week. In contrast to the previously published report, the most important advantage of the technique presented here is that perfusion of 70% of the liver is maintained throughout the whole procedure. The establishment of this technique provides a foundation for in vivo partial liver engineering in rats, including decellularization and recellularization.

Twelve male (aged 12 - 13 weeks) Lewis rats were used to assess the effect of selective liver lobe perfusion. The experiment was performed in four groups (n = 3 rats per group). Using different perfusion periods of 20 minutes, 2 hours, 3 hours, and 4 hours, following the steps described above, we successfully achieved in vivo single lobe perfusion.
In Vivo Perfusion of the Left...

Watch this Scientific Journal Video about A Novel Surgical Technique As a Foundation for In Vivo Partial Liver Engineering in Rat at JoVE.com

A Novel Surgical Technique As a Foundation for In Vivo Partial Liver Engineering in Rat

We establish a novel surgical technique for an in vivo single liver lobe perfusion model in rat as a prerequisite for further studying in vivo partial liver engineering in the future.

A Novel Surgical Technique As a Foundation for In Vivo Partial Liver Engineering in Rat

Organ engineering is a novel strategy to generate liver organ substitutes that can potentially be used in transplantation. Recently, in vivo liver ...

Over the last few years, liver engineering has become a hot topic around the world due to it's potential of generating transplant able liver grafts. However viable long term function and the transplantation of engineered organs are still a vision of the future. Recently in-vivo liver lobe profusion has become a promising strategy to start liver engineering.A major advantage of this technique is that the in-vivo repopulated partial liver scaffold subjected scatological blood profusion. This provides the scaffold with the proper temperature, sufficient oxygen, nutrients and growth factors in contrast to ex-vivo profusion with artificial culture medium. Another advantage is that remaining liver maintains hepatic function and thereby principally allows long term survival.However the in-vivo single lobe profusion model is technically challenging and post operative survival has yet to be achieved. Here we are going to present another surgical model with long term survival as a foundation for further in-vivo single liver lobe engineering. Before we demonstrate the surgical model, we'd like to give a brief introduction to rat liver anatomy.To establish our single liver lobe profusion model we selected the left lateral lobe. This is the only liver lobe with a distinct vascular supply and drainage allowing to create a bypass. This is a 3-D reconstruction of the portal venous system in rat.Our focus here is on the left portal vein which will later serve as the fluid inlet. This is a 3-D reconstruction of the hepatic venous system in rat. Here our focus is on the left lateral hepatic vein which will later serve as a fluid outlet.This illustration of liver vascular anatomy highlights the vascular access points used for out partial perfusion model. This animation illustrates the scheme of generating the in-vivo left lateral liver lobe perfusion model. In order to establish the surgical model we are going to generate a circuit bypass within the left lateral lobe.For this purpose we need to block the following vessels the left portal vein, the left hepatic artery, the left bile duct, the left median protal vein, hepatic artery and bile duct, and the left lateral hepatic vein. Then we need to cannulate the left portal vein with a 24 gage catheter. Afterwards the left lateral hepatic vein is cannulated using a 22 gage catheter.Then the catheter in the left portal vein is connected to a perfusion pump. Dry gauze is placed at the outlet of the catheter in the left lateral hepatic vein to absorb waste fluid. This way a bypass is created.Then the left lateral lobe perfused with heparinized saline At a flow rate of 0.5 milliliters per minute. Physiological perfusion to the left lateral lobe is restored after reopening the blocked vessels. Now the surgical perfusion model is established.All procedures demonstrated in this video were assessed and approved by the local authorities. The operation field of the abdomen is disinfected with three rounds of iodine tincture followed by two rounds of 70%alcohol. Sterile gauze is placed on the abdomen leaving only the operation field exposed.A transverse incision is made on the abdominal wall of the rat. A 4-0 prolene suture is used to fix the xiphoid process and pull it toward the head. Both sides of the upper abdominal walls are retracted using two subcoastal hooks to reach full exposure of the organ.Then we can see the liver lobes. Here's the left lateral lobe which is used for selective perfusion. We cover the duodenum and the small intestine in the abdominal cavity with moistened gauze to ovoid dryness.We expose the hilum of the liver by lifting up the median lobes with moistened gauze. The rat is placed under a sterile microscope. We dissect the left portal vein.We then ligate the left protal vein with a 6-0 silk suture. The left hepatic artery, the left bile duct, as well as the left median portal vein, the left median hepatic artery, and the left median bile duct are blocked using micro-clamps. We block the left lateral hepatic vein with micro-clamps at the base of the left lateral lobe.To create the fluid inlet, the stem of the portal vein is punctured with a 24 gage needle dwelling catheter. But the catheter is not inserted. We then remove the needle from the catheter and connect the catheter to a perfusion pump.To expel air from the tube and the catheter, we perfuse with heparinized saline for a minute. We then turn on off the pump. Next the needle free catheter, which is now connected to the perfusion pump, is inserted into the left portal vein.In this way we minimize manipulations of the cannulated vessel. Here's an exposed region of the left lateral hepatic vein we are going to cannulate in a similar way. First we create a drainage hole in the left lateral hepatic vein by puncturing it with a 22 gage or 24 gage needle dwelling catheter.We recommend that catheter is slightly smaller than the vessel. We then start to perfuse the left lateral lobe with heparinized saline at a flow rate of 0.5 milliliters per minute. The out flowing waste fluid is absorbed with gauze.To minimize intraabdominal contamination with waste fluid we reinsert the needle free catheter into the left lateral hepatic vein. Thus the cannulated left lateral hepatic vein serves as a fluid outlet. We continue perfusing the left lateral lobe with heparinized saline.Bloody fluid can be seen dripping from the outlet. The arrow indicates that the left lateral lobe turned yellow during perfusion with heparinized saline. At the end of perfusion the catheters are taken out of the vessels.The drainage opening on the left lateral hepatic vein is closed with a single 11-0 pollumite suture. The inlet opening on the left portal vein is closed with an 11-0 pollumite suture as well. Re perfusion starts with backflow from the suprahepatic vena cava after removing the clamp on the left lateral hepatic vein.Physiological perfusion is further restored after removing the clamp from the left hepatic artery and bile duct, as well as the left median vascular structures. Complete re perfusion is achieved after reopening the left portal vein as indicated by a color change to dark red. Perfusion of left later lobe.The white arrow in this image indicates that the target liver lobe was indeed selectively perfused. Here the white arrows show that the remaining lobes, which represent about 70%of the liver retained physiological perfusion throughout the whole procedure. Re perfusion of the left lateral lobe.Here the red arrow indicates that the left lateral lobe is physiologically re perfused after reopening the blocked vessels. The blue arrow shows that the left median lobe sustained ischemia. The selectively perfused left lateral lobe was histologically examined using H E staining.Figure A shows that in the perfused left lateral lobe no blood cells are detectable in the branch of the portal vein and the sinusoids. As expected red cells are visible in the branch of the hepatic artery. In figure B the inferior caudate lobe serves as control.Blood cells are clearly visible and the branches of the protal vein and hepatic artery as well as the sinusoids. Figure C demonstrates that in the perfused left lateral lobe there are no blood cells visible in the central vein. In contrast, figure D demonstrates that in the control inferior caudate lobe blood cells are visible in the central vein.We achieved a 100%one week survival rate in 12 consecutive procedures. We compared our in-vivo liver lobe perfusion model with the model of Pan and colleagues. The main differences in methodology and results between Pan and our group are:they selected the right inferior lobe while we chose the left lateral lobe as target liver lobe;they blocked vena cava and main portal vein leading to portal hypertension.In contrast we maintained portal perfusion of 70%of the liver;they sacrificed the rats inter operatively while our one week survival rate is 100%The advantages of our novel surgical model are:that it's technically challenging but feasible;and that it is well tolerated as demonstrated by the 100%survival rate. However one limitation is that the left median lobe sustained ischemia due to the blockage of the portal vein. Potential applications of our technique include:that is can be used for in-vivo partial organ treatment by perfusion with drugs;in-vivo partial organ decellularization as chemical resection;in-vivo cell culture system in comparison with ex-vivo;and in-vivo liver engineering.

a-novel-surgical-technique-as-foundation-for-vivo-partial-liver

Research

JoVE Journal

Bioengineering

Creating Two-Dimensional Patterned Substrates for Protein and Cell Confinement

Microcontact printing provides a rapid, highly reproducible method for the creation of well-defined patterned substrates.1 While microcontact printing can be employed to directly print a large number of molecules, including proteins,2 DNA,3 and silanes,4 the formation of self-assembled monolayers (SAMs) from long chain alkane thiols on gold provides a simple way to confine proteins and cells to specific patterns containing adhesive and resistant regions. This confinement can be used to control cell morphology and is useful for examining a variety of questions in protein and cell biology. Here, we describe a general method for the creation of well-defined protein patterns for cellular studies.5 This process involves three steps: the production of a patterned master using photolithography, the creation of a PDMS stamp, and microcontact printing of a gold-coated substrate. Once patterned, these cell culture substrates are capable of confining proteins and/or cells (primary cells or cell lines) to the pattern.
The use of self-assembled monolayer chemistry allows for precise control over the patterned protein/cell adhesive regions and non-adhesive regions; this cannot be achieved using direct protein stamping. Hexadecanethiol, the long chain alkane thiol used in the microcontact printing step, produces a hydrophobic surface that readily adsorbs protein from solution. The glycol-terminated thiol, used for backfilling the non-printed regions of the substrate, creates a monolayer that is resistant to protein adsorption and therefore cell growth.6 These thiol monomers produce highly structured monolayers that precisely define regions of the substrate that can support protein adsorption and cell growth. As a result, these substrates are useful for a wide variety of applications from the study of intercellular behavior7 to the creation of microelectronics.8
While other types of monolayer chemistry have been used for cell culture studies, including work from our group using trichlorosilanes to create patterns directly on glass substrates,9 patterned monolayers formed from alkane thiols on gold are straight-forward to prepare. Moreover, the monomers used for monolayer preparation are commercially available, stable, and do not require storage or handling under inert atmosphere. Patterned substrates prepared from alkane thiols can also be recycled and reused several times, maintaining cell confinement.10

Self-assembled monolayers (SAMs) formed from long chain alkane thiols on gold provide well-defined substrates for the formation of protein patterns and cell confinement. Microcontact printing of hexadecanethiol using a polydimethylsiloxane (PDMS) stamp followed by backfilling with a glycol-terminated alkane thiol monomer produces a pattern where protein and cells adsorb only to the stamped hexadecanethiol region.

Microcontact printing provides a rapid, highly reproducible method for the creation of well-defined patterned substrates.1  While microcontact printing ...

Cellular Lipid Extraction for Targeted Stable Isotope Dilution Liquid Chromatography-Mass Spectrometry Analysis

The metabolism of fatty acids, such as arachidonic acid (AA) and linoleic acid (LA), results in the formation of oxidized bioactive lipids, including numerous stereoisomers1,2. These metabolites can be formed from free or esterified fatty acids. Many of these oxidized metabolites have biological activity and have been implicated in various diseases including cardiovascular and neurodegenerative diseases, asthma, and cancer3-7. Oxidized bioactive lipids can be formed enzymatically or by reactive oxygen species (ROS). Enzymes that metabolize fatty acids include cyclooxygenase (COX), lipoxygenase (LO), and cytochromes P450 (CYPs)1,8. Enzymatic metabolism results in enantioselective formation whereas ROS oxidation results in the racemic formation of products.
While this protocol focuses primarily on the analysis of AA- and some LA-derived bioactive metabolites; it could be easily applied to metabolites of other fatty acids. Bioactive lipids are extracted from cell lysate or media using liquid-liquid (l-l) extraction. At the beginning of the l-l extraction process, stable isotope internal standards are added to account for errors during sample preparation. Stable isotope dilution (SID) also accounts for any differences, such as ion suppression, that metabolites may experience during the mass spectrometry (MS) analysis9. After the extraction, derivatization with an electron capture (EC) reagent, pentafluorylbenzyl bromide (PFB) is employed to increase detection sensitivity10,11. Multiple reaction monitoring (MRM) is used to increase the selectivity of the MS analysis. Before MS analysis, lipids are separated using chiral normal phase high performance liquid chromatography (HPLC). The HPLC conditions are optimized to separate the enantiomers and various stereoisomers of the monitored lipids12. This specific LC-MS method monitors prostaglandins (PGs), isoprostanes (isoPs), hydroxyeicosatetraenoic acids (HETEs), hydroxyoctadecadienoic acids (HODEs), oxoeicosatetraenoic acids (oxoETEs) and oxooctadecadienoic acids (oxoODEs); however, the HPLC and MS parameters can be optimized to include any fatty acid metabolites13.
Most of the currently available bioanalytical methods do not take into account the separate quantification of enantiomers. This is extremely important when trying to deduce whether or not the metabolites were formed enzymatically or by ROS. Additionally, the ratios of the enantiomers may provide evidence for a specific enzymatic pathway of formation. The use of SID allows for accurate quantification of metabolites and accounts for any sample loss during preparation as well as the differences experienced during ionization. Using the PFB electron capture reagent increases the sensitivity of detection by two orders of magnitude over conventional APCI methods. Overall, this method, SID-LC-EC-atmospheric pressure chemical ionization APCI-MRM/MS, is one of the most sensitive, selective, and accurate methods of quantification for bioactive lipids.

This protocol will demonstrate the extraction and analysis of free and esterified bioactive fatty acids from cells. Fatty acids are accurately quantified using stable isotope dilution, chiral liquid chromatography, electron capture atmospheric chemical ionization multiple reaction monitoring mass spectrometry (SID-LC-ECAPCI-MRM/MS).

The metabolism of fatty acids, such as arachidonic acid (AA) and linoleic acid (LA), results in the formation of oxidized bioactive lipids, including ...

Engineering a Bilayered Hydrogel to Control ASC Differentiation

Natural polymers over the years have gained more importance because of their host biocompatibility and ability to interact with cells in vitro and in vivo. An area of research that holds promise in regenerative medicine is the combinatorial use of novel biomaterials and stem cells. A fundamental strategy in the field of tissue engineering is the use of three-dimensional scaffold (e.g., decellularized extracellular matrix, hydrogels, micro/nano particles) for directing cell function. This technology has evolved from the discovery that cells need a substrate upon which they can adhere, proliferate, and express their differentiated cellular phenotype and function 2-3. More recently, it has also been determined that cells not only use these substrates for adherence, but also interact and take cues from the matrix substrate (e.g., extracellular matrix, ECM)4. Therefore, the cells and scaffolds have a reciprocal connection that serves to control tissue development, organization, and ultimate function. Adipose-derived stem cells (ASCs) are mesenchymal, non-hematopoetic stem cells present in adipose tissue that can exhibit multi-lineage differentiation and serve as a readily available source of cells (i.e. pre-vascular endothelia and pericytes). Our hypothesis is that adipose-derived stem cells can be directed toward differing phenotypes simultaneously by simply co-culturing them in bilayered matrices1. Our laboratory is focused on dermal wound healing. To this end, we created a single composite matrix from the natural biomaterials, fibrin, collagen, and chitosan that can mimic the characteristics and functions of a dermal-specific wound healing ECM environment.

This protocol focuses on utilizing the inherent ability of stem cells to take cue from their surrounding extracellular matrix and be induced to differentiate into multiple phenotypes. This methods manuscript extends our description and characterization of a model utilizing a bilayered hydrogel, composed of PEG-fibrin and collagen, to simultaneously co-differentiate adipose-derived stem cells1.

Natural polymers over the years have gained more importance because of their host biocompatibility and ability to interact with cells in vitro and in ...

Viral Nanoparticles for In vivo Tumor Imaging

The use of nanomaterials has the potential to revolutionize materials science and medicine. Currently, a number of different nanoparticles are being investigated for applications in imaging and therapy. Viral nanoparticles (VNPs) derived from plants can be regarded as self-assembled bionanomaterials with defined sizes and shapes. Plant viruses under investigation in the Steinmetz lab include icosahedral particles formed by Cowpea mosaic virus (CPMV) and Brome mosaic virus (BMV), both of which are 30 nm in diameter. We are also developing rod-shaped and filamentous structures derived from the following plant viruses: Tobacco mosaic virus (TMV), which forms rigid rods with dimensions of 300 nm by 18 nm, and Potato virus X (PVX), which form filamentous particles 515 nm in length and 13 nm in width (the reader is referred to refs. 1 and 2 for further information on VNPs).
From a materials scientist's point of view, VNPs are attractive building blocks for several reasons: the particles are monodisperse, can be produced with ease on large scale in planta, are exceptionally stable, and biocompatible. Also, VNPs are "programmable" units, which can be specifically engineered using genetic modification or chemical bioconjugation methods 3. The structure of VNPs is known to atomic resolution, and modifications can be carried out with spatial precision at the atomic level4, a level of control that cannot be achieved using synthetic nanomaterials with current state-of-the-art technologies.
In this paper, we describe the propagation of CPMV, PVX, TMV, and BMV in Vigna ungiuculata and Nicotiana benthamiana plants. Extraction and purification protocols for each VNP are given. Methods for characterization of purified and chemically-labeled VNPs are described. In this study, we focus on chemical labeling of VNPs with fluorophores (e.g. Alexa Fluor 647) and polyethylene glycol (PEG). The dyes facilitate tracking and detection of the VNPs 5-10, and PEG reduces immunogenicity of the proteinaceous nanoparticles while enhancing their pharmacokinetics 8,11. We demonstrate tumor homing of PEGylated VNPs using a mouse xenograft tumor model. A combination of fluorescence imaging of tissues ex vivo using Maestro Imaging System, fluorescence quantification in homogenized tissues, and confocal microscopy is used to study biodistribution. VNPs are cleared via the reticuloendothelial system (RES); tumor homing is achieved passively via the enhanced permeability and retention (EPR) effect12. The VNP nanotechnology is a powerful plug-and-play technology to image and treat sites of disease in vivo. We are further developing VNPs to carry drug cargos and clinically-relevant imaging moieties, as well as tissue-specific ligands to target molecular receptors overexpressed in cancer and cardiovascular disease.

Viral Nanoparticles for In vivo Tumor Imaging

Plant viral nanoparticles (VNPs) are promising platforms for applications in biomedicine. Here, we describe the procedures for plant VNP propagation, purification, characterization, and bioconjugation. Finally, we show the application of VNPs for tumor homing and imaging using a mouse xenograft model and fluorescence imaging.

The use of nanomaterials has the potential to revolutionize materials science and medicine. Currently, a number of different nanoparticles are being ...

Density Gradient Multilayered Polymerization (DGMP): A Novel Technique for Creating Multi-compartment, Customizable Scaffolds for Tissue Engineering

Complex tissue culture matrices, in which types and concentrations of biological stimuli (e.g. growth factors, inhibitors, or small molecules) or matrix structure (e.g. composition, concentration, or stiffness of the matrix) vary over space, would enable a wide range of investigations concerning how these variables affect cell differentiation, migration, and other phenomena. The major challenge in creating layered matrices is maintaining the structural integrity of layer interfaces without diffusion of individual components from each layer1. Current methodologies to achieve this include photopatterning2-3, lithography4, sequential functionalization5, freeze drying6, microfluidics7, or centrifugation8, many of which require sophisticated instrumentation and technical skills. Others rely on sequential attachment of individual layers, which may lead to delamination of layers9. 
DGMP overcomes these issues by using an inert density modifier such as iodixanol to create layers of varying densities10. Since the density modifier can be mixed with any prepolymer or bioactive molecule, DGMP allows each scaffold layer to be customized. Simply varying the concentration of the density modifier prevents mixing of adjacent layers while they remain aqueous. Subsequent single step polymerization gives rise to a structurally continuous multilayered scaffold, in which each layer has distinct chemical and mechanical properties. The density modifier can be easily removed with sufficient rinsing without perturbation of the individual layers or their components. This technique is therefore well suited for creating hydrogels of various sizes, shapes, and materials.
A protocol for fabricating a 2D-polyethylene glycol (PEG) gel, in which alternating layers incorporate RGDS-350, is outlined below. We use PEG because it is biocompatible and inert. RGDS, a cell adhesion peptide11, is used to demonstrate spatial restriction of a biological cue, and the conjugation of a fluorophore (Alexa Fluor 350) enables us to visually distinguish various layers. This procedure can be adapted for other materials (e.g. collagen, hyaluronan, etc.) and can be extended to fabricate 3D gels with some modifications10.

Density Gradient Multilayered Polymerization DGMP: A Novel Technique for Creating Multi-compartment, Customizable Scaffolds for Tissue Engineering

Here we describe a unique strategy for creating biocompatible, layered matrices with continuous interfaces between distinct layers for tissue engineering. Such a scaffold could provide an ideal customizable environment to modulate cell behavior by various biological, chemical or mechanical cues

Complex tissue culture matrices, in which types and concentrations of biological stimuli (e.g. growth factors, inhibitors, or small molecules) or matrix ...

Skin Tattooing As A Novel Approach For DNA Vaccine Delivery

Nucleic acid-based vaccination is a topic of growing interest, especially plasmid DNA (pDNA) encoding immunologically important antigens. After the engineered pDNA is administered to the vaccines, it is transcribed and translated into immunogen proteins that can elicit responses from the immune system. Many ways of delivering DNA vaccines have been investigated; however each delivery route has its own advantages and pitfalls. Skin tattooing is a novel technique that is safe, cost-effective, and convenient. In addition, the punctures inflicted by the needle could also serve as a potent adjuvant. Here, we a) demonstrate the intradermal delivery of plasmid DNA encoding enhanced green fluorescent protein (pCX-EGFP) in a mouse model using a tattooing device and b) confirm the effective expression of EGFP in the skin cells using confocal microscopy.

Skin tattooing is a potent and safe way to delivery DNA vaccine intradermally. Here, a DNA plasmid encoding EGFP is delivered by tattooing to the skin of a laboratory mouse, and the expression of EGFP in the skin cells is then inspected by confocal microscopy.

Nucleic acid-based vaccination is a topic of growing interest, especially plasmid DNA (pDNA) encoding immunologically important antigens. After the ...

Fluorescence-quenching of a Liposomal-encapsulated Near-infrared Fluorophore as a Tool for In Vivo Optical Imaging

Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous number of imaging techniques currently available and the progress in instrumentation, there is still a need for highly sensitive probes that are suitable for in vivo imaging. One typical problem of available preclinical fluorescent probes is their rapid clearance in vivo, which reduces their imaging sensitivity. To circumvent rapid clearance, increase number of dye molecules at the target site, and thereby reduce background autofluorescence, encapsulation of the near-infrared fluorescent dye, DY-676-COOH in liposomes and verification of its potential for in vivo imaging of inflammation was done. DY-676 is known for its ability to self-quench at high concentrations. We first determined the concentration suitable for self-quenching, and then encapsulated this quenching concentration into the aqueous interior of PEGylated liposomes. To substantiate the quenching and activation potential of the liposomes we use a harsh freezing method which leads to damage of liposomal membranes without affecting the encapsulated dye. The liposomes characterized by a high level of fluorescence quenching were termed Lip-Q. We show by experiments with different cell lines that uptake of Lip-Q is predominantly by phagocytosis which in turn enabled the characterization of its potential as a tool for in vivo imaging of inflammation in mice models. Furthermore, we use a zymosan-induced edema model in mice to substantiate the potential of Lip-Q in optical imaging of inflammation in vivo. Considering possible uptake due to inflammation-induced enhanced permeability and retention (EPR) effect, an always-on liposome formulation with low, non-quenched concentration of DY-676-COOH (termed Lip-dQ) and the free DY-676-COOH were compared with Lip-Q in animal trials.

Fluorescence-quenching of a Liposomal-encapsulated Near-infrared Fluorophore as a Tool for In Vivo Optical Imaging

The use of fluorophores for in vivo imaging can be greatly limited by opsonization, rapid clearance, low detection sensitivity and cytotoxic effects on the host. Encapsulation of fluorophores in liposomes by film hydration and extrusion leads to fluorescence quenching and protection which enables in vivo imaging with high detection sensitivity.

Optical imaging offers a wide range of diagnostic modalities and has attracted a lot of interest as a tool for biomedical imaging. Despite the enormous ...

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 ...

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 ...

Tissue Engineering by Intrinsic Vascularization in an In Vivo Tissue Engineering Chamber

In reconstructive surgery, there is a clinical need for an alternative to the current methods of autologous reconstruction which are complex, costly and trade one defect for another. Tissue engineering holds the promise to address this increasing demand. However, most tissue engineering strategies fail to generate stable and functional tissue substitutes because of poor vascularization. This paper focuses on an in vivo tissue engineering chamber model of intrinsic vascularization where a perfused artery and a vein either as an arteriovenous loop or a flow-through pedicle configuration is directed inside a protected hollow chamber. In this chamber-based system angiogenic sprouting occurs from the arteriovenous vessels and this system attracts ischemic and inflammatory driven endogenous cell migration which gradually fills the chamber space with fibro-vascular tissue. Exogenous cell/matrix implantation at the time of chamber construction enhances cell survival and determines specificity of the engineered tissues which develop. Our studies have shown that this chamber model can successfully generate different tissues such as fat, cardiac muscle, liver and others. However, modifications and refinements are required to ensure target tissue formation is consistent and reproducible. This article describes a standardized protocol for the fabrication of two different vascularized tissue engineering chamber models in vivo.

Tissue Engineering by Intrinsic Vascularization in an In Vivo Tissue Engineering Chamber

This is a guideline for constructing in vivo vascularized tissue using a microsurgical arteriovenous loop or a flow-through pedicle configuration inside a tissue engineering chamber. The vascularized tissues generated can be employed for organ regeneration and replacement of tissue defects, as well as for drug testing and disease modeling.

In reconstructive surgery, there is a clinical need for an alternative to the current methods of autologous reconstruction which are complex, costly and ...