Name: a model of cardiac remodeling through constriction of the abdominal aorta in rats
Uploaded: 2016-12-02T10:30:00
Description: Watch this Scientific Journal Video about A Model of Cardiac Remodeling Through Constriction of the Abdominal Aorta in Rats at JoVE.com

The authors' work was supported by a grant from Ministry of Science and Technology (MOST 103-2320-B-002-068-MY2), the National Health Research Institute (NHRI-EX104-10418SC), and National Taiwan University (NTU 104R4000).

All animal experiments were conducted in accordance with the Guide for the Care and Use of Laboratory Animals, published by the US National Institutes of Health (NIH publication no. 85-23, revised 1996). This protocol was approved by and in accordance with the guidelines set forth by the Institutional Animal Care and Use Committee at National Taiwan University.
1. Animal Surgery
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	<li>Prepare a 22 G syringe needle by blunting the tip of the needle on a honing stone. Using pliers, plicate...

<ol>
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Hypertensive heart disease, a major health problem that contributes greatly to morbidity and mortality, can lead to cardiac hypertrophy and heart failure5. The pathogenesis and progression of hypertensive heart disease in humans is complex, so an appropriate animal model is critical to investigate the underlying mechanisms and to test novel therapeutics that aim to improve cardiac structure and function5. The abdominal aortic constriction model, which simulates chronic heart disease, is an effective...

Heart failure is a complex clinical syndrome, the symptoms of which include fatigue, dyspnea, exercise intolerance, and fluid retention in peripheral tissues. It is the leading cause of death in developed countries1. Aside from inherited cardiomyopathy caused by mutations in sarcomere proteins or ion channels2, myocardial dysfunction can be caused by a variety of medical conditions, including hypertension, valvular heart diseases, obesity, and diabetes3. Changes in myocardial structure, electrical conduction, and energy metabolism lead to inadequate cardiac pumping capacity to meet circulatory demands, which ultimately results in heart failure3,4. Investigating the mechanisms underlying heart failure, therefore, is critical in the field of cardiovascular research. Identifying molecular mechanisms leading to heart failure progression can eventually aid in the discovery of novel therapeutic targets or useful biomarkers1. It is therefore important to develop heart failure animal models that share key clinical features with heart failure in humans5.
Cardiac hypertrophy and remodeling plays a critical role in the development of heart failure. Hypertensive heart disease is the key contributing factor of cardiac hypertrophy and the maladaptive remodeling seen in human patients1. To mimic these human conditions, animal models are often established through surgical procedures. In particular, the transverse or abdominal aorta can be constricted to increase the resistance against the left ventricle, which ultimately leads to a pressure overload in the heart. This phenomenon usually results in cardiac hypertrophy, a physiological compensation of the cardiomyocytes to meet the functional demand of the cardiovascular system. However, the functional demand overrides the normal physiological compensatory mechanisms, leading to cardiac fibrosis and contractile impairment. Transverse aortic constriction (TAC) surgery often involves complicated procedures, including thoracotomy, mechanical ventilation, and separation of the thymus and fat tissue from the aortic arch. In contrast, abdominal aortic constriction requires simpler experimental techniques6-8. The abdominal aorta, between the left and right renal arteries, is constricted during the surgery. Cardiac hypertrophy and remodeling can be observed several weeks after the abdominal aortic constriction surgery6-8; they produce robust hypertensive heart disease similar to that generated by the transverse aortic constriction surgery9,10. Here, we describe a protocol to conduct abdominal aortic constriction in rats using an efficient, highly-reproducible, and minimally-invasive method. The abdominal aorta adjacent to the renal arteries is constricted by a 0.72 mm loop formed by a 4-0 silk thread. Ten weeks after the surgery, cardiac hypertrophy and remodeling can be observed. The rat model of abdominal aortic constriction-induced cardiac hypertrophy provides a platform for studying disease mechanisms and pathophysiology, as well as the development of potential therapeutics.

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a model of cardiac remodeling through constriction of the abdominal aorta in rats

Heart failure is one of the leading causes of death worldwide. It is a complex clinical syndromethat includes fatigue, dyspnea, exercise intolerance, and fluid retention. Changes in myocardial structure, electrical conduction, and energy metabolism develop with heart failure, leading to contractile dysfunction, increased risk of arrhythmias, and sudden death. Hypertensive heart disease is one of the key contributing factors of cardiac remodeling associated with heart failure. The most commonly-used animal model mimicking hypertensive heart disease is created via surgical interventions, such as by narrowing the aorta. Abdominal aortic constriction is a useful experimental technique to induce a pressure overload, which leads to heart failure. The surgery can be easily performed, without the need for chest opening or mechanical ventilation. Abdominal aortic constriction-induced cardiac pathology progresses gradually, making this model relevant to clinical hypertensive heart failure. Cardiac injury and remodeling can be observed 10 weeks after the surgery. The method described here provides a simple and effective approach to produce a hypertensive heart disease animal model that is suitable for studying disease mechanisms and for testing novel therapeutics.

10 weeks after the abdominal aortic constriction surgery, the resulting cardiac pathology was analyzed. The cardiac histology was measured by calculating the ratio of the heart weight to the body weight and by detecting the amount of collagen in the heart. Cardiac injury was confirmed by measuring plasma cardiac troponin concentration.
As shown in Figure 1A, the cardiac size was enlarged after abdominal aortic c...

Watch this Scientific Journal Video about A Model of Cardiac Remodeling Through Constriction of the Abdominal Aorta in Rats at JoVE.com

A Model of Cardiac Remodeling Through Constriction of the Abdominal Aorta in Rats

A rat model of abdominal aortic constriction that induces cardiac hypertrophy and remodeling is described. An efficient, highly-reproducible, and minimally-invasive method is used to provide a simple yet useful platform for research in myocardial hypertrophy and dysfunction.

Heart failure is one of the leading causes of death worldwide. It is a complex clinical syndromethat includes fatigue, dyspnea, exercise intolerance, and ...

The overall goal of the surgical procedure is to provide a simple platform for studying myocardial hypertrophy, remodeling, and dysfunction. This method can help answer key questions in the cardiovascular field such as the signaling involving cardio hypertrophy and remodeling. As well as the discovery of novel therapeutic targets in hypertensive heart disease.The main advantage of this technique is that it is a minimally invasive method that requires very simple surgical techniques and yet the results are highly reproducible. The implications of these techniques extend to our therapy of hypertensive heart disease. Since constriction of the abdominal aorta induce pressure overload and eventually leads to cardio hypertrophy, remodeling, and heart failure.To begin prepare a 22 gauge syringe needle by using a honing stone to blunt the tip. Then using pliers, plicate the needle at a right angle. Prepare the required surgical materials including the recovery cage and autoclave the surgical instruments.Maintain the rats around 200 grams and keep them under 12 hour light-dark cycles at a controlled temperature with free access to food and water. Place the rat in a supine position on a surgery platform with a heating pad to maintain the body temperature. Completely shave the surgical area to avoid contamination of the wound through contact with fur.Then, with betadine or another cleasing reagent, scrub the cleanly shaven abdomen. Next, using a scalpel, make a two centimeter incision along the midline of the abdomen. Then, using normal saline, moisten the abdominal organs and keep the organs moist during surgery.Using cotton balls carefully displace the digestive organs to the side to expose the inferior vena cava and the posterior peritoneal region. Then identify the abdominal aorta which lies juxtaposed to and usually to the left of the inferior vena cava. Now, with forceps, pierce the peritoneum to uncover the vessels beneath.Gently isolate the abdominal aorta adjacent to the renal arteries and pass an eight centimeter long 4/0 silk suture underneath the vessel between the origins of the right and left renal arteries. Make a loose double knot with the suture and leave a three millimeter diameter loop. Then place the blunted and bent 22 gauge needle inside the loop.Tighten the knot around the aorta and the needle and then immediately remove the needle to achieve a 0.7 millimeter diameter constriction. With 6/0 sutures close the abdominal cavity. Then use simple interrupted sutures to close the muscle and skin incisions.Use iodine tincture to scrub the surgical site to prevent infection. To prevent postsurgical pain treat the animal with acetaminophen and closely observe the animal until it regains sufficient consciousness as indicated by free movement and food intake and maintains sternal recumbency. At 10 weeks postsurgery weigh the rat.After anesthetizing the animal and confirming the depth of anesthesia place the rat on a metal tray. Now make a five centimeter incision at the thoracic region around the midline of the xiphoid process. Using sharp forceps pierce the diaphragm.Then, with scissors, cut and remove the rib cage along the midclavicular lines on both sides to expose the heart. Carefully excise the heart along the cardiac and vascular borders. Then gently remove the heart without grabbing the tissue.Mount the heart on a modified Langendorff perfusion apparatus by tying the aortic trunk to the perfusion needle. Then use Krebs buffer to perfuse the heart and wash out the blood. Weigh the heart and calculate the heart weight to body weight ratio.Then, while wearing a mask, place the organ in 4%paraformaldehyde and fix it on ice overnight. After fixing the heart tissue place it on a tissue sectioning device, cut it into two millimeter thick slices, and place the sections in an embedding cassette. Following paraffin embedding and additional sectioning according to the text protocol, deparaffinize the slides by placing them into a tank with xylene for 30 minutes.Then rehydrate the tissue in a sequentially diluted alcohol series followed by distilled water. Next use adequate picrosirius red solution to completely cover the tissue sections and incubate for one hour. Then use a 0.5%acetic acid solution to rinse the slides two times.And rinse the samples twice in absolute alcohol. Air-dry the samples and mount them in synthetic resin with a cover slip. Then use visible light under a microscope at 200X magnification to image the slides.Finally, calculate the percentage of picrosirius red positive zone over the total area which indicates the extent of fibrosis. As shown here, cardiac volume increased after abdominal aortic constriction surgery. As demonstrated by a higher heart weight to body weight ratio which is an indicator of cardiac hypertrophy.By using picrosirius red staining, fibrotic myocardium with increased collagen content can be distinguished from normal areas. As demonstrated in these stained samples, cardiac fibrosis was increased after abdominal aortic constriction surgery as compared to controls. Once mastered the surgery can be done in 30 minutes if it is performed properly.Following this procedure, other methods like echo cardiography can be performed in order to answer additional questions about cardiac function. After it's development this technique paved the way for researchers in the field of hypertensive heart disease to explore the mechanisms involving cardiohypertrophy, remodeling, and failure. After watching this video you should have a good understanding of how to perform abdominal aortic constriction to induce cardiohypertrophy and myocardial remodeling in rats.

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