Name: implantation of electrospun vascular grafts with optimized structure in a rat model
Uploaded: 2018-06-27T13:00:00
Description: Watch this Scientific Journal Video about Implantation of Electrospun Vascular Grafts with Optimized Structure in a Rat Model at JoVE.com

This work was financially supported by NSFC projects (81522023, 81530059, 91639113, 81772000, 81371699, and 81401534).

The use of experimental animals was approved by the Animal Experiments Ethical Committee of Nankai University and carried out in conformity with the Guide for Care and Use of Laboratory Animals.
1. Fabrication of Electrospun PCL Grafts
NOTE: Herein, an electrospinning technique was utilized to fabricate vascular grafts.
<ol>
	<li>Prepare PCL solutions of 25 wt% and 10 wt%, by dissolving PCL in a mixture of methanol and chloroform, respectively, (1:5 volume ratio),...

<ol>
	<li>Coombs, K. E., Leonard, A. T., Rush, M. N., Santistevan, D. A., Hedberg-Dirk, E. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolated+effect+of+material+stiffness+on+valvular+interstitial+cell+differentiation.">Isolated effect of material stiffness on valvular interstitial cell differentiation.</a> J Biomed Mater Res A. 105 (1), 51-61 (2017).</li><li>Zhang, L., 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+sandwich+tubular+scaffold+derived+from+chitosan+for+blood+vessel+tissue+engineering.">A sandwich tubular scaffold derived from chitosan for blood vessel tissue engineering.</a> J Biomed Mater Res A. 77 (2), 277-284 (2006).</li><li>Thottappillil, N., Nair, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scaffolds+in+vascular+regeneration:+current+status.">Scaffolds in vascular regeneration: current status.</a> Vasc Health Risk Manag. 11, 79-91 (2015).</li><li>Pektok, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Degradation+and+healing+characteristics+of+small-diameter+poly+(e-caprolactone)+vascular+grafts+in+the+rat+systemic+arterial+circulation.">Degradation and healing characteristics of small-diameter poly (e-caprolactone) vascular grafts in the rat systemic arterial circulation.</a> Circulation. 118 (24), 2563-2570 (2008).</li><li>Innocente, 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=Paclitaxel-eluting+biodegradable+synthetic+vascular+prostheses:+a+step+towards+reduction+of+neointima+formation?.">Paclitaxel-eluting biodegradable synthetic vascular prostheses: a step towards reduction of neointima formation?.</a> Circulation. 120 (11 Suppl), S37-S45 (2009).</li><li>de Valence, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advantages+of+bilayered+vascular+grafts+for+surgical+applicability+and+tissue+regeneration.">Advantages of bilayered vascular grafts for surgical applicability and tissue regeneration.</a> Acta Biomater. 8 (11), 3914-3920 (2012).</li><li>Assmann, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acceleration+of+autologous+in+vivo+recellularization+of+decellularized+aortic+conduits+by+fibronectin+surface+coating.">Acceleration of autologous in vivo recellularization of decellularized aortic conduits by fibronectin surface coating.</a> Biomaterials. 34 (25), 6015-6026 (2013).</li><li>Hasan, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+scaffolds+for+tissue+engineering+of+vascular+grafts.">Electrospun scaffolds for tissue engineering of vascular grafts.</a> Acta Biomater. 10 (1), 11-25 (2014).</li><li>Baker, B. 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=The+potential+to+improve+cell+infiltration+in+composite+fiber-aligned+electrospun+scaffolds+by+the+selective+removal+of+sacrificial+fibers.">The potential to improve cell infiltration in composite fiber-aligned electrospun scaffolds by the selective removal of sacrificial fibers.</a> Biomaterials. 29 (15), 2348-2358 (2008).</li><li>Wang, 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=Creation+of+macropores+in+electrospun+silk+fibroin+scaffolds+using+sacrificial+PEO-microparticles+to+enhance+cellular+infiltration.">Creation of macropores in electrospun silk fibroin scaffolds using sacrificial PEO-microparticles to enhance cellular infiltration.</a> Journal of Biomedical Materials Research Part A. 101 (12), 3474-3481 (2013).</li><li>Lee, B. L. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Femtosecond+laser+ablation+enhances+cell+infiltration+into+three-dimensional+electrospun+scaffolds.">Femtosecond laser ablation enhances cell infiltration into three-dimensional electrospun scaffolds.</a> Acta Biomaterialia. 8 (7), 2648-2658 (2012).</li><li>Rnjak-Kovacina, J., Weiss, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increasing+the+pore+size+of+electrospun+scaffolds.">Increasing the pore size of electrospun scaffolds.</a> Tissue Eng Part B Rev. 17 (5), 365-372 (2011).</li><li>Zhong, S., Zhang, Y., Lim, C. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+large+pores+in+electrospun+nanofibrous+scaffolds+for+cellular+infiltration:+a+review.">Fabrication of large pores in electrospun nanofibrous scaffolds for cellular infiltration: a review.</a> Tissue Eng Part B Rev. 18 (2), 77-87 (2012).</li><li>Pham, Q. P., Sharma, U., Mikos, A. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrospun+poly(epsilon-caprolactone)+microfiber+and+multilayer+nanofiber/microfiber+scaffolds:+characterization+of+scaffolds+and+measurement+of+cellular+infiltration.">Electrospun poly(epsilon-caprolactone) microfiber and multilayer nanofiber/microfiber scaffolds: characterization of scaffolds and measurement of cellular infiltration.</a> Biomacromolecules. 7 (10), 2796-2805 (2006).</li><li>Rnjak-Kovacina, 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=Tailoring+the+porosity+and+pore+size+of+electrospun+synthetic+human+elastin+scaffolds+for+dermal+tissue+engineering.">Tailoring the porosity and pore size of electrospun synthetic human elastin scaffolds for dermal tissue engineering.</a> Biomaterials. 32 (28), 6729-6736 (2011).</li><li>Wang, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+thick+fibers+and+large+pores+of+electrospun+poly(epsilon-caprolactone)+vascular+grafts+on+macrophage+polarization+and+arterial+regeneration.">The effect of thick fibers and large pores of electrospun poly(epsilon-caprolactone) vascular grafts on macrophage polarization and arterial regeneration.</a> Biomaterials. 35 (22), 5700-5710 (2014).</li><li>Hutcheson, J. D., 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=Genesis+and+growth+of+extracellular-vesicle-derived+microcalcification+in+atherosclerotic+plaques.">Genesis and growth of extracellular-vesicle-derived microcalcification in atherosclerotic plaques.</a> Nat Mater. 15 (3), 335-343 (2016).</li><li>Tara, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Well-organized+neointima+of+large-pore+poly(L-lactic+acid)+vascular+graft+coated+with+poly(L-lactic-co-epsilon-caprolactone)+prevents+calcific+deposition+compared+to+small-pore+electrospun+poly(L-lactic+acid)+graft+in+a+mouse+aortic+implantation+model.">Well-organized neointima of large-pore poly(L-lactic acid) vascular graft coated with poly(L-lactic-co-epsilon-caprolactone) prevents calcific deposition compared to small-pore electrospun poly(L-lactic acid) graft in a mouse aortic implantation model.</a> Atherosclerosis. 237 (2), 684-691 (2014).</li></ol>

Cell infiltration is critical for the regeneration and remodeling of the vascular graft in vivo16. Limited cell infiltration is often related to the relatively small pores of the graft that hinder the migration of cells into the graft wall. To address this difficulty, we developed a modified method to prepare electrospun PCL vascular grafts with large-pore structure. In detail, the pore size increased with the increase of fiber thickness that could be readily controlled by the processing ...

Vascular grafts made from synthetic polymers are widely utilized in clinic for the therapy of cardiovascular diseases (CVDs). Unfortunately, in the case of small-diameter vascular grafts (D &#60;6 mm) there are no successful products available due to the low patency triggered by reduced blood flow velocity, which often leads to thrombosis, intimal hyperplasia, and other complications1.
Tissue engineering provides an alternative strategy to realize long-term patency and homeostasis based on a scaffold-guided vascular regeneration and reconstruction. In detail, the vascular graft, as a three-dimensional template, could provide mechanical support and structural guidance during the regeneration of vascular tissue and influence cellular functions, including cell adhesion, migration, proliferation, and secretion of extracellular-matrix2. Up to now, various synthetic polymers have been evaluated for applications in vascular tissue engineering. Among these polymers, poly(&#949;-caprolactone) (PCL) has been intensively investigated due to good cell compatibility and slow degradation ranging from several months to two years3. In a rat aorta model4,5,6, PCL vascular grafts processed by electrospinning exhibited excellent structural integrity and patency, as well as continuously increased cell invasion and neovascularization in the graft wall for up to 6 months. However, adverse tissue remodeling, including regression of cells and capillaries and calcification, were also observed at longer timepoints, up to 18 months.
Cellularization of the vascular graft is a key factor determining tissue regeneration and remolding7. Electrospinning, as a versatile technique, has been widely employed for the preparation of vascular grafts with nano-fibrous structure8. Unfortunately, the relatively small pore structure often leads to insufficient cell infiltration in the electrospun vascular graft, which limits the subsequent tissue regeneration. To resolve this problem, various techniques have been attempted to increase pore size and overall porosity, including the salt/polymer leaching9,10, modification of collector apparatus, post-treatment by laser radiation11, etc. In fact, the structure of electrospun grafts (including fiber diameter, pore size, and porosity) is closely related to the processing conditions12,13. During electrospinning, the fiber diameter can be readily controlled by changing the parameters, such as the concentration of the polymer solution, flow rate, voltage, etc.14,15, and therefore, the pore size and porosity have been enhanced accordingly.
We recently reported a modified PCL electrospun graft with macroporous structure (fibers with diameter of 5 - 7 &#181;m and pores of 30 - 40 &#181;m). In vivo implantation by replacing rat abdominal aorta showed high rate of patency, as well as good endothelialization and smooth muscle regeneration at 3 months post-surgery16. More importantly, no adverse tissue remodeling including calcification and cell regression could be observed even after one year of implantation.

<table>
	<tbody>
		<tr>
			<td>Poly(&#949;-caprolactone) (PCL) pellets (Mn=80,000)</td>
			<td>Sigma</td>
			<td>704067</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Tianjin Chemical Reagent Company</td>
			<td>1060</td>
			<td></td>
		</tr>
		<tr>
			<td>Alcohol</td>
			<td>Tianjin Chemical Reagent Company</td>
			<td>1083</td>
			<td></td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>Tianjin Chemical Reagent Company</td>
			<td>A1007</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Tianjin Fengchuan Company</td>
			<td>2296</td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td>Alfa Aesar</td>
			<td>A16046</td>
			<td></td>
		</tr>
		<tr>
			<td>Sprague Dawley rats</td>
			<td>Laboratory Animal Center of the Academy of Military Medical Sciences</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Normal saline</td>
			<td>Hebei Tiancheng Pharmaceutical company</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Chloral hydrate</td>
			<td>Tianjin Ruijinte chemical company</td>
			<td>2223</td>
			<td></td>
		</tr>
		<tr>
			<td>Heparin sodium Injection</td>
			<td>Tianjin Biochem Pharmaceutical company</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Gentamycin Sulfate Injection</td>
			<td>Jiangsu Lianshui Pharmaceutical company</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse anti-&#945;-SMA primary antibody</td>
			<td>Abcam</td>
			<td>ab7817</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse anti-smooth MYH primary antibody</td>
			<td>Abcam</td>
			<td>ab683</td>
			<td></td>
		</tr>
		<tr>
			<td>Rabbit polyclonal anti-rat elastin antibody</td>
			<td>Abcam</td>
			<td>ab23748</td>
			<td></td>
		</tr>
		<tr>
			<td>Rabbit anti-von Willebrand factor primary antibody</td>
			<td>Abcam</td>
			<td>ab6994</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-mouse IgG (Alexa Fluor 488)</td>
			<td>Invitrogen</td>
			<td>ab150117</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-rabbit IgG (Alexa Fluor 488)</td>
			<td>Invitrogen</td>
			<td>ab150077</td>
			<td></td>
		</tr>
		<tr>
			<td>5% normal goat serum</td>
			<td>Zhongshan Golden bridge</td>
			<td>ZLI9022</td>
			<td></td>
		</tr>
		<tr>
			<td>Hematoxylin and eosin (H&#38;E)</td>
			<td>Beijing leagene biotech</td>
			<td>DH0006</td>
			<td></td>
		</tr>
		<tr>
			<td>Masson&#39;s trichrome</td>
			<td>Beijing leagene biotech</td>
			<td>DC0032</td>
			<td></td>
		</tr>
		<tr>
			<td>Verhoeff-van Gieson (VVG)</td>
			<td>Beijing leagene biotech</td>
			<td>DC0059</td>
			<td></td>
		</tr>
		<tr>
			<td>Von Kossa</td>
			<td>Beijing leagene biotech</td>
			<td>DS0003</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical sutures needles with thread,3-0 silk</td>
			<td>Shanghai Jinhuan medical supplies company</td>
			<td>G3002b</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical sutures needles with thread,9-0 silk</td>
			<td>Shanghai Jinhuan medical supplies company</td>
			<td>H901</td>
			<td></td>
		</tr>
	</tbody>
</table>

implantation of electrospun vascular grafts with optimized structure in a rat model

Here, we present a protocol to fabricate macroporous PCL vascular graft and describe an evaluation protocol by using a rat model of abdominal aorta replacement. The electrospun vascular grafts often possess relatively small pores, which limit cell infiltration into the grafts and hinder the regeneration and remodeling of the neo-arteries. In this study, PCL vascular grafts with thicker fibers (5 - 6 &#181;m) and larger pores (~30 &#181;m) were fabricated by using a modified processing technique. The long-term performance of the graft was evaluated by implantation in a rat abdominal aorta model. Ultrasound analysis showed that the grafts remained patent without aneurysm or stenosis occurring even after 12 months of implantation. Macroporous structure improved the cell ingrowth and thus promoted tissue regenerated at 3 months. More importantly, there was no sign of adverse remodeling, such as calcification within the graft wall after 12 months. Therefore, electrospun PCL vascular grafts with modified macroporous processing hold potential to be an artery substitute for long-term implantation.

The PCL grafts were explanted at 3 months and 12 months post-operatively and analyzed by standard histological techniques for hematoxylin and eosin (H&#38;E), Masson trichrome, Verhoeff-van Gieson (VVG), Von Kossa, and immunofluorescence staining for &#945;-SMA, MYH, vWF, and elastin. The histological images were taken using an upright microscope, and the immunofluorescence images were taken using a &#64258;uorescence microscope.
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Watch this Scientific Journal Video about Implantation of Electrospun Vascular Grafts with Optimized Structure in a Rat Model at JoVE.com

Implantation of Electrospun Vascular Grafts with Optimized Structure in a Rat Model

Here, we present a modified electrospinning method to fabricate PCL vascular grafts with thick fibers and large pores, and describe a protocol to evaluate the in vivo performance in a rat model of abdominal aorta replacement.

Here, we present a protocol to fabricate macroporous PCL vascular graft and describe an evaluation protocol by using a rat model of abdominal aorta ...

The overall goal of this surgical intervention is to transplant an electrospun vascular graft into a rat abdominal aorta, and evaluate the longterm performance of the graft. This method has been established by Professor Deling Kong and other colleagues in our group, and it can help answer key questions in the study of electrospun vascular grafts, such as the effect of structure and the surface properties of the graft on the vascular regeneration. The main advantage of this technique is that it has good repeatability and high animal survival rate.Besides, the animal model is easy to manage at a low cost. This work will be conducted by our colleague, Doctor Wang. To begin, prepare the polymer solution by dissolving polycaprolactone in a 1-to-5 mixture of methanol and chloroform, and stirring it at room temperature for 12 hours.Load the polymer solution into a 10 milliliter glass syringe, and equip it with a blunt 21 gauge needle. Then, place a stainless steel mandrel on the collection instrument, and make sure that it is properly grounded. Adjust the working distance from needle tip to collector to 17 centimeters for the 25%polycaprolactone solution.Then, set the flow rate on the syringe pump to eight milliliters per hour. Next, set the voltage on the power supply to 11 kilovolts, and start the mandrel spinning at 40 RPMs in order to collect electrospun fibers for appropriate fiber distribution. With everything now set up, turn on the power supply and the syringe pump to begin collecting the electrospun fibers.After 4.5 minutes, turn off the syringe pump, power supply, and the mandrel motor. Allow the graft to dry in the hood for one hour. Then, remove the graft from the mandrel using absolute alcohol, and place it in a vacuum overnight to remove the residual solvent.Sterilize the graft with ethylene oxide, and allow it to dry in a sterile biological containment hood. Using standard techniques, obtain SEM images of the lumen of the grafts, and import them into ImageJ. Use the measurement tools to measure both the fiber diameter and average pore size in each image, to ensure consistency across samples.To obtain information on the mechanical properties of the graft material, first cut a tubular scaffold into three millimeter sections using a razor blade. Then, use calipers to measure the thickness of the scaffolds. Next, load the scaffolds into the grips of a tensile testing machine, so that there is one millimeter between the grips.Hold the scaffolds axially, at a rate of 10 millimeters per minute, until they rupture. Be sure to record both the tensile strength and ultimate elongation at break for the samples. Prior to surgery, fast male Sprague Dawley rats, weighing 240 to 270 grams, for 24 hours prior to the implantation surgery.Anesthetize the rat and prepare it for surgery as described in the accompanying text protocol. Confirm adequate anesthetization by ensuring that the rat has relaxed muscles and steady breathing. Then, place the rat under the operating microscope in a supine position.Using surgical scissors, perform a four to five centimeter long midline laparotomy incision, and expose the abdominal cavity. Carefully retract and wrap the intestines with gauze that has been moistened with saline solution. While looking through the operating microscope strip the abdominal aorta from the adjacent tissues.Identify and ligate all of the small branches of the descending aorta, using 9-0 monofilament nylon sutures. Next, use vascular clamps to clamp up to a one centimeter isolated section of the aorta. Then, use a pair of micro scissors to transect the abdominal aorta between the clamps.Flush the two ends of the aorta using heparinized saline solution to remove the residual blood. Peel off the adventitia of the clamped aorta using micro scissors. Then, place a one centimeter long section of the sterilized graft in the gap created by the removed section of aorta.Using 9-0 monofilament nylon sutures, construct four anastomoses using a figure eight suture pattern at nine o'clock, three o'clock, 12 o'clock, and then six o'clock positions of the proximal side. Then, construct the other four anastomoses between each of the sutures in the proximal side. Place the graft vertically to show the equal interval among the eight stitches under the operating microscope.After finishing the proximal suture, repeat the process on the distal side. Once the graft has been attached, remove the distal clamp to allow the blood to flow into the graft, then remove the proximal clamp. Using a sterile cotton ball, apply pressure to stop any observed bleeding at the suture points.Press for about three minutes, until hemostasis occurs. Next, return the intestines into the abdominal cavity, and flush the abdominal cavity using warm physiological saline solution containing gentamicin. Then, sew up the abdominal wall using 3-0 nylon suture in the muscle and skin layers.Use iodine on the incision after surgery only once. Return the rat to the company of others once it has fully recovered. The concentration of polycaprolactone in the electrospinning solution can affect both the fiber diameter, and the mechanical properties of the grafts.The higher concentration 25%solution produces vascular grafts with thicker fibers and larger pores than the 10%solution. After three months in vivo, histological staining revealed a layer of new tissue formed on the lumen of the graft, and a significant amount of collagen deposition within the graft itself. This new tissue layer is lined with endothelial cells, below which can be found a layer of both smooth muscle cells and circumferentially aligned elastin.After 12 months in vivo, the new tissue appeared well integrated, and the endothelial and smooth muscle layers remained intact. Once mastered, this technique can be completed in one to two hours, if it is performed appropriately. Following this procedure, other measures like color doppler ultrasound, can be performed in order to answer additional questions, like After watching this video, you should have a good understanding of how to fabricate the electrospun vascular grafts, and evaluate its in vivo performance in a rat abdominal artery replacement model.

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Research

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Biology

The Structure of Skilled Forelimb Reaching in the Rat: A Movement Rating Scale

Skilled reaching for food is an evolutionary ancient act and is displayed by many animal species, including those in the sister clades of rodents and primates. The video describes a test situation that allows filming of repeated acts of reaching for food by the rat that has been mildly food deprived. A rat is trained to reach through a slot in a holding box for food pellet that it grasps and then places in its mouth for eating. Reaching is accomplished in the main by proximally driven movements of the limb but distal limb movements are used for pronating the paw, grasping the food, and releasing the food into the mouth. Each reach is divided into at least 10 movements of the forelimb and the reaching act is facilitated by postural adjustments. Each of the movements is described and examples of the movements are given from a number of viewing perspectives. By rating each movement element on a 3-point scale, the reach can be quantified. A number of studies have demonstrated that the movement elements are altered by motor system damage, including damage to the motor cortex, basal ganglia, brainstem, and spinal cord. The movements are also altered in neurological conditions that can be modeled in the rat, including Parkinson's disease and Huntington's disease. Thus, the rating scale is useful for quantifying motor impairments and the effectiveness of neural restoration and rehabilitation. Because the reaching act for the rat is very similar to that displayed by humans and nonhuman primates, the scale can be used for comparative purposes. from a number of viewing perspectives. By rating each movement element on a 3-point scale, the reach can be quantified. A number of studies have demonstrated that the movement elements are altered by motor system damage, including damage to the motor cortex, basal ganglia, brainstem, and spinal cord. The movements are also altered in neurological conditions that can be modeled in the rat, including Parkinson's disease and Huntington's disease. Thus, the rating scale is useful for quantifying motor impairments and the effectiveness of neural restoration and rehabilitation.

Experiments on animals were performed in accordance with the guidelines and regulations set forth by the University of Lethbridge Animal Care Committee in accordance with the regulations of the Canadian Council on Animal Care.

The skilled reaching scale divides the movement by a forelimb in a reach for food act into composite elements each of which are evaluated with a three-point scale. The rating scale is described for a normal rat and can be applied toward evaluating neurological motor disorders.

Skilled reaching for food is an evolutionary ancient act and is displayed by many animal species, including those in the sister clades of rodents and ...

Implantation of Engineered Tissue in the Rat Heart

Rodent surgery is often an important component in assessing the utility of engineered tissues. A wide variety of surgical procedures can be performed in common laboratory rats or mice and these quite frequently serve as an intermediate step between bench-top experiments and large animal testing or human trials. Given that rodents provide an established, cost-effective, and physiologically-relevant model system in which to test novel combinations of scaffolding materials and cells, they are particularly well-suited for cardiovascular tissue engineering studies. Presently, we describe an open-heart surgical procedure to implant engineered tissue containing myogenic progenitor cells in the atrioventricular (AV) groove of a rat heart. These implants are intended to create an electrical conduit between the right atrium and right ventricle with the ultimate goal of providing an alternative treatment to conventional pacemaker implantation in pediatric patients with complete heart block[1]. The engineered tissue is implanted in the AV-groove by means of a thoracotomy. For our purposes, Lewis rats are anesthetized and invasively ventilated to maintain positive airway pressure during the sterile surgical procedure. The approach to the heart is performed by a right thoracotomy through an antero-lateral incision at the 5th intercostal space. The tissue construct is fixed in the AV groove using a single 7-0 Prolene suture and positioned between the right ventricle and atrium at the ventral portion of the heart. The epicardium is partially removed to allow direct contact between the recipient myocardial cells and those contained in the engineered tissue. Following implantation, the chest wall is closed in layers, any pneumothorax is evacuated, and the animal is extubated and treated with analgesic.

Here, we describe a cardiac surgical procedure to implant engineered tissue in the atrioventricular (AV)-groove of an adult Lewis rat.

Rodent surgery is often an important component in assessing the utility of engineered tissues. A wide variety of surgical procedures can be performed in ...

Whole-mount Immunohistochemical Analysis for Embryonic Limb Skin Vasculature: a Model System to Study Vascular Branching Morphogenesis in Embryo

Whole-mount immunohistochemical analysis for imaging the entire vasculature is pivotal for understanding the cellular mechanisms of branching morphogenesis. We have developed the limb skin vasculature model to study vascular development in which a pre-existing primitive capillary plexus is reorganized into a hierarchically branched vascular network. Whole-mount confocal microscopy with multiple labelling allows for robust imaging of intact blood vessels as well as their cellular components including endothelial cells, pericytes and smooth muscle cells, using specific fluorescent markers. Advances in this limb skin vasculature model with genetic studies have improved understanding molecular mechanisms of vascular development and patterning. The limb skin vasculature model has been used to study how peripheral nerves provide a spatial template for the differentiation and patterning of arteries. This video article describes a simple and robust protocol to stain intact blood vessels with vascular specific antibodies and fluorescent secondary antibodies, which is applicable for vascularized embryonic organs where we are able to follow the process of vascular development.

We introduce a whole-mount immunohistochemistry and laser scanning confocal microscopy with multiple labelling for analyzing intricate vascular network formation in mouse embryonic limb skin.

Whole-mount immunohistochemical analysis for imaging the entire vasculature is pivotal for understanding the cellular mechanisms of branching ...

Rat Mesentery Exteriorization: A Model for Investigating the Cellular Dynamics Involved in Angiogenesis

Microvacular network growth and remodeling are critical aspects of wound healing, inflammation, diabetic retinopathy, tumor growth and other disease conditions1, 2. Network growth is commonly attributed to angiogenesis, defined as the growth of new vessels from pre-existing vessels. The angiogenic process is also directly linked to arteriogenesis, defined as the capillary acquisition of a perivascular cell coating and vessel enlargement. Needless to say, angiogenesis is complex and involves multiple players at the cellular and molecular level3. Understanding how a microvascular network grows requires identifying the spatial and temporal dynamics along the hierarchy of a network over the time course of angiogenesis. This information is critical for the development of therapies aimed at manipulating vessel growth.
The exteriorization model described in this article represents a simple, reproducible model for stimulating angiogenesis in the rat mesentery. It was adapted from wound-healing models in the rat mesentery4-7, and is an alternative to stimulate angiogenesis in the mesentery via i.p. injections of pro-angiogenic agents8, 9. The exteriorization model is attractive because it requires minimal surgical intervention and produces dramatic, reproducible increases in capillary sprouts, vascular area and vascular density over a relatively short time course in a tissue that allows for the two-dimensional visualization of entire microvascular networks down to single cell level. The stimulated growth reflects natural angiogenic responses in a physiological environment without interference of foreign angiogenic molecules. Using immunohistochemical labeling methods, this model has been proven extremely useful in identifying novel cellular events involved in angiogenesis. Investigators can readily correlate the angiogenic metrics during the time course of remodeling with time specific dynamics, such as cellular phenotypic changes or cellular interactions4, 5, 7, 10, 11.

This article describes a simple model for stimulating angiogenesis in the rat mesentery. The model produces dramatic increases in capillary sprouting, vascular area and vascular density over a relatively short time course in a tissue that allows en face visualization of entire microvascular networks down to the single cell level.

Microvacular network growth and remodeling are critical aspects of wound healing, inflammation, diabetic retinopathy, tumor growth and other disease ...

Functional Reconstitution and Channel Activity Measurements of Purified Wildtype and Mutant CFTR Protein

The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a unique channel-forming member of the ATP Binding Cassette (ABC) superfamily of transporters. The phosphorylation and nucleotide dependent chloride channel activity of CFTR has been frequently studied in whole cell systems and as single channels in excised membrane patches. Many Cystic Fibrosis-causing mutations have been shown to alter this activity. While a small number of purification protocols have been published, a fast reconstitution method that retains channel activity and a suitable method for studying population channel activity in a purified system have been lacking. Here rapid methods are described for purification and functional reconstitution of the full-length CFTR protein into proteoliposomes of defined lipid composition that retains activity as a regulated halide channel. This reconstitution method together with a novel flux-based assay of channel activity is a suitable system for studying the population channel properties of wild type CFTR and the disease-causing mutants F508del- and G551D-CFTR. Specifically, the method has utility in studying the direct effects of phosphorylation, nucleotides and small molecules such as potentiators and inhibitors on CFTR channel activity. The methods are also amenable to the study of other membrane channels/transporters for anionic substrates.

Described here is a rapid and effective procedure for functional reconstitution of purified wild-type and mutant CFTR protein that preserves activity for this chloride channel, which is defective in Cystic Fibrosis. Iodide efflux from reconstituted proteoliposomes mediated by CFTR allows studies of channel activity and the effects of small molecules.

The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a unique channel-forming member of the ATP Binding Cassette (ABC) superfamily of ...

Evaluating Vascular Hyperpermeability-inducing Agents in the Skin with the Miles Assay

The primary function of the vascular endothelium in vertebrate organisms is to serve as a barrier between the blood and each tissue of the body, whereby the permeability of the endothelium to blood cells, plasma macromolecules, and water can be adapted according to the physiological need. In certain diseases, cytokines and growth factors are released that target the endothelial barrier to transiently increase vascular permeability; however, their prolonged presence may cause chronic vascular hyperpermeability and thereby tissue-damaging edema. The Miles assay is an in vivo technique that allows researchers to study vascular hyperpermeability through the proxy measurement of vascular leakage. Here, we provide a detailed protocol on how to perform this procedure in the mouse, which is the most widely used model organism to study mammalian physiology and pathology. The procedure involves the intravenous injection of Evans blue dye to label the circulating albumin followed by multiple intradermal injections of permeability-inducing agents and vehicle control solutions into opposing flanks of the mouse. Consequently, Evans blue dye gradually leaks into the dermis, where it accumulates and can be extracted for quantification as leakage induced by the permeability-inducing agent relative to the vehicle. The Miles assay can be performed in wild type or genetically modified mouse models and may be combined with drug administration to study molecular mechanisms that regulate vascular permeability and identify agents/targets capable of inducing or blocking hyperpermeability.

Here, we present a protocol to measure the vascular leakage induced by intradermal administration of permeability promoting agents into the murine skin. This technique can be used to determine the ability of molecules to promote or inhibit vascular leakage or to study the molecular mechanisms that regulate vascular permeability.

The primary function of the vascular endothelium in vertebrate organisms is to serve as a barrier between the blood and each tissue of the body, whereby ...

Optimized Scratch Assay for In Vitro Testing of Cell Migration with an Automated Optical Camera

Cell migration is an important process that influences many aspects of health, such as wound healing and cancer, and it is, therefore, crucial for developing methods to study the migration. The scratch assay has long been the most common in vitro method to test compounds with anti- and pro-migration properties because of its low cost and simple procedure. However, an often-reported problem of the assay is the accumulation of cells across the edge of the scratch. Furthermore, to obtain data from the assay, images of different exposures must be taken over a period of time at the exact same spot to compare the movements of the migration. Different analysis programs can be used to describe the scratch closure, but they are labor intensive, inaccurate, and forces cycles of temperature changes. In this study, we demonstrate an optimized method for testing the migration effect, e.g. with the naturally occurring proteins Human- and Bovine-Lactoferrin and their N-terminal peptide Lactoferricin on the epithelial cell line HaCaT. A crucial optimization is to wash and scratch in PBS, which eliminates the aforementioned accumulation of cells along the edge. This could be explained by the removal of cations, which have been shown to have an effect on keratinocyte cell-cell connection. To ensure true detection of migration, pre-treating with mitomycin C, a DNA synthesis inhibitor, was added to the protocol. Finally, we demonstrate the automated optical camera, which eliminates excessive temperature cycles, manual labor with scratch closure analysis, while improving on reproducibility and ensuring analysis of identical sections of the scratch over time.

Optimized Scratch Assay for In Vitro Testing of Cell Migration with an Automated Optical Camera

Here we describe a procedure to test the cell migration in vitro with an automated optical camera microscope. The scratch assay has been widely used where the closure of the scratch is followed for a set period. The optical microscope enables dependable and cheap detection of cell migration.

Cell migration is an important process that influences many aspects of health, such as wound healing and cancer, and it is, therefore, crucial for ...

Mass Spectrometry Analysis to Identify Ubiquitylation of EYFP-tagged CENP-A (EYFP-CENP-A)

Studying the structure and the dynamics of kinetochores and centromeres is important in understanding chromosomal instability (CIN) and cancer progression. How the chromosomal location and function of a centromere (i.e., centromere identity) are determined and participate in accurate chromosome segregation is a fundamental question. CENP-A is proposed to be the non-DNA indicator (epigenetic mark) of centromere identity, and CENP-A ubiquitylation is required for CENP-A deposition at the centromere, inherited through dimerization between cell division, and indispensable to cell viability.
Here we describe mass spectrometry analysis to identify ubiquitylation of EYFP-CENP-A K124R mutant suggesting that ubiquitylation at a different lysine is induced because of the EYFP tagging in the CENP-A K124R mutant protein. Lysine 306 (K306) ubiquitylation in EYFP-CENP-A K124R was successfully identified, which corresponds to lysine 56 (K56) in CENP-A through mass spectrometry analysis. A caveat is discussed in the use of GFP/EYFP or the tagging of high molecular weight protein as a tool to analyze the function of a protein. Current technical limit is also discussed for the detection of ubiquitylated bands, identification of site-specific ubiquitylation(s), and visualization of ubiquitylation in living cells or a specific single cell during the whole cell cycle.
The method of mass spectrometry analysis presented here can be applied to human CENP-A protein with different tags and other centromere-kinetochore proteins. These combinatory methods consisting of several assays/analyses could be recommended for researchers who are interested in identifying functional roles of ubiquitylation.

Mass Spectrometry Analysis to Identify Ubiquitylation of EYFP-tagged CENP-A EYFP-CENP-A

CENP-A ubiquitylation is an important requirement for CENP-A deposition at the centromere, inherited through dimerization between cell division, and indispensable to cell viability. Here we describe mass spectrometry analysis to identify ubiquitylation of EYFP-tagged CENP-A (EYFP-CENP-A) protein.

Studying the structure and the dynamics of kinetochores and centromeres is important in understanding chromosomal instability (CIN) and cancer ...

Single Cell Collection of Trophoblast Cells in Peri-implantation Stage Human Embryos

Human implantation, the apposition and adhesion to the uterine surface epithelia and subsequent invasion of the blastocyst into the maternal decidua, is a critical yet enigmatic biological event that has been historically difficult to study due to technical and ethical limitations. Implantation is initiated by the development of the trophectoderm to early trophoblast and subsequent differentiation into distinct trophoblast sublineages. Aberrant early trophoblast differentiation may lead to implantation failure, placental pathologies, fetal abnormalities, and miscarriage. Recently, methods have been developed to allow human embryos to grow until day 13 post-fertilization in vitro in the absence of maternal tissues, a time-period that encompasses the implantation period in humans. This has given researchers the opportunity to investigate human implantation and recapitulate the dynamics of trophoblast differentiation during this critical period without confounding maternal influences and avoiding inherent obstacles to study early embryo differentiation events in vivo. To characterize different trophoblast sublineages during implantation, we have adopted existing two-dimensional (2D) extended culture methods and developed a procedure to enzymatically digest and isolate different types of trophoblast cells for downstream assays. Embryos cultured in 2D conditions have a relatively flattened morphology and may be suboptimal in modeling in vivo three-dimensional (3D) embryonic architectures. However, trophoblast differentiation seems to be less affected as demonstrated by anticipated morphology and gene expression changes over the course of extended culture. Different trophoblast sublineages, including cytotrophoblast, syncytiotrophoblast and migratory trophoblast can be separated by size, location, and temporal emergence, and used for further characterization or experimentation. Investigation of these early trophoblast cells may be instrumental in understanding human implantation, treating common placental pathologies, and mitigating the incidence of pregnancy loss.

Here, we describe a method for warming vitrified human blastocysts, culturing them through the implantation period in vitro, digesting them into single cells and collecting early trophoblast cells for further investigation.

Human implantation, the apposition and adhesion to the uterine surface epithelia and subsequent invasion of the blastocyst into the maternal decidua, is a ...

Isolation of Primary Rat Hepatocytes with Multiparameter Perfusion Control

Primary hepatocytes are widely used in basic research on liver diseases and for toxicity testing in vitro. The two-step collagenase perfusion procedure for primary hepatocyte isolation is technically challenging, especially in portal vein cannulation. The procedure is also prone to occasional contamination and variations in perfusion conditions due to difficulties in the assembly, optimization, or maintenance of the perfusion setup. Here, a detailed protocol for an improved two-step collagenase perfusion procedure with multiparameter perfusion control is presented. Primary rat hepatocytes were successfully and reliably isolated by taking the necessary technical precautions at critical steps of the procedure, and by reducing the operational difficulty and mitigating the variability of perfusion parameters through the adoption of a special intravenous catheter, standardized sterile disposable tubing, temperature control, and real-time monitoring and alarm system. The isolated primary rat hepatocytes consistently exhibit high cell viability (85%-95%), yield (2-5 x 108 cells per 200-300 g rat) and functionality (albumin, urea and CYP activity). The procedure was complemented by an integrated perfusion system, which is compact enough to be set up in the laminar flow hood to ensure aseptic operation.

This protocol details the use of a special intravenous catheter, standardized sterile disposable tubing, temperature control complemented by real-time monitoring, and an alarm system for two-step collagenase perfusion procedure to improve the consistency in the viability, yield, and functionality of isolated primary rat hepatocytes.

Primary hepatocytes are widely used in basic research on liver diseases and for toxicity testing in vitro. The two-step collagenase perfusion procedure ...