Authors thank Viktoria Skude, Alexander Schlund, and Felix H&#246;rner for the excellent technical support.

NOTE: All experimental procedures were performed according to the EC guideline EC 2010/63/EU and have been approved by the local German legislation (35-9185.81/G[1]239/18). Ten male ApoE-/- mice with the C57BL/6J background, weighing 29.6-38.0 g, were housed on a 12 h light/dark cycle and fed a western diet (1.25% cholesterol and 21% fat) and water ad libitum for 12 weeks from the age of 8 weeks. HLI was performed on 20-week-old mice as described below.
1. Induction of HLI in ApoE-/- mice
<ol>
	<li>Prepare the required equipment and tools for surgery (see the Table of Materials and Figure 1).&#160;Sterilize the surgical instruments via autoclaving before use and use a glass Bead Sterilizer during the operation.</li>
	<li>Anesthetize the mouse with a subcutaneous injection (S.C.) of a mixture of midazolam (5 mg/kg), medetomidine (0.05 mg/ml/kg), and fentanyl (0.5 mg/kg) before all surgical procedures.
	<ol>
		<li>After onset of anesthesia, use the vet ointment on the eyes to prevent dryness, and confirm the absence of the pedal withdrawal reflex in the forelimb and hind limb.</li>
	</ol>
	</li>
	<li>Afterwards place the mouse on a heating pad to keep the core body temperature at approximately 37 &#176;C. Using cotton swabs and hair removal cream, carefully remove hair from the hind limb skin on the right side. 
	NOTE: The hair removal cream should be used in sufficient quantity to cover the hindlimb, especially the inguinal region where the incision will be made. The hair removal cream should be used for a duration of less than 3 minutes and should be subsequently removed with moistened cotton swabs 2 to 3 times.</li>
	<li>Lay the mouse in the supine position on the heating pad under a dissecting microscope. Use a skin antiseptic&#160;(see the&#160;Table of Materials)&#160;to disinfect the skin of the mouse. Afterwards, use pointed forceps and surgical scissors to make an approximately 3-4 mm incision in the middle of the inguinal region. See Figure 2 for a schematic of the procedure.</li>
	<li>Remove the subcutaneous fat tissue carefully with help of fine pointed forceps to expose the proximal femoral neurovascular bundle. Carefully use the fine pointed forceps to pierce the membrane of the femoral sheath. Use a cotton swab moistened with saline to move the femoral artery (FA) carefully away from the femoral nerve (FN) and femoral vein (FV).</li>
	<li>Pass two 7-0 absorbable sutures through the proximal FA, and make double knots using spring scissors to transect the FA between the two ties.</li>
	<li>To expose the distal FA, pass a 7-0 absorbable suture through the lower edge of the incision and gently drag the incision to the region of the right side of the knee of the hind limb.</li>
	<li>Move the subcutaneous tissue aside carefully to expose the neurovascular bundle. Use fine pointed forceps to pierce the membrane of the femoral sheath, and dissect the FA from the FV and FN.</li>
	<li>Pass two 7-0 absorbable sutures through the distal FA, and make double knots. Use spring scissors to transect the FA between the two ties. 
	NOTE: No ligation was performed on the left limb, which served as a control in each mouse.</li>
	<li>Afterwards, use 6-0 absorbable sutures to stitch the incision. Place the mouse on a heating pad in a clean cage and continue to monitor its vital parameters until recovery. Provide postoperative analgesics: Buprenorphine s.c. (0.1 mg/kg body weight every 8 hours for 48 h). 48 h after the operation, administer metamizole in drinking water (24 mg/5mL of water corresponds to a dose of 200 mg/kg 4 times daily).</li>
</ol>
2. Magnetic resonance imaging
NOTE: One day after DLFA, the mice must undergo MRI scans to assess FA blockage.
<ol>
	<li>Place the mouse in a transparent induction chamber, and anesthetize the mouse with 1.5-2% isoflurane in ambient air until loss of righting reflex.</li>
	<li>Place the mouse on a heated animal bed equipped with a bite holder and positioned toward the magnet with a laser-controlled system. Maintain the body temperature at 37&#177;1 &#176;C.</li>
	<li>During image acquisition, maintain anesthesia with 1.5-2% isoflurane in ambient air, and monitor the respiration using a pressure probe.</li>
	<li>Acquire images in the transverse slice orientation using a three-dimensional (3D) time of flight (TOF) angiography sequence with parameter echo time (TE)/repetition time (TR)/flip angle (FA) = 2 ms/12 ms/13&#176;, four averages, an acquisition matrix of 178 x 144 reconstructed to 256 x 192 and 121 slices, resulting in an isotropic resolution of 0.15 mm3. To suppress the signal from the veins, place a saturation slice distally to the hind limbs.</li>
</ol>
3. Clinical evaluation and follow-up
<ol>
	<li>Estimate the functional recovery in the 1st, 3rd, 5th, and 7th days after the surgery by using the functional scoring Tarlov scale18,19 (Table 1).</li>
</ol>
4. Histologic evaluation
<ol>
	<li>Seven days after the surgery, apply pentobarbital injection (115 mg/kg) to euthanize the mice.</li>
	<li>Perfuse phosphate-buffered saline (PBS) containing 1% paraformaldehyde (PFA) through the left cardiac ventricle (100 mL per mouse). Fix the bilateral gastrocnemius (Gm) of the mice in 4% PFA overnight at 4 &#176;C.</li>
	<li>Embed the sample in paraffin according to the previously described protocol20.
	<ol>
		<li>Cut 4-5 &#181;m thick sections of the paraffin-embedded tissue block on a microtome. With the help of a round paint brush, place the cut tissue sections in the water bath maintained at 42&#176;C.</li>
		<li>Insert the microscope slide into the water at a 45&#176; angle, and carefully position it underneath the group of sections to be collected.</li>
		<li>Carefully lift the slide from the water, and allow the sections to attach to the slide and dry overnight in the benchtop incubator at 37 &#176;C.</li>
	</ol>
	</li>
	<li>Perform hematoxylin/eosin (HE) staining of the paraffin sections.
	<ol>
		<li>Place the slides containing the sections in slide holders. Prepare 3 containers of fresh xylene, and place the slides in each container for 5 min to deparaffinize the sections.</li>
		<li>Rehydrate the sections by dipping the slices successively in 96%, 80%, 70%, 50%, 30% ethanol, and deionized water for 5 min each.</li>
		<li>Stain in hematoxylin solution for 10 min.</li>
		<li>Transfer the slices to a container of deionized water and rinse by placing under running tap water for 5 min.</li>
		<li>Using a microscope, check the intensity of hematoxylin staining. If the staining enables identification of the cell nuclei clearly, continue to the next step. If the staining intensity does not facilitate identification of cell nuclei or if the intensity of staining is faint, place the slide in the hematoxylin solution for 1 min, repeat the washing with water (step 4.4.4), and then check again.</li>
		<li>Counterstain in eosin-Y solution for 5 min.</li>
		<li>Dehydrate the sections by dipping the slices successively into containers containing deionized water and 30%, 50%, 70%, 80%, and 96% ethanol successively for a duration 10 s each. Next, place the sections sequentially in three containers of fresh xylene for 10 s each.</li>
		<li>Place the slides horizontally on microscopic slide storage maps with the sections facing upwards. Add enough mounting medium on the slide, and mount the slides with coverslips.</li>
	</ol>
	</li>
	<li>Perform the immunohistochemical (IHC) staining of the paraffin sections.
	<ol>
		<li>Repeat deparaffinization and rehydration steps 4.4.1-4.4.2. Then, immerse the sections in a container with 10 mM sodium citrate buffer, pH 6, and bring the sample to a boil in a microwave. 
		NOTE: As over- or under-heating of samples can cause inconsistent staining, maintain the temperature at just below the boiling point for 10 min.</li>
		<li>Next, cool the sections on a benchtop for 30 min. Thereafter, wash the sections in PBS three times for 5 min. Carefully dry the area around the sample, and draw a large circle around the sample using a hydrophobic pen. . 
		NOTE: Never touch the sample. Marking with a hydrophobic pen creates a hydrophobic boundary, which facilitates the use of a smaller volume of antibody solution.</li>
		<li>Quench endogenous peroxidase activity by placing the section in 0.3% H2O2 in PBS for 10 min. Block sections with 400 &#181;L of block buffer (PBS contain 3% bovine serum albumin and 0.3% of non-ionic detergent) for 1 h at room temperature in a humidified chamber.</li>
		<li>Wash the sections in PBS for 5 min. Next, add 100-400 &#181;L of diluted anti-CD31 antibody (1:250) enough to cover the section. Following this, incubate sections overnight at 4 &#176;C in a humidified chamber. 
		NOTE: Ensure that the section is completely covered with the antibody solution.</li>
		<li>Remove the primary antibody, and wash the sections thrice in PBS for a duration of 5 min each.</li>
		<li>Prepare the 3, 3&#39;-diaminobenzidine (DAB) mixture by adding 1 drop of the DAB concentrate to 1 mL of the DAB diluent, and mix well. Afterwards, add 100-400 &#181;L of DAB mixture to the sections, and monitor closely by eye for 2 min until an acceptable staining intensity is observed. 
		NOTE: Ensure that the section is completely covered with the DAB mixture.</li>
		<li>Afterwards, rinse under running tap water for 5 min. Perform hematoxylin staining as described in steps 4.4.3-4.4.5.</li>
		<li>Perform eosin-Y staining described in step 4.4.6. Perform dehydration steps described in step 4.4.7.</li>
		<li>Mounted the sections with coverslips by using mounting medium. Use ImageJ to estimate the percent of CD31 positive area (%) in 5 randomly selected fields (40x) that can be regarded as microvascular density as previously described21.</li>
	</ol>
	</li>
</ol>
5. Statistical analysis
<ol>
	<li>Use statistical analysis software to express the results as mean &#177; standard deviation and to perform unpaired t-test on the comparisons. Consider P &#60; 0.05 to be statistically significant.</li>
</ol>

The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

This study reports a modified, simplified, and surgically efficient approach to establish an HLI model in ApoE-/- mice using double ligation in the proximal and distal regions of the FA through a 3-4 mm incision without any required laboratory upgrades. The main characteristic of this method is the smaller size of the incision compared to previously reported studies describing mouse HLI models8,9,10,<sup cl...

There is an unmet need for preclinical animal models for research in vascular diseases such as peripheral artery disease (PAD). Despite the advanced developments in diagnosis and treatment, there were more than 200 million patients with PAD in 20181, and their number is constantly increasing. Although several novel therapeutic approaches2,3,4,5,6,7 have been described, successful translation of these therapeutic modalities into clinical application remains a daunting task. Therefore, reliable and relevant in vivo experimental models simulating the human disease condition are required to investigate the potential mechanism and efficiency of these new therapeutic approaches to treat PAD6,7.
Hyperlipidemia and atherosclerosis (AS) are the main risk factors for the development of PAD. ApoE-/- mice (on a high-fat diet) display abnormal fat metabolism and hyperlipidemia and subsequently develop atherosclerotic plaques rendering ApoE-/- mice as the best choice to simulate the clinically relevant PAD. Preclinical HLI animal models are generated through double ligation of the femoral artery (DLFA), which is the most widely used approach in laboratories all over the world8,9,10,11,12,13,14,15 to simulate acute-on-chronic ischemia. However, this approach usually requires a relatively large and invasive incision. Furthermore, it inevitably leads to the animals (especially mice) suffering from increased pain injury and inflammation, which also influences the subsequent experimental results5,6,16,17. This paper describes an acute-on-chronic HLI model in APOE-/- mice by using a very small incision.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr >
			<td >10x Phosphate buffer saline</td>
			<td >Roth</td>
			<td >9143.1</td>
			<td >Used for haematoxylin and eosin stain and immunohistochemistry stain</td>
		</tr>
		<tr >
			<td >30% H2O2</td>
			<td >Roth</td>
			<td >9681.2</td>
			<td>Used for immunohistochemistry stain</td>
		</tr>
		<tr >
			<td >6-0 absorbable sutures</td>
			<td>PROLENE</td>
			<td>8776H</td>
			<td>Used for stitching the skin</td>
		</tr>
		<tr >
			<td >6-0 absroable suture</td>
			<td >PROLENE</td>
			<td >EP8706</td>
			<td>Used in Surgery</td>
		</tr>
		<tr >
			<td >7-0 absorbable sutures</td>
			<td>PROLENE</td>
			<td >EH8021E</td>
			<td>Used for ligating the artery</td>
		</tr>
		<tr >
			<td >7-0 absroable suture</td>
			<td >PROLENE</td>
			<td >EP8755</td>
			<td>Used in Surgery</td>
		</tr>
		<tr >
			<td >Acetic acid</td>
			<td >Roth</td>
			<td>6755.1</td>
			<td>Used for haematoxylin and eosin stain</td>
		</tr>
		<tr >
			<td >Albumin Fraktion V</td>
			<td >Roth</td>
			<td >8076.2</td>
			<td>Used for immunohistochemistry stain</td>
		</tr>
		<tr >
			<td >Autoclave</td>
			<td >Systec GmbH</td>
			<td >Systec VX-150</td>
			<td>Used for the sterilisation of the surgical instruments</td>
		</tr>
		<tr >
			<td >Axio vert A1 microscope</td>
			<td >Carl Zeiss</td>
			<td >ZEISS Axio Vert.A1</td>
			<td>Used for viewing and taking the pictures from haematoxylin and eosin stain and immunohistochemistry stain</td>
		</tr>
		<tr >
			<td >Bruker BioSpec 94/20 AVIII</td>
			<td >Bruker Biospin MRI GmbH</td>
			<td >N/A</td>
			<td>Scan the femoral artery blockage</td>
		</tr>
		<tr >
			<td >Buprenovet Sine 0,3mg/ml</td>
			<td >Bayer AG</td>
			<td >2542 (WDT)</td>
			<td>Used in post operative pain-management. Dose - 0.1 mg/kg body weight every 8 hours for 48 h after operation</td>
		</tr>
		<tr >
			<td >CD31 antibody</td>
			<td >Abcam</td>
			<td >ab28364</td>
			<td>Used for immunohistochemistry stain</td>
		</tr>
		<tr >
			<td >Eosin Y solution 0.5 % in water</td>
			<td >Roth</td>
			<td >X883.1</td>
			<td>Used for haematoxylin and eosin stain</td>
		</tr>
		<tr >
			<td >Epitope Retrieval Solution pH 6</td>
			<td >Leica Biosystems</td>
			<td >6046945</td>
			<td>Used for immunohistochemistry stain</td>
		</tr>
		<tr >
			<td >Ethanol &#8805; 99,5 %</td>
			<td >Roth</td>
			<td >5054.1</td>
			<td>Used for haematoxylin and eosin stain and immunohistochemistry stain</td>
		</tr>
		<tr >
			<td >Fentanyl</td>
			<td>Cayman Chemical</td>
			<td >437-38-7</td>
			<td>Used for anesthesia</td>
		</tr>
		<tr >
			<td >Fine point forceps</td>
			<td >Medixplus</td>
			<td >93-4505S</td>
			<td>Used for separating the artery from nerve and vein</td>
		</tr>
		<tr >
			<td >Glass bead sterilisator</td>
			<td >Simon Keller</td>
			<td >Type 250</td>
			<td>Used for sterilisation of the surgical instruments</td>
		</tr>
		<tr >
			<td >Graefe iris forceps curved</td>
			<td >VUBU</td>
			<td >VUBU-02-72207</td>
			<td>Used for blunt separation of skin and subcutaneous tissue</td>
		</tr>
		<tr >
			<td >Hair Remover cream, Veet (with aloe vera)</td>
			<td >Reckitt Benckiser</td>
			<td >108972</td>
			<td>Remove hair from mice hind limbs</td>
		</tr>
		<tr >
			<td >Heating plate</td>
			<td >ST&#214;RK-TRONIC</td>
			<td >7042092</td>
			<td>Keep the satble temperature of mice</td>
		</tr>
		<tr >
			<td >Hematoxylin</td>
			<td >Roth</td>
			<td >T865.2</td>
			<td>Used for haematoxylin and eosin stain and immunohistochemistry stain</td>
		</tr>
		<tr >
			<td >Leica surgical microscope</td>
			<td >Leica</td>
			<td >M651</td>
			<td>Enlarge the field of view to facilitate the operation</td>
		</tr>
		<tr >
			<td >Liquid DAB+Substrate Chromogen System</td>
			<td >Dako</td>
			<td >K3468</td>
			<td>Used for immunohistochemistry stain</td>
		</tr>
		<tr >
			<td >Male ApoE-/- mice</td>
			<td >Charles River Laboratories</td>
			<td >N/A</td>
			<td>Used for establish the Peripheral artery disease mice model</td>
		</tr>
		<tr >
			<td >Medetomidine</td>
			<td>Cayman Chemical</td>
			<td>128366-50-7</td>
			<td>Used for anesthesia</td>
		</tr>
		<tr >
			<td >Micro Needle Holder</td>
			<td >Black &#38; Black Surgical</td>
			<td >B3B-18-8</td>
			<td>Holding the needle</td>
		</tr>
		<tr >
			<td >Micro suture tying forceps</td>
			<td >Life Saver Surgical Industries</td>
			<td >PS-MSF-145</td>
			<td>Used to assist in knotting during surgery</td>
		</tr>
		<tr >
			<td >Microtome</td>
			<td >Biobase</td>
			<td >Bk-Mt268m</td>
			<td>Used for tissue sectioning</td>
		</tr>
		<tr >
			<td >Midazolam</td>
			<td>Ratiopharm</td>
			<td>44856.01.00</td>
			<td>Used for anesthesia</td>
		</tr>
		<tr >
			<td >MR-compatible Small Animal Monitoring and Gating System Model 1025</td>
			<td>SA Instruments</td>
			<td>N/a</td>
			<td>monitoring vital signs of animal during MRI scan</td>
		</tr>
		<tr >
			<td >Octeniderm farblos</td>
			<td >Sch&#252;lke &#38; Mayr GmbH</td>
			<td >180212</td>
			<td>used for disinfection of the skin</td>
		</tr>
		<tr >
			<td >Ointment for the eyes and nose</td>
			<td >Bayer AG</td>
			<td >1578675</td>
			<td>Keep the eyes wet under the anesthesia</td>
		</tr>
		<tr >
			<td >Paraformaldehyde</td>
			<td >Roth</td>
			<td >0335.1</td>
			<td>Used for fixation of the tissue</td>
		</tr>
		<tr >
			<td >Pentobarbital</td>
			<td>Nembutal</td>
			<td >76-74-4</td>
			<td>Used for anesthesia</td>
		</tr>
		<tr >
			<td >Saline</td>
			<td>DeltaSelect</td>
			<td >1299.99.99</td>
			<td>Used for anesthesia</td>
		</tr>
		<tr >
			<td >Spring handle scissors with fine, sharp tips</td>
			<td >Black &#38; Black Surgical</td>
			<td >B66167</td>
			<td>Used for cutting the artery</td>
		</tr>
		<tr >
			<td >SuperCut Scissors</td>
			<td >Black &#38; Black Surgical</td>
			<td >B55992</td>
			<td>Used for cutting the skin</td>
		</tr>
		<tr >
			<td >Triton X-100</td>
			<td >Roth</td>
			<td >9002-93-1</td>
			<td>Used for immunohistochemistry stain</td>
		</tr>
		<tr >
			<td >Western diet, 1.25% Cholesterol</td>
			<td >ssniff Spezialdi&#228;ten GmbH</td>
			<td >E15723-34</td>
			<td>Diet for the mice</td>
		</tr>
		<tr >
			<td >Xylene</td>
			<td >Roth</td>
			<td >4436.3</td>
			<td>Used for haematoxylin and eosin stain and immunohistochemistry stain</td>
		</tr>
	</tbody>
</table>

a modified surgical model of hind limb ischemia in apoe-/- mice using a miniature incision

The purpose of this study is to introduce and evaluate a modified surgical approach to induce acute ischemia in mice that can be implemented in most animal laboratories.&#160;Contrary to the conventional approach for double ligation of the femoral artery (DLFA), a smaller incision on the right inguinal region was made to expose the proximal femoral artery (FA) to perform DLFA. Then, using a 7-0 suture, the incision was dragged to the knee region to expose the distal FA. Magnetic resonance imaging (MRI) on bilateral hind limbs was used to detect FA occlusion after the surgery. At 0, 1, 3, 5, and 7 days after the surgery, functional recovery of the hind limbs was visually assessed and graded using the Tarlov scale. Histologic evaluation was performed after euthanizing the animals 7 days after DLFA. The procedures were successfully performed on the right leg in ten ApoE-/- mice, and no mice died during subsequent observation. The incision sizes in all 10 mice were less than 5 mm (4.2 &#177; 0.63 mm). MRI results showed that FA blood flow in the ischemic side was clearly blocked. The Tarlov scale results demonstrated that hind limb function significantly decreased after the procedure and slowly recovered over the following 7 days. Histologic evaluation showed a significant inflammatory response on the ischemic side and reduced microvascular density in the ischemic hind limb. In conclusion, this study introduces a modified technique using a miniature incision to perform hind limb ischemia (HLI) using DLFA.

Characteristics of ApoE-/- mice 
DLFA surgeries were successfully performed on 10 mice to establish the HLI model, and none of the mice died after the procedure. To follow changes in body weight, mice were weighed before the DLFA procedure (Pre-DLFA) and 7 days after the DLFA surgery (Post-DLFA). Pre-DLFA weights ranged from 29.6 to 38.0 g (mean 34.74 &#177; 2.47 g), and post-DLFA weights ranged from 26.5 to 34.1 g (mean 30.77 &#177; 2.15 g), which were s...

Watch this Scientific Journal Video about A Modified Surgical Model of Hind Limb Ischemia in ApoE-/- Mice using a Miniature Incision at JoVE.com

A Modified Surgical Model of Hind Limb Ischemia in ApoE-/- Mice using a Miniature Incision

This article demonstrates an efficient surgical approach to establish acute ischemia in mice with a small incision. This approach can be applied by most research groups without any laboratory upgrades.

A Modified Surgical Model of Hind Limb Ischemia in ApoE-/- Mice using a Miniature Incision

The purpose of this study is to introduce and evaluate a modified surgical approach to induce acute ischemia in mice that can be implemented in most ...

a-modified-surgical-model-hind-limb-ischemia-apoe-mice-using

Research

JoVE Journal

Biology

3.7K Views.  Heidelberg University. This article demonstrates an efficient surgical approach to establish acute ischemia in mice with a small incision. This approach can be applied by most research groups without any laboratory upgrades.

Video: A Modified Surgical Model of Hind Limb Ischemia in ApoE-/- Mice using a Miniature Incision

Preventing the Spread of Malaria and Dengue Fever Using Genetically Modified Mosquitoes

In this candid interview, Anthony A. James explains how mosquito genetics can be exploited to control malaria and dengue transmission.   Population replacement strategy, the idea that transgenic mosquitoes can be released into the wild to control disease transmission, is introduced, as well as the concept of genetic drive and the design criterion for an effective genetic drive system. The ethical considerations of releasing genetically-modified organisms into the wild are also discussed.

In this candid interview, Anthony A. James explains how mosquito genetics can be exploited to control malaria and dengue transmission. Population replacement strategy, the idea that transgenic mosquitoes can be released into the wild to control disease transmission, is introduced as well as the concept of genetic drive and the design criterion for an effective genetic drive system. The ethical considerations of releasing genetically-modified organisms into the wild are also discussed.

In this candid interview, Anthony A. James explains how mosquito genetics can be exploited to control malaria and dengue transmission.   Population ...

Murine Model of Hindlimb Ischemia 

In the United States, peripheral arterial disease (PAD) affects about 10 million individuals, and is also prevalent worldwide. Medical therapies for symptomatic relief are limited. Surgical or endovascular interventions are useful for some individuals, but long-term results are often disappointing. As a result, there is a need for developing new therapies to treat PAD. The murine hindlimb ischemia preparation is a model of PAD, and is useful for testing new therapies. When compared to other models of tissue ischemia such as coronary or cerebral artery ligation, femoral artery ligation provides for a simpler model of ischemic tissue. Other advantages of this model are the ease of access to the femoral artery and low mortality rate. 
In this video, we demonstrate the methodology for the murine model of unilateral hindimb ischemia. The specific materials and procedures for creating and evaluating the model will be described, including the assessment of limb perfusion by laser Doppler imaging. This protocol can also be utilized for the transplantation and non-invasive tracking of cells, which is demonstrated by Huang et al.1.

Murine Model of Hindlimb Ischemia

The surgical procedure for induction of unilateral hindlimb ischemia is demonstrated, with confirmation of ischemia by laser Doppler perfusion imaging.

In the United States, peripheral arterial disease (PAD) affects about 10 million individuals, and is also prevalent worldwide.  Medical therapies for ...

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the function and regulation of protein folding was studied in vitro, in isolated tissue culture cells and in unicellular organisms. Recent studies have uncovered links between protein homeostasis (proteostasis), metabolism, development, aging, and temperature-sensing. These findings have led to the development of new tools for monitoring protein folding in the model metazoan organism Caenorhabditis elegans. In our laboratory, we combine behavioral assays, imaging and biochemical approaches using temperature-sensitive or naturally occurring metastable proteins as sensors of the folding environment to monitor protein misfolding. Behavioral assays that are associated with the misfolding of a specific protein provide a simple and powerful readout for protein folding, allowing for the fast screening of genes and conditions that modulate folding. Likewise, such misfolding can be associated with protein mislocalization in the cell. Monitoring protein localization can, therefore, highlight changes in cellular folding capacity occurring in different tissues, at various stages of development and in the face of changing conditions. Finally, using biochemical tools ex vivo, we can directly monitor protein stability and conformation. Thus, by combining behavioral assays, imaging and biochemical techniques, we are able to monitor protein misfolding at the resolution of the organism, the cell, and the protein, respectively.

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

To study the relationship between protein homeostasis, stress and aging, we monitored changes in protein folding by following protein dysfunction, protein localization in the cell and protein stability at the organismal, cellular and protein levels, using the genetically tractable metazoan Caenorhabditis elegans as a model system.

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the ...

Validation of a Mouse Model to Disrupt LINC Complexes in a Cell-specific Manner

Nuclear migration and anchorage within developing and adult tissues relies heavily upon large macromolecular protein assemblies called LInkers of the Nucleoskeleton and Cytoskeleton (LINC complexes). These protein scaffolds span the nuclear envelope and connect the interior of the nucleus to components of the surrounding cytoplasmic cytoskeleton. LINC complexes consist of two evolutionary-conserved protein families, Sun proteins and Nesprins that harbor C-terminal molecular signature motifs called the SUN and KASH domains, respectively. Sun proteins are transmembrane proteins of the inner nuclear membrane whose N-terminal nucleoplasmic domain interacts with the nuclear lamina while their C-terminal SUN domains protrudes into the perinuclear space and interacts with the KASH domain of Nesprins. Canonical Nesprin isoforms have a variable sized N-terminus that projects into the cytoplasm and interacts with components of the cytoskeleton. This protocol describes the validation of a dominant-negative transgenic mouse strategy that disrupts endogenous SUN/KASH interactions in a cell-type specific manner. Our approach is based on the Cre/Lox system that bypasses many drawbacks such as perinatal lethality and cell nonautonomous phenotypes that are associated with germline models of LINC complex inactivation. For this reason, this model provides a useful tool to understand the role of LINC complexes during development and homeostasis in a wide array of tissues.

Nuclear envelope proteins play a central role in many basic biological processes and have been implicated in a variety of human diseases. This protocol describes a new Cre/Lox-based mouse model that allows for the spatiotemporal control of LINC complexes disruption.

Nuclear migration and anchorage within developing and adult tissues relies heavily upon large macromolecular protein assemblies called LInkers of the ...

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 ...

Development of a Cell Co-Culture Model to Mimic Cardiac Ischemia/Reperfusion In Vitro

Ischemic heart disease is the leading cause of death and disability worldwide. Reperfusion causes additional injury beyond ischemia. Endothelial cells (ECs) can protect cardiomyocytes (CMs) from reperfusion injury through cell-cell interactions. Co-cultures can help investigate the role of cell-cell interactions. A mixed co-culture is the simplest approach but is limited as isolated treatments and downstream analyses of single cell types are not feasible. To investigate whether ECs can dose-dependently attenuate CM cell damage and whether this protection can be further optimized by varying the contact distance between the two cell lines, we used Mouse Primary Coronary Artery Endothelial Cells and Adult Mouse Cardiomyocytes to test three types of cell culture inserts which varied in their inter-cell layer distance at 0.5, 1.0, and 2.0 mm, respectively. In CMs-only, cellular injury as assessed by lactate dehydrogenase (LDH) release increased significantly during hypoxia and further upon reoxygenation when the distance was 2.0 mm compared to 0.5 and 1.0 mm. When ECs and CMs were in nearly direct contact (0.5 mm), there was only a mild attenuation of the reoxygenation injury of CMs following hypoxia. This attenuation was significantly increased when the spatial distance was 1.0 mm. With 2.0 mm distance, ECs attenuated CM injury during both hypoxia and hypoxia/reoxygenation, indicating that sufficient culture distancing is necessary for ECs to crosstalk with CMs, so that secreted signal molecules can circulate and fully stimulate protective pathways. Our findings suggest, for the first time, that optimizing the EC/CM co-culture spatial environment is necessary to provide a favorable in vitro model for testing the role of ECs in CM-protection against simulated ischemia/reperfusion injury. The goal of this report is to provide a step-by-step approach for investigators to use this important model to their advantage.

Development of a Cell Co-Culture Model to Mimic Cardiac Ischemia/Reperfusion In Vitro

Spatial distance is a key parameter in assessing hypoxia/reoxygenation injury in a co-culture model of separate endothelial and cardiomyocyte cell layers, suggesting, for the first time, that optimizing the co-culture spatial environment is necessary to provide a favorable in vitro model for testing the role of endothelial cells in cardiomyocyte protection.

Ischemic heart disease is the leading cause of death and disability worldwide. Reperfusion causes additional injury beyond ischemia. Endothelial cells ...

Generation of Hook Ischemia-Reperfusion Model using a Three-Day Developing Chick Embryo

Ischemia and reperfusion (I/R) disorders, such as myocardial infarction, stroke, and peripheral vascular disease, are a few of the leading causes of illness and death. Many in vitro and in vivo models are currently available for studying the I/R mechanism in disease or damaged tissues. However, to date, no in ovo I/R model has been reported, which would allow for a better understanding of I/R mechanisms and faster drug screening. This paper describes I/R modeling using a spinal needle customized hook in a 3-day chick embryo to understand I/R development and treatment mechanisms. Our model can be used to investigate anomalies at the DNA, RNA, and protein levels. This method is simple, quick, and inexpensive. The current model can be used independently or in conjunction with existing in vitro and in vivo I/R models.

This paper describes ischemia-reperfusion (I/R) modeling in a 3-day chick embryo using a spinal needle customized hook to better understand I/R development and treatment. This model is simple, quick, and inexpensive.

Ischemia and reperfusion (I/R) disorders, such as myocardial infarction, stroke, and peripheral vascular disease, are a few of the leading causes of ...

A Simple and Inexpensive Running Wheel Model for Progressive Resistance Training in Mice

Previously developed rodent resistance-based exercise models, including synergistic ablation, electrical stimulation, weighted-ladder climbing, and most recently, weighted-sled pulling, are highly effective at providing a hypertrophic stimulus to induce skeletal muscle adaptations. While these models have proven invaluable for skeletal muscle research, they are either invasive or involuntary and labor-intensive. Fortunately, many rodent strains voluntarily run long distances when given access to a running wheel. Loaded wheel running (LWR) models in rodents are capable of inducing adaptations commonly observed with resistance training in humans, such as increased muscle mass and fiber hypertrophy, as well as stimulation of muscle protein synthesis. However, the addition of moderate wheel load either fails to deter mice from running great distances, which is more reflective of an endurance/resistance training model, or the mice discontinue running nearly entirely due to the method of load application. Therefore, a novel high-load wheel running model (HLWR) has been developed for mice where external resistance is applied and progressively increased, enabling mice to continue running with much higher loads than previously utilized. Preliminary results from this novel HLWR model suggest it provides sufficient stimulus to induce hypertrophic adaptations over the 9 week training protocol. Herein, the specific procedures to execute this simple yet inexpensive progressive resistance-based exercise training model in mice are described.

This procedure describes a translatable progressive loaded running wheel resistance training model in mice. The primary advantage of this resistance training model is that it is entirely voluntary, thus reducing stress for the animals and the burden on the researcher.

Previously developed rodent resistance-based exercise models, including synergistic ablation, electrical stimulation, weighted-ladder climbing, and most ...

A Modified Technique for Transverse Aortic Constriction in Mice

Transverse aortic constriction (TAC) is a frequently used surgery in research regarding heart failure and cardiac hypertrophy based on the formation of pressure overload in mouse models. The main challenge of this procedure is to clearly visualize the transverse aortic arch and precisely band the target vessel. Classical approaches perform a partial thoracotomy to expose the transverse aortic arch. However, it is an open-chest model that causes a rather large surgical trauma and requires a ventilator during the surgery. To prevent unnecessary trauma and simplify the operating procedure, the aortic arch is approached via the proximal proportion of the sternum, reaching and binding the target vessel using a small self-made retractor that contains a snare. This procedure can be conducted without entering the pleura cavity and does not need a ventilator or microsurgical operation, which leaves the mice with physiological breathing patterns, simplifies the procedure, and significantly reduces operation time. Due to the less invasive approach and less operation time, mice can undergo fewer stress reactions and recover rapidly.

The present protocol describes a modified and simplified technique with a minimally invasive transverse aortic constriction (TAC) procedure using a self-made retractor. This procedure can be conducted without a ventilator or microscope and introduces pressure overload, eventually leading to cardiac hypertrophy or heart failure.

Transverse aortic constriction (TAC) is a frequently used surgery in research regarding heart failure and cardiac hypertrophy based on the formation of ...

Manipulation of Rhythmic Food Intake in Mice Using a Custom-Made Feeding System

Rhythmic gene expression is a hallmark of the circadian rhythm and is essential for driving the rhythmicity of biological functions at the appropriate time of day. Studies over the last few decades have shown that rhythmic food intake (i.e., the time at which organisms eat food during the 24 h day), significantly contributes to the rhythmic regulation of gene expression in various organs and tissues throughout the body. The effects of rhythmic food intake on health and physiology have been widely studied ever since and have revealed that restricting food intake for 8 h during the active phase attenuates metabolic diseases arising from a variety of obesogenic diets. These studies often require the use of controlled methods for timing the delivery of food to animals. This manuscript describes the design and use of a low-cost and efficient system, built in-house for measuring daily food consumption as well as manipulating rhythmic food intake in mice. This system entails the use of affordable raw materials to build cages suited for food delivery, following a user-friendly handling procedure. This system can be used efficiently to feed mice on different feeding regimens such as ad libitum, time-restricted, or arrhythmic schedules, and can incorporate a high-fat diet to study its effect on behavior, physiology, and obesity. A description of how wild-type (WT) mice adapt to the different feeding regimens is provided.

Restricting the timing of food intake has emerged as a promising intervention to attenuate diet-induced metabolic diseases. This manuscript details the construction and use of an efficient system built in-house for measuring and manipulating rhythmic food intake in mice.

Rhythmic gene expression is a hallmark of the circadian rhythm and is essential for driving the rhythmicity of biological functions at the appropriate ...