The authors wish to thank Valerie Schroeder for her assistance with technical aspects of this work. Work related to development of this model was supported by Cook Biotech, Inc. (West Lafayette, IN USA).

The use of animals in this protocol was approved by the University of Notre Dame Institutional Animal Care and Use Committee, followed all regulatory requirements and guidelines, and was conducted in a facility that is accredited by the Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC), International.
1. Selection of Animals
<ol>
	<li>Acquire pathogen-free Sprague Dawley rats from a reputable vendor or breeding colony. 
	Note: Often, the facility veterinari...

<ol>
	<li>Poussier, 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+review+of+available+prosthetic+material+for+abdominal+wall+repair.">A review of available prosthetic material for abdominal wall repair.</a> J. Visc. Surg. 150 (1), 52-59 (2013).</li><li>Hjort, H., Mathisen, T., Alves, A., Clermont, G., Boutrand, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-year+results+from+a+preclinical+implantation+study+of+a+long-term+resorbable+surgical+mesh+with+time-dependent+mechanical+characteristics.">Three-year results from a preclinical implantation study of a long-term resorbable surgical mesh with time-dependent mechanical characteristics.</a> Hernia. 16 (2), 191-197 (2012).</li><li>Ko, R., Kazacos, E. A., Snyder, S., Ernst, D. M. J., Lantz, G. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tensile+strength+comparison+of+small+intestinal+submucosa+body+wall+repair.">Tensile strength comparison of small intestinal submucosa body wall repair.</a> J. Surg. Res. 135 (1), 9-17 (2006).</li><li>Garcia-Moreno, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparing+the+host+tissue+response+and+peritoneal+behavior+of+composite+meshes+used+for+ventral+hernia+repair.">Comparing the host tissue response and peritoneal behavior of composite meshes used for ventral hernia repair.</a> J. Surg. Res. 193 (1), 470-482 (2015).</li><li>Soiderer, E. E., Lantz, G. C., Kazacos, E. A., Hodde, J. P., Wiegand, R. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphologic+study+of+three+collagen+materials+for+body+wall+repair.">Morphologic study of three collagen materials for body wall repair.</a> J. Surg. Res. 118 (2), 161-175 (2004).</li><li>Liu, Z., Tang, R., Zhou, Z., Song, Z., Wang, H., Gu, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+two+porcine-derived+materials+for+repairing+abdominal+wall+defect+in+rats.">Comparison of two porcine-derived materials for repairing abdominal wall defect in rats.</a> PLOS One. 6 (5), e20520 (2011).</li><li>Zhang, J., Wang, G. Y., Xiao, Y. P., Fan, L. Y., Wang, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+biomechanical+behavior+and+host+response+to+porcine-derived+small+intestine+submucosa,+pericardium+and+dermal+matrix+acellular+grafts+in+a+rat+abdominal+defect+model.">The biomechanical behavior and host response to porcine-derived small intestine submucosa, pericardium and dermal matrix acellular grafts in a rat abdominal defect model.</a> Biomaterials. 32 (29), 7086-7095 (2011).</li><li>Ma, J., Sahoo, S., Baker, A. R., Derwin, K. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigating+muscle+regeneration+with+a+dermis/small+intestinal+submucosa+scaffold+in+a+rat+full-thickness+abdominal+wall+defect+model.">Investigating muscle regeneration with a dermis/small intestinal submucosa scaffold in a rat full-thickness abdominal wall defect model.</a> J.Biomed.Mater.Res.Part B. 103 (2), 355-364 (2015).</li><li>Greca, F. H., Souza-Filho, Z. A., Giovanni, A., Rubin, M. R., Kuenzer, R. F., Reese, F. B., Araujo, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+porosity+on+the+integration+histology+of+two+polypropylene+meshes+for+the+treatment+of+abdominal+wall+defects+in+dogs.">The influence of porosity on the integration histology of two polypropylene meshes for the treatment of abdominal wall defects in dogs.</a> Hernia. 12 (1), 45-49 (2008).</li><li>Hiles, M., Record-Ritchie, R. D., Altizer, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Are+biologic+grafts+effective+for+hernia+repair?+A+systematic+review+of+the+literature.">Are biologic grafts effective for hernia repair? A systematic review of the literature.</a> Surg. Innov. 16 (1), 26-37 (2009).</li><li>Helton, W. S., Fisichella, P. M., Berger, R., Horgan, S., Espat, N. J., Abcarian, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Short-term+outcomes+with+small+intestinal+submucosa+for+ventral+abdominal+hernia.">Short-term outcomes with small intestinal submucosa for ventral abdominal hernia.</a> Arch. Surg. 140 (6), 560-562 (2005).</li><li>Franklin, M. E., Trevino, J. M., Portillo, G., Vela, I., Glass, J. L., Gonzalez, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+porcine+small+intestinal+submucosa+as+a+prosthetic+material+for+laparascopic+hernia+repair+in+infected+and+potentially+contaminated+fields:+long-term+follow-up.">The use of porcine small intestinal submucosa as a prosthetic material for laparascopic hernia repair in infected and potentially contaminated fields: long-term follow-up.</a> Surg. Endosc. 22 (9), 1941-1946 (2008).</li><li>Clarke, K. M., Lantz, G. C., Salisbury, S. K., Badylak, S. F., Hiles, M. C., Voytik, S. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intestine+submucosa+and+polypropylene+mesh+for+abdominal+wall+repair+in+dogs.">Intestine submucosa and polypropylene mesh for abdominal wall repair in dogs.</a> J. Surg. Res. 60 (1), 107-114 (1996).</li><li>Sarikava, A., Record, R., Wu, C. C., Tullius, B., Badylak, S. F., Ladisch, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antimicrobial+activity+associated+with+extracellular+matrices.">Antimicrobial activity associated with extracellular matrices.</a> Tissue Eng. 8 (1), 63-71 (2002).</li><li>Serra, R., Grande, R., Butrico, L., Rossi, A., Settimio, U. F., Caroleo, B., Amato, B., Gallelli, L., de Franciscis, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+wound+infections:+the+role+of+Pseudomonas+aeruginosa+and+Staphylococcus+aureus.">Chronic wound infections: the role of Pseudomonas aeruginosa and Staphylococcus aureus.</a> Expert Rev. Anti. Infect. Ther. 13 (5), 605-613 (2015).</li></ol>

Materials for the repair of ventral abdominal hernia are of great interest, particularly those that provide an initial mechanical bridge and are then able to incorporate into host tissue. In this regard, a variety of materials have been investigated, including SIS, porcine acellular dermal matrix, and porcine pericardium.6,7 These materials represent the extracellular matrices of those tissues and act as scaffolds into which cells can migrate and proliferate, thu...

Abdominal wall hernia is a commonly encountered clinical issue which may occur as a result of congenital defect, traumatic injury, or failed closure of surgical wounds involving the abdominal wall. Repair commonly involves using an implant to reinforce the abdominal wall, with a reduced rate of recurrence noted in patients treated with an implant compared to those in whom the abdominal wall is simply closed with suture.1
Surgical hernia repair often requires mechanical bridging of the defect with an implanted material. In this regard, both synthetic and natural materials have been used for hernia repair. Many synthetic materials are typically non-absorbable and include polypropylene, polyethylene terephthalate polyester, and expanded polytetrafluoroethylene, while other synthetic implants combine one of the non-absorbable materials with an absorbable polymer such as polygalactine.1 In contrast, natural material implants are generally derived from either animal or human cadaveric sources. Natural materials used for hernia repair are typically rich in collagen and act as a scaffold for ingrowth and integration of host tissue.
The desire to develop and optimize new materials for ventral abdominal hernia repair requires an appropriate animal model for evaluation of candidate materials. Studies have been conducted in a variety of species, including sheep,2 pigs,3 rabbits,4 rats,5,6,7,8 and dogs.9&#160; The advantage of using rats for such studies is that they offer an easily handled model available in a variety of inbred strains to allow for control of genetic variability. In addition, the smaller overall body surface area of the rat compared to the other species listed above permit evaluation of materials that may be experimental in nature and, therefore, not abundant.&#160; Further, reduced costs associated with rats versus other species allow for relatively increased ability to screen candidate materials for use in repair of ventral abdominal hernia.&#160; Considerations for materials typically include ease of handling by the surgeon, strength, ability to incorporate into host tissue, biocompatibility, and resistance to infection.
As an example, porcine small intestinal submucosa (SIS) is a natural biomaterial that has been used for a wide variety of tissue repair indications, including repair of ventral abdominal, inguinal, and diaphragmatic hernias.10,11,12 SIS is rapidly incorporated into host tissue and has been found to be generally resistant to infection and so the material has particular utility in contaminated fields.13,14&#160; In the rat model, SIS has demonstrated ease of handling, good tensile strength as determined by the&#160; uniaxial tensile failure test, and promotion of tissue ingrowth in terms of collagen deposition and neovascularization.6,7
Accurate surgical bridging of the defect is an essential feature of productive modeling when evaluating candidate repair materials. The animal must be sufficiently anesthetized and aseptic technique strictly followed. Further, an abdominal wall defect of standard size must be carefully created and then bridged in a manner that sufficiently secures the material to the margins of the defect.8 This protocol provides a standard method to be followed for surgical creation, and repair of, a ventral abdominal hernia using SIS as an example bridging material in a rat.

<table border="0" cellpadding="0" cellspacing="0" width="573">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Isoflurane (Isoflo)</td>
			<td style="width:71px;">Henry Schine Animal Health</td>
			<td align="right" style="width:119px;">17579</td>
			<td style="width:167px;">gas anesthetic</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Optixcare Eye Lubricant</td>
			<td style="width:71px;">Henry Schine Animal Health</td>
			<td style="width:119px;">OPX4240</td>
			<td>Ocular lubricant</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Oster clippers</td>
			<td style="width:71px;">Henry Schine Animal Health</td>
			<td align="right" style="width:119px;">6092</td>
			<td>hair clippers</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Betadine surgical scrub</td>
			<td style="width:71px;">Henry Schine Animal Health</td>
			<td align="right" style="width:119px;">1618</td>
			<td>antiseptic iodophor</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Sterile scalpel</td>
			<td style="width:71px;">Henry Schine Animal Health</td>
			<td align="right" style="width:119px;">329</td>
			<td>#10 scalpel</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">9&#34; x 12&#34; disposable surgical drape</td>
			<td style="width:71px;">Braintree Scientific, Inc.</td>
			<td style="width:119px;">SP-RPS</td>
			<td>Surgical drape</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">4-0 nylon suture</td>
			<td style="width:71px;">Braintree Scientific, Inc.</td>
			<td style="width:119px;">SUT 812</td>
			<td>Suture material</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">4-0 Absorbable Suture</td>
			<td style="width:71px;">Henry Schine Animal Health</td>
			<td align="right" style="width:119px;">29242</td>
			<td>Synthetic absorbable suture</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">9 mm Autoclips and applier</td>
			<td style="width:71px;">Braintree Scientific, Inc.</td>
			<td style="width:119px;">ACS KIT</td>
			<td>Surgical staples for closure of skin incision</td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:216px;">Torbugesic/analgesic</td>
			<td style="width:71px;">Henry Schine Animal Health</td>
			<td align="right" style="width:119px;">12084</td>
			<td>Butorphanol tartarate for post-operative analgesia</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Small intestinal submucosa (SIS)</td>
			<td style="width:71px;">Cook Biotech, Inc.</td>
			<td style="width:119px;"></td>
			<td>Implant material for bridging experimental abdominal wall defect</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Rats</td>
			<td style="width:71px;">Harlan, Inc.</td>
			<td style="width:119px;">Sprague Dawley</td>
			<td>Animal for hernia modeling</td>
		</tr>
	</tbody>
</table>

use of a rat model to study ventral abdominal hernia repair

Ventral abdominal hernia is a relatively common clinical condition that sometimes requires herniorraphy (surgical repair). The repair of ventral abdominal hernia typically requires implantation of a material to serve as a mechanical bridge across the defect in the abdominal wall. Biomaterials, such as porcine small intestinal submucosa (SIS), also serve as a lattice for cell growth into the implant and can naturally incorporate into the host tissue. Development of such repair materials benefits from use of animal models in which experimental abdominal wall defects are easily created and are amenable to repair in a reproducible fashion. The method offered here describes surgical creation and repair of ventral abdominal hernia in a rat model. When SIS is used to repair an experimental ventral abdominal hernia in this model, it is rapidly incorporated into host tissue within 28 days of implantation. Histologically, incorporation of their implanted material into host tissue is characterized by a robust fibrovascular response. Future refinements and applications of the rat abdominal hernia model may likely involve diabetic and/or obese animals as a means to more closely mimic common co-morbidities of man.

By 28 days after implantation, SIS typically demonstrates good incorporation into host tissue (Figure 2). In most cases, there is residual SIS apparent, though the tissue must often be explored to identify the implanted material. Histological analyses confirmed the gross pathological observations, illustrating good tissue incorporation with primarily fibrovascular tissue and very little residual SIS noted (Figure 3). These results demonstrate the utility ...

Watch this Scientific Journal Video about Use of a Rat Model to Study Ventral Abdominal Hernia Repair at JoVE.com

Use of a Rat Model to Study Ventral Abdominal Hernia Repair

This manuscript describes methods associated with creation and repair of a ventral abdominal wall defect (hernia). This model can be used to study repair strategies such as those that use implanted materials. In this manuscript, repair of the experimental hernia with porcine small intestinal submucosa is presented as an example.

Ventral abdominal hernia is a relatively common clinical condition that sometimes requires herniorraphy (surgical repair). The repair of ventral abdominal ...

The overall goal of this ventral abdominal hernia repair model is to facilitate the assessment of potential hernia repair biomaterials. This method can help answer key questions in the surgical biomaterials field about the suitability and biocompatibility of candidate materials for ventral abdominal hernia repair. The main advantage of this technique is that it utilizes a rat model, thereby allowing the evaluation of hernia repair materials that may be of limited supply.After confirming the appropriate level of anesthesia of a healthy 250 gram adult rat by toe pinch, apply lubricant to the animal's eyes and subcutaneously administer sterile saline. Use a pair of clippers to shave the ventral abdomen from the pubis to the sternum and from the lateral margins on the ventrum. Apply a moist paper towel to the shaved area to remove the clipped hair, and scrub the exposed skin with an iodoform antiseptic and a 70%ethanol wipe.After donning the appropriate personal protective equipment, thoroughly scrub both hands with soap and don a pair of sterile surgical gloves. Next, drape the animal. And use a scalpel to make an approximately three to four centimeter vertical incision down the ventral midline to abdominal musculature.Using forceps, gently lift the abdominal wall and create a small opening through the linea alba. Then, to protect the underlying viscera, insert another forceps through the hole into the abdominal cavity to create an approximately two by two centimeter full thickness defect, cutting approximately one centimeter lateral from each side of the midline on both ends of the linea alba incision. Next, lay a precut two by two centimeter section of implant material over the defect.Because the abdominal wall will retract laterally upon incision, it is important to establish the general anatomical boundaries, ensuring the creation of a defect in the tissue wall that corresponds to the size of the implant. And use a 4-0 nylon suture to suture the four corners of the bridging material to the abdominal wall in a simple interrupted suture pattern. Secure each edge of the material with three additional equally spaced sutures.Then examine the entire circumferential edge to ensure significant gaps do not exist. Any unsecured implant margins present an opening through which the abdominal viscera can potentially herniate. Therefore it is essential to make sure that all of the edges are anchored to the body wall.When the implant is secure, close the skin with surgical staples. Seven to 10 days after the surgery, remove the skin staples. 21 to 28 days after the surgery, the rat is euthanized.Open the skin and abdominal wall to expose the area of the implant. Note any gross pathological observations, including any adverse reactions and adhesion extent and tenacity to the underlying viscera. Then harvest a wide section of tissue that includes the implant and place the implant site sample into the appropriate fixative for the desired downstream processing procedure if the sample is to be used for histopathological examination.By 28 days after implantation, the small intestinal submucosa or SIS typically demonstrates a good incorporation into the host tissue. In most cases, residual SIS is apparent, although the tissue must often be explored to identify the implanted material. Histological analysis further confirms the gross pathological observations, illustrating a good tissue incorporation with primarily fibrovascular tissue and very little notable residual SIS in demonstrating the utility of the rat ventral abdominal hernia model.Once mastered, this technique can be completed in 30 minutes if it is performed properly. While attempting this procedure, it's important to remember to provide adequate postoperative analgesia to the animal. Following euthanasia and harvest of the implant, other methods like mechanical strength testing can be performed to answer additional questions like, is the reparative abdominal defect sufficiently strong?After watching this video, you should have a good understanding of how to surgically create a ventral abdominal hernia in the rat.

use-of-a-rat-model-to-study-ventral-abdominal-hernia-repair

Research

JoVE Journal

Bioengineering

The Three-Dimensional Human Skin Reconstruct Model: a Tool to Study Normal  Skin and Melanoma Progression

Most in vitro studies in experimental skin biology have been done in 2-dimensional (2D) monocultures, while accumulating evidence suggests that cells behave differently when they are grown within a 3D extra-cellular matrix and also interact with other cells (1-5). Mouse models have been broadly utilized to study tissue morphogenesis in vivo. However mouse and human skin have significant differences in cellular architecture and physiology, which makes it difficult to extrapolate mouse studies to humans. Since melanocytes in mouse skin are mostly localized in hair follicles, they have distinct biological properties from those of humans, which locate primarily at the basal layer of the epidermis. The recent development of 3D human skin reconstruct models has enabled the field to investigate cell-matrix and cell-cell interactions between different cell types. The reconstructs consist of a "dermis" with fibroblasts embedded in a collagen I matrix, an "epidermis", which is comprised of stratified, differentiated keratinocytes and a functional basement membrane, which separates epidermis from dermis. Collagen provides scaffolding, nutrient delivery, and potential for cell-to-cell interaction. The 3D skin models incorporating melanocytic cells recapitulate natural features of melanocyte homeostasis and melanoma progression in human skin. As in vivo, melanocytes in reconstructed skin are localized at the basement membrane interspersed with basal layer keratinocytes. Melanoma cells exhibit the same characteristics reflecting the original tumor stage (RGP, VGP and metastatic melanoma cells) in vivo. Recently, dermal stem cells have been identified in the human dermis (6). These multi-potent stem cells can migrate to the epidermis and differentiate to melanocytes.

In this report, we describe the three-dimensional skin reconstruct model which mimics human skin in architecture and composition. Melanocyte physiology, melanoma progression and the fate of dermal stem cells have been investigated using the skin reconstruct model. The model is also useful as a preclinical tool for drug assessment.

Most in vitro studies in experimental skin biology have been done in 2-dimensional (2D) monocultures, while accumulating evidence suggests that cells ...

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic valve leaflets are composed of interstitial cells suspended within an extracellular matrix (ECM) and are lined with an endothelial cell monolayer. The valve withstands a harsh, dynamic environment and is constantly exposed to shear, flexion, tension, and compression. Research has shown calcific lesions in diseased valves occur in areas of high mechanical stress as a result of endothelial disruption or interstitial matrix damage1-3. Hence, it is not surprising that epidemiological studies have shown high blood pressure to be a leading risk factor in the onset of aortic valve disease4. 
The only treatment option currently available for valve disease is surgical replacement of the diseased valve with a bioprosthetic or mechanical valve5. Improved understanding of valve biology in response to physical stresses would help elucidate the mechanisms of valve pathogenesis. In turn, this could help in the development of non-invasive therapies such as pharmaceutical intervention or prevention. Several bioreactors have been previously developed to study the mechanobiology of native or engineered heart valves6-9. Pulsatile bioreactors have also been developed to study a range of tissues including cartilage10, bone11 and bladder12. The aim of this work was to develop a cyclic pressure system that could be used to elucidate the biological response of aortic valve leaflets to increased pressure loads. 
The system consisted of an acrylic chamber in which to place samples and produce cyclic pressure, viton diaphragm solenoid valves to control the timing of the pressure cycle, and a computer to control electrical devices. The pressure was monitored using a pressure transducer, and the signal was conditioned using a load cell conditioner. A LabVIEW program regulated the pressure using an analog device to pump compressed air into the system at the appropriate rate. The system mimicked the dynamic transvalvular pressure levels associated with the aortic valve; a saw tooth wave produced a gradual increase in pressure, typical of the transvalvular pressure gradient that is present across the valve during diastole, followed by a sharp pressure drop depicting valve opening in systole. The LabVIEW program allowed users to control the magnitude and frequency of cyclic pressure. The system was able to subject tissue samples to physiological and pathological pressure conditions. This device can be used to increase our understanding of how heart valves respond to changes in the local mechanical environment.

Design of a Cyclic Pressure Bioreactor for the Ex Vivo Study of Aortic Heart Valves

A cyclic pressure bioreactor capable of subjecting heart valve tissue to physiological and pathological pressure conditions has been designed. A LabVIEW program allows users to control pressure magnitude, amplitude and frequency. This device can be used to study the mechanobiology of heart valve tissue or isolated cells.

The aortic valve, located between the left ventricle and the aorta, allows for unidirectional blood flow, preventing backflow into the ventricle. Aortic ...

Manufacturing Devices and Instruments for Easier Rat Liver Transplantation

Orthotopic rat liver transplantation is a popular model, which has been shown in a recent JoVE paper with the use of the "quick-linker" device. This technique allows for easier venous cuff-anatomoses after a reasonable learning curve. The device is composed of two handles, which are carved out from scalpel blades, one approximator, which is obtained by modifying Kocher's forceps, and cuffs designed from fine-bore polyethylene tubing. The whole process can be performed at a low-cost using common laboratory material. The present report provides a step-by-step protocol for the design of the required pieces and includes stencils.

We describe the design of the &#x201C;quick-linker&#x201D; device for easier orthotopic rat liver transplantation.

Orthotopic rat liver transplantation is a popular model, which has been shown in a recent JoVE paper with the use of the "quick-linker" device. This ...

Athymic Rat Model for Evaluation of Engineered Anterior Cruciate Ligament Grafts

Anterior cruciate ligament (ACL) rupture is a common ligamentous injury that often requires surgery because the ACL does not heal well without intervention. Current treatment strategies include ligament reconstruction with either autograft or allograft, which each have their associated limitations. Thus, there is interest in designing a tissue-engineered graft for use in ACL reconstruction. We describe the fabrication of an electrospun polymer graft for use in ACL tissue engineering. This polycaprolactone graft is biocompatible, biodegradable, porous, and is comprised of aligned fibers. Because an animal model is necessary to evaluate such a graft, this paper describes an intra-articular athymic rat model of ACL reconstruction that can be used to evaluate engineered grafts, including those seeded with xenogeneic cells. Representative histology and biomechanical testing results at 16 weeks postoperatively are presented, with grafts tested immediately post-implantation and contralateral native ACLs serving as controls. The present study provides a reproducible animal model with which to evaluate tissue engineered ACL grafts, and demonstrates the potential of a regenerative medicine approach to treatment of ACL rupture.

Animal models are important tools for the evaluation of tissue-engineered grafts. This paper presents the protocol for preparing an electrospun biodegradable polymer graft for use in anterior cruciate ligament tissue engineering, as well as a surgical protocol for implantation in a rat model.

Anterior cruciate ligament (ACL) rupture is a common ligamentous injury that often requires surgery because the ACL does not heal well without ...

In Vitro Permeation of FITC-loaded Ferritins Across a Rat Blood-brain Barrier: a Model to Study the Delivery of Nanoformulated Molecules

Brain microvascular endothelial cells, supported by pericytes and astrocytes endfeet, are responsible for the low permeation of large hydrosoluble drugs through the blood-brain barrier (BBB), causing difficulties for effective pharmacological therapies. In recent years, different strategies for promoting brain targeting have aimed to improve drug delivery and activity at this site, including innovative nanosystems for drug delivery across the BBB. In this context, an in vitro approach based on a simplified cellular model of the BBB provides a useful tool to investigate the effect of nanoformulations on the trans-BBB permeation of molecules. This study describes the development of a double-layer BBB, consisting of co-cultured commercially available primary rat brain microvascular endothelial cells and astrocytes. A multiparametric approach for the validation of the model, based on the measurement of the transendothelial electrical resistance and the apparent permeability of a high molecular weight dextran, is also described. As proof of concept for the employment of this BBB model to study the effect of different nanoformulations on the translocation of fluorescent molecules across the barrier, we describe the use of fluorescein isothiocyanate (FITC), loaded into ferritin nanoparticles. The ability of ferritins to improve the trans-BBB permeation of FITC was demonstrated by flux measurements and confocal microscopy analyses. The results suggest this is a useful system for validating nanosystems for delivery of drugs across the BBB.

In Vitro Permeation of FITC-loaded Ferritins Across a Rat Blood-brain Barrier: a Model to Study the Delivery of Nanoformulated Molecules

A method to establish an in vitro model of blood-brain barrier based on a co-culture of rat brain microvascular endothelial cells and astrocytes is described and validated. This system proved to be a valid tool to study the effect of nanoformulation on the trans-barrier permeation of fluorescent molecules.

Brain microvascular endothelial cells, supported by pericytes and astrocytes endfeet, are responsible for the low permeation of large hydrosoluble drugs ...

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

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

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

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

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

The Arteriovenous (AV) Loop in a Small Animal Model to Study Angiogenesis and Vascularized Tissue Engineering

A functional blood vessel network is a prerequisite for the survival and growth of almost all tissues and organs in the human body. Moreover, in pathological situations such as cancer, vascularization plays a leading role in disease progression. Consequently, there is a strong need for a standardized and well-characterized in vivo model in order to elucidate the mechanisms of neovascularization and develop different vascularization approaches for tissue engineering and regenerative medicine.
We describe a microsurgical approach for a small animal model for induction of a vascular axis consisting of a vein and artery that are anastomosed to an arteriovenous (AV) loop. The AV loop is transferred to an enclosed implantation chamber to create an isolated microenvironment in vivo, which is connected to the living organism only by means of the vascular axis. Using 3D imaging (MRI, micro-CT) and immunohistology, the growing vasculature can be visualized over time. By implanting different cells, growth factors and matrices, their function in blood vessel network formation can be analyzed without any disturbing influences from the surroundings in a well controllable environment. 
In addition to angiogenesis and antiangiogenesis studies, the AV loop model is also perfectly suited for engineering vascularized tissues. After a certain prevascularization time, the generated tissues can be transplanted into the defect site and microsurgically connected to the local vessels, thereby ensuring immediate blood supply and integration of the engineered tissue. By varying the matrices, cells, growth factors and chamber architecture, it is possible to generate various tissues, which can then be tailored to the individual patient's needs.

The Arteriovenous AV Loop in a Small Animal Model to Study Angiogenesis and Vascularized Tissue Engineering

We describe a microsurgical approach for the generation of an arteriovenous (AV) loop as a model for analyzing vascularization in vivo in an isolated and well-characterized environment. This model is not only useful for the investigation of angiogenesis, but is also optimally suited for engineering axially vascularized and transplantable tissues.

A functional blood vessel network is a prerequisite for the survival and growth of almost all tissues and organs in the human body. Moreover, in ...

The Use of a &#946;-lactamase-based Conductimetric Biosensor Assay to Detect Biomolecular Interactions

Biosensors are becoming increasingly important and implemented in various fields such as pathogen detection, molecular diagnosis, environmental monitoring, and food safety control. In this context, we used &#946;-lactamases as efficient reporter enzymes in several protein-protein interaction studies. Furthermore, their ability to accept insertions of peptides or structured proteins/domains strongly encourages the use of these enzymes to generate chimeric proteins. In a recent study, we inserted a single-domain antibody fragment into the Bacillus licheniformis BlaP &#946;-lactamase. These small domains, also called nanobodies, are defined as the antigen-binding domains of single chain antibodies from camelids. Like common double chain antibodies, they show high affinities and specificities for their targets. The resulting chimeric protein exhibited a high affinity against its target while retaining the &#946;-lactamase activity. This suggests that the nanobody and &#946;-lactamase moieties remain functional. In the present work, we report a detailed protocol that combines our hybrid &#946;-lactamase system to the biosensor technology. The specific binding of the nanobody to its target can be detected thanks to a conductimetric measurement of the protons released by the catalytic activity of the enzyme.

The Use of a &amp;#946;-lactamase-based Conductimetric Biosensor Assay to Detect Biomolecular Interactions

In this work, we report a new method to study protein-protein interactions using a conductimetric biosensor based on the hybrid &#946;-lactamase technology. This method relies on release of protons upon hydrolysis of &#946;-lactams.

Biosensors are becoming increasingly important and implemented in various fields such as pathogen detection, molecular diagnosis, environmental ...

An Efficient and Reproducible Protocol for Distraction Osteogenesis in a Rat Model Leading to a Functional Regenerated Femur

This protocol describes the use of a newly developed external fixator for distraction osteogenesis in a rat femoral model. Distraction osteogenesis (DO) is a surgical technique leading to bone regeneration after an osteotomy. The osteotomized extremities are moved away from each other by gradual distraction to reach the desired elongation. This procedure is widely used in humans for lower and upper limb lengthening, treatment after a bone nonunion, or the regeneration of a bone defect following surgery for bone tumor excision, as well as in maxillofacial reconstruction. Only a few studies clearly demonstrate the efficiency of their protocol in obtaining a functional regenerated bone, i.e., bone that will support physiological weight-bearing without fracture after removal of the external fixator. Moreover, protocols for DO vary and reproducibility is limited by lack of information, making comparison between studies difficult. The aim of this study was to develop a reproducible protocol comprising an appropriate external fixator design for rat limb lengthening, with a detailed surgical technique that permits physiological weight-bearing by the animal after removal of the external fixator.

This study describes a reproducible and detailed protocol using a newly developed external fixator for distraction osteogenesis (DO) in a femoral rat model which permits physiological weight-bearing by the animal after removal of the external fixator.

This protocol describes the use of a newly developed external fixator for distraction osteogenesis in a rat femoral model. Distraction osteogenesis (DO) ...

Creating a Structurally Realistic Finite Element Geometric Model of a Cardiomyocyte to Study the Role of Cellular Architecture in Cardiomyocyte Systems Biology

With the advent of three-dimensional (3D) imaging technologies such as electron tomography, serial-block-face scanning electron microscopy and confocal microscopy, the scientific community has unprecedented access to large datasets at sub-micrometer resolution that characterize the architectural remodeling that accompanies changes in cardiomyocyte function in health and disease. However, these datasets have been under-utilized for&#160;investigating the role of cellular architecture remodeling in cardiomyocyte function. The purpose of this protocol is to outline how to create an accurate finite element model of a cardiomyocyte using high resolution electron microscopy and confocal microscopy images. A detailed and accurate model of cellular architecture has significant potential to provide new insights into cardiomyocyte biology, more than experiments alone can garner. The power of this method lies in its ability to computationally fuse information from two disparate imaging modalities of cardiomyocyte ultrastructure to develop one unified and detailed model of the cardiomyocyte. This protocol outlines steps to integrate electron tomography and confocal microscopy images of adult male Wistar (name for a specific breed of albino rat) rat cardiomyocytes to develop a half-sarcomere finite element model of the cardiomyocyte. The procedure generates a 3D finite element model that contains an accurate, high-resolution depiction (on the order of ~35 nm) of the distribution of mitochondria, myofibrils and ryanodine receptor clusters that release the necessary calcium for cardiomyocyte contraction from the sarcoplasmic reticular network (SR) into the myofibril and cytosolic compartment. The model generated here as an illustration does not incorporate details of the transverse-tubule architecture or the sarcoplasmic reticular network and is therefore a minimal model of the cardiomyocyte. Nevertheless, the model can already be applied in simulation-based investigations into the role of cell structure in calcium signaling and mitochondrial bioenergetics, which is illustrated and discussed using two case studies that are presented following the detailed protocol.

This protocol outlines a novel method to create a spatially detailed finite element model of the intracellular architecture of cardiomyocytes from electron microscopy and confocal microscopy images. The power of this spatially detailed model is demonstrated using case studies in calcium signaling and bioenergetics.

With the advent of three-dimensional (3D) imaging technologies such as electron tomography, serial-block-face scanning electron microscopy and confocal ...