Name: implantation of an isoproterenol mini-pump to induce heart failure in mice
Uploaded: 2019-10-03T13:00:00.000+00:00
Duration: 5 min 8 s
Description: Watch this Scientific Journal Video about Implantation of an Isoproterenol Mini-Pump to Induce Heart Failure in Mice at JoVE.com

The authors acknowledge NIH K08 HL133491 for funding support.

This protocol adheres to the animal care guidelines of the University of California, Los Angeles (ARC protocol #2010-075). Readers are advised to adhere to their own IACUC-approved protocol, as peri-procedure mouse care and analgesia management may be institution-specific.
1. Preparation of isoproterenol osmotic pump
NOTE: This procedure has been applied successfully on 9+ week-old female mice weighing 18+ g from over 100 inbred mouse strains, as well as, in male mice in a subset of strains. There is no maximum body weight limit for this procedure. Always include age-matched controls, as it is unknown whether the age of treatment affects isoproterenol-induced susceptibility to heart failure development.
<ol>
	<li>Weigh and record the body weight for each mouse.</li>
	<li>Calculate the appropriate amount and concentration of isoproterenol for each mouse (See Table 1 ; Supplemental File). 
	NOTE: The osmotic pumps used in this experiment (Table of Materials) have a reservoir volume of 100 &#181;L and are designed to deliver drugs at continuous flow rates for up to 28 days. Prepare an extra 20 &#181;L of isoproterenol solution per pump to account for the volume loss in the filling tube during pump loading.</li>
	<li>Weigh out the appropriate amount of isoproterenol (Table 1) using an analytical balance and dissolve it in 120 &#181;L of sterile 0.9% NaCl solution. Pipette vigorously or vortex for 1 min to completely solubilize isoproterenol. 
	NOTE: Prepare the osmotic pumps in a laboratory biosafety cabinet. Pumps should be handled with surgical gloves. Sterile technique is recommended throughout the preparation of the osmotic pumps and during the surgical implantation procedure.</li>
	<li>Weigh and record the empty osmotic pump together with its flow moderator and then remove the flow moderator.</li>
	<li>Aspirate 120 &#181;L of isoproterenol solution into a 1.0 mL syringe and attach the 27-gauge blunt-tipped filling tube provided with the osmotic pumps. 
	NOTE: Make sure the syringe and filling tube are free of air bubbles.</li>
	<li>While holding the pump in the upright position, insert the filling tube through the pump opening at the top until the tip of the filling tube sits near the bottom of the pump reservoir.</li>
	<li>Load the osmotic pump by pushing the syringe plunger slowly until the isoproterenol solution fills up to the pump opening.</li>
	<li>Carefully remove the filling tube and wipe off the excess solution.</li>
	<li>Insert back the flow moderator to close the pump and wipe off any excess solution.</li>
	<li>Confirm that over 90% of the reservoir volume has been filled by reweighing the osmotic pump. 
	NOTE: Control pumps are prepared in the same manner by filling the pump reservoir with sterile 0.9% NaCl solution.</li>
</ol>
2. Preparation of surgical instruments
<ol>
	<li>Clean all surgical instruments, including fiber optic O-ring light microscope illuminator, 2 forceps, needle holder, hot bead sterilizers, glass beads, and scissors (Table of Materials).</li>
	<li>Autoclave surgical instruments at 121&#176; C for 30 min to sterilize instruments prior to surgery.</li>
</ol>
3. Isoproterenol osmotic pump surgical implantation
<ol>
	<li>Induce anesthesia by placing the mouse in an induction chamber with 3% isoflurane in 95% O2 and 5% CO2. Maintain anesthesia with 2% isoflurane via a nosecone.</li>
	<li>Administer 5 mg/kg carprofen s.c. to the scruff of the neck between the shoulder blades for analgesia.</li>
	<li>Place ophthalmic ointment on the eyes to prevent corneal dehydration.</li>
	<li>Check the depth of anesthesia by monitoring the respiration rate, toe pinch reflex, and color of the mucous membrane.</li>
	<li>Place the mouse in a supine position on a heated pad. Remove hair from the lower abdomen and disinfect the skin with betadine or chlorhexidine. 
	NOTE: To minimize post-operative infection, ensure that the surgical field is free of incident hair.</li>
	<li>Use a pair of surgical scissors to cut a 1 cm-long midline skin incision. Use a pair of blunt-ended scissors to carefully dissect the skin from the underlying peritoneal walls. 
	NOTE: An intraperitoneal delivery is preferred to accommodate the size of the pump.</li>
	<li>Pull the peritoneal walls away from the underlying bowel with forceps and cut a 0.8 cm hole in the peritoneal walls using fine surgical scissors.</li>
	<li>Insert the osmotic pump into the peritoneal cavity with the flow moderator end first.</li>
	<li>Close the hold in the peritoneal walls using 5.0 absorbable sutures in an interrupted fashion. Use 6.0 non-absorbable sutures to close the skin incision in an interrupted fashion.</li>
	<li>Place the mouse in a dedicated incubator to keep it warm and dry during recovery. Assess recovery from anesthesia by monitoring the mouse every 30 mins in the first two hours for return of normal breathing and movement.</li>
	<li>Once the mouse has fully recovered from anesthesia, return it to routine housing. Continue to monitor the animal for complications daily up to 3 days and then every 2 to 3 days thereafter until the end of the experiment. 
	NOTE: Animals should be monitored for evidence of post-operative pain or infection, signs of weight loss, lack of mobility, abnormal posture, failure to groom, and excessive licking or biting of the incision area.</li>
	<li>Administer carprofen 5mg/kg s.c. every 24 h for up to 48 h and thereafter as needed.</li>
	<li>Administer 0.25 mg/mL amoxicillin in drinking water for 5 days to prevent surgical site infections.</li>
	<li>Remove non-absorbable sutures after 7 to 10 days.</li>
</ol>
4. Echocardiographic assessment under anesthesia
NOTE: Echocardiographic assessment can be performed repeatedly to monitor serial cardiac remodeling over several weeks. We performed echocardiographic measurements at weekly intervals over 3 weeks.
<ol>
	<li>Induce anesthesia in an induction chamber at 1.25% to 1.5% of isoflurane. Once appropriately sedated, secure the mouse onto the echocardiography platform with tape allowing the mouse to continue receiving anesthesia through a nose cone.</li>
	<li>Decrease isoflurane to a maintenance dosage of 1% to minimize negative chronotropic and inotropic effects of over-sedation. Take note of respiratory and heart rates throughout the study and adjust isoflurane dosage as needed.</li>
	<li>Remove the chest hair with a depilatory lotion and wipe the chest free of hair.</li>
	<li>Place the ultrasound gel on the chest and position the ultrasound probe to image the heart.</li>
	<li>In B-mode, image the left ventricle (LV) in the parasternal long-axis view. Adjust the echocardiography platform to align the aortic valve and the LV apex in the plane of the ultrasound beam.</li>
	<li>Tilt the echocardiography platform to place the LV long axis at 90 degrees to the ultrasound beam and the LV maximum diameter at the center of the image.</li>
	<li>Image the LV short axis by turning the ultrasound probe 90 degrees.</li>
	<li>In M-mode measure LV wall thickness and internal dimensions.</li>
	<li>Place the mouse back into the cage. Monitor for return of normal breathing and spontaneous body movements.</li>
</ol>

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The authors have nothing to disclose.

We have applied this method to over 100+ strains of inbred mice to assess cardiac outcomes due to chronic beta-adrenergic stimulation2,13. Significant differences in susceptibility to isoproterenol are known to exist among mouse strains and may be customized to the strain of interest as needed16. This may be due to the variation in beta-adrenergic receptor function between mouse strains17, strain-dependent differenc...

Heart failure with reduced ejection fraction (HFrEF) is accompanied by a well-recognized compensatory response of the sympathetic nervous system to maintain cardiovascular homeostasis1. Hemodynamic stress and deleterious effects on the heart and circulation were observed with chronic activation. These have become the cornerstone of contemporary pharmacotherapy for heart failure and are important mechanisms in the progression of heart failure and therapeutic antagonism of neurohormonal systems1.
Several mouse models are available for basic investigations of heart failure. Genetic models are attractive for exploring molecular therapies and investigating signaling pathways. However, these models may not be relevant to common forms of heart failure. Other common models include left anterior descending (LAD) artery ligation, transaortic constriction (TAC), and isoproterenol (ISO), each aiming at a different pathological etiology2,3,4,5,6. LAD artery ligation induces an anterior wall myocardial infarction thus creating a model specific for ischemic cardiomyopathy. TAC induces acute pressure overload to create a hypertensive model of heart failure. Although the pressure gradient can be measured, allowing for the stratification of hypertrophy, the acute onset of hypertension lacks direct clinical relevance4. Both LAD and TAC models require a high level of surgical expertise to execute. Acute ISO model of heart failure mimics stress-induced cardiomyopathy, also known as Takotsubo disease, which is characterized by a marked increase in catecholamines and activity in the left ventricle that mimics acute myocardial infarction7,8. In contrast, chronic ISO models of heart failure present symptoms characteristics of advanced heart failure, with chronically elevated levels of catecholamines1. The advantages of the chronic ISO model are that it provides chronic adrenergic stimulation that mimics advanced heart failure and that it is relatively easy to create. The investigator should choose a model that best recapitulates their pathology of interest.
The overall goal of this method is to induce heart failure in mice using an implanted mini pump that releases ISO continuously to mimic chronic sympathetic activation found in heart failure patients1. The method is simple and reproducible. Although there is clear variation among mouse strains, ISO administered over 3 to 4 weeks at 30 mg/kg/day is sufficient to induce cardiac remodeling in most mice. Specifically, ISO leads to a pro-hypertrophic compensatory phase during week 1 followed by wall thinning, ventricular dilation and decrease in systolic function by week 2 and 32. Success for the ISO model creation can be assessed in vivo by serial echocardiography demonstrating hypertrophy, dilation, and ventricular dysfunction, as well as ex vivo via histological and molecular assessment of harvested cardiac tissue for intramyocardial lipid accumulation, fibrosis, ER stress, apoptosis, and gene expression9,10,11,12.

<table><tbody><tr><td>Micro-Osmotic Pump System with Flow Moderator in Place</td><td>Alzet</td><td>Model 1004</td><td>Includes filling tube, flow moderator and pump body</td></tr><tr><td>(-)-Isoproterenol hydrochloride</td><td>Sigma-Aldrich</td><td>16504-1G</td><td>(-)-Isoproterenol hydrochloride is a powder that needs to be stored at -20&amp;deg;C.</td></tr><tr><td>1 ml sterile syringe</td><td>VWR</td><td>BD309602</td><td></td></tr><tr><td>30 W LED Fiber optic O-ring light microscope illuminator</td><td>AmScope</td><td>SKU: LED-30WR</td><td></td></tr><tr><td>5-0 COATED VICRYL (polyglactin 910) Suture</td><td>Ethicon</td><td>J303H</td><td>5-0, absorbable</td></tr><tr><td>Fine Scissors - Sharp</td><td>FST</td><td>14060-09</td><td></td></tr><tr><td>Glass beads</td><td>FST</td><td>18000-46</td><td></td></tr><tr><td>Hot bead sterilizers</td><td>FST</td><td>18000-50</td><td></td></tr><tr><td>Iris forceps</td><td>WPI</td><td>15915</td><td></td></tr><tr><td>Look Sharpoint 6-0, 18&quot; Black Nylon Monofilament Suture</td><td>LOOK</td><td>AA-2176</td><td>6-0, non-absorbable</td></tr><tr><td>Needle holder</td><td>WPI</td><td>15926</td><td></td></tr><tr><td>Normal Saline, 0.9% NaCl</td><td>Fisher</td><td>89167-772</td><td></td></tr></tbody></table>

implantation of an isoproterenol mini-pump to induce heart failure in mice

Isoproterenol (ISO), is a non-selective beta-adrenergic agonist, that is used widely to induce cardiac injury in mice. While the acute model mimics stress-induced cardiomyopathy, the chronic model, administered through an osmotic pump, mimics advanced heart failure in humans. The purpose of the described protocol is to create the chronic ISO-induced heart failure model in mice using an implanted mini-pump. This protocol has been used to induce heart failure in 100+ strains of inbred mice. Techniques on surgical pump implantation are described in detail and may be relevant to anyone interested in creating a heart failure model in mice. In addition, the weekly cardiac remodeling changes based on echocardiographic parameters for each strain and expected time to model development are presented. In summary, the method is simple and reproducible. Continuous ISO administered via the implanted mini-pump over 3 to 4 weeks is sufficient to induce cardiac remodeling. Finally, the success for ISO model creation may be assessed in vivo by serial echocardiography demonstrating hypertrophy, ventricular dilation, and dysfunction.

In our previously published study, we administered an ISO dosage of 30 mg/kg/d over 21 days via the osmotic pump across 105 Hybrid Mouse Diversity Panel (HMDP) strains2,13. We assessed outcomes using echocardiogram performed at baseline, week 1, 2 and 3 of ISO treatment (Figure 1). Similar to a prior study where the authors studied the impact of isoproterenol among 23 mouse strains14, we observed striking inte...

Watch this Scientific Journal Video about Implantation of an Isoproterenol Mini-Pump to Induce Heart Failure in Mice at JoVE.com

Implantation of an Isoproterenol Mini-Pump to Induce Heart Failure in Mice

The chronic administration of isoproterenol via an implanted osmotic pump has been used widely to mimic advanced heart failure in mice. Here, we describe detailed methods in surgical mini-pump implantation for the continuous isoproterenol administration over 3 weeks, as well as, echocardiographic assessment for the successful model creation.

Isoproterenol (ISO), is a non-selective beta-adrenergic agonist, that is used widely to induce cardiac injury in mice. While the acute model mimics ...

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11.0K Views.  University of California. The chronic administration of isoproterenol via an implanted osmotic pump has been used widely to mimic advanced heart failure in mice. Here, we describe detailed methods in surgical mini-pump implantation for the continuous isoproterenol administration over 3 weeks, as well as, echocardiographic assessment for the successful model creation.

Video: Implantation of an Isoproterenol Mini-Pump to Induce Heart Failure in Mice

Cell-based Therapy for Heart Failure in Rat: Double Thoracotomy for Myocardial Infarction and Epicardial Implantation of Cells and Biomatrix

Cardiac cell therapy has gained increasing interest and implantation of biomaterials associated with cells has become a major issue to optimize myocardial cell delivery. Rodent model of myocardial infarction (MI) consisting of Left Anterior Descending Artery (LAD) ligation has commonly been performed via a thoracotomy; a second open-heart surgery via a sternotomy has traditionally been performed for epicardial application of the treatment. Since the description of LAD ligation model, post-surgery mortality rate has dropped from 35-13%, however the second surgery has remained critical. In order to improve post-surgery recovery and reduce pain and infection, minimally invasive surgical procedures are presented.&#160;Two thoracotomies were performed, the initial one for LAD ligation and the second one for treatment epicardial administration. Biografts consisting of cells associated with solid or gel type matrices were applied onto the infarcted area.&#160;LAD ligation resulted in loss of heart function as confirmed by echocardiography performed after 2 and 6 weeks. Goldner trichrome staining performed on heart sections confirmed transmural scar formation. First and second surgeries resulted in less that 10%&#160;post-operative mortality.&#160;

Implantation of a biograft to treat myocardial infarction induced by LAD ligation in a rodent model has conventionally required two open-heart surgeries. In order to reduce mortality and provide optimal conditions for fixation of solid and gelatinous biomatrices associated with cells, minimally invasive procedures have been developed.

Cardiac cell therapy has gained increasing interest and implantation of biomaterials associated with cells has become a major issue to optimize myocardial ...

Bioengineering

Transplantation of a 3D Bioprinted Patch in a Murine Model of Myocardial Infarction

Testing regenerative properties of 3D bioprinted cardiac patches in vivo using murine models of heart failure via permanent left anterior descending (LAD) ligation is a challenging procedure and has a high mortality rate due to its nature. We developed a method to consistently transplant bioprinted patches of cells and hydrogels onto the epicardium of an infarcted mouse heart to test their regenerative properties in a robust and feasible way. First, a deeply anesthetized mouse is carefully intubated and ventilated. Following left lateral thoracotomy (surgical opening of the chest), the exposed LAD is permanently ligated and the bioprinted patch transplanted onto the epicardium. The mouse quickly recovers from the procedure after chest closure. The advantages of this robust and quick approach include a predicted 28-day mortality rate of up to 30% (lower than the 44% reported by other studies using a similar model of permanent LAD ligation in mice). Moreover, the approach described in this protocol is versatile and could be adapted to test bioprinted patches using different cell types or hydrogels where high numbers of animals are needed to optimally power studies. Overall, we present this as an advantageous approach which may change preclinical testing in future studies for the field of cardiac regeneration and tissue engineering.

This protocol aims to transplant a 3D bioprinted patch onto the epicardium of infarcted mice modeling heart failure. It includes details regarding anesthesia, the surgical chest opening, permanent ligation of the left anterior descending (LAD) coronary artery and application of a bioprinted patch onto the infarcted area of the heart.

Testing regenerative properties of 3D bioprinted cardiac patches in vivo using murine models of heart failure via permanent left anterior descending (LAD) ...

Technique of Minimally Invasive Transverse Aortic Constriction in Mice for Induction of Left Ventricular Hypertrophy

Transverse aortic constriction (TAC) in mice is one of the most commonly used surgical techniques for experimental investigation of pressure overload-induced left ventricular hypertrophy (LVH) and its progression to heart failure. In the majority of the reported investigations, this procedure is performed with intubation and ventilation of the animal which renders it demanding and time-consuming and adds to the surgical burden to the animal. The aim of this protocol is to describe a simplified technique of minimally invasive TAC without intubation and ventilation of mice. Critical steps of the technique are emphasized in order to achieve low mortality and high efficiency in inducing LVH.
Male C57BL/6 mice (10-week-old, 25-30 g, n=60) were anesthetized with a single intraperitoneal injection of a mixture of ketamine and xylazine. In a spontaneously breathing animal following a 3-4 mm upper partial sternotomy, a segment of 6/0 silk suture threaded through the eye of a ligation aid was passed under the aortic arch and tied over a blunted 27-gauge needle. Sham-operated animals underwent the same surgical preparation but without aortic constriction. The efficacy of the procedure in inducing LVH is attested by a significant increase in the heart/body weight ratio. This ratio is obtained at days 3, 7, 14 and 28 after surgery (n = 6 - 10 in each group and each time point). Using our technique, LVH is observed in TAC compared to sham animals from day 7 through day 28. Operative and late (over 28 days) mortalities are both very low at 1.7%.
In conclusion, our cost-effective technique of minimally invasive TAC in mice carries very low operative and post-operative mortalities and is highly efficient in inducing LVH. It simplifies the operative procedure and reduces the strain put on the animal. It can be easily performed by following the critical steps described in this protocol.

The aim of this protocol is to describe step-by-step the technique of minimally invasive transverse aortic constriction (TAC) in mice. By elimination of intubation and ventilation which are mandatory for the commonly used standard procedure, minimally invasive TAC simplifies the operative procedure and reduces the strain put on the animal.

Transverse aortic constriction (TAC) in mice is one of the most commonly used surgical techniques for experimental investigation of pressure ...

Establishing a Swine Model of Post-myocardial Infarction Heart Failure for Stem Cell Treatment

Although advances have been achieved in the treatment of heart failure (HF) following myocardial infarction (MI), HF following MI remains one of the major causes of mortality and morbidity around the world. Cell-based therapies for cardiac repair and improvement of left ventricular function after MI have attracted considerable attention. Accordingly, the safety and efficacy of these cell transplantations should be tested in a preclinical large animal model of HF prior to clinical use. Pigs are widely used for cardiovascular disease research due to their similarity to humans in terms of heart size and coronary anatomy. Therefore, we sought to present an effective protocol for the establishment of a porcine chronic HF model using closed-chest coronary balloon occlusion of the left circumflex artery (LCX), followed by rapid ventricular pacing induced with pacemaker implantation. Eight weeks later, the stem cells were administered by intramyocardial injection in the peri-infarct area. Then the infarct size, cell survival, and left ventricular function (including echocardiography, hemodynamic parameters, and electrophysiology) were evaluated. This study helps establish a stable preclinical large animal HF model for stem cell treatment.

We sought to establish a swine model of heart failure induced by left circumflex artery blockage and rapid pacing to test the effect and safety of intramyocardial administration of stem cells for cell-based therapies.

Although advances have been achieved in the treatment of heart failure (HF) following myocardial infarction (MI), HF following MI remains one of the major ...

A Surgical Model of Heart Failure with Preserved Ejection Fraction in Tibetan Minipigs

More than half of heart failure (HF) cases are classified as heart failure with preserved ejection fraction (HFpEF) worldwide. Large animal models are limited for investigating the fundamental mechanisms of HFpEF and identifying potential therapeutic targets. This work provides a detailed description of the surgical procedure of descending aortic constriction (DAC) in Tibetan minipigs to establish a large animal model of HFpEF. This model used a precisely controlled constriction of the descending aorta to induce chronic pressure overload in the left ventricle. Echocardiography was used to evaluate the morphological and functional changes in the heart. After 12 weeks of DAC stress, the ventricular septum was hypertrophic, but the thickness of the posterior wall was significantly reduced, accompanied by dilation of the left ventricle. However, the LV ejection fraction of the model hearts was maintained at &gt;50% during the 12-week period. Furthermore, the DAC model displayed cardiac damage, including fibrosis, inflammation, and cardiomyocyte hypertrophy. Heart failure marker levels were significantly elevated in the DAC group. This DAC-induced HFpEF in minipigs is a powerful tool for investigating molecular mechanisms of this disease and for preclinical testing.

The present protocol describes a step-by-step procedure to establish a minipig model of heart failure with preserved ejection fraction using descending aortic constriction. The methods for evaluating cardiac morphology, histology, and function of this disease model are also presented.

More than half of heart failure (HF) cases are classified as heart failure with preserved ejection fraction (HFpEF) worldwide. Large animal models are ...

Ultrasound-Guided Induced Pluripotent Stem Cell-Derived Cardiomyocyte Implantation in Myocardial Infarcted Mice

The key objective of cell therapy after myocardial infarction (MI) is to effectively enhance the cell grafted rate, and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are a promising cell source for cardiac repair after ischemic damage. However, a low grafted rate is a significant obstacle for effective cardiac tissue regeneration after transplantation. This protocol shows that multiple hiPSC-CM ultrasound-guided percutaneous injections into an MI area effectively increase cell transplantation rates. The study also describes the entire hiPSC-CM culture process, pretreatment, and ultrasound-guided percutaneous delivery methods. In addition, the use of human mitochondrial DNA help detect the absence of hiPSC-CMs in other mouse organs. Lastly, this paper describes the changes in cardiac function, angiogenesis, cell size, and apoptosis at the infarcted border zone in mice 4 weeks after cell delivery. It can be concluded that echocardiography-guided percutaneous injection of the left ventricular myocardium is a feasible, relatively invasive, satisfactory, repeatable, and effective cellular therapy.

Ultrasound-guided cell delivery around the site of myocardial infarction in mice is a safe, effective, and convenient way of cell transplantation.

The key objective of cell therapy after myocardial infarction (MI) is to effectively enhance the cell grafted rate, and human induced pluripotent stem ...

Induction of Right Ventricular Failure by Pulmonary Artery Constriction and Evaluation of Right Ventricular Function in Mice

The mechanism of right ventricular failure (RVF) requires clarification due to the uniqueness, high morbidity, high mortality, and refractory nature of RVF. Previous rat models imitating RVF progression have been described. Compared with rats, mice are more accessible, economical, and widely used in animal experiments. We developed a pulmonary artery constriction (PAC) approach which is comprised of banding the pulmonary trunk in mice to induce right ventricular (RV) hypertrophy. A special surgical latch needle was designed that allows for easier separation of the aorta and the pulmonary trunk. In our experiments, the use of this fabricated latch needle reduced the risk of arteriorrhexis and improved the surgical success rate to 90%. We used different padding needle diameters to precisely create quantitative constriction, which can induce different degrees of RV hypertrophy. We quantified the degree of constriction by evaluating the blood flow velocity of the PA, which was measured by noninvasive transthoracic echocardiography. RV function was precisely evaluated by right heart catheterization at 8 weeks after surgery. The surgical instruments made inhouse were composed of common materials using a simple process that is easy to master. Therefore, the PAC approach described here is easy to imitate using instruments made in the lab and can be widely used in other labs. This study presents a modified PAC approach that has a higher success rate than other models and an 8-week postsurgery survival rate of 97.8%. This PAC approach provides a useful technique for studying the mechanism of RVF and will enable an increased understanding of RVF.

Here, we provide a useful approach for studying the mechanism of right ventricular failure. A more convenient and efficient approach to pulmonary artery constriction is established using surgical instruments made inhouse. In addition, methods to evaluate the quality of this approach by echocardiography and catheterization are provided.

The mechanism of right ventricular failure (RVF) requires clarification due to the uniqueness, high morbidity, high mortality, and refractory nature of ...

Biology

Investigating HFpEF Pathophysiology in a Hyperlipidemia&#45;Induced Mouse Model

A Murine Model of Hyperlipidemia&#45;Induced Heart Failure with Preserved Ejection Fraction

The pathophysiology of heart failure with preserved ejection fraction (HFpEF) driven by lipotoxicity is incompletely understood. Given the urgent need for animal models that accurately mimic cardio-metabolic HFpEF, a hyperlipidemia-induced murine model was developed by reverse engineering phenotypes seen in HFpEF patients. This model aimed to investigate HFpEF, focusing on the interplay between lipotoxicity and metabolic syndrome. Hyperlipidemia was induced in wild-type (WT) mice on a 129J strain background through bi-weekly intraperitoneal injections of poloxamer-407 (P-407), a block co-polymer that blocks lipoprotein lipase, combined with a single intravenous injection of adeno-associated virus 9-cardiac troponin T-low-density lipoprotein receptor (AAV9-cTnT-LDLR). Extensive assessments were conducted between 4 and 8 weeks post-treatment, including echocardiography, blood pressure recording, whole-body plethysmography, echocardiography (ECG) telemetry, activity wheel monitoring (AWM), and biochemical and histological analyses. The LDLR/P-407 mice exhibited distinctive features at four weeks, including diastolic dysfunction, preserved ejection fraction, and increased left ventricular wall thickness. Notably, blood pressure and renal function remained within normal ranges. Additionally, ECG and AWM revealed heart blocks and reduced activity, respectively. Diastolic function deteriorated at eight weeks, accompanied by a significant decline in respiratory rates. Further investigation into the double treatment model revealed elevated fibrosis, wet/dry lung ratios, and heart weight/body weight ratios. The LDLR/P-407 mice exhibited xanthelasmas, ascites, and cardiac ischemia. Interestingly, sudden deaths occurred between 6 and 12 weeks post-treatment. The murine HFpEF model offers a valuable and promising experimental resource for elucidating the intricacies of metabolic syndrome contributing to diastolic dysfunction within the context of lipotoxicity-mediated HFpEF.

Author Spotlight: Exploring the Relationship Between Lipotoxicity and HFpEF 

This protocol presents a detailed approach to replicating a murine model of hyperlipidemia-induced heart failure with preserved ejection fraction (HFpEF). The design combines the administration of adeno-associated virus 9-cardiac troponin T-low-density lipoprotein receptor (AAV9-cTnT-LDLR) and poloxamer-407 (P-407).

The pathophysiology of heart failure with preserved ejection fraction (HFpEF) driven by lipotoxicity is incompletely understood. Given the urgent need for ...

Viral Transgene Expression in Rodent Hearts and the Assessment of Cardiac Arrhythmia Risk

Heart disease is the leading cause of morbidity and mortality worldwide. Due to the ease of handling&#160;and abundance of transgenic strains, rodents have become essential models for cardiovascular research. However, spontaneous lethal cardiac arrhythmias that often cause mortality in heart disease patients are rare in rodent models of heart disease. This is primarily due to the species differences in cardiac electrical properties between human&#160;and rodents and poses a challenge to the study of cardiac arrhythmias using rodents. This protocol describes an approach to enable efficient transgene expression in mouse and rat ventricular myocardium using echocardiography-guided intramuscular injections of recombinant virus (adenovirus and adeno-associated virus). This work also outlines a method to enable reliable assessment of cardiac susceptibility to arrhythmias using isolated, Langendorff-perfused mouse and rat hearts with both adrenergic and programmed electrical stimulations. These techniques are critical for studying heart rhythm disorders associated with adverse cardiac remodeling after injuries, such as myocardial infarction.

The present protocol describes methods for transgene expression in rat and mouse hearts by direct intramyocardial injection of the virus under echocardiography guidance. Methods for the assessment of the susceptibility of hearts to ventricular arrhythmias by the programmed electrical stimulation of isolated, Langendorff-perfused hearts are also explained here.

Heart disease is the leading cause of morbidity and mortality worldwide. Due to the ease of handling&#160;and abundance of transgenic strains, rodents ...

A Modified Technique for Transverse Aortic Constriction in Mice

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

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

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