Name: ultrasound based assessment of coronary artery flow and coronary flow reserve using the pressure overload model in mice
Uploaded: 2015-04-13T13:00:00
Description: Watch this Scientific Journal Video about Ultrasound Based Assessment of Coronary Artery Flow and Coronary Flow Reserve Using the Pressure Overload Model in Mice at JoVE.com

We thank Fred Roberts for exemplary technical support and also appreciate the help from the histology core in Beth Israel Hospital. We thank Brigham Women&#8217;s Hospital Cardiovascular Physiology Core for providing with the instrumentation and the funds for this work. This work was supported in part by a Department of Medicine Sundry Fund.

NOTE: All procedures were performed in mice in accordance with American Veterinary Medical Association (AVMA) guidelines and approved Institutional Animal Care and Use Committees (IACUC) protocols.
1. Study Design
<ol>
	<li>Use 8-10 week old male C57BL/6 mice (BW~25 g) in the study.</li>
	<li>Randomize the mice (n = 11) into two groups, the study group selected for aortic banding (n = 8), and the control group (n = 3) to undergo sham operation via thoracotomy.</li>
	<li>Prepare the animal fo...

<ol>
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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relation+of+coronary+flow+reserve+and+diastolic+function+to+fractional+pulse+pressure+in+hypertensive+patients.">Relation of coronary flow reserve and diastolic function to fractional pulse pressure in hypertensive patients.</a> Echocardiography (Mount Kisco, N.Y). 30, 1084-1090 (2013).</li><li>Kawata, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prognostic+value+of+coronary+flow+reserve+assessed+by+transthoracic+Doppler+echocardiography+on+long-term+outcome+in+asymptomatic+patients+with+type+2+diabetes+without+overt+coronary+artery+disease).">Prognostic value of coronary flow reserve assessed by transthoracic Doppler echocardiography on long-term outcome in asymptomatic patients with type 2 diabetes without overt coronary artery disease).</a> Cardiovascular diabetology. 12, 121 (2013).</li><li>Miller, D. 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Correlations between myocardial positron emission tomography and poststenotic intracoronary Doppler flow reserve.</a> Circulation. 94, 2447-2454 (1996).</li><li>Wada, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coronary+flow+velocity+reserve+in+three+major+coronary+arteries+by+transthoracic+echocardiography+for+the+functional+assessment+of+coronary+artery+disease:+a+comparison+with+fractional+flow+reserve.">Coronary flow velocity reserve in three major coronary arteries by transthoracic echocardiography for the functional assessment of coronary artery disease: a comparison with fractional flow reserve.</a> European heart journal cardiovascular Imaging. 15, 399-408 (2014).</li><li>Hartley, C. 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In this ultrasound based study, non-invasive assessment of coronary flow was reproducibly performed in real time, over days, in live experimental mice; furthermore, the protocol demonstrated the potential to detect coronary artery dysfunction that was present at an early stage and was associated with deficiency in myocardial perfusion. This method could ultimately be leveraged as a clinical tool for cardiovascular risk stratification and/or assessing response to therapeutic intervention.
First...

Clinical aortic stenosis (AS) is well known to promote a progressive increase in left ventricular (LV) afterload. To compensate for this chronically rising hemodynamic load, LV hypertrophy (LVH) ensues as an adaptive response1,2. The development of LVH is often associated with abnormalities in coronary microcirculation. It is thought that microvascular dysfunction contributes to chronic ischemia in these patients 5. In addition to coronary flow 3,4, coronary flow reserve (CFR) represents functional change of coronary arteries 1,3 and is defined as the ratio of maximal flow velocity in hyperemia to baseline flow velocity or resting flow velocity4,6,7. CFR is decreased during LV remodeling 1-3,5-9 and is used as an index of the extent of functional severity of coronary dysfunction 1,10,17. It is known to be impaired in many forms of dilated cardiomyopathy 10 and also coronary stenosis6. CFR is also a prognostic marker for poor clinical outcomes 12.
LV remodeling in the setting of cardiac dysfunction such as ischemia or LVH is also accompanied by extensive fibrosis, changes in coronary microcirculation and thickening of coronary arteries 1,2. As a result of these changes in coronary physiology, there is likely remodeling of the coronary arteries. This helps mitigate the effects of low oxygen diffusion and LV diastolic dysfunction that could result in susceptibility to myocardial ischemia 1,2,13.
Genetically modified mice are now a widely prevalent investigational tool for mimicking human disease conditions such as coronary atherosclerosis 5,7,10,12,17. Particularly the pressure overload model in mice has been widely studied 14,17. The trans-aortic constriction model (TAC) has been shown to be associated with extensive fibrosis, and coronary stenosis resulting, in part, from medial thickening of coronary arteries and with accompanying changes in coronary flow patterns 1,11,17,19 similar to what is seen in the setting of LVH in humans. While it is known that prolonged pressure overload leads to decompensated heart failure in about 4-8 weeks, the effects on coronary flow dynamics and flow reserve in these models, early in the process of disease progression, and at different stages after banding, are yet to be clearly delineated.
Numerous strains of mice are currently available for research use, including well-characterized LDLR-/- or ApoE-/- mice 10-12, and these have prompted development of sensitive techniques for assessing cardiovascular function and morphology in living mice 11-15. Such techniques include MRI, PET, contrast CT, high frequency ultrasound, and electron beam tomography 2,9,17,19, all of which provide promising alternatives to invasive methods such as cardiac catheterizations and coronary angiography 12. However, in mice with very small size of the coronary arteries and high heart rates (HR), imaging of coronary circulation still constitutes a technical challenge for many currently available techniques 4,12. Interestingly, there has been an exponential rise in technical advances in the field of transthoracic Doppler echocardiography (TTDE), including the development of high-frequency array scan heads with center frequencies from 15 to 50 MHz allowing axial resolutions of approximately 30-100 &#956;m, at depths of 8-40 mm, and frame rates greater than 400 frames-captured/sec. In turn, TTDE-based techniques have emerged as a potentially powerful tool for imaging larger 2 or even smaller vessels such as coronary arteries 5,12.
Another critical advance that has allowed investigators to conduct diagnostic imaging studies of the vasculature in small animals is the carefully controlled use of anesthetics that maintain the heart and respiratory rate of the animals during imaging 11. Controlled anesthesia maintenance is particularly important for studies related to vasodilation in mice, and the effect of anesthesia also needs to be further explored in this context 10,11. In humans, on the other hand, TTDE-derived CFR measurements have become a more commonly used tool for evaluation of stenosed and non-obstructed epicardial coronary arteries, predominantly in left anterior descending (LAD) coronary artery 5,16. However, the prognostic role of CFR and coronary flow changes in asymptomatic patients or mice with preserved LV systolic function at rest has been much less explored 16. Therefore, the aim of the study was to first establish a clear step-by-step protocol, to evaluate changes in coronary flow using TTDE in a pressure overload mouse model; second, this study examined the prognostic significance of CFR and coronary flow changes in response to pressure overload stress in these mice. We hypothesized that TTDE based assessment of CFR and coronary flow may be useful in the early detection of coronary dysfunction that may precede LV dysfunction.

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ultrasound based assessment of coronary artery flow and coronary flow reserve using the pressure overload model in mice

Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow reserve (CFR) in humans. Reduced CFR is accompanied by marked intramyocardial and pericoronary fibrosis and is used as an indication of the severity of dysfunction. This study explores, step-by-step, the real-time changes measured in the coronary flow velocity, CFR and systolic to diastolic peak velocity (S/D) ratio in the setting of an aortic banding model in mice. By using a Doppler transthoracic imaging technique that yields reproducible and reliable data, the method assesses changes in flow in the septal coronary artery (SCA), for a period of over two weeks in mice, that previously either underwent aortic banding or thoracotomy. 
During imaging, hyperemia in all mice was induced by isoflurane, an anesthetic that increased coronary flow velocity when compared with resting flow. All images were acquired by a single imager. Two ratios, (1) CFR, the ratio between hyperemic and baseline flow velocities, and (2) systolic (S) to diastolic (D) flow were determined, using a proprietary software and by two independent observers. Importantly, the observed changes in coronary flow preceded LV dysfunction as evidenced by normal LV mass and fractional shortening (FS). 
The method was benchmarked against the current gold standard of coronary assessment, histopathology. The latter technique showed clear pathologic changes in the coronary artery in the form of peri-coronary fibrosis that correlated to the flow changes as assessed by echocardiography. 
The study underscores the value of using a non-invasive technique to monitor coronary circulation in mouse hearts. The method minimizes redundant use of research animals and demonstrates that advanced ultrasound-based indices, such as CFR and S/D ratios, can serve as viable diagnostic tools in a variety of investigational protocols including drug studies and the study of genetically modified strains.

Of the 11 mice that were studied (banded, n=8 and sham, n = 3), adequate and reproducible images were obtained by a single observer at several time-points: at baseline (D-1), D2, D6 and D13. Also, the flow velocity at the constrictive site was measured as 2225 &#177; 110.9 mm/s, compared with 277.5 &#177; 10.51 mm/s in the sham mice on the day after the surgery (p&#60;0.05). The increase in velocity was the verification of the successful establishment of the pressure overload model. The SCA flow velocity, also referred t...

Watch this Scientific Journal Video about Ultrasound Based Assessment of Coronary Artery Flow and Coronary Flow Reserve Using the Pressure Overload Model in Mice at JoVE.com

Ultrasound Based Assessment of Coronary Artery Flow and Coronary Flow Reserve Using the Pressure Overload Model in Mice

Coronary flow reserve (CFR) is useful for assessment of myocardial oxygen demand and evaluation of cardiovascular risk. This study establishes a step-by-step transthoracic Doppler echocardiographic (TTDE) method for longitudinal monitoring of the changes in CFR, as measured from coronary artery in mice, under the experimental pressure overload of aortic banding.

Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow ...

ultrasound-based-assessment-coronary-artery-flow-coronary-flow

Research

JoVE Journal

Medicine

Use of a Hanging Weight System for Coronary Artery Occlusion in Mice

Murine studies of acute injury are an area of intense investigation, as knockout mice for different genes are becoming increasingly available 1-38. Cardioprotection by ischemic preconditioning (IP) remains an area of intense investigation. To further elucidate its molecular basis, the use of knockout mouse studies is particularly important 7, 14, 30, 39. Despite the fact that previous studies have already successfully performed cardiac ischemia and reperfusion in mice, this model is technically very challenging. Particularly, visual identification of the coronary artery, placement of the suture around the vessel and coronary occlusion by tying off the vessel with a supported knot is technically difficult. In addition, re-opening the knot for intermittent reperfusion of the coronary artery during IP without causing surgical trauma adds additional challenge. Moreover, if the knot is not tied down strong enough, inadvertent reperfusion due to imperfect occlusion of the coronary may affect the results. In fact, this can easily occur due to the movement of the beating heart.
Based on potential problems associated with using a knotted coronary occlusion system, we adopted a previously published model of chronic cardiomyopathy based on a hanging weight system for intermittent coronary artery occlusion during IP 39. In fact, coronary artery occlusion can thus be achieved without having to occlude the coronary by a knot. Moreover, reperfusion of the vessel can be easily achieved by supporting the hanging weights which are in a remote localization from cardiac tissues.
We tested this system systematically, including variation of ischemia and reperfusion times, preconditioning regiments, body temperature and genetic backgrounds39. In addition to infarct staining, we tested cardiac troponin I (cTnI)
as a marker of myocardial infarction in this model. In fact, plasma levels of cTnI correlated with infarct sizes (R2=0.8). Finally, we could show in several studies that this technique yields highly reproducible infarct sizes during murine IP and myocardial infarction6, 8, 30, 40, 41. Therefore, this technique may be helpful for researchers who pursue molecular mechanisms involved in cardioprotection by IP using a genetic approach in mice with targeted gene deletion. Further studies on cardiac IP using transgenic mice may consider this technique.

A murine model for myocardial ischemia and ischemic preconditioning is an important tool study cardioprotective mechanisms in vivo. Here, we report an easy applicable in situ model for cardiac IP using a hanging-weight system for coronary artery occlusion.

Murine studies of acute injury are an area of intense investigation, as knockout mice for different genes are becoming increasingly available 1-38. ...

Coronary Artery Ligation and Intramyocardial Injection in a Murine Model of Infarction

Mouse models are a valuable tool for studying acute injury and chronic remodeling of the myocardium in vivo. With the advent of genetic modifications to the whole organism or the myocardium and an array of biological and/or synthetic materials, there is great potential for any combination of these to assuage the extent of acute ischemic injury and impede the onset of heart failure pursuant to myocardial remodeling. 
Here we present the methods and materials used to reliably perform this microsurgery and the modifications involved for temporary (with reperfusion) or permanent coronary artery occlusion studies as well as intramyocardial injections. The effects on the heart that can be seen during the procedure and at the termination of the experiment in addition to histological evaluation will verify efficacy. 
Briefly, surgical preparation involves anesthetizing the mice, removing the fur on the chest, and then disinfecting the surgical area. Intratracheal intubation is achieved by transesophageal illumination using a fiber optic light. The tubing is then connected to a ventilator. An incision made on the chest exposes the pectoral muscles which will be cut to view the ribs. For ischemia/reperfusion studies, a 1 cm piece of PE tubing placed over the heart is used to tie the ligature to so that occlusion/reperfusion can be customized. For intramyocardial injections, a Hamilton syringe with sterile 30gauge beveled needle is used. When the myocardial manipulations are complete, the rib cage, the pectoral muscles, and the skin are closed sequentially. Line block analgesia is effected by 0.25% marcaine in sterile saline which is applied to muscle layer prior to closure of the skin. The mice are given a subcutaneous injection of saline and placed in a warming chamber until they are sternally recumbent. They are then returned to the vivarium and housed under standard conditions until the time of tissue collection. At the time of sacrifice, the mice are anesthetized, the heart is arrested in diastole with KCl or BDM, rinsed with saline, and immersed in fixative. Subsequently, routine procedures for processing, embedding, sectioning, and histological staining are performed. 
Nonsurgical intubation of a mouse and the microsurgical manipulations described make this a technically challenging model to learn and achieve reproducibility. These procedures, combined with the difficulty in performing consistent manipulations of the ligature for timed occlusion(s) and reperfusion or intramyocardial injections, can also affect the survival rate so optimization and consistency are critical.

Numerous genetic manipulations and/or intramyocardial injections of genes, proteins, cells, and/or biomaterials are superimposed upon the dimension of time in studies of acute ischemia/ reperfusion injury and chronic remodeling in mice. This video illustrates the microsurgical procedures for ischemia/reperfusion, permanent coronary artery ligation, and intramyocardial injection studies.

Mouse models are a valuable tool for studying acute injury and chronic remodeling of the myocardium in vivo.  With the advent of genetic modifications to ...

Modified Technique for Coronary Artery Ligation in Mice

Myocardial infarction (MI) is one of the most important causes of mortality in humans1-3. In order to improve morbidity and mortality in patients with MI we need better knowledge about pathophysiology of myocardial ischemia. This knowledge may be valuable to define new therapeutic targets for innovative cardiovascular therapies4. Experimental MI model in mice is an increasingly popular small-animal model in preclinical research in which MI is induced by means of permanent or temporary ligation of left coronary artery (LCA)5. In this video, we describe the step-by-step method of how to induce experimental MI in mice.
The animal is first anesthetized with 2% isoflurane. The unconscious mouse is then intubated and connected to a ventilator for artificial ventilation. The left chest is shaved and 1.5 cm incision along mid-axillary line is made in the skin. The left pectoralis major muscle is bluntly dissociated until the ribs are exposed. The muscle layers are pulled aside and fixed with an eyelid-retractor. After these preparations, left thoracotomy is performed between the third and fourth ribs in order to visualize the anterior surface of the heart and left lung. The proximal segment of LCA artery is then ligated with a 7-0 ethilon suture which typically induces an infarct size ~40% of left ventricle. At the end, the chest is closed and the animals receive postoperative analgesia (Temgesic, 0.3 mg/50 ml, ip). The animals are kept in a warm cage until spontaneous recovery.

The surgical procedure used to induce experimental myocardial infarction in mice begins with left thoracotomy between the third and the fourth ribs in order to visualize the anterior surface of the heart and left lung. The left coronary artery is ligated, the chest is closed and the mouse is allowed to recover spontaneously.

Myocardial infarction (MI) is one of the most important causes of mortality in humans1-3. In order to improve morbidity and mortality in patients with MI ...

Ultrasound Assessment of Endothelial-Dependent Flow-Mediated Vasodilation of the Brachial Artery in Clinical Research

The vascular endothelium is a monolayer of cells that cover the interior of blood vessels and provide both structural and functional roles. The endothelium acts as a barrier, preventing leukocyte adhesion and aggregation, as well as controlling permeability to plasma components. Functionally, the endothelium affects vessel tone.
Endothelial dysfunction is an imbalance between the chemical species which regulate vessel tone, thombroresistance, cellular proliferation and mitosis. It is the first step in atherosclerosis and is associated with coronary artery disease, peripheral artery disease, heart failure, hypertension, and hyperlipidemia.
The first demonstration of endothelial dysfunction involved direct infusion of acetylcholine and quantitative coronary angiography. Acetylcholine binds to muscarinic receptors on the endothelial cell surface, leading to an increase of intracellular calcium and increased nitric oxide (NO) production. In subjects with an intact endothelium, vasodilation was observed while subjects with endothelial damage experienced paradoxical vasoconstriction.
There exists a non-invasive, in vivo method for measuring endothelial function in peripheral arteries using high-resolution B-mode ultrasound. The endothelial function of peripheral arteries is closely related to coronary artery function. This technique measures the percent diameter change in the brachial artery during a period of reactive hyperemia following limb ischemia.
This technique, known as endothelium-dependent, flow-mediated vasodilation (FMD) has value in clinical research settings. However, a number of physiological and technical issues can affect the accuracy of the results and appropriate guidelines for the technique have been published. Despite the guidelines, FMD remains heavily operator dependent and presents a steep learning curve. This article presents a standardized method for measuring FMD in the brachial artery on the upper arm and offers suggestions to reduce intra-operator variability.

Endothelial dysfunction is associated with numerous disease states and is predictive of adverse cardiovascular events in humans. Flow-mediated vasodilation (FMD) is a non-invasive ultrasound method of evaluating endothelial function. Methodological choices and operator experience may affect results. A systematic approach to FMD in human studies is discussed here.

The vascular endothelium is a monolayer of cells that cover the interior of blood vessels and provide both structural and functional roles. The ...

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 ...

Direct Re-implantation of Left Coronary Artery into the Aorta in Adults with Anomalous Origin of Left Coronary Artery from the Pulmonary Artery (ALCAPA)

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital anomaly which is one of leading causes of myocardial ischemia and infarction in children. If left untreated, it results in a 90% mortality rate in the first year of life. In patients who survive to the adulthood, the coronary steal phenomenon and retrograde left-sided coronary flow provide a substrate for chronic subendocardial ischemia, which may lead to left ventricular dysfunction, ischemic mitral regurgitation, malignant ventricular arrhythmias, and sudden cardiac death. The average age of life-threatening presentation is 33 years and of sudden cardiac death 31 years. Therefore, surgical correction is highly recommended as soon as the diagnosis is made, regardless of age. In adult-type ALCAPA originating from the right-facing sinus of the pulmonary artery, direct re-implantation of the ALCAPA into the aorta is the more physiologically sound repair technique to re-establish the dual-coronary perfusion system and is recommended. This protocol describes the technique of direct re-implantation of adult-type ALCAPA into the aorta.

Direct Re-implantation of Left Coronary Artery into the Aorta in Adults with Anomalous Origin of Left Coronary Artery from the Pulmonary Artery ALCAPA

Surgical correction of ALCAPA is highly recommended, regardless of age or the degree of intercoronary collateralization. This protocol presents a technique for the direct re-implantation of adult-type ALCAPA into the aorta to re-establish the dual-coronary perfusion. Whenever feasible, direct re-implantation is preferred to other surgical correction techniques.

Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital anomaly which is one of leading causes of myocardial ...

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and drugs. It is widely used in many studies on the physiological functions of vascular smooth muscle, the pathogenesis of vascular diseases such as hypertension, and the development of smooth muscle relaxant drugs. The mouse is a widely used model animal with a large pool of disease models and genetically modified strains. We introduced this method to measure the isometric contraction of mouse mesenteric artery in detail. A 1.4-mm segment of mouse mesenteric resistance artery was isolated and mounted on a myograph chamber by passing two steel wires through its lumen. After equilibration and normalization steps, the vessel segment was potentiated by a high-K+ solution twice prior to the contraction assay. As an example of the application of this method in drug development, we measured the relaxant effect of a novel natural substance, neoliensinine, isolated from a Chinese herb, embryos of the lotus seed (Nelumbo nucifera Gaertn.) on mouse mesenteric arteries. The vessel segments mounted on the myograph chamber were stimulated with a high-K+ solution. When the force tension reached a stable sustained phase, cumulative doses of neoliensinine were added to the chamber. We found that neoliensinine had a dose-dependent relaxant effect on smooth muscle contraction, thus suggesting that it bears potential activity against hypertension. In addition, as the vessel segment can survive at least 4 hours after mounting and maintain contractility induced by the high-K+ solution for many times, we suggest that the wire myograph system may be used for the time-consuming process of drug screening.

The wire myograph technique is used to investigate vascular smooth muscle functions and screen new drugs. We report a detailed protocol for measuring the isometric contractility of the mouse mesenteric artery and for screening new relaxants of vascular smooth muscle.

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and ...

Evaluation of Coronary Flow Reserve After Myocardial Ischemia Reperfusion in Rats

Coronary artery disease is the leading cause of death worldwide. After an acute myocardial infarction, early and successful myocardial intervention via recanalization of the coronary artery is the most effective strategy for reducing the size of ischemic myocardium. The coronary microvasculature cannot be visualized and imaged&#160;in vivo, but there are several invasive and noninvasive techniques that can be used to assess parameters which depend directly on coronary microvascular function. The endothelial function after ischemia reperfusion can be assessed also at the level of the coronary circulation via the coronary flow reserve (CFR).&#160;In this study, peak velocity of left anterior descending (LAD) coronary arteries was measured in rats in vivo via Transthoracic Doppler Echocardiography during resting and stress challenge (induced by Dobutamine). A normal heart can increase its coronary blood flow up to four times above the resting values during stress induction. Following ischemia reperfusion, we found a significantly diminished CFR, which can be used as a marker of coronary microvascular dysfunction. CFR has opened a window on the importance of microvascular dysfunction and has been shown to predict cardiovascular risk independent of whether the severe obstructive disease is present.

Coronary flow reserve (CFR), is defined as the ratio of maximal coronary blood flow to the resting coronary blood flow. We present a protocol for evaluating CFR in rats via ultrasound, which offers the opportunity to predict cardiovascular risk factors in the absence of obstructive coronary disease.

Coronary artery disease is the leading cause of death worldwide. After an acute myocardial infarction, early and successful myocardial intervention via ...

Murine Myocardial Infarction Model using Permanent Ligation of Left Anterior Descending Coronary Artery

Myocardial infarction (MI) and acute coronary diseases are among the most prominent causes of death in population with western lifestyle. The murine models of MI with permanent ligation of left-anterior descending (LAD) coronary artery closely mimics MI in humans. Murine models benefit from the extensive genetic engineering available nowadays. Here we propose a reproducible murine surgical model of myocardial infarction by permanent LAD coronary ligation. Our technique comprises anesthesia with ketamine/xylazine that can be rapidly reversed by administration of an antagonist, intubation without tracheotomy for mechanical-assisted ventilation, ventilation with application of extrinsic positive end-expiratory pressure (PEEP) to avoid alveolar collapse, a thoracotomy method limiting to the minimum surgical lesions made to skeletal muscles, and lung inflation without thoracentesis. This method is sparsely invasive, reproducible and reduces post-surgery mortality and complications.

Herein we describe a surgical procedure showing how to achieve permanent ligation of the left-anterior descending coronary artery in mice. This model is of high relevance to investigate the pathophysiology of myocardial infarction and the concomitant biological processes.

Myocardial infarction (MI) and acute coronary diseases are among the most prominent causes of death in population with western lifestyle. The murine ...

In Vitro Model of Coronary Angiogenesis

Here, we describe an in vitro culture assay to study coronary angiogenesis. Coronary vessels feed the heart muscle and are of clinical importance. Defects in these vessels represent severe health risks such as in atherosclerosis, which can lead to myocardial infarctions and heart failures in patients. Consequently, coronary artery disease is one of the leading causes of death worldwide. Despite its clinical importance, relatively little progress has been made on how to regenerate damaged coronary arteries. Nevertheless, recent progress has been made in understanding the cellular origin and differentiation pathways of coronary vessel development. The advent of tools and technologies that allow researchers to fluorescently label progenitor cells, follow their fate, and visualize progenies in vivo have been instrumental in understanding coronary vessel development. In vivo studies are valuable, but have limitations in terms of speed, accessibility, and flexibility in experimental design. Alternatively, accurate in vitro models of coronary angiogenesis can circumvent these limitations and allow researchers to interrogate important biological questions with speed and flexibility. The lack of appropriate in vitro model systems may have hindered the progress in understanding the cellular and molecular mechanisms of coronary vessel growth. Here, we describe an in vitro culture system to grow coronary vessels from the sinus venosus (SV) and endocardium (Endo), the two progenitor tissues from which many of the coronary vessels arise. We also confirmed that the cultures accurately recapitulate some of the known in vivo mechanisms. For instance, we show that the angiogenic sprouts in culture from SV downregulate COUP-TFII expression similar to what is observed in vivo. In addition, we show that VEGF-A, a well-known angiogenic factor in vivo, robustly stimulates angiogenesis from both the SV and Endo cultures. Collectively, we have devised an accurate in vitro culture model to study coronary angiogenesis.

In vitro models of coronary angiogenesis can be utilized for the discovery of the cellular and molecular mechanisms of coronary angiogenesis. In vitro explant cultures of sinus venosus and endocardium tissues show robust growth in response to VEGF-A and display a similar pattern of COUP-TFII expression as in vivo.

Here, we describe an in vitro culture assay to study coronary angiogenesis. Coronary vessels feed the heart muscle and are of clinical importance. Defects ...