This work was supported by the Key R&#38;D project of Sichuan Provincial Science and Technology Plan (2022YFS0438), the National Natural Science Foundation of China (82104533), the China Postdoctoral Science Foundation (2020M683273), and the Science &#38; Technology Department of Sichuan Province (2021YJ0175).

The animal protocol was reviewed and approved by the Management Committee from Chengdu University of Traditional Chinese Medicine (Record No. 2021-11). Male Sprague Dawley (SD) rats (260-300 g, 8-10 weeks old) were used for the present study. The rats were kept in an animal chamber and were free to drink and eat during the experiment.
1. Solution preparation
<ol>
	<li>Prepare physiological salt solution (PSS) by dissolving 118 mM of NaCl, 4.7 mM of K+, 2.5 mM of CaCl2, 1.2 mM of KH2PO4, 1.2 mM of MgCl2&#8729;6H2O, 25 mM of NaHCO3, 11 mM of D-glucose, and 5 mM of HEPES (see Table of Materials).</li>
	<li>Prepare high K+ salt solution by dissolving 58 mM of NaCl, 60 mM of K+, 2.5 mM of CaCl2, 1.2 mM of KH2PO4, 1.2 mM of MgCl2&#8729;6H2O, 25 mM of NaHCO3, 11 mM of D-glucose, and 5 mM of HEPES.</li>
	<li>Saturate the above two solutions and bubble with a mixed gas of 95% O2 and 5% CO2. Meanwhile, maintain the pH values of the solution between 7.38 and 7.42 with 2 mM NaOH. 
	NOTE: For details information on solution preparation, please see reference15.</li>
</ol>
2. Rat coronary artery dissection
<ol>
	<li>Anesthetize the rat by inhalation of 2% isoflurane. Confirm deep anesthesia by toe pinch and, if needed, administer additional anesthetics. Then immediately open the thoracic cavity to expose the heart on the portable operating table following a previously published report12.</li>
	<li>After dissociating and removing the heart, drain the residual blood from all the heart chambers by mildly squeezing with medical plastic forceps. Quickly place the pre-processed heart in a Petri dish containing 95% O2 + 5% CO2 saturated PSS at 4 &#176;C, having a pH value of 7.40.</li>
	<li>To accurately identify the anatomical position of the coronary arteries, adjust the posture of the isolated heart under the light microscope according to the schematic diagram (Figure 2A). 
	NOTE: On the frontal view, the right auricle and the pulmonary artery were on the upper left and the upper right, respectively.
	<ol>
		<li>Cut the left and right ventricular cavities along the interventricular septum from the root of the pulmonary artery with surgical scissors and tweezers (Figure 2B).</li>
	</ol>
	</li>
	<li>To dissociate the left and right coronary arteries from the myocardial tissue, dissect the right ventricle under an optical anatomic microscope to thoroughly expose the right coronary artery branch. Then identify the position of the left coronary artery by rotating the heart tissue 45&#176; clockwise (Figure 2D).</li>
	<li>After removing the surrounding sticky myocardial tissue, explicitly discern the pulsing left (about 5 mm) and right (about 5 mm) coronary arteries. Separate the coronary arteries in the middle immediately and completely immerse in PSS at 4 &#176;C. Acquire an arterial ring of about 2 mm by vertically cutting the detached artery with anatomical scissors to record the vascular tension under different stimuli (Figure 2E).</li>
</ol>
3. Suspension and fixation of arterial ring
NOTE: For details on this step, please see reference14.
<ol>
	<li>Prepare two 2 cm stainless steel wires (see Table of Materials) and pre-soak in 4 &#176;C PSS solution saturated with 95% O2 + 5% CO2. Pass both the wires parallelly through the arterial ring along with the vessel&#39;s direction under an optical anatomical microscope and with wires of equal length exposed at both ends of the vascular cavity.</li>
	<li>Fix the arterial ring with the steel wire front and back in the bath of the wire micrograph filled with bubbling PSS with 95% O2 + 5% CO2. Rotate the horizontal screw knob for an appropriate front and rear spacing so that the two wires are horizontal and the arterial ring is in a natural state of relaxation.</li>
	<li>After installing the DMT bath on the thermostatic apparatus, open the data acquisition software (see Table of Materials) to ensure that the corresponding path signal was recorded. Set the following parameters: eyepiece calibration (mm/div): 0.36; target pressure (kPa): 13.3; IC1/IC100: 0.9; online averaging time: 2 s; delay time: 60 s. The steps of arterial ring fixation are shown in Figure 3.</li>
</ol>
4. Standardization of vascular tension in rat arterial ring
NOTE: For different cavity samples, optimal initial tension was necessary for vessels to maintain exceptional activity in vitro. For details, please see reference15.
<ol>
	<li>Achieve the optimal initial tension of the arterial ring by applying a reasonable tension along the diameter of the vessel. 
	NOTE: Based on the previous study16, the maximal agonist-induced tension was accomplished at the factor k value of 0.90 with the initial stretch tension of 1.16 &#177; 0.04 mN/mm (reference values for different vessel samples: k value, 0.90-0.95; initial tension, 1.16-1.52 mN/mm).</li>
	<li>At this point, set the displayed vascular tension value to zero. Afterward, apply a 3 mN pull stimulus to the arterial ring by rotating the spiral axis of the bath.</li>
	<li>After incubation for 1 h in oxygen-saturated PSS buffer at 37 &#176;C, pH 7.40, set the tension value to 0 mN again on the tension control panel of the wire micrograph. The setting process of the initial tension of the arterial ring is shown in Figure 4.</li>
</ol>
5. Reactivity detection of coronary artery ring
<ol>
	<li>Perform the contractile activity of the coronary artery ring with the wire myograph technique14, and validate in three separate operations by stimulating with 60 mM of K+ solution for 10 min each.</li>
	<li>After each stimulation, flush the bath with oxygen-saturated PSS until vascular tone returns to its initial state. 
	NOTE: Only when the tension fluctuation of the three parallel measurements was less than 10%, and the amplitude of each contraction was greater than 1 mN/mm, qualified and highly active arterial rings could be used for further experiments. The activity verification of the rat coronary ring is shown in Figure 5.</li>
</ol>
6. Post-surgical treatment
<ol>
	<li>After surgery, euthanize the animals following institutionally approved protocols. 
	NOTE: For the present study, the animals were euthanized by inhaling excess isoflurane.</li>
</ol>

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The authors have nothing to disclose.

The disturbance of coronary microcirculation, which involves a wide range of patients with CAD, has been gradually recognized and concerned the basis for adequate myocardium perfusion. Considering the serious complications of sudden coronary heart disease and cardiovascular disease, timely drug prevention and treatment are extremely important for a clinical individual with CAD17. Inevitably, the secrecy of coronary artery anatomy and the complexity of its physiological structure have severely rest...

Coronary artery disease (CAD) has been widely recognized and concerned as a typical and representative cardiovascular disease, being the leading cause of death in both developed and developing countries1,2. As a blood and oxygen supply route for normal cardiac physiological function, circulating blood enters and nourishes the heart through two main coronary arteries and a blood vascular network on the surface of the myocardium3,4. Cholesterol and fat deposits in the coronary arteries cut off the heart&#39;s blood supply and the violent inflammatory response of the vascular system, causing atherosclerosis, stable angina, unstable angina, myocardial infarction, or sudden cardiac death5,6. In response to pathological stenosis of the coronary arteries, compensatory accelerated physiological heartbeat satisfies the blood supply of the heart itself or vital organs of the body by increasing the output of the left ventricle7. If prolonged coronary stenosis is not relieved in time, extensive new blood vessels may develop in certain areas of the heart8. At present, the clinical treatment of CAD often adopts drug thrombolysis or surgical mechanical thrombolysis and an exogenous bionic vascular bypass with frequent medication and great surgical disability9. Therefore, the functional investigation of coronary artery physiological activity is still an urgent breakthrough for cardiovascular diseases10.
There are no available technical means to detect coronary physiological activity, except for wireless telemetry systems, which can dynamically record in vivo coronary pressure, vascular tension, blood oxygen saturation, and pH values11. Therefore, considering coronary arteries&#39; textural secrecy and complexity, accurate identification and isolation of coronary arteries are undoubtedly the best choices for exploring multiple mechanisms of CAD in vitro4.
A series multi myograph system, in particular a wire micrograph microvascular tension detector (see Table of Materials), is a very mature marketable device for recording in vitro tissue tension changes of small vascular, lymphatic, and bronchial tubes with the characteristics of high precision and continuous dynamic recording12. The said system has been extensively employed to record in vitro tissue tension characteristics of cavity structures with diameters of 60 &#181;m to 10 mm. The continuous heating features of the platform of the wire micrograph largely offset the stimulation of the adverse external environment. Meanwhile, the constant inputs of the gas mixture and the pH values allow us to obtain more accurate vascular tension data in a similar physiological state13. However, considering the complexity of anatomical localization of rat coronary arteries (Figure 1), its isolation has been perplexing and limiting the mechanism&#39;s exploration of diversified cardiovascular disease and drug development. Therefore, the present protocol introduces the anatomical location and separation process of the rat coronary artery in detail, followed by tension measurement on the platform of the wire micrograph14.

<table><tbody><tr><td>Apigenin</td><td>Sangon Biotech Co., Ltd., Shanghai, China</td><td>150731</td><td></td></tr><tr><td>CaCl&lt;sub&gt;2&lt;/sub&gt;</td><td>Sangon Biotech Co., Ltd., Shanghai, China</td><td>A501330</td><td></td></tr><tr><td>D-glucose</td><td>Sangon Biotech Co., Ltd., Shanghai, China</td><td>A610219</td><td></td></tr><tr><td>HEPES</td><td>Xiya Reagent Co., Ltd., Shandong, China</td><td>S3872</td><td></td></tr><tr><td>KCl</td><td>Sangon Biotech Co., Ltd., Shanghai, China</td><td>A100395</td><td></td></tr><tr><td>KH&lt;sub&gt;2&lt;/sub&gt;PO&lt;sub&gt;4&lt;/sub&gt;</td><td>Sangon Biotech Co., Ltd., Shanghai, China</td><td>A100781</td><td></td></tr><tr><td>LabChart Professional version 8.3&amp;nbsp;</td><td>ADInstruments, Australia</td><td>&amp;mdash;</td><td></td></tr><tr><td>MgCl&lt;sub&gt;2&lt;/sub&gt;&amp;middot;6H&lt;sub&gt;2&lt;/sub&gt;O</td><td>Sangon Biotech Co., Ltd., Shanghai, China</td><td>A100288</td><td></td></tr><tr><td>Multi myograph system&amp;nbsp;</td><td>Danish Myo Technology, Aarhus, Denmark</td><td>620M</td><td></td></tr><tr><td>NaCl</td><td>Sangon Biotech Co., Ltd., Shanghai, China</td><td>A100241</td><td></td></tr><tr><td>NaHCO&lt;sub&gt;3&lt;/sub&gt;</td><td>Sangon Biotech Co., Ltd., Shanghai, China</td><td>A100865</td><td></td></tr><tr><td>Steel wires</td><td>Danish Myo Technology, Aarhus, Denmark</td><td>400447</td><td></td></tr><tr><td>U46619</td><td>Sigma, USA</td><td>D8174</td><td></td></tr></tbody></table>

standardized rat coronary ring preparation and real-time recording of dynamic tension changes along vessel diameter

As a key event of cardiovascular system diseases, coronary artery disease (CAD) has been widely regarded as the main culprit of atherosclerosis, myocardial infarction, and angina pectoris, which seriously threaten the life and health of people all over the world. However, how to record the dynamic biomechanical characteristics of isolated blood vessels has long puzzled people. Meanwhile, precise positioning and isolation of coronary arteries to measure in vitro dynamic vascular tension changes have become a trend in CAD drug development. The present protocol describes the macroscopic identification and microscopic separation of rat coronary arteries. The contraction and dilation function of the coronary artery ring along the vessel diameter was monitored using the established multi myograph system. The standardized and programmed protocols of coronary ring tension measurement, from sampling to data acquisition, tremendously improve the repeatability of the experimental data, which ensures the authenticity of vascular tension records after physiological, pathological, and drug intervention.

Anatomically positioned, rat coronary arteries distributed and hidden deep in myocardial tissue were not easily recognized. By comparing the coronary arteries of humans (Figure 1A) and rats (Figure 1B), rapid and accurate separation of rat coronary arteries was conducted according to the sampling process in Figure 2. After precisely locating the right auricle, pulmonary artery, and apex from the front under an optical microscope, th...

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Standardized Rat Coronary Ring Preparation and Real-Time Recording of Dynamic Tension Changes Along Vessel Diameter

The present protocol describes the wire myograph technique for measuring vascular reactivity of the rat coronary artery.

As a key event of cardiovascular system diseases, coronary artery disease (CAD) has been widely regarded as the main culprit of atherosclerosis, ...

standardized-rat-coronary-ring-preparation-real-time-recording

Universidad de Cartagena UDEC

Research

JoVE Journal

Medicine

3.0K Views.  Chengdu University of Traditional Chinese Medicine. The present protocol describes the wire myograph technique for measuring vascular reactivity of the rat coronary artery.

Video: Standardized Rat Coronary Ring Preparation and Real-Time Recording of Dynamic Tension Changes Along Vessel Diameter

Cardiac Stress Test Induced by Dobutamine and Monitored by Cardiac Catheterization in Mice

Dobutamine is a &beta;-adrenergic agonist with an affinity higher for receptor expressed in the heart (&beta;1) than for receptors expressed in the arteries (&beta;2). When systemically administered, it increases cardiac demand. Thus, dobutamine unmasks abnormal rhythm or ischemic areas potentially at risk of infarction. 
Monitoring of heart function during a cardiac stress test can be performed by either ecocardiography or cardiac catheterization. The latter is an invasive but more accurate and informative technique that the former.
Cardiac stress test induced by dobutamine and monitored by cardiac catheterization accomplished as described here allows, in a single experiment, the measurement of the following hemodynamic parameters: heart rate (HR), systolic pressure, diastolic pressure, end-diastolic pressure, maximal positive pressure development (dP/dtmax) and maximal negative pressure development (dP/dtmin), at baseline conditions and under increasing doses of dobutamine.
As expected, in normal mice we observed a dobutamine dose-related increase in HR, dP/dtmax and dP/dtmin. Moreover, at the highest dose tested (12 ng/g/min) the cardiac decompensation of high fat diet-induced obese mice was unmasked.

We describe the protocol to perform a cardiac stress test induced by dobutamine and monitored by cardiac catheterization in normal mice. Also we show its application to unmask subclinical cardiac disease in high fat diet-induced obese mice.

Dobutamine is a &beta;-adrenergic agonist with an affinity higher for receptor expressed in the heart (&beta;1) than for receptors expressed in the ...

Hemodynamic Characterization of Rodent Models of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a rare disease of the pulmonary vasculature characterized by endothelial cell apoptosis, smooth muscle proliferation and obliteration of pulmonary arterioles. This in turn results in right ventricular (RV) failure, with significant morbidity and mortality. Rodent models of PAH, in the mouse and the rat, are important for understanding the pathophysiology underlying this rare disease. Notably, different models of PAH may be associated with different degrees of pulmonary hypertension, RV hypertrophy and RV failure. Therefore, a complete hemodynamic characterization of mice and rats with PAH is critical in determining the effects of drugs or genetic modifications on the disease. 
Here we demonstrate standard procedures for assessment of right ventricular function and hemodynamics in both rat and mouse PAH models. Echocardiography is useful in determining RV function in rats, although obtaining standard views of the right ventricle is challenging in the awake mouse. Access for right heart catheterization is obtained by the internal jugular vein in closed-chest mice and rats. Pressures can be measured using polyethylene tubing with a fluid pressure transducer or a miniature micromanometer pressure catheter. Pressure-volume loop analysis can be performed in the open chest. After obtaining hemodynamics, the rodent is euthanized. The heart can be dissected to separate the RV free wall from the left ventricle (LV) and septum, allowing an assessment of RV hypertrophy using the Fulton index (RV/(LV+S)). Then samples can be harvested from the heart, lungs and other tissues as needed.

Pulmonary arterial hypertension (PAH) is a disease of pulmonary arterioles that leads to their obliteration and the development of right ventricular failure. Rodent models of PAH are critical in understanding the pathophysiology of PAH. Here we demonstrate hemodynamic characterization, with right heart catheterization and echocardiography, in the mouse and rat.

Pulmonary arterial hypertension (PAH) is a rare disease of the pulmonary vasculature characterized by endothelial cell apoptosis, smooth muscle ...

Simultaneous Electrocardiography Recording and Invasive Blood Pressure Measurement in Rats

For studies related to cardiovascular physiology or pathophysiology, blood pressure (BP) and electrocardiography are basic observational parameters. Research focusing on cardiovascular disease models, potential cardiovascular therapeutic targets or pharmaceutical agents requires assessment of systemic arterial pressure and heart rhythm changes. In situations where radio telemetry systems are not available or affordable, the technique of femoral artery cannulation is an alternative way to obtain intra-arterial pressure waveform recordings and systemic BP measurements. This technique is economical and can be performed with standard equipment in animal facilities. However, invasive arterial pressure recording requires cannulation of small arteries, which can be a challenging surgical skill. Here, we present step-by-step protocols for femoral artery cannulation procedures. Key procedures include the calibration of the data acquisition system, tissue dissection and femoral artery cannulation, and setup of the arterial cannulation system for pressure recording. Surface electrocardiography recording procedures are also included. We also present examples of BP recordings from normotensive and hypertensive rats. This protocol allows reliable direct recordings of systemic BP with simultaneous electrocardiography.

Here, we describe a setup for simultaneous recording of electrocardiography and intra-arterial blood pressure (BP) in experimental rats, which can be done with standard equipment in animal facilities and can be applied to physiological or pharmacological studies to investigate pathogenic or therapeutic mechanisms in cardiovascular medicine.

For studies related to cardiovascular physiology or pathophysiology, blood pressure (BP) and electrocardiography are basic observational parameters. ...

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, ...

Echocardiographic Assessment of Cardiac Anatomy and Function in Adult Rats

The use of experimental animal models has become crucial in cardiovascular science. Most studies using rodent models are focused on two-dimensional imaging to study the cardiac anatomy of the left ventricle and M-mode echo to assess its dimensions. However, this could limit a comprehensive study. Herein, we describe a protocol that allows an assessment of the heart chamber size, left ventricular function (systolic and diastolic) and valvular function. A conventional medical ultrasound machine was used in this protocol and different echo views were obtained through left parasternal, apical and suprasternal windows. In the left parasternal window, the long and short axis were acquired to analyze left chamber dimensions, right ventricle and pulmonary artery dimensions, and mitral, pulmonary and aortic valve function. The apical window allows the measurement of heart chamber dimensions and evaluation of systolic and diastolic parameters. It also allows Doppler assessment with detection and quantification of heart valve disturbances (regurgitation or stenosis). Different segments and walls of the left ventricle are visualized throughout all views. Finally, the ascending aorta, aortic arch, and descending aorta can be imaged through the suprasternal window. A combination of ultrasound imaging, Doppler flow and tissue Doppler assessment have been obtained to study cardiac morphology and function. This represents an important contribution to improve the assessment of cardiac function in adult rats with impact for research using these animal models.

A non-invasive protocol for transthoracic echocardiography assessment of cardiac anatomy and function for adult rats is presented in the current study. The heart valves, all four cardiac chambers and the ascending aorta, aortic arch and descending aorta are studied in detail.

The use of experimental animal models has become crucial in cardiovascular science. Most studies using rodent models are focused on two-dimensional ...

Real-Time Analysis of Calcium and Contractility in Isolated Lymph Vessels

Real-time Evaluation of Absolute, Cytosolic, Free Ca2+ and Corresponding Contractility in Isolated, Pressurized Lymph Vessels

The lymphatic vasculature, now often referred to as &#34;the third circulation,&#34; is located in many vital organ systems. A principal mechanical function of the lymphatic vasculature is to return fluid from extracellular spaces back to the central venous ducts. Lymph transport is mediated by spontaneous rhythmic contractions of lymph vessels (LVs). LV contractions are largely regulated by the cyclic rise and fall of cytosolic, free calcium ([Ca2+]i).
This paper presents a method to concurrently calculate changes in absolute concentrations of [Ca2+]i and vessel contractility/rhythmicity in real time in isolated, pressurized LVs. Using isolated rat mesenteric LVs, we studied changes in [Ca2+]i and contractility/rhythmicity in response to drug addition. Isolated LVs were loaded with the ratiometric Ca2+-sensing indicator Fura-2AM, and video microscopy coupled with edge-detection software was used to capture [Ca2+]i&#160;and diameter measurements continuously in real time.
The Fura-2AM signal from each LV was calibrated to the minimum and maximum signal for each vessel and used to calculate absolute [Ca2+]i. Diameter measurements were used to calculate contractile parameters (amplitude, end diastolic diameter, end systolic diameter, calculated flow) and rhythmicity (frequency, contraction time, relaxation time) and correlated with absolute [Ca2+]i measurements.

Author Spotlight: Innovative Methods in Lymphedema and Hypertension Research

This protocol describes a method to simultaneously measure cytosolic, free calcium [Ca2+]i and vessel diameter in contracting lymph vessels in real time and then calculate absolute Ca2+ concentrations as well as contractility/rhythmicity parameters. This protocol can be used to study Ca2+ and contractile dynamics across a variety of experimental conditions.

The lymphatic vasculature, now often referred to as &#34;the third circulation,&#34; is located in many vital organ systems. A principal mechanical ...

Immunology and Infection

Improved Rodent Model of Myocardial Ischemia and Reperfusion Injury

Myocardial ischemia and reperfusion injury (MIRI), induced by coronary heart disease (CHD), causes damage to the cardiomyocytes. Furthermore, evidence suggests that thrombolytic therapy or primary percutaneous coronary intervention (PPCI) does not prevent reperfusion injury. There is still no ideal animal model for MIRI. This study aims to improve the MIRI model in rats to make surgery easier and more feasible. A unique method for establishing MIRI is developed by using a soft tube during a key step of the ischemic period. To explore this method, thirty rats were randomly divided into three groups: sham group (n = 10); experimental model group (n = 10); and existing model group (n = 10). Findings of triphenyltetrazolium chloride staining, electrocardiography, and percent survival are compared to determine the accuracies and survival rates of the operations. Based on the study results, it has been concluded that the improved surgery method is associated with a higher survival rate, elevated ST-T segment, and larger infarct size, which is expected to mimic the pathology of MIRI better.

Myocardial ischemia-reperfusion model of rat heart is improved by using a self-made retractor, polyvinyl chloride tube, and a unique knotting method. Electrocardiogram, triphenyltetrazolium chloride and histological staining, and percent survival analysis results showed that the improved model group has higher success and survival rates than the already existing model group.

Myocardial ischemia and reperfusion injury (MIRI), induced by coronary heart disease (CHD), causes damage to the cardiomyocytes. Furthermore, evidence ...

O-Ring Aortic Banding Versus Traditional Transverse Aortic Constriction for Modeling Pressure Overload-Induced Cardiac Hypertrophy

Aortic banding in mice is one of the most commonly used experimental models for cardiac pressure overload-induced cardiac hypertrophy and the induction of heart failure. The previously used technique is based on a threaded suture around the aortic arch tied over a blunted 27 G needle to create stenosis. This method depends on the surgeon manually tightening the thread and, thus, leads to high variance in the diameter size. A newly refined method described by Melleby et al. promises less variance and more reproducibility after surgery. The new technique, o-ring- aortic banding (ORAB), uses a non-slip rubber ring instead of a suture with a thread, resulting in reduced variation in pressure overload and reproducible phenotypes of cardiac hypertrophy. During surgery, the o-ring is placed between the brachiocephalic and left carotid arteries. Successful constriction is confirmed by echocardiography. After 1 day, correct placement of the ring results in an increased flow velocity in the transverse aorta over the o-ring-induced stenosis. After 2 weeks, impaired cardiac function is proven by decreased ejection fraction and increased wall thickness. Importantly, besides less variance in the diameter size, ORAB is associated with lower intra- and post-operative mortality rates compared with transverse aortic constriction (TAC). Thus, ORAB represents a superior method to the commonly used TAC surgery, resulting in more reproducible results and a possible reduction in the number of animals needed.

The present protocol describes a new technique of aortic banding in mice to induce pressure overload cardiac hypertrophy. For banding, a rubber ring with a fixed inner diameter is used. This new technique promises less variance and more reproducible data for future experiments.

Aortic banding in mice is one of the most commonly used experimental models for cardiac pressure overload-induced cardiac hypertrophy and the induction of ...

Mechanical Control of Relaxation Using Intact Cardiac Trabeculae

Diastolic dysfunction is a common phenotype across cardiovascular disease presentations. In addition to elevated cardiac stiffness (elevated left ventricular end-diastolic pressure), impaired cardiac relaxation is a key diagnostic indicator of diastolic dysfunction. While relaxation requires the removal of cytosolic calcium and deactivation of sarcomeric thin filaments, targeting such mechanisms has yet to provide effective treatments. Mechanical mechanisms, such as blood pressure (i.e., afterload), have been theorized to modify relaxation. Recently, we showed that modifying the strain rate of a stretch, not afterload, was both necessary and sufficient to modify the subsequent relaxation rate of myocardial tissue. The strain rate dependence of relaxation, called the mechanical control of relaxation (MCR), can be assessed using intact cardiac trabeculae. This protocol describes the preparation of a small animal model, experimental system and chamber, isolation of the heart and subsequent isolation of a trabecula, preparation of the experimental chamber, and experimental and analysis protocols. Evidence for lengthening strains in the intact heart suggests that MCR might provide new arenas for better characterization of pharmacological treatments, along with a method to assess myofilament kinetics in intact muscles. Therefore, studying the MCR may elucidate a path to novel approaches and new frontiers in the treatment of heart failure.

Rapid myocardial and cardiac relaxation is essential for normal physiology. Mechanical relaxation mechanisms are now known to be dependent on strain rate. This protocol provides an overview of the acquisition and analysis of experiments to further study the mechanical control of relaxation.

Diastolic dysfunction is a common phenotype across cardiovascular disease presentations. In addition to elevated cardiac stiffness (elevated left ...

Monitoring Cardiac Function of Rats Using the Pressure-Volume Conductance Technique

Real-Time Detection of Ferulic Acid Effects on Rat Left Ventricle Using Pressure-Volume Conductivity Catheter

Decreased cardiac function can have a negative impact on other organs. The left ventricular pressure-volume relationship is considered to be a valid method for evaluating cardiac function. Real-time monitoring of cardiac function is important for drug evaluation. Under closed-chest conditions, the miniature transducer, which is an important component of the pressure-volume catheter, enters the left ventricle of the rat through the right carotid artery. The device visualizes the changes in cardiac function during the experiment in the form of a pressure-volume loop. The actual volume of the ventricle is calculated by altering the conductivity of the blood by injecting 50 &#181;L of a 20% sodium chloride solution into the rat's left jugular vein. The actual volume of the rat's ventricular cavity is calculated by measuring the conductivity of the blood in a known volume using a pressure-volume conductance catheter. This protocol allows for continuous observation of the effects of drugs on the heart and will promote the rationale for the use of specialty ethnic drugs in cardiovascular disease.

Author Spotlight: Advantages of Pressure-Volume Loop Measurement Method in Cardiovascular Research

This protocol describes a method for measuring left ventricular pressure and volume using the pressure-volume conductance technique. This method enables continuous real-time monitoring of the effects of drugs on the heart.

Decreased cardiac function can have a negative impact on other organs. The left ventricular pressure-volume relationship is considered to be a valid ...