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>

<ol>
	<li>Hartupee, J., Mann, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurohormonal+activation+in+heart+failure+with+reduced+ejection+fraction.">Neurohormonal activation in heart failure with reduced ejection fraction.</a> Nature Review Cardiology. 14 (1), 30-38 (2017).</li><li>Wang, J. J., 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=Genetic+Dissection+of+Cardiac+Remodeling+in+an+Isoproterenol-Induced+Heart+Failure+Mouse+Model.">Genetic Dissection of Cardiac Remodeling in an Isoproterenol-Induced Heart Failure Mouse Model.</a> PLoS Genetics. 12 (7), 1006038 (2016).</li><li>Balakumar, P., Singh, A. P., Singh, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rodent+models+of+heart+failure.">Rodent models of heart failure.</a> Journal of Pharmacological and Toxicological Methods. 56 (1), 1-10 (2007).</li><li>Patten, R. D., Hall-Porter, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Small+animal+models+of+heart+failure:+development+of+novel+therapies,+past+and+present.">Small animal models of heart failure: development of novel therapies, past and present.</a> Circulation: Heart Failure. 2 (2), 138-144 (2009).</li><li>Huang, W. Y., Aramburu, J., Douglas, P. S., Izumo, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transgenic+expression+of+green+fluorescence+protein+can+cause+dilated+cardiomyopathy.">Transgenic expression of green fluorescence protein can cause dilated cardiomyopathy.</a> Nature Medicine. 6 (5), 482-483 (2000).</li><li>Breckenridge, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Heart+failure+and+mouse+models.">Heart failure and mouse models.</a> Disease Model and Mechanism. 3 (3-4), 138-143 (2010).</li><li>Wittstein, I. S., 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=Neurohumoral+features+of+myocardial+stunning+due+to+sudden+emotional+stress.">Neurohumoral features of myocardial stunning due to sudden emotional stress.</a> New England Journal of Medicine. 352 (6), 539-548 (2005).</li><li>Templin, C., 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=Clinical+Features+and+Outcomes+of+Takotsubo+(Stress)+Cardiomyopathy.">Clinical Features and Outcomes of Takotsubo (Stress) Cardiomyopathy.</a> New England Journal of Medicine. 373 (10), 929-938 (2015).</li><li>Shao, Y., 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=A+mouse+model+reveals+an+important+role+for+catecholamine-induced+lipotoxicity+in+the+pathogenesis+of+stress-induced+cardiomyopathy.">A mouse model reveals an important role for catecholamine-induced lipotoxicity in the pathogenesis of stress-induced cardiomyopathy.</a> European Journal of Heart Failure. 15 (1), 9-22 (2013).</li><li>Kudej, R. K., 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=Effects+of+chronic+beta-adrenergic+receptor+stimulation+in+mice.">Effects of chronic beta-adrenergic receptor stimulation in mice.</a> Journal of Molecular Cell Cardiology. 29 (10), 2735-2746 (1997).</li><li>Zhuo, X. Z., 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=Isoproterenol+instigates+cardiomyocyte+apoptosis+and+heart+failure+via+AMPK+inactivation-mediated+endoplasmic+reticulum+stress.">Isoproterenol instigates cardiomyocyte apoptosis and heart failure via AMPK inactivation-mediated endoplasmic reticulum stress.</a> Apoptosis. 18 (7), 800-810 (2013).</li><li>El-Demerdash, E., Awad, A. S., Taha, R. M., El-Hady, A. M., Sayed-Ahmed, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probucol+attenuates+oxidative+stress+and+energy+decline+in+isoproterenol-induced+heart+failure+in+rat.">Probucol attenuates oxidative stress and energy decline in isoproterenol-induced heart failure in rat.</a> Pharmacology Research. 51 (4), 311-318 (2005).</li><li>Rau, C. D., 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=Mapping+genetic+contributions+to+cardiac+pathology+induced+by+Beta-adrenergic+stimulation+in+mice.">Mapping genetic contributions to cardiac pathology induced by Beta-adrenergic stimulation in mice.</a> Circulation Cardiovascular Genetics. 8 (1), 40-49 (2015).</li><li>Berthonneche, C., 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=Cardiovascular+response+to+beta-adrenergic+blockade+or+activation+in+23+inbred+mouse+strains.">Cardiovascular response to beta-adrenergic blockade or activation in 23 inbred mouse strains.</a> PLoS One. 4 (8), 6610 (2009).</li><li>Chang, S. C., Ren, S., Rau, C. D., Wang, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isoproterenol-Induced+Heart+Failure+Mouse+Model+Using+Osmotic+Pump+Implantation.">Isoproterenol-Induced Heart Failure Mouse Model Using Osmotic Pump Implantation.</a> Methods Molecular Biology. 1816, 207-220 (2018).</li><li>Shusterman, V., 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=Strain-specific+patterns+of+autonomic+nervous+system+activity+and+heart+failure+susceptibility+in+mice.">Strain-specific patterns of autonomic nervous system activity and heart failure susceptibility in mice.</a> American Journal of Physiology-Heart Circulation Physiology. 282 (6), 2076-2083 (2002).</li><li>Faulx, M. D., 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=Strain-dependent+beta-adrenergic+receptor+function+influences+myocardial+responses+to+isoproterenol+stimulation+in+mice.">Strain-dependent beta-adrenergic receptor function influences myocardial responses to isoproterenol stimulation in mice.</a> American Journal of Physiology-Heart Circulation Physiology. 289 (1), 30-36 (2005).</li><li>Zhang, G. X., 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=Cardiac+oxidative+stress+in+acute+and+chronic+isoproterenol-infused+rats.">Cardiac oxidative stress in acute and chronic isoproterenol-infused rats.</a> Cardiovascular Research. 65 (1), 230-238 (2005).</li><li>Boluyt, M. O., 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=Isoproterenol+infusion+induces+alterations+in+expression+of+hypertrophy-associated+genes+in+rat+heart.">Isoproterenol infusion induces alterations in expression of hypertrophy-associated genes in rat heart.</a> American Journal of Physiology. 269 (2), 638-647 (1995).</li><li>Hohimer, A. R., Davis, L. E., Hatton, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Repeated+daily+injections+and+osmotic+pump+infusion+of+isoproterenol+cause+similar+increases+in+cardiac+mass+but+have+different+effects+on+blood+pressure.">Repeated daily injections and osmotic pump infusion of isoproterenol cause similar increases in cardiac mass but have different effects on blood pressure.</a> Canadian Journal of Physiology and Pharmacology. 83 (2), 191-197 (2005).</li><li>Cross, H. R., Murphy, E., Koch, W. J., Steenbergen, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Male+and+female+mice+overexpressing+the+beta(2)-adrenergic+receptor+exhibit+differences+in+ischemia/reperfusion+injury:+role+of+nitric+oxide.">Male and female mice overexpressing the beta(2)-adrenergic receptor exhibit differences in ischemia/reperfusion injury: role of nitric oxide.</a> Cardiovascular Research. 53 (2), 662-671 (2002).</li><li>Klingman, G. I., McKay, G., Ward, A., Morse, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+isoproterenol+treatment+of+mice:+effects+on+catecholamines+and+rectal+temperature.">Chronic isoproterenol treatment of mice: effects on catecholamines and rectal temperature.</a> Journal of Pharmaceutical Sciences. 62 (5), 798-801 (1973).</li></ol>

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 differences in autonomic nervous system activity16, beta-adrenergic receptor (beta-AR) density and/or coupling17 and other genetic differences among strains. Based on in vivo serial echocardiography as well as ex vivo cardiac tissue histology and gene expression with and without ISO, chronic isoproterenol treatment induced striking differences spanning from cellular processes, extracellular matrix to inflammatory responses2,13. The following considerations may be relevant to the application of this heart failure model.
Close to 30% of mice implanted with isoproterenol osmotic pump died before the end of the experimental protocol2,13. Of these, over 90% died within the first 48 hours after pump implantation. The deaths appeared strain specific, with BXA-12/PgnJ, BXD-34/TyJ, BTBRT&#60;+&#62;tf/J, NZW/LacJ, BXD40/TyJ, and BALB/cJ being the most susceptible strains. Moreover, we observed that mice weighing &#60; 20 g had a higher early post-operative mortality (death within 48 h). Allowing mice to mature to at least 9 to 10 weeks of age or &#62; 20 g may minimize early post-operative mortality. Therefore, it may be important to account for strain-specific differences and early post-operative mortality when planning an experiment. We did not perform an autopsy to determine the cause of death. Hence, we are not able to determine the failure rate of the osmotic pumps. Of the mice that were sacrificed we detected no visual defects.
Isoflurane is known to be negatively chronotropic and inotropic. Care should be taken to minimize sedation and impact of isoflurane on echocardiographic measurements. If the sternum casts a bony shadow and degrades image qualities, reposition the mouse to image the heart through a different intercostal space. If the interventricular wall thickness measurement is complicated by the presence of the right ventricular wall, reimage through a different intercostal space to minimize poorly delineated borders. Accurate measurements are critical to downstream comparative analyses.
There exists literature documenting the use of osmotic minipumps in rats18,19. Readers should note that this protocol has only been used with mice and that other literature should be referenced for experimentation with other species.
Past literature suggests that daily injections of isoproterenol and continuous administration via osmotic pumps cause similar ventricular weight relative to body weight20. However, there are differences in hemodynamics. Daily injections cause immediate hypotension and tachycardia followed by rebound hypertension within a few hours. Continuous administration causes immediate hypotension on the day of pump implantation followed by normalization of blood pressure to mild hypertension by day 220. The overall hemodynamic trends more closely mimic chronically activated sympathetic hormones in heart failure patients.
At week 1 of isoproterenol, contractility was increased or supernormal. By week 2 and 3, contractility was back to normal for most strains and decreased for some strains. In the background of ongoing isoproterenol, normal contractility as measured by fractional shortening (FS) and ejection fraction (EF) may, in fact, represent impaired contractile reserve. If the investigator desires to induce a more profound degree of cardiac impairment, one may increase the ISO dosage or lengthen the ISO treatment period to 4 weeks, while weighing the risk of increased post-operative mortality. Finally, the data we presented were based on female mice only. Female mice have demonstrated higher post-ischemic contractile function and lesser ATP-depletion in an ischemia reperfusion injury model as compared to male mice21. Moreover, in a chronic ISO model, male mice have demonstrated an elevated heart to body weight ratio and reduced total norepinephrine levels in parotid and submaxillary glands as compared to females22. The user may need to consider gender-based differences in the observed outcomes when applying this approach to females and males.

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 inter-strain variation among echocardiographic parameters. The summary of weekly changes based on echocardiographic parameters and expected time to model development is presented (Figure 2 and Figure 3)2,15. Although variations were observed among mouse strains, on average, interventricular septal wall thickness at end diastole (IVSd) and fractional shortening (FS) increase in the first week but decrease by later time points; left ventricular internal diameter at end diastole (LVIDd) and left ventricular mass (LVM) increase over a period of 3 weeks (Figure 3). These findings are consistent with a pro-hypertrophic compensatory phase during week 1 of isoproterenol followed by wall thinning, ventricular dilation and decrease in systolic function. Our previously published study also demonstrated the upregulation of several gene subsets associated with left ventricular hypertrophy, including fibrotic marker Lgals3 and heart failure marker Nppb by week 32. Other differentially regulated genes include those involved in angiogenesis, secreted signal glycoprotein, polysaccharide binding, actin cytoskeleton, chemokine signaling pathway, proteinaceous extracellular matrix, and collagen2. These results are corroborated by echocardiographic and histological findings: mouse hearts demonstrated visibly larger left ventricular chamber dimensions under ISO and greater amounts of fibrosis under ISO treatment relative to saline control (Figure 4).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/59646/59646fig01.jpg" /> 
Figure 1: Chronic Isoproterenol (ISO)-Induced Heart Failure Model via Mini-Pump. 
This figure has been adapted with permission from Wang et al.2 and Chang et al.15 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59646/59646fig01large.jpg" targe="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/59646/59646fig02.jpg" /> 
Figure 2: Variation in echocardiographic measures of cardiac structure and function among the Hybrid Mouse Diversity Panel (HMDP) mouse strains. 
Black bars represent measurements under the baseline condition in ranked order. White bars represent measurements after 3 weeks of continuous ISO infusion. IVSd = interventricular septal wall thickness; LVIDd = left ventricular internal diameter at end diastole; LVM = left ventricular mass; FS = fractional shortening. Error bars represent the standard errors of the means (SEM). This figure has been adapted with permission from Wang et al.2 and Chang et al.15.
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/59646/59646fig03.jpg" /> 
Figure 3: The average changes in echocardiographic measures compared to baseline at each ISO time point for each classical inbred strain. 
This figure has been adapted with permission from Wang et al.2 and Chang et al.15. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59646/59646fig03large.jpg" targe="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/59646/59646fig04.jpg" /> 
Figure 4: Echocardiographic and histologic changes after chronic isoproterenol infusion. 
(A) Representative M-mode echocardiogram images from 2 mice at baseline and at week 3 of isoproterenol are shown. Note enlargement of the left ventricular internal dimensions in both mice as well as the development of endocardial fibrosis (red arrow) in mouse #2. (B) Masson&#39;s trichrome stain of the left ventricle in the short axis demonstrates extensive fibrosis with isoproterenol treatment (scale bar: 2 mm). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59646/59646fig04large.jpg" targe="_blank">Please click here to view a larger version of this figure.</a>
<table fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Body Weight (g)</td>
			<td>Daily dosage (&#956;g/day)</td>
			<td>Flow Rate (&#956;L/day)</td>
			<td>Concentration (&#956;L/day)</td>
			<td>Isoproterenol (mg/120 &#181;l)</td>
		</tr>
		<tr>
			<td>20</td>
			<td>600</td>
			<td>2.64</td>
			<td>227</td>
			<td>27.3</td>
		</tr>
		<tr>
			<td>21</td>
			<td>630</td>
			<td>2.64</td>
			<td>239</td>
			<td>28.6</td>
		</tr>
		<tr>
			<td>22</td>
			<td>660</td>
			<td>2.64</td>
			<td>250</td>
			<td>30</td>
		</tr>
		<tr>
			<td>23</td>
			<td>690</td>
			<td>2.64</td>
			<td>261</td>
			<td>31.4</td>
		</tr>
		<tr>
			<td>24</td>
			<td>720</td>
			<td>2.64</td>
			<td>273</td>
			<td>32.7</td>
		</tr>
		<tr>
			<td>25</td>
			<td>750</td>
			<td>2.64</td>
			<td>284</td>
			<td>34.1</td>
		</tr>
		<tr>
			<td>26</td>
			<td>780</td>
			<td>2.64</td>
			<td>295</td>
			<td>35.4</td>
		</tr>
		<tr>
			<td>27</td>
			<td>810</td>
			<td>2.64</td>
			<td>307</td>
			<td>36.8</td>
		</tr>
		<tr>
			<td>28</td>
			<td>840</td>
			<td>2.64</td>
			<td>318</td>
			<td>38.2</td>
		</tr>
		<tr>
			<td>29</td>
			<td>870</td>
			<td>2.64</td>
			<td>330</td>
			<td>39.5</td>
		</tr>
		<tr>
			<td>30</td>
			<td>900</td>
			<td>2.64</td>
			<td>341</td>
			<td>40.9</td>
		</tr>
	</tbody>
</table>
Table 1: Isoproterenol concentration and preparation for representative body weights at the osmotic pump rate of 30 mg/kg/d. This table has been adapted with permission from Wang et al.2 and Chang et al.15.
Supplemental File.&#160;<a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59646/Weight_dosage_and_flow_rate_calculator_v3.xlsx" targe="_blank">Please click here to download this file.</a>

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 ...

implantation-an-isoproterenol-mini-pump-to-induce-heart-failure

Nanyang Technological University

Research

JoVE Journal

Medicine

11.1K Views.  University of California. De chronische toediening van isoproterenol via een osmotische pomp is op grote schaal gebruikt om veranderingen in geavanceerd hartfalen bij muizen samen te vatten. Deze methode is eenvoudig en vereist minder chirurgische expertise dan andere modellen, zoals LAD en TAC. Het aantonen van de procedure zal Dr.Vincent Ren, een onderzoeker van dr. Yibin Wang's laboratorium.Bereken na het wegen en registreren van het lichaamsgewicht van elke muis de juiste hoeveelheid en concentratie isoprot...

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

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) ...

Bioengineering

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 ...

Refined CLARITY-Based Tissue Clearing for Three-Dimensional Fibroblast Organization in Healthy and Injured Mouse Hearts

Cardiovascular disease is the most prevalent cause of mortality worldwide and is often marked by heightened cardiac fibrosis that can lead to increased ventricular stiffness with altered cardiac function. This increase in cardiac ventricular fibrosis is due to activation of resident fibroblasts, although how these cells operate within the 3-dimensional (3-D) heart, at baseline or after activation, is not well understood. To examine how fibroblasts contribute to heart disease and their dynamics in the 3-D heart, a refined CLARITY-based tissue clearing and imaging method was developed that shows fluorescently labeled cardiac fibroblasts within the entire mouse heart. Tissue resident fibroblasts were genetically labeled using Rosa26-loxP-eGFP florescent reporter mice crossed with the cardiac fibroblast expressing Tcf21-MerCreMer knock-in line. This technique was used to observe fibroblast localization dynamics throughout the entire adult left ventricle in healthy mice and in fibrotic mouse models of heart disease. Interestingly, in one injury model, unique patterns of cardiac fibroblasts were observed in the injured mouse heart that followed bands of wrapped fibers in the contractile direction. In ischemic injury models, fibroblast death occurred, followed by repopulation from the infarct border zone. Collectively, this refined cardiac tissue clarifying technique and digitized imaging system allows for 3-D visualization of cardiac fibroblasts in the heart without the limitations of antibody penetration failure or previous issues surrounding lost fluorescence due to tissue processing.

A refined method of tissue clearing was developed and applied to the adult mouse heart. This method was designed to clear dense, autofluorescent cardiac tissue, while maintaining labeled fibroblast fluorescence attributed to a genetic reporter strategy.

Cardiovascular disease is the most prevalent cause of mortality worldwide and is often marked by heightened cardiac fibrosis that can lead to increased ...

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 ...

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 ...

Biology

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 ...

Exploring HR-Dependent Cardiac Performance Using an Atrial-Pacing Protocol

A Pacing-Controlled Procedure for the Assessment of Heart Rate-Dependent Diastolic Functions in Murine Heart Failure Models

Heart failure with preserved ejection fraction (HFpEF) is a condition characterized by diastolic dysfunction and exercise intolerance. While exercise-stressed hemodynamic tests or MRI can be used to detect diastolic dysfunction and diagnose HFpEF in humans, such modalities are limited in basic research using mouse models. A treadmill exercise test is commonly used for this purpose in mice, but its results can be influenced by body weight, skeletal muscle strength, and mental state. Here, we describe an atrial-pacing protocol to detect heart rate (HR)-dependent changes in diastolic performance and validate its usefulness in a mouse model of HFpEF. The method involves anesthetizing, intubating, and performing pressure-volume (PV) loop analysis concomitant with atrial pacing. In this work, a conductance catheter was inserted via a left ventricular apical approach, and an atrial pacing catheter was placed in the esophagus. Baseline PV loops were collected before the HR was slowed with ivabradine. PV loops were collected and analyzed at HR increments ranging from 400 bpm to 700 bpm via atrial pacing. Using this protocol, we clearly demonstrated HR-dependent diastolic impairment in a metabolically induced HFpEF model. Both the relaxation time constant (Tau) and the end-diastolic pressure-volume relationship (EDPVR) worsened as the HR increased compared to control mice. In conclusion, this atrial pacing-controlled protocol is useful for detecting HR-dependent cardiac dysfunctions. It provides a new way to study the underlying mechanisms of diastolic dysfunction in HFpEF mouse models and may help develop new treatments for this condition.

Author Spotlight: Investigating HR-Dependent Cardiac Function in Mouse Models Through a Novel Atrial-Pacing Approach 

The present protocol describes obtaining the pressure-volume relationship through transesophageal pacing, which serves as a valuable tool in evaluating diastolic function&#160;in mouse models of heart failure.

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

Samenvatting

Meer video's verkennen

Hoofdstukken in deze video