Rodent Model Of Heart Failure Research Articles

Radiofrequency Renal Denervation Improves Vascular Reactivity in a Rodent Model of Heart Failure

BackgroundWe have previously reported that radiofrequency (RF) renal denervation (RDN) exerts cardioprotective effects in the setting of myocardial ischemia‐reperfusion (MI‐R) injury. The protective actions of RF‐RDN in MI‐R injury are related in part to attenuated oxidative stress and increased nitric oxide (NO) bioavailability. More recently we have demonstrated that RF‐RDN protects the failing heart independent of reductions in blood pressure. The mechanisms by which RF‐RDN affords these benefits have not been fully described, including the effects on vascular function.MethodsMale Wistar‐Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) at 20 weeks of age were subjected to 45 minutes of transient LAD coronary artery ligation followed by reperfusion for 12 weeks. Four weeks following reperfusion animals were subjected to either bilateral RF‐RDN or a sham procedure (SHAM) with n=12 in all groups. At 12 weeks after reperfusion, thoracic aorta was harvested and vascular reactivity was evaluated. Vasoactivity was assessed for the endothelium‐dependent vasodilators acetylcholine (ACh, 0.1nM–10mM) and the calcium ionophore A23187 (A23187, 10nM‐1mM). In addition, vascular reactivity to the endothelium‐independent vasodilator sodium nitroprusside (SNP, 0.1nM–10 mM) was investigated. The effects of RF‐RDN therapy on cardiac structure and function were also determined via biweekly 2‐D serial echocardiography.ResultsRF‐RDN significantly improved cardiovascular function as reflected in improved left ventricle (LV) ejection fraction at 12 weeks following reperfusion in both SHRs (46.8 ± 2.4% vs. 30.4 ± 2.5%, p<0.01) and WKYs (50.4 ± 3.0% vs 35.4 ± 2.7%; p<0.05). RF‐RDN treatment significantly improved endothelium mediated vasorelaxation in both hypertensive and normotensive animals as reflected in ACh EC50 (SHR: 98.8 ± 19.2 nM vs. 349.6 ± 25.0 nM, p<0.0001; WKY: 10.03 ± 1.32 nM vs. 44.97 ± 12.03 nM, p<0.01). Similar improvements were seen in smooth muscle mediated vasorelaxation due to SNP (SHR: 29.4 ± 4.2 nM vs. 145.3 ± 14.2 nM, p<0.0001; WKY: 11.68 ± 1.28 nM vs 39.68 ± 7.47 nM, p<0.01). RF‐RDN also improved vasorelaxation to the direct endothelium‐dependent vasodilator, A23187, in hypertensive animals (SHR: 10.8 ± 1.3 nM vs. 23.2 ± 2.7 nM, p<0.001) but not normotensive animals. We did not observe any significant reductions in blood pressure in either the SHR or WKY rats following RF‐RDN at anytime during the experimental protocol.ConclusionRF‐RDN significantly improved LV function in the setting of heart failure independent of blood pressure reductions. Therapy improved vascular function suggesting that the cardiovascular benefits afforded by RF‐RDN may be partially due to improved vascular function. The improved vascular reactivity and cardiac function observed following RF‐RDN may be a result of reduced oxidative stress and increased NO bioavailability. Experiments are currently underway to evaluate this possibility. Our results reveal a novel mechanism related to the beneficial effects of RF‐RDN in heart failure.

101 - Can Clinically Relevant Readouts of Exercise Tolerance, Left Atrial Size and BNP be Back-Translated in a Rodent Model of Heart Failure With Preserved Ejection Fraction

101 - Can Clinically Relevant Readouts of Exercise Tolerance, Left Atrial Size and BNP be Back-Translated in a Rodent Model of Heart Failure With Preserved Ejection Fraction

(462) - Presence of Endothelial to Mesenchymal Transition in End Stage Human Myocardial Samples-Documentation in Human Heart Failure for the First Time

Endothelial to Mesenchymal Transition (EndMT) and the reverse phenomenon of mesenchymal to endothelial transitioning (MET) has been shown to contribute to fibrosis in rodent models of heart failure. There are no studies documenting the same in human cardiac tissue. We performed immunofluorescence dual staining on end stage heart failure myocardial samples. Staining for endothelial and mesenchymal markers were performed with Anti-VE-Cadherin and anti-Fibroblast specific protein 1. Presence of dual stained cells using fluorescence microscopy was considered as positive for the presence of EndMT. Vascular density was assessed using standard techniques with Anti-CD31. Of the end stage heart failure samples, 18 were from left ventricular core during LVAD implant and 15 at time of heart transplant. Mean age was 55y with 82% males and 74% white. 70% of all samples had evidence of EndMT with positive samples having from 1 to 5 dual stained cells per high power field. There was no significant difference between patient characteristics between those with evidence of EndMT versus not, except a higher prevalence of diabetes in the latter group. (Fig 1B) 74% of the end-stage heart failure samples and 60% of the post-VAD samples showed the presence of EndMT cells. Vascular Density was higher in the samples exhibiting EndMT phenomenon. (Figure 1A). We have documented for the first time, the existence of endothelial-mesenchymal transition in human end stage myocardial samples corroborating earlier pioneering studies in rodents. Interestingly the existence of such dual staining cells in end stage hearts (which is highly fibrotic) suggests a possible role of ongoing fibrosis with endothelial to mesenchymal transitioning or potential anti-fibrotic mechanism though mesenchymal to endothelial transitioning. Further studies of the later process will be warranted to explore potential anti-fibrotic therapeutic implications.

Hypoxia Inducible Factor (HIF) Adaptation After Mechanical Circulatory Unloading of the Heart. A Gene Expression Analysis Study of Paired Myocardial Samples

Background: Endothelial to Mesenchymal Transition (EndMT) and the reverse phenomenon of mesenchymal to endothelial transitioning (MET) has been shown to contribute to fibrosis in rodent models of heart failure. There are no studies documenting the same in human cardiac tissue. Methods: We performed immunofluorescence dual staining on end stage heart failure myocardial samples obtained from our bio repository. Staining for endothelial and mesenchymal markers were performed with Anti-VE-Cadherin (Santa Cruz Biotechnologies) and anti-Fibroblast specific protein 1 (Dako Antibodies) respectively using standard immunofluoresence techniques. Presence of dual staining on fluorescence microscopy was considered as positive for the presence of EndMT. Vascular density was assessed using a DAB (3-3’ Diaminobenzidine) technique with Anti-CD31 (PECAM, Abcam). Results: Of the end stage heart failure samples, 18 were from left ventricular core during LVAD implant and 5 during a direct transplant as status 1A (axillary intraaortic balloon pump). 10 hearts of patients bridged to transplant with a continuous flow LVAD (Days under support 3436228) were also studied. Mean age was 55y with 82% males and 74% white. 70% of all samples had evidence of EndMT. The number of cells ranged from 1 to 5 per high power field. There was no significant difference between patient characteristics between those with evidence of EndMT versus not, except a higher prevalence of diabetes in the latter group. (Fig 1B) 74% of the end-stage heart failure samples and 60% of the post-VAD samples showed the presence of EndMT cells. Vascular Density was higher in the samples exhibiting EndMT phenomenon. (Figure 1A). Conclusion: We have documented for the first time, the existence of endothelial-mesenchymal transition in human end stage myocardial samples corroborating earlier pioneering studies in rodents. Interestingly the existence of such dual staining cells in end stage hearts (which is highly fibrotic) suggests a possible role of ongoing fibrosis with endothelial to mesenchymal transitioning or potential antifibrotic mechanism though mesenchymal to endothelial transitioning. Further studies of the later process will be warranted to explore potential anti-fibrotic therapeutic implications.

The CD4(+) AT2R(+) T cell subpopulation improves post-infarction remodelling and restores cardiac function.

Myocardial infarction (MI) is a major condition causing heart failure (HF). After MI, the renin angiotensin system (RAS) and its signalling octapeptide angiotensin II (Ang II) interferes with cardiac injury/repair via the AT1 and AT2 receptors (AT1R, AT2R). Our study aimed at deciphering the mechanisms underlying the link between RAS and cellular components of the immune response relying on a rodent model of HF as well as HF patients. Flow cytometric analyses showed an increase in the expression of CD4+ AT2R+ cells in the rat heart and spleen post-infarction, but a reduction in the peripheral blood. The latter was also observed in HF patients. The frequency of rat CD4+ AT2R+ T cells in circulating blood, post-infarcted heart and spleen represented 3.8 ± 0.4%, 23.2 ± 2.7% and 22.6 ± 2.6% of the CD4+ cells. CD4+ AT2R+ T cells within blood CD4+ T cells were reduced from 2.6 ± 0.2% in healthy controls to 1.7 ± 0.4% in patients. Moreover, we characterized CD4+ AT2R+ T cells which expressed regulatory FoxP3, secreted interleukin-10 and other inflammatory-related cytokines. Furthermore, intramyocardial injection of MI-induced splenic CD4+ AT2R+ T cells into recipient rats with MI led to reduced infarct size and improved cardiac performance. We defined CD4+ AT2R+ cells as a T cell subset improving heart function post-MI corresponding with reduced infarction size in a rat MI-model. Our results indicate CD4+ AT2R+ cells as a promising population for regenerative therapy, via myocardial transplantation, pharmacological AT2R activation or a combination thereof.

Abstract 19826: Cardiac DGAT1 Deficiency Decreases Triglyceride Turnover and Alters Substrate Utilization

Triglyceride (TG) metabolism in the heart has been suggested to regulate PPARα activity and fatty acid oxidation. Reduced TG content and turnover has also been shown in rodent models of heart failure. We found that patients with heart failure displayed decreased mRNA levels of diacylglycerol:acyltransferase 1 (DGAT1), the rate limiting enzyme in TG synthesis (0.56±0.06 fold of NF, p=0.0001) and a lower myocardial TG content (3.65±0.41 vs. 8.27±1.48 mg/g tissue in NF, n=8-11, p=0.019). Therefore we hypothesized reduced TG synthesis caused metabolic remodeling in heart failure. In mice with tamoxifen-inducible cardiac specific deletion of DGAT1 (iKO) TG turnover was reduced. 13 C NMR spectroscopy in perfused hearts revealed a 30% reduction in incorporation of labeled fatty acids (FA) into TG in iKO (40 minute peak area 7.86±0.26 vs. 5.73±0.50) with no changes in total TG content. To test whether these changes affect myocardial energetics and contractile function, we simultaneously measured high energy phosphate content and contractile function using 31 P NMR in isolated perfused hearts. Contractile function and PCr/ATP ratio was unchanged in iKO hearts perfused with FA, lactate and glucose. Furthermore, there is no difference between genotypes in the expression of PPARα or its downstream target genes at baseline or after 5 weeks of high fat diet, indicating that TG turnover has minimal effect on PPARα activity. However, iKO hearts showed increased oxidation of exogenous fatty acid (67.0±4.1% vs. 48.5±5.3%) and reduced glucose oxidation (12.9±4.2% vs. 27.4±4.5%, n=5-7). These observations suggest that reduced TG synthesis diverts exogenous FA from the TG pool towards oxidative metabolism. To evaluate the dependence of iKO hearts upon exogenous FA, hearts were perfused with glucose as the only substrate. The ability to utilize TG was reduced in iKO resulting in a 50% higher TG content after 20 min perfusion, which was associated with a reduced left ventricular developed pressure (119±6 vs. 97±7 mmHg for control and iKO respectively). Taken together, we found that DGAT1 deficiency in the heart reduced TG turnover and increased reliance on the oxidation of exogenous FA, a phenotype that may contribute to the lack of metabolic flexibility in heart failure.

Proteomic Analysis of a Rodent Model of Heart Failure With Preserved Ejection Fraction - the Goto Kakizaki Rat

Proteomic Analysis of a Rodent Model of Heart Failure With Preserved Ejection Fraction - the Goto Kakizaki Rat

Dietary saturated fat and docosahexaenoic acid differentially effect cardiac mitochondrial phospholipid fatty acyl composition and Ca2+uptake, without altering permeability transition or left ventricular function

High saturated fat diets improve cardiac function and survival in rodent models of heart failure, which may be mediated by changes in mitochondrial function. Dietary supplementation with the n3-polyunsaturated fatty acid docosahexaenoic acid (DHA, 22:6n3) is also beneficial in heart failure and can affect mitochondrial function. Saturated fatty acids and DHA likely have opposing effects on mitochondrial phospholipid fatty acyl side chain composition and mitochondrial membrane function, though a direct comparison has not been previously reported. We fed healthy adult rats a standard low-fat diet (11% of energy intake from fat), a low-fat diet supplemented with DHA (2.3% of energy intake) or a high-fat diet comprised of long chain saturated fatty acids (45% fat) for 6 weeks. There were no differences among the three diets in cardiac mass or function, mitochondrial respiration, or Ca2+-induced mitochondrial permeability transition. On the other hand, there were dramatic differences in mitochondrial phospholipid fatty acyl side chains. Dietary supplementation with DHA increased DHA from 7% to ∼25% of total phospholipid fatty acids in mitochondrial membranes, and caused a proportional depletion of arachidonic acid (20:4n6). The saturated fat diet increased saturated fat and DHA in mitochondria and decreased linoleate (18:2n6), which corresponded to a decrease in Ca2+ uptake by isolated mitochondria compared to the other diet groups. In conclusion, despite dramatic changes in mitochondrial phospholipid fatty acyl side chain composition by both the DHA and high saturated fat diets, there were no effects on mitochondrial respiration, permeability transition, or cardiac function.

Hyperpolarization‐Activated Cyclic Nucleotide‐Gated Channels and Ventricular Arrhythmias in Heart Failure: A Novel Target for Therapy?

Arrhythmias are a common and often fatal complication of heart failure accounting for 50% to 70% of cardiac deaths due to tachyarrhythmic mechanisms.[1][1] In the failing heart, disturbances in cardiac rhythm are the likely result of cardiac remodeling consisting of structural and/or

Mechanical unloading reverses transverse tubule remodelling and normalises local calcium-induced calcium release in a rodent model of heart failure

Calcium-induced calcium release (CICR) is crucial for contraction in cardiomyocytes. The transverse (t)-tubule system guarantees the proximity of the triggers for calcium release (L-type calcium channel, dihydropyridine receptors) and the sarcoplasmic reticulum calcium-release channels (ryanodine receptors). Transverse tubule disruption occurs early in heart failure. Clinical studies of left ventricular assist devices in heart failure indicate that mechanical unloading induces reverse remodelling. We hypothesise that unloading of failing hearts normalises t-tubule structure and improves CICR.Heart failure was induced in Lewis rats by left coronary artery ligation for 12 weeks; sham-operated animals were used as controls. Failing hearts were mechanically unloaded for 4 weeks by heterotopic abdominal heart transplantation (HF-UN). Heart failure reduced the t-tubule density as measured by di-8-ANEPPS staining in isolated left ventricular myocytes, and this was reversed by unloading. The deterioration in the regularity of the t-tubule system in heart failure was also reversed in HF-UN. Scanning ion conductance microscopy showed the reappearance of normal surface striations in HF-UN. Electron microscopy revealed recovery of normal t-tubule microarchitecture in HF-UN. L-type calcium current density, measured with whole-cell patch clamping, was reduced in heart failure but unaffected by unloading. The variance of the time-to-peak of the calcium transient, an index of CICR dyssynchrony, was increased in heart failure and normalised by unloading. The increased calcium spark frequency observed in heart failure was reduced in HF-UN. These results could be explained by the recoupling of orphaned ryanodine receptors in heart failure, as indicated by immunofluorescence.Our data show that mechanical unloading of the failing heart reverses the pathological remodelling of the t-tubule system and improves CICR. FundingBritish Heart Foundation.

Suicidal erythrocyte death, eryptosis, as a novel mechanism in heart failure-associated anaemia

Suicidal death of erythrocytes (eryptosis) is characterized by cell shrinkage and exposure of phosphatidylserine (PS) residues at the cell surface. Excessive eryptosis may lead to anaemia. We aimed to study the role of eryptosis in heart failure (HF)-associated anaemia. We measured eryptosis in rodent models of HF. Typical measures of eryptosis including PS-exposure, increased intracellular Ca(2+) levels, and decreased cell volume were determined by flow cytometry. Transgenic REN2 rats displayed mild anaemia which was associated with a two-fold increase in erythrocyte PS-exposure when compared with Sprague Dawley (SD) control rats (P < 0.01). Upon stimulation with eryptotic triggers such as oxidative stress, hyperosmotic shock and energy depletion, eryptosis was more prominent in REN2 as shown by increased PS-exposure, cytosolic Ca(2+) influx, and cell shrinkage (P < 0.05 vs. SD). Increasing cytosolic Ca(2+) levels resulted in a stronger increase in PS-exposure in REN2 erythrocytes (P < 0.01 vs. SD). Accordingly, inhibition of Ca(2+) entry blunted the increased PS-exposure upon oxidative stress. The REN2 rats had significantly higher reticulocytes (REN2: 10.6 ± 2.3%; SD: 5.4 ± 0.1%; P < 0.05) and erythrocyte turnover was increased, indicated by increased clearance of eryptotic erythrocytes. Eryptosis was also increased in a rat model of hypertensive cardiac remodelling (uninephrectomized rats implanted with deoxycorticosterone acetate pellets), in mice after transverse aortic constriction, as well as in a small proof-of-concept study in human HF patients. Eryptosis is increased during HF development and could contribute to HF-associated anaemia. Eryptosis may therefore become a novel target for therapy in HF-associated anaemia.

Influence of ivabradine on reverse remodelling during mechanical unloading

Ivabradine (Iva) has shown beneficial structural and functional effects in clinical and experimental heart failure (HF), but its action in combination with mechanical unloading (MU), such as during treatment with left ventricular assist devices (LVAD), is unknown. The aim of this study was to investigate the effects of Iva during MU, in a rodent model of HF. We studied the chronic effects (4 weeks) of Iva (10 mg/kg/day) alone and in combination with MU [induced by heterotopic abdominal heart transplantation (HATx)] on whole-heart and cellular structure, function, and excitation-contraction (E-C) coupling in a rodent (rat) model of HF, 12 weeks post-left coronary artery (LCA) ligation. Effects of Iva were compared with those of β-blockade using metoprolol [(Met), 250 mg/kg/day]. Iva, but not Met, reversed myocardial fibrosis, alone and in combination with MU. MU-induced restoration of deranged E-C coupling was enhanced by Iva to a greater extent than Met: both Iva and Met enhanced the recovery of the Ca(2+) transient amplitude and the sarcoplasmic reticulum (SR) Ca(2+) content, but Iva alone maintained MU-induced normalization of L-type Ca(2+) current and t-tubule abnormalities. Met prevented MU-induced reduction in the myocardial size (myocardial atrophy); Iva had no effect on this parameter. Iva shows beneficial structural and E-C coupling effects during MU: Iva reverses myocardial fibrosis and enhances the restoration of deranged E-C coupling, displaying more beneficial effects than that of Met. These results suggest that Iva may prove effective in enhancing functional recovery in heart failure patients receiving LVAD therapy.

Abstract 113: SUMO1 Gene Transfer Rescues Cardiac Function in a Large Animal Model of Heart Failure

Recently, small ubiquitin-related modifier 1 (SUMO1) was found to enhance the activity and stability of the cardiac sarcoplasmic reticulum Ca2+ ATPase, SERCA2a. In both, human and rodent models of heart failure (HF), the total amount of myocardial SUMO1 is decreased and its knock down results in severe HF. Adeno-associated vector (AAV) mediated SUMO1 gene transfer significantly improves cardiac function in murine models of HF. As a critical step towards clinical translation, we evaluated the effects of SUMO1 gene transfer in a swine model of ischemic heart failure. One month after balloon occlusion of the proximal LAD, 21 animals were randomized to receive either AAV1.SUMO1 at two doses, AAV1.SERCA2a, AAV1.SUMO1+AAV1.SERCA2a, or saline via antegrade coronary infusion. In addition, three pigs served as controls and underwent sham procedures. The ejection fraction and the maximum dP/dt significantly increased after gene transfer of SUMO1 at both doses, SERCA2a and the combination of SUMO1 and SERCA2a (p=0.034, p=0.028) compared to saline infusion. The increase in maximum dP/dt was most pronounced in the group that received both SUMO1 and SERCA2a. Furthermore, the increase in end-systolic and end-diastolic volumes was normalized in the treatment groups, while they further deteriorated in the saline group (p=0.001, p=0.022). SUMO1 and SERCA2a gene transfer significantly improved cardiac function and concomitant gene delivery of SUMO1 and SERCA2a had a synergistic effect on improving these parameters in the HF animals. These results strongly support the critical role of SUMO1 for SERCA2a function and underline the therapeutic potential in heart failure patients.

Mechanical unloading reverses transverse tubule remodelling and normalizes local Ca2+‐induced Ca2+release in a rodent model of heart failure

AimsCa2+-induced Ca2+ release (CICR) is critical for contraction in cardiomyocytes. The transverse (t)-tubule system guarantees the proximity of the triggers for Ca2+ release [L-type Ca2+ channel, dihydropyridine receptors (DHPRs)] and the sarcoplasmic reticulum Ca2+ release channels [ryanodine receptors (RyRs)]. Transverse tubule disruption occurs early in heart failure (HF). Clinical studies of left ventricular assist devices in HF indicate that mechanical unloading induces reverse remodelling. We hypothesize that unloading of failing hearts normalizes t-tubule structure and improves CICR.Methods and resultsHeart failure was induced in Lewis rats by left coronary artery ligation for 12 weeks; sham-operated animals were used as controls. Failing hearts were mechanically unloaded for 4 weeks by heterotopic abdominal heart transplantation (HF-UN). HF reduced the t-tubule density measured by di-8-ANEPPS staining in isolated left ventricular myocytes, and this was reversed by unloading. The deterioration in the regularity of the t-tubule system in HF was also reversed in HF-UN. Scanning ion conductance microscopy showed the reappearance of normal surface striations in HF-UN. Electron microscopy revealed recovery of normal t-tubule microarchitecture in HF-UN. L-type Ca2+ current density, measured using whole-cell patch clamping, was reduced in HF but unaffected by unloading. The variance of the time-to-peak of the Ca2+ transient, an index of CICR dyssynchrony, was increased in HF and normalized by unloading. The increased Ca2+ spark frequency observed in HF was reduced in HF-UN. These results could be explained by the recoupling of orphaned RyRs in HF, as indicated by immunofluorescence.ConclusionsOur data show that mechanical unloading of the failing heart reverses the pathological remodelling of the t-tubule system and improves CICR.

Assessment of Cardiac Safety for PPARγ Agonists in Rodent Models of Heart Failure: A Translational Medicine Perspective

PPARγ-modulators, a class of anti-diabetic drugs as represented by thiazolidinediones (TZD), have been associated with cardiovascular risks in type-2 diabetes in humans but a similar liability has not been demonstrated in preclinical models. This gap between clinical and preclinical observations may reflect the lack of a translational model for cardiac safety assessment because preclinical efficacy for glycemic control for PPARγ-modulators is routinely conducted in animals with diabetic background while drug safety study is performed in young and health animals with little risk of heart failure, in contrast to the complex pathophysiological conditions of patients subjected to the treatment of TZDs. Therefore, some key steps are important to address this translational gap. First, it is essential to use an appropriate translational model that mimics most of human pathophysiology for the assessment of cardiovascular safety for TZDs. Second, it calls for the discovery of a translational biomarker (most likely a collection of biomarkers due to multiple risk factors contributed to the complex disease) to be able to sensitively detect the disease progression and in response to therapy. Specific examples are provided in this review for the use of a rodent model of myocardial infarction-induced heart failure to address the cardiac safety concern in response to chronic treatment of rosiglitazone. Multiple biomarkers, including physiological, biochemical, pharmacogenomic and imaging biomarkers, were applied to assess the cardiovascular risk in this heart failure model. The data and strategic approach are discussed from translational medicine perspectives.

Assessment of Cardiac Safety for PPARγ Agonists in Rodent Models of Heart Failure: A Translational Medicine Perspective

Assessment of Cardiac Safety for PPARγ Agonists in Rodent Models of Heart Failure: A Translational Medicine Perspective

Regulation of the (pro)renin–renin receptor in cardiac remodelling

The (pro)renin–renin receptor [(P)RR] was discovered as an important novel component of the renin–angiotensin system (RAS). The functional significance of (P)RR is widely studied in renal and vascular pathologies and has sparked interest for a potential role in cardiovascular disease. To investigate the role of (P)RR in cardiac pathophysiology, we aimed to assess (P)RR regulation in adverse cardiac remodelling of the failing heart. In particular, we evaluated the expression of (P)RR in different models of heart failure and across different species. Significantly increased levels of (P)RR mRNA were found in post-myocardial infarcted (MI) hearts of rats (1.6-fold, P < 0.05) and mice (5-fold, P < 0.01), as well as in transgenic rats with overexpression of the mouse renin gene (Ren2) (2.2-fold, P < 0.01). Moreover, we observed a strong increase of (P)RR expression in hearts of dilated cardiomyopathy (DCM) patients (5.3-fold, P < 0.001). Because none of the tested commercially available antibodies appeared to detect endogenous (P)RR, a (P)RR-specific polyclonal antibody was generated to study (P)RR protein levels. (P)RR protein levels were significantly increased in the post-MI rat heart (1.4-fold, P < 0.05) as compared to controls. Most interestingly in DCM patients, a significant 8.7-fold (P < 0.05) increase was observed. Thus, protein expression paralleled gene expression. These results demonstrate that (P)RR expression is strongly up-regulated both in rodent models of heart failure and in the failing human heart, hinting to a potential role for (P)RR in cardiac pathophysiology.

Highlights from the Literature

Highlights from the Literature

Rodent models of heart failure: an updated review

Heart failure (HF) is one of the major health and economic burdens worldwide, and its prevalence is continuously increasing. The study of HF requires reliable animal models to study the chronic changes and pharmacologic interventions in myocardial structure and function and to follow its progression toward HF. Indeed, during the past 40years, basic and translational scientists have used small animal models to understand the pathophysiology of HF and find more efficient ways of preventing and managing patients suffering from congestive HF (CHF). Each species and each animal model has advantages and disadvantages, and the choice of one model over another should take them into account for a good experimental design. The aim of this review is to describe and highlight the advantages and drawbacks of some commonly used HF rodents models, including both non-genetically and genetically engineered models, with a specific subchapter concerning diastolic HF models.

Abstract 9970: Combined Clenbuterol and Metoprolol Therapy Improves Cardiac Function and Calcium Handling in a Rodent Model of Heart Failure, but Does Not Prevent Myocardial Atrophy or Enhance Myocyte Recovery Associated with Mechanical Unloading

Clenbuterol (CL) a β 2 -AR agonist has been successfully employed alongside β 1 -AR blockade in combination with left ventricular assist devices (LVAD) to prevent myocardial atrophy, and promote myocardial recovery in patients with severe heart failure (HF). CL is known to have beneficial effects on excitation contraction (EC) coupling in HF and during mechanical unloading (MU) in animal models. However, CL-induced cardiac hypertrophy and tachycardia have discouraged its use in clinical HF therapy. We compared the chronic effects (4 wks) of CL (2mg/kg/day) and metoprolol (M) (200mg/kg/day) alone and in combination with MU (heterotopic abdominal transplantation) on heart/cardiomyocyte size, function and cellular EC coupling in a rat model of HF (LAD ligation). CL improved ejection fraction compared to untreated HF group, an effect further augmented by M (EF (%): HF 36.2 ± 2.3, p&lt;0.01 vs CL 40.78 ± 2.1, p&lt;0.001 vs M+CL 44.3 ± 2.3 (all groups n=8). CL caused a rise in heart rate (HR) but, when combined with M, HR was reduced (both groups p&lt;0.01 vs HF). CL caused cardiac hypertrophy whereas combined M+CL did not (heart weight:body weight ratio (g/g x 1000)): HF 3.6 ± 0.28, p&lt; 0.05 vs CL 4.2 ± 0.38, Μ+CL 3.6 ± 0.24, p&gt;0.05 vs HF (all groups n=8). Both groups failed to prevent MU-induced myocyte atrophy, but myocyte size was greater in MU+CL group compared with MU+M+CL (cell volume measured by di-8-ANNEPS staining and confocal microscopy (µm3)): MU+ CL 30025 ± 8562, p&lt;0.001 vs MU + M+CL 18750 ± 7500, (both groups n= 50). Myocyte Ca 2+ cycling was studied using the fluorescent dye Indo-1 AM. Ca 2+ transient amplitude was elevated in M+CL group but was not affected by CL (ratio units): HF 0.14 ± 0.06, p&lt;0.001 vs M+CL 0.19 ± 0.09 (both groups n=26). CL alone and M + CL augmented sarcoplasmic reticulum Ca2 + content equally (ratio units): CL 0.20 ± 0.04, M + CL 0.22 ± 0.06, both groups p&lt;0.01 vs HF, (all groups n=20). MU alone normalised HF cardiomyocyte EC parameters with no additional benefit derived by M+CL therapy. We show that combination of CL and M enhances whole heart function and cellular EC coupling in HF without increase in heart size or HR, but does not affect the consequences of MU on cell size and function. Whether such effects can be exploited in the treatment of HF patients requires further studies.