This research was supported by grants of the DZHK (German Centre for Cardiovascular Research) to CK and WMK, the BMBF (German Ministry of Education and Research) to CK in the framework of VasBio, and to WMK in the framework of VasBio, SYMPATH, and PROVID, and the German Research Foundation (DFG) to WMK (SFB-TR84 A2, SFB-TR84 C9, SFB 1449 B1, SFB 1470 A4, KU1218/9-1, and KU1218/11-1).

All procedures were performed following the &#34;Guide for the Care and Use of Laboratory Animals&#34; (Institute of Laboratory Animal Resources, 8th edition 2011) and approved by the local governmental animal care and use committee of the German State Office for Health and Social Affairs (Landesamt f&#252;r Gesundheit und Soziales (LaGeSO), Berlin; protocol no. G0030/18). First, congestive heart failure was surgically induced in juvenile Sprague-Dawley rats ~100 g body weight (bw) (see Table of Materials</strong...

<ol>
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Here, a detailed surgical technique for aortic debanding in a rat AoB model is reported that can be utilized to investigate the reversibility of PH-LHD and the cellular and molecular mechanisms that drive reverse remodeling in the pulmonary vasculature and the RV. Three weeks of aortic constriction in juvenile rats results in PH-LHD evident as increased LV pressures, LV hypertrophy, and concomitantly increased RV pressures and RV hypertrophy. Aortic debanding at week 3 post-AoB was able to unload the LV and fully reverse...

Heart failure is the leading cause of death in developed countries and is expected to increase by 25% over the next decade. Pulmonary hypertension (PH) - a pathological increase of blood pressure in the pulmonary circulation - affects approximately 70% of patients with end-stage heart failure; the World Health Organization classifies PH as pulmonary hypertension due to left heart disease (PH-LHD)1. PH-LHD is initiated by impaired systolic and/or diastolic left ventricular (LV) function that results in elevated filling pressure and passive congestion of blood into the pulmonary circulation2. Albeit initially reversible, PH-LHD gradually becomes fixed due to active pulmonary vascular remodeling in all compartments of the pulmonary circulation, i.e., arteries, capillaries, and veins3,4. Both reversible and fixed PH increase RV afterload, initially driving adaptative myocardial hypertrophy but ultimately causing RV dilatation, hypokinesis, fibrosis, and decompensation that progressively lead to RV failure1,2,5,6. As such, PH accelerates disease progression in heart failure patients and increases mortality, particularly in patients undergoing surgical treatment by implantation of left ventricular assist devices (LVAD) and/or heart transplantation7,8,9. Currently, no curative therapies exist that could reverse the process of pulmonary vascular remodeling, so fundamental mechanistic research in appropriate model systems is needed.
Importantly, clinical studies show that PH-LHD as a frequent complication in patients with aortic stenosis can improve rapidly in the early post-operative period following aortic valve replacement10. Analogously, high (&#62;3 Wood Units) pre-operative pulmonary vascular resistance (PVR) that was, however, reversible on nitroprusside was sustainably normalized after heart transplantation in a 5-year follow-up study11. Similarly, an adequate reduction of both reversible and fixed PVR and improvement of RV function in LHD patients could be realized within several months by unloading the left ventricle using implantable pulsatile and non-pulsatile ventricular assist devices12,13,14. Currently, the cellular and molecular mechanisms that drive reverse remodeling in the pulmonary circulation and RV myocardium are unclear. Yet, their understanding may provide important insight into physiological pathways that may be therapeutically exploited to reverse lung vascular and RV remodeling in PH-LHD and other forms of PH.
A suitable preclinical model that adequately replicates the pathophysiological and molecular features of PH-LHD can be used for translational studies in pressure overload-induced congestive heart failure due to surgical aortic banding (AoB) in rats4,15,16. In comparison to similar heart failure due to pressure overload in the murine model of transverse aortic constriction (TAC)17, banding of the ascending aorta above the aortic root in AoB rats does not produce hypertension in the left carotid artery as the banding site is proximal of the outflow of the left carotid artery from the aorta. As a result, AoB does not cause left-sided neuronal injury in the cortex as is characteristic for TAC18, and which may affect the study outcome. Compared to other rodent models of surgically induced PH-LHD, rat models in general, and AoB in particular, prove to be more robust, reproducible and replicate the remodeling of the pulmonary circulation characteristic for PH-LHD patients. At the same time, perioperative lethality is low19. Increased LV pressures and LV dysfunction in AoB rats induce PH-LHD development, resulting in elevated RV pressures&#160;and RV&#160;remodeling. As such, the AoB rat model has proven extremely useful in a series of previous studies by independent groups, including ourselves, to identify pathomechanisms of pulmonary vascular remodeling and test potential treatment strategies for PH-LHD4,15,20,21,22,23,24,25.
In the present study, the AoB rat model was utilized to establish a surgical procedure of aortic debanding to study mechanisms of reverse remodeling in the pulmonary vasculature and the RV. Previously, myocardial reverse remodeling models such as aortic debanding in mice26 and rats27 have been developed to investigate the cellular and molecular mechanisms regulating the regression of left ventricular hypertrophy and test potential therapeutic options to promote myocardial recovery. Moreover, a limited number of earlier studies have explored the effects of aortic debanding on PH-LHD in rats and showed that aortic debanding might reverse medial hypertrophy in pulmonary arterioles, normalize the expression of pre-pro-endothelin 1 and improve pulmonary hemodynamics27,28, providing evidence for the reversibility of PH in rats with heart failure. Here, the technical procedures of the debanding surgery are optimized and standardized, e.g., by applying a tracheotomy instead of endotracheal intubation or by using titanium clips of a defined inner diameter for aortic banding instead of polypropylene sutures with a blunt needle26,27, thus providing for better control of the surgical procedures, increased reproducibility of the model and an improved survival rate.
From a scientific perspective, the significance of the PH-LHD debanding model does not solely lie in demonstrating the reversibility of the cardiovascular and pulmonary phenotype in heart failure, but more importantly, in the identification of molecular drivers that trigger and/or sustain reverse remodeling in pulmonary arteries as promising candidates for future therapeutic targeting.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Amoxicillin</td>
			<td>Ratiopharm</td>
			<td>PC: 04150075615985</td>
			<td>Antibiotic</td>
		</tr>
		<tr>
			<td>Anti-BNP antibody</td>
			<td>Abcam</td>
			<td>ab239510</td>
			<td>Western Blotting</td>
		</tr>
		<tr>
			<td>Aquasonic 100 Ultrasound gel</td>
			<td>Parker Laboratories</td>
			<td>BT-025-0037L</td>
			<td>Echocardiography consumables</td>
		</tr>
		<tr>
			<td>Bepanthen</td>
			<td>Bayer</td>
			<td>6029009.00.00</td>
			<td>Eye ointment 
			eye ointment</td>
		</tr>
		<tr>
			<td>Carprosol (Carprofen)</td>
			<td>CP-Pharma</td>
			<td>401808.00.00</td>
			<td>Analgesic</td>
		</tr>
		<tr>
			<td>Clip holder</td>
			<td>Weck stainless USA</td>
			<td>523140S</td>
			<td>Surgical instruments</td>
		</tr>
		<tr>
			<td>Fine scissors Tungsten carbide</td>
			<td>Fine Science Tools</td>
			<td>14568-12</td>
			<td>Surgical scissors</td>
		</tr>
		<tr>
			<td>Fine scissors Tungsten carbide</td>
			<td>Fine Science Tools</td>
			<td>14568-09</td>
			<td>Surgical scissors</td>
		</tr>
		<tr>
			<td>High-resolution imaging system</td>
			<td>FUJIFILM VisualSonics, Amsterdam, Netherlands</td>
			<td>VeVo 3100</td>
			<td>Echocardiography machine. Images were acquired with pulse-wave Doppler mode, M-mode and B-mode</td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>CP-Pharma</td>
			<td>400806.00.00</td>
			<td>Anesthetic</td>
		</tr>
		<tr>
			<td>Ketamine</td>
			<td>CP-Pharma</td>
			<td>401650.00.00</td>
			<td>Anesthetic</td>
		</tr>
		<tr>
			<td>Mathieu needle holder</td>
			<td>Fine Science Tools</td>
			<td>12010-14</td>
			<td>Surgical instruments</td>
		</tr>
		<tr>
			<td>Mechanical ventilator (Rodent ventilator)</td>
			<td>UGO Basile S.R.L.</td>
			<td>7025</td>
			<td>Volume controlled respirator</td>
		</tr>
		<tr>
			<td>Metal clip</td>
			<td>Hemoclip</td>
			<td>523735</td>
			<td>Surgical consumables</td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>Leica</td>
			<td>M651</td>
			<td>Manual surgical microscope for microsurgical procedures</td>
		</tr>
		<tr>
			<td>Millar Mikro-Tip pressure catheters</td>
			<td>ADInstruments</td>
			<td>SPR-671</td>
			<td>Hemodynamics assessment</td>
		</tr>
		<tr>
			<td>Moria Iris forceps</td>
			<td>Fine Science Tools</td>
			<td>11373-12</td>
			<td>Surgical forceps</td>
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			<td>Noyes spring scissors</td>
			<td>Fine Science Tools</td>
			<td>15013-12</td>
			<td>Surgical scissors</td>
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			<td>Povidone iodine/iodophor solution</td>
			<td>B/Braun</td>
			<td>16332M01</td>
			<td>Disinfection</td>
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			<td>PowerLab</td>
			<td>ADInstruments</td>
			<td>4_35</td>
			<td>Hemodynamics assessment</td>
		</tr>
		<tr>
			<td>Prolene Suture, 4-0</td>
			<td>Ethicon</td>
			<td>EH7830</td>
			<td>Surgical consumables</td>
		</tr>
		<tr>
			<td>Rib spreader (Alm selfretaining retractor blunt, 70 mm, 2 3/4&#8243;)</td>
			<td>Austos</td>
			<td>AE-BV010R</td>
			<td>Surgical instruments</td>
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			<td>Serrated Graefe forceps</td>
			<td>Fine Science Tools</td>
			<td>11052-10</td>
			<td>Surgical forceps</td>
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			<td>Silk Suture, 4-0</td>
			<td>Ethicon</td>
			<td>K871</td>
			<td>Surgical consumables</td>
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			<td>Skin disinfiction solution (colored)</td>
			<td>B/Braun</td>
			<td>19412M07</td>
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			<td>Spectra 360 Elektrode gel</td>
			<td>Parker Laboratories</td>
			<td>TB-250-0241H</td>
			<td>Echocardiography consumables</td>
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			<td>Sponge points tissue</td>
			<td>Sugi</td>
			<td>REF 30601</td>
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			<td>Sprague-Dawley rat</td>
			<td>Janvier Labs, Le Genest-Saint-Isle, France</td>
			<td></td>
			<td>Study animals</td>
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			<td>Tracheal cannula</td>
			<td></td>
			<td></td>
			<td>Outer diameter 2 mm</td>
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			<td>Xylazin</td>
			<td>CP-Pharma</td>
			<td>401510.00.00</td>
			<td>Anesthetic</td>
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a model of reverse vascular remodeling in pulmonary hypertension due to left heart disease by aortic debanding in rats

Pulmonary hypertension due to left heart disease (PH-LHD) is the most common form of PH, yet its pathophysiology is poorly characterized than pulmonary arterial hypertension (PAH). As a result, approved therapeutic interventions for the treatment or prevention of PH-LHD are missing. Medications used to treat PH in PAH patients are not recommended for treatment of PH-LHD, as reduced pulmonary vascular resistance (PVR) and increased pulmonary blood flow in the presence of increased left-sided filling pressures may cause left heart decompensation and pulmonary edema. New strategies need to be developed to reverse PH in LHD patients. In contrast to PAH, PH-LHD develops due to increased mechanical load caused by congestion of blood into the lung circulation during left heart failure. Clinically, mechanical unloading of the left ventricle (LV) by aortic valve replacement in aortic stenosis patients or by implantation of LV assist devices in end-stage heart failure patients normalizes not only pulmonary arterial and right ventricular (RV) pressures but also PVR, thus providing indirect evidence for reverse remodeling in the pulmonary vasculature. Using an established rat model of PH-LHD due to left heart failure triggered by pressure overload with subsequent development of PH, a model is developed to study the molecular and cellular mechanisms of this physiological reverse remodeling process. Specifically, an aortic debanding surgery was performed, which resulted in reverse remodeling of the LV myocardium and its unloading. In parallel, complete normalization of RV systolic pressure and significant but incomplete reversal of RV hypertrophy was detectable. This model may present a valuable tool to study the mechanisms of physiological reverse remodeling in the pulmonary circulation and the RV, aiming to develop therapeutic strategies for treating PH-LHD and other forms of PH.

First, successful aortic debanding was confirmed by transthoracic echocardiography performed before and after the debanding procedure in AoB animals (Figure 6). To this end, the aortic arch was assessed in&#160;parasternal long axis&#160;(PLAX) B-mode view. The position of the clip on the ascending aorta in AoB animals and its absence after the Deb surgery was visualized (Figure 6A,B). Next, aortic blood flow was evaluated by pulsed-wave Doppler...

Watch this Scientific Journal Video about A Model of Reverse Vascular Remodeling in Pulmonary Hypertension Due to Left Heart Disease by Aortic Debanding in Rats at JoVE.com

A Model of Reverse Vascular Remodeling in Pulmonary Hypertension Due to Left Heart Disease by Aortic Debanding in Rats

The present protocol describes a surgical procedure to remove ascending-aortic banding in a rat model of pulmonary hypertension due to left heart disease. This technique studies endogenous mechanisms of reverse remodeling in the pulmonary circulation and the right heart, thus informing strategies to reverse pulmonary hypertension and/or right ventricular dysfunction.

Pulmonary hypertension due to left heart disease (PH-LHD) is the most common form of PH, yet its pathophysiology is poorly characterized than pulmonary ...

Our protocol describes a surgical procedure to remove ascending aortic banding in a rat model of pulmonary hypertension due to left heart disease, which leads to the reversal of pulmonary hypertension. This technique presents a valuable tool to study mechanisms of physiological reverse remodeling in the pulmonary circulation and the right ventricle. It can help in developing strategies for treating pulmonary hypertension.After the surgical instruments are prepared, place an anesthetized rat in a supine position on a sterilized surgical table. Then, fix the animal's abdomen and limbs with an adhesive tape, and disinfect animal skin with povidone-iodine/iodophor solution. Note scars and sutures from the primary surgical aortic banding, or AoB, surgery.After ensuring adequate depth of anesthesia with toe pinching, remove the sutures from the primary AoB surgery. Then, perform a tracheotomy by making a 7-to 10-millimeters-long cervical midline incision with fine scissors. With the help of a pair of blunt forceps, dissect the cervical soft tissue to expose the infrahyoid muscles.Then, by splitting the muscles in the midline, visualize the trachea. When done, make a two-millimeter trachea incision between two cartilaginous rings using angled Noyes spring scissors to insert the tracheal cannula of outer diameter two millimeters into the trachea. Then, secure the cannula with a 4-0 silk suture.Connect the other end of the tracheal cannula to a mechanical ventilator while keeping the dead space minimum. Keep perioperative lung ventilation at a respiratory rate of 90 breaths per minute at a tidal volume of 8.5 milliliters per kilogram of body weight. For the aortic debanding, make a 20-millimeter-long skin incision between the second and third ribs using fine scissors.With the help of smaller surgical scissors, spread and cut the muscles layer by layer, followed by making a 10-millimeter lateral incision along the intercostal space between the second and third rib. Use a rib spreader to expand the intercostal space between the second and third rib, to create a surgical window. With the help of blunt forceps, separate the thymus from the heart and conduit arteries to visualize the aorta with the clip.Hold the clip with the help of the forceps, followed by removing the connective tissue around the clip to expose the aorta. Open the clip with a needle holder, and remove the clip from the thoracic cavity. Before closing the chest, open up lung atelectasis and ensure adequate lung recruitment without over-distention with mechanical ventilation, with a tidal volume of 9.5 milliliters per kilogram body weight for 10 minutes, and return to a tidal volume of 8.5 milliliters per kilogram body weight.Later, close the deep muscles by a simple interrupted suture using 4-0 silk, and connect the upper muscles with a simple continuous suture. Then, close the skin with a simple continuous suture. Disconnect the tracheal cannula from the ventilation machine while observing the rat for spontaneous breathing.If the animal fails to breathe spontaneously upon disconnection, reconnect the ventilator and continue ventilating for an additional five minutes before repeating the procedure. After spontaneous breathing is reestablished, remove the cannula from the trachea and clean the liquid around the trachea with sponge points. Close the trachea with a simple suture using 6-0 Prolene, and close the infrahyoid muscles in a simple interrupted suture using 4-0 silk.Connect the skin in a simple continuous suture, followed by cleaning and disinfecting the muscles and the skin in the process with povidone-iodine/iodophor solution. After completing the surgical procedure, move a single animal to a recovery cage with supplemental oxygen and an infrared lamp, and place the oxygen mask close to the rat's snout. In the study, the position of the clip on the ascending aorta in the AoB animals and its absence after the debanding, or Deb, surgery was visualized.Also, aortic blood flow was evaluated by pulsed-wave Doppler imaging before and after the clip in AoB animals prior to the debanding and in corresponding aortic segments after the Deb surgery. The results showed a marked attenuation of the blood flow gradient in line with the functional debanding. At week five, the Deb rats expressed brain natriuretic peptide, or BNP, at levels comparable to the sham animals, indicating the reversal of left ventricle, or LV, failure by the aortic debanding.The evaluation of LV function by transthoracic echocardiography revealed an increased LV ejection fraction and LV volume in the Deb animals compared to the AoB rats. The debanding surgery performed at week three after AoB resulted in a significant reduction of left ventricular systolic pressure and LV hypertrophy in comparison to the AoB animals. Compared to the AoB rats at week three and week five, the Deb animals also showed a significant reduction in right ventricular systolic pressure and right ventricular hypertrophy, demonstrating a successful reversal of pulmonary hypertension due to left heart disease.The most critical steps in this procedure are removal of the clip and the recruitment of the lung after the aortic debanding. These steps, when correctly performed, increase animal survival.

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Research

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Ascending Aortic Constriction in Rats for Creation of Pressure Overload Cardiac Hypertrophy Model

Ascending aortic constriction is the most common and successful surgical model for creating pressure overload induced cardiac hypertrophy and heart failure. Here, we describe a detailed surgical procedure for creating pressure overload and cardiac hypertrophy in rats by constriction of the ascending aorta using a small metallic clip. After anesthesia, the trachea is intubated by inserting a cannula through a half way incision made between two cartilage rings of trachea. Then a skin incision is made at the level of the second intercostal space on the left chest wall and muscle layers are cleared to locate the ascending portion of aorta. The ascending aorta is constricted to 50&#8211;60% of its original diameter by application of a small sized titanium clip. Following aortic constriction, the second and third ribs are approximated with prolene sutures. The tracheal cannula is removed once spontaneous breathing was re-established. The animal is allowed to recover on the heating pad by gradually lowering anesthesia. The intensity of pressure overload created by constriction of the ascending aorta is determined by recording the pressure gradient using trans-thoracic two dimensional Doppler-echocardiography. Overall this protocol is useful to study the remodeling events and contractile properties of the heart during the gradual onset and progression from compensated cardiac hypertrophy to heart failure stage.

We describe a stepwise procedure for creating pressure overload and left ventricular hypertrophy in Wistar rats by constriction of the ascending aorta using a small metallic clip. This model is extensively used for studying remodeling changes during cardiac hypertrophy and for identifying and evaluating strategies for regression of such changes.

Ascending aortic constriction is the most common and successful surgical model for creating pressure overload induced cardiac hypertrophy and heart ...

Assessment of Vascular Function in Patients With Chronic Kidney Disease

Patients with chronic kidney disease (CKD) have significantly increased risk of cardiovascular disease (CVD) compared to the general population, and this is only partially explained by traditional CVD risk factors. Vascular dysfunction is an important non-traditional risk factor, characterized by vascular endothelial dysfunction (most commonly assessed as impaired endothelium-dependent dilation [EDD]) and stiffening of the large elastic arteries. While various techniques exist to assess EDD and large elastic artery stiffness, the most commonly used are brachial artery flow-mediated dilation (FMDBA) and aortic pulse-wave velocity (aPWV), respectively. Both of these noninvasive measures of vascular dysfunction are independent predictors of future cardiovascular events in patients with and without kidney disease. Patients with CKD demonstrate both impaired FMDBA, and increased aPWV. While the exact mechanisms by which vascular dysfunction develops in CKD are incompletely understood, increased oxidative stress and a subsequent reduction in nitric oxide (NO) bioavailability are important contributors. Cellular changes in oxidative stress can be assessed by collecting vascular endothelial cells from the antecubital vein and measuring protein expression of markers of oxidative stress using immunofluorescence. We provide here a discussion of these methods to measure FMDBA, aPWV, and vascular endothelial cell protein expression.

The degree of vascular dysfunction and contributing physiological mechanisms can be assessed in patients with chronic kidney disease by measuring brachial artery flow-mediated dilation, aortic pulse-wave velocity, and vascular endothelial cell protein expression.

Patients with chronic kidney disease (CKD) have significantly increased risk of cardiovascular disease (CVD) compared to the general population, and this ...

Permanent Ligation of the Left Anterior Descending Coronary Artery in Mice: A Model of Post-myocardial Infarction Remodelling and Heart Failure

Heart failure is a syndrome in which the heart fails to pump blood at a rate commensurate with cellular oxygen requirements at rest or during stress. It is characterized by fluid retention, shortness of breath, and fatigue, in particular on exertion. Heart failure is a growing public health problem, the leading cause of hospitalization, and a major cause of mortality. Ischemic heart disease is the main cause of heart failure.
Ventricular remodelling refers to changes in structure, size, and shape of the left ventricle. This architectural remodelling of the left ventricle is induced by injury (e.g., myocardial infarction), by pressure overload (e.g., systemic arterial hypertension or aortic stenosis), or by volume overload. Since ventricular remodelling affects wall stress, it has a profound impact on cardiac function and on the development of heart failure. A model of permanent ligation of the left anterior descending coronary artery in mice is used to investigate ventricular remodelling and cardiac function post-myocardial infarction. This model is fundamentally different in terms of objectives and pathophysiological relevance compared to the model of transient ligation of the left anterior descending coronary artery. In this latter model of ischemia/reperfusion injury, the initial extent of the infarct may be modulated by factors that affect myocardial salvage following reperfusion. In contrast, the infarct area at 24 hr after permanent ligation of the left anterior descending coronary artery is fixed. Cardiac function in this model will be affected by 1) the process of infarct expansion, infarct healing, and scar formation; and 2) the concomitant development of left ventricular dilatation, cardiac hypertrophy, and ventricular remodelling.
Besides the model of permanent ligation of the left anterior descending coronary artery, the technique of invasive hemodynamic measurements in mice is presented in detail.

Heart failure is the leading cause of hospitalization and a major cause of mortality. A model of permanent ligation of the left anterior descending coronary artery in mice is applied to investigate ventricular remodelling and cardiac dysfunction post-myocardial infarction. The technique of invasive hemodynamic measurements in mice is presented.

Heart failure is a syndrome in which the heart fails to pump blood at a rate commensurate with cellular oxygen requirements at rest or during stress. It ...

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.

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 ...

Shunt Surgery, Right Heart Catheterization, and Vascular Morphometry in a Rat Model for Flow-induced Pulmonary Arterial Hypertension

In this protocol, PAH is induced by combining a 60 mg/kg monocrotalin (MCT) injection with increased pulmonary blood flow through an aorto-caval shunt (MCT+Flow). The shunt is created by inserting an 18-G needle from the abdominal aorta into the adjacent caval vein. Increased pulmonary flow has been demonstrated as an essential trigger for a severe form of PAH with distinct phases of disease progression, characterized by early medial hypertrophy followed by neointimal lesions and the progressive occlusion of the small pulmonary vessels. To measure the right heart and pulmonary hemodynamics in this model, right heart catheterization is performed by inserting a rigid cannula containing a flexible ball-tip catheter via the right jugular vein into the right ventricle. The catheter is then advanced into the main and the more distal pulmonary arteries. The histopathology of the pulmonary vasculature is assessed qualitatively, by scoring the pre- and intra-acinar vessels on the degree of muscularization and the presence of a neointima, and quantitatively, by measuring the wall thickness, the wall-lumen ratios, and the occlusion score.

This protocol describes a surgical procedure to create a model for flow-induced pulmonary arterial hypertension (PAH) in rats and the procedures to analyze the principle hemodynamic and histological end-points in this model.

In this protocol, PAH is induced by combining a 60 mg/kg monocrotalin (MCT) injection with increased pulmonary blood flow through an aorto-caval shunt ...

Induction and Phenotyping of Acute Right Heart Failure in a Large Animal Model of Chronic Thromboembolic Pulmonary Hypertension

The development of acute right heart failure (ARHF) in the context of chronic pulmonary hypertension (PH) is associated with poor short-term outcomes. The morphological and functional phenotyping of the right ventricle is of particular importance in the context of hemodynamic compromise in patients with ARHF. Here, we describe a method to induce ARHF in a previously described large animal model of chronic PH, and to phenotype, dynamically, right ventricular function using the gold standard method (i.e., pressure-volume PV loops) and with a non-invasive clinically available method (i.e., echocardiography). Chronic PH is first induced in pigs by left pulmonary artery ligation and right lower lobe embolism with biological glue once a week for 5 weeks. After 16 weeks, ARHF is induced by successive volume loading using saline followed by iterative pulmonary embolism until the ratio of the systolic pulmonary pressure over systemic pressure reaches 0.9 or until the systolic systemic pressure decreases below 90 mmHg. Hemodynamics are restored with dobutamine infusion (from 2.5 &#181;g/kg/min to 7.5 &#181;g/kg/min). PV-loops and echocardiography are performed during each condition. Each condition requires around 40 minutes for induction, hemodynamic stabilization and data acquisition. Out of 9 animals, 2 died immediately after pulmonary embolism and 7 completed the protocol, which illustrates the learning curve of the model. The model induced a 3-fold increase in mean pulmonary artery pressure. The PV-loop analysis showed that ventriculo-arterial coupling was preserved after volume loading, decreased after acute pulmonary embolism and was restored with dobutamine. Echocardiographic acquisitions allowed to quantify right ventricular parameters of morphology and function with good quality. We identified right ventricular ischemic lesions in the model. The model can be used to compare different treatments or to validate non-invasive parameters of right ventricular morphology and function in the context of ARHF.

We present a protocol to induce and phenotype an acute right heart failure in a large animal model with chronic pulmonary hypertension. This model can be used to test therapeutic interventions, to develop right heart metrics&#160;or to improve the understanding of acute right heart failure pathophysiology.

The development of acute right heart failure (ARHF) in the context of chronic pulmonary hypertension (PH) is associated with poor short-term outcomes. The ...

Left Atrial Stenosis Induced Pulmonary Venous Arterialization and Group 2 Pulmonary Hypertension in Rat

The mechanism of mitral stenosis-induced pulmonary venous arterialization and group 2 pulmonary hypertension (PH) is unclear. There is no rodent model of group 2 PH, due to mitral stenosis (MS), to facilitate the investigation of disease mechanisms and potential therapeutic strategies. We present a novel rat model of pulmonary venous congestion-induced pulmonary venous arterialization and group 2 PH caused by left atrial stenosis (LAS). LAS is achieved by constricting the left atrium using a half-closed titanium clip. After the LAS surgery, a rat model with a transmitral inflow velocity greater than or equal to 2.0 m/s on echocardiography gradually develops pulmonary venous arterialization and group 2 PH over an 8- to 10-week period. In this protocol, we provide the step-by-step procedure of how to perform the LAS surgery. The presented LAS rat model mimics MS in humans and is useful for studying the underlying molecular mechanism of pulmonary venous arterialization and for the preclinical evaluation of therapies for group 2 PH.

Left atrial stenosis (LAS) is a novel surgical technique used for studying group 2 pulmonary hypertension (PH) and mechanisms underlying pulmonary venous arterialization. Here, we present a protocol to constrict the left atrium using a titanium clip to cause pulmonary venous arterialization and moderate PH in a rat.

The mechanism of mitral stenosis-induced pulmonary venous arterialization and group 2 pulmonary hypertension (PH) is unclear. There is no rodent model of ...

The Left Pneumonectomy Combined with Monocrotaline or Sugen as a Model of Pulmonary Hypertension in Rats

In this protocol, we detail the correct procedural steps and necessary precautions to successfully perform a left pneumonectomy and induce PAH in rats with the additional administration of monocrotaline (MCT) or SU5416 (Sugen). We also compare these two models to other PAH models commonly used in research. In the last few years, the focus of animal PAH models has moved towards studying the mechanism of angioproliferation of plexiform lesions, in which the role of increased pulmonary blood flow is considered as an important trigger in the development of severe pulmonary vascular remodeling. One of the most promising rodent models of increased pulmonary flow is the unilateral left pneumonectomy combined with a "second hit" of MCT or Sugen. The removal of the left lung leads to increased and turbulent pulmonary blood flow and vascular remodeling. Currently, there is no detailed procedure of the pneumonectomy surgery in rats. This article details a step-by-step protocol of the pneumonectomy surgical procedure and post-operative care in male Sprague-Dawley rats. Briefly, the animal is anesthetized and the chest is opened. Once the left pulmonary artery, pulmonary vein, and bronchus are visualized, they are ligated and the left lung is removed. The chest then closed and the animal recovered. Blood is forced to circulate only on the right lung. This increased vascular pressure leads to a progressive remodeling and occlusion of small pulmonary arteries. The second hit of MCT or Sugen is used one week post-surgery to induce endothelial dysfunction. The combination of increased blood flow in the lung and endothelial dysfunction produces severe PAH. The primary limitation of this procedure is that it requires general surgical skills.

The rodent left pneumonectomy is a valuable technique in pulmonary hypertension research. Here, we present a protocol to describe the rat pneumonectomy procedure and postoperative care to ensure minimal morbidity and mortality.

In this protocol, we detail the correct procedural steps and necessary precautions to successfully perform a left pneumonectomy and induce PAH in rats ...

Studying Left Ventricular Reverse Remodeling by Aortic Debanding in Rodents

To better understand the left ventricular (LV) reverse remodeling (RR), we describe a rodent model wherein, after aortic banding-induced LV remodeling, mice undergo RR upon removal of the aortic constriction. In this paper, we describe a step-by-step procedure to perform a minimally invasive surgical aortic debanding in mice. Echocardiography was subsequently used to assess the degree of cardiac hypertrophy and dysfunction during LV remodeling and RR and to determine the best timing for aortic debanding. At the end of the protocol, terminal hemodynamic evaluation of the cardiac function was conducted, and samples were collected for histological studies. We showed that debanding is associated with surgical survival rates of 70-80%. Moreover, two weeks after debanding, the significant reduction of ventricular afterload triggers the regression of ventricular hypertrophy (~20%) and fibrosis (~26%), recovery of diastolic dysfunction as assessed by the normalization of left ventricular filling and end-diastolic pressures (E/e&#39;&#160;and LVEDP). Aortic debanding is a useful experimental model to study LV RR in rodents. The extent of myocardial recovery is variable between subjects, therefore, mimicking the diversity of RR that occurs in the clinical context, such as aortic valve replacement. We conclude that the aortic banding/debanding model represents a valuable tool to unravel novel insights into the mechanisms of RR, namely the regression of cardiac hypertrophy and the recovery of diastolic dysfunction.

Here we describe a step-by-step protocol of surgical aorta debanding in the well-established mice model of aortic-constriction. This procedure not only allows studying the mechanisms underlying the left ventricular reverse remodeling and regression of hypertrophy but also to test novel therapeutic options that might accelerate myocardial recovery.

To better understand the left ventricular (LV) reverse remodeling (RR), we describe a rodent model wherein, after aortic banding-induced LV remodeling, ...

A Rat Model of Pressure Overload Induced Moderate Remodeling and Systolic Dysfunction as Opposed to Overt Systolic Heart Failure

In response to an injury, such as myocardial infarction, prolonged hypertension or a cardiotoxic agent, the heart initially adapts through the activation of signal transduction pathways, to counteract, in the short-term, for the cardiac myocyte loss and or the increase in wall stress. However, prolonged activation of these pathways becomes detrimental leading to the initiation and propagation of cardiac remodeling leading to changes in left ventricular geometry and increases in left ventricular volumes; a phenotype seen in patients with systolic heart failure (HF). Here, we describe the creation of a rat model of pressure overload induced moderate remodeling and early systolic dysfunction (MOD) by ascending aortic banding (AAB) via a vascular clip with an internal area of 2 mm2. The surgery is performed in 200 g Sprague-Dawley rats. The MOD HF phenotype develops at 8-12 weeks after AAB and is characterized noninvasively by means of echocardiography. Previous work suggests the activation of signal transduction pathways and altered gene expression and post-translational modification of proteins in the MOD HF phenotype that mimic those seen in human systolic HF; therefore, making the MOD HF phenotype a suitable model for translational research to identify and test potential therapeutic anti-remodeling targets in HF. The advantages of the MOD HF phenotype compared to the overt systolic HF phenotype is that it allows for the identification of molecular targets involved in the early remodeling process and the early application of therapeutic interventions. The limitation of the MOD HF phenotype is that it may not mimic the spectrum of diseases leading to systolic HF in human. Moreover, it is a challenging phenotype to create, as the AAB surgery is associated with high mortality and failure rates with only 20% of operated rats developing the desired HF phenotype.

We describe the creation of a rat model of pressure overload induced moderate remodeling and early systolic dysfunction where signal transduction pathways involved in the initiation of the remodeling process are activated. This animal model will aid in identifying molecular targets for applying early therapeutic anti-remodeling strategies for heart failure.

In response to an injury, such as myocardial infarction, prolonged hypertension or a cardiotoxic agent, the heart initially adapts through the activation ...